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Hokkaido University Collection of Scholarly and Academic Papers (136.069 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 21 - 40 de 172

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. Synthesis of 2,5-disubstituted pyrroles via dehydrogenative condensation of secondary alcohols and 1,2-amino alcohols by supported platinum catalysts

    Siddiki, S. M. A. H.; Touchy, Abeda S.; Chaudhari, Chandan; Kon, Kenichi; Toyao, Takashi; Shimizu, Ken-ichi
    Direct synthesis of 2,5-disubstituted pyrroles has been achieved via acceptorless dehydrogenative heterocyclization of 1,2-aminoalcohols and secondary alcohols by utilizing a heterogeneous carbon-supported Pt catalyst (Pt/C). The optimized method gave 92% yield of 2-ethyl-5-phenyl-1H-pyrrole as a desired product from 2-amino-1-butanol and 1-phenylethanol in the presence of 0.1 mol% of Pt/C and 1.1 equiv. of KOtBu. It has been revealed that Pt/C demonstrates superior catalytic activity to a number of catalysts tested in this study including other transition metal-loaded carbon and various metal-oxide-supported Pt catalysts. In addition, the turnover number (TON) obtained in the present system was found to be higher than...

  6. Synthesis of 2,5-disubstituted pyrroles via dehydrogenative condensation of secondary alcohols and 1,2-amino alcohols by supported platinum catalysts

    Siddiki, S. M. A. H.; Touchy, Abeda S.; Chaudhari, Chandan; Kon, Kenichi; Toyao, Takashi; Shimizu, Ken-ichi
    Direct synthesis of 2,5-disubstituted pyrroles has been achieved via acceptorless dehydrogenative heterocyclization of 1,2-aminoalcohols and secondary alcohols by utilizing a heterogeneous carbon-supported Pt catalyst (Pt/C). The optimized method gave 92% yield of 2-ethyl-5-phenyl-1H-pyrrole as a desired product from 2-amino-1-butanol and 1-phenylethanol in the presence of 0.1 mol% of Pt/C and 1.1 equiv. of KOtBu. It has been revealed that Pt/C demonstrates superior catalytic activity to a number of catalysts tested in this study including other transition metal-loaded carbon and various metal-oxide-supported Pt catalysts. In addition, the turnover number (TON) obtained in the present system was found to be higher than...

  7. A fingerprint of metal-oxide powders: energy-resolved distribution of electron traps

    Nitta, Akio; Takase, Mai; Takashima, Mai; Murakami, Naoya; Ohtani, Bunsho
    Here we propose a method for the identification of metal-oxide powders with the energy-resolved distribution of electron traps and conduction-band bottom position reflecting a surface structure and a bulk structure, respectively, as a fingerprint, based on the degree of coincidence for a given pair of samples, measured using newly developed reversed double-beam photoacoustic spectroscopy.

  8. A DFT and multi-configurational perturbation theory study on O-2 binding to a model heme compound via the spin-change barrier

    Kitagawa, Y.; Chen, Y.; Nakatani, Naoki; Nakayama, Akira; Hasegawa, Jun-ya
    Dioxygen binding to a model heme compound via intersystem crossing (ISC) was investigated with a multi-state multi-configurational self-consistent field method with second-order perturbation theory (MS-CASPT2) and density functional theory (DFT) calculations. In elongated Fe-O distances, the energy levels of the S-0 and T-1 states are separated, which decreases the probability of intersystem crossing in these structures. At the DFT(B97D) level of calculation, the Fe-O distances of the S-0 and T-1 states were 1.91 and 2.92 angstrom, respectively. The minimum energy intersystem crossing point (MEISCP) was located as a transition state at a Fe-O distance of 2.17 angstrom with an energy...

  9. Unprecedented selectivity in molecular recognition of carbohydrates by a metal-organic framework

    Yabushita, Mizuho; Li, Peng; Bernales, Varinia; Kobayashi, Hirokazu; Fukuoka, Atsushi; Gagliardi, Laura; Farha, Omar K.; Katz, Alexander
    Metal-organic framework (MOF) material NU-1000 adsorbs dimers cellobiose and lactose from aqueous solution, in amounts exceeding 1250 mg g(NU-1000)(-1) while completely excluding the adsorption of the monomer glucose, even in a competitive mode with cellobiose. The MOF also discriminates between dimers consisting of alpha and beta linkages, showing no adsorption of maltose. Electronic structure calculations demonstrate that key to this selective molecular recognition is the number of favorable CH-pi interactions made by the sugar with pyrene units of the MOF.

  10. Portable ultrahigh-vacuum sample storage system for polarization-dependent total-reflection fluorescence x-ray absorption fine structure spectroscopy

    Watanabe, Yoshihide; Nishimura, Yusaku F.; Suzuki, Ryo; Uehara, Hiromitsu; Nimura, Tomoyuki; Beniya, Atsushi; Isomura, Noritake; Asakura, Kiyotaka; Takakusagi, Satoru
    A portable ultrahigh-vacuum sample storage system was designed and built to investigate the detailed geometric structures of mass-selected metal clusters on oxide substrates by polarization-dependent total-reflection fluorescence x-ray absorption fine structure spectroscopy (PTRF-XAFS). This ultrahigh-vacuum (UHV) sample storage system provides the handover of samples between two different sample manipulating systems. The sample storage system is adaptable for public transportation, facilitating experiments using air-sensitive samples in synchrotron radiation or other quantum beam facilities. The samples were transferred by the developed portable UHV transfer system via a public transportation at a distance over 400 km. The performance of the transfer system was...

  11. Mechanochemical Synthesis of a Carboxylated Carbon Catalyst and Its Application in Cellulose Hydrolysis

    Shrotri, Abhijit; Kobayashi, Hirokazu; Fukuoka, Atsushi
    A carbon catalyst containing a high density of carboxyl groups was prepared by solvent-free mechanochemical oxidation of activated carbon by using persulfate salts as the oxidant. The mechanochemical oxidation preferentially oxidized the carbon to introduce carboxyl groups without incorporation of sulfonated groups. The material exhibited hydrophilic behavior and was easily dispersed in water. Upon mix-milling, the oxidized carbon showed good catalytic activity for the hydrolysis of cellulose, even at a low catalyst loading. Glucose was obtained in 85% yield from mix-milled cellulose in the presence of a trace amount of HCl after a reaction time of 20min.

  12. Direct Synthesis of Cyclic Imides from Carboxylic Anhydrides and Amines by Nb2O5 as a Water-Tolerant Lewis Acid Catalyst

    Ali, Md. A.; Moromi, Sondomoyee K.; Touchy, Abeda S.; Shimizu, Ken-ichi
    In the 20 types of heterogeneous and homogenous catalysts screened, Nb2O5 showed the highest activity for the synthesis of N-phenylsuccinimide by dehydrative condensation of succinic anhydride and aniline. Nb2O5 was used in the direct imidation of a wide range of carboxylic anhydrides with NH3 or amines with various functional groups and could be reused. Kinetic studies showed that the Lewis acid Nb2O5 catalyst was more water tolerant than both the Lewis acidic oxide TiO2 and the homogeneous Lewis acid ZrCl4, which resulted in higher yields of imides through the use of Nb2O5.

  13. Dynamics of Photoelectrons and Structural Changes of Tungsten Trioxide Observed by Femtosecond Transient XAFS

    Uemura, Yohei; Kido, Daiki; Wakisaka, Yuki; Uehara, Hiromitsu; Ohba, Tadashi; Niwa, Yasuhiro; Nozawa, Shunsuke; Sato, Tokushi; Ichiyanagi, Kohei; Fukaya, Ryo; Adachi, Shin-ichi; Katayama, Tetsuo; Togashi, Tadashi; Owada, Sigeki; Ogawa, Kanade; Yabashi, Makina; Hatada, Keisuke; Takakusagi, Satoru; Yokoyama, Toshihiko; Ohtani, Bunsho; Asakura, Kiyotaka
    The dynamics of the local electronic and geometric structures of WO3 following photoexcitation were studied by femtosecond time-resolved X-ray absorption fine structure (XAFS) spectroscopy using an X-ray free electron laser (XFEL). We found that the electronic state was the first to change followed by the local structure, which was affected within 200 ps of photoexcitation.

  14. Chirality induction using circularly polarized light into a branched oligofluorene derivative in the presence of an achiral aid molecule

    Wang, Yue; Kanibolotsky, Alexander L.; Skabara, Peter J.; Nakano, Tamaki
    Chirality induction into a uniform, star-shaped fluorene oligomer with a central truxene moiety (T3) was achieved using circularly polarized light in the presence of achiral fluorene or phenanthrene. Induction into T3 alone was difficult, suggesting that close chain packing realized through interactions of T3 with small molecules plays a role in chirality induction.

  15. Structure determination of the rutile-TiO2(110)-(1 × 2) surface using total-reflection high-energy positron diffraction (TRHEPD)

    Mochizuki, I; Ariga, H; Fukaya, Y; Wada, K; Maekawa, M; Kawasuso, A; Shidara, T; Asakura, K; Hyodo, T
    The exact structure of the rutile-TiO2(110)-(1×2) surface, which had been under debate over the past 30 years, was investigated using the newly developed technique of total-reflection high-energy positron diffraction (TRHEPD), which is a positron counterpart of reflection high-energy electron diffraction (RHEED). The rocking-curves for the 00-spot obtained from the experimental diffraction patterns were compared to the curves for various models calculated with a full-dynamical theory. It was found that the rocking-curves matched those for a surface consisting of a Ti2O3 configuration, originally suggested by Onishi and Iwasawa [H. Onishi and Y. Iwasawa, Surf. Sci., 1994, 313, L783], but with a...

  16. Phase transition behaviors of the supported DPPC bilayer investigated by sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM)

    Wu, Heng-Liang; Tong, Yujin; Peng, Qiling; Li, Na; Ye, Shen
    The phase transition behaviors of a supported bilayer of dipalmitoylphosphatidyl-choline (DPPC) have been systematically evaluated by in situ sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM). By using an asymmetric bilayer composed of per-deuterated and perprotonated monolayers, i.e., DPPC-d(75)/DPPC and a symmetric bilayer of DPPC/DPPC, we were able to probe the molecular structural changes during the phase transition process of the lipid bilayer by SFG spectroscopy. It was found that the DPPC bilayer is sequentially melted from the top (adjacent to the solution) to bottom leaflet (adjacent to the substrate) over a wide temperature range. The conformational...

  17. Titania modification with a ruthenium(II) complex and gold nanoparticles for photocatalytic degradation of organic compounds

    Zheng, Shuaizhi; Wei, Zhishun; Yoshiiri, Kenta; Braumueller, Markus; Ohtani, Bunsho; Rau, Sven; Kowalska, Ewa
    Titania of fine anatase nanoparticles (ST01) was modified successively with two components, i.e., a ruthenium(II) complex with phosphonic anchoring groups [Ru(bpy)(2)(4,4'-(CH2PO3H2)(2)bpy)](2+) bpy = 2,2'-bipyridine ((RuCP)-C-II) and gold nanoparticles (Au). Various compositions of two titania modifiers were investigated, i.e., Au, Au + (RuCP)-C-II, Au + 0.5Ru(II)CP, (RuCP)-C-II, 0.5Ru(II)CP and 0.25Ru(II)CP, where Au and (RuCP)-C-II correspond to 0.81 mol% and 0.34 mol% (with respect to titania), respectively. In the case of hybrid photocatalysts, the sequence of modification (ruthenium(II) complex adsorption or gold deposition) was investigated to check its influence on the resultant properties and thus photocatalytic performance. Diffuse reflectance spectroscopy (DRS), X-ray...

  18. Hydrolysis of woody biomass by a biomass-derived reusable heterogeneous catalyst

    Kobayashi, Hirokazu; Kaiki, Hiroyuki; Shrotri, Abhijit; Techikawara, Kota; Fukuoka, Atsushi
    Biomass is the sole carbon-based renewable resource for sustaining the chemical and fuel demands of our future. Lignocellulose, the primary constituent of terrestrial plants, is the most abundant non-food biomass, and its utilisation is a grand challenge in biorefineries. Here we report the first reusable and cost-effective heterogeneous catalyst for the depolymerisation of lignocellulose. Air oxidation of woody biomass (Eucalyptus) provides a carbonaceous material bearing an aromatic skeleton with carboxylic groups (2.1 mmol g(-1)) and aliphatic moieties. This catalyst hydrolyses woody biomass (Eucalyptus) to sugars in high yields within 1 h in trace HCl aq. Furthermore, after the reaction, the...

  19. Synthesis of poly(1,10-phenanthroline-5,6-diyl)s having a pi-stacked, helical conformation

    Yang, Weixi; Nakano, Tamaki
    5,6-Dibromo-1,10-phenanthroline and 2,9-di-n-butyl-5,6-dibromo-1,10-phenanthroline were polymerized using a Ni catalyst to afford helical polymers in which the phenanthroline moieties are densely stacked on top of each other. Polymerization of the latter monomer using a chiral catalyst led to a preferred-handed helix. This is the first Ni-catalyzed helix-sense-selective polymerization of aromatic compounds.

  20. Electronic spectra of azaindole and its excited state mixing: A symmetry-adapted cluster configuration interaction study

    Arulmozhiraja, Sundaram; Coote, Michelle L.; Hasegawa, Jun-ya
    Electronic structures of azaindole were studied using symmetry-adapted cluster configuration interaction theory utilizing Dunning's cc-pVTZ basis set augmented with appropriate Rydberg spd functions on carbon and nitrogen atoms. The results obtained in the present study show good agreement with the available experimental values. Importantly, and contrary to previous theoretical studies, the excitation energy calculated for the important n-pi* state agrees well with the experimental value. A recent study by Pratt and co-workers concluded that significant mixing of pi-pi* and n-pi* states leads to major change in the magnitude and direction of the dipole moment of the upper state vibrational level...

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