研究者データベース

朝倉 清髙(アサクラ キヨタカ)
触媒科学研究所 触媒表面研究部門
教授

基本情報

所属

  • 触媒科学研究所 触媒表面研究部門

職名

  • 教授

学位

  • 理学博士(東京大学)

ホームページURL

J-Global ID

研究キーワード

  • XFEL   MARX-Raman   機械触媒   STM   EXAFS   蛍光EXAFS   金ナノクラスター   TPRF-XAFS   濃度傾斜表面   XANAM   触媒   マイクロエレクトロメカノキャタリスト   高速XAFS   Operando Spectrum   Quick XAFS   VSbO4-Sb2O4   ディッピング   偏光全反射   偏光全反射蛍光EXAFS   規整不均一触媒   化学波   担体金属相互作用   チップ型触媒   自己組織構造   オペランド分光   その場観測   飽和炭化水素   Operando XAFS   科学波   MEMC   表面顕微分光   触媒表面科学 脱硫触媒   酸化物表面   光電子顕微鏡   XAFS分光学   構造化学   反応化学   表面化学   Surface MIcroscopy   Catalysis Surface ScienceXAFS spectroscopySpectromicroscopyOxide surface   Surface Oxide Surface   XAFS spectroscopy EXPEEM   Surface chemistry Reaction Structure   

研究分野

  • ナノテク・材料 / 分析化学
  • ものづくり技術(機械・電気電子・化学工学) / 触媒プロセス、資源化学プロセス
  • ナノテク・材料 / 機能物性化学
  • ライフサイエンス / 補綴系歯学
  • ナノテク・材料 / ナノ構造物理
  • ナノテク・材料 / ナノ構造化学
  • ナノテク・材料 / グリーンサステイナブルケミストリー、環境化学
  • 自然科学一般 / 磁性、超伝導、強相関系
  • ものづくり技術(機械・電気電子・化学工学) / 計測工学
  • ナノテク・材料 / 基礎物理化学

職歴

  • 2015年10月 - 現在 触媒科学研究所 触媒表面研究部門 教授
  • 2015年10月 - 2018年03月 北海道大学触媒科学研究所 所長
  • 2014年04月 - 2015年09月 北海道大学 触媒化学研究センター センター長
  • 1999年04月 - 2015年09月 北海道大学 触媒化学研究センター 教授
  • 1994年05月 - 1999年03月 東京大学理学部スペクトル化学研究センター 助教授
  • 1992年10月 - 1994年05月 東京大学理学部化学教室 講師
  • 1993年03月 - 1994年04月 フリッツハーバ研究所 アレキサンダーホンフンボルト奨学生
  • 1984年09月 - 1992年09月 東京大学理学部化学 助手

学歴

  • 1981年04月 - 1984年09月   東京大学   理学系研究科   化学専攻
  • 1977年04月 - 1981年03月   東京大学   理学部   化学科

所属学協会

  • International XAFS Society   王立化学協会   日本原子力学会   日本放射光学会   中間子学会   コロイドおよび界面部会   物理学会   応用物理学会   日本化学会   日本表面科学会   触媒学会 5165   PF-UA   米国化学会   日本XAFS研究会   Atomic Society of Japan   American Chemical Society   

研究活動情報

論文

  • Naoyoshi Murata, Takuya Suzuki, Yunli Lin, Hiroaki Nitani, Yasuhiro Niwa, Takahiro Wada, Motohiro Uo, Kiyotaka Asakura
    ACS Applied Materials & Interfaces 14 34 39507 - 39514 2022年08月31日 [査読有り][通常論文]
  • Junya Kogo, Ryusaku Sato, Kaori Niki, Kiyotaka Asakura
    e-Journal of Surface Science and Nanotechnology 2022年07月07日 [査読有り]
  • Kosaku Kato, Yohei Uemura, Kiyotaka Asakura, Akira Yamakata
    The Journal of Physical Chemistry C 2022年06月09日
  • Daiki Kido, Md. Mijanur Rahman, Tatsuya Takeguchi, Kiyotaka Asakura
    Chemistry Letters 51 5 538 - 541 2022年03月18日 [査読有り][通常論文]
  • 朝倉清髙, 近藤寛, 唯美津木, 岩澤康裕
    International Tables for Crystallography I 2022年03月11日 [査読有り][招待有り]
  • Bing Hu, Bapurao Bharate, Juan D. Jimenez, Jochen Lauterbach, Naoto Todoroki, Toshimasa Wadayama, Kotaro Higashi, Tomoya Uruga, Yasuhiro Iwasawa, Hiroko Ariga-Miwa, Satoru Takakusagi, Kiyotaka Asakura
    The Journal of Physical Chemistry C 126 2 1006 - 1016 2022年01月20日 [査読有り]
  • Koki Matsumoto, Dr, Masaru Kato, Prof. Ichizo Yagi, Siqi Xie, Prof. Kiyotaka Asakura, Prof. Shin-ichiro Noro, Prof. Norimitsu Tohnai, Dr. Stéphane Campidelli, Prof. Takashi Hayashi, Prof. Akira Onoda
    Chemistry A European Journal 28 e202103545  2021年11月 [査読有り]
  • Nazmul Hasan MD Dostagir, Rattanawalee Rattanawan, Min Gao, Jin Ota, Jun-ya Hasegawa, Kiyotaka Asakura, Atsushi Fukouka, Abhijit Shrotri
    ACS Catalysis 11 15 9450 - 9461 2021年08月06日 [査読有り]
  • Md Harun Al Rashid, Arnoldus Lambertus Dipu, Yuta Nishikawa, Hitoshi Ogihara, Yuta Inami, Shoji Iguchi, Ichiro Yamanaka, Shinchi Nagamatsu, Daiki Kido, Bing Hu, Kiyotaka Asakura
    Radiation Physics and Chemistry 189 109727 - 109727 2021年07月 [査読有り]
  • Bang Lu, Daiki Kido, Yuta Sato, Haoran Xu, Wang-Jae Chun, Kiyotaka Asakura, Satoru Takakusagi
    The Journal of Physical Chemistry C 125 22 12424 - 12432 2021年05月24日 [査読有り][招待有り]
  • Yuki Wakisaka, Hiromitsu Uehara, Qiuyi Yuan, Daiki Kido, Takahiro Wada, Motohiro Uo, Yohei Uemura, Toshihiko Yokoyama, Yutaro Kamei, Seiichi Kuroda, Akihiro Ohira, Satoru Takakusagi, Kiyotaka Asakura
    Electronic Structure 2020年12月 [査読有り][招待有り]
  • Yohei Uemura, Toshihiko Yokoyama, Tetsuo Katayama, Shunsuke Nozawa, Kiyotaka Asakura
    Applied Sciences 10 21 7818 - 7818 2020年11月04日 [査読有り][招待有り]
     
    The birth of synchrotron radiation (SR) facilities and X-ray free electron lasers (XFELs) has led to the development of new characterization tools that use X-rays and opened frontiers in science and technology. Ultrafast X-ray absorption fine structure (XAFS) spectroscopy for photocatalysts is one such significant research technique. Although carrier behavior in photocatalysts has been discussed in terms of the band theory and their energy levels in reciprocal space (k-space) based on optical spectroscopic results, it has rarely been discussed where photocarriers are located in real-space (r-space) based on direct observation of the excited states. XAFS provides information on the local electronic and geometrical structures around an X-ray-absorbing atom and can address photocarrier dynamics in the r-space observed from the X-ray-absorbing atom. In this article, we discuss the time dependent structure change of tungsten trioxide (WO3) and bismuth vanadate (BiVO4) photocatalysts studied by the ultrafast pump-probe XAFS method in the femtosecond to nanosecond time scale with the Photon Factory Advanced Ring (PF-AR) and the SPring-8 Angstrom Compact free-electron LAser (SACLA). WO3 shows a femtosecond decay process of photoexcited electrons followed by a structural change to a metastable state with a hundred picosecond speed, which is relaxed to the ground-state structure with a nanosecond time constant. The Bi L3 edge of BiVO4 shows little contribution of the Bi 6s electron to the photoabsorption process; however, it is sensitive to the structural change induced by the photoexcited electron. Time-resolved XAFS measurements in a wide range time domain and with varied wavelengths of the excitation pump laser facilitate understanding of the overall details regarding the photocarrier dynamics that have a significant influence on the photocatalytic performance.
  • Yuki Wakisaka, Bing Hu, Daiki Kido, Md. Harun Al Rashid, Wenhan Chen, Kaiyue Dong, Takahiro Wada, Bapurao Bharate, Quiyi Yuan, Shingo Mukai, Yasuo Takeichi, Satoru Takakusagi, Kiyotaka Asakura
    Journal of Synchrotron Radiation 27 6 1618 - 1625 2020年11月01日 [査読有り][通常論文]
     
    A bent crystal Laue analyser (BCLA) is an X-ray energy analyser used for fluorescence X-ray absorption fine-structure (XAFS) spectroscopy to separate the fluorescence X-ray emission line of a target atom from the elastic scattering X-rays and other fluorescence emission lines. Here, the feasibility of the BCLA for total reflection fluorescence XAFS (TRF-XAFS), which has a long X-ray footprint on the substrate surface owing to grazing incidence, was tested. The focal line of the BCLA was adjusted on the X-ray footprint and the XAFS signal for one monolayer of Pt deposited on a 60 nm Au film with high sensitivity was obtained. Although range-extended XAFS was expected by the rejection of Au fluorescence arising from the Au substrate, a small glitch was found in the Au L 3 edge because of the sudden change of the complex refraction index of the Au substrate at the Au edge. This abnormal spectrum feature can be removed by reflectivity correction using Au foil absorption data. BCLA combined with TRF-XAFS spectroscopy (BCLA + TRF-XAFS) is a new technique for the in situ surface analysis of highly dispersed systems even in the presence of a liquid overlayer.
  • Shun Tsunekawa, Futaba Yamamoto, Ke-Hsuan Wang, Masanari Nagasaka, Hayato Yuzawa, Satoru Takakusagi, Hiroshi Kondoh, Kiyotaka Asakura, Takeshi Kawai, Masaaki Yoshida
    The Journal of Physical Chemistry C 2020年10月20日 [査読有り][通常論文]
  • Problems in EXAFS analysis and its future prospects
    Daiki Kido, Kiyotaka Asakura
    Accounts of Materials and Surface Research 5 4 148 - 170 2020年10月 [査読有り][招待有り]
  • Daiki Kido, Yohei Uemura, Yuki Wakisaka, Hiroko Ariga-Miwa, Satoru Takakusagi, Kiyotaka Asakura
    E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 18 268 - 268 2020年09月 [査読有り][通常論文]
  • Junichi Mizuno, Melbert Jeem, Yuki Takahashi, Masaya Kawamoto, Kiyotaka Asakura, Seiichi Watanabe
    ACS Applied Nano Materials 3 2 1783 - 1791 2020年02月28日
  • Akihiro Koide, Yohei Uemura, Daiki Kido, Yuki Wakisaka, Satoru Takakusagi, Bunsho Ohtani, Yasuhiro Niwa, Shunsuke Nozawa, Kohei Ichiyanagi, Ryo Fukaya, Shin-Ichi Adachi, Tetsuo Katayama, Tadashi Togashi, Shigeki Owada, Makina Yabashi, Yusaku Yamamoto, Misaki Katayama, Keisuke Hatada, Toshihiko Yokoyama, Kiyotaka Asakura
    Physical chemistry chemical physics : PCCP 22 5 2615 - 2621 2020年02月07日 [査読有り][招待有り]
     
    Understanding the excited state of photocatalysts is significant to improve their activity for water splitting reaction. X-ray absorption fine structure (XAFS) spectroscopy in X-ray free electron lasers (XFEL) is a powerful method to address dynamic changes in electronic states and structures of photocatalysts in the excited state in ultrafast short time scales. The ultrafast atomic-scale local structural change in photoexcited WO3 was observed by W L1 edge XAFS spectroscopy using an XFEL. An anisotropic local distortion around the W atom could reproduce well the spectral features at a delay time of 100 ps after photoexcitation based on full potential multiple scattering calculations. The distortion involved the movement of W to shrink the shortest W-O bonds and elongate the longest one. The movement of the W atom could be explained by the filling of the dxy and dzx orbitals, which were originally located at the bottom of the conduction band with photoexcited electrons.
  • Felix E. Feiten, Shuntaro Takahashi, Oki Sekizawa, Yuki Wakisaka, Tomohiro Sakata, Naoto Todoroki, Tomoya Uruga, Toshimasa Wadayama, Yasuhiro Iwasawa, Kiyotaka Asakura
    Physical Chemistry Chemical Physics 2020年 [査読有り][通常論文]
     

    We have developed a novel analytical method combining model building and statistical evaluation to determine the structure of multimetallic nanoparticles from EXAFS of a single adsorption edge.

  • M. H. Al Rashid, A. Dipu, Y. Nishikawa, H. Ogihara, Y. Inami, S. Obuchi, I. Yamanaka, S. Nagamatsu, D. Kido, K. Asakura
    e-Journal of Surface Science and Nanotechnology 18 24 - 27 2020年 [査読有り][通常論文]
  • Barrow Elizabeth, Seuser Grant S, Ariga-Miwa Hiroko, Chen Donna A, Lauterbach Jochen, Asakura Kiyotaka
    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 20 1 379 - 387 2019年12月31日 [査読有り][招待有り]
  • Takashi Toyao, Kah Wei Ting, S. M. A. Hakim Siddiki, Abeda S. Touchy, Wataru Onodera, Zen Maeno, Hiroko Ariga-Miwa, Yasuharu Kanda, Kiyotaka Asakura, Ken-ichi Shimizu
    CATALYSIS SCIENCE & TECHNOLOGY 9 19 5413 - 5424 2019年10月 
    The structure and performance of TiO2-supported Re (Re/TiO2) catalysts for selective hydrogenation of carboxylic acid derivatives have been investigated. Re/TiO2 promotes selective hydrogenation reactions of carboxylic acids and esters that form the corresponding alcohols, and of amides that generate the corresponding amines. These processes are not accompanied by reduction of aromatic moieties. A Re loading amount of 5 wt% and a catalyst pretreatment with H-2 at 500 degrees C were identified as being optimal to obtain the highest catalytic activity for the hydrogenation processes. The results of studies using various characterization methods, including X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy (STEM), indicate that the Re species responsible for the catalytic hydrogenation processes have sub-nanometer to a few nanometer sizes and average oxidation states higher than 0 and below +4. The presence of either a carboxylic acid and/or its corresponding alcohol is critical for preventing the Re/TiO2 catalyst from promoting production of dearomatized byproducts. Although Re/TiO2 is intrinsically capable of hydrogenating aromatic rings, carboxylic acids, alcohols, amides, and amines strongly adsorb on the Re species, which leads to suppression of this process. Moreover, the developed catalytic system was applied to selective hydrogenation of triglycerides that form the corresponding alcohols.
  • Kashaboina Upendar, Nishikawa Yuta, Wakisaka Yuki, Sirisit Natee, Nagamatsu Shin-ichi, Bao Deling, Ariga-Miwa Hiroko, Takakusagi Satoru, Inami Yuta, Kuriyama Fumiya, Dipu Arnoldus Lambertus, Ogihara Hitoshi, Iguchi Shoji, Yamanaka Ichiro, Wada Takahiro, Asakura Kiyotaka
    CHEMISTRY LETTERS 48 9 1145 - 1147 2019年09月 [査読有り][通常論文]
  • F. Mauriello, H. Ariga-Miwa, E. Paone, R. Pietropaolo, S. Takakusagi, K. Asakura
    Catalysis Today 357 511 - 517 2019年06月 [査読有り][通常論文]
  • T. Fujikawa, K. Asakura, J. Kogo, K. Niki, J.J. Rehr
    J Electron Spectrosc. 233 57 - 63 2019年04月 [査読有り][通常論文]
  • Lyu Hao, Hisatomi Takashi, Goto Yosuke, Yoshida Masaaki, Higashi Tomohiro, Katayama Masao, Takata Tsuyoshi, Minegishi Tsutomu, Nishiyama Hiroshi, Yamada Taro, Sakata Yoshihisa, Asakura Kiyotaka, Domen Kazunari
    CHEMICAL SCIENCE 10 11 3196 - 3201 2019年03月21日 [査読有り][通常論文]
     
    Photocatalytic water splitting is a viable approach to the large-scale production of renewable solar hydrogen. The apparent quantum yield for this reaction has been improved, but the lifespan of photocatalysts functioning under sunlight at ambient pressure have rarely been examined, despite the critical importance of this factor in practical applications. Herein, we show that Al-doped SrTiO3 (SrTiO3: Al) loaded with a RhCrOx (rhodium chromium oxide) cocatalyst splits water with an apparent quantum yield greater than 50% at 365 nm. Moreover, following the photodeposition of CoOOH and TiO2, this material maintains 80% of its initial activity and a solar-to-hydrogen energy conversion efficiency greater than or equal to 0.3% over a span of 1300 h under constant illumination by simulated sunlight at ambient pressure. This result is attributed to reduced dissolution of Cr in the cocatalyst following the oxidative photodeposition of CoOOH. The photodeposition of TiO2 further improves the durability of this photocatalyst. This work demonstrates a concept that could allow the design of longterm, large-scale photocatalyst systems for practical sunlight-driven water splitting.
  • Yuta Inami, Hitoshi Ogihara, Shinichi Nagamatsu, Kiyotaka Asakura, Ichiro Yamanaka
    ACS Catalysis 9 2448 - 2457 2019年 [査読有り][通常論文]
  • S. Takahashi, N. Todoroki, R. Myochi, T. Nagao, N. Taguchi, T. Ioroi, F.E. Feiten, Y. Wakisaka, K. Asakura, O. Sekizawa, T. Sakata, K. Higashi, T. Uruga, Y. Iwasawa, T. Wadayama
    J Electroanal Chem 2019年 [査読有り][通常論文]
  • Sayantani Maiti, Dipak Das, Kamalesh Pal, Jordi Llorca, Lluís Soler, Sara Colussi, Alessandro Trovarelli, Kaustubh R Priolkar, Prabhakar R Sarode, Kiyotaka Asakura, Md. Motin Seikh, Arup Gayen
    :Applied Catalysis A 57 73 - 83 2019年01月 [査読有り][通常論文]
     
    This work reports the outstanding catalytic activity behavior of sol-gel synthesized nanostructured CuxFe1-xAl2O4 (0.3 ≤ x ≤ 0.8; named as CuFeAln, where n = 30, 40, 50, 60, 70 and 80) hercynites towards methanol steam reforming (MSR) for hydrogen generation. Based on the durability studies, we had categorized the higher Cu-doped hercynites (CuFeAl70 and CuFeAl80) as the more effective in regard to activity and stability (maintenance of a methanol conversion of ∼80% with low CO selectivity of 2% after 50 h of continuous operation at 275 °C for CuFeAl80) when compared with the lower Cu-doped counterparts (CuFeAl30 and CuFeAl40). The specific surface area of all the materials was about 50 m2 g−1 and they had similar reduction characteristics as obtained from H2-TPR analysis. The lower reducibility below 280 °C of CuFeAl70 and CuFeAl80 was correlated with the higher stability of these samples during time on stream operation. The powder XRD analyses had shown pure phase hercynite formation with the gradual increase of Cu-doping, while there occurred a phase segregation in the reforming atmosphere leading to the formation of metallic copper. High resolution microstructural analyses had confirmed single phase hercynite formation at nanoscale and a reduction of copper subsequent to ageing as well as certain growth of the copper metal particles (from ∼5 nm to ∼8 nm) corroborating the XRD studies. The surface features from in-situ XPS had also suggested formation of reduced copper species, which was much lower for the higher Cu-doped samples. Cu K edge XANES spectral analyses also pointed to lower occurrence of reduced copper in the aged samples of higher Cu-doped hercynites. The experimental findings had been explained on the basis of partial breakdown of the spinel lattice structure leading to the formation of CuO, followed by its reduction to metallic copper nanocrystallites in the MSR atmosphere. A definite ratio of the reduced to oxidized copper species was maintained with time on stream and this caused nearly stable conversion behavior of the catalysts in methanol steam reforming.
  • A Study of FeNx/C Catalyst for the Selective Oxidation of Unsaturated Alcohols by Molecular Oxygen
    Jinping Zhang, Shinichi Nagamatsu, Junmou Du, Chaoli Tong, Huihuang Fang, Dehui Deng, PhD, Xi Liu, PhD, Kiyotaka Asakura, PhD, Youzhu Yuan
    J.Cat. 367 16 - 26 2018年11月 [査読有り][通常論文]
  • S. Takakusagi, Y. Iwasawa, K. Asakura
    The Chemical Records 2018年09月 [査読有り][招待有り]
  • Natee Sirisit, Daiki Kido, Yuki Wakisaka, Hiroko Ariga-Miwa, Satoru, Takakusagi, Kiyotaka Asakura, Oki Sekizawa Tomohiro, Sakata Tomoya, Uruga, Yasuhiro Iwasawa
    e-Journal of Surface Science and Nanotechnology 16 387 - 390 2018年09月 [査読有り][通常論文]
     
    Creative Commons Free use with citation.
  • Yuhui Hou, Shinichi Nagamatsu, Kiyotaka Asakura, Atsushi Fukuoka, Hirokazu Kobayashi
    Communications Chemistry 1 1 41  2018年08月 [査読有り][通常論文]
     
    The partial oxidation of methane is a promising method for the efficient production of syngas. To implement this process using common stainless steel reactors, an inexpensive catalyst that functions at 650 degrees C or below is necessary. However, base metal catalysts typically require much higher temperatures, and they are deactivated by re-oxidation and coke formation. Here we report that modification of a zeolite-supported 3 wt% cobalt catalyst with a trace amount of mono-atomically dispersed rhodium (0.005 wt%) dramatically improves catalytic performance and durability. Cobalt/mordenite is nearly inactive due to the oxidation of cobalt, but the catalyst modified with rhodium continuously gives 85-86% methane conversion and 90-91% CO selectivity with an H-2/CO ratio of 2.0 without serious coking at 650 degrees C. During the reaction, mono-atomically dispersed rhodium converts cobalt oxide to Co-0 active species via hydrogen spillover. Use of the zeolite support is key to the high catalytic performance.
  • Yuki Wakisaka, Daiki Kido, Hiromitsu Uehara, Qiuyi Yuan, Felix E. Feiten, Shingo Mukai, Satoru Takakusagi, Yohei Uemura, Toshihiko Yokoyama, Takahiro Wada, Motohiro Uo, Oki Sekizawa, Tomoya Uruga, Yasuhiro Iwasawa, Kiyotaka Asakura
    The Chemical Records 2018年08月 [査読有り][通常論文]
  • Prabhakar Ravaji Sarode, K. Asakura, K. R. Priolkar, M. S. Hegde
    AIP Conference Proceedings 1953 2018年05月08日 [査読有り][通常論文]
     
    To understand the higher catalytic properties, the structure of 2 at. % palladium supported on TiO2 has been investigated by Extended X-ray absorption fine structure (EXAFS) spectroscopy. This nanocatalytic material of composition Ti0.98Pd0.02O2-δ has been synthesized by solution combustion method The analysis of EXAFS shows the oxide ion sublattice aroundPd ions is destabilized in the solid solution. Instead of ideal six coordination, Pd ion has 4+2, coordinations creating long and short bonds. The long Pd-O bonds are at 2.52 Å which are much higher than average Ti-O bonds of 1.947 Å.
  • Reaction Stoichiometry and Mechanism of Pt Deposition via Surface Limited Redox Replacement of Copper UPD Layer on Au (111)
    Qiuyi Yuan, Yuki Wakisaka, Yohei Uemura, Takahiro Wada, Hiroko Ariga-Miwa, Satoru Takakusagi, Kiyotaka Asakura, Stanko R Brankovic
    The Journal of Physical Chemistry C 122 29 16664 - 16673 2018年05月 [査読有り][通常論文]
  • 朝倉 清高
    Catalysts 8 5 204 - 209 2018年05月01日 [査読有り][通常論文]
     
    Pt-Au nanostructures are important and well-studied fuel cell catalysts for their promising catalytic performance. However, a detailed quantitative local structure analysis, using extended X-ray absorption fine structure (EXAFS) spectroscopy, have been inhibited by interference between Pt and Au L3-edges. In this paper, Pt L3-edge XAFS analysis, free of Au L3 edge, is demonstrated for a Pt-Au reference sample using a low-cost log–spiral bent crystal Laue analyzer (BCLA). This method facilitates the EXAFS structural analysis of Pt-Au catalysts, which are important to improve fuel cell catalysts.
  • 高草木達, 朝倉 清高
    表面と真空 61 5 1 - 6 2018年05月 [査読有り][招待有り]
  • K Asakura, H Abe, M Kimura
    J.Synchrotron Radiation 25 967 - 971 2018年05月 [査読有り][通常論文]
  • Wakisaka Y, Uehara H, Yuan Q, Kido D, Wada T, Uemura Y, Kamei Y, Kuroda S, Ohira A, Takakusagi S, Asakura K
    Photon Factory Activity Report 2017 35 2018年04月 [査読無し][通常論文]
  • Incorporation of Multinuclear Copper Active Sites into Nitrogen-Doped Graphene for Electrochemical Oxygen Reduction.
    M. Kato, M. Muto, N. Matsubara, Y. Uemura, Y. Wakisaka, T. Yoneuchi, D. Matsumura, T. Ishihara, T. Tokushima, S.-i. Noro, S. Takakusagi, K. Asakura, I. Yagi
    ACS Applied Energy Materials 1 5 2358 - 2364 2018年04月 [査読有り][通常論文]
  • José Contreras-Mora, Hiroko Ariga-Miwa, Satoru Takakusagi, Christopher T. Williams, Kiyotaka Asakura
    J. Phys. Chem. C 122 11 6318 - 6322 2018年03月22日 [査読有り][通常論文]
     
    Phosphorous (P) diffusion in bulk Ni2P was investigated by the density functional theory (DFT) to find the origin of the low-temperature P diffusion into the surface. The Ni2P bulk structure consists of two types of layers, Ni3P2 and Ni3P1, stacked along the [0001] direction. Two types of P vacancies in Ni2P were studied: V1P (P deficient in N3P2) and V2P (P deficient in N3P1). V1P was a slightly more stable point defect than V2P by 0.20 eV. The P diffusions to vacancies (V1P and V2P) had large diffusion barriers of more than 1 eV, except the P diffusion path along the [0001] direction through an interstitial site in Ni3P1 (I1→2P) and then to V1P, which showed the lowest energy barrier of about 0.18 eV. The DFT calculations suggested that the two adjacent vacancies (both V1P) allow the local rearrangement of the structure to form a tetrahedral structure at the intermediate state. We have proposed a new diffusion mechanism in the intermetallic compound named the interstitial–vacancy diffusion mechanism.
  • Tao Ma, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura
    Thin Solid Films 646 12 - 16 2018年01月31日 [査読有り][通常論文]
     
    Graphene, a two-dimensional material, can be grown on a metal substrate using chemical vapor deposition — this growth process is notably influenced by the crystal orientation and the roughness of the substrate surface. We prepared epitaxial Cu(111) films on sapphire substrates using thermal evaporation at various substrate temperatures and studied their crystal orientation and roughness. The well crystallized Cu(111) film with a smooth surface was obtained when the substrate was maintained at 473 K during the deposition. High quality graphene with few intrinsic defects was grown on this Cu film.
  • Takashi Toyao, S. M. A. H. Siddiki, Yoshitsugu Morita, Takashi Kamachi, Abeda S. Touchy, Wataru Onodera, Kenichi Kon, Shinya Furukawa, Hiroko Ariga, Kiyotaka Asakura, Kazunari Yoshizawa, Ken-ichi Shimizu
    CHEMISTRY-A EUROPEAN JOURNAL 23 59 14848 - 14859 2017年10月 [査読有り][通常論文]
     
    Herein, we report a heterogeneous TiO2-supported Re catalyst (Re/TiO2) that promotes various selective hydrogenation reactions, which includes the hydrogenation of esters to alcohols, the hydrogenation of amides to amines, and the N-methylation of amines, by using H-2 and CO2. Initially, Re/TiO2 was evaluated in the context of the selective hydrogenation of 3-phenylpropionic acid methyl ester to afford 3-phenylpropanol (p(H2)=5 MPa, T=180 degrees C), which revealed a superior performance over other catalysts that we tested in this study. In contrast to other typical heterogeneous catalysts, hydrogenation reactions with Re/TiO2 did not produce dearomatized byproducts. DFT studies suggested that the high selectivity for the formation of alcohols in favor of the hydrogenation of aromatic rings is ascribed to the higher affinity of Re towards the COOCH3 group than to the benzene ring. Moreover, Re/TiO2 showed a wide substrate scope for the hydrogenation reaction (19 examples). Subsequently, this Re/TiO2 catalyst was applied to the hydrogenation of amides, the N-methylation of amines, and the N-alkylation of amines with carboxylic acids or esters.
  • 脇坂 祐輝, 岩崎 裕也, 上原 広充, 向井 慎吾, 城戸 大貴, 高草木 達, 上村 洋平, 和田 敬広, Yuan Qiuyi, 関澤 央輝, 宇留賀 朋哉, 岩澤 康裕, 朝倉 清高
    表面科学 38 8 378 - 383 公益社団法人 日本表面科学会 2017年09月 [査読有り][招待有り]
     

    A log-spirally bent crystal Laue analyzer has been investigated and developed for highly sensitive in situ surface X-ray absorption fine structure (XAFS) measurement. Both calculations and experiments were conducted to obtain its intensity distributions on the different positions of the analyzer. A home-made log-spirally bent crystal Laue analyzer was made and evaluated. It was revealed that higher XAFS signals were obtained with the home-made analyzer than with the commercial one.

  • Hua Huang, Takahiro Wada, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura, Yasuhiro Iwasawa
    CHEMICAL PHYSICS LETTERS 683 18 - 21 2017年09月 [査読有り][通常論文]
     
    High-performance catalysts are often composed of two or more active phases, which are believed to interact with each other at the mesoscopic scale structure. Unlike conventional powder catalysts flat surfaces is advantageous in that its surface structure can be precisely designed. We prepared precisely designed Sb2O4/VSbO4/Si catalysts containing Sb2O4 ribbons with finely controlled width and separation by electron lithography. We demonstrated that the acrolein generation rate on the catalysts was related to the width and separation of the Sb2O4 ribbons. This work shows the possibility to regulate catalyses by inhomogeneity of the surface structure at the mesoscopic level. (C) 2017 Elsevier B.V. All rights reserved.
  • Qiuyi Yuan, Satoru Takakusagi, Yuki Wakisaka, Yohei Uemura, Takahiro Wada, Hiroko Ariga, Kiyotaka Asakura
    CHEMISTRY LETTERS 46 8 1250 - 1253 2017年08月 [査読有り][通常論文]
     
    We studied the initial stage of a Pt monolayer produced by surface-limited redox replacement (SLRR) using polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS). Different from the widely accepted understanding that metallic monolayer islands are formed, our XAFS showed that the Pt monolayer, initially present on the Au(111) substrate, was mainly in the form of a planar [PtCl4](2-) complex with its molecular plane parallel to Au(111). This result provides a new insight into the mechanism of SLRR.
  • Yohei Uemura, Daiki Kido, Akihiro Koide, Yuki Wakisaka, Yasuhiro Niwa, Shunsuke Nozawa, Kohei Ichiyanagi, Ryo Fukaya, Shin-Ichi Adachi, Tetsuo Katayama, Tadashi Togashi, Shigeki Owada, Makina Yabashi, Keisuke Hatada, Akihide Iwase, Akihiko Kudo, Satoru Takakusagi, Toshihiko Yokoyama, Kiyotaka Asakura
    Chemical communications (Cambridge, England) 53 53 7314 - 7317 2017年06月29日 [査読有り][招待有り]
     
    Ultrafast excitation of photocatalytically active BiVO4 was characterized by femto- and picosecond transient X-ray absorption fine structure spectroscopy. An initial photoexcited state (≪500 fs) changed to a metastable state accompanied by a structural change with a time constant of ∼14 ps. The structural change might stabilize holes on oxygen atoms since the interaction between Bi and O increases.
  • Yohei Uemura, Daiki Kido, Akihiro Koide, Yuki Wakisaka, Yasuhiro Niwa, Shunsuke Nozawa, Kohei Ichiyanagi, Ryo Fukaya, Shin-Ichi Adachi, Tetsuo Katayama, Tadashi Togashi, Shigeki Owada, Makina Yabashi, Keisuke Hatada, Akihide Iwase, Akihiko Kudo, Satoru Takakusagi, Toshihiko Yokoyama, Kiyotaka Asakura
    Chemical communications (Cambridge, England) 53 53 7314 - 7317 2017年06月29日 [査読有り][招待有り]
     
    Ultrafast excitation of photocatalytically active BiVO4 was characterized by femto- and picosecond transient X-ray absorption fine structure spectroscopy. An initial photoexcited state (≪500 fs) changed to a metastable state accompanied by a structural change with a time constant of ∼14 ps. The structural change might stabilize holes on oxygen atoms since the interaction between Bi and O increases.
  • Tadashi Ohba, Hitoshi Kubo, Yusuke Ohshima, Yuichi Makita, Noriaki Nakamura, Hiromitsu Uehara, Satoru Takakusagi, Kiyotaka Asakura
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 90 6 720 - 727 2017年06月 [査読有り][通常論文]
     
    Noble metal nanoparticles always show bond length contraction with the decrease in particle size. PVP-protected small Pd metal nanoparticles (MNPs) were reported to have the unique characteristic of expanding Pd-Pd bond lengths with decreases in particle size. To investigate the origin of this phenomenon in more detail, this work examined Pd MNPs supported on SiO2 (Pd MNPs/SiO2) via extended X-ray absorption fine structure (EXAFS) analysis, where the SiO2 support was used to stabilize the MNPs to prevent unexpected aggregation at higher temperatures. EXAFS data showed that each sample had a face-centered cubic (fcc) structure and that the smallest particles had the longest Pd-Pd bonds. Temperature dependent EXAFS measurements also revealed significant static disorder in the bond-elongated Pd MNPs/SiO2 samples. The XAFS spectral features of these bond-elongated Pd MNPs on SiO2 are in good agreement with those for palladium carbide, and we conclude that the lattice expansion in Pd MNPs can be attributed to the formation of palladium carbide.
  • Motohiro Uo, Takahiro Wada, Kiyotaka Asakura
    DENTAL MATERIALS JOURNAL 36 2 214 - 221 2017年04月 [査読有り][通常論文]
     
    The bioactive effects of strontium released from surface pre-reacted glass-ionomer (S-PRG) fillers may aid in caries prevention. In this study, the local structure of strontium taken up by teeth was estimated by extended X-ray absorption fine structure analysis. Immersing teeth into S-PRG filler eluate increased the strontium content in enamel and dentin by more than 100 times. The local structure of strontium in enamel and dentin stored in distilled water was the same as that in synthetic strontium-containing hydroxyapatite (SrHAP). Moreover, the local structure of strontium in enamel and dentin after immersion in the S-PRG filler eluate was also similar to that of SrHAP. After immersion in the S-PRG filler eluate, strontium was suggested to be incorporated into the hydroxyapatite (HAP) of enamel and dentin at the calcium site in HAP.
  • 朝倉 清高
    表面科学 38 11 541 - 541 公益社団法人 日本表面科学会 2017年
  • 村田尚義, 和田敬広, 鈴木卓弥, 向井慎吾, 上原広充, 仁谷浩明, 丹羽尉博, 朝倉清高
    放射光 30 1 21 - 26 2017年01月 [査読有り][通常論文]
  • NISHIMURA Yusaku F, BENIYA Atsushi, SUZUKI Ryo, ASAKURA Kiyotaka, TAKAKUSAGI Satoru, WATANABE Yoshihide
    KEK Progress Report (Web) 2016-8 ROMBUNNO.144 (WEB ONLY)  2017年01月 [査読無し][通常論文]
  • 朝倉 清高
    日本結晶学会誌 59 1 24 - 28 2017年01月 [査読有り][招待有り]
  • Takuya Masuda, Yu Sun, Hitoshi Fukumitsu, Hiromitsu Uehara, Satoru Takakusagi, Wang-Jae Chun, Toshihiro Kondo, Kiyotaka Asakura, Kohei Uosaki
    JOURNAL OF PHYSICAL CHEMISTRY C 120 29 16200 - 16210 2016年07月 [査読有り][通常論文]
     
    Organic molecular layers with viologen moieties as electron transfer mediators were constructed on hydrogen-terminated Si(111) surfaces, and metal catalysts for multielectron transfer reactions were incorporated into the molecular layers by immersing the viologen-modified Si(111) electrodes in aqueous solutions containing various metal complexes (K2PdCl4, NaAuCl4, and K2PtCl4). Significant enhancements were achieved for CO2 reduction at the Au-modified Si(111) electrode and for both hydrogen reaction (HER) and CO2 reduction at the Pd-modified Si(111) electrode. X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) analysis showed that Au complexes were spontaneously reduced to metal nanoparticles during the metal insertion, and therefore, actual catalysts for CO2 reduction at the Au-modified Si(111) electrode were Au metal nanoparticles. In contrast, Pd complexes were inserted into the molecular layers and partly reduced during HER and CO2 reduction. Pd complexes and relatively small Pd nanoparticles (<2 nm) were considered to be actual catalysts for HER and CO2 reduction. Interestingly, at the Pt-modified Si(111) electrode, not only highly efficient HER but also highly selective CO2 reduction in preference to HER were achieved, despite the fact that HER is dominant at Pt pure metal electrodes even in CO2-saturated aqueous solutions. On the basis of XPS and XAFS analysis, Pt complexes were incorporated into the molecular layers and acted as confined molecular catalysts for both HER and CO2 reduction without being converted into Pt metal nanoparticles. This should be the major reason for the anomalously high selectivity of the Pt-modified Si(111) electrode for CO2 reduction, unlike pure Pt metal electrocatalysts.
  • Satoru Takakusagi, Akitoshi Kunimoto, Natee Sirisit, Hiromitsu Uehara, Tadashi Ohba, Yohei Uemuara, Takahiro Wada, Hiroko Ariga, Wang-Jae Chun, Yasuhiro Iwasawa, Kiyotaka Asakura
    JOURNAL OF PHYSICAL CHEMISTRY C 120 29 15785 - 15791 2016年07月 [査読有り][招待有り]
     
    Ni and Pt structures evaporated onto a TiO2(110) surface premodified with ortho-mercaptobenzoic acid (o-MBA) were studied using polarization-dependent total reflection fluorescence X-ray absorption fine structure analysis to determine the effects of the premodification on the dispersion of the metal atoms over the TiO2(110) surface. Ni was found to be atomically dispersed with the formation of S-Ni-O bonds (where the S is provided by the o-MBA and the 0 is present in the TiO2 lattice) on the surface. In contrast, Pt underwent aggregation to form small clusters. The varying behavior of these metals on the o-MBA-modified TiO2(110) surface is discussed based on the energy difference between sulfur-metal-oxygen and metal-metal bond formations, and we propose a new indicator for single metal dispersion on the TiO2(110) surface.
  • Takahiro Kaito, Hiroyuki Tanaka, Hisashi Mitsumoto, Seiho Sugawara, Kazuhiko Shinohara, Hiroko Ariga, Hiromitsu Uehara, Satoru Takakusagi, Kiyotaka Asakura
    JOURNAL OF PHYSICAL CHEMISTRY C 120 21 11519 - 11527 2016年06月 [査読無し][通常論文]
     
    In order to examine the relationship between the oxygen reduction reaction (ORR) activity of a fuel cell catalyst and its structure and/or electronic state, carbon-supported Pt and Pt alloys having various structures, compositions, and morphologies were studied. Regardless of the atomic ordering or morphology (core-shell or random alloy) of the catalyst, the ORR activity was primarily dependent on the Pt-Pt bond distance. Among these materials, Pt2Co, having the shortest Pt-Pt distance, exhibited the highest ORR activity. The activities of this catalyst per unit surface. area and per unit mass were approximately 10 times and 6 times higher than those of a commercially available carbon supported Pt electrocatalyst (Pt/C). This work also found a monotonic increase in catalytic activity with decreasing Pt-Pt distance.
  • Yoshihide Watanabe, Yusaku F. Nishimura, Ryo Suzuki, Hiromitsu Uehara, Tomoyuki Nimura, Atsushi Beniya, Noritake Isomura, Kiyotaka Asakura, Satoru Takakusagi
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A 34 2 23201  2016年03月 [査読有り][通常論文]
     
    A portable ultrahigh-vacuum sample storage system was designed and built to investigate the detailed geometric structures of mass-selected metal clusters on oxide substrates by polarization-dependent total-reflection fluorescence x-ray absorption fine structure spectroscopy (PTRF-XAFS). This ultrahigh-vacuum (UHV) sample storage system provides the handover of samples between two different sample manipulating systems. The sample storage system is adaptable for public transportation, facilitating experiments using air-sensitive samples in synchrotron radiation or other quantum beam facilities. The samples were transferred by the developed portable UHV transfer system via a public transportation at a distance over 400 km. The performance of the transfer system was demonstrated by a successful PTRF-XAFS study of Pt-4 clusters deposited on a TiO2(110) surface. (C) 2015 American Vacuum Society.
  • Takahiro Wada, Naoyoshi Murata, Hiromitsu Uehara, Takuya Suzuki, Hiroaki Nitani, Yasuhiro Niwa, Motohiro Uo, Kiyotaka Asakura
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 18 10 7374 - 7380 2016年03月 [査読有り][通常論文]
     
    Of late, battery-driven high-performance gas sensors have gained acceptability in practical usage, whose atomic-scale structure has been revealed by m-fluorescence X-ray absorption fine structure analysis. We studied the chemical distribution of Pd species in the Pd/Al2O3 catalyst overlayer in the real gas sensor at various degrees of deterioration. In a freshly prepared sensor, all Pd species were in the PdO form; in a heavily deteriorated sensor, Pd/Al2O3 in the external region changed to metallic Pd particles, while the PdO structure in the inner region near the heater remained unchanged. The Pd species distribution was in agreement with the simulated thermal distribution. Temperature control was crucial to maintain the high performance of the gas sensor. The improved sensor allows homogeneous heating and has a lifetime of more than 5 years.
  • Masaaki Yoshida, Takehiro Mineo, Yosuke Mitsutomi, Futaba Yamamoto, Hirokatsu Kurosu, Satoru Takakusagi, Kiyotaka Asakura, Hiroshi Kondoh
    CHEMISTRY LETTERS 45 3 277 - 279 2016年03月 [査読有り][通常論文]
     
    A cobalt-phosphate (Co-P-i) oxygen evolution cocatalyst on a SrTiO3 photoelectrode was investigated by Co and P K-edge X-ray absorption fine structure (XAFS) spectroscopy. Formation of an edge-sharing CoO6 octahedral structure nanocluster in the Co-P-i cocatalyst was verified by the Co K-edge XAFS spectra under the photoelectrochemical reaction. The P K-edge XAFS spectrum for the Co-P-i cocatalyst showed a pre-edge peak derived from the hybridization of Co(3d)-O(2p)-P(3p) valence orbitals. Therefore, it was spectroscopically demonstrated that a phosphate species binds to the Co edge of the CoO6 cluster in the Co-P-i cocatalyst. The phosphate species is likely to stabilize the CoO6 cluster for efficient oxygen evolution activity.
  • I Mochizuki, H Ariga, Y Fukaya, K Wada, M Maekawa, A Kawasuso, T Shidara, K Asakura, T Hyodo
    Physical chemistry chemical physics 18 10 7085 - 7092 2016年03月 [査読有り][通常論文]
     
    The exact structure of the rutile-TiO2(110)-(1 x 2) surface, which had been under debate over the past 30 years, was investigated using the newly developed technique of total-reflection high-energy positron diffraction (TRHEPD), which is a positron counterpart of reflection high-energy electron diffraction (RHEED). The rocking-curves for the 00-spot obtained from the experimental diffraction patterns were compared to the curves for various models calculated with a full-dynamical theory. It was found that the rocking-curves matched those for a surface consisting of a Ti2O3 configuration, originally suggested by Onishi and Iwasawa [H. Onishi and Y. Iwasawa, Surf. Sci., 1994, 313, L783], but with a further modification of atomic positions close to the ones proposed by Wang et al. [Q. Wang, A. R. Oganov, Q. Zhu and X. F. Zhou, Phys. Rev. Lett., 2014, 113, 266101]. This result demonstrates that TRHEPD can distinguish between the existence and absence of the oxygen atoms on the topmost surface, and between the Ti atoms residing in positions at the interstitial-vertical sites and those at interstitial-horizontal sites.
  • Yoshihide Watanabe, Yusaku F. Nishimura, Ryo Suzuki, Hiromitsu Uehara, Tomoyuki Nimura, Atsushi Beniya, Noritake Isomura, Kiyotaka Asakura, Satoru Takakusagi
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A 34 2 023201  2016年03月 [査読有り][招待有り]
     
    A portable ultrahigh-vacuum sample storage system was designed and built to investigate the detailed geometric structures of mass-selected metal clusters on oxide substrates by polarization-dependent total-reflection fluorescence x-ray absorption fine structure spectroscopy (PTRF-XAFS). This ultrahigh-vacuum (UHV) sample storage system provides the handover of samples between two different sample manipulating systems. The sample storage system is adaptable for public transportation, facilitating experiments using air-sensitive samples in synchrotron radiation or other quantum beam facilities. The samples were transferred by the developed portable UHV transfer system via a public transportation at a distance over 400 km. The performance of the transfer system was demonstrated by a successful PTRF-XAFS study of Pt-4 clusters deposited on a TiO2(110) surface. (C) 2015 American Vacuum Society.
  • 望月 出海, 有賀 寛子, 深谷 有喜, 和田 健, 一宮 彪彦, 朝倉 清高, 兵頭 俊夫
    日本物理学会講演概要集 71 2483 - 2483 一般社団法人日本物理学会 2016年
  • 脇坂 祐輝, 城戸 大貴, 上原 広充, 上村 洋平, 高草木 達, 和田 敬広, Yuan Qiuyi, 朝倉 清高
    表面科学学術講演会要旨集 36 106 - 106 公益社団法人 日本表面科学会 2016年 
    広い立体角をもつ分光器Bent Crystal Laue Monochromator(BCLA)は、高感度な蛍光XAFSを可能とし、表面への応用が期待されてきたが、未だに十分な感度が達成されていない。われわれはこの5年間BCLAの改良に取り組んできた。 本講演ではその取り組みを総括し、現状(表面感度について)を述べ、今後の展開について議論したい。特に、HOPGを基板としたモデル燃料電池Pt触媒へのこの手法の応用についても議論する。
  • 鈴木 秀士, 向井 慎吾, 田 旺帝, 野村 昌治, 朝倉 清高
    表面科学学術講演会要旨集 36 53 - 53 公益社団法人 日本表面科学会 2016年 
    我々はNC-AFMと放射光X線を組み合わせたナノ表面元素分析のためのX線支援非接触原子間力顕微鏡(XANAM)の開発を行っている。これまで探針下のAu表面に対してAu-L3吸収端のX線を照射すると、探針-試料間の原子間力、特に共有結合力成分に変化が生ずる事を示してきた。今回は、Ni薄膜およびナノ粒子について観測し、X線エネルギーに対する変化について解析を行った結果を報告する。
  • 兵頭 俊夫, 望月 出海, 一宮 彪彦, 設楽 哲夫, 深谷 有喜, 圓谷 志郎, 境 誠司, 社本 真一, 和田 健, 前川 雅樹, 河裾 厚男, 有賀 寛子, 朝倉 清高
    表面科学学術講演会要旨集 36 244 - 244 公益社団法人 日本表面科学会 2016年 
    表面の原子配置に超敏感な全反射高速陽電子回折(TRHEPD)の特徴と、KEK物構研低速陽電子実験施設のTRHEPDステーションの最近の成果、特にルチル型TiO2(110)(1×2)の表面構造決定、およびCu(111)面上とCo(0001)面上のグラフェンの構造(バックリングの有無と、基板との距離)の決定について報告する。
  • Wang-Jae Chun, Satoru Takakusagi, Yohei Uemura, Kyoko Bando, Kiyotaka Asakura
    X-ray and Neutron Techniques for Nanomaterials Characterization 609 - 664 2016年01月01日 [査読有り][通常論文]
     
    Definition of the Topic X-ray absorption fine structure (XAFS) is an absorption spectroscopy which provides the material local structure with a bond distance of less than sub-Å precision. It does not require any long-range order nor special environment. Therefore, it is the suitable technique to characterize the catalytic nanomaterials under working conditions. This chapter presents an overview of the principle, emerging technology, and applications of XAFS in characterizing nanomaterials in catalysis. Overview Catalysts are materials that accelerate the reaction rate. The structure characterizations are difficult using diffraction methods because catalysts are often used as nanoclusters highly dispersed on oxide surfaces. In addition, the structures before, during, and after catalytic reactions are different from each other, and the in situ observation techniques of catalyst structures are highly required. X-ray absorption fine structure (XAFS) method is the most appropriate technique to investigate the catalyst nanomaterial structure under working conditions. We will review the history and principle of XAFS, followed by experimental setup and preparation of the sample. The analysis of XAFS will be briefly described, where the error estimations using Hamilton ratio method are discussed. We will mention its application to nanoparticles - monometallic and bimetallic under reaction conditions. We also describe the two emerging technologies in XAFS, called as ultrafast time-resolved XAFS and polarization-dependent total reflection fluorescence XAFS (PTRF-XAFS), which can provide new structural information we never have had with other characterization methods. Finally, we discuss its future perspective.
  • Yohei Uemura, Daiki Kido, Yuki Wakisaka, Hiromitsu Uehara, Tadashi Ohba, Yasuhiro Niwa, Shunsuke Nozawa, Tokushi Sato, Kohei Ichiyanagi, Ryo Fukaya, Shin-ichi Adachi, Tetsuo Katayama, Tadashi Togashi, Sigeki Owada, Kanade Ogawa, Makina Yabashi, Keisuke Hatada, Satoru Takakusagi, Toshihiko Yokoyama, Bunsho Ohtani, Kiyotaka Asakura
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 55 4 1364 - 1367 2016年01月 [査読有り][通常論文]
     
    The dynamics of the local electronic and geometric structures of WO3 following photoexcitation were studied by femtosecond time-resolved X-ray absorption fine structure (XAFS) spectroscopy using an X-ray free electron laser (XFEL). We found that the electronic state was the first to change followed by the local structure, which was affected within 200 ps of photoexcitation.
  • Radovan Kukobat, Daiki Minami, Takuya Hayashi, Yoshiyuki Hattori, Takafumi Matsuda, Motoo Sunaga, Bhuvnesh Bharti, Kiyotaka Asakura, Katsumi Kaneko
    CARBON 94 518 - 523 2015年11月 [査読有り][通常論文]
     
    We report a bimetallic Zn/Al complex as an efficient inorganic dispersant for SWCNT, synthesized from Zn(CH3COO)(2) and Al(NO3)(3). The Zn/Al complex shows more than four times greater efficiency at dispersing SWCNT than widely used surfactants (CTAB and SDS). Besides remarkable dispersibility, the Zn/Al complex does not foam upon any shaking treatment and it can be used just after quick dissolution of the powdered form, which is a marked advantage over surfactants. The Zn/Al complex, containing amorphous Al(CH3COO)(3) and a complex of Zn2+ and NO3- ions, should have a unique dispersion mechanism, differing from the surfactants. Al(CH3COO)(3) has higher affinity for SWCNT than ions, adsorbing onto its surface in the first layer and attracting Zn2+ and NO3- ions. Charge transfer interactions between the Zn/Al complex and SWCNT, as evidenced by optical absorption spectroscopy, should induce a charge on SWCNT; the zeta potential of such coated SWCNT was +55 mV, indicating a high dispersion stability in aqueous media. Hence, the Zn/Al complex can widen the applications of SWCNT to various technologies such as the transparent and conductive films, as well as high performance composite polymers. (C) 2015 Elsevier Ltd. All rights reserved.
  • Tao Ma, Kotaro Miyazaki, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 88 8 1029 - 1035 2015年08月 [査読有り][通常論文]
     
    The cleanliness of transferred graphene is of significant importance for its application as the window material in environmental cells used for electron microscopy and spectroscopy. We investigated the dependence of the cleanliness of graphene on transfer routes, including FeCl3 etching, (NH4)(2)S2O8 etching, electrochemical delamination, and O(2-)bubbling, by means of transmission electron microscopy and X-ray photoelectron spectroscopy. It was found that electrochemical delamination provided the cleanest graphene with only a small amount of poly(methyl methacrylate) (PMMA) residue existing on the surface.
  • Takahiro Wada, Naoyoshi Murata, Takuya Suzuki, Hiromitsu Uehara, Hiroaki Nitani, Yasuhiro Niwa, Motohiro Uo, Kiyotaka Asakura
    NANO-MICRO LETTERS 7 3 255 - 260 2015年07月 [査読有り][通常論文]
     
    We have directly investigated the chemical state of the Pd species in a real mu-gas sensor device by examining the mu-fluorescence X-ray absorption fine structure. The mu-gas sensor device was heavily damaged by a heating process in which the temperature was ill-controlled, resulting in decrease of methane selectivity. We found that the PdO in the fresh mu-gas sensor was reduced to Pd metal particles as the methane selectivity decreased. Based on the investigation results, we modified the device structure so as to heat up homogeneously. The lifetime of the sensor was then successfully increased by more than 5 years.
  • Zhenxin Zhang, Toru Murayama, Masahiro Sadakane, Hiroko Ariga, Nobuhiro Yasuda, Norihito Sakaguchi, Kiyotaka Asakura, Wataru Ueda
    NATURE COMMUNICATIONS 6 7731  2015年07月 [査読有り][通常論文]
     
    The development of metal oxide-based molecular wires is important for fundamental research and potential practical applications. However, examples of these materials are rare. Here we report an all-inorganic transition metal oxide molecular wire prepared by disassembly of larger crystals. The wires are comprised of molybdenum(VI) with either tellurium(IV) or selenium(IV): {(NH4)(2)[XMo6O21]}(n) (X = tellurium(IV) or selenium(IV)). The ultrathin molecular nanowires with widths of 1.2 nm grow to micrometre-scale crystals and are characterized by single-crystal X-ray analysis, Rietveld analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, thermal analysis and elemental analysis. The crystals can be disassembled into individual molecular wires through cation exchange and subsequent ultrasound treatment, as visualized by atomic force microscopy and transmission electron microscopy. The ultrathin molecular wire-based material exhibits high activity as an acid catalyst, and the band gap of the molecular wire-based crystal is tunable by heat treatment.
  • 朝倉 清高
    Nano-Micro Lett. 7 3 255 - 260 2015年07月 [査読有り][通常論文]
     
    We have directly investigated the chemical state of the Pd species in a real mu-gas sensor device by examining the mu-fluorescence X-ray absorption fine structure. The mu-gas sensor device was heavily damaged by a heating process in which the temperature was ill-controlled, resulting in decrease of methane selectivity. We found that the PdO in the fresh mu-gas sensor was reduced to Pd metal particles as the methane selectivity decreased. Based on the investigation results, we modified the device structure so as to heat up homogeneously. The lifetime of the sensor was then successfully increased by more than 5 years.
  • Tadashi Ohba, Hitoshi Kubo, Yusuke Ohshima, Yuichi Makita, Noriaki Nakamura, Hiromitsu Uehara, Satoru Takakusagi, Kiyotaka Asakura
    CHEMISTRY LETTERS 44 6 803 - 805 2015年06月 [査読有り][通常論文]
     
    Pd nanoparticles exhibit the abnormal behavior of the Pd lattice expanding as the size of the Pd nanoparticles decreases. We measured extended X-ray absorption fine structure of poly(N-vinyl-2-pyrrolidone)-protected Pd nanoparticles and confirmed that the Pd Pd bond distance in small Pd nanoparticles with a diameter of less than 3 nm was elongated by 2% compared with that in Pd foil. The origin of the unusual bond elongation was discussed.
  • Tadashi Ohba, Hitoshi Kubo, Yusuke Ohshima, Yuichi Makita, Noriaki Nakamura, Hiromitsu Uehara, Satoru Takakusagi, Kiyotaka Asakura
    CHEMISTRY LETTERS 44 6 803 - 805 2015年06月 [査読有り][通常論文]
     
    Pd nanoparticles exhibit the abnormal behavior of the Pd lattice expanding as the size of the Pd nanoparticles decreases. We measured extended X-ray absorption fine structure of poly(N-vinyl-2-pyrrolidone)-protected Pd nanoparticles and confirmed that the Pd Pd bond distance in small Pd nanoparticles with a diameter of less than 3 nm was elongated by 2% compared with that in Pd foil. The origin of the unusual bond elongation was discussed.
  • F. Mauriello, H. Ariga, M. G. Musolino, R. Pietropaolo, S. Takakusagi, K. Asakura
    APPLIED CATALYSIS B-ENVIRONMENTAL 166 121 - 131 2015年05月 [査読有り][通常論文]
     
    The transfer hydrogenolysis of glycerol promoted by supported palladium catalysts is reported. The reactions were carried out under mild conditions (453K and 5 bar of N-2) in absence of added hydrogen by using the reaction solvent, 2-propanol, as hydrogen source. The catalytic results are interpreted in terms of metal (Pd)-metal (Co or Fe) interaction that modifies the electronic properties of palladium and affords bimetallic PdM sites (M= Co or Fe), thus enhancing the catalytic properties of the systems in the conversion of glycerol as well as in the selectivity to 1,2-propanediol and 1-propanol. The transfer hydrogenolysis mechanism is here elucidated and involves the glycerol dehydration to 1-hydroxyacetone and the subsequent hydrogenation of 1-hydroxyacetone to propylene glycol. (C) 2014 Elsevier B.V. All rights reserved.
  • 朝倉 清高
    Top. Catal. 58 194 - 200 2015年05月 [査読有り][招待有り]
  • Qiuyi Yuan, Hiroko Ariga, Kiyotaka Asakura
    TOPICS IN CATALYSIS 58 4-6 194 - 200 2015年04月 [査読有り][通常論文]
     
    Ni2P has demonstrated high catalytic activity for hydrodesulfurization and has recently been employed as a catalyst in a variety of other reactions. We have thoroughly reviewed the literature concerning Ni2P single crystal surfaces, with the aim of determining the relationship between surface structure and catalytic properties. Published results to date indicate that Ni2P single crystal surfaces exhibit reconstructed structures, and so the bulk terminated structure may not be stable. We have also reviewed the surface structures and electronic states of (1 x 1) and reconstructed Ni2P(0001) and (). Based on these reviews, this paper presents general rules regarding stabilization of the Ni2P surface structure and discusses the role of phosphorus in the single crystal surfaces.
  • Qiuyi Yuan, Hiroko Ariga, Kiyotaka Asakura
    TOPICS IN CATALYSIS 58 4-6 194 - 200 2015年04月 [査読有り][通常論文]
     
    Ni2P has demonstrated high catalytic activity for hydrodesulfurization and has recently been employed as a catalyst in a variety of other reactions. We have thoroughly reviewed the literature concerning Ni2P single crystal surfaces, with the aim of determining the relationship between surface structure and catalytic properties. Published results to date indicate that Ni2P single crystal surfaces exhibit reconstructed structures, and so the bulk terminated structure may not be stable. We have also reviewed the surface structures and electronic states of (1 x 1) and reconstructed Ni2P(0001) and (). Based on these reviews, this paper presents general rules regarding stabilization of the Ni2P surface structure and discusses the role of phosphorus in the single crystal surfaces.
  • Naoyoshi Murata, Makoto Kobayashi, Yukari Okada, Takuya Suzuki, Hiroaki Nitani, Yasuhiro Niwa, Hitoshi Abe, Takahiro Wada, Shingo Mukai, Hiromitsu Uehara, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura
    REVIEW OF SCIENTIFIC INSTRUMENTS 86 3 034102  2015年03月 [査読有り][通常論文]
     
    We present the design and performance of a high-temperature in situ cell with a large solid angle for fluorescence X-ray absorption fine structure (XAFS) spectra. The cell has a large fluorescence XAFS window (116 mm(phi)) near the sample in the cell, realizing a large half-cone angle of 56 degrees. We use a small heater (25 x 35 mm(2)) to heat the sample locally to 873 K. We measured a Pt-SnO2 thin layer on a Si substrate at reaction conditions having a high activity. In situ measurement enables the analysis of the difference XAFS spectra between before and during the reaction to reveal the structure change during the operation. (C) 2015 AIP Publishing LLC.
  • 大濱 彰博, 石井 晃, 有賀 寛子, 朝倉 清高
    日本物理学会講演概要集 70 1463 - 1463 一般社団法人日本物理学会 2015年
  • Yuan Qiuyi, Ariga Hiroko, Asakura Kiyotaka
    表面科学学術講演会要旨集 35 147 - 147 公益社団法人 日本表面科学会 2015年 
    The reconstructed Ni2P(10-10) c(2X4) surface can be oxidized by NO. But the resultant structure and its temperature dependency remain unclear. We studied NO oxidation of Ni2P(10-10) surface by scanning tunneling microscope, X-ray photoelectron spectroscopy and low-energy electron diffraction. The phosphorus rich c(2X4) covered surface converted into uncovered (1X1) surface after NO dosing. The reaction rate of NO oxidation can be tuned by controlling dosing temperature. The higher temperature gives a faster reaction rate and a higher coverage of c(2X4) after NO dosing.
  • 加藤 優, 君島 堅一, 柴田 真里, 野津 英男, 荻野 和也, 猪熊 喜芳, 太田 鳴海, 小柳津 暢久, 上原 広充, 大場 惟史, 上村 洋平, 高草木 達, 朝倉 清高, 八木 一三
    表面科学学術講演会要旨集 35 357 - 357 公益社団法人 日本表面科学会 2015年 
    固体高分子形燃料電池の酸素還元電極触媒としては主に白金系合金が用いられているが、埋蔵量やコスト面に問題を抱えているため、安価かつ高活性な非白金系酸素還元電極触媒の開発が近年盛んに行われている。本発表では、銅系酸素還元電極触媒の中で特に高い触媒活性を示す銅二核錯体触媒に着目し、その高い触媒活性を示す理由を解明するためにin situ XAFS測定を行ったので、その結果に関して報告する。
  • 朝倉 清高, 大場 惟史, 上原 広允, 高草木 達
    表面科学学術講演会要旨集 35 324 - 324 公益社団法人 日本表面科学会 2015年 
    Pdナノ粒子は脱硝触媒、部分水素化触媒等で広く用いられる。Pdナノ粒子において,ナノ粒子化すると格子が拡張するという奇妙な現象が報告されてきた.本研究では,この格子拡張をEXAFSで直接調べ,Pd-Pd結合の伸長に起因することを確認し,また水素吸蔵に伴う現象でないことをしめした.この奇妙なナノ粒子に関する現象について,可能性を議論したい.
  • 鈴木 秀士, 向井 慎吾, 田 旺帝, 野村 昌治, 朝倉 清高
    表面科学学術講演会要旨集 35 28 - 28 公益社団法人 日本表面科学会 2015年 
    我々はナノ表面元素分析のためのX線支援非接触原子間力顕微鏡(XANAM)の開発を行っている。これはNC-AFMと放射光X線を組み合わせた手法で、これまで探針下のAu表面に対してAu-L3吸収端のX線を照射すると、探針-試料間の原子間力が変化することを、フォーススペクトルのX線エネルギー依存性から実験的に示した。今回はX線誘起の成分をフォーススペクトルから抽出し、その理論的解釈について報告する。
  • 朝倉 清高
    表面科学学術講演会要旨集 35 180 - 180 公益社団法人 日本表面科学会 2015年 
    触媒のナノ構造をしらべ、活性向上を図るには、触媒が反応中に変化する様子を時々刻々、反応環境雰囲気で追跡できるOperando XAFS法が重要になる。触媒におけるオペランドXAFSについて歴史的な観点から述べ、これに加えて、時間分解XAFSの現状と単結晶表面を使った三次元触媒構造解析手法である偏光全反射蛍光XAFS法について 議論したい。
  • Joseph D. Kistler, Pedro Serna, Kiyotaka Asakura, Bruce C. Gates
    X-Ray Absorption and X-Ray Emission Spectroscopy: Theory and Applications 2-2 773 - 808 2015年01月01日 [査読有り][招待有り]
     
    Mononuclear (single-metal-atom) complexes on supports are an important class of industrial catalyst, exemplified by the silica-supported chromium complexes used for ethylene polymerization and the anion-exchange-resin-supported rhodium complexes used for methanol carbonylation. These materials incorporate isolated metal cations bonded to oxygen or nitrogen atoms of the supports, respectively. The zeolite is an excellent support for preparation of highly uniform mono-iridium complexes. This chapter shows the value of x-ray absorption fine structure (XAFS) spectroscopy for the characterization of supported metal complexes, and the points are illustrated primarily with data characterizing samples synthesized precisely from molecular precursors on crystalline supports. The examples emphasize the results of experiments with flow-through cells and treatment of samples in reactive atmospheres. The chapter also illustrates how techniques such as infrared (IR) spectroscopy and scanning transmission electron microscopy (STEM) can complement x-ray absorption spectroscopy (XAS).
  • Tomohiro Seki, Taichi Ozaki, Takuma Okura, Kiyotaka Asakura, Aya Sakon, Hidehiro Uekusa, Hajime Ito
    CHEMICAL SCIENCE 6 4 2187 - 2195 2015年 [査読有り][通常論文]
     
    In this study, we report the interconvertible tetracolored solid state photoluminescence of gold(I) isocyanide complex 2 upon various external stimuli through solid state structural changes. Soaking complex 2 in acetone yields blue emission as a result of the formation of 2B. The subsequent removal of acetone yields 2G through a crystal-to-crystal phase transition, which exhibits green emission. This green-emitting solid 2G exhibits stepwise emission color changes to yellow and then to orange upon mechanical stimulation by ball-milling, which corresponds to the formation of 2Y and 2O, respectively. 2B could be recovered upon the addition of acetone to 2G, 2Y, and 2O. Thus, these four emitting solid states of 2 can be switched between repeatedly by means of acetone soaking and the application of mechanical stimulation. Importantly, single crystal and powder X-ray diffraction (PXRD) studies fully show the detailed molecular arrangements of 2B, 2G, and 2Y. This is the first mechanochromic compound to show interconvertible four color emission in the solid state. We also present the first example of using PXRD measurements and the Rietveld refinement technique for the structural analysis of a ground powder in a luminescence mechanochromism study. We obtained complete molecular-level structural information of the crystalline states of 2B, 2G, 2Y, and 2O. In comparison with a more solvophobic analogue 1, we suggest that the weak interaction of 2 with acetone in the solid state would allow a solvent inclusion/release mode, which is an important structural factor for the unprecedented multicolor mechanochromic luminescence.
  • Masaru Kato, Ken'ichi Kimijima, Mari Shibata, Hideo Notsu, Kazuya Ogino, Kiyoshi Inokuma, Narumi Ohta, Hiromitsu Uehara, Yohei Uemura, Nobuhisa Oyaizu, Tadashi Ohba, Satoru Takakusagi, Kiyotaka Asakura, Ichizo Yagi
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 17 14 8638 - 8641 2015年 [査読有り][通常論文]
     
    A dinuclear copper(II) complex of 3,5-diamino-1,2,4-triazole is one of the highly active copper-based catalysts for the oxygen reduction reaction (ORR) in basic solutions. Our in situ X-ray absorption near edge structure measurements revealed that deprotonation of the triazole ligand might cause coordination geometrical changes, resulting in the enhancement of the ORR activity.
  • Yoshikiyo Hatakeyama, Kiyotaka Asakura, Satoshi Takahashi, Ken Judai, Keiko Nishikawa
    JOURNAL OF PHYSICAL CHEMISTRY C 118 48 27973 - 27980 2014年12月 [査読有り][通常論文]
     
    Au nanoparticles (AuNPs) of varied sizes were synthesized in typical ionic liquids using the sputter deposition technique. Because AuNPs are dispersed freely in each ionic liquid without bonding to particular stabilizing agents, they are sometimes called naked AuNPs. To characterize the structure of naked AuNPs, we obtained a size distribution curve from small-angle X-ray scattering (SAXS) experiments and extracted the value of the peak position as the size of the most abundant AuNPs in each ionic liquid. The size was controlled by the type of ionic liquid and preparation temperature. To elucidate the local structure of the AuNPs in relation to their particle size, we measured the X-ray absorption fine structures (XAFS) at the Au L-3-edges. The analyses of the extended XAFS revealed that the Au-Au bond lengths for AuNPs similar to 1 nm in size are 2.76 to 2.81 angstrom, in contrast with the 2.88 angstrom bond lengths for bulk Au. Comparing our SAXS and XAFS results with previously reported theoretical studies, we conclude that the surface Au atoms of the naked AuNPs in ionic liquids have shorter bond lengths than the inner atoms.
  • TAKAKUSAGI Satoru, OGAWA Takafumi, UEHARA Hiromitsu, ARIGA Hiroko, SHIMIZU Ken-ichi, ASAKURA Kiyotaka
    Chem Lett 43 11 1797-1799 (J-STAGE) - 1799 2014年11月05日 [査読有り][通常論文]
  • Masaaki Yoshida, Takumi Yomogida, Takehiro Mineo, Kiyofumi Nitta, Kazuo Kato, Takuya Masuda, Hiroaki Nitani, Hitoshi Abe, Satoru Takakusagi, Tomoya Uruga, Kiyotaka Asakura, Kohei Uosaki, Hiroshi Kondoh
    JOURNAL OF PHYSICAL CHEMISTRY C 118 42 24302 - 24309 2014年10月 [査読有り][通常論文]
     
    Photoexcited hole transfer to MnOx cocatalysts on SrTiO3 photoelectrodes was examined under controlled potential conditions during UV irradiation using in situ Mn K-edge X-ray absorption fine structure (XAFS) spectroscopy. The absorption edges of spectra were found to shift to higher energies during irradiation, indicating that MnOx cocatalysts were oxidized by the migration of photoexcited holes accompanied by a positive potential shift of the MnOx cocatalysts. This oxidation process was promoted by the application of a positive applied potential, suggesting that the photoexcited hole transfer was enhanced by upward band bending at the cocatalystphotoelectrode interface. Structural changes of the MnOx cocatalyst were found to depend on the UV photon intensity; thus, the observations of photoexcited electron transfer by XAFS are associated with the photoelectrochemical activity during water splitting.
  • Kiyotaka Asakura, Hans-Joachim Freund, Katsuyuki Fukutani
    CHEMICAL RECORD 14 5 756 - 758 2014年10月 [査読無し][招待有り]
  • Masaaki Yoshida, Takumi Yomogida, Takehiro Mineo, Kiyofumi Nitta, Kazuo Kato, Takuya Masuda, Hiroaki Nitani, Hitoshi Abe, Satoru Takakusagi, Tomoya Uruga, Kiyotaka Asakura, Kohei Uosaki, Hiroshi Kondoh
    JOURNAL OF PHYSICAL CHEMISTRY C 118 42 24302 - 24309 2014年10月 [査読有り][通常論文]
     
    Photoexcited hole transfer to MnOx cocatalysts on SrTiO3 photoelectrodes was examined under controlled potential conditions during UV irradiation using in situ Mn K-edge X-ray absorption fine structure (XAFS) spectroscopy. The absorption edges of spectra were found to shift to higher energies during irradiation, indicating that MnOx cocatalysts were oxidized by the migration of photoexcited holes accompanied by a positive potential shift of the MnOx cocatalysts. This oxidation process was promoted by the application of a positive applied potential, suggesting that the photoexcited hole transfer was enhanced by upward band bending at the cocatalystphotoelectrode interface. Structural changes of the MnOx cocatalyst were found to depend on the UV photon intensity; thus, the observations of photoexcited electron transfer by XAFS are associated with the photoelectrochemical activity during water splitting.
  • Masaaki Yoshida, Takumi Yomogida, Takehiro Mineo, Kiyofumi Nitta, Kazuo Kato, Takuya Masuda, Hiroaki Nitani, Hitoshi Abe, Satoru Takakusagi, Tomoya Uruga, Kiyotaka Asakura, Kohei Uosaki, Hiroshi Kondoh
    JOURNAL OF PHYSICAL CHEMISTRY C 118 42 24302 - 24309 2014年10月 [査読有り][通常論文]
     
    Photoexcited hole transfer to MnOx cocatalysts on SrTiO3 photoelectrodes was examined under controlled potential conditions during UV irradiation using in situ Mn K-edge X-ray absorption fine structure (XAFS) spectroscopy. The absorption edges of spectra were found to shift to higher energies during irradiation, indicating that MnOx cocatalysts were oxidized by the migration of photoexcited holes accompanied by a positive potential shift of the MnOx cocatalysts. This oxidation process was promoted by the application of a positive applied potential, suggesting that the photoexcited hole transfer was enhanced by upward band bending at the cocatalystphotoelectrode interface. Structural changes of the MnOx cocatalyst were found to depend on the UV photon intensity; thus, the observations of photoexcited electron transfer by XAFS are associated with the photoelectrochemical activity during water splitting.
  • Micro XAFS Analysis of Micro Gas Sensor
    Takahiro Wada, Naoyoshi Murata, Hiromitsu Uehara, Takuya Suzuki, Makoto Kobayashi, Yukari Okada, Yasuhiro Niwa, Hiroaki Nitani, Motohiro Uo, Kiyotaka Asakura
    Photon Factory Activity Report 2013 PART B 31 109  2014年08月 [査読無し][通常論文]
  • Kyoko K. Bando, Takahiro Wada, Satoru Takakusagi, Shigeo Ted Oyama, Kiyotaka Asakura
    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 248 2014年08月 [査読有り][通常論文]
  • Takahiro Kaito, Hisashi Mitsumoto, Seiho Sugawara, Kazuhiko Shinohara, Hiromitsu Uehara, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura
    REVIEW OF SCIENTIFIC INSTRUMENTS 85 8 084104 - 084104-8 2014年08月 [査読有り][通常論文]
     
    A new spectroelectrochemical cell to investigate the structure of Pt/Au nanoclusters using Pt and Au K-edge X-ray absorption fine structure (XAFS) measurements under the electrochemical conditions is developed. K-edge XAFS measurements for Pt and Au require a sample as thick as 1-2 cm, which prevents homogeneous potential distribution. We can measure in situ Pt and Au K-edge XAFS spectra and determine reasonable electrochemical surface areas using our developed spectroelectrochemical cell. This work provides a new approach to analyze Pt/Au core-shell nanoclusters. The new cell is designed to be applied to both spectra with high absorption-edge energies such as the K-edge of Pt and Au and those with low absorption-edge energy such as Pt L-edge. (C) 2014 AIP Publishing LLC.
  • 朝倉清高, 上村洋平
    表面科学 34 128  2014年08月 [査読有り][招待有り]
  • Takahiro Kaito, Hisashi Mitsumoto, Seiho Sugawara, Kazuhiko Shinohara, Hiromitsu Uehara, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura
    REVIEW OF SCIENTIFIC INSTRUMENTS 85 8 084104  2014年08月 [査読有り][通常論文]
     
    A new spectroelectrochemical cell to investigate the structure of Pt/Au nanoclusters using Pt and Au K-edge X-ray absorption fine structure (XAFS) measurements under the electrochemical conditions is developed. K-edge XAFS measurements for Pt and Au require a sample as thick as 1-2 cm, which prevents homogeneous potential distribution. We can measure in situ Pt and Au K-edge XAFS spectra and determine reasonable electrochemical surface areas using our developed spectroelectrochemical cell. This work provides a new approach to analyze Pt/Au core-shell nanoclusters. The new cell is designed to be applied to both spectra with high absorption-edge energies such as the K-edge of Pt and Au and those with low absorption-edge energy such as Pt L-edge. (C) 2014 AIP Publishing LLC.
  • Takahiro Kaito, Hisashi Mitsumoto, Seiho Sugawara, Kazuhiko Shinohara, Hiromitsu Uehara, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura
    REVIEW OF SCIENTIFIC INSTRUMENTS 85 8 084104-1 - 084104-8 2014年08月 [査読有り][通常論文]
     
    A new spectroelectrochemical cell to investigate the structure of Pt/Au nanoclusters using Pt and Au K-edge X-ray absorption fine structure (XAFS) measurements under the electrochemical conditions is developed. K-edge XAFS measurements for Pt and Au require a sample as thick as 1-2 cm, which prevents homogeneous potential distribution. We can measure in situ Pt and Au K-edge XAFS spectra and determine reasonable electrochemical surface areas using our developed spectroelectrochemical cell. This work provides a new approach to analyze Pt/Au core-shell nanoclusters. The new cell is designed to be applied to both spectra with high absorption-edge energies such as the K-edge of Pt and Au and those with low absorption-edge energy such as Pt L-edge. (C) 2014 AIP Publishing LLC.
  • 鴻野健太郎, 有賀寛子, 高草木達, 大谷茂樹, 朝倉清高
    表面科学 35 8 415 - 419 2014年08月 [査読有り][招待有り]
  • 北山 冬馬, 宮崎 晃太朗, 馬 涛, 朝倉清高
    光アライアンス 25 8 29 - 32 日本工業出版 2014年08月 [査読有り][招待有り]
  • Keisuke Fujikawa, Hiroko Ariga, Satoru Takakusagi, Hiromitsu Uehara, Tadashi Ohba, Kiyotaka Asakura
    e-Journal of Surface Science and Nanotechnology 12 322 - 329 2014年07月05日 [査読有り][通常論文]
     
    We have developed a new Reverse Monte Carlo code, called the micro Reverse Monte Carlo (m-RMC), which is applicable to structure analysis of nanomaterials and surface species. In the m-RMC, Reverse Monte Carlo is applied to an ensemble of replica files, each of which contains one molecule or one small cluster, because the Extended X-ray Absorption Fine Structure (EXAFS) is sensitive to short-range structures and has negligible interaction between molecules or clusters. We apply the m-RMC to face-centered cubic metals (Cu, Pd, and Pt) and discuss the advantages, validation, and problems of the m-RMC. The bond distance and some cumulant coefficients can be determined from the EXAFS using m-RMC. Some 50-100 replica files are sufficient to reproduce the EXAFS oscillations and radial distributions. The bond distance can be determined, including the asymmetric distributions, by m-RMC. We also apply m-RMC to α-MoO 3 and Au clusters. The m-RMC analysis of MoO3 shows that three radial distribution peaks appear corresponding to three types of Mo-O bonds. The m-RMC analysis of Au cluster indicates the presence of Au 55 cuboctahedral structure with Au-Au distance at 0.288 nm. We obtain a 3 D image of Au55 nanocluster from the unified file. The m-RMC method can be applied to the analysis of the EXAFS for chemical systems with appropriate care. © 2014 The Surface Science Society of Japan.
  • Yohei Uemura, Hiromitsu Uehara, Yasuhiro Niwa, Shunsuke Nozawa, Tokushi Sato, Shinichi Adachi, Bunsho Ohtani, Satoru Takakusagi, Kiyotaka Asakura
    CHEMISTRY LETTERS 43 7 977 - 979 2014年07月 [査読有り][通常論文]
     
    The electronic state modification and the decay process of WO3 after photoabsorption were followed using picosecond X-ray absorption fine structure (XAFS) spectroscopy. The W d(e(g)) orbital was filled by transition from the oxygen valence state. The decay process is explained mostly by a first-order process with a rate constant k = 0.5 +/- 0.1 ns(-1). The UV optical length is extremely important to follow the photoreduction process using XAFS spectroscopy.
  • Xinlei Zheng, Haiqiang Lin, Jianwei Zheng, Hiroko Ariga, Kiyotaka Asakura, Youzhu Yuan
    TOPICS IN CATALYSIS 57 10-13 1015 - 1025 2014年06月 [査読無し][通常論文]
     
    Cu/SBA-15 catalysts containing a small amount of Pt (Cu-Pt/SBA-15) were prepared by sequential adsorption-reduction method and examined for chemoselective hydrogenation of dimethyl oxalate(DMO) to ethylene glycol (EG). The Cu-Pt/SBA-15 catalyst with an optimal Cu/Pt atomic ratio of 10 showed a DMO conversion close to 100 % with a 98 % selectivity to EG at a temperature as low as 463 K. The results showed that the best Cu-Pt/SBA-15 enhanced the space time yield of EG by about 1.47 times compared with Cu/SBA-15. The introduction of Pt with stronger ability for H-2 adsorption and activation substantially enhanced the reducibility of the Cu2+ species and further promoted the chemisorption capacity of H-2. After reduction, a portion of Cu was alloyed with Pt, which was beneficial for the generation and stabilization of a balanced Cu+/Cu-0 ratio during the hydrogenation process.
  • T. Kaito, H. Mitsumoto, S. Sugawara, K. Shinohara, H. Uehara, H. Ariga, S. Takakusagi, Y. Hatakeyama, K. Nishikawa, K. Asakura
    Journal of Physical Chemistry C. 118 16 8481 - 8490 2014年04月 [査読有り][通常論文]
     
    A carbon-supported Pt-shell Au-core electrocatalyst (Pt/Au/C) was prepared by sequential deposition of Pt ions on the surface of Au nanoparticles supported on carbon. The area-specific activity of the oxygen reduction reaction (ORR) for the prepared Pt/Au/C in 0.1 M HClO4, aqueous solution was approximately 2 times higher than that for a commercial carbon-supported Pt electrocatalyst (Pt/C). The core-shell structure was confirmed using electrochemical methods and Pt and Au K-edge X-ray absorption fine structure (XAFS) analysis. XAFS analyses indicated that the Pt-Pt bond distance for the Pt/Au/C catalyst was shorter than that for Pt foil and the Pt/C catalyst. In addition, the Au Au distance was much shorter than that for Au foil. The reason for the high ORR activity of Pt/Au/C is considered to be shorter Pt-Pt bond distance as compared to that of Pt/C.
  • Observation of Photoexcited Carrier Transfer in MnOx/SrTiO3 Photoelectrode by In Situ X-ray Absorption Fine Structure
    Masaaki Yoshida, Takumi YOMOGIDA, Takehiro MINEO, Kiyofumi NITTA, Kazuo KATO, Takuya MASUDA, Hiroaki NITANI, Hitoshi Abe, Satoru TAKAKUSAGI, Tomoya URUGA, Kiyotaka ASAKURA, Kohei UOSAKI, Hiroshi KONDOH
    225th ECS Meeting 2014年03月 [査読無し][通常論文]
  • Hiromitsu Uehara, Yohei Uemura, Takafumi Ogawa, Kentaro Kono, Ryoichi Ueno, Yasuhiro Niwa, Hiroaki Nitani, Hitoshi Abe, Satoru Takakusagi, Masaharu Nomura, Yasuhiro Iwasawa, Kiyotaka Asakura
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 16 27 13748 - 13754 2014年 [査読有り][通常論文]
     
    We measured the in situ polarization-dependent X-ray absorption fine structure of platinum nanoparticles (PtNPs) deposited on a flat highly oriented pyrolytic graphite (HOPG) substrate under electrochemical conditions using a back-side illumination method. In this method, the thin HOPG substrate with PtNPs deposited on one side was used as a window for incident and fluorescent X-rays, as well as an electrode. A bent crystal Laue analyzer (BCLA) was applied to the extraction of the Pt L-alpha fluorescent X-ray signals from strong scattered X-rays. Pt L-3 edge XAFS spectra were observed for various electrode potentials and polarization directions.
  • 鈴木 秀士, 向井 慎吾, 田 旺帝, 野村 昌治, 朝倉 清高
    表面科学学術講演会要旨集 34 127 - 127 公益社団法人 日本表面科学会 2014年 
    我々はナノスケール表面元素分析のためのX線支援非接触原子間力顕微鏡(XANAM)の開発を行ってきた。これは非接触原子間力顕微鏡(NC-AFM)と放射光X線を組み合わせた手法である。qPlus sensorを導入したことで、探針直下の元素情報に由来する信号計測の精度が向上できたことを報告したが、今回、そのデータの詳細な分析と、そのデータをサポートする新たなデータが得られたので報告する。
  • 藤川 圭介, 高草木 達, 朝倉 清高
    表面科学学術講演会要旨集 34 34 - 34 公益社団法人 日本表面科学会 2014年 
    MRMC(Micro Reverse Monte Carlo〕法は,非対称分布を考慮して,XAFSを解析できる手法である.この手法を用いて,AuおよびIナノ粒子の構造解析を行った. 解が一意的であるかということに関して問題はあるものの,熱振動の分布や動径分布関数を求めることができ,ナノ粒子の構造解析に有力な手法となる.
  • Matsui H, Matsui F, Maejima N, Daimon H, Matsushita T, Ariga H, Asakura K
    e-Journal of Surface Science and Nanotechnology 12 53 - 56 The Surface Science Society of Japan 2014年 [査読有り][通常論文]
     
    The surface alloying is the important topics in Ni2P study which is expected for next generation hydrodesulfurization and hydrodenitrogenation catalyst. The atomic structure and catalytic properties of a single crystalline Ni2P surface modified with W (W-Ni2P) was investigated by photoelectron diffraction (PED) and spectroscopy. PED is an element and site selective surface structure analysis method that enables observation of three-dimensional atomic configurations of the surface local structure. The selective replacement of W to the Ni site in the Ni2P crystal was clarified by PED. Chemical reactivities for NO molecules of the W-Ni2P and the clean Ni2P surfaces were compared. On the clean Ni2P surface, the NO adsorption did not occur, whereas W-Ni2P surface showed remarkable activity for NO adsorption. [DOI: 10.1380/ejssnt.2014.53]
  • 垣内孝宏, 光本, 久司, 朝倉 清高
    自動車技術 68 7 98 - 103 自動車技術会 2014年 [査読有り][招待有り]
  • 酸化物単結晶上金属ナノ構造の反応特性と制御
    高草木達, 朝倉清高
    触媒誌 56 306  2014年 [査読有り][招待有り]
  • Detection of oxygen vacancy in rutile TiO2 single crystal by μSR measurement.
    朝倉 清高
    JPS Conference Proceedings. 2 010307  2014年 [査読有り][通常論文]
  • New Prospects for the characteriation of heterogeneous catlasyts by using slow muon spectroscopy.
    朝倉 清高
    JPS Conference Proceedings. 2 010306  2014年 [査読有り][通常論文]
  • Electrodeposition Study on a TiO2 Single Crystal Electrode: Pt on a Nb-doped TiO2(110).
    朝倉 清高
    Chem. Lett. 43 1797 - 1799 2014年 [査読有り][通常論文]
  • Wenjing Li, Linmin Ye, Pei Long, Jin Chen, Hiroko Ariga, Kiyotaka Asakura, Youzhu Yuan
    RSC ADVANCES 4 55 29072 - 29082 2014年 [査読有り][通常論文]
     
    Supported bimetallic Ru-Fe catalysts were prepared using a step-deposition-reduction method. The selective hydrogenolysis of acetic acid to ethanol was investigated as a reaction, which is considered to be related to the transformation of biomass-derived carboxylic acids to fuels and value-added chemicals. An SBA-15-supported Ru-Fe catalyst displayed significant improvements in catalytic performance for the hydrogenolysis of acetic acid to ethanol compared with monometallic catalysts and that with SiO2 as a carrier. When the Ru/Fe atomic ratio was set at 2/1, the prepared catalyst could give a nearly 100% conversion of acetic acid and 88% selectivity to ethanol. The catalyst showed considerable stability in terms of structure and performance for a long-term run on stream. Characterization results indicated that a small portion of Fe species was alloyed with Ru, whereas the other portion of Fe species, likely FeO1+x (0 < x < 0.5), was dispersed on the catalyst surfaces. The Fe species were crucial for the stabilization of Ru-Fe bimetallic nanoparticles and activation of acetic acid molecules in the hydrogenolysis reaction. Moreover, several other carboxylic acids, such as propionic acid, levulinic acid, and lactic acid, could also be efficiently converted to their corresponding alcoholic chemicals or lactone using the optimized Ru-Fe/SBA-15 catalyst under relatively mild conditions.
  • 朝倉清高, 上村洋平
    . 表面科学 34 128  2014年 [査読有り][招待有り]
  • Hiroko Ariga, Mayumi Kawashima, Satoru Takakusagi, Kiyotaka Asakura
    CHEMISTRY LETTERS 42 12 1481 - 1483 2013年12月 [査読有り][通常論文]
     
    The electronic and structural properties of a phosphorus-terminated structure of Ni2P(0001) surface (Ni3PP) are investigated by density functional theory (DFT) calculations. Phosphorus adsorption largely stabilizes the Ni2P(0001) surface by creating Ni-P bonds on the Ni trimer. Atomic hydrogen can adsorb on the topmost P site although its adsorption energy is much lower than its adsorption energy on the Ni trimer site of the Ni3P2 surface. Our results suggest that the Ni trimer is the key factor for high catalytic activity.
  • Hiroko Ariga, Mayumi Kawashima, Satoru Takakusagi, Kiyotaka Asakura
    CHEMISTRY LETTERS 42 12 1481 - 1483 2013年12月 [査読有り][通常論文]
     
    The electronic and structural properties of a phosphorus-terminated structure of Ni2P(0001) surface (Ni3PP) are investigated by density functional theory (DFT) calculations. Phosphorus adsorption largely stabilizes the Ni2P(0001) surface by creating Ni-P bonds on the Ni trimer. Atomic hydrogen can adsorb on the topmost P site although its adsorption energy is much lower than its adsorption energy on the Ni trimer site of the Ni3P2 surface. Our results suggest that the Ni trimer is the key factor for high catalytic activity.
  • Satoru Takakusagi, Wang-Jae Chun, Hiromitsu Uehara, Kiyotaka Asakura, Yasuhiro Iwasawa
    TOPICS IN CATALYSIS 56 15-17 1477 - 1487 2013年11月 [査読有り][通常論文]
     
    This short review reports the three dimensional structure analysis of oxide-supported metal species and the origin of the metal-support interaction, using single crystal oxide surfaces and polarization-dependent total-reflection X-ray absorption fine structure (PTRF-XAFS) method. The PTRF-XAFS revealed that metal species interact strongly with oxygen anions of oxide surfaces and that surface pre-modification is a promising way to stabilize the surface monoatomic species of easily-aggregating Cu and Au and to prepare finely-tuned surface metal-organic species with regulated molecular structures and orientations.
  • Fudong Liu, Hong He, Zhihua Lian, Wenpo Shan, Lijuan Xie, Kiyotaka Asakura, Weiwei Yang, Hua Deng
    JOURNAL OF CATALYSIS 307 340 - 351 2013年11月 [査読有り][通常論文]
     
    An iron vanadate (FeVO4) catalyst supported on TiO2 with high dispersion has been developed and applied in the selective catalytic reduction (SCR) of NOx with NH3, showing high activity, N-2 selectivity, and H2O/SO2 durability in medium temperature range. The formation of Fe3+-O-V5+ linkages with low coordination number of vanadium atoms was evidenced by EXAFS, indicating the presence of abundant surface defects for reactant adsorption and activation. The XPS showed that the FeVO4 phase was surface-enriched with VOx species acting as true active sites, and thus, high NH3-SCR activity and H2O/SO2 durability could be preserved similar to that of V2O3/TiO2. Additionally, the presence of electronic inductive effect between Fe3+ and V5+ as confirmed by XANES and XPS could effectively decrease the unwanted NH3 unselective oxidation, thus resulting in high N-2 selectivity at high temperatures. This FeVO4/TiO2 catalyst is a potential candidate for the deNO(x) process for stationary flue gas or diesel exhaust. (C) 2013 Elsevier Inc. All rights reserved.
  • あたしい光電子顕微鏡PEEMの開発とその特徴
    武藤正男, 菅育正, 津野 勝, 朝倉 清高
    機能材料 33 51 - 54 2013年10月 [査読無し][招待有り]
  • Hiromitsu Uehara, Muhammad Haneef Bin Hanaffi, Yuichiro Koike, Keisuke Fujikawa, Shushi Suzuki, Hiroko Ariga, Satoru Takakusagi, Wang-Jae Chun, Yasuhiro Iwasawa, Kiyotaka Asakura
    CHEMICAL PHYSICS LETTERS 570 64 - 69 2013年05月 [査読有り][通常論文]
     
    The structures of Ni clusters formed on a highly-stepped TiO2(110) surface were studied by polarization-dependent total reflection fluorescence X-ray absorption fine structure analysis. When 0.8 monolayers of Ni were deposited, three-dimensional Ni clusters with 1-2 nm diameters and heights less than 1 nm were formed. Conversely, when 0.07 monolayers of Ni were deposited, an anisotropic Ni trimer with a Ni-Ni distance of 0.260 nm was created at the [001] step. We revealed that the surface modification to enhance the metal-anion interaction can control the deposited metal structure. (C) 2013 Elsevier B.V. All rights reserved.
  • Fudong Liu, Kiyotaka Asakura, Pengyang Xie, Jianguo Wang, Hong He
    CATALYSIS TODAY 201 131 - 138 2013年03月 [査読有り][通常論文]
     
    Environmental-friendly iron titanate (FeTiOx) catalyst is a potential candidate for the substitution of conventional V2O5-WO3 (MoO3)/TiO2 catalyst for the selective catalytic reduction of NOx with NH3 (NH3-SCR) for the NOx elimination from stationary and mobile sources for environmental protection. To understand in-depth the nature of active structure in this FeTiOx catalyst for further catalyst redesign and activity improvement, the study of X-ray absorption near-edge spectroscopy (XANES) and extended X-ray absorption fine-structure spectroscopy (EXAFS) combined with theoretical calculation is carefully performed. Different from the crystal structure of hematite Fe2O3, homogeneous edge shared Fe3+ -(O)(2)-Ti4+ structure in FeTiOx catalyst prepared from Ti(SO4)(2) precursor is obviously formed with crystallite phase, which shows the electronic inductive effect between Fe3+ and Ti4+ species, resulting in the high NO adsorption and oxidation ability of Fe3+ species and thus high catalytic activity and N-2 selectivity in the NH3-SCR reaction. In the future study, this specific edge shared Fe3+-(O)(2)-Ti4+ structure can be stabilized onto certain catalyst supports with large surface area for practical use, such as the catalytic removal of NOx from flue gas and diesel engine exhaust. (C) 2012 Elsevier B. V. All rights reserved.
  • Ying Huang, Hiroko Ariga, Xinlei Zheng, Xinping Duan, Satoru Takakusagi, Kiyotaka Asakura, Youzhu Yuan
    Journal of Catalysis 307 74 - 83 2013年 [査読有り][通常論文]
     
    We present the application of a one-step urea-assisted gelation method to prepare a SiO2-supported bimetallic catalyst composed of copper (Cu) and silver (Ag). Results show the remarkably enhanced performance of the catalyst for selective hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). Coupled with a series of characterization and kinetic studies, the improved activity is attributed to the formation of Cu nanoparticles containing Ag nanoclusters on the SiO2 surface. The coherent interactions between the Cu and Ag species help create the active Cu+/Cu 0 species in a suitable proportion and prevent the transmigration of bimetallic nanoparticles during the hydrogenation process. The optimized CuAg/SiO2 catalyst with an Ag/Cu atomic ratio of 0.05 has a balanced Cu+/Cu0 ratio and highly dispersed bimetal particles, which account for its high turnover frequency, EG selectivity of 97.0%, and excellent catalytic stability during the hydrogenation of DMO to EG for longer than 150 h. © 2013 Elsevier Inc. All rights reserved.
  • Ying Huang, Hiroko Ariga, Xinlei Zheng, Xinping Duan, Satoru Takakusagi, Kiyotaka Asakura, Youzhu Yuan
    Journal of Catalysis 307 0 74 - 83 2013年 [査読有り][通常論文]
     
    We present the application of a one-step urea-assisted gelation method to prepare a SiO2-supported bimetallic catalyst composed of copper (Cu) and silver (Ag). Results show the remarkably enhanced performance of the catalyst for selective hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). Coupled with a series of characterization and kinetic studies, the improved activity is attributed to the formation of Cu nanoparticles containing Ag nanoclusters on the SiO2 surface. The coherent interactions between the Cu and Ag species help create the active Cu+/Cu 0 species in a suitable proportion and prevent the transmigration of bimetallic nanoparticles during the hydrogenation process. The optimized CuAg/SiO2 catalyst with an Ag/Cu atomic ratio of 0.05 has a balanced Cu+/Cu0 ratio and highly dispersed bimetal particles, which account for its high turnover frequency, EG selectivity of 97.0%, and excellent catalytic stability during the hydrogenation of DMO to EG for longer than 150 h. © 2013 Elsevier Inc. All rights reserved.
  • Masaaki Yoshida, Takumi Yomogida, Takehiro Mineo, Kiyofumi Nitta, Kazuo Kato, Takuya Masuda, Hiroaki Nitani, Hitoshi Abe, Satoru Takakusagi, Tomoya Uruga, Kiyotaka Asakura, Kohei Uosaki, Hiroshi Kondoh
    CHEMICAL COMMUNICATIONS 49 71 7848 - 7850 2013年 [査読有り][通常論文]
     
    The Mn-oxide/Nb:SrTiO3 photoelectrode for oxygen evolution reaction was investigated by in situ Mn K-edge XAFS spectroscopy under UV irradiation. The oxidization of the Mn oxide was observed via photoexcited carrier transfer, which results in the positive potential shift of the Mn oxide cocatalyst toward oxygen evolution reaction.
  • Satoru Takakusagi, Hirotaka Nojima, Hiroko Ariga, Hiromitsu Uehara, Kotaro Miyazaki, Wang-Jae Chun, Yasuhiro Iwasawa, Kiyotaka Asakura
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 15 33 14080 - 14088 2013年 [査読有り][通常論文]
     
    Three-dimensional structures of vacuum-deposited Cu species formed on TiO2(110) surfaces premodified with three mercaptobenzoic acid (MBA) isomers were studied using polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS). We explored the possibility of fine tuning and orientation control of the surface Cu structures, including their coordination and configuration against the surface, according to the different mercapto group positions of the three MBA isomers (o(-), m(-), and p-MBA). Almost linear S-Cu-O (lattice O of TiO2) surface compounds were formed on the three MBA-modified TiO2(110) surfaces; however, the orientation of the Cu species on the o- and m-MBA-modified TiO2(110) surfaces (40-45 degrees inclined from the surface normal) was different from that on the p-MBA-modified TiO2(110) surface (60 degrees from the surface normal). This work suggests that the selection of a different MBA isomer for premodification of a single crystal TiO2(110) surface enables fine tuning and orientation control of surface Cu complexes.
  • Naoyoshi Murata, Takuya Suzuki, Makoto Kobayashi, Fumiaki Togoh, Kiyotaka Asakura
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 15 41 17938 - 17946 2013年 [査読有り][通常論文]
     
    The atomic scale structure and its dependence on Pt concentration of a Pt-doped SnO2 (Pt-SnO2) thin film produced by a sputter-deposition method was investigated, which showed high-performance as a methane gas sensor. Extended X-ray absorption fine structure (EXAFS) and X-ray diffraction (XRD) analyses showed that Pt-SnO2 has a rutile structure similar to SnO2 crystals at less than 10 at% Pt where the Pt ion was located at the Sn position in the rutile structure. There was no evidence that Pt metal clusters were formed in the Pt-SnO2 films. The Pt-SnO2 structure became amorphous at greater than 11 at% Pt. We found a good correlation between the methane activity and local structure of Pt.
  • Wang-Jae Chun, Kotaro Miyazaki, Naoki Watanabe, Yuichiro Koike, Satoru Takakusagi, Keisuke Fujikawa, Masaharu Nomura, Yasuhiro Iwasawa, Kiyotaka Asakura
    JOURNAL OF PHYSICAL CHEMISTRY C 117 1 252 - 257 2013年01月 [査読有り][通常論文]
     
    The structure of Au clusters on the TiO2(110) surface and the cluster-substrate interaction were investigated by polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS). The TiO2(110) (1 X 1) and (1 X 2) surfaces were compared in terms of substrate structural effects on Au cluster structure. We could not find evidence for the direct Au-substrate bonding and observed that the substrate morphology did not significantly affect the size and structure of Au clusters. Finally, we precisely determined that the Au clusters favored a geometry with icosahedral Au-55 symmetry. We discuss the possible interaction mechanism between Au and TiO2(110) that leads to these results.
  • Masao Kimura, Yohei Uemura, Toru Takayama, Reiko Murao, Kiyotaka Asakura, Masaharu Nomura
    Journal of Physics: Conference Series 430 1 012074  2013年 [査読有り][通常論文]
     
    In situ QXAFS studies of the reduction of α-Fe2O 3 and CaFe2O4 were conducted to determine their reduction kinetics and mechanisms. The reduction of α-Fe 2O3 involved two steps, the first being a very fast process in which Fe3+ was reduced to Fe2+ and the second being the reduction of Fe2+ to Fe metal over a longer period. In contrast, the reduction of Fe in CaFe2O4 was a single first-order reaction, although an induction period was clearly observed at the beginning of the reduction process. The reduction processes were successfully studied using a combination of in situ QXAFS spectra at the Ca and Fe K-edges.
  • Ariga H, Miyamoto T, Takakusagi S, Otani S, Oyama TS, Asakura K
    Abstracts of Papers of the American Chemical Society 246 2013年 [査読有り][通常論文]
  • Asakura, Kiyotaka, Takakusagi, Satoru, Ariga, Hiroko, Chun, Wang-Jae, Suzuki, Shushi, Koike, Yuichiro, Uehara, Hiromitsu, Miyazaki, Kotaro, Iwasawa, Yasuhiro
    FARADAY DISCUSSIONS 162 165 - 177 Royal Society of Chemistry 2013年 [査読有り][通常論文]
     
    Three-dimensional Au structures on bare and organic-compound-modified TiO2(110) surfaces were interrogated by Au L-3-edge polarization dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) spectroscopy. On the bare TiO2(110) surface, icosahedral Au-55 nanoclusters were the main product found. When the surfaces were modified with ortho or meso mercaptobenzoic acid (o-MBA or m-MBA), Au was atomically dispersed. Sulfur atoms in the o- and m-MBA formed strong covalent bonds with Au to produce stable Au-MBA (o-and m-forms) surface complexes. On the other hand, only oxygen atoms on the surface did not make a strong enough interaction to stabilize the Au species. We discuss how the Au species formed on the modified TiO2(110) surface and the possibility to control the Au structure by the surface modification method.
  • T. Miyamoto, Y. Kitajima, K. Asakura
    e-J. Surf. Sci. Nanotech. 10 609 - 612 The Surface Science Society of Japan 2012年11月 [査読有り][通常論文]
     
    L3 X-ray absorption near edge peak often provides amount of empty d state of the X-ray absorbing atoms. Monovalent Ag compounds formally have a d10 state and it shows a small peak at the edge due to the s-d hybridization. Rocksalt structure of AgCl also gives the edge peaks though the local symmetry (Oh) of Ag does not allow the s-d hybridization. In this paper we have considered the origin based on the molecular orbital picture. We proposed the edge peak occurs owing to the s-d hybridization with the two-electron excitation created by the metal ligand covalency. [DOI: 10.1380/ejssnt.2012.609]
  • Isabella Ascone, Kiyotaka Asakura, Graham N. George, Soichi Wakatsuki
    JOURNAL OF SYNCHROTRON RADIATION 19 849 - 850 2012年11月 [査読有り][通常論文]
  • 朝倉清高
    触媒 54 6 414-419 - 419 触媒学会 2012年10月10日 [査読無し][通常論文]
  • Takahiro Wada, Kyoko K. Bando, S. Ted Oyama, Takeshi Miyamoto, Satoru Takakusagi, Kiyotaka Asakura
    CHEMISTRY LETTERS 41 10 1238 - 1240 2012年10月 [査読有り][通常論文]
     
    In situ X-ray absorption spectroscopy was used to study the effect of H2S pretreatment on the activation of Ni2P catalysts for the thiophene hydrodesulfurization (HDS) reaction. It was found that H2S treatment produced Ni-S bonds that were slightly longer and that had higher coordination numbers than those formed during reaction. The longer Ni-S bonds formed by H2S treatment were changed to the shorter Ni-S bonds by the catalytic reaction, and these shorter bonds were associated with high activity. The work provides evidence that a NiPS phase is active in the HDS reaction.
  • Tatsuya Takeguchi, Toshiro Yamanaka, Kiyotaka Asakura, Ernee Noryana Muhamad, Kohei Uosaki, Wataru Ueda
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 134 35 14508 - 14512 2012年09月 [査読有り][通常論文]
     
    A randomly mixed monodispersed nanosized Pt-Ru catalyst, an ultimate catalyst for CO oxidation reaction, was prepared by the rapid quenching method. The mechanism of CO oxidation reaction on the Pt-Ru anode catalyst was elucidated by investigating the relation between the rate of CO oxidation reaction and the current density. The rate of CO oxidation reaction increased with an increase in unoccupied sites kinetically formed by hydrogen oxidation reaction, and the rate was independent of anode potential. Results of extended X-ray absorption fine structure spectroscopy showed the combination of NPt-Ru(NPt-Ru + NPt-Pt) (sic) M-Ru/(M-Pt + M-Ru) and NRu-Pt/(NRu-Pt + NRu-Ru) (sic) M-Pt/(M-Ru + M-Pt), where NPt-Ru(NRu-Pt), NPt-Pt(NRu-Ru), M-Pt, and M-Ru are the coordination numbers from Pt(Ru) to Ru(Pt) and Pt (Ru) to Pt (Ru) and the molar ratios of Pt and Ru, respectively. This indicates that Pt and Ru were mixed with a completely random distribution. A high-entropy state of dispersion of Pt and Ru could be maintained by rapid quenching from a high temperature. It is concluded that a nonelectrochemical shift reaction on a randomly mixed Pt-Ru catalyst is important to enhance the efficiency of residential fuel cell systems under operation conditions.
  • Takeshi Miyamoto, Takahiro Wada, Hironobu Niimi, Shushi Suzuki, Makoto Kato, Masato Kudo, Kiyotaka Asakura
    JAPANESE JOURNAL OF APPLIED PHYSICS 51 4 2012年04月 [査読有り][通常論文]
     
    We present the prototype of a new, collinear-type energy-filtered X-ray photoemission electron microscope (EXPEEM) using a multi-pole, aberration-corrected air-core coil Wien filter (WF) analyzer. We have designed the new WF with 12-pole electrodes and magnetic poles to reduce spherical aberrations and fringe effects. We assess the performance of the WF using an electron energy analyzer for PEEM. The sensitivity is enhanced 10-100 fold compared with a simple, two electrodes plus two magnetic poles type WF. Cu 2p(2/3) and Au 4f(7/2) photoelectron energy selected images are obtained in a laboratory-scale source within several minutes. The energy and spatial resolutions of our prototype EXPEEM are estimated to be 3 eV and 7 mu m, respectively. (C) 2012 The Japan Society of Applied Physics
  • 朝倉清高, 有賀寛子, 高草木達, 宮本剛志
    触媒 54 2 138-140 - 140 触媒学会 2012年03月10日 [査読無し][通常論文]
  • Takahiro Wada, Kyoko K. Bando, Takeshi Miyamoto, Satoru Takakusagi, S. Ted Oyama, Kiyotaka Asakura
    JOURNAL OF SYNCHROTRON RADIATION 19 19 205 - 209 2012年03月 [査読有り][通常論文]
     
    Structural changes in Ni2P/MCM-41 were followed by quick extended X-ray absorption fine structure (QEXAFS) and were directly related to changes in X-ray absorption near-edge structure (XANES) which had been used earlier for the study of the active catalyst phase. An equation is proposed to correct the transient QEXAFS spectra up to second-order in time to remove spectral distortions induced by structural changes occurring during measurements. A good correlation between the corrected QEXAFS and the XANES spectral changes was found, giving support to the conclusions derived from the XANES in the previous work, namely that the formation of a Ni-S bond in a surface NiPS phase is involved in the active site for the hydrodesulfurization reaction.
  • Kyoko K. Bando, Takahiro Wada, Takeshi Miyamoto, Kotaro Miyazaki, Satoru Takakusagi, Yuichiro Koike, Yasuhiro Inada, Masaharu Nomura, Aritomo Yamaguchi, Travis Gott, S. Ted Oyama, Kiyotaka Asakura
    JOURNAL OF CATALYSIS 286 165 - 171 2012年02月 [査読有り][通常論文]
     
    Supported Ni2P catalysts are active for hydrodesulfurization (HDS) of petroleum feedstocks and have attracted considerable attention. In order to find out the structure of the active catalyst and to obtain insight into the reaction mechanism of thiophene HDS over Ni2P/MCM-41, we conducted a simultaneous time-resolved (STR) study with in situ X-ray absorption fine structure (XAFS) spectroscopy and Fourier transform infrared (FTIR) spectroscopy together with time-resolved product analysis. At 513 K. adsorbed tetrahydrothiophene (THT) was observed by RIR, following the formation of a nickel phosphosulfide phase (NiPS). Detection of the HDS products coincided with the THT formation. All these experimental data indicated that NiPS worked as the active phase and identified THT as a reaction intermediate for the HDS reaction. The STR study proved to be a powerful tool for the precise study of reaction intermediates and the catalytic reaction path. (C) 2011 Elsevier Inc. All rights reserved.
  • 原口惟, 和田敬広, 大南祐介, 松平宣明, 有賀寛子, 高草木達, 朝倉清高
    表面科学 33 8 426 - 430 The Surface Science Society of Japan 2012年 [査読有り][通常論文]
     
    Well-defined inhomogeneous α-Sb2O4/VSbO4 catalysts were prepared using an electron lithography method to investigate the effects of µm order structures on an atomic scale catalytic reaction. X-ray photoelectron spectroscopy (XPS) and laser microscopy revealed that µm order structures were successfully developed on a Si substrate where an α-Sb2O4 micro line with a controlled width was deposited on VSbO4. We carried out a propene partial oxidation reaction on this surface and found that the acrolein formation rate was significantly influenced by the width and interval of the α-Sb2O4 µm line. The results of this study indicate the possibility of controlling the surface reaction by the inhomogeneity of the surface structure in the µm order.
  • Alkali-Metal-Promoted Catalysis with Platinum / Titanium Dioxide for Formaldehyde Oxidation at Ambient Temperatures
    C. Zhang, F. Liu, Y. Zhai, H. Ariga, N. Yi, Y. Liu, K. Asakura, M. Flytzani-stephanopoulos, H. He
    Angewandte Chemie International Edition in English 51 1 - 6 2012年 [査読有り][通常論文]
  • 芦間 英典, 田 旺帝, 山本 光, 朝倉 清高
    表面科学学術講演会要旨集 32 26 - 26 公益社団法人 日本表面科学会 2012年 
    Rh(100)表面の酸素吸着構造をLEEDとHREELSにより検討したところ、過去に報告されたRh-Oの振動とは異なる損失ピークを有する新たな酸素吸着Rh(100)表面が見出された。酸素吸着量を調整して詳細を検討した結果、この表面はsubsurfaceに位置する酸素で誘起された周期構造であると結論した。本講演では、HREELS、LEEDおよびDFTの結果から、この新たな表面の構造に関して議論する。
  • 黄 華, 原口 惟, 和田 敬広, 有賀 寛子, 高草木 達, 朝倉 清高
    表面科学学術講演会要旨集 32 113 - 113 公益社団法人 日本表面科学会 2012年 
    電子線リソグラフィー法を用いてSb2O4の線幅や間隔を変化させた不均一規制αーSb2O4/VSbO4 触媒を調製し,プロピレンの部分酸化反応を調べた.アクロレンへの選択性がSb2O4のミクロレベルの構造により変化することを見出した.これをリモートコントロール機構で説明した.
  • S. Ted Oyama, Haiyan Zhao, Hans-Joachim Freund, Kiyotaka Asakura, Radoslaw Wlodarczyk, Marek Sierka
    JOURNAL OF CATALYSIS 285 1 1 - 5 2012年01月 [査読有り][通常論文]
     
    The hydrodesulfurization (HDS) of the refractory compound 4,6-dimethyldibenzothiophene (DMDBT) normally proceeds through a hydrogenation pathway that removes the planarity of the ring system and makes the hindered sulfur atom more accessible to the desulfurization centers. In this study, a highly active dispersed bimetallic NiFeP catalyst is found to have high selectivity for a direct desulfurization pathway, which does not require prior hydrogenation. The compound has equal numbers of Ni and Fe atoms which extended X-ray absorption fine structure analysis indicates are distributed randomly in the hexagonal Fe2P structure, with just a slight enrichment of Fe on the surface. This is supported by density functional theory calculations. The remarkable properties of the catalyst are ascribed to a ligand effect of Fe on the active Ni atoms. (C) 2011 Elsevier Inc. All rights reserved.
  • Ya-nan Wang, Xinping Duan, Jianwei Zheng, Haiqiang Lin, Youzhu Yuan, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura
    CATALYSIS SCIENCE & TECHNOLOGY 2 8 1637 - 1639 2012年 [査読有り][通常論文]
     
    The performance of an SBA-15-supported Cu catalyst for hydrogenation of dimethyl oxalate to ethylene glycol is markedly promoted with Au. A key genesis of the high activity of the catalyst is ascribed to the formation of Cu-Au alloy nanoparticles which stabilize the active species and retard their agglomeration during the hydrogenation process.
  • Kiyotaka Asakura
    Catalysis 24 24 281 - 322 2012年 [査読有り][通常論文]
     
    Polarization-dependent total reflection fluorescence-extended X-ray absorption fine structure (PTRF-EXAFS) is a powerful tool to investigate the structures of highly dispersed metal clusters on oxide surfaces that provide a model system for supported metal catalysts. PTRF-EXAFS provides three-dimensional structural information of the dispersed metal clusters, in addition to the metal-support interface structure in the presence of a gas phase. Results from PTRF-EXAFS have revealed that the metal species interacts strongly with surface anions. Finally the future of PTRFEXAFS is discussed in combination with the next generation light sources, such as X-ray free electron laser (XFEL) and energy recovery linac (ERL). © The Royal Society of Chemistry 2012.
  • Takuya Masuda, Hitoshi Fukumitsu, Satoru Takakusagi, Wang-Jae Chun, Toshihiro Kondo, Kiyotaka Asakura, Kohei Uosaki
    ADVANCED MATERIALS 24 2 268 - 272 2012年01月 [査読有り][通常論文]
  • Changbin Zhang, Fudong Liu, Yanping Zhai, Hiroko Ariga, Nan Yi, Yongchun Liu, Kiyotaka Asakura, Maria Flytzani-Stephanopoulos, Hong He
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 51 38 9628 - 9632 2012年 [査読有り][通常論文]
  • Combined in Situ QXAFS and FTIR Observation of a Ni Phosphide Catalyst - Determination of Active Species for a Hydrodesulfurization Reaction -
    Kyoko K. Bando, Takahiro Wada, Takeshi Miyamoto, Kotaro Miyazaki, Satoru Takakusagi, Yuichiro Koike, Yasuhiro Inada, Masaharu Nomura, Aritomo Yamaguchi, T. Gott, S. Ted. Oyama, Kiyotaka Asakura
    Photon Factory Activity Report 2011 PART A 29 2012年 [査読無し][通常論文]
  • Bodong Li, Juan Wang, Youzhu Yuan, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura
    ACS CATALYSIS 1 11 1521 - 1528 2011年11月 [査読有り][通常論文]
     
    Carbon nanotube-supported RuFe bimetallic catalysts (RuFe/CNT) were prepared through a coimpregnation method for the selective hydrogenolysis of 20 wt % glycerol aqueous solution to produce glycols (1,2-propanediol and ethylene glycol). The Ru/CNT catalyst with smaller Ru nanoparticles (NPs) was significantly active for C-C bond cleavage, giving a considerable amount of CH(4) in the hydrogenolysis product. The RuFe/CNT catalyst with bimetallic NPs having an average size similar to Ru/CNT was more efficient for C-O bond cleavage, affording higher selectivity to glycols. Almost 100% glycerol conversion and over 75% selectivity to glycol could be obtained using the optimized RuFe/CNT catalyst under relatively mild conditions. The bimetallic RuFe/CNT catalyst was structurally robust and showed excellent reusability. Transmission electron microscopic images revealed that, when an appropriate amount of Fe entity was added, the RuFe bimetallic NPs were uniformly dispersed on the CNT surfaces and had an average size of similar to 3 nm. X-ray photoelectron spectroscopy indicated that a portion of the Fe species were interacted with Ru moieties, forming Ru-Fe alloys on the Ru domain, whereas other Fe species were in the forms of iron oxides, likely FeO and FeO(1+x) (0 < x < 0.5), mostly presenting on the periphery of RuFe bimetallic NPs. The occurrence of iron oxide species is crucial for the stability of RuFe bimetallic NPs during catalytic runs; but excess iron oxides block the surfaces of RuFe bimetallic NPs, resulting in a decrease in catalytic activity. Higher performance of the RuFe/CNT catalyst is attributed to the synergistic effects of the formation of Ru-Fe alloys and the interactions between the RuFe bimetallic NPs and iron oxides on CNT surfaces.
  • Wang-Jae Chun, Kotaro Miyazaki, Naoki Watanabe, Yuichiro Koike, Satoru Takakusagi, Keisuke Fujikawa, Masaharu Nomura, Kiyotaka Asakura
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 119 1395 890 - 893 2011年11月 [査読有り][通常論文]
     
    The bonding features and three dimensional structures of metal clusters on single crystal oxide surfaces can be determined by the polarization dependent total reflection fluorescence XAFS (PTRF-XAFS) method. K-edge XAFS has a cos(2) theta polarizationdependence to give successfully three dimensional structure while L-3 edge XAFS has a weaker polarization dependence though the L-3 edge is suitable for Au and Pt samples. In order to overcome this issue, we have developed an angle-resolved total reflection fluorescence XAFS (ARTRF-XAFS) method to determine more precise three dimensional structures of Au clusters using the L-3 edge by increase the number of data points. In this paper we described the methodologies of the ARTRF-XAFS and the results of Au clusters on the TiO2(110) surface. (C) 2011 The Ceramic Society of Japan. All rights reserved.
  • Shuhei Hoshika, Futami Nagano, Toru Tanaka, Takahiro Wada, Kiyotaka Asakura, Kenichi Koshiro, Denis Selimovic, Yusei Miyamoto, S. K. Sidhu, Hidehiko Sano
    JOURNAL OF ADHESIVE DENTISTRY 13 5 411 - 416 2011年10月 [査読有り][通常論文]
     
    Purpose: To investigate the effect of Colloidal Platinum Nanoparticles (CPN) on the bond strength between dentin and 4-META/MMA-TBB resin using different concentrations of CPN. Materials and Methods: Twenty-five extracted human third molars were stored in 0.5% chloramine T. The occlusal dentin slices were prepared by grinding occlusal surfaces of each tooth and polishing with 600-grit silicon carbide paper under running water. One control and four experimental groups (2 specimens per group) were used as follows: a) dentin surfaces treated with 10-3 solution, followed by rinsing with water and subsequently an acrylic rod bonded with hand-mixed 4META/MMA-TBB resin (Super-Bond C&B, Sun Medical) (control); b) dentin surfaces treated with 10-3 etching solution, followed by rinsing with water and application of CPN (100% or 10%) as a primer solution for 60 s and rinsed with water for 20 s, then an acrylic rod bonded with Super-Bond C&B(Etch-CPN [100% or 10%]); c) dentin surfaces treated with CPN (100% or 10%) for 60 s, rinsed with water for 20 s, followed by application of 10-3 solution, then an acrylic rod bonded with Super-Bond C&B (CPN-Etch [100% or 10%]). After storage in 37 C water, specimens were sectioned into beams (cross-sectional area: 1 mm(2)) for microtensile bond strength testing at a crosshead speed of 1mm/min. The data were analyzed using the Games-Howell method (p < 0.05; n = 15). Results: Etch-CPN (100), CPN-Etch(100) and CPN-Etch (10) showed significantly higher bond strengths compared to the control. When using 10% CPN, the highest bond strength was demonstrated. The bond strength of 4META/MMA-TBB resin was approximately doubled by CPN application. Conclusion: The results of this study showed that higher bond strengths are obtained when treating dentin with a lower concentration of CPN. Further evaluation to optimize conditions such as the application time and rinsing time are required.
  • Alvin B. Hernandez, Hiroko Ariga, Satoru Takakusagi, Kumiko Kinoshita, Shushi Suzuki, Shigeki Otani, S. Ted Oyama, Kiyotaka Asakura
    CHEMICAL PHYSICS LETTERS 513 1-3 48 - 52 2011年09月 [査読有り][通常論文]
     
    Nickel phosphide (Ni2P) is an emerging catalyst for hydrodesulfurization and other important environment- and energy-related catalytic reactions. To understand its high performance, the surface structure of a Ni2P (0 0 0 1) single crystal surface was investigated using dynamical LEED analysis. The obtained surface structure for Ni2P (0 0 0 1)-1 x 1 is a P-covered Ni3P2 structure (Ni3P_P structure) as opposed to the expected bulk terminated surface structures. This Letter discusses the driving force for the formation of the Ni3P_P surface, which involves the minimization of dangling bonds. (C) 2011 Elsevier B. V. All rights reserved.
  • Kiyotaka Asakura
    CATALYSIS SURVEYS FROM ASIA 15 2 57 - 57 2011年06月 [査読有り][通常論文]
  • 朝倉 清高
    放射光 24 3 160 - 162 日本放射光学会 2011年05月31日 [査読無し][通常論文]
  • Chi-Wen Tsai, Hao Ming Chen, Ru-Shi Liu, Kiyotaka Asakura, Ting-Shan Chan
    JOURNAL OF PHYSICAL CHEMISTRY C 115 20 10180 - 10186 2011年05月 [査読有り][通常論文]
     
    This investigation demonstrates the photocatalytic properties and activities of N-doped InTaO4 photocatalysts, which were prepared by impregnating Ni and the use of a modified Ni@NiO core-shell nanostructure-cocatalytic method for the reduction of CO2 to methanol. X-ray absorption spectroscopy (XAS) clearly indicates the oxygen vacancies and mechanism of a series of InTaO4-based photocatalysts. Nitrogen doping produces visible-light-responsive photocatalytic activity and further enhances absorbance. The cocatalytic method not only dramatically enhances absorbance, but also efficiently avoids electron-hole recombination that would otherwise be caused by electrons and holes separated from the crystal. The photocatalytic activity that was determined by the methanol yield demonstrates that N-doped samples give approximately twice the yield of undoped ones, whereas the cocatalytic method gives about triple the yield. A mechanism is aided in attempts to elucidate the correlation between structures and activities.
  • Kyoko K. Bando, Yuichiro Koike, Toshihide Kawai, Gosuke Tateno, S. Ted Oyama, Yasuhiro Inada, Masaharu Nomura, Kiyotaka Asakura
    JOURNAL OF PHYSICAL CHEMISTRY C 115 15 7466 - 7471 2011年04月 [査読有り][通常論文]
     
    Ni2P/K-USY (K-promoted ultrastable Y-type zeolite) is an efficient catalyst for hydrotreatment of petroleum feedstocks. The structural changes of the passivated catalyst during activation were followed by quick XAFS (X-ray absorption fine structure) with online gas analysis. Activation was conducted by temperature-programmed reduction (TPR) from ambient temperature to 773 Kunder a flow of H-2. The Ni species was present as Ni(OH)(2) in the passivated sample. Two peaks were detected by gas analysis during TPR. The quick XAFS analysis revealed that the first peak at 390 K was due to desorption of water from Ni(OH)(2) accompanied by formation of atomically dispersed Ni2+ species. The second peak, observed at 773 K, was due to the regeneration of Ni2P by the simultaneous reductive reaction of the atomically dispersed Ni oxide and the phosphate species, followed by growth of Ni2P nanocrystals. No formation of Ni metallic phase was observed.
  • Fudong Liu, Kiyotaka Asakura, Hong He, Wenpo Shan, Xiaoyan Shi, Changbin Zhang
    APPLIED CATALYSIS B-ENVIRONMENTAL 103 3-4 369 - 377 2011年04月 [査読有り][通常論文]
     
    Iron titanate catalyst (FeTiOx) is a potential candidate for the substitution of conventional V2O5-WO3 (MoO3)/TiO2 and Fe/Cu-zeolite catalysts for the selective catalytic reduction (SCR) of NOx with NH3 because of its high SCR activity and N-2 selectivity in the medium temperature range. Due to the presence of small amount of SO2 in typical diesel exhaust derived from combustion of sulfur-containing fuels, it is very important to investigate the influence of sulfation on SCR activity, catalyst structure and reaction mechanism. After sulfation under the SCR condition, the surface area and pore volume of FeTiOx catalyst decreased to a certain extent due to the formation of sulfate species. According to the characterizations of FeTiOx catalyst using X-ray diffraction, X-ray absorption fine structure spectroscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy of SO2 + O-2 treatment, the sulfate species mainly formed on iron sites in a chelating bidentate conformation, resulting in the enhancement of Bronsted acidity and Lewis acid strength simultaneously. NH3 adsorption was greatly enhanced in the high temperature range, while NOx adsorption was severely inhibited due to the stronger acidity of sulfate species. The operation temperature window of the sulfated catalyst shifted ca. 50 degrees C towards high temperature range accordingly. The reaction mechanism study shows that the Langmuir-Hinshelwood reaction pathway was cut off by the sulfation process, resulting in the activity loss at low temperatures: only Eley-Rideal reaction pathway between adsorbed NH3 species and gaseous or weakly adsorbed NO dominated in the SCR reaction, which made this catalyst resistant to SO2 poisoning at relatively high temperatures. (c) 2011 Elsevier B.V. All rights reserved.
  • Fudong Liu, Kiyotaka Asakura, Hong He, Yongchun Liu, Wenpo Shan, Xiaoyan Shi, Changbin Zhang
    CATALYSIS TODAY 164 1 520 - 527 2011年04月 [査読有り][通常論文]
     
    The influence of calcination temperature on the microstructure, redox behavior, reactant adsorption capability and catalytic activity of iron titanate catalyst (FeTiOx) for the selective catalytic reduction (SCR) of NOx with NH3 was investigated in detail using various characterization methods. After high temperature calcination (above 600 degrees C), the apparent SCR activity of FeTiOx catalyst obviously decreased, which was mainly due to decrease of surface area, pore volume, mobility of lattice oxygen and reactant adsorption capability. However, well crystallized pseudobrookite Fe2TiO5 showed much higher intrinsic SCR activity after normalization by surface area. This is mainly owing to the formation of larger proportion of monodentate nitrate, which is the real reactive nitrate species in the NOx reduction process, among total nitrate species on the surface of FeTiOx catalysts with higher crystallization degree. This implies a possibility that the FeTiOx catalyst after high temperature calcination (600 or 700 degrees C) with higher thermal stability could be loaded onto porous support with large surface area to further improve its dispersion and thus the apparent SCR activity for practical use, such as the DeNO(x) process for diesel engines. (C) 2010 Elsevier B. V. All rights reserved.
  • Hideyuki Takahashi, Norikazu Konishi, Hironobu Ohno, Kazunari Takahashi, Yuichiro Koike, Kiyotaka Asakura, Atsushi Muramatsu
    APPLIED CATALYSIS A-GENERAL 392 1-2 80 - 85 2011年01月 [査読有り][通常論文]
     
    The synthesis system of uniform and well-crystallized alloy nanoparticulate catalysts has been studied based on the calculation of pH dependent metal complex concentrations in an aqueous solution. Results of both the prediction based on calculation and EXAFS analysis clearly demonstrated that [Pd2+(EDTA)] and Te-citric acid complex species were generated independently in the solution. Since the formations of metal complexes are restricted to [Pd2+(EDTA)] and Te-citric acid complexes in the pH range between 5 and 10, only Pd20Te7 was successfully synthesized when the reducing agent was introduced into the [Pd2+(EDTA)] complex/Te-citric acid complex system at room temperature. Moreover. PdTe nanoparticles can be synthesized predominantly in pores of silica-gel by controlling the temperature of the Pd-EDTA/Te-citric acid/hydrazine mixed solution with a metal loading of 0.5 wt% Pd. The main phase of the well-crystallized alloy nanoparticles formed in the pores was Pd20Te7, leading to remarkable stability in catalytic activity, compared with those of the conventional catalysts. (C) 2010 Elsevier B.V. All rights reserved.
  • K. Asakura, A. Satsuma, T. Setoyama
    Catalysis Today 164 164 1月1日  2011年 [査読有り][通常論文]
  • Mariani, C., Tornero-Lopez, A., Alcaraz, J.L., Andringa, S., Aoki, S., Aoyama, Y., Argyriades, J., Asakura, K., Ashie, R., Berghaus, F., Berns, H., Bhang, H., Blondel, A., Borghi, S., Bouchez, J., Burguet-Castell, J., Casper, D., Catala, J., Cavata, C., Cervera, A., Chen, S.M., Cho, K.O., Choi, J.H., Dore, U., Espinal, X., Fechner, M., Fernandez, E., Fujii, Y., Fukuda, Y., Gomez-Cadenas, J., Gran, R., Hara, T., Hasegawa, M., Hasegawa, T., Hayato, Y., Helmer, R.L., Hiraide, K., Hosaka, J., Ichikawa, A.K., Iinuma, M., Ikeda, A., Ishida, T., Ishihara, K., Ishii, T., Ishitsuka, M., Itow, Y., Iwashita, T., Jang, H.I., Jeon, E.J., Jeong, I.S., Joo, K.K., Jover Manas, G., Jung, C.K., Kajita, T., Kameda, J., Kaneyuki, K., Kato, I., Kearns, E., Kim, C.O., Khabibullin, M., Khotjantsev, A., Kielczewska, D., Kim, J.Y., Kim, S.B., Kitching, P., Kobayashi, K., Kobayashi, T., Konaka, A., Koshio, Y., Kropp, W., Kudenko, Yu., Kuno, Y., Kurimoto, Y., Kutter, T., Learned, J., Likhoded, S., Lim, I.T., Loverre, P.F., Ludovici, L., Maesaka, H., Mallet, J., Matsuno, S., Matveev, V., McConnel Mahn, K., McGrew, C., Mikheyev, S., Minamino, A., Mine, S., Mineev, O., Mitsuda, C., Miura, M., Moriguchi, Y., Moriyama, S., Nakadaira, T., Nakahata, M., Nakamura, K., Nakano, I., Nakaya, T., Nakayama, S., Namba, T., Nambu, R., Nawang, S., Nishikawa, K., Nitta, K., Nova, F., Novella, P., Obayashi, Y., Okada, A., Okumura, K., Oser, S.M., Oyama, Y., Pac, M.Y., Pierre, F., Rodriguez, A., Saji, C., Sakuda, M., Sanchez, F., Scholberg, K., Schroeter, R., Sekiguchi, M., Shiozawa, M., Shiraishi, K., Sitjes, G., Smy, M., Sobel, H., Sorel, M., Stone, J., Sulak, L., Suzuki, A., Suzuki, Y., Tada, M., Takahashi, T., Takenaga, Y., Takeuchi, Y., Taki, K., Takubo, Y., Tamura, N., Tanaka, M., Terri, R., T'Jampens, S., Totsuka, Y., Vagins, M., Walter, C.W., Wang, W., Wilkes, R.J., Whitehead, L., Yamada, S., Yamada, Y., Yamamoto, S., Yanagisawa, C., Yershov, N., Yokoyama, H., Yokoyama, M., Yoo, J., Yoshida, M., Zalipska, J.
    Phys.Rev.D 83 83 054023 - 054023 2011年 [査読有り][通常論文]
  • 高草木 達, 長濱 俊介, 宮崎 晃太郎, 角山 寛規, 佃 達哉, 田 旺帝, 野村 昌治, 朝倉 清高
    表面科学学術講演会要旨集 31 0 109 - 109 公益社団法人 日本表面科学会 2011年 [査読無し][通常論文]
     
    金は二酸化チタンなどの酸化物上にナノ粒子として担持することで低温CO酸化反応等に対し高い触媒活性を示し、また活性はサイズに大きく依存する。しかしそのサイズ依存性の起源については未だ不明な点が多い。本研究では、サイズのそろったAuクラスターを化学合成し、TiO2(110)表面に凝集させることなく担持することでモデル触媒の精密作成を行った。
  • EXAFS analysis of the effect of chelating agent on formation of RhTe nanoparticles
    Masafumi Nakaya, Noritoshi Yagihashi, Atsushi Muramatsu, Kiyotaka Asakura
    PF Activity report 2010 28 44  2011年 [査読無し][通常論文]
  • PTRF-XAFS Study of Atomically Dispersed Cu Species on a TiO2(110) Surface Premodified with Functional Organic Molecules
    Satoru Takakusagi, Hirotaka Nojima, Kotaro Miyazaki, Takahiro Wada, Hiroko Ariga, Wang-Jae Chun, Masaharu Nomura, Yasuhiro Iwasawa, Kiyotaka Asakura
    Photon Factory Activity Report 2010 PART B 28 2011年 [査読無し][通常論文]
  • Satoru Takakusagi, Ken-ichi Fukui, Ryugo Tero, Kiyotaka Asakura, Yasuhiro Iwasawa
    LANGMUIR 26 21 16392 - 16396 2010年11月 [査読有り][通常論文]
     
    We studied the methanol adsorption behavior of Pt nanoparticles that were vacuum-deposited on a TiO(2)(110) surface at room temperature by using an ultrahigh vacuum (UHV) scanning tunneling microscope (STM). A large number of bright spots were observed on fivefold-coordinated Ti (Ti(5c)) rows of the TiO(2)(110) surface after exposure of the Pt/TiO(2)(110) to methanol vapor. We assigned the bright spots to methoxy species. These were mobile and were found to hop along the Ti(5c) rows. In situ time-resolved STM observations of the formation and migration of the bright spots on the Pt/TiO(2)(110) were carried out in the presence of methanol. The bright spots were produced at the periphery of the Pt nanoparticles and migrated to the substrate Ti(5c) rows. We discuss the spillover process and behavior of the methoxy species on the Pt/TiO(2)(110).
  • Kiyotaka Asakura
    CATALYSIS TODAY 157 1-4 2 - 7 2010年11月 [査読有り][通常論文]
     
    Developments in surface science have provided atomic-scale surface images and helped us to understand surface reactions at an atomic-scale Two big gaps the pressure gap and material gap were believed to exist between real catalyst systems and surface science targets however they are now being filled Nonlinear optical phenomenon of sum-frequency generation glancing-angle X-ray and scanning probe techniques have been developed as ambient pressure surface analysis methods Great efforts have made it possible to perform X-ray photoelectron spectroscopy measurements in the presence of gas-phase reactants Recent improvements in surface analysis techniques for nonconducting targets enable us to investigate metal clusters on well-defined oxide surfaces to fill the material gap We are now able to initiate and control the surface reactions artificially by adjusting physical parameters Surface science has reached a new stage not only for determining the surface structures electronic properties and reaction mechanisms but also for synthesizing highly active surfaces and controlling catalytic reactions artificially (C) 2010 Elsevier BV All rights reserved
  • Shuhei Hoshika, Futami Nagano, Toru Tanaka, Takatsumi Ikeda, Takahiro Wada, Kiyotaka Asakura, Kenichi Koshiro, Denis Selimovic, Yusei Miyamoto, S K Sidhu, Hidehiko Sano
    Dental Materials Journal 29 6 682 - 689 2010年11月 [査読無し][通常論文]
     
    The purpose of this study was to investigate the effect of application time of colloidal platinum nanoparticles (CPN) on bond strength. Dentin surfaces were subjected to one of the following treatments: (A) Etching with 10% citric acid-3% FeCl(3 )solution (10-3 solution); (B) Etching with 10-3 solution followed by applying CPN as a primer solution for 10, 20, 30, or 60 seconds; and (C) Priming with CPN for 10, 20, 30, or 60 seconds followed by etching with 10-3 solution. An acrylic rod was bonded to each treated dentin surface using 4-META/MMA-TBB resin. Bonded specimens were sectioned into beams for microtensile bond strength testing. In groups (B) and (C), highest bond strength was obtained when dentin surfaces were treated with CPN for 30 seconds. This meant that the CPN primer solution either enhanced the penetration of resin into dentin or the degree of conversion of 4-META/MMA-TBB resin. Within the limitations of this study, treatment with 0.1 mN CPN primer solution followed by 20 seconds of water rinsing resulted in high bond strength.
  • Motohiro Uo, Kiyotaka Asakura, Kana Watanabe, Fumio Watari
    CHEMISTRY LETTERS 39 8 852 - 853 2010年08月 [査読有り][通常論文]
     
    The bronchoalveolar lavage fluid (BALF) from a patient with pneumoconiosis induced by cemented tungsten carbide (WC) was analyzed by micro-X-ray absorption fine structure (XAFS) analysis. The BALF precipitate was dried and subjected to fluorescence XAFS using polycapillary focused X-rays. The W L-1-edge XANES spectrum of the BALF precipitate could be identified as that of WC. Thus, a low concentration of WC could be detected from BALF using micro-XAFS without excess biopsy.
  • Donghui Guo, Yuta Nakagawa, Hiroko Ariga, Shushi Suzuki, Kumiko Kinoshita, Takeshi Miyamoto, Satoru Takakusagi, Kiyotaka Asakura, Shigeki Otani, S. Ted Oyama
    SURFACE SCIENCE 604 17-18 1347 - 1352 2010年08月 [査読有り][通常論文]
     
    The surface structure of Ni2P (10 (1) over bar0), a model for highly active hydrodesulfurization catalysts, was studied using scanning tunneling microscopy (STM) and low energy electron diffraction (LEED) in order to understand the reconstruction of the surface layers. Annealing at 573 K revealed a (1 x 1) LEED pattern which changed to a c(2 x 4) arrangement by further heating to 723 K. Atomic scale STM images were obtained for both the (1 x 1) and c(2 x 4) structures. Bright spots observed in the STM images were interpreted to be due to surface phosphorus atoms and this was supported by a density functional theory (INT) simulation. Several possible models for the c(2 x 4) reconstructed structures were proposed including a P-dimer defect model, a missing-row model and a missing-row + added-row model. The last model gave the best explanation for the c(2 x 4) structure. The mechanism for the c(2 x 4) reconstruction on the Ni2P (10 (1) over bar0) surface is discussed. (C) 2010 Elsevier B.V. All rights reserved.
  • Ted S. Oyama, Haiyan Zhao, Hans-Joachim Freund, Kiyotaka Asakura, Radoslaw Wlodarczyk, Marek Sierka
    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 240 240 2010年08月 [査読有り][通常論文]
  • Ted Shigeo Oyama, Yong-Kul Lee, Kiyotaka Asakura, Kyoko K. Bando, Yuji Yoshimura
    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 240 240 2010年08月 [査読有り][通常論文]
  • K. Edamoto, H. Inomata, K. Ozawa, Y. Nakagawa, K. Asakura, S. Otani
    SOLID STATE COMMUNICATIONS 150 25-26 1120 - 1123 2010年07月 [査読有り][通常論文]
     
    The electronic structure of Ni2P(10 (1) over bar0) has been investigated by photoemission spectroscopy (PES) utilizing synchrotron radiation. The surface prepared by Ar+ ion sputtering (3 kV, 15 min) and annealing (400 degrees C) gave a c(4 x 2) low-energy electron diffraction pattern. In the PES spectra measured for this surface, a Ni 3d-P 3p hybrid band (main band) and a satellite were observed at 0-4 eV and at 8 eV, respectively. Resonant PES study showed that the satellite is associated with the photoemission process leading to a two-hole bound state. The angle-resolved PES measurements showed that there were at least two surface states; one was observed at about 04 eV around the (Gamma) over bar point and the other was observed at about 0.6 eV along the boundary of the surface Brillouin zone along the [0001] direction. (C) 2010 Elsevier Ltd. All rights reserved.
  • Takeshi Miyamoto, Hironobu Niimi, Yoshinori Kitajima, Toshio Naito, Kiyotaka Asakura
    JOURNAL OF PHYSICAL CHEMISTRY A 114 12 4093 - 4098 2010年04月 [査読有り][通常論文]
     
    A peak appearing at the L-2,L-3 X-ray absorption edge often provides the number of empty d states of the X-ray absorbing atoms. Ag+ compounds have a d(10) state (no d empty states) but Show a small peak at the edge. In this research, we systematically studied the edge peak of Ag+ compounds to Understand its origin oil the basis of the molecular Orbital picture and to obtain a relation of the edge peak intensity to chemical and physical quantities. The edge peak call be formally assigned to the transition from 2p to 5s enhanced by the s-d hybridization. The peak intensity has a negative correlation with I coordination charge but has a positive correlation with the strength of the covalent bond, which is in the reverse order to the other d(n) (n < 10) elements.
  • 朝倉 清高
    真空 53 1 19 - 24 日本真空協会 2010年01月20日 [査読無し][通常論文]
     
    The catalyst is a key technology for the realization of the sustainable society. The mechanism of heterogeneous catalyst is now being established based on the surface science approach which is supported by the ultrahigh vacuum techniques. Recently ambient pressure techniques are developing. The surface reaction can be now understood based on the machinery concepts of molcules and atoms. Spatiotemporal behavior of the surface atoms and molecules are revealed and what force works between the reactants. In the near future, the surface reaction can be controlled by physical means.
  • Kiyotaka Asakura, Hironobu Niimi, Makoto Kato
    ADVANCES IN IMAGING AND ELECTRON PHYSICS, VOL 162 162 162 1 - 43 2010年 [査読有り][通常論文]
  • Uo M, Asakura K, Watanabe E, Lin HY, Yanagi T, Shimizu H, Watari F
    Nano Biomedicine 2 2 103 - 106 ナノ・バイオメディカル学会 2010年 [査読有り][通常論文]
     
    The elements in discolored nails were assessed by X-ray fluorescence analysis (XRF), and the chemical state of Zn in the nail samples was assessed by X-ray absorption fine structure (XAFS) analysis. Compared to the normal nail, a part of the yellow nail contained a considerably high amount of Ca, whereas the black nail contained higher amounts of Ca and Zn. The chemical state of Zn in the yellow nail was similar to that in the normal nail. The Zn in the black nail was in a slightly different chemical state, suggesting the existence of different chemical species of Zn in the black nail.
  • S. Ted Oyama, Travis Gott, Kiyotaka Asakura, Satoru Takakusagi, Kotaro Miyazaki, Yuichiro Koike, Kyoko K. Bando
    JOURNAL OF CATALYSIS 268 2 209 - 222 2009年12月 [査読有り][通常論文]
     
    The hydrodesulfurization (HDS) of thiophene was studied over Ni2P/MCM-41 by in situ Fourier transform infrared (FTIR) spectroscopy and X-ray absorption near-edge structure (XANES) measurements at atmospheric pressure and 393-723 K (120-450 degrees C). FTIR showed the presence of adsorbed molecular thiophene principally on the MCM-41 support. In the presence of hydrogen new bands in the aliphatic CH stretching region (2953, 2918, and 2876 cm(-1)) and the CH2 scissoring region (1464 cm(-1)) appeared and grew with temperature up to 553 K (280 degrees C). These were assigned to a tetrahydrothiophene surface intermediate, whose presence is consistent with the high hydrogenation activity of nickel phosphide. XANES measurements between 353 and 573 K (180-300 degrees C) also showed growth of a signal (8330.9 eV) attributed to Ni-S interactions of either the adsorbed tetrahydrothiophene or a surface phosphosulfide. Transient XANES measurements showed that the sulfur species responded dynamically at the same rate as the steady-state rate, indicating that it was associated with an intermediate in the reaction. (c) 2009 Elsevier Inc. All rights reserved.
  • Takeshi Miyamoto, Yoshinori Kitajima, Hideyuki Sugawara, Toshio Naito, Tamotsu Inabe, Kiyotaka Asakura
    JOURNAL OF PHYSICAL CHEMISTRY C 113 47 20476 - 20480 2009年11月 [査読有り][通常論文]
     
    The Ag(DMe-DCNQI)(2) (DMe-DCNQI = 2,5-dimethyl-N,N'-dicyanoquinonediimine, or DM) charge-transfer salt is a promising material for production by photolithography as it displays a unique photoinduced change in conduction. Photoproducts (beta 1 and gamma) of Ag(DM)(2) were investigated using the X-ray absorption fine structure (XAFS) technique in order to understand the origin of their conduction properties. In contrast to the metallic conduction exhibited by a pristine sample (alpha), beta 1 is a semiconductor, whereas gamma is an insulator, even though the original Ag(DM)(2) composition is maintained in both the beta 1 and the gamma forms. A redox mechanism has been postulated to explain the photoinduced change in conduction. However, measurement of the Ag L-3-edge XANES (X-ray absorption near-edge structure) did not provide any evidence of electron transfer from the DM radical anion to the Ag cation in the beta 1 and gamma products. Ag K-edge extended X-ray absorption fine structure (EXAFS) data demonstrated that beta 1 is a mixture of the original pristine alpha phase and a newly found alpha' phase, which has a shorter bond distance between the Ag cations and the N atoms of DM molecules. The conduction electrons remain in the DM column of alpha and alpha', but the domain boundaries between alpha and alpha' present an activation barrier for the conduction electrons to cross these boundaries, which provides a rationale for the semiconductive behavior of beta 1. The Ag K-edge EXAFS results showed that the gamma photoproduct has a different local structure from alpha, with a shorter distance and smaller coordination number of the Ag-N bond. The DM radical anions in the gamma compound form covalent bonds between themselves, resulting in a loss of the columnar structure. The complex local structure around Ag cations explains the insulating behavior of the gamma compound.
  • Yun-Chieh Yeh, Hao Ming Chen, Ru-Shi Liu, Kiyotaka Asakura, Man-Yin Lo, Yu-Min Peng, Ting-Shan Chan, Jyh-Fu Lee
    CHEMISTRY OF MATERIALS 21 17 4030 - 4036 2009年09月 [査読有り][通常論文]
     
    Carbon-supported PdCFe/C catalyst was synthesized by impregnation method. X-ray absorption spectroscopy (XAS) revealed the incorporation of C atoms in PdFe/C clusters and high-temperature annealing was facilitated the formation of the Pd-Fe-C alloy. The catalytic activity oxygen operated via reduction reaction (ORR) of Pd-Fe-C alloy demonstrated the strong dependence upon composition of Pd-Fe-C catalysis, the half-wave potential raise with the increase of iron content. A cyclic voltammetry (CV) test conducted in methanol/perchloric acid mixed solution was employed to elucidate the tolerance of PdCFe/C electrocatalysts for methanol, which exhibited the methanol-proof character of PdCFe/C electrocatalysts.
  • S. Ted Oyama, Travis Gott, K. Asakura, Kyoko K. Bando
    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 238 238 2009年08月 [査読有り][通常論文]
  • Wang-Jae Chun, Yuichiro Koike, Hidenori Ashima, Kumiko Kinoshita, Kaoru Ijima, Keisuke Fujikawa, Shushi Suzuki, Masaharu Nomura, Yasuhiro Iwasawa, Kiyotaka Asakura
    CHEMICAL PHYSICS LETTERS 470 1-3 99 - 102 2009年02月 [査読有り][通常論文]
     
    Preparing highly dispersed monoatomic Cu species on a TiO2(110) surface was successfully achieved on a TiO2(110) surface that had been precovered with an acetic anhydride layer. Polarization-dependent total reflection fluorescence X-ray absorption. ne structure (PTRF-XAFS) spectra indicated that the three-dimensional structures of the monoatomic Cu species were stabilized on the surface by two 0.196-nm-long C-O bonds, namely, Cu-O (acetate) and Cu-O (bridging surface oxygen) bonds. The Cu species diffusion was effectively blocked by the acetate species with its molecular plane perpendicular to the [001] diffusion direction created by the dissociative adsorption of acetic anhydride. (C) 2009 Elsevier B.V. All rights reserved.
  • Kumiko Kinoshita, Shushi Suzuki, Wang-Jae Chun, Satoru Takakusagi, Kiyotaka Asakura
    SURFACE SCIENCE 603 3 552 - 557 2009年02月 [査読有り][通常論文]
     
    The carboxylic acids are stably adsorbed on TiO2(110) surfaces at room temperature. To demonstrate the neutralization mechanism proposed by Ashima et al. [H. Ashima, W.-J. Chun, K. Asakura, Surf Sci. 601 (2007) 1822.] that explains the stable adsorption of carboxylic acids, we studied the full-coverage adsorption structure of acetic anhydride on a TiO2(110) surface by STM (scanning tunneling microscopy). We directly observed three postulated species on the TiO2(110) surface; normal acetates (termed acetate A) forming a (2 x 1) ordered structure, a minor acetate species (termed acetate B) which was present between the bridging oxygen and the 5-fold Ti, and the oxygen vacancies. We determined the ratio of these three species. This ratio was in good agreement with the postulated conversion reaction of acetate B to A. (C) 2009 Elsevier B.V. All rights reserved.
  • Shushi Suzuki, Golam Md Moula, Tsuyoshi Miyamoto, Yuta Nakagawa, Kumiko Kinosthita, Kiyotaka Asakura, S. Ted Oyama, Shigeki Otani
    JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 9 1 195 - 201 2009年01月 [査読有り][通常論文]
     
    The surface structures of nickel phosphide (Ni2P) single crystals were studied by scanning tunneling microscopy (STM) and photoemission electron microscopy (PEEM). Atomically resolved 1 x 1 images of the Ni2P(0001) and (1010) surfaces are successfully obtained with STM, whose respective dimensions of (0.59 nm x 0.59 nm) and (0.34 nm x 0.59 nm) match the unit cell lengths. The Ni2P(0001) surface has two possible terminations in which the Ni:P ratios are 3:1 (Ni3P termination) or 3:2 (Ni3P2 termination). In the Ni3P terminated surface the Ni atoms have a square pyramidal structure, and in the Ni3P2 terminated surface the Ni atoms have a tetrahedral structure. Only the P is visible in the STM for Ni2P(0001) and this is explained as being due to the greater extension of the phosphorus p orbitals than the Ni d orbitals at the surface. The surface domain sizes of the Ni3P and Ni3P2 termination structures of Ni2P(0001) are determined to be 500 mu m by means of PEEM using a Hg-Xe lamp through a low-pass UV-filter. Evidence is found for dissociative adsorbed hydrogen on the Ni3P termination surface of Ni2P(0001), but not on the Ni3P2 surface, indicating that the square pyramidal sites on the Ni3P surface have high reactivity
  • 高草木 達, 宮崎 晃太郎, 和田 敬浩, 野島 大孝, 角山 寛規, 佃 達哉, 田 旺帝, 野村 昌治, 朝倉 清高
    表面科学学術講演会要旨集 29 0 231 - 231 公益社団法人 日本表面科学会 2009年 [査読有り][通常論文]
     
    金は二酸化チタンなどの酸化物上にナノ粒子として担持することで低温CO酸化反応等に対して高い触媒活性を示し、また活性はサイズに大きく依存する。しかしそのサイズ依存性の起源については未だ不明な点が多い。本研究では、サイズのそろったAu11クラスターを化学合成し、Auと相互作用に強いチオール基を持つ有機分子であらかじめ修飾したTiO2(110)表面に固定化することで、モデル触媒の精密作成を試みた。
  • Go Hamasaka, Soichiro Kawamorita, Atsuko Ochida, Ryuto Akiyama, Kenji Hara, Atsushi Fukuoka, Kiyotaka Asakura, Wang Jae Chun, Hirohisa Ohmiya, Masaya Sawamura
    ORGANOMETALLICS 27 24 6495 - 6506 2008年12月 [査読有り][通常論文]
     
    Solid-supported phosphine ligands silica-SMAPs {[silica gel 60N]-SMAP (1a) or [CARiACT Q-10]-SMAP (1b)}, which are composed of a caged, compact trialkylphosphine (SMAP) as a ligand and silica gel (silica get 60N or CARiACT Q-10) as a support,'were synthesized through surface functionalization. The supported phosphines (1a,b) were structurally characterized by solid-state (13)C, (29)Si, and (31)P cross-polarization/magic angle spinning (CP/MAS) NMR spectroscopies and N(2) adsorption measurements. Complexation of 1a,b with [RhCl(cod)](2) afforded a mono(phosphine)-rhodium complex Silica-SMAP-RhCl(cod) exclusively, even in the presence of excess ligands, as proved by solid-state (13)C and (31)P CP/MAS NMR spectroscopies and Rh K-edged X-ray'absorption fine structure (XAFS) measurements. Heterogeneous catalysts that were prepared from [RhCl(C(2)H(4))(2)](2) and 1a,b showed exceptionally high catalytic activities for the reaction of sterically hindered ketones (including di-tertbutyl ketone) and triorganosi lanes such as Et(3)SiH and (t-Bu)Me(2)SiH. The catalyst from 1b showed no leaching of rhodium after reaction and was reusable without decrease of the activity.
  • Yusuke Ominami, Makoto Suzuki, Kiyotaka Asakura, Cary Y. Yang
    NANOTECHNOLOGY 19 40 2008年10月 [査読有り][通常論文]
     
    We studied the growth mode of vertically aligned carbon nanofibers (CNFs) on Ni catalyst strips fabricated using a focused ion beam (FIB). We found that the CNF growth on Ni catalysts was strongly affected by the geometry of the microfabricated Ni catalyst strips. Selective growth of vertically aligned CNFs requires ion milling from the outside edge of the sample so that the milled materials are effectively evacuated. The CNF diameter and density on the strip depends on its width. Possible mechanisms to control CNF growth using microfabricated catalysts are analyzed with a liquid model using surface free energies.
  • Motohiro Uo, Kiyotaka Asakura, Kazuchika Tamura, Yasunori Totsuka, Shigeaki Abe, Tsukasa Akasaka, Fumio Watari
    CHEMISTRY LETTERS 37 9 958 - 959 2008年09月 [査読有り][通常論文]
     
    Ti, a Ni-Ti alloy, and stainless steel (SUS304) were implanted in rat soft tissues for 6 months. The chemical states of the component elements contained in the tissues surrounding those metallic implants were analyzed by fluorescence X-ray absorption line structure (XAFS). Titanium oxide and a nickel aquo complex, which Would be Caused by the erosion of Ti and Ni, were detected in the Surrounding tissues. The concentrations of Ti and Ni in the tissues were 1-3 and 300 ppm, respectively. Thus, the dissolved conditions and concentrations of those practical metallic materials in vivo were successfully confirmed.
  • Md Golam Moula, Shinsuke Sato, Katsumi Irokawa, Hironobu Niimi, Shushi Suzuki, Kiyotaka Asakura, Haruo Kuroda
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 81 7 836 - 842 2008年07月 [査読有り][通常論文]
     
    We observed the IR-induced reaction of C2H5OH on MoO3, using a pulsed and tunable infrared free electron laser (IR-FEL). The IR-FEL-induced reaction showed wavelength dependency and requires light stronger than a certain threshold level. The C2H5OH was converted mainly to C2H4 only when the MoO3 was irradiated with focused IR-FEL at 967 and 814cm(-1) corresponding to Mo=O stretching modes. whereas IR light at 1200cm(-1) induced no reaction. The origin of this IR-FEL-induced reaction is discussed.
  • Kumiko Kinoshita, Georg Hermann Simon, Thomas Koenig, Markus Heyde, Hans-Joachim Freund, Yuta Nakagawa, Shushi Suzuki, Wan-Jae Chun, Shiaeo Ted Oyama, Shigeki Otani, Kiyotaka Asakura
    JAPANESE JOURNAL OF APPLIED PHYSICS 47 7 6088 - 6091 2008年07月 [査読有り][通常論文]
     
    A Ni2P(0001) single crystal surface has been studied in the framework of model catalysis with a low temperature scanning tunneling microscope (STM) under ultrahigh vacuum (UHV). We observed a previously unreported (root 3 x root 3) R30 degrees reconstruction and Successfully recorded its atomically-resolved STM images. Two types of atomic arrangements have been found for this (root 3 x root 3) R30 degrees structure depending oil annealing conditions during preparation. One shows a filled and the other one an empty network of polygons. Upon annealing to 940 K, only the latter empty type of structure has been observed.
  • Yuichiro Koike, Keisuke Fujikawa, Shushi Suzuki, Wang-Jae Chun, Kaoru Ijima, Masaharu Nomura, Yasuhiro Iwasawa, Kiyotaka Asakura
    JOURNAL OF PHYSICAL CHEMISTRY C 112 12 4667 - 4675 2008年03月 [査読有り][通常論文]
     
    Three-dimensional structures of Ni clusters deposited on a TiO2(110) surface were studied using polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) analysis. Three-dimensional Ni clusters were formed with a slightly anisotropic structure at 1 x 10(14) atoms/cm(2). The PTRF-XAFS results for a 1 x 10(14) atoms/cm(2) sample revealed the formation of one- atomic -layer Ni clusters with a distorted (110)(fcc) plane structure. We found a Ni-Ni distance of 0.240 nm with Ni-O interaction at 0.23 nm. The structure was stabilized by interaction of surface oxygen atoms. The origin of cluster size self-regulation was the strong Ni-O interaction and matching of the crystal lattice between TiO2(110) and distorted Ni(110) structures.
  • Tinku Baidya, K. R. Priolkar, P. R. Sarode, M. S. Hegde, K. Asakura, G. Tateno, Y. Koike
    JOURNAL OF CHEMICAL PHYSICS 128 12 2008年03月 [査読有り][通常論文]
     
    Ce1-x-yTixPtyO2-delta(x=0.15; y=0.01) and Ce(1-x-y)Ti(x)PdyO(2-delta)(x= 0.25; y=0.02 and 0.05) are found to be good CO oxidation catalysts [T. Baidya et al., J. Phys. Chem. B 110, 5262 (2006); T. Baidya et al., J. Phys. Chem. C 111, 830 (2007). A detailed structural study of these compounds has been carried out by extended x-ray absorption fine structure along with x-ray diffraction and x- ray photoelectron spectroscopy. The gross cubic fluorite structure of CeO2 is retained in the mixed oxides. Oxide ion sublattice around Ti as well as Pt and Pd ions is destabilized in the solid solution. Instead of ideal eight coordinations, Ti, Pd, and Pt ions have 4+3, 4+3, and 3+4 coordinations creating long and short bonds. The long Ti-O, Pd-O, and Pt-O bonds are similar to 2.47 angstrom (2.63 angstrom for Pt-O) which are much higher than average Ce-O bonds of 2.34 angstrom. (C) 2008 American Institute of Physics.
  • Fumio Watari, Kazuchika Tamura, Atsruro Yokoyama, Kenichiro Shibata, Tsukasa Akasaka, Bunshi Fugetsu, Kiyotaka Asakura, Motohiro Uo, Yasunori Totsuka, Yoshinori Sato, Kazuyuki Tohji
    Biological Aspects and Structure Formation 127 - 144 2008年03月 [査読有り][通常論文]
     
    ISBN: 9783527619443
  • Toshihide Kawai, Wang-Jae Chun, Kiyotaka Asakura, Yuichiro Koike, Masaharu Nomura, Kyoko K. Bando, S. Ted Oyama, Hitoshi Sumiya
    REVIEW OF SCIENTIFIC INSTRUMENTS 79 1 014101  2008年01月 [査読有り][通常論文]
     
    The design and performance of a new high-pressure and high-temperature cell for measurement of x-ray absorption fine structure (XAFS) spectra of solid catalysts working in a flowing liquid are presented. The cell has flat, high-purity sintered cubic boron nitride (c-BN) windows which can tolerate high temperature (900 K) and high pressure (10 MPa). The c-BN is a new material which has the highest tensile strength, second only to diamond, and is also chemically and thermally stable. The use of the cell is demonstrated for measurements of PtPd/Al2O3 and Ni2P/SiO2 hydrodesulfurization catalysts at reaction conditions. A technique called delta chi (Delta chi), involving determining the difference between XAFS spectra of the sample at reaction conditions and the bare sample, is introduced. (c) 2008 American Institute of Physics.
  • Hao Ming Chen, Ru-Shi Liu, Kiyotaka Asakura, Ling-Yun Jang, Jyh-Fu Lee
    JOURNAL OF PHYSICAL CHEMISTRY C 111 50 18550 - 18557 2007年12月 [査読有り][通常論文]
     
    By utilizing the X-ray absorption approach, the gold ions evolving from the Au-Cl complex to Au rods have been elucidated. The theoretical simulation of X-ray absorption spectra further revealed the evolution of gold and concluded that ultrafine small clusters of gold (Au(13)) formed after a reducing agent was added to the growth solution. A redesigned seed-assisted growth method, a serial addition of growth solution, was employed to achieve the goal of the consecutive support of gold. The development approach was found to successfully fabricate ID gold nanorods/wires with a tunable size from 50 nm to 1.7 mu m.
  • Ryo Niishiro, Ryoko Konta, Hideki Kato, Wang-Jae Chun, Kiyotaka Asakura, Akihiko Kudo
    JOURNAL OF PHYSICAL CHEMISTRY C 111 46 17420 - 17426 2007年11月 [査読有り][通常論文]
     
    The effects upon the photophysical and photocatalytic properties of the codoping of rhodium and antimony in rutile-type TiO2 were investigated. TiO2 codoped with rhodium and antimony (TiO2:Rh/Sb) had an absorption band in the visible light region. Its energy gap was 2.1 eV. The TiO2:Rh/Sb powder showed photocatalytic activity for the oxidation of water to form O-2 in the presence of Ag+ ions as an electron acceptor under visible light irradiation (lambda > 440 nm), whereas TiO2 doped with only rhodium showed no activity. The photocatalytic activity strongly depended on the amount and ratio of the Sb/Rh dopant. Electron spin resonance, diffuse reflection spectroscopy, and X-ray absorption near-edge structure analyses revealed that the doped rhodium exists in a trivalent oxidation state in the active photocatalyst. The photocatalytic activity was decreased remarkably even by a small amount of Rh4+ ions. Antimony played an important role in suppressing the formation of Rh4+ ions by charge compensation. Thus, it has been clarified that Rh3+ is the species responsible for the photocatalytic activity under visible light irradiation in the TiO2:Rh/Sb photocatalyst.
  • Tetsuya Tsutsumi, Takeshi Miyamoto, Hironobu Niimi, Yoshinori Kitajima, Yuji Sakai, Makoto Kato, Toshio Naito, Klyotaka Asakura
    SOLID-STATE ELECTRONICS 51 10 1360 - 1366 2007年10月 [査読有り][通常論文]
     
    Energy-filtered X-ray photoemission electron microscopy (EXPEEM) is a new surface chemical imaging method that combines X-ray photoelectron spectroscopy (XPS) and photoemission electron microscopy (PEEM). We have developed a collinear type EXPEEM system using a Wien-filter-type electron energy analyzer. The collinear arrangement has the advantage of carrying out an easy alignment of the electron optical axis. We have measured EXPEEM images, mu-X-ray absorption near edge structure (mu-XANES) and mu-XPS of Au on Ta and Ag(DM)(2). We discuss the advantage of EXPEEM and future applications to organic devices. (C) 2007 Elsevier Ltd. All rights reserved.
  • H. Niimi, M. Kato, T. Kawasaki, T. Miyamoto, S. Suzuki, W. J. Chun, M. Kudo, N. Kawahara, M. Doi, K. Tsukamoto, K. Asakura
    SURFACE SCIENCE 601 20 4742 - 4747 2007年10月 [査読有り][通常論文]
     
    We have developed an in-lab energy-filtered X-ray photoemission electron microscopy (EXPEEM) combining a high-brilliance X-ray source and a new Wien filter-type energy analyzer, which can accept photoelectrons in a wide angle. To obtain high energy resolution, we enlarged the inner diameter of the filter and reduced aberrations of an analyzer using multipole electrodes and air-core coils. We obtained an energy-filtered image of photoelectrons. (c) 2007 Elsevier B.V. All rights reserved.
  • Takeshi Miyamoto, Hironobu Niimi, Wang-Jae Chun, Yoshinori Kitajima, Hideyuki Sugawara, Tamotsu Inabe, Toshio Naito, Kiyotaka Asakura
    CHEMISTRY LETTERS 36 8 1008 - 1009 2007年08月 [査読有り][通常論文]
     
    UV-vis light converts A-(DM)(2) (DM = 2,5-dimethyl-N,N'-dicyanoquionediimine; DMe-DCNQI) to several solids with metallic, semiconducting, or insulating conductivities depending on the irradiation conditions. Ag valence state in each photochemical product was determined by Ag L-3-edge XANES. The XANES result requires the correction of the redox mechanism to explain the photoinduced conductivity change of Ag(DM)(2) photoproducts.
  • Toshio Naito, Hideyuki Sugawara, Tamotsu Inabe, Yoshinori Kitajima, Takeshi Miyamoto, Hironobu Niimi, Kiyotaka Asakura
    ADVANCED FUNCTIONAL MATERIALS 17 10 1663 - 1670 2007年07月 [査読有り][通常論文]
     
    A charge-transfer complex of 2,5-dimethyl-N,N'-dicyanoquinonediimine (DM) with silver (crystalline Ag(DM)(2), defined as a) is irreversibly transformed by UV-vis illumination. Depending on the illumination conditions, three new types of solids (defined as gamma, delta, and epsilon) with different structural and physical properties are obtained and examined by a variety of analytical techniques, including solid-state, high-resolution, cross-polarization magic angle spinning (CP-MAS) (CNMR)-C-13, elemental analysis (EA), mass spectrometry (MS), X-ray absorption fine structure (XAFS), and powder X-ray diffraction (XRD). The CP-MAS, EA, MS, and XAFS results indicate that compound gamma is a glass state of Ag(DM)(2). The transformation from crystalline (a) to amorphous (gamma) solid Ag(DM)(2) is an irreversible exothermic glass transition (glass-transition temperature 155.2 degrees C; Delta H=-1.26.8 kJ mol(-1)), which implies that the glass form is thermodynamically more stable than the crystalline form. Compound delta (Ag(DM)(1.5)) consists of silver nanoparticles (diameter (7 +/- 2) nm) dispersed in a glassy matrix of neutral DM molecules, The =N-CN-Ag coordination bonds of the a form are not maintained in the delta form. Decomposition of a by intense illumination results in a white solid (epsilon), identified as being composed of silver nanoparticles (diameter (60 +/- 10) nm). Physical and spectroscopic (XAFS) measurements, together with XRD analysis, indicate that the silver nanoparticles in both delta and epsilon are crystalline with lattice parameters similar to bulk silver; however, the magnetic susceptibilities differ from bulk silver.
  • Hironobu Niimi, Wang-Jae Chun, Shushi Suzuki, Kiyotaka Asakura, Makoto Kato
    REVIEW OF SCIENTIFIC INSTRUMENTS 78 6 063710  2007年06月 [査読有り][通常論文]
     
    The aberration of a multipole Wien filter for energy-filtered x-ray photoemission electron microscopy was analyzed and the optimized Fourier components of the electric and magnetic fields for the third-order aperture aberration corrections were obtained. It was found that the third-order aperture aberration correction requires 12 electrodes and magnetic poles. (c) 2007 American Institute of Physics.
  • Hidenori Ashima, Wang-Jae Chun, Kiyotaka Asakura
    SURFACE SCIENCE 601 8 1822 - 1830 2007年04月 [査読有り][通常論文]
     
    We have studied the adsorption structure of acetic anhydride on a TiO2 (1 1 0) surface using XPS (X-ray photoelectron spectroscopy), LEED (low energy electron diffraction) and HREELS (high resolution electron energy loss spectroscopy) to determine the origins of the unique adsorption properties of carboxylic acids on a TiO2(1 1 0) surface. The C 1s XPS data indicated that the saturation carbon amount of adsorbed acetic anhydride was 12 +/- 3% larger than that of the adsorbed acetic acid. LEED showed p(2 x 1) weak spots for the acetic anhydride adsorbed surface. The HREELS spectra revealed the dissociative adsorption of acetic anhydride. Based on these findings, we concluded that the neutralization of the bridging oxygen atoms associated with the dissociative adsorption is necessary for the stable adsorption of carboxylates on the 5-fold Ti sites. (c) 2007 Elsevier B.V. All rights reserved.
  • Motohiro Uo, Kiyotaka Asakura, Atsuro Yokoyama, Makoto Ishikawa, Kazuchika Tamura, Yasunori Totsuka, Tsukasa Akasaka, Fumio Watari
    DENTAL MATERIALS JOURNAL 26 2 268 - 273 2007年03月 [査読有り][通常論文]
     
    Tissues contacting Ti dental implants were subjected to X-ray absorption fine structure (XAFS) analysis to examine the chemical state of Ti transferred from the placed implant into the surrounding tissue. Nine tissues that contacted pure Ti cover screws for several months were excised in a second surgery whereby healing abutments were set. Six tissues that surrounded implants retrieved due to their failure were also excised. Ti distributions in the excised specimens were confirmed by X-ray scanning analytical microscopy (XSAM), and the specimens were subjected to fluorescence XAFS analysis to determine the chemical states of the low concentrations of Ti in the tissues surrounding Ti dental implants. Ti mostly existed in the metallic state and was considered to be debris derived from the abrasion of implant pieces during implant surgery. Oxidized forms of Ti, such as anatase and rutile, were also detected in a few specimens-and existed in either a pure state or mixed state with metallic Ti. It was concluded that the existence of Ti in the tissue did not cause implant failure. Moreover, the usefulness of XAFS for analysis of the chemical states of rarely contained elements in biological tissue was demonstrated.
  • Wang-Jae Chun, Yuichiro Koike, Kaoru Ijima, Keisuke Fujikawa, Hidenori Ashima, Masaharu Nomura, Yasuhiro Iwasawa, Kiyotaka Asakura
    CHEMICAL PHYSICS LETTERS 433 4-6 345 - 349 2007年01月 [査読有り][通常論文]
     
    Highly dispersed monoatomic Cu species on a TiO2 (110) surface were successfully prepared by a new method in which the TiO2 (110) surface was premodified with a 3-thiophenecarboxylic layer. Polarization-dependent total reflection fluorescence-X-ray absorption fine structure (PTRF-XAFS) showed the three dimensional structure of the monoatomic Cu species which were stabilized on the surface through the formation of Cu-S (adsorbate) and Cu-O (bridging oxygen) bonds. (c) 2006 Elsevier B.V. All rights reserved.
  • Hao Ming Chen, Ru-Shi Liu, Kiyotaka Asakura, Jyh-Fu Lee, Ling-Yun Jang, Shu-Fen Hu
    JOURNAL OF PHYSICAL CHEMISTRY B 110 39 19162 - 19167 2006年10月 [査読有り][通常論文]
     
    This investigation describes the formation of a metal nanorattle with a pure metal shell by varying experimental parameters. The galvanic replacement reaction between silver and chloroauric acid was adopted to prepare hollow metal nanoparticles. This approach is extended to produce nanorattles of Au cores and Au shells by starting with AucoreAgshell nanoparticles as templates. The effect of temperature on the nanostructure of the final product is also considered. The composition of the shell in nanorattles can be controlled by varying the reaction temperature (to form pure gold or gold-silver alloy, for example). X-ray absorption fine structure spectroscopy is conducted to elucidate the fine structure of these nanoparticles. Partial alloying between the Au core and the Ag shell is observed by extended X-ray absorption fine structure (EXAFS).
  • S. Suzuki, Y. Koike, K. Fujikawa, N. Matsudaira, M. Nakamura, W. -J. Chun, M. Nomura, K. Asakura
    CATALYSIS TODAY 117 1-3 80 - 83 2006年09月 [査読有り][通常論文]
     
    We have measured the NC-AFM frequency shift dependence on the X-ray energy around the AuL(3) absorption edge energy. We found a peak in the frequency shift just above the An region at the AuL(3) absorption edge energy while we could not detect any peak in the frequency shift when the NC-AFM tip was placed above the Si regions. This novel phenomenon indicated that the combination of energy-variable X-rays and NC-AFM provides us a new way to nano level chemical mapping at surface. We briefly discussed some possible mechanisms. (C) 2006 Elsevier B.V. All rights reserved.
  • Toshio Naito, Hideyuki Sugawara, Tamotsu Inabe, Takeshi Miyamoto, Hironobu Niimi, Kiyotaka Asakura
    JOURNAL OF NON-CRYSTALLINE SOLIDS 352 23-25 2628 - 2630 2006年07月 [査読有り][通常論文]
     
    We present a novel way to fabricate electronic devices from a molecular charge transfer salt Ag(DM)(2) by simple illumination, which realizes a junction-structure in the single molecular crystal. The electrical conductivity of the selected parts of samples can be controlled by illimination time and power. The electrical behavior gradually turned semiconducting from metallic one by illumination. X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray absorption fine structure indicated that illumination should transfer some electrons from the conducting DM columns to the Ag ions. The X-ray powder diffraction pattern indicated that original crystal lattice was maintained after the illumination. These observations imply that the illumination practically effected doping (or rather dedoping) on the material. (c) 2006 Elsevier B.V. All rights reserved.
  • T. Kawai, K. K. Bando, Y-K. Lee, S. T. Oyama, W-J Chun, K. Asakura
    JOURNAL OF CATALYSIS 241 1 20 - 24 2006年07月 [査読有り][通常論文]
     
    Strict environmental regulations and declining quality of petroleum feedstocks have made sulfur removal one of the most important current problems in refining. A novel, high-activity Ni2P/SiO2 catalyst with exceptional activity in deep hydrodesulfurization (HDS) was studied by in situ extended X-ray absorption fine structure (EXAFS). The measurements were conducted at realistic conditions of high pressure (3 MPa) and high temperature (613 K) and were made possible by the use of a low-volume cell with cubic boron nitride windows. The spectra thus obtained reveal that the bulk Ni2P structure is stable at reaction conditions, but that the active surface has Ni-S bonds. (c) 2006 Elsevier Inc. All rights reserved.
  • K Fujikawa, S Suzuki, Y Koike, WJ Chun, K Asakura
    SURFACE SCIENCE 600 10 L117 - L121 2006年05月 [査読有り][通常論文]
     
    We have studied the growth mode and morphology of Ni clusters on a TiO2(1 10) surface with a wide terrace using scanning tunneling microscopy (STM) at a low coverage (less than 3 atoms nm(-2)). The Ni clusters are formed on the terrace at the low coverage of 0.2 atoms nm(-2). Their average dimensions are constant in three directions up to 1 atoms nm(-2). The Ni clusters have an oval shape with average sizes of 1.8 nm (along [001]) x 1.4 nm (along [110]) x 0.38 nm (in the [110] directions). Above the coverage of 1.0 atoms nm(-2), an increase in the cluster height occurs, retaining an almost constant lateral size. It is proposed that the interaction of the Ni cluster and the support surface regulates the Ni cluster size. (c) 2006 Elsevier B.V. All rights reserved.
  • M Ushiro, K Uno, T Fujikawa, Y Sato, K Tohji, F Watari, WJ Chun, Y Koike, K Asakura
    PHYSICAL REVIEW B 73 14 144103  2006年04月 [査読有り][通常論文]
     
    Metal impurities in the carbon nanotubes and carbon nanofibers play an important role in understanding their physical and chemical properties. We apply the Ni K-edge x-ray absorption fine structure analyses to the local electronic and geometric structures around embedded Ni impurities used as catalysts in a carbon nanofiber in combination with multiple scattering analyses. We find almost Ni catalysts as metal particles are removed by the purification treatment. Even after the purification, residual 100 ppm Ni species are still absorbed; most of them are in monomer structure with Ni-C bond length 1.83 angstrom, and each of them is substituted for a carbon atom in a graphene sheet.
  • Y Koike, K Ijima, WJ Chun, H Ashima, T Yamamoto, K Fujikawa, S Suzuki, Y Iwasawa, M Nomura, K Asakura
    CHEMICAL PHYSICS LETTERS 421 1-3 27 - 30 2006年04月 [査読有り][通常論文]
     
    The structure of low coverage Ni atoms on the TiO2(1 10) surface was studied using polarization dependent EXAFS. We found that Ni atoms interacted with oxygen atoms at the (1 in) step edges, where atomically dispersed Ni species were found with Ni-O distances at 0.199 +/- 0.002 and 0.204 +/- 0.003 nm in parallel and perpendicular directions to the TiO2(1 10) surface, respectively. The location corresponded to the virtual Ti site if the next TiO2 layer was created on the topmost TiO2 surface. The Ni location was mainly determined by the dangling bond directions of the surface oxygen atoms. (c) 2006 Elsevier B.V. All rights reserved.
  • T. Naito, H. Sugawara, T. Inabe, Y. Kitajima, T. Miyamoto, H. Niimi, K. Asakura
    JOURNAL OF LOW TEMPERATURE PHYSICS 142 3-4 383 - 386 2006年02月 [査読有り][通常論文]
     
    Thermal analysis of Ag(DM)(2), where DM = 2,5-dimethyl-NN'-dicyanoquinonediimine, clarified that the salt had an insulating amorphous phase (>= 155 degrees C). Characterization of this and related solid states of Ag(DM)(2) indicated that a photo-induced process should be essential in controlling the number of carriers and thus conduction behavior of the salt by illumination. In fact, while heating could do nothing but make the salt insulating when the sample temperature exceeded 155 degrees C, ultraviolet-visible light illumination (< 155 degrees C) could gradually change the properties to be semiconducting with retaining the crystal lattice (average structure).
  • KK Bando, T Kawai, K Asakura, T Matsui, L Le Bihan, H Yasuda, Y Yoshimura, ST Oyarna
    CATALYSIS TODAY 111 3-4 199 - 204 2006年02月 [査読有り][通常論文]
     
    Supported Pd-Pt catalysts are efficient for hydrodesulfurization (HDS) and hydrodearomatization (HDA) reactions of diesel fuel and their activity varied with the kinds of supports. Concerning HDA, alumina supported catalysts showed four times higher TOF (turn over frequency) than silica supported one. In order to elucidate the difference in activity, the structural analysis of the active phase was performed. After reduction pretreatment, relatively uniform and large metallic alloy Pd-Pt particles were formed on SiO2, whereas, Pd and Pt atoms formed rather segregated particles on Al2O3. Subsequent X-ray absorption of fine structure (XAFS) analysis under HDS conditions showed no contribution of sulfur for SiO2 supported catalyst, whereas, formation of sulfided metal species was observed in XAFS spectra for the Al2O3 supported catalyst. It is suggested that on Pd-Pt/SiO2, thin sulfide layer on the metal cluster surface blocked the active sites and lowered the HDA activity. Presence of partially sulfided phase originated from rather segregated structure like Pd-PUAl2O3 is thought to be requisite for high HDA activity. (c) 2005 Elsevier B.V. All rights reserved.
  • R Takamatsu, K Asakura, WJ Chun, T Miyazaki, M Nakano
    CHEMISTRY LETTERS 35 2 224 - 225 2006年02月 [査読有り][通常論文]
     
    We investigated local structures around cadmium (Cd) sorbed on montmorillonite at various PH values by EXAFS (extend X-ray absorption fine structure). We found two sorption types, an outer-sphere complex and a surface precipitate. The outer-sphere complex was mainly formed at a lower PH which had an identical structure to aqueous Cd2+, while the surface precipitate was found at high PH which had a one-layer Cd-5(OH)(8)(NO3)(2) (H2O)(2)-like structure.
  • MG Moula, S Suzuki, WJ Chun, S Otani, ST Oyama, K Asakura
    CHEMISTRY LETTERS 35 1 90 - 91 2006年01月 [査読有り][通常論文]
     
    The first clear atomic-scale images of a Ni2P(0001) surface have been obtained by means of a scanning tunneling (STM) microscope. The STM image shows an ordered hexagonal syrninctry of the (0001) face, which can be assigned to phosphorus atoms on Ni3P1- and Ni3P2-terminated Surface. The high temperature annealing is crucial to get a well-ordered atomic structure.
  • M Uo, K Asakura, T Kohgo, F Watari
    CHEMISTRY LETTERS 35 1 66 - 67 2006年01月 [査読有り][通常論文]
     
    Se localilzation in the human oral mucosae which contain dental amalgam or dental silver alloy particles was analyzed by X-ray scanning analytical microscopy (XSAM). Se distribution was visualized, and the localization in the neighbor of amalgam or silver particles was confirmed. The chemical state of Se was analyzed by X-ray absorption fine structure (XAFS) analysis. Se was estimated as the low valency state. The possibility of using XSAM and XAFS for the analysis of the distribution and chemical state of rarely contained elements in biological tissue was Suggested.
  • T. Naito, H. Sugawara, T. Inabe, T. Miyamoto, H. Niimi, K. Asakura
    Molecular Crystals and Liquid Crystals 455 311-316, SUPPL 2P - 316 2006年 [査読有り][通常論文]
  • Toshio Naito, Hideyuki Sugawara, Tamotsu Inabe, Takeshi Miyamoto, Hironobu Niimi, Kiyotaka Asakura
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 455 311 - 316 2006年 [査読有り][通常論文]
     
    The conductivity of a silver salt of N,N'-dicyanoquinonediimine irreversibly varied in approximate proportion to an illumination of a wide range of wavelengths. Depending on the illumination conditions, four different states (beta, gamma, delta, and epsilon) were obtained with different structures. The b structure is in particular important, where the formal charge of the N,N'-dicyanoquinonediimine molecules continuously decreased to -0.4 - -0.35 with retaining the crystal structure, when we kept the temperature < 155 degrees C during the illumination. The non-illuminated area of the sample retained its original electrical property with a well-defined interface, which enabled a fabrication of a junction-structure in the single crystal.
  • Mayuko Ushiro, Kiyotaka Asakura, Kenryo Ohminami, Shin-Ichi Nagamatsu, Takashi Fujikawa
    e-Journal of Surface Science and Nanotechnology 3 427 - 432 2005年12月09日 [査読有り][通常論文]
     
    We carry out Ni K-edge X-ray Absorption Near Edge Structure (XANES) analyses to study local electronic and geometric structure around Ni impurities after HCl treatment in carbon nanotubes (CNTs) by applying full multiple scattering calculations. For the trace Ni species in CNT after the treatment, we consider possible models consistent with Ni-C distance and coordination number estimated by previous Extended X-ray Absorption Fine Structure (EXAFS) analyses. The present analyses allow us to distinguish between two defect models for the Ni location a crack-like defect and Stone-Wales defect. We also find that the curvature of CNTs affects the calculated XANES spectra, which can provide useful information about outer or inner adsorption on CNT walls. Ab initio density functional calculation supports the presence of Ni atoms at the outside of the nanotube. © 2005 The Surface Science Society of Japan.
  • HM Chen, HC Peng, RS Liu, K Asakura, CL Lee, JF Lee, SF Hu
    JOURNAL OF PHYSICAL CHEMISTRY B 109 42 19553 - 19555 2005年10月 [査読有り][通常論文]
     
    In this paper, we report a new approach to fabricate gold nanowires by controlling the volume of the growth solution. The shape evolutions ranging from fusiform nanoparticles to 1-D rods were observed. Increasing the addition of the growth solution can control the length of nanorods. The length of the rods can be extended to 2 mu m, and nanorods with aspect ratios of up to similar to 70 could be obtained.
  • T Naito, T Inabe, H Niimi, K Asakura
    SYNTHETIC METALS 152 1-3 289 - 292 2005年09月 [査読有り][通常論文]
     
    Molecular materials have been recently spotlighted as promising candidates for advanced functional materials. We have developed a novel and simple doping method for a molecular material which utilizes a light-induced solid state reaction. The electrical behavior of a single crystal of a molecular charge-transfer salt of silver(I) ion qualitatively becomes differed after illumination with ultraviolet-visible (UV-VIS) light. The X-ray photoelectron spectroscopy also demonstrated that there was neutral silver species concentrated in the illuminated part of the pressed pellet sample, while only silver (I) ions were detected in the rest part and non-illuminated samples. Raman spectra of the pressed pellet sample showed that the formal charge of the constituent organic pi-acceptor molecule, which is responsible for the conductivity of this material, varied in accordance with the time of illumination. Illumination with UV-VIS light upon only half of a thin single crystal of the same material transformed it to junction structure, exhibiting a rectifying character. This doping method has opened a new way for fabrication of devices from molecular solids.
  • M Uo, K Asakura, A Yokoyama, K Tamura, Y Totsuka, T Akasaka, F Watari
    CHEMISTRY LETTERS 34 6 776 - 777 2005年06月 [査読有り][通常論文]
     
    X-ray absorption fine structure (XAFS) analysis was applied for the analysis of titanium (Ti) in the human oral mucosa in contact with Ti dental implants from two different patients. Metallic Ti and an oxide (anatase) were detected. The metallic Ti was distributed in particulate form, which would be debris formed by the abrasion during the operation of implantation. The possibility of using XAFS for the analysis of the chemical state of rarely contained elements in biological tissue was suggested.
  • K Asakura, WJ Chun, K Tohji, Y Sato, F Watari
    CHEMISTRY LETTERS 34 3 382 - 383 2005年03月 [査読有り][通常論文]
     
    Local structure around Ni impurities in a carbon nanotube was studied by X-ray absorption fine structure (XAFS). The Ni was present in the form of Ni particles before the purification process. After the purification Ni content was decreased to a few hundreds ppm. The Ni K-edge XAFS could be measured by a 19 element solid-state detector. The Ni species was strongly bound to the carbon of the carbon nanotube with a Ni-C covalent bonds at 0.173 nm.
  • Y Ohminami, S Suzuki, N Matsudaira, T Nomura, WJ Chun, K Ijima, M Nakamura, K Mukasa, M Nagase, K Asakura
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 78 3 435 - 442 2005年03月 [査読有り][通常論文]
     
    We have prepared microfabricated alpha-Sb2O4 thin films on VSbO4 by electron lithography. The VSbO4 thin films were prepared on a Si substrate by a sol-gel method combined with a spin coating. The size, separation and arrangement of the alpha-Sb2O4 overlayer were controlled by electron-beam lithography. We could successfully draw 0.5 mu m wide lines with a separation of 2 pm. A preliminary study on the catalysis showed an enhancement of the selectivity in a propene conversion reaction to acrolein on a microfabricated alpha-Sb2O4/VSbO4.
  • H Niimi, M Kato, T Tsutsumi, T Kawasaki, H Matsudaira, S Suzuki, WJ Chun, Y Kitajima, M Kudo, K Asakura
    APPLIED SURFACE SCIENCE 241 1-2 131 - 134 2005年02月 [査読有り][通常論文]
     
    We discussed a new design of a Wien filter energy analyzer for an energy-filtered X-ray photoemission electron microscopy system. We have demonstrated that the second-order aberration and the third-order aperture aberration can be corrected by the multipole Wien filter by adjusting multipole components of electric and magnetic fields up to octupole components. The three-dimensional charge simulation method indicated that 12 electrodes and magnetic poles can effectively reproduce these ideal electric and magnetic fields. (C) 2004 Elsevier B.V. All rights reserved.
  • T. Kawai, S. Sato, W. -J. Chun, K. Asakura, K. -K. Bando, T. Matsui, Y. Yoshimura, T. Kubota, Y. Okamoto, Y-K. Lee, T. S. Oyama
    PHYSICA SCRIPTA T115 T115 822 - 824 2005年 [査読有り][通常論文]
     
    The local structure around Ni in a nickel phosphide catalyst supported on SiO2 was investigated by an in situ X-ray absorption. ne structure (XAFS) method during the reduction process of the catalyst and the hydrodesulfurization (HDS) reaction of thiophene. In the passivated sample, the Ni phosphide was partially oxidized but during the reduction process Ni2P particles were regenerated. The particles had Ni-P and Ni-Ni distances of 0.220 and 0.259 nm, respectively, corresponding closely to those of bulk Ni2P. In situ XAFS clearly revealed that Ni2P structure was stable under the reaction conditions at atmospheric pressure and was an active structure for the HDS process.
  • K. Asakura, C. R. Bian, S. Suzuki, W. -J. Chun, N. Watari, S. Ohnishi, P. Lu, N. Toshima
    PHYSICA SCRIPTA T115 T115 781 - 783 2005年 [査読有り][通常論文]
     
    We have carried out EXAFS analyses on polymer-protected CuPd nanoparticles with sizes of about 1.4 nm. We found that the Cu-Pd heterobond was preferentially created in the CuPd nanoparticle and we called this type of structure a "heterobondphilic structure". DFT calculation indicated the electron transfer from Cu to Pd which stabilized the CuPd nanoparticle. The catalytic activities and their relation to the heterobondphilic structure were discussed.
  • K. Asakura, C. R. Bian, S. Suzuki, W. J. Chun, N. Watari, S. Ohnishi, P. Lu, N. Toshima
    Physica Scripta T T115 781 - 783 2005年 [査読有り][通常論文]
     
    We have carried out EXAFS analyses on polymer-protected CuPd nanoparticles with sizes of about 1.4 nm. We found that the Cu-Pd heterobond was preferentially created in the CuPd nanoparticle and we called this type of structure a "heterobondphilic structure". DFT calculation indicated the electron transfer from Cu to Pd which stabilized the CuPd nanoparticle. The catalytic activities and their relation to the heterobondphilic structure were discussed. © Physica Scripta 2005.
  • H Yasufuku, Y Ohminami, T Tsutsumi, H Niimi, N Matsudaira, K Asakura, M Kato, Y Sakai, Y Kitajima, Y Iwasawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 43 11A 7682 - 7688 2004年11月 [査読有り][通常論文]
     
    We have shown the possibility of a Wien filter as an energy analyzer for the energy-filtered X-ray photoemission electron microscopy (EXPEEM) by obtaining images of An islands on a Ta substrate using an inner shell photoelectron excited by an X-ray with a photon energy of 2300 eV. When the photoelectron with kinetic energy of nearly 0 eV was selected, brighter An islands were observed. When the kinetic energies of photoelectrons passing the Wien filter are set at those of Au 3d(5/2) and Ta 3p(3/2) photoelectrons, the An and Ta regions appeared brighter, respectively, indicating that the chemical imaging was successful using a high energy X-ray and a Wien filter energy analyzer.
  • H Niimi, T Tsutsumi, H Matsudaira, T Kawasaki, S Suzuki, WJ Chun, M Kato, Y Kitajima, Y Iwasawa, K Asakura
    APPLIED SURFACE SCIENCE 237 1-4 641 - 644 2004年10月 [査読有り][通常論文]
     
    Energy-filtered X-ray photoemission electron microscopy (EXPEEM) is a microscopy technique which has the potential to provide surface chemical mapping during surface chemical processes on the nanometer scale. We studied the possibilities of EXPEEM using a Wien filter type energy analyzer in the high energy X-ray region above 1000 eV. We have successfully observed the EXPEEM images of Au islands on a Ta sheet using An 3d(5/2) and Ta 3d(5/2) photoelectron peaks which were excited by 2380 eV X-rays emitted from an undulator (BL2A) at Photon Factory. Our recent efforts to improve the sensitivity of the Wien filter energy analyzer will also be discussed. (C) 2004 Elsevier B.V. All rights reserved.
  • T Naito, T Inabe, H Niimi, K Asakura
    ADVANCED MATERIALS 16 20 1786 - + 2004年10月 [査読有り][通常論文]
     
    Single crystals of a silver/organic charge-transfer complex are doped by illumination via optical fibers (see Figure). Continuous illumination with UV-visible light induces electron transfer between the organic pi-acceptor and a silver ion in the organic charge-transfer complex in the solid state. Illumination of one half of a single crystal produces a p-n junction rectifier in a single step.
  • WJ Chun, K Ijima, Y Ohminami, S Suzuki, K Asakura
    JOURNAL OF SYNCHROTRON RADIATION 11 11 291 - 294 2004年05月 [査読有り][通常論文]
     
    EXAFS oscillations of MoO3, which has a highly asymmetric local structure, have been calculated using backscattering amplitudes and phase shifts derived from the FEFF8 code and using Debye-Waller factors from an equation-of-motion method. They were compared with polarization-dependent empirical EXAFS data of the alpha-MoO3 single crystal at various temperatures. The theoretical EXAFS oscillations of Mo-O bonds for the [001] direction of the single crystal, where two symmetric Mo-O bonds exist, reproduced well the experimental data. On the other hand, the calculated data for the [100] direction, which contain two asymmetric Mo-O bonds with different bond lengths, agree well with the experimental data only after adjustment of the amplitude reduction factors for different Mo-O bonds. EXAFS oscillations of MoO3 powder were also calculated by the same method, and theoretical parameters that could reproduce the experimental data were found. These results suggest that the equation-of-motion method can evaluate the Debye-Waller factors efficiently in molecules with asymmetric local structures and can reduce curve-fitting parameters.
  • S Sato, H Niimi, S Suzuki, WJ Chun, K Irokawa, H Kuroda, K Asakura
    CHEMISTRY LETTERS 33 5 558 - 559 2004年05月 [査読有り][通常論文]
     
    We have carried out ethanol conversion reactions on the MoO3 under the pulse infrared irradiations (period = 2 s) with several wavelengths emitted from free-electron-laser. We found a piece of evidence to show the dependence of activities in the ethanol conversion rate on the infrared wavelengths. When the wavelength was tuned to 967 cm(-1), which corresponded to the absorption frequency of 0.167 nm Mo=O bond, C2H5OH was converted mainly to CH4 with CH3CHO as a minor product while no reaction occurred at 1200 cm(-1) where no resonant vibration mode Of MoO3 was present. The reaction products were different from those produced in thermal reactions.
  • S Suzuki, Y Koike, K Fujikawa, WJ Chun, M Nomura, K Asakura
    CHEMISTRY LETTERS 33 5 636 - 637 2004年05月 [査読有り][通常論文]
     
    We have measured a frequency shift of the noncontact atomic force microscopy (NC-AFM) cantilever above Au islands when we scanned the X-ray energy around the Au L-3 absorption edge. We have found a clear peak of the frequency shift just above the Au L-3 absorption edge. This novel phenomenon suggested that the combination of energy-variable X-rays and NC-AFM provides us a new way of nano level chemical mapping of surfaces.
  • K Ijima, Y Koike, WJ Chun, Y Saito, Y Tanizawa, T Shido, Y Iwasawa, M Nomura, K Asakura
    CHEMICAL PHYSICS LETTERS 384 1-3 134 - 138 2004年01月 [査読有り][通常論文]
     
    The geometrical structure of a low coverage Ni species on an alpha-Al2O3 (0 0 0 1) single crystal surface has been studied using a polarization-dependent total reflection fluorescence extended X-ray absorption fine structure (PTRF-EXAFS) spectroscopy to reveal the bonding feature between the metal and the oxide surface. The Ni species on the alpha-Al2O3 (0 0 0 1) surface is atomically dispersed with a Ni-O distance at 0.198 +/- 0.003 nm. The adsorption site is determined to be a threefold oxygen site on top of a deep Al atom accompanied with a relaxation of the nearest neighbor oxygen atoms. (C) 2003 Elsevier B.V. All rights reserved.
  • Niimi, H., Tsutsumi, T., Matsudaira, H., Kawasaki, T., Suzuki, S., Chun, W.J., Kato, M., Kitajima, Y., Iwasawa, Y. and Asakura, K.: "Recent progresses in an energy filtered high energy XPEEM using a Wien filter type energy analyzer". Appl.Surf.Sci. 23・・・
    2004年 [査読無し][通常論文]
     
    Niimi, H., Tsutsumi, T., Matsudaira, H., Kawasaki, T., Suzuki, S., Chun, W.J., Kato, M., Kitajima, Y., Iwasawa, Y. and Asakura, K.: "Recent progresses in an energy filtered high energy XPEEM using a Wien filter type energy analyzer". Appl.Surf.Sci. 237:641-644,(2004).*
  • S Suzuki, Y Ohminami, T Tsutsumi, MM Shoaib, M Ichikawa, K Asakura
    CHEMISTRY LETTERS 32 12 1098 - 1099 2003年12月 [査読有り][通常論文]
     
    We have observed MoO3 (010) surface on an atomic level by NC-AFM(Noncontact atomic force microscopy) for the first time. White arrays with 0.40 and 0.37 nm dimensions along [100] and [001], respectively, were observed, which corresponded to the topmost oxygen atoms of MoO3 (010).
  • Y Tanizawa, T Shido, WJ Chun, K Asakura, M Nomura, Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B 107 47 12917 - 12929 2003年11月 [査読有り][通常論文]
     
    Three-dimensional analysis of structures for dispersed Cu species on a TiO2(110) surface has been performed by a polarization-dependent total-reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) technique. The dispersed Cu species were prepared by a chemical reaction between Cu(DPM)(2) and a TiO2(110) surface and reduced with H-2. The Cu(DPM)(2) dissociatively adsorbed on the 2-fold site of bridging oxygen atoms of the TiO2(110) surface to form a Cu(DPM)(O-)(2) species. Subsequent reduction of the Cu species with H-2 at 363 K produced Cu-3 trimers that were bound to the bridging oxygen atoms with the trimer plane inclined at about 30degrees from the TiO2(110) normal. There were direct Cu-O bonds at the Cu-3 trimer/TiO2(110) interface in addition to Cu-Cu bonds. Further reduction at 473 K produced three-dimensional prismatic small Cu-6 clusters by vertical growth in the [110] direction of the Cu fee lattice. Orientations of the Cu-3 triangle and Cu-6 prism clusters may be regulated by the interaction between the Cu atoms and the bridging oxygen atoms on the anisotropic TiO2(110) surface.
  • T Kawai, S Sato, S Suzuki, WJ Chun, K Asakura, KK Bando, T Matsui, Y Yoshimura, T Kubota, Y Okamoto, YK Lee, ST Oyama
    CHEMISTRY LETTERS 32 10 956 - 957 2003年10月 [査読有り][通常論文]
     
    Local structure around Ni in a nickel phosphide catalyst supported on K-USY was investigated by an in situ X-ray absorption fine structure (XAFS) method during the reduction process of the catalyst and the hydrodesulfurization (HDS) reaction of thiophene. In the passivated sample, Ni phosphide was partially oxidized but after the reduction, 1.1 nm diameter Ni2P particles were formed with Ni-P and Ni-Ni distances at 0.218 and 0.261 nm, respectively, corresponding to those of bulk Ni2P. In situ XAFS clearly revealed that the Ni2P structure was stable under reaction conditions and was an active structure for the HDS process.
  • K Asakura
    CATALYSIS SURVEYS FROM ASIA 7 2-3 177 - 182 2003年09月 [査読有り][通常論文]
     
    This short review deals with some recent XAFS (X-ray absorption. ne structure) applications to catalysts in Japan. The high transmission ability of X rays makes it possible to carry out in situ work on catalysts. First, in situ XAFS works underflow and high-pressure reaction conditions will be described. The time-resolved XAFS work will be another important topic because it can provide the possibility of observing the change of the reaction active site and the reaction intermediate. Finally, PTRF-XAFS will be described, which is a unique technique and provides three-dimensional local structures of highly dispersed surface species.
  • H Kato, K Asakura, A Kudo
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 125 10 3082 - 3089 2003年03月 [査読有り][通常論文]
     
    NiO-loaded NaTaO3 doped with lanthanum showed a high photocatalytic activity for water splitting into H-2 and O-2 in a stoichiometric amount under UV irradiation. The photocatalytic activity of NiO-loaded NaTaO3 doped with lanthanum was 9 times higher than that of nondoped NiO-loaded NaTaO3. The maximum apparent quantum yield of the NiO/NaTaO3:La photocatalyst was 56% at 270 nm. The factors affecting the highly efficient photocatalytic water splitting were examined by using various characterization techniques. Electron microscope observations revealed that the particle sizes of NaTaO3:La crystals (0.1-0.7 mum) were smaller than that of the nondoped NaTaO3 crystal (2-3 mum) and that the ordered surface nanostructure with many characteristic steps was created by the lanthanum doping. The small particle size with a high crystallinity was advantageous to an increase in the probability of the reaction of photogenerated electrons and holes with water molecules toward the recombination. Transmission electron microscope observations and extended X-ray absorption fine structure analyses indicated that NO cocatalysts were loaded on the edge of the nanostep structure of NaTaO3:La photocatalysts as ultrafine particles. The H-2 evolution proceeded on the ultrafine NiO particles loaded on the edge while the O-2 evolution occurred at the groove of the nanostep structure. Thus, the reaction sites for H-2 evolution were separated from those of O-2 evolution over the ordered nanostep structure. The small particle size and the ordered surface nanostep structure of the NiO/NaTaO3:La photocatalyst powder contributed to the highly efficient water splitting into H-2 and O-2.
  • S. T. Oyama, R. Radhakrishnan, M. Seman, J. N. Kondo, K. Domen, K. Asakura
    Journal of Physical Chemistry B 107 8 1845 - 1852 2003年02月27日 [査読有り][通常論文]
     
    Oxidation of organic substrates on metal oxide catalysts can be viewed as entailing a transfer of electrons from the organic moeity to the catalytic center, and is expected to involve the electron-accepting levels in the metal center. This investigation deals with the study of the electron-transfer processes associated with the C-H bond breaking reaction in adsorbed methoxide species in the course of methanol oxidation on supported MoO3. It is shown that the activity of a series of catalysts duly correlates with the unoccupied density of electronic states of the parent metal oxides. The unoccupied levels are probed with near-edge X-ray absorption spectroscopy (NEXAFS). The particular system chosen for study is that of methanol oxidation on supported molybdenum oxide, a reaction in which C-H bond breaking is rate-determining. The findings of this study are in good agreement with the known facts about the reaction and allow a deeper understanding of various reported effects. For example, the positive relationships between the catalytic activity and the decreasing electronegativity of the support ion, the increasing reducibility of the dispersed molybdenum centers, and the increasing size of the molybdenum ensembles can all be explained by the increasing ease of accommodation of charge by the metal centers. The findings in this study should be of importance in understanding other C-H bond breaking reactions and multicomponent catalyst systems.
  • Cui-Rong Bian, Shushi Suzuki, Kiyotaka Asakura, Lu Ping, Naoki Toshima
    Journal of Physical Chemistry B 106 34 8587 - 8598 2002年08月29日 [査読有り][通常論文]
     
    Polymer-protected Cu/Pd bimetallic nanoclusters colloidally dispersed in a glycol solution were investigated by means of extended X-ray absorption fine structure (EXAFS). Cu/Pd alloy structures were observed in a wide range of Cu/Pd composition. Shorter Cu-Pd bond distances and more coordination numbers of Cu around Pd and Pd around Cu were found for the nanoclusters with Cu/Pd = 4:1, 3:2, and 1:1 than those expected in random alloy structures, indicating stronger interaction between Cu and Pd atoms. We proposed a "heterobond-philic" model for a new type of bimetallic nanoclusters. The preferential formation of the Cu-Pd bond may be the origin for the unique catalytic properties for hydration and hydrogenation reactions.
  • H Yasufuku, Y Ohminami, T Tsutsumi, K Asakura, M Kato, Y Sakai, Y Kitajima, Y Iwasawa
    CHEMISTRY LETTERS 8 842 - 843 2002年08月 [査読有り][通常論文]
     
    We observed surface images of the Au islands periodically deposited on a Ta sheet by means of an energy-filtered XPEEM using a retarding Wien-filter energy analyzer and a high energy X-ray. By changing the passing photoelectron kinetic energy (E-kin), we had a brighter Au island image at the E-kin = 0 eV and 60 eV while we had a brighter Ta substrate image at E-kin = 102 eV, corresponding to a Ta 3p(3/2) photoelectron peak.
  • CR Bian, S Suzuki, K Asakura, L Ping, N Toshima
    JOURNAL OF PHYSICAL CHEMISTRY B 106 34 8587 - 8598 2002年08月 [査読有り][通常論文]
     
    Polymer-protected Cu/Pd bimetallic nanoclusters colloidally dispersed in a glycol solution were investigated by means of extended X-ray absorption fine structure (EXAFS). Cu/Pd alloy structures were observed in a wide range of Cu/Pd composition. Shorter Cu-Pd bond distances. and more coordination numbers of Cu around Pd and Pd around Cu were found for the nanoclusters with Cu/Pd = 4:1, 3:2, and 1: 1 than those expected in random alloy structures, indicating stronger interaction between Cu and Pd atoms. We proposed a "heterobond-philic" model for a new type of bimetallic nanoclusters. The preferential formation of the Cu-Pd bond may be the origin for the unique catalytic properties for hydration and hydrogenation reactions.
  • WJ Chun, K Asakura, H Ishii, T Liu, Y Iwasawa
    TOPICS IN CATALYSIS 20 1-4 89 - 95 2002年07月 [査読有り][通常論文]
     
    To investigate the effect of alkali impurity in Mo/SiO2 on the MoOx structure on SiO2 surfaces SiO2-supported Mo oxides were prepared with various amounts of Na ions in a class-1 clean bench with a laminar flow in a class-1000 clean room. The Na concentrations were varied in the range 0-5000 ppm, while the Mo loading on SiO2 was maintained at 0.7 wt%. The Mo-Na/SiO2 samples obtained were characterized by diffuse reflectance UV-visible and Raman spectroscopy. Three types of Mo species were identified: octahedral monooxo Mo monomer species, Na2Mo2O7 and MoO3. At less than 100 ppm Na both octahedral Mo monomers and MoO3 species were formed on SiO2. The MoO3 species was transformed to Na2Mo2O7 at 2000 ppm Na, where the Na ions interact directly with the Mo species on the surface. The octahedral monooxo Mo monomer species seems not to be influenced significantly by Na impurity.
  • Y Notoya, K Hayakawa, T Fujikawa, T Kubota, T Shido, K Asakura, Y Iwasawa
    CHEMICAL PHYSICS LETTERS 357 5-6 365 - 370 2002年05月 [査読有り][通常論文]
     
    A recent experimental result shows that Pt L-edge XANES spectra for Pt small cluster with similar to20 Pt atoms are sensitive to CO adsorption. In the present study we try to extract useful information about geometric and electronic structures of these cluster by applying a full multiple-scattering approach for the XANES analyses. Although IR analyses show that [CO](top)/[CO](bridge) is nearly constant for wide range of [Co](ad), it is difficult to estimate the ratio because of the large difference of the IR transition intensity for different adsorbed CO molecules. The present XANES analyses provide us useful new information [CO](top)/[CO](bridge) = 1-2. (C) 2002 Published by Elsevier Science B.V.
  • Aritomo Yamaguchi, Akane Suzuki, Takafumi Shido, Yasuhiro Inada, Kiyotaka Asakura, Masaharu Nomura, Yasuhiro Iwasawa
    Journal of Physical Chemistry B 106 9 2415 - 2422 2002年03月07日 [査読有り][通常論文]
     
    Temperature-programmed decarbonylation processes of Mo(CO)6 entrapped in NaY and HY zeolites were investigated in situ by the time-resolved energy-dispersive X-ray absorption fine structure (DXAFS) technique. The DXAFS study revealed that the decarbonylation of Mo(CO)6 in both NaY and HY proceeded through molybdenum subcarbonyl species and that the subsequent formation of decarbonylated species is affected by the stability of the subcarbonyl intermediate species. In the case of Mo(CO)6/NaY, stable Mo(CO)3(OL)3 (OL, oxygen atoms of the zeolite framework) species were formed at 400-500 K and Mo(II) oxocarbide dimeric species Mo2(C)Ox were formed above 500 K. In the case of Mo(CO)6/HY, on the other hand, unstable Mo(CO)3(OL)x (x = 1-2) species were formed around 450 K and they reacted easily with protons in zeolite supercages to be converted to Mo(II) monomer species. An unstable intermediate species was observed, and its structure was determined by DXAFS for the first time.
  • RS Mulukutla, T Shido, K Asakura, T Kogure, Y Iwasawa
    APPLIED CATALYSIS A-GENERAL 228 1-2 305 - 314 2002年03月 [査読有り][通常論文]
     
    Nanoparticles of rhodium oxides were prepared in the MCM-41 mesoporous molecular sieve and were characterized by XRD, TEM. H2-TPR and EXAFS. It was found that the particle size, location and structure of the rhodium oxide particles were greatly influenced by the hydrothermal synthesis conditions. The Rh K-edge EXAFS study revealed that the nanoparticles of RhOx, with the size <3 nm has a hexagonal structure with a Rh-Rh bond distance of 0.273 nm, while the nanoparticles of RhOx with 6-8 nm size possessed a distorted orthorhombic structure without any long range order. The RhOx nanoparticles were employed as catalysts forNO-CO reactions. The rhodium oxides with <3 nm particles located in the mesopore channels of MCM-41 exhibited a promoting effect of excess O-2 on the conversion of NO to N-2 and N2O in the catalytic NO-CO reaction. The rhodium oxides of 6-8 nm size located in the bulk of MCM-41 and a supported RhOx/MCM-41 catalyst showed poisoning effects of excess O-2 on the NO and CO conversions. The promotional effects of O-2 observed for the catalyst with RhOx nanoparticles in the mesopores were attributed not to the small size of RhOx, but to the location of RhOx in the MCM-41 channel. (C) 2002 Elsevier Science B.V. All rights reserved.
  • A Yamaguchi, A Suzuki, T Shido, Y Inada, K Asakura, M Nomura, Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B 106 9 2415 - 2422 2002年03月 [査読有り][通常論文]
     
    Temperature-programmed decarbonylation processes of Mo(CO)(6) entrapped in NaY and HY zeolites were investigated in situ by the time-resolved energy-dispersive X-ray absorption fine structure (DXAFS) technique. The DXAFS study revealed that the decarbonylation of Mo(CO)(6) in both NaY and HY proceeded through molybdenum subcarbonyl species and that the subsequent formation of decarbonylated species is affected by the stability of the subcarbonyl intermediate species. In the case of Mo(CO)(6)/NaY, stable Mo(CO)(3)(O-L)(3) (O-L, oxygen atoms of the zeolite framework) species were formed at 400-500 K and Mo(II) oxocarbide dimeric species Mo-2(C)O-x were formed above 500 K. In the case of Mo(CO)(6)/HY, on the other hand, unstable MO(CO)(3)(O-L)(x) (x = 1-2) species were formed around 450 K and they reacted easily with protons in zeolite supercages to be converted to Mo(II) monomer species. An unstable intermediate species was observed, and its structure was determined by DXAFS for the first time.
  • K Asakura, S Sato, K Irokawa, H Kuroda
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 41 1 118 - 119 2002年02月 [査読有り][通常論文]
     
    Ethanol dehydrogenation reaction was initiated on MoO3 excited by FEL-IR. When the FEL-IR with wavelength = 10.34 mum was irradiated, dark spot appeared at the irradiated point After the 120 min irradiation, we found a small amount of acetaldehyde in the gas phase.
  • K Ijima, Y Ohminami, S Suzuki, K Asakura
    TOPICS IN CATALYSIS 18 1-2 125 - 127 2002年 [査読有り][通常論文]
     
    We observed the polarization-dependent XAFS of an alpha-MoO3 single crystal. Polarization-dependent XANES spectra change with the polarization direction and the 1s --> 4d pre-edge peak is shown to be a good indicator for the Mo=O (double bond oxygen) bond direction. The three Mo-O bond lengths at 0.175, 0.195 and 0.223 nm can clearly be distinguished in the Fourier transforms of polarization-dependent EXAFS spectra. Curve-fitting analysis was carried out on a powder MoO3 spectrum based on the phase shift and amplitude functions derived from the polarization-dependent EXAFS spectra.
  • T Shido, A Yamaguchi, Y Inada, K Asakura, M Nomura, Y Iwasawa
    TOPICS IN CATALYSIS 18 1-2 53 - 58 2002年 [査読有り][通常論文]
     
    A time-resolved energy dispersive XAFS (DXAFS) technique is applied to elucidate the local structure of catalyst precursors and active species during the preparation of catalysts. The structure of ion-exchanged copper species in ZSM-5 zeolite during temperature-programmed reduction and the structure of molybdenum carbonyl species in NaY zeolite during temperature-programmed decarbonylation were investigated by the DXAFS technique. The way of the analysis of XAFS data during the dynamic processes is also discussed. The XANES spectra were analyzed to determine the ratio of different species involved in the system as a function of temperature as well as the curve-fitting analysis of the time-resolved EXAFS. The detailed analysis of the XANES and EXAFS shed light on the structural changes during the dynamic processes. In Cu-ZSM-5, a stepwise reduction process of Cu species and the subsequent growth of Cu particles during the reduction were elucidated. In Mo-NaY, the formation of Mo subcarbonyl monomer species as an intermediate of molybdenum oxycarbide dimer species was observed. This paper demonstrates that the DXAFS technique is useful to study the chemistry of catalyst preparation and can provide vital information that cannot be obtained by other techniques.
  • A. Yamaguchi, Y. Inada, T. Shido, K. Asakura, M. Nomura, Y. Iwasawa
    Studies in Surface Science and Catalysis 132 785 - 788 2001年12月01日 [査読無し][通常論文]
     
    The reduction processes of Cu-ZSM-5 were investigated by a time-resolved dispersive XAFS (DXAFS) technique. Two Cu-ZSM-5 samples with different Cu loadings were prepared by an ion-exchange method. In the low loading sample (84 % ion exchanged), Cu2+ cations were highly dispersed in the channel of ZSM-5, while CuO particles were formed in the high loading sample (104 % ion exchanged). The isolated Cu2+ cations were reduced to isolated Cu+ cations at 400-450 K and the Cu+ ions were reduced to Cu0 at 550-650 K. The curve fitting analysis of the DXAFS data revealed that Cu4 clusters were initially formed and then grew up to big particles. On the contrary, the CuO particles were reduced directly to Cu0 big metallic particles around 450 K.
  • R Radhakrishnan, C Reed, ST Oyama, M Seman, JN Kondo, K Domen, Y Ohminami, K Asakura
    JOURNAL OF PHYSICAL CHEMISTRY B 105 36 8519 - 8530 2001年09月 [査読有り][通常論文]
     
    Molybdenum oxide catalysts (1 wt %) supported on SiO2 (L-90, 95 m(2)/g), SiO2 (EH-5, 350 m(2)/g), Al2O3 (96 m(2)/g), and TiO2 (52 m(2)/g) were characterized using Raman spectroscopy and near-edge and extended X-ray absorption fine structure (NEXAFS and EXAFS, respectively) spectroscopies. The structural possibilities (tetrahedral and distorted octahedral) for the Mo active center were explored using ab initio calculations through the Hartree-Fock method using a 3-21G(d) basis set. The Raman vibrational frequencies and bond lengths obtained from EXAFS were compared to ab initio calculations to arrive at the likely structures for the isolated Mo centers on each support. The studies revealed a mixture of tetrahedral Mo sites along with crystalline MoO3 for the MoO3/SiO2 (L-90) catalyst. The Mo sites for the MoO3/SiO2 (EH-5) catalyst were found to be a mixture of isolated, tetrahedral, and distorted octahedral sites. The MoO3/Al2O3 catalyst was found to have isolated, tetrahedral sites. Finally, the MoO3/TiO2 catalyst was found to have distorted octahedral Mo active centers. Complementary information from Raman, NEXAFS, and EXAFS spectra and ab initio calculations were required to arrive at the structural assignments for the Mo centers in the present study. Importantly, however, the calculations indicate the possible existence of other stable geometries and help explain the many diverging conclusions in the literature concerning the structure of supported molybdenum oxide catalysts.
  • R Radhakrishnan, ST Oyama, Y Ohminami, K Asakura
    JOURNAL OF PHYSICAL CHEMISTRY B 105 38 9067 - 9070 2001年09月 [査読有り][通常論文]
     
    The structure of a MnOx/Al2O3 catalyst used for ozone decomposition was evaluated using extended X-ray absorption fine structure (EXAFS) and in situ Raman spectroscopy. EXAFS results suggest that the manganese center is surrounded by four or five oxygen atoms with a Mn-O distance of 0.21 nm. The Raman frequency for the Mn-O band was found to be 660 cm(-1). The structural possibilities were explored with ab initio quantum calculations using the Hartree-Fock method. The structure that best agreed with experimental results and literature information was the four oxygen coordinated manganese center. During the ozone decomposition reaction, an adsorbed peroxide species was observed on the catalyst surface at 880 cm(-1). The predicted vibrational frequencies calculated for peroxide species on the manganese structure were within 3% of the experimental data.
  • K Asakura, K Ijima
    JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 119 2-3 185 - 192 2001年08月 [査読有り][通常論文]
     
    Polarization dependent total reflection fluorescence extended X-ray absorption fine structure (PTRF-EXAFS) is reviewed briefly. This technique gives 3-dimensional information about the local structure around the X-ray absorbing atom even if the atom is highly-dispersed on the surface. We have applied the technique to the Mo oxide species dispersed on single crystal oxide surfaces, such as Al2O3(0001), MgO(100) and TiO2(110). Tetrahedral Mo species is found on MgO(100) surface while tetragonal pyramid species and octahedral dimer Mo species are found on Al2O3 and TiO2 surfaces, respectively. The structure dependences on support can be explained by the acidity and basicity of the support oxides. (C) 2001 Elsevier Science B.V. All rights reserved.
  • RS Mulukutla, T Shido, K Asakura, Y Iwasawa
    SCRIPTA MATERIALIA 44 8-9 1695 - 1698 2001年05月 [査読有り][通常論文]
     
    Nanoparticles of rhodium oxides of size <3 nm or 6-8 nm were synthesized in the mesoporous MCM-41 molecular sieve (Rh-MCM-41) via sol-gel method. The size of the RhOx particles was varied depending on the synthesis conditions. Rh-MCM-41 samples were characterized by XRD; TEM, Si-29 Solid State NMR; BET analysis; XPS and Rh K edge EXAFS. Rh-MCM-41 with <3 nm sized RhOx had exhibited novel promotional effect in the formation of N-2 and N2O in the NO-CO catalytic reaction where as the RhOx with size 6-8 nm showed a negative effect. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
  • A Yamaguchi, T Shido, Y Inada, T Kogure, K Asakura, M Nomura, Y Iwasawa
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 74 5 801 - 808 2001年05月 [査読有り][通常論文]
     
    The reduction process of Cu-ZSM-5 was investigated by a time-resolved energy-dispersive XAFS (DXAFS) technique. The spectra were recorded every second and the entire spectra were analyzed to elucidate the dynamic change of the local structure around the Cu species. Two Cu-ZSM-5 samples with different Cu loadings were prepared by an ion-exchange method followed by calcination. In the low-loading sample (84% ion-exchanged), Cu2+ cations dispersed isolatedly in the channels of ZSM-5, while in the high-loading sample (104% ion-exchanged) CuO particles were formed. The isolated Cu2+ cations were reduced to isolated Cu2+ cations at 400-450 K and the Cu+ ions were reduced to CuO at 550-650 K. The curve fitting analysis of the DXAFS data revealed that Cu4-6 clusters were initially formed in the reduction process. The clusters went out to the outer surface and grew into big particles. On the contrary, the CuO particles on the outer surfaces were reduced directly to Cu-0 metallic particles at ca. 450 K. The dynamic structure change around the Cu species in the zeolite during the reduction with H-2 was monitored in situ by DXAFS technique for the first time.
  • R Radhakrishnan, ST Oyama, JGG Chen, K Asakura
    JOURNAL OF PHYSICAL CHEMISTRY B 105 19 4245 - 4253 2001年05月 [査読有り][通常論文]
     
    Manganese oxide catalysts supported on Al2O3, ZrO2, TiO2, and SiO2 supports were used to study the effect of support on ozone decomposition kinetics. In-situ laser Raman spectroscopy, temperature-programmed oxygen desorption, surface area measurements, and extended and near-edge X-ray absorption fine structure (EXAFS and NEXAFS) showed that the manganese oxide was highly dispersed on the surface of the supports. The EXAFS spectra suggested that the manganese active centers on all of the surfaces were surrounded by five oxygen atoms. These metal centers were found to be of a monomeric type for the Al2O3-supported catalyst and multinuclear for the other supports. The NEXAFS spectra for the catalysts showed a chemical shift to lower energy, and an intensity change in the L-edge features which followed the trend Al2O3 > ZrO2 > TiO2 > SiO2. The trends provided insights into the positive role of available empty d-states required in the reduction step of a redox reaction. The catalysts were tested for their ozone decomposition reactivity and reaction rates were found to have a fractional order dependency (n < 1) with ozone partial pressure. The apparent activation energies for the reaction were found to be low (3-15 kJ/mol). The support was found to influence the desorption step (a reduction step) and this effect manifested itself in the preexponential factor of the rate constant for desorption. Trends for this preexponential factor correlated with the NEXAFS trends and reflected the ease of electron donation from the adsorbed species to the active center.
  • A Yamaguchi, Y Inada, T Shido, K Asakura, M Nomura, Y Iwasawa
    JOURNAL OF SYNCHROTRON RADIATION 8 8 654 - 656 2001年03月 [査読有り][通常論文]
     
    The time-resolved reduction process of copper cations in ZSM-5 during temperature-programmed reduction (300-700 K) was studied by energy dispersive X-ray absorption fine structure (DXAFS). The Cu K-edge DXAFS spectra for isolated Cu2+ species in the channels of ZSM-5 were recorded at an interval of 1 s during the reduction. The curve fitting analysis of the EXAFS data and the XANES analysis revealed that the isolated Cu2+ species in the channels were reduced stepwise. They were reduced to isolated Cu+ species at 400-450 K and the Cu+ species to Cu-0 metallic clusters at 550-650 K. Small clusters like Cu-4 were initially formed, followed by particle growth. A small part of them went out to the outer surfaces of ZSM-5 during the reduction.
  • Y Tanizawa, WJ Chun, T Shido, K Asakura, Y Iwasawa
    JOURNAL OF SYNCHROTRON RADIATION 8 8 508 - 510 2001年03月 [査読有り][通常論文]
     
    Cu K-edge XAFS of Cu/TiO2(110) was measured by polarization-dependent total-reflection fluorescence XAFS technique. XAFS of [001], [1(1) over bar 0], and [110] directions were measured to elucidate the three dimensional structure of Cu species on the TiO2(110) surface prepared by the deposition of Cu(DPM)(2) followed by reduction with H-2. Simulation of the EXAFS functions as well as conventional curve fitting analysis revealed that plane Cu3-4 small clusters with similar structure to Cu(111) plane were formed by the reduction at 363 K. The small clusters converted into spherical metallic Cu particles by the reduction at 473 K.
  • T Shido, A Yamaguchi, A Suzuki, Y Inada, K Asakura, M Nomura, Y Iwasawa
    JOURNAL OF SYNCHROTRON RADIATION 8 8 628 - 630 2001年03月 [査読有り][通常論文]
     
    The decarbonylation process of Mo(CO)(6) in the NaY supercages was studied by means of a time resolved dispersive XAFS method during temperature programmed decarbonylation. XANES analysis demonstrated that the decarbonylation proceeded through two steps and that a stable intermediate existed between 440-490 K. The curve fitting analysis revealed that the intermediate was a molybdenum monomer subcarbonyl species coordinated by three CO ligands and three oxygen atoms of zeolite framework. Molybdenum dimer subcarbonyl species were not observed. This study demonstrated that DXAFS technique is a powerful method to study the dynamic behaviour of the Mo carbonyl species during decarbonylation process.
  • WJ Chun, Y Tanizawa, T Shido, Y Iwasawa, M Nomura, K Asakura
    JOURNAL OF SYNCHROTRON RADIATION 8 8 168 - 172 2001年03月 [査読有り][通常論文]
     
    An in situ polarization-dependent total-reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) spectroscopy system has been developed, which enables PTRF-XAFS experiments to be performed in three different orientations at various temperatures (273-600 K) and pressures (10(-10) similar to 760 torr). The system consists of a measurement chamber and a preparation chamber. The measurement chamber has a high-precision six-axis goniometer and a multi-element solid-state detector. Using a transfer chamber, also operated under ultra-high-vacuum conditions, the sample can be transferred to the measurement chamber from the preparation chamber, which possesses low-energy electron diffraction, Auger electron spectroscopy and X-ray photoelectron spectroscopy facilities, as well as a sputtering gun and an annealing system. The in situ PTRF-EXAFS for Cu species on TiO2 (110) has been measured in three different orientations, revealing anisotropic growth of Cu under the influence of the TiO2 (110) surface.
  • WJ Chun, K Asakura, Y Iwasawa
    CATALYSIS TODAY 66 1 97 - 103 2001年03月 [査読有り][通常論文]
     
    Structure of Mo species deposited on a TiO2(110) surface has been studied using in situ polarization-dependent total reflection fluorescence EXAFS (PTRF-EXAFS). We found anisotropic ordering of the Mo species reflecting the anisotropic structure of TiO2 surface when Mo(CO)(6) was deposited under reductive conditions. Mo chains were produced with its Mo-Mo bonding parallel to the [001]direction of the TiO2 substrate. The results provide a possible way to regulate the structure of Mo species on TiO2(110) by the preparation conditions. (C) 2001 Elsevier Science B.V. All rights reserved.
  • M Olea, M Kunitake, T Shido, K Asakura, Y Iwasawa
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 74 2 255 - 265 2001年02月 [査読有り][通常論文]
     
    The adsorption kinetics on Au/Ti(OH)(4)* (a newly developed Au catalyst, active for low-temperature CO oxidation) for CO, O-2, and CO2 in the temperature range 298-473 K was determined by temporal analysis of products (TAP) technique. The response signals from the single-pulse TAP experiments were analyzed using a statistical approach, and they were fitted to analytical models in order to establish the adsorption/desorption parameters. The pulse response of a non-adsorbing gas (argon) was used as a "reference". The experiments revealed that: CO molecules reversibly adsorbed on the catalyst surface; O-2 molecularly adsorbed, irreversibly for high pulse intensities and reversibly for low pulse ones; CO2 molecules irreversibly adsorbed on the surface, probably as carbonates. This catalyst exhibited an apparent negative activation energy for irreversible adsorption of O-2.
  • A Yamaguchi, A Suzuki, T Shido, Y Inada, K Asakura, M Nomura, Y Iwasawa
    CATALYSIS LETTERS 71 3-4 203 - 208 2001年 [査読有り][通常論文]
     
    The temperature-programmed decarbonylation process of Mo(CO)(6) in NaY zeolite was studied by means of a time-resolved energy-dispersive XAFS method. The XANES analysis demonstrated that the decarbonylation proceeded by two successive steps via a stable intermediate which existed between 440 and 490 K, The curve fitting analysis of the EXAFS data revealed that the intermediate was a molybdenum monomer subcarbonyl species Mo(CO)(3)(O-L)(3) coordinated by three CO ligands and three oxygen atoms of zeolite framework (O-L). Molybdenum dimer subcarbonyl species were not observed. This study demonstrated that the DXAFS technique is a powerful method to study the dynamic behavior of the Mo carbonyl species during decarbonylation process.
  • T Shido, A Yamaguchi, K Asakura, Y Iwasawa
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 163 1-2 67 - 77 2000年12月 [査読有り][通常論文]
     
    This paper attempts to review our recent work to provide an aspect of catalysis "surface catalytic reactions assisted by gas phase molecules", describing the previous representative results and also presenting new data. In this concept, reaction intermediates are activated by gas phase molecules which adsorb weakly or are undetectable at the surface. The examples are the ethanol dehydrogenation on Nb/SiO2, the water gas shift reactions on MgO, ZnO and Rh/CeO2, and the NO-CO reaction on Co/Al2O3. (C) 2000 Elsevier Science B.V. All rights reserved.
  • T Shido, G Okita, K Asakura, Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B 104 51 12263 - 12268 2000年12月 [査読有り][通常論文]
     
    Bismuth-aluminum binary-oxide layers and clusters on an Al2O3 surface were prepared by supporting bismuth triethoxides on Al2O3, followed by calcination at 673 K. The Bi-Al binary oxides were characterized by EXAFS and XPS, and their catalytic activities for ethanol-selective oxidation were investigated. XPS data revealed that Bi atoms were supported on the Al2O3 surface in a Stranski-Krastanov (SK) growth mode, while EXAFS data demonstrated that Bi atoms made bondings with Al atoms at 0.353-0.361 nm through oxygen atoms (Bi-O, 0.211-0.212 nm) irrespective of Bi loadings and that the coordination numbers (CN) of the Bi-Al bond did not significantly change with Bi loadings (CN, 1.0-1.5). It is likely from these results that below 9 wt % Bi loading, Bi-Al (rich) binary-oxide monolayers are formed at the Al2O3 surface and that above 9 wt % Bi loading, Bi (rich)-Al binary-oxide clusters grow on the surface. In the low-Bi-loading catalysts, Bi-O and Bi-Al bonds were observed at 0.211 and 0.353-0.355 nm, respectively, while no Bi-Bi bond was observed, which suggests that Bi atoms are dispersed in the oxide layers. On the other hand, in the high-Bi-loading catalysts, Bi-Bi and long Bi-O bonds were observed at 0.363-0.369 and 0.276-0.279 nm, respectively, in addition to Bi-O at 0.212 nm and Bi-Al at 0.359-0.361 nm. The distances of the long Bi-O and Bi-Bi bonds were comparable to their distances in gamma -Bi2O3, and the BI-AI distance was also close to that in bismuth binary oxides with the gamma -Bi2O3 phase. These results suggest that the Bi (rich)-Al binary-oxide clusters have a gamma -Bi2O3-like structure. The catalytic activity of these binary oxides at the Al2O3 surface for ethanol-selective oxidation strongly depended on the structure around bismuth atoms. The initial rate for acetaldehyde formation steeply increased around 9 wt % Bi loading. The activation energy for the 11.0 wt % Bi/Al2O3 catalyst was 53 kJ mol(-1), while that for the 7.6 wt % Bi/Al2O3 catalyst was 96 kJ mol(-1), reflecting the different local structure of the active Bi sites.
  • S Takakusagi, M Kato, Y Sakai, K Fukui, K Asakura, Y Iwasawa
    JOURNAL OF MICROSCOPY-OXFORD 200 3 240 - 250 2000年12月 [査読有り][通常論文]
     
    We have developed a new X-ray photoemission electron microscopy system combined with low energy electron microscopy, photoemission electron microscopy, mirror electron microscopy (MEM), secondary electron emission microscopy (SEEM) and Auger electron emission microscopy, which provides multi-angle information on the distribution and change of element, chemical state, structure, etc. at solid surfaces under the working conditions such as high temperature and gas atmosphere. The performance of each microscopical method was examined and typical images are presented. The dynamic behaviour of fabricated surfaces has been imaged in real time by SEEM and MEM.
  • AI Kozlov, AP Kozlova, K Asakura, Y Matsui, T Kogure, T Shido, Y Iwasawa
    JOURNAL OF CATALYSIS 196 1 56 - 65 2000年11月 [査読有り][通常論文]
     
    Supported gold catalysts highly active for low-temperature CO oxidation were prepared by using AuPPh3NO3 complex as a Au-metal precursor and wet as-precipitated iron hydroxide and titanium hydroxide as support precursors. Effects of catalyst preparation conditions on the performance for low-temperature CO oxidation were studied. Metal-hydroxide precipitation conditions and heating rates of temperature-programmed calcination altered significantly the performance of the supported gold catalysts. To elucidate key factors responsible for the effects the catalysts were characterized by EXAFS, TEM, XRD, and N-2 adsorption. Changes in the activities of both Au/Fe oxide and Au/Ti oxide catalysts originated mainly from changes of the Au particle size distribution. It was also found that states of the mesoporous support precursors upon attaching the An precursor onto them and during the temperature-programmed calcination appeared to be of great importance in obtaining dispersed Au nanoparticles on oxide surfaces. (C) 2000 Academic Press.
  • K Asakura, K Nakatani, T Kubota, Y Iwasawa
    JOURNAL OF CATALYSIS 194 2 309 - 317 2000年09月 [査読有り][通常論文]
     
    The catalytic performance and structures of multicomponent "MoVNbTe" oxides have been studied to find the correlation among the performance, active phases, and preparation conditions. The catalyst with the composition MoV0.4Nb0.1Te0.2Ox showed high activity and selectivity for propane ammoxidation reaction (ca. 50% selectivity to acrylonitrile at ca. 90% conversion) when it was pretreated at 830-900 K for 2 h under O-2-free or less than 100 ppm O-2-contaminated N-2 or He flow conditions. Active phases were characterized by XRD, which gave 2 theta = 14.1 degrees, 24.9 degrees, 26.9 degrees, 29.1 degrees, 32.4 degrees, 33.2 degrees, and 35.4 degrees in addition to the peaks at 22.1 degrees, 28.2 degrees, 36.2 degrees, 44.7 degrees, and 50.0 degrees reported previously. XPS revealed the presence of Mo5+ in addition to Mo6+. In the presence of more than 1000 ppm O-2 contamination during the pretreatment, alpha-MoO3 was formed at the surface region, resulting in reduction of the activity for propane ammoxidation. The activation energy for propane conversion was 32.0 kcal/mol, which was a little smaller than the 36.1 kcal/mol for propene ammoxidation. The reaction rate (v) for propane ammoxidation on the MoVNbTe oxide catalyst at 693 K is given by v = k [propane](0.8) [O-2](0.4) [NH3](-0.4). The active phases and reaction mechanism are discussed on the basis of the characterization by XRD and XPS and the kinetic data. (C) 2000 Academic Press.
  • KK Bando, N Ichikuni, K Soga, K Kunimori, H Arakawa, K Asakura
    JOURNAL OF CATALYSIS 194 1 91 - 104 2000年08月 [査読有り][通常論文]
     
    The structure transformations of Rh particles in Rh ion-exchanged zeolite catalysts (RhY) and in Li-doped RhY catalysts (Li/RhY) were studied by means of EXAFS (extended X-ray absorption fine structure) in order to reveal the origin of the different CO2 hydrogenation catalyses of the two catalysts. CH4 was mainly produced from CO2 + H-2 on RhY, while CO was found on Li-doped RhY under similar reaction conditions. The geometric and electronic structure of Rh species in Y zeolite had little difference between the two catalysts before the reaction. However, EXAFS revealed that the structures of Rh species under the reaction conditions were quite different. During the reaction, we found disassembly of Rh particles in RhY, while Rh particles were stably present in Li/RhY. We discuss the different reaction mechanisms and catalytic properties of RhY and Li-doped RhY catalysts on the basis of their different dynamic structures which might be controlled by Li additive. (C) 2000 Academic Press.
  • T Shido, KAB Asakura, Y Noguchi, Y Iwasawa
    APPLIED CATALYSIS A-GENERAL 194 365 - 374 2000年03月 [査読有り][通常論文]
     
    Mo dimer oxy-carbide species were synthesized in the supercage of NaY zeolite by adsorption of Mo(CO)(6) vapor at saturation, followed by thermal decomposition in vacuum. TPD, EXAFS,: XPS and XRF data revealed that a Mo dimer was attached in a supercage by a saturation adsorption-thermal decomposition at 573 K and that up to four Mo dimers in a supercage were stepwisely formed without aggregation after four cycles, The Mo dimer oxy-carbide species exhibited a unique methanol decomposition reaction to produce CH4, CO2, and H-2 in an approximate ratio of 1 : 1 : 2. This reaction was characteristic of the Mo dimer oxy-carbide species and was never observed fbr other Mo species such as oxidized and reduced Mo species in NaY supercages. (C) 2000 Elsevier Science B.V. All rights reserved.
  • A Yamaguchi, T Shido, Y Inada, T Kogure, K Asakura, M Nomura, Y Iwasawa
    CATALYSIS LETTERS 68 3-4 139 - 145 2000年 [査読有り][通常論文]
     
    The time-resolved reduction process of copper cations in/on ZSM-5 during temperature-programmed reduction (300-700 K) was studied by energy-dispersive X-ray absorption fine structure (DXAFS) as well as transmission electron microscopy (TEM). Two Cu-ZSM-5 samples with different Cu loadings were prepared by an ion-exchange method. The Cu K-edge DXAFS spectra for isolated Cu2+ species in the channels of ZSM-5 and CuO particles on the outer surfaces of ZSM-5 were recorded at an interval of 1 s during the reduction. The curve fitting analysis of the EXAFS data and the XANES analysis revealed that the isolated Cu2+ species in the channels were reduced stepwise. They were reduced to isolated Cu+ species at 400-450 K and the Cu+ species to Cu-0 metallic clusters at 550-650 K. Small clusters like Cu-4 were initially formed, followed by particle growth. A small part of them went out to the outer surfaces of ZSM-5 during the reduction. In contrast, CuO particles on the outer surfaces were reduced directly to Cu-0 metallic particles around 450 K.
  • K Asakura, WJ Chun, Y Iwasawa
    TOPICS IN CATALYSIS 10 3-4 209 - 219 2000年 [査読有り][通常論文]
     
    We review recent development of a polarization-dependent total-reflection fluorescence EXAFS technique applied to Co3O4/Al2O3(0001), Pt/Al2O3(0001), and Mo/TiO2(110). We would like to stress that the polarization-dependent total-reflection fluorescence EXAFS has become a practical tool for a characterization of three-dimensional local structure of active sites in model supports.
  • T Inoue, ST Oyama, H Imoto, K Asakura, Y Iwasawa
    APPLIED CATALYSIS A-GENERAL 191 1-2 131 - 140 2000年01月 [査読有り][通常論文]
     
    Characterization and catalytic performance of modified Pt on SbOx for the selective oxidation of i-C4H10 and i-C4H8 to methacrolein are summarized and reconsidered in this paper. XRD revealed that the main oxide phase in Pt/SbOx catalysts under the reaction conditions was Sb6O13, while Raman spectroscopy also indicated the presence of small alpha-Sb2O3 crystallites (senarmontite), forming on or around Pt particles, with small highly dispersed O = SbOy decorating the Pt surface. These species were responsible for breaking up large Pt ensembles and suppressing the total oxidation reaction. Synergistic combination of the modified Pt and the defect pyrochlore-type Sb6O13 was essential for the selective oxidation of i-C4H10. (C) 2000 Elsevier Science B.V. All rights reserved.
  • YZ Yuan, K Asakura, HL Wan, K Tsai, Y Iwasawa
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 72 12 2643 - 2653 1999年12月 [査読無し][通常論文]
     
    The adsorption of CO and H-2 on a SiO2-supported Au6Pt cluster [(AuPPh3)(6)Pt(PPh3)](NO3)(2) (1) has been studied by means of FTIR, TPD, and EXAFS. CO adsorbed on 1/SiO2 to form a CO-adduct complex, which exhibited an IR band at ca. 1972 cm(-1). The adsorbed CO was desorbed below 403 K, showing a peak maximum at 363 K in TPD. There was little change in the coordination number of Pt-Au in Pr L-3-edge EXAFS upon CO adsorption, but the coordination number of Au-Au in Au L-3-edge EXAFS slightly increased and the peak ascribed to Pt-(Au)-P in the Pr L-3-edge EXAFS Fourier transform remarkably increased. The increase in the intensity of the Pt-(Au)-P peak was interpreted by the multiple scattering effect owing to the change of Pt-Au-P bond angle. The original EXAFS oscillations at both Pt and Au L-3-edges were regenerated after evacuation of the CO-adsorbed sample for 2 h at 353 K, indicating the recovery of the original cluster structure. This is entirely different from the case of the cluster 1 in solution, where the cluster framework is fragmented by the CO adsorption-desorption process. The adsorption of H-2 on 1/SiO2 was totally reversible at room temperature: it provided no contribution to the EXAFS oscillation.
  • YZ Yuan, K Asakura, HL Wan, K Tsai, Y Iwasawa
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 72 12 2643 - 2653 1999年12月 [査読有り][通常論文]
     
    The adsorption of CO and H-2 on a SiO2-supported Au6Pt cluster [(AuPPh3)(6)Pt(PPh3)](NO3)(2) (1) has been studied by means of FTIR, TPD, and EXAFS. CO adsorbed on 1/SiO2 to form a CO-adduct complex, which exhibited an IR band at ca. 1972 cm(-1). The adsorbed CO was desorbed below 403 K, showing a peak maximum at 363 K in TPD. There was little change in the coordination number of Pt-Au in Pr L-3-edge EXAFS upon CO adsorption, but the coordination number of Au-Au in Au L-3-edge EXAFS slightly increased and the peak ascribed to Pt-(Au)-P in the Pr L-3-edge EXAFS Fourier transform remarkably increased. The increase in the intensity of the Pt-(Au)-P peak was interpreted by the multiple scattering effect owing to the change of Pt-Au-P bond angle. The original EXAFS oscillations at both Pt and Au L-3-edges were regenerated after evacuation of the CO-adsorbed sample for 2 h at 353 K, indicating the recovery of the original cluster structure. This is entirely different from the case of the cluster 1 in solution, where the cluster framework is fragmented by the CO adsorption-desorption process. The adsorption of H-2 on 1/SiO2 was totally reversible at room temperature: it provided no contribution to the EXAFS oscillation.
  • K Asakura, H Nagahiro, N Ichikuni, Y Iwasawa
    APPLIED CATALYSIS A-GENERAL 188 1-2 313 - 324 1999年11月 [査読有り][通常論文]
     
    We have investigated the structure of Pt(A)/MgO and PtMo6/MgO catalysts which were prepared from Pt(C5H7O2)(2) and [PtMo6O24](8-) followed by calcination, respectively, and their catalytic activities for the propane + O-2 reaction. The Pt(A)/MgO and PtMo6/MgO catalysts with atomically dispersed Pt ions were found to be as active as metallic Pt particles supported on MgO for propane combustion. A distorted spinel-like structure around Pt ion embedded at the MgO surface was proposed for the active Pt species by means of EXAFS. The atomically dispersed Pt structure was reduced with propane at 623 K to form Pt-6 clusters with Pt-O bonding to the MgO support. The Pt cluster chemically attached to the MgO surface was selective for the propane dehydrogenation. Restructuring of the Pt clusters to the atomically dispersed Pt structure was observed by oxidation with O-2 at 623 K. (C) 1999 Elsevier Science B.V. All rights reserved.
  • A Yamaguchi, K Asakura, Y Iwasawa
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 146 1-2 65 - 76 1999年10月 [査読有り][通常論文]
     
    This paper attempts to extend our previous studies on the chemical design and characterization of attached metal atoms at surfaces of a Nb/SiO(2) catalysts prepared by using a suitable metal-complex precursor and the elucidation of catalytic reaction mechanisms in a molecular scale. The paper also reports a new aspect of catalysis on a Co/Al(2)O(3) catalyst which includes surface catalytic reactions assisted by gas phase molecules undetectable at the surface. On the basis of this concept, one may design new catalytic systems where the reaction intermediates, stable and unreactive in vacuum, can be activated or controlled by gas phase molecules in situ under catalytic reaction conditions. (C) 1999 Elsevier Science B.V. All rights reserved.
  • H Liu, AI Kozlov, AP Kozlova, T Shido, K Asakura, Y Iwasawa
    JOURNAL OF CATALYSIS 185 2 252 - 264 1999年07月 [査読有り][通常論文]
     
    The active oxygen species and mechanism for catalytic CO oxidation with O-2 on a highly active TiO2-supported Au catalyst (denoted as Au/Ti(OH)(4)*), which was prepared by supporting a Au-phophine complex on as-precipitated wet titanium hydroxide followed by calcination at 673 K, have been studied by means of oxygen isotope exchange, O-2 temperature-programmed desorption (O-2 TPD), electron spin resonance (ESR), and Fourier-transformed infrared spectroscopy (FT-IR). Surface lattice oxygen atoms on the Au/Ti(OH)(4)* catalyst were inactive for oxygen exchange with O-2 and CO and also for CO oxidation at room temperature. The surface lattice oxygen atoms were exchanged only with the oxygen atoms of CO2, probably via carbonates. O-2 did not dissociate to atomic oxygen on the catalyst. The catalyst showed a paramagnetic signal at g = 2.002 due to unpaired electrons trapped at oxygen vacancies mainly at the surface. O-2 adsorbed on the oxygen vacancies to form superoxide O-2(-) with g(1) = 2.020, g(2) = 2.010, and g(3) = 2.005, which are characteristic of O-2(-) with an angular arrangement. Upon CO exposure, all the adsorbed oxygen species disappeared. The adsorbed oxygen on Au/Ti(OH)(4)* desorbed below 550 K. O-2(-) species were also observed on TiO2* prepared by calcination of as-precipitated wet titanium hydroxide at 673 K, but were unreactive with CO. FT-IR spectra revealed that CO reversibly adsorbed on both Au particles and Ti4+ sites on the Au/Ti(OH)(4)* surface. No band for adsorbed CO was observed on the TiO2*, which indicates that the presence of Au particles has a profound effect on the surface state of Ti oxide. No shifts of vco peaks on Au/Ti(OH)(4)* occurred upon O-2 adsorption, suggesting that O-2 was not directly bound to the An particles on which CO adsorbed. Annealing of Au/Ti(OH)(4)* under O-2 atmosphere significantly suppressed the O-2 adsorption and the CO oxidation due to a decrease in the amount of oxygen vacancies, while CO adsorption was not affected by annealing. From the systematic oxygen isotope exchange experiments along with O-2-TPD, ESR, and FT-IR, it is most likely that CO adsorbed on Au metallic particles and O-2(-) adsorbed on oxygen vacancies at the oxide surface adjacent to the Au particles contribute to the low-temperature catalytic CO oxidation. The mechanism for the catalytic CO oxidation on the active Au/Ti(OH)(4)* catalyst is discussed in detail and compared with mechanisms reported previously. (C) 1999 Academic Press.
  • K Fukui, K Asakura, K Niimi, Ishizue, I, H Nakagawa
    JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 101 299 - 302 1999年06月 [査読有り][通常論文]
     
    Absorption and luminescence spectra of amorphous CdI2 thin film were measured at liquid nitrogen temperature. Two emission bands were observed at 2.3 and 3.1 eV, and the intensity ratio between them depends on the excitation energy. The 3.1 eV emission is explained in terms of the MX6 model which explains the emission mechanism of the CdI2 crystal, but the other is not explained. (C) 1999 Elsevier Science B.V. All rights reserved.
  • Y Yamaguchi, S Takakusagi, Y Sakai, M Kato, K Asakura, Y Iwasawa
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 141 1-3 129 - 137 1999年05月 [査読有り][通常論文]
     
    We have developed a XPEEM (X-ray photoemission electron microscopy) for a new surface imaging. XPEEM is a PEEM using X-ray as an excitation source and installed with an energy filter to select an X-ray photoelectron peak specific to the target atoms. XPEEM can image the distribution of elements, chemical states and chemical species at the working surface in a mesoscopic scale. (C) 1999 Elsevier Science B.V. All rights reserved.
  • K Asakura, T Kubota, WJ Chun, Y Iwasawa, K Ohtani, T Fujikawa
    JOURNAL OF SYNCHROTRON RADIATION 6 6 439 - 441 1999年05月 [査読有り][通常論文]
     
    Pt L-3-edge XANES spectra were measured on the inorganic oxide-supported Pt small particles with and without adsorbed hydrogen. A peak about 8 eV above the edge appeared in the difference spectra between the Pt samples with and without hydrogen adsorption. The peak position in difference spectra was invariant with the particle sizes, the amount of adsorbed hydrogen and coadsorbates, and kind of supports. The peak intensity was only proportional to the amount of adsorbed hydrogen. Multiple scattering calculation could reproduce the peak induced by the hydrogen adsorption and showed the peak energy was independent of the number and the adsorption site of hydrogen on Pt surface. The Pt L-3-edge XANES will be a good tool for the quantitative analysis of the adsorbed hydrogen on small metal Pt particles.
  • RS Mulukutla, K Asakura, T Kogure, S Namba, Y Iwasawa
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 1 8 2027 - 2032 1999年04月 [査読有り][通常論文]
     
    Rhodium-containing MCM-41 mesoporous molecular sieves (RhMlCM-41) were synthesized by adding RhCl3 . 3H(2)O to a mixed silicate-surfactant gel prior to hydrothermal synthesis. The obtained Rh-MCM-41 samples were characterized by XRD, N-2 adsorption, TEM, Si-29 solid-state NMR and XPS. It was found that rhodium oxide nanoparticles <3 nm were located in the MCM-41 mesopore channels or 6 nm rhodium oxide particles were dispersed in the MCM-41 matrices, depending on the hydrothermal synthesis temperature and the aging conditions. The unit eel and pore wall thickness of Rh-MCM-41 synthesized at 423 K were 5.71 and 2.31 nm, respectively, which were larger than those of the corresponding pure Si-MCM-41. The increase in the pore wall thickness may be due to enhancement of cross-linking of =Si-OH in the silicate gel by the presence of Rh ions.
  • T Kubota, Y Kitajima, K Asakura, Y Iwasawa
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 72 4 673 - 681 1999年04月 [査読有り][通常論文]
     
    We measured Pd Ls-edge X-ray absorption near-edge structure (XANES) spectra for small Pd particles dispersed on inorganic oxide supports (SiO2 and Al2O3) and the spectra changes induced by the adsorption and the absorption of hydrogen. When the XANES spectra were measured under the atmosphere of H-2 a new peak appeared at about 8 eV above the inflection point of the absorption edge. The peak position was invariant but its intensity decreased with the decrease of Pd particle size. This peak is caused by hydrogen absorption in the Pd particles. Hydrogen at the subsurface region little affected the Pd L-3-edge XANES spectra. A new peak also appeared for the Pd sample accompanied with hydrogen adsorbed on the surface. The peak energy relative to the edge was independent of the Pd particle size and the peak intensity increased with the amount of adsorbed hydrogen. The XANES spectra can quantify the adsorbed and absorbed hydrogen atoms. We presented a model of Pd particles composed of surface, subsurface and bulk atoms.
  • K Asakura, Y Noguchi, Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B 103 7 1051 - 1058 1999年02月 [査読有り][通常論文]
     
    Mo dimers were prepared in the supercage of NaY zeolite by cycles of saturated adsorption of Mo(CO)(6) at room temperature and subsequent thermal decomposition at 573 K. The obtained samples were characterized by temperature-programmed desorption, extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectra, and X-ray fluorescence. Two Mo(CO)(6) molecules per supercage were immobilized in each process. After the thermal decomposition of the adsorbed Mo(CO)(6) in the supercage, the resultant Mo(1)/NaY could accept two more Mo(CO)(6) molecules per supercage. Mo loading was found to increase linearly by two Mo(CO)(6) molecules in a supercage per one deposition cycle, and was saturated with eight Mo atoms per supercage after the four cycles. EXAFS analysis revealed that Mo(II) oxocarbide dimer species [Mo-2(C)(O)(x)] with the Mo-Mo distance of 0.285 nm was formed in the supercage by the 573 K thermal decomposition of the adsorbed Mo(CO)(6). The structures of Mo oxocarbide dimers were invariant regardless of the Mo loading.
  • K Asakura, Y Noguchi, Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B 103 7 1051 - 1058 1999年02月 [査読有り][通常論文]
     
    Mo dimers were prepared in the supercage of NaY zeolite by cycles of saturated adsorption of Mo(CO)(6) at room temperature and subsequent thermal decomposition at 573 K. The obtained samples were characterized by temperature-programmed desorption, extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectra, and X-ray fluorescence. Two Mo(CO)(6) molecules per supercage were immobilized in each process. After the thermal decomposition of the adsorbed Mo(CO)(6) in the supercage, the resultant Mo(1)/NaY could accept two more Mo(CO)(6) molecules per supercage. Mo loading was found to increase linearly by two Mo(CO)(6) molecules in a supercage per one deposition cycle, and was saturated with eight Mo atoms per supercage after the four cycles. EXAFS analysis revealed that Mo(II) oxocarbide dimer species [Mo-2(C)(O)(x)] with the Mo-Mo distance of 0.285 nm was formed in the supercage by the 573 K thermal decomposition of the adsorbed Mo(CO)(6). The structures of Mo oxocarbide dimers were invariant regardless of the Mo loading.
  • Yamaguchi, Y., Takakusagi, S., Sakai, Y., Kato, M., Asakura, K., and Iwasawa, Y. : “X-ray Photoemission Electron Microscopy (XPEEM) as a New Promising Tool for the Real-Time Chemical Imaging of Active Surfaces”, J. Mol. Catal., 141 : 129-137 (1999) *
    1999年 [査読無し][通常論文]
  • Kubota, T., Kitajima, Y., Asakura, K., and Iwasawa, Y. : “Pd L3-edge XANES Spectra of SiO2-Supported Pd Small Particles and their Change Induced by Hydrogen Adsorption and Absorption”, Bull. Chem. Soc. Jpn., 72 : 673-681 (1999) *
    1999年 [査読無し][通常論文]
  • Asakura, K., Noguchi, Y., and Iwasawa, Y. : “XAFS Studies on the Structure of Mo Species in NaY Zeolite Derived from Mo(CO)6”, Jpn. J. Appl. Phys., 38 Suppl. 38-1 : 85-86 (1999) *
    1999年 [査読無し][通常論文]
  • Kozlova, A. P., Kozlov, A. I., Sugiyama, S., Matsui, Y., Asakura, K., and Iwasawa, Y. : “Study of Au Species in Tremendously Active Au Catalysts Derived from Au-Phosphine Complex Au(PPh3)(NO3) and As-Precipitated Wet Fe(OH)3*”, J. Catal., 181 : 37-48 (・・・
    1999年 [査読無し][通常論文]
     
    Kozlova, A. P., Kozlov, A. I., Sugiyama, S., Matsui, Y., Asakura, K., and Iwasawa, Y. : “Study of Au Species in Tremendously Active Au Catalysts Derived from Au-Phosphine Complex Au(PPh3)(NO3) and As-Precipitated Wet Fe(OH)3*”, J. Catal., 181 : 37-48 (1999) *
  • Bando, K. K., Ichikuni, N., Arakawa, H., and Asakura, K. : “EXAFS Observation of Li Additive Effect on Structure of Rh Particles Supported on Zeolite”, Jpn. J. Appl. Phys., 38 Suppl.38-1 : 81-84 (1999) *
    1999年 [査読無し][通常論文]
  • Mulukutla, R. S., Asakura, K., Kogure, T., Namba, S., and Iwasawa, Y. : “Synthesis and Characterization of Rh2O3 Nanoparticles in Mesoporous MCM-41”, Phys. Chem. Chem. Phys., 1 : 2027 (1999) *
    1999年 [査読無し][通常論文]
  • Yamaguchi, A., Asakura, K., and Iwasawa, Y. : “A new Aspect of Catalysis at Designed Surfaces: the Role of Gas Phase Molecules in Surface Catalytic Reactions”, J. Mol. Catal., 146 : 65-76 (1999) *
    1999年 [査読無し][通常論文]
  • Asakura, K., Chun, W.-J., and Iwasawa, Y. : “Anisotropic Arrangement of Mo Species Highly Dispersed on TiO2 (110) Surface Demonstrated by Polarization Dependent Total Reflection Fluorescence EXAFS”, J. J. Appl. Phys., 38 Suppl. 38-1 : 40-43 (1999) *
    1999年 [査読無し][通常論文]
  • Asakura, K., Nagahiro, H., Ichikuni, N., and Iwasawa, Y. : “Structure and Catalytic Combustion Activity of Atomically Dispersed Pt Species at MgO Surface”, Appl. Catal., 188 : 313-324 (1999) *
    1999年 [査読無し][通常論文]
  • Asakura, K., Kubota, T., Chun, W.-J., Iwasawa, Y., Ohtani, K., and Fujikawa, T. : “Pt L3-edge XANES Studies about the Hydrogen Adsorption on Small Pt Particles”, J. Synchrotoron Rad., 6 : 439-441 (1999) *
    1999年 [査読無し][通常論文]
  • Kozlov, A., Kozlov, A. a, Asakura, K., and Iwasawa, Y. : “Zeolite-Encapsulated V(V) Picolinate Peroxo Complexes Active for Catalytic Hydrocarbon Oxidations”, J. Mol. Catal., 137 : 223-237 (1999) *
    1999年 [査読無し][通常論文]
  • A Kozlov, A Kozlova, K Asakura, Y Iwasawa
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 137 1-3 223 - 237 1999年01月 [査読有り][通常論文]
     
    Zeolite-encapsulated vanadium (IV) picolinate complexes were prepared by treatment of dehydrated VO(2+)-NaY zeolite with molten picolinic acids. Treatment of the NaY-encapsulated VO(pic)(2) complex with urea hydrogen peroxide adduct in acetonitrile allowed to generate peroxovanadium species. The structure of vanadium peroxo species was studied by UV-vis, Raman and XAFS spectroscopies which suggested the formation of monoperoxo monopicolinate complex which could be active intermediate for various oxidation reactions with the catalysts. To elucidate effect of the encapsulation on catalytic performance, the catalytic properties of the encapsulated complexes were compared with that of corresponding homogeneous catalyst H[VO(O-2)(pic)(2)]. H2O. The novel 'ship-in-a-bottle' catalysts retain solution-like activities in aliphatic and aromatic hydrocarbon oxidations as well as in alcohol oxidation. In addition, the encapsulated vanadium picolinate catalysts showed a number of distinct features such as preferable oxidation of smaller substrates in competitive oxidations, increased selectivity of the oxidation of terminal CH3- group in isomeric octanes and preferable (sometimes exclusive) formation of alkyl hydroperoxides in alkane oxidations. The distinct features were explained in terms of intrazeolitic location of the active complexes that imposed transport discrimination and substrate orientation. On the basis of the experimental data, a possible mechanism was discussed. Stability of the vanadium complexes during the liquid phase oxidations and leaching from the NaY zeolite matrix were also examined. (C) 1999 Elsevier Science B.V. All rights reserved.
  • K Asakura, Y Noguchi, Y Iwasawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 38 38 85 - 86 1999年 [査読有り][通常論文]
     
    We carried out XAFS characterization on Mo species in the supercage which was prepared in the supercage of NaY zeolite by cycles of saturation adsorption of Mo(CO)(6) at room temperature and subsequent thermal decomposition at 573 K. XAFS analysis revealed that Mo dimer with the Mo-Mo distance of 0.285 nm was formed in the supercage, the structure of which was unchanged during the saturation adsorption/thermal decomposition cycles.
  • AP Kozlova, AI Kozlov, S Sugiyama, Y Matsui, K Asakura, Y Iwasawa
    JOURNAL OF CATALYSIS 181 1 37 - 48 1999年01月 [査読有り][通常論文]
     
    Iron-oxide-supported gold catalysts were prepared by supporting a Au phosphine complex Au(PPh3)(NO3) on as-precipitated wet iron hydroxide Fe(OH)(3)*, followed by temperature-programmed calcination. The Au/Fe(OH); catalysts calcined at the temperatures 573-773 K showed extremely high catalytic performance for CO oxidation at temperatures as low as 203-253 K. Interaction of the Au(PPh3)(NO3) gold precursor with the Fe(OH)(3)* upon supporting, transformation of the precursor during the heat treatments, and state of the gold in the catalysts were studied by FT-IR, XRD, TEM, XPS, and EXAFS. The gold precursor dissociated on the Fe(OH)(3)* surface to produce [Au(PPh3)](+) species which partially decomposed at 473 K and was transformed to small gold metallic particles with coordination numbers of 7.4-8.0 for Au-Au bond at calcination temperatures greater than or equal to 573 K. In contrast, decomposition of the gold complex over crystalline Fe2O3* resulted in large gold particles. The Au/Fe2O3* sample was inactive at 203-253 K and exhibited very low activity for CO oxidation at room temperature. The efficiency of the as-precipitated wet Fe(OH)(3)* as a support is explained in terms of a higher stability of [Au(PPh3)](+) on the Fe(OH)(3)* as compared to the Fe2O3* due to more effective interaction of the Au species with OH groups and defects of the amorphous Fe(OH)(3)* surface. The results demonstrate the importance of support-metal precursor interactions, both upon supporting and during calcination, in the formation of highly active catalysts with small Au particles for low-temperature CO oxidation. (C) 1999 Academic Press.
  • P. Lu, T. Teranishi, K. Asakura, M. Miyake, N. Toshima
    Journal of Physical Chemistry B 103 44 9673 - 9682 1999年 [査読有り][通常論文]
  • KK Bando, N Ichikuni, H Arakawa, K Asakura
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 38 38 81 - 84 1999年 [査読有り][通常論文]
     
    The Rh ion-exchanged zeolite catalyst (RhY) shows extraordinarily high activity for CO2 conversion and the main product was methane. When we doped Li into RhY (Li/RhY), the main product drastically changed from methane to CO and promotion of ethanol formation was observed. In this work, we observed EXAFS spectra for RhY and Li/RhY and elucidated the structural difference between them, in order to reveal the origin of the different catalyses toward CO2 hydrogenation. We found disassembly and re-assembly of Rh particles in RhY during the reaction where Rh atoms could easily move around the pore and external surface of zeolite. On the other hand, the Rh atoms in Li/RhY were tightly bound in the Rh particles under the influence of Li additive and the Rh atoms kept their structure unchanged during the reaction. It was suggested that the difference in catalytic reactivity was due to that in the mobility of Rh particles.
  • K Asakura, WJ Chun, Y Iwasawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 38 38 40 - 43 1999年 [査読有り][通常論文]
     
    Mo species on TiO2(110) surface were studied by means of Polarization Dependent Total Reflection Fluorescence EXAFS. The structure and orientation of Mo species are strongly affected by the pretreatment conditions and impurity. Mo dimer oriented to [1<1(1)over bar 0 >] direction and Mo chain structure along [001] are present when they are prepared under oxidative conditions and reductive conditions, respectively. On the other hand, Mo tetrahedral monomer is formed when Na+ and K+ are present on the surface.
  • WJ Chun, K Asakura, Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B 102 45 9006 - 9014 1998年11月 [査読有り][通常論文]
     
    The structure of well-dispersed Mo oxides on TiO2( 110) was investigated by means of polarization-dependent total-reflection fluorescence X-ray absorption fine structure (PTRF-EXAFS) in three different directions of the single-crystal surface. A model sample for supported Mo oxide catalysts was prepared by impregnation of (NH4)(6)Mo7O24. 4H(2)O dissolved in ultrapure water, followed by calcination at 773 K. Direct comparison of the observed EXAFS and the calculated one was performed based on three-dimensional model structures. We found that anisotropic Mo dimers were preferentially formed on the TiO2(110) surface, with Mo-Mo distance (0.335 nm) parallel to the [1(1) over bar 0] direction of the surface. It was also found that the Mo dimers were attached to the surface, showing Mo-Ti (interfacial) distance at 0.296 nm.
  • J Lauterbach, K Asakura, PB Rasmussen, HH Rotermund, M Bar, MD Graham, IG Kevrekidis, G Ertl
    PHYSICA D 123 1-4 493 - 501 1998年11月 [査読有り][通常論文]
     
    The effect of well-defined palladium boundaries on the formation of reaction-diffusion patterns during the oxidation of CO on Pt(1 1 0) has been investigated. The Pd boundaries were created by microlithography technique. Reaction-diffusion patterns formed on this surface were observed by photoemission electron microscopy (PEEM). On a multilayer Pd-covered Pt(1 1 0) surface, depending on the partial pressures, Pd areas may act as a reservoir of CO for adjacent Pt regions. Therefore, patterns forming on the bare Pt areas exhibit a pronounced interaction with the artificial Pt/Pd boundaries. Copyright (C) 1998 Elsevier Science B.V.
  • HC Liu, T Hirota, K Asakura, Y Iwasawa
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS 94 17 2639 - 2646 1998年09月 [査読有り][通常論文]
     
    The effect of H(2)O vapor on the oxygen isotope exchange between (18)O(2) and surface lattice oxygen (16)O* on a Pt(4+)/MgO catalyst that was prepared by using Pt(acac)(2) as a precursor has been systematically investigated in the temperature range 423-573 K for the first time. The oxygen isotope exchange on the Pt(4+)/MgO catalyst with isolated Pt(4+) ions embedded at the top-layer lattice of MgO proceeded, whereas the oxygen isotope exchange on a conventional Pt(0)/MgO catalyst with metallic Pt particles (1.9 nm in size) did not proceed under similar conditions. It was found that the presence of H(2)O vapor increased the oxygen exchange rate by about a factor of ten. Both the single oxygen exchange, (18)O(2) + (16)O* --> (18)O (16)O + (18)O*, and the multiple oxygen exchange, (18)O(2) + 2 (16)O* --> (16)O(2) + 2 (18)O*, were promoted by H(2)O. The multiple oxygen exchange reaction proceeded only in the presence of H(2)O. The H(2)(18)O molecules readily dissociate to form hydroxyl groups on Pt(4+)/MgO and exchange with surface lattice (16)O* atoms to form H(2)(16)O molecules. In the presence of water vapor, surface lattice oxygen atoms and hydroxyl groups may be active oxygen species for oxygen exchange with gaseous oxygen. The adsorbed water (hydroxyl groups) activates the surface lattice oxygen atoms of Pt(4+)/MgO, where about four lattice oxygen atoms per Pt(4+) ion can be exchanged with gaseous oxygen. The H(2)O-promoted oxygen isotope exchange may proceed on surface defects on Pt(4+)/MgO.
  • WJ Chun, K Asakura, Y Iwasawa
    CATALYSIS TODAY 44 1-4 309 - 314 1998年09月 [査読有り][通常論文]
     
    The surface structure analysis of a model catalyst MoOx/TiO2(110) was for the first time performed by polarization-dependent total-reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) in three different directions of the crystal surface. Two samples of MoOx/TiO2(110) were prepared by an impregnation of (NH4)(6)Mo7O24. 4H(2)O using ultra high purity water and normal distilled water. The PTRF-XAFS analysis revealed that anisotropic Mo dimer species was preferentially formed on the TiO2(110) surface, with Mo-Mo bond (0.335 nm) parallel to the [1 (1) over bar 0] direction when the ultra high purity water was used as the solvent. On the other hand, the Mo oxide on the surface prepared using normal distilled water had a symmetric tetrahedral structure (MoO4) with Mo-O of 0.176 nm, which was due to the coexistence of alkaline metals at the surface. (C) 1998 Elsevier Science B.V. All rights reserved.
  • YZ Yuan, K Asakura, AP Kozlova, HL Wan, KR Tsai, Y Iwasawa
    CATALYSIS TODAY 44 1-4 333 - 342 1998年09月 [査読有り][通常論文]
     
    Supported gold catalysts derived from interaction of a Au-phosphine complex Au(PPh3)(NO3) (1) with conventional titanium oxide TiO2 and as-precipitated titanium hydroxide Ti(OH)(4)* (*, as-precipitated) have been characterized by means of XRD, XPS, EXAFS, and P-31 CP/MAS-NMR. The Au complex 1 was supported on TiO2 and Ti(OH)(4)* without loss of Au-P bonding at room temperature. The Au complex 1 on TiO2 was readily and completely decomposed to form metallic gold particles by calcination at 473 K, whereas only a small part of the complex 1 on Ti(OH)(4)(*) was transformed to metallic gold particles. By calcination of 1/Ti(OH)(4)* at 573 K the formation of both metallic gold particles and crystalline titanium oxides became notable as evidenced by XRD, XPS and P-31 CP/MAS-NMR. The mean diameter of Au particles in 1/Ti(OH)(4)* calcined at 673 K was less than 30 Angstrom as estimated from Au(2 0 0) diffraction, which was about one-tenth of that for the corresponding 1/TiO2, Thus the as-precipitated titanium hydroxide Ti(OH)(4)* was able to stabilize the Au complex 1 to lead to the simultaneous decomposition of Au complex and Ti(OH);. The catalyst 1/Ti(OH)(4)* calcined at 673 K afforded remarkably high catalytic activity for low-temperature CO oxidation at 273-373 K as compared to the catalyst 1/TiO2. (C) 1998 Elsevier Science B.V. All rights reserved.
  • RS Mulukutla, K Asakura, S Namba, Y Iwasawa
    CHEMICAL COMMUNICATIONS 14 1425 - 1426 1998年07月 [査読有り][通常論文]
     
    Nanosized rhodium oxide-containing MCM-41 (Rh-MCM-41) mesoporous molecular sieves are synthesized and characterized by XRD, TEM, N-2 adsorption, NMR, XPS and EXAFS.
  • K Ohtani, T Fujikawa, T Kubota, K Asakura, Y Iwasawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 37 7 4134 - 4139 1998年07月 [査読有り][通常論文]
     
    Recent studies on Pd Lj-edge X-ray absorption near edge structure (XANES) spectra for pure small Pd clusters show that the spectra are strongly influenced by hydrogen adsorption and absorption, in this paper, the full multiple scattering method is applied to study the difference in measured spectra. The calculated XANES spectra are not so sensitive to the detailed positions and the electronic structures of the interacting hydrogen atoms, however they are sensitive to the induced structural and electronic state change in the host small Pd clusters. The size effect on the peak at similar to 7 eV from the edge is well explained by the induced lattice expansion after hydrogen absorption.
  • AP Kozlova, S Sugiyama, AI Kozlov, K Asakura, Y Iwasawa
    JOURNAL OF CATALYSIS 176 2 426 - 438 1998年06月 [査読有り][通常論文]
     
    Iron oxide supported gold catalysts were prepared by supporting the Au-phosphine complex Au(PPh3)(NO3) onto various iron oxide supports. Among the prepared catalysts only the use of amorphous as-precipitated iron hydroxide Fe(OH)(3)* as a support for Au(PPh3)(NO3) allowed us to obtain the tremendously active catalytic material for low-temperature CO oxidation. The supports and the Au catalysts were characterized by BET, SEM, XRD, FT-IR, XPS, and Raman. Initial structures of the employed supports were found to influence dramatically the gold particle size and the catalytic activity. The most active catalyst consisted of small gold particles and poorly crystallized iron oxide support with a mixture of alpha-Fe2O3 and gamma-Fe2O3. The gamma-Fe2O3 formation occurred by the presence of the PPh3 as a ligand for gold. The presence of gamma-Fe2O3 influenced positively the catalytic activity of the Au-containing samples. (C) 1998 Academic Press.
  • K Okumura, K Asakura, Y Iwasawa
    LANGMUIR 14 13 3607 - 3613 1998年06月 [査読有り][通常論文]
     
    GeO2 sub-monolayers on SiO2 surfaces were prepared by the chemical vapor deposition (CVD) reaction of Ge(OMe)(4) with OH groups on SiO2 at 393 K. followed by calcination at 693 K. The characterization of the obtained GeO2/SiO2 was conducted by FT-IR, XRD, and EXAFS. Isolated OH groups on SiO2 preferentially reacted with Ge(OMe)(4). The Si-OH peak was significantly depleted by the CVD reaction of Ge(OMe)4 and partially reappeared to half of the original Si-OH peak after calcination. The linear increase of the Ge-OH peak and the linear decrease of the Si-OH peak with increased Ge loading suggest a monolayer growth of GeO2. The coverage of GeO2 at saturation for the sample prepared by the one-cycle CVD process was estimated to be 1/5 monolayer of the SiO2 surface, which corresponds to 7.4 wt % Ge loading. There existed only isolated Ge-OH groups on the GeO2 layers, which is contrasted to the case of bulk GeO2, which shows both isolated and hydrogen-bonded OH groups. The surface of the GeO2 layers on SiO2 has no acidic character, whereas GeO2/Al2O3 showed both Bronsted and Lewis acid sites. EXAFS spectra showed a significantly lower Ge-Ge signal compared with that for bulk GeO2. The local structure around Ge in GeO2/SiO2 was determined to be similar to hexagonal type GeO2.
  • A Kozlov, K Asakura, Y Iwasawa
    MICROPOROUS AND MESOPOROUS MATERIALS 21 4-6 571 - 579 1998年05月 [査読有り][通常論文]
     
    Encapsulated vanadium complexes with various pyridine-2-carboxylic acids and Schiff bases were synthesized from a dehydrated form of VO(2+)-NaY zeolite by a flexible ligand method and a template synthesis method. It was suggested by X-ray powder diffraction and X-ray photoelectron spectroscopy that the complexes were located in the zeolite supercages. Detailed characterization of the vanadium species was performed by XAFS, FT-IR, ESR and UV-vis spectroscopies in comparison with the corresponding free complexes and reference samples prepared by an impregnation method. Difference in spectroscopic features of the encapsulated and impregnated VO(pic), samples was explained in terms of coordination of zeolite -OH groups to the vanadium complexes. The encapsulated vanadium complexes were active for catalytic selective oxidation of hydrocarbons with H2O2 and t-BuOOH. (C) 1998 Elsevier Science B.V. All rights reserved.
  • WJ Chun, K Asakura, Y Iwasawa
    CHEMICAL PHYSICS LETTERS 288 5-6 868 - 872 1998年05月 [査読有り][通常論文]
     
    We have carried out the three-dimensional structure analysis for Mo oxides on TiO2(110) using total-reflection fluorescence EXAFS (extended X-ray absorption fine structure) in three different directions of the polarized vector of the incident X-rays parallel to the [1(1) over bar 0], [001] and [110] directions of the TiO2(110) plane. It is concluded that the Mo dimer species are selectively formed on the surface, with the Mo-Mo bond (0.335 nm) parallel to the [1(1) over bar 0] direction and also with Mo-Ti(0.296 nm) and Mo-O(0.220 nm) interfacial bonds. (C) 1998 Elsevier Science B.V. All rights reserved.
  • Xu, X, YZ Yuan, K Asakura, Y Iwasawa, HL Wan, KR Tsai
    CHEMICAL PHYSICS LETTERS 286 1-2 163 - 170 1998年04月 [査読有り][通常論文]
     
    B3LYP studies have been performed on the phosphine-stabilized gold-platinum clusters by using model clusters such as [(AuPH3)(6)Pt(PH3)](2+) and [(AuPH3)(6)Pt(H-2)(PH3)](2+). Two stationary points have been located, one dihydrogen complex and the other dihydrido complex, which are the possible intermediates in the H-2-D-2 equilibration. Pt is characterized as being the active site, but Au atoms also play an important role in the activation of H-2. The electron transfer from the metal core to the sigma* anti-bonding orbital of H-2 not only activates the hydrogen molecule, but also induces large metal core movement which provides open Au sites for bonding of the second H-2 or D-2. (C) 1998 Elsevier Science B.V.
  • K Sayama, K Yase, H Arakawa, K Asakura, A Tanaka, K Domen, T Onishi
    JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY 114 2 125 - 135 1998年04月 [査読有り][通常論文]
     
    Both the structure of Pt-intercalated K4Nb6O17 catalyst and the photocatalytic activity on the water splitting in aqueous carbonate salt solution were studied using various kinds of analytical measurements such as FT-IR, EXAFS, TEM, SEM and TPR. K4Nb6O17 was the layered semiconductor which have two kinds of interlayer spaces (interlayers I and II), and it was found by FT-IR that the [Pt(NH3)(4)](2+) cation was preferentially intercalated only into the interlayer I of K4Nb6O17. Fine Pt metal particles less than 6 Angstrom (1 Angstrom=0.1 nm) were prepared homogeneously in the interlayer space I by the photoreduction method. By H-2 reduction, some Pt particles grew more than 15 Angstrom and contributed to the destruction of the layered sheet. The photocatalytic water splitting reaction occurred by the addition of carbonate salt in spite of the exposure of Pt on the outer surface of catalyst. The photocatalytic activity of the Pt/K4Nb6O17 prepared by the photoreduction was higher than that prepared by the H-2 reduction. The deactivation of the catalyst was not observed in the carbonate aqueous solution for long time. The reaction mechanism that the Pt particles in the interlayer I acted as H-2 evolution site and the O-2 evolved in the interlayer II was proposed. (C) 1998 Elsevier Science S.A. All rights reserved.
  • A Kozlov, K Asakura, Y Iwasawa
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS 94 6 809 - 816 1998年03月 [査読有り][通常論文]
     
    Encapsulated vanadium picolinic complexes have been synthesized by treatment of a dehydrated form of VO2+-NaY zeolite with molten picolinic acids and characterized by X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), X-ray absorption near-edge structure (XANES), EPR, FTIR and UV-VIS spectroscopies, and XRD. It was suggested by XRD and XPS that the complexes were located in the zeolite cavities. Differences in the spectroscopic properties of encapsulated and impregnated samples were explained in terms of coordination of vanadium complexes with zeolite -OH groups. The stability of VO(pic)(2) and its adduct with pyridine depended strongly on the complex location. The encapsulated vanadium picolinate complex retained solution-like activity in the liquid-phase oxidation of hydrocarbons and alcohols with hydrogen peroxide.
  • K Okumura, K Asakura, Y Iwasawa
    CATALYSIS TODAY 39 4 343 - 350 1998年03月 [査読有り][通常論文]
     
    Structures of Rh/l AL (atomic layer) GeO2/SiO2 were studied during reduction and oxidation processes by means of in situ XAFS (X-ray absorption fine structure). It was found that RhGe bimetallic particles with Rh-Rh and Rh-Ge distances at 0.266 and 0.242 nm were formed after reduction at 723 K, respectively. Subsequent oxidation at 673 K regenerated 1 AL GeO2 structure on the SiO2 surface. This reversible structure transformation is discussed in relation to reactivity and volatility of Ge oxide species. (C) 1998 Elsevier Science B.V.
  • Y Yamaguchi, WJ Chun, S Suzuki, H Onishi, K Asakura, Y Iwasawa
    RESEARCH ON CHEMICAL INTERMEDIATES 24 2 151 - 168 1998年 [査読有り][通常論文]
     
    This paper reports the visualization of mobile pyridine on the terraces and site-specific adsorption of pyridine on the particular step sites on a TiO2(110)-(1x1) surface by scanning tunneling microscopy (STM), the anisotropic structure and reactivity of molybdenum oxides dispersed on TiO2(110)-(1x1) characterized by polarization-dependent total-reflection fluorescence x-ray absorption fine structure (PTRF-EXAFS), and the energy dispersive and real-time images of Au mesh on Si(111) recorded by a new x-ray photoemission electron miscroscopy (XPEEM).
  • KK Bando, K Soga, K Kunimori, N Ichikuni, K Asakura, K Okabe, H Kusama, K Sayama, H Arakawa
    ADVANCES IN CHEMICAL CONVERSIONS FOR MITIGATING CARBON DIOXIDE 114 114 455 - 458 1998年 [査読有り][通常論文]
     
    Hydrogenation of CO2 over Rh ion exchanged zeolite catalysts (RhY) was studied. The RhY catalyst showed high activity for hydrogenation of CO2. The main product transformed from methane to CO and formation of ethanol was promoted in accordance with Li addition. Characterization of surface sites and adsorbed species was performed.
  • K Asakura, K Okumura, T Inoue, T Kubota, WJ Chun, Y Iwasawa
    RECENT ADVANCES IN CATALYTIC MATERIALS 497 99 - 108 1998年 [査読有り][通常論文]
     
    The catalytic interaction of noble metal and main group elements in Rh/one-atomic layer GeO2/SiO2 and Pt/SbOx was investigated. The high temperature reduction produced RhGe and PtSb bimetallic particles in which Pt and Rh were electronically modified to retard catalytic activity. However, unique selective catalyses of Ph/one-atomic layer GeO2/SiO2 for CO hydrogenation reaction to oxygenate compounds and for NO+CO reaction to N-2 were found. Under the low temperature reduction of Rh/one-atomic layer GeO2/SiO2 and the high temperature calcination of Pt/SbOx, the oxide phases, GeO2 and SbOx, were stable and the selective reduction of ethylacetate to ethanol and the selective oxidation of iso-C4H10 to methacrolein were observed. The high selectivities were ascribed to synergistic interaction between the noble metals and the main group element oxides through the diffusion of adsorbed species and reaction intermediates. The possibility of chemical control of noble metal-catalyses by main group elements is discussed.
  • T Inoue, K Asakura, W Li, ST Oyama, Y Iwasawa
    APPLIED CATALYSIS A-GENERAL 165 1-2 183 - 197 1997年12月 [査読有り][通常論文]
     
    New Pt/SbOx catalysts active for the selective oxidation of iso-C4H10 and iso-C4H8 to methacrolein were investigated by pulse reactivity measurements, X-ray diffraction (XRD) analysis, and Raman spectroscopy. XRD revealed that the main oxide phase in Pt/SbOx catalysts after calcination or reaction condition was Sb6O13 whereas Raman spectroscopy also showed the presence of Sb2O3 (senarmontite), As a result of the interaction between Pt and SbOx the total oxidation chemistry of Pt was shut down, and instead a selective oxidation behavior appeared. Investigation of iso-C4H8 oxidation by lattice oxygen in Pt/SbOx revealed that Pt was essential for SbOx to undergo redox cycles, and that without Pt, not much SbOx was reoxidized under reaction conditions. The overall results were consistent with small Sb2O3 oxide crystallites forming on or around Pt particles, with small highly dispersed antimony species, possibly O=SbOy decorating the surface. These species were responsible for breaking up large Pt ensembles and suppressing the total oxidation reaction. (C) 1997 Elsevier Science B.V.
  • K Okumura, K Asakura, Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B 101 48 9984 - 9990 1997年11月 [査読有り][通常論文]
     
    We prepared a new Rh/one-atomic-layer GeO2/SiO2 Catalyst by supporting Rh-6(CO)(16) precursor on the one-atomic-layer GeO2/SiO2. The obtained catalyst was active for conversion of ethyl acetate to ethanol by H-2 reduction under mild reaction conditions, Three different structures and chemical states of Rh species on the one-atomic-layer GeO2/SiO2, characterized by EXAFS, TPD, TEM, and FT-IR, were formed depending on the prereduction temperature, Rh carbonyl cluster, Rh metal, and RhGe alloy. The Rh atoms in the metallic stare were most active for the ethanol formation, The one-atomic-layer GeO2 was much more effective as support for the Rh metallic particles than three-dimensional GeO2-particles dispersed on SiO2. Rh/bulk-GeO2 and Rh/SiO2 were inactive for this reaction. Ethyl acetate dissociatively adsorbed on the one-atomic-layer GeO2, while hydrogen adsorbed on the Rh metallic particles. The present study exemplifies the advantageous applications of an inorganic oxide monolayer to preparation of supported metal catalysts.
  • K Ohtani, T Fujikawa, T Kubota, K Asakura, Y Iwasawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 36 10 6504 - 6510 1997年10月 [査読有り][通常論文]
     
    Recent experimental studies on the Pt L-edge X-ray absorption near edge structure (XANES) spectra of Pt clusters show that the spectra are greatly influenced by hydrogen adsorption. In this paper the full multiple scattering method, which we developed, is applied to study the difference in measured XANES spectra before and after the hydrogen adsorption. Hydrogen atoms are more plausible on adsorbed sites out of the cluster than on absorbed sites inside the cluster though the calculated spectra are not so sensitive to the adsorption sites. The adsorbed hydrogen atoms have rather negative charge due to the charge transfer from Pt atoms, In the charge transfer process Pt 6s (or 6p) electrons play a more important role than 5d electrons, Furthermore the small difference in the XANES spectra for Pt foil and small cluster is studied, and lye find that it is due to the large fraction of surface Pt atoms in the latter system.
  • T Inoue, K Asakura, Y Iwasawa
    JOURNAL OF CATALYSIS 171 2 457 - 466 1997年10月 [査読有り][通常論文]
     
    New Pt/SbOx catalysts active for the selective oxidation of i-C4H10 and i-C4H8 were characterized by means of XRD, TEM, and XAFS as well as H-2 and CO adsorption. Pt was present as metallic particles, while SbOx existed as Sb6O13 phase. It was suggested that the surface layer of the Pt particles was modified with SbOy (y<x) under the i-C4H10 and i-C4H8 selective oxidation reaction conditions at 773 K, This modification of Pt particles by SbOy induces high selectivity to MAL in both i-C4H10 and i-C4H8 oxidation reactions. Activation of i-C4H10 (i-C4H10 dehydrogenation) is suggested to occur on the Pt-SbOy sites in the presence of oxygen, while the Sb6O13 phase is responsible for selective oxidation of dehydrogenated intermediates. The degree of the Sb modification depends on the reaction conditions. When the Pt/SbOx catalyst was reduced with H-2 at 473 K, Pt-Sb alloy particles (Pt-Pt = 0.274 nm and Pt-Sb = 0.260 nm) were formed, and the Sb6O13 was partly reduced to alpha-Sb6O4. This heavily reduced state of the surface was nonselective for the i-C4H10 oxidation. (C) 1997 Academic Press.
  • T Inoue, K Asakura, Y Iwasawa
    JOURNAL OF CATALYSIS 171 1 184 - 190 1997年10月 [査読有り][通常論文]
     
    It was found that Pt/SbOx catalysts were active for the selective oxidation of i.C4H10 and i-C4H8 to methacrolein (MAL) at 773 K. The SbOx itself was inactive for the selective oxidation of i-C4H10, while i-C4H8 was converted to MAL on the SbOx. Small amounts of Pt (0.2-0.72 wt%) supported on the SbOx promoted the i-C4H10 oxidation with good selectivity to MAL (typically 50-60%) and MAL + i-C4H8 (80-90%). The selective oxidation of i-C4H8 to MAL was also markedly enhanced by Pt. The performance of Pt/SbOx catalysts for the i-C4H10 selective oxidation may be attributed to combinative catalysis of Pt particles modified with SbOy (y < x) and Sb6O13 produced under the oxidation conditions. (C) 1997 Academic Press.
  • K Okumura, N Ichikuni, K Asakura, Y Iwasawa
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS 93 17 3217 - 3227 1997年09月 [査読有り][通常論文]
     
    The behaviors of Rh particles and GeO2 submonolayers supported on SiO2 during oxidation and reduction have been investigated, revealing a structural change in the outermost support surface of supported metal catalysts, by means of XAFS, XRD, TEM and FTIR. Partial reduction of the GeO2 overlayers in Rh/GeO2/SiO2 occurred to form RhGe alloy particles by reduction with H-2 at 423-723 K, as proved by direct Rh-Ge bonding observed by EXAFS at both the Rh-and the Ge-K edges. The RhGe alloy particles were transformed to Rh oxides and GeO2 submonolayers by calcination at 673 K; conversely, these oxide phases were converted back to RhGe alloy particles by reduction at 423-723 K. These transformations on SiO2 took place reversibly during the oxidation-reduction treatments. This is a unique structural change at the Rh/GeO2 overlayer interface in contrast to the behaviors of Rh and Ge on bulk GeO, which were irreversible owing to subsidence of Rh into the GeO2 bulk.
  • YZ Yuan, AP Kozlova, K Asakura, HL Wan, K Tsai, Y Iwasawa
    JOURNAL OF CATALYSIS 170 1 191 - 199 1997年08月 [査読有り][通常論文]
     
    Supported Au catalysts were prepared by attaching Au phosphine complexes, Au(PPh3)(NO3) (1) and [Au-9(PPh3)(8)](NO3)(3) (2), on as-precipitated metal hydroxides M(OH)(x)* (*, as-precipitated; M = Mn2+, Co2+, Fe3+, Ni2+, Zn2+, Mg2+, Cu2+, Ti4+, Ce4+, and La3+), followed by temperature-programmed calcination in a flow of dry air. The obtained Au catalysts showed high catalytic activities in low-temperature CO oxidation. Among the obtained Au catalysts 1/Mn(OH)(2)* and 1/Co(OH)(2)* were most highly active even at 203 K. 1/Fe(OH)(3)* and 1/Ti(OH)(4)* also catalyzed CO oxidation at low temperatures 203-273 K, whereas 1/Fe2O3 and 1/TiO2 prepared by supporting 1 on conventional Fe2O3 and TiO2 showed negligible activity under the similar reaction conditions. It was estimated by TEM and XRD that the mean diameter of Au particles in 1/Fe(OH)(3)* was about 2.9 nm, which was about 10 times smaller than that for 1/Fe2O3. EXAFS for 1/Ti(OH)(4)* revealed that the coordination number of Au-Au bond was 8-10, while that for 1/TiO2 was 11.0, which also indicates that Au particle size for 1/Ti(OH)(4)* is smaller than that for 1/TiO2. The catalysts obtained by attaching the Au complexes on commercially available metal hydroxides also showed negligible activity for the low-temperature CO oxidation under identical conditions. These results demonstrate that supported Au catalysts with small Au particles, tremendously active for the low-temperature CO oxidation, can be prepared by attaching the Au phosphine complexes on the as-precipitated metal hydroxides. Sodium cations exhibited positive effect on the Au catalysis, whereas chloride anions drastically decreased the CO oxidation activity. (C) 1997 Academic Press.
  • YZ Yuan, K Asakura, HL Wan, KR Tsai, Y Iwasawa
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 122 2-3 147 - 157 1997年08月 [査読有り][通常論文]
     
    Structures and catalytic properties of a SiO2-supported [Au6Pt] cluster, [(AuPPh3)(6)Pt(PPh3)](NO3)(2) (1), were characterized by FT-IR, in-situ EXAFS, and TPR, and also by the reactions such as H-2-D-2 equilibration, ethene hydrogenation, and CO oxidation to get insight into the key issues of metal catalysis. The cluster 1 was supported on SiO2 without fragmentation of the cluster framework at room temperature under Ar atmosphere. The cluster framework of 1/SiO2 was stable up to 400 K under vacuum. EXAFS analysis revealed that after heat-treatment of 1/SiO2 at 473 K under vacuum the coordination numbers of Pt-Au and Au-Au(Pt) decreased compared to those for the original clusters due to cluster deformation and after treatment of 1/SiO2 at 773 K the Au particles and Pt-P-# species (P-#: phosphine species) were produced. The combination of TPR and EXAFS showed that the reduction at 603 K caused complete cleavage of Pt-Au and Au-P-# bonds accompanied with the formation of Au particles, while Pt-P-# bonds remained at 773 K. The incipient 1/SiO2 showed catalytic activity in H-2-D-2 and ethene hydrogenation at 303 K without change of the cluster framework. The catalysis of 1/SiO2 was suggested to be referred to the platinum atom which was embedded in the six gold cluster by the results of CO-adsorption, EXAFS, and pulse reaction analysis. This is contrasted to the fact that both Pt(PPh3)(4)/SiO2 and [Au-9(PPh3)(8)](NO3)(3)/SiO2 showed no catalytic activity for these reactions.
  • K Asakura, WJ Chun, M Shirai, K Tomishige, Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B 101 28 5549 - 5556 1997年07月 [査読有り][通常論文]
     
    Structures of Pt species derived from Pt-4(mu-CH3COO)(8) on an alpha-Al2O3(0001) single-crystal surface were studied by means of in-situ polarization-dependent total reflection fluorescence XAFS (EXAFS and XANES) techniques. The Pt-4 cluster framework was destroyed upon the deposition of Pt-4(mu-CH3COO)(8) by the reaction on the alpha-Al2O3 surface at room temperature. The isolated Pt species were converted to one-atomic layer thick Pt rafts with the Pt-Pt distance of 0.273 nm when the cluster was treated with H-2 at 373 K. The raftlike Pt clusters were stabilized by the formation of direct Pt-O-Al bonding with the alpha-Al2O3 surface. The raftlike Pt clusters were redispersed to isolated oxidized Pt species by the reaction with NO. They were also transferred to three-dimensional Pt particles by reduction with H-2 at 773 K.
  • WJ Chun, K Asakura, Y Iwasawa
    JOURNAL DE PHYSIQUE IV 7 C2 921 - 922 1997年04月 [査読有り][通常論文]
     
    Polarization-dependent X-ray Absorption Fine Structure spectra of Mo oxides on a rutile TiO2 (110) single crystal in a total-reflection fluorescence mode were measured in 3 different orientations of the crystal to an electric vector of synchrotron radiation. We found that the Mo dimer species was formed on the TiO2(110) surface, with Mo-Mo bond parallel to the [1(1) over bar0$] direction.
  • K Asakura, Y Yuan, Y Iwasawa
    JOURNAL DE PHYSIQUE IV 7 C2 863 - 865 1997年04月 [査読有り][通常論文]
     
    structure and behavior of [(PPh3)Pt(Au(PPh3))(6)](1) supported on SiO2 surface have been studied by in-situ EXAFS. The structure of the cluster 1 is maintained after deposition on SiO, at room temperature. Upon adsorption of CO little change in coordination number for Pt-Au is found in Pt L-3-edge EXAFS though the coordination number of Au-Au slightly increases in Au L-3-edge EXAFS and the peak corresponding to Pt(-Au-)P remarkably increases in the Fourier transformation of Pt L-3-edge EXAFS. We have interpreted the increase in the intensity of the peak corresponding to Pt(-Au-)P by the multiple scattering effect owing to the change of Pt-Au-P angle. The original EXAFS oscillations are regenerated for both Pt and Au L-3-edges after the evacuation for 2 h at 353 K accompanied by the desorption of CO. From these EXAFS results and the analogy to the PtAu6 chemistry in solution, the PtAu6 framework transforms its structure to a more compact one by CO adsorption with the change in the angle of Pt-Au-P. Unlike the PtAu6 cluster in solution, CO reversibly desorbs from the cluster without collapse of the PtAu6 framework.
  • K Asakura, J Lauterbach, HH Rotermund, G Ertl
    SURFACE SCIENCE 374 1-3 125 - 141 1997年03月 [査読有り][通常論文]
     
    The formation and development of spatio-temporal concentration patterns associated with the catalytic oxidation of carbon monoxide on a Pt(100) surface modified by deposition of sub monolayers of Au was investigated by means of photoemission electron microscopy (PEEM). The presence of Au atoms essentially reduces the adsorption probability for oxygen and the diffusion coefficient for chemisorbed CO, leading to alterations of the velocities for propagation of O- and GO-waves. At the boundaries between domains of differing Au content, phenomena of refraction and reflection occurred. The refraction obeys Snell's law, while total reflection as found in optics does not occur for chemical waves at less than the critical angle. The observed effects as well as characteristic differences to the previously studied Pt(110) surfaces were explained qualitatively on the basis of the elementary steps involved. (C) 1997 Elsevier Science B.V.
  • K. Okumura, K. Asakura, Y. Iwasawa
    Journal of Physical Chemistry B 101 48 9984 - 9990 1997年 [査読有り][通常論文]
  • K Okumura, K Asakura, Y Iwasawa
    CHEMISTRY LETTERS 10 985 - 986 1997年 [査読有り][通常論文]
     
    A new Rh/one-atomic layer GeO2/SiO2 catalyst was prepared by supporting Rh-6(CO)(16) precursor on the one-atomic layer GeO2/SiO2 followed by reduction at 423-523 K. The obtained catalyst was active and selective for conversion of ethyl acetate to ethanol by H-2 under mild reaction conditions, whereas Rh/bulk-GeO2 and Rh/SiO2 were inactive for this reaction. Rh carbonyl cluster, Rh metal, and RhGe alloy were formed on the one-atomic layer GeO2/SiO2 depending on the pre-reduction temperature. A combination of metallic Rh particles and one-atomic layer GeO2 was most active for the ethanol production.
  • A Kozlov, K Asakura, Y Iwasawa
    CHEMISTRY LETTERS 4 313 - 314 1997年 [査読有り][通常論文]
     
    Encapsulated vanadium(IV) picolinato complex was synthesized by treatment of VO2+-NaY zeolite with molten picolinic acid. The structure of the 'ship-in-a-bottle' species was determined by EXAFS, XANES, ESR, IR and UV-vis spectroscopies. It was suggested by XPS and XRD that the complex was located in the zeolite cage. VO(pic)(2)-NaY has been shown to retain solution like activity in oxidation of alkanes, alcohols and benzene with hydrogen peroxide.
  • T Kubota, K Asakura, Y Iwasawa
    CATALYSIS LETTERS 46 3-4 141 - 144 1997年 [査読有り][通常論文]
     
    X-ray absorption near-edge structure (XANES) spectra at the Pt L-3-edge for Pt particles supported on SiO2 under CO adsorption and CO + H-2 coadsorption were recorded to analyze the amount of adsorbed hydrogen in the coadsorbed state on the Pt particles. Adsorbed CO on the Pt particles revealed a new peak at 6 eV above the Pt L-3-edge in the difference spectra before and after CO adsorption in the coverage range 0.10-0.51. Subsequent adsorption of hydrogen at various coverages on the CO-preadsorbed Pt particles broadened and shifted the peak to the higher energy side. The peak was deconvoluted to two components due to adsorbed hydrogen and CO by a linear least-squares fitting technique. It was found that the fitting coefficient with respect to adsorbed hydrogen was proportional to the amount of adsorbed hydrogen. The XANES difference spectra provide a quantitative analysis method for adsorbed hydrogen on supported Pt particles in the presence of coadsorbates like CO.
  • KK Bando, K Asakura, H Arakawa, K Isobe, Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY 100 32 13636 - 13645 1996年08月 [査読有り][通常論文]
     
    trans-[(RhCp*CH3)2(mu-CH2)(2)] (Cp* = pentamethylcyclopentadienyl) was chemically attached to inorganic oxides such as SiO2, Al2O3, TiO2, and MgO to prepare Rh dimer catalysts. The catalytic activities of the obtained supported Rh dimers for ethene hydroformylation depended on the kinds of supports. The SiO2-attached Rh dimers showed highest activity and selectivity for the hydroformylation. Surface structure and behavior of he Rh sites during CO insertion process were examined by in situ FT-IR and EXAFS techniques. Similarly to the previous observation that Rh-Rh metal bonding in the Rh dimers on SiO2 alternately broken and formed in the course of the catalytic hydroformylation, Rh dimers on TiO2 showed a reversible bond break formation, but CO-bridged Rh dimers inactive for the hydroformylation were produced unlike the case of Rh dimer/SiO2. On Al2O3 mast of Rh dimers were degraded to monomers which exhibited no activity for the hydroformylation. The Rh dimers on MgO were aggregated to metal clusters. These structural behaviors of Rh sites are discussed in terms of the interaction between the Rh dimer and the support.
  • WJ Chun, K Asakura, Y Iwasawa
    APPLIED SURFACE SCIENCE 100 143 - 146 1996年07月 [査読有り][通常論文]
     
    We have developed the polarization-dependent total-reflection fluorescence extended X-ray absorption fine structure (PTRF-EXAFS) method which can provide information about the orientation and anisotropic structures of dispersed metal sites on a support by employing parallel or perpendicular polarization of synchrotron radiation. In this paper we have reviewed our recent results concerning Pt cluster on alpha-Al2O3(0001) and Mo oxides on Ti0(2)(110). We also discuss the advantage and disadvantage of the PTRF-EXAFS technique.
  • WJ Chun, K Asakura, Y Iwasawa
    JOURNAL OF SYNCHROTRON RADIATION 3 4 160 - 162 1996年07月 [査読有り][通常論文]
     
    A CdTe solid-state detector was applied to the measurement of polarization-dependent total-reflection fluorescence XAFS spectra. The data revealed that the detector has good sensitivity, and this, together with its compact size, make it appropriate for in-situ measurements and removal of X-ray Bragg diffraction. The detector efficiently recorded the high-energy K-edge XAFS spectra for molybdenum oxides supported on TiO2 (110).
  • T Kubota, K Asakura, N Ichikuni, Y Iwasawa
    CHEMICAL PHYSICS LETTERS 256 4-5 445 - 448 1996年07月 [査読有り][通常論文]
     
    We measured Pt L(2,3)-edge X-ray absorption near edge structure (XANES) spectra for the Pt particles supported on SiO2, Al2O3 and MgO with and without adsorbed hydrogen. The new peaks appeared at 6-8 eV above the Pt L(2,3)-edges in difference spectra between those in vacuum and under hydrogen. The intensity of the new peak was found to be proportional to the amount of adsorbed hydrogen but independent of the kind of the supports, These results suggest that the XANES difference spectra provide a new method for in situ characterization of adsorbed hydrogen on supported Pt particles without interference of the support.
  • WJ Chun, M Shirai, K Tomishige, K Asakura, Y Iwasawa
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 107 1-3 55 - 65 1996年05月 [査読有り][通常論文]
     
    A chamber for observation in situ of polarized total-reflection fluorescence extended X-ray absorption fine structure (PTRF-XAFS) spectra was constructed, which makes it possible to measure the PTRF-XAFS spectra in situ under preparation, treatment, and reaction conditions from high vacuum(1X10(-9) Pa) to high pressure(1X10(5) Pa) and from low temperature(100 K) to high temperature(800 K). The PTRF-XAFS technique can provide information on asymmetric or anisotropic structure of active metal and metal-oxide sites supported on single crystal substrates as models for supported catalysts, by measuring bondings of supported species in two or three different directions parallel and perpendicular to the surface independently. Typical EXAFS and XANES spectra for Cu2+/alpha-SiO2 (0001), CoOx/alpha-Al2O3 (0001), [Pt](4)/alpha-Al2O3 (0001), and V2O5/ZrO2 (100) taken by the PTRF-XAFS chamber are discussed in relation to their catalytic properties.
  • YZ Yuan, K Asakura, HL Wan, KR Tsai, Y Iwasawa
    CHEMISTRY LETTERS 9 755 - 756 1996年 [査読有り][通常論文]
     
    Supported gold catalysts were prepared by attaching phosphine-stabilized gold complex and cluster on as-precipitated metal hydroxides M(OH)*(x) (M=Mn2+, Co2+, Fe3+, Ni2+, Zn2+, Mg2+,and Cu2+), followed by thermal decomposition and calcination. The obtained catalysts were remarkably active for CO oxidation at low temperatures below 273 K.
  • YZ Yuan, K Asakura, HL Wan, K Tsai, Y Iwasawa
    CHEMISTRY LETTERS 2 129 - 130 1996年 [査読有り][通常論文]
     
    A novel catalyst of [(PPh(3))Pt(AuPPh(3))(6)] (NO3)(2) 1 supported on SiO2 was very active in H-2-D-2 equilibration with a TOF of 29.8 s(-1), while it showed low activity for ethene hydrogenation and CO oxidation at 303 K. It was found that the catalysis of 1/SiO2 was not caused by platinum particle impurity but by the platinum atom which bound to the gold atoms in the cluster. The cluster framework of 1/SiO2 was stable during the reactions at 303 K. The change of Au-Pt bond in 1/SiO2 by heat treatment and the catalytic performance of produced cluster fragments were characterized by EXAFS, FT-IR and kinetic investigation.
  • YZ Yuan, K Asakura, HL Wan, K Tsai, Y Iwasawa
    CATALYSIS LETTERS 42 1-2 15 - 20 1996年 [査読有り][通常論文]
     
    A phosphine-stabilized mononuclear gold complex Au(PPh(3))(NO3) (1) and a phosphine-stabilized gold cluster [An(9)(PPh(3))(8)](NO3)(3) (2) were used as precursors for preparation of supported gold catalysts. Both complexes 1 and 2 supported on inorganic oxides such as alpha-Fe2O3, TiO2, and SiO2 were inactive for CO oxidation, whereas the 1 or 2/oxides treated under air or CO or 5% H-2/Ar atmosphere were found to be active for CO oxidation. The catalytic activity depended on not only the treatment conditions but also the kinds of the precursor and the supports used. The catalysts derived from 1 showed higher activity than those derived from 2. alpha-Fe2O3 and TiO2 were much more efficient supports than SiO2 for the gold particles which were characterized by XRD and EXAFS.
  • K Asakura, T Kubota, N Ichikuni, Y Iwasawa
    11TH INTERNATIONAL CONGRESS ON CATALYSIS - 40TH ANNIVERSARY, PTS A AND B 101 101 911 - 919 1996年 [査読有り][通常論文]
     
    We measured Pt L(3), L(2) and L(1)-edges X-ray absorption near edge structure (XANES) spectra of Pt particles dispersed on metal oxide supports (SiO2, Al2O3 and MgO) with and without hydrogen adsorption. The difference spectra obtained by subtracting the spectra in vacuum from the ones with adsorbed hydrogen were independent of kind of the support and only dependent on the amount of adsorbed hydrogen. It was suggested that the change can not be only explained by the change of density of Pt 5d unoccupied state but by creation of a resonance state associated with the localized Pt-H interaction. We also found a linear relation between the change in the XANES spectra and the amount of adsorbed hydrogen, which provides a new characterization method for adsorbed hydrogen on supported Pt particles.
  • Toshiaki Ohta, Kiyotaka Asakura, Toshihiko Yokoyama
    Analytical Spectroscopy Library 7 C 307 - 351 1996年 [査読有り][通常論文]
  • K Tomishige, K Asakura, Y Iwasawa
    JOURNAL OF CATALYSIS 157 2 472 - 481 1995年12月 [査読有り][通常論文]
     
    The Rh-Sn/SiO2 catalyst prepared by the selective reaction between Sn (CH3)(4) vapor and Rh particles on SiO2 was remarkably active for the NO dissociation and the catalytic NO-H-2 reaction, To obtain structural information on the behavior of molecularly adsorbed intermediates related to the high activity of the bimetallic ensemble catalyst surface, in situ EXAFS and FTIR were employed, in parallel with reaction kinetics. We observed the molecular reaction intermediate, bent-type NO, by EXAFS with the aid of FTIR, The reaction mechanism is discussed on the basis of the characterization of adsorbed species and surface bimetallic structure. (C) 1995 Academic Press, Inc.
  • M Shirai, M Nomura, K Asakura, Y Iwasawa
    REVIEW OF SCIENTIFIC INSTRUMENTS 66 12 5493 - 5498 1995年12月 [査読有り][通常論文]
     
    We have constructed a chamber for the in situ structural study of metals and metal oxides supported on single-crystal surfaces by polarized total-reflection fluorescence x-ray absorption fine structure (PTRF-XAFS) spectroscopy. This chamber makes it possible to measure in situ PTRF-XAFS spectra under a variety of conditions; from high vacuum (1X10(-9)Pa) to high pressure (1x10(5) Pa) and from low temperature (100 K) to high temperature (800 K). A wide degree (degrees) of rotation of the sample along the x-ray Light axis can be attained in order to measure the asymmetric or anisotropic structure of active sites on the single-crystal substrates in two different directions-parallel and perpendicular to the surface. The chamber is mounted on XYZ and rotation tables to achieve total-reflection conditions of the incident x ray to the sample. The advantage of this in situ PTRF-XAFS technique has been demonstrated by measuring extended x-ray absorption fine structure spectra of Pt/alpha-Al2O3(0001) and x-ray absorption near-edge structure spectra of vanadium oxide on ZrO2(100) under reaction conditions (C) 1995 American Institute of Physics.
  • WJ CHUN, K TOMISHIGE, M HAMAKADO, Y IWASAWA, K ASAKURA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS 91 22 4161 - 4170 1995年11月 [査読有り][通常論文]
     
    Pt-4-cluster/SiO2 catalyst, prepared from the [Pt-4(mu-CH3COO)(8)] cluster, has shown remarkably high catalytic activity with 100% selectivity to CO2 and H-2 for the decomposition of formic acid as compared with the Pt-particle/SiO2 catalyst. In order to elucidate the genesis and the mechanism for catalysis by Pt-4-cluster/SiO2, the samples were characterized by kinetics, Pt L(III)-edge extended X-ray absorption fine structure (EXAFS), and FTIR spectroscopy. EXAFS and IR data revealed that the surface structure of the catalyst changed from the tetramer to dimers during an induction period, then to monomers which were active for the catalysis. Eventually Pt particles were formed which were of much lower catalytic activity. The structural transformations of the Pt-4-cluster/SiO2 catalyst are discussed in relation to the catalytic reaction profiles.
  • MD GRAHAM, M BAR, IG KEVREKIDIS, K ASAKURA, J LAUTERBACH, HH ROTERMUND, G ERTL
    PHYSICAL REVIEW E 52 1 76 - 93 1995年07月 [査読有り][通常論文]
     
    The exploration of pattern formation by reaction-diffusion systems in complex bounded domains has begun only recently. While theoretical and numerical information points to a strong interaction between patterns and boundaries, experiments are rare and for heterogeneous catalytic reactions practically nonexistent. By constructing (using microlithography) catalytic surfaces of arbitrary shape acid size, we are able to study this interaction for the catalytic oxidation of CO on Pt(110). Experiments along these lines shed light on issues such as anisotropic diffusion and the behavior of individual defects. In addition, certain geometries give rise to patterns that have not been observed on the untreated catalyst and bring to light surface mechanisms that have no analog in homogeneous reaction-diffusion systems. Simple domains of controlled size constitute paradigms that make the comparisons between theory and experiment more fruitful, as we demonstrate through modeling and simulation of such examples. This approach opens the way for systematically probing certain aspects of pattern formation unique to heterogeneous catalysis.
  • K ASAKURA, J LAUTERBACH, HH ROTERMUND, G ERTL
    JOURNAL OF CHEMICAL PHYSICS 102 20 8175 - 8184 1995年05月 [査読有り][通常論文]
  • K ASAKURA, K TOMISHIGE, M SHIRAI, WJ CHUN, T YOKOYAMA, Y IWASAWA
    PHYSICA B 208 1-4 637 - 640 1995年03月 [査読有り][通常論文]
     
    We have constructed an in situ chamber for polarization dependent total reflection fluorescence EXAFS. Using this chamber we have determined structures and orientations of Pt clusters derived from Pt-4(CH3COO)(8) on an alpha-Al2O3(0 0 0 1) single crystal surface under in situ conditions.
  • K ASAKURA, H ISHII, S KONISHI, Y KITAJIMA, T OHTA, H KURODA
    PHYSICA B 208 1-4 465 - 466 1995年03月 [査読有り][通常論文]
     
    A local structure of P on Ni(7911) step surface was studied by means of surface EXAFS. The adsorption of 0.1 ML P induced facetting of Ni(7911) to (111) and (135) surfaces. As results of polarization-dependent EXAFS measurements, P was found to be adsorbed on the (135) surface with a large replacement of step Ni atoms.
  • M Shirai, WJ Chun, K Tomishige, K Asakura, Y Iwasawa
    SCIENCE AND TECHNOLOGY IN CATALYSIS 1994 92 92 263 - 268 1995年 [査読有り][通常論文]
     
    An in-situ Polarized Total-Reflection Fluorescence X-ray Absorption Fine Structure (PTRF-XAFS) technique was developed as a new powerful method to provide three-dimensional information on anisotropic structures of metal and metal- oxide sites supported on inorganic oxide surfaces and also on orientation of chemical bonds on their active sites, by taking fluorescence XAFS(EXAFS aid XANES) spectra separately in two different directions parallel to the support surface(s-polarization) and in a direction normal to the surface(p-polarization). This technique was used to analyze the anisotropic structures of Pt sites on alpha-Al2O3(0001) prepared by using Pt-4(CH3COO)(8) cluster in the course of catalyst preparation and NO adsorption and also to analyze the orientation of V=O bond of V2O5-monolayer developed on ZrO2(100). These samples are regarded as models of catalyst surfaces. The anisotropic structure analysis shows that platinum atoms are atomically dispersed on the alumina, or aggregated to one-atomic Pt layers and spherical Pt particles, depending on the atmosphere and conditions, and that the exposed V=O bonds are oriented to a 45 degrees-direction from the normal to the ZrO2(100) surface.
  • K TOMISHIGE, K ASAKURA, Y IWASAWA
    JOURNAL OF CATALYSIS 149 1 70 - 80 1994年09月 [査読有り][通常論文]
     
    Rh-Sn/SiO2 catalysts, prepared by the selective reaction between Sn (CH3)(4) and small Rh metallic particles supported on SiO2, showed much higher catalytic activities for NO-H-2 reaction and NO dissociation than Rh/SiO2 and coimpregnation Rh-Sn/SiO2. In order to examine the important factors for the efficient catalysis of the Rh-Sn/SiO2 catalysts, the samples were characterized by Sn K- and Rh K-edge EXAFS, FTIR, H-2 and CO adsorption, and TEM. For the Rh-Sn/SiO2 catalysts (Sn/Rh greater than or equal to 0.4), the surface concentration of Sn to Rh was estimated to be Sn-s/Rh-s 3, where a Rh atom is surrounded by six Sn atoms. According to the results of the Sn K-edge EXAFS analysis, the bond distance between a Sn atom and the nearest-neighbor atom in the first layer atoms was 0.270 nn, and the bond distance between a Sn atom and a metal atom in the second layer was 0.290 nm, suggesting a relaxation of the first bimetallic layer. A surface model structure of Rh-Sn particles on SiO2 as a catalytically active bimetallic ensemble is discussed. (C) 1994 Academic Press, Inc.
  • T TERANISHI, M HARADA, K ASAKURA, H ASANUMA, Y SAITO, N TOSHIMA
    JOURNAL OF PHYSICAL CHEMISTRY 98 33 7967 - 7975 1994年08月 [査読有り][通常論文]
     
    Polystyrene-based chelate resin, functionalized by tridentate iminodiacetic acid moieties, has the special ability to increase the specific surface area by complexing with multivalent cations and drying after being washed with the organic solvent miscible with water. The extended X-ray absorption fine structure (EXAFS) technique was applied to analyze the structure of the chelate resin-Fe(II) and -Fe(III) complexes. The EXAFS data for the chelate resin-Fe(III) complex, which has the largest surface area among the various chelate resin-metal complexes investigated, indicate that the Fe(III) ion has the coordination number of 6 with one iminodiacetic acid moiety and three water molecules, which are retained in a dry state. The surplus positive charge, due to the 1:1 complexation of Fe(III) ion with IDA moiety (-2), repulses other surplus positive charges or Fe(III) ions, resulting in preventing the pores from shrinking and in making the surface area quite large. In contrast, in the case of the chelate resin-Fe(II) complex, the coordination number of the Fe(II) ion is 4, suggesting the coordination of Fe(II) to four or five oxygen and/or nitrogen atoms including one or two iminodiacetic acid moieties and one water molecule which cannot be removed by drying after being washed with the solvent. It has also been confirmed that the chelate resin-Fe(II) complex can adsorb an NO gas by coordination of NO to the vacant orbital of Fe(II) ions, resulting in the 5-coordinate structure.
  • J LAUTERBACH, K ASAKURA, HH ROTERMUND
    SURFACE SCIENCE 313 1-2 52 - 63 1994年06月 [査読有り][通常論文]
     
    The photoemission electron microscope (PEEM) makes it possible to image a surface via its work function. On a CO-covered Pt(100) surface, we prepared oxygen islands which appear dark in the PEEM image due to their higher work function. As the surface is heated to temperatures above 650 K we observe the conversion of these dark islands into very bright ones with work functions much lower than even that of the clean surface arising from an inverted dipole moment of oxygen atoms beneath the surface. We found an activation energy for this conversion of about 15 kcal/mol. Partially transformed oxygen islands were used to study the reactivity and the formation of this species further. CO and H2 both react with subsurface oxygen rather slowly, while at the interface between the subsurface and the chemisorbed phase, both adsorbents accelerate the conversion of parts of the remaining oxygen atoms towards the subsurface state. In contrast, additional oxygen adsorption does not contribute to a further transformation. We propose a qualitative microscopic model for the formation of subsurface oxygen based on experimental evidence.
  • MD GRAHAM, IG KEVREKIDIS, K ASAKURA, J LAUTERBACH, K KRISCHER, HH ROTERMUND, G ERTL
    SCIENCE 264 5155 80 - 82 1994年04月 [査読有り][通常論文]
     
    The effect of boundaries on pattern formation was studied for the catalytic oxidation of carbon monoxide on platinum surfaces. Photolithography was used to create microscopic reacting domains on polycrystalline foils and single-crystal platinum (110) surfaces with inert titanium overlayers. Certain domain geometries give rise to patterns that have not been observed on the untreated catalyst and bring to light surface mechanisms that have no analog in homogeneous reaction-diffusion systems.
  • M HARADA, K ASAKURA, N TOSHIMA
    JOURNAL OF PHYSICAL CHEMISTRY 98 10 2653 - 2662 1994年03月 [査読有り][通常論文]
     
    The colloidal dispersions of polymer-protected platinum/rhodium bimetallic cluster particles are easily prepared by refluxing solutions of hexachloroplatinic(IV) acid and rhodium(III) chloride in ethanol/water (1/1 v/v) in the presence of poly(N-vinyl-2-pyrrolidone). These colloidal dispersions of the Pt/Rh bimetallic cluster particles are very stable and have a size distribution from 2 to 7 nm in diameter. The electronic spectra and the transmission electron micrographs suggest that the colloidal dispersions are not a mixture of monometallic Rh and monometallic Pt particles but are mostly composed of Pt/Rh alloy particles. Electron microprobe analysis indicates that the metal composition of each alloy particle with nearly average diameter is kept as the charged mole ratio of Pt/Rh. Extended X-ray absorption fine structure analyses, high-resolution electron microprobe analysis, and scanning tunneling microscopy indicate that colloidal alloy particles consist of an assembly of Pt/Rh bimetallic microclusters, each of which has a Pt core and a modified Pt core structure of colloidal dispersions of Pt/Rh(1/4) and Pt/Rh(1/1 or 4/1) bimetallic clusters, respectively. The importance of the microcluster is discussed in detail for the formation of Pt/Rh bimetallic cluster particles.
  • K TOMISHIGE, K ASAKURA, Y IWASAWA
    CHEMISTRY LETTERS 2 235 - 238 1994年02月 [査読有り][通常論文]
     
    In - situ EXAFS technique was successful by applied for the first time to observe the molecular reaction intermediate for NO - H-2 reaction on highly active Rh - Sn/SiO2 catalysts. The EXAFS data, with. the aid of FTIR, revealed the existence the bent - type NO with the bond distance of 0.256 nm with Sn atoms (Rh - NO - Sn) on the bimetallic surface in the steady - state reaction conditions. The tilted NO was dissociated to form Sn - O bond at 0.205 nm.
  • M SHIRAI, T INOUE, H ONISHI, K ASAKURA, Y IWASAWA
    JOURNAL OF CATALYSIS 145 1 159 - 165 1994年01月 [査読有り][通常論文]
  • K. ASAKURA, J. LAUTERBACH, H. ROTERMUND, G. ERTL
    Physical Review B 50 11 8043 - 8046 1994年 [査読有り][通常論文]
  • M SHIRAI, K ASAKURA, Y IWASAWA
    CATALYSIS LETTERS 26 3-4 229 - 234 1994年 [査読有り][通常論文]
     
    The oriented structure of the exposed V=O bond of vanadium oxides on ZrO2(100) was studied by in situ polarized total-reflection fluorescence X-ray absorption near-edge structure (XANES) spectroscopy. The pre-edge peak intensity of s-polarized XANES was half the intensity of the p-polarized one. Moreover, both pre-edge peaks decreased in a similar way and eventually became zero by the reaction of V=O bonds with NH3 at 423 K, suggesting that all of the observed V=O bonds behaved as active sites. The present technique suggests that the exposed V=O bonds are oriented to a 45-degrees-direction from the normal to the ZrO2(100) surface.
  • M HARADA, K ASAKURA, Y UEKI, N TOSHIMA
    JOURNAL OF PHYSICAL CHEMISTRY 97 41 10742 - 10749 1993年10月 [査読有り][通常論文]
     
    The structures of the colloidal dispersions of the Pd/Rh bimetallic clusters, prepared by refluxing the solution of their salts in water/ethanol in the presence of Poly(N-vinyl-2-pyrrolidone), were investigated by means of an extended X-ray absorption fine structure (EXAFS) technique. On the basis of the EXAFS measurements of the Pd/Rh(1/1) alloy foil, the Pd-Rh bond distance in this alloy foil is about 2.70 angstrom, different neither from the Pd-Pd bond distance in the Pd foil nor the Rh-Rh bond distance in the Rh foil. Comparison of the difference of the peak height between the Pd foil and the Pd/Rh(1/1) alloy foil with that between the Rh foil and the same alloy foil has also shown that the disorder in the Pd foil or in the Rh foil is nearly the same as that in the Pd/Rh(1/1) alloy foil, even at room temperature. Under the condition that each contribution has the corresponding bond distance with the same disorder, the contributions of Pd-Pd, Pd-Rh, Rh-Rh, and Rh-Pd bonds can be completely distinguished from each other in the Pd/Rh bimetallic cluster. From the electron microprobe analysis and the obtained coordination numbers of the colloidal dispersions of the Pd/Rh(1/1 and 1/2) bimetallic clusters, it can be concluded that the small particles (less than 20 angstrom in diameter) mainly consist of Rh clusters and the large particles (more than 35 angstrom in diameter) of Pd clusters. The bimetallic alloy clusters have diameters in the range 25-35 angstrom. The small sum of coordination numbers around the Rh atom of the dispersions suggests that the Rh microcluster particles coexist in the colloidal dispersions and that the Rh atoms of the bimetallic alloy clusters are highly dispersed on the surface.
  • JJ INUKAI, K ASAKURA, Y IWASAWA
    JOURNAL OF CATALYSIS 143 1 22 - 31 1993年09月 [査読有り][通常論文]
  • M HARADA, K ASAKURA, N TOSHIMA
    JOURNAL OF PHYSICAL CHEMISTRY 97 19 5103 - 5114 1993年05月 [査読有り][通常論文]
     
    Colloidal dispersions of the poly(N-vinyl-2-pyrrolidone)-protected gold/palladium bimetallic clusters were prepared by successive reduction in order to compare the catalytic activity and the structure of the clusters. The catalytic activity of the colloidal dispersions of the Au/Pd(1/4) clusters for the selective partial hydrogenation depends on the reduction order in the preparation of the clusters. The clusters prepared by successive reduction starting from the reduction of gold ions (Au --> Pd) have higher activity than those prepared by the reverse order (Pd --> Au). The EXAFS measurements indicate that the Au/Pd(1/4 and 1/1) bimetallic clusters prepared by the successive (Pd --> Au) reduction have the cluster-in-cluster structure. In the case of the successive (Au --> Pd) reduction, however, the dispersions contain both large monometallic Au clusters and monometallic Pd clusters, not Au/Pd bimetallic clusters. Mixing the dispersions of the Au and Pd monometallic clusters changes their structures at room temperature in solution, resulting in bimetallic alloy structures in the course of time, which is suggested by both the TEM observation and the electronic spectra.
  • S YAMAMOTO, K ASAKURA, K MOCHIDA, A NITTA, H KURODA
    JOURNAL OF PHYSICAL CHEMISTRY 97 3 565 - 568 1993年01月 [査読有り][通常論文]
     
    The photochemical reaction of dihydrotetraruthenium tridecacarbonyl, H2Ru4(CO)13, was investigated by UV-visible and FT-IR absorption spectroscopies at 77 K in both a 3-methylpentane matrix and a polystyrene film. Upon irradiation at 313 nm, H2RU4(CO)13 undergoes clean CO dissociation yielding selectively a single product. One CO is released from each parent carbonyl cluster that reacts. Upon warming to 298 K, the efficient recombination of CO trapped in nearby sites with the photoproduct completely regenerates the parent cluster H2Ru4(CO)13. From these and other results, the photo product is identified as the coordinatively unsaturated cluster H2RU4(CO)12. The photoinduced CO dissociation is dependent on the excitation wavelength, which can be interpreted in terms of the electronic structure of the corresponding excited states. At 298 K, UV-visible light irradiation does not produce any changes in the absorption spectra irrespective of the excitation wavelength. This can be attributed to geminate recombination in which released CO efficiently recombines with H2Ru4(CO)12. The UV-visible and IR spectra of matrix isolated H2RU4(CO)12 agree with those of the photoproduct formed when H2Ru4(CO)13 adsorbed on the surface of silica is irradiated. This spectral agreement allows the photoproduct on silica to be assigned as H2RU4(CO)12, which supports our previous postulate about the photochemical process occurring when H2RU4(CO)13 absorbed on the surface of silica is irradiated.
  • H AYATO, S ODA, Y SATOW, K ASAKURA, H KURODA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 32 32 640 - 642 1993年 [査読有り][通常論文]
     
    Local structures of rock salt type AgBr1-xIx solid solutions with x varying from 0.07 to 0.4, substances interesting from both viewpoints of crystal structure and excellent properties as a photographic material, have been investigated by EXAFS analysis of three sets of spectra, i.e., I K-edge, Br K-edge and Ag K-edge, at various temperature from 10K to room temperature. The Br-Ag and I-Ag interatomic distances in the solid solution were different from each other and deviated from the average Ag-(Br,I), or virtual crystal, distance determined from X-ray diffraction at any temperature. The iodide content x dependence of I-Ag and Br-Ag interatomic distances changed with temperature. At low temperature the I-Ag and Br-Ag distances increased with increasing the iodide content, whereas at room temperature they did not exhibit significant change with composition. This suggested that the bonding nature of the AgBr1-xIx solid solution is rather ionic at low temperature, while it is rather covalent at room temperature.
  • H ISHII, K ASAKURA, T OHTA, Y KITAJIMA, H KURODA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 32 32 368 - 370 1993年 [査読有り][通常論文]
     
    The surface structure of Cl/Ni(7 9 11) was studied by means of SEXAFS. At the initial stage of chemisorption (approximately 0.1 ML), chlorine atoms adsorb mainly on the terrace 3-fold site in contrast to sulfur and phosphorus on Ni(7 9 11), where the adsorption on the step 4-fold site is predominant.
  • R SEKINE, M KAWAI, K ASAKURA, T HIKITA, M KUDO
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 32 32 431 - 433 1993年 [査読有り][通常論文]
     
    adsorbed structure of copper and calcium dipivaloylmethanates [M(DPM)2, M=Cu and Ca] complexes on amorphous SiO2 are determined by extended X-ray absorption fine structure (EXAFS). There are no significant changes in the M-O bond length and the oxygen coordination numbers around M between the isolated M(DPM)2 and the adsorbed M(DPM)2. Furthermore clear existence of Cu C coordination is observed for the adsorbed Cu(DPM)2. Therefore, it is concluded that the M-O bond and the ring structure of DPM ligand remain unchanged after the adsorption. Introducing water vapor at 673 K to the Cu(DPM)2/SiO2 system results in the removal of ligand DPM from the adsorbed Cu(DPM)2. The remained species is found to be Cu metal particle by the EXAFS and the X-ray absorption near-edge structure(XANES).
  • M HARADA, K ASAKURA, N TOSHIMA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 32 32 451 - 453 1993年 [査読有り][通常論文]
     
    The colloidal dispersions of the palladium-rhodium bimetallic clusters, prepared by refluxing the solution of their salts in water/ethanol in the presence of poly(N-vinyl-2-pyrrolidone) under nitrogen, are analyzed by EXAFS spectroscopy, showing that the bond distance between the Pd atom and Rh atom in the cluster is about 2.70 angstrom on the basis of the EXAFS measurements of the Pd/Rh alloy foils. The coordination numbers of the Pd/Rh dispersions indicate that the small particles in size mainly consist of Pd/Rh bimetallic clusters and the large particles, of palladium clusters.
  • H ISHII, K ASAKURA, H NAMBA, T OHTA, Y KITAJIMA, N KOSUGI, H KURODA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 32 32 365 - 367 1993年 [査読有り][通常論文]
     
    The surface structure of (square-root 3 x square-root 3)R30-degrees S/Ni(7 9 11) was investigated at room temperature by the SEXAFS method. We found that the mixture of the step 4-fold site and terrace 3-fold hollow site could explain the observed polarization dependence of the EXAFS amplitude successfully. It should be noted that a (square-root 3 x square-root 3)R30-degrees LEED pattern can be observed only at low temperature for S adsorption on Ni(111). Present results suggest that the S atoms adsorbed on the step 4-fold site play an important role on stabilizing the S atoms on the terrace site, which yield the (square-root 3 x square-root 3)R30-degrees LEED pattern.
  • K TOMISHIGE, K ASAKURA, Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 2 184 - 185 1993年01月 [査読有り][通常論文]
     
    The Rh-Sn/SiO2 catalysts prepared by the selective reaction of Me4Sn with Rh/SiO2 show remarkably high activities for NO dissociation and NO catalytic reduction with H-2 as compared with Rh/SiO2.
  • M SHIRAI, K ASAKURA, Y IWASAWA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 32 32 413 - 415 1993年 [査読有り][通常論文]
     
    Asymmetiric structures of active metal oxides (Cu oxide, Co oxide) on single crystal surfaces were determined by polarized total-reflection fluorescence XAFS spectroscopy (PTRF-XAFS). An asymmetric particle structure (or growth mode) of small spinel-like Co3O4 was directly demonstrated by this method.
  • S YAMAMOTO, K ASAKURA, K MOCHIDA, A NITTA, H KURODA
    JOURNAL OF PHYSICAL CHEMISTRY 97 3 656 - 660 1993年01月 [査読有り][通常論文]
     
    The photochemical formation of coordinatively unsaturated metal carbonyl clusters on the surface of metal oxide supports has the potential of leading to interesting new materials that can be used as selective catalysts. In line with our work on this theme, the photochemical reaction of dihydrotetraruthenium tridecacarbonyl, H2RU4(CO)13, adsorbed on the surface of silica was investigated by DRS UV-visible, FT-IR, and EXAFS spectroscopies. When irradiated by UV-visible light, H2RU4(CO)13 loses one carbon monoxide ligand, producing selectively a coordinatively unsaturated H2RU4(CO)12 on the surface of silica. The initial photoproduct, H2RU4(CO)12, is interacting weakly with surface hydroxyl groups, which are the only functionality available to act as a stabilizing ligand, and the dissociated carbon monoxide is lost from the surface. This process prevents secondary reactions, thus leading to the selective formation and stabilization of the coordinatively unsaturated H2RU4(CO)12, which is unstable in solutions and undergoes secondary reactions.
  • K ASAKURA, S KONISHI, T OHTA, Y KITAJIMA, H KURODA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 32 32 359 - 361 1993年 [査読有り][通常論文]
     
    We have studied the local structure around the phosphine adsorbed on the Ni(111) surface at room temperature that shows amorphous structure in LEED observation. The P-Ni distance is about 2.23 angstrom. The angular dependency of EXAFS demonstrates that the Ni surface is locally reconstructed to the rectangular unit cell structure and P is located almost at the center of a rectangular plane of 4 Ni atoms. The local structure is the same as that of the annealed P/Ni(111) surface. The annealing treatment produces a long-range order.
  • K TOMISHIGE, K ASAKURA, Y IWASAWA
    CATALYSIS LETTERS 20 1-2 15 - 22 1993年 [査読有り][通常論文]
     
    Rh-Sn/SiO2 catalysts prepared by the reaction of (CH3)4Sn with Rh metal particles supported on SiO2 have remarkably high activities for NO-H-2 reaction and NO dissociation. The bimetallic surface structure of Rh-Sn/SiO2 composed of an isolated Rh atom surrounded by six Sn atoms, is presented by Rh K-edge and Sn K-edge EXAFS, FT-IR, TEM and CO adsorption.
  • K ASAKURA, M SHIRAI, Y IWASAWA
    CATALYSIS LETTERS 20 1-2 117 - 124 1993年 [査読有り][通常論文]
     
    An in situ polarization-dependent total reflection fluorescence yield EXAFS system has been developed to analyze the asymmetric structures of catalytically active metal sites on single crystal surfaces. This technique separately reveals the bonding feature parallel and perpendicular to the support surface. The systems of Cu ion on alpha-quartz(0001), Co oxide on alpha-alumina(0001), and Pt4 on alpha-alumina(0001) were investigated as model surfaces of supported catalytic systems. The location of Cu sites on alpha-quartz(0001), the epitaxial growth mode of Co3O4 on alpha-alumina(0001), and the Pt raft structure with metal-support interaction in Pt4/alpha-alumina(0001) were observed.
  • K ASAKURA, Y YAMAZAKI, H KURODA, M HARADA, N TOSHIMA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 32 32 448 - 450 1993年 [査読有り][通常論文]
     
    The structures of SiO2-supported PtPd alloy clusters with the size of about 20 angstrom which were prepared from the PtPd colloid solutions were investigated by means of EXAFS. The phase shift and amplitude functions were derived from PtPd foils with the atomic ratio of 1:9, 1:1 and 9:1. The curve fitting analyses showed that the PtPd clusters were present in a ''cluster-in-cluster'' structure in which the homogeneous clusters were composed of several smaller clusters composed of the atoms of each metal.
  • ZM WANG, T SUZUKI, N UEKAWA, K ASAKURA, K KANEKO
    JOURNAL OF PHYSICAL CHEMISTRY 96 26 10917 - 10922 1992年12月 [査読有り][通常論文]
     
    Ultrafine Ti(IV)-doped alpha-FeOOH particles were dispersed on the high-surface-area carbon fibers of uniform micropores in order to elucidate the role of the surface electronic factor in the micropore filling of supercritical NO. EXAFS and XANES showed that dispersed Ti-doped alpha-FeOOH particles are ultrafine and have the same local structure as that of bulk alpha-FeOOH particles. The microporosity of the samples did not change significantly by the doping of Ti(IV) in dispersed alpha-FeOOH on the basis of N2 adsorption. Also, the surface acidic site concentration measured by the irreversible NH3 adsorption was almost constant regardless of the Ti doping. However, doping of Ti(IV) in the dispersed alpha-FeOOH enhanced the micropore filling of supercritical NO by 40%, at the maximum. The enhancement of the NO micropore filling by Ti doping was presumed to come from the increase of quasi-free electrons in the dispersed alpha-FeOOH fine particles due to mixed valence formation, which is enhanced by the surface segregation of Ti(IV) from the XPS examinations.
  • M HARADA, K ASAKURA, Y UEKI, N TOSHIMA
    JOURNAL OF PHYSICAL CHEMISTRY 96 24 9730 - 9738 1992年11月 [査読有り][通常論文]
     
    The mild oxidation and reduction processes of the Pd/Pt bimetallic clusters protected by poly(N-vinyl-2-pyrrolidone) were investigated with an extended X-ray absorption fine structure (EXAFS) technique. From the intensity of the EXAFS spectrum due to the Pd-O bond, each Pd atom on the surface of the Pd/Pt(4/1) cluster is estimated to be surrounded by the 0.21-2.3 atoms of oxygen, depending on the extent of the oxidation. Depending on the contact time with molecular oxygen, the Pd-O bond of the bimetallic clusters has a different coordination distance from 1.96 to 2.17 angstrom, about 0.15 angstrom longer than the first coordination distance of palladium oxide (2.03 angstrom). The longest distance in the oxidized cluster may suggest a weaker interaction between palladium and oxygen atoms than that of palladium oxide. The structure change by treatment with hydrogen is more remarkable in the Pd/Pt(4/1) bimetallic clusters prepared by refluxing in ethanol/water under air than that prepared under nitrogen. For example, the coordination number of Pd atoms around the Pt atom of the clusters prepared under air changes from 3.9 +/- 0.3 to 4.3 +/- 0.5 and then 5.8 +/- 0.8 due to the extent of the hydrogenation, while that of the clusters prepared under nitrogen changes from 3.8 +/- 0.4 to 3.9 +/- 0.6 and then to 4.3 +/- 0.4. The similar phenomenon has also been observed for the Pd/Pt(1/1) bimetallic clusters. From these data, the easy oxidation of the Pd atoms on the surface of the cluster and the high stability of the Pt atoms in the core may be concluded to result in the increasing reactivity of the bimetallic clusters by contact with oxygen.
  • S YAMAMOTO, K ASAKURA, A NITTA, H KURODA
    JOURNAL OF PHYSICAL CHEMISTRY 96 23 9565 - 9568 1992年11月 [査読有り][通常論文]
     
    The photochemical reaction of dihydroirontriosmium tridecacarbonyl, H2FeOs3(CO)13, was investigated by UV-visible and Fr-IR absorption spectroscopies at 77 K both in a polystyrene film and a 3-methylpentane matrix. Upon UV-visible light irradiation (irrespective of the excitation wavelength from 313 to 435 nm), H2FeOs3(CO)13 undergoes clean CO dissociation yielding selectively a single product. One CO is released from each parent carbonyl cluster that reacts. Upon warming to 298 K the efficient recombination of CO trapped in nearby sites with the photoproduct completely regenerates the parent cluster. From these results, the photoproduct is identified as the coordinatively unsaturated cluster H2FeOs3(CO)12 with a coordinatively unsaturated site at the -Os atom having no bridging CO ligand. The UV-visible and IR spectra of matrix-isolated H2FeOS3(CO)12 agree with that of the photoproduct formed when H2FeOs3(CO)13 adsorbed on the surface of silica is irradiated. This spectral agreement allows the photoproduct on silica to be assigned as H2FeOs3(CO)12, which supports our previous postulate about the photochemical process occurring when the H2FeOs3(CO)13/silica system is irradiated.
  • N TOSHIMA, M HARADA, Y YAMAZAKI, K ASAKURA
    JOURNAL OF PHYSICAL CHEMISTRY 96 24 9927 - 9933 1992年11月 [査読有り][通常論文]
     
    The colloidal dispersions of the poly(N-vinyl-2-pyrrolidone)-protected gold/palladium bimetallic clusters were prepared by simultaneous reduction of HAuC14 and PdCl2 in the presence of poly(N-vinyl-2-pyrrolidone). The bimetallic clusters were relatively uniform in size (e.g., 1.6 nm in average diameter) and were used as a catalyst for the selective partial hydrogenation of 1,3-cyclooctadiene at 30-degrees-C under 1 atm of hydrogen. The initial rate of the hydrogenation depended on the metal composition of the cluster catalyst, and the maximum catalytic activities were achieved at Au/Pd - 1/4. The catalytic activities of the mixtures of the monometallic Au and Pd clusters were higher than those expected for the two kinds of the monometallic clusters without reciprocal actions. The structures of the bimetallic clusters were studied using extended X-ray absorption fine structure (EXAFS). The structural parameters were determined by fitting the experimental data for the two absorption edges simultaneously using improved computer program. As a consequence of this improvement, the coordination numbers of Au atoms around the Pd atom and of Pd atoms around the Au atom could be determined with greater confidence. The EXAFS data of the Au/Pd(1/4 and 1/1) bimetallic clusters prepared by simultaneous reduction indicate that the surface of the particle entirely consists of palladium atoms and the core of gold atoms (an Au core structure).
  • R SEKINE, M KAWAI, K ASAKURA, T HIKITA, M KUDO
    SURFACE SCIENCE 278 1-2 175 - 182 1992年11月 [査読有り][通常論文]
     
    Adsorbed states of copper and calcium dipivaloylmethanate [M(DPM)2 (M = CU, Ca)] complexes on SiO2 are determined by means of infrared (IR) spectroscopy and extended X-ray absorption fine structure (EXAFS). Since the H atom of surface OH moves into the DPM ligands, the [GRAPHICS] structure of the DPM ligand changes into the [GRAPHICS] structure in adsorbed M(DPM)2. No significant changes in the M-O bond length and the oxygen coordination numbers around M are observed between isolated M(DPM)2 and adsorbed M(DPM)2 by EXAFS. In spite of the difference in the metals included, the complexes adsorb on SiO2 in a basically identical mechanism, where the adsorbates are stabilized by the ligand-surface interaction.
  • K ASAKURA, Y IWASAWA
    JOURNAL OF PHYSICAL CHEMISTRY 96 18 7386 - 7389 1992年09月 [査読有り][通常論文]
     
    The structure and behavior of ZrO2 on Pd black were studied by means of extended X-ray absorption fine structure (EXAFS). The reversible structure change of ZrO2 with the reduction at 773 K and oxidation at 673 K was observed. The Zr-Zr distances on ZrO2/Pd after oxidation at 673 K were determined to be 0.345 and 0.363 nm (named delta-ZrO2), while ZrO2/Pd after reduction at 773 K showed the tetragonal ZrO2 structure with a Zr-Zr distance at 0.366 nm. The delta-structure is stable against the H-2 reduction at 473 K. The delta-ZrO2 Structure is suggested to be stabilized by the interface Pd oxide.
  • S YAMAMOTO, Y MIYAMOTO, RM LEWIS, M KOIZUMI, Y MORIOKA, K ASAKURA, H KURODA
    JOURNAL OF PHYSICAL CHEMISTRY 96 15 6367 - 6371 1992年07月 [査読有り][通常論文]
     
    The photochemical reaction of silica-supported H2FeOs3(CO)13 induced by irradiation with visible light was investigated by using FT-IR and UV-visible reflectance spectroscopies. The structure of the photoproduct was studied by laser Raman and EXAFS spectroscopies. H2FeOs3(CO)13 molecules that are adsorbed in a molecularly dispersed state on the surface of silica were found to lose one CO ligand when irradiated with light in the region of the first electronic transition of the carbonyl cluster. The reaction yielded a coordinatively unsaturated species, H2FeOs3(CO)12. It was concluded that this unstable photoproduct is stabilized on the surface of silica and does not undergo secondary reactions because of an interaction with surface hydroxyl groups.
  • Y IZUMI, TH LIU, K ASAKURA, T CHIHARA, H YAMAZAKI, Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS 14 2287 - 2297 1992年07月 [査読有り][通常論文]
     
    The clusters [Ru6C(CO)16Me]- supported on SiO2, Al2O3 and TiO2 were characterized by means of extended X-ray absorption fine structure (EXAFS), temperature-programmed desorption (TPD) and Fourier-transform IR spectroscopy in relation to developments of new catalytic systems. The EXAFS analysis revealed that the Ru6C cluster framework which has an interstitial carbon atom was stable at 473 (SiO2), 523 (Al2O3) and 473 K (TiO2) under CO or CO + H-2. The supported clusters produced methane upon heating in vacuum by the reaction with surface hydrogen-bonded OH groups, whereas in the presence of CO + H-2 acetaldehyde was preferably produced, unlike [Ru6C(CO)16Me]- in a homogeneous system where only methane was formed. The selectivity to acetaldehyde was larger with SiO2 (77%) than with Al2O3 (15) or TiO2 (10%).
  • K ASAKURA, K OOI, Y IWASAWA
    JOURNAL OF MOLECULAR CATALYSIS 74 1-3 345 - 351 1992年07月 [査読有り][通常論文]
     
    A new Fe carbonyl cluster [Fe3(CO)6] with a Fe-Fe distance of 0.273 nm, which is longer than that in Fe3(CO)12 (0.262 nm) and in Fe metal (0.248 nm), was prepared by supporting Fe3(CO)12 On SiRx/SiO2(R=CH3, C6H5) followed by treatment at 368 K in vacuum. The Fe clusters on SiMe2/SiO2 showed a higher activity - by a factor of 200 - than the Fe species on SiO2 for propene hydrogenation.
  • T LIU, K ASAKURA, U LEE, Y MATSUI, Y IWASAWA
    JOURNAL OF CATALYSIS 135 2 367 - 385 1992年06月 [査読有り][通常論文]
  • M SHIRAI, K ASAKURA, Y IWASAWA
    CHEMISTRY LETTERS 6 1037 - 1040 1992年06月 [査読有り][通常論文]
     
    Cu oxides were supported on alpha-quartz(0001) by CVD of Cu(DPM)2 (DPM: dipyvaloylmethanate) and the subsequent calcination. The structure of the Cu species in the submonolayer was determined by polarized total-reflection fluorescence extended X-ray absorption fine structure (EXAFS) spectroscopy. Both s- and p-polarized EXAFS data revealed that Cu atoms were dispersed in a monomer form on the three-fold hollow sites of the quartz surface with the Cu-O distance of 0.201 nm.
  • K ASAKURA, H SHIRASAKI, S NARITA, T KOJIMA, A KATAURA
    ACTA OTO-LARYNGOLOGICA 112 3 545 - 551 1992年05月 [査読有り][通常論文]
     
    We examined the serial changes of intravenously applied dye leakage and preliminarily examined histamine release into nasal lavage fluid after topical stimulation with capsaicin in guinea pigs. A significant increase in the dye leakage response was detected for 30-40 min, with the maximum response occurring between 5 and 10 min after topical capsaicin stimulation. The dye leakage response to nasal capsaicin challenge was abolished by pretreatment with topical lidocaine, general substance P analogue, topical or general high dosage capsaicin. The dye leakage response to topical capsaicin challenge was significantly reduced following pretreatment with antihistamine, diphenhydramine or atropine sulfate, although it was not affected by pretreatment with an antileukotriene, FPL 55712. Topical methacholine challenge did not induce a dye leakage response. An increase in the concentration of histamine in the nasal lavage fluid was noted at 5 min after topical capsaicin challenge. The concentrations of released histamine tended to be positively correlated with those of leaked dye in the nasal lavage fluids. The histamine release induced by topical stimulation with capsaicin tended to be reduced following general and topical pretreatments with high dosage of capsaicin, and was almost completely abolished following atropine pretreatment. From this study it was concluded that nasal capsaicin stimulation can reflexively induce an intravenously applied dye leakage into the nasal cavity, and that C-fiber related cholinergic nerve reflex and histamine release might, at least partially, be related to this response.
  • K ASAKURA, Y IWASAWA, SK PURNELL, BA WATSON, MA BARTEAU, BC GATES
    CATALYSIS LETTERS 15 4 317 - 327 1992年 [査読有り][通常論文]
     
    Scanning tunneling microscopy (STM) and tunneling spectroscopy (TS) were used to characterize the structure of a model metal-supported dispersed metal oxide, ZrO2 on Pd(100). STM images illustrate changes in the surface morphology of the ZrO2 resulting from various chemical treatments. When the sample was treated in O2, the ZrO2 appeared as a smooth, featureless overlayer of varying thickness wetting the Pd. After treatment in H-2, the ZrO2 formed non-wetting particles on the Pd, with a sharp Pd-ZrO2 interface. TS provided a fingerprint that verified the presence of a semiconducting overlayer on a metallic support. These results appear to be consistent with X-ray absorption spectra of ZrO2 supported on Pd black, reported elsewhere.
  • K ASAKURA, J INUKAI, Y IWASAWA
    JOURNAL OF PHYSICAL CHEMISTRY 96 2 829 - 834 1992年01月 [査読有り][通常論文]
     
    The SiO2-attached one-atomic-layer titanium oxides (TiO2) were prepared by using the surface reaction between the OH groups of SiO2 and Ti(i-OC3H4)4 followed by calcination at 773 K. The one atomic layer TiO2 was characterized to have an anatase-like one-atomic-layer structure with (101) orientation by means of extended X-ray absorption fine structure spectra, X-ray diffraction, and X-ray fluorescence. The Pt or Pd supported on the one atomic layer TiO2 was also studied from chemical and structural interests. The amount of H-2 or CO adsorbed on these samples did not decrease with the reduction in H-2 at 773 K unlike the large suppression of the adsorption on Pt/TiO2 or Pd/TiO2 catalysts in the strong metal-support interaction state. The anatase structure of the one atomic layer TiO2 was maintained for the Pt-deposited sample, whereas the anatase structure was transformed to a rutile structure with (110) orientation keeping the one atomic layer structure for the Pd-deposited sample. The transformation from anatase to rutile structure could be mediated by interaction with Pd particles.
  • M SHIRAI, K ASAKURA, Y IWASAWA
    CATALYSIS LETTERS 15 3 247 - 254 1992年 [査読有り][通常論文]
     
    Anisotropic structure analyses for [CoO(x)]/alpha-Al2O3 (0001) and [Co3O4]n/alpha-Al2O3 (0001) which were derived from Co2(CO)8/alpha-Al2O3 (0001) were performed by a polarized total-reflection fluorescence extended X-ray absorption fine structure (EXAFS) technique. Both s- and p-polarized EXAFS data revealed that the cobalt atoms of [CoO(x)] were located on three-fold hollow sites of alpha-Al2O3 (0001) in a monomer form and that a thin spinel structure [Co3O4] grew with the (001) plane parallel to alpha-Al2O3 (0001).
  • Yasuo Izumi, Tai-Hui Liu, Kiyotaka Asakura, Teiji Chihara, Hiroshi Yamazaki, Yasuhiro Iwasawa
    Journal of the Chemical Society, Dalton Transactions 14 2287 - 2297 1992年 [査読有り][通常論文]
     
    The clusters [Ru6C(CO)16Me]- supported on SiO2, Al2O3 and TiO2 were characterized by means of extended X-ray absorption fine structure (EXAFS), temperature-programmed desorption (TPD) and Fourier-transform IR spectroscopy in relation to developments of new catalytic systems. The EXAFS analysis revealed that the Ru6C cluster framework which has an interstitial carbon atom was stable at 473 (SiO2), 523 (Al2O3) and 473 K (TiO2) under CO or CO + H2. The supported clusters produced methane upon heating in vacuum by the reaction with surface hydrogen-bonded OH groups, whereas in the presence of CO + H2 acetaldehyde was preferably produced, unlike [Ru6C(CO)16Me]- in a homogeneous system where only methane was formed. The selectivity to acetaldehyde was larger with SiO2 (77%) than with Al2O3 (15) or TiO2 (10%).
  • Y IZUMI, K ASAKURA, Y IWASAWA
    JOURNAL OF CATALYSIS 132 2 566 - 570 1991年12月 [査読有り][通常論文]
  • M SHIRAI, K ASAKURA, Y IWASAWA
    JOURNAL OF PHYSICAL CHEMISTRY 95 24 9999 - 10004 1991年11月 [査読有り][通常論文]
     
    New submonolayer niobic acid catalysts were prepared by the reaction of Nb(OC2H5)5 with surface OH groups of SiO2, followed by H2O treatment. The surface structures were characterized by means of EXAFS, XRD, XRF, and FT-IR. The niobic acids on SiO2 up to 8.0 wt % Nb loadings were found to grow in a monolayer mode. These catalysts showed activities 20 times as large as that of a niobic acid bulk catalyst for the esterification of acetic acid with ethanol. The activity was referred to Lewis acid sites in the monolayer structure, which was stable even after evacuation at high temperatures such as 873 K.
  • N TOSHIMA, M HARADA, T YONEZAWA, K KUSHIHASHI, K ASAKURA
    JOURNAL OF PHYSICAL CHEMISTRY 95 19 7448 - 7453 1991年09月 [査読有り][通常論文]
     
    Extended X-ray absorption fine structure (EXAFS) was applied to the determination of the structure of colloidal dispersions of the poly(N-vinyl-2-pyrrolidone)-protected palladium/platinum bimetallic clusters, which work as the catalysts for selective partial hydrogenation of 1,3-cyclooctadiene to cyclooctene. The catalytic activity was found to depend on the structure of the bimetallic clusters. The EXAFS data on the Pd/Pt (4/1) bimetallic clusters, which are the most active catalysts, indicate a Pt core structure, in which the 42 Pd atoms are on the surface of the cluster particle and 13 Pt atoms are at the center of the particle, forming a core. In contrast, the Pd/Pt (1/1) bimetallic clusters are suggested to have a modified Pt core structure, in which 28 Pt atoms connect directly with each other, being located both in the core and on the surface, and 27 Pd atoms form three islands on the surface of the cluster particle.
  • MS TZOU, M KUSUNOKI, K ASAKURA, H KURODA, G MORETTI, WMH SACHTLER
    JOURNAL OF PHYSICAL CHEMISTRY 95 13 5210 - 5215 1991年06月 [査読有り][通常論文]
     
    The structures of bimetallic CuPt particles in freshly reduced and outgassed CuPt/NaY zeolites were characterized by extended X-ray absorption fine structure (EXAFS) at the Cu K-edge and Pt L3-edge. In order to understand the effect of copper on the coordinative environment of platinum, reduced Cu/NaY and Pt/NaY were also studied. It is found that the structure of CuPt bimetallic particles is dependent on the atomic ratio of Cu and Pt in the zeolites. At room temperature, some of the Cu atoms are oxidized, presumably by reacting with protons on the zeolite surface. By outgassing in helium at 500-degrees-C, additional Cu atoms were leached from the surface of the CuPt particles to expose more Pt atoms on the surface. Thus, an enhancement in the activity of toluene hydrogenation was observed. Due to the leaching of Cu atoms upon outgassing in helium or under vacuum, hydrogen chemisorption is not an appropriate method to estimate the number of surface Pt atoms in bimetallic CuPt particles supported in NaY.
  • Y OKAMOTO, T IMANAKA, K ASAKURA, Y IWASAWA
    JOURNAL OF PHYSICAL CHEMISTRY 95 9 3700 - 3705 1991年05月 [査読有り][通常論文]
     
    The structure and electronic state of molybdenum subcarbonyl species anchored in alkali-metal cation exchanged zeolites were elucidated by means of EXAFS, IR, and XPS analyses. The subcarbonyl species were produced at 373 K by evacuating Mo(CO)6 entrapped in the zeolite. The structure of the Mo-subcarbonyl species was found to be monomeric Mo(CO)3(OZ)3 with a fac configuration (OZ: zeolite framework oxygen). The Mo-C bond distance is very short (0.186-0.189 nm), suggesting strong d --> pi* back donations from the Mo atom to the CO ligands. The electron density of Mo in Mo(CO)3(OZ)3 increases with increasing basic strength of OZ in the order HY approximately LiY < NaY approximately CsY.
  • K ASAKURA, Y IWASAWA
    JOURNAL OF PHYSICAL CHEMISTRY 95 4 1711 - 1716 1991年02月 [査読有り][通常論文]
     
    One-atomic-layer niobium oxide catalysts were prepared on SiO2 surface by using two-stage attaching reactions between Nb(OC2H5)5 and silanols and were characterized by X-ray diffraction (XRD), electron probe microanalysis (EPMA), X-ray fluorescence (XRF), and extended X-ray absorption fine structure (EXAFS). The EXAFS analysis revealed the growth of one-atomic-layer niobium oxide structure on SiO2, showing the existence of Nb-Si bond at 0.327 +/- 0.003 nm. The niobium oxide one-atom layers on SiO2 were found to be more active and selective for C2H4 formation (intramolecular dehydration) from C2H5OH in the temperature range 373-573 K than a conventional impregnation Nb2O5/SiO2 catalyst and Nb2O5 bulk.
  • Y IZUMI, K ASAKURA, Y IWASAWA
    JOURNAL OF CATALYSIS 127 2 631 - 644 1991年02月 [査読有り][通常論文]
  • MS TSOU, K ASAKURA, Y YAMAZAKI, H KURODA
    CATALYSIS LETTERS 11 1 33 - 40 1991年 [査読有り][通常論文]
     
    PtRh bimetallic particles, evidenced by EXAFS at Pt L3-edge and Rh K-edge, were prepared in the supercages of NaY zeolites. Bimetallic catalysts, PtRh/NaY, were more reactive in CO-O2 and CO-NO reactions than their corresponding monometallic catalysts, Pt/NaY and Rh/NaY.
  • H KURODA, T YOKOYAMA, K ASAKURA, Y IWASAWA
    FARADAY DISCUSSIONS 92 92 189 - 198 1991年 [査読有り][通常論文]
     
    Temperature dependence of EXAFS was systematically investigated on small metal (Rh or Ru) particles on three different supports, SiO2, NaY zeolite and TiO2. The observed EXAFS oscillations were analysed by the ratio method combined with the cumulant expansion method. The results of these analyses of EXAFS data revealed the existence of a considerable static disorder. It is also shown that the Debye temperature characteristic of particle surface can be determined from analysis of the temperature dependence of the mean-square relative displacement derived from EXAFS. In Rh/TiO2, the surface Debye temperature was found to be ca. 100 K higher in its strong metal-support interaction (SMSI) state in comparison with the normal state, supporting the decoration model for the SMSI state.
  • N ICHIKUNI, K ASAKURA, Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 2 112 - 113 1991年01月 [査読有り][通常論文]
     
    New Nb dimers on an SiO2 surface, prepared from the reaction between [Nb(eta-5-C5H5)H-mu-(eta-5, eta-1-C5H4)]2 and surface OH groups, are found to have an oxygen-bridged dimeric structure, as characterised by extended X-ray fine structure (EXAFS), which is active and selective for the dehydration of ethanol in contrast to the dehydrogenation ability of the Nb monomer catalyst.
  • Haruo Kuroda, Toshihiko Yokoyama, Kiyotaka Asakura, Yasuhiro Iwasawa
    Faraday Discussions 92 189 - 198 1991年 [査読有り][通常論文]
     
    Temperature dependence of EXAFS was systematically investigated on small metal (Rh or Ru) particles on three different supports, SiO2, NaY zeolite and TiO2. The observed EXAFS oscillations were analysed by the ratio method combined with the cumulant expansion method. The results of these analyses of EXAFS data revealed the existence of a considerable static disorder. It is also shown that the Debye temperature characteristic of particle surface can be determined from analysis of the temperature dependence of the mean-square relative displacement derived from EXAFS. In Rh/TiO2, the surface Debye temperature was found to be ca. 100 K higher in its strong metal-support interaction (SMSI) state in comparison with the normal state, supporting the decoration model for the SMSI state.
  • T LIU, Y MATSUI, U LEE, K ASAKURA, Y IWASAWA
    CATALYTIC SCIENCE AND TECHNOLOGY, VOL 1 1 267 - 272 1991年 [査読有り][通常論文]
  • R SEKINE, M KAWAI, K ASAKURA, Y IWASAWA
    ATOMIC LAYER GROWTH AND PROCESSING 222 333 - 338 1991年 [査読有り][通常論文]
  • K ASAKURA, K KITAMURABANDO, Y IWASAWA, H ARAKAWA, K ISOBE
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 112 25 9096 - 9104 1990年12月 [査読有り][通常論文]
  • K ASAKURA, Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS 86 14 2657 - 2662 1990年07月 [査読有り][通常論文]
  • K ASAKURA, KK BANDO, Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS 86 14 2645 - 2655 1990年07月 [査読有り][通常論文]
  • N TOSHIMA, T YONEZAWA, M HARADA, K ASAKURA, Y IWASAWA
    CHEMISTRY LETTERS 5 815 - 818 1990年05月 [査読有り][通常論文]
  • T YAMAMURA, M TADOKORO, N NAKAMURA, K TANAKA, K ASAKURA
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 63 4 999 - 1004 1990年04月 [査読有り][通常論文]
  • K ASAKURA, K KITAMURABANDO, K ISOBE, H ARAKAWA, Y IWASAWA
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 112 8 3242 - 3244 1990年04月 [査読有り][通常論文]
  • T SHIDO, K ASAKURA, Y IWASAWA
    JOURNAL OF CATALYSIS 122 1 55 - 67 1990年03月 [査読有り][通常論文]
  • JM CODDINGTON, RF HOWE, YS YONG, K ASAKURA, Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS 86 6 1015 - 1016 1990年03月 [査読有り][通常論文]
  • K KITAMURABANDO, K ASAKURA, H ARAKAWA, Y SUGI, K ISOBE, Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 3 253 - 255 1990年02月 [査読有り][通常論文]
  • T YAMAMURA, H KURIHARA, N NAKAMURA, R KURODA, K ASAKURA
    CHEMISTRY LETTERS 1 101 - 104 1990年01月 [査読有り][通常論文]
  • M SHIRAI, N ICHIKUNI, K ASAKURA, Y IWASAWA
    CATALYSIS TODAY, VOL 8, NO 1 57 - 66 1990年 [査読有り][通常論文]
  • XANES study on the electronic state of supported platinum particles and the classification of the metal-support interactions
    Hideaki Yoshitake, Kiyotaka Asakura, Yasuhiro Iwasawa
    Photon Factory Activity Report 137  1990年 [査読無し][通常論文]
  • EXAFS measurements on the copper dipivaloylmethanates (Cu(DPM)2) reacted with hydroxyls on oxide surface
    Rika Sekine, Maki Kawai, Hideaki Yoshitake, Kiyotaka Asakura, Yasuhiro Iwasawa
    Photon Factory Activity Report 129  1990年 [査読無し][通常論文]
  • T YOKOYAMA, K ASAKURA, Y IWASAWA, H KURODA
    JOURNAL OF PHYSICAL CHEMISTRY 93 26 8323 - 8327 1989年12月 [査読有り][通常論文]
  • A KUDO, K SAYAMA, A TANAKA, K ASAKURA, K DOMEN, K MARUYA, T ONISHI
    JOURNAL OF CATALYSIS 120 2 337 - 352 1989年12月 [査読有り][通常論文]
  • K ASAKURA, M NISHIMURA, Y IWASAWA
    JOURNAL OF MOLECULAR CATALYSIS 55 1-3 159 - 169 1989年11月 [査読有り][通常論文]
  • H YOSHITAKE, K ASAKURA, Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS I 85 8 2021 - 2034 1989年08月 [査読有り][通常論文]
  • K ASAKURA, Y IWASAWA
    PHYSICA B 158 1-3 142 - 144 1989年06月 [査読有り][通常論文]
  • K ASAKURA, Y IWASAWA
    PHYSICA B 158 1-3 152 - 153 1989年06月 [査読有り][通常論文]
  • K ASAKURA, Y IWASAWA
    JOURNAL OF PHYSICAL CHEMISTRY 93 10 4213 - 4218 1989年05月 [査読有り][通常論文]
  • T SHIDO, K ASAKURA, Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS I 85 2 441 - 453 1989年02月 [査読有り][通常論文]
  • XANES study on the density of d-state of SMSI-platinum and related catalysts
    Hideaki Yoshitake, Kiyotaka Asakura, Yasuhiro Iwasawa
    Photon Factory Activity Report 38  1989年 [査読無し][通常論文]
  • Kiyotaka Asakura, Mutsuto Aoki, Yasuhiro Iwasawa
    CATALYSIS LETTERS 1 11 395 - 403 1988年11月 [査読有り][通常論文]
     
    A new-one-atomic layer ZrO2/ZSM-5 hybrid catalyst was prepared by using the repeated reactions between Zr(OC2H5)(4) and of the OH groups of the external surfaces of ZSM-5, followed by calcination. The one-atomic layer ZrO2 attached on the ZSM-5 surface was characterized by means of X-ray diffraction, X-ray fluorescence and EXAFS. The ZrO2 overlayer is suggested to epitaxially grow on the ZSM-5(001) plane in a [111] direction of tetragonal ZrO2. The one-atomic layer ZrO2/ZSM-5 is a unique catalyst which produces selectively isopentane from CH3OH.
  • Y IZUMI, K ASAKURA, Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 19 1327 - 1328 1988年10月 [査読有り][通常論文]
  • K ASAKURA, Y IWASAWA
    CHEMISTRY LETTERS 4 633 - 636 1988年04月 [査読有り][通常論文]
  • K ASAKURA, Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS I 84 7 2445 - 2456 1988年 [査読有り][通常論文]
  • K ASAKURA, Y IWASAWA, M YAMADA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS I 84 7 2457 - 2464 1988年 [査読有り][通常論文]
  • H YOSHITAKE, K ASAKURA, Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS I 84 12 4337 - 4346 1988年 [査読有り][通常論文]
  • K ASAKURA, Y IWASAWA
    MATERIALS CHEMISTRY AND PHYSICS 18 5-6 499 - 512 1988年01月 [査読有り][通常論文]
  • K ASAKURA, Y IWASAWA, H KURODA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS I 84 84 1329 - & 1988年 [査読有り][通常論文]
  • EXAFS measurements on the copper catalyst prepared by the novel method
    Hideaki Yoshitake, Kiyotaka Asakura, Rika Kuwabara, Yasuhiro Iwasawa
    Photon Factory Activity Report 29  1988年 [査読無し][通常論文]
  • Y SATOW, K ASAKURA, H KURODA
    JOURNAL OF PHYSICS C-SOLID STATE PHYSICS 20 31 5027 - 5035 1987年11月 [査読有り][通常論文]
  • M NISHIMURA, K ASAKURA, Y IWASAWA
    CHEMISTRY LETTERS 4 573 - 576 1987年 [査読有り][通常論文]
  • 佐藤 能雅, 朝倉 清高, 黒田 晴雄
    日本結晶学会誌 29 11 - A5-11-A5 The Crystallographic Society of Japan 1987年
  • Shigenobu Yano, Tomoaki Tanase, Fumihiko Shimizu, Masanobu Hidai, Sadao Yoshikawa, Kiyotaka Asakura
    Nippon Kagaku Kaishi 1987 3 322 - 327 1987年 [査読有り][通常論文]
     
    Both D-glucose (D-G1C) and D-mannose (D-Man) reacted with nickel(II)-tinen complex, [Ni(H2O)2(tmen)2]Cl2 (tmen = l-dimethylamino-2-(methylamino)ethane) to give the identical green complex [3], containing only D-mannose as a sugar component. In order to elu cidate the factor that caused the stereoselective uptake of one of the two C-2 epimeric aldoses by nickel(II) complexes, we have investigated the nickel(II) complexes containing N-glycosides by means of EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy. X-Ray absorption measurements were carried out with a laboratory EXAFS system for the samples (a) nickel foil, (b) [Ni(L-Rha-tn)2]2+]2+, (c) nickel binuclear complex [2], μ-Man-[Ni2(CH3OH) and (d) complex [3] (unknown sample). The results of the present EXAFS study show that the complex [3] has a nickel polynuclear structure involving the N-mannofuranoside bridging. In addition, it is assumed that the coordination ability of the N-mannofuranoside bridging brings about the stereoselective complexation. © 1987, The Chemical Society of Japan. All rights reserved.
  • The structure of Mo(CO)6 supported in the zeolite NaY
    Kiyotaka Asakura, Hideaki Yoshitake, Yasuo Izumi, Junji Inukai, Rika Kuwabara, Yasuhiro Iwasawa, Haruo Kuroda, Russel F.Howe
    Photon Factory Activity Report 245  1987年 [査読無し][通常論文]
  • The structure studies on the TiO2 one-atomic layer by means of EXAFS
    Kiyotaka Asakura, Junji Inukai, Hideaki Yoshitake, Yasuo Izumi, Rika Kuwabara, Yasuhiro Iwasawa, Haruo Kuroda
    Photon Factory Activity Report 244  1987年 [査読無し][通常論文]
  • EXAFS study on the structure of the ZSM-5-attached one atomic ZrO2 catalyst
    Kiyotaka Asakura, Hideaki Yoshitake, Yasuhiro Iwasawa, Haruo Kuroda
    Photon Factory Activity Report 239  1987年 [査読無し][通常論文]
  • High pressure in-situ EXAFS studies on the catalytic reaction mechanism. The oxidation of CO on the Co(II) oxide cluster
    Kiyotaka Asakura, Yasuhiro Iwasawa, Hideaki Yoshitake, Haruo Kuroda
    Photon Factory Activity Report 235  1987年 [査読無し][通常論文]
  • EXAFS studies on the Se-Nb catalyst obtained by use of the two-step fixation reaction
    Kiyotaka Asakura, Yasuo Izumi, Rika Kuwabara, Hideaki Yoshitake, Junji Inukai, Yasuhiro Iwasawa, Haruo Kuroda
    Kiyotaka Asakura, Yasuo Izumi, Rika Kuwabara, Hideaki Yoshitake, Junji Inukai, Yasuhiro Iwasawa, Haruo Kuroda 182  1987年 [査読無し][通常論文]
  • The structure change of P2O5-V2O5 during the C4H8 oxidation reaction
    Kiyotaka Asakura, Hideaki Yoshitake, Yasuhiro Iwasawa, Haruo Kuroda
    Photon Factory Activity Report 180  1987年 [査読無し][通常論文]
  • T YOKOYAMA, N KOSUGI, K ASAKURA, Y IWASAWA, H KURODA
    JOURNAL DE PHYSIQUE 47 C-8 273 - 276 1986年12月 [査読有り][通常論文]
  • K ASAKURA, Y IWASAWA, H KURODA
    JOURNAL DE PHYSIQUE 47 C-8 317 - 320 1986年12月 [査読有り][通常論文]
  • K ASAKURA, Y SATOW, H KURODA
    JOURNAL DE PHYSIQUE 47 C-8 185 - 188 1986年12月 [査読有り][通常論文]
  • K ASAKURA, Y IWASAWA, H KURODA
    NIPPON KAGAKU KAISHI 11 1539 - 1546 1986年11月 [査読有り][通常論文]
  • M NISHIMURA, K ASAKURA, Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 22 1660 - 1661 1986年11月 [査読有り][通常論文]
  • IKEMOTO, I, K KIKUCHI, K IWAI, M YAMASHITA, M NOMURA, K ASAKURA, N KOSUGI, K YAKUSHI, H KURODA
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 59 10 3271 - 3272 1986年10月 [査読有り][通常論文]
  • M NISHIMURA, K ASAKURA, Y IWASAWA
    CHEMISTRY LETTERS 9 1457 - 1460 1986年09月 [査読有り][通常論文]
  • K ASAKURA, Y IWASAWA
    CHEMISTRY LETTERS 6 859 - 862 1986年06月 [査読有り][通常論文]
  • A KASE, K ASAKURA, C EGAWA, Y IWASAWA
    CHEMISTRY LETTERS 6 855 - 858 1986年06月 [査読有り][通常論文]
  • K ASAKURA, Y IWASAWA, H KURODA
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 59 2 647 - 648 1986年02月 [査読有り][通常論文]
  • EXAFS study on the one-atomic layer SiO2-attached Nb oxide catalyst
    Kiyotaka Asakura, Yasuhiro Iwasawa, Hideaki Yoshitake, Toshihiko Yokoyama, Haruo Kuroda
    Photon Factory Activity Report 211  1986年 [査読無し][通常論文]
  • A KOBAYASHI, N SASAGAWA, Y SASAKI, K ASAKURA, T YOKOYAMA, H ISHII, N KOSUGI, H KURODA, H KOBAYASHI
    CHEMISTRY LETTERS 1 1 - 4 1985年 [査読有り][通常論文]
  • K ASAKURA, M YAMADA, Y IWASAWA, H KURODA
    CHEMISTRY LETTERS 4 511 - 514 1985年 [査読有り][通常論文]
  • K ASAKURA, M NOMURA, H KURODA
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 58 5 1543 - 1550 1985年 [査読有り][通常論文]
  • Y IWASAWA, K ASAKURA, H ISHII, H KURODA
    ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE NEUE FOLGE 144 144 105 - 115 1985年 [査読有り][通常論文]
  • K ASAKURA, IKEMOTO, I, H KURODA, T KOBAYASHI, H SHIRAKAWA
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 58 7 2113 - 2120 1985年 [査読有り][通常論文]
  • Y. Iwasawa, K. Asakura, H. Ishii, H. Kuroda
    Zeitschrift fur Physikalische Chemie 144 144 105 - 115 1985年 [査読有り][通常論文]
     
    The dynamic behaviour of active sites of a Si02-attached Mo(VI)-dimer catalyst during ethanol oxidation were studied by means of EXAFS. Catalytic ethanol oxidation was found to proceed by cooperative catalysis of the two adjacent Mo ions of the dimer catalyst in conjunction with the reversible structural oscillation of the active sites (shortening⇄ expanding of Mo - Mo and Mo - O bonds). © 1985, R. Oldenbourg Verlag, München
  • N KOSUGI, T YOKOYAMA, K ASAKURA, H KURODA
    CHEMICAL PHYSICS 91 2 249 - 256 1984年 [査読有り][通常論文]
  • H KURODA, IKEMOTO, I, K ASAKURA, H ISHII, H SHIRAKAWA, T KOBAYASHI, H OYANAGI, T MATSUSHITA
    SOLID STATE COMMUNICATIONS 46 3 235 - 238 1983年 [査読有り][通常論文]
  • M NOMURA, K ASAKURA, U KAMINAGA, T MATSUSHITA, K KOHRA, H KURODA
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 55 12 3911 - 3914 1982年 [査読有り][通常論文]

書籍

講演・口頭発表等

  • Operando EXAFS Studies on the In Catalysts for CH4 Conversion during the Activation Processes  [通常講演]
    Kiyotaka Asakura, Shoji Iguchi, Ichiro Yamanaka
    22nd International Vacuum Congress 2022年09月 口頭発表(一般)
  • Novel Multi Atom Resonance X-ray Raman Scattering - from theory and experimental approaches  [招待講演]
    Kiyotaka Asakura, Kaori Niki, Takashi Fujikawa
    8nternational Conference on Inelastic X-ray Scattering 2022年08月 口頭発表(招待・特別)
  • Kiyotaka ASAKURA, Bing HU, Naoto TODOROKI, Toshimasa WADAYAMA, Kotaro HIGASHI, Tomoya URUGA, Yasuhiro IWASAWA, Hiroko ARIGA, Satoru TAKAKUSAGI
    TOCAT9 2022年07月 口頭発表(一般)
  • Kiyotaka Asakura
    XAFS 2022 2022年07月 口頭発表(招待・特別)
  • 朝倉 清高, Hu Bing, 轟 直人, 和田山 智正, 東 晃太朗, 宇留賀 朋哉, 岩澤 康裕, 三輪(有賀) 寛子, 高草木 達
    第130回触媒討論会 2022年03月 口頭発表(一般)
  • XAFSの基礎 ー XAFSの一般的な測定法と解析法  [招待講演]
    朝倉清高
    日本化学会第102春季年会 2022年03月 公開講演,セミナー,チュートリアル,講習,講義等
  • K.Asakura, S.Takakusagi
    米国化学会春季年会 2022年03月 口頭発表(招待・特別)
  • Kiyotaka Asakura
    The 13 International Iwasawa Conference 2022年03月 口頭発表(招待・特別)
  • 水素社会を目指した触媒と量子ビーム  [招待講演]
    朝倉清高, 三輪(有賀)寛子
    量子ビームサイエンスフェスタ 2022年03月 口頭発表(招待・特別)
  • Possibility of multi atom resonance x-ray raman  [招待講演]
    Kiyotaka Asakura
    Pacifichem2021 2021年12月 口頭発表(招待・特別)
  • カーボンニュートラルを実現する触媒開発と量子ビーム  [招待講演]
    朝倉清高
    北大 KEK-Day 2021年12月 口頭発表(招待・特別)
  • TRHEPD で観測された非対称TiO2(110) (1x2) のDFTによる表面電子状態  [通常講演]
    岩﨑 正弥, 三輪 寛子, 朝倉 清高
    第128回触媒討論会 2021年09月 口頭発表(一般)
  • Upendar Kashaboina, 川佑太, Deling Bao, 高草木達, 井波雄太, 栗山史也, Arnoldus Lambertus Dipu, 荻原仁志, 井口翔之, 山中一郎, 和田敬広, 朝倉清高
    第24回日本XAFS討論会 2021年09月 口頭発表(一般)
  • 放射光と XAFS そして触媒科学 その過去と未来  [招待講演]
    朝倉清高
    第41回触媒学会若手会夏の研修会 2021年08月 口頭発表(基調)
  • 朝倉清高
    日本化学会第101春季年会 2021年03月 口頭発表(招待・特別)
  • TRHEPD で観測された非対称TiO2(110) (1×2) のDFTによる表面電子状態  [通常講演]
    北大触媒研, 岩﨑正弥, 三輪(有賀)寛子, 朝倉清高
    表面真空学会東北・北海道支部講演会 2021年03月 口頭発表(一般)
  • 朝倉清高, 城戸大貴
    応用物理学会 KOSEN SC 第2回 VR学術講演会 2020年12月 ポスター発表
  • PEEM(光電子顕微鏡)を利用した生き物の観測の可能性  [招待講演]
    朝倉清高
    日本顕微鏡学会第63回シンポジウム 2020年11月 口頭発表(招待・特別)
  • 高温反応条件下でのXAFS―反応解析の可能性  [通常講演]
    KASHABOINA, Upenda, 鮑徳玲, 城戸大貴, 三輪(有賀)寛子, 高草木達, 脇坂祐輝, 西川祐太, 井波雄太, 栗山史也, ARNOLDUS LAMBERTUS,Dipu, 荻原仁志, 井口翔之, 山中一郎, 和田敬広, 朝倉清高
    第126回触媒討論会 2020年09月 口頭発表(一般)
  • 脇坂祐輝, 和田敬広, 城戸大貴, Bing Hu, Md. Harun Al Rashid, Wenhan Chen, Kaiyue Dong, 高草木達, Quiyi Yua, 武市泰男, 朝倉清高
    第23回日本XAFS討論会 2020年09月 口頭発表(一般)
  • MARX-Ramanは実在するか  [通常講演]
    朝倉清高
    応用物理学会 KOSEN SC 第 1 回 第1回VR学術講演会 2020年07月 ポスター発表
  • PTRF-XAFS investigation on the 3-dimensional structure of the single-atom metal dispersed on single crystal oxides  [招待講演]
    Kiyotaka Asakura, Satoru Takakusagi
    ACS Spring 2022 2020年03月 口頭発表(招待・特別)
  • Anormalous Au-Au Bond Distance Contraction in PtAu Nanoparticle  [招待講演]
    Kiyotaka Asakura
    11th Internationl Iwasawa Conference 2020年03月 口頭発表(招待・特別)
  • 放射光リモート実験の課題と将来像ーリモート等実験諮問委員会からの提言 企画趣旨説明  [招待講演]
    朝倉清高
    日本放射光学会 2020年01月 シンポジウム・ワークショップパネル(公募)
  • 硬X線XAFSデータベースに向けて
    朝倉清高
    第33回日本放射光学会年会 2020年01月 口頭発表(招待・特別)
  • Operando XAFS studies on supported metal catalysts – Its possibilities to highpressure and high temperature measurements  [招待講演]
    朝倉 清高
    The 9th East Asia Joint Symposium in Environmental Catalysis and Eco-materials 2019年11月 口頭発表(招待・特別)
  • XAFS構造解析の基礎  [通常講演]
    朝倉 清高
    日本化学会第99回春季年会 2019年03月 口頭発表(招待・特別)
  • 硬X線XAFSのデータベース  [招待講演]
    朝倉 清高
    2019年03月 口頭発表(招待・特別)
  • XAFS database 構築に向けて  [招待講演]
    朝倉 清高
    第4回キャタリストインフォマティクス 2018年11月 口頭発表(招待・特別)
  • Curious Emission XAFS spectra  [招待講演]
    朝倉 清高
    統合物質機構国内シンポジウム 2018年10月 口頭発表(招待・特別)
  • ガルバニック交換反応による一原子層成長の偏光全反射蛍光XAFSによるその場観測  [通常講演]
    朝倉 清高
    第10回岩澤コンファレンス 2018年10月 口頭発表(招待・特別)
  • Multiatom Resonance X-ray(MARX) Raman Spectroscopy and interface molecular reation  [通常講演]
    朝倉 清高
    第122回 触媒討論会 2018年09月 口頭発表(一般)
  • “The sensitivity and resolution development of X-ray spectroscopy – smaller, faster, thinner and sparser samples”  [招待講演]
    朝倉 清高
    EuChem 2018年08月 口頭発表(招待・特別)
  • Ultrafast XAFS Studies on the Photoabsorption Processes.  [通常講演]
    朝倉 清高
    TOCAT8 2018年08月 口頭発表(一般)
  • Elucidation of local structure change of photocatalysts during the photoabsoprtion process by use of fs-ps pump-probe XAFS method  [招待講演]
    朝倉 清高
    5th ICAT conference and preconference of TOCAT8 2018年08月 口頭発表(招待・特別)
  • 触媒は生きている  [招待講演]
    朝倉 清高
    夢化学21 2018年07月 公開講演,セミナー,チュートリアル,講習,講義等
  • Elucidation of local structure change of photocatalysts during the photoabsorption process by use of fs-ps pump-probe XAFS method  [招待講演]
    朝倉 清高
    International conference on XAFS, XAFS2018 2018年07月 口頭発表(招待・特別)
  • メソスコピックスケールの構造制御による触媒作用のコントロール  [通常講演]
    朝倉清高, HUA, Huang
    121回触媒討論会 2018年03月 口頭発表(一般)
  • Ultra-Fast XAFS for the Local Structure Analysis of Photocatalysts  [招待講演]
    朝倉 清高
    EU/e-ICAT International Symposium in Eidhoven 2017年11月 口頭発表(招待・特別)
  • Polarization -dependent fluorescnecne XAFS Studies on Fuel Cell Catalysts  [招待講演]
    朝倉 清高
    International Symposium on Novel Energy Nanomaterials, Catalysts and Surfaces for Future Earth UEC 100th Anniversary Commemorative Event 2017年10月 口頭発表(基調)
  • A SPring-8 New Beam Line for the Fuel Cell Analysis  [招待講演]
    朝倉 清高
    IUCr2017 2017年08月 口頭発表(招待・特別)
  • XAFS の基礎  [招待講演]
    朝倉 清高
    XAFS Summer School 2017 2017年08月 口頭発表(招待・特別)
  • XAFS database in Japan  [招待講演]
    朝倉 清高
    Q2XAFS 2017 2017年08月 シンポジウム・ワークショップパネル(指名)
  • XAFS Past,present and futer  [招待講演]
    朝倉 清高
    日本XAFS研究会 2017年08月 口頭発表(基調)
  • Operando XAFS法による触媒構造の その場観察と触媒作用機構に関する研究  [招待講演]
    朝倉 清高
    触媒学会 2016年09月 口頭発表(招待・特別)
  • 反射陽電子回折による TiO2(110)(1x2) 表面構造  [通常講演]
    有賀寛子, 朝倉清高, 兵頭俊男, 望月出海, 触媒学会
    触媒学会 2016年09月 口頭発表(一般)
  • X-ray free electron laser based ultra-fast X-ray absorption spectroscopy analysis on a photocatalyst, WO3, during photo absorption process  [通常講演]
    朝倉 清高
    International Congress on Catalysis 2016年07月 口頭発表(一般)
  • In situ XAFS analysis for energy related catalyst -Fuel cell and Hydrodesulferization Catalysts  [招待講演]
    朝倉 清高
    International Symposium on Catalytic Activation and Selective Conversion of Energy-Related Molecules Satellite Symposium of 16th International Congress on Catalysis 2016年07月 口頭発表(基調)
  • Metal dispersion and defect on TiO2 (110) surface-Expectation for ultra slow muon(USM) experiments  [招待講演]
    朝倉 清高
    USMM & CMSI workshop 2016年01月 口頭発表(招待・特別)
  • Catalyst Informatics 触媒科学研究所の取り組みと今後  [招待講演]
    朝倉 清高
    第1回理研-北大-産総研「触媒研究」合同シンポジウム -知の発掘と革新触媒創造をめざすキャタリストインフォマティクス- 2015年12月 口頭発表(招待・特別)
  • 電極表面のXAFS-どこまで低濃度の触媒がみえるか?  [招待講演]
    朝倉 清高
    第46回セミコンファレンス 電気化学と放射光 2015年12月 口頭発表(招待・特別)
  • 最先端XAFSの開発と触媒ナノ物質の学理の探求  [招待講演]
    朝倉 清高
    表面科学会講演大会 2015年12月 口頭発表(招待・特別)
  • PF-UA と新光源への期待  [招待講演]
    朝倉 清高
    PF研究会 X線顕微分析の新展開: STXMから硬X線複合分析まで 2015年10月 口頭発表(招待・特別)
  • Polarization dependent total reflection fluorescence XAFS and control of the metal surface structure.  [通常講演]
    朝倉 清高
    XAFS16 2015年08月 口頭発表(招待・特別)
  • 触媒とは何か?ー 人類の持続的発展を陰で支えるキーテクノロジー  [通常講演]
    朝倉 清高
    ACADEMIC FANTASISTA 2015 夏休み特別講義 2015年08月 公開講演,セミナー,チュートリアル,講習,講義等
  • An Interpretation of ps Transient XANES of WO3 in Photoabsorption and Decay Processes.  [通常講演]
    朝倉 清高
    New Trends in X-ray Absorption Spectroscopy and Multiple Scattering Theory 2015年07月 口頭発表(招待・特別)
  • 光電子放出顕微鏡(PEEM)の最近の進歩とオペランド観察  [通常講演]
    朝倉 清高
    日本学術振興会第167委員会 2015年07月 口頭発表(招待・特別)
  • 可視光応答型水分解WO3触媒における励起構造のPump-Probe XAFS 観察  [通常講演]
    朝倉 清高
    物性研究所 短期研究会 機能物性融合科学研究会シリーズ(3)「反応と輸送」 2015年06月 口頭発表(招待・特別)
  • 光電子顕微鏡 MyPEEM  [通常講演]
    朝倉 清高
    HOPE 会議 2015年04月 口頭発表(招待・特別)
  • Polarization dependent total reflection XAFS(PTRF-XAFS) studies on the structure of metal species on the TiO2 (110) surfaces  [招待講演]
    朝倉 清高
    IMPRS 2015年02月 公開講演,セミナー,チュートリアル,講習,講義等
  • Summary and Discussion  [招待講演]
    朝倉 清高
    The 74th Okazaki Conference Frontier of X-ray absorption spectroscopy and molecular scinence 2015年02月 口頭発表(招待・特別)
  • 触媒とは何か? ~人類の持続的発展を陰で支えるキーテクノロジー~  [通常講演]
    朝倉 清高
    第40回知の拠点セミナー, 2015年01月 公開講演,セミナー,チュートリアル,講習,講義等
  • XAFSと放射光 総括 −次世代の為に− ユーザーのユーザーによるユーザーのための放射光を  [招待講演]
    朝倉 清高
    放射光学会 2015年01月 口頭発表(招待・特別)
  • X線吸収分光法による白金表面水素  [招待講演]
    朝倉 清高
    第14回中性子学会 2014年12月 口頭発表(招待・特別)
  • マイクロリバースモンテカルロ法によるXAFS構造解析II  [通常講演]
    朝倉 清高
    表面科学会学術大会 2014年11月 ポスター発表
  • Atomically dispersed Au on a modified oxide surface  [通常講演]
    朝倉 清高
    ISSS-7 2014年11月 口頭発表(一般)
  • In situ Structure Analysis of Solid Catalysts by Time-Resolved XAFS  [通常講演]
    朝倉 清高
    CRC-SU (Stockholm University) Joint International Symposium on Chemical Theory for Complex Systems: Interplay between Theory and Experiments: New Trends in Catalysis 2014年10月 口頭発表(招待・特別)
  • “Ni2P (1010) surface ‐ its stability and reactivity”  [通常講演]
    朝倉 清高
    Catalysis Research Center – Fritz‐Haber‐Institut Mini‐Symposium 2014年10月 口頭発表(招待・特別)
  • Time resolved X-ray absorption spectroscopic approach to the change of the structure and electronic state for WO3 in the light absorption process  [通常講演]
    朝倉 清高
    CRC International Symposium on Novel Photocatalysts for Environmental Purification and Energy Generation 2014年10月 口頭発表(招待・特別)
  • In situ XAFSによる平坦電極表面に展開したPtナノ粒子の構造と水素吸着  [招待講演]
    朝倉 清高
    2014年電気化学秋季大会 2014年09月 口頭発表(招待・特別)
  • 全反射高速陽電子回折によるTiO2(110)(1X2)表面構造解析  [通常講演]
    朝倉 清高
    第114回触媒討論会 2014年09月 口頭発表(一般)
  • Catalyst and muon spectroscopy  [通常講演]
    朝倉 清高
    第3回領域会議公開シンポジウム 2014年09月 口頭発表(一般)
  • マイクロリバースモンテカルロ法によるXAFS構造解析II  [通常講演]
    朝倉 清高
    XAFS討論会 2014年09月 口頭発表(一般)
  • XANESを考える  [招待講演]
    朝倉 清高
    XAFS夏の学校 2014年08月 口頭発表(基調)
  • Ni2P(101b0) reconstructed strructure and its catalytic activity  [通常講演]
    朝倉 清高
    Pre ICOMC 2014 2014年07月 ポスター発表
  • In situ XAFS observations of fuel cell catalyst  [通常講演]
    朝倉 清高
    Pre ICOMC 2014 2014年07月 ポスター発表
  • tPt表面への吸着水素のXAFSによるin-situ 観測  [招待講演]
    朝倉 清高
    第30回ライラックセミナー 2014年06月 口頭発表(招待・特別)
  • 朝倉 清高
    246th ACS National Meeting 2014年03月 口頭発表(招待・特別)
  • 朝倉 清高
    触媒・電池元素戦略研究拠点 第3回公開シンポジウム 2013年11月 口頭発表(招待・特別)
  • Preparation and structure of a single Au atom on the TiO2(110) surface: Control of the Au-metal oxide surface interaction  [招待講演]
    朝倉 清高
    Iwasawa Conference 2013年10月 口頭発表(招待・特別)
  • Defect and its interaction with hydrogen on the SnO2  [通常講演]
    朝倉 清高
    USM2013 2013年08月 口頭発表(一般)
  • Surface X-ray Absorption Fine Structure for the Investigation of 3 dimensional Structure Analysis of Surface Active Sites.  [通常講演]
    朝倉 清高
    ISHHC16 2013年08月 ポスター発表
  • In-situ time resolved XAFS studies on catalysts  [招待講演]
    朝倉 清高
    2013 XAFS Workshop in Korea 2013年07月 口頭発表(基調)
  • 触媒反応とミュオン  [通常講演]
    朝倉 清高
    創成領域研究超低速ミュオン 班会議 2013年05月 口頭発表(一般)
  • Preparation and structure of a single Au atom on the TiO2(110) surface: Control of the Au-metal oxide surface interaction  [招待講演]
    朝倉 清高
    Faraday Discussion 162 2013年04月 口頭発表(招待・特別)
  • In situ XAFS studies on Ni2P hydrodesulfurization catalysts under the working conditions  [招待講演]
    朝倉 清高
    WE Heraeus Seminar 2013年03月 口頭発表(招待・特別)
  • 触媒の表面科学的アプローチーPressure gap とMaterial Gapを超えるために  [招待講演]
    朝倉 清高
    日本表面科学会東北北海道支部会 2013年03月 口頭発表(招待・特別)
  • Polarization Dependent Fluorescence X-ray Absorption Fine Structure Studies on the Metal Species at the Interface of Organic Molecule: Its Possibility to the Application of Bio-interface  [招待講演]
    朝倉 清高
    CRC International symposium 2013年02月 口頭発表(招待・特別) 札幌 触媒化学研究センター
  • Ni2P 触媒表面研究―単結晶から実触媒まで  [招待講演]
    朝倉 清高
    北海道大学触媒化学研究センター研究発表会 2013年01月 口頭発表(招待・特別)
  • 電気化学モデル電極系のin-situ 3D XAFS解析の可能性について  [通常講演]
    上原 広充, 上村 洋平, 鴻野 健太郎, 小川 貴史, 丹羽 尉博, 仁谷 浩明, 阿部 仁, 野村 昌治, 高草木 達, 朝倉 清高
    放射光学会合同シンポジウム 2013年01月 口頭発表(一般)
  • 光電子放出顕微鏡による化学マッピング  [招待講演]
    朝倉 清高
    顕微鏡学会第11回シンポジウム「ソフト・ハードマターの多様性を観る」 2012年11月 口頭発表(招待・特別)
  • Study on the Catalytic Reaction Mechanism of Supported Nanoclusters by Simultaneous Time-Resolved Measurements.  [招待講演]
    朝倉 清高
    International Conference on Emerging Advance Nanomaterials 2012 2012年10月 口頭発表(招待・特別)
  • 規整不均一α-Sb2O4/VSbO4触媒の調製とその反応活性  [通常講演]
    朝倉 清高
    触媒学会 2012年09月 口頭発表(一般)
  • Catalytic Properties and Surface Structures of Nickel Phosphide as a New Type of Hydrotreatment Catalyst  [招待講演]
    朝倉 清高
    The 2nd FHI-CRC Joing Symposium on Complex Surfaces in material Science 2012年09月 口頭発表(招待・特別)
  • 奇妙なX線発光について  [通常講演]
    朝倉 清高
    日本XAFS研究会 2012年09月 口頭発表(一般)
  • センサー,燃料電池酸化物の欠陥の動き  [招待講演]
    朝倉 清高
    超低速ミュオンシンポジウム 2012年08月 口頭発表(招待・特別)
  • Polarization Dependent Total Reflection Fluorescence XAFS studies on the Metal-Support Interaction.  [通常講演]
    朝倉 清高
    XAFS15 2012年07月 口頭発表(一般)
  • What is the origin for peaks at the L 3 XANES spectra of AgCl?  [招待講演]
    朝倉 清高
    XAFS Theory Work Shop XAFS theory and nano particles 2012年07月 口頭発表(招待・特別)
  • Operando XAFS Investigations on the Hydrodesulfurization Reaction Mechanism of Ni2P catalysts.  [通常講演]
    朝倉 清高
    IACIS 2012年05月 ポスター発表
  • モデル脱硫触媒としてのNi2P単結晶の表面構造と反応活性  [通常講演]
    朝倉 清高
    触媒討論会 2012年03月 口頭発表(一般)
  • Direct Observation of Metal-Support Interaction Observed in r and k Spaces  [通常講演]
    朝倉 清高
    Green and Sustainable Chemsitry for Next Generation 2012年02月 口頭発表(招待・特別)
  • モデル脱硫触媒としてのNi2P単結晶の表面構造と反応活性  [通常講演]
    朝倉 清高
    北大線形加速器を利用した陽電子回折実験の可能性 2012年01月 口頭発表(一般)
  • 酸化物上の金属ナノ微粒子とガス吸着  [招待講演]
    金属学会 2007年 口頭発表(招待・特別)
  • In脱水素メタンカップリング触媒の高温オペランド XAFS観察  [通常講演]
    KASHABOINA, Upenda, 鮑徳玲, 城戸大貴, 三輪(有賀)寛 子, 高草木達, 西川祐太, 井波雄太, 栗山史也, DIPU, Arnoldus Lambertus, 荻原仁志, 井口翔之, 山中一郎, 和田 敬広, 朝倉清高
    まぼろしの第125回触媒討論会 その他

その他活動・業績

  • Daiki Kido, Hiromitsu Uehara, Satoru Takakusagi, Jun-ya Hasegawa, Kiyotaka Asakura, Yohei Uemura, Yuki Wakisaka, Akihiro Koide, Toshihiko Yokoyama, Yasuhiro Niwa, Shunsuke Nozawa, Kohei Ichiyanagi, Ryo Fukaya, Shin-ichi Adachi, Harry Jenkins, Tokushi Sato 2022年05月14日 
    We have determined the local structure of photoexcited metastable WO$_3$ created 150 ps after 400 nm laser irradiation by the pulse pump--probe L$_3$-edge extended X-ray absorption fine structure spectroscopy and the constrained thorough search analysis. We have found a highly distorted octahedral local structure with one of the shortest W=O bonds being further shortened to 1.66 \AA while the other five bonds were elongated even though theoretical calculations predicted the reverse change. We discuss this contradiction and propose a possible structure for the metastable state.
  • Daiki Kido, Hiromitsu Uehara, Satoru Takakusagi, Jun-ya Hasegawa, Kiyotaka Asakura, Yohei Uemura, Yuki Wakisaka, Akihiro Koide, Toshihiko Yokoyama, Yasuhiro Niwa, Shunsuke Nozawa, Kohei Ichiyanagi, Ryo Fukaya, Shin-ichi Adachi, Harry Jenkins, Tokushi Sato 2022年05月14日 
    We used pump--probe L$_3$-edge extended X-ray absorption fine structure spectroscopy and the constrained thorough search method to study the local structure of photoexcited metastable WO$_3$ created 150 ps after 400 nm laser irradiation pulse. We found a highly distorted octahedral local structure with one of the shortest W=O bonds being further shortened to 1.66 {\AA} while the other five bonds were elongated even though theoretical calculations predicted the reverse change. We discuss this contradiction and propose a possible structure for the metastable state.
  • In脱水素メタンカップリング触媒の高温オペランドXAFS観察
    KASHABOINA Upendar, 鮑徳玲, 城戸大貴, 三輪(有賀)寛子, 高草木達, 西川祐太, 井波雄太, 栗山史也, DIPU Arnoldus Lambertus, 荻原仁志, 井口翔之, 山中一郎, 和田敬広, 朝倉清高 触媒 = Catalysts & Catalysis 2020年 [査読無し][通常論文]
  • 東智弘, LYU Hao, 久富隆史, 吉田真明, 高田剛, 片山正士, 嶺岸耕, 朝倉清高, 堂免一成, 堂免一成 触媒討論会討論会A予稿集 122nd 107 2018年09月19日 [査読無し][通常論文]
  • 鳥屋尾隆, 鳥屋尾隆, SIDDIKI S. M. A. H., 森田能次, 蒲池高志, 蒲池高志, 三輪寛子, 朝倉清高, 吉澤一成, 吉澤一成, 清水研一, 清水研一 触媒討論会講演予稿集 121st 2018年
  • 三輪(有賀) 寛子, 朝倉 清高 触媒 = Catalysts & catalysis 59 (5) 279 -283 2017年10月
  • 朝倉 清高, 上村 洋平, 城戸 大貴 触媒 = Catalysts & catalysis 59 (2) 63 -68 2017年04月
  • 加藤優, 加藤優, 松原直啓, 武藤鞠佳, 上村洋平, 脇坂祐輝, 松村大樹, 高草木達, 朝倉清高, 八木一三, 八木一三 電気化学会大会講演要旨集(CD-ROM) 84th 2017年
  • 脇坂 祐輝, 高草木 達, 朝倉 清高, 上原 広充, Yuan Qiuyi, 和田 敬広, 上村 洋平, 城戸 大貴, 亀井 優太郎, 黒田 清一, 大平 昭博 表面科学学術講演会要旨集 37 (0) 2017年 [査読無し][通常論文]
     
    燃料電池電極触媒に用いられるPtナノ粒子表面の電子状態・局所構造を電気化学条件下で三次元的に理解することは触媒反応・劣化機構の解明において重要である。そこでモデル試料としてPt多結晶薄膜に対して、偏光依存全反射蛍光XAFS分光法を用いて、異なる電位間におけるPt表面の状態変化について面内・面直でとらえることを試み、XANES理論計算との比較を行った。
  • 望月 出海, 有賀 寛子, 深谷 有喜, 和田 健, 前川 雅樹, 河裾 厚男, 設楽 哲夫, 朝倉 清高, 兵頭 俊夫 表面科学 = Journal of the Surface Science Society of Japan 37 (9) 451 -456 2016年09月
  • 城戸大貴, 上村洋平, 脇坂祐輝, 丹羽尉博, 野澤俊介, 足立伸一, 片山哲夫, 矢橋牧名, 有賀寛子, 高草木達, 横山利彦, 大谷文章, 朝倉清高 日本化学会春季年会講演予稿集(CD-ROM) 96th ROMBUNNO.2B1‐07 2016年03月10日 [査読無し][通常論文]
  • 村田 尚義, 岡村 誠, 鈴木 卓弥, 野中 篤, 大西 久男, 朝倉 清高 Proceedings of the Chemical Sensor Symposium 60 123 -125 2016年03月
  • 和田 敬広, 村田 尚義, 上原 広充, 鈴木 卓弥, 仁谷 浩明, 丹羽 尉博, 宇尾 基弘, 朝倉 清高 PF News 33 (4) 13 -19 2016年02月 [査読有り][招待有り]
  • 望月出海, 有賀寛子, 深谷有喜, 和田健, 朝倉清高, 一宮彪彦, 兵頭俊夫 表面科学学術講演会講演要旨集 35th 217 2015年12月01日 [査読無し][通常論文]
  • Force components in XANAM measurements for surface chemical analysis
    S. Suzuki, S. Mukai, Y. Koike, K. Kinoshita, K. Fujikawa, W.J. Chun, M. Nomura, K. Asakura Proceedings of 10th International Symposium on Atomic Level Characterizations for New Materials and Devices '15 (ALC'15) 00 2015年10月 [査読無し][通常論文]
  • 上村洋平, 城戸大貴, 脇坂祐輝, 上原広充, 大場惟史, 丹羽尉博, 野澤俊介, 佐藤篤志, 一柳光平, 深谷亮, 足立伸一, 片山哲夫, 矢橋牧名, 高草木達, 大谷文章, 横山利彦, 朝倉清高 日本化学会講演予稿集 95th (2) 490 2015年03月11日 [査読無し][通常論文]
  • 有賀寛子, 下村浩一郎, PANT A.D, 鳥養映子, 永嶺兼忠, 朝倉清高 日本表面科学会東北・北海道支部講演会講演予稿集 2014 16 2015年03月09日 [査読無し][通常論文]
  • 増田卓也, 増田卓也, 増田卓也, 上原広充, 高草木達, CHUN Wang‐Jae, 近藤敏啓, 朝倉清高, 魚崎浩平, 魚崎浩平 電気化学会大会講演要旨集(CD-ROM) 82nd ROMBUNNO.1E02 2015年03月09日 [査読無し][通常論文]
  • 村田尚義, 岡村誠, 岡田夕佳里, 鈴木卓弥, 野中篤, 大西久男, 和田敬広, 宇尾基弘, 朝倉清高 Chemical Sensors 31 (Supplement B) 2015年
  • 西村友作, 上原広充, 磯村典武, 鈴木涼, 紅谷篤史, 朝倉清高, 高草木達, 渡邊佳英 物構研サイエンスフェスタ要旨集 3rd 2015年
  • 上村洋平, 脇坂祐輝, 城戸大貴, 上原広充, 大場惟史, 丹羽尉博, 野澤俊介, 佐藤篤志, 深谷亮, 一柳光平, 足立伸一, 大谷文章, 高草木達, 横山利彦, 朝倉清高 物構研サイエンスフェスタ要旨集 3rd 44 2015年 [査読無し][通常論文]
  • A challenge toward surface elemental mapping by 3D XANAM spectroscopy
    S. Suzuki, S. Mukai, W.-J. Chun, M. Nomura, K. Asakura Photon Factory Activity Report 2014 32B 186 2015年 [査読無し][通常論文]
  • 國本明駿, 高草木達, 有賀寛子, 上原広充, 大場惟史, 朝倉清高 表面科学学術講演会講演要旨集 34th 86 2014年11月06日 [査読無し][通常論文]
  • 朝倉清高, 有賀寛子, 望月出水, 和田健, 兵頭俊夫, 深谷有喜 触媒討論会討論会A予稿集 114th 358 2014年09月18日 [査読無し][通常論文]
  • Iwasawa Yasuhiro, Fukuoka Atsushi, Asakura Kiyotaka, Yamashita Hiromi TOPICS IN CATALYSIS 57 (10-13) 811 2014年06月 [査読有り][通常論文]
  • 高草木達, 木工淳, IMRAN BIN ABDUL, R. M. Nabil, 上原広充, 有賀寛子, 朝倉清高 日本化学会講演予稿集 94th (3) 760 2014年03月12日 [査読無し][通常論文]
  • 高草木達, 木工淳, MOHAMAD NABIL Imran, bin A. R, 上原広充, 有賀寛子, 朝倉清高 触媒討論会講演予稿集 113th 255 2014年03月10日 [査読無し][通常論文]
  • Kiyotaka Asakura, Hiroko Ariga, Satoru Takakusagi, S. Ted Oyama ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 247 2014年03月 [査読無し][通常論文]
  • 朝倉清高, 有賀寛子, 望月出海, 深谷有喜, 和田健, 兵頭俊夫 Photon Factory News 31 (4) 38 -41 2014年03月 [査読無し][通常論文]
  • 蓬田匠, 吉田真明, 峯尾岳大, 新田清文, 加藤和男, 増田卓也, 仁谷浩明, 阿部仁, 高草木達, 宇留賀朋哉, 朝倉清高, 魚崎浩平, 近藤寛 日本放射光学会年会・放射光科学合同シンポジウム予稿集 27th 116 2014年01月11日 [査読無し][通常論文]
  • 村田尚義, 岡村誠, 鈴木卓弥, 野中篤, 中島崇, 大西久男, 朝倉清高 Chemical Sensors 30 (Supplement B) 2014年
  • 有賀寛子, 望月出海, 深谷有喜, 和田健, 兵頭俊夫, 朝倉清高 物構研サイエンスフェスタ要旨集 2013 3 2014年 [査読無し][通常論文]
  • 有賀寛子, 朝倉清高, 深谷有喜, 望月出海, 和田健, 兵頭俊夫 物構研サイエンスフェスタ要旨集 2013 25 2014年 [査読無し][通常論文]
  • 大場惟史, 上原広充, 有賀寛子, 高草木達, 牧田勇一, 大嶋優輔, 久保仁志, 中村紀章, 朝倉清高 物構研サイエンスフェスタ要旨集 2013 53 2014年 [査読無し][通常論文]
  • 上村洋平, 上原広充, 丹羽尉博, 野澤俊介, 佐藤篤志, 足立伸一, 大谷文章, 高草木達, 朝倉清高 物構研サイエンスフェスタ要旨集 2013 54 2014年 [査読無し][通常論文]
  • 西村友作, 渡邊佳英, 二村智行, 千葉昭雄, 森貴広, 上原広充, 高草木達, 朝倉清高 物構研サイエンスフェスタ要旨集 2013 85 2014年 [査読無し][通常論文]
  • X-ray Energy Dependency of XANAM Spectrum by a qPlus Sensor Probe
    S. Suzuki, S. Mukai, W.-J. Chun, M. Nomura, K. Asakura Photon Factory Activity Report 2013 31B 292 2014年 [査読無し][通常論文]
  • 有賀寛子, 宮本剛史, ALVIN Hernandez, 高草木達, 大谷茂樹, 大山Ted, 朝倉清高 表面科学学術講演会講演要旨集 33rd 125 2013年11月26日 [査読無し][通常論文]
  • 北山冬馬, 朝倉清高, 高草木達, 有賀寛子, 上原広充, 宮崎晃太朗, 津野勝重, 工藤雅嗣, 平岩端 表面科学学術講演会講演要旨集 33rd 180 2013年11月26日 [査読無し][通常論文]
  • 望月出海, 有賀寛子, 深谷有喜, 和田健, 兵頭俊夫, 朝倉清高, 前川雅樹, 河裾厚男 表面科学学術講演会講演要旨集 33rd 108 2013年11月26日 [査読無し][通常論文]
  • 鴻野健太郎, 有賀寛子, 高草木達, 上原広充, 大谷茂樹, OYAMA S.Ted, 朝倉清高 表面科学学術講演会講演要旨集 33rd 40 2013年11月26日 [査読無し][通常論文]
  • 木工淳, 高草木達, ラフマン モハマド・ナビル, イムラン・ビン・アブドル, 上原広充, 有賀寛子, 朝倉清高 表面科学学術講演会講演要旨集 33rd 31 2013年11月26日 [査読無し][通常論文]
  • 高草木達, 小川貴史, 上原広充, 有賀寛子, 朝倉清高 触媒討論会討論会A予稿集 112th 413 2013年09月11日 [査読無し][通常論文]
  • 松井公佑, 松井文彦, 前島尚行, 有賀寛子, 朝倉清高, 松下智裕, 大門寛 日本物理学会講演概要集 68 (2) 806 -806 2013年08月26日 [査読無し][通常論文]
  • 望月出海, 有賀寛子, 深谷有喜, 和田健, 兵頭俊夫, 朝倉清高, 前川雅樹, 河裾厚男 日本物理学会講演概要集 68 (2) 806 -806 2013年08月26日 [査読無し][通常論文]
  • 望月出海, 有賀寛子, 深谷有喜, 和田健, 兵頭俊夫, 朝倉清高, 前川雅樹, 河裾厚男 アイソトープ・放射線研究発表会要旨集 50th 47 2013年06月20日 [査読無し][通常論文]
  • 吉田真明, 蓬田匠, 峯尾岳大, 新田清文, 加藤和男, 増田卓也, 仁谷浩明, 阿部仁, 高草木達, 宇留賀朋哉, 朝倉清高, 魚崎浩平, 近藤寛 電気化学会大会講演要旨集 80th 45 2013年03月29日 [査読無し][通常論文]
  • 蓬田匠, 吉田真明, 峯尾岳大, 新田清文, 加藤和男, 増田卓也, 仁谷浩明, 阿部仁, 高草木達, 宇留賀朋哉, 朝倉清高, 魚崎浩平, 近藤寛 電気化学会大会講演要旨集 80th 46 2013年03月29日 [査読無し][通常論文]
  • 高草木達, 野島大孝, 宮崎晃太郎, 有賀寛子, 上原広充, 田旺帝, 岩澤康裕, 朝倉清高 触媒討論会講演予稿集 111th 228 2013年03月11日 [査読無し][通常論文]
  • 吉田真明, 蓬田匠, 峯尾岳大, 前田彩綾, 新田清文, 加藤和男, 増田卓也, 仁谷浩明, 阿部仁, 高草木達, 宇留賀朋哉, 朝倉清高, 魚崎浩平, 近藤寛 触媒討論会講演予稿集 111th 41 -43 2013年03月11日 [査読無し][通常論文]
  • 鴻野健太郎, 有賀寛子, 高草木達, 大谷茂樹, OYAMA S. Ted, 朝倉清高 日本化学会講演予稿集 93rd (2) 460 2013年03月08日 [査読無し][通常論文]
  • 高草木達, 野島大孝, 宮崎晃太郎, 有賀寛子, 上原広充, CHUN Wang‐Jae, 岩澤康裕, 朝倉清高 日本化学会講演予稿集 93rd (3) 757 2013年03月08日 [査読無し][通常論文]
  • 有賀寛子, 宮本剛史, HERNANDEZ Alvin, 木下久美子, 高草木達, 大谷茂樹, 大山Ted, 朝倉清高 日本化学会講演予稿集 93rd (2) 504 2013年03月08日 [査読無し][通常論文]
  • 垣内孝宏, 光本久司, 菅原生豊, 篠原和彦, 朝倉清高 自動車技術会学術講演会前刷集 (96-13) 2013年
  • 峯尾 岳大, 宇留賀 朋哉, 朝倉 清高, 魚崎 浩平, 近藤 寛, 吉田 真明, 蓬田 匠, 新田 清文, 加藤 和男, 増田 卓也, 仁谷 浩明, 阿部 仁, 高草木 達 Abstract of annual meeting of the Surface Science of Japan 33 (0) 2013年 [査読無し][通常論文]
     
    水分解用半導体光電極上のリン酸コバルト(Co-Pi)酸素生成助触媒について、Co-K端およびP-K端、K-K端XAFS測定を行い、光電極反応下でのCo-Pi助触媒の構造と化学状態の変化を調べた。これまでCo-Pi中のコバルト種は3価以上であることが知られていたが、本研究では反応初期過程においてコバルト2価種が観測され、光電極反応の進行とともにCo-Piの化学状態が変化することが分かった。
  • 吉田 真明, 高草木 達, 宇留賀 朋哉, 朝倉 清高, 魚崎 浩平, 近藤 寛, 権 成浩, 蓬田 匠, 峯尾 岳大, 新田 清文, 加藤 和男, 増田 卓也, 仁谷 浩明, 阿部 仁 Abstract of annual meeting of the Surface Science of Japan 33 (0) 2013年 [査読無し][通常論文]
     
    In-Situ X線吸収分光法により、光触媒反応中における酸化マンガン助触媒の価数変化を測定し、励起キャリアの移動を観測することを目的として実験を行った。酸化マンガンを担持したチタン酸ストロンチウム光触媒に硝酸銀水溶液中で紫外光を照射すると、酸化マンガン助触媒が3価から4価に酸化され、光触媒上から酸化マンガン助触媒へ励起ホールが移動する様子を観測できることを見出した。
  • Introduction of a qPlus sensor type cantilever for XANAM measurements
    S. Suzuki, S. Mukai, W.-J. Chun, M. Nomura, K. Asakura Photon Factory Activity Report 2012 30B 92 2013年 [査読無し][通常論文]
  • Improvement of XANAM with a qPlus sensor for enhancing chemical sensitivity on surface analysis
    S. Suzuki, S. Mukai, Y. Koike, K. Kinoshita, K. Fujikawa, W.J. Chun, M. Nomura, K. Asakura Proceedings of 9th International Symposium on Atomic Level Characterizations for New Materials and Devices '13 (ALC'13) in press. 2013年 [査読無し][通常論文]
  • 吉田真明, 蓬田匠, 峯尾岳大, 前田彩綾, 新田清文, 加藤和男, 増田卓也, 仁谷浩明, 阿部仁, 高草木達, 宇留賀朋哉, 朝倉清高, 魚崎浩平, 近藤寛 表面科学学術講演会講演要旨集 32nd 32 2012年11月20日 [査読無し][通常論文]
  • 柳橋宣利, 中谷昌史, 朝倉清高, 村松淳司 触媒討論会討論会A予稿集 110th 256 2012年09月14日 [査読無し][通常論文]
  • 朝倉清高, 原口惟, 和田敬広, 有賀寛子, 高草木達 触媒討論会討論会A予稿集 110th 355 2012年09月14日 [査読無し][通常論文]
  • 高草木達, NABIL Imran bin, Abdul R. M, 木工淳, 上原広充, 有賀寛子, 朝倉清高 触媒討論会討論会A予稿集 110th 340 2012年09月14日 [査読無し][通常論文]
  • 蓬田匠, 吉田真明, 畑廷尚, 豊島遼, 新田清文, 加藤和男, 増田卓也, 仁谷浩明, 阿部仁, 高草木達, 宇留賀朋哉, 朝倉清高, 魚崎浩平, 近藤寛 Photon Fact News 30 (2) 20 -23 2012年08月 [査読無し][通常論文]
  • 朝倉 清高, 有賀 寛子, 高草木 達, 宮本 剛志 觸媒 = Catalyst 54 (2) 138 -140 2012年03月10日 [査読無し][通常論文]
  • 高草木達, 小川貴史, 上原広充, 有賀寛子, 朝倉清高 日本化学会講演予稿集 92nd (2) 216 2012年03月09日 [査読無し][通常論文]
  • 畠山義清, 大西慧, 加藤淳一, 朝倉清高, 西川恵子 日本化学会講演予稿集 92nd (3) 937 2012年03月09日 [査読無し][通常論文]
  • 吉田真明, 蓬田匠, 畑廷尚, 豊島遼, 新田清文, 加藤和男, 増田卓也, 仁谷浩明, 阿部仁, 高草木達, 宇留賀朋哉, 朝倉清高, 魚崎浩平, 近藤寛 日本化学会講演予稿集 92nd (2) 501 2012年03月09日 [査読無し][通常論文]
  • 和田敬広, 阪東恭子, 高草木達, 朝倉清高 日本放射光学会年会・放射光科学合同シンポジウム予稿集 25th 136 2012年01月06日 [査読無し][通常論文]
  • 柳橋 宣利, 中谷 昌史, 朝倉 清高, 村松 淳司 石油学会 年会・秋季大会講演要旨集 2012 (0) 32 -32 2012年 [査読無し][通常論文]
     
    共役ジエンのアセトキシ化は化成品の原料となる不飽和グリコールジエステルを製造するための重要なプロセスである。現在、工業的にはPd-Te系触媒を利用しその反応を行っている。これに対し、Rh-Te系触媒は転化率および選択率が高いため、Pd-Teの代替として期待されている。しかしながら、構造が不均一なため反応中にRhの溶出が生じるため実用化に至っていない。そこで、本研究では液相で均一な還元が可能な液相還元法を用いた均一な構造を有するRh-Te合金ナノ粒子触媒の合成法について検討した。
  • 蓮田匠, 吉田真明, 畑廷尚, 豊島遼, 新田清文, 加藤和男, 増田卓也, 仁谷浩明, 阿部仁, 高草木達, 宇留賀朋哉, 朝倉清高, 魚崎浩平, 近藤寛 PFシンポジウム要旨集 29th 61 2012年 [査読無し][通常論文]
  • 吉田 真明, 高草木 達, 宇留賀 朋哉, 朝倉 清高, 魚崎 浩平, 近藤 寛, 蓬田 匠, 峯尾 岳大, 前田 彩綾, 新田 清文, 加藤 和男, 増田 卓也, 仁谷 浩明, 阿部 仁 Abstract of annual meeting of the Surface Science of Japan 32 (0) 32 -32 2012年 [査読無し][通常論文]
     
    XAFS法により水分解光電極上の酸化マンガン助触媒の電子状態を測定し、光電極上から助触媒への励起キャリアの移動を観測した。光照射下で酸化マンガンのMn-K端XAFSを測定すると、3価から4価に酸化される様子が観測され、酸化マンガン上に励起ホールが移動することが示された。一方、酸化マンガンの電着量が少ないサンプルでは2価に還元される様子が観測され、一部の酸化マンガン粒子は酸素生成反応に寄与しないことが示唆された。
  • XANAM with Quartz tuning fork cantilever
    S. Suzuki, S. Mukai, W.-J. Chun, M. Nomura, K. Asakura Photon Factory Activity Report 2011 29B 78 2012年 [査読無し][通常論文]
  • 和田敬広, 阪東恭子, 高草木達, OYAMA S. T, 朝倉清高 PFシンポジウム要旨集 29th 21 2012年 [査読無し][通常論文]
  • 朝倉清高, 有賀寛子, 高草木達, 鈴木秀志, 大谷茂樹, 大山茂, ALVIN Henandez, 木下久美子 表面科学学術講演会講演要旨集 31st 174 2011年12月15日 [査読無し][通常論文]
  • 小川貴史, 高草木達, 上原広充, 有賀寛子, 朝倉清高 表面科学学術講演会講演要旨集 31st 110 2011年12月15日 [査読無し][通常論文]
  • 原口惟, 和田敬広, 有賀寛子, 高草木達, 朝倉清高 表面科学学術講演会講演要旨集 31st 175 2011年12月15日 [査読無し][通常論文]
  • Bodong Li, Juan Wang, Youzhu Yuan, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura ACS CATALYSIS 1 (11) 1521 -1528 2011年11月 [査読無し][通常論文]
     
    Carbon nanotube-supported RuFe bimetallic catalysts (RuFe/CNT) were prepared through a coimpregnation method for the selective hydrogenolysis of 20 wt % glycerol aqueous solution to produce glycols (1,2-propanediol and ethylene glycol). The Ru/CNT catalyst with smaller Ru nanoparticles (NPs) was significantly active for C-C bond cleavage, giving a considerable amount of CH(4) in the hydrogenolysis product. The RuFe/CNT catalyst with bimetallic NPs having an average size similar to Ru/CNT was more efficient for C-O bond cleavage, affording higher selectivity to glycols. Almost 100% glycerol conversion and over 75% selectivity to glycol could be obtained using the optimized RuFe/CNT catalyst under relatively mild conditions. The bimetallic RuFe/CNT catalyst was structurally robust and showed excellent reusability. Transmission electron microscopic images revealed that, when an appropriate amount of Fe entity was added, the RuFe bimetallic NPs were uniformly dispersed on the CNT surfaces and had an average size of similar to 3 nm. X-ray photoelectron spectroscopy indicated that a portion of the Fe species were interacted with Ru moieties, forming Ru-Fe alloys on the Ru domain, whereas other Fe species were in the forms of iron oxides, likely FeO and FeO(1+x) (0 < x < 0.5), mostly presenting on the periphery of RuFe bimetallic NPs. The occurrence of iron oxide species is crucial for the stability of RuFe bimetallic NPs during catalytic runs; but excess iron oxides block the surfaces of RuFe bimetallic NPs, resulting in a decrease in catalytic activity. Higher performance of the RuFe/CNT catalyst is attributed to the synergistic effects of the formation of Ru-Fe alloys and the interactions between the RuFe bimetallic NPs and iron oxides on CNT surfaces.
  • Wang-Jae Chun, Kotaro Miyazaki, Naoki Watanabe, Yuichiro Koike, Satoru Takakusagi, Keisuke Fujikawa, Masaharu Nomura, Kiyotaka Asakura J.Ceram. Soc. Jpn. 119 (1395) 890 -893 2011年11月 [査読無し][通常論文]
     
    The bonding features and three dimensional structures of metal clusters on single crystal oxide surfaces can be determined by the polarization dependent total reflection fluorescence XAFS (PTRF-XAFS) method. K-edge XAFS has a cos(2) theta polarizationdependence to give successfully three dimensional structure while L-3 edge XAFS has a weaker polarization dependence though the L-3 edge is suitable for Au and Pt samples. In order to overcome this issue, we have developed an angle-resolved total reflection fluorescence XAFS (ARTRF-XAFS) method to determine more precise three dimensional structures of Au clusters using the L-3 edge by increase the number of data points. In this paper we described the methodologies of the ARTRF-XAFS and the results of Au clusters on the TiO2(110) surface. (C) 2011 The Ceramic Society of Japan. All rights reserved.
  • Chi-Wen Tsai, Hao Ming Chen, Ru-Shi Liu, Kiyotaka Asakura, Lei Zhang, Jiujun Zhang, Man-Yin Lo, Yu-Min Peng ELECTROCHIMICA ACTA 56 (24) 8734 -8738 2011年10月 [査読無し][通常論文]
     
    The C-containing iron nitride electrocatalyst is fabricated by chelating N-containing species and Fe(2+) with a carbon support under heat treatment in an NH(3) atmosphere, which induces the oxygen reduction reaction activity. This is the first demonstration of forming Fe(x)C species on iron nitride materials. The correlation between the electrochemical properties and structures are aided to elucidate their features under investigation by using X-ray absorption spectroscopy. A rotating ring disk electrode test is conducted in sulfuric acid solution and the results reveal the low H(2)O(2) yield and approximately 4e(-) transfer process of the carbon-containing FeN/C electrocatalyst. (C) 2011 Elsevier Ltd. All rights reserved.
  • 有賀寛子, フェルナンデス アルビン, 木下久美子, 高草木達, 大谷茂樹, 大山S.Ted, 朝倉清高 触媒討論会討論会A予稿集 108th 312 2011年09月13日 [査読無し][通常論文]
  • 松井公佑, 松井文彦, 後藤謙太郎, 前島尚行, 松下智裕, 有賀寛子, 朝倉清高, 大門寛 触媒討論会討論会A予稿集 108th 14 2011年09月13日 [査読無し][通常論文]
  • Alvin B. Hernandez, Hiroko Ariga, Satoru Takakusagi, Kumiko Kinoshita, Shushi Suzuki, Shigeki Otani, S. Ted Oyama, Kiyotaka Asakura Chemical Physics Letters 513 (1-3) 48 -52 2011年09月 [査読無し][通常論文]
     
    Nickel phosphide (Ni2P) is an emerging catalyst for hydrodesulfurization and other important environment- and energy-related catalytic reactions. To understand its high performance, the surface structure of a Ni2P (0 0 0 1) single crystal surface was investigated using dynamical LEED analysis. The obtained surface structure for Ni2P (0 0 0 1)-1 x 1 is a P-covered Ni3P2 structure (Ni3P_P structure) as opposed to the expected bulk terminated surface structures. This Letter discusses the driving force for the formation of the Ni3P_P surface, which involves the minimization of dangling bonds. (C) 2011 Elsevier B. V. All rights reserved.
  • Chi-Wen Tsai, Hao Ming Chen, Ru-Shi Liu, Kiyotaka Asakura, Ting-Shan Chan JOURNAL OF PHYSICAL CHEMISTRY C 115 (20) 10180 -10186 2011年05月 [査読無し][通常論文]
     
    This investigation demonstrates the photocatalytic properties and activities of N-doped InTaO4 photocatalysts, which were prepared by impregnating Ni and the use of a modified Ni@NiO core-shell nanostructure-cocatalytic method for the reduction of CO2 to methanol. X-ray absorption spectroscopy (XAS) clearly indicates the oxygen vacancies and mechanism of a series of InTaO4-based photocatalysts. Nitrogen doping produces visible-light-responsive photocatalytic activity and further enhances absorbance. The cocatalytic method not only dramatically enhances absorbance, but also efficiently avoids electron-hole recombination that would otherwise be caused by electrons and holes separated from the crystal. The photocatalytic activity that was determined by the methanol yield demonstrates that N-doped samples give approximately twice the yield of undoped ones, whereas the cocatalytic method gives about triple the yield. A mechanism is aided in attempts to elucidate the correlation between structures and activities.
  • 和田 敬広, 阪東 恭子, 河合 寿秀, 朝倉 清高 觸媒 = Catalyst 53 (3) 150 -155 2011年04月10日 [査読無し][通常論文]
  • Kyoko K. Bando, Yuichiro Koike, Toshihide Kawai, Gosuke Tateno, S. Ted Oyama, Yasuhiro Inada, Masaharu Nomura, Kiyotaka Asakura JOURNAL OF PHYSICAL CHEMISTRY C 115 (15) 7466 -7471 2011年04月 [査読無し][通常論文]
     
    Ni2P/K-USY (K-promoted ultrastable Y-type zeolite) is an efficient catalyst for hydrotreatment of petroleum feedstocks. The structural changes of the passivated catalyst during activation were followed by quick XAFS (X-ray absorption fine structure) with online gas analysis. Activation was conducted by temperature-programmed reduction (TPR) from ambient temperature to 773 Kunder a flow of H-2. The Ni species was present as Ni(OH)(2) in the passivated sample. Two peaks were detected by gas analysis during TPR. The quick XAFS analysis revealed that the first peak at 390 K was due to desorption of water from Ni(OH)(2) accompanied by formation of atomically dispersed Ni2+ species. The second peak, observed at 773 K, was due to the regeneration of Ni2P by the simultaneous reductive reaction of the atomically dispersed Ni oxide and the phosphate species, followed by growth of Ni2P nanocrystals. No formation of Ni metallic phase was observed.
  • 松井 公佑, 松井 文彦, 後藤 謙太郎, 前島 尚行, 松下 智裕, 有賀 寛子, 朝倉 清高, 大門 寛 日本物理学会講演概要集 66 (1) 927 -927 2011年03月03日 [査読無し][通常論文]
  • 高草木達, 野島大孝, 宮崎晃太朗, 和田敬広, 有賀寛子, 田旺帝, 野村昌治, 朝倉清高 日本放射光学会年会・放射光科学合同シンポジウム予稿集 24th 143 2011年01月07日 [査読無し][通常論文]
  • 松井公佑, 松井文彦, 後藤謙太郎, 前島尚行, 松下智裕, 有賀寛子, 朝倉清高, 大門寛 日本放射光学会年会・放射光科学合同シンポジウム予稿集 24th 2011年
  • 和田敬広, 阪東恭子, 宮本剛志, 有賀寛子, 高草木達, OYAMA S. Ted, 朝倉清高 PFシンポジウム要旨集 28th 28 2011年 [査読無し][通常論文]
  • Approach to XANAM imaging by Quartz tuning fork cantilever
    S. Suzuki, S. Mukai, T. Suzuki, T. Kurimoto, W.-J. Chun, M. Nomura, K. Asakura Photon Factory Activity Report 2010 28B 72 2011年 [査読無し][通常論文]
  • Photoinduced conductivity change and structure transformation.
    Acta Crysta A 67 C678 2011年 [査読無し][通常論文]
  • Hideyuki Takahashi, Norikazu Konishi, Hironobu Ohno, Kazunari Takahashi, Yuichiro Koike, Kiyotaka Asakura, Atsushi Muramatsu APPLIED CATALYSIS A-GENERAL 392 (1-2) 80 -85 2011年01月 [査読無し][通常論文]
     
    The synthesis system of uniform and well-crystallized alloy nanoparticulate catalysts has been studied based on the calculation of pH dependent metal complex concentrations in an aqueous solution. Results of both the prediction based on calculation and EXAFS analysis clearly demonstrated that [Pd2+(EDTA)] and Te-citric acid complex species were generated independently in the solution. Since the formations of metal complexes are restricted to [Pd2+(EDTA)] and Te-citric acid complexes in the pH range between 5 and 10, only Pd20Te7 was successfully synthesized when the reducing agent was introduced into the [Pd2+(EDTA)] complex/Te-citric acid complex system at room temperature. Moreover. PdTe nanoparticles can be synthesized predominantly in pores of silica-gel by controlling the temperature of the Pd-EDTA/Te-citric acid/hydrazine mixed solution with a metal loading of 0.5 wt% Pd. The main phase of the well-crystallized alloy nanoparticles formed in the pores was Pd20Te7, leading to remarkable stability in catalytic activity, compared with those of the conventional catalysts. (C) 2010 Elsevier B.V. All rights reserved.
  • Kiyotaka Asakura Catalysis Today 157 (1-4) 2 -7 2010年11月17日 [査読無し][通常論文]
     
    Developments in surface science have provided atomic-scale surface images and helped us to understand surface reactions at an atomic-scale. Two big gaps, the pressure gap and material gap, were believed to exist between real catalyst systems and surface science targets however, they are now being filled. Nonlinear optical phenomenon of sum-frequency generation, glancing-angle X-ray, and scanning probe techniques have been developed as ambient pressure surface analysis methods. Great efforts have made it possible to perform X-ray photoelectron spectroscopy measurements in the presence of gas-phase reactants. Recent improvements in surface analysis techniques for nonconducting targets enable us to investigate metal clusters on well-defined oxide surfaces to fill the material gap. We are now able to initiate and control the surface reactions artificially by adjusting physical parameters. Surface science has reached a new stage not only for determining the surface structures, electronic properties, and reaction mechanisms but also for synthesizing highly active surfaces and controlling catalytic reactions artificially. © 2010 Elsevier B.V. All rights reserved.
  • 高草木達, 野島大孝, 宮崎晃太朗, 和田敬広, 有賀寛子, 田旺帝, 野村昌治, 朝倉清高 表面科学学術講演会講演要旨集 30th 67 2010年11月04日 [査読無し][通常論文]
  • 原口惟, 和田敬広, 有賀寛子, 高草木達, 朝倉清高 表面科学学術講演会講演要旨集 30th 412 2010年11月04日 [査読無し][通常論文]
  • Shuhei Hoshika, Futami Nagano, Toru Tanaka, Takatsumi Ikeda, Takahiro Wada, Kiyotaka Asakura, Kenichi Koshiro, Denis Selimovic, Yusei Miyamoto, Sk Sidhu, Hidehiko Sano DENTAL MATERIALS JOURNAL 29 (6) 682 -689 2010年11月 [査読無し][通常論文]
     
    The purpose of this study was to investigate the effect of application time of colloidal platinum nanoparticles (CPN) on bond strength. Dentin surfaces were subjected to one of the following treatments: (A) Etching with 10% citric acid-3% FeCl3 solution (10-3 solution); (B) Etching with 10-3 solution followed by applying CPN as a primer solution for 10, 20, 30, or 60 seconds; and (C) Priming with CPN for 10, 20, 30, or 60 seconds followed by etching with 10-3 solution. An acrylic rod was bonded to each treated dentin surface using 4-META/MMA-TBB resin. Bonded specimens were sectioned into beams for microtensile bond strength testing. In groups (B) and (C), highest bond strength was obtained when dentin surfaces were treated with CPN for 30 seconds. This meant that the CPN primer solution either enhanced the penetration of resin into dentin or the degree of conversion of 4-META/MMA-TBB resin. Within the limitations of this study, treatment with 0.1 mN CPN primer solution followed by 20 seconds of water rinsing resulted in high bond strength.
  • Satoru Takakusagi, Ken-ichi Fukui, Ryugo Tero, Kiyotaka Asakura, Yasuhiro Iwasawa LANGMUIR 26 (21) 16392 -16396 2010年11月 [査読無し][通常論文]
     
    We studied the methanol adsorption behavior of Pt nanoparticles that were vacuum-deposited on a TiO(2)(110) surface at room temperature by using an ultrahigh vacuum (UHV) scanning tunneling microscope (STM). A large number of bright spots were observed on fivefold-coordinated Ti (Ti(5c)) rows of the TiO(2)(110) surface after exposure of the Pt/TiO(2)(110) to methanol vapor. We assigned the bright spots to methoxy species. These were mobile and were found to hop along the Ti(5c) rows. In situ time-resolved STM observations of the formation and migration of the bright spots on the Pt/TiO(2)(110) were carried out in the presence of methanol. The bright spots were produced at the periphery of the Pt nanoparticles and migrated to the substrate Ti(5c) rows. We discuss the spillover process and behavior of the methoxy species on the Pt/TiO(2)(110).
  • 朝倉清高, 高草木達, 有賀寛子, CHUN Wang Jae 触媒討論会討論会A予稿集 106th 344 2010年09月15日 [査読無し][通常論文]
  • 野島大孝, 高草木達, 宮崎晃太朗, 和田敬広, 有賀寛子, CHUN Wang Jae, 野村昌治, 朝倉清高 触媒討論会討論会A予稿集 106th 341 2010年09月15日 [査読無し][通常論文]
  • 和田 敬広, 阪東 恭子, 宮本 剛志, 有賀 寛子, 高草木 達, OYAMA S. Ted, 朝倉 清高 觸媒 = Catalyst 52 (6) 462 -464 2010年09月04日 [査読無し][通常論文]
  • Donghui Guo, Yuta Nakagawa, Hiroko Ariga, Shushi Suzuki, Kumiko Kinoshita, Takeshi Miyamoto, Satoru Takakusagi, Kiyotaka Asakura, Shigeki Otani, S. Ted Oyama SURFACE SCIENCE 604 (17-18) 1347 -1352 2010年08月 [査読無し][通常論文]
     
    The surface structure of Ni2P (10 (1) over bar0), a model for highly active hydrodesulfurization catalysts, was studied using scanning tunneling microscopy (STM) and low energy electron diffraction (LEED) in order to understand the reconstruction of the surface layers. Annealing at 573 K revealed a (1 x 1) LEED pattern which changed to a c(2 x 4) arrangement by further heating to 723 K. Atomic scale STM images were obtained for both the (1 x 1) and c(2 x 4) structures. Bright spots observed in the STM images were interpreted to be due to surface phosphorus atoms and this was supported by a density functional theory (INT) simulation. Several possible models for the c(2 x 4) reconstructed structures were proposed including a P-dimer defect model, a missing-row model and a missing-row + added-row model. The last model gave the best explanation for the c(2 x 4) structure. The mechanism for the c(2 x 4) reconstruction on the Ni2P (10 (1) over bar0) surface is discussed. (C) 2010 Elsevier B.V. All rights reserved.
  • Motohiro Uo, Kiyotaka Asakura, Kana Watanabe, Fumio Watari CHEMISTRY LETTERS 39 (8) 852 -853 2010年08月 [査読無し][通常論文]
     
    The bronchoalveolar lavage fluid (BALF) from a patient with pneumoconiosis induced by cemented tungsten carbide (WC) was analyzed by micro-X-ray absorption fine structure (XAFS) analysis. The BALF precipitate was dried and subjected to fluorescence XAFS using polycapillary focused X-rays. The W L-1-edge XANES spectrum of the BALF precipitate could be identified as that of WC. Thus, a low concentration of WC could be detected from BALF using micro-XAFS without excess biopsy.
  • 枝元 一之, 猪股 裕幸, 安野 信行, 小澤 健一, 中川 雄太, 朝倉 清高, 大谷 茂樹 表面科学 : hyomen kagaku = Journal of the Surface Science Society of Japan 31 (7) 324 -330 2010年07月10日 [査読無し][通常論文]
  • K. Edamoto, H. Inomata, K. Ozawa, Y. Nakagawa, K. Asakura, S. Otani SOLID STATE COMMUNICATIONS 150 (25-26) 1120 -1123 2010年07月 [査読無し][通常論文]
     
    The electronic structure of Ni2P(10 (1) over bar0) has been investigated by photoemission spectroscopy (PES) utilizing synchrotron radiation. The surface prepared by Ar+ ion sputtering (3 kV, 15 min) and annealing (400 degrees C) gave a c(4 x 2) low-energy electron diffraction pattern. In the PES spectra measured for this surface, a Ni 3d-P 3p hybrid band (main band) and a satellite were observed at 0-4 eV and at 8 eV, respectively. Resonant PES study showed that the satellite is associated with the photoemission process leading to a two-hole bound state. The angle-resolved PES measurements showed that there were at least two surface states; one was observed at about 04 eV around the (Gamma) over bar point and the other was observed at about 0.6 eV along the boundary of the surface Brillouin zone along the [0001] direction. (C) 2010 Elsevier Ltd. All rights reserved.
  • Takeshi Miyamoto, Hironobu Niimi, Yoshinori Kitajima, Toshio Naito, Kiyotaka Asakura JOURNAL OF PHYSICAL CHEMISTRY A 114 (12) 4093 -4098 2010年04月 [査読無し][通常論文]
     
    A peak appearing at the L-2,L-3 X-ray absorption edge often provides the number of empty d states of the X-ray absorbing atoms. Ag+ compounds have a d(10) state (no d empty states) but Show a small peak at the edge. In this research, we systematically studied the edge peak of Ag+ compounds to Understand its origin oil the basis of the molecular Orbital picture and to obtain a relation of the edge peak intensity to chemical and physical quantities. The edge peak call be formally assigned to the transition from 2p to 5s enhanced by the s-d hybridization. The peak intensity has a negative correlation with I coordination charge but has a positive correlation with the strength of the covalent bond, which is in the reverse order to the other d(n) (n < 10) elements.
  • Catal Today 157 2 -7 2010年 [査読無し][通常論文]
  • 枝元 一之, 猪股 裕幸, 安野 信行, 小澤 健一, 中川 雄太, 朝倉 清高, 大谷 茂樹 表面科学 31 (7) 324 -330 2010年 [査読無し][通常論文]
  • Kiyotaka Asakura, Hironobu Niimi, Makoto Kato ADVANCES IN IMAGING AND ELECTRON PHYSICS, VOL 162 162 1 -43 2010年 [査読無し][通常論文]
  • 枝元 一之, 猪股 裕幸, 安野 信行, 小澤 健一, 中川 雄太, 朝倉 清高, 大谷 茂樹 表面科学 : hyomen kagaku = Journal of the Surface Science Society of Japan 31 (7) 324 -330 2010年 [査読無し][通常論文]
  • S. Ted Oyama, Travis Gott, Kiyotaka Asakura, Satoru Takakusagi, Kotaro Miyazaki, Yuichiro Koike, Kyoko K. Bando JOURNAL OF CATALYSIS 268 (2) 209 -222 2009年12月 [査読無し][通常論文]
     
    The hydrodesulfurization (HDS) of thiophene was studied over Ni2P/MCM-41 by in situ Fourier transform infrared (FTIR) spectroscopy and X-ray absorption near-edge structure (XANES) measurements at atmospheric pressure and 393-723 K (120-450 degrees C). FTIR showed the presence of adsorbed molecular thiophene principally on the MCM-41 support. In the presence of hydrogen new bands in the aliphatic CH stretching region (2953, 2918, and 2876 cm(-1)) and the CH2 scissoring region (1464 cm(-1)) appeared and grew with temperature up to 553 K (280 degrees C). These were assigned to a tetrahydrothiophene surface intermediate, whose presence is consistent with the high hydrogenation activity of nickel phosphide. XANES measurements between 353 and 573 K (180-300 degrees C) also showed growth of a signal (8330.9 eV) attributed to Ni-S interactions of either the adsorbed tetrahydrothiophene or a surface phosphosulfide. Transient XANES measurements showed that the sulfur species responded dynamically at the same rate as the steady-state rate, indicating that it was associated with an intermediate in the reaction. (c) 2009 Elsevier Inc. All rights reserved.
  • Takeshi Miyamoto, Yoshinori Kitajima, Hideyuki Sugawara, Toshio Naito, Tamotsu Inabe, Kiyotaka Asakura JOURNAL OF PHYSICAL CHEMISTRY C 113 (47) 20476 -20480 2009年11月 [査読無し][通常論文]
     
    The Ag(DMe-DCNQI)(2) (DMe-DCNQI = 2,5-dimethyl-N,N'-dicyanoquinonediimine, or DM) charge-transfer salt is a promising material for production by photolithography as it displays a unique photoinduced change in conduction. Photoproducts (beta 1 and gamma) of Ag(DM)(2) were investigated using the X-ray absorption fine structure (XAFS) technique in order to understand the origin of their conduction properties. In contrast to the metallic conduction exhibited by a pristine sample (alpha), beta 1 is a semiconductor, whereas gamma is an insulator, even though the original Ag(DM)(2) composition is maintained in both the beta 1 and the gamma forms. A redox mechanism has been postulated to explain the photoinduced change in conduction. However, measurement of the Ag L-3-edge XANES (X-ray absorption near-edge structure) did not provide any evidence of electron transfer from the DM radical anion to the Ag cation in the beta 1 and gamma products. Ag K-edge extended X-ray absorption fine structure (EXAFS) data demonstrated that beta 1 is a mixture of the original pristine alpha phase and a newly found alpha' phase, which has a shorter bond distance between the Ag cations and the N atoms of DM molecules. The conduction electrons remain in the DM column of alpha and alpha', but the domain boundaries between alpha and alpha' present an activation barrier for the conduction electrons to cross these boundaries, which provides a rationale for the semiconductive behavior of beta 1. The Ag K-edge EXAFS results showed that the gamma photoproduct has a different local structure from alpha, with a shorter distance and smaller coordination number of the Ag-N bond. The DM radical anions in the gamma compound form covalent bonds between themselves, resulting in a loss of the columnar structure. The complex local structure around Ag cations explains the insulating behavior of the gamma compound.
  • 朝倉 清高, Takakusagi Satoru マテリアルインテグレ-ション 22 (9) 2 -5 2009年09月
  • Yun-Chieh Yeh, Hao Ming Chen, Ru-Shi Liu, Kiyotaka Asakura, Man-Yin Lo, Yu-Min Peng, Ting-Shan Chan, Jyh-Fu Lee CHEMISTRY OF MATERIALS 21 (17) 4030 -4036 2009年09月 [査読無し][通常論文]
     
    Carbon-supported PdCFe/C catalyst was synthesized by impregnation method. X-ray absorption spectroscopy (XAS) revealed the incorporation of C atoms in PdFe/C clusters and high-temperature annealing was facilitated the formation of the Pd-Fe-C alloy. The catalytic activity oxygen operated via reduction reaction (ORR) of Pd-Fe-C alloy demonstrated the strong dependence upon composition of Pd-Fe-C catalysis, the half-wave potential raise with the increase of iron content. A cyclic voltammetry (CV) test conducted in methanol/perchloric acid mixed solution was employed to elucidate the tolerance of PdCFe/C electrocatalysts for methanol, which exhibited the methanol-proof character of PdCFe/C electrocatalysts.
  • Yuichiro Koike, Wang-Jae Chun, Kaoru Ijima, Shushi Suzuki, Kiyotaka Asakura MATERIALS TRANSACTIONS 50 (3) 509 -515 2009年03月 [査読無し][通常論文]
     
    Metal-oxide surface interaction is important in catalysis. We have studied Ni on TiO2 (110) and Al2O3 (0001) by means of polarization-dependent total-reflection fluorescence extended X-ray absorption fine structure (PTRF-EXAFS) observations to elucidate the origin of metal-oxide interactions. Ni atoms interact with the dangling bond of the oxygen atoms. The Ni atoms are positively charged and bonded with more than two oxygen atoms. [doi:10.2320/matertrans.MBW200830]
  • 朝倉 清高, 吉朝 朗, 有馬 寛, 福井 宏之, 奥部 真樹, 片山 芳則, 大高 理 日本結晶学会誌 51 (1) 65 -66 2009年02月28日 [査読無し][通常論文]
  • 田 旺帝, 鈴木 秀士, 小池 祐一郎, 大西 洋, 笹原 亮, 朝倉 清高 表面科学 : hyomen kagaku = Journal of the Surface Science Society of Japan 30 (2) 84 -91 2009年02月10日 [査読無し][通常論文]
  • 朝倉 清高 表面科学 : hyomen kagaku = Journal of the Surface Science Society of Japan 30 (2) 117 -118 2009年02月10日 [査読無し][通常論文]
  • Wang-Jae Chun, Yuichiro Koike, Hidenori Ashima, Kumiko Kinoshita, Kaoru Ijima, Keisuke Fujikawa, Shushi Suzuki, Masaharu Nomura, Yasuhiro Iwasawa, Kiyotaka Asakura CHEMICAL PHYSICS LETTERS 470 (1-3) 99 -102 2009年02月 [査読無し][通常論文]
     
    Preparing highly dispersed monoatomic Cu species on a TiO2(110) surface was successfully achieved on a TiO2(110) surface that had been precovered with an acetic anhydride layer. Polarization-dependent total reflection fluorescence X-ray absorption. ne structure (PTRF-XAFS) spectra indicated that the three-dimensional structures of the monoatomic Cu species were stabilized on the surface by two 0.196-nm-long C-O bonds, namely, Cu-O (acetate) and Cu-O (bridging surface oxygen) bonds. The Cu species diffusion was effectively blocked by the acetate species with its molecular plane perpendicular to the [001] diffusion direction created by the dissociative adsorption of acetic anhydride. (C) 2009 Elsevier B.V. All rights reserved.
  • Kumiko Kinoshita, Shushi Suzuki, Wang-Jae Chun, Satoru Takakusagi, Kiyotaka Asakura SURFACE SCIENCE 603 (3) 552 -557 2009年02月 [査読無し][通常論文]
     
    The carboxylic acids are stably adsorbed on TiO2(110) surfaces at room temperature. To demonstrate the neutralization mechanism proposed by Ashima et al. [H. Ashima, W.-J. Chun, K. Asakura, Surf Sci. 601 (2007) 1822.] that explains the stable adsorption of carboxylic acids, we studied the full-coverage adsorption structure of acetic anhydride on a TiO2(110) surface by STM (scanning tunneling microscopy). We directly observed three postulated species on the TiO2(110) surface; normal acetates (termed acetate A) forming a (2 x 1) ordered structure, a minor acetate species (termed acetate B) which was present between the bridging oxygen and the 5-fold Ti, and the oxygen vacancies. We determined the ratio of these three species. This ratio was in good agreement with the postulated conversion reaction of acetate B to A. (C) 2009 Elsevier B.V. All rights reserved.
  • UO M. Nano Biomedicine 1 (2) 133 -136 2009年 [査読無し][通常論文]
  • K. K. Bando, T. Wada, T. Miyamoto, K. Miyazaki, S. Takakusagi, T. Gott, A. Yamaguchi, M. Nomura, S. T. Oyama, K. Asakura 14TH INTERNATIONAL CONFERENCE ON X-RAY ABSORPTION FINE STRUCTURE (XAFS14), PROCEEDINGS 190 012158 2009年 [査読無し][通常論文]
     
    Supported Ni2P catalysts are efficient for the hydrodesulfurization (HDS) of liquid fuels. In situ extended x-ray absorption fine-structure (EXAFS) analysis of the Ni2P catalyst under realistic HDS conditions revealed the formation of Ni-S bonds in the catalyst system. In order to identify the origin of these bonds, a quick x-ray absorption fine structure (QXAFS) system was set up, which enabled measurement of one Ni K-edge EXAFS spectrum in 10 sec. In addition, a Fourier transform infrared (FTIR) unit was incorporated to the QXAFS system, which allowed simultaneous measurements of XAFS and IR spectra on the same sample. The catalyst (12.2 wt% Ni2P/MCM-41) was activated under H-2 at 723 K to regenerate an active phosphide phase. After activation, a reaction gas mixture (thiophene/He/H-2 = 0.1 / 1.9 / 98, at a total flow rate of 102 ml/min) was introduced. Under the reaction conditions, there was a change in the pre-edge area of XANES, which corresponded to the evolution of Ni-S bonds in EXAFS. The simultaneous measurements of XANES and IR revealed that this Ni-S could be attributed to the formation of a Ni phosphosulfide species rather than bonding between Ni and S of adsorbed thiophene. The combined in situ techniques proved to be an effective tool for the characterization of working catalysts.
  • 1. 田旺帝, W.-J. Chun, S. Suzuki, Y. Koike, H. Onishi, A. Sasahara and K. Asakura, Principles pertaining to the metal-support interaction on metal oxide surfaces.
    表面科学 30,84-91(2009/,84-91 2009年 [査読無し][通常論文]
  • Shushi Suzuki, Golam Md Moula, Tsuyoshi Miyamoto, Yuta Nakagawa, Kumiko Kinosthita, Kiyotaka Asakura, S. Ted Oyama, Shigeki Otani JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 9 (1) 195 -201 2009年01月 [査読無し][通常論文]
     
    The surface structures of nickel phosphide (Ni2P) single crystals were studied by scanning tunneling microscopy (STM) and photoemission electron microscopy (PEEM). Atomically resolved 1 x 1 images of the Ni2P(0001) and (1010) surfaces are successfully obtained with STM, whose respective dimensions of (0.59 nm x 0.59 nm) and (0.34 nm x 0.59 nm) match the unit cell lengths. The Ni2P(0001) surface has two possible terminations in which the Ni:P ratios are 3:1 (Ni3P termination) or 3:2 (Ni3P2 termination). In the Ni3P terminated surface the Ni atoms have a square pyramidal structure, and in the Ni3P2 terminated surface the Ni atoms have a tetrahedral structure. Only the P is visible in the STM for Ni2P(0001) and this is explained as being due to the greater extension of the phosphorus p orbitals than the Ni d orbitals at the surface. The surface domain sizes of the Ni3P and Ni3P2 termination structures of Ni2P(0001) are determined to be 500 mu m by means of PEEM using a Hg-Xe lamp through a low-pass UV-filter. Evidence is found for dissociative adsorbed hydrogen on the Ni3P termination surface of Ni2P(0001), but not on the Ni3P2 surface, indicating that the square pyramidal sites on the Ni3P surface have high reactivity
  • Motohiro UO, Fumio WATARI, Kiyotaka ASAKURA, Naoyuki KATAYAMA, Shin ONODERA, Harukazu TOHYAMA, Koichi HAMADA, Somei OHNUKI Nano Biomedicine 1 (2) 133 -136 2009年 [査読無し][通常論文]
  • S.T. Oyama, T. Gott, K. Asakura, S. Takusagi, K. Miyazaki, Y. Koike and K.K. Bando
    268 209-222. 2009年 [査読無し][通常論文]
  • Go Hamasaka, Soichiro Kawamorita, Atsuko Ochida, Ryuto Akiyama, Kenji Hara, Atsushi Fukuoka, Kiyotaka Asakura, Wang Jae Chun, Hirohisa Ohmiya, Masaya Sawamura ORGANOMETALLICS 27 (24) 6495 -6506 2008年12月 [査読無し][通常論文]
     
    Solid-supported phosphine ligands silica-SMAPs {[silica gel 60N]-SMAP (1a) or [CARiACT Q-10]-SMAP (1b)}, which are composed of a caged, compact trialkylphosphine (SMAP) as a ligand and silica gel (silica get 60N or CARiACT Q-10) as a support,'were synthesized through surface functionalization. The supported phosphines (1a,b) were structurally characterized by solid-state (13)C, (29)Si, and (31)P cross-polarization/magic angle spinning (CP/MAS) NMR spectroscopies and N(2) adsorption measurements. Complexation of 1a,b with [RhCl(cod)](2) afforded a mono(phosphine)-rhodium complex Silica-SMAP-RhCl(cod) exclusively, even in the presence of excess ligands, as proved by solid-state (13)C and (31)P CP/MAS NMR spectroscopies and Rh K-edged X-ray'absorption fine structure (XAFS) measurements. Heterogeneous catalysts that were prepared from [RhCl(C(2)H(4))(2)](2) and 1a,b showed exceptionally high catalytic activities for the reaction of sterically hindered ketones (including di-tertbutyl ketone) and triorganosi lanes such as Et(3)SiH and (t-Bu)Me(2)SiH. The catalyst from 1b showed no leaching of rhodium after reaction and was reusable without decrease of the activity.
  • Motohiro Uo, Kiyotaka Asakura, Kazuchika Tamura, Yasunori Totsuka, Shigeaki Abe, Tsukasa Akasaka, Fumio Watari CHEMISTRY LETTERS 37 (9) 958 -959 2008年09月 [査読無し][通常論文]
     
    Ti, a Ni-Ti alloy, and stainless steel (SUS304) were implanted in rat soft tissues for 6 months. The chemical states of the component elements contained in the tissues surrounding those metallic implants were analyzed by fluorescence X-ray absorption line structure (XAFS). Titanium oxide and a nickel aquo complex, which Would be Caused by the erosion of Ti and Ni, were detected in the Surrounding tissues. The concentrations of Ti and Ni in the tissues were 1-3 and 300 ppm, respectively. Thus, the dissolved conditions and concentrations of those practical metallic materials in vivo were successfully confirmed.
  • Kumiko Kinoshita, Georg Hermann Simon, Thomas Koenig, Markus Heyde, Hans-Joachim Freund, Yuta Nakagawa, Shushi Suzuki, Wan-Jae Chun, Shiaeo Ted Oyama, Shigeki Otani, Kiyotaka Asakura JAPANESE JOURNAL OF APPLIED PHYSICS 47 (7) 6088 -6091 2008年07月 [査読無し][通常論文]
     
    A Ni2P(0001) single crystal surface has been studied in the framework of model catalysis with a low temperature scanning tunneling microscope (STM) under ultrahigh vacuum (UHV). We observed a previously unreported (root 3 x root 3) R30 degrees reconstruction and Successfully recorded its atomically-resolved STM images. Two types of atomic arrangements have been found for this (root 3 x root 3) R30 degrees structure depending oil annealing conditions during preparation. One shows a filled and the other one an empty network of polygons. Upon annealing to 940 K, only the latter empty type of structure has been observed.
  • Md Golam Moula, Shinsuke Sato, Katsumi Irokawa, Hironobu Niimi, Shushi Suzuki, Kiyotaka Asakura, Haruo Kuroda BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 81 (7) 836 -842 2008年07月 [査読無し][通常論文]
     
    We observed the IR-induced reaction of C2H5OH on MoO3, using a pulsed and tunable infrared free electron laser (IR-FEL). The IR-FEL-induced reaction showed wavelength dependency and requires light stronger than a certain threshold level. The C2H5OH was converted mainly to C2H4 only when the MoO3 was irradiated with focused IR-FEL at 967 and 814cm(-1) corresponding to Mo=O stretching modes. whereas IR light at 1200cm(-1) induced no reaction. The origin of this IR-FEL-induced reaction is discussed.
  • 朝倉 清高 表面科学 = Journal of The Surface Science Society of Japan 29 (5) 278 -278 2008年05月10日 [査読無し][通常論文]
  • 朝倉 清高 触媒 = Catalysts & Catalysis 50 (2) 203 -204 2008年03月10日 [査読無し][通常論文]
  • Tinku Baidya, K. R. Priolkar, P. R. Sarode, M. S. Hegde, K. Asakura, G. Tateno, Y. Koike JOURNAL OF CHEMICAL PHYSICS 128 (12) 124711 2008年03月 [査読無し][通常論文]
     
    Ce1-x-yTixPtyO2-delta(x=0.15; y=0.01) and Ce(1-x-y)Ti(x)PdyO(2-delta)(x= 0.25; y=0.02 and 0.05) are found to be good CO oxidation catalysts [T. Baidya et al., J. Phys. Chem. B 110, 5262 (2006); T. Baidya et al., J. Phys. Chem. C 111, 830 (2007). A detailed structural study of these compounds has been carried out by extended x-ray absorption fine structure along with x-ray diffraction and x- ray photoelectron spectroscopy. The gross cubic fluorite structure of CeO2 is retained in the mixed oxides. Oxide ion sublattice around Ti as well as Pt and Pd ions is destabilized in the solid solution. Instead of ideal eight coordinations, Ti, Pd, and Pt ions have 4+3, 4+3, and 3+4 coordinations creating long and short bonds. The long Ti-O, Pd-O, and Pt-O bonds are similar to 2.47 angstrom (2.63 angstrom for Pt-O) which are much higher than average Ce-O bonds of 2.34 angstrom. (C) 2008 American Institute of Physics.
  • Yuichiro Koike, Keisuke Fujikawa, Shushi Suzuki, Wang-Jae Chun, Kaoru Ijima, Masaharu Nomura, Yasuhiro Iwasawa, Kiyotaka Asakura JOURNAL OF PHYSICAL CHEMISTRY C 112 (12) 4667 -4675 2008年03月 [査読無し][通常論文]
     
    Three-dimensional structures of Ni clusters deposited on a TiO2(110) surface were studied using polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) analysis. Three-dimensional Ni clusters were formed with a slightly anisotropic structure at 1 x 10(14) atoms/cm(2). The PTRF-XAFS results for a 1 x 10(14) atoms/cm(2) sample revealed the formation of one- atomic -layer Ni clusters with a distorted (110)(fcc) plane structure. We found a Ni-Ni distance of 0.240 nm with Ni-O interaction at 0.23 nm. The structure was stabilized by interaction of surface oxygen atoms. The origin of cluster size self-regulation was the strong Ni-O interaction and matching of the crystal lattice between TiO2(110) and distorted Ni(110) structures.
  • Development of XANAM
    S. Suzuki, Y. Koike, K. Kinoshita, Y. Nakagawa, K. Fujikawa, W.-J. Chun, M. Nomura, K. Asakura Photon Factory Activity Report 2007 25A 58 2008年 [査読無し][通常論文]
  • Growth of CNF on Nanoscale catalsyt strip fabricated with FIB
    Nanotechnology 19 405302 2008年 [査読無し][通常論文]
  • Toshihide Kawai, Wang-Jae Chun, Kiyotaka Asakura, Yuichiro Koike, Masaharu Nomura, Kyoko K. Bando, S. Ted Oyama, Hitoshi Sumiya REVIEW OF SCIENTIFIC INSTRUMENTS 79 (1) 014101 2008年01月 [査読無し][通常論文]
     
    The design and performance of a new high-pressure and high-temperature cell for measurement of x-ray absorption fine structure (XAFS) spectra of solid catalysts working in a flowing liquid are presented. The cell has flat, high-purity sintered cubic boron nitride (c-BN) windows which can tolerate high temperature (900 K) and high pressure (10 MPa). The c-BN is a new material which has the highest tensile strength, second only to diamond, and is also chemically and thermally stable. The use of the cell is demonstrated for measurements of PtPd/Al2O3 and Ni2P/SiO2 hydrodesulfurization catalysts at reaction conditions. A technique called delta chi (Delta chi), involving determining the difference between XAFS spectra of the sample at reaction conditions and the bare sample, is introduced. (c) 2008 American Institute of Physics.
  • Hao Ming Chen, Ru-Shi Liu, Kiyotaka Asakura, Ling-Yun Jang, Jyh-Fu Lee JOURNAL OF PHYSICAL CHEMISTRY C 111 (50) 18550 -18557 2007年12月 [査読無し][通常論文]
     
    By utilizing the X-ray absorption approach, the gold ions evolving from the Au-Cl complex to Au rods have been elucidated. The theoretical simulation of X-ray absorption spectra further revealed the evolution of gold and concluded that ultrafine small clusters of gold (Au(13)) formed after a reducing agent was added to the growth solution. A redesigned seed-assisted growth method, a serial addition of growth solution, was employed to achieve the goal of the consecutive support of gold. The development approach was found to successfully fabricate ID gold nanorods/wires with a tunable size from 50 nm to 1.7 mu m.
  • Ryo Niishiro, Ryoko Konta, Hideki Kato, Wang-Jae Chun, Kiyotaka Asakura, Akihiko Kudo JOURNAL OF PHYSICAL CHEMISTRY C 111 (46) 17420 -17426 2007年11月 [査読無し][通常論文]
     
    The effects upon the photophysical and photocatalytic properties of the codoping of rhodium and antimony in rutile-type TiO2 were investigated. TiO2 codoped with rhodium and antimony (TiO2:Rh/Sb) had an absorption band in the visible light region. Its energy gap was 2.1 eV. The TiO2:Rh/Sb powder showed photocatalytic activity for the oxidation of water to form O-2 in the presence of Ag+ ions as an electron acceptor under visible light irradiation (lambda > 440 nm), whereas TiO2 doped with only rhodium showed no activity. The photocatalytic activity strongly depended on the amount and ratio of the Sb/Rh dopant. Electron spin resonance, diffuse reflection spectroscopy, and X-ray absorption near-edge structure analyses revealed that the doped rhodium exists in a trivalent oxidation state in the active photocatalyst. The photocatalytic activity was decreased remarkably even by a small amount of Rh4+ ions. Antimony played an important role in suppressing the formation of Rh4+ ions by charge compensation. Thus, it has been clarified that Rh3+ is the species responsible for the photocatalytic activity under visible light irradiation in the TiO2:Rh/Sb photocatalyst.
  • Tetsuya Tsutsumi, Takeshi Miyamoto, Hironobu Niimi, Yoshinori Kitajima, Yuji Sakai, Makoto Kato, Toshio Naito, Klyotaka Asakura SOLID-STATE ELECTRONICS 51 (10) 1360 -1366 2007年10月 [査読無し][通常論文]
     
    Energy-filtered X-ray photoemission electron microscopy (EXPEEM) is a new surface chemical imaging method that combines X-ray photoelectron spectroscopy (XPS) and photoemission electron microscopy (PEEM). We have developed a collinear type EXPEEM system using a Wien-filter-type electron energy analyzer. The collinear arrangement has the advantage of carrying out an easy alignment of the electron optical axis. We have measured EXPEEM images, mu-X-ray absorption near edge structure (mu-XANES) and mu-XPS of Au on Ta and Ag(DM)(2). We discuss the advantage of EXPEEM and future applications to organic devices. (C) 2007 Elsevier Ltd. All rights reserved.
  • H. Niimi, M. Kato, T. Kawasaki, T. Miyamoto, S. Suzuki, W. J. Chun, M. Kudo, N. Kawahara, M. Doi, K. Tsukamoto, K. Asakura SURFACE SCIENCE 601 (20) 4742 -4747 2007年10月 [査読無し][通常論文]
     
    We have developed an in-lab energy-filtered X-ray photoemission electron microscopy (EXPEEM) combining a high-brilliance X-ray source and a new Wien filter-type energy analyzer, which can accept photoelectrons in a wide angle. To obtain high energy resolution, we enlarged the inner diameter of the filter and reduced aberrations of an analyzer using multipole electrodes and air-core coils. We obtained an energy-filtered image of photoelectrons. (c) 2007 Elsevier B.V. All rights reserved.
  • Toshio Naito, Hideyuki Sugawara, Tamotsu Inabe, Yoshinori Kitajima, Takeshi Miyamoto, Hironobu Niimi, Kiyotaka Asakura ADVANCED FUNCTIONAL MATERIALS 17 (10) 1663 -1670 2007年07月 [査読無し][通常論文]
     
    A charge-transfer complex of 2,5-dimethyl-N,N'-dicyanoquinonediimine (DM) with silver (crystalline Ag(DM)(2), defined as a) is irreversibly transformed by UV-vis illumination. Depending on the illumination conditions, three new types of solids (defined as gamma, delta, and epsilon) with different structural and physical properties are obtained and examined by a variety of analytical techniques, including solid-state, high-resolution, cross-polarization magic angle spinning (CP-MAS) (CNMR)-C-13, elemental analysis (EA), mass spectrometry (MS), X-ray absorption fine structure (XAFS), and powder X-ray diffraction (XRD). The CP-MAS, EA, MS, and XAFS results indicate that compound gamma is a glass state of Ag(DM)(2). The transformation from crystalline (a) to amorphous (gamma) solid Ag(DM)(2) is an irreversible exothermic glass transition (glass-transition temperature 155.2 degrees C; Delta H=-1.26.8 kJ mol(-1)), which implies that the glass form is thermodynamically more stable than the crystalline form. Compound delta (Ag(DM)(1.5)) consists of silver nanoparticles (diameter (7 +/- 2) nm) dispersed in a glassy matrix of neutral DM molecules, The =N-CN-Ag coordination bonds of the a form are not maintained in the delta form. Decomposition of a by intense illumination results in a white solid (epsilon), identified as being composed of silver nanoparticles (diameter (60 +/- 10) nm). Physical and spectroscopic (XAFS) measurements, together with XRD analysis, indicate that the silver nanoparticles in both delta and epsilon are crystalline with lattice parameters similar to bulk silver; however, the magnetic susceptibilities differ from bulk silver.
  • Hidenori Ashima, Wang-Jae Chun, Kiyotaka Asakura SURFACE SCIENCE 601 (8) 1822 -1830 2007年04月 [査読無し][通常論文]
     
    We have studied the adsorption structure of acetic anhydride on a TiO2 (1 1 0) surface using XPS (X-ray photoelectron spectroscopy), LEED (low energy electron diffraction) and HREELS (high resolution electron energy loss spectroscopy) to determine the origins of the unique adsorption properties of carboxylic acids on a TiO2(1 1 0) surface. The C 1s XPS data indicated that the saturation carbon amount of adsorbed acetic anhydride was 12 +/- 3% larger than that of the adsorbed acetic acid. LEED showed p(2 x 1) weak spots for the acetic anhydride adsorbed surface. The HREELS spectra revealed the dissociative adsorption of acetic anhydride. Based on these findings, we concluded that the neutralization of the bridging oxygen atoms associated with the dissociative adsorption is necessary for the stable adsorption of carboxylates on the 5-fold Ti sites. (c) 2007 Elsevier B.V. All rights reserved.
  • Preparative study of XANAM surface chemical mapping
    S. Suzuki, M. Nakamura, K. Kinoshita, Y. Koike, K. Fujikawa, W.-J. Chun, M. Nomura, K. Asakura Photon Factory Activity Report 2006 24B 49 2007年 [査読無し][通常論文]
  • Handbook of Biomeneralization -Medical and Clinical Aspects
    Fumio Watari, Kazuchika Tamura, Atsuro Yokoyama, Ken-ichiro Shibata, Tsukasa Akasaka, Bunshi Fugetsu, Kiyotaka Asakura, Motohiro Uo, Yasunori Totsuka, Yoshinori Sato, Kazuyuki Tohji 127 -144 2007年 [査読無し][通常論文]
  • Mayuko Ushiro, Kiyotaka Asakura, Kenryo Ohminami, Shin-ichi Nagamatsu, Takashi Fujikawa X-RAY ABSORPTION FINE STRUCTURE-XAFS13 882 786 -+ 2007年 [査読無し][通常論文]
     
    Residual Ni species after Ni removal treatment of carbon nanofibers have been investigated by use of XAFS analyses. Most of the Ni impurities are in Ni monomer which is located on defects in carbon nanofibers. The XAFS analyses combined with the multiple scattering theory give useful information on nano-structures of small amount species. Molecular orbital calculation also support the results from the XAFS analyses.
  • Akane Suzuki, Yasuhiro Inada, Kiyotaka Asakura, Masaharu Nomura X-RAY ABSORPTION FINE STRUCTURE-XAFS13 882 675 -+ 2007年 [査読無し][通常論文]
     
    We have clarified the adsorption and release mechanism of hydrogen to/from Pt clusters on an MCM-41 surface by using the XAFS technique. After reduction, the icosahedral Pt13 cluster of r(Pt-Pt) =0.273 nm is formed. In contrast, a very small oxidized metal particle of r(Pt-Pt) = 0.254 nm is formed after the oxidation. We have measured time-resolved energy dispersive XAFS in order to clarify the adsorption and release mechanism of hydrogen to/from Pt clusters on an MCM-41 surface. Although the reduction process can be explained as the sum of the initial and the final species, a third species should be considered in the oxidation process.
  • Toshihide Kawai, Kyoko K. Bando, Yong-Kul Lee, S. Ted Oyama, Wang-Jae Chun, Kiyotaka Asakura X-RAY ABSORPTION FINE STRUCTURE-XAFS13 882 (1) 616 -+ 2007年 [査読無し][通常論文]
     
    A Ni2P/SiO2 catalyst that is highly active for hydrodesulfurization (HDS) reaction was studied by in situ extended x-ray absorption fine structure (EXAFS) under the real reaction conditions. The measurements were conducted at realistic conditions of high pressure (3 MPa) and high temperature (613 K) in the presence of model oil. We used a low-volume cell with cubic boron nitride windows. The obtained spectra revealed that the bulk Ni2P structure was stable at reaction conditions and that the active surface had Ni-S bonds under reaction conditions, which played an important role for HDS reactions.
  • Masaharu Nomura, Yuichiro Koike, Masato Sato, Atsushi Koyama, Yasuhiro Inada, Kiyotaka Asakura X-RAY ABSORPTION FINE STRUCTURE-XAFS13 882 896 -+ 2007年 [査読無し][通常論文]
     
    A new XAFS beamline NW10A using bending magnet radiation from 6.5 GeV PF-AR has been constructed. NW10A consists of a Si(311) double crystal monochromator and a Pt-coated bent cylindrical focusing mirror and provides focused X-ray beam between 8 and 42 keV. The obtained flux through a linin square slit is 1x10(10) ph/s at 20 keV and 7x10(9) ph/s at 30keV, which are 20 and 200 times more intense than obtained at BL-10B. Platinum K-edges do not degrade the quality of XAFS spectra when higher orders are properly reduced. High quality Ce K-edge XAFS spectra are easily obtained.
  • S. Suzuki, M. Nakamura, K. Kinoshita, Y. Koike, K. Fujikawa, N. Matsudaira, W. -J. Chun, M. Nomura, K. Asakura PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY 61 1117 -1121 2007年 [査読無し][通常論文]
     
    We have made remarkable progress in detecting X-ray-induced frequency shift signals, which will promote development of a chemically sensitive NC-AFM. A high-performance controller provides a tenfold higher signal to noise ratio than that previously reported. We confirmed that the frequency shift or complementary Z-feedback signal dependence on X-ray energy has a peak. An important feature of the signal is that it does not follow the absorption spectrum of a surface element. These new findings are important to elucidate this novel X-ray-induced phenomenon.
  • , Aberration-corrected multipole wien filter for EXPEEM.
    Rev.Sci.Instrum. 78 063710 2007年 [査読無し][通常論文]
  • Motohiro Uo, Kiyotaka Asakura, Atsuro Yokoyama, Makoto Ishikawa, Kazuchika Tamura, Yasunori Totsuka, Tsukasa Akasaka, Fumio Watari Dental Materials Journal 26 (2) 268 -273 2007年 [査読無し][通常論文]
     
    Tissues contacting Ti dental implants were subjected to X-ray absorption fine structure (XAFS) analysis to examine the chemical state of Ti transferred from the placed implant into the surrounding tissue. Nine tissues that contacted pure Ti cover screws for several months were excised in a second surgery whereby healing abutments were set. Six tissues that surrounded implants retrieved due to their failure were also excised. Ti distributions in the excised specimens were confirmed by X-ray scanning analytical microscopy (XSAM), and the specimens were subjected to fluorescence XAFS analysis to determine the chemical states of the low concentrations of Ti in the tissues surrounding Ti dental implants. Ti mostly existed in the metallic state and was considered to be debris derived from the abrasion of implant pieces during implant surgery. Oxidized forms of Ti, such as anatase and rutile, were also detected in a few specimens-and existed in either a pure state or mixed state with metallic Ti. It was concluded that the existence of Ti in the tissue did not cause implant failure. Moreover, the usefulness of XAFS for analysis of the chemical states of rarely contained elements in biological tissue was demonstrated.
  • Wang-Jae Chun, Yuichiro Koike, Kaoru Ijima, Keisuke Fujikawa, Hidenori Ashima, Masaharu Nomura, Yasuhiro Iwasawa, Kiyotaka Asakura CHEMICAL PHYSICS LETTERS 433 (4-6) 345 -349 2007年01月 [査読無し][通常論文]
     
    Highly dispersed monoatomic Cu species on a TiO2 (110) surface were successfully prepared by a new method in which the TiO2 (110) surface was premodified with a 3-thiophenecarboxylic layer. Polarization-dependent total reflection fluorescence-X-ray absorption fine structure (PTRF-XAFS) showed the three dimensional structure of the monoatomic Cu species which were stabilized on the surface through the formation of Cu-S (adsorbate) and Cu-O (bridging oxygen) bonds. (c) 2006 Elsevier B.V. All rights reserved.
  • X-ray absorption near edge structure(XANES) studies of Ag species in Ag(DM)2 and its phtochemical products
    Chem. Lett. 36 1008 -1009 2007年 [査読無し][通常論文]
  • Photochemical transormation of moelcuar cyrstals into device.
    Special Publication - Royal Society of Chemistry. 306 2007年 [査読無し][通常論文]
  • X-ray absorption near edge structure(XANES) studies of Ag species in Ag(DM)2 and its phtochemical products
    36 1008 -1009 2007年 [査読無し][通常論文]
  • Photochemical transormation of moelcuar cyrstals into device.
    306 2007年 [査読無し][通常論文]
  • Md. Golam Moula, Shushi Suzuki, Wang-Jae Chun, Shigeki Otani, S. Ted Oyama, Kiyotaka Asakura SURFACE AND INTERFACE ANALYSIS 38 (12-13) 1611 -1614 2006年12月 [査読無し][通常論文]
     
    The Ni2P (0001) single crystal surface was characterized by low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) to determine the atomic-scale structure of the surface. LEED patterns revealed the presence of a sharp (1 x 1) structure and a reconstructed structure (2/3 x 2/3), while STM measurements showed only a well-ordered (1 x 1) hexagonal structure. We found that the reconstructed (2/3 x 2/3) structure might be related to a Ni rearrangement that maintains the phosphorus (1 x 1) structure. Copyright (C) 2006 John Wiley & Sons, Ltd.
  • Hao Ming Chen, Ru-Shi Liu, Kiyotaka Asakura, Jyh-Fu Lee, Ling-Yun Jang, Shu-Fen Hu JOURNAL OF PHYSICAL CHEMISTRY B 110 (39) 19162 -19167 2006年10月 [査読無し][通常論文]
     
    This investigation describes the formation of a metal nanorattle with a pure metal shell by varying experimental parameters. The galvanic replacement reaction between silver and chloroauric acid was adopted to prepare hollow metal nanoparticles. This approach is extended to produce nanorattles of Au cores and Au shells by starting with AucoreAgshell nanoparticles as templates. The effect of temperature on the nanostructure of the final product is also considered. The composition of the shell in nanorattles can be controlled by varying the reaction temperature (to form pure gold or gold-silver alloy, for example). X-ray absorption fine structure spectroscopy is conducted to elucidate the fine structure of these nanoparticles. Partial alloying between the Au core and the Ag shell is observed by extended X-ray absorption fine structure (EXAFS).
  • S. Suzuki, Y. Koike, K. Fujikawa, N. Matsudaira, M. Nakamura, W. -J. Chun, M. Nomura, K. Asakura CATALYSIS TODAY 117 (1-3) 80 -83 2006年09月 [査読無し][通常論文]
     
    We have measured the NC-AFM frequency shift dependence on the X-ray energy around the AuL(3) absorption edge energy. We found a peak in the frequency shift just above the An region at the AuL(3) absorption edge energy while we could not detect any peak in the frequency shift when the NC-AFM tip was placed above the Si regions. This novel phenomenon indicated that the combination of energy-variable X-rays and NC-AFM provides us a new way to nano level chemical mapping at surface. We briefly discussed some possible mechanisms. (C) 2006 Elsevier B.V. All rights reserved.
  • 小池 祐一郎, 居島 薫, 芦間 英典, 藤川 敬介, 鈴木 秀士, 野村 昌治, 岩澤 康裕, 田 旺帝, 朝倉 清高 表面科学 = Journal of The Surface Science Society of Japan 27 (7) 414 -419 2006年07月10日 [査読無し][通常論文]
     
    We developed a UHV-Polarization dependent Total-Reflection Fluorescence Extended X-ray Absorption Fine Structure System (UHV-PTRF-EXAFS System), which enables us to prepare a clean and well-defined oxide single crystal surface. We have determined the adsorption sites and structures of highly dispersed Ni atoms on α-Al2O3(0001) and TiO2(110) using the system. In both cases, Ni atoms adsorbed at imaginary cation sites, where metal cations in next layer should be located. These results have indicated that Ni atoms selectively interact with oxygen dangling bonds.
  • T. Kawai, K. K. Bando, Y-K. Lee, S. T. Oyama, W-J Chun, K. Asakura JOURNAL OF CATALYSIS 241 (1) 20 -24 2006年07月 [査読無し][通常論文]
     
    Strict environmental regulations and declining quality of petroleum feedstocks have made sulfur removal one of the most important current problems in refining. A novel, high-activity Ni2P/SiO2 catalyst with exceptional activity in deep hydrodesulfurization (HDS) was studied by in situ extended X-ray absorption fine structure (EXAFS). The measurements were conducted at realistic conditions of high pressure (3 MPa) and high temperature (613 K) and were made possible by the use of a low-volume cell with cubic boron nitride windows. The spectra thus obtained reveal that the bulk Ni2P structure is stable at reaction conditions, but that the active surface has Ni-S bonds. (c) 2006 Elsevier Inc. All rights reserved.
  • T. Kawai, K. K. Bando, Y-K. Lee, S. T. Oyama, W-J Chun, K. Asakura JOURNAL OF CATALYSIS 241 (1) 20 -24 2006年07月 [査読無し][通常論文]
     
    Strict environmental regulations and declining quality of petroleum feedstocks have made sulfur removal one of the most important current problems in refining. A novel, high-activity Ni2P/SiO2 catalyst with exceptional activity in deep hydrodesulfurization (HDS) was studied by in situ extended X-ray absorption fine structure (EXAFS). The measurements were conducted at realistic conditions of high pressure (3 MPa) and high temperature (613 K) and were made possible by the use of a low-volume cell with cubic boron nitride windows. The spectra thus obtained reveal that the bulk Ni2P structure is stable at reaction conditions, but that the active surface has Ni-S bonds. (c) 2006 Elsevier Inc. All rights reserved.
  • 赤木 和人, 朝倉 清高 表面科学 = Journal of The Surface Science Society of Japan 27 (5) 249 -249 2006年05月10日 [査読無し][通常論文]
  • K Fujikawa, S Suzuki, Y Koike, WJ Chun, K Asakura SURFACE SCIENCE 600 (10) L117 -L121 2006年05月 [査読無し][通常論文]
     
    We have studied the growth mode and morphology of Ni clusters on a TiO2(1 10) surface with a wide terrace using scanning tunneling microscopy (STM) at a low coverage (less than 3 atoms nm(-2)). The Ni clusters are formed on the terrace at the low coverage of 0.2 atoms nm(-2). Their average dimensions are constant in three directions up to 1 atoms nm(-2). The Ni clusters have an oval shape with average sizes of 1.8 nm (along [001]) x 1.4 nm (along [110]) x 0.38 nm (in the [110] directions). Above the coverage of 1.0 atoms nm(-2), an increase in the cluster height occurs, retaining an almost constant lateral size. It is proposed that the interaction of the Ni cluster and the support surface regulates the Ni cluster size. (c) 2006 Elsevier B.V. All rights reserved.
  • 宇尾基弘, 赤坂司, 亘理文夫, 朝倉清高, 横山敦郎 北海道外科雑誌 51 (1) 2006年
  • Improvement of XANAM apparatus for chemical mapping
    S. Suzuki, M. Nakamura, K. Kinoshita, Y. Koike, K. Fujikawa, N. Matsudaira, W.-J. Chun, M. Nomura, K. Asakura Photon Factory Activity Report 2005 23B 73 2006年 [査読無し][通常論文]
  • XAFS analyses of Ni species trapped in Graphene sheet of Carbon nanofibers
    Phys.Rev.B, 73 144103 -144111 2006年 [査読無し][通常論文]
  • EXAFS studies on sorption of Cd ions on montmorillonite
    Chem.Lett 35 225 -226 2006年 [査読無し][通常論文]
  • 小池 祐一郎, 居島 薫, 芦間 英典, 藤川 敬介, 鈴木 秀士, 野村 昌治, 岩澤 康裕, 田 旺帝, 朝倉 清高 表面科学 27 (7) 414 -419 2006年 [査読無し][通常論文]
     
    We developed a UHV-Polarization dependent Total-Reflection Fluorescence Extended X-ray Absorption Fine Structure System (UHV-PTRF-EXAFS System), which enables us to prepare a clean and well-defined oxide single crystal surface. We have determined the adsorption sites and structures of highly dispersed Ni atoms on α-Al2O3(0001) and TiO2(110) using the system. In both cases, Ni atoms adsorbed at imaginary cation sites, where metal cations in next layer should be located. These results have indicated that Ni atoms selectively interact with oxygen dangling bonds.
  • M Uo, K Asakura, T Kohgo, F Watari CHEMISTRY LETTERS 35 (1) 66 -67 2006年01月 [査読無し][通常論文]
     
    Se localilzation in the human oral mucosae which contain dental amalgam or dental silver alloy particles was analyzed by X-ray scanning analytical microscopy (XSAM). Se distribution was visualized, and the localization in the neighbor of amalgam or silver particles was confirmed. The chemical state of Se was analyzed by X-ray absorption fine structure (XAFS) analysis. Se was estimated as the low valency state. The possibility of using XSAM and XAFS for the analysis of the distribution and chemical state of rarely contained elements in biological tissue was Suggested.
  • MG Moula, S Suzuki, WJ Chun, S Otani, ST Oyama, K Asakura CHEMISTRY LETTERS 35 (1) 90 -91 2006年01月 [査読無し][通常論文]
     
    The first clear atomic-scale images of a Ni2P(0001) surface have been obtained by means of a scanning tunneling (STM) microscope. The STM image shows an ordered hexagonal syrninctry of the (0001) face, which can be assigned to phosphorus atoms on Ni3P1- and Ni3P2-terminated Surface. The high temperature annealing is crucial to get a well-ordered atomic structure.
  • 3 dimensional adsorption structure of metal by means of PTRFXAFS
    27 414 -419 2006年 [査読無し][通常論文]
  • 小池 裕一郎, 田 旺帝, 朝倉 清高 表面 43 (12) 595 -604 2005年12月 [査読無し][通常論文]
  • 鵜城 真優子, 宇野 奏絵, 朝倉 清高, 藤川 高志 日本物理学会講演概要集 60 (1) 900 -900 2005年03月04日 [査読無し][通常論文]
  • Y Ohminami, S Suzuki, N Matsudaira, T Nomura, WJ Chun, K Ijima, M Nakamura, K Mukasa, M Nagase, K Asakura BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 78 (3) 435 -442 2005年03月 [査読無し][通常論文]
     
    Y. Ohminami, S. Suzuki, N. Matsudaira, T. Nomura, W.J. Chun, K. Ijima, K. Nakamura, K. Mukasa, M. Nagase and K. Asakura, Preparation and characterization of a microfabricated oxide-on-oxide catalyst of a-Sb2O4/VSbO4. Bull.Chem.Soc.Jpn. 78(3),435-442(2005).*
  • Controlled Surface structure of Cu species by modified TiO2(110) surface with chemisorbed acetic acid
    W.J. Chun, Y. Koike, K. Ijima, H. Ashima, K. Fujikawa, K. Asakura, Y. Iwasawa PF activity Report (22) 51 2005年 [査読無し][通常論文]
  • A Challenge to XANAM- a New Nanoscale Chemical Mapping Microscopy
    S. Suzuki, Y. Koike, K. Fujikawa, N. Matsudaira, W.-J. Chun, M. Nomura, K. Asakura Photon Factory Activity Report 2004 22B 75 2005年 [査読無し][通常論文]
  • A Development of a New EXPEEM System (3) - Chemical Mapping of TaOx
    T. Tsutsumi, T. Kawasaki, T. Miyamoto, H. Niimi, S. Suzuki, W.-J. Chun, K. Asakura, Y. Iwasawa Photon Factory Activity Report 2004 22B 53 2005年 [査読無し][通常論文]
  • M. Uo, K. Asakura, A. Yokoyama, K. Tamura, Y. Totsuka, T. Akasaka and F. Watari, Analysis of Titanium Dental Implants Surrounding Soft Tissue Using X-ray Absorption Fine Structure (XAFS) Analysis. Chem Lett. 34,776-777(2005).*
    2005年 [査読無し][通常論文]
  • K. Asakura, C. R. Bian, S. Suzuki, W. -J. Chun, N. Watari, S. Ohnishi, P. Lu, N. Toshima PHYSICA SCRIPTA T115 781 -783 2005年 [査読無し][通常論文]
     
    We have carried out EXAFS analyses on polymer-protected CuPd nanoparticles with sizes of about 1.4 nm. We found that the Cu-Pd heterobond was preferentially created in the CuPd nanoparticle and we called this type of structure a "heterobondphilic structure". DFT calculation indicated the electron transfer from Cu to Pd which stabilized the CuPd nanoparticle. The catalytic activities and their relation to the heterobondphilic structure were discussed.
  • 小池 裕一郎, 田 旺帝, 朝倉 清高 表面 43 (12) 595 -604 2005年 [査読無し][通常論文]
  • H. Chen, H.C. Peng, R.S. Liu, K. Asakura, C.L. Lee, J.F. Lee and S.F. Hu, Controlling the shape and length of Au nanorods. J.Phys.Chen.B. 109,19553-19555(2005).*
    2005年 [査読無し][通常論文]
  • H. Niimi, M. Kato, T. Tsutsumi, T. Kawasaki, H. Matsudaira, S. Suzuki, W.J. Chun, Y. Kitajima, M. Kudo and K. Asakura, Development of imaging energy analyzer using multipole Wien filter. Appl. Surf.Sci. 241(1-2),131-134(2005).*
    2005年 [査読無し][通常論文]
  • T. KAWAI, K.K. BANDO, S.T. OYAMA, W.-J. CHUN and K. ASAKURA, A New High Pressure and High Temperature Cell for an Operando EXAFS Observation of Hydrodesulfurization Catalysts. PF activity report. 22,19(2005).
    2005年 [査読無し][通常論文]
  • M. Ushiro, K. Asakura, K. Ohminami, S.I. Nagamatsu and T. Fujikawa, Structure and Bonding of Trace Ni Catalyst in Carbon Nanotube Studied by Ni K-Edge XANES. e-J.Surf.Sci.Nanotech. 3,427-432(2005).*
    2005年 [査読無し][通常論文]
  • K. Asakura, W.J. Chun, K. Tohji, Y. Sato and F. Watari, XAFS studies on the local structures of Ni impurities in a CNT. Chem Lett. 34(3),382(2005).*
    2005年 [査読無し][通常論文]
  • T. Naito, T. Inabe, H. Niimi and K. Asakura, A new optical doping method toward molecular electronics. Synthetic Metals. 152,289-292(2005).*
    2005年 [査読無し][通常論文]
  • T. Kawai, S. Sato, W.J. Chun, K. Asakura, K.K. Bando, T. Matsui, Y. Yoshimura, T. Kubota, Y. Okamoto, Y.K. Lee and S.T. Oyama, In situ X-ray absorption fine structure studies on the structure of Ni2P supported on SiO2. Physica Scripta. T115,822-824(200・・・
    2005年 [査読無し][通常論文]
     
    T. Kawai, S. Sato, W.J. Chun, K. Asakura, K.K. Bando, T. Matsui, Y. Yoshimura, T. Kubota, Y. Okamoto, Y.K. Lee and S.T. Oyama, In situ X-ray absorption fine structure studies on the structure of Ni2P supported on SiO2. Physica Scripta. T115,822-824(2005).*
  • 山口 良隆, 熊倉 陽, 山口 有朋, 山田 康洋, 千田 哲也, 朝倉 清高 海上技術安全研究所報告 4 (2) 306 -306 2004年06月30日 [査読無し][通常論文]
  • OYAMA S. T, LEE Y. K, 朝倉 清高, 田 旺帝, 河合 秀寿, 葭村 雄二, 阪東 恭子, KIM J. H, SONG C 触媒 = Catalysts & Catalysis 46 (2) 188 -190 2004年03月10日 [査読無し][通常論文]
  • 朝倉 清高, 高松 利恵子 表面科学 : hyomen kagaku = Journal of the Surface Science Society of Japan 25 (1) 2004年01月10日 [査読無し][通常論文]
  • Surface structure of Ni on TiO2(110) surface
    CHUN, Wang Jae, Koike, Y, Ijima, K, Fujikawa, K, Chun, W. J, Asakura, K, Iwasawa, Y 2004年 [査読無し][通常論文]
  • A Deflection Spectrum Peak of NC-AFM Cantilever at the Au L3 Edge Energy
    S. Suzuki, Y. Koike, K. Fujikawa, W.-J. Chun, M. Nomura, K. Asakura Photon Factory Activity Report 2003 21B 98 2004年 [査読無し][通常論文]
  • Recent progresses in an energy filtered high energy XPEEM using a Wien filter type energy analyzer.
    H. Niimi, T. Tsutsumi, H. Matsudaira, T. Kawasaki, S. Suzuki, W.-J. Chun, M. Kato, Y. Kitajima, Y. Iwasawa, K. Asakura Appl. Surf. Sci. 237 641-644 2004年 [査読有り][通常論文]
  • In-situ XAFS measurement of Pd-Pt/Al2O3 under HDS reaction conditions
    K K Bando, T Kawai, K Asakura, T Matsui, M Harada, M Imamura, Y Yoshimura Photon Factory Activity Report 21 75 2004年 [査読無し][通常論文]
  • Suzuki, S., Koike, Y., Fujikawa, K., Chun, W.-J., Nomura, M. and Asakura, K.: "A possibility of XANAM(X-ray Aided Non-contact Atomic Force Microscopy)". Chem.Lett. 33(5):636-637,(2004).*
    2004年 [査読無し][通常論文]
  • Naito, T., Inabe, T., Niimi, N. and Asakura, K.: "Light induced transformation of molecular materials into devices". Advanced Materials. 16:18,(2004)*
    2004年 [査読無し][通常論文]
  • 1. Ijima, K., Koike, Y., Chun, W.-J., Satio, Y., Tanizawa, Y., Shido, T., Iwasawa, Y., Nomura, M. and Asakura, K.: "A local structure of low coverage Ni species on the a-Al2O3(0001) surface- a polarization Dependent XAFS studies". Chem,Phys.Lett. 384:1・・・
    2004年 [査読無し][通常論文]
     
    1. Ijima, K., Koike, Y., Chun, W.-J., Satio, Y., Tanizawa, Y., Shido, T., Iwasawa, Y., Nomura, M. and Asakura, K.: "A local structure of low coverage Ni species on the a-Al2O3(0001) surface- a polarization Dependent XAFS studies". Chem,Phys.Lett. 384:134-138,(2004)*
  • Yasufuku, H., Ohminami, Y., Tsutsumi, T., Niimi, H., Matsudaira, N., Asakura, K., Kato, M., Sakai, Y., Kitajima, Y. and Iwasawa, Y.: "Observation of element specific energy filtered X-ray Photoemission electron microscopy(EXPEEM) images of Au on Ta usi・・・
    2004年 [査読無し][通常論文]
     
    Yasufuku, H., Ohminami, Y., Tsutsumi, T., Niimi, H., Matsudaira, N., Asakura, K., Kato, M., Sakai, Y., Kitajima, Y. and Iwasawa, Y.: "Observation of element specific energy filtered X-ray Photoemission electron microscopy(EXPEEM) images of Au on Ta using a Wien filter type energy analyzer". Jpn.J.Appl.Phys. 43(11):7682-7688,(2004).*
  • Sato,S. Niimi,H. Suzuki,S. Chun, W.J. Irokawa, K. Kuroda, H. and Asakura, K.:"Surface Reactions on MoO3 Induced by Tunable Pulse IRFEL" :Chem.Lett. 33(5),558-559,(2004)*
    2004年 [査読無し][通常論文]
  • Chun, W.J., Ijima, K., Ohminami, Y., Suzuki, S. and Asakura, K.: "Theoretical Debye Waller Factors of a-MoO3 Estimated by an Equation-of-Motion Method". J.Synchrotron Rad. 11:91-294,(2004).*
    2004年 [査読無し][通常論文]
  • Y Tanizawa, T Shido, WJ Chun, K Asakura, M Nomura, Y Iwasawa JOURNAL OF PHYSICAL CHEMISTRY B 107 (47) 12917 -12929 2003年11月 [査読無し][通常論文]
     
    "Three-dimensional local structure analysis of Cu species on TiO2(110) surface studied by polarization-dependent total reflection fluorescence X-ray absorption fine structure(PTRF-XAFS)",Y. Tanizawa, T. Shido, Y. Iwasawa, M. Nomura, W.-J. Chun and K. Asakura, J.Phys.Chem., 107,12917-12929(2003).*
  • 堤 哲也, 大南 祐介, 朝倉 清高, 安福 秀幸, 嘉藤 誠, 境 悠治, 北島 義典, 岩澤 康裕 表面科学 24 (8) 509 -511 2003年08月10日 [査読無し][通常論文]
  • 朝倉 清高, BIAN Cui-Rong, LU Ping, 戸嶋 直樹, 亘 紀子, 大西 楢平 触媒 = Catalysts & Catalysis 45 (2) 184 -186 2003年03月10日 [査読無し][通常論文]
  • 鈴木 秀士, 大南 祐介, 朝倉 清高 ペトロテック = Petrotech 26 (3) 206 -210 2003年03月01日 [査読無し][通常論文]
  • 末継 淳, 朝倉 清高, 宮崎 毅 日本土壌肥料学会講演要旨集 49 (0) 28 -28 2003年 [査読無し][通常論文]
  • "In situ XAFS studies on the structure of nickel phosphide catalyst supported on K-USY",T. Kawai, S. Sato, W. J. Chun, K. Asakura, K. K. Bando, T. Matsui, Y. Yoshimura, T. Kubota, Y. Okamoto, Y. K. Lee and S. T. Oyama, Chem.Lett., 32,956-957(2003).*
    2003年 [査読無し][通常論文]
  • 2003年 [査読無し][通常論文]
     
    "Observation of Energy-filtered Images and Energy Dispersive images of Au/Ta photoelectron by EXPEEM with a Wien Filter Type Energy Analyzer",T. Tsutsumi, Y. Ohminami, K. Asakura, H. Yasufuku, M. Kato, Y. Sakai, Y. Kitajima and Y. Iwasawa, Hyomen Kagaku, 24,509-511(2003).*
  • "Highly efficient water splitting into H-2 and O-2 over lanthanum-doped NaTaO3 photocatalysts with high crystallinity and surface nanostructure",H. Kato, K. Asakura and A. Kudo, Journal of the American Chemical Society, 125,3082-3089(2003).*
    2003年 [査読無し][通常論文]
  • "Control of reactivity in C-H bond breaking reactions on oxide catalysts: Methanol oxidation on supported molybdenum oxide",S. T. Oyama, R. Radhakrishnan, M. Seman, J. N. Kondo, K. Domen and K. Asakura, J. Phys. Chem B, 107,1845-1852(2003).*
    2003年 [査読無し][通常論文]
  • "The first observation of a non-contact AFM image of MoO3(010) on an atomic level",S. Suzuki, Y. Ohminami, T. Tsutsumi, M. M. Shoaib, M. Ichikawa and K. Asakura, Chem.Lett., 32,1098(2003).*
    2003年 [査読無し][通常論文]
  • "Recent development in the in-situ XAFS and related work for the characterization of catalysts in Japan.",K. Asakura, Cataly. Surv. Asia, 7,177-182(2003).*
    2003年 [査読無し][通常論文]
  • 田 旺帝, 朝倉 清高 放射光 15 (6) 363 -366 2002年11月30日 [査読無し][通常論文]
  • 朝倉 清高 触媒 44 (7) 579 -579 2002年10月10日 [査読無し][通常論文]
  • 鈴木 秀士, 大南 祐介, 居島 薫, 中村 基訓, 武笠 幸一, 永瀬 雅夫, 朝倉 清高 触媒 44 (6) 386 -388 2002年09月10日 [査読無し][通常論文]
  • 鈴木 あかね, 山口 有朋, 千原 貞次, 稲田 康宏, 紫藤 貴文, 朝倉 清高, 湯浅 真, 阿部 正彦, 野村 昌治, 岩澤 康裕 触媒 44 (6) 401 -403 2002年09月10日 [査読無し][通常論文]
  • H Yasufuku, Y Ohminami, T Tsutsumi, K Asakura, M Kato, Y Sakai, Y Kitajima, Y Iwasawa CHEMISTRY LETTERS (8) 842 -843 2002年08月 [査読無し][通常論文]
     
    Yasufuku, H., Y. Ohminami, T. Tsutsumi, K. Asakura, M. Kato, Y. Sakai, Y. Kitajima and Y. Iwasawa:"Observation of Energy Filtered Image for X-ray Photoemission Electron Microscopy(XPEEM) Using a Retarding Wien Filter Energy Analyzer",Chem.Lett.:842-843(2002).*
  • WJ Chun, K Asakura, H Ishii, T Liu, Y Iwasawa TOPICS IN CATALYSIS 20 (1-4) 89 -95 2002年07月 [査読無し][通常論文]
     
    To investigate the effect of alkali impurity in Mo/SiO2 on the MoOx structure on SiO2 surfaces SiO2-supported Mo oxides were prepared with various amounts of Na ions in a class-1 clean bench with a laminar flow in a class-1000 clean room. The Na concentrations were varied in the range 0-5000 ppm, while the Mo loading on SiO2 was maintained at 0.7 wt%. The Mo-Na/SiO2 samples obtained were characterized by diffuse reflectance UV-visible and Raman spectroscopy. Three types of Mo species were identified: octahedral monooxo Mo monomer species, Na2Mo2O7 and MoO3. At less than 100 ppm Na both octahedral Mo monomers and MoO3 species were formed on SiO2. The MoO3 species was transformed to Na2Mo2O7 at 2000 ppm Na, where the Na ions interact directly with the Mo species on the surface. The octahedral monooxo Mo monomer species seems not to be influenced significantly by Na impurity.
  • 朝倉 清高, 岩澤 康裕 表面科学 23 (6) 332 -338 2002年06月10日 [査読無し][通常論文]
  • 紫藤 貴文, 山口 有朋, 鈴木 あかね, 稲田 康宏, 朝倉 清高, 野村 昌治, 岩澤 康裕 表面科学 23 (6) 339 -344 2002年06月10日 [査読無し][通常論文]
  • Y Notoya, K Hayakawa, T Fujikawa, T Kubota, T Shido, K Asakura, Y Iwasawa CHEMICAL PHYSICS LETTERS 357 (5-6) 365 -370 2002年05月 [査読無し][通常論文]
     
    A recent experimental result shows that Pt L-edge XANES spectra for Pt small cluster with similar to20 Pt atoms are sensitive to CO adsorption. In the present study we try to extract useful information about geometric and electronic structures of these cluster by applying a full multiple-scattering approach for the XANES analyses. Although IR analyses show that [CO](top)/[CO](bridge) is nearly constant for wide range of [Co](ad), it is difficult to estimate the ratio because of the large difference of the IR transition intensity for different adsorbed CO molecules. The present XANES analyses provide us useful new information [CO](top)/[CO](bridge) = 1-2. (C) 2002 Published by Elsevier Science B.V.
  • Ijima, K., Y. Ohminami, S. Suzuki and K. Asakura:"Polarization dependent EXAFS measurements of an alpha-molybdenum trioxide single crystal",Topics in Catal.: 18,125-127(2002).*
    2002年 [査読無し][通常論文]
  • Yamaguchi, A., A. Suzuki, T. Shido, Y. Inada, K. Asakura, M. Nomura and Y. Iwasawa: "In-situ time-resolved energy dispersive XAFS study on the decarbonylation processes of Mo(CO)6 entrapped in NaY and HY zeolites",J.Phys.Chem.: 106,2415-2422(2002).*
    2002年 [査読無し][通常論文]
  • T Shido, A Yamaguchi, Y Inada, K Asakura, M Nomura, Y Iwasawa TOPICS IN CATALYSIS 18 (1-2) 53 -58 2002年 [査読無し][通常論文]
     
    A time-resolved energy dispersive XAFS (DXAFS) technique is applied to elucidate the local structure of catalyst precursors and active species during the preparation of catalysts. The structure of ion-exchanged copper species in ZSM-5 zeolite during temperature-programmed reduction and the structure of molybdenum carbonyl species in NaY zeolite during temperature-programmed decarbonylation were investigated by the DXAFS technique. The way of the analysis of XAFS data during the dynamic processes is also discussed. The XANES spectra were analyzed to determine the ratio of different species involved in the system as a function of temperature as well as the curve-fitting analysis of the time-resolved EXAFS. The detailed analysis of the XANES and EXAFS shed light on the structural changes during the dynamic processes. In Cu-ZSM-5, a stepwise reduction process of Cu species and the subsequent growth of Cu particles during the reduction were elucidated. In Mo-NaY, the formation of Mo subcarbonyl monomer species as an intermediate of molybdenum oxycarbide dimer species was observed. This paper demonstrates that the DXAFS technique is useful to study the chemistry of catalyst preparation and can provide vital information that cannot be obtained by other techniques.
  • Bian, C. R., S. Suzuki, K. Asakura, L. Hei and N. Toshima: "EXAFS studies on the structure of the PVP-Stabilzied Cu/Pd particles colloidally dispersed in solution",J.Phys.Chem.: 106,8587-8598(2002).*
    2002年 [査読無し][通常論文]
  • Mulukutla, R. S., T. Shindo, K. Asakura, T. K e and Y. Iwasawa, "Characterization of rhodium oxide nanoparticles in MCM-41 and their catalytic performances for NO-CO reactions in excess O2",Applied Catalysis A:, 228,305-314(2002).*
    2002年 [査読無し][通常論文]
  • Asakura, K., S. Sato, K. Irokawa and H. Kuroda:"Surface reaction induced by FEL-IR",Jpn.J.Appl.Phys., 41-1:118-119(2002).*
    2002年 [査読無し][通常論文]
  • " X線吸収分光法-XAFSとその応用ー(太田俊明編)"
    アイピーシ 2002年 [査読無し][通常論文]
  • 能登屋 康晴, 早川 久仁子, 藤川 高志, 久保田 岳志, 紫藤 貴文, 朝倉 清高, 岩澤 康裕 表面科学 22 (8) 517 -521 2001年08月10日 [査読無し][通常論文]
     
    A recent experimental result shows that Pt L-edge XANES spectra for Pt small cluster are sensitive to CO adsorption. In the present study we try to extract useful information about geometric and electronic structures of these cluster by applying a full multiple-scattering approach for the XANES analyses. Detailed analyses provide us with information that some extent of change transfer plays an important role for the CO adsorption. We also discuss the plausible adsorption site on the Pt clusters.
  • M Olea, M Kunitake, T Shido, K Asakura, Y Iwasawa BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 74 (2) 255 -265 2001年02月 [査読無し][通常論文]
     
    The adsorption kinetics on Au/Ti(OH)(4)* (a newly developed Au catalyst, active for low-temperature CO oxidation) for CO, O-2, and CO2 in the temperature range 298-473 K was determined by temporal analysis of products (TAP) technique. The response signals from the single-pulse TAP experiments were analyzed using a statistical approach, and they were fitted to analytical models in order to establish the adsorption/desorption parameters. The pulse response of a non-adsorbing gas (argon) was used as a "reference". The experiments revealed that: CO molecules reversibly adsorbed on the catalyst surface; O-2 molecularly adsorbed, irreversibly for high pulse intensities and reversibly for low pulse ones; CO2 molecules irreversibly adsorbed on the surface, probably as carbonates. This catalyst exhibited an apparent negative activation energy for irreversible adsorption of O-2.
  • Observation of the surface chemical process on micro-structured surface by emission electron microscopy and related techniques
    K. Asakura, Y. Ohminami, K. Ijima, S. Suzuki, Y. Yamaguchi, S. Takakusagi, Y. Iwasawa, M. Kato, Y. Sasaki Proceedings of 6th International Symposium on Advanced Physical Fields, Growth of well-defined Nanostructures 2001 60 2001年 [査読無し][通常論文]
  • Mulukutla,R.S.;Shido,T.; Asakura,K.; Iwasawa,Y."Nanoparticles of RhOx in the MCM-41: a Novel Catalyst for NO-CO Reaction in Excess O2",Sacripta Mater.,44:1965-1968(2001).*
    2001年 [査読無し][通常論文]
  • Yamaguchi,A.;Suzuki,A.;Shido,T.;Inada,Y.;Asakura,K.;Nomura, M.; Iwasawa,Y."Energy Dispersive XAFS Study on theDecarbonylation Process of Mo(CO)6 in NaY Zeolite",Catal. Lett.,71203-208(2001).*
    2001年 [査読無し][通常論文]
  • Shido, T.;Yamaguchi,A.;Suzuki, A.; Inada, Y., Asakura, K., Nomura, M. and Iwasawa, Y,"DXAFS study on the decarbonylation process of Mo(CO)6 in NaY supercages",J. Synchrotron Radiation,8:628-630(2001).
    2001年 [査読無し][通常論文]
  • Chun, W. J. ;Tanizawa, Y.;Shido,T.;Iwasawa,Y.;Nomura,M. and Asakura,K."Development of an in-situ polarization-dependent total reflection fluorescence XAFS measurement system",J.Synchrotron Rad.,8:168-171(2001).*
    2001年 [査読無し][通常論文]
  • Radhakrishnan,R.;Reed,C.;Oyama,S.T.;Seman,M.;Kondo,J.N.;Domen,K.;Ohminami,Y.;Asakura,K."Variability in the Structure of Supported MoO3 Catalysts: Studies Using Raman and X-ray Absorption Spectroscopy with ab initio Calculations",J.Phys.Chem.B,105:8519-・・・
    2001年 [査読無し][通常論文]
     
    Radhakrishnan,R.;Reed,C.;Oyama,S.T.;Seman,M.;Kondo,J.N.;Domen,K.;Ohminami,Y.;Asakura,K."Variability in the Structure of Supported MoO3 Catalysts: Studies Using Raman and X-ray Absorption Spectroscopy with ab initio Calculations",J.Phys.Chem.B,105:8519-8530(2001).*
  • Radhakrishnan,R.; Oyama,S.T.;Chen, J. G. ;Asakura,K.,"Electron transfer ffects in ozone decomposition on supported manganese oxide",Journal of Physical Chemistry B,105,4245-4253(2001).*
    2001年 [査読無し][通常論文]
  • Chun,W. J. ; Asakura, K. and Iwasawa,Y."Anisotropic ordering of Mo species deposted on TiO2(110) characterized by polarization dependent total reflection fluorescence EXAFS (PTRF-EXAFS)",Catal.Today,66:97-103(2001).*
    2001年 [査読無し][通常論文]
  • Yamaguchi,A.;Shido,T.;Inada,Y.;Kogure,K.;Asakura,K.;Nomura, M.; and Iwasawa,Y."In-situ Time-Resolved Energy Dispersive XAFS Study on the Reduction Processes of Cu-ZSM-5 Catalysts",Bull.Chem.Soc.Jpn.,74:801-808(2001).
    2001年 [査読無し][通常論文]
  • Notoya,Y.;Hayakawa,K.;Fujikawa,T.;Kubota,T.;Shiodo,T.;Asakura,K.and Iwasawa,Y."Multiple scattering approach to the Pt L2-edge XANES of CO adsorption on small Pt particles",Chem.Phys.Lett.,357:365-370(2001).*
    2001年 [査読無し][通常論文]
  • Radhakrishnan, R. ;Oyama,S.T.;Ohminami,Y.and Asakura,K."Structure of MnOx/Al2O3 catalyst: A study using EXAFS, in situ laser raman spectroscopy and ab initio calculations",Journal of Physical Chemistry B,105,9067-9070(2001).*
    2001年 [査読無し][通常論文]
  • 界面ハンドブック<岩澤、梅澤、澤田、辻井編>
    エヌティーエス出版 2001年 [査読無し][通常論文]
  • 朝倉 清高 放射光 13 (5) 402 -403 2000年11月01日 [査読無し][通常論文]
  • AI Kozlov, AP Kozlova, K Asakura, Y Matsui, T Kogure, T Shido, Y Iwasawa JOURNAL OF CATALYSIS 196 (1) 56 -65 2000年11月 [査読無し][通常論文]
     
    Supported Gold Catalysts Prepared from a Gold Phosphine Precursor and as-Precipitated Metal Hydroxide Precursors: Effect of Preparation Conditions on the Catalytic Performance
    Kozlov, A. I., Kozlova, A. P., Asakura, K., Matsui, Y., Kogure, T., Shido, T. and Iwasawa, Y., J. Catal., 196, 56-65 (2000)*
  • 山口 有朋, 紫藤 貴文, 稲田 康宏, 朝倉 清高, 野村 昌治, 岩澤 康裕 触媒 42 (6) 419 -421 2000年09月10日 [査読無し][通常論文]
  • 朝倉 清高 触媒 42 (5) 328 -332 2000年08月10日 [査読無し][通常論文]
  • R Radhakrishman, W Li, ST Oyama, K Asakura, JGG Chen ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 220 U391 -U391 2000年08月 [査読無し][通常論文]
  • ST Oyama, R Radhakrishnan, K Asakura, K Domen, J Nomura, M Seman ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 220 U268 -U268 2000年08月 [査読無し][通常論文]
  • 朝倉 清高 化学と工業 = Chemistry and chemical industry 53 (8) 887 -889 2000年08月01日 [査読無し][通常論文]
  • KK Bando, N Ichikuni, K Soga, K Kunimori, H Arakawa, K Asakura JOURNAL OF CATALYSIS 194 (1) 91 -104 2000年08月 [査読無し][通常論文]
     
    Characterization of Rh Particles and Li-Promoted Rh Particles in Y Zeolite during CO2 Hydrogenation-a New Mechanism for Catalysis Controlled by the Dynamic Structure of Rh Particles and the Li Additive Effect
    Bando, K. K., Ichikuni, N., Soga, K., Kunimori, K., Arakawa, H. and Asakura, K., J. Catal., 194, 91-104 (2000)*
  • 朝倉 清高 表面科学 21 (5) 294 -299 2000年05月10日 [査読無し][通常論文]
     
    We describe the features of a polarization-dependent total-reflection fluorescence EXAFS technique (TPRF EXAFS) and its application to Mo/TiO2(110) systems. This technique uses the polarization dependence of EXAFS expressed by the following equation, χ(k)=3Σicos2θi · χi(k), where θi and χi are an angle between electric polarization vector and the i-th bond direction and an EXAFS oscillation accompanying i-th bond, respectively. By changing the orientation of the sample against polarization vector, we can obtain 3-dimensional information of the chemical species dispersed on surface. TPRF EXAFS has revealed how Mo species on TiO2(110) changes its structure depending on the preparation conditions. Mo dimer species is stabilized under oxidative conditions while Mo chain is present under reductive conditions. We would like to stress that the TPRF EXAFS has become a practical tool for a characterization of 3 dimensional local structures of active sites on model supports.
  • 『表面科学』 21 294 -299 2000年 [査読無し][通常論文]
  • Surface Catalytic Reactions Assisted by Gas Phase Molecules on Supported Co Ensemble Catalysts Yamaguchi, A., Shido, T., Asakura, K. and Iwasawa, Y., Studies Surf. Sci. Catal., 130, 605-610 (2000)*
    2000年 [査読無し][通常論文]
  • Characterization and Selective Oxidation Catalysis of Modified Pt Particles on SbOx Inoue, T., Oyama, S. T., Imoto, H., Asakura, K. and Iwasawa, Y., Appl. Catal. A, 191, 131-140 (2000)*
    2000年 [査読無し][通常論文]
  • Takakusagi, S., Yamaguchi, Y. Kato, M., Sakai, Y., Fukui, K., Asakura, K. and Iwasawa, Y.,"Development of an XPEEM system with multi-probes, and its applicartion to surface imaging at static and dynamic states.",J. Microscopy,200,240-250 (2000)*
    2000年 [査読無し][通常論文]
  • The effect of Li on Structure of Supported Rh Particles in Zeolite Bando, K. K., Ichikuni, N., Arakawa, H. and Asakura, K.,Mol. Cryst. and Liq. Cryst., 341, 473-478 (2000)*
    2000年 [査読無し][通常論文]
  • Time-Resolved DXAFS Study on the Reduction Processes of Cu Cations in ZSM-5, Yamaguchi, A., Shido, T., Inada, Y., Kogure, T., Asakura, K., Nomura, M. and Iwasawa, Y., Catal. Lett., 68, 139-145(2000)*
    2000年 [査読無し][通常論文]
  • Preparation, Characterization, and Catalytic Performacne of Bi/Al2O3 Binary Oxide Layers and Clusters on an Al2O3 surface Shido, T., Okita, G., Asakura, K. and Iwasawa, Y.,J. Phys. Chem., 104, 12263-12268(2000)*
    2000年 [査読無し][通常論文]
  • A Novel Effect of Li Additive :Dynamic Control of Rh Mobility during CO2 Hydrogenation Reaction Bando, K. K., Arakawa, H., Ichikuni, N. and Asakura, K., Stud. Surf. Sci. Catal., 130, 3759- 3764(2000)*
    2000年 [査読無し][通常論文]
  • Asakura, K., Chun, W.-J. and Iwasawa, Y.,"Polarization-Dependent Total-Reflection Fluorescence EXAFS Study on Active Structures on Single Crystal Oxides as Model Catalyst Surfaces", Topics in Catal., 10, 209-219 (2000)*
    2000年 [査読無し][通常論文]
  • 阪東 恭子, 荒川 裕則, 一國 伸之, 朝倉 清高 触媒 41 (6) 406 -408 1999年09月10日 [査読無し][通常論文]
  • 朝倉 清高, 紫藤 貴文, 野口 義明, 岩澤 康裕 触媒 41 (2) 116 -118 1999年03月10日 [査読無し][通常論文]
  • 朝倉 清高, 田 旺帝, 岩澤 康裕 真空 42 (3) 450 -450 1999年03月 [査読無し][通常論文]
  • 朝倉 清高, 山口 良隆, 高草木 達, 嘉藤 誠, 境 悠治, 岩澤 康裕 真空 42 (3) 467 -467 1999年03月 [査読無し][通常論文]
  • Lu, P., Teranishi, T., Asakura, K., Miyake, M., and Toshima, N. : “Polymer-Protected Ni/Pd Bimetallic Nanoclusters: Perparation, Characterization, and Catalysis for Hydrogenation of Nitrobenzene”, J. Phys. Chem. B , 103 : 9673-9682 (1999) *
    1999年 [査読無し][通常論文]
  • 高松 利恵子, 宮崎 毅, 中野 政詩, 川村 雄行, 朝倉 清高 粘土科学 38 (2) 118 -119 1998年12月28日 [査読無し][通常論文]
  • 久保田 岳志, 岡本 康昭, 朝倉 清高[他] 島根大学総合理工学部紀要. シリーズA 32 71 -84 1998年12月24日 
    We investigated Γt andΓd L-edge X-ray absorption near edge structure(XANES)spectra for the metal particles supported on some inorganic oxides(Si0_2,Al_20_3,MgO and Ti0_2)with and without adsorbed hydrogen. The new peaks appeared at 6-8eV above the Pt L-edge in difference spectra between those in vacuum and with adsorbed hydrogen. The intensity of the new peak was decreased by evacuation at room temperature,and then intensity of peak was found to be proportional to the hydrogen coverages but independent of the kind of the supports We also measured XANES spectra at Pt L-edge for Pt particles supported on Si0_2 under CO adsorption and CO+H_2coadsorption. Coadsorption of hydrogen and CO broadened and shifted the peak in Pt L-XANES to the higher energy side. It was found that the peak can be represented by two components due to adsorbed hydrogen and CO. It was found that the fitting component with respect to adsorbed hydrogen was proportional to the amount of adsorbed hydrogen and this linear relationship was same as hydrogen mono-adsorption. In Pd L-edgeXANES spectra,new peak appeared after hydrogen adsorption and it was found that their intensity of peak can be related with amount of adsorbed hydrogen and ratio of adsorbed hydrogen or Pd atoms in subsurface region to total Pd atoms. XANES changes its structure with interaction between catalysts and adsorbates sensitively,so XANES is expected as new method for in-situ characterization.
  • 高松 利恵子, 宮崎 毅, 中野 政詩, 河村 雄行, 朝倉 清高 粘土科学討論会講演要旨集 0 (42) 56 -57 1998年10月06日 [査読無し][通常論文]
  • 山口 有朋, 柴藤 貴文, 朝倉 清高, 岩澤 康裕 触媒 40 (6) 360 -363 1998年09月10日 [査読無し][通常論文]
  • 久保田 岳志, 朝倉 清高, 北島 義典, 岩澤 康裕 触媒 40 (6) 380 -383 1998年09月10日 [査読無し][通常論文]
  • 大谷 国広, 藤川 高志, 久保田 岳志, 朝倉 清高, 岩沢 康裕 表面科学 19 (8) 486 -490 1998年08月10日 [査読無し][通常論文]
  • 山口 良隆, 高草木 達, 嘉藤 誠, 境 悠治, 朝倉 清高, 岩沢 康裕 表面科学 19 (8) 498 -502 1998年08月10日 [査読無し][通常論文]
  • 山口 良隆, 朝倉 清高, 高草木 達 表面 35 (12) 621 -628 1997年12月 [査読無し][通常論文]
  • 田 旺帝, 朝倉 清高, 岩澤 康裕 触媒 39 (6) 510 -513 1997年09月10日 [査読無し][通常論文]
  • 大谷 国広, 藤川 高志, 久保田 岳志, 朝倉 清高, 岩沢 康裕 日本物理学会講演概要集 52 (1) 389 -389 1997年03月17日 [査読無し][通常論文]
  • 井上 朋也, 朝倉 清高, 岩澤 康裕 触媒 38 (6) 502 -505 1996年09月10日 [査読無し][通常論文]
  • 朝倉 清高 触媒 38 (5) 356 -357 1996年08月10日 [査読無し][通常論文]
  • 朝倉 清高 表面科学 17 (4) 194 -200 1996年04月10日 [査読無し][通常論文]
     
    CO酸化反応中の白金(100),(110)表面を,表面の仕事関数の違いを手がかりとしたPEEM (Photoemission electron microscope)法により観察すると,様々なパターンが生じていることがわかる。このパターン形成の様子は,表面に金をsubmonolayer蒸着することで著しく変化する。本稿では,金によるパターンの変化の様子を紹介するとともに,ミクロの立場からパターンの変化の原因を解説する。最後に金蒸着表面と清浄表面の境界で起こる新しい現象について述べ,新しい表面反応制御法を探る。
  • 朝倉 清高, LARUTERBACH J, ROTERMUND H. H, ERTL G 触媒 37 (6) 434 -437 1995年09月10日 [査読無し][通常論文]
  • 朝倉 清高 ペトロテック = Petrotech 18 (7) 545 -550 1995年07月01日 [査読無し][通常論文]
  • 籏野 嘉彦, 太田 俊明, 赤井 俊雄, 朝倉 清高, 河内 宣之, 田中 健一郎, 西山 岩男, 渡辺 誠 放射光 8 (1) 106 -107 1995年02月20日 [査読無し][通常論文]
  • K ASAKURA, J LAUTERBACH, HH ROTERMUND, G ERTL PHYSICAL REVIEW B 50 (11) 8043 -8046 1994年09月 [査読無し][通常論文]
     
    The phenomenology of spatiotemporal concentration patterns associated with the catalytic oxidation of CO on a Pt(110) surface for conditions of excitability as monitored by photoemission electron microscopy is affected by deposition of submonolayer quantities of Au. This is due to continuous variation of the intrinsic kinetic parameters while the degree of homogeneity of the medium on the mesoscopic scale remains unaltered.
  • 富重 圭一, 朝倉 清高, 岩沢 康裕 触媒 35 (6) p398 -401 1993年09月 [査読無し][通常論文]
  • 大川 祐司, 難波 秀利, 朝倉 清高, 黒田 晴雄, 今川 大, 藤川 高志 秋の分科会講演予稿集 1992 (2) 456 -456 1992年09月14日 [査読無し][通常論文]
  • Yasuo Izumi, Tai-Hui Liu, Kiyotaka Asakura, Teiji Chihara, Hiroshi Yamazaki, Yasuhiro Iwasawa Photon Factory Activity Report 1990 8 188 -188 1992年 [査読無し][通常論文]
  • 綾戸 宏, 織田 昌平, 佐藤 能雅, 朝倉 清高, 黒田 晴雄 年会講演予稿集 46 (2) 204 -204 1991年09月12日 [査読無し][通常論文]
  • 朝倉 清高 触媒 33 (3) p244 -246 1991年04月 [査読無し][通常論文]
  • 岡本 穏冶, 朝倉 清高, 山崎 好直, 黒田 晴雄, 藤川 高志, 斎藤 聡 春の分科会講演予稿集 1991 (2) 556 -556 1991年03月11日 [査読無し][通常論文]
  • 吉武 英昭, 朝倉 清高, 岩沢 康裕 触媒 32 (6) p384 -387 1990年09月 [査読無し][通常論文]
  • 明山 浩一, 近藤 寛, 田村 雅史, 朝倉 清高, 黒田 晴雄, 小杉 信博 年会講演予稿集 45 (2) 297 -297 1990年03月16日 [査読無し][通常論文]
  • 石井 秀司, 朝倉 清高, 北島 義典, 船橋 学, 難波 秀利, 小杉 信博, 太田 俊明, 黒田 晴雄 年会講演予稿集 45 (2) 439 -439 1990年03月16日 [査読無し][通常論文]
  • 朝倉 清高, 岩沢 康裕 触媒 32 (2) p55 -58 1990年03月 [査読無し][通常論文]
  • Kiyotaka Asakura, Yasuo Izumi, Masayuki Shirai, Yasuhiro Iwasawa Photon Factory Activity Report 1988 6 41 -41 1990年 [査読無し][通常論文]
  • Kiyotaka Asakura, Junji Inukai, Yasuo Izumi, Yasuhiro Iwasawa Photon Factory Activity Report 1988 6 71 -71 1990年 [査読無し][通常論文]
  • 紫藤 貴文, 朝倉 清高, 岩沢 康裕 触媒 31 (6) p449 -452 1989年09月 [査読無し][通常論文]
  • 朝倉 清高 触媒 31 (5) p290 -295 1989年08月 [査読無し][通常論文]
  • 吉武 英昭, 朝倉 清高, 岩沢 康裕 触媒 30 (6) p380 -383 1988年09月 [査読無し][通常論文]
  • 朝倉 清高, 岩沢 康裕, 黒田 晴雄 日本化学会誌 1986 (11) 1539 -1546 1986年 [査読無し][通常論文]
     
    The structures of the Ru catalysts derived from Ru3(CO)12 supported on the various oxides such as MgO, K-doped A12O3, A12O3, TiO2, SiO2, V2O5, and MnO2 were studied by means of EXAFS (extended X-ray absorption fine structure). The surface Ru structures are illustrated in Fig. 9. The structures obtained by supporting Ru3(CO)12 onto the oxides depended on the acidity and basicity of supports. [HRu3(CO)11]- was formed on the basic supports like MgO and K-doped Al2O3, whereas was created on the amphoteric support like A12O8. On the more acidic supports like TiO2, SiO2 and V2O5, Ru3(CO)12 was physisorbed. The structures formed after the thermal treatments and H2 reduction of the incipient surface Ru species can be explained in terms of the electronegativity of metal ions in the support oxides. On MgO and A12O3 in which the electronegativities of the metal ions are relatively small, the chemical bonds between the surport oxygen and Ru atoms were formed after the thermal decomposition and H2 reduction. On TiO2, SiO2 and V2O5 in which the metal ions have large electronegativities, the Ru metal particles with no Ru-O bonding were observed. In the case of MnO2, the oxidation of the Ru cluster by the support was observed in addition to the metal-support interaction mentioned above. © 1986, The Chemical Society of Japan. All rights reserved.
  • 黒田 晴雄, 佐藤 佳晴, 朝倉 清高 日本結晶学会誌 27 (3) 209 -213 1985年 [査読無し][通常論文]
  • 朝倉 清高 触媒 26 (5) p390 -392 1984年09月 [査読無し][通常論文]
  • EXAFS Study on the Structure of Heteropolymolybdates in Solution
    Yukiyoshi Sasaki, Akiko Kobayashi, Tomoji Ozeki, Haruo Kuroda, Nobuhiro Kosugi, Kiyotaka Asakura, Hiromu Ishii, Toshihiko Yokoyama Photon Factory Activity Report 1982/83, VI-64, National Laboratory for High Energy Physics, KEK 1983年 [査読無し][通常論文]
  • XAS Studies on Bimetallic Rh-Co Carbonyl-Derived Catalysts I. Preliminary Experiments on Rh/SiO2
    H. Kuroda, N. Kosugi, T. Yokoyama, H. Ishii, K. Asakura, M. Ichikawa, T. Fukushima Photon Factory Activity Report 1982/83, VI-63, National Laboratory for High Energy Physics, KEK 1983年 [査読無し][通常論文]
  • XANES Studies on Mixed-Valency and Abnormal Valency in the Complexes of Ferrocene Derivatives
    Kimiko Sato, Makoto Iwai, Yasuo Watanabe, Satoru Nakashima, Hirotoshi Sano, Isao Ikemoto, Nobuhiro Kosugi, Kiyotaka Asakura, Hiromu Ishii, Toshihiko Yokoyama, Haruo Kuroda Photon Factory Activity Report 1982/83, VI-62, National Laboratory for High Energy Physics, KEK 1983年 [査読無し][通常論文]
  • EXAFS Study of Catalysts for Photodecomposition of H2O
    K. Domen, A. Kudo, T. Onishi, N. Kosugi, K. Asakura, H. Ishii, T. Yokoyama, H. Kuroda Photon Factory Activity Report 1982/83, VI-61, National Laboratory for High Energy Physics, KEK 1983年 [査読無し][通常論文]
  • Study on the Structure of the Active Sites for the Formation of Oxygenated Compounds from CO-H2 under Mild Conditions
    S. Naito, N. Kosugi, K. Asakura, H. Ishii, T. Yokoyama, K. Tamaru, H. Kuroda Photon Factory Activity Report 1982/83, VI-60, National Laboratory for High Energy Physics, KEK 1983年 [査読無し][通常論文]
  • Surface Structure of SMSI Catalyst I. Rh/TiO2 Catalyst
    H. Kuroda, N. Kosugi, K. Asakura, H. Ishii, T. Yokoyama, Y. Iwasawa Photon Factory Activity Report 1982/83, VI-59, National Laboratory for High Energy Physics, KEK 1983年 [査読無し][通常論文]
  • XANES of Highly-Conductive Mixed-Valence Organic Charge Transfer Salts I. (TMTSF)2X and Related Materials
    H. Kuroda, I. Ikemoto, K. Kikuchi, N. Kosugi, K. Asakura, H. Ishii, T. Yokoyama Photon Factory Activity Report 1982/83, VI-58, National Laboratory for High Energy Physics, KEK 1983年 [査読無し][通常論文]
  • EXAFS and XANES Studies of Metal-Halide-Doped Polyacetylenes I. FeCl3-Doped Polyacetylenes
    H. Kuroda, I. Ikemoto, N. Kosugi, K. Asakura, H. Ishii, H. Shirakawa, T. Kobayashi, H. Oyanagi, T. Matsushita Photon Factory Activity Report 1982/83, VI-56, National Laboratory for High Energy Physics, KEK 1983年 [査読無し][通常論文]
  • XANES of Metal Carbonyl Molecules I. Gas- and Liquid-Phase Fe(CO)5
    H. Kuroda, N. Kosugi, T. Yokoyama, K. Asakura, H. Ishii Photon Factory Activity Report 1982/83, VI-55, National Laboratory for High Energy Physics, KEK 1983年 [査読無し][通常論文]
  • EXAFS and XANES Studies of Chemically Fixed Mo and Cr Catalysts
    H. Kuroda, N. Kosugi, H. Ishii, K. Asakura, T. Yokoyama Photon Factory Activity Report 1982/83, VI-54, National Laboratory for High Energy Physics, KEK 1983年 [査読無し][通常論文]
  • Polarized XANES Studies of Transition Metal Complexes I. Square Planar CuCl42- Complex
    H. Kuroda, N. Kosugi, T. Yokoyama, K. Asakura, H. Ishii Photon Factory Activity Report 1982/83, VI-37, National Laboratory for High Energy Physics, KEK 1983年 [査読無し][通常論文]
  • EXAFS and XANES of FeCl3 Dissolved in Organic Solvents
    H. Kuroda, N. Kosugi, K. Asakura, H. Ishii, M. Nomura Photon Factory Activity Report 1982/83, VI-36, National Laboratory for High Energy Physics, KEK 1983年 [査読無し][通常論文]
  • EXAFS and XANES of FeCl3 Aqueous Solutions
    H. Kuroda, N. Kosugi, K. Asakura, H. Ishii, M. Nomura Photon Factory Activity Report 1982/83, VI-35, National Laboratory for High Energy Physics, KEK 1983年 [査読無し][通常論文]
  • EXAFS Study of Behavior of Rh6(CO)16 on Al2O3
    H. Kuroda, N. Kosugi, K. Asakura, H. Ishii, Y. Iwasawa Photon Factory Activity Report 1982/83, VI-34, National Laboratory for High Energy Physics, KEK 1983年 [査読無し][通常論文]
  • 河本雅弥, 工藤雅嗣, 水野潤一, JEEM Melbert, 渡辺精一, 朝倉清高 応用物理学会秋季学術講演会講演予稿集(CD-ROM) 80th 2019年

特許

受賞

  • 2021年08月 日本真空表面学会 論文賞
     Thorough Search Analysis of Extended X-ray Absorption Fine Structure Data for Complex Molecules and Nanomaterials Applications 
    受賞者: Daiki Kido;Yohei Uemura;Yuki Wakisaka;Hiroko Ariga-Miwa;Satoru Takakuasgi;Kiyotaka Asakura
  • 2021年03月 日本化学会 学術賞
     in-situ XAFSによる動的触媒表面解析の確立 
    受賞者: 朝倉清高
  • 2017年06月 American Vacuum Society VTD Shop Note Awards
     Portable ultrahigh-vacuum sample storage system for polarization-dependent total-reflection fluorescence x-ray absorption fine structure spectroscopy 
    受賞者: Ryo Suzuki;Hiromitsu Uehara;Tomoyuki Nimura;Atsushi Beniya;Noritake Isomura;Kiyotaka Asakura;Satoru Takakusagi
  • 2017年03月 Chemical Society of Japan BCSJ Sellected paper
     An Origin for Lattice Expansion in PVP-protected Small Pd Metal Nanoparticles. 
    受賞者: 朝倉 清高
  • 2016年03月 触媒学会 学会賞
     Operando XAFS法による触媒構造のその場観察と触媒作用機構に関する研究 
    受賞者: 朝倉 清高
  • 2015年10月 北海道発明協会 北海道発明協会会長賞
     表面の電子状態を観察する特殊な顕微鏡 
    受賞者: 株式会社菅製作所;代表取締役社長;菅 育正;EOS津野 代表;津野 勝重;大学院工学院;表面構造化学研究部門;朝倉 清高;大学院理工学研究科;環境機能科学専攻;内藤 俊雄;エムブイエス・エンジニアリング株式会社;代表取締役;宮崎 英機
  • 2015年08月 日本化学会 BCSJ 論文賞
     
    受賞者: 朝倉 清高
  • 2015年05月 日本表面科学会 学会賞
     最先端X線吸収分光手法の開発と触媒ナノ物質の学理の探求 
    受賞者: 朝倉 清高
  • 2013年02月 表面科学会 フェロー
     「放射光によるモデル触媒表面の動的観察とその精密設計」 
    受賞者: 朝倉 清高
  • 2012年09月 IXAS IXAS 功労賞
     
    受賞者: 朝倉 清高
  • 1993年03月 触媒学会 触媒学会奨励賞
     in-situ EXAFS法による触媒活性表面の動的解析 
    受賞者: 朝倉 清高

共同研究・競争的資金等の研究課題

  • 日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2020年04月 -2024年03月 
    代表者 : 朝倉 清高, 増田 卓也, 三輪 寛子, 和田 敬広
  • 国立研究開発法人新エネルギー・産業技術総合開発機構:燃料電池
    研究期間 : 2015年06月 -2020年03月
  • 表面X線分光による燃料電池用白金合金ナノ粒子のin situ解析と酸素還元活性
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    研究期間 : 2016年11月 -2019年03月 
    代表者 : 朝倉 清高, FEITEN FELIX
     
    Felix E.Feiten博士との共同研究成果について報告する。
    (1) 燃料電池における高活性化の中核を担う酸素還元触媒について、in situ条件下の偏光XAFS法の測定を展開した。とくに、HOPG基板上にArc Plasma法によりPtナノ粒子とPtナノ合金粒子を展開した。HOPG基板を用いているため、Pt量は10^15 個cm^-2と微量であり、高感度なXAFS測定が必要である。そこで、BCLA+BI-XAFS法という高感度XAFS測定法を開発して、適用した。その結果Pt-Ptの結合距離を精度良く決定することができた。特にPtCoNAuナノ粒子では高活性と高耐久性を示す。XAFS測定の結果、CoNをコアとし、その周辺にPtをシェルとしたコアシェル構造で存在し、そのPt-Ptの結合距離が2.74Aと通常のPt-Ptの結合距離より短くなっていることを見いだした。また、AuはPtの表面のステップサイトに有り、白金の溶解を防いでいることがわかり、失活防止の原因を解明した。 (2) このBCLA+BI-XAFS法は高感度でXAFSを測定するだけでなく、Range Extended XAFS法が通常の装置でもできるところに特徴がある。元素番号が隣同士のPtとAuが共存すると互いに干渉し、XAFSを測定することができないが、BCLA+BI-XAFS法ではそれぞれの信号を分離することができ、干渉なく測定できるRange Extended XAFSが可能であることを見いだした。これにより、PtのXAFSを精度良く測定できた。 (3) さらに、超高感度を実現するために特殊な電気化学測定XAFSセルを開発し、これまで全く測定ができていない10^14 個cm^-2の測定にも成功した。 以上の結果は1報の論文に発表し、現在2報を投稿中である。
  • 日本学術振興会:科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2011年04月 -2016年03月 
    代表者 : 鳥養 映子, 朝倉 清高, 杉山 純, 菅原 洋子, 下村 浩一郎, 吉野 淳二, 永嶺 謙忠, 新村 信雄, 金 秀光, 前川 禎通, 渡辺 政廣, 金谷 利治, 菅野 了次, 常行 真司, 笠井 秀明, 中西 寛, 池田 正二, 野崎 洋, 原田 雅史, 高阪 勇輔, 川浦 宏之, 楠木 正巳
     
    物質と生命の機能には、境界の存在が不可欠であり、その界面における物質、エネルギー、情報の伝達と反応が本質的に重要である。伝導と反応を伴う諸現象を超低速ミュオン顕微鏡で局所的に観測し、その機構を「動的過程を伴う相互作用のスピン選択性」という統一的な視点から解明する新しい学術分野の開拓を目指し、スピン伝導・イオン伝導・触媒化学反応・生命分子反応に関する研究を進めた。既存のミュオン施設を用いた実験と理論で、スピン流とイオン流の測定原理を確立した。触媒化学、生命科学の分野において、ミュオンが酸素欠陥や水素の状態、生体物質中の電子伝達に敏感であることを実証、これら新しい分野への展開をはかった。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2011年04月 -2015年03月 
    代表者 : 宇尾 基弘, 朝倉 清高, 横山 敦朗, 會田 英紀, 本郷 敏雄, 和田 敬広, 亘理 文夫
     
    材料の表面状態や生体組織界面の状態、金属材料から生体組織中への微量金属元素の溶出、蓄積は種々の歯科・生体材料の生体親和性に大きく影響する。本研究ではX線マイクロビームを用いた位置特異的な元素分布・状態分析技術を用いて、歯科用合金に隣接した粘膜中に含まれる微量金属元素の分析を行い、歯科用合金からの粘膜中への合金積分の蓄積を確認した。またXAFSによる表面処理インプラント表層のチタンの状態解析を行い、深さ方向による酸化チタンの構造変化が確認された。
  • 文部科学省:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2014年 -2015年 
    代表者 : 朝倉 清高
  • 固体高分子形燃料電池実用化推進技術開発/基盤技術開発/MEA材料の構造・反応・物質移動解析/サブテーマ“時空間分解X線吸収微細構造(XAFS)等による触媒構造反応解析
    ネド:燃料電池
    研究期間 : 2008年09月 -2013年02月 
    代表者 : 朝倉 清高
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2011年 -2013年 
    代表者 : 高草木 達, 角山 寛規, 朝倉 清高, 有賀 寛子
     
    実用上重要な酸化物担持金属触媒の特性(活性・選択性)は、金属クラスターのサイズや酸化物担体担体との相互作用に強く依存する。本研究では、単原子から10 nmまでのサイズの金クラスターを、サイズ分布の小さな状態で二酸化チタン単結晶表面へ担持するための方法論の開発を試み、担持後のクラスターに関してSTM/AFMや偏光全反射蛍光XAFS等の表面科学的手法を適用して、原子レベルの構造評価を行った。また構造と活性の相関を得るために、単結晶表面での触媒反応測定のための超高真空装置を開発した。
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2011年 -2012年 
    代表者 : 朝倉 清高
     
    本研究の目的は,これまでまったく不可能であった溶液と接したナノクラスターおよび金属薄膜の化学状態分析やマッピングを実現する光電子スペクトル(XPS)や光電子放出顕微鏡(PEEM)を開発するために,その鍵となる光電子透過窓作製に挑戦することである.このために,以下の4つの点をおこなった(1)窓中を透過する電子の軌道計算(2)電子透過窓の試作とその性能チェック(3)既存のEXPEEM装置の改良(4)液体測定用セルの作製困難と考えられた電子線透過窓付き溶液セルの開発に成功するとともに,PEEM像取得に成功した.また,既存のEXPEEM装置の改造を行った.電磁場重畳型し,絶縁体サンプルにも測定ができるようにするとともに,ピンホールを正確に入れられるようにすることで,万が一の事故にも対応できるようにした.その結果,溶液存在下でのEXPEEM像の測定に成功した.
  • 日本学術振興会:科学研究費助成事業 特定領域研究
    研究期間 : 2010年 -2011年 
    代表者 : 朝倉 清高, 有賀 寛子
     
    電位、総電荷量、イオン濃度などをパラメータとして、TiO_2(110)表面に電気化学的手法によって、金属クラスターを形成させ、そのサイズ、形、露出結晶面をSTMや偏光全反射蛍光XAFS法で調べて、表面クラスターの構造を原子レベルで決定し、ナノクラスター構造の制御を目的に実験を展開した。 その結果、印加電圧により、粒径や成長様式の異なるPtを得ることができた。具体的には、ポテンシャルをAg/AgCl電極に対して、-0.05Vにしたときには、数nm程度のPt粒子が成長するのに対して、-0.15Vでは、20-40nmにわたる粒径をもつナノ粒子が形成された。このように、粒子径をポテンシャルやそのかける時間で制御できることがわかった。一方、Ptの析出するサイトについてのポテンシャル依存性は認められなかった。すなわち、ステップおよびテラスにPtナノクラスターが均一に分布し、Underpotential電位での析出は観測することができなかった。 また表面をメルカプト安息香酸で修飾した表面においては、CuやAuが単原子状に高分散できることをみいだした。 これは、SとCuとの強い相互作用に起因するものである。微粒子になりやすいAuについてもメルカプト安息香酸で修飾することで、高分散化することが可能であることがわかった。こうしたメルカプト安息香酸による表面の修飾は、新しい金属高分散化法として、期待される。 また、ステップを多数持つ表面においては、Niがステップとの相互作用により、1次元小クラスターとなることが見いだされた。さらにAuのナノ粒子を酸素プラズマで処理すると、表面Auナノクラスターのサイズが小さくなることがわかった。 以上の成果は表面のナノ構造をもつクラスター制御の新しい方法論を提供したものといえる。
  • 日本学術振興会:科学研究費助成事業 特定領域研究
    研究期間 : 2008年 -2009年 
    代表者 : 朝倉 清高, 鈴木 秀士, 高草木 達
     
    酸化物上の金属ナノクラスターは、触媒,ガスセンサー,光材料,様々な分野で応用されている。ナノクラスターの粒子サイズを自由に制御することができれば、高活性・高選択的触媒開発も可能である。TiO_2(110)表面は中でも広く研究が進んでいる表面である。この表面におけるナノ粒子の核形成には、表面に存在する格子欠陥や線状欠陥であるステップが重要といわれながら、ナノ粒子の形や大きさを制御するために必要な基板酸化物と金属との相互作用の本質は十分にわかっていない。酸化物表面特にTiO_2(110)表面に形成した欠陥とその表面に構築する金属ナノクラスターとの相互作用を明らかにし、欠陥等を利用した酸化物表面のナノクラスター構造制御法を開発することを目的とする。 本年はAuを少量蒸着し、その挙動を改質したTiO_2(110)表面で検討したところ、欠陥を多く含む表面で、大きな構造変化を観測し、Auの13程度のナノクラスターからなることを見出した。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2006年 -2009年 
    代表者 : 宇尾 基弘, 朝倉 清高, 亘理 文夫, 横山 敦朗, 赤坂 司, 阿部 薫明
     
    生体組織中の一部に微量存在する溶出微量金属元素や微小異物などをXAFS法により状態分析を行い、チタン、ニッケル-チタン合金、クロム基合金などの生体内での挙動を明らかにした。歯科・生体材料周囲に存在するチタンは多くの場合、金属状態であり埋入時の摩耗に由来すると推測されたが、一部で二酸化チタンとして存在するものもあり、生体内での溶出・再析出によると考えられた。またニッケル-チタン合金などからのニッケルがイオン状態で溶出していることも確認され、溶出Niの生体への為害性が懸念された。さらに生体内のSeなどの微量元素の状態分析や試作X線微小光学系を用いた微小部XAFS分析についても検討を行い、XAFS法の生物試料分析への有用性を見出した。
  • 日本学術振興会:科学研究費助成事業 基盤研究(S)
    研究期間 : 2004年 -2008年 
    代表者 : 朝倉 清高, 田 旺帝, 鈴木 秀士, 野村 昌治, 阪東 恭子
     
    高活性脱硫触媒Ni_2Pの活性点構造およびメカニズムをオペランド高速XAFS法で決定した。これと同時に単結晶Ni_2Pの表面科学的研究をすすめ、Ni_2Pの活性構造を明らかにするとともに、その表面構造が条件により大きく変化することを見出した。新しい表面化学顕微鏡法であるXANAM, EXPEEMの開発を行った。このような機能と構造を解明することで、Ni2Pの活性を十倍以上高めることができた。
  • 日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2004年 -2007年 
    代表者 : 野村 昌治, 岩澤 康裕, 朝倉 清高, 稲田 康宏, 唯 美津木, 丹羽 尉博, 佐々木 岳彦, 鈴木 あかね
     
    構造や電子状態が不明な溶液中および固体表面での短寿命金属化学種を対象とし、サブナノ秒までの時間分解能でその場構造解析およびその場電子状態解析を行なうための時間分解XAFS実験法の開発を目的とした。平成16年度にはNW2Aビームラインでの放射光X線パルスとPF-ARリングのRFマスタークロック信号とのジッターを評価し、サブナノ秒での時間分解に十分な13.3psであることを確認した。平成17〜18年度には、XAFSスペクトルとして必要なX線エネルギー領域全体を一度に測定するための分散型XAFS装置に適用する一次元検出器として、通常は二次元検出器として用いられるCCD素子を1行の一次元検出部+残り行の電荷メモリ部として使用することにより、CCD素子上の電荷の行転送を用いて時間分解記録を行うための高速一次元X線検出システムの開発を行った。X線のパルス間隔(1.26μs)以内に行転送が可能な素子としてATMEL社製のTH7888Aを採用し、約800nsでの行転送をRFマスタークロック信号で駆動するための回路およびメモリ部に展開した電荷データをユニポーラ16ビットのADCで読み出す回路の設計と開発を行った。また、短寿命な光励起状態を生み出すための高出力パルスNd : YAGレーザー(POWERLITE 8000)を平成18年度に導入し、平成19年度にかけてナノ秒パルスレーザーと放射光X線パルスとの同期によるポンプープローブ測定システムを確定した。入射X線はCCD素子に光学カップリングして取り付けたP46蛍光体付きテーパー型ファイバープレートで可視光へ変換して検出した。また、CCD素子上の検出行以外のエリアへ光が入射するのを防ぐためのスリットシステムを開発した。この高速CCD検出システムをキネティックスモードで動作した時のスペクトル測定の結果、1パルスのX線での吸収端近傍構造の検出にも成功し、1.26μsで繰り返されるX線パルスをそのままの時間スケールで約1000本まで測定することが可能な世界最速の一次元検出システムの開発に成功した。
  • 物理的手段による表面反能素過程の精密制御
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    研究期間 : 2004年 -2006年 
    代表者 : 朝倉 清高, MOULA Md Golam
     
    波長可変型パルス赤外光源である赤外自由電子レーザを用いて、触媒活性サイトにある特定の化学結合の振動状態を選択的に励起し、特定の素反応過程をのみを優先的に進行させて、新規な表面反応の制御法を開発することを目的に、パルス赤外光による触媒反応のメカニズムの解明をめざして研究を展開した。具体的には、MoO_3,Ni_2Pを触媒として取り上げ、パルス赤外光の波長依存性、反応中の中間体の同定、反応素過程の解明、反応中の触媒の構造研究を行い、パルス赤外光による触媒活性化メカニズムを明らかにした。また,必要な実験装置の整備立ち上げを行い、その活性変化の強度依存性、波長依存性を調べた。その結果、Mo-Oの共鳴振動数の光を照射したときにみに、エタノールの脱水反応が進行することを見いだした。これは、赤外線により固体上で光触媒反応を引き起こすことができることを意味している。さらに、多光子吸収過程により、吸収された赤外線がMo-Oの結合を切断し、活性サイトを作り出すという新しい機構を提案した。さらにNi2Pに展開するため、その表面のキャラクタリゼーションを行い、世界で初めてその原子像の取得に成功し、原子レベルでの構造決定を行った。
  • 燃料電池表面のXAFS解析
    新エネルギー技術研究開発費
    研究期間 : 2006年
  • XAFS analysis of fuel cell surface
    New Energy Technology Research and Development
    研究期間 : 2006年
  • 日本学術振興会:科学研究費助成事業 萌芽研究
    研究期間 : 2002年 -2003年 
    代表者 : 朝倉 清高, 鈴木 秀士, 田 旺帝
     
    本研究は、チップ型触媒とマイクロエレクトロマシンシステム(MEMS)を一体化した集積型インテリジェント触媒-マイクロエレクトロメカノキャタリスト(MEMC)を創製することを最終の目的としており,そのプロトタイプを作製して,インテリジェント触媒としての可能性探求を行う。 具体的には、以下の基礎技術の確立、可能性の探求を行った。 1.Siに酸化物触媒の図形をリソグラフィー法で設計制作した。とくにVSbO4-Sb2O4の短冊状に交互に蒸着し、その幅をミクロンオーダで制御した新しいマイクロキャタリストの作成技術を確立した。また、こうした短冊状の形を有する触媒の活性が向上することも見いだした。 2.酸化物触媒図形と近接して、電極を付与し、集積型インテリジェント触媒の原型を作った。CuをSb2O4の直下に選択的に埋め込むことで、Sb2O4に電場をかけることができる。 3.小表面積触媒の触媒作用を有効に調べる高感度反応装置を設計・制作した。特にパルスガスを断続的に触媒表面に吹き付け、質量分析器をそれと連動させながら、働かせることで、わずかな生成物をとらえることができるようになった。 4.MEMCの触媒作用を調べるためのEXPEEM法、XANAM法などのキャラクタリゼーション手法を開発した。すなわち、不均一な分布を持つMEMCの各部分ごとに元素、化学分析できるEXPEEM法やXANAM法を開発することで、in-situ条件下での状態変化をしることができ、化学反応のメカニズムの解明につながることが期待される。 今後、これまでの成果をもとに、MEMCの本格的な開発研究に取り組み、外部電場により、触媒作用を制御した新しいインテリジェント触媒実現を目指す。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 1999年 -2000年 
    代表者 : 朝倉 清高, 鈴木 秀士
     
    1,規整不均一触媒の調製 2つサイトが相互作用をし、高い選択性を示すVSbO4-Sb_2O_4触媒に関して、Si基板上にゾルゲル法で、平坦なVSbO_4酸化薄膜を展開し、これにレジストを塗布し、望ましいパターンを電子線リソグラフィー法で描画した後Sb_2O_4膜を展開した。XPSやXRD,AFMの測定の結果、この膜が500℃比較まで安定であり、その形が破壊されず、反応に用いることができることがわかった。 2,XPEEM装置の改良 X線源をつけ、実験室系のXPEEMの試みを行った。1スペクトル測定に長時間のため込みを必要とすることが判明し、当初の計画通り、物質構造科学研究所への移設を行いつつある。 3,反応装置の立ち上げ 規整不均一触媒の反応性を調べるため、反応装置の設計製作を行った。設計の方針として以下のことがあげられる。 (1)質量分析器による高感度、高速分析 (2)差動排気方式による高圧力反応の追跡、 (3)赤外線導入型加熱装置によるサンプル集中加熱(ホルダー等の影響をのぞく) (4)SEM,LEED,AES等分析装置との連携 (5)熱電対による温度の厳密制御 現在、調製を終了し、標準サンプル、テストサンプルで、その性能を試験している。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 1999年 -2000年 
    代表者 : 野村 昌治, 岩澤 康裕, 朝倉 清高, 松下 正, 稲田 康宏, 舟橋 重信
     
    エネルギー分散型XAFS実験装置に設置できるように小型の弯曲機構を備えたミラーベント機構およびミラーを開発し、鉛直方向のビームの集光および高次光の抑制に効果的であることを確認した。フォトダイオードアレーを検出器として用いて光学系および検出系の評価実験を行った。本XAFS実験光学系では試料をビームの集光点付近に設置するが、従来行われていた二等辺三角形の分光結晶の底辺を保持しながら頂点を押す方式では十分に小さい集光を得られない。このため試料の厚さむらがスペクトルに反映してしまう問題があった。この問題点を解決するために長方形の分光結晶を円形に弯曲させる結晶ベント機構およびこのベント機構を分光器に取り付けるためのベント機構取付台を製作し、集光の評価を行った。また、フォトダイオードアレーの場合は読み出し速度に限界があり、将来の高速時分割実験の律速となるため、CCDをキネティックスモードで使用することとし、このためのキネティックス用光学システムを製作した。 in situ触媒反応について、銅を担持したCu-ZSM-5触媒はNOの分解に対して高い活性を示し、この活性が銅のredox反応と関係していることが知られている。今回はこの触媒の40Torrの水素中における昇温還元反応を時間分解能1秒の時分割XAFS法で追跡し、反応開始時に二価であった銅が400〜450K付近で一価に還元され、更に550〜650Kで0価に還元されていることが分かった。XAFSの解析より、550K付近では平均としてCu_3構造をとっていたものが昇温とともにクラスターがZSM-5のケージから外に移動して成長し、670KではCu_<7.8>となっていると解釈できる。 ストップトフロー反応装置を用いた溶液反応については予備的な実験を行い、本研究で用いた光学系、検出系を用いて解析に耐えるスペクトルを得られることを確認した。
  • 遷移金属ー典型元素化合物表面の化学と物理
    研究期間 : 1999年
  • 1.不均一規整表面の合成と触媒作用
    研究期間 : 1999年
  • Chemistry and Physics of Transition metal - main group element compounds
    研究期間 : 1999年
  • 1. well-defined inhomogeneous
    研究期間 : 1999年
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 1997年 -1998年 
    代表者 : 岩澤 康裕, 佐々木 岳彦, 大西 洋, 朝倉 清高
     
    次世代化合物半導体デバイスや100%の選択性を有する高効率完全触媒の開発には、表面の反応を利用し、原子・分子レベルで精密に制御された表面を作る技術の確立が必要であるが、これを達成するためには、原子・分子レベルでの表面化学現象を追跡し、化学反応素過程を解明する必要があるだけでなく、それらが集合して形成する原子集団やその表面における化学反応プロセス全体の挙動を明らかにする必要がある。特に、このサブミクロン〜ミクロン領域における表面化学反応の結果、脱離してくる反応生成物の種類やその脱離方向の角度分布をリアルタイムで調べることにより、表面反応プロセスを総合的に理解することができる。そこで本研究では、新しいリアルタイム表面イメージングシステムであるin-situ複合表面イメージングシステムを開発し、STM(走査トンネル顕微鏡)とESDIAD(電子刺激脱離イオン角度分布)を組み合わせて、表面の化学状態や原子の動きと反応脱離生成物の同定および脱離角度分布をリアルタイムで観察し、反応素過程の原子・分子レベルでの解明を行うことを目的とした。その結果、半導体や酸化物半導体上における金属の空間的な動きを直接PEEMやMEM法などの表面イメージング法でリアルタイムに観察することに成功するとともに、吸着種1個1個を分離して、STM観測することに成功した。さらに、メタノールの分解反応過程を直接追跡し、分解反応に必要な表面との相互作用を明らかにした。
  • 新しい表面解析手段の開発 高速XAFSによる活性表面の構造と設計と顕微法による実空間実時間表面観察
    研究期間 : 1998年
  • 顕微法による実空間実時間表面観察
    研究期間 : 1998年
  • Development of new surface science techniue Quick EXAFS spectrsocopy3. Real time chemical imaging of surface4. Surface XAFS studies on surface oxide physics and chemistry
    研究期間 : 1998年
  • Real time chemical imaging of surface
    研究期間 : 1998年
  • 日本学術振興会:科学研究費助成事業 重点領域研究
    研究期間 : 1997年 -1997年 
    代表者 : 朝倉 清高, 大西 洋
     
    われわれは、表面の不純物濃度や温度を傾斜させることで表面の非線型反応性を制御することを目的として、表面反応の動的な解析を行うのに必要なリアルタイムイメージングシステムを開発し、複雑な化学過程を直接捉える試みを行った。 リアルタイムイメージングシステムについては、昨年度ほぼ完成し、本年更に、改良を加えた。主な改良点は、 1.冷却CCDカメラを装着し、高感度で像観察できるようにした。 2.蒸着源を改良し、より正確に蒸着できるようにした。 3.電子線源を取り付けて、電子励起2次電子像を観測できるようにした。 こうした改良により、Si(111)表面にAuを蒸着したもので、AuのX線励起PEEM像の画像化することに成功した。全電子を用いて、画像化しているが、現左X線源を改良し、調整を進めることで、エネルギー選別光電子スペクトル像測定を試みている。さらに電子線源を取り付け、サンプルバイアスを変化させることで、Auger電子放出顕微鏡(AEEM)を可能とした。 Agの昇華過程とAgアイランド上の傾斜化過程の観察を行った。Agアイランドの昇華過程を電子線励起2次電子像(SEEM像)により観察し、それに伴う傾斜構造の形成過程を調べた様子を示した。周辺から昇華し、それに伴い、Agのアイランドの厚みに傾斜が生じている。傾斜や厚みについては、今後、さらに詳細に解析する必要がある。
  • 日本学術振興会:科学研究費助成事業 重点領域研究
    研究期間 : 1996年 -1996年 
    代表者 : 朝倉 清高, 大西 洋
     
    白金表面では、CO酸化反応中に、時間空間的に変化する化学波やスパイラル波に代表される自己組織構造が形成される。これまで、TiO2や金を蒸着することで、この時空間パターンの形成条件、進行方向、形状を制御する試みを行ってきたが、時空間パターンが進行する向きを決定することは困難であった。本研究では、金濃度傾斜表面を用いて白金上の時空間パターンの進行の向きを制御することを目的として、以下の実験を行った。 1.金の濃度傾斜度を知るため、PEEM(Photo emisson electron microscopy)を元素分析能をもつXPEEM装置への改良を行った。 本装置の特徴は、これまでの表面の仕事関数を用いて、表面の顕微イメージ像を測定するPEEMと異なり、X線光電子を弁別することで、元素の分布のイメージ像を検出することができる点、光源を切り替えるだけで、PEEM法と同じ場所を調べることができる点、および反応条件下のin-situ条件で測定できる点である。本装置では、X線源として、Mgターゲットを用い、分光結晶によりサンプル上に集光した。更に、飛び出した光電子はWien filterにより、分光され、電子レンズにより結像する。これまでに全電子像の測定とスペクトル像の観測する事ができ、現在最終調整により光電子像測定の段階に入っている。 2.金の濃度傾斜表面を作り、PEEMを用いて予備的な測定を行った。その結果、金の蒸着量に対応して、自己組織構造が変化していくことを確認することができた。
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 1996年 -1996年 
    代表者 : 朝倉 清高
     
    本研究は、白金の表面第2層に形成されるサブサーフェス酸素の存在を実証し、このサブサーフェス酸素の触媒作用を研究することを目的として、以下の実験を行った。 1.PEEM(Photo emisson electron microscopy)を元素分析能を持つXPEEM装置への改良を行った。この装置はサブサーフェス酸素を同定するのに必要な装置である。本装置の特長は、これまでの表面の仕事関数を用いて、表面の顕微イメージ像を測定するPEEMと異なり、X線光電子を弁別することで、元素の分布のイメージ像を検出することができる点及び光源を切り替えるだけで、PEEM法と同じ場所を調べることができる点にある。本装置では、X線源として、Maターゲットを用い、分光結晶によりサンプル上に集光した。更に、飛び出した光電子はWien filterにより、分光され、電子レンズにより結像する。これまで全電子像の測定とスペクトル像の観測する事ができ、現在最終調整により光電子像測定の段階に入っている。 2.サブサーフェス酸素の対照実験のため、Pt/Sb203及び、Au-Pt錯体における酸素の酸化反応の研究を行った。特に、Pt/Sb203では、イソブタンからメタクロレインを高選択的に得ることができることも見いだした。 3.又、サブサーフェス酸素以外にもサブサーフェス水素も存在する可能性があることから、水素吸着したPt微粒子のXANESスペクトルを測定し、Ptのサブサフェース水素の存在を否定した。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 1996年 -1996年 
    代表者 : 岩澤 康裕, 福井 賢一, 大西 洋, 朝倉 清高
     
    固体表面の化学反応は、基礎的・応用的な観点から今日もっとも注目されている化学現象の一つである。本研究の目的は、新しい原理に基づくX線光電子顕微鏡(XPEEM)を開発して反応中の表面をその場観察し、表面上の化学種の動きをリアルタイムに追跡することである。 そのための手段として、既存の低速電子顕微鏡(LEEM)を基本にして、新しいXPEEM装置を設計・製作した。LEEM装置の顕微鏡部に電子エネルギー弁別器(ウィーンフィルター)を付加することによって、X線励起による光電子をエネルギー弁別したうえで空間分析を高分解能で測定し、固体表面の元素別、あるいは化学状態別の分布図をリアルタイムに記録できるように設計した。これまでに、エネルギー弁別器の取付とたち上げが完了し、現在、XPEEMシステムとしての最適化を行っている。その過程で、シリコン表面のX線励起による全光電子像(位置分解能〜1μm)と、金4f光電子のエネルギースペクトルの測定に成功している。 XPEEM装置の製作と平行して、二酸化チタン単結晶表面上に蒸着した金属原子・吸着分子の加熱・気相分子共存下における反応過程を走査トンネル顕微鏡(STM)を用いてリアルタイム観察した。また、タングステン層を埋め込んだシリコンウェファー上にSiO_2薄膜を作成し、さらに銅超微粒子をスピンコートすることによって担持金属触媒のモデル表面を作成した。埋め込まれたタングステン層によって吸着分子の赤外吸収が増強され、通常不可能な反射吸収測定によって吸着分子の振動状態を解析できることを実証した。これらの手法にXPEEMを組み合わせ相補的に用いることによって、これら表面の元素分布あるいは化学状態分布の動きを、反応中に可視化することをめざす。
  • 日本学術振興会:科学研究費助成事業 一般研究(C)
    研究期間 : 1995年 -1995年 
    代表者 : 朝倉 清高
     
    本研究では、偏光全反射蛍光EXAFS法を発展させ、低温から室温まで測定温度を変化させてEXAFSを測定し、基板と超微粒子との結合の強さや相互作用ポテンシヤルを決定し、理論計算と比較することにより、基板と金属超微粒子との界面化学結合状態や電子移行の度合についての新しい知見を得るとともに、超微粒子の物性や反応性に対し、基板の持つ物理的化学的な役割に関し、構造的側面から明らかにする事を目的とし,以下の事柄を行った. 1)全反射蛍光EXAFSによるPt/A1203,Mo/Ti02の表面構造の決定 室温において、新たにPt/A1203,Mo/Ti02の系の全反射蛍光EXAFSを測定し,その表面構造の決定に成功した. 2)低温用in-situ全反射蛍光EXAFS装置の製作 温度を低温50K-300Kまで変化させ,EXAFSを測定するための装置を設計製作した.特徴としては,活性処理後,反応後,外気と触れさせずにin-situ条件で,測定セルに移し,偏光全反射蛍光EXAFSを測定できるようにしたものである. 3)検出器の評価 セルを用いた場合,蛍光を取り出せる有効面積が減るため,通常よりも小型の検出器を使用する必要がある.そこで,CdTe,小型シンチレーションについてその性能と本研究に応用したときの長所短所を検討した.その結果,CdTeは,感度が高く,非常にコンパクトにできるものの,雑音レベルが小型シンチレーシヨンより高いため,本実験には適さず,小型シンチレーシヨンカウンターを用いて測定することにした. 温度可変EXAFSの測定 平成7年11月文部省高エネルギー研究所の放射光実験施設で第1回の測定を試みたが,低温装置と全反射調節装置との接合があわず,全反射ビームを取り出すことができなかった.現在,その点を改良し,平成8年春の実験に備えている.
  • 日本学術振興会:科学研究費助成事業 重点領域研究
    研究期間 : 1995年 -1995年 
    代表者 : 岩澤 康裕, 大西 洋, 朝倉 清高
     
    我々はこれまで、金属の有機錯体やカルボニル化合物をSiO_2などの無機酸化物担体上に担持分散した固定化触媒を調製し、その表面構造をEXAFSなどの分光法を用いて明かにしてきた。明確な構造と組成を持つ前駆体を用いことによって、表面構造を精緻に設計し、触媒作用を支配する基本的因子を原子・分子レベルで調べることが可能となる。さらに、表面での構造変換により、全く新しい触媒機能を生み出すことも期待できるからである。 金は化学的に安定で触媒的には不活性な元素に分類されてきた。しかし、Pt(111)表面にAuを添加して表面合金を形成させるとシクロヘキセンの脱水素反応に高活性を示す。また、TiO_2、Fe_2O_3などに強固に担持されたAuの微粒子はCOなどの低温酸化反応に極めて高い活性を示す。これら顕著な例にもかかわらず、クラスター微粒子に取り込まれたAuの触媒作用は明らかでない。 本研究ではこれらの観点から、アルカリ金属的電子状態のAuクラスター骨格に1個のPt原子を埋め込んだ[PtAu_6]クラスターをSiO_2表面に固定化した新しい金バイメタル触媒を調製し、その触媒特性を検討した。通常複数個のPt原子の存在により初めて活性化される水素の解離、エチレンの水素化反応、COの酸化反応を選び、Auクラスター骨格に埋め込まれたPt原子の反応性を調べた。これらの触媒反応、特にH_2-D_2交換反応においては、本新規触媒がかなり高い触媒活性を示すことを見いだした。反応中、バイメタルクラスター骨格が保たれているかどうかを、PtおよびAuのEXAFSスペクトルから解析したところ、447Kまでは完全にクラスター骨格が保たれていることが分かった。これらの結果は、Pt-Au結合のアシストによってPt原子1個が触媒作用を発揮しうることを示しており、不均一系金属触媒作用を考えるうえで重要な示唆を与える。
  • 日本学術振興会:科学研究費助成事業 一般研究(B)
    研究期間 : 1995年 -1995年 
    代表者 : 岩澤 康裕, 佐々木 岳彦, 大西 洋, 朝倉 清高
     
    本研究の目的は、電子線励起により固体表面から脱離する中性化学種を共鳴多光子イオン化法で選択的にイオン化し、飛行時間および脱離方位を独立に決定することによって、脱離種の角度分布と並進エネルギー分布を測定し、表面吸着種の配向状態・量子状態・分子間相互作用などを決定することによって、光励起選択エピタキシ-反応過程を原子・分子レベルで解明することにある。本年度われわれは脱離イオン種の角度分布と飛行時間を同時に測定できるESDIAD/TOF装置を開発した。 本ESDIAD/TOF装置は半球型の4枚グリッドとマイクロチャネルプレートからなる検出系と偏向によるチョッピングでパルス化が可能な電子銃からなる。連続電子ビームによるESDIAD観察モードの他にパルス電子を用いたESDIAD観察と脱離イオンのTOF測定が行える。パルス電子(パルス幅100ns以上で可変)によるESDIAD観察は、脱離イオンの飛行に影響を与えないようパルスに同期した断続的通電加熱によって、試料表面で起きる反応を20msの時間分解能で観察できる。これにより、反応中の吸着分子の配向変化、反応中間体を検出できる。TOF測定は100nsの幅のパルス電子を入射し10msの時間分解能で脱離イオンをパルスカウンティングする。1KH_2〜10KH_2でパルス電子を入射して、積算することにより0.1〜1s単位の変化を追跡することができる。TOF測定により、脱離種の同定と並進エネルギー分布の測定が可能となる。 装置製作と並行して、Cu(110)表面上の吸着酸素をHREELS、TPDを用いて調べ、再構成していない銅表面に吸着した酸素原子が酸化反応に活性であることを明らかにした。反応活性が高い吸着直後の酸素原子と、再構成した表面にとりこまれた不活性な酸素原子をESDIAD/TOFで比較して、酸素の結合状態の反応性の相関を明らかにする予定である。
  • 日本学術振興会:科学研究費助成事業 一般研究(A)
    研究期間 : 1993年 -1994年 
    代表者 : 太田 俊明, 朝倉 清高, 難波 秀利, 北島 義典, 横山 利彦, 田島 裕之
     
    本研究では、まず、走査型トンネル顕微鏡(STM)測定装置を備えた表面分析用超高真空チェンバーの設計・製作を行った。この装置では、STMの他、4枚グリッド背面LEED光学系を用いてのLEED-Auger測定と、Mg,AlツインアノードX線管と半球型電子エネルギー分析装置を用いたX線光電子分光測定が行える。次に、STM測定系の評価のため、(5√3×2)-rect.S/Ni(111)のSTM像を観測した。この結果は既に報告されているものと良く一致した。続いて(√17×√17)R14°S/Cu(100)系のSTM及びSK吸収端SEXAFSの測定を行い、表面構造を検討した。この2つの手法を併用することは表面構造解析上極めて有効である。なぜなら、STMは主として表面最外層の情報を与えるため吸着原子の面内位置や長距離的な描像がわかり、SEXAFSは吸着原子と基板原子との相対位置を精度良く決定することができ、両者は完全に相補的であるためである。この系のSTM測定の結果、我々は単位格子中に2種類の非等価なS原子が存在することを見出した。SEXAFSの結果を併せて考えることによって、最外層のCu原子が再配列した新しいモデルを提供した。単位格子中の4個のS原子は再構成されたCuの表面層上のhollow位置に吸着し、残りの4個のS原子は再構成されていないCuの第二層のhollow位置に存在していることが決定できた。
  • 日本学術振興会:科学研究費助成事業 重点領域研究
    研究期間 : 1992年 -1992年 
    代表者 : 朝倉 清高
     
    高温排気急冷処理により、貴金属微粒子の活性が相転移的に1桁から2桁向上する現象を用いて、小分子の活性化をはかることが本研究の目的である。 本年度は、その現象の本質を解明するため、偏光全反射蛍光EXAFS装置の開発を行い、担持金属微粒子の形態変化を観察する。この手法の特徴は表面平行方向と垂直方向の結合情報を分離することができ、よりくわしい活性点構造を知ることができることである。 単結晶アルミナに担持した白金の構造変化をin-situ条件でこの変更全反射蛍光EXAFS法で測定したところ、基板に平行及び垂直方向の結合を分離して測定することに成功し、その構造を3次元的に決定した。 さらにアンモニアとNOとの白金金属上での反応中の構造変化を追跡し、反応中骨格構造がダイナミックに変化していることを見いだした。 今後は温度変化をさせながら、IN-SITUで形態変化を偏光全反射蛍光EXAFSでとらえ、相転移的活性向上現象の原因を解明する。また、この相転的活性向上現象を用いて小分子活性化を試みる予定である。
  • In-situ蛍光XAFS法による金属表面におけるS,PとCOの共吸着構造
    日本学術振興会:科学研究費助成事業 奨励研究(A)
    研究期間 : 1991年 -1991年 
    代表者 : 朝倉 清高
  • 日本学術振興会:科学研究費助成事業 重点領域研究
    研究期間 : 1991年 -1991年 
    代表者 : 岩澤 康裕, 朝倉 清高, 有賀 哲也
     
    レ-ザ-・デポジション法は、半導体基板上に直接サブミクロン・オ-ダ-の回路パタ-ンを作製しうる次世代極微細デバイス作製技術として多くの注目を集めている.その実現のためにはキ-プロセスである表面反応素過程を解明する必要がある.本研究では、界面構造を基板表面にたいして平行方向と垂直方向に独立に決定しうる新しい表面構造解析手法である偏光全反射蛍光EXAFSと、表面での化学反応過程の解明にきわめて有効な高感度振動分光法である高分解能電子エネルギ-損失分光法を用いて、表面での化学反応により超薄膜形成過程の追跡を試みてきた.今年度は、主としてα‐アルミナ表面上にジコバルトオクタカルボニル(dicobaltoctacarbonyl)のCVDにより成長させた酸化コバルト超薄層に関して、偏光全反射蛍光EXAFSにより検討した.実験は、高エネルギ-物理学研究所放射光実験施設のビ-ムラインBLー7CおよびBLー14Aにおいて行なった.s偏光、p偏光のいずれの場合にも、高いS/B比のEXAFSスペクトルが得られた.これのフ-リエ変換により得られた動径分布関数のピ-ク位置は、スピネル構造を有するバルクCo_3O_4と一致した.しかし、各ピ-クの強度比はs偏光とp偏光とで著しく異なった.このことから、α‐アルミナ(0001)表面上にCo_3O_4の超薄層が特定の方位に成長していることがわかった.さらに、モデルを用いたシミュレ-ションにより、Co_3O_4とα‐アルミナとのエピタキシャル関係を明らかにした.
  • 日本学術振興会:科学研究費助成事業 一般研究(B)
    研究期間 : 1990年 -1991年 
    代表者 : 黒田 晴雄, 朝倉 清高, 難波 秀利
     
    本研究では、Ni(7 9 11)表面に周期的に配列したステップを触媒などの表面反応の「活性点」、あるいは、表面欠陥の一つのモデルと考え、シンクロトロン放射を利用して、表面EXAFS、および、角度分解光電子分光と、それらの偏向依存性を有効に活かしてステップの原子スケ-ルでの局所構造を明らかにし、さらに、ステップに局在した電子状態を検出して、その分散関係を決定し、世界で初めて、ステップの物理的な実像を明らかにした。さらに、表面での反応を活性化することが知られているアルカリ金属と、それとは逆に、失活させるイオウなどのステップでの吸着状態を調べて、触媒などの表面反応を考察する上での重要な知見を得た。主な結果を次に要約する。 (1)Ni(7 9 11)表面上のステップでは、結晶形から予想されるような原子配列が実現されていることが示された。イオウは吸着量の少ない範囲ではそのステップの4ーfoldサイトに選択性良く吸着することが分かり、その原子配置が決定された。イオウの吸着量、試料温度を系統的に変えて吸着構造の変化を調べたところ、室温で吸着量を増加させるとステップサイトに吸着しているイオウを基点として、イオウの(/3×/3)R30゚構造の超格子が形成されることが分かった。この構造はNi(7 9 11)表面のテラスと同じ原子配置のNi(111)面では室温では存在しないために、ステップに前吸着しているイオウがその後の吸着構造を支配していると考えられる。 (2)Ni(7 9 11)表面のステップサイトに局在化した電子準位を初めて見出し、その分散関係を決定した。その電子準位は、ステップに垂直な方向にかなり局在していて1次元性を有していると考えられる。 さらに、ステップにアルカリ金属などの異種原子が密に吸着することにより1次元的な金属状態を出現させる可能性を見出すことができ、今後、表面を舞台とした新しい低次元の物性研究の展開が期待できる。
  • 日本学術振興会:科学研究費助成事業 総合研究(B)
    研究期間 : 1990年 -1990年 
    代表者 : 黒田 晴雄, 岩澤 康裕, 朝倉 清高, 宇田川 康夫, 太田 俊明
     
    EXAFS(広域X線構造微細構造)やXANES(X線吸収端構造)の応用が近年急速に拡大されているが、それにしたがって、EXAFSやXANESの測定方法の標準化、EXAFSデ-タの解析方法の確立、EXAFSやXANESに関する理論の検討、さらには、EXAFやXANESに関するデ-タベ-スの作成等の必要性が高まり、数年前から世界各国の関連分野の研究者の協力のもとに「XAFS国際ワ-クショップ」が開かれて、その報告がまとめられた。また、1992年にわが国で第7回XAFS国際会議を開催することになっており、そこでも上記の問題が会議の重要な課題になる。このような状況を踏まえて本研究課題では、国際ワ-クショップの報告を研究分担者に配布するとともに、各分担者が国際ワ-クショップの報告に取り上げられている個々の課題を分担して検討し、また、EXAFSならびにXANESの解析のためのプログラムに整備を推進した。それらの結果を持ち寄った国内ワ-クショップを1回開催し、分担して検討してきた内容の報告を求めるとともに、国際ワ-クショップの勧告に関する総合討論を行なった。また、現在、EXAFS解析プログラムがいくつか国内で作成されていろいろな研究グル-プによって利用されているが、それらのプログラムの妥当性と各研究グル-プが採用している解析手順の妥当性の相互比較を行なうために、国際ワ-クショップで作成された標準デ-タ等を各分担者に配布して、各分担者にその解析を求めた。以上のような活動の他に、第7回XAFS国際会議の企画・立案のための会議を数回開催し、同国際会議の開催に向けての準備活動を推進した。
  • 二段階固定化法によりシリカ表面に精密合成した酸化バナジウム超薄膜触媒に関する研究
    日本学術振興会:科学研究費助成事業 奨励研究(A)
    研究期間 : 1989年 -1989年 
    代表者 : 朝倉 清高
  • 日本学術振興会:科学研究費助成事業 重点領域研究
    研究期間 : 1989年 -1989年 
    代表者 : 岩澤 康裕, 朝倉 清高
     
    本研究はキラル結晶における不斉導入反応の反応機構を偏光EXAFS法を用いて検討し、その素過程を明かにすることが目的である。そこで、以下の手順に従い研究を進めた。 (1)反応条件下でin-situ偏光EXAFS測定システムの開発した。特に、EXAFSの入射X線の電場ベクトル依存性を利用し、反応場の立体局所構造解析を行える。ゴニオメ-タの設計製作を行った。これとあわせて、反応進行中のEXAFSが測定できるようなEXAFSin-situ測定セルの設計製作も行った。 (2)反応条件下でのin-situ EXAFSの有効性を評価するため、固体表面に固定化した活性点での反応条件下に置けるEXAFSの測定を行った。具体的にはシリカ表面にRhのダイマ-を固定化し、そのCO挿入条件下における活性点構造の変化から、金属結合補助型CO挿入メカニズムを提案した。 (3)本研究の助成金により購入した薬品を用いて、4,4′-dimethylchalconeを合成し、その単結晶を成長させた。また、EXAFSをもちいて、臭素化過程を行うことになっているが、予備実験として、IRにより速度論的な解討を加えた。 (4)文部省高エネルギ-物理学研究所にある放射光実験施設に対し、EXAFS測定のマシンタイムの申請を行い、現在、それが受理されマシンタイムの配分をまっている段階である。
  • 全反射蛍光偏光EXAFS法による白金表面上におけるエチレン水素化反応機構の研究
    日本学術振興会:科学研究費助成事業 奨励研究(A)
    研究期間 : 1988年 -1988年 
    代表者 : 朝倉 清高
  • 日本学術振興会:科学研究費助成事業 特定研究
    研究期間 : 1987年 -1987年 
    代表者 : 岩澤 康裕, 朝倉 清高
     
    本研究者らはこれまで, Mo, Cr, Fe, Co, Ru, Rhなどの有機錯体を用いて一定の構造を持つ金属サイトをシリカやアルミナ表面に設計し, その触媒機能と触媒作用機構を明らかにしてきた. これらの研究を通じて(1)従来困難であった触媒表面の分子設計が有機金属化合物を利用することにより可能なこと, (2)均一系とは異なった機能と物性が作れること, (3)固体触媒の触媒作用の研究に大きな障壁となっていた表面状態の複雑さと不明確さなどの問題を解決する方法となり得ること, を見いだしてきた. 61年度の本特定研究のもとでの研究により, Nbのπアリル錯体を用いてシリカやチタニア表面に新しいNbモノマー構造を作ることに成功した. モノマー構造を持つ初めての固体Nb触媒であり, 高い脱水素活性を示すことも従来の固体Nb触媒には見られない特質である. 本研究では, 選択的に進行するエタノールの脱水素反応の機構を研究し, 新しいタイプの反応分子間の共同触媒作用機構を見いだし, 自己幇助型脱水素反応機構と名づけた. すなわち, まずエタノールはNbモノマー上で解離吸着し, エトキシル基と水酸基となるが, 気相にエタノールが存在しない場合には673Kではじめてエチレンと水とに分解される. ところが気相のエタノールがさらに1分子吸着すると, エトキシル基が活性化され, 400Kでさえ脱水素が起こりアセトアルデヒドと水素が等量生成される. 第一に吸着するエタノールから生成するエトキシル基はそれ自体はα位のC-H結合で切断が起こりエチレンに転換されるが, そこに第二のエタノール分子が吸着するとβ位でC-H結合の切断が起こるようになる. しかも遥かに低い反応温度で脱水素生成物であるアセトアルデヒドが生成する. これは対称性の変化というよりもむしろ電子的供与効果と関連づけれら, Nbの4d軌道を通してエトキシル基のβ水素が活性化されている. この機構は触媒作用のひとつの概念を提供する.
  • 偏光全反射蛍光 EXAFS 法による固体触媒表面の研究
    日本学術振興会:科学研究費助成事業 奨励研究(A)
    研究期間 : 1985年 -1985年 
    代表者 : 朝倉 清高

教育活動情報

主要な担当授業

  • 表面ナノ材料科学特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 工学院
    キーワード : 表面、ナノ材料、リソグラフィー炭素材料、表面物性、触媒
  • 表面ナノ解析科学特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 工学院
    キーワード : 表面、触媒、ナノ材料、量子ビーム、STMなど
  • 表面ナノ材料科学特論
    開講年度 : 2021年
    課程区分 : 博士後期課程
    開講学部 : 工学院
    キーワード : 表面、ナノ材料、リソグラフィー炭素材料、表面物性、触媒
  • 表面ナノ解析科学特論
    開講年度 : 2021年
    課程区分 : 博士後期課程
    開講学部 : 工学院
    キーワード : 表面、触媒、ナノ材料、量子ビーム、STMなど
  • 表面工学
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 表面電子状態、表面結晶横造、表面計測法、吸着、逆格子,触媒作用,電子状態 
  • 環境と人間
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 触媒、化学物質、環境とエネルギー、持続的な社会発展
  • 量子力学
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 粒子性・波動性、波動関数、不確定性原理、フーリエ展開、演算子、シュレディンガー方程式、調和振動子、水素原子構造、多電子原子の構造、パウリの原理
  • 一般教育演習(フレッシュマンセミナー)
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 量子ビーム、プラズマ、触媒、ナノ材料

大学運営

学内役職歴

  • 2014年4月1日 - 2016年3月31日 教育研究評議会評議員
  • 2016年4月1日 - 2018年3月31日 教育研究評議会評議員
  • 2014年4月1日 - 2015年9月30日 触媒化学研究センター長
  • 2015年10月1日 - 2016年3月31日 触媒科学研究所長
  • 2016年4月1日 - 2018年3月31日 触媒科学研究所長

委員歴

  • 2022年07月 - 現在   国際X線吸収分光学会   会長
  • 2022年05月 - 現在   日本化学会北海道支部   副支部長
  • 2018年06月 - 現在   IVC22組織委員会   IVC22組織委員
  • 2018年05月 - 現在   Committee member of Accounts of Materials and Surface Research
  • 2021年04月 - 2023年03月   PF-UA   PF-UA機構外運営委員
  • 2018年08月 - 2022年07月   Vice Chair
  • 2016年08月 - 2022年07月   PCCP coeditor
  • 2021年05月 - 2022年05月   触媒学会   会長
  • 2018年05月 - 2022年05月   触媒学会   理事
  • 2020年05月 - 2021年11月   日本結晶学会   結晶学会講演大会実行委員
  • 2019年10月 - 2021年09月   日本放射光学会   会長
  • 2020年05月 - 2021年04月   触媒学会   副会長
  • 2018年05月 - 2020年05月   触媒学会   北海道支部長
  • 2015年04月 - 2019年03月   触媒学会   代議員
  • 2016年10月 - 2018年09月   日本放射光学会   評議員
  • 2014年04月 - 2018年03月   北海道大学   評議員
  • 2015年05月 - 2017年03月   日本表面科学会   副会長
  • 2015年04月 - 2017年03月   表面科学会   理事
  • 2015年04月 - 2017年03月   表面科学会東北北海道支部   支部長
  • 2012年04月 - 2015年03月   PF-UA   庶務幹事
  • 2011年05月 - 2015年03月   触媒学会   教育企画委員
  • 2008年 - 2013年   日本XAFS研究会   会長   日本XAFS研究会
  • 2010年04月 - 2012年03月   PF懇談会   会長
  • 2005年   日本XAFS研究会   幹事   日本XAFS研究会

学術貢献活動

  • synchrotron Radiation News guest Editor
    期間 : 2019年10月01日 - 2020年12月20日
    役割 : 企画立案・運営等
    種別 : 査読等
    主催者・責任者 : 朝倉清高

その他

  • 2016年08月 - 2016年08月  PCCP副編集委員 
    PCCP副編集委員


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