Faculty Profiles - AKIYAMA Tsuyoshi

Papers - AKIYAMA Tsuyoshi

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Improvement of the photoelectric conversion efficiencies of a half-photocell using electrodeposited poly(2,2!-bithiophene) through the incorporation of meso-tetra(3- thienyl)porphyrin and electrodeposited poly(3,4-ethylenedioxythiophene) Reviewed

Kengo Kanbe, Yu Kumagawa, Shuya Hirata, Takeo Oku, Tsuyoshi Akiyama

Japanese Journal of Applied Physics 63 12005 2024.12

Fabrication and photocurrent generation properties of C60-ethylenediamine adduct microparticles film modified with poly(3-hexylthiophene-2,5-diyl) Reviewed

Moyu Tanaka, Kengo Kanbe, Shoto Banya, Takeo Oku, Tsuyoshi Akiyama

Molecular Crystals and Liquid Crystals 768 ( 13 ) 541 - 551 2024.5

Enhancement of photochromic molecule decolorization by coating a thin Ti(O) layer over gold nanoparticles Reviewed International coauthorship

Suguru Higashida, Ryota Toku, Genta Nakano, Ryo Mizutsu, Ryosuke Asato, Marine Louis, Tsuyoshi Akiyama, Tsuyoshi Kawai

Chemistry Letters 53 upad002 2023.12

Fabrication and photoelectric conversion of densely packed C60–ethylenediamine adduct microparticle films-modified electrode covered with electrochemically deposited polythiophene thin-films Reviewed

Shoto Banya, Yu Kumagawa, Daisuke Izumoto, Moyu Tanaka, Kengo Kanbe, Takeo Oku and Tsuyoshi Akiyama

RSC Advances 13 31244 - 31251 2023.10

Photothermal therapeutic ability of copper open-shell nanostructures that are effective in the second biological transparency window based on symmetry breaking-induced plasmonic properties Reviewed

Kosuke Sugawa, Arisa Suzuki, Jotaro Honda, Taiku Yabuki, Yutaro Hayakawa, Masato Furuya, Hiroki Ikake, Hironobu Tahara, Tsuyoshi Kimura, Yasuhiro Kosuge, Satoshi Kurumi, Tsuyoshi Akiyama, Kouichi Takasea and Joe Otsuki

Journal of Materials Chemistry B 11 6837 - 6852 2023.8

Photocurrent Generation Properties of Half-Photocell Consisting of Electropolymerized Hierarchical Polythiophene Thin Films as Photoexciting Electron Donor and C60 as Electron Acceptor Reviewed

Kengo Kanbe, Tsuyoshi Akiyama, Takeo Oku

ECS Advances 2 020505 2023.6

Dye fluorescence enhancement by plasmonic nanostructured gold–titania film composites obtained by the combination of electrodeposition and surface sol-gel process Reviewed

Akiyama T., Aiba K., Otsuki T., Koyama N., Oku T., Sugawa K., Yamada S.

Journal of Sol-Gel Science and Technology 104 ( 3 ) 666 - 672 2022.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Sol-Gel Science and Technology

Plasmonic nanostructured gold–titania film composites were fabricated and evaluated their dye fluorescence enhancement properties. The plasmonic nanostructured gold was fabricated by electrodeposition. The ragged and overlapped particle structures were observed in the nanostructured-gold. The sizes of the deposited structures varied from several tens of nanometers to the submicrometer level. Titania thin films were prepared via the self-assembly of thiols on the nanostructured-gold and a surface sol-gel process. Formation of the plasmonic nanostructured gold–titania film composites was confirmed by X-ray photoelectron spectroscopy. Porphyrin dye was deposited as a fluorescent probe on the outermost layer of the titania film. The degrees of ground-state excitation of porphyrin dye by plasmonic electric fields were evaluated in various composites with different numbers of repetitions (1–40 times) of surface sol-gel processes for titania layer formation. The enhancement ratios of porphyrin varied with the thickness of the titania film, which functioned as a spacer. In particular, apparent fluorescence enhancement of the porphyrin dye was observed at wavelengths longer than 550 nm using the composites. [Figure not available: see fulltext.].

DOI： 10.1007/s10971-022-05828-7

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Electrochemical fabrication of hierarchical thin films consisting of different polythiophenes and change in photoelectric conversion properties with film thickness Reviewed

Kanbe K., Akiyama T., Kumagawa Y., Hirata S., Tsujiai T., Oku T.

Japanese Journal of Applied Physics 61 ( 6 ) 2022.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

Hierarchical polybithiophene/poly(3,4-ethylenedioxythiophene) films with polybithiophene layers of various thicknesses were prepared on an indium tin oxide glass transparent electrode by sequential electrochemical polymerization. In the presence of methyl viologen as a sacrificial electron acceptor, cathodic photocurrents were generated under monochromatic light irradiation. The irradiation light wavelength dependence of the incident photon-To-electron conversion efficiency changed drastically with the thickness of the polybithiophene layer. The main reason for the change in the photoelectric conversion properties was light absorption by the polybithiophene layer.

DOI： 10.35848/1347-4065/ac6408

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Preparation of silver-nanoparticle-loaded C60-ethylenediamine adduct microparticles and their application to photoelectric conversion Reviewed

Matsuoka K.I., Banya S., Hosoi I., Koyama N., Suzuki K., Jeyadevan B., Oku T., Fujita K., Yamada S., Akiyama T.

Applied Physics Express 14 ( 6 ) 2021.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics Express

We report here new types of suprastructure products consisting of C60-ethylenediamine microparticles and silver nanoparticles that were loaded onto the surfaces of the microparticles by electrostatic adsorption. The suprastructure products could be deposited on the surface of an indium tin oxide electrode by electrostatic deposition. These modified electrodes generated cathodic photocurrents in the presence of ascorbic acid and oxygen. The photocurrent generation behavior implies an ensemble of the electron-transfer processes of silver-nanoparticle-mediated electron transfer acting in the cathodic direction and plasmon-induced charge separation acting in the anodic direction.

DOI： 10.35848/1882-0786/abff9f

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Fabrication and surface-enhanced Raman scattering properties of thin-film assemblies of classified silver nanoparticles Reviewed

Koyama N., Akiyama T., Oku T.

Japanese Journal of Applied Physics 60 ( 2 ) 2021.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

The classification of citrate-stabilized silver nanoparticles was performed by a combination of centrifugation and redispersion. Repeated classification processes led to a convergence of similarly sized nanoparticles, which in turn decreased their size deviations. This tendency corresponds to the change in the zeta potentials of the silver nanoparticles. Densely packed sphere-shaped silver nanoparticle thin-film assemblies were fabricated by a liquid-liquid interfacial precipitation process using appropriately classified silver nanoparticles. The surface-enhanced Raman scattering efficiencies of these thin-film assemblies of silver nanoparticles were varied and could be optimized by the number of classification processes.

DOI： 10.35848/1347-4065/abd36c

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One-pot synthesis of visible-light-responsive titanium oxide photocatalyst with embedded silver nanoparticles Reviewed

Higashida S., Yoshida S., Koyama N., Suzuki K., Oku T., Akiyama T.

Journal of Sol-Gel Science and Technology 2021.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Sol-Gel Science and Technology

A composite powder of titanium oxide and silver nanoparticles was obtained by using a combination of the sol–gel process and ultraviolet light induced reduction of silver ion via one-pot synthesis. After calcination, silver nanoparticles were embedded in an anatase crystalline titanium oxide matrix, as revealed by transmission electron microscopy. Silver nanoparticles with sizes ranging from a few nanometers to several tens of nanometers were observed in the titanium oxide matrix. The crystalline titanium oxide-silver nanoparticle composite powder decomposed the methylene blue dye upon visible light irradiation. The decomposition rate of the dye using the crystalline titanium oxide-silver nanoparticle composite powders was considerably faster than that in the case of the reference titanium oxide powder without silver nanoparticle. Thus, plasmon-induced charge separation from the silver nanoparticle to the conduction band of titanium oxide expected to occur, and holes on silver nanoparticles or induced active oxygen decomposed methylene blue in the solution or adsorbed on titanium oxide. [Figure not available: see fulltext.]

DOI： 10.1007/s10971-021-05510-4

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Open-shell singlet diradicaloid difluoreno[4,3-b:3',4'-d]furan and its radical cation and dianion Reviewed

Mori S., Akita M., Suzuki S., Asano M.S., Murata M., Akiyama T., Matsumoto T., Kitamura C., Kato S.I.

Chemical Communications 56 ( 44 ) 5881 - 5884 2020.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Chemical Communications

Difluoreno[4,3-b:3',4'-d]furan (DFFu) was preparedviaa short, scalable, multi-step synthesis, and characterized by crystallography, spectroscopic measurements, and theoretical calculations. Even though the results revealed an open-shell singlet diradical character, DFFu is stable under ambient conditions. The radical cationic and dianionic species of DFFu were also synthesized and characterized.

DOI： 10.1039/d0cc01638a

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Fabrication and surface-enhanced Raman scattering properties of two- dimensional gold and silver nanoparticle mixed assemblies by liquid–liquid interfacial precipitation method Reviewed International journal

Natsuki Koyama, Shoto Banya, Tsuyoshi Akiyama, Kosuke Sugawa, Takeo Oku

Applied Physics Express 13 055001-1 - 055001-4 2020.4

Language：English Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Applied Physics

We fabricated two-dimensional assemblies of gold and silver nanoparticles on polycation coated substrates by a liquid–liquid interfacial precipitation method. The assembling of the metal nanoparticles on the substrate was evaluated by absorption spectroscopy and scanning electron microscopy. Raman scattering signals of Rhodamine 6G were detected on the metal nanoparticle-modified substrates. In particular, the intensities of the Raman scattering signals of the mixed gold and silver nanoparticle-modified substrates were larger than the intensities expected from a simple proportional sum of the Raman scattering signals of the individual assembly films composed of only gold or silver nanoparticles.

DOI： 10.35848/1882-0786/ab8965

Fabrication and photocatalytic behavior of titanium oxide–gold nanoparticles composite ultrathin films prepared using surface sol–gel process Reviewed

Mitsukawa S., Akiyama T., Hinoue M., Shima K., Takishita T., Higashida S., Koyama N., Sugawa K., Ogawa M., Sakaguchi H., Oku T.

Journal of Sol-Gel Science and Technology 2020.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Sol-Gel Science and Technology

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. Abstract: Ultrathin films consisting of titanium oxide and gold nanoparticles were prepared using a combination of the surface sol–gel process and liquid/liquid interfacial precipitation. The composite films had a titanium oxide/gold nanoparticle layer/titanium oxide film structure, comprising a gold nanoparticle thin-film layer sandwiched within titanium oxide films of nanometer-order thickness. Upon heating the titanium oxide–gold nanoparticle composite films to 450 °C, they underwent a phase change from the amorphous to the anatase phase, which was confirmed via Raman scattering analysis. It was observed that, even after heating, the plasmonic absorption band due to the presence of gold nanoparticles was maintained in the composite films. The photocatalytic degradation efficiencies of methylene blue dye were evaluated in films under 520 nm light irradiation. The results suggested that the sandwich-like structure of this titanium oxide/gold nanoparticle layer/titanium oxide is promising for the visible-light-induced degradation of methylene blue dye. [Figure not available: see fulltext.]

DOI： 10.1007/s10971-019-05214-w

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Infrared wire-grid polarizer with an ultrathin photoimprinted polymer film Reviewed

Itsunari Yamada, Tsuyoshi Akiyama

Optical Engineering 2019.5

Development of fullerene thin-film assemblies and fullerene-diamine adducts towards practical nanocarbon-based electronic materials Reviewed

Akiyama T.

Bulletin of the Chemical Society of Japan 92 ( 7 ) 1181 - 1199 2019.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Bulletin of the Chemical Society of Japan

Fullerenes are attractive spherical aromatic molecules with good electron acceptor capabilities and good utility as an n-type organic semiconductor. By using a fullerene-amine addition reaction, it was possible to fabricate ultrathin-film assemblies of fullerene on the surface of substrates, which were confirmed by photoelectric conversion applications. Addition reactions between fullerenes and primary aliphatic diamines can also occur to form insoluble adduct particles consisting of fullerenes and diamines. In one example, C -ethylenediamine adduct particles can be solubilized by addition of alkylacid chloride to residual amino groups of the adducts. Spin-coated or dip-coated thin-films of C -ethylenediamine adducts from their solutions are useful as n-type organic semiconductors which was confirmed with solar cell application. In this account, the history of the fabrication and application of fullerene thin-film assemblies and fullerene-diamine adducts using the fullerene-amine addition reaction is introduced and summarized from the early studies to more recent developments. 60 60

DOI： 10.1246/bcsj.20190079

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Fabrication and photovoltaic properties of an invert-type organic thin-film solar cells incorporation of phosphorescent material into electron transport layer Reviewed International journal

Yusuke Matsumiya, Tsuyoshi Akiyama, Itsunari Yamada, Takeo Oku

AIP Conference Proceedings 2019.1

Precise Control of Localized Surface Plasmon Wavelengths Is Needed for Effective Enhancement of Triplet−Triplet Annihilation- Based Upconversion Emission International journal

Shota Jin, Kosuke Sugawa, Naoto Takeshima, Hironobu Tahara, Shuto Igari, Satoshi Yoshinari, Yuri Kurihara, Shiryu Watanabe, Masami Enoki, Kenta Sato, Wataru Inoue, Kyo Tokuda, Tsuyoshi Akiyama, Ryuzi Katoh, Kouichi Takase, Hiroaki Ozawa, Toshiya Okazaki, Takayuki Watanabe, and Joe Otsuki

ACS Photonics 2018.11

Time-dependent non-linear size change of C<inf>60</inf>-ethylenediamine adduct particles in formation process Reviewed

Akiyama T., Ono Y., Miyamura H., Saito J., Kimura K., Higashida S., Oku T.

Journal of Nanoparticle Research 20 ( 9 ) 2018.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Nanoparticle Research

© 2018, Springer Nature B.V. Addition reaction between C60and ethylenediamine occurred at room temperature in an ambient condition. C60-ethylenediamine adduct particles were prepared by mixing toluene solutions of C60and ethyelenediamine. Average diameter of the C60-ethylenediamine adduct particles was changed non-linearly according to the reaction time, which were observed using transmission electron microscopy. Early stage of the reaction, the diameter of the adduct particles was changed from about 250 to about 430 nm. Then, the size of the adduct particles was converged to about 300 nm. During this addition reaction, the crystalline sizes of adduct particles were constant about 2–3 nm, regardless of the sizes of the adduct particles, which were determined by X-ray diffraction measurement. [Figure not available: see fulltext.].

DOI： 10.1007/s11051-018-4353-9

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Insertion effect of spin-coated films of C60-ethylenediamine adduct on organic thin-film solar cells Reviewed

Atsutaka Yamada, Daisuke Izumoto, Tsuyoshi Akiyama*, Katsuhiko Fujita, Atsushi Suzuki, and Takeo Oku

AIP Conference Proceedings 1929 020020-1 - 020020-5 2018.1

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Papers - AKIYAMA Tsuyoshi