Tokyo University of Science, Yamaguchi
Onoda, Japan

Tokyo University of Science, Yamaguchi is a private university in San'yō-Onoda, Yamaguchi, Japan. The school was first established as a junior college in 1987. It became a four-year college in 1995. Wikipedia.

Time filter
Source Type

Zhang H.,Wuhan University of Science and Technology | Toshima N.,Tokyo University of Science, Yamaguchi | Toshima N.,Japan Science and Technology Agency
Journal of Colloid and Interface Science | Year: 2013

Integration of 'green chemistry' principles into nanotechnology is one of the key issues in nanoscience research today. In this work, three series of Au/Pt bimetallic nanoparticles (BNPs) with a structure of Au-rich core/Pt-rich shell were prepared using simultaneous reduction with rapid injection of NaBH4, simultaneous reduction with dropwise addition of NaBH4, and simultaneous alcohol reduction. The effects of particle size, electronic structure and composition upon the catalytic activities for aerobic glucose oxidation of the BNPs were also investigated. Catalytically highly active PVP-protected Au/Pt BNPs of about 1.5nm in diameter were synthesized using simultaneous reduction with rapid injection of NaBH4. The prepared colloidal Au/Pt BNPs catalysts possessed a high and durable catalytic activity for aerobic glucose oxidation, which were stably kept for more than 2months under ambient conditions. The maximum activities normalized with Au content of the BNPs with Au/Pt atomic ratio of 4/6 were nearly 10 times higher than that of Au nanoparticles (NPs) with nearly the same particle size. The higher catalytic activity of the prepared Au/Pt BNPs than the Au NPs can be ascribed to the following two factors; (1) the small average diameter, usually about 1.5nm, and (2) the presence of negatively charged Au and Pt atoms due to electron donation from protecting polymer (PVP: poly(N-vinyl-2-pyrrolidone)) by electronic charge transfer effects upon catalytically active sites. In contrast, the Au/Pt BNPs, synthesized by alcohol reduction and dropwise addition of NaBH4 into the starting solution and having the large mean particle sizes, showed a low catalytic activity. © 2012 Elsevier Inc.

Zhang H.,Wuhan University of Science and Technology | Toshima N.,Tokyo University of Science, Yamaguchi | Toshima N.,Japan Science and Technology Agency
Catalysis Science and Technology | Year: 2013

Clean syntheses, based on the use of natural renewable reagents, in water solution under mild conditions, are highly desirable processes and often the catalytic step is a key factor for the successful application. Gold (Au) and Au-containing bimetallic and trimetallic nanoparticles (BNPs and TNPs) have been extensively investigated as the promising catalysts for the clean syntheses of gluconic acid, which is an important intermediate in the field of food industry and pharmaceutical applications, by glucose oxidation using atmospheric oxygen or hydrogen peroxide as an oxidant. With significant research efforts, a lot of new efficient catalytic systems, based on the peculiar properties of nanometric Au NPs, have been developed for aerobic glucose oxidation. In this minireview, we provide an overview of the recent development of Au-containing BNPs and TNPs for the improved catalytic performance toward glucose oxidation. This journal is © The Royal Society of Chemistry 2013.

Zhang H.,Wuhan University of Science and Technology | Toshima N.,Tokyo University of Science, Yamaguchi | Toshima N.,Japan Science and Technology Agency
Applied Catalysis A: General | Year: 2012

Catalytically highly active PVP-protected AgAu bimetallic nanoparticles (BNPs) less than 2 nm in diameter were fabricated by simultaneous physical mixture of aqueous dispersions of Au clusters with Ag+ ions. The prepared AgAu BNPs, the dispersion of which was stably kept for more than 2 months under ambient conditions, were characterized by UV-vis, ICP, HR-TEM, and EDS in HR-STEM. The prepared BNP colloidal catalysts possessed a high activity for aerobic glucose oxidation. The highest activity of 3.77 mol-glucose s -1 mol-metal-1 was observed for the BNPs prepared with Ag/Au atomic ratio of 2/8, which was more than two times higher than that of Au nanoparticles with nearly the same particle sizes. © 2012 Elsevier B.V.

Zhang H.,Tokyo University of Science, Yamaguchi | Zhang H.,Japan Science and Technology Agency | Watanabe T.,Tokyo University of Science, Yamaguchi | Okumura M.,Japan Science and Technology Agency | And 5 more authors.
Nature Materials | Year: 2012

Catalysis using gold is emerging as an important field of research in connection with green chemistry. Several hypotheses have been presented to explain the markedly high activities of Au catalysts. So far, the origin of the catalytic activities of supported Au catalysts can be assigned to the perimeter interfaces between Au nanoclusters and the support. However, the genesis of the catalytic activities of colloidal Au-based bimetallic nanoclusters is unclear. Moreover, it is still a challenge to synthesize Au-based colloidal catalysts with high activity. Here we now present the crown-jewel concept (Supplementary Fig. S1) for preparation of catalytically highly Au-based colloidal catalysts. Aug Pd colloidal catalysts containing an abundance of top (vertex or corner) Au atoms were synthesized according to the strategy on a large scale. Our results indicate that the genesis of the high activity of the catalysts could be ascribed to the presence of negatively charged top Au atoms.

Adachi T.,Tokyo University of Science, Yamaguchi | Hoshi H.,Tokyo University of Science, Yamaguchi
Materials Letters | Year: 2013

Pt and carbon electrodes for dye-sensitized solar cells (DSSCs) were prepared. An activated Pt electrode, carbon electrodes based on graphite and activated carbon, and Pt/carbon electrodes were prepared by wet processes. The structures of the electrodes were studied by a scanning electron microscopy. For the Pt/carbon electrodes, it was shown that Pt nanoparticles are effectively deposited over the surface of carbon materials. Using these counter electrodes, DSSCs were fabricated and their photocurrent-voltage characteristics were studied. The performance of a Pt/activated carbon electrode was superior to that for the activated Pt electrode. There is a possibility that Pt consumption can be reduced by using the Pt/activated carbon electrode. © 2012 Published by Elsevier B.V.

Toshima N.,Tokyo University of Science, Yamaguchi
Macromolecular Symposia | Year: 2011

Here we applied metal nanoparticles as a dopant of liquid crystals. Since liquid crystal molecules are self-assembled, it is not so easy to disperse metal nanoparticles in liquid crystal media. We first prepared metal nanoparticles protected by liquid crystal molecules by reduction of metal ions in the presence of liquid crystal molecules. This liquid crystal molecule-protected metal nanoparticles can be easily dispersed in liquid crystal media to fabricate liquid crystal sol containing metal nanoparticles. A simple liquid crystal molecule, 4′-pentylbiphenyl-4-carbonitrile (abbreviated as 5CB) was used in the present experiments at first. 5CB sol containing metal nanoparticles could construct novel twisted nematic liquid crystal devices (TN-LCDs), which revealed the electrooptic properties depending on the kind of metal of nanoparticles. During the experiments we discovered that 5CB-protected metal nanoparticles could move in liquid crystal media by applying the voltage. This phenomenon is inconvenient for liquid crystal displays, especially those driven by a matrix of thin-film transistors (TFTs). In order to avoid this phenomenon, we prepared polymer-protected metal nanoparticles and applied them to liquid crystal devices, which provided good performance as the devices, i.e., low driving voltage, rapid response at low temperature, and so on. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yoshida A.,Tokyo University of Science, Yamaguchi | Toshima N.,Tokyo University of Science, Yamaguchi
Journal of Electronic Materials | Year: 2014

We report the thermoelectric properties of organic-inorganic hybrid thin films composed of conductive polymer, poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS), and inorganic gold nanomaterials. Two kinds of material with different shapes, namely rod-shaped gold nanorods (AuNRs) and spherical gold nanoparticles (AuNPs), were used in this study. The PEDOT:PSS/AuNR hybrid films showed an enhancement in electrical conductivity (σ ≈ 2000 S cm-1) and concurrently a decrease in the Seebeck coefficient (S ≈ 12 μV K-1) with increase in the AuNR concentration. This behavior indicates the presence of the hybrid effect of AuNR on the thermoelectric properties. From scanning electron microscopy (SEM) observation of the highly concentrated PEDOT:PSS/AuNR hybrid films, the formation of a percolated structure of AuNRs was confirmed, which probably contributed to the large enhancement in σ. For the highly concentrated PEDOT:PSS/AuNP films, a dense distribution of AuNPs in the film was also observed, but this did not lead to a major change in the σ value, probably due to the less conductive connections between NPs. This suggests that one-dimensional particles with larger aspect ratio (rods and wires) are favorable nanocomponents for development of highly conductive hybrid materials. © 2013 TMS.

Toshima N.,Tokyo University of Science, Yamaguchi | Jiravanichanun N.,Tokyo University of Science, Yamaguchi
Journal of Electronic Materials | Year: 2013

Thermoelectric properties of hybrid films composed of poly(3,4- ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) and gold nanoparticles (AuNPs) stabilized with 3-mercaptopropinoic acid (Au-MPA NPs) and 6-mercaptohexanoic acid (Au-MHA NPs) were investigated. Several factors such as the size and content of the AuNPs and the chain length of the NP stabilizer were found to influence the thermoelectric properties of the hybrid film. The Seebeck coefficient can be raised by varying the size of the Au-MPA NPs or the content of Au-MHA NPs. The enhancement in the Seebeck coefficient is suggested to be a result of reduced carrier concentration due to the increased number of AuNPs. This could be the first report on the fact that AuNPs enhance the Seebeck coefficient in PEDOT/PSS hybrid films. © 2013 TMS.

Toshima N.,Tokyo University of Science, Yamaguchi
Pure and Applied Chemistry | Year: 2013

Energy has emerged as a strategic priority not only in research but also in all aspects of human lives. Most worldwide problems could be solved if energy were plentiful. In order to solve the energy problem, the following methods could be applicable: the creation of electricity from renewable energy resources, increase in conversion efficiency from fossil fuels to electricity, recovery of electricity from exhaust heat energy, and reduction of energy consumption. Nanotechnologies have already shown good promise in addressing and offering solutions in these priority areas. Here, we have demonstrated the application of metal nanoparticles (NPs) to electrocatalysts for the polyelectrolyte fuel cell (increase in conversion efficiency) and to additives to form hybrids with organic thermoelectric materials of conducting polymers (recovery of energy from exhaust heat). Thus, Pt monometallic and AuPt bimetallic NPs were used for electrocatalysts with high performance, and Pt and Au NPs were applied to hybrid thermoelectric materials to fabricate hybrid films with increasing thermoelectric performance for conversion of the exhaust heat near room temperature. © 2013 IUPAC.

Toshima N.,Tokyo University of Science, Yamaguchi
Kobunshi | Year: 2014

Thermal management is very important for the life of human beings. In fact most energy content of fossil fuel is lost as waste heat without use. Organic thermoelectric materials can be used for recovering such electric energy from waste heat in a low grade. Here we review recent progress in the development of organic thermoelectric materials. The research on organic thermoelectric materials started in 1999 by using conducting polyaniline. Relatively good thermoelectric performance (ZT=0.1) was achieved for stretched polyphenylenevinylene derivatives in 2007. Now polythiophene derivatives (PEDOT) with high electrical conductivity were found to have a high thermoelectric performance by controlling the oxidation level and dopant concentration. Much effort has been concentrated on the development of organic-inorganic hybrid thermoelectric materials, too. Hybridization of PEDOT with semiconducting and metallic nanomaterials as well as multi-walled, single-walled and double-walled carbon nanotubes, was extensively investigated. The hybrid materials of PEDOT and double-walled carbon nanotubes was found to have the highest performance at the present. © 2014 The Society of Polymer Science, Japan.

Loading Tokyo University of Science, Yamaguchi collaborators
Loading Tokyo University of Science, Yamaguchi collaborators