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Hokkaido University Collection of Scholarly and Academic Papers (135.521 recursos)

HUSCAP (Hokkaido University Collection of Scholarly and Academic Papers) contains peer-reviewed journal articles, proceedings, educational resources and any kind of scholarly works of Hokkaido University.

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Mostrando recursos 1 - 20 de 169

  1. Influence of an Electronic Structure of N-TiO2 on Its Photocatalytic Activity towards Decomposition of Acetaldehyde under UV and Fluorescent Lamps Irradiation

    Tryba, Beata; Wozniak, Magdalena; Zolnierkiewicz, Grzegorz; Guskos, Nikos; Morawski, Antoni; Colbeau-Justin, Christophe; Wrobel, Rafal; Nitta, Akio; Ohtani, Bunsho
    The electronic structure of N-TiO2 samples prepared by a sol-gel method was investigated by EPR (Electronic Paramagnetic Resonance) measurements and the energy-resolved distribution of electron traps. In EPR spectra, some of the resonance lines assigned to paramagnetic species of nitrogen and Ti3+ were detected. Sample prepared at 300 degrees C revealed the highest intensity line of the nitrogen paramagnetic centers, whereas that prepared at 400 degrees C showed a paramagnetic line for Ti3+. Measurements of the electron trap distribution showed higher density of electron traps for sample prepared at 400 degrees C than that at 300 degrees C. Sample prepared...

  2. A coordination strategy to realize a sextuply-bonded complex

    Chen, Yue; Hasegawa, Jun-ya; Yamaguchi, Kazuya; Sakaki, Shigeyoshi
    Synthesis of higher-order multiple bond is a great challenge in chemistry. However, no stable compound with a sextuple bond has been reported, except for Mo2 in an inert matrix at low temperature. Here, we propose a strategy to construct a sextuple bond in a dinuclear transition metal complex based on the complete active space second-order perturbation theory (CASPT2) and density functional theory calculations. When the dinuclear core M2 (M = W, Mo, and Re+) is capped by two neutral electron-donating ligands at both M-M ends, a sextuple bond can be realized. The proposed ligands stabilize the M2 core by the...

  3. Decahedral-shaped anatase titania photocatalyst particles: Synthesis in a newly developed coaxial-flow gas-phase reactor

    Janczarek, Marcin; Kowalska, Ewa; Ohtani, Bunsho
    Decahedral-shaped anatase particles (DAPs) were prepared by a gas-phase process consisting of titanium (IV) chloride oxidation. The use of a coaxial-flow gas-phase reactor resulted in high reaction yield (ca. 70%) and good reproducibility of DAPs production. The influence of controlled and resultant preparation parameters on the process course and on DAPs properties (such as specific surface area, particle size and particle morphology) is discussed in detail. Correlations between preparation parameters and product properties indicated the best conditions for obtaining DAPs of high quality and thus with a high level of photocatalytic activity for various reaction systems.

  4. Selective synthesis of carbon monoxide via formates in reverse water-gas shift reaction over alumina-supported gold catalyst

    Ishito, Nobuhiro; Hara, Kenji; Nakajima, Kiyotaka; Fukuoka, Atsushi
    Thermal decomposition of formic acid on SiO2, CeO2 and gamma-Al2O3 was studied as an elementary step of reverse water-gas shit reaction (RWGS) over supported Au catalysts. gamma-Al2O3 showed the highest CO selectivity among the tested oxides in the decomposition of formic acid. Infrared spectroscopy showed the formation of four formate species on gamma-Al2O3: three eta(1)-type and one mu(2)-type species, and these formates decomposed to CO at 473 K or higher. Au-loaded gamma-Al2O3 samples were prepared by a deposition precipitation method and used as catalysts for RWGS. The supported Au catalyst gave CO with high selectivity over 99% from CO2 and...

  5. TiO2-Supported Re as a General and Chemoselective Heterogeneous Catalyst for Hydrogenation of Carboxylic Acids to Alcohols

    Toyao, Takashi; Siddiki, S. M. A. Hakim; Touchy, Abeda S.; Onodera, Wataru; Kon, Kenichi; Morita, Yoshitsugu; Kamachi, Takashi; Yoshizawa, Kazunari; Shimizu, Ken-ichi
    TiO2-supported Re, Re/TiO2, was found to promote selective hydrogenation of carboxylic acids having aromatic and aliphatic moieties to the corresponding alcohols. Re/TiO2 showed superior results compared to other transition-metal-loaded TiO2 and supported Re catalysts for selective hydrogenation of 3-phenylpropionic acid. 3phenylpropanol was produced in 97% yield under mild conditions (5 MPa H-2 at 140 degrees C). Contrary to typical heterogeneous catalysts, Re/TiO2 does not lead to the formation of dearomatized byproducts. The catalyst is recyclable and shows a wide substrate scope in the synthesis of alcohols (22 examples; up to 97% isolated yield).

  6. Great Challenges in Catalysis and Photocatalysis

    Ohtani, Bunsho

  7. Preparation of Titania on Stainless Steel by the Spray-ILGAR Technique as Active Photocatalyst under UV Light Irradiation for the Decomposition of Acetaldehyde

    Chandren, Sheela; Ismail, Kamarulafizam; Nur, Hadi; Ohtani, Bunsho
    One of the methods used to produce buffer layers for thin film solar cells is the Spray ion layer gas reaction (SPRAY-ILGAR). This method has exhibited astonishing efficiencies in the fabrication of homogenous compact metal chalcogenide films. The same approach can be applied in the preparation of photocatalyst on a substrate, in order to acquire a homogeneous and durable layer. In this work, the Spray-ILGAR technique has been utilized in the preparation of titania photocatalysts on stainless steel, which was carried out at Helmholtz-Zentrum Berlin for Materials and Energy, in Berlin, Germany. The characterizations and photocatalytic testing of the synthesized...

  8. Complete furanics-sugar separations with metal-organic framework NU-1000

    Yabushita, Mizuho; Li, Peng; Kobayashi, Hirokazu; Fukuoka, Atsushi; Farha, Omar K.; Katz, Alexander
    Metal-organic framework NU-1000 selectively adsorbs furanics, while completely excluding the adsorption of monomeric sugars from the same aqueous mixture. The highly refined degree of molecular recognition exhibited by NU-1000 is exemplified with it selectively adsorbing 5-hydroxymethylfurfural, even in the presence of up to a 300-fold excess of glucose in solution.

  9. Complete furanics-sugar separations with metal-organic framework NU-1000

    Yabushita, Mizuho; Li, Peng; Kobayashi, Hirokazu; Fukuoka, Atsushi; Farha, Omar K.; Katz, Alexander
    Metal-organic framework NU-1000 selectively adsorbs furanics, while completely excluding the adsorption of monomeric sugars from the same aqueous mixture. The highly refined degree of molecular recognition exhibited by NU-1000 is exemplified with it selectively adsorbing 5-hydroxymethylfurfural, even in the presence of up to a 300-fold excess of glucose in solution.

  10. Theoretical Study on Highly Active Bifunctional Metalloporphyrin Catalysts for the Coupling Reaction of Epoxides with Carbon Dioxide

    Hasegawa, Jun-ya; Miyazaki, Ray; Maeda, Chihiro; Ema, Tadashi
    Highly active bifunctional metalloporphyrin catalysts were developed for the coupling reaction of epoxides with CO2 to produce cyclic carbonates. The bifunctional catalysts have both quaternary ammonium halide groups and a metal center. To elucidate the roles of these catalytic groups, DFT calculations were performed. Control reactions using tetrabutylammonium halide as a catalyst were also investigated for comparison. In the present article, the results of our computational studies are overviewed. The computational results are consistent with the experimental data and are useful for elucidating the structure-activity relationship. The key features responsible for the high catalytic activity of the bifunctional catalysts are...

  11. Theoretical Study on Highly Active Bifunctional Metalloporphyrin Catalysts for the Coupling Reaction of Epoxides with Carbon Dioxide

    Hasegawa, Jun-ya; Miyazaki, Ray; Maeda, Chihiro; Ema, Tadashi
    Highly active bifunctional metalloporphyrin catalysts were developed for the coupling reaction of epoxides with CO2 to produce cyclic carbonates. The bifunctional catalysts have both quaternary ammonium halide groups and a metal center. To elucidate the roles of these catalytic groups, DFT calculations were performed. Control reactions using tetrabutylammonium halide as a catalyst were also investigated for comparison. In the present article, the results of our computational studies are overviewed. The computational results are consistent with the experimental data and are useful for elucidating the structure-activity relationship. The key features responsible for the high catalytic activity of the bifunctional catalysts are...

  12. Fe3O4@HKUST-1 and Pd/Fe3O4@ HKUST-1 as magnetically recyclable catalysts prepared via conversion from a Cu-based ceramic

    Toyao, Takashi; Styles, Mark J.; Yago, Tokuichiro; Sadiq, Muhammad M.; Ricco, Raffaele; Suzuki, Kiyonori; Horiuchi, Yu; Takahashi, Masahide; Matsuoka, Masaya; Falcaro, Paolo
    Nanocomposites obtained by integrating iron oxide magnetic nanoparticles (Fe3O4) into a metal-organic framework (HKUST-1 or Cu-3(BTC)(2), BTC = 1,3,5-benzenetricarboxylate) are synthesized through conversion from a composite of a Cu-based ceramic material and Fe3O4. In situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) measurements reveal that the presence of Fe3O4 leads to the fast conversion and synthesis of HKUST-1 with small particle sizes. The prepared MOF composite (Fe3O4@HKUST-1) is found to catalyze the one-pot sequential deacetalization-Knoevenagel condensation reaction as a magnetically collectable and recyclable catalyst. In addition, Pd nanoparticles are also incorporated into the material (Pd/Fe3O4@HKUST-1) by addition of...

  13. Fe3O4@HKUST-1 and Pd/Fe3O4@ HKUST-1 as magnetically recyclable catalysts prepared via conversion from a Cu-based ceramic

    Toyao, Takashi; Styles, Mark J.; Yago, Tokuichiro; Sadiq, Muhammad M.; Ricco, Raffaele; Suzuki, Kiyonori; Horiuchi, Yu; Takahashi, Masahide; Matsuoka, Masaya; Falcaro, Paolo
    Nanocomposites obtained by integrating iron oxide magnetic nanoparticles (Fe3O4) into a metal-organic framework (HKUST-1 or Cu-3(BTC)(2), BTC = 1,3,5-benzenetricarboxylate) are synthesized through conversion from a composite of a Cu-based ceramic material and Fe3O4. In situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) measurements reveal that the presence of Fe3O4 leads to the fast conversion and synthesis of HKUST-1 with small particle sizes. The prepared MOF composite (Fe3O4@HKUST-1) is found to catalyze the one-pot sequential deacetalization-Knoevenagel condensation reaction as a magnetically collectable and recyclable catalyst. In addition, Pd nanoparticles are also incorporated into the material (Pd/Fe3O4@HKUST-1) by addition of...

  14. Isolation and phototransformation of enantiomerically pure iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C-2]picolinate

    Wang, Yue; Harada, Takunori; Shiota, Yoshihito; Yoshizawa, Kazunari; Wang, Heng; Wang, Sheng; Ye, Xichong; Ogasawara, Masamichi; Nakano, Tamaki
    Here we report the resolution of phosphorescent light-emitting iridium(III) bis[(4,6-difluorophenyl) pyridinato-N, C-2]-picolinate into its respective enantiomers by using chiral HPLC and the photo-induced transformation of the isolated enantiomers.

  15. Noble metal-modified octahedral anatase titania particles with enhanced activity for decomposition of chemical and microbiological pollutants

    Wei, Z.; Endo, M.; Wang, K.; Charbit, E.; Markowska-Szczupak, A.; Ohtani, B.; Kowalska, E.
    Octahedral anatase particles (OAPs) were prepared by hydrothermal (HT) reaction of titanate nanowires (TNWs). OAPs were modified with noble metals (Au, Ag, Cu and Pt) by two photodeposition methods: in the absence and in the initial presence of oxygen in the system. Photocatalytic activities for oxidative decomposition of acetic acid and anaerobic dehydrogenation of methanol under UV/vis irradiation and for oxidation of 2-propanol under visible light irradiation were investigated. Antibacterial activities for bacteria (Escherichia coli) and fungi (Candida albicans) were investigated in the dark and under UV irradiation and/or visible light irradiation. It was found that the kind of metal...

  16. Size-controlled gold nanoparticles on octahedral anatase particles as efficient plasmonic photocatalyst

    Wei, Zhishun; Rosa, Lorenzo; Wang, Kunlei; Endo, Maya; Juodkazis, Saulius; Ohtani, Bunsho; Kowalska, Ewa
    Octahedral anatase particles (OAPs), prepared by ultrasonication-hydtothermal reaction (US-HT), were modified with 2 wt% of gold by photodeposition. COnditions of US-HT process such as durations of US and durations of HT were varied to obtain OAPs products different by physicochemical and morphological properties. Au/OAPs samples were characterized by X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS). The photocatalytic activity was tested under UV irradiation for decomposition of acetic acid (CO2 system) and dehydrogenation of methanol (H-2 system) under aerobic and anaerobic conditions, respectively, and for oxidation of 2-propanol under visible light...

  17. Photo Racemization and Polymerization of (R)-1,1 '-Bi(2-naphthol)

    Zhang, Zhaoming; Wang, Yue; Nakano, Tamaki
    (R)-1,1'-Bi(2-naphthol) ((R)-BINOL) in an acetonitrile solution lost optical activity upon irradiation with an Hg-Xe lamp. HPLC resolution of the product indicated that (R)-BINOL was racemized upon irradiation, and SEC analysis suggested that a polymeric product was formed in the course of racemization. It is proposed that polymerization of BINOL can occur before it is racemized and that a unit in a polymer derived from BINOL may lose its optical activity afterwards due to in-chain racemization and/or reduction. The polymeric products seem to consist not only of BINOL residues but also of residues derived from acetonitrile as well as those derived...

  18. A heterojunction photocatalyst composed of zinc rhodium oxide, single crystal-derived bismuth vanadium oxide, and silver for overall pure-water splitting under visible light up to 740 nm

    Kobayashi, Ryoya; Takashima, Toshihiro; Tanigawa, Satoshi; Takeuchi, Shugo; Ohtani, Bunsho; Irie, Hiroshi
    We recently reported the synthesis of a solid-state heterojunction photocatalyst consisting of zinc rhodium oxide (ZnRh2O4) and bismuth vanadium oxide (Bi4V2O11), which functioned as hydrogen (H2) and oxygen (O2) evolution photocatalysts, respectively, connected with silver (Ag). Polycrystalline Bi4V2O11 (p-Bi4V2O11) powders were utilized to form ZnRh2O4/Ag/p-Bi4V2O11, which was able to photocatalyze overall pure-water splitting under red-light irradiation with a wavelength of 700 nm (R. Kobayashi et al., J. Mater. Chem. A, 2016, 4, 3061). In the present study, we replaced p-Bi4V2O11 with a powder obtained by pulverizing single crystals of Bi4V2O11 (s-Bi4V2O11) to form ZnRh2O4/Ag/s-Bi4V2O11, and demonstrated that this heterojunction photocatalyst...

  19. Rhodium-doped titania photocatalysts with two-step bandgap excitation by visible light—influence of the dopant concentration on photosensitization efficiency

    Kuncewicz, J.; Ohtani, Bunsho
    Development of photocatalysts active under visible light has been achieved through the modification of titania with rhodium (Rh) ions. Depending on the concentration of the precursor of Rh species, various crystalline phases and modification modes have been obtained. Lower Rh concentrations (below 0.5%) resulted in doped rutile particles, while higher (above 1%) gave mainly surface modified anatase particles. High photocatalytic activities were obtained for surface enriched doped rutile-titania with an extremely low amount of trivalent rhodium (Rh3+) ions (about 0.0005 mol%). Almost four orders of magnitude higher Rh concentration (2%) also provided highly active materials, however, they were composed of...

  20. Supported rhenium nanoparticle catalysts for acceptorless dehydrogenation of alcohols: structure-activity relationship and mechanistic studies

    Kon, Kenichi; Onodera, Wataru; Toyao, Takashi; Shimizu, Ken-ichi
    Al2O3-supported Re with different oxidation states and Re-0 metal nanoparticles on various supports are prepared, characterized and tested for the dehydrogenation of 2-octanol. The activity of Re/Al2O3 increases with the fraction of metallic Re. The activity of metallic Re depends on the support oxides, and the support with moderate electronegativity (Al2O3) gives the highest turnover frequency (TOF) per surface Re-0 site. Re/Al2O3 is effective for acceptorless dehydrogenation of various aliphatic secondary alcohols to ketones. The kinetic isotope effects on the dehydrogenation of 2-propanol show that dissociation of the alpha-C-H bond of 2-propanol is the rate-limiting step. The IR study of...

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