Yoshimoto Abe
Tokyo University of Science
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Publication
Featured researches published by Yoshimoto Abe.
Chemical Physics Letters | 1997
Kazuhiro Sayama; Rintaro Yoshida; Hitoshi Kusama; Kiyomi Okabe; Yoshimoto Abe; Hironori Arakawa
H2 and O2 gas evolution in a stoichiometric ratio (H2:O2 = 2:1) has been realized over a RuO2-WO3 photocatalyst suspended in an aqueous solution containing an Fe3+/Fe2+ redox system. O2 gas was evolved and Fe3+ ions were reduced to Fe2+ ions on a WO3 powder catalyst excited by visible light at less than 460 nm and UV light. Fe2+ ions excited by UV light at less than 280 nm were oxidized back to Fe3+ ions with the evolution of H2 gas. The reaction mechanism is similar to the Z-scheme in photosynthesis.
Chemical Communications | 2000
Kazuhiro Sayama; Kohjiro Hara; Nahoko Mori; Makoto Satsuki; Sadaharu Suga; Shingo Tsukagoshi; Yoshimoto Abe; Hideki Sugihara; Hironori Arakawa
Porous TiO2 electrodes sensitized using merocyanine dyes containing a carboxyl group and a long alkyl chain, in particular 3-carboxymethyl-5-[2-(3-alkyl-2-benzothiazoli- nyldene)ethylidene]-2-thioxo-4-thiazolidinone, showed remarkably high solar–energy efficiency (4.2%, AM-1.5, 100 mW cm−2).
Chemical Communications | 2003
Kazuhiro Sayama; Atsushi Nomura; Zhigang Zou; Ryu Abe; Yoshimoto Abe; Hironori Arakawa
The nanocrystalline BiVO4 film electrode on conducting glass showed an excellent efficiency (IPCE = 29% at 420 nm) for the decomposition of water under visible light.
Journal of Polymer Science Part A | 1999
Norihiro Takamura; Takahiro Gunji; Hideaki Hatano; Yoshimoto Abe
Polymethylsilsesquioxane (PMS) and polyvinylsilsesquioxane (PVS) were prepared by acid-catalyzed controlled hydrolytic polycondensation of methyl- and vinyltrimethoxysilane (MTS and VTS), respectively. The spinnabilities and molecular weights of polysilsesquioxanes were easily controlled by the reaction conditions, such as the molar ratios of water, hydrochloric acid, and methanol to MTS or VTS; nitrogen flow rate; temperature; and stirring rate. PMS and PVS showed spinnability of more than 200 cm when their molecular weights were up to 42,000 (PMS) and 19,000 (PVS) Mw. Transparent, colorless, and flexible films of 0.02–0.10 mm thick were prepared by casting a 20 wt % acetone–methanol (V/V = 1) solution of PMS and PVS on a polymethylpentene shale, followed by heating at 80°C for 3 weeks. The tensile strength of the films, approximately 26 (PMS) and 17 (PVS) MPa, was found to be correlated with the structure of the polysilsesquioxanes. The surface contact angle and electroconductivity of films were also measured.
Chemical Communications | 2001
Kazuhiro Sayama; Kazuaki Mukasa; Ryu Abe; Yoshimoto Abe; Hironori Arakawa
The stoichiometric splitting of water into H2 and O2 (H2/O2 = 2) under visible light irradiation (lambda > 420 nm) took place for the first time using a mixture of Pt-WO3 and Pt-SrTiO3 (Cr-Ta-doped) photocatalysts and an IO3-/I- shuttle redox mediator.
Journal of Materials Science | 1998
Yoshimoto Abe; Takahiro Kudo; Hiroshi Tomioka; Takahiro Gunji; Yukinori Nagao; Takahisa Misono
A one-pot reaction of zirconium oxychloride octahydrate (ZOC) with ethyl acetoacetate (Hetac) in the presence of triethylamine was investigated. The reaction was carried out in molar ratios of Hetac/ZOC=1.0, 1.5, 2.0 to give highly viscous solutions with good spinnability and stability to self-condensation. Polyzirconoxanes (PZOs) were isolated as white powders by reprecipitation of the solutions with tetrahydrofuron (THF)-hexane that were soluble in acetone, methanol and THF. The molecular weight of PZO was Mn=1000–2000, and was dependent on the molar ratio and the reaction time. Dry spinning of the solution (Hetac/ZOC=1.5) containing 3mol% tris(acetylacetonato)yttrium [Y(acac)3] gave continuous precursor fibres (3.0Y–PZO). Yttria stabilized zirconia fibres of 12–18 μm diameter with a tensile strength of 1.4GPa were obtained by heat treatment of the 3.0Y–PZO at 1100 or 1200 °C. The fibre consisted of submicrometre-sized particles of tetragonal crystallites.
Applied Organometallic Chemistry | 1998
Yoshimoto Abe; Yuki Honda; Takahiro Gunji
The preparation of organic‐inorganic polymer hybrids consisting of carbon‐carbon and siloxane chains was investigated by radical polymerization of 3-methacryloxypropyltrimethoxysilane (MAS) followed by acid-catalyzed hydrolytic polycondensation. The condensation of poly(3-methacryloxypropyltrimethoxysilane) (S-PMA) of various molecular weights Mn = 830‐12000 prepared by polyaddition provided transparent and flexible free-standing hybrid gel films. The mechanical properties of these films were highly dependent on the carbon‐carbon chain length: with an increase in the carbon‐ carbon chain length, the elasticity of gel films increased, while the tensile strength and Young’s modulus decreased. Hydrolyzability of S-PMA decreased with an increase in the carbon‐carbon chain length, resulting in the formation of rubber-like films with flexibility. # 1998 John Wiley & Sons, Ltd.
Journal of Non-crystalline Solids | 1988
Yoshimoto Abe; N. Sugimoto; Yukinori Nagao; Takahisa Misono
Abstract The preparation of monolithic gels as a precursor for SiO 2 TiO 2 glasses via polytitanosiloxanes was investigated. The gels were obtained from polytitanosiloxanes formed by condensation polymerization of titanium chelates and silicic acid. Silicic acid was extracted with tetrahydrofuran from an aqueous sodium metasilicate solution neutralized with hydrochloric acid. Titanium chelates used were bis(acetylacetonato)titanium diisopropoxide (ATP) and bis(ethyl acetoacetato)titanium diisopropoxide (ETP). Monolithic gels with a TiO 2 content of less than 20 mol% were formed by the reaction of silicic acid with ATP, whereas the reaction with ETP provided transparent monolithic SiO 2 TiO 2 gels of 5.7–94 mol% TiO 2 . Heat treatment of the gels gave monolithic SiO 2 TiO 2 glasses.
Journal of Non-crystalline Solids | 2000
Yoshimoto Abe; Keiko Kagayama; Norihiro Takamura; Takahiro Gunji; Toshio Yoshihara; Nobuko Takahashi
Abstract Coating characteristics of polysilsesquioxanes with various molecular weights prepared by acid-catalyzed hydrolytic polycondensation of trimethoxysilane RSi(OMe) 3 (R=Me, Vinyl) were investigated in relation to the structure. Homogeneous, smooth and crack-free coating films of thickness from 0.25 to 0.95 μm were prepared by 1–10 times dip-coating of an acetone–methanol solution of polysilsesquioxanes on polymer, metal and ceramic substrates. Their mechanical, optical and electrical properties were investigated. The adhesion and hardness of coating films showed the maximum values based on the evaluation of JIS (Japanese Industrial Standard) K5400. They also increased with increasing molecular weight, T 3 unit of polysilsesquioxanes, heating time and sintering temperature. The coating films were revealed to be thermally stable on heating to 800°C. The refractive index of coating films decreased gradually with increasing temperatures up to about 800°C. The transmittance of coating films was higher than 98% at 500 nm. The surface resistivity of the coating films increased with the increase of sintering temperature.
Journal of Non-crystalline Solids | 1989
Takahiro Gunji; Yukinori Nagao; Takahisa Misono; Yoshimoto Abe
Abstract Continuous oxide fibers SiO 2 TiO 2 were obtained by drying spinning of precursor fibers from polytitanosiloxanes (PTS) prepared by the reaction of silicic acid (SA) with titanium chelate (PTP) in the molar ratio of SA/PTP = 0.5 (PTS-0.5) and 1.0 (PTS-1). The precursor fibers, being golden-yellow, turned black and then white on pyrolysis. The fibers underwent decomposition with removal of organic groups to form black fibers at 200–500°C and white fibers at about 1000°C. Crystallization of TiO 2 took place at 850°C (PTS-0.5) and 950°C (PTS-1). Rearrangement of SiOTi linkage of the polymer back-bone into SiOTi m ay lead to the formation of TiO 2 clusters and subsequent crystallization of TiO 2 .
Collaboration
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National Institute of Advanced Industrial Science and Technology
View shared research outputsNational Institute of Advanced Industrial Science and Technology
View shared research outputsNational Institute of Advanced Industrial Science and Technology
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