Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Sou Ryuzaki Last modified date:2019.07.05

Assistant Professor / Department of Fundamental Organic Chemistry / Institute for Materials Chemistry and Engineering

1. Priastuti Wulandari, Yolla Sukma Handayani, Rachmat Hidayat, Pangpang Wang, Soh Ryuzaki, Koichi Okamoto, Kaoru Tamada, Surface plasmon resonance effect of silver nanoparticles on the enhanced efficiency of inverted hybrid organic-inorganic solar cell, Journal of Nonlinear Optical Physics and Materials, 10.1142/S0218863518500170, 27, 2, 2018.06, 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/cm
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/cm
2 nevertheless implies reduced conductivity due to AgSC8 incorporation..
2. Ayumi Ishijima, Pangpang Wang, Soh Ryuzaki, Koichi Okamoto, Kaoru Tamada, Comparison of LSPR-mediated enhanced fluorescence excited by S- and P-polarized light on a two-dimensionally assembled silver nanoparticle sheet, Applied Physics Letters, 10.1063/1.5056211, 113, 17, 2018.10, 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..
3. Kazutaka Tateishi, Pangpang Wang, Soh Ryuzaki, Mitsuru Funato, Yoichi Kawakami, Koichi Okamoto, Kaoru Tamada, Micro-photoluminescence mapping of light emissions from aluminum-coated InGaN/GaN quantum wells, Applied Physics Express, 10.7567/1882-0786/ab0911, 12, 5, 2019.01, 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..
4. Pangpang Wang, Soh Ryuzaki, Lumei Gao, Shuhei Shinohara, Noboru Saito, Koichi Okamoto, Kaoru Tamada, Sunao Yamada, Comparison of the mechanical strength of a monolayer of silver nanoparticles both in the freestanding state and on a soft substrate, Journal of Applied Physics, 10.1063/1.5063567, 125, 13, 2019.04, 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..
5. Haruka Takekuma, Kyohei Tagomori, Shuhei Shinohara, Shihomi Masuda, Yang Xu, Yinthai Chan, Pangpang Wang, Soh Ryuzaki, Koichi Okamoto, Kaoru Tamada, How to make microscale pores on a self-assembled Ag nanoparticle monolayer, Colloids and Interface Science Communications, 10.1016/j.colcom.2019.100175, 30, 2019.05, 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..
6. N. Saito, S. Ryuzaki, P. Wang, S. Park, N. Sakai, T. Tatsuma, K. Okamoto, and K. Tamada, Durability improvements of two-dimensional metal nanoparticle sheets by molecular cross-linked structures between nanoparticles, Japanese Journal of Applied Physics, 52, 06GD03, 2018.02.
7. N. Saito, P. Wang, K. Okamoto, S. Ryuzaki, and K. Tamada, Large patternable metal nanoparticle sheets by photo/e-beam lithography, Nanotechnology, 28, 435705, 2017.08.
8. K. Tateishi, P. Wang, S. Ryuzaki, M. Funato, Y. Kawakami, K. Okamoto, K. Tamada, Micro-photoluminescence mapping of surface plasmon enhanced light emissions from InGaN/GaN quantum wells, Applied Physic Letters , 111, 172105, 2017.08.
9. S. Masuda, Y. Yanase, E. Usukura, S. Ryuzaki, P. Wang, K. Okamoto, T. Kuboki, S. Kidoaki, and K. Tamada, High-resolution imaging of a cell-attached nanointerface using a gold-nanoparticle two-dimensional sheet, Sci. Rep., 7, 3720, 1, 2017.07.
10. Z-Y. Juang, C-C Tseng, Y. Shi, W-P Hsieh, S. Ryuzaki, N. Saito, C.-E Hsiung, W- H Chang, Y. Hernandez, Y. Han, K. Tamada, and L-J Li, Graphene-Au nanoparticle based vertical heterostructures: A novel route towards high-ZT Thermoelectric devices, Nano Energy, 38, 385, 2017.06.
11. S. Ryuzaki, M. Tsutsui, Y. He, K. Yokota, A. Arima, T. Morikawa, M. Taniguchi, and T. Kawai, Rapid structural analysis of nanomaterials in aqueous solutions, Nanotechnology , 28, 155501, 2017.02.
12. K. Okamoto, D. Tanaka, R. Degawa, X. Li, P. Wang, S. Ryuzaki, and K. Tamada, Electromagnetically induced transparency of a plasmonic metamaterial light absorber based on multilayered metallic nanoparticle sheets, Sci. Rep. , 6, 36165, 1, 2016.11.
13. A. Arima, M. Tsutsui, Y. He, S. Ryuzaki, and M. Taniguchi, Electrical trapping mechanism of single-microparticles in a pore sensor, AIP Adv., 6, 115004, 2016.10.
14. Wang Pangpang, Sou Ryuzaki, Daisuke Tanaka, Shohei Araki, K. Okamoto, Kaoru Tamada, Silver Nanoparticles with Tunable Work Functions, Applied Physics Letters, 107, 151601, 2015.10.
15. Sou Ryuzaki, Jakob A. S. Meyer, Søren Petersen, Kasper Nørgaard, Tue Hassenkam, Bo W. Laursen, Local charge transport properties of monolayer reduced graphene oxide sheets prepared under self-generated pressure, Applied Physics Letters, 105, 093109, 2014.09.
16. Yuhui He, Makusu Tsutsui, Sou Ryuzaki, Kazumichi Yokota, Masateru Taniguchi, Tomoji Kawai, Graphene/hexagonal boron nitride/graphene nanopore for electrical detection of single molecules, NPG Asia Materials, e104; doi:10.1038/am.2014.29, 1, 2014.06.
17. Sou Ryuzaki, Jun Onoe, Anomaly in the electric resistivity of one-dimensional uneven peanut-shaped C60 polymer film at a low temperature, Applied Physics Letters, 104, 113301, 2014.03.