Advance

FUJISHIMA Musashi

    Department of Applied Chemistry　Associate Professor
Last Updated :2024/04/25

Researcher Information

URL

Research funding number

  • 90388497

J-Global ID

Research Areas

  • Nanotechnology/Materials / Inorganic materials

Published Papers

  • Shin-ichi Naya; Atsunobu Akita; Yoko Morita; Musashi Fujishima; Hiroaki Tada
    Chemical Science Royal Society of Chemistry (RSC) 2041-6520 2022 
    In the represented plasmonic photocatalyst consisting of Au nanoparticles (NPs) and TiO2, the combination of crystal facet engineering of TiO2 and atom-level-interface control between Au NP and TiO2 gives rise to a drastic activity enhancement.
  • Kota Kurokawa; Musashi Fujishima; Shin-ichi Naya; Hiroaki Tada
    CHEMICAL COMMUNICATIONS ROYAL SOC CHEMISTRY 57 (59) 7232 - 7235 1359-7345 2021/07 
    An atomically commensurate interface gives rise to Au truncated pyramids < 10 nm on single-crystalline SrTiO3 nanocubes (NCs) in a simple deposition-precipitation process without a surface modifier, and the resulting hybrid nanocrystals exhibit a high level of photocatalytic activity for a plasmonic oxygen evolution reaction at light wavelengths (lambda(ex)) <= 1200 nm.
  • Atsunobu Akita; Musashi Fujishima; Hiroaki Tada
    LANGMUIR AMER CHEMICAL SOC 37 (5) 1838 - 1842 0743-7463 2021/02 
    An in situ reduction technique consisting of chemisorption of 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS and subsequent reaction with HAuCl4 has been developed for depositing Au nanoparticles (NPs) uniformly in the depth direction of a mesoporous TiO2 nanocrystalline film (Au/TMCTS/mp-TiO2). The TMCTS monolayer is further converted into silicon oxide by heating in the air (Au/SiOx/mp-TiO2). In the absorption spectra of Au/SiOx/mp-TiO2 prepared at varying HAuCl4 concentrations (C), the localized surface plasmon resonance (LSPR) band of Au NPs significantly broadens C approximate to 1.22 mM at 546 nm to be split into two peaks around 500 and 700 nm at C >= 2.43 mM, whereas such a phenomenon is not observed for the usual Au NP-loaded TiO2 particles. Three-dimensional-finite difference time domain simulations showed that the unique optical property of Au/SiOx/mp-TiO2 stems from the effective LSPR coupling of very close Au NPs and partial fusions in the nanospaces of mp-TiO2. Further, the optical hot spots in Au/TMCTS/mp-TiO2 as well as Au/SiOx/mp-TiO2, generate an intense local electric field giving increase to a great enhancement of the absorption in the infrared spectrum of the TMCTS monolayer on mp-TiO2.
  • Hiroaki Tada; Shin-ichi Naya; Musashi Fujishima
    JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 124 (47) 25657 - 25666 1932-7447 2020/11 
    Nanohybrid crystals consisting of metals and semiconductors can be the key materials for the solar-to-chemical transformations including the artificial photosynthesis. For the effective interplay between the components, the construction of high-quality interface is pivotal. This feature article highlights the importance of the quality of the interface at an atomic level on the activity of nanohybrid photocatalysts. First, the recent development of the techniques for synthesizing nanohybrids with heteroepitaxial junction (HEPI) between the components is described. Second, the HEPI-junction-induced effects on the elemental steps in photocatalysis including light harvesting, interfacial charge transfer, charge separation, and surface redox reactions are discussed. Third, the applications of the nanohybrids with HEPI junction to photocatalytic multiple-electron redox reactions are dealt with. Finally, the conclusions are summarized with possible future subjects and prospects of the nanohybrid photocatalysts with HEPI junction.
  • Reki Takahashi; Musashi Fujishima; Hiroaki Tada; Tetsuro Soejima
    CHEMNANOMAT WILEY-V C H VERLAG GMBH 6 (10) 1485 - 1495 2199-692X 2020/10 
    This study describes a one-pot synthetic strategy consisting of concerted stabilization and photo and chemical reductions of metal ions to yield precise anisotropic nanostructures. Photoirradiation of an aqueous precursor solution containing Au3+, Ag+, Br-, and polyvinylpyrrolidone (PVP) forms Janus nanoparticles (NPs) composed of Au having a tiny Ag shell and AgBr. The Au NPs are initially generated by photoreduction of Au(3+)in the precursor solution, in which the formation of silver halides is strongly inhibited by the coordination bond between Ag(+)and the carbonyl groups in PVP. The coordinated PVP chains are adsorbed on the surfaces of the Au NPs, with the concomitant release of free Ag(+)ions. The part of the surface of the Au NP is covered with a few Ag atoms via chemical reduction of Ag(+)by PVP. AgBr nanocrystals grow at a bare site on the surface of each Au NP, resulting in the formation of nearly monodisperse Janus Au-AgBr NPs in high yield. A characteristic light absorption profile emerges due to the interface formed between Au and AgBr, which is demonstrated by finite-difference time-domain simulation. The precise nanostructures may be leveraged to elucidate mechanisms of photoelectrochemical processes and to construct advanced plasmonic photocatalysts.
  • Seina Kawano; Musashi Fujishima; Hiroaki Tada
    CATALYSIS COMMUNICATIONS ELSEVIER 144 1566-7367 2020/09 
    UV-light irradiation of gold nanoparticle-loaded ZnO with a heteroepitaxial junction (Au#ZnO) in aerated ethanol aqueous solution gives rise to two-electron oxygen reduction reaction (ORR) to yield more than 1 mM hydrogen peroxide at only 1-h irradiation. The photocatalytic activity has been revealed to remarkably increase with increasing Au particle size as the result of the increase in H2O2 formation rate and the decrease in its decomposition rate. The outstanding photocatalytic activity of Au#ZnO can mainly stem from the enhancement of charge-separation and the reduction in the loss of H2O2 by the non-adsorptivity of ZnO.
  • Kenta Awa; Shin-ichi Naya; Musashi Fujishima; Hiroaki Tada
    JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 124 (14) 7797 - 7802 1932-7447 2020/04 
    SnO2 nanorods were hydrothermally grown on rutile TiO2 seed crystals (SnO2-NR#TiO2), where symbol # denotes the heteroepitaxial junction between SnO2 and TiO2. Furthermore, Au nanoparticles (NPs) were loaded on the surfaces of TiO2 and SnO2 of SnO2-NR#TiO2 by the deposition precipitation method (Au/[SnO2-NR#TiO2]). Au/[SnO2-NR#TiO2] possesses broad and strong absorption due to the localized surface plasmon resonance (LSPR) of Au NPs around 550 nm, while both TiO2 and SnO2 are almost transparent to visible light. On excitation of the LSPR (lambda(ex) > 430 nm), Au/[SnO2-NR#TiO2] exhibits much higher photocatalytic activity for two-electron oxygen reduction reaction than two-component systems of Au/TiO2 and Au/SnO2 and their physical mixture. The striking photocatalytic activity of the three-component system stems from the efficient charge separation due to the LSPR-driven vectorial interfacial electron transfer in the direction of Au (on TiO2 -> TiO2 -> SnO2 -> Au (on SnO2). Consequently, Au NPs on TiO2 and SnO2 work as the oxidation and reduction sites, respectively, and thus, the excellent electrocatalytic activity of Au NP for two-electron oxygen reduction reaction and low catalytic activity of SnO2 for H2O2 decomposition would also contribute to the high photocatalytic activity.
  • Tatsuhiro Onishi; Miwako Teranishi; Shin-ichi Naya; Musashi Fujishima; Hiroaki Tada
    JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 124 (11) 6103 - 6109 1932-7447 2020/03 
    This study has shown that the electrocatalytic activity of gold nanoparticles (Au NPs) is the key factor governing the performance of Au NPloaded TiO2 plasmonic electrodes for the water oxidation reaction. Au NPs were loaded onto the mesoporous rutile TiO2 nanocrystalline film (Au/mp-TiO2) and rutile TiO2 nanowire array (Au/TiO2-NWA) electrodes by the deposition-precipitation method. Faceted Au NPs with sharp edges and corners are formed on TiO2-NWA, while the Au NPs on mp-TiO2 are almost non-faceted and hemisphere-like. An ultrathin Cu shell layer was formed selectively on the Au surface of Au/TiO2-NWA to yield Au(core)-Cu(shell) NPs on TiO2-NWA (Au@Cu/TiO2-NWA) by the photodeposition technique. Electrochemical measurements showed that the electrocatalytic activity of the water oxidation reaction significantly depends on the shape of Au NPs and Cu shell formation, and their order of dependence is Au/mp-TiO2 < Au/TiO2-NWA < Au@Cu/TiO2-NWA. Furthermore, the action spectra of incident photon-to-current conversion efficiency indicated that the increase in the electrocatalytic activity enhances the photocurrent at a given excitation wavelength, simultaneously extending the spectral response range.
  • Shin-ichi Naya; Musashi Fujishima; Hiroaki Tada
    Catalysts MDPI 9 (9) 745  2019/08 [Refereed][Invited]
     
    Nanoscale composites consisting of silver and silver halide (Ag-AgX, X = Cl, Br, I) have attracted much attention as a novel type of visible-light photocatalyst (the so-called plasmonic photocatalysts), for solar-to-chemical transformations. Support-free Au-Ag alloy nanoparticle-incorporated AgBr crystals (Au-Ag@AgBr) were synthesized by a photochemical method. At the initial step, Au ion-doped AgBr particles were prepared by adding an aqueous solution of AgNO3 to a mixed aqueous solution of KBr and HAuBr4. At the next step, UV-light illumination (lambda = 365 nm) of a methanol suspension of the resulting solids yielded Au-Ag alloy nanoparticles with a mean size of approximately 5 nm in the micrometer-sized AgBr crystals. The mole percent of Au to all the Ag in Au-Ag@AgBr was controlled below < 0.16 mol% by the HAuBr4 concentration in the first step. Finite-difference time-domain calculations indicated that the local electric field enhancement factor for the alloy nanoparticle drastically decreases with an increase in the Au content. Also, the peak of the localized surface plasmon resonance shifts towards longer wavelengths with increasing Au content. Au-Ag@AgBr is a highly promising plasmonic photocatalyst for sunlight-driven chemical transformations due to the compatibility of the high local electric field enhancement and sunlight harvesting efficiency.
  • Tada Hiroaki; Naya Shin-ichi; Fujishima Musashi
    ELECTROCHEMISTRY COMMUNICATIONS ELSEVIER SCIENCE INC 97 22 - 26 1388-2481 2018/12 [Refereed]
     
    In contrast to the bulk, Au nanoparticles possess unique absorption characteristics due to localized surface plasmon resonance in the visible-to-near-infrared region. Recently, Au nanoparticle-based plasmonic photocatalysts have emerged as promising visible-light photocatalysts for "solar hydrogen" production. This mini review deals with guidelines for the design of highly active plasmonic photocatalysts, highlighting the effect of a heteroepitaxial junction in Au(core)-CdS(shell) nanohybrids on their activity for water splitting, and as a photosensitizer for metal oxide electrodes to improve their performance in photoelectrochemical hydrogen generation from water.
  • Onishi Tatsuhiro; Fujishima Musashi; Tada Hiroaki
    ACS OMEGA AMER CHEMICAL SOC 3 (9) 12099 - 12105 2470-1343 2018/09 [Refereed]
     
    One-compartment H2O2-photofuel cells using monoclinic scheelite BiVO4 film deposited on fluorine- doped tin oxide (ms-BiVO4/FTO) as the photoanode, Prussian blue film-coated FTO cathode, and deaerated aqueous electrolyte solution of 0.1 M NaClO4 and 0.1 M H2O2 were constructed. Mesoporous TiO2 photoanode cells with the same cathode and electrolyte solution were also prepared for comparison. The ms-BiVO4/FTO photoanode was prepared by a two-step route consisting of spin coating of a precursor solution on FTO and subsequent heating at 500 degrees C in the air. The thickness of the ms-BiVO4 film was controlled in the range from 50 to 500 nm by the number of the spin-coating times. There is an optimum thickness of the ms-BiVO4 film in the cell performances under illumination of simulated sunlight (AM 1.5, 100 mW cm(-2), 1 sun). Under the optimum conditions, the ms-BiVO4/FTO photoanode cell provides a short-circuit current (J(sc)) = 0.81 mA cm(-2) and an open-circuit voltage (V-oc) = 0.61 V, far surpassing the values of J(sc) = 0.01 mA cm(-2) and V-oc = 0.31 V for the conventional mesoporous TiO2 photoanode cell. The striking cell performance is ascribable to the high visible-light activity of ms-BiVO4 for H2O2 oxidation and its low thermocatalytic activity for the decomposition.
  • Takumi Masuda; Musashi Fujishima; Hiroaki Tada
    Electrochemistry Communications Elsevier Inc. 93 31 - 34 1388-2481 2018/08 [Refereed]
     
    Mesoporous TiO2 nanocrystalline film was coated on fluorine-doped tin oxide electrode (mp-TiO2/FTO) by the doctor blade method, and Prussian blue film was electrodeposited on FTO (PB/FTO). A two-compartment H2O2-PFC with the structure of mp-TiO2/FTO (photoanode)|0.1 M KClO4 (pH 3)|Nafion (separator)|0.1 M KClO4 with 0.1 M H2O2 (pH 3)|PB/FTO (cathode) was constructed. Under UV-light irradiation, the two-compartment PFC provides short-circuit current (Jsc) = 1.14 mA cm−2 and open-circuit potential (Voc) = 952 mV much greater than the values of Jsc = 0.197 mA cm−2 and Voc = 607 mV for the one-compartment cell. Importantly, the electromotive force for the two-compartment H2O2-PFC exceeds the thermodynamic value of 534 mV calculated from the electrode potentials for the half-reactions.
  • Musashi Fujishima; Takuya Ikeda; Ryo Akashi; Hiroaki Tada
    ACS Omega American Chemical Society 3 (6) 6104 - 6112 2470-1343 2018/06 [Refereed]
     
    Hemisphere-like gold nanoparticles (NPs) were loaded on TiO2 (Au/TiO2) by the deposition-precipitation method. Subsequent photodeposition of CdS on the Au surface of Au/TiO2 at 50 °C yields Au(core)-CdS(shell) hybrid quantum dots with a heteroepitaxial (HEPI) junction on TiO2 (Au@#CdS/TiO2), whereas nonHEPI Au@CdS/TiO2 was formed by CdS photodeposition at 25 °C. In the HEPI system, the shape of the Au core changes to an angular shape, whereas it remains in a hemisphere-like shape in the nonHEPI system. The hot photodeposition technique was applied to the Au NP-loaded mesoporous TiO2 nanocrystalline film (Au/mp-TiO2). Using Au@CdS/mp-TiO2 and Au@#CdS/mp-TiO2 as the photoanodes, two-electrode quantum dot-sensitized photoelectrochemical cells were fabricated for hydrogen (H2) generation from water, and the performances of the cells were evaluated under illumination of simulated sunlight. In the photocurrent and the rate of H2 evolution, the Au@#CdS/mp-TiO2 photoanode cell surpasses the CdS/mp-TiO2 and Au@CdS/mp-TiO2 ones. Three-dimensional finite-difference time-domain calculations for the model systems indicated that the angular shape Au core generates an intense electric field at the corners and edges, extending the electric field distribution over the Au core-CdS shell interface. The striking shape effect on the cell performances can originate from the promotion of the CdS excitation and charge separation due to the near-field enhancement by the deformed Au core.
  • Shin-Ichi Naya; Takahiro Kume; Ryo Akashi; Musashi Fujishima; Hiroaki Tada
    Journal of the American Chemical Society American Chemical Society 140 (4) 1251 - 1254 1520-5126 2018/01 [Refereed]
     
    A key material for artificial photosynthesis including water splitting is heteronanostructured (HNS) photocatalysts. The photocatalytic activity depends on the geometry and dimension, and the quality of junctions between the components. Here we present a half-cut Au(core)-CdS(shell) (HC-Au@CdS) nanoegg as a new HNS plasmonic photocatalyst for water splitting. UV-light irradiation of Au nanoparticle (NP)-loaded ZnO (Au/ZnO) at 50 °C induces the selective deposition of hexagonal CdS on the Au surface of Au/ZnO with an epitaxial (EPI) relation of CdS{0001}/Au{111}. The subsequent selective dissolution of the ZnO support at room temperature yields HC-Au CdS with the Au NP size and EPI junction (#) retained. Red-light irradiation (λex = 640 nm) of HC-Au@#CdS gives rise to continuous stoichiometric water splitting with an unprecedentedly high external quantum yield of 0.24%.
  • Atsunobu Akita; Takumi Masuda; Keigo Fujiwara; Musashi Fujishima; Hiroaki Tada
    Journal of the Electrochemical Society Electrochemical Society Inc. 165 (5) F300 - F304 1945-7111 2018 [Refereed]
     
    We have studied the factors affecting the performances of one-compartment hydrogen peroxide photofuel cell (H2O2-PFC) consisting of TiO2 photoanode, cathode, and an aqueous electrolyte solution. As the photoanode, a dense TiO2 film was formed on fluorine-doped tin oxide by a dip-coating method (d-TiO2/FTO) with the thickness controlled below ∼0.5 μm, and a mesoporous TiO2 nanocrystalline film with a thickness of 3.6 μm was coated on FTO (mp-TiO2/FTO) by a doctor blade method. The d-TiO2/FTO provides performances superior to mp-TiO2/FTO in spite that the decrease in the surface area. Building a compact TiO2 underlayer by a spray method (d-TiO2/s-TiO2/FTO) results in further improvement of the cell performances. On the other hand, the replacement of glassy carbon cathode by Prussian Blue-electrodeposited FTO drastically increases the cell performances due to its excellent electrocatalytic activity for the H2O2 reduction. A one-compartment H2O2-PFC with the structure of d-TiO2/s-TiO2/FTO (photoanode) | 0.1 M NaClO4 and 0.1 M H2O2 (pH 3, electrolyte solution) | PB/FTO (cathode) exhibits short-circuit current (Jsc) of 1.57 mA cm−2 and open-circuit voltage (Voc) of 787 mV.
  • Keigo Fujiwara; Atsunobu Akita; Seina Kawano; Musashi Fujishima; Hiroaki Tada
    ELECTROCHEMISTRY COMMUNICATIONS ELSEVIER SCIENCE INC 84 71 - 74 1388-2481 2017/11 [Refereed]
     
    Hydrogen peroxide-fuel cell (H2O2-FC) possesses a theoretical power generating efficiency of 119% much larger than hydrogen/oxygen (H-2/O-2)-FC (82.9%) with a thermodynamic electromotive force of 1.09 V. This communication presents the prototype of H2O2-photofuel cell (PFC) without using noble metal catalyst. The H2O2-PFC is comprised of mesoporous anatase TiO2 nanocrystalline film coated on fluorine-doped tin oxide electorode (mp-TiO2/FTO, photoanode), glassy carbon (cathode), and an aqueous electrolyte solution containing 0.1 M NaClO4 and 0.1 M H2O2. Under UV-light irradiation, the H2O2-PFC stably works, providing a short-circuit current of 0.24 mA cm(-2) and an open-circuit voltage of 0.72 V at ambient temperature and pressure, while current hardly flows in the dark. Further, the PFC responds to visible-light due to the charge-transfer complex formation of H2O2 on the TiO2 surface.
  • Kaoru Kitazono; Ryo Akashi; Keigo Fujiwara; Atsunobu Akita; Shin-ichi Naya; Musashi Fujishima; Hiroaki Tada
    CHEMPHYSCHEM WILEY-V C H VERLAG GMBH 18 (20) 2840 - 2845 1439-4235 2017/10 [Refereed]
     
    A major challenge in chemistry for the synthesis of hetero-nanostructures is to build up atomically commensurate interfaces for smooth interfacial charge transfer. Photodeposition of CdSe on a CdS-preloaded mesoporous TiO2 nanocrystalline film yields CdS(core)-CdSe(shell) quantum dots (CdS@CdSe/mp-TiO2) with a heteroepitaxial nanojunction at 298K. Two-electrode quantum-dot-sensitized photoelectrochemical (QD-SPEC) cells with the structure photoanode |0.25M Na2S, 0.35M Na2SO3 (solvent=water)| cathode were fabricated. The CdS@CdSe QD-SPEC cell affords a solar-to-current efficiency (STCE) of 0.03% without external bias under illumination of simulated sunlight (>430 nm, AM 1.5, one sun). By applying 0.1V between the electrodes, the STCE increases up to 0.048%, far surpassing the CdS/mp-TiO2 and CdSe/mp-TiO2 photoanode cells. The CdS-CdSe interfacial analysis by high-resolution transmission electron microscopy and the band energy analysis taking the size quantization and the electrolyte effect indicate that the excellent performance of the CdS@CdSe/mp-TiO2 photoanode originates from the effective charge separation due to the cascade-like band edge alignment and the heteroepitaxial junction between CdS and CdSe QDs. In addition, high surface coverage of TiO2 with QDs can contribute to the reduction in the loss of the electron transport from TiO2 to the electron collecting electrode.
  • Takuya Ikeda; Ryo Akashi; Musashi Fujishima; Hiroaki Tada
    APPLIED PHYSICS LETTERS AMER INST PHYSICS 111 (11) 0003-6951 2017/09 [Refereed]
     
    UV-light irradiation of Au nanoparticle (NP)-loaded mesoporous TiO2 nanocrystalline films in an ethanol solution of Cd(NO3)(2) and S-8 at 298K gives rise to selective CdS deposition on Au NPs to yield Au(core)-CdS(shell) hybrid quantum dots (Au@ CdS/mp-TiO2). Two-electrode quantum dotsensitized photoelectrochemical cells with the structure of photoanode vertical bar 0.25M Na2S, 0.35M Na2SO3 (solvent = water)vertical bar cathode were fabricated. The Au@ CdS/mp-TiO2 photoanode cell yields hydrogen (H-2) with a rate of 0.18 ml h(-1) [solar-to-current efficiency (STCE) = 0.028%] without external bias far surpassing the rate of 0.028 ml h(-1) (solar-to-current efficiency = 0.006%) for the CdS/mp-TiO2 photoanode cell under illumination of simulated sunlight (lambda> 430 nm, AM 1.5, one sun). The 3D finite-difference time-domain calculations for a model Au@ CdS/TiO2 system indicate that an intense local electric field with an enhancement factor of similar to 10(3) is generated at the Au-CdS-TiO2 three-phase interface. The striking effect of the Au core stems from the enhancement of the excitation of the CdS shell and subsequent charge separation by the intense local electric field. Published by AIP Publishing.
  • Shin-ichi Naya; Yoshihiro Hayashido; Ryo Akashi; Kaoru Kitazono; Tetsuro Soejima; Musashi Fujishima; Hisayoshi Kobayashi; Hiroaki Tada
    JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 121 (38) 20763 - 20768 1932-7447 2017/09 [Refereed]
     
    Silver-silver halides (Ag-AgX, X = Cl, Br, I) have emerged as a new type of visible-light photocatalyst for solar-to-chemical transformations. The key to improving the activity of the plasmonic photocatalyts is the compatibility of local electric field enhancement (LEFE) and effective utilization of the sunlight as the energy source. A Ag nanoparticle (NP) possesses an intense LEFE effect, while the absorption peak is situated near the blue edge of the visible region. On the other hand, the Au NP has an absorption matching well the solar spectrum, but the LEFE is much smaller than that of a Ag NP. The optical property of a Au-x-Ag1-x alloy NP varies between those of Ag and Au NPs depending on the composition x, and thus, Au-x-Ag1-x alloy NP-incorporated AgX (Au-x-Ag1-x@AgX) can be a promising plasmonic photocatalyst. At the first step, gold ion-doped AgBr NPs are formed on mesoporous TiO2 film by the successive ionic layer adsorption and reaction (SILAR) method. At the second step, UV-light irradiation (lambda > 320 nm) of the sample in methanol yields Au-x-Ag1-x alloy particles having diameter of similar to 5 nm in the interior of AgBr with crystallite size of similar to 50 nm. The peak wavelength for the localized surface plasmon resonance can be tuned in the range between 500 and 600 nm through the alloy composition. On the basis of the experimental and density functional theory calculation results, we propose a plausible reaction mechanism.
  • Atsunobu Akita; Keigo Fujiwara; Musashi Fujishima; Hiroaki Tada
    APPLIED PHYSICS LETTERS AMER INST PHYSICS 110 (14) 0003-6951 2017/04 [Refereed]
     
    A simple dry process for preparing an ultrathin SiO2 shell on gold nanoparticle (Au NP) has been developed. The adsorption and reaction of 1,3,5,7-tetramethylcyclotetrasiloxane on Au NP-loaded ZnO (Au/ZnO) from gas phase at 353K yields a multilayer of polymethylsiloxane (PMS) on the Au surface, while a monolayer is formed on the ZnO surface. The postheating in the air at 773K transforms the PMS layer to a uniform SiO2 layer with thickness (l(SiO2)) of similar to 2 nm on the surface of every Au NP (Au@SiO2/ZnO). UV-visible absorption spectra show that the SiO2 shell enhances the localized surface plasmon resonance of Au NP with its peak redshifted from 530 nm to 571 nm. The 3D finite-difference time-domain calculations for Au@SiO2(l(SiO2) = 2 nm)/ZnO indicate that a strong local electric field is generated at the Au-SiO2-ZnO three-phase interface along the peripheral edge of Au NP with an enhancement factor of similar to 10(7). Published by AIP Publishing.
  • Keigo Fujiwara; Ryo Negishi; Musashi Fujishima; Hiroaki Tada
    JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 120 (44) 25418 - 25424 1932-7447 2016/11 [Refereed]
     
    Tris(acetylacetonato)iron(III) (Fe(acac)(3)) is chemisorbed on strontium titanate (SrTiO3) via partial ligand-exchange between the acac ligand and the surface Ti-OH group. Postheating at 773 K in the air yields extremely small iron(III) oxide clusters on SrTiO3 (Fe2O3/SrTiO3). The Fe2O3 loading amount per unit surface area of SrTiO3 (Gamma/Fe ions nm(-2)) was controlled by the Fe(acac)(3) concentration. The surface modification gives rise to visible-light activity for the oxidation of 2-naphthol used as a model water pollutant simultaneously with the UV-light activity significantly boosted. The visible-light activity is sensitive to Gamma to reach a maximum at Gamma approximate to 0.36. Valence band-X-ray photoelectron spectroscopy (VB-XPS) and electrochemical measurements indicated that the surface modification by the Fe2O3 nanoclusters (NCs) generates new vacant surface levels below the conduction band minimum of SrTiO3, while the VB maximum level is invariant. The band energy diagram of Fe2O3/SrTiO3 suggested that the visible-light activity can be induced by the photo excitation of the electrons in the VB of SrTiO3 to the vacant surface levels or the bulk-to-surface interfacial electron transfer (IFET) in contrast to the visible-light-driven surface-to-bulk IFET in Fe2O3/TiO2. Eventually, the high visible-light activity of Fe2O3/SrTiO3 stems from the effective charge separation and the electrocatalytic activity of the Fe2O3 NCs for the oxygen reduction reaction.
  • Musashi Fujishima; Yasunari Nakabayashi; Kouichi Takayama; Hisayoshi Kobayashi; Hiroaki Tada
    JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 120 (31) 17365 - 17371 1932-7447 2016/08 [Refereed]
     
    Photoelectrochemical experiments and density functional theory calculations indicated that visible-light irradiation of the CdS quantum dots (QDs)-TiO2 direct coupling system (CdS/TiO2) causes the electron injection from the valence band (VB) of CdS into the conduction band (CB) of TiO2 (path 2) in addition to the inter-CB electron transfer from CdS to TiO2 (path 1). Path 2 can be induced by the sub-bandgap excitation of CdS QDs to extend the spectral response of the CdS/TiO2 system. For path 2 as well as path 1 to effectively work, CdS QDs should be directly deposited on the TiO2 surface with high coverage. According to the guideline, a photocatalytic growth of the preformed seed (PCGS) technique has been developed. Transmission electron microscopy observation and X-ray photoelectron spectroscopy measurements of the CdS/TiO2 prepared by the PCGS technique indicated that the TiO2 surface is highly covered by CdS QDs. The technique was applied to mesoporous TiO2 nanocrystalline films (mp-TiO2) to yield CdS/mp-TiO2. CdS QD-sensitized photoelectrochemical (QD-SPEC) cells with a structure of CdS/mp-TiO2 (photoanode)|aqueous sulfide solution|Ag/AgCl (reference electrode)|Pt (cathode) were fabricated. The rate of hydrogen (H-2) generation in the QD-SPEC cell under illumination of simulated sunlight (AM 1.5, 1 sun, lambda > 430 nm) increases with an increase in the TiO2-surface coverage by CdS QDs.
  • Mari Yoshii; Yusuke Murata; Yasunari Nakabayashi; Takuya Ikeda; Musashi Fujishima; Hiroaki Tada
    JOURNAL OF COLLOID AND INTERFACE SCIENCE ACADEMIC PRESS INC ELSEVIER SCIENCE 474 34 - 40 0021-9797 2016/07 [Refereed]
     
    CdSe quantum dots (QDs) have successfully been formed on the TiO2 surface by the photodeposition of Se QDs and their subsequent transformation into CdSe QDs (CdSe/TiO2) (Fujishima et al., 2014). The addition of mercaptoacetic acid (MAA) in the second step of the two-step photodeposition process significantly decreases the CdSe particle size and the contact angle against the TiO2 surface to increase the TiO2-surface coverage by CdSe QDs with the particle size distribution sharpened. X-ray photoelectron and Raman spectroscopy measurements indicated that MAA is densely chemisorbed on the surface of CdSe QDs through Cd-S bond, whereas sparsely adsorbed on the TiO2 surface. Photoelectrochemical (PEC) cells using CdSe/TiO2 as the photoanode for hydrogen (H-2) generation from aqueous sulfide solution were fabricated. The rate of H-2 generation strongly depends on the concentration of MAA (C) added in the photoanode preparation, and the photoanode prepared at C = 0.04 mM affords a maximum solar-to-hydrogen conversion efficiency of 0.028%. (C) 2016 Published by Elsevier Inc.
  • Kentaro Tanaka; Yasuaki Jin-nouchi; Musashi Fujishirna; Hiroaki Tada
    JOURNAL OF COLLOID AND INTERFACE SCIENCE ACADEMIC PRESS INC ELSEVIER SCIENCE 457 (1) 248 - 253 0021-9797 2015/11 [Refereed]
     
    PbSe quantum dots (QDs) were formed on TiO2 by a two-step photodeposition technique. At the first step, UV-light irradiation of TiO2 in an ethanol solution of H2SeO3 yields Se QDs on the TiO2 surface in a highly dispersed state (Se/TiO2). At the second step, UV-light irradiation of Se/TiO2 in an ethanol solution of Pb(ClO4)(2) transforms Se QDs into several tens of nanometer-sized cubic deposits identified as PbSe (PbSe/TiO2) by X-ray diffraction, electronic absorption measurements and X-ray photoelectron spectroscopy. Photochronopotentiometry measurements suggested that the PbSe QDs are formed on TiO2 via the Pb2+ ion-assisted reduction of Se particles. (C) 2015 Published by Elsevier Inc.
  • Musashi Fujishima; Kentaro Tanaka; Naoki Sakami; Masataka Wada; Katsuyuki Morii; Takanori Hattori; Yasutaka Sumida; Hiroaki Tada
    JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 118 (17) 8917 - 8924 1932-7447 2014/05 [Refereed]
     
    We have developed a current doubling-induced two step photodeposition (CD-2PD) technique for forming selenium quantum dots (QIDs) and metal selenide QDs on TiO2, and proposed a reaction mechanism. Large aggregates of Se particles (similar to 100 nm) are generated on TiO2 from aqueous and 2-methyl-2-propanol solutions of H2SeO3 by UV-light irradiation. In contrast, highly dispersed selenium QDs are formed on TiO2 from the H2SeO3 ethanol and methanol solutions (Se/Ti02). The mean particle size increases with an increase in irradiation time (t(p1)) to reach 8.7 nm at t(p1),, = 2 h. The rates of Se photodeposition in the latter solvents are much faster than those in the latter solvents. These striking differences can be attributed to the current doubling effect of ethanol and methanol by photoelectrochemical measurements. Subsequent UV-light irradiation of Se(t(p1), = 20 min)/TiO2 in ethanol and methanol solutions containing Cd2+ ions converts the Se QDs into homogeneous CdSe QDs (similar to 2 nm). The application of this in situ CD-2PD technique to the mesoporous TiO2 nanocrystalline film enables the uniform incorporation of CdSe QDs into the film (CdSeimp-TiO2). QD-sensitized solar cells employing the CdSeimp-TiO2 photoanodes afford much higher power conversion efficiencies than that using a photoanode prepared in the aqueous solution.
  • Musashi Fujishima; Kentaro Tanaka; Naoki Sakami; Masataka Wada; Katsuyuki Morii; Takanori Hattori; Yasutaka Sumida; Hiroaki Tada
    J. Phys. Chem. C 118 12077 - 12086 2014/04 [Refereed]
  • Qiliang Jin; Musashi Fujishima; Anna Iwaszuk; Michael Nolan; Hiroald Tada
    JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 117 (45) 23848 - 23857 1932-7447 2013/11 [Refereed]
     
    Cu(acac)(2) is chemisorbed on TiO2 particles [P-25 (anatase/rutile = 4/1 w/w), Degussa] via coordination by surface Ti-OH groups without elimination of the acac ligand. Post-heating of the Cu(acac)(2)-adsorbed TiO2 at 773 K yields molecular scale copper(II) oxide clusters on the surface (CuO/TiO2). The copper loading amount (Gamma/Cu ions nm(-2)) is controlled in a wide range by the Cu(acac)(2) concentration and the chemisorption-calcination cycle number. Valence band (VB) X-ray photoelectron and photoluminescence spectroscopy indicated that the VB maximum of TiO2 rises up with increasing Gamma, while vacant midgap levels are generated. The surface modification gives rise to visible-light activity and concomitant significant increase in UV-light activity for the degradation of 2-naphthol and p-cresol. Prolonging irradiation time leads to the decomposition to CO2, which increases in proportion to irradiation time. The photocatalytic activity strongly depends on the loading, Gamma, with an optimum value of Gamma for the photocatalytic activity. Electrochemical measurements suggest that the surface CuO clusters promote the reduction of adsorbed O-2. First principles density functional theory simulations dearly show that, at Gamma < 1, unoccupied Cu 3d levels are generated in the midgap region, and at Gamma > 1, the VB maximum rises and the unoccupied Cu 3d levels move to the conduction band minimum of TiO2. These results suggest that visible-light excitation of CuO/TiO2 causes the bulk-to-surface interfacial electron transfer at low coverage and the surface-to-bulk interfacial electron transfer at high coverage. We conclude that the surface CuO clusters enhance the separation of photogenerated charge carriers by the interfacial electron transfer and the subsequent reduction of adsorbed O-2 to achieve the compatibility of high levels of visible and UV-light activities.
  • Qiliang Jin; Hiroshi Arimoto; Musashi Fujishima; Hiroaki Tada
    CATALYSTS MDPI AG 3 (2) 444 - 454 2073-4344 2013/06 [Refereed]
     
    The purpose of this study is to present an "environmental catalyst" possessing both thermocatalytic activity and visible-light activity for the decomposition of organic pollutants. Molecule-sized MnOx clusters are highly dispersed on the surface of TiO2 (anatase/rutile = 4/1 w/w, P-25, Degussa) by the chemisorption-calcination cycle technique using Mn(acac)(3) complex as a precursor (MnOx/TiO2). The thermo- and photo-catalytic activities of MnOx/TiO2 were studied for the degradation of 2-naphthol used as a model water pollutant. In contrast to the FeOx/TiO2 system, MnOx/TiO2 exhibits high thermocatalytic activity exceeding those of bulk beta-beta-MnO2 and Mn2O3. Also, visible-light activity is induced by the surface modification of TiO2 with MnOx clusters, whereas its UV-light activity decreases.
  • Anna Iwaszuk; Michael Nolan; Qiliang Jin; Musashi Fujishima; Hiroaki Tada
    JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 117 (6) 2709 - 2718 1932-7447 2013/02 [Refereed]
     
    A number of NiO clusters have been formed on TiO2 (anatase/rutile = 4/1 w/w, P-25, Degussa) in a highly dispersed state (NiO/TiO2) by the chemisorption-calcination cycle technique. The NiO/TiO2 causes high visible-light activities for the degradations of 2-naphthol and p-cresol exceeding those of FeOx/TiO2 (Tada et al. Angew. Chem., Int. Ed. 2011, 50, 3501-3505). The main purpose of this study is to clarify the origin at an electronic level by the density functional simulation for NiO, Ni2O2, Ni3O3, and Ni4O4 clusters supported on TiO2 rutile (110) and anatase (001) surfaces. The clusters adsorb strongly on both rutile and anatase with adsorption energies ranging from -3.18 to -6.15 eV, creating new interfacial bonds between the clusters and both surfaces. On rutile, intermetallic Ni-Ti bonds facilitate stronger binding compared with anatase. The electronic structure shows that the top of the valence bands (VBs) of rutile and anatase arises from electronic states on the NiO cluster. On the other hand, the conduction band of rutile is from the Ti 3d states, whereas NiO cluster levels are generated near the conduction band minimum of anatase. This is in contrast to the SnO2/rutile TiO2 system, where the density of states near the conduction band minimum increases with the VB unmodified. In the NiO/TiO2 system, the band gaps of both rutile and anatase are narrowed by up to 0.8 eV compared with pristine TiO2, which pushes the photoactivity into the visible region. In view of the calculated electronic structure, we have attributed the enhanced photocataltyic activity both to the charge separation due to the excitation from the Ni 3d surface sub-band to the TiO2 conduction band and the action of the NiO species as a mediator for the electron transfer from the TiO2 conduction band to O-2.
  • Sho-ichi Eda; Koki Moriyasu; Musashi Fujishima; Satoyuki Nomura; Hiroaki Tada
    RSC ADVANCES ROYAL SOC CHEMISTRY 3 (26) 10414 - 10419 2046-2069 2013 [Refereed]
     
    Rutile TiO2 nanorods (NRs) have been synthesized by a low-temperature route, using polyethylene glycol as a multi-functional agent for restricting particle growth, controlling particle shape, promoting crystallization, and dispersing particles. CuS nanocrystals were then photodeposited on the surface of the TiO2 NRs at 298 K (CuS-TiO2 NRs). CuS-TiO2 NRs exhibit strong absorption due to the interband transitions and the localized surface plasmon resonance in the visible-near infrared region. A dipole particle suspension (DPS) cell using a polydimethylsiloxane suspension of CuS-TiO2 NRs has been fabricated. This all-inorganic DPS cell exhibits a large solar transmittance change by applying an electric voltage. Application of this new type of DPS cell to smart windows would greatly help to reduce energy consumption by air conditioning systems in buildings and automobiles.
  • Qiliang Jin; Hironori Yamamoto; Kotaro Yamamoto; Musashi Fujishima; Hiroaki Tada
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS ROYAL SOC CHEMISTRY 15 (46) 20313 - 20319 1463-9076 2013 [Refereed]
     
    This study first presents a "TiO2-based eco-catalyst" working in the dark and under visible-light irradiation for the degradation of environmental organic pollutants. Molecular scale cobalt(III) oxide clusters are formed on the surface of highly active anatase TiO2 nanoparticles (Co2O3-TiO2) by the chemisorption-calcination cycle method. Co2O3-TiO2 exhibits very high visible-light activities for the degradation of 2-naphthol and formic acid used as model organic pollutants. Unprecedented thermocatalytic activity is concomitantly endowed on TiO2 by the surface modification. Prolonging reaction time in the Co2O3-TiO2 photo-and thermo-catalyzed reactions leads to the decomposition of 2-naphthol and formic acid to CO2. The essential action mechanisms of the Co2O3 clusters in the photocatalysis and thermocatalysis of Co2O3-TiO2 were discussed on the basis of spectroscopic and electrochemical data.
  • Sho-ichi Eda; Musashi Fujishima; Hiroaki Tada
    APPLIED CATALYSIS B-ENVIRONMENTAL ELSEVIER SCIENCE BV 125 288 - 293 0926-3373 2012/08 [Refereed]
     
    Monoclinic sheelite BiVO4 nanorods (ms-BiVO4 NRs) have been synthesized from an aqueous solution of Bi(NO3)(3) and NH4VO3 at 370K containing polyethylene glycol (PEG), while micron-sized BiVO4 crystals (ms-BiVO4 MCs) are formed without PEG. The UV-vis absorption spectra of the PEG solutions of NH4VO3 suggested the formation of a complex consisting of VO3- ion and PEG. In this synthetic route, PEG can suppress the reactivity of VO3- ions by the stabilization to further act as a soft template for the formation of ms-BiVO4 NRs. The as-grown ms-BiVO4 NRs exhibit a high level of photocatalytic activity for the degradation of Cu(acac)(2) without sacrificial agents under illumination of visible-light (lambda > 430 nm). The local symmetry of VO4 tetrahedron affecting the light absorption intensity in addition to the large surface area and high crystallinity have been suggested to be a crucial factor to achieve the high visible-light-activity of ms-BiVO4. (C) 2012 Elsevier B.V. All rights reserved.
  • Qiliang Jin; Musashi Fujishima; Michael Nolan; Anna Iwaszuk; Hiroaki Tada
    JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 116 (23) 12621 - 12626 1932-7447 2012/06 [Refereed]
     
    Surface modification of rutile TiO2 with extremely small SnO2 clusters gives rise to a great increase in its UV light activity for degradation of model organic water pollutants, while the effect is much smaller for anatase TiO2. This crystal form sensitivity is rationalized in terms of the difference in the electronic modification of TiO2 through the interfacial Sn-O-Ti bonds. The increase in the density of states near the conduction band minimum of rutile by hybridization with the SnO2 cluster levels intensifies the light absorption, but this is not seen with modified anatase. The electronic transition from the valence band to the conduction band causes the bulk-to-surface interfacial electron transfer to enhance charge separation. Further, electrons relaxed to the conduction minimum are smoothly transferred to O-2 due to the action of the SnO2 species as an electron transfer promoter.
  • Yoshihiro Muramatsu; Qiliang Jin; Musashi Fujishima; Hiroaki Tada
    APPLIED CATALYSIS B-ENVIRONMENTAL ELSEVIER SCIENCE BV 119 74 - 80 0926-3373 2012/05 [Refereed]
     
    Uniform and adhesive TiO2 nanotube arrays (TiO2-NTAs) have been prepared by a two-step anodization in ethylene glycol solution containing NRIF. The UV-light-activity of TiO2-NTAs prepared by changing the electrolytic voltage and calcination temperature was studied for the degradation of 2-naphthol. Further, the surface of TiO2-NTA has been modified with iron oxide species at a molecular scale by the chemisorption-calcination cycle technique. The iron oxide-surface modification endows TiO2-NTA with a high level of visible-light-activity, concomitantly increasing the UV-light-activity. Under optimum conditions, the iron oxide-surface modified TiO2-NTA exhibits a UV-light-activity comparable with that of highly active TiO2 particles (P-25. Degussa). (C) 2012 Elsevier B.V. All rights reserved.
  • Yoshihiro Muramatsu; Qiliang Jin; Musashi Fujishima; Hiroaki Tada
    Appl. Catal. B: Environ. 114 705 - 711 2012/03 [Refereed]
  • Musashi Fujishima; Qiliang Jin; Hironori Yamamoto; Hiroaki Tada; Michael Nolan
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS ROYAL SOC CHEMISTRY 14 (2) 705 - 711 1463-9076 2012 [Refereed]
     
    [Sn(acac)(2)]Cl-2 is chemisorbed on the surfaces of anatase TiO2 via ion-exchange between the complex ions and H+ released from the surface Ti-OH groups without liberation of the acetylacetonate ligand (Sn(acac)(2)/TiO2). The post-heating at 873 K in air forms tin oxide species on the TiO2 surface in a highly dispersed state on a molecular scale ((SnO2)(m)/TiO2). A low level of this p block metal oxide surface modification (similar to 0.007 Sn ions nm(-2)) accelerates the UV-light-activities for the liquid- and gas-phase reactions, whereas in contrast to the surface modification with d block metal oxides such as FeOx and NiO, no visible-light response is induced. Electrochemical measurements and first principles density functional theory (DFT) calculations for (SnO2)(m)/TiO2 model clusters (m = 1, 2) indicate that the bulk (TiO2)-to-surface interfacial electron transfer (BS-IET) enhances charge separation and the following electron transfer to O-2 to increase the photocatalytic activity.
  • Musashi Fujishima; Hiroaki Takatori; Hiroaki Tada
    JOURNAL OF COLLOID AND INTERFACE SCIENCE ACADEMIC PRESS INC ELSEVIER SCIENCE 361 (2) 628 - 631 0021-9797 2011/09 [Refereed]
     
    TiO2 nanoparticles (NPs) were deposited on the surfaces of SiO2 microspheres with a mesoporous structure prepared by a hydrolysis-controlled sol-gel technique. The TiO2 NPs were firmly combined on the surfaces of SiO2 microspheres through the interfacial Si-O-Ti bonds. The coupling causes the bandgap widening up to 3.37 eV, enhancing the photocatalytic activity for the decomposition of acetaldehyde under illumination of UV-light (330 < lambda < 400 nm). Density functional theory calculations for model clusters suggested that the observed results are derived from the lowering in the valence band edge energy with the interfacial bond formation. (C) 2011 Elsevier Inc. All rights reserved.
  • Kazuki Nagasuna; Tomoki Akita; Musashi Fujishima; Hiroaki Tada
    LANGMUIR AMER CHEMICAL SOC 27 (11) 7294 - 7300 0743-7463 2011/06 [Refereed]
     
    UV light irradiation of TiO2 (lambda > 320 nm) in a mixed solution of AgNO3 and S-8 has led to the formation of Ag2S quantum dots (QDs) on TiO2, while Ag nanoparticles (NPs) are photodeposited without S-8. Photoelectrochemical measurements indicated that the Ag2S photodeposition proceeds via the preferential reduction of Ag+ ions to Ag-0, followed by the chemical reaction with S-8. The application of this in situ photodeposition technique to mesoporous (mp) TiO2 nanocrystalline films coated on fluorine-doped SnO2 (FTO) electrodes enables formation of Ag2S QDs (Ag2S/mp-TiO2/FTO). Ag2S/mp-TiO2/FTO has the interband transition absorption in the whole visible region, While in the spectrum of Ag/mp-TiO2/FTO, a localized surface plasmon resonance absorption of Ag NPs is present centered at 490 nm. Ag2S QD-sensitized photoelectrochemical cells using the Ag2S/mp-TiO2/FTO and Ag/mp-TiO2/FTO photoanodes were fabricated. Under illumination of one sun, the Ag2S photoanode cell yielded H-2 at a rate of 0.8 mL . h(-1) with a total conversion efficiency of 0.29%, whereas the Ag/mp-TiO2/FTO photoanode is inactive.
  • Qiliang Jin; Musashi Fujishima; Hiroaki Tada
    JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 115 (14) 6478 - 6483 1932-7447 2011/04 [Refereed]
     
    Fe(acac)(3) is chemisorbed on the surfaces of anatase TiO(2) via partial ligand exchange between the acetylacetonate and surface Ti-OH groups [Fe(acac)(2)/TiO(2)]. The postheating at 773 K in air forms iron oxide species on the TiO(2) surface in a highly dispersed state at a molecular level ((FeO(x))(m)/TiO(2)). As a result of the iron oxide surface modification, the band gap of TiO(2) decreases, while the absorption due to the d-d transition clearly observed for the usual impregnation samples is very weak. (FeO(x))(m)/TiO(2) gives rise to a noticeable visible light activity concomitantly with a significant increase in UV light activity, whereas Fe(acac)(2)/TiO(2) hardly responds to visible light. Valence-band X-ray photoelectron spectra of (FeO(x))(m)/TiO(2) showed that the band gap narrowing results from the rise in the valence band top with surface modification. Also, photoluminescence spectroscopy indicated that the surface iron oxide species rapidly capture the excited electrons in the conduction band of TiO(2) to suppress recombination via surface oxygen vacancy levels. Furthermore, the surface iron oxide species act as excellent mediators for electron transfer from TiO(2) to O(2).
  • Shigeki Kanda; Tomoki Akita; Musashi Fujishima; Hiroaki Tada
    JOURNAL OF COLLOID AND INTERFACE SCIENCE ACADEMIC PRESS INC ELSEVIER SCIENCE 354 (2) 607 - 610 0021-9797 2011/02 [Refereed]
     
    UV-light irradiation to TiO2 in an aqueous ethanol solution of (NH4)(2)MoS4 under deaerated conditions has yielded molybdenum(IV) sulfide nanoparticles on a TiO2 surface (MoS2/TiO2) to be transformed into molybdenum(VI) oxide species highly dispersed at a molecular level by a subsequent heating at 773 K in air (m-MoO3/TiO2). In HCOOH aqueous solutions, the MoS2/TiO2 system exhibits a high level of photocatalytic activity for H-2 generation, while the m-MoO3/TiO2 system shows unique photochromism. (C) 2010 Elsevier Inc. All rights reserved.
  • Hiroaki Tada; Musashi Fujishima; Hisayoshi Kobayashi
    CHEMICAL SOCIETY REVIEWS ROYAL SOC CHEMISTRY 40 (7) 4232 - 4243 0306-0012 2011 [Refereed]
     
    Heteronanojunction systems consisting of narrow gap semiconductors represented by metal sulfides and TiO(2) are highly expected as visible-light-active photocatalysts and the key materials for various photoelectrochemical devices. The common central issue is increasing efficiency of the light-induced interfacial electron transfer from the metal sulfide quantum dots (QDs) to TiO(2). We have newly developed simple and versatile low-temperature photodeposition techniques for directly coupling metal sulfide QDs and TiO(2) by taking advantage of its photocatalysis and the photoinduced surface superhydrophilicity. This critical review summarizes the recent developments in the photodeposition techniques and their unique characteristics. Subsequently to the Introduction, a theoretical view of the interfacial electron transfer is presented to obtain the guidelines for the design of the heteronanojunction systems. Then, the itemized description is given for the photodepositions of several kinds of metal sulfides on TiO(2) followed by the summary of the features of the photodeposition technique. Finally, the applications of the resulting heteronanojunction systems to the photocatalysts and QD-sensitized solar cells are described, and the excellent performances are discussed by relating with the features of the photodeposition technique (87 references).
  • Qiliang Jin; Takuro Ikeda; Musashi Fujishima; Hiroaki Tada
    CHEMICAL COMMUNICATIONS ROYAL SOC CHEMISTRY 47 (31) 8814 - 8816 1359-7345 2011 [Refereed]
     
    The electronic modification of TiO2 with highly dispersed NiO particles smaller than ca. 2 nm by the chemisorption-calcination-cycle technique has given rise to a high level of visible-light-activity exceeding that of iron oxide-surface modified TiO2 simultaneously with the UV-light-activity being significantly increased.
  • Hiroaki Tada; Qiliang Jin; Hiroaki Nishijima; Hironori Yamamoto; Musashi Fujishima; Shin-ichi Okuoka; Takanori Hattori; Yasutaka Sumida; Hisayoshi Kobayashi
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION WILEY-V C H VERLAG GMBH 50 (15) 3501 - 3505 1433-7851 2011 [Refereed]
  • Yasuaki Jin-nouchi; Takanori Hattori; Yasutaka Sumida; Musashi Fujishima; Hiroaki Tada
    CHEMPHYSCHEM WILEY-V C H VERLAG GMBH 11 (17) 3592 - 3595 1439-4235 2010/12 [Refereed]
  • Masashi Fujii; Kazuki Nagasuna; Musashi Fujishima; Tomoki Akita; Hiroaki Tada
    JOURNAL OF PHYSICAL CHEMISTRY C AMER CHEMICAL SOC 113 (38) 16711 - 16716 1932-7447 2009/09 [Refereed]
     
    Ultraviolet light irradiation (lambda(ex) > 300 nm) to a mixed ethanol solution of cadmium perchlorate and elemental sulfur (S-8) under deaerated conditions has led to deposition of CdS quantum dots on the surfaces of TiO2 particles and films (CdS/TiO2). High-resolution transmission electron rnicroscopy (HRTEM) confirmed that the hexagonal CdS crystals are in good contact with TiO2. The loading amount and band gap of CdS can be controlled by irradiation time. Photoelectrochemical measurements using cyclic voltammetry and photochronopotentiometry indicated the photodeposition of CdS on TiO2 preferentially proceeds via an atomic route (Cd-0 + S -> CdS), whereas that on An nanoparticle-loaded TiO2 (Au/TiO2) follows an ionic route (Cd2+ + S2- -> CdS). This difference was revealed to result from the predominant adsorption of Cd2+ over S-8 on TiO2 (adsorbent-selective adsorption) in the former system and the selective adsorption Of S-8 and Cd2+ ions on Au and TiO2, respectively, (site-selective adsorption) in the latter system.
  • Musashi Fujishima; Yohei Okawa; Kumao Uchida
    JOURNAL OF THE AMERICAN CERAMIC SOCIETY WILEY-BLACKWELL 91 (11) 3749 - 3752 0002-7820 2008/11 [Refereed]
     
    Hierarchical trimodal porous hydroxyapatite (tpHAP) was fabricated by colloidal crystal templating using single-size latex particles with controlled calcination. In the overall framework structure, the tpHAP was revealed to have three kinds of pores, i.e., periodically ordered submicrometer-sized macropores of inverse opal structure, sponge-like larger macropores, and mesopores. The sponge-like macropores should be formed through removal of a sacrificial latex template, which fused in the process of low-temperature calcination. It was also found that high-temperature calcination leads to an increase in the crystallinity of the tpHAP, which resulted in deterioration of the ordered macropore arrays and a decrease in specific surface areas. Because of the trimodal porous structure, the tpHAP will serve as a multifunctional porous bioceramic in the fields of medical implants, tissue engineering, and drug delivery systems.
  • Musashi Fujishima; Yuki Matsuo; Hiroaki Takatori; Kumaci Uchida
    ELECTROCHEMISTRY COMMUNICATIONS ELSEVIER SCIENCE INC 10 (10) 1482 - 1485 1388-2481 2008/10 [Refereed]
     
    Novel acid-base complexes were prepared from k-carrageenan (Cg) and 2-mercaptoimidazole (MIm). FTIR absorption measurements revealed that Cg and MIm interact through proton exchange reactions between the sulfonic acid groups of Cg and the imino nitrogen atoms of MIm. DSC thermograms suggested that the extent of the Cg-MIm intermolecular interactions could be modulated by the doping amount of MIm. From the TG curves, the thermal stability of the complexes was found to improve with an increase in the doping amount. Furthermore, the degree of water absorbability of the complexes was reduced to half of that of Cg. The Cg-MIm complex at the smallest doping amount showed the highest level of proton conductivity, which exceeds the conductivity of Cg. The enhanced conductivity is thought to be derived from the softening effect of MIm based on the increased mobility of the polymer chains of Cg. (c) 2008 Elsevier B.V. All rights reserved.
  • Musashi Fujishima; Hiroaki Takatori; Kasumi Yamai; Yuki Nagao; Hiroshi Kitagawa; Kumao Uchida
    JOURNAL OF MATERIALS SCIENCE SPRINGER 43 (9) 3130 - 3134 0022-2461 2008/05 [Refereed]
     
    A kappa-carrageenan-Pt nanoparticle composite (Cg-Pt) was synthesized and its proton conductivity was examined by a complex-plane impedance method. The synthesized Cg-Pt was characterized by transmission electron microscope (TEM) observation, powder X-ray diffraction (XRD), Fourier transformed infrared (FT-IR) absorption measurements, and thermogravimetry/mass spectrometry (TG/MS) analysis. It was revealed that the a.c. electrical conductivity of Cg-Pt strongly depends on relative humidity (RH) and exceeds the conductivity of Cg under conditions of high humidity. From the temperature dependence of the a.c. conductivity, activation energies for protonic conduction were estimated to be 0.47 and 0.34 eV for Cg-Pt and Cg, respectively. The origin of the differences in the conductivities and activation energies are discussed.
  • Musashi Fujishima; Syoei Sakata; Takuya Iwasaki; Kumao Uchida
    JOURNAL OF MATERIALS SCIENCE SPRINGER 43 (6) 1890 - 1896 0022-2461 2008/03 [Refereed]
     
    Biodegradable inverse opal (IoPPC) was synthesized from a multifunctional carboxylic acid and polyols by colloidal crystal templating. The IoPPC was prepared by infiltration of the monomer solution into interparticle voids of silica colloidal crystal template, polycondensation of the infiltrated film, and removal of the template. The synthesized IoPPC was characterized by infrared absorption, X-ray diffraction measurements, differential scanning calorimetry, and thermogravimetry/mass spectrometry analysis. In order to clarify the effect of biodegradation on the inverse opal structure and the optical reflection property, the IoPPC was implanted in subcutaneous tissue of the lower back of three mice (ICR, 10 weeks, female). After the 2 weeks implantation, fragmented samples were harvested from the implant location and investigated by scanning electron microscope observations and optical reflection measurements. It was found that the reflection peak for the harvested samples decayed from that for the sample without implantation. Such a spectral change is considered to be attributed to the deterioration of the regularity of the inverse opal structures through biodegradation. The finding of this study will serve in the development of reflection-based sensing in various biomedical applications.
  • Musashi Fujishima; Syoci Sakata; Masakazu Kikoku; Daiju Ogawa; Kumao Uchida
    CHEMISTRY LETTERS CHEMICAL SOC JAPAN 36 (12) 1510 - 1511 0366-7022 2007/12 [Refereed]
     
    Macroporous poly(lactic acid) with inverse opal structure (IoPLA) was fabricated by colloidal crystal templating. IoPLA shows an intense near-infrared (NIR) reflection, which comes from the optical diffraction upon the periodic macroporous structure composed of uniformly sized pores. It is demonstrated that in vivo implantation of IoPLA leads to destruction of the inverse opal structure. causing a notable decrease in the intensity of the NIR reflection peak. IoPLA with this degradation-dependent optical property might become an implantable photonic bandgap material that can report the state of degradation and co-occurring events in a nondestructive, real-time manner.
  • Musashi Fujishima; Michio Enyo; Seiichi Kanda; Ryuichi Ikeda; Hiroshi Kitagawa
    CHEMISTRY LETTERS CHEMICAL SOC JAPAN 35 (5) 546 - 547 0366-7022 2006/05 [Refereed]
     
    Hydrogen electrode reaction (HER) was investigated for a copper coordination polymer, catena-mu-N,N'-bis(hydroxyethyl)dithiooxamidatocopper(II) (CuCP) by galvanostatic transient measurements using a palladium cathode. Individual steps in the Volmer-Tafel reaction were successfully observed for the colloidal CuCP in alkaline solution under hydrogen absorption. The Volmer step was found to be promoted with CuCP and its hydrogen-absorbed polymer (CuCPH) from shorter decay times in transient curves and smaller overpotentials in Tafel plots. In contrast, the inhibition of the Tafel step was observed, which is due to the larger overpotentials. Difference in reducibility between the polymers and plausible reduction mechanisms is discussed.
  • M. Fujishima; M. Yamauchi; R. Ikeda; T. Kubo; K. Nakasuji; H. Kitagawa
    Solid State Phenomena Trans Tech Publications Ltd 111 107 - 110 1662-9779 2006 [Refereed]
     
    This study reports hydrogen absorption property of newly-synthesized RAP (rubeanic-acid polymer)-protected palladium nanoparticle (RAP-Pd). From powder X-ray diffraction measurements, the lattice constant of Pd nanoparticle was revealed to increase by 0.11 Å under 600 Torr hydrogen gas condition at room temperature, indicating that the hydrogen absorption occurs in the Pd nanoparticle. Solid-state2H-NMR spectrum under deuterium gas showed that three different components exist in RAP-Pd, which are derived from imino group, terminal amino group in the RAP and absorbed deuterium atom inside the Pd nanoparticle. This result gives an expectation of the hydrogen absorption in RAP itself.
  • M. Fujishima; M. Yamauchi; R. Ikeda; T. Kubo; K. Nakasuji; H. Kitagawa
    SCIENCE AND TECHNOLOGY OF HYBRID MATERIALS TRANS TECH PUBLICATIONS LTD 111 107 - 110 1012-0394 2006 [Refereed]
     
    This study reports hydrogen absorption property of newly-synthesized RAP (rubeanic-acid polymer)-protected palladium nanoparticle (RAP-Pd). From powder X-ray diffraction measurements, the lattice constant of Pd nanoparticle was revealed to increase by 0.11 angstrom under 600 Torr hydrogen gas condition at room temperature, indicating that the hydrogen absorption occurs in the Pd nanoparticle. Solid-state H-2-NMR spectrum under deuterium gas showed that three different components exist in RAP-Pd, which are derived from imino group, terminal amino group in the RAP and absorbed deuterium atom inside the Pd nanoparticle. This result gives an expectation of the hydrogen absorption in RAP itself.
  • M Fujishima; R Ikeda; T Kawamura; H Kitagawa
    SYNTHETIC METALS ELSEVIER SCIENCE SA 135 (1-3) 411 - 412 0379-6779 2003/04 [Refereed]
     
    The ab initio molecular orbital calculations were carried out to clarify the electronic states of copper coordination polymers: (HOC2H4)(2)dtoaCu and H(2)dtoaCu. The intradimer Cu-Cu distance of H(2)dtoaCu has been predicted to be longer than that of (HOC2H4)(2)dtoaCu. Lowest unoccupied and highest occupied molecular orbitals, which are composed of copper 3d(x2-y2) and ligand p(sigma) orbitals, are considered to contribute to electrical conduction and superexchange interaction between Cu(II) ions, respectively.
  • M. Fujishima; Y. Nagao; R. Ikeda; S. Kanda; H. Kitagawa
    Synthetic Metals 133-134 433 - 435 0379-6779 2003/03 [Refereed]
     
    The magnetic properties of copper coordination polymers with dithiooxamide [H2dtoaCu] and its substituent N,N′-bis-(hydroxyethyl)dithiooxamide [(HOC2H4)2dtoaCu] have been investigated. They indicate different temperature dependence, which was analyzed by Bleaney-Bowers equation. The estimated J values of H2dtoaCu and (HOC2H4)2dtoaCu are -861 and -594 K, respectively. The large negative J values are derived from intradimer antiferromagnetic coupling through the ligands. The absolute J value of H2dtoaCu is larger than that of (HOC2H4)2dtoaCu, which is considered to be due to the difference of the superexchange interaction between Cu(II) ions via ligands. The electronic structure of the coordination polymer is supposed to depend on the substituent groups. © 2002 Elsevier Science B.V. All rights reserved.
  • Y Nagao; M Fujishima; R Ikeda; S Kanda; H Kitagawa
    SYNTHETIC METALS ELSEVIER SCIENCE SA 133 431 - 432 0379-6779 2003/03 [Refereed]
     
    AC conductivity measurements were carried out for a two-dimensional coordination polymer, N,N'-bis-(2-hydroxyethyl)dithiooxamida-tocopper(II) with an impedance analyzer in order to estimate the protonic conductivity. This polymer was found to exhibit a high protonic conduction of sigma(p) = 1.2 x 10(-5) S cm(-1) under relative humidity of 83% and 300 K. (C) 2003 Elsevier Science B.V. All rights reserved.
  • Highly proton-conductive copper coordination polymer, H2dtoaCu (H2dtoa =dithiooxamide anion)
    Hiroshi Kitagawa; Yuki Nagao; Musashi Fujishima; Ryuichi Ikeda; Seiichi Kanda
    Inorganic Chemistry Communications 6 (4) 346 - 348 2003/03 [Refereed]
  • M Fujishima; R Ikeda; S Kanda; H Kitagawa
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS TAYLOR & FRANCIS LTD 379 223 - 228 1058-725X 2002 [Refereed]
     
    Hydrogen doping was electrochemically performed on the title coordination polymer, catena-mu-N,N'-bis-(hydroxyethyl)dithiooxamidatocopper(II), (HOC2H4)(2)dtoaCu. From X-ray photoelectron spectroscopy, the oxidation state of Cu(II) in (HOC2H4)(2)dtoaCu was revealed to be reduced to the Cu(I,II) mixed-valence state on hydrogen doping. While the spin susceptibility increases during initial hydrogen doping, it decreases and then shows no temperature dependence as the hydrogen doping proceeds. The temperature-independent behavior is supposed to be derived from Pauli paramagnetism.
  • M. Fujishima; S. Kanda; T. Mitani; H. Kitagawa
    Synthetic Metals 119 (1-3) 485 - 486 0379-6779 2001/03 [Refereed]
     
    The hydrogen doping was electrochemically performed on the title coordination polymer, catena-μ-N,N′-bis-(hydroxyethyl) dithiooxamidatocopper(II), and the hydrogen-induced structural and physical properties were investigated. From powder X-ray diffraction (XRD) measurement the main framework of two-dimensional coordination polymer was found to be unchanged during hydrogen doping. From IR measurement doped hydrogen atoms were revealed to bond to nitrogen atoms of the ligands.

Books etc

  • 水素エネルギーと材料技術
    Musashi Fujishima; Miho Yamauchi; Hiroshi Kitagawa (Contributor第４章５高分子材)シーエムシー出版 2005/04

MISC

Industrial Property Rights

Research Grants & Projects

  • フォトニック結晶構造をもつ生分解性バイオチップの開発
    文部科学省：科学研究費補助金・若手研究B
    Date (from‐to) : 2009 -2010 
    Author : Musashi Fujishima
  • 生分解性フォトニック結晶の開発とナノリザーバーデバイスへの応用
    科学技術振興事業団：シーズ発掘試験
    Date (from‐to) : 2007 -2008 
    Author : Musashi Fujishima
  • 生分解／ｐＨ応答が可能なフォトニックデバイスの開発とインプラント型ＤＤＳへの応用
    日本学術振興会：科学研究費補助金・基盤研究C
    Date (from‐to) : 2006 -2007 
    Author : Musashi Fujishima
  • 水素機能性を有する新規な有機―無機ハイブリッド系ナノ材料の開発
    日本板硝子材料工学助成会：第２８回研究助成
    Date (from‐to) : 2006 -2007 
    Author : Musashi Fujishima
  • 生分解性を有する超プロトン伝導体の創製
    文部科学省：科学研究費補助金・若手研究B
    Date (from‐to) : 2005 -2006 
    Author : Musashi Fujishima
  • 環境調和型超プロトン伝導体の開発
    財団法人日本証券奨学財団：平成１７年度研究調査助成金
    Date (from‐to) : 2005 -2006 
    Author : Musashi Fujishima
  • 再生可能資源を用いた超プロトン伝導体の創製
    財団法人カシオ科学振興財団：第２３回研究助成
    Date (from‐to) : 2005 -2006 
    Author : Musashi Fujishima
  • 再生可能資源を用いた有機－無機ハイブリッド型固体電解質の開発
    関西エネルギー・リサイクル科学研究振興財団：第１４回研究助成（エネルギー・リサイクル分野）
    Date (from‐to) : 2005 -2006 
    Author : Musashi Fujishima

Other link

researchmap


Copyright © MEDIA FUSION Co.,Ltd. All rights reserved.