MF研究者総覧

研究者データベース

詳細
雲林院　宏(ウジイ　ヒロシ)
電子科学研究所　光科学研究部門
教授
researchmap個人ページ
Last Updated :2024/05/13

基本情報

所属

  • 電子科学研究所　光科学研究部門

職名

  • 教授

学位

  • 博士（理学）（東北大学）

ホームページURL

J-Global ID

プロフィール

  • Hiroshi Uji-i (Ph.D.-Science) is a Research professor of chemistry department at KU Leuven (Belgium) and a full professor of Research Institute for Electronic Science at Hokkaido University (Japan). He received his B Sc and M Sc in Applied physics at Osaka University (Japan), and PhD in chemistry at Tohoku University (Japan).

研究キーワード

  • 探針増強ラマン顕微鏡   単一細胞エンドスコピー   薬輸送システム   プラズモニクス   

研究分野

  • ナノテク・材料 / 光工学、光量子科学
  • ナノテク・材料 / ナノバイオサイエンス

担当教育組織

職歴

  • 2015年07月 - 現在 北海道大学 電子科学研究所 教授
  • 2011年10月 - 現在 ルーバン大学 化学科 研究教授
  • 2004年09月 - 2011年09月 ルーバン大学 化学科 上級博士研究員
  • 2002年09月 - 2004年08月 ルーバン大学 化学科 博士研究員

学歴

  • 1999年04月 - 2002年03月   東北大学   大学院理学研究科   化学科
  • 1997年04月 - 1999年03月   大阪大学   大学院工学研究科   応用物理専攻
  • 1993年04月 - 1997年03月   大阪大学   工学部   応用物理学科

研究活動情報

論文

  • Kenji Hirai, James A. Hutchison, Hiroshi Uji-i
    Chemistry - A European Journal 2023年11月 [査読有り][招待有り]
     
    Optical cavity/molecule strong coupling offers attractive opportunities to modulate photochemical or photophysical processes. When atoms or molecules are placed in an optical cavity, they can coherently exchange photonic energy with optical cavity vacuum fields, entering the strong coupling interaction regime. Recent work suggests that the thermodynamic and kinetic properties of molecules can be significantly changed by strong coupling, resulting in the emergence of intriguing photochemical and photophysical phenomena. As more and more physico‐chemical systems are studied under strong coupling conditions, optical cavities have also advanced in their sophistication, responsiveness, and (multi)functionality. In this review, we highlight some of these recent developments, particularly focusing on Fabry‐Perot microcavities.
  • Wannes Peeters, Shuichi Toyouchi, Yasuhiko Fujita, Mathias Wolf, Beatrice Fortuni, Eduard Fron, Tomoko Inose, Johan Hofkens, Takahiko Endo, Yasumitsu Miyata, Hiroshi Uji-i
    ACS Omega 8 41 38386 - 38393 2023年09月20日
  • Hideki Fujiwara, Seigo Daikokuya, Tatsuki Mirokuin, Kyohei Hayashi, Mizuki Matsuzaka, Yuri Ohashi, Christophe Pin, Hideo Kaiju, Kenji Hirai, Hiroshi Uji-i
    ACS Applied Nano Materials 6 15 13885 - 13893 2023年07月22日
  • Kenji Hirai, James A. Hutchison, Hiroshi Uji-i
    Chemical Reviews 123 13 8099 - 8126 2023年06月 [査読有り][招待有り]
  • Beatrice Fortuni, Monica Ricci, Raffaele Vitale, Tomoko Inose, Qiang Zhang, James Andell Hutchison, Kenji Hirai, Yasuhiko Fujita, Shuichi Toyouchi, Sandra Krzyzowska, Indra Van Zunder, Susana Rocha, Hiroshi Uji-i
    ACS Sensors 8 6 2340 - 2347 2023年05月23日 [査読有り][通常論文]
  • Guilin Feng, Nozomu Suzuki, Qiang Zhang, Jiangrao Li, Tomoko Inose, Farsai Taemaitree, Muhammed Shameem K M, Shuichi Toyouchi, Yasuhiko Fujita, Kenji Hirai, Hiroshi Uji-i
    Chemical Communications 2023年 
    We report covalently patterned graphene with acetic acid as a new potential candidate for graphene-enhanced Raman scattering (GERS). Rhodamine 6G molecule in direct contact with the covalently modified region shows...
  • Guilin Feng, Tomoko Inose, Nozomu Suzuki, Han Wen, Farsai Taemaitree, Mathias Wolf, Shuichi Toyouchi, Yasuhiko Fujita, Kenji Hirai, Hiroshi Uji-i
    Nanoscale 15 10 4932 - 4939 2023年 
    We report an efficient photo-induced covalent modification (PICM) of graphene by short-chain fatty acids (SCFAs) with an alkyl chain at the liquid-solid interface for spatially resolved chemical functionalization of graphene....
  • Han Wen, Jiangtao Li, Qiang Zhang, Tomoko Inose, Wannes Peeters, Beatrice Fortuni, Hitoshi Asakawa, Akito Masuhara, Kenji Hirai, Shuichi Toyouchi, Yasuhiko Fujita, Hiroshi Uji-i
    Nano Letters 2022年12月09日
  • Naoaki Oshita, Kazuki Umemoto, Ryota Sato, Taisei Kimura, Takayuki Chiba, Satoshi Asakura, Hiroshi Uji-i, Akito Masuhara
    Applied Physics Express 15 6 065002 - 065002 2022年06月01日 
    Abstract Quantum-confined cesium lead tribromide perovskite quantum dots (PeQDs) are attractive photonic sources for versatile optoelectronic devices and thus the synthetic routes have been explored via various techniques. However, the lack of a general method to fabricate the quantum-confined PeQD with remarkable stability at colloidal state has been one of the major obstacles to device applications. Herein, we propose a simple and robust ligand-assisted reprecipitation method associated with didodecyl dimethyl ammonium bromide for quantum-confined PeQDs with remarkable stability at colloidal state. This method will shed a light on the field of colloidal PeQDs synthesis for the next generation of photonic sources.
  • Kenji Hirai, Hiroto Ishikawa, Yasufumi Takahashi, James Andell Hutchison, Hiroshi Uji-I
    Chemistry (Weinheim an der Bergstrasse, Germany) 28 47 e202201260  2022年05月30日 
    Site-selective chemistry opens new paths for the synthesis of technologically important molecules. When a reactant is placed inside a Fabry-Perot (FP) cavity, energy exchange between molecular vibrations and resonant cavity photons results in vibrational strong coupling (VSC). VSC has recently been implicated in modified chemical reactivity at specific reactive sites. However, as a reaction proceeds inside an FP cavity, the refractive index of the reaction solution changes, detuning the cavity mode away from the vibrational mode and weakening the VSC effect. Here we overcome this issue, developing actuatable FP cavities to allow automated tuning of cavity mode energy to maintain maximized VSC during a reaction. As an example, the site-selective reaction of the aldehyde over the ketone in 4-acetylbenzaldehyde is achieved by automated cavity tuning to maintain optimal VSC of the ketone carbonyl stretch during the reaction. A nearly 50% improvement in site-selective reactivity is observed compared to an FP cavity with static mirrors, demonstrating the utility of actuatable FP cavities as microreactors for organic chemistry.
  • Shuichi Toyouchi, Mathias Wolf, Guilin Feng, Yasuhiko Fujita, Beatrice Fortuni, Tomoko Inose, Kenji Hirai, Steven De Feyter, Hiroshi Uji-i
    The Journal of Physical Chemistry Letters 13 17 3796 - 3803 2022年04月22日
  • Han Wen, Tomoko Inose, Kenji Hirai, Taiki Akashi, Shoji Sugioka, Jiangtao Li, Wannes Peeters, Eduard Fron, Beatrice Fortuni, Yoshihiko Nakata, Susana Rocha, Shuichi Toyouchi, Yasuhiko Fujita, Hiroshi Uji-i
    NANOSCALE 14 14 5439 - 5446 2022年04月 
    Tip-enhanced Raman scattering (TERS) microscopy is an advanced technique for investigation at the nanoscale because of its excellent properties, such as its label-free functionality, non-invasiveness, and ability to simultaneously provide topographic and chemical information. The probe plays a crucial role in TERS technique performance. Widely used AFM-TERS probes fabricated with metal deposition suffer from relatively low reproductivity as well as limited mapping and storage lifetime. To solve the reproducibility issue, silver nanowire (AgNW)-based TERS probes were developed, which, thanks to the high homogeneity of the liquid-phase synthesis of AgNW, can achieve high TERS performance with excellent probe reproductivity, but still present short lifetime due to probe oxidation. In this work, a simple Au coating method is proposed to overcome the limited lifetime and improve the performance of the AgNW-based TERS probe. For the Au-coating, different [Au]/[Ag] molar ratios were investigated. The TERS performance was evaluated in terms of changes in the enhancement factor (EF) and signal-to-noise ratio through multiple mappings and the storage lifetime in air. The Au-coated AgNWs exhibited higher EF than pristine AgNWs and galvanically replaced AgNWs with no remarkable difference between the two molar ratios tested. However, for longer scanning time and multiple mappings, the probes obtained with low Au concentration showed much longer-term stability and maintained a high EF. Furthermore, the Au-coated AgNW probes were found to possess a longer storage lifetime in air, allowing for long and multiple TERS mappings with one single probe.
  • Mathias Wolf, Kenji Hirai, Shuichi Toyouchi, Brent Daelemans, Eduard Fron, Hiroshi Uji-i
    Journal of Materials Chemistry C 10 25 9471 - 9477 2022年 
    Metal-organic frameworks (MOFs) are an interesting candidate for applications in nonlinear optics (NLO). However, current design strategies for MOFs in NLO are typically limited to either engineering the MOF itself...
  • Indra Van Zundert, Maria Bravo, Olivier Deschaume, Pierre Cybulski, Carmen Bartic, Johan Hofkens, Hiroshi Uji-i, Beatrice Fortuni, Susana Rocha
    PHARMACEUTICS 13 12 2021年12月 
    The application of antibodies in nanomedicine is now standard practice in research since it represents an innovative approach to deliver chemotherapy agents selectively to tumors. The variety of targets or markers that are overexpressed in different types of cancers results in a high demand for antibody conjugated-nanoparticles, which are versatile and easily customizable. Considering up-scaling, the synthesis of antibody-conjugated nanoparticles should be simple and highly reproducible. Here, we developed a facile coating strategy to produce antibody-conjugated nanoparticles using 'click chemistry' and further evaluated their selectivity towards cancer cells expressing different markers. Our approach was consistently repeated for the conjugation of antibodies against CD44 and EGFR, which are prominent cancer cell markers. The functionalized particles presented excellent cell specificity towards CD44 and EGFR overexpressing cells, respectively. Our results indicated that the developed coating method is reproducible, versatile, and non-toxic, and can be used for particle functionalization with different antibodies. This grafting strategy can be applied to a wide range of nanoparticles and will contribute to the development of future targeted drug delivery systems.
  • Mathias Wolf, Shuichi Toyouchi, Peter Walke, Kazuki Umemoto, Akito Masuhara, Hiroshi Fukumura, Yuta Takano, Michio Yamada, Kenji Hirai, Eduard Fron, Hiroshi Uji-i
    RSC ADVANCES 12 1 389 - 394 2021年12月 
    Organic materials have attracted considerable attention in nonlinear optical (NLO) applications as they have several advantages over inorganic materials, including high NLO response, and fast response time as well as low-cost and easy fabrication. Lithium-containing C-60 (Li@C-60) is promising for NLO over other organic materials because of its strong NLO response proven by theoretical and experimental studies. However, the low purity of Li@C-60 has been a bottleneck for applications in the fields of solar cells, electronics and optics. In 2010, highly purified Li@C-60 was finally obtained, encouraging further studies. In this study, we demonstrate a facile method to fabricate thin films of Li@C-60 and their strong NLO potential for high harmonic generation by showing its comparatively strong emission of degenerate-six-wave mixing, a fifth-order NLO effect.
  • Yu Kitamura, Emi Terado, Zechen Zhang, Hirofumi Yoshikawa, Tomoko Inose, Hiroshi Uji-i, Masaharu Tanimizu, Akihiro Inokuchi, Yoshinobu Kamakura, Daisuke Tanaka
    CHEMISTRY-A EUROPEAN JOURNAL 27 66 16274 - 16274 2021年11月 
    Exploring the desired crystal by decision tree analysis. A decision tree uses digitized information to find the synthetic conditions for a new metal-organic framework that exhibits proton conductivity. More information on optimizing the synthesis can be found in the Full Paper by D. Tanaka et al. (DOI: 10.1002/chem.202102404).
  • Yu Kitamura, Emi Terado, Zechen Zhang, Hirofumi Yoshikawa, Tomoko Inose, Hiroshi Uji-i, Masaharu Tanimizu, Akihiro Inokuchi, Yoshinobu Kamakura, Daisuke Tanaka
    CHEMISTRY-A EUROPEAN JOURNAL 27 66 16347 - 16353 2021年11月 
    Novel metal-organic frameworks containing lanthanide double-layer-based secondary building units (KGF-3) were synthesized by using machine learning (ML). Isolating pure KGF-3 was challenging, and the synthesis was not reproducible because impurity phases were frequently obtained under the same synthetic conditions. Thus, dominant factors for the synthesis of KGF-3 were identified, and its synthetic conditions were optimized by using two ML techniques. Cluster analysis was used to classify the obtained powder X-ray diffractometry patterns of the products and thus automatically determine whether the experiments were successful. Decision-tree analysis was used to visualize the experimental results, after extracting factors that mainly affected the synthetic reproducibility. Water-adsorption isotherms revealed that KGF-3 possesses unique hydrophilic pores. Impedance measurements demonstrated good proton conductivities (sigma=5.2x10(-4) S cm(-1) for KGF-3(Y)) at a high temperature (363 K) and relative humidity of 95 % RH.
  • Qiang Zhang, Tomoko Inose, Monica Ricci, Jiangtao Li, Ya Tian, Han Wen, Shuichi Toyouchi, Eduard Fron, Anh Thi Ngoc Dao, Hitoshi Kasai, Susana Rocha, Kenji Hirai, Beatrice Fortuni, Hiroshi Uji-i
    ACS Applied Nano Materials 4 9 9886 - 9894 2021年09月07日 
    Intracellular pH variations are a crucial indicator of physiological and pathological conditions. As such, cancer is known to have a direct interplay with pH dysregulation. For investigation of the pH alterations in cells, metal nanoparticles have been widely used as surface-enhanced Raman scattering (SERS)-based sensors thanks to their high pH sensitivity. However, these SERS probes allow for detection of the pH exclusively at the acidic compartments of the cells (endolysosomes), where particles are entrapped after their endocytosis. Consequently, the results obtained with metal nanoparticles are limited, and the relationship between the pH values detected in the cells and their physiological conditions remains unclear. Herein, we propose an alternative approach based on gold-deposited silver nanowire endoscopy to study cytosolic and nuclear pH variations with high spatiotemporal resolution and sensitivity. The sensing probe was fabricated by depositing gold nanostructures on silver nanowires (Au-dep AgNWs) via visible-laser-light irradiation and modifying the surface with a pH-responsive Raman reporter (4-mercaptobenzoic acid). The high pH sensitivity was demonstrated by immersing the probe in solutions with different pH values (4.4-9.3). The endoscopic probe was then inserted into either the nucleus or cytosol of a living HeLa cell for site-specific pH sensing. The same experiments were performed after the addition of a hypoxia mimetic agent (CoCl2) and an anticancer drug (cisplatin), individually. Notably, our probe accurately detected specific pH variations upon these treatments over time. Similar pH alterations were not measured in untreated cells. The results reported in this work clearly show that Au-dep AgNW endoscopy is a promising powerful tool for pH-sensing applications in biological systems.
  • Kenji Hirai, Atsushi Nagahashi, Taisei Kitagawa, Hiroshi Uji-i
    Metamaterials, Metadevices, and Metasystems 2021 2021年08月01日
  • Monica Ricci, Beatrice Fortuni, Raffaele Vitale, Qiang Zhang, Yasuhiko Fujita, Shuichi Toyouchi, Gang Lu, Susana Rocha, Tomoko Inose, Hiroshi Uji-i
    Analytical Chemistry 93 12 5037 - 5045 2021年03月30日 
    Recently, our group introduced the use of silver nanowires (AgNWs) as novel non-invasive endoscopic probes for detecting intracellular Raman signals. This method, although innovative and promising, relies exclusively on the plasmonic waveguiding effect for signal enhancement. It, therefore, requires sophisticated operational tools and protocols, drastically limiting its applicability. Herein, an advanced strategy is offered to significantly enhance the performance of these endoscopic probes, making this approach widely accessible and versatile for cellular studies. By uniformly forming gold structures on the smooth AgNW surface via a galvanic replacement reaction, the density of the light coupling points along the whole probe surface is drastically increased, enabling high surface-enhanced Raman scattering (SERS) efficiency upon solely focusing the excitation light on the gold-etched AgNW. The applicability of these gold-etched AgNW probes for molecular sensing in cells is demonstrated by detecting site-specific and high-resolved SERS spectra of cell compartment-labeling dyes, namely, 4',6-diamidino-2-phenylindole in the nucleus and 3,3'-dioctadecyloxacarbocyanine on the membrane. The remarkable spectral sensitivity achieved provides essential structural information of the analytes, indicating the overall potential of the proposed approach for cellular studies of drug interactions with biomolecular items.
  • Kenji Hirai, Hiroshi Uji-i
    Chemistry Letters 50 4 727 - 732 2021年01月13日 
    Even without external photon pumping, cavity vacuum fields can be strongly coupled with molecular transitions (electronic excitation and molecular vibration), resulting in the formation of polaritonic states. The energy states of molecular systems are altered under strong coupling, revealing intriguing phenomena, such as improvements in energy/exciton transfer and modulation of chemical reactions. In this review, we highlight recent advances in cavity strong coupling, including exciton strong coupling and vibrational strong coupling, from a chemistry-based viewpoint.
  • Kazushi Yamaguchi, Kohei Otomo, Yuichi Kozawa, Motosuke Tsutsumi, Tomoko Inose, Kenji Hirai, Shunichi Sato, Tomomi Nemoto, Hiroshi Uji-I
    ACS omega 6 1 438 - 447 2021年01月12日 
    We developed adaptive optical (AO) two-photon excitation microscopy by introducing a spatial light modulator (SLM) in a commercially available microscopy system. For correcting optical aberrations caused by refractive index (RI) interfaces at a specimen's surface, spatial phase distributions of the incident excitation laser light were calculated using 3D coordination of the RI interface with a 3D ray-tracing method. Based on the calculation, we applied a 2D phase-shift distribution to a SLM and achieved the proper point spread function. AO two-photon microscopy improved the fluorescence image contrast in optical phantom mimicking biological specimens. Furthermore, it enhanced the fluorescence intensity from tubulin-labeling dyes in living multicellular tumor spheroids and allowed successful visualization of dendritic spines in the cortical layer V of living mouse brains in the secondary motor region with a curved surface. The AO approach is useful for observing dynamic physiological activities in deep regions of various living biological specimens with curved surfaces.
  • Kenji Hirai, Hiroto Ishikawa, Thibault Chervy, James Andell Hutchison, Hiroshi Uji-i
    Chemical Science 12 36 11986 - 11994 2021年 

    The coupling of (photo)chemical processes to optical cavity vacuum fields is an emerging method for modulating molecular and material properties. Recent reports have shown that strong coupling of the vibrational...

  • Keito Okada, Yoko Tanaka, Tomoko Inose, Hiroshi Ujii, Hirofumi Yoshikawa, Daisuke Tanaka
    Dalton Transactions 50 16 5411 - 5415 2021年 

    The thermodynamic (PCN-222) and kinetic (PCN-224) products of porphyrinic Zr-metal–organic frameworks (MOFs) were synthesized via an anodic dissolution approach for the first time.

  • Kazuki Umemoto, Hinako Ebe, Ryota Sato, Junya Enomoto, Naoaki Oshita, Taisei Kimura, Tomoko Inose, Takahiro Nakamura, Takayuki Chiba, Satoshi Asakura, Hiroshi Uji-i, Akito Masuhara
    ACS Sustainable Chemistry & Engineering 8 44 16469 - 16476 2020年11月09日 
    Owing to their excellent photoluminescence (PL) properties in a narrow linewidth below 30 nm and high photoluminescence quantum yield (PLQY), organometal halide perovskite nanocrystals (PeNCs) are promising photonic sources for wide-color gamut displays. However, with a top-down approach, luminescent PeNCs comparable to those prepared through bottom-up synthesis is still a significant subject, including the optimization of milling processes. Herein, we propose a novel and simple ultrasound-assisted bead milling process based on the characteristics of facile crystallization. During the milling process, irradiated ultrasounds disperse milling beads that facilitate an intense collision between the beads and the perovskite precursors. Thus, this bead milling can be easily performed without planetary ball milling, and it provides brightly luminescent colloidal PeNCs with high PLQY. We established that mechanochemical conditions significantly enhance the optical properties by exploring various milling conditions. Furthermore, the color adjustment can be realized by changing the halide composition. Therefore, this novel milling process has great potential and versatility for preparing diverse perovskite nanomaterials for optoelectronic applications.
  • Farsai Taemaitree, Beatrice Fortuni, Yoshitaka Koseki, Eduard Fron, Susana Rocha, Johan Hofkens, Hiroshi Uji-i, Tomoko Inose, Hitoshi Kasai
    NANOSCALE 12 42 21951 - 21951 2020年11月
  • Guofeng Zhang, Susana Rocha, Gang Lu, Haifeng Yuan, Hiroshi Uji-i, George A. Floudas, Klaus Muellen, Liantuan Xiao, Johan Hofkens, Elke Debroye
    ACS OMEGA 5 37 23931 - 23939 2020年09月 
    Mapping the spatial and temporal heterogeneities in miscible polymer blends is critical for understanding and further improving their material properties. However, a complete picture on the heterogeneous dynamics is often obscured in ensemble measurements. Herein, the spatial and temporal heterogeneities in fully miscible polystyrene/oligostyrene blend films are investigated by monitoring the rotational diffusion of embedded individual probe molecules using defocused wide-field fluorescence microscopy. In the same blend film, three significantly different types of dynamical behaviors (referred to as modes) of the probe molecules can be observed at the same time, namely, immobile, continuously rotating, and intermittently rotating probe molecules. This reveals a prominent spatial heterogeneity in local dynamics at the nanometer scale. In addition to that, temporal heterogeneity is uncovered by the nonexponential characteristic of the rotational autocorrelation functions of single-molecule probes. Moreover, the occurrence probabilities of these different modes strongly depend on the polystyrene: oligostyrene ratios in the blend films. Remarkably, some probe molecules switch between the continuous and intermittent rotational modes at elevated temperature, indicating a possible alteration in local dynamics that is triggered by the dynamic heterogeneity in the blends. Although some of these findings can be discussed by the self-concentration model and the results provided by ensemble averaging techniques (e.g., dielectric spectroscopy), there are implications that go beyond current models of blend dynamics.
  • Kenji Hirai, James A Hutchison, Hiroshi Uji-i
    ChemPlusChem 85 9 1981 - 1988 2020年08月03日 [査読有り][通常論文]
     
    Vibrational polaritonic chemistry is emerging as an exciting new sub-field of chemistry, one in which strong interactions with optical cavity vacuum fields are another degree of freedom alongside temperature, solvent, catalyst, and so on to modify thermochemical reactivity. The field stands at a fascinating juncture with experimental works on a variety of organic reactions continuing to blossom, just as many theoretical works appear which diverge significantly in their predictions compared to experiments. The outlook for the field is no doubt an exciting one as it seeks to unify the observed novel optical cavity-induced chemical phenomena with satisfying accompanying physical theory. In this minireview we highlight experimental works on vibrational polaritonic chemistry that have appeared most recently, focusing on the chemistry of the rate-limiting steps to provide mechanistic insight. We hope this review will encourage synthetic chemists to enter the field and we discuss the opportunities and challenges that lie ahead as polaritonic chemistry grows into the future.
  • Qiang Zhang, Han Wen, Kiri Watanabe, Ibuki Kotani, Monica Ricci, Beatrice Fortuni, Anh Thi Ngoc Dao, Akito Masuhara, Kenji Hirai, Hitoshi Kasai, Tomoko Inose, Hiroshi Uji-i
    ACS Applied Nano Materials 3 8 7643 - 7650 2020年07月09日 [査読有り][通常論文]
     
    Intracellular pH affects many biological processes such as apoptosis, proliferation, endocytosis, and multidrug resistance. In view of this, highly sensitive pH sensing in live cells is essential for understanding biological dynamics. Although surface enhanced Raman scattering (SERS) using noble metal nanoparticles functionalized with acidic ligands has been proposed for highly sensitive intracellular pH sensing, the dependence of SERS pH sensitivity on nanoparticle morphology has been overlooked. The apparent dissociation constant (pK(a)) of acid ligands is known to be sensitive to nanoparticle curvature. Thus, nanoparticle morphology should reflect SERS pH sensitivity. Here, we compared pK a behaviors and SERS pH sensitivities of nearly spherical isotropic and flowerlike anisotropic gold-coated silver nanoparticles (AuAgNPs and AuAgNFs, respectively). We found that the NPs with higher curvature such as AuAgNFs show a narrower pH-sensitive range (pH 5-8) compared to the nearly spherical nanoparticles, providing higher sensitivity to the pH range. Taking advantage of the narrow pH range of AuAgNFs, pH changes are successfully monitored as a function of time in cells treated with and without anticancer drugs, respectively. The results indicate that the pH-sensitive range of SERS-sensing can be tailored by controlling nanoparticle morphology. This tenability is a crucial requirement for pH-sensing applications in various biological systems.
  • Ryo Ohtani, Kenichi Kawano, Masanao Kinoshita, Saeko Yanaka, Hikaru Watanabe, Kenji Hirai, Shiroh Futaki, Nobuaki Matsumori, Hiroshi Uji-i, Masaaki Ohba, Koichi Kato, Shinya Hayami
    Angewandte Chemie International Edition 59 41 17931 - 17937 2020年06月30日 [査読有り][通常論文]
     
    Cell membranes contain lateral systems that consist of various lipid compositions and actin cytoskeleton, providing two-dimensional (2D) platforms for chemical reactions. However, such complex 2D environments have not yet been used as a synthetic platform for artificial 2D nanomaterials. Herein, we demonstrate the direct synthesis of 2D coordination polymers (CPs) at the liquid-cell interface of the plasma membrane of living cells. The coordination-driven self-assembly of networking metal complex lipids produces cyanide-bridged CP layers with metal ions, enabling "pseudo-membrane jackets" that produce long-lived micro-domains with a size of 1-5 mu m. The resultant artificial and visible phase separation systems remain stable even in the absence of actin skeletons in cells. Moreover, we show the cell application of the jackets by demonstrating the enhancement of cellular calcium response to ATP.
  • Masaki Takeda, Masaaki Yokoyama, Kazuki Umemoto, Bozhang Lyu, Yoshihito Takahashi, Sasiphapa Rodbuntum, Junya Enomoto, Keitaro Tozawa, Tomohiro Nohara, Keisuke Tabata, Ryota Sato, Takayuki Chiba, Satoshi Asakura, Hiroshi Uji-i, Akito Masuhara
    JAPANESE JOURNAL OF APPLIED PHYSICS 59 2020年06月 [査読有り][通常論文]
     
    Highly luminescent CH3NH3PbBr3 perovskite nanocrystals (PeNCs) with a high photoluminescence quantum yield value of 80% are prepared by a forced thin film reactor for continuous production. In this system, the rotating and stationary disks form a confined micro space which demonstrates a unique mixing process through continuous injection of solvents. We found that the unique mixing system leads to colloidal PeNCs with 4 nm-10 nm, which are much smaller than those of a representative T-junction system (15 nm-65 nm). It suggests that a confined micro space is effective for the capping of n-octylamine to the surface of PeNCs, resulting in suppression of the aggregation of the PeNCs and crystal growth. Also, with increasing flow velocity, the optical properties show almost no fluctuation. This system is a promising continuous system to prepare colloidal PeNCs, and can provide a synthetic protocol to be applied for light-emitting diodes as well as various other optoelectronic devices. (C) 2020 The Japan Society of Applied Physics.
  • Monica Ricci, Martin G. T. A. Rutten, Shuichi Toyouchi, Sepa Nanayakkara, Beatrice Fortuni, Raffaele Vitale, Susana Rocha, Daniela A. Wilson, Johan Hofkens, Kei Saito, Hiroshi Uji-I
    ACS OMEGA 5 20 11547 - 11552 2020年05月 
    Despite having great value across a wide variety of scientific fields, two-photon polymerizations currently suffer from two significant problems: the need for photoinitiators, which generate toxic side products, and the irreversibility of the process. Hence, the design of a versatile approach that circumvents these issues represents a major scientific challenge. Herein, we report a two-photon absorption strategy where reversible [2 + 2] cycloaddition of bis-thymines was achieved without the need for any photoinitiator. The cycloaddition and cycloreversion reactions could be induced by simply changing the irradiation wavelength, and repeated writing and erasing cycles were performed. The simplicity, reversibility, and biocompatibility of this strategy open up a whole new toolbox for applications across a wide variety of scientific fields.
  • Kangwei Xia, Wei-Yi Chiang, Cesar Javier Lockhart de la Rosa, Yasuhiko Fujita, Shuichi Toyouchi, Haifeng Yuan, Jia Su, Hiroshi Masuhara, Stefan De Gendt, Steven De Feyter, Johan Hofkens, Hiroshi Uji-i
    NANOSCALE 12 20 11063 - 11069 2020年05月 
    Graphene, a single atomic layer of sp(2)hybridized carbon, is a promising material for future devices due to its excellent optical and electrical properties. Nevertheless, for practical applications, it is essential to deposit patterned metals on graphene in the micro and nano-meter scale in order to inject electrodes or modify the 2D film electrical properties. However, conventional methods for depositing patterned metals such as lift-off or etching leave behind contamination. This contamination has been demonstrated to deteriorate the interesting properties of graphene such as its carrier mobility. Therefore, to fully exploit the unique properties of graphene, the controlled and nano-patterned deposition of metals on graphene films without the use of a sacrificial resist is of significant importance for graphene film functionalization and contact deposition. In this work, we demonstrate a practical and low-cost optical technique of direct deposition of metal nano-patterned structures without the need for a sacrificial lift-off resist. The technique relies on the laser induced reduction of metal ions on a graphene film. We demonstrate that this deposition is optically driven, and the resolution is limited only by the diffraction limit of the light source being used. Patterned metal features as small as 270 nm in diameter are deposited using light with a wavelength of 532 nm and a numerical aperture of 1.25. Deposition of different metals such as Au, Ag, Pd, Pb and Pt is shown. Additionally, change in the Fermi level of the graphene film through the nano-patterned metal is demonstrated through the electrical characterization of four probe field effect transistors.
  • Shuichi Toyouchi, Mathias Wolf, Yusuke Nakao, Yasuhiko Fujita, Tomoko Inose, Beatrice Fortuni, Kenji Hirai, Johan Hofkens, Steven De Feyter, James Hutchison, Hiroshi uji-i
    Nano Letters 20 4 2460 - 2467 2020年03月10日 [査読有り][通常論文]
     
    Silver nanowires have attracted considerable attention as subdiffraction limited diameter waveguides in a variety of applications including cell endoscopy and photonic integrated circuitry. Optical signal transport occurs by coupling light into propagating surface plasmons, which scatter back into light further along the wire. However, these interconversions only occur efficiently at wire ends, or at defects along the wire, which are not controlled during synthesis. Here, we overcome this limitation, demonstrating the visible laser light-induced fabrication of gold nanostructures at desired positions on silver nanowires, and their utility as efficient in/out coupling points for light. The gold nanostructures grow via plasmon-induced reduction of Au(III) and are shown to be excellent "hotspots" for surface-enhanced Raman scattering.
  • Yuki Tezuka, Kazuki Umemoto, Masaki Takeda, Yoshihito Takahashi, Hinako Ebe, Junya Enomoto, Sasiphapa Rodbuntum, Tomohiro Nohara, Daniela Fontecha, Satoshi Asakura, Takayuki Chiba, Madalina Ioana Furis, Tsukasa Yoshida, Hiroshi Uji-i, Akito Masuhara
    JAPANESE JOURNAL OF APPLIED PHYSICS 59 SDDC04-1 - SDDC04-5 2020年03月 [査読有り][通常論文]
     
    Organic-inorganic hybrid lead halide perovskite nanocrystals (PeNCs) have received great attention as a light source for perovskite LEDs (PeLEDs) owing to the superior optical properties. However, PeNCs typically use octylamine (OAm) as capping ligands which have insulating properties. Exploring a desirable short alkylamine instead of OAm is required for the improvement of PeLEDs. Here, as one of the strategies to solve this issue, the effects of alkylamine chain length for optical properties of PeNCs and PeLED characteristics are investigated. Pentylamine is an optimal short alkylamine and precipitate luminescent PeNCs with high PLQY values of 90%. Importantly, pentylamine maintains a relatively high PLQY of 48% after spin-coating, due to the durability pentylamine has to ethyl acetate as a washing solvent. PeNCs capped with pentylamine also demonstrate an external quantum efficiency of over 1% with luminance of over 2000 cd cm(-2), indicating that pentylamine has the potential to overcome the insulator properties of PeNC thin film. (C) 2019 The Japan Society of Applied Physics
  • Kenji Hirai, Rie Takeda, James A Hutchison, Hiroshi Uji-I
    Angewandte Chemie (International ed. in English) 59 13 5332 - 5335 2020年01月22日 [査読有り][通常論文]
     
    Light-molecule strong coupling has emerged within the last decade as an entirely new method to control chemical reactions. A few years ago it was discovered that the chemical reactivity could be altered by vibrational strong coupling (VSC). While the potential of VSC in organic chemistry appears enormous, only a limited number of reactions have been investigated under VSC to date, including solvolysis and deprotection reactions. Here we investigate the effect of VSC on a series of aldehydes and ketones undergoing Prins cyclization, an important synthetic step in pharmaceutical chemistry. We observe a decrease of the second-order rate constant with VSC of the reactant carbonyl stretching groups. We measure an increased activation energy due to VSC, but proportional changes in activation enthalpy and entropy suggest no substantive change in reaction pathway. The addition of common cycloaddition reactions to the stable of VSC-modified chemical reactions is another step towards establishing VSC as a genuine tool for synthetic chemistry.
  • Mathias Wolf, Kenji Hirai, Shuichi Toyouchi, Eduard Fron, Wannes Peeters, Steven De Feyter, Hiroshi Uji-i
    Chemical Communications 56 87 13331 - 13334 2020年 

    The potential of nonlinear optical microscopy for the label-free visualization of heterogeneities and defects in metal–organic frameworks is demonstrated.

  • Shuichi Toyouchi, Tomoko Inose, Kenji Hirai, Hiroshi Uji-i
    Photosynergetic Responses in Molecules and Molecular Aggregates 117 - 133 2020年
  • Farsai Taemaitree, Beatrice Fortuni, Yoshitaka Koseki, Eduard Fron, Susana Rocha, Johan Hofkens, Hiroshi Uji-i, Tomoko Inose, Hitoshi Kasai
    Nanoscale 12 32 16710 - 16715 2020年 

    FRET Nanoprodrugs (FRET-NPDs) were synthesized and internalized in cancer cells to study their intracellular dynamics and degradation.

  • Kenji Hirai, Taisei Kitagawa, Hideki Fujiwara, Jenny Pirillo, Yuh Hijikata, Tomoko Inose, Hiroshi Uji-i
    Chemical Communications 56 67 9651 - 9654 2020年 [査読有り][通常論文]
     

    A fluorophore encapsulated in a metal–organic framework showed photochromic multicolour fluorescence.

  • Hans Van Gorp, Peter Walke, Joan Teyssandier, Brandon E. Hirsch, Hiroshi Uji-i, Kazukuni Tahara, Yoshito Tobe, Mark Van der Auweraer, Steven De Feyter
    JOURNAL OF PHYSICAL CHEMISTRY C 124 3 1980 - 1990 2020年01月 [査読有り][通常論文]
     
    The covalent functionalization of carbon-based materials through aryldiazonium chemistry has emerged as a powerful tool for physicochemical property modification. However, the characterization techniques traditionally used to assess the stability of any modification, such as thermogravimetric analysis (TGA), do not allow covalent detachment to be discriminated from the loss of physisorbed material. Here, we present a general method to differentiate these two processes by combining scanning probe microscopy with Raman spectroscopy. Using covalently modified highly oriented pyrolytic graphite (HOPG), we show that the thermally induced covalent bond breaking between the aryl groups and the HOPG surface can be directly monitored through this combined approach. Moreover, temperature-dependent Raman spectroscopy allows the kinetics of this bond breaking to be studied. Desorption activation energies can thus be initially estimated for aryl groups bearing different substituents. Finally, we highlight that the pristine HOPG structure can be restored at a relatively low temperature, opening the way for reversible covalent modification. Our results alight on a general methodology for the full characterization of covalently modified carbon materials.
  • Zhi Li, Joachim F. R. Van Guyse, Victor R. de la Rosa, Hans Van Gorp, Peter Walke, Miriam C. Rodriguez Gonzalez, Hiroshi Uji-i, Richard Hoogenboom, Steven De Feyter, Stijn F. L. Mertens
    ADVANCED FUNCTIONAL MATERIALS 29 36 2019年09月 
    The modification of solid surfaces with supramolecular hosts is a powerful method to tailor interfacial properties and confer chemical selectivity, but often involves multistep protocols that hinder facile upscaling. Here, the one-step covalent modification of highly oriented pyrolytic graphite (HOPG) with a beta-cyclodextrin (beta-CD) derivative, which efficiently forms inclusion complexes with hydrophobic guests of suitable size, is demonstrated. The grafted beta-CD-HOPG surface is investigated toward electrochemical detection of ferrocene and dopamine. The enrichment of the analytes at the electrode surface, through inclusion in beta-CD, leads to an enhanced electrochemical response and an improved detection limit. Furthermore, the modified beta-CD-HOPG electrode discriminates analytes that form host-guest complexes with beta-CD against a 100-fold higher background of electroactive substances that do not. Atomic force microscopy, scanning tunneling microscopy, and Raman spectroscopy confirm the covalent nature of the modification and reveal high stability toward solvent rinsing, ultrasonication, and temperatures up to 140 degrees C. The one-step covalent modification therefore holds substantial promise for the routine production of inexpensive, yet robust and highly performant electrochemical sensors. Beyond electrochemical sensor development, our strategy is valuable to prepare materials where accurate spatial positioning of functional units and efficient current collection are crucial, e.g. in photoelectrodes or electrocatalysts.
  • Inose T, Toyouchi S, Lu G, Umemoto K, Tezuka Y, Lyu B, Masuhara A, Fron E, Fujita Y, Hirai K, Uji-I H
    Chemical communications (Cambridge, England) 55 77 11630 - 11633 2019年09月 [査読有り][通常論文]
     
    We report a simple method to control the end shape of silver nanowires by adding pure water in the conventional polyol synthesis. The use of 0.2-0.4% (v/v) water in ethylene glycol as a solvent provides pencil-like silver nanowires with sharp ends in a high yield. We have demonstrated remote excitation of SHG on the sharp nanowires, promising a point light source for super resolution microscopy.
  • Matteo Boretto, Nina Maenhoudt, Xinlong Luo, Aurelie Hennes, Bram Boeckx, Bich Bui, Ruben Heremans, Lisa Perneell, Hiroto Kobayashi, Indra Van Zundert, Hilde Brems, Benoit Cox, Marc Ferrante, Hiroshi Uji-i, Kian Peng Koh, Thomas D'Hooghe, Arne Vanhie, Ignace Vergote, Christel Meuleman, Carla Tomassetti, Diether Lambrechts, Joris Vriens, Dirk Timmerman, Hugo Vankelecom
    NATURE CELL BIOLOGY 21 8 1041 - + 2019年08月 
    Endometrial disorders represent a major gynaecological burden. Current research models fail to recapitulate the nature and heterogeneity of these diseases, thereby hampering scientific and clinical progress. Here we developed long-term expandable organoids from a broad spectrum of endometrial pathologies. Organoids from endometriosis show disease-associated traits and cancer-linked mutations. Endometrial cancer-derived organoids accurately capture cancer subtypes, replicate the mutational landscape of the tumours and display patient-specific drug responses. Organoids were also established from precancerous pathologies encompassing endometrial hyperplasia and Lynch syndrome, and inherited gene mutations were maintained. Endometrial disease organoids reproduced the original lesion when transplanted in vivo. In summary, we developed multiple organoid models that capture endometrial disease diversity and will provide powerful research models and drug screening and discovery tools.
  • Thanh Hai Phan, Hans Van Gorp, Zhi Li, Thi Mien Trung Huynh, Yasuhiko Fujita, Lander Verstraete, Samuel Eyley, Wim Thielemans, Hiroshi Uji-i, Brandon E. Hirsch, Stijn F. L. Mertens, John Greenwood, Oleksandr Ivasenko, Steven De Feyter
    ACS NANO 13 5 5559 - 5571 2019年05月 
    A convenient covalent functionalization approach and nanopatterning method of graphite and graphene is developed. In contrast to expectations, electrochemically activated dediazotization of a mixture of two aryl diazonium compounds in aqueous media leads to a spatially inhomogeneous functionalization of graphitic surfaces, creating covalently modified surfaces with quasi-uniform spaced islands of pristine graphite or graphene, coined nanocorrals. Cyclic voltammetry and chronoamperometry approaches are compared. The average diameter (45-130 nm) and surface density (20-125 corrals/pm2) of these nanocorrals are tunable. These chemically modified nanostructured graphitic (CMNG) surfaces are characterized by atomic force microscopy, scanning tunneling microscopy, Raman spectroscopy and microscopy, and X-ray photoelectron spectroscopy. Mechanisms leading to the formation of these CMNG surfaces are discussed. The potential of these surfaces to investigate supramolecular self-assembly and on-surface reactions under nanoconfinement conditions is demonstrated.
  • Xueting Zhai, Zhuoyao Li, Zichen Lu, Guilin Wang, Ping Li, Yongqian Gao, Xiao Huang, Wei Huang, Hiroshi Uji-i, Gang Lu
    JOURNAL OF COLLOID AND INTERFACE SCIENCE 542 207 - 212 2019年04月 
    Bismuth vanadate (BiVO4) microcrystals enclosed with up to 42 low and high index facets were synthesized through truncation of BiVO4 octahedral crystals via a simple and highly reproducible hydrothermal method. The size and shape of the truncated BiVO4 crystals could be tuned by varying the acid concentration, reaction temperature and reaction period. Compared to the BiVO4 octahedral crystals without truncation, the 42-faceted ones showed an enhanced photocatalytic activity in the degradation of rhodamine B molecules due to the enhanced charge separation on the exposed low and high index facets. This was confirmed at sub-particle level by the photo-deposition of gold and manganese oxide nanopartides selectively on hot electron and hole accumulated facets, respectively. Our results will provide a guideline for the synthesis of more efficient BiVO4 and many other multinary metal oxide-based photocatalysts. Moreover, the synthesized microcrystals are perfect materials for the study of photocatalytic property of BiVO4 at single and sub-particle level. (C) 2019 Elsevier Inc. All rights reserved.
  • Rashad Baiyasi, Seyyed Ali Hosseini Jebeli, Qingfeng Zhang, Liang Su, Johan Hofkens, Hiroshi Uji-i, Stephan Link, Christy F. Landes
    ACS PHOTONICS 6 3 699 - 708 2019年03月 
    Plasmonic nanostructures offer promising applications as nanocatalysts, but optimizing their structure-function relationship using optical superlocalization techniques is hindered by the formation of distorted point spread functions (PSFs). Previously reported localization bias for remotely excited Alexa-647 adsorbed to Ag nanowires is investigated here for its potential to provide useful information about surface interactions. Two main classes of abnormal PSFs are examined: single-lobed PSFs, in which the localization bias arises from various emitter positions around the nanowire, and bilobed PSFs arising from emitters near the top edge of the nanowire. The amount of localization bias for these two populations diverges for ground truth widths less than 300 nm and suggests the latter adsorption and resulting orientation arise more frequently under experimental conditions than is predicted by simulation. Nanowires with widths in the range of 200 to 300 nm are found to have the greatest potential for distinguishing between single-lobed and bilobed PSFs in experiment. Finally, we present a fitting method for abnormal PSFs using a basis of Hermite-Gaussian functions and show that orientation information is encoded in bilobed PSFs.
  • Gangamallaiah Velpula, Roald Phillipson, Jian Xiang Lian, David Cornil, Peter Walke, Ken Verguts, Steven Brems, Hiroshi Uji-i, Stefan De Gendt, David Beljonne, Roberto Lazzaroni, Kunal S. Mali, Steven De Feyter
    ACS NANO 13 3 3512 - 3521 2019年03月 
    Graphene-based two-dimensional (2D) materials are promising candidates for a number of different energy applications. A particularly interesting one is in next generation supercapacitors, where graphene is being explored as an electrode material in combination with room temperature ionic liquids (ILs) as electrolytes. Because the amount of energy that can be stored in such supercapacitors critically depends on the electrode-electrolyte interface, there is considerable interest in understanding the structure and properties of the graphene/IL interface. Here, we report the changes in the properties of graphene upon adsorption of a homologous series of alkyl imidazolium tetrafluoroborate ILs using a combination of experimental and theoretical tools. Raman spectroscopy reveals that these ILs cause n-type doping of graphene, and the magnitude of doping increases with increasing cation chain length despite the expected decrease in the density of surface-adsorbed ions. Molecular modeling simulations show that doping originates from the changes in the electrostatic potential at the graphene/IL interface. The findings described here represent an important step in developing a comprehensive understanding of the graphene/IL interface.
  • Benoit Cox, Emma Laporte, Annelies Vennekens, Hiroto Kobayashi, Charlotte Nys, Indra Van Zundert, Hiroshi Uji-i, Alithe Vercauteren Drubbel, Benjamin Beck, Heleen Roose, Matteo Boretto, Hugo Vankelecom
    JOURNAL OF ENDOCRINOLOGY 240 2 287 - 308 2019年02月 
    The pituitary is the master endocrine gland, harboring stem cells of which the phenotype and role remain poorly characterized. Here, we established organoids from mouse pituitary with the aim to generate a novel research model to study pituitary stem cell biology. The organoids originated from the pituitary cells expressing the stem cell marker SOX2 were long-term expandable, displayed a stemness phenotype during expansive culture and showed specific hormonal differentiation ab ility, although limited, after subrenal transplantation. Application of the protocol to transgenically injured pituitary harboring an activated stem cell population, resulted in more numerous organoids. Intriguingly, these organoids presented with a cystic morphology, whereas the organoids from undamaged gland were predominantly dense and appeared more limited in expandability. Transcriptomic analysis revealed distinct epithelial phenotypes and showed that cystic organoids more resembled the pituitary phenotype, at least to an immature state, and displayed in vitro differentiation, although yet moderate. Organoid characterization further exposed facets of regulatory pathways of the putative stem cells of the pituitary and advanced new injury-activated markers. Taken together, we established a novel organoid research model revealing new insights into the identity and regulation of the putative pituitary stem cells. This organoid model may eventually lead to an interesting tool to decipher pituitary stem cell biology in both healthy and diseased gland.
  • Shuichi Toyouchi, Tomoko Inose, Yasuhiko Fujita, Hiroshi Uji-i
    2019 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) 2019年 
    In this contribution, various applications of plasmonic waveguide to spectroscopy and microscopy will be introduce. Specifically, we will introduce waveguiding remote excitation of surface enhanced Raman scattering inside a live cell or material surface as well as single molecule fluorescence microscopy. Nonlinear plasmonic effect will be also discussed. (c) 2019 The Author(s)
  • B. Fortuni, T. Inose, M. Ricci, Y. Fujita, I. van Zundert, A. Masuhara, E. Fron, H. Mizuno, L. Latterini, S. Rocha, H. Uji-i
    Scientific Reports 9 2019年01月 [査読有り][通常論文]
     
    Most targeting strategies of anticancer drug delivery systems (DDSs) rely on the surface functionalization of nanocarriers with specific ligands, which trigger the internalization in cancer cells via receptor-mediated endocytosis. The endocytosis implies the entrapment of DDSs in acidic vesicles (endosomes and lysosomes) and their eventual ejection by exocytosis. This process, intrinsic to eukaryotic cells, is one of the main drawbacks of DDSs because it reduces the drug bioavailability in the intracellular environment. The escape of DDSs from the acidic vesicles is, therefore, crucial to enhance the therapeutic performance at low drug dose. To this end, we developed a multifunctionalized DDS that combines high specificity towards cancer cells with endosomal escape capabilities. Doxorubicin-loaded mesoporous silica nanoparticles were functionalized with polyethylenimine, a polymer commonly used to induce endosomal rupture, and hyaluronic acid, which binds to CD44 receptors, overexpressed in cancer cells. We show irrefutable proof that the developed DDS can escape the endosomal pathway upon polymeric functionalization. Interestingly, the combination of the two polymers resulted in higher endosomal escape efficiency than the polyethylenimine coating alone. Hyaluronic acid additionally provides the system with cancer targeting capability and enzymatically controlled drug release. Thanks to this multifunctionality, the engineered DDS had cytotoxicity comparable to the pure drug whilst displaying high specificity towards cancer cells. The polymeric engineering here developed enhances the performance of DDS at low drug dose, holding great potential for anticancer therapeutic applications.
  • Kazuki Umemoto, Masaki Takeda, Yuki Tezuka, Takayuki Chiba, Matthew Schuette White, Tomoko Inose, Tsukasa Yoshida, Satoshi Asakura, Shuichi Toyouchi, Hiroshi Uji-i, Akito Masuhara
    CRYSTENGCOMM 20 44 7053 - 7057 2018年11月 [査読無し][通常論文]
     
    Separation of mono-dispersed CH3NH3PbBr3 perovskite quantum dots (PeQDs) using the Ostwald ripening process during aging of the perovskite nanocrystals (PeNCs) in a colloidal solution is proposed for color-tunable PeQD synthesis. Monodispersed PeNCs with size ranging from 5 to 17 nm with a spherical or square shape have been successfully prepared. Photo-luminescence spectroscopy revealed the quantum confinement effect on the spherical small QDs.
  • 雲林院 宏
    The Journal of Physical Chemistry Letters 9 24 7117 - 7122 2018年11月 [査読有り][通常論文]
     
    TERS is a powerful tool for nanoscale optical characterization of surfaces. However, even after 20 years of development, the parameters for optimal TERS tips are still up for debate. As a result, routine measurements on bulk or dielectric substrates remain exceptionally challenging. Herein we help to alleviate this by using electrical cutting to strategically modify silver nanowire TERS probes. Following cutting, the tips present a large, spherical apex and are often nanostructured with numerous nanoparticles, which we argue improve light collection and optical coupling. This doubles TERS signals on a highly enhancing, gap-mode substrate compared to our standard nanowire tips while maintaining a high reproducibility and resolution. More interestingly, on a dielectric substrate (graphene on SiO2) the tips give similar to 7x higher signals than our standard tips. Further investigations point to the nonlocal nature of the enhancement using standard, smooth TERS probes without gap-mode, making such nanostructuring highly beneficial in these cases.
  • Herlinde De Keersmaecker, Rafael Camacho, David Manuel Rantasa, Eduard Fron, Hiroshi Uji-i, Hideaki Mizuno, Susana Rocha
    ACS NANO 12 10 9842 - 9854 2018年10月 
    Protein-protein interactions (PPIs) form the basis of cellular processes, regulating cell behavior and fate. PPIs can be extremely transient in nature, which hinders their detection. In addition, traditional biochemical methods provided limited information on the spatial distribution and temporal dynamics of PPIs that is crucial for their regulation in the crowded cellular environment. Given the pivotal role of membrane micro- and nano-domains in the regulation of PPIs at the plasma membrane, the development of methods to visualize PPIs with a high spatial resolution is imperative. Here, we present a super resolution fluorescence microscopy technique that can detect and map short-lived transient protein-protein interactions on a nanometer scale in the cellular environment. This imaging method is based on single-molecule fluorescence microscopy and exploits the effect of the difference in the mobility between cytosolic and membrane-bound proteins in the recorded fluorescence signals. After the development of the proof of concept using a model system based on membrane-bound modular protein domains and fluorescently labeled peptides, we applied this imaging approach to investigate the interactions of cytosolic proteins involved in the epidermal growth factor signaling pathway (namely, Grb2, c-Raf, and PLC gamma 1). The detected clusters of Grb2 and c-Raf were correlated with the distribution of the receptor at the plasma membrane. Additionally, the interactions of wild type PLC gamma 1 were compared with those detected with truncated mutants, which provided important information regarding the role played by specific domains in the interaction with the membrane. The results presented here demonstrate the potential of this technique to unravel the role of membrane heterogeneity in the spatiotemporal regulation of cell signaling.
  • Peter Walke, Yasuhiko Fujita, Wannes Peeters, Shuichi Toyouchi, Wout Frederickx, Steven De Feyter, Hiroshi Uji-I
    Nanoscale 10 16 7556 - 7565 2018年04月28日 [査読有り][通常論文]
     
    Tip-enhanced Raman scattering (TERS) microscopy is a unique analytical tool to provide complementary chemical and topographic information of surfaces with nanometric resolution. However, difficulties in reliably producing the necessary metallized scanning probe tips has limited its widespread utilisation, particularly in the case of cantilever-based atomic force microscopy. Attempts to alleviate tip related issues using colloidal or bottom-up engineered tips have so far not reported consistent probes for both Raman and topographic imaging. Here we demonstrate the reproducible fabrication of cantilever-based high-performance TERS probes for both topographic and Raman measurements, based on an approach that utilises noble metal nanowires as the active TERS probe. The tips show 10 times higher TERS contrasts than the most typically used electrochemically-etched tips, and show a reproducibility for TERS greater than 90%, far greater than found with standard methods. We show that TERS can be performed in tapping as well as contact AFM mode, with optical resolutions around or below 15 nm, and with a maximum resolution achieved in tapping-mode of 6 nm. Our work illustrates that superior TERS probes can be produced in a fast and cost-effective manner using simple wet-chemistry methods, leading to reliable and reproducible high-resolution and high-sensitivity TERS, and thus renders the technique applicable for a broad community.
  • Wout Frederickx, Susana Rocha, Yasuhiko Fujita, Koen Kennes, Herlinde De Keersmaecker, Steven De Feyter, Hiroshi Uji-I, Willem Vanderlinden
    ACS Nano 12 1 168 - 177 2018年01月23日 [査読有り][通常論文]
     
    Correlative imaging by fluorescence and force microscopy is an emerging technology to acquire orthogonal information at the nanoscale. Whereas atomic force microscopy excels at resolving the envelope structure of nanoscale specimens, fluorescence microscopy can detect specific molecular labels, which enables the unambiguous recognition of molecules in a complex assembly. Whereas correlative imaging at the micrometer scale has been established, it remains challenging to push the technology to the single-molecule level. Here, we used an integrated setup to systematically evaluate the factors that influence the quality of correlative fluorescence and force microscopy. Optimized data processing to ensure accurate drift correction and high localization precision results in image registration accuracies of ∼25 nm on organic fluorophores, which represents a 2-fold improvement over the state of the art in correlative fluorescence and force microscopy. Furthermore, we could extend the Atto532 fluorophore bleaching time ∼2-fold, by chemical modification of the supporting mica surface. In turn, this enables probing the composition of macromolecular complexes by stepwise photobleaching with high confidence. We demonstrate the performance of our method by resolving the stoichiometry of molecular subpopulations in a heterogeneous EcoRV-DNA nucleoprotein ensemble.
  • Rebeca Sola-Llano, Yasuhiko Fujita, Luis Gómez-Hortigüela, Almudena Alfayate, Hiroshi Uji-I, Eduard Fron, Shuichi Toyouchi, Joaquín Pérez-Pariente, Iñigo López-Arbeloa, Virginia Martínez-Martínez
    ACS Photonics 5 1 151 - 157 2018年01月17日 [査読有り][通常論文]
     
    A cyanine dye (PIC) was occluded into two 1D-nanopoporus Mg-containing aluminophosphates with different pore size (MgAPO-5 and MgAPO-36 with AFI and ATS zeolitic structure types, with cylindrical channels of 7.3 Å diameter and elliptical channels of 6.7 Å × 7.5 Å, respectively) by crystallization inclusion method. Different J-aggregates are photophysically characterized as a consequence of the different pore size of the MgAPO frameworks, with emission bands at 565 nm and at 610 nm in MgAPO-5 and MgAPO-36, respectively. Computational results indicate a more linear geometry of the J-aggregates inside the nanochannels of the MgAPO-36 sample than those in MgAPO-5, which is as a consequence of the more constrained environment in the former. For the same reason, the fluorescence of the PIC monomers at 550 nm is also activated within the MgAPO-36 channels. Owing to the strategic distribution of the fluorescent PIC species in MgAPO-36 crystals (monomers at one edge and J-aggregates with intriguing emission properties at the other edge) an efficient and one-directional antenna system is obtained. The unidirectional energy transfer process from monomers to J-aggregates is demonstrated by remote excitation experiments along tens of microns of distance.
  • Kazuki Umemoto, Yong-Jin Pu, Cigdem Yumusak, Markus Clark Scharber, Matthew Schuette White, Niyazi Serdar Sariciftci, Tsukasa Yoshida, Jun Matsui, Hiroshi Uji-i, Akito Masuhara
    Microsystem Technologies 24 1 619 - 623 2018年01月01日 [査読有り][通常論文]
     
    Cuboid fine crystals of methylammonium lead tribromide (MAPbBr3) perovskite have been synthesized by ligand-free reprecipitation method employing N,N-dimethylformamide (DMF) and 1,2,4-trichlorobenzene (TCB) as good and poor solvents, respectively. A small amount of DMF solution dissolving precursor chemicals of MAPbBr3 was rapidly injected to TCB under vigorous stirring to promote the reprecipitation. Mean crystal size could be varied between 70 and 600 nm by controlled addition of cyclohexane to TCB, since cyclohexane has been found to play a role to retard droplet diffusion. Cyclohexane was miscible with TCB but poorly miscible with DMF. Thus, addition of cyclohexane to TCB retarded diffusion of the injected droplets of DMF solution for reprecipitation of MAPbBr3. As the mixing of good and poor solvents was retarded, the recrystallization process was also slowed down, resulted in a small number of nuclei and their growth to large size. Moreover, extreme addition of cyclohexane has resulted in a hollow core spherical particles of MAPbBr3 due to aggregation of the cuboid fine crystals at the boundary between the added droplet and the poor solvent, so that the spheres formed preserving the shape of the droplet. Due to the limited miscibility of cyclohexane to DMF, increasing the cyclohexane content resulted in reduced rate of diffusion of the injected MAPbBr3 solution, thus increasing the size of the crystals.
  • Shuichi Toyouchi, Mathias Wolf, Yasuhiko Fujita, Hiroshi Uji-I
    Proceedings of SPIE - The International Society for Optical Engineering 10712 2018年 [査読有り][通常論文]
     
    We have experimentally demonstrated remote plasmonic optical trapping on a chemically-synthesized silver nanowire (AgNW) induced by nonlinear optical effects, i.e. sum-frequency generation (SFG) and four wave-mixing (FWM). AgNWs were spin coated on a clean cover slip, and then covered with quantum dot (QD) aqueous solution. Two femtosecond IR laser pulses having different energies were focused on one end of the AgNW. SFG and FWM signal was observed at not only the excitation spot but also another end of AgNW through launching propagating plasmon modes. As results, it was found that QDs were trapped on the AgNW when two pulses were overlapped in time. QD resonance wavelength dependence on the trapping behavior indicates that trapping site on AgNW can be controlled.
  • Somia Rahmoun, Fabrice Mairesse, Hiroshi Uji-i, Johan Hofkens, Tadeusz Sliwa
    SIGNAL IMAGE AND VIDEO PROCESSING 11 8 1469 - 1476 2017年11月 [査読有り][通常論文]
     
    Even though polymer chains are well studied, the convolution and diffraction effect of microscopes may cause the quality of the images to be blurry and/or noisy. This paper aims to present an automatic method to extract the curve representing a polymer chain. This curve is useful for chemical studies; for instance, the length of a polymer chain and its curvature are related to its chemical properties. A movement of the polymer chain may lead to complex geometries with possible intersections. In response to this, we developed an approach computing a piecewise curve traversing the shape. This technique relies on computing several geodesics by browsing distinct parts of the shape. Fusing these elements together allows the entire shape to be represented. The curve orientation is already preserved by considering the fusion as a graph traversal problem. The method provides promising results, validated by experts and approved by simulation.
  • B. Fortuni, T. Inose, S. Uezono, S. Toyouchi, K. Umemoto, S. Sekine, Y. Fujita, M. Ricci, G. Lu, A. Masuhara, J. A. Hutchison, L. Latterini, H. Uji-i
    CHEMICAL COMMUNICATIONS 53 82 11298 - 11301 2017年10月 [査読有り][通常論文]
     
    A simple and fast one-step fabrication method of silver nanoparticles (AgNPs) on a polydimethylsiloxane (PDMS) film and their improvement as highly sensitive surface enhanced Raman scattering (SERS) substrates via atomically thin Au coatings is demonstrated. The thin Au layer provides oxidation resistivity while maintaining the broad spectral range SERS sensitivity of Ag nanoparticles.
  • Y. Fujita, R. Aubert, P. Walke, H. Yuan, B. Kenens, T. Inose, C. Steuwe, S. Toyouchi, B. Fortuni, M. Chamtouri, K. P. F. Janssen, S. De Feyter, M. B. J. Roeffaers, H. Uji-i
    NANOSCALE 9 35 13025 - 13033 2017年09月 [査読有り][通常論文]
     
    A highly reproducible and controllable deposition procedure for gold nanostructures on a titanium dioxide (TiO2) surface using femtosecond laser light has been demonstrated. This is realized by precisely focusing onto the TiO2 surface in the presence of a pure gold ion solution. The deposition is demonstrated both in dot arrays and line structures. Thanks to the multi-photon excitation, we observe that the deposition area of the nanostructures can be confined to a degree far greater than the diffraction limited focal spot. Finally, we demonstrate that catalytic activity with visible light irradiation is enhanced, proving the applicability of our new deposition technique to the catalytic field.
  • Maha Chamtouri, Bart Kenens, Remko Aubert, Gang Lu, Tomoko Inose, Yasuhiko Fujita, Akito Masuhara, Johan Hofkens, Hiroshi Uji-I
    ACS Omega 2 7 4032 - 4038 2017年07月31日 [査読有り][通常論文]
     
    Owing to their fundamental importance and practical applications, anatase TiO2 crystals with well-defined {001} and {101} facets attracted intensive research interests. In this study, we systematically investigated solvent dependence of the photoreaction of the different coexposed crystal facets during noble metal photodeposition. By examining the deposition position in each solvent, we revealed that solvents play a pivotal role on the facet selectivity. On the basis of density functional theory calculations, the solvent molecules were found to modify both the crystal facet electronic structure and the {001}-{001} heterojunction. These modifications are not only the origin of diverse charge-carrier pathways but are also responsible for carrier accumulation at specific facets that increase their reductive power. These findings are vital for a better understanding of photocatalytic materials and an improved design for the next-generation materials.
  • Gang Lu, Haifeng Yuan, Liang Su, Bart Kenens, Yasuhiko Fujita, Maha Chamtouri, Maria Pszona, Eduard Fron, Jacek Waluk, Johan Hofkens, Hiroshi Uji-i
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 8 13 2774 - 2779 2017年07月 [査読有り][通常論文]
     
    We reveal nanoscale morphological changes on the surface of a silver nanowire (AgNW) in the conventional surface-enhanced Raman scattering (SERS) measurement condition. The surface morphology changes are due to the surface plasmon-mediated photochemical etching of silver in the presence of certain Raman probes, resulting in a dramatic increase of Raman scattering intensity. This observation indicates that the measured SERS enhancement does not always originate from the as-designed/fabricated structures themselves, but sometimes with contribution from the morphological changes by plasmon-mediated photochemical reactions. Our work provides a guideline for more reliable SERS measurements and demonstrates a novel method for simple and site specific engineering of SERS substrate and AgNW probes for designing and fabricating new SERS systems, stable and efficient TEAS mapping, and single-cell SERS endoscopy.
  • B. Fortuni, Y. Fujita, M. Ricci, T. Inose, R. Aubert, G. Lu, J. A. Hutchison, J. Hofkens, L. Latterini, H. Uji-i
    CHEMICAL COMMUNICATIONS 53 37 5121 - 5124 2017年05月 [査読有り][通常論文]
     
    A novel one-step in situ synthesis of gold nanostars (AuNSs) on a pre-cured polydimethylsiloxane (PDMS) film is proposed for the fabrication of highly sensitive surface-enhanced Raman scattering (SERS) substrates. Plasmonic activity of the substrates was investigated by collecting SERS maps of 4-mercaptobenzoic acid (4-MBA). The applicability of these flexible substrates is further demonstrated by SERS-based pesticide detection on fruit skin.
  • Zhi Li, Hans Van Gorp, Peter Walke, Thanh Hai Phan, Yasuhiko Fujita, John Greenwood, Oleksandr Ivasenko, Kazukuni Tahara, Yoshito Tobe, Hiroshi Uji-, Stijn F. L. Mertens, Steven De Feyter
    NANOSCALE 9 16 5188 - 5193 2017年04月 [査読有り][通常論文]
     
    Altering the chemical reactivity of graphene can offer new opportunities for various applications. Here, we report that monolayers of densely packed n-pentacontane significantly reduce the covalent grafting of aryl radicals to graphitic surfaces. The effect is highly local in nature and on fully covered substrates grafting can occur only at monolayer imperfections such as interdomain borders and vacancy defects. Grafting partially covered substrates primarily results in the covalent modification of uncoated areas.
  • Remko Aubert, Bart Kenens, Maha Chamtouri, Yasuhiko Fujita, Beatrice Fortuni, Gang Lu, James A. Hutchison, Tomoko Inose, Hiroshi Uji-I
    ACS Omega 2 10 6309 - 6313 2017年 [査読有り][通常論文]
     
    Enhancement of visible-light photocurrent generation by sol-gel anatase TiO2 films was achieved by binding small polyol molecules to the TiO2 surface. Binding ethylene glycol onto the surface, enhancement factors up to 2.8 were found in visible-light photocurrent generation experiments. Density functional theory calculations identified midgap energy states that emerge as a result of the binding of a range of polyols to the TiO2 surface. The presence and energy of the midgap state is predicted to depend sensitively on the structure of the polyol, correlating well with the photocurrent generation results. Together, these results suggest a new, facile, and cost-effective route to precise surface band gap engineering of TiO2 toward visible-light-induced photocatalysis and energy storage.
  • Roald Phillipson, Cesar J. Lockhart de la Rosa, Joan Teyssandier, Peter Walke, Deepali Waghray, Yasuhiko Fujita, Jinne Adisoejoso, Kunal S. Mali, Inge Asselierghs, Cedric Huyghebaert, Hiroshi Uji-i, Stefan De Gendt, Steven De Feyter
    NANOSCALE 8 48 20017 - 20026 2016年12月 [査読有り][通常論文]
     
    One current key challenge in graphene research is to tune its charge carrier concentration, i.e., p-and n-type doping of graphene. An attractive approach in this respect is offered by controlled doping via well-ordered self-assembled networks physisorbed on the graphene surface. We report on tunable n-type doping of graphene using self-assembled networks of alkyl-amines that have varying chain lengths. The doping magnitude is modulated by controlling the density of the strong n-type doping amine groups on the surface. As revealed by scanning tunneling and atomic force microscopy, this density is governed by the length of the alkyl chain which acts as a spacer within the self-assembled network. The modulation of the doping magnitude depending on the chain length was demonstrated using Raman spectroscopy and electrical measurements on graphene field effect devices. This supramolecular functionalization approach offers new possibilities for controlling the properties of graphene and other two-dimensional materials at the nanoscale.
  • Rebeca Sola-Llano, Virginia Martinez-Martinez, Yasuhiko Fujita, Luis Gomez-Hortigueela, Almudena Alfayate, Hiroshi Uji-i, Eduard Fron, Joaquin Perez-Pariente, Inigo Lopez-Arbeloa
    CHEMISTRY-A EUROPEAN JOURNAL 22 44 15700 - 15711 2016年10月 [査読有り][通常論文]
     
    In this work, hemicyanine dye LDS722 is encapsulated into the 1D elliptical nanochannels of MgAPO-11 aluminophosphate by a crystallization inclusion method. The synthesis of the hybrid material has been optimized through a systematic variation of the crystallization conditions in order to obtain pure and large crystals (around 20mx30m) suitable for optical applications. The tight fitting between the molecular size of the guest dye and the pore dimensions of the host has favored a rigid planar conformation of the dye, restricting its inherent flexibility, which is confirmed by molecular simulations. Consequently, the encapsulation of LDS722 into MgAPO-11 has led to an astonishing enhancement of the fluorescence with respect to the dye into MgAPO-5, with slightly larger cylindrical channels, and with respect to the dye in solution. Moreover, the perfect alignment of LDS722 (dye with intrinsic nonlinear-optical properties) along the channels of MgAPO-11 has revealed attractive second-order nonlinear properties, such as second harmonic generation, proven through microscopy measurements in single crystals.
  • Yasuhiko Fujita, Peter Walke, Steven De Feyter, Hiroshi Uji-i
    JAPANESE JOURNAL OF APPLIED PHYSICS 55 8 2016年08月 [査読有り][通常論文]
     
    Tip-enhanced Raman scattering (TERS) microscopy is a promising technique for use in surface analysis, allowing both topographic and spectroscopic information to be obtained simultaneously at a scale below 10 nm. One proposed method to further improve spatial resolution is the use of propagating surface plasmons as an excitation light source (i.e.,remote excitation). However, this requires a specialized tip that can only be fabricated via expensive procedures, such as electron-beam lithography. Here, we propose a new method for fabricating silver nanowire-based tips that are suitable for remote excitation-TERS, removing the need for such techniques. A silver nanowire was fixed onto a tungsten-tip using a micromanipulator, before gold nanoparticles were attached in a site-specific manner using AC-dielectrophoresis. All the processes were completed using an optical microscope in the ambient. The background intensities in TERS spectra were suppressed with remote excitation relative to the conventional excitation configuration, indicating an increase in TERS sensitivity. (C) 2016 The Japan Society of Applied Physics.
  • Yasuhiko Fujita, Peter Walke, Steven De Feyter, Hiroshi Uji-i
    JAPANESE JOURNAL OF APPLIED PHYSICS 55 8 2016年08月 [査読有り][通常論文]
     
    Tip-enhanced Raman scattering (TERS) microscopy is a technique that combines the chemical sensitivity of Raman spectroscopy with the resolving power of scanning probe microscopy. The key component of any TERS setup is a plasmonically-active noble metal tip, which serves to couple far-field incident radiation with the near-field. Thus, the design and implementation of reproducible probes are crucial for the continued development of TERS as a tool for nanoscopic analysis. Here we discuss conventional methods for the fabrication of TERS-ready tips, highlighting the problems therein, as well as detailing more recent developments to improve reducibility. In addition, the idea of remote excitation-TERS is enlightened upon, whereby TERS sensitivity is further improved by using propagating surface plasmons to separate the incident radiation from the tip apex, as well as how this can be incorporated into the fabrication process. (C) 2016 The Japan Society of Applied Physics
  • Damiano Genovese, Alessandro Aliprandi, Eko A. Prasetyanto, Matteo Mauro, Michael Hirtz, Harald Fuchs, Yasuhiko Fujita, Hiroshi Uji-, Sergei Lebedkin, Manfred Kappes, Luisa De Cola
    ADVANCED FUNCTIONAL MATERIALS 26 29 5271 - 5278 2016年08月 [査読有り][通常論文]
     
    A Pt(II) complex, bearing an oligo-ethyleneoxide pendant, is able to self-assemble in ultralong ribbons that display mechanochromism upon nanoscale mechanical stimuli, delivered through atomic force microscopy (AFM). Such observation paves the way to fine understanding and manipulation of the mechanochromic properties of such material at the nanoscale. AFM allows quantitative assessment of nanoscale mechanochromism as arising from static pressure (piezochromism) and from shear-based mechanical stimuli (tribochromism), and to compare them with bulk pressure-dependent luminescence observed with diamond-anvil cell (DAC) technique. Confocal spectral imaging reveals that mechanochromism only takes place within short distance from the localized mechanical stimulation, which allows to design high-density information writing with AFM nanolithography applied on individual self-assembled ribbons. Each ribbon hence serves as an individual microsystem for data storage. The orange luminescence of written information displays high contrast compared to cyan native luminescence; moreover, it can be selectively excited with visible light. In addition, ribbons show photochromism, i.e., the emission spectrum changes upon exposure to light, in a similar way as upon mechanical stress. Photochromism is here conveniently used to conceal and eventually erase information previously written with nanolithography by irradiation.
  • Hannelore Bove, Christian Steuwe, Eduard Fron, Eli Slenders, Jan D'Haen, Yasuhiko Fujita, Hiroshi Uji-i, Martin vandeVen, Maarten Roeffaers, Marcel Ameloot
    NANO LETTERS 16 5 3173 - 3178 2016年05月 [査読有り][通常論文]
     
    Although adverse health effects of carbon black (CB) exposure are generally accepted, a direct, label-free approach for detecting CB particles in fluids and at the cellular level is still lacking. Here, we report nonincandescence related white-light (WL) generation by dry and suspended carbon black particles under illumination with femtosecond (fs) pulsed near-infrared light as a powerful tool for the detection of these carbonaceous materials. This observation is done for four different CB species with diameters ranging from 13 to 500 nm, suggesting this WL emission under fs near-infrared illumination is a general property of CB particles. As the emitted radiation spreads over the whole visible spectrum, detection is straightforward and flexible. The unique property of the described WL emission allows optical detection and unequivocal localization of CB particles in fluids and in cellular environments while simultaneously colocalizing different cellular components using various specific fluorophores as shown here using human lung fibroblasts. The experiments are performed on a typical multiphoton laser-scanning microscopy platform, widely available in research laboratories.
  • Yasuhiko Fujita, Peter Walke, Gang Lu, Maha Chamtouri, Steven De Feyter, Hiroshi Uji-i
    ADVANCED MATERIALS TECHNOLOGIES 1 2 2016年05月 [査読有り][通常論文]
  • Haifeng Yuan, Elke Debroye, Kris Janssen, Hiroyuki Naiki, Christian Steuwe, Gang Lu, Michele Moris, Emanuele Orgiu, Hiroshi Uji-i, Frans De Schryver, Paolo Samori, Johan Hofkens, Maarten Roeffaers
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 7 3 561 - 566 2016年02月 [査読有り][通常論文]
     
    Organometal halide perovskites show promising features for cost-effective application in photovoltaics. The material instability remains a major obstacle to broad application because of the poorly understood degradation pathways. Here, we apply simultaneous luminescence and electron microscopy on perovskites for the first time, allowing us to monitor in situ morphology evolution and optical properties upon perovskite degradation. Interestingly, morphology, photoluminescence (PL), and cathodoluminescence of perovskite samples evolve differently upon degradation driven by electron beam (e-beam) or by light. A transversal electric current generated by a scanning electron beam leads to dramatic changes in PL and tunes the energy band gaps continuously alongside film thinning. In contrast, light-induced degradation results in material decomposition to scattered particles and shows little PL spectral shifts. The differences in degradation can be ascribed to different electric currents that drive ion migration. Moreover, solution-processed perovskite cuboids show heterogeneity in stability which is likely related to crystallinity and morphology. Our results reveal the essential role of ion migration in perovskite degradation and provide potential avenues to rationally enhance the stability of perovskite materials by reducing ion migration while improving morphology and crystallinity. It is worth noting that even moderate e-beam currents (86 pA) and acceleration voltages (10 kV) readily induce significant perovskite degradation and alter their optical properties. Therefore, attention has to be paid while characterizing such materials using scanning electron microscopy or transmission electron microscopy techniques.
  • Liang Su, Haifeng Yuan, Gang Lu, Susana Rocha, Michel Orrit, Johan Hofkens, Hiroshi Uji-i
    ACS NANO 10 2 2455 - 2466 2016年02月 [査読有り][通常論文]
     
    Optical antennas made of metallic nanostructures dramatically enhance single-molecule fluorescence to boost the detection sensitivity. Moreover, emission properties detected at the optical far field are dictated by the antenna. Here we study the emission from molecule antenna hybrids by means of super resolution localization and defocused imaging. Whereas gold nanorods make single-crystal violet molecules in the tip's vicinity visible in fluorescence, super-resolution localization on the enhanced molecular fluorescence reveals geometrical centers of the nanorod antenna instead. Furthermore, emission angular distributions of dyes linked to the nanorod surface resemble that of nanorods in defocused imaging. The experimental observations are consistent with numerical calculations using the finite-difference time-domain method.
  • Rocha, S., De Keersmaecker, H., Fron, E., Abe, M., Makino, A., Uji-i, H., Hofkens, J., Kobayashi, T., Miyawaki, A., Mizuno, H.
    Food as Medicine: Functional Food Plants of Africa 2016年
  • Masoumeh Keshavarz, Hans Engelkamp, Jialiang Xu, Els Braeken, Matthijs B. J. Otten, Hiroshi Uji-i, Erik Schwartz, Matthieu Koepf, Anja Vananroye, Jan Vermant, Roeland J. M. Nolte, Frans De Schryver, Jan C. Maan, Johan Hofkens, Peter C. M. Christianen, Alan E. Rowan
    ACS NANO 10 1 1434 - 1441 2016年01月 [査読有り][通常論文]
     
    The thermal motion of polymer chains in a crowded environment is anisotropic and highly confined. Whereas theoretical and experimental progress has been made, typically only indirect evidence of polymer dynamics is obtained either from scattering or mechanical response. Toward a complete understanding of the complicated polymer dynamics in crowded media such as biological cells, it is of great importance to unravel the role of heterogeneity and molecular individualism. In the present work, we investigate the dynamics of synthetic polymers and the tube-like motion of individual chains using time resolved fluorescence microscopy. A single fluorescently labeled polymer molecule is observed in a sea of unlabeled polymers, giving access to not only the dynamics of the probe chain itself but also to that of the surrounding network. We demonstrate that it is possible to extract the characteristic time constants and length scales in one experiment, providing a detailed understanding of polymer dynamics at the single chain level. The quantitative agreement with bulk rheology measurements is promising for using local probes to study heterogeneity in complex, crowded systems.
  • Somia Rahmoun, Fabrice Mairesse, Hiroshi Uji-i, Johan Hofkens, Tadeusz Sliwa
    IMAGE AND SIGNAL PROCESSING (ICISP 2016) 9680 79 - 88 2016年 [査読有り][通常論文]
     
    In the molecular field, researchers analyze dynamics of polymers by microscopy: several measurements such as length and curvature are performed in their studies. To achieve correct analysis they need to extract the curve representing as good as possible the observed polymer shape which is a grayscale thick curve with noise and blur. We propose, in this paper, a method to extract such a curve. A polymer chain moves in a snake-like fashion (Reptation): it can self-intersect and form several complex geometries. To efficiently extract the different geometries, we generate the curve by computing a piecewise centerline browsing the shape by geodesics: each shape gives a set of separate geodesics. By fusion, we obtain the complete curve traveling the shape. To keep the correct curve orientation, the fusion is considered as a graph traversal problem. Promising results show that the extracted curve properly represents the shape and can be used for polymer study.
  • Bart Kenens, Maha Chamtouri, Remko Aubert, Kana Miyakawa, Yasufumi Hayasaka, Hiroyuki Naiki, Hiroki Watanabe, Tomoko Inose, Yasuhiko Fujita, Gang Lu, Akito Masuhara, Hiroshi Uji-i
    RSC ADVANCES 6 100 97464 - 97468 2016年 [査読有り][通常論文]
     
    Metal nanoparticle photo-deposition on TiO2 enhances the semiconductor catalytic activity. We show for the first time that strong adsorption of simple diol-molecules improves the photo-deposition, by introducing a TiO2 midgap state and blocking active sites. The resulting photo-deposited gold nanoparticles are mono-dispersed and well-distributed over the TiO2 particles. The photo-catalytic activity of the Au/TiO2 systems obtained in ethyleneglycol was significantly enhanced compared to those prepared in conventional solvents, such as water and ethanol.
  • Koen Kennes, Peter Dedecker, James A. Hutchison, Eduard Fron, Hiroshi Uji-I, Johan Hofkens, Mark Van Der Auweraer
    ACS Omega 1 6 1383 - 1392 2016年 [査読有り][通常論文]
     
    The fluorescence intermittency or “blinking” of single molecules of ATTO647N (ATTO) in the conductive matrix polyvinylcarbazole (PVK) is described in the presence of an external applied electric field. It is shown that due to the energy distribution of the highest occupied molecular orbital (HOMO) level of PVK, which is energetically close to the HOMO of ATTO, sporadic electron transfer occurs. As a result, the on/off dynamics of blinking can be influenced by the electric field. This field will, depending on the respective position and orientation of the dye/polymer system with respect to those of the electrodes, either enhance or suppress electron transfer from PVK to ATTO as well as the back electron transfer from reduced ATTO to PVK. After the charge-transfer step, the applied field will pull the hole in PVK away from the dye, increasing the overall time the dye resides in a dark state.
  • Eduard Fron, Herlinde De Keersmaecker, Susana Rocha, Yannick Baeten, Gang Lu, Hiroshi Uji-, Mark Van der Auweraer, Johan Hofkens, Hideaki Mizuno
    JOURNAL OF PHYSICAL CHEMISTRY B 119 47 14880 - 14891 2015年11月 [査読有り][通常論文]
     
    LSSmOrange is a fluorescent protein with a large energy gap between the absorption and emission bands (5275 cm(-1)). The electronic structure of the LSSmOrange chromophore, 2-[(5-)-2-hydroxy-dihydrooxazole]-4-(p-hydroxybenzylidene)-5-imidazolinone, is affected by deprotonation of the p-hydroxybenzylidene group. We investigated LSSmOrange by time-resolved spectroscopy in the femtosecond and nanosecond range. The ground state chromophore was almost exclusively in the neutral form, which had a main absorption band at 437 nm with a small shoulder at 475 nm. The absorption at a wavelength within the former band promoted the protein to the excited state where excited state proton transfer (ESPT) could lead to deprotonation in 0.8 ps. Following ESPT, the chromophore emitted fluorescence with a maximum at 573 nm and a decay time of 3500 ps. Although deprotonation by ESPT occurs, we unexpectedly found a slow accumulation of the anionic form in the ground state upon repeated high intensity excitation. This accumulation of the anionic form was accompanied by a shift of the absorption band to 553 nm without changing the emission band. MALDI-MS revealed that this shift is accompanied by decarboxylation of E222, which is interacting with the imidazolinone ring of the chromophore. We concluded that the photoinduced decarboxylation induced a conformational change that affected local environment around the hydroxyl group, resulting in a stable deprotonated form of the chromophore.
  • John Greenwood, Thanh Hai Phan, Yasuhiko Fujita, Zhi Li, Oleksandr Lvasenko, Willem Vanderlinden, Hans Van Gorp, Wout Frederickx, Gang Lu, Kazukuni Tahara, Yoshito Tobe, Hiroshi Uji-i, Stijn F. L. Mertens, Steven De Feyter
    ACS NANO 9 5 5520 - 5535 2015年05月 [査読有り][通常論文]
     
    We shine light on the covalent modification of graphite and graphene substrates using diazonium chemistry under ambient conditions. We report on the nature of the chemical modification of these graphitic substrates, the relation between molecular structure and film morphology, and the impact of the covalent modification on the properties of the substrates, as revealed by local microscopy and spectroscopy techniques and electrochemistry. By careful selection of the reagents and optimizing reaction conditions, a high density of covalently grafted molecules is obtained, a result that is demonstrated in an unprecedented way by scanning tunneling microscopy (STM) under ambient conditions. With nanomanipulation, i.e., nanoshaving using STM, surface structuring and functionalization at the nanoscale is achieved. This manipulation leads to the removal of the covalently anchored molecules, regenerating pristine sp(2) hybridized graphene or graphite patches, as proven by space-resolved Raman microscopy and molecular self-assembly studies.
  • Liang Su, Gang Lu, Bart Kenens, Susana Rocha, Eduard Fron, Haifeng Yuan, Chang Chen, Pol Van Dorpe, Maarten B. J. Roeffaers, Hideaki Mizuno, Johan Hofkens, James A. Hutchison, Hiroshi Uji-i
    NATURE COMMUNICATIONS 6 2015年02月 [査読有り][通常論文]
     
    The enhancement of molecular absorption, emission and scattering processes by coupling to surface plasmon polaritons on metallic nanoparticles is a key issue in plasmonics for applications in (bio) chemical sensing, light harvesting and photocatalysis. Nevertheless, the point spread functions for single-molecule emission near metallic nanoparticles remain difficult to characterize due to fluorophore photodegradation, background emission and scattering from the plasmonic structure. Here we overcome this problem by exciting fluorophores remotely using plasmons propagating along metallic nanowires. The experiments reveal a complex array of single-molecule fluorescence point spread functions that depend not only on nanowire dimensions but also on the position and orientation of the molecular transition dipole. This work has consequences for both single-molecule regime-sensing and super-resolution imaging involving metallic nanoparticles and opens the possibilities for fast size sorting of metallic nanoparticles, and for predicting molecular orientation and binding position on metallic nanoparticles via far-field optical imaging.
  • Haifeng Yuan, Kris P. F. Janssen, Thomas Franklin, Gang Lu, Liang Su, Xian Gu, Hiroshi Uji-i, Maarten B. J. Roeffaers, Johan Hofkens
    RSC ADVANCES 5 9 6829 - 6833 2015年 [査読有り][通常論文]
     
    We report an investigation on the effect of stabilization agents and surface curvatures on oxidative etching of three classes of anisotropically shaped gold nanoparticles namely, rods, bipyramids and prisms. In particular, the dual role of the stabilizing agent CTAB in the etching process is explored, showing how it acts both as a source of bromine ions, accelerating etching and as a protection agent, resulting in anisotropic reshaping.
  • Corinna Raimondo, Bart Kenens, Federica Reinders, Marcel Mayor, Hiroshi Uji-i, Paolo Samori
    NANOSCALE 7 33 13836 - 13839 2015年 [査読有り][通常論文]
     
    pi-pi Intermolecular interactions among adjacent conjugated azobenzenes chemisorbed on (non-) flat Au surfaces can be tuned by varying the curvature of the Au nanoparticles. Here we show that such interactions rule the thermal cis-trans isomerization kinetics, towards a better control on the azobenzene bistability for its optimal integration as a responsive material.
  • Min Li, Duncan den Boer, Patrizia Iavicoli, Jinne Adisoejoso, Hiroshi Uji-i, Mark Van der Auweraer, David B. Amabilino, Johannes A. A. W. Elemans, Steven De Feyter
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 136 50 17418 - 17421 2014年12月 [査読有り][通常論文]
     
    Changing abruptly the potential between a scanning tunneling microscope tip and a graphite substrate induces "high-conductance" spots at the molecular level in a monolayer formed by a manganese chloride-porphyrin molecule. These events are attributed to the pulse-induced formation of mu-oxo-porphyrin dimers. The pulse voltage must pass a certain threshold for dimer formation, and pulse polarity determines the yield.
  • Kuan-Lin Liu, Alexey V. Kubarev, Jordi Van Loon, Hiroshi Uji-i, Dirk E. De Vos, Johan Hofkens, Maarten B. J. Roeffaers
    ACS NANO 8 12 12650 - 12659 2014年12月 [査読有り][通常論文]
     
    Dealuminated zeolites are widely used acid catalysts in research and the chemical industry. Bulk-level studies have revealed that the improved catalytic performance results from an enhanced molecular transport as well as from changes in the active sites. However, fully exploiting this information in rational catalyst design still requires insight in the intricate interplay between both. Here we introduce fluorescence and stimulated Raman scattering microscopy to quantify subcrystal reactivity as well as acid site distribution and to probe site accessibility in the set of individual mordenite zeolites. Dealumination effectively introduces significant heterogeneities between different particles and even within individual crystals. Besides enabling direct rationalization of the nanoscale catalytic performance, these observations reveal valuable information on the industrial dealumination process itself.
  • Yasuhiko Fujita, Rie Chiba, Gang Lu, Noriko N. Horimoto, Shinji Kajimoto, Hiroshi Fukumura, Hiroshi Uji-
    CHEMICAL COMMUNICATIONS 50 69 9839 - 9841 2014年09月 [査読有り][通常論文]
     
    A chemically synthesized silver nanowire was used for atomic-resolution STM imaging and tip-enhanced Raman scattering (TERS) spectroscopy, yielding excellent reproducibility. This TERS tip will open a new venue to surface analysis, such as molecular finger printing at nanoscales.
  • Gang Lu, Herlinde De Keersmaecker, Liang Su, Bart Kenens, Susana Rocha, Eduard Fron, Chang Chen, Pol Van Dorpe, Hideaki Mizuno, Johan Hofkens, James A. Hutchison, Hiroshi Uji-i
    ADVANCED MATERIALS 26 30 5124 - 5128 2014年08月 [査読有り][通常論文]
  • Robrecht M. A. Vergauwe, Hiroshi Uji-i, Karen De Ceunynck, Jan Vermant, Karen Vanhoorelbeke, Johan Hofkens
    JOURNAL OF PHYSICAL CHEMISTRY B 118 21 5660 - 5669 2014年05月 [査読有り][通常論文]
     
    The von Willebrand factor (VWF) is a human plasma protein that plays a key role in the initiation of the formation of thrombi under high shear stress in both normal and pathological situations. It is believed that VWF undergoes a conformational transition from a compacted, globular to an extended form at high shear stress. In this paper, we develop and employ an approach to visualize the large-scale conformation of VWF in a (pressure-driven) Poiseuille flow of water-glycerol buffers with wide-field single molecule fluorescence microscopy as a function of shear stress. Comparison of the imaging results for VWF with the results of a control with lambda-phage double-stranded DNA shows that the detection of individual VWF multimers in flow is feasible. A small fraction of VWF multimers are observed as visibly extended along one axis up to lengths of 2.0 mu m at high applied shear stresses. The size of this fraction of molecules seems to exhibit an apparent dependency on shear stress. We further demonstrate that the obtained results are independent of the charge of the fluorophore used to label VWF. The obtained results support the hypothesis of the conformational extension of VWF in shear flow.
  • Susana Rocha, Herlinde De Keersmaecker, James A. Hutchison, Karen Vanhoorelbeke, Johan A. Martens, Johan Hofkens, Hiroshi Uji-i
    LANGMUIR 30 16 4743 - 4751 2014年04月 [査読有り][通常論文]
     
    Important cellular events such as division require drastic changes in the shape of the membrane. These remodeling processes can be triggered by the binding of specific proteins or by changes in membrane composition and are linked to phospholipid metabolism for which dedicated enzymes, named phospholipases, are responsible. Here wide-field fluorescence microscopy is used to visualize shape changes induced by the action of phospholipase A1 on dye-labeled supported membranes of POPC (1-palmitoyl-2-oleolysn-glycero-3-phosphocholine). Time-lapse imaging demonstrates that layers either shrink and disappear or fold and collapse into vesicles. These vesicles can undergo further transformations such as budding, tubulation, and pearling within 5 min of formation. Using dye-labeled phospholipases, we can monitor the presence of the enzyme at specific positions on the membrane as the shape transformations occur. Furthermore, incorporating the products of hydrolysis into POPC membranes is shown to induce transformations similar to those observed for enzyme action. The results suggest that phospholipase-mediated hydrolysis plays an important role in membrane transformations by altering the membrane composition, and a model is proposed for membrane curvature based on the presence and shape of hydrolysis products.
  • Karen De Ceunynck, Susana Rocha, Simon F. De Meyer, J. Evan Sadler, Hiroshi Uji-i, Hans Deckmyn, Johan Hofkens, Karen Vanhoorelbeke
    JOURNAL OF BIOLOGICAL CHEMISTRY 289 13 8903 - 8915 2014年03月 [査読有り][通常論文]
     
    Background: ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type-1 repeats) cleaves pro-thrombotic ultra-large von Willebrand factor (VWF) strings. Results: Customized single particle tracking enabled visualization of single ADAMTS13 enzymes that bind to long platelet-decorated VWF strings. Conclusion: ADAMTS13 readily bind to multiple available sites on VWF strings. Significance: Single molecule imaging can be used to study interactions between enzymes and large biopolymers in flow. von Willebrand factor (VWF) strings are removed from the endothelial surface by ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type-1 repeats)-mediated proteolysis. To visualize how single ADAMTS13 molecules bind to these long strings, we built a customized single molecule fluorescence microscope and developed single particle tracking software. Extensive analysis of over 6,000 single inactive ADAMTS13(E225Q) enzymes demonstrated that 20% of these molecules could be detected in at least two consecutive 60-ms frames and followed two types of trajectories. ADAMTS13(E225Q) molecules either decelerated in the vicinity of VWF strings, whereas sometimes making brief contact with the VWF string before disappearing again, or readily bound to the VWF strings and this for 120 ms or longer. These interactions were observed at several sites along the strings. Control experiments using an IgG protein revealed that only the second type of trajectory reflected a specific interaction of ADAMTS13 with the VWF string. In conclusion, we developed a dedicated single molecule fluorescence microscope for detecting single ADAMTS13 molecules (nm scale) on their long, flow-stretched VWF substrates (m scale) anchored on living cells. Comprehensive analysis of all detected enzymes showed a random interaction mechanism for ADAMTS13 with many available binding sites on the VWF strings.
  • James A. Hutchison, Hiroshi Uji-i, Ania Deres, Tom Vosch, Susana Rocha, Sibylle Mueller, Andreas A. Bastian, Joerg Enderlein, Hassan Nourouzi, Chen Li, Andreas Herrmann, Klaus Muellen, Frans De Schryver, Johan Hofkens
    NATURE NANOTECHNOLOGY 9 2 131 - 136 2014年02月 [査読有り][通常論文]
     
    Developing molecular systems with functions analogous to those of macroscopic machine components, such as rotors(1,2), gyroscopes(3) and valves(4), is a long-standing goal of nanotechnology. However, macroscopic analogies go only so far in predicting function in nanoscale environments, where friction dominates over inertia(5,6). In some instances, ratchet mechanisms have been used to bias the ever-present random, thermally driven (Brownian) motion and drive molecular diffusion in desired directions(7). Here, we visualize the motions of surface-bound molecular rotors using defocused fluorescence imaging, and observe the transition from hindered to free Brownian rotation by tuning medium viscosity. We show that the otherwise random rotations can be biased by the polarization of the excitation light field, even though the associated optical torque is insufficient to overcome thermal fluctuations. The biased rotation is attributed instead to a fluctuating-friction mechanism(8,9) in which photoexcitation of the rotor strongly inhibits its diffusion rate.
  • Liang Su, Haifeng Yuan, Gang Lu, Johan Hofkens, Maarten Roeffaers, Hiroshi Uji-i
    NANOPHOTONICS AND MICRO/NANO OPTICS II 9277 2014年 [査読有り][通常論文]
     
    Fluorescence correlation spectroscopy (FCS), a powerful tool to resolve local properties, dynamical process of molecules, rotational and translational diffusion motions, relies on the fluctuations of florescence observables in the observation volume. In the case of rare transition events or small dynamical fluctuations, FCS requires few molecules or even single molecules in the observation volume at a time to minimize the background signals. Metal nanoparticle which possess unique localized surface plasmon resonance (LSPR) have been used to reduce the observation volume down to sub-diffraction limited scale while maintain at high analyst concentration up to tens of micromolar. Nevertheless, the applications of functionalized nanoparticles in living cell are limited due to the continuous diffusion after cell uptake, which makes it difficult to target the region of interests in the cell. In this work, we demonstrate the use of silver nanowires for remote excitation FCS on fluorescent molecules in solution. By using propagation surface plasmon polaritons (SPPs) which supported by the silver nanowire to excite the fluorescence, both illumination and observation volume can be reduced simultaneously. In such a way, less perturbation is induced to the target region, and this will broaden the application scope of silver nanowire as tip in single cell endoscopy.
  • De Ceunynck K. E. P, Rocha S. N, De Meyer S. F, Uji-I H, Deckmyn H, Hofkens J, Vanhoorelbeke K
    JOURNAL OF THROMBOSIS AND HAEMOSTASIS 11 120 - 121 2013年07月 [査読有り][通常論文]
  • Luminita Marin, Maria-Cristina Popescu, Andrei Zabulica, Hiroshi Uji-, Eduard Fron
    CARBOHYDRATE POLYMERS 95 1 16 - 24 2013年05月 [査読有り][通常論文]
     
    The obtaining of bio-polymer dispersed liquid crystal (bio-PDLC) systems based on a chitosan polymer matrix is reported here for the first time. The new PDLC composites have been obtained by encapsulation of 4-cyano-4'-pentylbiphenyl (5CB) as low molecular weight liquid crystal into chitosan, and they have been characterized by polarized optical microscopy, differential scanning calorimetry, electron and transmission scanning microscopy, Raman and fluorescence spectroscopy. Submicrometric liquid crystalline droplets with uniform size distribution and density have been obtained for low liquid crystal content into the PDLCs. The droplets have a radial configuration being anchored into chitosan matrix by an interface ordering coupling phenomenon. (C) 2013 Elsevier Ltd. All rights reserved.
  • Takanori Tada, Yukiteru Katsumoto, Karel Goossens, Hiroshi Uji-i, Johan Hofkens, Tatsuya Shoji, Noboru Kitamura, Yasuyuki Tsuboi
    JOURNAL OF PHYSICAL CHEMISTRY C 117 20 10818 - 10824 2013年05月 [査読有り][通常論文]
     
    We discovered for aqueous thermoresponsive polymer solutions that only a slight change in stereoregularity of the polymer can drastically accelerate phase separation. Single molecule fluorescence tracking (SMT) for an isotactic-slight-rich (meso-diad-rich) polymer sample solution revealed an interpolymer nanonetwork even before phase separation, and also revealed a novel phase in which translational molecular motion was frozen after phase separation. For such systems, fluorescence correlation spectroscopy (FCS) provided quantitative information on molecular diffusion. The results on FCS well agreed with the interpolymer nanonetwork model that was proposed on the-basis of SMT measurement. We demonstrate such a novel method to control phase separation dynamics and also the interpolymer nanonetwork model.
  • Jialiang Xu, Sergey Semin, Dorota Niedzialek, Paul H. J. Kouwer, Eduard Fron, Eduardo Coutino, Matteo Savoini, Yuliang Li, Johan Hofkens, Hiroshi Uji-, David Beljonne, Theo Rasing, Alan E. Rowan
    ADVANCED MATERIALS 25 14 2084 - 2089 2013年04月 [査読有り][通常論文]
     
    While highly desired in integrated optical circuits, multiresponsive and tunable nonlinear optical (NLO) active 1D (sub) wavelength scale superstructures from organic materials are rarely reported due to the strong tendency of organic molecules to self-assembly in centrosymmetric modes. Here a solution-processed assembly approach is reported to generate non-centrosymmetric single-crystalline organic microfibers with a cumulative dipole moment for anisotropic combined second-and third-order NLO.
  • Bart Kenens, Maksym Rybachuk, Johan Hofkens, Hiroshi Uji-I
    Journal of Physical Chemistry C 117 6 2547 - 2553 2013年02月14日 [査読有り][通常論文]
     
    Metallic nanowires constitute a distinctive class of nanostructures that are able to guide surface plasmons in subwavelength dimensions. The effective use of light in- and out-coupling in low dimensional systems, such as excitation of surface plasmon polaritons along metallic nanowires, has been proposed to reduce physical dimensions of opto-electronic and nano-optical components and for high-resolution microscopy applications. Our investigation of light in- and out-coupling on silver nanowire systems by scanning optical coupling microscopy (SOCM) performed in combination with atomic force microscopy (AFM) revealed that the maximum coupling was obtained when the exciting laser light is projected at the end of the nanowire with a positioning accuracy of approximately 100 nm. Furthermore, it was found that a nanoparticle positioned at the end of a nanowire imparts an enhanced (by almost the factor of 4) plasmon in- and out-coupling light efficiency as compared to a free nanowire under the same excitation conditions. These findings are supported by theoretical simulations, which in addition provide a correlation between the nanoparticle size and the out-coupling light efficiency. Our investigations demonstrate that a combination of SOCM and AFM methods provide reliable qualitative and quantitative evaluation of plasmon in- and out-coupling characteristics on metallic nanowire systems. © 2012 American Chemical Society.
  • Aniruddha Paul, Bart Kenens, Johan Hofkens, Hiroshi Uji-i
    LANGMUIR 28 24 8920 - 8925 2012年06月 [査読有り][通常論文]
     
    In this contribution, we report an effective and relatively simple route to grow triangular flat-top silver nanoparticles (NPs) directly on a solid substrate from smaller NPs through a wet photochemical synthesis. The method consists of fixing small, preformed nanotriangles (NTs) on a substrate and subsequently irradiating them with light in a silver seed solution. Furthermore, the use of linearly polarized light allows for exerting control on the growth direction of the silver nanotriangles on the substrate. Evidence for the role of surface plasmon resonances in governing the growth of the NTs is obtained by employing linear polarized light. Thus, this study demonstrates that light-induced, directional synthesis of nanoparticles on solid substrates is in reach, which is of utmost importance for plasmonic applications.
  • Hongzhen Lin, Silvia P. Centeno, Liang Su, Bart Kenens, Susana Rocha, Michel Sliwa, Johan Hofkens, Hiroshi Uji-i
    CHEMPHYSCHEM 13 4 973 - 981 2012年03月 [査読有り][通常論文]
     
    Photoactivation localization microscopy (PALM) was applied to study surface-enhanced fluorescence (SEF) on metal nanostructures (SEF-PALM). The detection of fluorescence from individual single molecules can be used to image the point-spread-function and spatial distribution of the fluorescence emitted in the vicinity of a metal surface. Due to the strong scattering effect, the angular distribution of the fluorescence is altered by metals, resulting in a spatial shift of fluorescence spots with respect to the metal nanostructures, and has to be taken into account in the analysis. SEF-PALM can be used to discriminate effects of labelling density when estimating the enhancement factor in SEF. Furthermore, nanostructures with sizes below the diffraction limit can be resolved using this technique. SEF-PALM is established as a powerful tool to study plasmon-mediated phenomena on metal nanostructures.
  • Katrien G. M. Laurier, Michel Poets, Frederik Vermoortele, Gert De Cremer, Johan A. Martens, Hiroshi Uji-i, Dirk E. De Vos, Johan Hofkens, Maarten B. J. Roeffaers
    CHEMICAL COMMUNICATIONS 48 10 1559 - 1561 2012年 [査読有り][通常論文]
     
    We report a one-step photocatalytic synthesis method of dendritic silver nanostructures. These self-organised structures show an excellent Raman enhancement enabling the detection of analytes from dilute solutions by surface-enhanced Raman spectroscopy.
  • Jian Ye, James Andell Hutchison, Hiroshi Uji-i, Johan Hofkens, Liesbet Lagae, Guido Maes, Gustaaf Borghs, Pol Van Dorpe
    NANOSCALE 4 5 1606 - 1611 2012年 [査読有り][通常論文]
     
    Detailed understanding of the underlying mechanisms of surface enhanced Raman scattering (SERS) remains challenging for different experimental conditions. We report on an excitation wavelength dependent SERS of 4-aminothiophenol molecules on gold nanorings. SERS and normal Raman spectra, combined with well-characterized surface morphology, optical spectroscopy and electromagnetic (EM) field simulations of gold nanoring substrates indicate that the EM enhancement occurs at all three excitation wavelengths (532, 633 and 785 nm) employed but at short wavelengths (532 and 633 nm) charge transfer (CT) results in additional strong enhancements of particular Raman transitions. These results pave the way to further understanding the origin of the SERS mechanism.
  • Ania Deres, George A. Floudas, Klaus Muellen, Mark Van der Auweraer, Frans De Schryver, Joerg Enderlein, Hiroshi Uji-i, Johan Hofkens
    MACROMOLECULES 44 24 9703 - 9709 2011年12月 [査読有り][通常論文]
     
    Single molecule defocused wide-field fluorescence microscopy (SMDWM) has been used to monitor the 3D reorientation of single molecules in a thin polymer film (similar to 300 nm) of monodisperse poly(n-butyl methacrylate) near the glass temperature (T-epsilon). Stroboscopic illumination allows for estimating reliable correlation times of single molecule rotational diffusion owing to the drastic lengthening of the observable trajectories. We demonstrate that homogeneity is restored similar to 19 K above the T-g determined with calorimetry. The rotational correlation times obtained from SMDWM show similar temperature dependence as the ones measured with established bulk measurements, such as dielectric spectroscopy and rheology, on the same polymer sample. Single molecular reorientation is coupled to the segmental rather than terminal relaxation of the surrounding polymer matrix. SMDWM revealed that spatial heterogeneity is more pronounced than temporal heterogeneity within the measurement time scale (hours to days), whereas this information is hidden in the bulk measurement.
  • Martin Lehmann, Susana Rocha, Bastien Mangeat, Fabien Blanchet, Hiroshi Uji-i, Johan Hofkens, Vincent Piguet
    PLOS PATHOGENS 7 12 2011年12月 [査読有り][通常論文]
     
    Virus assembly and interaction with host-cell proteins occur at length scales below the diffraction limit of visible light. Novel super-resolution microscopy techniques achieve nanometer resolution of fluorescently labeled molecules. The cellular restriction factor tetherin (also known as CD317, BST-2 or HM1.24) inhibits the release of human immunodeficiency virus 1 (HIV-1) through direct incorporation into viral membranes and is counteracted by the HIV-1 protein Vpu. For super-resolution analysis of HIV-1 and tetherin interactions, we established fluorescence labeling of HIV-1 proteins and tetherin that preserved HIV-1 particle formation and Vpu-dependent restriction, respectively. Multicolor super-resolution microscopy revealed important structural features of individual HIV-1 virions, virus assembly sites and their interaction with tetherin at the plasma membrane. Tetherin localization to micro-domains was dependent on both tetherin membrane anchors. Tetherin clusters containing on average 4 to 7 tetherin dimers were visualized at HIV-1 assembly sites. Combined biochemical and super-resolution analysis revealed that extended tetherin dimers incorporate both N-termini into assembling virus particles and restrict HIV-1 release. Neither tetherin domains nor HIV-1 assembly sites showed enrichment of the raft marker GM1. Together, our super-resolution microscopy analysis of HIV-1 interactions with tetherin provides new insights into the mechanism of tetherin-mediated HIV-1 restriction and paves the way for future studies of virus-host interactions.
  • Karen De Ceunynck, Susana Rocha, Hendrik B. Feys, Simon F. De Meyer, Hiroshi Uji-i, Hans Deckmyn, Johan Hofkens, Karen Vanhoorelbeke
    JOURNAL OF BIOLOGICAL CHEMISTRY 286 42 36361 - 36367 2011年10月 [査読有り][通常論文]
     
    Platelet-decorated von Willebrand factor (VWF) strings anchored to the endothelial surface are rapidly cleaved by ADAMTS13. Individual VWF string characteristics such as number, location, and auxiliary features of the ADAMTS13 cleavage sites were explored here using imaging and computing software. By following changes in VWF string length, we demonstrated that VWF strings are cleaved multiple times, successively shortening string length in the function of time and generating fragments ranging in size from 5 to over 100 mu m. These are larger than generally observed in normal plasma, indicating that further proteolysis takes place in circulation. Interestingly, in 89% of all cleavage events, VWF strings elongate precisely at the cleavage site before ADAMTS13 proteolysis. These local elongations are a general characteristic of VWF strings, independent of the presence of ADAMTS13. Furthermore, large elongations, ranging in size from 1.4 to 40 mu m, occur at different sites in space and time. In conclusion, ADAMTS13-mediated proteolysis of VWF strings under flow is preceded by large elongations of the string at the cleavage site. These elongations may lead to the simultaneous exposure of many exosites, thereby facilitating ADAMTS13-mediated cleavage.
  • Johan Hofkens, Hiroshi Uji-i
    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 242 2011年08月 [査読有り][通常論文]
  • K. E. De Ceunynck, S. Rocha, H. B. Feys, S. F. De Meyer, H. Deckmyn, H. Uji-I, J. Hofkens, K. Vanhoorelbeke
    JOURNAL OF THROMBOSIS AND HAEMOSTASIS 9 308 - 308 2011年07月 [査読有り][通常論文]
  • Hongzhen Lin, Tatsumi Ohta, Aniruddha Paul, James A. Hutchison, Kirilenko Demid, Oleg Lebedev, Gustaaf Van Tendeloo, Johan Hofkens, Hiroshi Uji-i
    JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY 221 2-3 220 - 223 2011年06月 [査読有り][通常論文]
     
    This report describes the effect of light irradiation on the synthesis of silver nanowires by the well-known polyol method. High quality nanowires are produced in high yields when the reaction suspension is irradiated with 400-500 nm light during the nucleation stage. These studies suggest that light accelerates the formation of the nanoparticle seeds most appropriate for nanowire growth. (C) 2011 Published by Elsevier B.V.
  • M. Lehmann, S. Rocha, B. Mangeat, F. Blanchet, H. Uji-i, J. Hofkens, V. Piguet
    BRITISH JOURNAL OF DERMATOLOGY 164 4 918 - 918 2011年04月 [査読有り][通常論文]
  • Rob Ameloot, Elena Gobechiya, Hiroshi Uji-i, Johan A. Martens, Johan Hofkens, Luc Alaerts, Bert F. Sels, Dirk E. De Vos
    ADVANCED MATERIALS 22 24 2685 - + 2010年06月 [査読有り][通常論文]
     
    Processing metal organic frameworks with spatial and temporal control over crystal formation will increase the applicability of these highly porous materials. By exploiting solvent effects, stable synthesis solutions can be obtained, which can be used in combination with soft lithographic techniques to deposit oriented crystals in patterns by in situ crystallization (see figure).
  • Martin Gudmand, Susana Rocha, Nikos S. Hatzakis, Kalina Peneva, Klaus Muellen, Dimitrios Stamou, Hiroshi Uji-I, Johan Hofkens, Thomas Bjornholm, Thomas Heimburg
    BIOPHYSICAL JOURNAL 98 9 1873 - 1882 2010年05月 [査読有り][通常論文]
     
    We monitored the action of phospholipase A(2) (PLA(2)) on L- and D-dipalmitoyl-phosphatidylcholine (DPPC) Langmuir monolayers by mounting a Langmuir-trough on a wide-field fluorescence microscope with single molecule sensitivity. This made it possible to directly visualize the activity and diffusion behavior of single PLA(2) molecules in a heterogeneous lipid environment during active hydrolysis. The experiments showed that enzyme molecules adsorbed and interacted almost exclusively with the fluid region of the DPPC monolayers. Domains of gel state L-DPPC were degraded exclusively from the gel-fluid interface where the buildup of negatively charged hydrolysis products, fatty acid salts, led to changes in the mobility of PLA(2). The mobility of individual enzymes on the monolayers was characterized by single particle tracking. Diffusion coefficients of enzymes adsorbed to the fluid interface were between 3.2 mu m(2)/s on the L-DPPC and 4.9 mu m(2)/s on the D-DPPC monolayers. In regions enriched with hydrolysis products, the diffusion dropped to approximate to 0.2 mu m(2)/s. In addition, slower normal and anomalous diffusion modes were seen at the L-DPPC gel domain boundaries where hydrolysis took place. The average residence times of the enzyme in the fluid regions of the monolayer and on the product domain were between approximate to 30 and 220 ms. At the gel domains it was below the experimental time resolution, i.e., enzymes were simply reflected from the gel domains back into solution.
  • Eduard Fron, Ania Deres, Susana Rocha, Gang Zhou, Klaus Muellen, Frans C. De Schryver, Michel Sliwa, Hiroshi Uji-i, Johan Hofkens, Tom Vosch
    JOURNAL OF PHYSICAL CHEMISTRY B 114 3 1277 - 1286 2010年01月 [査読有り][通常論文]
     
    Insight into the exciton dynamics Occurring in a polyfluorene-perylenediimide (PF-PDI) copolymer with a reaction Mixture ratio of 100 fluorene units to 1 N,N'-bis(phenyl)-1,6,7,12-tetra(p-tert-octylphenoxy)-perylene-3,4,9,10-tetracarboxylic acid diimide (PDI) is presented here. Time-correlated single photon counting and femtosecond transient absorption spectroscopy measurements on the PF-PDI copolymer have been employed to investigate the excited-state properties of the polyfluorene subunit where the exciton is localized (PF) and the incorporated PDI chromophore. The experimental results were compared with those obtained from a polyfluorene polymer (model PF) and a N,N'-bis(2,6-diisopropylphenyl)-1,6,7,12-tetra(p-tert-octylphenoxy)perylene-14,91, I 0-tetracarboxylic acid diimide (model PDI) which were used as reference compounds. Because of the high polydispersity of the PF-PDI copolymer, there is a polymer fraction present that contains no PDI chromophores (polyfluorene polymer fraction (PIT polymer fraction)), and wide-field imaging of single polymers chains of the synthesized PF-PDI copolymer was used to estimate this PF polymer fraction. Following the primary excitation of the PIT in the PF-PDI copolymer, energy hopping between PF's can occur. A fraction of the energy of the absorbed photons will be transferred to a PDI chromophore via energy transfer from a PIT. In a polar solvent, a charge transfer state having the S, of the PDI moiety as a precursor state is found to form with high efficiency oil a nanosecond time scale. The data suggest that a fraction of the absorbed energy is directed, transferred, and used in charge separation, providing a clear view of a multistep mechanism of exciton dissociation into charges.
  • Kerstin Blank, Susana Rocha, Gert De Cremer, Maarten B. J. Roeffaers, Hiroshi Uji-i, Johan Hofkens
    SINGLE MOLECULE SPECTROSCOPY IN CHEMISTRY, PHYSICS AND BIOLOGY 96 495 - + 2010年 [査読有り][通常論文]
     
    Single-molecule fluorescence experiments are a powerful tool to analyze reaction mechanisms of enzymes. Because of their unique potential to detect heterogeneities in space and time, they have provided unprecedented insights into the nature and mechanisms of conformational changes related to the catalytic reaction. The most important finding from experiments with single enzymes is the generally observed phenomenon that the catalytic rate constants fluctuate over time (dynamic disorder). These fluctuations originate from conformational changes occurring on time scales, which are similar to or slower than that of the catalytic reaction. Here, we summarize experiments with enzymes that show dynamic disorder and introduce new experimental strategies showing how single-molecule fluorescence experiments can be applied to address other open questions in medical and industrial enzymology, such as enzyme inactivation processes, reactant transfer in cascade reactions, and the mechanisms of interfacial catalysis.
  • Chang Chen, James Andell Hutchison, Pol Van Dorpe, Ronald Kox, Iwijn De Vlaminck, Hiroshi Uji-i, Johan Hofkens, Liesbet Lagae, Guido Maes, Gustaaf Borghs
    SMALL 5 24 2876 - 2882 2009年12月 [査読有り][通常論文]
     
    The focusing of plasmons to obtain a strong and localized electromagnetic field enhancement for surface-enhanced Raman scattering (SERS) is increasing the interest in using plasmonic devices as molecular sensors. In this Full Paper, the successful fabrication and demonstration of a solid-state plasmonic nanoslit-cavity device equipped with nanoantennas on a freestanding thin silicon membrane as a substrate for SERS is reported. Numerical calculations predict a strong and spatially localized enhancement of the optical field in the nanoslit (6 nm in width) upon irradiation. The predicted enhancement factor of SERS was 5.3 x 10(5), localized in an area of just 6 x 1.5 nm(2). Raman spectroscopy and imaging confirm an enhancement factor of approximate to 10(6) for SERS from molecules chemisorbed at the nanoslit, and demonstrate the electromagnetic-field-enhancing function of the plasmonic nanoantennas. The freestanding membrane is open on both sides of the nanoslit, offering the potential for through-slit molecular translocation studies, and opening bright new perspectives for SERS applications in real-time (bio)chemical analysis.
  • Tom Vosch, Eduard Fron, Jun-ichi Hotta, Ania Deres, Hiroshi Uji-i, Abdenacer Idrissi, Jaesung Yang, Dongho Kim, Larissa Puhl, Andreas Haeuseler, Klaus Muellen, Frans C. De Schryver, Michel Sliwa, Johan Hofkens
    JOURNAL OF PHYSICAL CHEMISTRY C 113 27 11773 - 11782 2009年07月 [査読有り][通常論文]
     
    Perylenediimide (PDI) dyes have attracted a great deal of attention as they possess excellent photochemical stability, high extinction coefficients, and fluorescence quantum yields. The use of multiple PDI chromophores in one synthetic architecture increases their versatile use and functionality even more. However, bringing multiple chromophores in close proximity also leads to interactions among the chromophores and opens up new photophysical pathways. Here, the synthesis and photophysical characterization, both at the ensemble and single molecule level, of a diphenyl-acetylene linked perylenediimide trimer (3PDIAc) is presented. Forster type energy transfer processes like energy hopping and singlet-singlet annihilation among the chromophores are investigated. Despite the lower singlet-singlet annihilation rate of the phenoxy substituted perylenediimide chromophores (356 ps) versus for example perylenemonoimide (10 ps), the system still behaves as a single photon emitter. Sequential fitting of the dipole emission pattern recorded with defocused wide field imaging of single 3PDIAc, immobilized in a PMMA polymer film, demonstrated that emission can switch between sequential emission of all of the chromophores or emission from one chromophore that likely is the lowest in energy.
  • Tai-Yang Kim, Hiroshi Uji-i, Martina Moeller, Benoit Muls, Johan Hofkens, Ulrike Alexiev
    BIOCHEMISTRY 48 18 3801 - 3803 2009年05月 [査読有り][通常論文]
     
    Heterotrimeric G-proteins interact with their G-protein-coupled receptors (GPCRs) via key binding elements comprising the receptor-specific C-terminal segment of the alpha-subunit and the lipid anchors at the alpha-subunit N-terminus and the gamma-subunit C-terminus. Direct information about diffusion and interaction of GPCRs and their G-proteins is mandatory for all understanding of the signal transduction mechanism. By using single-particle tracking, we show that the encounters of the alpha-subunit C-terminus With the GPCR rhodopsin change after receptor activation. Slow as well as less restricted diffusion compared to the inactive state within domains 60-280 nm in length was found for the receptor-bound C-terminus, indicating short-range order in rhodopsin packing.
  • James A. Hutchison, Silvia P. Centeno, Hideho Odaka, Hiroshi Fukumura, Johan Hofkens, Hiroshi Uji-i
    NANO LETTERS 9 3 995 - 1001 2009年03月 [査読有り][通常論文]
     
    We demonstrate that focused laser excitation at the end of silver nanowires of 50-150 nm diameter excites SERS hot-spots at points of nanoparticle adsorption many micrometers along the wire due to the plasmon waveguide effect. The total SERS Intensity detected at the hot-spots following wire-end excitation correlates with the known wavelength, polarization, and distance dependences of surface plasmon polariton (SPP) propagation in nanowires. The SERS spectra obtained at the hot-spots following wire-end excitation show very little background compared to when excitation occurs directly at the hot-spot, suggesting that a much smaller SERS excitation volume Is achieved by remote, waveguide excitation. The ability to transfer SERS excitation over several micrometers, through a structure with a subdiffraction limit diameter, Is discussed with respect to potential high-resolution SERS imaging applications.
  • Peter Dedecker, Benoit Muls, Ania Deres, Hiroshi Uji-i, Jun-ichi Hotta, Michel Sliwa, Jean-Philippe Soumillion, Klaus Muellen, Joerg Enderlein, Johan Hofkens
    ADVANCED MATERIALS 21 10-11 1079 - 1090 2009年03月 [査読有り][通常論文]
     
    Today's miniature devices and biological systems share the fact that their dynamics and properties cannot be understood, in terms of macroscopic concepts, but require a thorough understanding of the nanoscale structuring This structuring is often very heterogeneous both in time and in space, and is difficult or impossible to resolve with traditional approaches. In this Progress Report, we will discuss how single-molecule microscopy - and defocused wide-field field imaging in particular-can be used to shed light on these phenomena.
  • Susana Rocha, James A. Hutchison, Kalina Peneva, Andreas Herrmann, Klaus Muellen, Michael Skjot, Christian I. Jorgensen, Allan Svendsen, Frans C. De Schryver, Johan Hofkens, Hiroshi Uji-i
    CHEMPHYSCHEM 10 1 151 - 161 2009年01月 [査読有り][通常論文]
     
    Many of the biological processes taking place in cells are mediated by enzymatic reactions occurring in the cell membrane. Understanding interfacial enzymatic catalysis is therefore crucial to the understanding of cellular function. Unfortunately, a full picture of the overall mechanism of interfacial enzymatic catalysis, and particularly the important diffusion processes therein, remains unresolved. Herein we demonstrate that single-molecule wide-field fluorescence microscopy can yield important new information on these processes. We image phospholipase enzymes acting upon bilayers of their natural phospholipid substrate, tracking the diffusion of thousands of individual enzymes while simultaneously visualising local structural changes to the substrate layer. We study several enzyme types with different affinities and catalytic activities towards the substrate. Analysis of the trajectories of each enzyme type allows us successfully to correlate the mobility of phospholipase with its catalytic activity at the substrate. The methods introduced herein represent a promising new approach to the study of interfacial/heterogeneous catalysis systems.
  • Dominik Woll, Els Braeken, Ania Deres, Frans C. De Schryver, Hiroshi Uji-i, Johan Hofkens
    CHEMICAL SOCIETY REVIEWS 38 2 313 - 328 2009年 [査読有り][通常論文]
     
    This tutorial review summarizes the most important results and developments in the field of polymer science by means of single molecule fluorescence spectroscopy (SMFS) at ambient temperatures. A broad range of topics will be addressed and it will be discussed which single molecule methods are suitable to get the maximum amount of information about polymer structure, polymer dynamics and the photophysics of incorporated or embedded dye molecules. In particular, we will report on the use of polymer films for immobilization of molecules, the visualization of dynamics near the glass transition temperature T-g, the reptation of polymer chains, the conformation adopted by polymer chains and the in situ observation of the polymerization reaction itself.
  • Chang Chen, James Andell Hutchison, Francesca Clemente, Ronald Kox, Hiroshi Uji-I, Johan Hofkens, Liesbet Lagae, Guido Maes, Gustaaf Borghs, Pol Van Dorpe
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 48 52 9932 - 9935 2009年 [査読有り][通常論文]
  • M. Linh Tran, Silvia P. Centeno, James A. Hutchison, Hans Engelkamp, Duoduo Liang, Gustaaf Van Tendeloo, Bert F. Sels, Johan Hofkens, Hiroshi Uji-i
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 130 51 17240 - + 2008年12月 [査読有り][通常論文]
     
    A simple and low-cost method to create metal-metal hybrid nanostructures possessing fairly regularly spaced "hot-spots" of surface plasmon resonances is proposed. The nanohybrid structure was prepared via self-assembly during a simple drop-casting procedure, using chemically synthesized silver nanowires and silver nanoparticles prepared in a single batch of a polyol process. Wide field illumination of these nanohybrids produced hot-spots with spacings of around 500 nm to 1 mu m. The intensity of the emission/scattering from the hot-spots fluctuates over time. The proposed structure can be useful for the development of molecular-sensors or as a substrate for surface enhanced Raman/fluorescence spectroscopy.
  • Kazukuni Tahara, Shengbin Lei, Wael Mamdouh, Yui Yamaguchi, Tomoyuki Ichikawa, Hiroshi Uji-i, Motohiro Sonoda, Keiji Hirose, Frans C. De Schryver, Steven De Feyter, Yoshito Tobe
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 130 21 6666 - + 2008年05月 [査読有り][通常論文]
     
    We present here the formation of a modular 2D molecular network composed of two different types of square-shaped butadiyne-bridged macrocycles, having intrinsic molecular voids, aligned alternately at the solid-liquid interface. Site-selective inclusion of a guest cation took place at every other molecular void in the molecular network with two different recognition sites.
  • Maarten B. J. Roeffaers, Rob Ameloot, Mukulesh Baruah, Hiroshi Uji-i, Metin Bulut, Gert De Cremer, Ulrich Mueller, Pierre A. Jacobs, Johan Hofkens, Bert F. Sels, Dirk E. De Vos
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 130 17 5763 - 5772 2008年04月 [査読有り][通常論文]
     
    Understanding the internal structure of ZSM-5 crystallites is essential for improving catalyst performance. In this work, a combination of fluorescence microscopy, AFM, SEM, and optical observations is employed to study intergrowth phenomena and pore accessibility in a set of five ZSM-5 samples with different crystal morphologies. An amine-functionalized perylene dye is used to probe acid sites on the external crystal surface, while DAMPI (4-(4-diethylaminostyryl)-N-methylpyridinium iodide) is used to map access to the straight channels in MFI from the outer surface. The use of these dyes is validated by studying the well-understood rounded-boat type ZSM-5 crystals. Next coffin-shaped ZSM-5 crystals are considered; we critically evaluate the seemingly conflicting 2-component and 3-component models that have been proposed to account for the hourglass structure in these crystals. The data prove that observation of an hourglass structure is essentially unrelated to a 901 rotation of the pyramidal crystal components under the (010) face. Hence, in perfectly formed coffin-shaped crystals, the straight channels can be accessed from (010). However, in other crystal batches, sections with a 90 degrees rotation can be found; they are indeed located inside the crystal sections under (010) but often only partially occupy these pyramidal components. In such a case, both straight and sinusoidal pores surface at the hexagonal face. The results largely support the 3-component model, but with the added notion that 900 rotated sections (as proposed in the 2-component model) are most likely to be formed inside the defect-rich, pyramidal crystal sections under the (010) faces.
  • Jaesung Yang, Mira Park, Zin Seok Yoon, Takaaki Hori, Xiaobin Peng, Naoki Aratani, Peter Dedecker, Jun-ichi Hotta, Hiroshi Uji-i, Michel Sliwa, Johan Hofkens, Atsuhiro Osuka, Dongho Kim
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 130 6 1879 - 1884 2008年02月 [査読有り][通常論文]
     
    By using single molecule fluorescence spectroscopy we have investigated the excitation energy migration processes occurring in a series of cyclic porphyrin arrays bearing a close proximity in overall architectures to the LH2 complexes in purple bacterial photosynthetic systems. We have revealed that the conformational heterogeneity induced by the structural flexibility in large cyclic porphyrin arrays, which provides the nonradiative deactivation channels as an energy sink or trap, reduces significantly the energy migration efficiency. Our study provides detailed information on the energy migration efficiency of the artificial light-harvesting arrays at the single molecule level, which will be a guideline for future applications in single molecular photonic devices in the solid state.
  • Nathalie Katsonis, Andrea Minoia, Tibor Kudernac, Toshiki Mutai, Hong Xu, Hiroshi Uji-i, Roberto Lazzaroni, Steven De Feyter, Ben L. Feringa
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 130 2 386 - + 2008年01月 [査読有り][通常論文]
     
    Upon deposition of an achiral solution of diarylethene 1 on the achiral surface of graphite, a highly ordered monolayer with large homachiral domains is formed by self-assembly. Scanning tunneling micro ropy and molecolar dynamics show that the building blocks forming this monolayer are chiral dinners. We suggest that the mechanism of formation of these chiral dinners is first, surface-Induced atropoisomerism, which provides diarylethene 1 with a fixed helicity, and second, shape recognition between atropoisomers having similar helicites.
  • Dominik Woell, Hiroshi Uji-i, Tobias Schnitzler, Jun-ichi Hotta, Peter Dedecker, Andreas Herrmann, Frans C. De Schryver, Klaus Muellen, Johan Hofkens
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 47 4 783 - 787 2008年 [査読有り][通常論文]
  • Kalina Peneva, Gueorgui Mihov, Fabian Nolde, Susana Rocha, Jun-ichi Hotta, Kevin Braeckmans, Johan Hofkens, Hiroshi Uji-i, Andreas Herrmann, Klaus Muellen
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 47 18 3372 - 3375 2008年 [査読有り][通常論文]
  • Peter Dedecker, Jun-Ichi Hotta, Cristina Flors, Michel Sliwa, Hiroshi Uji-, Maarten B. J. Roeffaers, Ryoko Ando, Hideaki Mizuno, Atsushi Miyawaki, Johan Hofkens
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 129 51 16132 - 16141 2007年12月 [査読有り][通常論文]
     
    The fast and reversible on/off switching of the fluorescence emission of the GFP-like fluorescent protein Dronpa has attracted considerable interest for applications in subdiffraction imaging. In this paper we study the use of a donut-mode beam in combination with two more overlapping laser beams to increase the imaging resolution through selective switching to the nonfluorescent photoswitched state. We devise and run a series of numerical simulations to determine suitable photophysical parameters of prospective, thermally stable photoswitchable molecules, in terms of photoswitching quantum yields, fatigue resistance, and possible presence of transient nonfluorescent states. Many of our findings are applicable to other measurements that make use of donut beams, and these guidelines can be used in the synthesis and screening of novel pholoswitchable compounds. We experimentally demonstrate the possibility of obtaining increased resolution by making use of the efficient and thermally stable Dronpa photoswitching, using equipment that is commonly available.
  • Cristina Flors, Jun-ichi Hotta, Hiroshi Uji-i, Peter Dedecker, Ryoko Ando, Hideaki Mizuno, Atsushi Miyawaki, Johan Hofkens
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 129 45 13970 - 13977 2007年11月 [査読有り][通常論文]
     
    The photophysical properties and photoswitching scheme of the reversible photoswitchable green fluorescent protein-like fluorescent proteins Dronpa-2 and Dronpa-3 were investigated by means of ensemble and single-molecule fluorescence spectroscopy and compared to those of the precursor protein Dronpa. The faster response to light and the faster dark recovery of the new mutants observed in bulk also hold at the single-molecule level. Analysis of the single-molecule traces allows us to extract the efficiencies and rate constants of the pathways involved in the forward and backward switching, and we find important differences when comparing the mutants to Dronpa. We rationalize our results in terms of a higher conformational freedom of the chromophore in the protein environment provided by the P-can. This thorough understanding of the photophysical parameters has allowed us to optimize the acquisition parameters for camera-based sub-diffraction-limit imaging with these photochromic proteins. We show that Dronpa and its mutants are useful for fast photoactivation-localization microscopy (PALM) using common wide-field microscopy equipment, as individual fluorescent proteins can be localized several times. We provide a new approach to achieve fast PALM by introducing simultaneous two-color stroboscopic illumination.
  • Maarten B. J. Roeffaers, Gert De Cremer, Hiroshi Uji-i, Benlot Muls, Bert F. Sels, Pierre A. Jacobs, Frans C. De Schryver, Dirk E. De Vos, Johan Hofkens
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 104 31 12603 - 12609 2007年07月 [査読有り][通常論文]
     
    The ever-improving time and space resolution and molecular detection sensitivity of fluorescence microscopy offer unique opportunities to deepen our insights into the function of chemical and biological catalysts. Because single-molecule microscopy allows for counting the turnover events one by one, one can map the distribution of the catalytic activities of different sites in solid heterogeneous catalysts, or one can study time-dependent activity fluctuations of individual sites in enzymes or chemical catalysts. By experimentally monitoring individuals rather than populations, the origin of complex behavior, e.g., in kinetics or in deactivation processes, can be successfully elucidated. Recent progress of temporal and spatial resolution in single-molecule fluorescence microscopy is discussed in light of its impact on catalytic assays. Key concepts are illustrated regarding the use of fluorescent reporters in catalytic reactions. Future challenges comprising the integration of other techniques, such as diffraction, scanning probe, or vibrational methods in single-molecule fluorescence spectroscopy are suggested.
  • Mira Park, Min-Chul Yoon, Zin Seok Yoon, Takaaki Hori, Xiaobin Peng, Naoki Aratani, Jun-ichi Hotta, Hiroshi Uji-i, Michel Sliwa, Johan Hofkens, Atsuhiro Osuka, Dongho Kim
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 129 12 3539 - 3544 2007年03月 [査読有り][通常論文]
     
    Covalently linked cyclic porphyrin arrays have been synthesized to mimic natural light-harvesting apparatuses and to investigate the highly efficient energy migration processes occurring in these systems for future applications in molecular photonics. To avoid an ensemble-averaged picture, we performed a single-molecule spectroscopic study on the energy migration processes of cyclic porphyrin arrays and a linear model compound embedded in a rigid polymer matrix by recording fluorescence intensity trajectories, by performing coincidence measurements, and by doing wide-field defocused imaging. Our study demonstrates efficient energy migration within the cyclic porphyrin arrays at the single-molecule level. By comparison with the data of the linear model compound, we could pinpoint the role of the dipole-dipole coupling between diporphyrin subunits and the rigidity of the cyclic structures on the energy transfer processes.
  • Sergey M. Melnikov, Edwin K. L. Yeow, Hiroshi Uji-i, Mircea Cotlet, Klaus Muellen, Frans C. De Schryver, Joerg Enderlein, Johan Hofkens
    JOURNAL OF PHYSICAL CHEMISTRY B 111 4 708 - 719 2007年02月 [査読有り][通常論文]
     
    Forster type resonance energy transfer (FRET) in donor-acceptor peryleneimide-terrylenediimide dendrimers has been examined at the single molecule level. Very efficient energy transfer between the donor and the acceptor prevent the detection of donor emission before photobleaching of the acceptor. Indeed, in solution, on exciting the donor, only acceptor emission is detected. However, at the single molecule level, an important fraction of the investigated individual molecules (about 10-15%) show simultaneous emission from both donor and acceptor chromophores. The effect becomes apparent mostly after photobleaching of the majority of donors. Single molecule photon flux correlation measurements in combination with computer simulations and a variety of excitation conditions were used to determine the contribution of an exciton blockade to this two-color emission. Two-color defocused wide-field imaging showed that the two-color emission goes hand in hand with an unfavorable orientation between one of the donors and the acceptor chromophore.
  • Xiaohong Cheng, An Ver Heyen, Wael Mamdouh, Hiroshi Uji-i, Frans De Schryver, Sigurd Hoeger, Steven De Feyter
    LANGMUIR 23 3 1281 - 1286 2007年01月 [査読有り][通常論文]
     
    Shape-persistent macrocycles with interiors in the nanometer regime were prepared by the oxidative cyclization of the appropriate bisacetylene precursors under high-dilution conditions. These compounds contain polycyclic aromatic hydrocarbons in the ring backbone and are decorated with extra annular oligoalkyl or silyl side groups. Interestingly, after depositing them on different surfaces and investigating the self-assembled structures by means of scanning tunneling microscopy (STM) and atomic force microscopy (AFM), various nanostructures were observed. STM showed that these macrocycles are organized in two-dimensional (2D) layers, whereas AFM showed, in addition, the formation of 2D crystallites and one-dimensional fibrils. These results reveal the importance of the extra annular substitution of the macrocycles in creating patterned surfaces and nanoscale objects.
  • Maarten B. J. Roeffaers, Bert F. Sels, Hiroshi Uji-i, Bart Blanpain, Pieter L'hoest, Pierre A. Jacobs, Frans C. De Schryver, Johan Hofkens, Dirk E. De Vos
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 46 10 1706 - 1709 2007年 [査読有り][通常論文]
  • S. De Feyter, A. Miura, H. Uji-i, P. Jonkheijm, A. P. H. J. Schenning, E. W. Meijer, Z. Chen, F. Wuerthner, N. Schuurmans, J. van Esch, B. Feringa, F. C. De Schryver
    NANOSCIENCE AND TECHNOLOGY, PTS 1 AND 2 121-123 369 - 372 2007年 [査読有り][通常論文]
     
    With scanning tunneling microscopy (STM), the intramolecular conformational and intermolecular ordering aspects have been investigated of a variety of organic molecules physisorbed at the liquid-solid interface. By balancing the interplay between intramolecular and intermolecular interactions (hydrogen bonding), leading to control of the molecular conformation, foldamers were created which order into well-defined two-dimensional crystals. The nature of the hydrogen bonding groups in conjugated oligomers leads to the formation of infinite stacks and cyclic multimers, expressing the chiral nature of the molecules.
  • Peter Dedecker, Cristina Flors, Jun-ichi Hotta, Hiroshi Uji-i, Johan Hofkens
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 46 44 8330 - 8332 2007年 [査読有り][通常論文]
  • Kazukuni Tahara, Shuhei Furukawa, Hiroshi Uji-i, Tsutomu Uchino, Tomoyuki Ichikawa, Jian Zhang, Wael Mamdouh, Motohiro Sonoda, Frans C. De Schryver, Steven De Feyter, Yoshito Tobe
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 128 51 16613 - 16625 2006年12月 [査読有り][通常論文]
     
    The self-assembly of a series of hexadehydrotribenzo[12] annulene (DBA) derivatives has been scrutinized by scanning tunneling microscopy (STM) at the liquid-solid interface. First, the influence of core symmetry on the network structure was investigated by comparing the two-dimensional (2D) ordering of rhombic bisDBA 1a and triangular DBA 2a (Figure 1). BisDBA 1a forms a Kagome network upon physisorption from 1,2,4-trichlorobenzene (TCB) onto highly oriented pyrolytic graphite (HOPG). Under similar experimental conditions, DBA 2a shows the formation of a honeycomb network. The core symmetry and location of alkyl substituents determine the network structure. The most remarkable feature of the DBA networks is the interdigitation of the nonpolar alkyl chains: they connect the pi-conjugated cores and direct their orientation. As a result, 2D open networks with voids are formed. Second, the effect of alkyl chain length on the structure of DBA patterns was investigated. Upon increasing the length of the alkyl chains (DBAs 3c-e) a transition from honeycomb networks to linear networks was observed in TCB, an observation attributed to stronger molecule-substrate interactions. Third, the effect of solvent on the structure of the nonpolar DBA networks was investigated in four different solvents: TCB as a polar aromatic solvent, 1-phenyloctane as a solvent having both aromatic and aliphatic moieties, n-tetradecane as an aliphatic solvent, and octanoic acid as a polar alkylated solvent. The solvent dramatically changes the structure of the DBA networks. The solvent effects are discussed in terms of factors that influence the mobility of molecules at the liquid-solid interface such as solvation.
  • Josep Puigmarti-Luis, Andrea Minoia, Hiroshi Uji-i, Concepcio Rovira, Jerome Cornil, Steven De Feyter, Roberto Lazzaroni, David B. Amabilino
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 128 39 12602 - 12603 2006年10月 [査読有り][通常論文]
  • Jun-ichi Hotta, Hiroshi Uji-i, Johan Hofkens
    OPTICS EXPRESS 14 13 6273 - 6278 2006年06月 [査読有り][通常論文]
     
    We demonstrated the fabrication of a phase shaper for generating a 'doughnut mode' laser beam using a thin, circular polymer film on a substrate. The fabrication method is based on a combination of spin-coating and drop-casting. The alignment procedure to get ideal 'doughnut modes' is described. The intensity distribution at the focus is analyzed with single molecule spectroscopy. (c) 2006 Optical Society of America.
  • S Furukawa, H Uji-i, K Tahara, T Ichikawa, M Sonoda, FC De Schryver, Y Tobe, S De Feyter
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 128 11 3502 - 3503 2006年03月 [査読有り][通常論文]
  • H Uji-i, SM Melnikov, A Deres, G Bergamini, F De Schryver, A Herrmann, K Mullen, J Enderlein, J Hofkens
    POLYMER 47 7 2511 - 2518 2006年03月 [査読有り][通常論文]
     
    Defocused wide-field fluorescence microscopy was used to follow the 3D molecular rotational diffusion of a fluorescent probe molecule in a polymer thin film. The technique allows for visualizing the molecular reorientation both in-plane and out-of-plane. The local environmental change driven by heterogeneous dynamics of the polymer can be probed on a scale of I mu m as demonstrated by parallel imaging of several molecules. A multi-component rotational diffusion decay is observed which might reflect both different relaxation regimes of the polymer as well as rapid changes of the local environment. (c) 2006 Elsevier Ltd. All rights reserved.
  • MBJ Roeffaers, BF Sels, H Uji-i, FC De Schryver, PA Jacobs, DE De Vos, J Hofkens
    NATURE 439 7076 572 - 575 2006年02月 [査読有り][通常論文]
     
    Catalytic processes on surfaces have long been studied by probing model reactions on single-crystal metal surfaces under high vacuum conditions. Yet the vast majority of industrial heterogeneous catalysis occurs at ambient or elevated pressures using complex materials with crystal faces, edges and defects differing in their catalytic activity. Clearly, if new or improved catalysts are to be rationally designed, we require quantitative correlations between surface features and catalytic activity - ideally obtained under realistic reaction conditions(1-3). Transmission electron microscopy(4-6) and scanning tunnelling microscopy(7,8) have allowed in situ characterization of catalyst surfaces with atomic resolution, but are limited by the need for low-pressure conditions and conductive surfaces, respectively. Sum frequency generation spectroscopy can identify vibrations of adsorbed reactants and products in both gaseous and condensed phases(9), but so far lacks sensitivity down to the single molecule level. Here we adapt real-time monitoring of the chemical transformation of individual organic molecules by fluorescence microscopy(10-12) to monitor reactions catalysed by crystals of a layered double hydroxide immersed in reagent solution. By using a wide field microscope, we are able to map the spatial distribution of catalytic activity over the entire crystal by counting single turnover events. We find that ester hydrolysis proceeds on the lateral {10 (1) over bar0} crystal faces, while transesterification occurs on the entire outer crystal surface. Because the method operates at ambient temperature and pressure and in a condensed phase, it can be applied to the growing number of liquid-phase industrial organic transformations to localize catalytic activity on and in inorganic solids. An exciting opportunity is the use of probe molecules with different size and functionality, which should provide insight into shape-selective or structure-sensitive catalysis(13-15) and thus help with the rational design of new or more productive heterogeneous catalysts.
  • W. Verheijen, H. Uji-i, C. Flors, J. Hotta, J. Hofkens
    ULTRASENSITIVE AND SINGLE-MOLECULE DETECTION TECHNOLOGIES 6092 2006年 [査読有り][通常論文]
     
    The dynamical behavior of individual enzymes is studied by confocal microscopy. This technique makes it possible to gain insights into the detailed spectrum of molecular conformational changes and activities. We report the direct observation of a single CalB lipase-catalyzed reaction for extended periods of time (hours). A model in which a broad spectrum of conformations is involved is has to be invoked in order to explain the stretched exponential behavior of the off-times histograms.
  • H Uji-i, P Foubert, FC De Schryver, S De Feyter, E Gicquel, A Etoc, C Moucheron, A Kirsch-De Mesmaeker
    CHEMISTRY-A EUROPEAN JOURNAL 12 3 758 - 762 2006年01月 [査読有り][通常論文]
     
    Topological modifications of plasmid DNA adsorbed on a variety of surfaces were investigated by using atomic force microscopy (AFM). On mica modified with 3-aminopropyltriethoxysilane (APS) or poly-L-lysine, the interaction between the plasmid DNA and the surface "freezes" the plasmid DNA conformation deposited from solution, and the AFM images resemble the projection of the three-dimensional conformation of the plasmid DNA in solution. Modified mica with low concentrations of Mg2+ leads to a decrease in the interaction strength between plasmid DNA and the substrate, and the AFM images reflect the relaxed or equilibrium conformation of the adsorbed plasmid DNA. Under these optimized deposition conditions, topological modifications of plasmid DNA were produced under irradiation in the presence of [Ru(TAP)(3)](2+) (TAP=1,4,5,8-tetraazaphenanthrene), which is a nonintercalating complex, and were followed as a function of illumination time. The observed structural changes correlate well with the conversion of the supercoiled covalently closed circular form (ccc form) into the open circular form (oc form), induced by a singlestrand photocleavage. The AFM results obtained after fine-tuning of the plasmid DNA-substrate interaction compare well with those observed from gel electrophoresis, indicating that under the appropriate deposition conditions, AFM is a reliable technique to investigate irradiation-induced topological changes in plasmid DNA.
  • S. De Feyter, H. Uji-i, W. Mamdouh, A. Miura, J. Zhang, P. Jonkheijm, A. P. H. J. Schenning, E. W. Meijer, Z. Chen, F. Wuerthner, N. Schuurmans, J. van Esch, B. L. Feringa, A. E. Dulcey, V. Percec, F. C. De Schryver
    INTERNATIONAL JOURNAL OF NANOTECHNOLOGY 3 4 462 - 479 2006年 [査読有り][通常論文]
     
    The liquid/solid interface provides an ideal environment to investigate self-assembly phenomena, and scanning tunnelling microscopy (STM) is one of the preferred methodologies to probe the structure and the properties of physisorbed monolayers on the nanoscale. Physisorbed monolayers are of relevance in areas such as lubrication, patterning of surfaces on the nanoscale, and thin film based organic electronic devices, to name a few. It's important to gain insight in the factors which control the ordering of molecules at the liquid/solid interface in view of the targeted properties. STM provides detailed insight into the importance of molecule-substrate (epitaxy) and molecule-molecule interactions to direct the ordering of both achiral and chiral molecules on the atomically flat surface. The electronic properties of the self-assembled physisorbed molecules can be probed by taking advantage of the operation principle of STM, revealing spatially resolved intramolecular differences within these physisorbed molecules.
  • W Mamdouh, H Uji-i, JS Ladislaw, AE Dulcey, Percec, V, FC De Schryver, S De Feyter
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 128 1 317 - 325 2006年01月 [査読有り][通常論文]
     
    The effect of solvent on the two-dimensional (2D) supramolecular ordering of monodendron 1 at the liquid-solid interface has been systematically investigated by means of scanning tunneling microscopy (STM). Solvents range from those with hydrophilic solvating properties, such as alkylated alcohols and acids, to hydrophobic solvents such as alkylated aromatics and alkanes. Dramatic differences in the 2D ordering are observed depending on the nature of the solvent. Of particular interest is the fact that in hydrophobic solvating solvents, such as aliphatic and aromatic hydrocarbons, solvent molecules are coadsorbed in the 2D molecular network while this is not the case for alkylated alcohols or acids. Furthermore, in the case of the coadsorbing solvents, a striking influence of the alkyl chain length has been observed on the 2D pattern formed. The solvent and alkyl chain length dependences are discussed in terms of molecule-molecule interactions (homo and hetero) and molecule-substrate interactions.
  • B Muls, H Uji-i, S Melnikov, A Moussa, W Verheijen, JP Soumillion, J Josemon, K Mullen, J Hofkens
    CHEMPHYSCHEM 6 11 2286 - 2294 2005年11月 [査読有り][通常論文]
     
    Wide-field imaging of individual multichromophoric molecules and successive photobleaching were used to determine, accurately, the relative position of the chromophores in such systems. First, a polyphenylene dendrimer with well-defined geometry was used to establish the accuracy in localization that can be obtained by this methodology. For a signal-to-noise ratio of 20, interchromophoric distances could be measured with 4 nm accuracy. Next, the method was used to determine the end-to-end distribution of an end-capped polyfluorene polymer. From comparison between the experimental and simulated distributions, information on the conformation of the polymer could be deduced. It was found that the polymer has a nonlinear conformation. A conjugation length of six monomer units gave the best fit of the experimental data to the proposed model.
  • H Fukumura, D L-i, H Uji-i, S Nishio, H Sakai, A Ohuchi
    CHEMPHYSCHEM 6 11 2383 - 2388 2005年11月 [査読有り][通常論文]
     
    The structures of self-assembled monolayers of dioctadecyl selenide (CH3(CH2)(17))(2)Se and dioctadecyl telluride (CH3(CH2)(17))(2)Te, as well as dioctadecyl ether (CH3(CH2)(17))(2)O and dioctadecyl sulfide (CH3(CH2)(17))(2)S, on graphite at the liquid-solid interface were systematically investigated by scanning tunneling microscopy (STM). Both dioctadecyl selenide and telluride formed monolayer structures in which the tilt angle between the molecular axis of the alkyl chain and the lamellae axis was 90 degrees, while dioctadecyl ether assembled with a tilt angle of 60 degrees. Dioctadecyl sulfide was found to make two different self-assembled structures having tilt angles of 60 and 90 degrees. When selenide was embedded in ether compounds in mixed self-assembled monolayers, the alkyl chains of the selenide become blurred, implying that the alkyl chains in the monolayers were unstable. This is in contrast with the structure of co-adsorbed monolayers of the ether and sulfide compounds, where the images of all alkyl chains hod high spatial resolution. For the co-adsorbed monolayers, the image contrast of chalcogen atoms was normalized compared with that of alkyl chains of the ether compound in the some image frame. The normalized image contrast was found to be independent of the measurement conditions involving tip shapes, having the following trend, Te > Se > S > C > O. The difference in the normalized image contrast among chalcogen atoms are discussed based on fundamental parameters like polarizability and atomic radii.
  • MMS Abdel-Mottaleb, E Gomar-Nadal, M Surin, H Uji-i, W Mamdouh, J Veciana, Lemaur, V, C Rovira, J Cornil, R Lazzaroni, DB Amabilino, S De Feyter, FC De Schryver
    JOURNAL OF MATERIALS CHEMISTRY 15 43 4601 - 4615 2005年11月 [査読有り][通常論文]
     
    The self-assembly of a series of tetrathiafulvalene (TTF) derivatives at the interface between non-volatile organic solutions and the graphite surface has been studied by scanning tunnelling microscopy (STM). The TTFs have been prepared such that they bear none, one, two (in different constitutions) or four alkyl chains of different lengths and different functional groups. The STM images reveal that the packing of the TTF cores can effectively be controlled by changing the substitution pattern on the heterocycle. Several structures are seen at the interphase - parquet-type packing, single and double core tapes, and even isolated molecules - all of which have the TTF core essentially coplanar with the surface. Molecular modelling has shown that several orientations of the molecules are practically equal in energy on the graphite, which explains the polymorphous packing of some of the molecules. Solvent effects also play a role in determining the 2D structures.
  • H Uji-i, A Miura, A Schenning, EW Meijer, ZJ Chen, F Wurthner, FC De Schryver, M Van der Auweraer, S De Feyter
    CHEMPHYSCHEM 6 11 2389 - 2395 2005年11月 [査読有り][通常論文]
     
    By means of scanning tunneling microscopy (STM), the self-assembly of two organic donor-acceptor-donor triads (donor=oligo(p-phenylene vinylene) (OPV); acceptor=perylene diimide (PDI)) and their mixtures has been investigated at the liquid/solid interface, Both triads differ in the nature of the substituents and, therefore, in the redox properties of the central perylene diimide unit (H or Cl). Thanks to the submolecular resolution, the distinct electronic properties of the units, within a triad and between the two triads, are reflected by the relative STM contrast in the bias-dependent imaging experiments. Moreover, scanning tunneling spectroscopy reveals an inverse rectifying behavior of the OPV and H-substituted PDI units, which is discussed in the framework of quasi-resonant tunneling. A striking difference is observed for the Cl-substituted triad.
  • S Nishio, D I-i, H Matsuda, M Yoshidome, H Uji-i, H Fukumura
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 44 7B 5417 - 5420 2005年07月 [査読有り][通常論文]
     
    A nanospace polymerization reaction was initiated using a scanning tunneling microscope in a monolayer of a diacetylene derivative, 10, 12-nonacosadiynoic acid (NCDA), at a solid-liquid interface to obtain molecular wires. The polymerization threshold with respect to the applied voltage was 2 V, which was I V lower than that observed at a solid-air interface. The presence of ionic species considerably enhanced the reaction probability. At more than 2 V, the addition of N(CH(3))(4)ClO(4) resulted in the expansion of the reaction region and the increase in reaction probability regardless of the sign of the bias voltage applied. Different from the case at the solid-air interface, polymerization at the solid-liquid interface was probably induced through the multiple vibrational excitation of NCDA by repetitive collisions with charged carriers activated by the strong electric field involved in electron avalanche.
  • H Uji-i, S Nishio, H Fukumura
    CHEMICAL PHYSICS LETTERS 408 1-3 112 - 117 2005年06月 [査読有り][通常論文]
     
    Two kinds of self-assembled structures of 1-pyrenehexadecanoic acid at a solution-graphite interface were investigated using scanning tunneling microscopy. The pyrenyl groups of 1-pyrenehexadecanoic acid formed a pi-stacked assembly when it was co-adsorbed with 4,4'-dipyridyl although the pyrenyl groups remained isolated in the one-component self-assembled structure. On the basis of the Davidov splitting model, the shift of the pyrenyl group's electronic levels, upon formation of the pi-stacked assembly, was estimated from the observed structures. The energy shift was found to be consistent with the observed change in the electron-tunneling spectra between these two different structures. (c) 2005 Elsevier B.V. All rights reserved.
  • APHJ Schenning, P Jonkheijm, FJM Hoeben, J van Herrikhuyzen, SCJ Meskers, EW Meijer, LM Herz, C Daniel, C Silva, RT Phillips, RH Friend, D Beljonne, A Miura, S De Feyter, M Zdanowska, H Uji-i, FC De Schryver, Z Chen, F Wurthner, M Mas-Torrent, D den Boer, M Durkut, P Hadley
    SYNTHETIC METALS 147 1-3 43 - 48 2004年12月 [査読有り][通常論文]
     
    We have demonstrated that it is possible to program pi-conjugated molecules to self-assemble into cylindrical aggregates in solution. By incorporating energy or electron traps in our stacks, energy and electron transfer processes in these one-dimensional assemblies have been studied in solution. The transfer of the single OPV cylinders from solution to a solid support as isolated objects was only possible when specific concentrations and specific solid supports were used. So far, however, we have not been able to measure any current through our fibers. (C) 2004 Elsevier B.V All rights reserved.
  • S Nishio, M Yoshidome, H Uji-i, J Hobley, H Fukumura, KA Zachariasse
    CHEMISTRY LETTERS 33 11 1506 - 1507 2004年11月 [査読有り][通常論文]
     
    N,N-Dimethyl-p-[15-(1-pyrenyl)pentadecanyt]aniline (Py15DMA); 15-(p-N,N-dimethylaminophenyl)pentadecanylpyrene-1-carboxylate (Py(COO)16 DMA); and 1,16-di(1-pyrene)hexadecane (Py16Py) monolayers sorbed at a liquid-solid interface were probed using an STM. High definition images were obtained of sufficient quality to determine the structural parameters of the monolayers.
  • N Schuurmans, H Uji-i, W Mamdouh, FC De Schryver, BL Feringa, J van Esch, S De Feyter
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 126 43 13884 - 13885 2004年11月 [査読有り][通常論文]
  • W Mamdouh, H Uji-i, A Gesquiere, S De Feyter, DB Amabilino, MMS Abdel-Mottaleb, J Veciana, FC De Schryver
    LANGMUIR 20 22 9628 - 9635 2004年10月 [査読有り][通常論文]
     
    The effect that molecular chirality has on the formation of monolayer structures by pure enantiomers and their racemates at the liquid/solid interface has been investigated for two chiral compounds (1 and 2) which differ from each other by the presence or absence of an ester function in their respective molecular structures. 1 shows pseudoracemate formation when the achiral graphite support is exposed to a solution containing a racemate while 2 shows racemic conglomerate formation. This difference is rationalized in terms of the orientation of the pure enantiomers with respect to the graphite substrate and highlights the importance of molecular structure and its influence on balancing the interplay between molecular conformation and molecular packing on the surface. For 1, nonstoichiometric mixtures of both enantiomers have been investigated, and the results are discussed in the framework of the sergeant and soldiers principle. These results are important for the understanding and prediction of spontaneous resolution in monolayer systems.
  • W Mamdouh, H Uji-i, AE Dulcey, Percec, V, S De Feyter, FC De Schryver
    LANGMUIR 20 18 7678 - 7685 2004年08月 [査読有り][通常論文]
     
    We have investigated the two-dimensional ordering of chiral and achiral monodendrons at the liquid-solid interface. The chiral molecules self-assemble into extended arrays of dimers. As expected, the R enantiomer forms the mirror image type pattern of the chiral two-dimensional structure formed by the S enantiomer. A racemic mixture applied from solution onto the substrate undergoes spontaneous segregation: the enantiomers separate on the surface and appear in different domains. In contrast to the chiral molecules, the achiral analogue self-assembles into cyclic tetramers. Moreover, the pattern formed by the achiral molecule strongly depends on the solvent used. In the case of 1-phenyloctane, solvent molecules are coadsorbed in a 2:1 (dendron:solvent) ratio whereas in I-octanol, no solvent molecules are coadsorbed. By the appropriate solvent choice, the distance between the potential "supramolecular containers" can be influenced.
  • A Miura, ZJ Chen, H Uji-i, S De Feyter, M Zdanowska, P Jonkheijm, APHJ Schenning, EW Meijer, F Wurthner, FC De Schryver
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 125 49 14968 - 14969 2003年12月 [査読有り][通常論文]
  • H Uji-i, K Hatanaka, J Hobley, H Fukumura
    APPLIED PHYSICS LETTERS 79 16 2660 - 2662 2001年10月 [査読有り][通常論文]
     
    A nanometer-scale surface modification of tin-doped indium oxide (ITO) in organic solvent was performed using a scanning tunneling microscope (STM). The surface modification was attributed to localized field evaporation upon applying 10 V between the tunneling gap. White light sparking beneath the STM tip (nanospark) was observed during and after the surface modification. The addition of ionic species into the otherwise pure solvent also induced a nanospark even when applying lower voltages, but in this case, surface modification did not occur. Thus, it is proposed that a part of the ITO becomes dissolved in solution as ions, which results in electron avalanche in the presence of these induced ions. (C) 2001 American Institute of Physics.
  • J Hobley, M Goto, M Kishimoto, H Fukumura, H Uji-I, M Irie
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 345 623 - + 2000年 [査読有り][通常論文]
     
    LIMIT is a new approach for creating highly space selective patterns of molecules in thin polymer films. photochromic implants of <800 nm dimensions are now possible using interference modulated implantation. In this way implanted diffraction gratings have been made which operate as photo-switching optical devices. Here we report the implantation of four different classes of organic photochromic molecule.
  • A Kashihara, H Uji'i, J Toyoda
    ARTIFICIAL INTELLIGENCE IN EDUCATION 50 714 - 716 1999年 [査読有り][通常論文]
     
    This paper discusses how to help learners reflect on what they have explored domain concepts/knowledge in hyperspace. The approach presented here is to visualize a knowledge structure that the learners would construct in exploring, In this paper, we address the following important problems to be resolved towards the knowledge structure visualization: (1) how to get learners' exploration processes, (2) how to help the learners keep and achieve exploration in hyperspace, and (3) how to visualize the knowledge structure understandably.
  • H Fukumura, H Uji-i, H Banjo, H Masuhara, DM Karnakis, N Ichinose, S Kawanishi, K Uchida, M Irie
    APPLIED SURFACE SCIENCE 127 761 - 766 1998年05月 [査読有り][通常論文]
     
    Laser molecular implantation enables us to dope space-selectively a surface layer of a polymer film with intact organic molecules. Thus it is applicable towards building various kinds of devices utilizing functional organic molecules. This paper presents that photochromic molecules can be implanted in polymer surfaces by using 351 nm or 355 nm nanosecond lasers and the implanted molecules can be switched repetitively by the alternate irradiation of UV and visible lights. As an example of the space selectivity, the fabrication of gratings by laser implantation is demonstrated and evaluated from an application view point. (C) 1998 Elsevier Science B.V.

その他活動・業績

  • 研究者の最新動向 ナノ・プロドラッグ 新たな抗がん薬輸送システムの細胞内挙動
    小関 良卓, Taemaitree Farsai, Fortuni Beatrice, Rocha Susana, 雲林院 宏, 猪瀬 朋子, 笠井 均 Precision Medicine 4 (8) 753 -758 2021年08月 
    従来のポリマーキャリア系ナノ薬剤と比較して、高密度であることを特徴とする抗がん性ナノ・プロドラッグは、動物実験において上市薬より約10倍高い薬効を示す有望な新規ナノ薬剤であるが、生体内における詳細な挙動は不明であった。本稿では、フェルスター共鳴エネルギー移動(FRET)による蛍光波長の変化を利用した顕微鏡観察により、これまで困難であったナノ・プロドラッグのがん細胞内における動態、特に、細胞内においてナノ粒子状態から溶解状態へ至る過程を明らかにすることに成功したので、その詳細を解説する。(著者抄録)
  • 小関 良卓, Taemaitree Farsai, Fortuni Beatrice, Rocha Susana, 雲林院 宏, 猪瀬 朋子, 笠井 均 細胞 52 (13) 769 -773 2020年11月 
    従来のポリマーキャリア系ナノ薬剤と比較して、高密度であることを特徴とする抗がん性ナノ・プロドラッグは、動物実験において上市薬より約10倍高い薬効を示す有望な新規ナノ薬剤であるが、生体内における詳細な挙動は不明であった。本稿では、フェルスター共鳴エネルギー移動(FRET)による蛍光波長の変化を利用した顕微鏡観察により、これまで困難であったナノ・プロドラッグのがん細胞内における動態、特に、細胞内においてナノ粒子状態から溶解状態へ至る過程を明らかにすることに成功したので、その詳細を解説する。(著者抄録)
  • プラズモン導波路を用いた単一細胞解析と操作
    豊内 秀一, 猪瀬 朋子, 平井 健二, 雲林院 宏 細胞 52 (2) 97 -100 2020年02月 
    本稿では、細胞内における分子相互作用や反応の解析から操作までを行う新たな単一細胞内視鏡法の紹介をする。特にプラズモン導波路を用いて、単一細胞内に安全に光を導入するリモート励起法を用いた「細胞内増強ラマン散乱分光」と、非線形光学現象を用いたナノ物質のトラッピング法に関して解説をする。単一細胞レベル遺伝子導入や細胞内物質の取り出しなどへの応用に向けた最新のナノテクノロジーの基礎となる最新技術として紹介したい。(著者抄録)
  • プラズモン導波路を用いた単一細胞解析と操作
    豊内秀一, 猪瀬朋子, 平井健二, 雲林院宏 月間「細胞」2020年 2月号 51 -54 2020年 [査読無し][通常論文]
  • 藤田康彦, 猪瀬朋子, 雲林院宏 光化学 48 (1) 2 -9 2017年 [査読有り][通常論文]
  • 猪瀬朋子, 藤田康彦, 雲林院宏 生物物理 56 (6) 327 -329 2016年 [査読有り][通常論文]
  • Rocha Susana, De Keersmaecker Herlinde, 阿部 充宏, 雲林院 宏, Hofkens Johan, 小林 俊秀, 宮脇 敦史, 水野 秀昭 顕微鏡 49 (3) 205 -210 2014年12月 
    蛍光顕微鏡は標的分子を特異的に標識、観察できる手法として生命科学の分野で広く利用されている。蛍光タンパク質発現による標識技術の開発によって生細胞での非侵襲的な標識が容易となり、ライブセルイメージングへ応用されている。近年、超高解像度顕微鏡と総称される光の回折限界を超えた蛍光顕微鏡法が開発された。本稿ではそのひとつ、photoactivated localization microscopy(PALM)について概説する。PALMは光スイッチング蛍光タンパク質で標的分子を標識し、その確率的なスイッチングを利用して空間的に近接する分子を時間的に分離して観察、座標情報を曲線回帰により求める。PALMは蛍光タンパク質標識・発現した標的分子を数十nmの解像度で観察できる。また、著者等の開発したプローブを用いて脂質ラフトが染色・観察できる。さらに、生細胞へ応用し、分子動態の解析も可能である。(著者抄録)
  • Hiroshi Ujii ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 247 2014年03月 [査読無し][通常論文]
  • Ulrike Alexiev, Martina Moeller, Tai-Yang Kim, Kathrin Winkler, Hiroshi Ujii, Benoit Muls, Johan Hofkens BIOPHYSICAL JOURNAL 187A -187A 2007年01月 [査読無し][通常論文]
  • H. Uji-i, M. Yoshidome, J. Hobley, K. Hatanaka, H. Fukumura Phys. Chem. Chem. Phys. 5 (19) 4231 -4235 2003年10月 [査読無し][通常論文]
     
    Static and dynamic structures in self-assembled monolayers containing 1-pyrenehexadecanoic acid (PHDA) at a liquid-solid interface were investigated with scanning tunneling microscopy. Uni-component adsorption layers made a specific structure having ring figures corresponding to pyrene groups, whereas the co-adsorption of PHDA and 4,4'-bipyridyl resulted in two different structures depending on their concentrations and the ambient temperature. When the concentration of 4,4'-bipyridyl was high and the temperature at around 290 K, a dynamic bistable structure was observed within a stacked row of molecules without causing any disorder to the assembly as a whole. The bistability is considered to be due to molecular desorption-adsorption process occurring at the anti-parallel configuration of two neighbouring PHDA molecules.

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
    研究期間 : 2023年04月 -2028年03月 
    代表者 : 雲林院 宏, 平井 健二, 五月女 光
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2023年04月 -2028年03月 
    代表者 : 矢貝 史樹, 雲林院 宏, VACHA Martin, 相良 剛光, 羽會部 卓, 原野 幸治, 重田 育照
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2022年04月 -2026年03月 
    代表者 : 笠井 均, 小関 良卓, 雲林院 宏, 根本 知己, 石岡 千加史
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2021年04月 -2025年03月 
    代表者 : 雲林院 宏, 松崎 典弥, 金蔵 孝介, 猪瀬 朋子, 笠井 均
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2021年07月 -2024年03月 
    代表者 : 古川 修平, 猪瀬 朋子, 亀井 謙一郎, 雲林院 宏
     
    心疾患と脳血管疾患は、長年日本における死因の第2, 3位を占めており、今後社会の高齢化が加速する中で、その治療は公衆衛生上最も重要な課題の一つである。生体内で産生されるNOは、血管弛緩・拡張を惹起することが知られており、その効果を活用した治療薬への応用が期待されている。しかしながら、現在の治療法ではNOを体内の狙った場所へ伝達することが困難であり、今後NOをより汎用性の高い治療薬として活用するためには、治療部位でのNOガス拡散の時空間的挙動と血管機能の相関を解明し、必要最低限のNOの利用へとつなげる必要がある。 本研究「生体ガスポンプ・プローブ法を用いた一酸化窒素拡散挙動と血管機能相関の可視化」では、血管機能の制御・改善に向け、一酸化窒素 (NO)を放出する多孔性ナノ粒子を用いて、単一細胞内・血管組織におけるNOの拡散ダイナミクス及び空間分布情報とNOにより惹起される細胞機能の相関を可視化し、生体内NOの真の挙動を明らかにする。 初年度は、細胞内におけるNOの発生位置を固定するために、単一細胞内視鏡技術に用いる銀ナノワイヤー上に光によりNO発生が可能な亜鉛とニトロイミダゾールからなる多孔性金属錯体（NOF-1)の固定化技術の確立を目指した。様々な合成条件（反応温度、試薬濃度、ナノワイヤー分散度）の検討の結果、銀ナノワイヤー上へのNOF-1の固定化条件を見出した。また、同様の条件を用いることで、銀ナノワイヤーのみならず金ナノロッド上への固定化にも成功した。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2021年07月 -2023年03月 
    代表者 : 淺川 雅, 古山 渓行, 雲林院 宏
     
    原子間力顕微鏡（AFM）に用いる探針の終端構造を単原子レベルで精密設計することで、液中原子分解能AFM像の解釈を「推測」から「原子・分子スケールで理解する」ことへ進化させることを目指している。探針先端の精密設計は液中AFM計測の再現性を大幅に向上することにも繋がるため、専門家でなくても液中原子スケールAFM計測が実現できる汎用レベルの基盤的分析手法へ発展できる。そこで構造有機化学分野の精密分子設計の知見から、観察試料と相互作用する探針先端が高い再現性で同じ化学構造を持ったAFM探針を調製する方法論を検討してきた。探針先端に取り付ける骨格構造には三角錐の頂点に3つの架橋構造と1つの終端構造を持ついくつかの剛直分子を候補として計画し、テトラフェニルメタン分子やその他の骨格構造の有機合成を行なった。またシリコン製探針の先端への架橋方法について、シラン化やホスホン酸を用いたカップリング反応条件の検討・最適化を進めた。さらに探針先端に骨格構造を取り付けた後の評価手法として、終端構造に蛍光分子を導入し、3次元分子配向に加えて回転・揺らぎなどのダイナミクスを直接計測できるdefocused imagingを実施するための装置設計を実施した。AFM装置と蛍光観察装置を融合したシステムにより探針先端の1分子スケール評価を実現するために、アクティブ除振台にAFMと同時に配置できる光学系の構築を完了した。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2020年04月 -2023年03月 
    代表者 : 猪瀬 朋子, 雲林院 宏, 宮田 耕充
     
    遷移金属ジカルコゲナイド（TMDs）シートの電子供与体および電子受容体分子による表面修飾は、TMDsの電子状態操作が可能なため、TMDs発光特性の制御に利用されている。本年度、代表者はまず、分担者・宮田作製のWSe2シートにテトラフルオロ-1,4-ベンゾキノン（TFBQ）を修飾した後、修飾したシートのラマン分光・蛍光発光測定を行い、WSe2シート層数と発光特性の相関を明らかにすることを目指した。具体的には、まず、TFBQ修飾前のCVD法で合成されたSi基板上WSe2シートの発光スペクトル測定を行い、観察されたスペクトルのピーク波長でWSe2シートのマッピングを行った。その結果、シート層数の増加に伴い、発光スペクトルピークの長波長シフトが確認された。これは、層数増加に伴いバンドギャップが小さくなることに由来する。また、多層部位では間接遷移型に伴う蛍光強度の低下が確認された。このような、層数増加に伴う発光スペクトルの長波長シフトおよび発光強度の低下は、TFBQ修飾後においても観察された。TFBQ修飾前と比較すると、TFBQ修飾後、WSe2シートの発光スペクトルの短波長シフトが確認され、また、単層よりも二層領域でより大きな短波長シフトが観察された。これは、TFBQのWSe2シート酸化作用により、トリオンの生成が抑制され、エキシトン発光の影響が大きくなったためと考察される。また、トリオンの束縛エネルギーが小さい二層部位においては、酸化によるより大きな短波長シフトが観察された。この結果から、本年度は、光学顕微鏡を用いてWSe2シート層数と発光特性の相関を確認することができ、さらに、WSe2シート2層の領域で、より顕著な発光特性変化を確認することに成功した。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2020年07月 -2022年03月 
    代表者 : 雲林院 宏, 猪瀬 朋子
     
    本研究では、プラズモン導波路として機能する化学合成で作成した直径100nm、長さ数十マイクロメートルの銀ナノワイヤー(AgNW)をAFMカンチレバー先端に導入することで、10nm以下の高い空間分解能を有する新たな「リモート励起探針増強蛍光（RE-TEF）顕微鏡」の開発を目指した。本研究では、ガルバニック置換反応、光誘起金ナノ粒子局所析出法、２本のAgNWを並べる方法を比較開発し、これらを用いたRE-TEFでは、30 nm程度の空間分解能でスペクトルマッピングが可能であり、新規光DNAマッピング解析、２次元半導体材料解析、細胞内増強ラマン測定に応用できることを示した。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2019年04月 -2022年03月 
    代表者 : 田中 啓文, 雲林院 宏, 田中 大輔
     
    LSIなど半導体回路の配線は多くが金属を用いており微細化により、抵抗が上がるなどの問題に直面している。GNRは厚み0.3nmであるが良導体であり、ナノ配線に使えるようになれば半導体産業へ与えるインパクトが大きい。本課題では①ラジカル開始剤を用いたアンジップにより得られたGNRの多機能化。②誘電泳動法によるグラフェンナノリボンの架橋構造の作製。③GNRとSWNTの混合懸濁液の誘電泳動によりGNRのみを架橋する条件を理論的考察。④探針増強ラマン法によりアンジップにより得られたGNRのエッジ構造評価などを行い、この分野の発展に寄与する大きな成果を得た。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2018年04月 -2021年03月 
    代表者 : 平井 健二, 猪瀬 朋子, 雲林院 宏
     
    機能性材料を目的の場所に配置することが出来れば、電子素子、光学素子、マイクロデバイスの開発が可能となる。本研究では、様々な機能性材料を望みの場所で合成する方法を開発した。具体的には、プローブとしての利用が可能な銀ナノワイヤ（AgNW）上で金ナノ粒子（AuNP）を合成し、プラズモン加熱を利用した機能性材料の合成を行った。AuNPにレーザーを照射することで、AuNP近傍を加熱することが可能である。この加熱方法を利用して酸化亜鉛や有機金属構造体を局所的に合成することに成功した。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2017年04月 -2021年03月 
    代表者 : 雲林院 宏, 猪瀬 朋子
     
    本研究では、薬輸送システム（DDS）の細胞内挙動を追従し、より効果的な化学治療設計に貢献することを目的とした。具体的には、細胞内部に侵入して抗がん剤分子と細胞内物質の相互作用を解析する「単一細胞内視鏡法」を新たに開発した。これにより、抗がん剤分子とDNAなど細胞内物質との相互作用を直接観測することが可能となり、今後の化学治療法開発へ大きな貢献が期待される。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2017年04月 -2019年03月 
    代表者 : 雲林院 宏
     
    物理学から生物学まで、広い分野で応用されている光圧は遠方場から近接場へとその舞台を変えつつある。その中で、局在プラズモン共鳴（LSPR）はナノ物質輸送への応用が期待されている。本研究では、複数のプラズモン導波路を利用したリモート励起多機能光トラッピングを新たに提案する。導波路を伝わる伝搬プラズモンにより導波路先端でLSPRを励起（リモート励起）し、複数の導波路を交互にON/OFFすることによってLSPR位置をnmレベルで動的に制御する方法を新たに開発する。さらに、nm領域でトラップされている物質輸送の様子を、光学顕微鏡で観測する手法を新たに提案・開発することを目的とした。 本研究では、プラズモン導波路としては、化学的に合成した減衰係数の低い径１００ナノメートル、長さ１０から２０ マイクロメートル程度の銀ナノワイヤーを用いた。近赤外フェムト秒レーザー光をプラズモン導波路に伝搬させると、導波路上を光が伝搬している部分では３次の非線形現象である４波混合が優先的に起こり、導波路の端では２次の非線形である和収差や第２次高調波が優先的に起こることを、蛍光顕微鏡を駆使することで実験的に証明した。この現象を利用し、 2次の非線形光学現象である和収差に共鳴する量子ドットは導波路の両端のみにトラップされるが、3次の非線形現象である４波混合と共鳴する量子ドットは導波路全体にトラップされることを見出した。これにより、非線形光学現象によって、光トラップの場所依存の制御の可能性を初めて示唆した。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2017年04月 -2019年03月 
    代表者 : 雲林院 宏
     
    分子・光結合は量子情報システムや微弱光スイッチングデバイスなどへの応用が期待されている一方で、複雑な設計が要求され、かつ室温での操作が困難である。反面、局在プラズモン共鳴は光エネルギーをnmスケールに閉じ込め、そのスケールで分子と光の相互作用を引き起こすことが可能である。近年、この特性を生かした室温での分子・光結合の実現を試みる研究が世界的に多くなされている。本研究では、さらに一歩進めて、プラズモン増強多光子励起過程を巧みに利用して、nmスケールで化学反応を制御することを目指した。具体的には、局在プラズモン共鳴増強を利用して、多光子励起異性化反応をnmスケールで制御し、かつそれにより巨視的光応答性制御を実現する新手法を開発する。本研究では，局所プラズモン共鳴増強を利用して、多光子励起による光異性化反応をnmスケールで制御し、それにより巨視的光応答性制御を実現する新手法の開発を目指した。 具体的には、化学合成によって得られた銀ナノワイヤー（AgNW）上での蛍光性ジアリルエテン（fDAE）誘導体の非線形光学光異性化反応について調べた。使用したfDAE誘導体は、閉環構造で蛍光を発し、開環構造では蛍光を発さない。近赤外フェムト秒レーザーをプラズモン導波路であるAgNW上に伝搬させたときに、蛍光体と非蛍光体が繰り返し観測されれば、伝搬光により異性化反応が制御されている証拠となる。820nmの励起光を伝搬させると、その強度が高い場合、３光子吸収による閉環反応が誘起されて蛍光を発し、強度が弱い場合は２光子励起による開環反応が優先的に誘起されて蛍光が消光した。これにより、プラズモン導波路を伝搬する近赤外光により、光反応を多光子過程で誘起することが可能であることを初めて明らかにした。これにより、 プラズモンを利用することで、多光子光反応のnmスケールでの制御を達成した。

教育活動情報

主要な担当授業

  • 大学院共通授業科目（一般科目）：自然科学・応用科学
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : ナノ構造、微細加工、デバイス、システム、光機能性材料、光化学、分子性物質、導電性、磁性、薄膜、電子顕微鏡、走査型プローブ顕微鏡、ナノワイヤー、二次元電子ガス、物性理論
  • ナノマテリアル特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 情報科学研究科
    キーワード : ナノ材料、ナノテクノロジー、光物理、光科学、バイオテクノロジー
  • ナノマテリアル特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 情報科学院
    キーワード : ナノ材料、ナノテクノロジー、光物理、光科学、バイオテクノロジー
  • ナノマテリアル特論
    開講年度 : 2021年
    課程区分 : 博士後期課程
    開講学部 : 情報科学研究科
    キーワード : ナノ材料、ナノテクノロジー、光物理、光科学、バイオテクノロジー
  • ナノマテリアル特論
    開講年度 : 2021年
    課程区分 : 博士後期課程
    開講学部 : 情報科学院
    キーワード : ナノ材料、ナノテクノロジー、光物理、光科学、バイオテクノロジー
  • 環境と人間（1単位）
    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 : 最先端技術、極微細技術、数理、バイオサイエンス、細胞、先端医療、光、レーザー、自己組織化、生物、知能、情報
  • 応用物性工学
    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 : 固体物理、固体、結晶、導電体、半導体、表面プラズモン
  • 生体医工学基礎
    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 : ナノ構造、微細加工、デバイス、システム、光機能性材料、光化学、分子性物質、導電性、磁性、薄膜、電子顕微鏡、走査型プローブ顕微鏡、ナノワイヤー、二次元電子ガス、物性理論
  • 生体工学概論
    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 : ナノ構造、微細加工、デバイス、システム、光機能性材料、光化学、分子性物質、導電性、磁性、薄膜、電子顕微鏡、走査型プローブ顕微鏡、ナノワイヤー、二次元電子ガス、物性理論

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