Papers - IKEDA Shigeru
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High sintering resistance of platinum nanoparticles embedded in a microporous hollow carbon shell fabricated through a photocatalytic reaction Reviewed
Yun Hau Ng, Shigeru Ikeda, Takashi Harada, Takao Sakata, Hirotaro Mori, Akio Takaoka, Michio Matsumura
LANGMUIR 24 ( 12 ) 6307 - 6312 2008.6
Joint Work
Authorship：Lead author Publisher：AMER CHEMICAL SOC
Platinum (Pt) nanoparticles encapsulated in microporous carbon with a hollow structure (nPt@hC) were fabricated on the basis of a titanium(IV) oxide (TiO2) photocatalytic reaction. From the tomogram of a sample studied by using a transmission electron microscope (TEM), the Pt nanoparticles were found to be embedded in the carbon shell and were physically separated from each other by the carbon matrix. Owing to this unique structure, the Pt particles showed high resistance to sintering when subjected to thermal treatment at temperatures up to 800 degrees C. As a result, hydrogenation reactions using various heat-treated nPt@hCs as catalysts indicated that loss of catalytic activity was minimized. Thus, the present system will be a promising system for optimizing catalyst nanostructures utilized in processes requiring rigorous conditions.
DOI： 10.1021/la800045u
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Precise determination of the first hyperpolarizability of a fluorescent triindole derivative with dicyanovinyl groups by the deconvolution method Reviewed
Ikeda Shigeru, Kumagai Hironobu, Ooi Hideo, Konishi Koji, Hiyoshi Hidetaka, Wada Tatsuo
CHEMICAL PHYSICS LETTERS 458 ( 4-6 ) 337 - 340 2008.6
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Pore formation in silicon by wet etching using micrometre-sized metal particles as catalysts Reviewed
Chia-Lung Lee, Kazuya Tsujino, Yuji Kanda, Shigeru Ikeda, Michio Matsumura
JOURNAL OF MATERIALS CHEMISTRY 18 ( 9 ) 1015 - 1020 2008.3
Joint Work
Publisher：ROYAL SOC CHEMISTRY
Au, Pt, or Ag particles with particle sizes of ca. 1 mm were used as catalysts for boring pores in p-type Si( 100) wafers by wet etching in aqueous solutions containing hydrofluoric acid and hydrogen peroxide. Boring speed was fastest when Pt particles were used as the catalyst. However, the sidewalls of the pores and the surface of the wafer were covered with a nanoporous silicon layer of ca. 500 nm in thickness, and the pore showed a tapered structure. When micrometre-sized Ag particles were used, no deep pores were formed because the particles were unstable in the solution. In contrast to Pt and Ag particles, Au particles bored straight pores under some conditions. However, the morphology of pores depended on the shape of the Au particles. Spherical Au particles formed straight pores, whereas non-spherical Au particles formed pores with spiral sidewalls. When Au particles formed aggregates consisting of a small number of particles (< 10 particles), crooked pores tended to be formed. In contrast, when the aggregates were composed of a larger number of particles, straight pores were formed and the boring speed was faster than the pores formed with isolated Au particles.
DOI： 10.1039/b715639a
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Photocatalytic route for synthesis of hollow porous carbon/Pt nanocomposites with controllable density and porosity Reviewed
Yuri Hau Ng, Shigeru Ikeda, Takashi Harada, Sangin Park, Takao Sakata, Hirotaro Mori, Michio Matsumura
CHEMISTRY OF MATERIALS 20 ( 3 ) 1154 - 1160 2008.2
Joint Work
Authorship：Lead author Publisher：AMER CHEMICAL SOC
Simultaneous photoreduction of Pt(IV) ions and photooxidative polymerization of phenol on the surface of titanium(IV) oxide (TiO2) under ultraviolet light irradiation induced the formation of a composite, Pt-loaded TiO2 covered with a layer of phenolic polymer. Subsequent carbonization of the polymer layer and removal of TiO2 core particles yielded hollow carbon incorporated with platinum nanoparticles (nPt@hC). By varying the photoirradiation time, appreciable changes in density and porosity of the polymer layer and the carbon shell in nPt@hC were observed: prolonged irradiation induced a densification of the carbon matrix, resulting in a decrease in pore volume. Mainly due to the modulation of active surface of Pt nanoparticles, the densification of carbon was found to influence catalytic activity for hydrogenation of normal olefins.
DOI： 10.1021/cm702034w
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Origin of visible light absorption in GaN-Rich (Ga1-xZnx)(N1-xOx) photocatalysts Reviewed
Takeshi Hirai, Kazuhiko Maeda, Masaaki Yoshida, Jun Kubota, Shigeru Ikeda, Michio Matsumura, Kazunari Domen
JOURNAL OF PHYSICAL CHEMISTRY C 111 ( 51 ) 18853 - 18855 2007.12
Joint Work
Authorship：Lead author Publisher：AMER CHEMICAL SOC
Photoluminescence (PL) and photoluminescence excitation (PLE) spectra of (Ga1-xZnx)(N1-xOx) with compositions of x = 0.05-0.20 (i.e., GaN-rich) were measured at 10 K in an attempt to clarify the origin of the visible light activity of this material as a photocatalyst. It was found that the PL spectra of GaN-rich (Ga1-xZnx)(N1-xOx) can be interpreted to correspond to impurity levels, specifically acceptor levels formed by the substitution of Zn for Ga in GaN. The PL and PLE spectra suggest that the visible light absorption of this material occurs via the Zn-related acceptor levels.
DOI： 10.1021/jp709811k
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Size-selective photocatalytic reactions by titanium(IV) oxide coated with a hollow silica shell in aqueous solutions Reviewed
Shigeru Ikeda, Hideyuki Kobayashi, Yoshimitsu Ikoma, Takashi Harada, Tsukasa Torimoto, Bunsho Ohtani, Michio Matsumura
PHYSICAL CHEMISTRY CHEMICAL PHYSICS 9 ( 48 ) 6319 - 6326 2007.12
Joint Work
Authorship：Lead author Publisher：ROYAL SOC CHEMISTRY
A novel core-shell composite photocatalyst, commercially available titanium(IV) oxide (TiO2) particles directly incorporated into a hollow amorphous silica shell, was fabricated by successive coating of TiO2 with a carbon layer and a silica layer followed by heat treatment to remove the carbon layer. The composite induced efficient photocatalytic reactions when relatively small substrates were used, such as methanol dehydration and decomposition of acetic acid, without any reduction in the intrinsic activity of original TiO2, but did not exhibit efficient photocatalytic activity for decomposition of large substrates, methylene blue and polyvinyl alcohol. The uniquesize-selective properties of the composites are due to their structural characteristics, i.e., the presence of a pore system and a void space in the silica shell and between the shell and medial TiO2 particles, respectively. The loading of alkylsilyl groups on the surface of the composite led to highly photostable. oatability: the floated sample also induced efficient photocatalytic reaction for decomposition of acetic acid while retaining floatation at the gas/water interface.
DOI： 10.1039/b709891j
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Encapsulation of titanium(IV) oxide particles in hollow silica for size-selective photocatalytic reactions Reviewed
Shigeru Ikeda, Yoshimitsu Ikoma, Hideyuki Kobayashi, Takashi Harada, Tsukasa Torimoto, Bunsho Ohtani, Michio Matsumura
CHEMICAL COMMUNICATIONS 3753-3755 ( 36 ) 3753 - 3755 2007.9
Joint Work
Authorship：Lead author Publisher：ROYAL SOC CHEMISTRY
A core-shell composite of TiO2 particles encapsulated in a hollow silica was fabricated, and the core-shell composite showed size-selective photocatalytic activity for decomposition of organics without reducing the intrinsic activity of the naked TiO2 core.
DOI： 10.1039/b704468b
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Selective adsorption of glucose - Derived carbon precursor on amino-functionalized porous silica for fabrication of hollow carbon spheres with porous walls Reviewed
Shigeru Ikeda, Koji Tachi, Yun Hau Ng, Yoshimitsu Ikoma, Takao Sakata, Hirotaro Mori, Takashi Harada, Michio Matsumura
CHEMISTRY OF MATERIALS 19 ( 17 ) 4335 - 4340 2007.8
Joint Work
Authorship：Lead author Publisher：AMER CHEMICAL SOC
Coating of polysuccharide (PS) generated by hydrothermal treatment of glucose on Stober's silica particles was examined. Uniform surface coverage of PS was achieved when the silica particles, the surfaces of which had been modified with amino groups, were mixed during the hydrothermal reaction of glucose. On the other hand, bare silica could not be coated with PS upon addition to the hydrothermal reaction solution; instead, this produced spherical PS particles with diameters of a few tens of nanometers beside silica particles. The significant effect of surface amino-functionalization of silica particles on the coverage of PS is attributable to induction of an electrostatic attraction between the positively charged amino-functionalized silica surface and negatively charged PS. When silica (core)-porous silica (shell) spheres were used instead of Stober's silica, efficient filling of the pores of the silica shell with PS could also be achieved by amino-functionalization of the surface of the porous silica shell. The silica (core)- PS (shell) materials as-obtained were converted into isolated hollow carbon spheres with well-developed porous shell structures by heat treatment under a vacuum followed by treatment with aqueous hydrofluoric acid.
DOI： 10.1021/cm0702969
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A simple method for preparing highly active palladium catalysts loaded on various carbon supports for liquid-phase oxidation and hydrogenation reactions Reviewed
Takashi Harada, Shigeru Ikeda, Mayu Miyazaki, Takao Sakata, Hirotaro Mori, Michio Matsumura
JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 268 ( 43102 ) 59 - 64 2007.5
Joint Work
Authorship：Lead author Publisher：ELSEVIER SCIENCE BV
Preparation of nanosized palladium (Pd) catalysts supported on various carbon supports using a simple liquid-phase reduction of aqueous Pd complexes with potassium borohydride (KBH4) was investigated. We found that addition of appropriate amounts of sodium hydroxide (NaOH) into aqueous solutions of sodium tetrachloropalladate (Na2PdCl4) followed by reduction with KBH4 produced highly dispersed Pd nanoparticles less than 5 nm in diameter on any carbon supports. Ultraviolet-visible light (UV-vis) absorption spectra of aqueous Na2PdCl4 solutions in the presence of various amounts of NaOH clarified the occurrence of partial or complete ligand exchange of the Pd complex from chloride ions (C1(-)) to hydroxide ions (OH-). Hence, the production of small Pd nanoparticles on carbon supports is likely to be induced by structural change in the precursor complex prior to the reduction with KBH4. Moreover, evaluation of catalytic activities for liquid-phase oxidation of benzyl alcohol into benzaldehyde using oxygen and hydrogenation of the C=C bond in cinnamaldehyde with hydrogen revealed that catalytic functions were significantly dependent on the size and the dispersion of Pd particles; i.e., both reactions proceeded efficiently on small Pd catalysts highly dispersed on carbon supports but did not occur efficiently on Pd particles of relatively large sizes or with poor dispersion on those supports. (c) 2006 Elsevier B.V. All rights reserved.
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Evaluation of electron-hole recombination properties of titanium(IV) oxide particles with high photocatalytic activity Reviewed
Shin-Ya Murakami, Hiroshi Kominami, Yoshiya Kera, Shigeru Ikeda, Hidenori Noguchi, Kohei Uosaki, Bunsho Ohtani
RESEARCH ON CHEMICAL INTERMEDIATES 33 ( 43164 ) 285 - 296 2007.3
Joint Work
Publisher：VSP BV
Electron-hole recombination in nano-sized titanium(IV) oxide (TiO2) particles with various physical properties, which have been shown to be highly active photocatalysts, was evaluated by quantitative analysis of reduced titanium species (Ti3+), which might be formed at crystalline defective sites in TiO2 particles through photo-irradiation in the presence of a hole scavenger under deaerated conditions. These highly active photocatalyst samples were synthesized by hydrothermal crystallization in organic media (HyCOM method) and post-calcination. The Ti3+ density decreased with increasing calcination temperature (T-c), and a linear correlation was observed between the Ti3+ density and rate constant for electron-hole recombination evaluated by femtosecond pump-probe diffuse reflection spectroscopy. Reaction rate (R-Ag) and the amount of silver ions (Ag+) adsorbed on TiO2 particles ([Ag+]ads) were measured for photocatalytic silver metal deposition along with oxygen formation from an aqueous Ag+ solution under deaerated conditions, and the slope of the R-Ag versus [Ag+](ads) plot was determined. Kinetic investigation of this reaction showed that the reciprocal of the slope was approximately related to the ratio of the rates for electron-hole recombination and electron trapping (k(r)/k(e) ratio). The k(r)/k(e) ratio decreased as T-c increased, and the logarithm of the k(r)/k(e) ratio was linearly related with Ti3+ density. These two parameters were used as a measure for the recombination properties of TiO2 photocatalysts with various physical properties.
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Fabrication of hollow carbon nanospheres encapsulating platinum nanoparticles using a photocatalytic reaction Reviewed
Yun Hau Ng, Shigeru Ikeda, Takashi Harada, Suguru Higashida, Takao Sakata, Hirotaro Mori, Michio Matsumura
ADVANCED MATERIALS 19 ( 4 ) 597 - 602 2007.2
Joint Work
Authorship：Lead author Publisher：WILEY-V C H VERLAG GMBH
The fabrication of Pt nanoparticles encapsulated in hollow carbon nanospheres using TiO2 nanoparticles as both the photocatalyst and the inorganic mold is demonstrated (see figure). These spheres are found to have high surface area and ultrathin shells with well-developed microporosity, and thus can be used as catalysts. This new imprinting method can be used to synthesize any desired nanostructures using predesigned TiO2 photocatalysts.
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Ligand-free platinum nanoparticles encapsulated in a hollow porous carbon shell as a highly active heterogeneous hydrogenation catalyst Reviewed
Shigeru Ikeda, Satoru Ishino, Takashi Harada, Natsumi Okamoto, Takao Sakata, Hirotaro Mori, Susumu Kuwabata, Tsukasa Torimoto, Michio Matsumura
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 45 ( 42 ) 7063 - 7066 2006.10
Joint Work
Authorship：Lead author Publisher：WILEY-V C H VERLAG GMBH
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Preparation of platinized strontium titanate covered with hollow silica and its activity for overall water splitting in a novel phase-boundary photocatalytic system Reviewed
Shigeru Ikeda, Ko Hirao, Satoru Ishino, Michio Matsumura, Bunsho Ohtani
CATALYSIS TODAY 117 ( 43103 ) 343 - 349 2006.9
Joint Work
Authorship：Lead author Publisher：ELSEVIER SCIENCE BV
Platinum-loaded strontium titanate (Pt-SrTiO3) (core) -silica (shell) powder was prepared by double-layer winding of a carbon and a silica layer on Pt-SrTiO3 followed by heat treatment to remove the carbon layer. Scanning electron microscope (SEM) observation and analyses of the BET surface area suggested that the powder has a void space between Pt-SrTiO3 (core) and silica (shell). When the surface of the powder was partially modified with a fluoroalkylsilylation agent, thus-obtained material assembled at a gas-water interface and acted as a photocatalyst for overall water splitting to produce hydrogen (H-2) and oxygen (O-2). Probably due to the suppression of a backward reaction, production of water from H-2 and O-2, on the platinum, the overall efficiency of this system was higher than that of the conventional suspension system. Moreover, while the Pt-SrTiO3 powders directly covered with fluoroalkylethylsilyl groups showed low photostability, i.e., prolonged irradiation precipitated some of the surface-modified particles in water owing to photocatalytic decomposition of surface fluoroalkylethylsilyl groups, this material could retain its location at the phase boundary. (C) 2006 Elsevier B.V. All rights reserved.
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Photocatalytic activity of hydrothermally synthesized tantalate pyrochlores for overall water splitting Reviewed
S Ikeda, M Fubuki, YK Takahara, M Matsumura
APPLIED CATALYSIS A-GENERAL 300 ( 2 ) 186 - 190 2006.1
Joint Work
Authorship：Lead author Publisher：ELSEVIER SCIENCE BV
Tantalate and mobate pyrochlores, Ca2M2O7 (M = Nb, Ta) and A(2)Ta(2)O(6) (A = Na, K), were prepared by a hydrothermal method. These oxides were crystallized directly from tantalum or niobium alkoxide in the presence of sodium, potassium or calcium cation in basic solutions at temperatures between 373 and 448 K, and their crystallinity was improved by calcination in air. Stoichiometric liberations Of H-2 and O-2 were achieved over tantalate pyrochlores loaded with a small amount of nickel oxide (NiO) as a catalyst for H2 production, while the NiO-loaded mobate pyrochlore showed no photocatalytic, activity. The photocatalytic functions of the tantalate pyrochlores were attributed to their energy levels of the bottom of conduction bands being much more negative than those of the niobate pyrochlores. (c) 2005 Elsevier B.V. All rights reserved.
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Direct observation of amphiphilic silica particles assembled at an oil-water interface Reviewed
S Ikeda, YK Takahara, S Ishino, M Matsumura, B Ohtani
CHEMISTRY LETTERS 34 ( 10 ) 1386 - 1387 2005.10
Joint Work
Authorship：Lead author Publisher：CHEMICAL SOC JAPAN
The location of amphiphilic silica particles, on which have both hydrophobic and hydrophilic surfaces, at a n-decane-water interface was investigated. By scanning electron microscopy observation of the particles fixed at the interface with a curable poly(dimethylsiloxane), we found that each hemisphere of a amphiphilic particle are immersed in the oil or aqueous phase.
DOI： 10.1246/cl.2005.1386
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Porous polystyrene microspheres having dimpled surface structures prepared within micellar assemblies of amphiphilic silica particles in water Reviewed
YK Takahara, S Ikeda, K Tachi, T Sakata, T Hasegawa, H Mori, M Matsumura, B Ohtani
CHEMICAL COMMUNICATIONS 4205-4207 ( 33 ) 4205 - 4207 2005.9
Joint Work
Authorship：Lead author Publisher：ROYAL SOC CHEMISTRY
Production of porous polystyrene microspheres having dimpled surface structures was demonstrated using amphiphilic and hydrophobic silica particles as structure-directing agents.
DOI： 10.1039/b507123b
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Photocatalytic preparation of encapsulated gold nanoparticles by jingle-bell-shaped cadmium sulfide-silica nanoparticles Reviewed
Pal, B; Torimoto, T; Ikeda, S; Shibayama, T; Sugawara, K; Takahashi, H; Ohtani, B
TOPICS IN CATALYSIS 35 ( 43163 ) 321 - 325 2005.7
Joint Work
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YK Takahara, Y Hanada, T Ohno, S Ushiroda, S Ikeda, M Matsumura
JOURNAL OF APPLIED ELECTROCHEMISTRY 35 ( 43289 ) 793 - 797 2005.7
Joint Work
Authorship：Lead author Publisher：SPRINGER
Cyclohexane was oxidized under visible light in a titanium dioxide suspension containing hydrogen peroxide. Cyclohexanol and cyclohexanone were detected as products. Under similar experimental conditions, nonyl aldehyde was oxidized to nonylic acid. The reaction rate for the oxidation on rutile particles was faster than that on anatase particles. When hydrogen peroxide was added to suspensions of these particles, both rutile and anatase particles became yellow-colored due to the formation of peroxide complexes on their surfaces. The difference between the reaction rates for rutile and anatase particles suggests that the properties of the peroxide complexes formed on these particles are different. The properties of these complexes were studied by UV-vis spectroscopy.
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Asymmetrically modified silica particles: A simple particulate surfactant for stabilization of oil droplets in water Reviewed
YK Takahara, S Ikeda, S Ishino, K Tachi, K Ikeue, T Sakata, T Hasegawa, H Mori, M Matsumura, B Ohtani
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 127 ( 17 ) 6271 - 6275 2005.5
Joint Work
Authorship：Lead author Publisher：AMER CHEMICAL SOC
Spherical silica particles that are able to assemble at a phase boundary of a dual-phase mixture of water and an immiscible organic solvent were prepared by a partial modification of their surface hydroxyl groups with an alkylsilylation agent. Scanning electron microscopic observation of these particles in which their remaining surface hydroxyl groups had been selectively modified with colloidal gold particles revealed that each particle has an asymmetric surface structure: one side of the surface is hydrophilic and the other is hydrophobic. We found that these particles could form a micellar structure in water in the presence of an organic solution of a toluene/polystyrene mixture. The micellar structure was evidenced by formation of golf-ball-like polystyrene particles with dimples imprinting morphologies of the hydrophobic part of modified silica particles.
DOI： 10.1021/ja043581r
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SI Mostafa, S Ikeda, B Ohtani
JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 225 ( 2 ) 181 - 188 2005.1
Joint Work
Publisher：ELSEVIER SCIENCE BV
Synthesis procedures are described for the complexes [M(L-H)(AcO)(H(2)O)(2)] (M(II) = Mn, Ni), [M(L-H)Cl(n)(H(2)O)(m)] (M = Fe(III), n = 2, m = 2; M = Pd(II), n = 1, m = 1; m = Ag(I), n = 0, m = 2) and [M(L-H)(2)(H(2)O)(n)] (M = Co(II), n = 2; M = Cu(II), [WO(2)](2+), n=0) where L is the Schiff-base derived from salicylaldehyde and 3-aminopropyltriethoxysaline (APTSsal) that is chemically anchored on Y-zeolite. Characterization of these complexes was accomplished by elemental analyses, infrared and diffuse-reflectance spectra and magnetic moment. The anchored Schiff-bases imposed stable planar coordination sphere on the metal ions, allowing epoxidation of 1-octene in the axial position in the presence of molecular oxygen. The epoxidation of 1-octene was also achieved by employing the partly modified Y-zeolite with n-octadecyltrichlorosilane (OTS) Schiff-base complexes in the presence of 30% H(2)O(2) under a phase-boundary system. (C) 2004 Elsevier B.V. All rights reserved.