研究者詳細 - 鳥本　司

論文 - 鳥本　司

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*Single-step synthesis of gold-silver alloy nanoparticles in ionic liquids by a sputter deposition technique 査読有り

Ken-ichi Okazaki, Tomonori Kiyama, Kaori Hirahara, Nobuo Tanaka, Susumu Kuwabata and Tsukasa Torimoto

Chem. Commun. 頁： 691-693 2008年2月

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 simultaneous sputter deposition of gold and silver onto ionic liquids formed bimetallic alloy nanoparticles, which exhibited composition-sensitive surface plasmon resonance, the peak wavelength being red-shifted with an increase in the surface area of the gold foil targets sputtered.

Development of new techniques for scanning electron microscope observation using ionic liquid 査読有り

Satoshi Arimoto, Masaharu Sugimura, Hitoshi Kageyamaa, Tsukasa Torimoto, Susumu Kuwabata

Electrochimica Acta 53 巻頁： 6228-6234 2008年

記述言語：英語掲載種別：研究論文（学術雑誌）

Based on our previous discovery that ionic liquid (IL) can be observed by a scanning electron microscope (SEM) without charging the liquid, we have developed several novel techniques for SEM observation. Coating of insulating sample with IL is useful for providing electronic conductivity to the samples like metal or carbon coating by vacuum vapor deposition. In this case, dilution of the IL with appropriate volatile solvent like alcohol is effective for coating thin layer of IL on the sample. As a biological sample, seaweed including IL was attempted to be observed by SEM. A seaweed leaf swollen by water was put in an IL bath and the bath was put in an outgassed desiccator to replace water in the seaweed leaf with IL. The resulting sample gave a SEM image of the swollen seaweed whose thickness was several times larger than dried one. Furthermore, the introduction of the IL in vacuum chamber allowed us to develop the in situ electrochemical SEM observation system. Using this system, we observed changes in polypyrrole film thickness caused by the redox reaction of the film and the electrochemical deposition of silver and its oxidative dissolution. It was also found that the energy dispersive X-ray fluorescence (EDX) analysis was available even for the electrode polarized in IL.

Development of in situ electrochemical scanning electron microscopy with ionic liquids as electrolytes 査読有り

Satoshi Arimoto, Daisuke Oyamatsu, Tsukasa Torimoto, Susumu Kuwabata

CHEMPHYSCHEM 9 巻頁： 763-767 2008年

記述言語：英語掲載種別：研究論文（学術雑誌）

We report that ionic liquids (ILs) can be observed by electron microscopy without any charging of the liquid. Based on this, we present an in situ electrochemical scanning electron microscopy (in situ ECSEM) system. The key technology that enables in situ ECSEM is that charges can be removed from an IL by grounding it with a Pt wire, even if the IL is in an insulating gloss cell. As a first demonstration, we describe the redox reaction of a polypyrrole (PPy) film accompanied by changes in its thickness when it is polarized by the film-deposited Pt electrode in the IL. Further more, energy-dispersive X-ray fluorescence (EDX) analysis can be employed for the electrode polarized in the IL. The component analysis by EDX of PPy in an IL containing K+ as a marker, reveals doping of electrolyte cations into the PPy film upon the latter's reduction and dedoping of cations from the film upon oxidation.

*Facile Synthesis of ZnS-AgInS2 Solid Solution Nanoparticles for a Color-Adjustable Luminophore 査読有り

Tsukasa Torimoto, Tomohiro Adachi, Ken-ichi Okazaki, Miwa Sakuraoka, Tamaki Shibayama, Bunsho Ohtani, Akihiko Kudo, and Susumu Kuwabata

J. Am. Chem. Soc. 129 巻 ( 41 ) 頁： 12388-12389 2007年11月

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）

Nanoparticles of ZnS-AgInS2 solid solution (ZAIS) were synthesized by the thermal decomposition of (AgIn)(x) Zn2(1-x)(S2CN(C2H5)(2)) 4 precursors in a hot oleylamine solution. X-ray powder diffraction analyses revealed that the resulting nanoparticle powders were not a mixture of ZnS and AgInS2 but a ZnS-AgInS2 Solid solution in which the fraction of ZnS was enlarged with a decrease in the value of x, that is, an increase in the content of Zn2+ in the precursors used. The energy gap of ZAIS nanoparticles could be controlled by the composition of solid solution. Intense emission was observed at room temperature, regardless of the kind of the particles, the peak wavelength of PL being blue-shifted from 720 to 540 nm with a decrease in the value of x. The highest quantum yield of ca. 24% was obtained for nanoparticles prepared with x = 0.86, which was much higher than the quantum yields reported for I-III-VI2-based semiconductor nanoparticles, such as CuInS2 and ZnS-CuInS2 solid solution.

Encapsulation of Titanium(IV) Oxide Particles in Hollow Silica for Size-selective Photocatalytic Reactions 査読有り

Shigeru Ikeda, Yoshimitsu Ikoma, Hideyuki Kobayashi, Takashi Harada, Tsukasa Torimoto, Bunsho Ohtani and Michio Matsumura

Chem. Commun. 頁： 3753-3755 2007年9月

*Photocatalytic Syntheses of Azoxybenzene by Visible Light Irradiation of Silica-Coated Cadmium Sulfide Nanocomposites 査読有り

B. Pal, T. Torimoto, K.-i. Okazaki and B. Ohtani

Chem. Commun. ( 5 ) 頁： 483-485 2007年2月

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）

Photoirradiation (l=5-436 nm) of a deaerated 2-propanol
aqueous solution containing nitrobenzene and rhodium-loaded
silica-coated cadmium sulfide nanoparticles produced azoxybenzene with relatively high selectivity (68%), the photocatalytic activity being enhanced with a decrease in the size of the semiconductor particle core.

Size-selective Photocatalytic Reactions by Titanium(IV) Oxide Coated with a Hollow Silica Shell in Aqueous Solutions 査読有り

Shigeru Ikeda, Hideyuki Kobayashi, Yoshimitsu Ikoma, Takashi Harada, Tsukasa Torimoto, Bunsho Ohtani and Michio Matsumura

Phys. Chem. Chem. Phys. 2007 巻頁： 6319-6326 2007年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

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.

One-step Synthesis and Photosensitivity of Size-quantized Cadmium Chalcogenide Nanoparticles Deposited on Porous Zinc Oxide Film Electrodes 査読有り

K.-i. Okazaki, N. Kojima, Y. Tachibana, Susumu K., and T. Torimoto

Chem. Lett. 36 巻頁： 712-713 2007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 cadmium chalcogenide nanoparticles were
effectively deposited on a porous zinc oxide particulate film electrode by a one-step hydrothermal method in which an increase in the concentration of 3-mercaptopropionic acid reduced the size of deposited nanoparticles. The photoelectrochemical properties of the resulting electrodes varied depending on the kind of metal chalcogenide nanoparticles deposited and their
size.

CdS Quantum Dots Sensitized TiO2 Sandwich Type Photoelectrochemical Solar Cells

Y. Tachibana, H. Y. Akiyama, Y. Ohtsuka, T. Torimoto, and S. Kuwabata

Chem. Lett. 36 巻頁： 88-89 2007年

Effect of Ionic Surfactants on the Iridescent Color in Lamellar Liquid Crystalline Phase of a Nonionic Surfactant

X. Chen, H. Mayama, G. Matsuo, T. Torimoto, B. Ohtani, and K. Tsujii

J. Colloid Interface Sci. 305 巻頁： 308-314 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）

A nonionic surfactant, n-dodecyl glyceryl itaconate (DGI), self-assembles into bilayer membranes in water having a spacing distance of submicrometer in the presence of small amounts of ionic surfactants, and shows beautiful iridescent color. Ionic surfactants have strong effects on this iridescent system. We have interestingly found that the iridescent color changes with time after mixing DGI and ionic surfactants and the color in equilibrium state changes greatly with concentration of the ionic surfactants. The time-dependent color change results from the transformation of DGI aggregate structure after being mixed with ionic surfactant. It is first found that the iridescent color of this nonionic system can be changed
from red to deep blue by altering the concentration of ionic surfactants added even though the total concentration of surfactant is almost constant. Such large blue shift of the iridescent color in equilibrium state cannot be fully explained by the ordinary undulation theory applied so far for this phenomenon. The flat lamellar sheets tend to curve by increasing the concentration of ionic surfactants to form separated onion-like and/or myelin-like structures. These separated structures of lamellar system result in the decrease of spacing distance between bilayer membranes because
some vacant spaces necessarily appear among these structures.

Double-Beam Photoacoustic Spectroscopic Studies on Transient Absorption of Titanium(IV)Oxide Photocatalyst Powders 査読有り

Naoya Murakami, Orlando Omar Prieto Mahaney, Ryu Abe, Tsukasa Torimoto, and Bunsho Ohtani

J. Phys. Chem. C 111 巻頁： 11927-11935 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）

In situ photoabsorption properties of titanium(IV) oxide (TiO2) powders under continuous ultraviolet irradiation
were investigated by double-beam photoacoustic (PA) spectroscopy. This PA measurement enabled observation
of two kinds of ultraviolet-light-induced intermediate species appearing on various kinds of TiO2 powder samples. Most of the samples (type 1) exhibited photoabsorption due to the production of trivalent titanium (Ti3+) species, while transient absorption assigned to trapped holes or surface peroxy species was also observed for anatase samples with a relatively large specific surface area (type 2). Time-resolved measurements and analyses of the kinetics of photoinduced Ti3+ species suggest that electrons accumulated in type-2 samples have high reactivity toward molecular oxygen compared to type-1 samples. Saturation limits of intensity of the PA signal attributed to Ti3+ species under deaerated conditions in the presence of surface-adsorbed methanol were estimated for both types of samples, and their linear relation with density of Ti3+ species estimated by a conventional photochemical technique was observed. This suggests that the present double-beam PA technique is an alternative feasible method for estimation of density of Ti3+ species, which is a potential measure of density of crystalline defects.

Pyrene-to-porphyrin excited singlet energy transfer in LBLdeposited LDH nanosheets 査読有り

11 巻頁： 428 2007年

Microscopic Structure of Separately Accommodated Phorphyrins and Viologens in Mesoporous Silica and Titania Nanosheet Hybrid Films 査読有り

Tatsuo Yui, Tsutomu Kajino, Takako Tsuchino, Ken-ichi Okazaki, Tsukasa Torimoto, Yoshiaki Fukushima, and Katsuhiko Takagi

Trans. Mater. Res. Soc. Jap. 32 巻頁： 449-452 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）

The microscopic structures of two nano-structured inorganic films, the one based on titania nanosheets
(TNS) and the other on mesoporous silica (MPS), were investigated. Clear stacking structure of the TNS and MPS films was observed for the XRD, SEM, and TEM analyses. Both porphyrin derivatives and viologens were separately and selectively adsorbed into the MPS nano-cavities and the TNS nano-layers, respectively by means of their absorption and energy-dispersive spectroscopies (EDS).

Controlling Surface Reactions of CdS Nanocrystals: Photoluminescence Activation, Photoetching and Photostability under Light Irradiation 査読有り

Keiichi Sato, Satoshi Kojima, Shinya Hattori, Taeko Chiba, Keiko Ueda-Sarson, Tsukasa Torimoto, Yasuhiro Tachibana, and Susumu Kuwabata

Nanotechnology 18 巻頁： 465702 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）

Photoluminescence enhancement, photoetching and photostability of CdS nanocrystals were investigated under light irradiation. Strongly photoluminescent nanocrystals were obtained when the nanocrystal was weakly photoexcited in an aqueous solution at pH = 11 in the presence of oxygen. With the support of XPS measurements, the following photoactivation mechanism is proposed: Cd2+ ions are released from the CdS surface owing to slow photocorrosion in the presence of oxygen, and Cd-OH bond formation occurs on the CdS surface under the alkaline conditions, removing the surface trap states. The wavelength of the irradiating light and the pH of the solution were determined as key parameters for nanocrystal surface modification. For the stability measurements the nanocrystals were extracted with an ammonium salt in a non-polar solvent. The photoluminescence quantum yield for the nanocrystals in the non-polar phase reached approximately 30%. The extracted nanocrystals were remarkably stable even under UV light irradiation, and the photoluminescence intensity was maintained for several months.

真空蒸着法を用いるイオン液体中でのナノ粒子合成招待有り

岡崎健一，桑畑　進，鳥本　司

触媒 49 巻頁： 630-635 2007年

コア・シェル型粒子の光化学的ナノ構造制御と機能材料への応用招待有り査読有り

鳥本　司, 大谷文章

38 巻頁： 103-110 2007年

イオン液体の電顕微鏡観察招待有り

桑畑進, 鳥本司

表面科学 28 巻頁： 322-326 2007年

Photo-Switching Behavior of CdS Nanoparticles Doped in a Polymer Film 査読有り

Y. Ohara, T. Nakabayashi, K. Iwasaki, T. Torimoto, B. Ohtani, and N. Ohta

Compt. Rend. Chim. 9 巻頁： 742-749 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

Light-emission intensity of CdS nanoparticles doped in a PMMAfilm is enhanced by a UV irradiation in air, but the emission intensity is strongly de-enhanced at a low pressure of 10−5 torr. Atmospheric gas as well as UV irradiation is essential for the enhancement, and these enhancement and de-enhancement processes are almost completely reversible. The emission of CdS nanoparticles doped in a PMMA film is also quenched by applying an external electric field, suggesting that the non-radiative
decay rate from the emissive exciton state is accelerated by an external electric field.

*Sputter Deposition onto Ionic Liquids: Simple and Clean Synthesis of Highly Dispersed Ultrafine Metal Nanoparticles

T. Torimoto, K.-i. Okazaki, T. Kiyama, K. Hirahara, N. Tanaka, and S. Kuwabata

App. Phys. Lett. 89 巻頁： 243117 2006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）

Sputter deposition of gold Au onto ionic liquids ILs resulted in the formation of highly dispersed Au nanoparticles without additional chemical species, such as reducing and/or stabilizing agents. The Au nanoparticles in 1-ethyl-3-methylimidazolium tetrafluoroborate had an average diameter (dav) of 5.5 nm with a standard deviation (s) of 0.86 nm, while sputter deposition onto N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide resulted in the formation of much smaller Au nanoparticles with dav of 1.9 nm and s of 0.46 nm. Prolongation of sputtering time results in a higher concentration of Au nanoparticles in ILs, but did not cause a remarkable change in their size.

Origin of Chiral Discrimination by a Two-Dimensionally Dhiral Self-Assembled Monolayer: A Quantum Chemical Study

T. Nishikawa, T. Torimoto, T. Nakanishi, T. Osaka, B. Ohtani

Chem. Phys. Lett. 432 巻頁： 502-507 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

Structural and energetic investigations based on semiempirical PM5 and ab initio HF and MP2 calculations suggested that the selfassembled monolayer of an atropisomeric compound, (R)- or (S)-1,10-binaphthalene-2,20-dithiol (BNSH), on a gold (111) surface selectively
adsorbs one enantiomer of phenylalanine (Phe), resulting in chiral discrimination, through hydrophobic, cation(NHþ3
Þ–p and NH(Phe)–p (BNSH) interactions in a nanometer-sized screw-hole-like pocket composed of three BNSH molecules in the monolayer.

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