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プロフィール情報
所属
学位
プロフィール情報
姓
龍﨑, リュウザキ名
奏, ソウID各種
201701011971508348
所属
業績リスト
研究キーワード
研究分野
経歴
- 2022年04月 - 現在 北海道大学 大学院理学研究院 化学部門 准教授
- 2014年01月 - 2022年03月 九州大学 先導物質化学研究所 助教
- 2017年10月 - 2021年03月 JSTさきがけ さきがけ研究員
- 2012年02月 - 2013年12月 大阪大学 産業科学研究所 特任助教
- 2011年05月 - 2012年02月 東京工業大学 原子炉工学研究所 特別研究員
- 2010年05月 - 2011年04月 コペンハーゲン大学 ナノサイエンスセンター 博士研究員
学歴
- 2007年04月 - 2010年03月 東京工業大学 大学院理工学研究科 原子核工学専攻 博士課程
- 2005年04月 - 2007年03月 東京工業大学 大学院理工学研究科 原子核工学専攻 修士課程
- 2001年04月 - 2005年03月 東京理科大学 理工学部 物理学科
委員歴
- 2014年04月 - 現在 ＤＶ−Ｘα研究協会 常任幹事
- 2020年04月 - 2022年03月 応用物理学会：有機分子・バイオエレクトロニクス分科会 常任幹事
- 2017年10月 - 2019年09月 JSAP Multidisciplinary Young Researcher Chapter 代表
- 2016年04月 - 2018年03月 応用物理学会：有機分子・バイオエレクトロニクス分科会 常任幹事
- 2015年04月 - 2016年03月 応用物理学会：有機分子・バイオエレクトロニクス分科会 幹事
受賞
- 2023年10月 株式会社リバネス Tech Planter 最優秀賞
受賞者: 龍崎奏 - 2023年10月 大日本印刷株式会社 Tech Planter DNP賞
受賞者: 龍崎奏 - 2023年05月 Royal Society of Chemistry、ナノ学会 Nanoscale Horizons Award
受賞者: 龍崎奏 - 2023年02月 北海道未来創造スタートアップ育成相互支援ネットワーク HSFC Demo Day 優秀賞
受賞者: 龍崎奏 - 2022年04月 科学技術振興機構CREST[細胞外微粒子] Young Innovator Award
- 2021年07月 DV-Xα研究協会 奨励賞
- 2017年12月 IOP Publishing, Nanotechnology Highlights of 2017
- 2017年08月 9th International Conference on Molecular Electronics and Bioelectronics The Best Poster Award
- 2016年03月 第63回応用物理学会春季学術講演会 講演奨励賞
- 2010年10月 財団法人手島工業教育資金団 手島記念博士論文賞
- 2007年03月 東京工業大学原子核工学専攻. 最優秀論文発表賞
論文
- Makusu Tsutsui, Sou Ryuzaki, Kazumichi Yokota, Yuhui He, Takashi Washio, Kaoru Tamada, Tomoji KawaiCommunications Materials 2 1 2021年12月
Abstract Controlling the fast electrophoresis of nano-objects in solid-state nanopores is a critical issue for achieving electrical analysis of single-particles by ionic current. In particular, it is crucial to slow-down the translocation dynamics of nanoparticles. We herein report that a focused electric field and associated water flow in a surround-gate nanopore can be used to trap and manipulate a nanoscale object. We fine-control the electroosmosis-induced water flow by modulating the wall surface potential via gate voltage. We find that a nanoparticle can be captured in the vicinity of the conduit by balancing the counteracting electrophoretic and hydrodynamic drag forces. By creating a subtle force imbalance, in addition, we also demonstrate a gate-controllable motion of single-particles moving at an extremely slow speed of several tens of nanometers per second. The present method may be useful in single-molecule detection by solid-state nanopores and nanochannels. - Effect of chemically induced permittivity changes on the plasmonic properties of metal nanoparticlesNoboru Saito, Sou Ryuzaki, Yuta Tsuji, Yutaka Noguchi, Rintaro Matsuda, Pangpang Wang, Daisuke Tanaka, Yusuke Arima, Koichi Okamoto, Kazunari Yoshizawa, Kaoru TamadaCommunications Materials 2 1 2021年12月
Abstract Understanding chemical effects on the plasmonic properties of a metal nanomaterial due to the surface molecules on that metal is of great importance in the field of plasmonics and these effects have yet to be completely elucidated. Here, we report mechanisms of the chemically induced change in the electronic state at the metal-ligand interface of silver nanoparticles due to the ligand molecules, and the effect of this change on the plasmonic properties of those nanoparticles. It was found that changes in the electron density of states at the metal-ligand interface cause alterations in the induced and permanent dipole moments, and eventually to the permittivity at the interface, when the wave function near the Fermi level is localized at the interface. These alterations play a key role in determining the plasmonic properties of silver nanoparticles. The present findings provide a more precise understanding of the interconnection between the electronic states at the metal-organic interface and the plasmonic properties of the metal. - Sou Ryuzaki, Takao Yasui, Makusu Tsutsui, Kazumichi Yokota, Yuki Komoto, Piyawan Paisrisarn, Noritada Kaji, Daisuke Ito, Kaoru Tamada, Takahiro Ochiya, Masateru Taniguchi, Yoshinobu Baba, Tomoji KawaiAnalytical Chemistry 93 18 7037 - 7044 2021年05月11日A rapid and simple cancer detection method independent of cancer type is an important technology for cancer diagnosis. Although the expression profiles of biological molecules contained in cancer cell-derived extracellular vesicles (EVs) are considered candidates for discrimination indexes to identify any cancerous cells in the body, it takes a certain amount of time to examine these expression profiles. Here, we report the shape distributions of EVs suspended in a solution and the potential of these distributions as a discrimination index to discriminate cancer cells. Distribution analysis is achieved by low-aspect-ratio nanopore devices that enable us to rapidly analyze EV shapes individually in solution, and the present results reveal a dependence of EV shape distribution on the type of cells (cultured liver, breast, and colorectal cancer cells and cultured normal breast cells) secreting EVs. The findings in this study provide realizability and experimental basis for a simple method to discriminate several types of cancerous cells based on rapid analyses of EV shape distributions.
- Haruka Takekuma, Junfu Leng, Kazutaka Tateishi, Yang Xu, Yinthai Chan, Sou Ryuzaki, Pangpang Wang, Koichi Okamoto, Kaoru TamadaACS Applied Electronic Materials 3 1 468 - 475 2021年01月26日High-density colloidal quantum dot (QD) thin films are promising materials for optoelectronic devices. Our experimental data revealed a unique layer number-dependent photoluminescence (PL) from multilayered QDs on a gold substrate. Compared with the PL intensity of QDs on glass substrates, the PL intensity of CdSe/ZnS QD multilayers on the gold substrate was enhanced approximately 10-fold with 6 layers (film thickness: 42 nm). This phenomenon was simply and reasonably explained by an optical simulation using the finite-difference time-domain method with the effective medium approximation, where the light confinement effect of the high-refractive index QD film acting as a "metamaterial optical resonator"was considered together with a long-range exciton-surface plasmon coupling and mirror effects. This result explains the QD film properties from both quantum physics and optical metamaterial viewpoints. This finding is important for the design of high-luminescence thin-film displays composed of condensed QD films.
- Shihomi Masuda, Thasaneeya Kuboki, Satoru Kidoaki, Shi Ting Lee, Sou Ryuzaki, Koichi Okamoto, Yusuke Arima, Kaoru TamadaACS Applied Nano Materials 3 11 11135 - 11142 2020年11月25日A plasmonic metasurface composed of homogeneously self-assembled gold nanoparticles can provide high-contrast fluorescence images confined to the nanointerface. In this study, we successfully demonstrated real-time, high-spatiotemporal-resolution imaging of adhered Venus-paxillin-3T3 live cells under a widefield microscope, where not only a high axial resolution but also a high lateral resolution down to the theoretical limit were confirmed through nascent cluster formation of paxillin. The improved lateral resolution on the sheet could be interpreted as the characteristic of localized surface plasmon resonance (LSPR)-mediated enhanced fluorescence and the metasurface acting as a nanothickness plane light emitter. We also found minimized photobleaching, owing to the increase in the emission efficiency via plasmon-exciton coupling. This simple nanomaterial-based technique will be a powerful tool to enhance interfacial signals and improve the quality of live-cell images, not only under widefield microscopes but also in combination with various super-resolution microscope systems in the future.
- Sou Ryuzaki, Rintaro Matsuda, Masateru TaniguchiMicromachines 11 10 893 - 893 2020年09月Nanopore devices are expected to advance the next-generation of nanobiodevices because of their strong sensing and analyzing capabilities for single molecules and bioparticles. However, the device throughputs are not sufficiently high. Although analytes pass through a nanopore by electrophoresis, the electric field gradient is localized inside and around a nanopore structure. Thus, analytes located far from a nanopore cannot be driven by electrophoresis. Here, we report nanopore structures for high-throughput sensing, namely, inverted pyramid (IP)-shaped nanopore structures. Silicon-based IP-shaped nanopore structures create a homogeneous electric field gradient within a nanopore device, indicating that most of the analytes can pass through a nanopore by electrophoresis, even though the analytes are suspended far from the nanopore entrance. In addition, the nanostructures can be fabricated only by photolithography. The present study suggests a high potential for inverted pyramid shapes to serve as nanopore devices for high-throughput sensing.
- Okamoto, K., Okura, K., Wang, P., Ryuzaki, S., Tamada, K.Nanophotonics 9 10 3409 - 3418 2020年© 2020 Koichi Okamoto et al., published by De Gruyter, Berlin/Boston 2020. We propose a unique random metal nanohemisphere on mirror (NHoM) structure to tune the surface plasmon (SP) resonance in a flexible manner. The SP resonance peak was split into two peaks owing to the strong coupling between the SP mode in the metal nanohemisphere and the mirror image mode generated in the metal substrate. This phenomenon is based on the fact that the strong coupling and the induced electromagnetic effects are similar to those pertaining to the Rabi splitting, Fano resonance, and electromagnetically induced transparency, thus providing quantum effect analogies. These phenomena have recently attracted increased attention and have been studied with nanocavities fabricated with top-down nanotechnologies. Compared with previous reports, NHoM structures can be fabricated in a much easier manner and are tunable in rather wider wavelength regions without nanofabrication technologies. The SP resonance peaks were enhanced, sharpened dramatically, and tuned flexibly, based on the optimization of the thickness of the spacer layer between the metal hemisphere and metal substrate. Experimental results were reproduced and were explained based on finite difference time domain (FDTD) simulations. These phenomena have never been observed previously on similar nanosphere on mirror (NSoM) because nanohemispherical structures were required. The NHoM nanocavity structure has a quality factor >200 that is surprisingly high for the localized SP mode of nanoparticles. Flexible tuning of the SP resonance with the use of NHoM is envisaged to lead to the development of new applications and technologies in the field of plasmonics and nanophotonics.
- Matsuda, R., Ryuzaki, S., Okamoto, K., Arima, Y., Tsutsui, M., Taniguchi, M., Tamada, K.Journal of Applied Physics 127 24 2020年© 2020 Author(s). Plasmonic nanopore structures have been expected to play a key role in next-generation nanopore devices because plasmonic-enhanced electric fields inside nanopores potentially enable the measurement of surface-enhanced Raman scattering (SERS) spectra of a single analyte passing through a nanopore. However, sufficient enhancement of the electric field inside a nanopore for SERS measurements has not been obtained. Here, we report finite-difference time-domain simulation studies of inverted cone-shaped plasmonic nanopore structures, which maximally show an ∼1000 times stronger SERS enhancement factor than that of a conventional cylindrical plasmonic nanopore structure. The enhancement was found to be achieved via nanofocusing and structural effects, causing a 1.3 and 4.7 times stronger plasmonic-enhanced electric field than that of a cylindrical structure, respectively. The present study suggests a high potential of inverted cone shapes as plasmonic nanopore structures for SERS measurement of an analyte passing through a nanopore.
- Leng, J., Xu, Y., Chan, Y., Wang, P., Ryuzaki, S., Okamoto, K., Tamada, K.ACS Applied Nano Materials 3 4 3214 - 3222 2020年Copyright © 2020 American Chemical Society. Homogeneously self-assembled colloidal semiconductor quantum dot monolayers (QD-SAMs) over large areas are promising materials for thin film optoelectronic device applications, especially for display. Although tuning of emission colors from QDs is generally achieved during wet chemical synthesis and before monolayer formation, we propose in this study a simple and effective method to adjust emission colors after the formation of QD-SAMs by a simple one-step heat treatment. CdSe-based core/shell or core/double shell structured QDs (CdSe/ZnS, CdSe/CdZnS, and CdSe/CdS/ZnS) covered with an optimal set of hydrophobic ligands can form homogeneous and stable QD-SAMs at the air-water interface. The QD-SAMs are subsequently transferred onto hydrophobized glass substrates by the Langmuir-Schaefer (LS) method and thermally treated in air. We found a blueshift of more than 35 nm for the emission wavelength (red to green) by a thermal treatment at 280 °C for 150 min with CdSe/ZnS QD-SAMs. The color can be adjusted by changing the heating temperature and the treatment time. The wavelength shift is in the order of CdSe/ZnS(4L) > CdSe/ZnS(6L) = (CdSe/CdZnS) > (CdSe/CdS/ZnS). The energy dispersive X-ray (EDX) microanalysis of a single QD reveals that the blueshift is mainly caused by atomic diffusion-induced alloying of core/shell type QDs. The main problem of this method is the decreasing emission intensity caused by oxidation during the heat treatment; however, this problem can be solved with the use of a SiO2 protective coating on the QD-SAMs. We believe that this simple technique is useful for manufacturing RGB-colored ultrathin QD-SAM films for QD displays such as QD film display, QD color-filter display, and QD light emitting diode.
- Wang, P., Ryuzaki, S., Gao, L., Shinohara, S., Saito, N., Okamoto, K., Tamada, K., Yamada, S.Journal of Applied Physics 125 13 2019年© 2019 Author(s). A 7-nm-thick monolayer comprising myristate-capped silver nanoparticles (AgNPs) was fabricated by first drop casting an AgNP solution on the surface of a 10-100 μl water drop placed on a solid substrate. With the natural evaporation of the water, a monolayer slowly descended onto the substrate, the latter containing an array of 2.5-μm-diameter and 200-nm-deep holes, and finally formed circular freestanding monolayers in the holes. Nanoindentation measurement based on atomic force microscopy was carried out on the circular freestanding monolayer at its center, and the extending and retracting force-indentation curves were recorded to analyze further the mechanical properties of the monolayer. The force-indentation curves were evidently nonlinear, and so a two-term continuum-mechanics theory was used to interpret the results. By fitting the force-indentation curves using a two-term equation, the prestress and Young’s modulus of the freestanding AgNP monolayer were obtained as approximately 0.05 N/m and several gigapascals, respectively, which are consistent with the results reported in the literature. For comparison, we also studied the mechanical responses of AgNP monolayers and bilayers on a soft polydimethylsiloxane (PDMS) substrate by using nanoindentation. Because the AgNP monolayer was stiffer than the PDMS substrate, it was possible to measure the mechanical response of the former despite it being only 7 nm thick. The mechanical strength of the freestanding AgNP monolayers was considered to be dominated by the attractive interactions between the interdigitated hydrocarbon chains of the myristate.
- Tateishi, K., Wang, P., Ryuzaki, S., Funato, M., Kawakami, Y., Okamoto, K., Tamada, K.Applied Physics Express 12 5 2019年© 2019 The Japan Society of Applied Physics. Micro-photoluminescence (PL) mapping was investigated for Al-coated InGaN/GaN quantum wells (QWs), which showed huge PL enhancement by the surface plasmon (SP) resonance. The obtained images show inhomogeneity at the micro-meter scale; in addition, the region with lower PL intensities tend to have a longer PL wavelength for bare QWs. This correlation changed with an Al coating, positive correlations were observed in an area with a relatively short peak wavelength with blue-shift. Conversely, negative correlations were observed at longer peak wavelengths. These results suggest that the quantum-confined Stark effect (QCSE) was screened by the enhanced electrical-field of the SP resonance.
- Takekuma, H., Tagomori, K., Shinohara, S., Masuda, S., Xu, Y., Chan, Y., Wang, P., Ryuzaki, S., Okamoto, K., Tamada, K.Colloids and Interface Science Communications 30 2019年© 2019 Elsevier B.V. In this short communication, we report a procedure for the fabrication of microscale pores on a rigid self-assembled Ag nanoparticle monolayer with nanothickness. Here, condensed water droplets on a hydrophobic substrate are used as a pore formation template for Langmuir-Schaefer film deposition. The optical properties of the Ag nanoparticle monolayer were influenced by the porous structure, e.g., the localized surface plasmon resonance (LSPR) peak was weakened and broadened for the porous monolayer compared with the homogeneous monolayer, even though the number of particles on the substrate should be the same between them. The pores obtained by this method were robust and could be used as a mask for metal deposition or local fluorescence imaging. This environmentally friendly technique can provide a micropatterned surface with a minimal cytotoxicity, which has high potential for LSPR mediated biosensing and bioimaging applications.
- Ishijima, A., Wang, P., Ryuzaki, S., Okamoto, K., Tamada, K.Applied Physics Letters 113 17 2018年© 2018 Author(s). Localized surface plasmon resonance (LSPR) excited by an oblique incidence of S- and P-polarized light to a two-dimensionally assembled silver nanoparticle sheet was investigated via enhanced fluorescence under total internal reflection fluorescence (TIRF) microscopy. The finite-difference-time-domain simulation demonstrated that the S-polarized light induced a strong plasmon coupling at a nanogap between the particles, which eventually led to a highly confined, strong, and "flattened" electric field on the entire surface. In contrast, the LSPR field excited by P-polarized light was located on the individual particles, having a relatively long tail in the axial direction (low confinement). The LSPR-mediated fluorescence appeared stronger under P-polarized light than under S-polarized light in the experiments using cyanine dye solutions, while the opposite result was obtained for the fluorescence bead snapshot (diameter: 200 nm). Magnified images of the single beads taken by a super-resolution digital CMOS camera (65 nm/pixel) revealed improved lateral resolution when S-polarized light was used on both the silver nanoparticle sheet and glass under TIRF microscopy.
- Wulandari, P., Handayani, Y.S., Hidayat, R., Wang, P., Ryuzaki, S., Okamoto, K., Tamada, K.Journal of Nonlinear Optical Physics and Materials 27 2 2018年© 2018 World Scientific Publishing Company. We investigate the effects of silver nanoparticles capped by 1-octanethiol (AgSC8) incorporated into the active layer of regioregular poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) in the fabrication of an inverted hybrid solar cell. The localized surface plasmon resonance (LSPR) excited in AgSC8 is expected to enhance the photon absorption as well as improve the efficiency of exciton generation and dissociation in this type of solar cell. The measured UV-visible absorption spectra show that photoactive polymer (P3HT:PCBM) layers with 2.09wt.% and 3.34wt.% AgSC8 incorporations remain homogeneous, while it appears aggregated with 5.02wt.% AgSC8 incorporation. Under the illumination of 100mW/cm2 simulated solar irradiation, the fabricated device exhibits an increased open circuit voltage (Voc) from 0.327V to 0.665V for the case with 3.34wt.% AgSC8 incorporation and an improved device power conversion efficiency (PCE) from 1.01% to 1.92%. These results suggest the favorably role of AgSC8 in photo-generation of exciton and its dissociation at the LSPR frequency of AgSC8. The decrease of short circuit current density (Jsc) from 10.316mA/cm2to8.668mA/cm2 nevertheless implies reduced conductivity due to AgSC8 incorporation.
- Saito, N., Ryuzaki, S., Wang, P., Park, S., Sakai, N., Tatsuma, T., Okamoto, K., Tamada, K.Japanese Journal of Applied Physics 57 3 2018年© 2018 The Japan Society of Applied Physics. The durability of two-dimensional metal nanoparticle sheets is a crucial factor for realizing next-generation optoelectronic devices based on plasmonics such as organic light-emitting diodes. Here, we report improvements in the durability of Ag nanoparticle sheets by forming alkanedithiol (DT16) cross-linked structures between the nanoparticles. The cross-linked structures in a sheet were fabricated by the self-assembly of DT16-capped Ag nanoparticles with 10% coverage (AgDT16). The durabilities for thermal, organic solvent, and oxidation reactions of AgDT16 sheets were found to be improved owing to the cross-linked structures by comparing Ag nanoparticle sheets without the cross-linked structures. The absorbance spectra revealed that the Ag nanoparticle sheets without the structure are markedly damaged by each durability test, whereas the AgDT16 sheets remain. The molecular cross-linked structures between nanoparticles in two-dimansional metal nanoparticle sheets were found to have the potential to play a key role in the realization of plasmonic optoelectronic devices including metal nanoparticles.
- Tateishi, K., Wang, P., Ryuzaki, S., Funato, M., Kawakami, Y., Okamoto, K., Tamada, K.Applied Physics Letters 111 17 2017年© 2017 Author(s). We conducted photoluminescence (PL) mapping to elucidate the detailed mechanism of PL enhancement based on the energy transfer from excitons to surface plasmon polaritons (SPPs) in silver-coated InGaN quantum wells (QWs). The PL mapping for bare InGaN QWs showed positive or negative correlations between the PL peak intensity and wavelength. These correlations are normally caused by exciton localization and the quantum confined Stark effect, respectively; however, they did not appear in the silver-coated region of the InGaN QWs, and the wavelength distribution shifted into shorter wavelengths due to the SP-induced PL enhancement. These results suggest that the energy transfer from the excitons to the SPPs should be much faster than that in the exciton localization and charge screening processes of the piezoelectric field in QWs.
- Ryuzaki, S., Tsutsui, M., He, Y., Yokota, K., Arima, A., Morikawa, T., Taniguchi, M., Kawai, T.Nanotechnology 28 15 155501 - 155501 2017年Rapid structural analysis of nanoscale matter in a liquid environment represents innovative technologies that reveal the identities and functions of biologically important molecules. However, there is currently no method with high spatio-temporal resolution that can scan individual particles in solutions to gain structural information. Here we report the development of a nanopore platform realizing quantitative structural analysis for suspended nanomaterials in solutions with a high z-axis and xy-plane spatial resolution of 35.8 +/- 1.1 and 12 nm, respectively. We used a low thickness-to-diameter aspect ratio pore architecture for achieving cross sectional areas of analyte (i.e. tomograms). Combining this with multiphysics simulation methods to translate ionic current data into tomograms, we demonstrated rapid structural analysis of single polystyrene (Pst) beads and single dumbbell-like Pst beads in aqueous solutions.
- Ryuzaki, S., Onoe, J.Organic Solar Cells: Materials, Devices, Interfaces, and Modeling 2017年
- Juang, Z.-Y., Tseng, C.-C., Shi, Y., Hsieh, W.-P., Ryuzaki, S., Saito, N., Hsiung, C.-E., Chang, W.-H., Hernandez, Y., Han, Y., Tamada, K., Li, L.-J.Nano Energy 38 385 - 391 2017年© 2017 Elsevier Ltd Monolayer graphene exhibits impressive in-plane thermal conductivity (> 1000 W m–1 K–1). However, the out-of-plane thermal transport is limited due to the weak van der Waals interaction, indicating the possibility of constructing a vertical thermoelectric (TE) device. Here, we propose a cross-plane TE device based on the vertical heterostructures of few-layer graphene and gold nanoparticles (AuNPs) on Si substrates, where the incorporation of AuNPs further inhibits the phonon transport and enhances the electrical conductivity along vertical direction. A measurable Seebeck voltage is produced vertically between top graphene and bottom Si when the device is put on a hot surface and the figure of merit ZT is estimated as 1 at room temperature from the transient Harman method. The polarity of the output voltage is determined by the carrier polarity of the substrate. The device concept is also applicable to a flexible and transparent substrate as demonstrated.
- Saito, N., Wang, P., Okamoto, K., Ryuzaki, S., Tamada, K.Nanotechnology 28 43 435705 - 435705 2017年 [査読有り][通常論文]
Techniques for micro/nano-scale patterning of large metal nanoparticle sheets can potentially be used to realize high-performance photoelectronic devices because the sheets provide greatly enhanced electrical fields around the nanoparticles due to localized surface plasmon resonances. However, no single metal nanoparticle sheet currently exists with sufficient durability for conventional lithographical processes. Here, we report large photo and/or e-beam lithographic patternable metal nanoparticle sheets with improved durability by incorporating molecular crosslinked structures between nanoparticles. The cross-linked structures were easily formed by a one-step chemical reaction; immersing a single nanoparticle sheet consisting of core metals, to which capping molecules ionically bond, in a dithiol ethanol solution. The ligand exchange reaction processes were discussed in detail, and we demonstrated 20 mu m wide line and space patterns, and a 170 nm wide line of the silver nanoparticle sheets. - Masuda, S., Yanase, Y., Usukura, E., Ryuzaki, S., Wang, P., Okamoto, K., Kuboki, T., Kidoaki, S., Tamada, K.Scientific Reports 7 1 3720 - 3720 2017年 [査読有り][通常論文]
This paper proposes a simple, effective, non-scanning method for the visualization of a cell-attached nanointerface. The method uses localized surface plasmon resonance (LSPR) excited homogeneously on a two-dimensional (2D) self-assembled gold-nanoparticle sheet. The LSPR of the gold-nanoparticle sheet provides high-contrast interfacial images due to the confined light within a region a few tens of nanometers from the particles and the enhancement of fluorescence. Test experiments on rat basophilic leukemia (RBL-2H3) cells with fluorescence-labeled actin filaments revealed high axial and lateral resolution even under a regular epifluorescence microscope, which produced higher quality images than those captured under a total internal reflection fluorescence (TIRF) microscope. This non-scanning-type, high-resolution imaging method will be an effective tool for monitoring interfacial phenomena that exhibit relatively rapid reaction kinetics in various cellular and molecular dynamics. - Arima, A., Tsutsui, M., He, Y., Ryuzaki, S., Taniguchi, M.AIP Advances 6 11 2016年Nanopore sensing via resistive pulse technique are utilized as a potent tool to characterize physical and chemical property of single -molecules and -particles. In this article, we studied the influence of particle trajectory to the ionic conductance through a pore. We performed the optical/electrical simultaneous sensing of electrophoretic capture dynamics of single-particles at a pore using a microchannel/nanopore system. We detected ionic current drops synchronous to a fluorescently dyed particle being electrophoretically drawn and become immobilized at a pore in the optical imaging. We also identified anomalous trapping events wherein particles were captured at nanoscale pin-holes formed unintentionally in a SiN membrane that gave rise to relatively small current drops. This method is expected to be a useful platform for testing novel nanopore sensor design wherein current behaves in unpredictable manner. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
- Okamoto, K., Tanaka, D., Degawa, R., Li, X., Wang, P., Ryuzaki, S., Tamada, K.Scientific Reports 6 36165 - 36165 2016年© The Author(s) 2016. In this study, we observed the peak splitting of absorption spectra for two-dimensional sheets of silver nanoparticles due to the electromagnetically induced transparency (EIT) effect. This unique optical phenomenon was observed for the multilayered nanosheets up to 20 layers on a metal substrate, while this phenomenon was not observed on a transparent substrate. The wavelength and intensities of the split peaks depend on the number of layers, and the experimental results were well reproduced by the calculation of the Transfer-Matrix method by employing the effective medium approximation. The Ag nanosheets used in this study can act as a plasmonic metamaterial light absorber, which has a such large oscillator strength. This phenomenon is a fundamental optical property of a thin film on a metal substrate but has never been observed because native materials do not have a large oscillator strength. This new type of EIT effect using a plasmonic metamaterial light absorber presents the potential for the development of future optic and photonic technologies.
- Wang, P., Tanaka, D., Ryuzaki, S., Araki, S., Okamoto, K., Tamada, K.Applied Physics Letters 107 15 2015年© 2015 AIP Publishing LLC. To improve the efficiencies of electronic devices, materials with variable work functions are required to decrease the energy level differences at the interfaces between working layers. Here, we report a method to obtain silver nanoparticles with tunable work functions, which have the same silver core of 5 nm in diameter and are capped by myristates and 1-octanethoilates self-assembled monolayers, respectively. The silver nanoparticles capped by organic molecules can form a uniform two-dimensional sheet at air-water interface, and the sheet can be transferred on various hydrophobic substrates. The surface potential of the two-dimensional nanoparticle sheet was measured in terms of Kelvin probe force microscopy, and the work function of the sheet was then calculated from the surface potential value by comparing with a reference material. The exchange of the capping molecules results in a work function change of approximately 150-250 meV without affecting their hydrophobicity. We systematically discussed the origin of the work function difference and found it should come mainly from the anchor groups of the ligand molecules. The organic molecule capped nanoparticles with tunable work functions have a potential for the applications in organic electronic devices.
- Ryuzaki, S., Meyer, J.A.S., Petersen, Sø., Nørgaard, K., Hassenkam, T., Laursen, B.W.Applied Physics Letters 105 9 2014年Charge transport properties of chemically reduced graphene oxide (RGO) sheets prepared by treatment with hydrazine were examined using conductive atomic force microscopy. The current-voltage (I-V) characteristics of monolayer RGO sheets prepared under atmospheric pressure followed an exponentially increase due to 2D variable-range hopping conduction through small graphene domains in an RGO sheet containing defect regions of residual sp(3) carbon clusters bonded to oxygen groups, whereas RGO sheets prepared in a closed container under moderate pressure showed linear I-V characteristics with a conductivity of 267.2-537.5 S/m. It was found that the chemical reduction under pressure results in larger graphene domains (sp(2) networks) in the RGO sheets when compared to that prepared under atmospheric pressure, indicating that the present reduction of GO sheets under the pressure is one of the effective methods to make well-reduced GO sheets. (C) 2014 AIP Publishing LLC.
- He, Y., Tsutsui, M., Ryuzaki, S., Yokota, K., Taniguchi, M., Kawai, T.NPG Asia Materials 6 6 2014年Graphene nanopore device, since its proposal, has witnessed tremendous progress toward the goal of single-molecule detection. However, one central challenge of preparing electrodes with nanometer precision on the graphene remains unsolved. Here we show theoretically the feasibility of graphene/hexagonal BN (h-BN)/graphene structure where top graphene layer acts as one electrical contact while the bottom layer as the other. Based on quantum chemistry/nonequilibrium Green's function investigation, we give clear physical pictures why ABC stacking of the above heterogeneous layers results in excellent insulating of the top and bottom graphene electrodes. On the other hand, when the target molecule is inside the nanopore the background conductance through the h-BN dielectric will not keep decreasing even though more layers of h-BN are inside the nanopore. The mechanism is illustrated as that the presence of the molecule will enhance the vertical transmission through the h-BN dielectric via quantum interference. We employ a single-level molecule model, and show quantitatively that the discussed effect can be utilized as a powerful signal amplifier for the molecule conductance, thus enhancing the measurability of single molecules by 3-4 orders.
- Ryuzaki, S., Onoe, J.Applied Physics Letters 104 11 2014年
- Sou Ryuzaki, Jun OnoeNANO REVIEWS & EXPERIMENTS 4 1 2013年Hetero-junction organic photovoltaic (OPV) cells consisting of donor (D) and acceptor (A) layers have been regarded as next-generation PV cells, because of their fascinating advantages, such as lightweight, low fabrication cost, resource free, and flexibility, when compared to those of conventional PV cells based on silicon and semiconductor compounds. However, the power conversion efficiency (h) of the OPV cells has been still around 8%, though more than 10% efficiency has been required for their practical use. To fully optimize these OPV cells, it is necessary that the low mobility of carriers/excitons in the OPV cells and the open circuit voltage (VOC), of which origin has not been understood well, should be improved. In this review, we address an improvement of the mobility of carriers/excitons by controlling the crystal structure of a donor layer and address how to increase the VOC for zinc octaethylporphyrin [Zn(OEP)]/ C60 hetero-junction OPV cells [ITO/Zn(OEP)/C60/Al]. It was found that crystallization of Zn(OEP) films increases the number of inter-molecular charge transfer (IMCT) excitons and enlarges the mobility of carriers and IMCT excitons, thus significantly improving the external quantum efficiency (EQE) under illumination of the photoabsorption band due to the IMCT excitons. Conversely, charge accumulation of photo-generated carriers in the vicinity of the donor/ acceptor (D/A) interface was found to play a key role in determining the VOC for the OPV cells.
- Furuhashi, M., Okamoto, Y., Onoshima, D., Ohshiro, T., Ryuzaki, S., Yokota, K., Tsutsui, M., Taniguchi, M., Nakatani, K., Baba, Y., Kawai, T.Applied Physics Letters 103 2 2013年Denaturation is a first step for further treatment of DNA and is expected to be carried out rapidly on an integrated chip. A microheater is a promising device for the denaturation because of easiness for fabrication and operation. In the present study, we fabricated a microheater and thermometers on a coverslip and investigated response of temperature to application of voltage. In addition, our experiment and simulation proved local heating at an aimed area. Finally, we demonstrated denaturation of DNA in buffer solution, the result of which proved that the DNA around the heater denatured within 60 ms. (C) 2013 AIP Publishing LLC.
- Ryuzaki, S., Onoe, J.Japanese Journal of Applied Physics 52 6 PART 2 2013年The equivalent circuit model of the heterojunction organic photovoltaic (OPV) cells consisting of 20-nm-thick zinc-octaethylporphyrin [Zn(OEP)] and 30 nm-thick C-60 films respectively used as donor and acceptor layers has been determined using impedance spectroscopy under dark and illumination (100 mW/cm(2), AM1.5) conditions. Under dark condition, the equivalent circuit consisting of a series resistance and two-RC (R: resistance, C: capacitance) circuits corresponding to individual layers well reproduced the impedance spectra. On the other hand, the four-RC circuit model, in which the additional two RC circuits corresponded to individual films in the vicinity of the Zn(OEP)/C-60 interface, could explain the impedance spectra obtained under illumination condition. (c) 2013 The Japan Society of Applied Physics
- Tsutsui, M., Maeda, Y., He, Y., Hongo, S., Ryuzaki, S., Kawano, S., Kawai, T., Taniguchi, M.Applied Physics Letters 103 1 2013年Manipulation of particles and molecules in fluid is a fundamental technology in biosensors. Here, we report electrical trapping and identification of single-nanoparticles using a low-aspect-ratio nanopore. Particle trapping and detrapping are implemented through a control of the cross-membrane electrophoretic voltage. This electrical method is found to enable placing an individual nanoparticle in vicinity of a lithographically-defined nanopore by virtue of the balance between the two counteracting factors, electrostatic and electroosmotic forces. We also demonstrate identification of trapped nanoparticles by the ionic current through the particle-pore gap space. This technique may find applications in electrode-embedded nanopore sensors. (C) 2013 AIP Publishing LLC.
- Ryuzaki, S., Nishiyama, M., Onoe, J.Diamond and Related Materials 33 12 - 15 2013年The electron transport properties of an air-exposed one-dimensional (1D) uneven peanutshaped C-60 polymer film were investigated by examining the temperature dependence (30-350 K) of the current-voltage (I-V) characteristics under ultrahigh vacuum conditions. Arrhenius plots of the resistance as a function of temperature showed two different electron conduction mechanisms. At temperatures above 140 K, it was found that electrons are conducted via a thermal excitation hopping mechanism, and the activation energy changed discontinuously from 124 to 99 meV at ca. 190 K because of a change in the 1D polymer chain-chain interactions. On the other hand, at temperatures below 100 K, the electron conduction behavior is consistent with a 2D variable-range hopping mechanism. (C) 2012 Elsevier B.V. All rights reserved.
- Ryuzaki, S., Onoe, J.IEEJ Transactions on Electronics, Information and Systems 132 8 1 - 8 2012年Change in electronic states before and after photo-irradiation at a Donor/Acceptor (D/A) interface in organic solar cells consisting of zinc-porphyrin and fullerene films has been examined using in situ impedance spectroscopy (IS), which makes it possible to non-destructively measure a built-in potential (V-bi) of both D and A films at the D/A interface. The accumulation of photo-generated carriers in the vicinity of the D/A interface was found to increase the V-bi of both D [Zn(OEP)] and A [C-60] films at the interface. In addition, it was noted that the sum of V-bi obtained on photo-irradiation was in good agreement with the open-circuit voltage (V-OC), of which the origin is still unsolved for organic solar cells. Thus, the charge accumulation of photo-generated carriers in the vicinity of the D/A interface plays a key role in determining V-OC. (c) 2013 Wiley Periodicals, Inc. Electron Comm Jpn, 96(8): 1-8, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.11542
- Ryuzaki, S., Onoe, J.Journal of Physics D: Applied Physics 44 26 2011年The correlation between open-circuit voltage (V-OC) and built-in potential (V-bi) upon photo-irradiation in the vicinity of the donor/acceptor (D/A) interface in zinc-octaethylporphyrin [Zn(OEP)]/C-60 heterojunction photovoltaic (OPV) cells is investigated by examining the capacitance-voltage (C-V) characteristics. Charge accumulation of photogenerated carriers in the vicinity of the D/A interface is found to enlarge V-bi of both D [Zn(OEP)] and A (C-60) films in the vicinity of the interface. In addition, it is noted that V-OC is in good agreement with the sum of V-bi of each film in the vicinity of the D/A interface. This suggests that charge accumulation of photogenerated carriers in the vicinity of the D/A interface plays a key role in determining V-OC for solar cells.
- Ryuzaki, S., Kai, T., Toda, Y., Adachi, S., Onoe, J.Journal of Physics D: Applied Physics 44 14 2011年We have examined the structural effects of zinc-octaethylporphyrin [Zn(OEP)] films used as a donor on the external quantum efficiency (EQE) of organic heterojunction photovoltaic (OPV) cells [ITO/Zn(OEP)/C-60/Al], and investigated what exactly causes the improvement of EQE. When the structure of the Zn(OEP) films changed from amorphous to crystalline, the maximum EQE increased from 36% to 42%, which is greater than that of around 35% for previously reported OPV cells using buffer materials (Peumans and Forrest 2001 Appl. Phys. Lett. 79 126). The crystallization of Zn(OEP) films is found to increase the number of inter-molecular charge-transfer (IMCT) excitons and to enlarge the mobility of carriers and IMCT excitons, thus significantly improving the EQE of the photoabsorption band under illumination due to the IMCT excitons.
- Ryuzaki, S., Hasegawa, T., Onoe, J.Journal of Applied Physics 105 11 2009年
- Ryuzaki, S., Onoe, J.Journal of Applied Physics 106 2 2009年
- Ryuzaki, S., Onoe, J.Journal of Applied Physics 103 3 2008年
- Toda, Y., Ryuzaki, S., Onoe, J.Applied Physics Letters 92 9 2008年
- Ryuzaki Sou, Ishii Tomohiko, Onoe JunJpn J Appl Phys 46 8 A 5363 - 5366 Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physics 2007年In situ X-ray photoelectron spectra (XPS) of metal–octaethylporphyrin [Pd(OEP), Cu(OEP), and Zn(OEP)] and C60 alternative-deposited films on a silicon substrate are presented for the fabrication of high-performance organic thin-film photovoltaic (PV) cells. XPS results indicated that only Zn(OEP) and C60 alternative-deposited films have a layered structure, whereas the other films have a mixed structure. This may be due to the difference in molecular symmetry between the anti- and syn-configurations of M(OEP): Zn(OEP) has a syn-configuration that can be stacked on a C60 film, whereas the other M(OEP)s have an anti-configuration that is difficult to be stacked on the film.
書籍等出版物
- 中野, 明彦, 吉森, 保, 華山, 力成 (担当:分担執筆)
羊土社 2021年12月 (ISBN: 9784758103992) 207p - 化学75-5月号「注目の論文：エクソソームの表面タンパク質を見分ける」龍崎奏 (担当:分担執筆)
2020年05月 - Organic Solar Cells : Materials, Devices, Interfaces, and ModelingSou Ryuzaki (担当:分担執筆)
2017年12月
講演・口頭発表等
- Fabrication of nanopore devices for Exosomes [招待講演]Sou Ryuzaki35th International Microprocesses and Nanotechnology Conference 2022年11月 口頭発表（招待・特別）
担当経験のある科目（授業）
共同研究・競争的資金等の研究課題
- 日本学術振興会：科学研究費助成事業 基盤研究(C)研究期間 : 2019年04月 -2022年03月代表者 : 龍崎 奏本研究では、金属マルチナノポア構造と量子ドットを組み合わせることで、新しい原理に基づく「白色レーザー」兼「単色波長可変レーザー」の技術開発と原理構築を行う。具体的には、直径100 nm程度の金属マルチナノポア構造を量子ドットが分散している溶液で満たし、量子ドットからの発光をナノポア構造とプラズモン共鳴させることでレージングさせる。三原色RGBに対応した3~7種類の発光特性を有する量子ドットを用い、さらにそれらの発光特性に対応したプラズモ ン共鳴波長を有する数種類のナノポア構造(共鳴波長は直径に依存)を同一基板上に作製する。そして、溶液中における各量子ドットの存在比率を調整すること で「白色レージング」または「単色レージング」を選択することが可能となる。本レーザー技術はLEDに変わる高効率照明としてや、ペタビット通信を可能のす るコア技術として期待でき、本研究によって次世代光源の技術創生を目指す。本年度は、量子ドットの発光特性を合成後に制御する方法を確立し、さらにプラズモンを始めたした光学現象を利用することで、量子ドットからの発光を増強させることに成功した。さらに、ナノポア内でより効率よく増強電場を発生させるためのプラズモニックナノポア構造の作製に成功した。
- 日本学術振興会：科学研究費助成事業 基盤研究(A)研究期間 : 2016年04月 -2020年03月代表者 : 馬場 嘉信, 龍崎 奏細胞外小胞であるエクソソームは、がんの発生・増殖・転移において極めて重要な役割を果たしていることが最近明らかになった。さらに、従来の血中マーカーより極めて大きい情報量を有し、次世代がん診断マーカーとして大きな期待が集まっている。本研究では、ナノ空間の特性を生かすことで、がん特異的エクソソームを超高精度に迅速解析できるデバイスの開発を行い、従来の数十倍以上の高速化と正確さを兼ね備えたがん超早期診断・予防システムの実現を目指した。
- 日本学術振興会：科学研究費助成事業 若手研究(A)研究期間 : 2015年04月 -2018年03月代表者 : 龍崎 奏, 谷口 正輝本研究では、低アスペクト（ポア厚/ポア径）ナノポア構造をSi3N4メンブレンに作製し、微粒子をナノポアに通過させ、その際のナノポアを流れるイオン電流の変化を数学的に解析することで、液中に浮遊している微粒子の1粒子形状解析に成功した。また、本解析技術によって生体微粒子（EV）の1粒子形状解析を行うことで、液中に浮遊しているEVの形状分布は分泌元のがん細胞の種類ごとに異なることを発見し、EVの形状は重要な生態情報であることが示唆された。さらに、グラフェンナノポアの作製や金属微粒子のパターニング技術開発にも成功し、今後、ナノポアによる形状解析の空間分解能を改良できる可能性が示唆された。
- 日本学術振興会：科学研究費助成事業研究期間 : 2014年04月 -2018年03月代表者 : 玉田 薫, 田中 大輔, 柳瀬 雄輝, 岡本 晃一, 龍崎 奏, 王 胖胖本研究は、金属ナノ粒子の多次元自己組織化とそこで発現する光学現象の理論的及び実験的解明、ならびにこの現象を用いた新規ナノ光デバイスの考案を目的として行った。科学的成果としては、金属ナノ粒子多次元自己組織化膜を金属基板上に積層した際に発現する呈色が「電磁誘導透明化 (EIT)」であることを明らかにしたこと、応用としては、目視型高感度センサーの開発や細胞接着ナノ界面の超解像度イメージングに成功したことが注目に値する。これら我々独自の研究を通じて、プラズモニック・ナノメタマテリアルの基盤分野を世界に向けて発信することができた。
- 日本学術振興会：科学研究費助成事業 若手研究(B)研究期間 : 2013年04月 -2015年03月代表者 : 龍崎 奏本研究課題では、ナノポアを通過する分子の速度を制御するサラウンドゲート電極と、ナノポアデバイスを融合することで、ナノポアを通過する分子の速度をゲート電圧で減速させることに成功し、さらにイオン電流変化からナノポア通過分子の構造解析に成功した。ゲート電圧によるナノポア通過分子の速度制御、およびナノポアを用いた構造解析はいずれも本研究が世界発である。具体的には、ナノ粒子を最大で240倍ほど減速させ、DNA 1分子の速度は10倍ほど減速させることに成功した。また、それらの粒子の3次元形状や、DNAのナノポア通過時の構造を定量的に解析することに成功した。