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Gao L.,Kyushu University | Kojima K.,Nissan Chemical Industry Ltd. | Nagashima H.,Kyushu University | Nagashima H.,Japan Science and Technology Agency
Tetrahedron | Year: 2015

Abstract Hyperbranched polystyrene bearing ammonium salts (HPS-NR3+Cl-) behaves as an excellent stabilizer of ruthenium, rhodium, iridium, palladium, and platinum nanoparticles from 1 to 3 nm in size uniformly dispersed in the polymer matrix. The catalytic performance of the resulting metal-polymer composites, M@HPS-NR3+Cl-, is dependent on the metal. This dependence was investigated by assessing the hydrogenation of alkenes and arenes. The utility of M@HPS-NR3+Cl- as reusable catalysts in aqueous/organic biphasic systems was demonstrated by examining the catalysis of the hydrogenation of aromatic compounds containing various functional groups by Ru@HPS-NR3+Cl-. © 2015 Elsevier Ltd. Source


Chaiyanurakkul A.,Mahidol University | Gao L.,Kyushu University | Nishikata T.,Kyushu University | Kojima K.,Nissan Chemical Industry Ltd. | And 2 more authors.
Chemistry Letters | Year: 2014

Platinum nanoparticles dispersed in the ammonium salts of hyperbranched polystyrene, Pt@HPS-NR3Cl, catalyzed the hydrogenation of ketones and aldehydes when water was used as the solvent without any coexisting organic solvents. The significant increase in the reaction rate was observed when an organodispersible Pt@HPS-N+(C8H17)3Cl-(1a) was used as the catalyst, whereas catalyst recycling was achieved with water-dispersible Pt@HPS-N+(C4H9)3Cl-(1b). © 2014 The Chemical Society of Japan. Source


Sanden S.,Abo Akademi University | Sanden S.,Tokyo University of Science | Akitsu K.,Tokyo University of Science | Torngren B.,Abo Akademi University | And 7 more authors.
Journal of Physical Chemistry C | Year: 2015

Plasmon-enhanced polymer-sensitized solar cells were manufactured by incorporating core-shell Au@SiO2 particles into the TiO2 photoanode. The plasmon-enhanced solar cells showed an improved performance due to an increased jsc leading to a higher power conversion efficiency compared to reference devices without Au@SiO2 particles, and a small increase in the Voc was also observed. The incident photon to current efficiency (IPCE) spectra showed that an enhanced absorption in the plasmon devices was the cause of the improved performance. By electrodynamics modeling of the Au@SiO2 particles, we conclude that a combination of scattering and near-field enhancement is the cause of the increased efficiency in these plasmon-enhanced solar cells. © 2015 American Chemical Society. Source


Gao L.,Kyushu University | Nishikata T.,Kyushu University | Kojima K.,Nissan Chemical Industry Ltd. | Chikama K.,Nissan Chemical Industry Ltd. | Nagashima H.,Kyushu University
Chemistry - An Asian Journal | Year: 2013

Gold nanoparticles (1 nm in size) stabilized by ammonium salts of hyperbranched polystyrene are prepared. Selection of the R groups provides access to both water- and organo-dispersible gold nanoparticles. The resulting gold nanoparticles are subjected to studies on catalysis in solution, which include reduction of 4-nitrophenol with sodium borohydride, aerobic oxidation of alcohols, and homocoupling of phenylboronic acid. In the reduction of 4-nitrophenol, the catalytic activity is clearly dependent on the size of the gold nanoparticles. For the aerobic oxidation of alcohols, two types of biphasic oxidation are achieved: one is the catalyst dispersing in the aqueous phase, whereas the other is in the organic phase. The catalysts are reusable more than four times without loss of the catalytic activity. Selective synthesis of biphenyl is achieved by the homocoupling of phenylboronic acid catalyzed by organo-dispersible gold nanoparticles. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Nyman M.,Abo Akademi University | Akitsu K.,Tokyo University of Science | Otani N.,Nissan Chemical Industry Ltd. | Matsumura M.,Nissan Chemical Industry Ltd. | And 3 more authors.
Synthetic Metals | Year: 2013

Using charge extraction techniques we have clarified the charge transport properties of novel polythiophene derivatives intended for use as sensitizers in polymer sensitized solar cells. The polymers are of low molecular weight in order to enable penetration into a mesoporous titanium dioxide film. Hydrophilic anchoring units are attached to the thiophene ring to facilitate attachment of the polymer to the titanium dioxide. The hole transporting properties were determined in order to clarify the possibility of using the polymers both as sensitizers and hole transporting material in a hybrid type device. We found that the mobilities are in the range of 1-4 × 10-8 cm 2/(V s). The low mobility is compensated by very long charge carrier lifetimes in the order of 100 ms resulting in a very promising charge carrier drift distance of 1 μm. © 2013 Elsevier B.V. All rights reserved. Source

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