Kyushu University Academic Staff Educational and Research Activities Database
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Sou Ryuzaki Last modified date:2021.07.13

Graduate School

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Academic Degree
Country of degree conferring institution (Overseas)
Field of Specialization
Total Priod of education and research career in the foreign country
Outline Activities
1. Plasmonic nanopore device
Developing plasmonic nanopore devices, which enable us to measure SERS of single molecules and single bioparticles passing through a nanopore.
2. Novel cancer detector
Developing a new technology for rapid cancer detection, screening, and diagnosis based on the detection of cell-derived extracellular vesicles.
3. Organic/Metal interface physics
Investigating organic/metal interface physics and applying the knowledge to some optoelectronic devices.
4. White laser
Examining white laser based on some kinds of quantum dos to achieve very high-speed information-communication technology.
5. Ultra high speed CCD
Developing 100-kHz-CCD sensors based on analog and digital circuits.
Research Interests
  • ultra high speed sensor
    keyword : CCD, analog circuit, digital circuit, algorithm
  • QD white laser
    keyword : plasmonics, quantum dots
  • Electronic Properties for Metal-nanoparticle/Organic-Molecule Interface Physics
    keyword : nanoparticle, interface physics, quantum size effect, plasmon
  • Structural Analysis for Single-molecules/bioparticles in Aqueous Solutions
    keyword : Nanopore devices, Single-molecule Science, Nanobio Sensors
Academic Activities
1. 龍﨑 奏, 尾上順, Chapter 6, Photoexcited Carrier Dynamics in Organic Solar Cells, Organic Solar Cells: Materials, Devices, Interfaces, and Modelling, 2015.03.
1. N. Saito, S. Ryuzaki, Y. Tsuji, Y. Noguchi, P. Wang, D. Tanaka, Y. Arima, K. Okamoto, K. Yoshizawa, K. Tamada., Effect of chemically induced permittivity changes on the plasmonic properties of metal nanoparticles, Communications Materials,, 2, 54, 1-8, 2021.06, 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..
2. S. Ryuzaki, T. Yasui, M. Tsutsui, K. Yokota, Y. Komoto, P. Paisrisarn, N. Kaji, D. Ito, K. Tamada, T. Ochiya, M. Taniguchi, Y. Baba, and T. Kawai., Rapid Discrimination of Extracellular Vesicles by Shape Distribution Analysis, ANALYTICAL CHEMISTRY, 10.1021/acs.analchem.1c00258, 93, 18, 7037-7044, 2021.05, 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..
3. M. Tsutsui, S. Ryuzaki, K. Yokota, H. Yuhui, T. Washio, K. Tamada, and T. Kawai., Field effect control of translocation dynamic in surround-gate nanopores, Communications Materials,, 2, 29, 1-9, 2021.03, 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 singlemolecule detection by solid-state nanopores and nanochannels..
4. Sou Ryuzaki, Makusu Tsutsui, Yuhui He, Kazumichi Yokota, Akihide Arima, Takanori Morikawa, Masateru Taniguchi, Tomoji Kawai, Rapid structural analysis of nanomaterials in aqueous solutions, Nanotechnology, 10.1088/1361-6528/aa5e66, 28, 15, 2017.03, 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..
5. Sou Ryuzaki, Jakob A.S. Meyer, Søren Petersen, Kasper Nørgaard, Tue Hassenkam, Bo W. Laursen, Local charge transport properties of hydrazine reduced monolayer graphene oxide sheets prepared under pressure condition, Applied Physics Letters, 10.1063/1.4895072, 105, 9, 2014.09, 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 sp3carbon 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 267.2-537.5S/m. It was found that the chemical reduction under pressure results in larger graphene domains (sp2networks) 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..
1. Sou Ryuzaki, Makusu Tsutsui, Masateru Taniguchi,, Nanopore devices for shape analysis of single nanobiomaterials in aqueous solutions, INTERNATIONAL CONFERENCE ON FUNCTIONAL NANOMATERIALS AND NANODEVICES, 2018.09.
2. S. Ryuzaki, M. Tsutsui, K. Yokota, and M. Taniguchi, Rapid structural analysis of nanomaterials in aqueous solutions, European Conference on Molecular Electronics (ECME), 2017.08.
3. S. Ryuzaki, D. Tanaka, P. Wang, K. Okamoto, Y. Chan, and K. Tamada, , Multi-nanopore structures for quantum dot laser, Singapore International Chemistry Conference, Singapore, 2016.12.
Membership in Academic Society
  • The Japan Society for Analytical Chemistry
  • American Chemical Society
  • MRS
  • The Society for Discrete Variational Xα
  • MRS−J
  • The Society of Nano Science and Technology
  • The Japan Society of Applied Physics