研究者詳細 - 鳥本　司

論文 - 鳥本　司

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単分散半導体ナノ粒子の調製とその応用招待有り

鳥本　司, 桑畑　進，米山　宏

マテリアルインテグレーション 12 巻頁： 53-59 1999年

Effects of Mordenite Support on Photodegradation of Gaseous Organic Compounds over TiO2 Photocatalyst 査読有り

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

Bull. Chem. Soc. Jpn. 72 巻 ( 7 ) 頁： 1615-1621 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）

Effects of mordenite as a support material for TiO2 on photodegradation rates of gaseous propionaldehyde, acetone, and propane were investigated using TiO2 (50 wt%)-loaded mordenite as a photocatalyst in reference to unsupported TiO2. The supported photocatalyst allowed adsorption of all the substrates several times greater than the unsupported photocatalyst, resulting in higher photooxidation rates for them. Detailed analysis suggests that the enhancement of the decomposition rate caused by the use of mordenite support is more remarkable for lower amounts of adsorption of the substrates on the support. The concentration of oxygen was found to have little influence on the photodegradation rates, suggesting that the rate of degradation of the organic substrates was not decided by photogenerated electron transfer processes but by the consumption of photogenerated holes by adsorbed organic substrates.

Fabrication of CdS Nanoparticle Chains along DNA Double Strands 査読有り

T. Torimoto, M. Yamashita, S. Kuwabata, T. Sakata, H. Mori, and H. Yoneyama

J. Phys. Chem. B 103 巻 ( 42 ) 頁： 8799-8803 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）

Positively charged CdS nanoparticles having diameter of 3.0 +/- 0.2 nm were prepared by the chemical modification of their surfaces with thiocholine. Chains of size-quantized CdS nanoparticles were prepared by using the electrostatic interaction between positively charged nanoparticle surfaces and the phosphate groups of DNA molecules. The observation by transmission electron microscopy revealed that the CdS nanoparticles were arranged in a quasi one dimension with dense packing. The line width of a nanoparticle array was equal to the diameter of CdS nanoparticles that was ca. 3.0 nm. The average distance between the centers of the adjacent nanoparticles was estimated to be 3.5 nm, which was almost equal to the length of 10 base pairs in DNA double strands.

Photoelectrochemical Characterization of Nearly Monodisperse CdS Nanoparticles-Immobilized Gold Electrodes 査読有り

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

Langmuir 15 巻 ( 4 ) 頁： 1503-1507 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）

Several kinds of nearly monodisperse size-quantized CdS particles (Q-CdS) capped with 2-aminoethanethiol were prepared by means of size selective photoetching and were covalently immobilized onto a gold electrode substrate coated previously with a self-assembled monolayer of 2-aminoethanethiol. The potential of the conduction band edge of Q-CdS estimated from the onset potential of photocurrents was negatively shifted with a decrease in the diameter of CdS nanoparticles, the results being in good accord with the theoretical prediction.

Preparation and Photoelectrochemical Properties of Two-Dimensionally Organized CdS Nanoparticle Thin Films 査読有り

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

Langmuir 15 巻 ( 5 ) 頁： 1853-1858 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）

Two-dimensionally organized CdS nanoparticle films were prepared with the use of the Langmuir-Blodgett (LB) technique. 2-Aminoethanethiol-modified CdS nanoparticles were spread on a water subphase which contained glutaraldehyde as a cross-linking agent for binding the surface-modified CdS nanoparticles with each other, and the cross-linking reaction was undertaken under several different compressions of the CdS nanoparticle layer spread on the water subphase. Surface pressure-area isotherms of the CdS monoparticulate layer taken after the cross-linking were largely different depending on the area used for the cross-linking. By transfer of the CdS monoparticulate film prepared at the air-water interface to the 2-aminoethanethiol-modified gold substrate using the LB technique, CdS monoparticulate films containing different surface concentrations were prepared on the gold substrate. It was easily done to cumulate the monoparticulate film on the gold substrate using the same transfer technique. The prepared CdS nanoparticles films showed n-type photosensitivities which were enhanced by increasing the number of cumulation of monoparticulate films.

Influence of Carbon Black as an Adsorbent used in TiO2 Photocatalyst Films on Photodegradation Behaviors of Propyzamide 査読有り

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

J. Catal. 177 巻頁： 240-246 1998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 photodecomposition of propyzamide in the aqueous solution was investigated using TiO2-carbon black composite films. It was found that the photodecomposition rate was largely influenced by the content of carbon black in the photocatalyst film. The decomposition rate increased with increasing the carbon black content up to an optimal value, beyond which the photocatalytic activity showed a decreasing tendency. The increase of the photodecomposition rate seems to result from increase of adsorbability for propyzamide in the TiO2-carbon black composite films. With further increase of carbon black from the optimum value, however, relative occupation of TiO2 to carbon black decreases, and the time needed for adsorbed propyzamide on carbon black to diffuse to TiO2 particles becomes great, resulting in the decrease of the apparent photocatalytic activity of the film. Experiments employing a circulating photoreactor system also showed that the TiO2-carbon black composite films had higher photocatalytic activities than the naked TiO2 film.

Effect of Structural Variation on Photocurrent Efficiency in Alkyl-Substituted Porphyrin Solid-State Thin Layer Photocells

M. A. Fox, J. V. Grant, D. Melamed, T. Torimoto, C.-y. Liu, and A. J. Bard

Chem. Mater. 10 巻 ( 7 ) 頁： 1771-1776 1998年

記述言語：英語掲載種別：研究論文（学術雑誌）

Three structurally variant alkyl-substituted porphyrins [zinc(II) 2,3,7,8,12,13,17,18-octa-n-decylporphyrin 2, metal(II) meso-5,10,15,20-tetra-n-undecylporphyrin 3 (metal = cobalt, copper, palladium, and zinc), and zinc(II) meso-5,10,15,20-tetrakis(phenoxy-n-nonyl)porphyrin 4] exist as photoconductive insulators and produce significant short circuit photocurrent and open circuit photopotential when irradiated as solid thin films in an indium-tin oxide sandwich cell. Liquid crystalline phase stability, the identity of the inserted metal, and the nature of its supramolecular packing all influence the observed photoelectrochemical response. Porphyrin 2, which has a stable liquid crystalline phase, produces higher steady-state photocurrents than do the corresponding meso-substituted porphyrins 3 and 4, although liquid crystallinity is not an absolute requirement for observation of a photoresponse. Among porphyrins 3, the zinc complex gave the highest steady-state photocurrent. When a phenyl ring orthogonal to the porphyrinic plane was present (as in 4), the observed photovoltaic response was significantly diminished, probably because of difficulties in achieving effective close packing.

Characteristic Features of Size-selective Photoetching of CdS Nanoparticles as a Means of Preparation of Monodisperse Particles 査読有り

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

J. Electrochem. Soc. 145 巻 ( 6 ) 頁： 1964-1968 1998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 photocorrosion behavior of CdS nanoparticle colloid containing particles ranging from 4 to 10 nm was investigated using two kinds of monochromatic light, one of which was prepared by passing light from a Xe lamp through interference filters, and the other was obtained by an Ar ion laser. CdS particles were photocorroded to smaller particles until irradiated photons were not absorbed anymore; and the CdS particles obtained after the complete photocorrosion by laser light were much smaller than those resulting from the use of monochromatic light of comparable wavelength. The size selective photocorrosion with the Ar ion laser allowed the preparation of much smaller particles than those in the original colloid. It was found that the rate of photocorrosion decreased when the pH of the colloid was raised, while the fluorescence intensity due to bandgap transition increased. The importance of hole trap sites in the photodissolution of CdS is discussed based on these findings.

Photocatalytic Reduction of CO2 Using Surface-modified CdS Photocatalysts in Organic Solvents

B.-J. Liu, T. Torimoto, and H. Yoneyama

J. Photochem. Photobiol. A : Chem. 113 巻頁： 93-97 1998年

記述言語：英語掲載種別：研究論文（学術雑誌）

The photocatalytic reduction of carbon dioxide on CdS particles with and without surface modification by several kinds of thiol compounds was investigated in various kinds of solvents. Formate and carbon monoxide were obtained as the major reduction products, and the ratio of the former to the latter was largely influenced by the kind of solvents when naked cadmium sulfide was used as the photocatalyst, and with increase of the dielectric constant of the solvent, the ratio increased. Even if CdS particles were modified by thiol compounds, the effect of the solvent was not eventually altered, but the ratio of formate to carbon monoxide became greater with increase of the surface modification of CdS. The observed effect of the surface modification of CdS is discussed in terms of involvement of Cd2+ sites adjacent to surface vacancies of CdS photocatalysts in adsorption of anion radicals of CO2.

Photocatalytic Reduction of Carbon Dioxide in the Presence of Nitrate Using TiO2 Nanocrystal Photocatalyst Embedded in SiO2 Matrices 査読有り

B.-J. Liu, T. Torimoto, and H. Yoneyama

J. Photochem. Photobiol. A : Chem. 115 巻 ( 2-3 ) 頁： 227-230 1998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）

Photocatalytic reduction of CO2 in the presence of nitrate ions in various solvents was studied using TiO2 nanocrystals embedded in SiO2 matrices as photocatalysts. Both formate and carbon monoxide were produced as the reduction products of CO2, ammonia as the reduction product of nitrate, and in addition to these products, urea was formed as a major reduction product of both CO2 and NO3-. The selectivity of these reactions was greatly influenced by the kind of solvents used, and with increasing the dielectric constant of solvents, the amount of formate and carbon monoxide produced decreased, while those of urea and ammonia increased. These results suggest that the reduction reaction of nitrate ions was the rate-determining step of the formation of urea.

半導体ナノ粒子表面上での光誘起電子移動招待有り

米山　宏，鳥本　司

触媒 40 巻頁： 544-551 1998年

Photoelectrochemical Properties of Size-Quantized CdS Thin Films Prepared by an Electrochemical Method 査読有り

T. Torimoto, S. Nagakubo, M. Nishizawa, and H. Yoneyama

Langmuir 14 巻 ( 25 ) 頁： 7077-7081 1998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 CdS thin films were prepared by sequential underpotential deposition of S and Cd on Au(lll). The prepared films in an aqueous solution containing triethanolamine as a sacrificial electron donor showed n-type photoelectrode behaviors. Action spectra of anodic photocurrents were red-shifted with an increase of the film thickness toward characteristic values of those of bulk materials. The energy gap of the film determined from the action spectra showed a remarkable tendency of decrease with an increase of the film thickness up to 3.5 nm. Beyond 3.5 nm the rate of decrease with increase in the film thickness declined. An energy gap value characteristic of bulk materials was obtained with CdS films greater than 6.8 nm.

Evaluation of Diffusibility of Adsorbed Propionaldehyde on Titanium Dioxide-Loaded Adsorbent Photocatalyst Films from Its Photodecomposition Rate 査読有り

N. Takeda, M. Ohtani, T. Torimoto, S. Kuwabata, and H. Yoneyama

J. Phys. Chem. B 101 巻 ( 14 ) 頁： 2644-2649 1997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）

Photocatalytic degradation of gaseous propionaldehyde over TiO2-loaded adsorbent films was investigated after adsorption equilibrium was obtained using silica, alumina, activated carbon, and several kinds of zeolites as adsorbents. Irradiation of one-tenth of the TiO2-loaded adsorbent film caused complete mineralization of the adsorbed substrate in the entire film, although the rates obtained in that case were much lower than one-tenth of the rates obtained with the total area irradiation, indicating a considerable contribution of supply of the adsorbed substrate from the nonirradiated part of the film to the irradiated part. The apparent diffusion coefficient D-app of adsorbed substrate was evaluated by applying the time course of CO2 evolution obtained in the area-selective photodecomposition reaction to a one-dimensional diffusion model. The D-app values estimated for various kinds of TiO2-loaded adsorbent supports explain well the differences in the photodecomposition rates obtained at these photocatalysts. On the basis of experimental results, the effect of diffusion of the adsorbed substrate on the photodecomposition kinetics is quantitatively discussed.

Effect of Activated Carbon Content in TiO2-loaded Activated Carbon on Photodegradation Behavior of Dichloromethane 査読有り

T. Torimoto, Y. Okawa, N. Takeda, and H. Yoneyama

J. Photochem. Photobiol. A: Chem. 103 巻頁： 153-157 1997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 effect of the amount of TiO2 loading on activated carbon support on the photodecomposition of dichloromethane was studied. The apparent adsorption constant of the TiO2-loaded activated carbon for dichloromethane was found to decrease with increase of the fraction of the loaded TiO2. It was found that the apparent rate constant of CO2 evolution became small with increase of the activated carbon content, suggesting that the adsorbed substrate on the activated carbon support was not easily involved in the photodecomposition reaction. However, the use of mixed suspensions of TiO2 and activated carbon showed lower activities than the TiO2-loaded activated carbon for photodegradation of dichloromethane. The role of the activated carbon support in the photodecomposition of dichloromethane is discussed.

Effect of Solvents on Photocatalytic Reduction of Carbon Dioxide Using TiO2 Nanocrystal Photocatalyst Embedded in SiO2 matrices 査読有り

B.-J. Liu, T. Torimoto, H. Matsumoto, and H. Yoneyama

J. Photochem. Photobiol. A: Chem 108 巻頁： 187-192 1997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）

Photocatalytic reduction of CO2 in various kinds of solvents was studied using TiO2 nanocrystals embedded in SiO2 matrices (Q-TiO2/SiO2) as the photocatalyst. It was found that the major reduction products were formate and carbon monoxide, and their total amount increased on increasing the concentration of CO2 dissolved. The ratio of formate to carbon monoxide was greatly influenced by the kind of solvent, and increased on increasing the dielectric constant of the solvent. If bulk TiO2 was used as the photocatalyst, the rate of CO2 reduction was low compared to that obtained with Q-TiO2/SiO2, but the ratio of formate to carbon monoxide obtained was not greatly different from that obtained with the Q-TiO2/SiO2. The effect of solvent on the reduction behavior of CO2 is discussed in terms of stabilization of reaction intermediates.

Photoelectrochemical Doping of TiO2 Particles and the Effect of Charge Carrier Density on the Photocatalytic Activity of Microporous Semiconductor Electrode Films 査読有り

T. Torimoto, R. J. Fox, III, and M. A. Fox

J. Electrochem. Soc. 143 巻 ( 11 ) 頁： 3712-3717 1996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）

Irradiation with a very high intensity laser pulse (355 nm) induces blue color in TiO2 powders and films. The blue color, which is assigned to the formation of Ti3+ in the particle, persists in air for several months. With an increase of the concentration of Ti3+ in a given particle, photocatalytic activity is decreased because of a decrease in the thickness of the space-charge layer as deep Ti3+ traps are populated.

Effects of Adsorbents Used as Supports for Titanium Dioxide Loading on Photocatalytic Degradation of Propyzamide 査読有り

T. Torimoto, S. Ito, S. Kuwabata, and H. Yoneyama

Environ. Sci. Technol. 30 巻 ( 4 ) 頁： 1275-1281 1996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）

Photodecomposition in aqueous solution of 3,5-dichloro-N-(3-methyl-1-butyn-3-yl)benzamide, whose popular name is propyzamide, was investigated using naked TiO2 and TiO2-loaded adsorbent supports as photocatalysts. The adsorbent supports used were zeolite (mordenite), silica, and activated carbon. The use of adsorbent supports was found to enhance the rate of mineralization of propyzamide and to reduce the concentration of solution-phase intermediates. The experimental results suggest that the adsorbent support concentrates a target substrate of low solution-phase concentration on its surface, providing the substrate-rich environment at the adsorbent/TiO2 interface, This concentration effect results in an enhanced rate of propyzamide mineralization. The intermediates are also retained on the adsorbent support and subsequently decomposed, thereby reducing the concentration of possibly toxic intermediates in the bulk solution.

Preparation and Properties of Size-Quantized TiO2 Particles Immobilized in Polyvinylpyrrolidinone Gel Films 査読有り

H. Uchida, S. Hirao, T. Torimoto, S. Kuwabata, T. Sakata, H. Mori, and H. Yoneyama

Langmuir 11 巻 ( 10 ) 頁： 3725-3729 1995年

記述言語：英語掲載種別：研究論文（学術雑誌）

Size-quantized TiO2 particles immobilized in polyvinylpyrrolidinone (Q-TiO2/PVPD) films, were prepared by electrophoretic deposition of Q-TiO2 colloids in 2-propanol in the presence of PVPD as a stabilizing agent. The Q-TiO2 prepared had the average diameter of 3.3 nm with a standard,deviation of 1.1 nm. Illumination of the Q-TiO2/PVPD film in water-free 2-propanol resulted in the production of acetone as a sole oxidation product and Ti3+ species as the reduction product, and when the Ti3+ species was accumulated, hydrogen evolution began to occur. The same was true for bulk TiO2 particles immobilized in the same matrix, which were prepared by soaking the Q-TiO2/PVPD film in water, but the rate of these photoinduced reactions was much slower than that of the Q-TiO2. The photoformation of Ti3+ in the TiO2 particles was suppressed by introduction of NO3- to 2-propanol, suggesting that the formation of the Ti3+ species is controlled by kinetics of electron transfer to accepters in solution.

Nanometric Surface Design of Size-quantized Semiconductor Microcrystals 招待有り

H. Yoneyama and T. Torimoto

Adv. Mater. 7 巻頁： 492-494 1995年

半導体超微粒子の調製と光触媒活性招待有り

米山　宏，鳥本　司

電気化学 63 巻頁： 2-5 1995年

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