Ryuzaki Sou

Faculty of Science　Chemistry　Inorganic and Analytical ChemistryAssociate Professor
Last Updated :2025/04/25

■Researcher basic information

Degree

  • PH.D, Tokyo Institute of Technology, Mar. 2010

Researchmap personal page

Home Page URL

J-Global ID

Research Keyword

  • Material Science
  • Plasmonics
  • Nanobiodeviec
  • Organic Device

Research Field

  • Nanotechnology/Materials, Analytical chemistry
  • Life sciences, Biophysics
  • Nanotechnology/Materials, Nanobioscience

Educational Organization

■Career

Career

  • Apr. 2022 - Present
    Hokkaido University, Faculty of Science Department of Chemistry, Associate Prof.
  • Jan. 2014 - Mar. 2022
    Kyushu University, Institute for Materials Chemistry and Engineering, Assistant Professor
  • Oct. 2017 - Mar. 2021
    Japan Science and Technology Agency, さきがけ研究員
  • Feb. 2012 - Dec. 2013
    Osaka University, The Institute of Scientific and Industrial Research, Assistant Professor
  • May 2011 - Feb. 2012
    Tokyo Institute of Technology, 原子炉工学研究所, Postdoc
  • May 2010 - Apr. 2011
    University of Copenhagen, Nano-Science Center, Postdoc

Educational Background

  • Apr. 2007 - Mar. 2010, Tokyo Institute of Technology, Graduate School of Science and Engineering, Department of Nuclear Engineering, Japan
  • Apr. 2005 - Mar. 2007, Tokyo Institute of Technology, Graduate School of Science and Engineering, Department of Nuclear Engineering, Japan
  • Apr. 2001 - Mar. 2005, Tokyo University of Science, Faculty of Science and Technology, Physics, Japan

Committee Memberships

  • Apr. 2014 - Present
    ＤＶ−Ｘα研究協会, 常任幹事, Society
  • Apr. 2020 - Mar. 2022
    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, Society
  • Oct. 2017 - Sep. 2019
    JSAP Multidisciplinary Young Researcher Chapter, 代表, Society
  • Apr. 2016 - Mar. 2018
    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, Society
  • Apr. 2015 - Mar. 2016
    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, Society

■Research activity information

Awards

  • Feb. 2024, プラズモニック化学研究会, 若手奨励賞最優秀賞　　　　　　　　　　　　　　　
  • Oct. 2023, 株式会社リバネス, Tech Planter 最優秀賞　　　　　　　　　　　　　　　
    龍崎奏
  • Oct. 2023, 大日本印刷株式会社, Tech Planter DNP賞　　　　　　　　　　　　　　　
    龍崎奏
  • May 2023, Royal Society of Chemistry, and The Society of Nano Science and Technology, Nanoscale Horizons Award　　　　　　　　　　　　　　　
    Sou Ryuzaki
  • Feb. 2023, 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　　　　　　　　　　　　　　　
    龍崎奏
  • Apr. 2022, 科学技術振興機構CREST[細胞外微粒子], Young Innovator Award　　　　　　　　　　　　　　　
  • Jul. 2021, DV-Xα研究協会, 奨励賞　　　　　　　　　　　　　　　
  • Dec. 2017, IOP Publishing, Nanotechnology, Highlights of 2017　　　　　　　　　　　　　　　
  • Aug. 2017, 9th International Conference on Molecular Electronics and Bioelectronics, The Best Poster Award　　　　　　　　　　　　　　　
  • Mar. 2016, 第63回応用物理学会春季学術講演会, 講演奨励賞　　　　　　　　　　　　　　　
  • Oct. 2010, 財団法人手島工業教育資金団, 手島記念博士論文賞　　　　　　　　　　　　　　　
  • Mar. 2007, 東京工業大学原子核工学専攻., 最優秀論文発表賞　　　　　　　　　　　　　　　

Papers

  • High-Q Plasmonic Nanocavities Enabled by Integration of Au Nanogap Dimers with a Distributed Bragg Reflector
    Keisuke Imaeda, Rin Miyazaki, Sou Ryuzaki, Kosei Ueno
    The Journal of Physical Chemistry C, 13 Mar. 2025
    Scientific journal
  • Coherent acoustic vibrations of Au nanoblocks and their modulation by Al2O3 layer deposition
    Keisuke Imaeda, Yuto Shikama, Shimba Ushikoshi, Satoshi Sakai, Sou Ryuzaki, Kosei Ueno
    The Journal of Chemical Physics, 14 Apr. 2024
    Scientific journal
  • Exploring Hybrid States and Their Ultrafast Dynamics in Exciton–Plasmon Strong Coupling Systems
    Hiroki Takeuchi, Keisuke Imaeda, Sou Ryuzaki, Kosei Ueno
    The Journal of Physical Chemistry C, 15 Feb. 2024
    Scientific journal
  • Transient Nascent Adhesion at the Initial Stage of Cell Adhesion Visualized on a Plasmonic Metasurface
    Shi Ting Lee, Thasaneeya Kuboki, Satoru Kidoaki, Yukiko Aida, Sou Ryuzaki, Koichi Okamoto, Yusuke Arima, Kaoru Tamada
    Advanced NanoBiomed Research, 2100100, 2100100, Wiley, Jan. 2022
    Scientific journal
  • Field effect control of translocation dynamics in surround-gate nanopores
    Makusu Tsutsui, Sou Ryuzaki, Kazumichi Yokota, Yuhui He, Takashi Washio, Kaoru Tamada, Tomoji Kawai
    Communications Materials, 2, 1, Springer Science and Business Media LLC, Dec. 2021
    English, Scientific journal, AbstractControlling 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 nanoparticles
    Noboru Saito, Sou Ryuzaki, Yuta Tsuji, Yutaka Noguchi, Rintaro Matsuda, Pangpang Wang, Daisuke Tanaka, Yusuke Arima, Koichi Okamoto, Kazunari Yoshizawa, Kaoru Tamada
    Communications Materials, 2, 1, Springer Science and Business Media {LLC}, Dec. 2021
    English, Scientific journal, AbstractUnderstanding 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.
  • Rapid Discrimination of Extracellular Vesicles by Shape Distribution Analysis
    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 Kawai
    Analytical Chemistry, 93, 18, 7037, 7044, American Chemical Society ({ACS}), 11 May 2021, [International Magazine]
    English, Scientific journal, 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.
  • Layer Number-Dependent Enhanced Photoluminescence from a Quantum Dot Metamaterial Optical Resonator
    Haruka Takekuma, Junfu Leng, Kazutaka Tateishi, Yang Xu, Yinthai Chan, Sou Ryuzaki, Pangpang Wang, Koichi Okamoto, Kaoru Tamada
    ACS Applied Electronic Materials, 3, 1, 468, 475, American Chemical Society ({ACS}), 26 Jan. 2021
    English, Scientific journal, 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.
  • High Axial and Lateral Resolutions on Self-Assembled Gold Nanoparticle Metasurfaces for Live-Cell Imaging
    Shihomi Masuda, Thasaneeya Kuboki, Satoru Kidoaki, Shi Ting Lee, Sou Ryuzaki, Koichi Okamoto, Yusuke Arima, Kaoru Tamada
    ACS Applied Nano Materials, 3, 11, 11135, 11142, American Chemical Society ({ACS}), 25 Nov. 2020
    Scientific journal, 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.
  • Pore Structures for High-Throughput Nanopore Devices
    Sou Ryuzaki, Rintaro Matsuda, Masateru Taniguchi
    Micromachines, 11, 10, 893, 893, {MDPI} {AG}, Sep. 2020, [International Magazine]
    English, Scientific journal, 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.
  • Flexibly tunable surface plasmon resonance by strong mode coupling using a random metal nanohemisphere on mirror
    Okamoto, K., Okura, K., Wang, P., Ryuzaki, S., Tamada, K.
    Nanophotonics, 9, 10, 3409, 3418, 2020
    Scientific journal, © 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.
  • Finite-difference time-domain simulations of inverted cone-shaped plasmonic nanopore structures
    Matsuda, R., Ryuzaki, S., Okamoto, K., Arima, Y., Tsutsui, M., Taniguchi, M., Tamada, K.
    Journal of Applied Physics, 127, 24, 2020
    Scientific journal, © 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.
  • Tuning the Emission Colors of Self-Assembled Quantum Dot Monolayers via One-Step Heat Treatment for Display Applications
    Leng, J., Xu, Y., Chan, Y., Wang, P., Ryuzaki, S., Okamoto, K., Tamada, K.
    ACS Applied Nano Materials, 3, 4, 3214, 3222, American Chemical Society ({ACS}), 2020
    Scientific journal, 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.
  • Comparison of the mechanical strength of a monolayer of silver nanoparticles both in the freestanding state and on a soft substrate
    Wang, P., Ryuzaki, S., Gao, L., Shinohara, S., Saito, N., Okamoto, K., Tamada, K., Yamada, S.
    Journal of Applied Physics, 125, 13, AMER INST PHYSICS, 2019
    English, Scientific journal, © 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.
  • Micro-photoluminescence mapping of light emissions from aluminum-coated InGaN/GaN quantum wells
    Tateishi, K., Wang, P., Ryuzaki, S., Funato, M., Kawakami, Y., Okamoto, K., Tamada, K.
    Applied Physics Express, 12, 5, IOP PUBLISHING LTD, 2019
    English, Scientific journal, © 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.
  • How to make microscale pores on a self-assembled Ag nanoparticle monolayer
    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, ELSEVIER, 2019
    English, Scientific journal, © 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.
  • Comparison of LSPR-mediated enhanced fluorescence excited by S- and P-polarized light on a two-dimensionally assembled silver nanoparticle sheet
    Ishijima, A., Wang, P., Ryuzaki, S., Okamoto, K., Tamada, K.
    Applied Physics Letters, 113, 17, 2018
    Scientific journal, © 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.
  • Surface plasmon resonance effect of silver nanoparticles on the enhanced efficiency of inverted hybrid organic-inorganic solar cell
    Wulandari, P., Handayani, Y.S., Hidayat, R., Wang, P., Ryuzaki, S., Okamoto, K., Tamada, K.
    Journal of Nonlinear Optical Physics and Materials, 27, 2, WORLD SCIENTIFIC PUBL CO PTE LTD, 2018
    English, Scientific journal, © 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.
  • Durability improvements of two-dimensional metal nanoparticle sheets by molecular cross-linked structures between nanoparticles
    Saito, N., Ryuzaki, S., Wang, P., Park, S., Sakai, N., Tatsuma, T., Okamoto, K., Tamada, K.
    Japanese Journal of Applied Physics, 57, 3, IOP PUBLISHING LTD, 2018
    English, Scientific journal, © 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.
  • Micro-photoluminescence mapping of surface plasmon enhanced light emissions from InGaN/GaN quantum wells
    Tateishi, K., Wang, P., Ryuzaki, S., Funato, M., Kawakami, Y., Okamoto, K., Tamada, K.
    Applied Physics Letters, 111, 17, AMER INST PHYSICS, 2017
    English, Scientific journal, © 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.
  • Rapid structural analysis of nanomaterials in aqueous solutions
    Ryuzaki, S., Tsutsui, M., He, Y., Yokota, K., Arima, A., Morikawa, T., Taniguchi, M., Kawai, T.
    Nanotechnology, 28, 15, 155501, 155501, IOP PUBLISHING LTD, 2017, [International Magazine]
    English, Scientific journal, 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.
  • Photoexcited carrier dynamics in organic solar cells
    Ryuzaki, S., Onoe, J.
    Organic Solar Cells: Materials, Devices, Interfaces, and Modeling, 2017
    Scientific journal
  • Graphene-Au nanoparticle based vertical heterostructures: A novel route towards high-ZT Thermoelectric devices
    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
    Scientific journal, © 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.
  • Large patternable metal nanoparticle sheets by photo/e-beam lithography
    Saito, N., Wang, P., Okamoto, K., Ryuzaki, S., Tamada, K.
    Nanotechnology, 28, 43, 435705, 435705, IOP PUBLISHING LTD, 2017, [Peer-reviewed], [International Magazine]
    English, Scientific journal, 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.
  • High-resolution imaging of a cell-attached nanointerface using a gold-nanoparticle two-dimensional sheet
    Masuda, S., Yanase, Y., Usukura, E., Ryuzaki, S., Wang, P., Okamoto, K., Kuboki, T., Kidoaki, S., Tamada, K.
    Scientific Reports, 7, 1, 3720, 3720, NATURE PUBLISHING GROUP, 2017, [Peer-reviewed], [International Magazine]
    English, Scientific journal, 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.
  • Electrical trapping mechanism of single-microparticles in a pore sensor
    Arima, A., Tsutsui, M., He, Y., Ryuzaki, S., Taniguchi, M.
    AIP Advances, 6, 11, AMER INST PHYSICS, 2016
    English, Scientific journal, 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/).
  • Electromagnetically induced transparency of a plasmonic metamaterial light absorber based on multilayered metallic nanoparticle sheets
    Okamoto, K., Tanaka, D., Degawa, R., Li, X., Wang, P., Ryuzaki, S., Tamada, K.
    Scientific Reports, 6, 36165, 36165, 2016, [International Magazine]
    English, Scientific journal, © 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.
  • Silver nanoparticles with tunable work functions
    Wang, P., Tanaka, D., Ryuzaki, S., Araki, S., Okamoto, K., Tamada, K.
    Applied Physics Letters, 107, 15, AMER INST PHYSICS, 2015
    English, Scientific journal, © 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.
  • Local charge transport properties of hydrazine reduced monolayer graphene oxide sheets prepared under pressure condition
    Ryuzaki, S., Meyer, J.A.S., Petersen, Sø., Nørgaard, K., Hassenkam, T., Laursen, B.W.
    Applied Physics Letters, 105, 9, AMER INST PHYSICS, 2014
    English, Scientific journal, 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.
  • Graphene/hexagonal boron nitride/graphene nanopore for electrical detection of single molecules
    He, Y., Tsutsui, M., Ryuzaki, S., Yokota, K., Taniguchi, M., Kawai, T.
    NPG Asia Materials, 6, 6, NATURE PUBLISHING GROUP, 2014
    English, Scientific journal, 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.
  • Anomaly in the electric resistivity of one-dimensional uneven peanut-shaped C60 polymer film at a low temperature
    Ryuzaki, S., Onoe, J.
    Applied Physics Letters, 104, 11, 2014
    Scientific journal
  • Basic aspects for improving the energy conversion efficiency of hetero-junction organic photovoltaic cells
    Sou Ryuzaki, Jun Onoe
    NANO REVIEWS & EXPERIMENTS, 4, 1, TAYLOR & FRANCIS LTD, 2013, [International Magazine]
    English, Scientific journal, 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.
  • High speed DNA denaturation using microheating devices
    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, AMER INST PHYSICS, 2013
    English, Scientific journal, 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.
  • In situ nondestructive impedance spectroscopic study of nanostructured heterojunction organic photovoltaic cells
    Ryuzaki, S., Onoe, J.
    Japanese Journal of Applied Physics, 52, 6 PART 2, IOP PUBLISHING LTD, 2013
    English, Scientific journal, 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
  • Trapping and identifying single-nanoparticles using a low-aspect-ratio nanopore
    Tsutsui, M., Maeda, Y., He, Y., Hongo, S., Ryuzaki, S., Kawano, S., Kawai, T., Taniguchi, M.
    Applied Physics Letters, 103, 1, AMER INST PHYSICS, 2013
    English, Scientific journal, 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.
  • Electron transport properties of air-exposed one-dimensional uneven peanut-shaped C60 polymer films
    Ryuzaki, S., Nishiyama, M., Onoe, J.
    Diamond and Related Materials, 33, 12, 15, ELSEVIER SCIENCE SA, 2013
    English, Scientific journal, 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.
  • Photo-generated carrier dynamics in the vicinity of the donor/acceptor interface of organic solar cells
    Ryuzaki, S., Onoe, J.
    IEEJ Transactions on Electronics, Information and Systems, 132, 8, 1, 8, WILEY, 2012
    English, Scientific journal, 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
  • Influence of charge accumulation of photogenerated carriers in the vicinity of donor/acceptor interface on the open-circuit voltage of zinc-porphyrin/ C60 heterojunction organic photovoltaic cells
    Ryuzaki, S., Onoe, J.
    Journal of Physics D: Applied Physics, 44, 26, IOP PUBLISHING LTD, 2011
    English, Scientific journal, 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.
  • Effects of inter-molecular charge-transfer excitons on the external quantum efficiency of zinc-porphyrin/C60 heterojunction photovoltaic cells
    Ryuzaki, S., Kai, T., Toda, Y., Adachi, S., Onoe, J.
    Journal of Physics D: Applied Physics, 44, 14, IOP PUBLISHING LTD, 2011
    English, Scientific journal, 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.
  • X-ray diffraction and infrared multiple-angle incidence resolution spectroscopic studies on the crystal structure and molecular orientation of zinc-porphyrin thin films on a SiO2/Si substrate
    Ryuzaki, S., Hasegawa, T., Onoe, J.
    Journal of Applied Physics, 105, 11, 2009
    Scientific journal
  • X-ray diffraction and scanning electron microscopic studies on the crystal structure and surface/interface morphology of zinc-octaethylporphyrin films on an indium tin oxide substrate spin coated with 3,4-polyethylenedioxythiophene: polystyrenesulfonate
    Ryuzaki, S., Onoe, J.
    Journal of Applied Physics, 106, 2, 2009
    Scientific journal
  • The crystallinity and surface morphology of zinc octaethylporphyrin thin films on an indium-tin-oxide substrate
    Ryuzaki, S., Onoe, J.
    Journal of Applied Physics, 103, 3, 2008
    Scientific journal
  • Femtosecond carrier dynamics in electron-beam-irradiated C60 film
    Toda, Y., Ryuzaki, S., Onoe, J.
    Applied Physics Letters, 92, 9, 2008
    Scientific journal
  • In situ X-ray photoelectron spectroscopic study of metalloporphyrin- fullerene alternative-deposited thin films
    Ryuzaki, S., Ishii, T., Onoe, J.
    Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 46, 8 A, 5363, 5366, INSTITUTE OF PURE AND APPLIED PHYSICS, 2007
    English, Scientific journal, 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.

Books and other publications

Lectures, oral presentations, etc.

  • Fabrication of nanopore devices for Exosomes　　　　　　　　　　　　　　　
    Sou Ryuzaki
    35th International Microprocesses and Nanotechnology Conference, 08 Nov. 2022, English, Invited oral presentation
    08 Nov. 2022 - 11 Nov. 2022, [Invited]

Courses

  • Inorganic Chemistry III　　　　　　　　　　　　　　　
    Hokkaido University
    Apr. 2022 - Present
  • Chemistry in Daily Life　　　　　　　　　　　　　　　
    Kyushu University
    2017 - 2019

Research Themes

  • Biosensor based on surface molecular information of extracellular vesicles
    Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    01 Apr. 2022 - 31 Mar. 2025
    龍崎 奏, 馬場 英司
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 22H01927
  • Metal multi-nanopore structures for quantum dot lasing
    Grants-in-Aid for Scientific Research
    01 Apr. 2019 - 31 Mar. 2022
    Ryuzaki Sou
    A novel laser has been developed by metal multi-nanopore structure with a diameter of ca.100 nm filled with a solution in which quantum dots (QDs) are dispersed. The Fabry-Perot type lasing is caused by plasmonic resonances between the emission from QDs and the metal multi-nanopore structure. In this study, the following results have been mainly achieved. (1) Development of a method to control the emission characteristics of quantum dots after synthesis, (2) Fabrication and characterization of plasmonic nanopores, (3) Revealing the correlation between electronic state at the metal-organic interface and plasmon resonance properties, (4) Fabry-Perot type lasing by the metal multi-nanopore structure.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Kyushu University, 19K05234
  • Exosome analysis device for cancer early diagnosis
    Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    01 Apr. 2016 - 31 Mar. 2020
    Baba Yoshinobu
    Exosomes are extracellular vesicles and play an important role for cancer tumorigenesis, cancer progression, and cancer metastasis. And, exosomes have more information than conventional blood biomarkers. Recently, researchers expected exosomes as the next-generation cancer diagnosis biomarkers. In this research, we proposed a device to demonstrate rapid and precise analysis of cancer specific exosomes using nanospace unique features. And furthermore, we had a goal to aim for cancer diagnosis system, which could achieve higher speed and more accurate diagnosis than conventional systems.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Nagoya University, 16H02091
  • Nanopore devices for structural analysis of nanobio materials
    Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (A)
    01 Apr. 2015 - 31 Mar. 2018
    Ryuzaki sou, TANIGUCHI Masateru
    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. 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 many kind of single vesicles and EVs. The present results indicate this structural analysis is very powerful tool to identify nano-bioparticles and have a potential as novel nanobio sensors from the view point of particle shapes.
    Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (A), Kyushu University, 15H05417
  • Complex 3D nanometamaterials composed of self-assembled metal nanoparticles
    Grants-in-Aid for Scientific Research
    01 Apr. 2014 - 31 Mar. 2018
    Tamada Kaoru, OKAMOTO Koichi, RYUZAKI Sou, WANG Pangpang, PARK Cheomin, WULANDARI Pristuti, LI Lain-Jong, CRAIG S. J. Vincent, CHAN Yin Thai, YANG Xu
    This study aimed at multidimensional self-assembly of metallic nanoparticles, and theoretical and experimental elucidation of novel optical phenomena developed in this study, and development of novel nano-optical devices using these phenomena. The main scientific achievement is to reveal the origin of color change observed on multidimensional self-assembled metal nanoparticle sheets on a metal substrate, as "electromagnetically induced transparency (EIT)". The main achievements in application are
    development of colorimetric sensors by use of EIT and super resolution imaging of cell attached nano interface. These our original studies disseminate the fundamental field of plasmonic and nanometamaterials to the world.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Kyushu University, 26246005
  • Nanopore devices for a structural analysis of single molecules
    Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)
    01 Apr. 2013 - 31 Mar. 2015
    RYUZAKI Sou
    Nanopore devices consisting of a surround gating electrode causing a decrease in speed of nanomaterials passing through the nanopore have been fabricated in order to analyze structures of the materials. The gating voltage via a gating electrode resulted in 240 times slower speed of nanoparticles passing through a nanopore than that without the gating voltage, and DNA also showed 10 times slower speed under the gating voltage. In addition, the shapes and structures of these materials passing through a nanopore were quantitatively revealed by analysing changes in ionic current due to the material translation.
    Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), Kyushu University, 25790029