Papers - IKEDA Shigeru
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Fabrication of CuInS2 films from electrodeposited Cu/In bilayers: effects of preheat treatment on their structural, photoelectrochemical and solar cell properties Reviewed
Sun Min Lee, Shigeru Ikeda, Tetsuro Yagi, Takashi Harada, Ahmed Ennaoui, Michio Matsumura
PHYSICAL CHEMISTRY CHEMICAL PHYSICS 13 ( 14 ) 6662 - 6669 2011.4
Joint Work
Authorship:Lead author Publisher:ROYAL SOC CHEMISTRY
Polycrystalline CuInS2 films were fabricated by sulfurization of electrodeposited Cu and In metallic precursor films in a Cu-rich composition at 520 degrees C in H2S (5% in Ar). Structural analyses revealed that the adherence of the thus-formed CuInS2 film to the Mo substrate was strongly dependent on heating profiles of the Cu/In bilayer film: a CuInS2 film with poor adherence having many crevices was formed when the Cu/In bilayer film was heated monotonously from room temperature to 520 degrees C in Ar within 25 min followed by sulfurization, whereas CuInS2 films with good adherence were obtained when the Cu/In films were pretreated at 110 degrees C in Ar for 10-60 min just before increasing the temperature up to 520 degrees C for sulfurization. It was also clarified that the CuInS2 film obtained without 110 degrees C pretreatment had pinholes inside the film, whereas the CuInS2 films formed after 110 degrees C pretreatment showed no notable pinholes. Photoelectrochemical responses of these CuInS2 films in an electrolyte solution containing Eu(III) indicated that the CuInS2 films obtained after 110 degrees C pretreatment had higher external quantum efficiency (EQE) values than those of films obtained without 110 degrees C pretreatment, mainly due to better adherence of 110 degrees C pretreated CuInS2 films to the Mo substrate than the CuInS2 film obtained without 110 degrees C pretreatment. The performance of solar cells with an Al:ZnO/Zn(S,O)/CdS/CuInS2/Mo structure also depended on the structural characteristics of the CuInS2 films, i.e., preliminary conversion efficiencies of ca. 5% were obtained for devices based on the CuInS2 films obtained after 110 degrees C pretreatment, whereas the device prepared by the CuInS2 film without 110 degrees C pretreatment showed the conversion efficiency less than 1.5%.
DOI: 10.1039/c0cp02204g
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Emission spectroscopy of divalent-cation-doped GaN photocatalysts Reviewed
Takeshi Hirai, Takashi Harada, Shigeru Ikeda, Michio Matsumura, Nobuo Saito, Hiroshi Nishiyama, Yasunobu Inoue, Yoshiyuki Harada, Nobuhito Ohno, Kazuhiko Maeda, Jun Kubota, Kazunari Domen
JOURNAL OF APPLIED PHYSICS 110 ( 11 ) 113526-1 - 113526-7 2011.2
Joint Work
Publisher:AMER INST PHYSICS
Photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectra of GaN particles doped with divalent cations (Mg(2+), Zn(2+), and Be(2+)), which promote photocatalytic overall water splitting, were investigated. The PL and TRPL spectra were mainly attributed to donor-acceptor pair recombination between the divalent cation dopants and divalent anion impurities (O(2)- and S(2-)) unintentionally introduced from raw materials, which form acceptor and donor levels, respectively. These levels are likely to provide holes and electrons required for photocatalytic reactions, contributing to the photocatalytic activity of the GaN-based photocatalysts for overall water splitting. (C) 2011 American Institute of Physics. [doi:10.1063/1.3665225]
DOI: 10.1063/1.3665225
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Photoreduction of Water by using Modified CuInS2 Electrodes Reviewed
Shigeru Ikeda, Takayuki Nakamura, Sun Min Lee, Tetsuro Yagi, Takashi Harada, Tsutomu Minegishi, Michio Matsumura
CHEMSUSCHEM 4 ( 2 ) 262 - 268 2011.2
Joint Work
Authorship:Lead author Publisher:WILEY-BLACKWELL
Polycrystalline CuInS2 films were fabricated by sulfurization of electrodeposited Cu and In metallic precursor films. Structural analyses revealed that the CuInS2 film formed compact agglomerates of crystallites with grain sizes of ca. 0.5-1.5 mu m. Photoelectrochemical characterization revealed that the film was p-type with a flat band potential of 0.3-0.4 V (vs Ag/AgCl at pH 4), which is suitable for water reduction but cannot be for water oxidation. Upon loading Pt deposits, the film worked as a hydrogen (H-2) liberation electrode under cathodic polarization. Moreover, by introduction of n-type thin layers such as CdS and ZnS on the CuInS2 surface before the Pt loading, appreciable improvements of H-2 liberation efficiency were achieved: for the CdS modified sample, spectral response data showed incident photon to current efficiency as high as 20% at wavelengths ranging from ca. 500 to 750 nm. Appreciable H-2 evolution on this sample under potentials of power-producing regions was also confirmed.
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Electrochemical method for slicing Si blocks into wafers using platinum wire electrodes Reviewed
Chia-Lung Lee, Yuji Kanda, Shigeru Ikeda, Michio Matsumura
SOLAR ENERGY MATERIALS AND SOLAR CELLS 95 ( 2 ) 716 - 720 2011.2
Joint Work
Publisher:ELSEVIER SCIENCE BV
Straight grooves were formed in single crystalline Si wafers and poly-crystalline Si blocks in an aqueous solution containing HF by an electrochemical method using Pt wires (phi=50 mu m) and a Pt foil as catalytic electrodes and a counter electrode, respectively. The grooves were formed by applying anodic potential of about 2.25 V vs. Ag/AgCl to the Pt wires, which were in contact with Si. The grooving rate and morphologies were dependent on HF concentrations. The grooving rate was also dependent on the pressure applied to the Si/Pt interface. Grooves with a width of about 55 mu m were formed at the edge of a 250-mu m-thick single crystalline wafer at a rate of 3.2 mm/h by processing in 15 mol dm(-3) HF under a pressure of about 54 x 10(4) g/cm(2). This pressure was necessary to increase the grooving rate. Possibly, an insulating porous silicon layer formed between Si and Pt was destroyed under this pressure. On applying this process to a poly-crystalline Si block, a Si wafer with a size of 1 x 1 cm(2) was obtained by the electrochemical method. However, the slicing speed was lowered as the depth of grooves increased and it took 120 h to obtain the wafer. The slow exchange of HF solution in the groove was thought to be the main reason for the slow speed of slicing the Si block. (C) 2010 Elsevier B.V. All rights reserved.
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Development of New Methods for Fine-Wiring in Si Using a Wet Catalytic Reaction Reviewed
Chia-Lung Lee, Tomohiko Sugita, Koji Tatsumi, Shigeru Ikeda, Michio Matsumura
TECHNOLOGY EVOLUTION FOR SILICON NANO-ELECTRONICS 470 129 - 134 2011.2
Joint Work
Publisher:TRANS TECH PUBLICATIONS LTD
Using a new wet process based on a catalytic reaction, pores and grooves were formed in Si using Au, Pt, or Ag as the catalyst. The diameter of the pore can be as small as 50 nm. However, to produce wiring in Si wafers, we primarily formed pores with a diameter of about 5 mu m. These pores were filled with Cu by electrochemical plating, forming Cu wires developed to the wafer surface. In the process, the catalyst particles remaining at the bottom of the pore acted as seeds for the deposition of Cu and helped fill the pores without the formation of voids. In order to control the position of pores and grooves formed in Si, methods using catalytic electrodes were also developed.
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Catalytic Activity and Regeneration Property of a Pd Nanoparticle Encapsulated in a Hollow Porous Carbon Sphere for Aerobic Alcohol Oxidation Reviewed
Takashi Harada, Shigeru Ikeda, Fumihiro Hashimoto, Takao Sakata, Keita Ikeue, Tsukasa Torimoto, Michio Matsumura
LANGMUIR 26 ( 22 ) 17720 - 17725 2010.11
Joint Work
Authorship:Lead author Publisher:AMER CHEMICAL SOC
A core-shell composite consisting of a palladium (Pd) nanoparticle and a hollow carbon shell (Pd@hmC) was employed as a catalyst for aerobic oxidation of various alcohols. The core-shell structure was synthesized by consecutive coatings of Pd nanoparticles with siliceous and carbon layers followed by removal of the intermediate siliceous layer. Structural characterizations using TEM and N-2 adsorption-desorption measurements revealed that Pd@hmC thus-obtained was composed of a Pd nanoparticle core of 3-6 nm in diameter and a hollow carbon shell with well-developed mesopore (ca. 2.5 nm in diameter) and micropore (ca. 0.4-0.5 nm in diameter) systems. When compared to some Pd-supported carbons. Pd@hmC showed a high level of catalytic activity for oxidation of benzyl alcohol into benzaldehyde using atmospheric pressure of O-2 as an oxidant. The Pd@hmC composite also exhibited a high level of catalytic activity for aerobic oxidations of other primary benzylic and allylic alcohols into corresponding aldehydes. The presence of a well-developed pore system in the lateral carbon shell enabled efficient diffusion of both substrates and products to reach the central Pd nanoparticles. leading to such high catalytic activities. This core-shell structure also provided high thermal stability of Pd nanoparticles toward coalescence and/or aggregation due to the physical isolation of each Pd nanoparticle from neighboring particles by the carbon shell: this specific property of Pd@hmC resulted in possible regeneration of catalytic activity for these aerobic oxidations by a high-temperature heat treatment of the sample recovered after catalytic reactions.
DOI: 10.1021/la102824s
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Multicomponent sulfides as narrow gap hydrogen evolution photocatalysts Reviewed
Shigeru Ikeda, Takayuki Nakamura, Takashi Harada, Michio Matsumura
PHYSICAL CHEMISTRY CHEMICAL PHYSICS 12 ( 42 ) 13943 - 13949 2010.11
Joint Work
Authorship:Lead author Publisher:ROYAL SOC CHEMISTRY
A series of mixed crystals composed of Cu2ZnSnS4, Ag2ZnSnS4 and ZnS was prepared by co-precipitation of the corresponding metal ions in aqueous sodium sulfide followed by annealing in a sulfur atmosphere. Ideal solid solutions of Cu2ZnSnS4 and Ag2ZnSnS4 with a kesterite structure ((CuxAg1-x)(2)ZnSnS4 (0 <= x <= 1)) were successfully obtained by this procedure, as confirmed by their X-ray diffraction (XRD) patterns and energy-diffuse X-ray (EDX) analyses. On the other hand, the solubility of ZnS in these kesterite compounds was found to be limited: the upper limit of the ratio of ZnS to (CuxAg1-x)(2)ZnSnS4 was less than 0.1, regardless of the Cu-Ag ratio in (CuxAg1-x)(2)ZnSnS4. Based on the results for dependence of their photoabsorption properties on atomic compositions, a plausible band structure is discussed. Evaluation of the photocatalytic activity for H-2 evolution of these mixed crystals from an aqueous solution containing S2- and SO32- ions upon loading Ru catalysts under simulated solar radiation (AM 1.5) revealed that active compounds for this reaction should contain both dissolved ZnS and Ag components. The dissolved ZnS in (CuxAg1-x)(2)ZnSnS4 gave upward shifts of their conduction band edges. Moreover, the presence of Ag in the solid solution provided n-type conductivity, leading to efficient migration of photogenerated electrons to the surface to induce water reduction into H-2.
DOI: 10.1039/c0cp00267d
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Determination of Oxygen Sources for Oxidation of Benzene on TiO2 Photocatalysts in Aqueous Solutions Containing Molecular Oxygen Reviewed
Thuan Duc Bui, Akira Kimura, Shigeru Ikeda, Michio Matsumura
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 132 ( 24 ) 8453 - 8458 2010.6
Joint Work
Publisher:AMER CHEMICAL SOC
Photocatalytic oxidation of benzene to CO2 was studied in aqueous solutions using different kinds of TiO2 powders, and isotopic oxygen tracers ((H2O)-O-18 and O-18(2)) were used to investigate the oxidation process. Phenol was produced as a main intermediate in solution. When anatase powders, which showed high activity for oxidation of benzene, were used, 70-90% of oxygen introduced into phenol was from water. On the other hand, when rutile powders were used, only 20-40% of the oxygen was from water. The rest was from molecular oxygen in both cases. The rate of phenol production by using molecular oxygen was nearly the same between anatase and rutile powders. Hence, the high activity of anatase powders for oxidation of benzene to CO2 is attributed to their high activity for oxidation of benzene to phenol, which is considered to be the rate-determining step, using water as the oxygen source. The processes using water and molecular oxygen as the oxygen sources are ascribed, respectively, to oxygen transfer and hole transfer processes in the initial step of benzene oxidation.
DOI: 10.1021/ja102305e
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Thuan Duc Bui, Akira Kimura, Shigeru Ikeda, Michio Matsumura
APPLIED CATALYSIS B-ENVIRONMENTAL 94 ( 43102 ) 186 - 191 2010.2
Joint Work
Publisher:ELSEVIER SCIENCE BV
TiO2-photocatalyzed reaction was conducted in pure benzene in which TiO2 particles were suspended. Benzene was oxidatively decomposed into CO2, as most of organic compounds. However, the rate of CO2 evolution from benzene was gradually lowered as the reaction continued, which was in contrast to the cases of other non-aromatic organic compounds, such as alcohols or acids. To clarify the reason for the decrease in activity of TiO2, intermediates produced in the solution phase and on the surface of TiO2 were analyzed using chemical and physical techniques. Several kinds of intermediates were identified: phenolic compounds, aldehydes, carboxylic acids, and polymeric substance. Of these products, catechol and polymeric substance, which were observed only on the surface of TiO2 powder, were found to be responsible for the lowering of the photocatalytic activity of TiO2. (C) 2009 Elsevier B.V. All rights reserved.
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Shigeru Ikeda, Ryo Kamai, Tetsuro Yagi, Michio Matsumura
JOURNAL OF THE ELECTROCHEMICAL SOCIETY 157 ( 1 ) B99 - B103 2010.1
Joint Work
Authorship:Lead author Publisher:ELECTROCHEMICAL SOC INC
Copper indium diselenide (CuInSe2) thin films were grown on a fluorine-doped tin oxide (FTO) glass substrate covered with a thin layer of cadmium sulfide (CdS) by an electrodeposition method. The annealing of the films in a sulfur atmosphere resulted in a partial replacement of selenium with sulfur to form CuIn(Se,S)(2) solid solutions. Structural characterizations of the annealed samples by using X-ray diffraction, energy-diffused X-ray analysis, and UV/visible/near-infrared absorption spectra revealed that the sulfur contents and the photoabsorption onsets strongly depended on the annealing temperature. The performance of FTO/CdS/CuIn(Se,S)(2)/Au superstrate-type solar cells was highest when the CuIn(Se,S)(2) layer was annealed at 350 degrees C in a sulfur atmosphere. A capacitance-voltage analysis of the CuIn(Se,S)(2)/CdS junctions showed that the hole density in CuIn(Se,S)(2) was increased by annealing at a high temperature, contributing to the improvement in the photocurrent. However, annealing at a high temperature led to the interdiffusion of CdS into the CuIn(Se,S)(2) layer, resulting in the lowering of the solar cell performance. As a result of the trade-off between these factors, annealing at 350 degrees C gave the best result for CuInSe2 films made by the electrodeposition method. (C) 2009 The Electrochemical Society. [DOI:10.1149/1.3254167] All rights reserved.
DOI: 10.1149/1.3254167
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Acceleration of groove formation in silicon using catalytic wire electrodes for development of a slicing technique Reviewed
Mohamed Shaker Salem, Chia-Lung Lee, Shigeru Ikeda, Michio Matsumura
JOURNAL OF MATERIALS PROCESSING TECHNOLOGY 210 ( 2 ) 330 - 334 2010.1
Joint Work
Publisher:ELSEVIER SCIENCE SA
A novel electrochemical technique for silicon slicing in which anodic potential is applied to a platinum wire, keeping it in contact with silicon, is proposed. Since silicon was dissolved in a solution containing hydrogen fluoride at the site of contact with the platinum wire electrode, a goove was formed in the silicon. The grooving speed depended on the concentration of hydrogen fluoride and additives in the solution. A grooving speed of 0.85 mm/h was obtained at room temperature using an electrolyte composed of 30 wt% hydrofluoric acid, 1 mM iodine, and 0.03 vol% glycerol. Iodine acted as a catalyst for the oxidaton of silicon, and glycerol prevented the filling of grooves with gases. Further increase in grooving speed to 1.0 mm/h was achieved by applying pulsed potentials oscillating between 1 and 2 V vs. Ag/AgCl in the same electrolyte. (C) 2009 Elsevier B.V. All rights reserved.
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Shigeru Ikeda, Hideyuki Kobayashi, Yoshimitsu Ikoma, Takashi Harada, Suzuko Yamazaki, Michio Matsumura
APPLIED CATALYSIS A-GENERAL 369 ( 43102 ) 113 - 118 2009.11
Joint Work
Authorship:Lead author Publisher:ELSEVIER SCIENCE BV
TiO(2) particles encapsulated in hollow silica shells with controlled shell thicknesses were fabricated. Compared to naked TiO(2) without coverage by a hollow silica shell, all of these composites showed low levels of photocatalytic activity for gas-phase decomposition of acetone into CO(2). The activities over these composites tended to decrease with increase in thickness of the lateral silica shell. These results can be explained by a decrease in the diffusion of acetone with increase in thickness of the silica shell, leading to hampering of supply of the substrate to the surfaces of core TiO(2) particles. In contrast, for the overall photodecomposition of gaseous 2-propanol into CO(2), the presence of the lateral silica shell was found to be beneficial, i.e., the composite induced a high level of activity compared to the activity of naked TiO(2). The enhancement of activity for this reaction was likely to be due to condensation of the intermediate product of acetone in the void spaces, leading to an increase in the collision probability between acetone and the surface of the TiO(2) core. (C) 2009 Elsevier B.V. All rights reserved.
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Formation of 100 mu m Deep Vertical Pores in Si Wafers by Wet Etching and Cu Electrodeposition Reviewed
Chia-Lung Lee, Shinsuke Tsuru, Yuji Kanda, Shigeru Ikeda, Michio Matsumura
JOURNAL OF THE ELECTROCHEMICAL SOCIETY 156 ( 12 ) D543 - D547 2009.10
Joint Work
Publisher:ELECTROCHEMICAL SOC INC
Pores with diameters of about 5 mu m were formed in n-type Si(100) wafers by wet etching using aggregated Au particles, each about 1 mu m, as catalysts. The pores were as deep as 100 mu m after etching for 5 h. In the pores of the Si wafers, which were almost perpendicular to the Si surface, Cu was electrochemically deposited from an aqueous solution of CuSO(4) using Au particles remaining at the bottom of the pores as seeds for deposition. When a potential of about - 0.275 V vs Ag/AgCl was applied to the Si wafer, Cu deposition started from the bottom of each pore and continued to fill the whole pore with a depth of about 70 mu m in 16 h. The selective Cu deposition in the pores is due to an electrocatalytic effect of Au/Cu for Cu plating. In these processes, therefore, Au particles acted as catalysts for pore formation and also as seeds for Cu electrodeposition, making it possible to fabricate connections through wafers by a simple method. However, it was difficult to increase the deposition rate by applying potentials more cathodic than - 0.40 V vs Ag/AgCl because Cu was deposited on the Si surface at these potentials. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3237139] All rights reserved.
DOI: 10.1149/1.3237139
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Yun Hau Ng, Shigeru Ikeda, Yoshihiro Morita, Takashi Harada, Keita Ikeue, Michio Matsumura
JOURNAL OF PHYSICAL CHEMISTRY C 113 ( 29 ) 12799 - 12805 2009.7
Joint Work
Authorship:Lead author Publisher:AMER CHEMICAL SOC
In an attempt to clarify the origin of the high activity and durability for aerobic oxidation of alcohols over a platinum (Pt)-carbon composite, i.e., Pt nanoparticles embedded in microporous carbon (nPt@hC), the catalytic reaction mechanism and microstructure of Pt nanoparticles were investigated in detail. By means of kinetic analyses, catalytic oxidation on nPt@hC was found to proceed through the formation of Pt-alcoholates, the beta-hydride elimination to form Pt-hydride species (Pt-H), and oxidation of Pt-H with molecular oxygen. It was also revealed that the P-hydride elimination step was a rate-determining step in this reaction. These findings and results of structural studies indicate that the achievement of high catalytic activity on nPt@hC is due to stabilization of its transition state of a positively charged carbocationic component by the electron-rich carbon matrix surrounding Pt nanoparticles, leading to lowering activation energy. Moreover, detailed investigation of the surface characteristics of Pt nanoparticles in nPt@hC after catalytic reactions by using various analytical methods revealed that the durability of nPt@hC for aerobic oxidation of alcohols is due to the suppression of aggregation of Pt nanoparticles and prevention of chemical poisoning of Pt surfaces.
DOI: 10.1021/jp903561q
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Shigeru Ikeda, Hideyuki Kobayashi, Tomohiko Sugita, Yoshimitsu Ikoma, Takashi Harada, Michio Matsumura
APPLIED CATALYSIS A-GENERAL 363 ( 43102 ) 216 - 220 2009.7
Joint Work
Authorship:Lead author Publisher:ELSEVIER SCIENCE BV
A composite of titanium(IV) oxide (TiO(2)) particles (core) and nanoporous silica (shell) was prepared by successive coating of a carbon layer and an octadecyl-functionalized silica layer on TiO(2), followed by heat treatment to remove the organic components. Transmission electron microscope (TEM) observation and nitrogen (N(2)) sorption analyses showed that the composite has a unique rattle-type structure, i.e., TiO(2) particles were encapsulated in the hollow silica shell having well-developed porosity. When the photocatalytic activity for gas phase decomposition of acetone over the composite was compared with that over naked TiO(2) without the lateral silica shell, the activity over the composite tended to become higher than that over naked TiO(2) as the initial amount of acetone in the system was reduced. The enhancement of decomposition rate under a diluted condition was due to condensation of acetone on the lateral silica shell, which resulted in enhancement of the collision rate between the substrate and the surface of the TiO(2) core. (C) 2009 Elsevier B.V. All rights reserved.
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Yun Hau Ng, Shigeru Ikeda, Sang-in Park, Yoshihiro Morita, Takashi Harada, Michio Matsumura
TOPICS IN CATALYSIS 52 ( 43258 ) 627 - 633 2009.4
Joint Work
Authorship:Lead author Publisher:SPRINGER/PLENUM PUBLISHERS
Photodeposition of Pt nanoparticle and phenolic polymer on TiO2 in a deaerated aqueous system containing hexachloroplatinic acid and phenol were investigated. We observed that reductive deposition of Pt nanoparticles with electrons proceeded rapidly, while the oxidative deposition of a phenolic polymer with positive holes was relatively slow. The difference ensured the encapsulation of Pt nanoparticles between the polymer layer and TiO2. Carbonization of the polymer components followed by removing TiO2 resulted in the formation of two types of Pt-carbon nanocomposites with different morphologies of carbons, depending on photoirradiation duration. These composites exhibited high levels of catalytic activity and reusability for aqueous oxidation of 1-phenylethanol with molecular oxygen.
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Electrochemical Grooving of Si Wafers Using Catalytic Wire Electrodes in HF Solution Reviewed
Chia-Lung Lee, Yuji Kanda, Takeshi Hirai, Shigeru Ikeda, Michio Matsumura
JOURNAL OF THE ELECTROCHEMICAL SOCIETY 156 ( 2 ) H134 - H137 2009.1
Joint Work
Publisher:ELECTROCHEMICAL SOC INC
Si wafers were electrochemically grooved in HF solution using metal wires (Pt and Au wires) as catalytic wire electrodes and a Pt plate as a counter electrode. By applying anodic potentials of about 2.0 V vs Ag/AgCl to the Pt or Au wire electrodes, which were in contact with Si, Si was etched at the place where the wires were in contact. As a result, grooves were formed in Si. The widths of the grooves formed using Pt wires with diameters of 30 and 50 mu m were about 35 and 55 mu m, respectively. The grooving rate was typically in the range of 400-600 mu m/h at room temperature. The grooving rate was faster for the thinner wire electrodes because the diffusion of chemical species to and from the Si/Pt interface became easier for the thinner electrodes. The grooving rate was increased by increasing the anodic potential or temperature, although the Si surface was roughened to some extent under such conditions.
DOI: 10.1149/1.3033735
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Efficient Reductive Alkylation of Aniline with Acetone over Pt Nanoparticles Encapsulated in Hollow Porous Carbon Reviewed
Takashi Harada, Shigeru Ikeda, Natsumi Okamoto, Yun Han Ng, Suguru Higashida, Tsukasa Torimoto, Michio Matsumura
CHEMISTRY LETTERS 37 ( 9 ) 948 - 949 2008.9
Joint Work
Authorship:Lead author Publisher:CHEMICAL SOC JAPAN
Reductive alkylation of aniline with acetone over various Pt catalysts was Studied Under atmospheric pressure of hydrogen at room temperature. It was found that our newly designed Pt catalyst, i.e., Pt nanoparticles encapsulated in hollow porous carbon. showed excellent catalytic activity in comparison with activities of other Pt catalysts. Moreover, one-pot reductive alkylation of nitrobenzene with acetone proceeded smoothly over the catalyst.
DOI: 10.1246/cl.2008.948
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Rhodium nanoparticle encapsulated in a porous carbon shell as an active heterogeneous catalyst for aromatic hydrogenation Reviewed
Takashi Harada, Shigeru Ikeda, Yun Hau Ng, Takao Sakata, Hirotaro Mori, Tsukasa Torimoto, Michio Matsumura
ADVANCED FUNCTIONAL MATERIALS 18 ( 15 ) 2190 - 2196 2008.8
Joint Work
Authorship:Lead author Publisher:WILEY-V C H VERLAG GMBH
Rhodium (Rh) nanoparticle (core)-carbon (shell) powder was prepared by double-layer coating of a silica layer and a mesoporous silica/carbon layer on an Rh nanoparticle followed by chemical etching with aqueous hydrofluoric acid to remove siliceous components. The use of various techniques for characterization of the structure showed that the powder thus-obtained had a rattle-like structure: Rh nanoparticles were encapsulated in the hollow carbon-shell having well-developed porosity. The porous wall structure of the lateral carbon shell provides channels and hydrophobic void spaces that allow efficient penetration and absorption of organic species present in aqueous media. This offers a microenvironment with a high concentration of organic substrates inside the shell. Moreover, the surfaces of medial Rh nanoparticles were free from any ligands, i.e., the active surface site(s) was exposed to induce organic transformations. These unique properties, which cannot be achieved by conventional Rh nanoparticles stabilized with organic agents, led to excellent catalytic activity for hydrogenation of various aromatic and heterocyclic rings in water.
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An efficient and reusable carbon-supported platinum catalyst for aerobic oxidation of alcohols in water Reviewed
Yun Hau Ng, Shigeru Ikeda, Takashi Harada, Yoshihiro Morita, Michio Matsumura
CHEMICAL COMMUNICATIONS 3181-3183 ( 27 ) 3181 - 3183 2008.7
Joint Work
Authorship:Lead author Publisher:ROYAL SOC CHEMISTRY
Platinum nanoparticles embedded in a hollow porous carbon shell prepared by a photocatalytic reaction acted as a reusable catalyst for the aerobic oxidation of alcohols under atmospheric pressure of oxygen in water.
DOI: 10.1039/b803912g