研究者詳細 - 鳥本　司

論文 - 鳥本　司

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作用スペクトル解析による懸濁系半導体光触媒の活性評価と制御

24 巻頁： 39-45 2003年

Quantitative Analysis of Defective Sites in Titanium(IV) Oxide Photocatalyst Powders 査読有り

S. Ikeda, N. Sugiyama, S. Murakami, H. Kominami, Y. Kera, H. Noguchi, K. Uosaki, T. Torimoto, and B. Ohtani

Phys. Chem. Chem. Phys. 5 巻頁： 778-783 2003年

記述言語：英語掲載種別：研究論文（学術雑誌）

The molar amounts of defective sites (Md) in several titanium(IV) oxide (TiO2) powders were determined using
photoinduced reactions of electron accumulation in deaerated aqueous solutions containing sacrificial hole
scavengers and subsequent reduction of methylviologen to its cation radical. Measurements of pH dependence of typical anatase and rutile TiO2 powders showed that these defective sites were of electronic energy just below
the conduction band edge of TiO2 in ranges of 0–0.35 V for anatase and 0–0.25 V for rutile. A linear relation of
Md with the rate constant of electron-hole recombination determined by femtosecond pump-probe diffuse reflection spectroscopy revealed that Md could be a quantitative parameter of recombination between a photoexcited electron and a positive hole. The fact that there was no linear relation between Md and the specific surface area suggests that the surface area was not directly reflected on Md . A reciprocal correlation between photocatalytic activity for water oxidation in aqueous silver sulfate solution and Md revealed that the rate of recombination is one of the predominant physical properties governing the activities of TiO2 powders in this reaction system.

サイズ選択光エッチングによる半導体ナノ粒子の単分散化と光電気化学特性制御

化学工業 53 巻 ( 7 ) 頁： 522-527 2002年

Photoelectrochemical Activities of Ultrathin Lead Sulfide Films Prepared by Electrochemical Atomic Layer Epitaxy

T. Torimoto, S. Takabayashi, H. Mori, and S. Kuwabata

J. Electroanal. Chem. 522 巻頁： 33-39 2002年

記述言語：英語掲載種別：研究論文（学術雑誌）

PbS ultrathin films were prepared by sequential underpotential deposition of S and Pb on Au(111) substrates. Observations of the resulting films with high resolution electron microscopy and energy dispersive X-ray spectrometry revealed the deposition of PbS thin films having the cubic rock salt crystal structure, the (200) planes of which were parallel to the Au surface. The scanning tunneling microscope images showed that the surface of the prepared PbS film was flat on an atomic level and no large protrusions were present, while etch pits with the height of the monatomic step of Au(111) were seen through the deposited films irrespective of the number of PbS monolayers. The PbS film-deposited Au electrodes showed anodic photocurrents in an aqueous solution containing triethanolamine as a sacrificial electron donor. The onset wavelength of their action spectra was largely blue-shifted from that of the bulk PbS due to the size quantization effects. The energy gap of the PbS thin films determined from the action spectra of anodic photocurrents decreased with an increase in the film thickness.

Quartz Crystal Microbalance Study on Photoelectrochemical Deposition of Lead(IV) Oxide on Titanium(IV) Oxide Nanoparticulate Films 査読有り

T. Torimoto, S. Si, and B. Ohtani

Electrochemistry 70 巻 ( 6 ) 頁： 438-441 2002年

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Photoelectrochemical quartz crystal microbalance measurements were used for in situ monitoring of the photoelectrochemical deposition of PbO2 onto a TiO2 nanoparticulate film electrode. It was found that the photodeposition behavior of PbO2 was influenced by pH of solution. At pH 3.8, the mass of the TiO2 film electrode decreased in the initial stage of irradiation due to the desorption of Pb2+ from the TiO2, surface and then linearly increased due to PbO2 deposition with an increase in the charge flowing as a photocurrent, while the initial decrease of the mass was much smaller at pH 1.8.

Discrimination of the Active Crystalline Phases in Anatase-Rutile Mixed Titanium(IV) Oxide Photocatalysts through Action Spectrum Analyses 査読有り

T. Torimoto, N. Nakamura, S. Ikeda, and B. Ohtani

Phys. Chem. Chem. Phys. 4 巻 ( 23 ) 頁： 5910-5914 2002年

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

The active crystalline phases in powdered titanium(IV) oxide (TiO2) photocatalysts of anatase–rutile mixtures
were investigated by measuring the action spectra of the photocatalytic reactions of H2 evolution, Ag deposition
and acetic acid decomposition. All of the pure anatase powders used in this study gave action spectra for the
three kinds of reaction that were blue-shifted by about 30 nm from those of the pure rutile powders, being consistent with their photoabsorption behavior observed in the diffuse reflectance spectra. On the other hand, the action spectra of the mixed TiO2 powders varied, depending both on the kind of photocatalytic reaction and the content of the crystalline phases. In the case of H2 evolution, the action spectra were intermediate between those of the pure anatase and rutile phases and were shifted toward that of the rutile phase with a decrease in the content of the anatase phase; i.e., the action spectra are governed mainly by the photoabsorption of each powder. The Ag deposition and acetic acid decomposition reactions gave action spectra of the mixed TiO2 powders that were similar to those of pure rutile and anatase phases, respectively, regardless of the content of the crystalline phases; the active phase in the former was rutile while that in the latter was anatase, even when these active phases were only minor parts of the mixed powder. The results indicate that the active crystalline phase differs with the kind of photocatalytic reaction even if the same mixed TiO2 powders were used as photocatalysts.

芳香族有機化合物を表面に固定した酸化チタン微粒子の調整と光科学特性の評価

池田　茂、　鳥本　司、　大谷文章

光触媒 7 巻頁： 48-51 2002年

作用スペクトル解析による光触媒活性構造の解明にかかわる研究と課題

鳥本　司、　大谷文章

光触媒 7 巻頁： 32-37 2002年

Visible Light-induced Hydrogen Evolution from Aqueous Suspensions of Titanium(IV) Oxide Modified with Binaphthol 査読有り

Electrochemistry 70 巻 ( 6 ) 頁： 442-446 2002年

記述言語：英語掲載種別：研究論文（学術雑誌）

The reaction between titanium(IV) oxide (TiO2) powders and 1,1'-binaphthalene-2,2'-diol (bn(OH)(2)), both of which are originally colorless, led to the formation of surface TiO2-bn(OH)(2) complexes giving a broad absorption in the visible-light region below ca. 550 nm. When the surface complex was made on TiO2 loaded with platinum deposits, the powder exhibited photocatalytic activity for H-2 evolution from deaerated triethanolamine solution under visible-light irradiation (>430 nm). On the basis of the experimental results, the reaction mechanism seems to involve visible-light excitation of the surface complexes, electron injection to TiO2, and its migration to platinum deposits, where reduction of H+ takes place.

半導体ナノ粒子の調製・固定化と光電気化学特性招待有り

69 巻 ( 11 ) 頁： 866-871 2001年

サイズ選択光エッチングによる単分散半導体ナノ粒子の作製招待有り

4 巻 ( 2 ) 頁： 27-30 2001年

Characterization of Ultrasmall CdS Nanoparticles Prepared by the Size-Selective Photoetching Technique 査読有り

T. Torimoto, H. Kontani, Y. Shibutani, S. Kuwabata, T. Sakata, H. Mori, and H. Yoneyama

J. Phys. Chem. B 105 巻 ( 29 ) 頁： 6838-6845 2001年

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Ultrasmall CdS nanoparticles were prepared by the size-selective photoetching technique. The smallest size of the CdS nanoparticles was obtained by the irradiation with the monochromatic light having the wavelength of 365 nm, while the absorbance of CdS nanoparticles monotonically decreased, for the whole wavelength, to null if the irradiation was performed using a wavelength less than 365 nm. The surface modification of US nanoparticles with thiophenol caused the red-shift of the absorption spectra due to the electric interaction between the bound thiophenol molecules and the CdS core, the degree being enhanced with a decrease in the particle size. H-1 NMR signals of thiophenol bound on the surface of the smallest US nanoparticles prepared by 365-nm irradiation were shifted upfield compared to those obtained for the larger thiophenol-modified CdS nanoparticles prepared by the longer wavelength irradiation, and the signals appeared in positions similar to those of chemically synthesized CdS cluster molecules. The observation with transmission electron microscopy revealed that the smallest thiophenol-modified CdS nanoparticles had an edged pyramidal shape with a size of about 1.7 nm in contrast to the larger CdS nanoparticles of almost spherical shape. The particle size and chemical compositions of the smallest thiophenol-modified US nanoparticles roughly agreed with those of Cd32S14(SC6H5)(36). 4DMF, which has been reported to be one of the largest chemically synthesized US cluster molecules. The similarity between the emission and excitation properties indicated that the smallest thiophenol-modified CdS nanoparticles had the energy structure almost equal to that of Cd32S14(SC6H5)(36). 4DMF.

Photoelectrochemical Properties of Size-Quantized Semiconductor Photoelectrodes Prepared by Two-Dimensional Cross-Linking of Monodisperse CdS Nanoparticles 査読有り

T. Torimoto, N. Tsumura, H. Nakamura, S. Kuwabata, T. Sakata, H. Mori, and H. Yoneyama

Electrochim. Acta 45 巻 ( 20 ) 頁： 3269-3276 2000年

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Two-dimensionally organized CdS nanoparticle films were prepared with the use of Langmuir-Blodgett (LB) technique. Propanethiol-modified CdS nanoparticles were spread on water subphase, which contained 1,6-hexanedithiol as a cross-linking agent for binding the surface-modified CdS nanoparticles with each other. Surface pressure-area isotherms of CdS monoparticle layer taken after the cross-linking were largely different from those obtained without addition of 1,6-hexanedithiol in water subphase. After the cross-linking, the CdS monoparticle layer was transferred from the air-water interface to 1,6-hexanedithiol-modified gold substrate using the LB technique to give CdS monoparticulate film electrodes with dense packing of the nanoparticles on the gold substrate. By repeating the same techniques, the monoparticulate him was cumulated with desired amounts. The prepared CdS nanoparticle films showed n-type photosensitivities in proportion to the cumulation number of the monoparticle layers for less than five layers. Beyond that value, a saturation tendency of the photocurrent appeared.

Electrochemical Preparation of ZnS/CdS Superlattice and Its Photoelectrochemical Properties

T. Torimoto, A. Obayashi, S. Kuwabata, and H. Yoneyama

Electrochem. Commun. 2 巻 ( 5 ) 頁： 359-362 2000年

記述言語：英語掲載種別：研究論文（学術雑誌）

Superlattice electrodes composed of three molecular layers of CdS and one to three molecular layers of ZnS were prepared on gold (111) film by using electrochemical atomic layer epitaxy. The prepared electrodes exhibited similar behavior to those of n-type semiconductor
electrodes. The energy gap was not changed at all by changing the number of molecular layers of ZnS and by increasing the number of periods in the superlattice structure up to four. The magnitude of the anodic photocurrent was, however, influenced by these variables. It increased with an increase in the number of periods in the superlattice structure and decreased with increasing number of molecular layers of ZnS.

半導体ナノ粒子アレイの作製と光電気化学特性招待有り

表面 38 巻 ( 7 ) 頁： 353-363 2000年

Titanium Dioxide/Adsorbent Hybrid Photocatalysts for Photodestruction of Organic Substances of Dilute Concentrations 招待有り

Catal Today 58 巻頁： 133-140 2000年

記述言語：英語掲載種別：研究論文（学術雑誌）

Utilities of hybrid photocatalyst consisting of TiO2 and an adsorbent such as activated carbon in photoinduced mineralization of organic substances of very dilute present concentrations are demonstrated for the photodecomposition of propionaldehyde in air atmosphere, and propyzamide and bromoform dissolved inwater. The substrates of target were adsorbed on the adsorbent
support, and then a high concentration environments of the substrate was formed around the loaded TiO2, resulting in an increase in the photodestruction rate. Evidences for the diffusion of propionaldeyde adsorbed on the mordenite support to the loaded TiO2 are presented. Merits of the use of the adsorbents as the support for TiO2 loading is discussed.

Preparation of Size-quantized ZnS Thin Films Using Electrochemical Atomic Layer Epitaxy and Their Photoelectrochemical Properties 査読有り

T. Torimoto, A. Obayashi, S. Kuwabata, H. Yasuda, H. Mori, and H. Yoneyama

Langmuir 16 巻 ( 16 ) 頁： 5820-5824 2000年

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Size-quantized ZnS thin films were prepared by sequential underpotential deposition of S and Zn on Au{111} substrates. Observations of the high-resolution electron microscope and the energy-dispersive X-ray spectrometer revealed that ZnS films were epitaxially deposited on the Au{111} facet with a stoichiometric composition. The scanning tunneling microscope images showed that the surface of the prepared films was flat in an atomic level and no large protrusion was contained, while etch pits with the height of the monatomic step of Au{111}, which were formed in the UPD of the first S layer on the naked Au surface, were seen through ZnS films with independence of the number of ZnS layers deposited. The ZnS film-deposited Au electrodes showed anodic photocurrents in an aqueous solution containing triethanolamine as a sacrificial electron donor. The energy gap determined from the action spectra decreased with an increase of the film thickness up to ca. 15.5 ZnS layers at which the bulk band gap was obtained.

Photoinduced Destruction of Bromoform Dissolved in Water Using TiO2-loaded Adsorbent 査読有り

H. Yoneyama, H. Kanemoto, N. Takeda, and T. Torimoto

Z. Phys. Chem. 213 巻頁： 43-48 1999年

Influences of Initial Particle Size on Preparation of Monodisperse CdS Nanoparticles with Size-selective Photoetching 査読有り

T. Torimoto, H. Kontani, T. Sakata, H. Mori, and H. Yoneyama

Chem. Lett. ( 5 ) 頁： 379-380 1999年

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

It was found that the size-selective photoetching of CdS particles prepared in Nafion films could be achieved only for particles having the particle sizes smaller than about 12 nm in the diameter. The particles greater than this threshold size were photocorroded until complete dissolution was attained.

(26) Effects of Surface Charges and Surface States of Chemically Modified Cadmium Sulfide Nanoparticles Immobilized to Gold Electrode Substrate on Photoinduced Charge Transfers 査読有り

M. Miyake, T. Torimoto, M. Nishizawa, T. Sakata, H. Mori, and H. Yoneyama

Langmuir 15 巻 ( 8 ) 頁： 2714-2718 1999年

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Cadmium sulfide nanoparticles (Q-CdS) modified with 2-mercaptoethanesulfonate and 2-amiaoethanethiol in a molar ratio of 2:1 were covalently immobilized onto-an Au surface covered with a self-assembled monolayer of 3,3'-dithiobis(succinimidylpropionate), and the resulting electrodes were further immobilized with Q-CdS using glutaraldehyde as a binding agent. The degree:of anodic photocurrents was greatly influenced by charged conditions of hole scavengers used because of the presence of sulfonate groups on the Q-CdS surfaces; triethylamine having positive charges gave large photocurrents, triethanolamine medium photocurrents, and formate small photocurrents. If Q-CdS having a large emission from their surface trap states was used, anodic photocurrents were depressed with increasing anodic polarization from the onset potentials which were ca. -1.1 V vs SCE for the use of any kinds of hole scavengers, and the greatest depression appeared at -0.25 V, beyond which a steep increase in anodic photocurrents was seen. In contrast, no significant depression in photocurrents was observed and anodic photocurrents were monotonically increased, in the case of using Q-CdS having an intense band-gap emission. When the energetic position at the emission maximum is correlated to the potential at which the greatest photocurrent depression appeared, photocurrent-potential characteristics are discussed in terms of involvements of surface states in the photoelectrode reactions.

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