研究者詳細 - 大久保　貴広

論文 - 大久保　貴広

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Formation of Nanowindow between Graphene Oxide and Carbon Nanohorn Assisted by Metal Ions 査読

Zhao Li, Moeto Toyota, Takahiro Ohkubo

Langmuir 41 2679 - 2687 2025年2月

Mesoporous carbon with extremely low micropore content synthesized from graphene oxide modified with alkali metal nitrates 査読

Zhao Li, Moeto Toyota, Takahiro Ohkubo

Microporous and Mesoporous Materials 2024年10月

Acidic layer-enhanced nanoconfinement of anions in cylindrical pore of single-walled carbon nanotube 査読

Takahiro Ohkubo, Hiroki Nakayasu, Yuki Takeuchi, Nobuyuki Takeyasu, Yasushige Kuroda

Journal of Colloid and Interface Science 629 238 - 244 2023年1月

Polyiodide Production Triggered by Acidic Phase of Aqueous Solution Confined in Carbon Nanospace 査読

Takahiro Ohkubo, Yuri Hirano, Hiroki Nakayasu, Yasushige Kuroda

CHEMISTRY LETTERS 51 ( 9 ) 971 - 974 2022年9月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CHEMICAL SOC JAPAN

Polyiodide species were synthesized by the acceleration of an acidic environment in the nanospace of single-walled carbon nanotubes (SWCNT) with light irradiation. Raman and EXAFS results strongly support the production of polyiodide species after the adsorption of CsI on SWCNT from aqueous solution. Interestingly, the reaction was initiated by the nano-confined acidic phase formed in a basic environment. The acidic phase plays an essential role as an oxidant for the production of the diiodine that is a source of polyiodide.

DOI： 10.1246/cl.220303

Adsorption enhancement of nitrogen gas by atomically heterogeneous nanospace of boron nitride 査読

Jun Kimura, Takahiro Ohkubo, Yuta Nishina, Koki Urita, Yasushige Kuroda

RSC Advances 11 ( 2 ) 838 - 846 2021年1月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Royal Society of Chemistry (RSC)

<p>Porous BN with atomically heterogeneous surfaces can more strongly adsorb dinitrogen molecules than typical porous carbon materials.</p>

DOI： 10.1039/d0ra08437a

Surplus adsorption of bromide ion into π-conjugated carbon nanospaces assisted by proton coadsorption 査読

Masayasu Nishi, Takahiro Ohkubo, Masaru Yamasaki, Hideyuki Takagi, Yasushige Kuroda

Journal of Colloid and Interface Science, Journal of colloid science 508 415 - 418 2017年12月

Asymmetric hydration structure around calcium ion restricted in micropores fabricated in activated carbons 招待査読

Takahiro Ohkubo, Tomoko Kusudo, Yasushige Kuroda

JOURNAL OF PHYSICS-CONDENSED MATTER 28 ( 46 ) 464003 - 7 2016年11月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

The adsorbed phase and hydration structure of an aqueous solution of Ca(NO3)(2) restricted in micropores fabricated in activated carbons (ACs) having different average pore widths (0.63 and 1.1 nm) were investigated with the analysis of adsorption isotherms and x-ray absorption fine structure (XAFS) spectra on Ca K-edge. The adsorbed density of Ca2+ per unit micropore volume in the narrower pore was higher than in the wider pore, while the adsorbed amount per unit mass of carbon with the narrower pore was half of the amount of ACs with the larger pore. On the other hand, variations in the bands assigned to double-electron (KMI) and 1s. 3d excitations in XAFS spectra demonstrate the formation of a distorted hydration cluster around Ca2+ in the micropore, although the structural parameters of hydrated Ca2+ in the micropores were almost consistent with the bulk aqueous solution, as revealed by the analysis of extended XAFS (EXAFS) spectra. In contrast to the hydration structure of monovalent ions such as Rb+, which generally presents a dehydrated structure in smaller than 1 nm micropores in ACs, the present study clearly explains that the non-spherically-symmetric structure of hydrated Ca2+ restricted in carbon micropores whose sizes are around 1 nm is experimentally revealed where any dehydration phenomena from the first hydration shell around Ca2+ could not be observed.

DOI： 10.1088/0953-8984/28/46/464003

Experimental Information on the Adsorbed Phase of Water Formed in the Inner Pore of Single-Walled Carbon Nanotube Itself 査読

Masayasu Nishi, Takahiro Ohkubo, Koki Urita, Isamu Moriguchi, Yasushige Kuroda

LANGMUIR 32 ( 4 ) 1058 - 1064 2016年2月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Thus far, nobody has successfully obtained the accurate information on the properties of the adsorbed phases of gases or vapors formed inside a cylindrical micropore of single-walled carbon nanotube (SWCNT) itself based on the experimental procedure. In this work, we succeeded in analyzing experimentally the properties of adsorbed nitrogen and water confined in the inner pore of SWCNT itself by opening the pore composed of close-ended SWCNT without any changes in the surface state and also by applying the unique method for characterization; both the amounts, as well as properties, of surface functional groups and the bundle structure are the same even after the treatments for introducing an open-ended structure to a close-ended one. As a result, the average pore sizes, as well as characteristic adsorption behavior, on the two types of sample were available from the analysis of respective difference adsorption isotherms of nitrogen measured at 77 K between the adsorbed amounts on the open-ended SWCNT and that on the close-ended one. The evaluated pore sizes well coincide with the results estimated by Raman data. These results strongly support that we could analyze the adsorbed phases formed only in the inner pore of SWCNTs by applying the present method. Furthermore, we could analyze the adsorbed phase of water formed inside the cylindrical micropore of SWCNTs, showing the difference in the densities of adsorbed water depending on the pore sizes from the value of bulk water; the densities of the adsorbed water were evaluated to be 0.62 and 0.71 g mL(-1) for SWCNTs having average pore sizes of 1.3 and 1.7 nm, respectively, which were in harmony with those obtained by the theoretical calculations reported by other researchers. The proposed analysis method makes it possible to recognize the focused states of the adsorbed water formed inside the cylindrical micropore of SWCNT more precisely and correctly. The method proposed will shed light on the discussion related to the detailed nature of various adsorbed gases into SWCNT, to the detailed role of adsorbed species formed inside pore in various phenomena, and to the designing the useful materials based on the gained knowledge.

DOI： 10.1021/acs.langmuir.5b04222

Nanospace-enhanced photoreduction for the synthesis of copper(I) oxide nanoparticles under visible-light irradiation 査読

Takahiro Ohkubo, Mitsuhiro Ushio, Koki Urita, Isamu Moriguchi, Bashir Ahmmad, Atsushi Itadani, Yasushige Kuroda

JOURNAL OF COLLOID AND INTERFACE SCIENCE 421 165 - 169 2014年5月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE

Nanoparticles of copper(l) oxide (cuprous oxide; Cu2O) were able to be synthesized from nano-restricted copper acetate (Cu(OAc)(2)) in micropores of single-wall carbon nanotubes (SWNTs) by visible-light photoreduction. The specific structure of confined Cu(OAc)(2) in the micropore is indispensable for the reduction process to Cu2O by the irradiation, because, in general, aqueous solution of Cu(OAc)(2) can be reduced under UV-light irradiated conditions. The present results strongly suggest that the micropore of SWNTs whose pore width is in the micropore-size range can play as nanoreactor space for the synthesis of Cu2O through the nano-restricted precursor whose reactivity is different from that in the bulk phase. (c) 2014 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcis.2014.01.035

State change of Na clusters in hard carbon electrodes and increased capacity for Na-ion batteries achieved by heteroatom doping 査読

Hideka Ando, Kenjiro Hashi, Shinobu Ohki, Yoshikiyo Hatakeyama, Yuta Nishina, Norihiro Kowata, Takahiro Ohkubo, Kazuma Gotoh

Carbon Trends 16 100387 - 100387 2024年9月

Structure-directing synthesis of porous CuO–SiO₂ nanocomposites using carbon nitride 査読

Yuki Takeuchi, Yasuhiro Toyoda, Kazuma Gotoh, Takahiro Ohkubo

CrystEngComm 2024年5月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Royal Society of Chemistry (RSC)

Structure-directing synthesis, such as by the template method, allows us to control the porous structure and morphological properties of solid-state materials. Traditionally, molecules and zero-, one-, and three-dimensional materials have...

DOI： 10.1039/d4ce00183d

Excellent capture of N2O functioning at RT and lower pressure by utilizing an NaCaA-85 zeolite 査読

Suguru Hiraki, Haruka Baba, Ikuka Kobayashi, Akira Oda, Takahiro Ohkubo, Yuka Ikemoto, Taro Moriwaki, Yasushige Kuroda

Chemical Communications 60 4597 - 4600 2024年3月

Coating Silver Tree‐like Fractal Structure with Silica Layer for Inhibiting Chemical Reactions of Analytes in Surface‐Enhanced Raman Scattering 査読

Hiroya Watanabe, Yurin Hishii, Kanna Kishimoto, Kohei Nogami, Qingyuan Ma, Tomoya Niki, Tomoki Kotani, Toshihiko Kiwa, Satoru Shoji, Takahiro Ohkubo, Jun Kano, Nobuyuki Takeyasu

physica status solidi (a) 220 ( 20 ) 2023年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Wiley

Silica coating is performed onto silver tree‐like fractal structures, which are self‐grown in a solution, through a wet process using tetraethyl orthosilicate. Surface‐enhanced Raman scattering (SERS) of para‐aminothiophenol (p‐ATP) is measured on the silver tree‐like fractal structures with/without silica layer at the excitation wavelength of 532 nm. p‐ATP is chemically transformed into dimercaptoazobenzene (DMAB) on the non‐coated silver tree‐like fractal structures, where DMAB peaks are clearly observed, during the SERS measurements. The DMAB peaks decrease/disappear on the silica‐coated ones although the p‐ATP peaks are observed. In the results, it is indicated that the chemical transformation is inhibited on the silica‐coated ones. The sensitivity is decreased by half compared to the non‐coated silver tree‐like fractal structures, where the lower detection limit is estimated to be ≈2 × 10⁻⁵ mol L⁻¹ for p‐ATP. The silica coating is advantageous for inhibiting chemical transformations of analytes, enabling identification/estimation of chemicals in unknown sample with SERS similarly to conventional Raman spectroscopy.

DOI： 10.1002/pssa.202300085

Polymer Template Synthesis of CuOx/Clay Nanocomposites with Controllable CuOx Formation 査読

Yuki Takeuchi, Takahiro Ohkubo

ChemistrySelect 8 ( 31 ) 2023年8月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Wiley

Abstract

Metal oxides have the excellent functions including high thermal stability, electrical properties, catalytic performance, and adsorption properties of acid gases such as CO₂ via the acid‐base interactions. However, they suffer from low reserves, porosity control, and low adsorption efficiency per weight compared with lightweight materials including carbon and silica. To solve these issues, various methods for supporting metal oxides on porous carriers, such as decomposition‐precipitation and impregnation, have been investigated, but controlling the formation of metal oxide on clay nanosheets remains as a challenge. Herein, we developed a soft‐template method for supporting metal oxide (CuO_x) nanoparticles on activated clay nanosheets. The intercalation of polyethyleneimine (PEI)−Cu²⁺ complexes between the layers of clay nanosheets followed by calcination to construct CuO_x and remove the PEI templates afforded CuO_x/clay nanocomposites. The constructed CuO_x/clay nanocomposites had the close porosity to that of clay. Tuning the Cu²⁺/PEI ratio in PEI−Cu²⁺ complex allowed to control CuO_x states (loadings, particle sizes, etc.). Tuning of the supporting conditions allowed constructing a structure suitable for CO₂ uptake. These findings will contribute to the development of the material science of metal oxide nanoparticles and their hybrid materials in diverse fields including CO₂ adsorbents, energy devices, and catalysts.

DOI： 10.1002/slct.202301644

Self-growth of silver tree-like fractal structures with different geometries 査読

Kohei Nogami, Kanna Kishimoto, Yuki Hashimoto, Hiroya Watanabe, Yurin Hishii, Qingyuan Ma, Tomoya Niki, Tomoki Kotani, Toshihiko Kiwa, Satoru Shoji, Takahiro Ohkubo, Jun Kano, Nobuyuki Takeyasu

APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING 128 ( 10 ) 2022年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER HEIDELBERG

Silver tree-like fractal structures are self-grown, where needle growths and branching are iterated, via rapid reduction of silver ions in a solution. Many self-similar frameworks exist at different scales in the whole structure, and geometry is characterized by a fractal dimension. Here, we perform a control of the fractal geometry by facile growth engineering related to the viscosity of the solvent, with acetone and ethanol, on the silver tree-like structure. The geometry changed from needle leaf-like to broadleaf-like structure as the viscosity increased, which resulted in the difference in the fractal dimensions ranging from 1.743 to 1.812, at 303 K. The silver fractal structures exhibited optical responses over a wide wavelength range from 400 to 900 nm, which was also visualized by the dark-field observations with an optical microscope. We demonstrated surface-enhanced Raman scattering (SERS) measurements of para-aminothiophenol at 532, 633, and 785 nm on the silver tree-like fractal structures with three types of different fractal geometries. Compared with the common SERS substrates, the merit of using dendrite structures is the availability of multiple laser wavelengths for SERS excitation and detection on the same sample, with keeping significant enhancement effect. This feature also allows us direct observation of plasmon-mediated chemical transformations of molecules through multi-color excitation SERS measurements.

DOI： 10.1007/s00339-022-05976-1

Orbital Trap of Xenon: Driving Force Distinguishing between Xe and Kr Found at a Single Ag(I) Site in MFI Zeolite at Room Temperature 査読

Akira Oda, Hiroe Kouzai, Kyoichi Sawabe, Atsushi Satsuma, Takahiro Ohkubo, Kazuma Gotoh, Yasushige Kuroda

The Journal of Physical Chemistry C 126 ( 19 ) 8312 - 8326 2022年5月

Identification of a Stable Ozonide Ion Bound to a Single Cadmium Site within the Zeolite Cavity 査読

Akira Oda, Kyoichi Sawabe, Takahiro Ohkubo, Yasushige Kuroda

The Journal of Physical Chemistry C 126 ( 1 ) 261 - 272 2022年1月

17O-ESR Evidence for Zeolite Matrix Isolation of a Square Planar ZnO3 Ring Radical with C2v Symmetry 査読

Akira Oda, Jun Kumagai, Kyoichi Sawabe, Takahiro Ohkubo, Yasushige Kuroda, Atsushi Satsuma

The Journal of Physical Chemistry C 125 ( 9 ) 5136 - 5145 2021年3月

Unprecedented CO2 adsorption behaviour by 5A-type zeolite discovered in lower pressure region and at 300 K 査読

Akira Oda, Suguru Hiraki, Eiji Harada, Ikuka Kobayashi, Takahiro Ohkubo, Yuka Ikemoto, Taro Moriwaki, Yasushige Kuroda

Journal of Materials Chemistry A 9 ( 12 ) 7531 - 7545 2021年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Royal Society of Chemistry ({RSC})

<p>The NaCaA-85 zeolite sample which works as an efficient adsorbent for CO₂ at RT and in low pressure range was found and its specificity is nicely explained by the model composed of CO₂ pinned by two types of Ca²⁺ ions through far-IR and DFT studies.</p>

DOI： 10.1039/D0TA09944A

A low-temperature oxyl transfer to carbon monoxide from the ZnII–oxyl site in a zeolite catalyst 招待査読

Akira Oda, Jun Kumagai, Takahiro Ohkubo, Yasushige Kuroda

Inorganic Chemistry Frontiers 8 ( 2 ) 319 - 328 2021年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Royal Society of Chemistry ({RSC})

<p>We demonstrated that the Zn^II–oxyl bond specifically formed by the zeolite lattice ligation has the capability of transferring the oxyl to CO even at 150 K with the generation of a single Zn^I˙ species.</p>

DOI： 10.1039/D0QI01112F

Experimental Description of Biomimetic NiII–Superoxo δ-Bond: Franck–Condon Analyses on Its Vibronically-Resolved Spectrum 査読

Akira Oda, Tsubasa Nanjo, Takahiro Ohkubo, Yasushige Kuroda

The Journal of Physical Chemistry C 124 ( 21 ) 11544 - 11557 2020年5月

Spectroscopic Determination of the Site in MFI Zeolite where Cobalt(I) Performs Two-Electron Reduction of O2 at Room Temperature 査読

Akira Oda, Yuki Mamenari, Takahiro Ohkubo, Yasushige Kuroda

The Journal of Physical Chemistry C 123 ( 29 ) 17842 - 17854 2019年7月

Carbon-nanotube-based Photocatalysts for Water Splitting in Cooperation with BiVO4 and [Co(bpy)(3)](3+/2+) 査読

Izawa Takumi, Kalousek Vit, Miyamoto Daiki, Murakami Noritake, Miyake Hideaki, Tajima Tomoyuki, Kurashige Wataru, Negishi Yuichi, Ikeue Keita, Ohkubo Takahiro, Takaguchi Yutaka

CHEMISTRY LETTERS 48 ( 5 ) 410 - 413 2019年5月

Room-Temperature Activation of the C–H Bond in Methane over Terminal ZnII–Oxyl Species in an MFI Zeolite: A Combined Spectroscopic and Computational Study of the Reactive Frontier Molecular Orbitals and Their Origins 査読

Akira Oda, Takahiro Ohkubo, Takashi Yumura, Hisayoshi Kobayashi, Yasushige Kuroda

Inorganic Chemistry 58 ( 1 ) 327 - 338 2019年1月

Room temperature O transfer from N2O to CO mediated by the nearest Cd(i) ions in MFI zeolite cavities 査読

Akira Oda, Takahiro Ohkubo, Yasushige Kuroda

Dalton Transactions 48 ( 7 ) 2308 - 2317 2019年

掲載種別：研究論文（学術雑誌）出版者・発行元：Royal Society of Chemistry (RSC)

<p>We report on a new functionality of cadmium created by zeolite lattice: room temperature O transfer from N₂O to CO mediated by nearest monovalent cadmium ions in MFI zeolite. The unprecedented reactivity of Cd^I and its origin are discussed on the basis of experiments coupled with quantum chemical calculations.</p>

DOI： 10.1039/c8dt04425b

A facile synthesis of a SnO2/Graphene oxide nano-nano composite and its photoreactivity 査読

Tomoyuki Tajima, Haruko Goto, Masayasu Nishi, Takahiro Ohkubo, Yuta Nishina, Hideaki Miyake, Yutaka Takaguchi

Materials Chemistry and Physics 212 149 - 154 2018年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Elsevier Ltd

A novel SnO2/graphene oxide (GO) nano-nano composite was prepared by a facile sol–gel process. X-Ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and nitrogen adsorption–desorption isotherms measurements confirmed the formation of a SnO2/GO nano-nano composite. The photoreaction of this SnO2/GO nano-nano composite was studied via the photodegradation of rhodamine B (RhB). Interestingly, the degradation mode of RhB in oxygen-saturated solution is photocatalytic reaction, but the degradation mode in argon-saturated solution is not photocatalytic reaction.

DOI： 10.1016/j.matchemphys.2018.03.046

Selective molecular-gating adsorption in a novel copper-based metal–organic framework 査読

Atsushi Kondo, Taiki Yashiro, Naoya Okada, Shotaro Hiraide, Takahiro Ohkubo, Hideki Tanaka, Kazuyuki Maeda

Journal of Materials Chemistry A 6 ( 14 ) 5910 - 5918 2018年4月

Why do zeolites induce an unprecedented electronic state on exchanged metal ions? 査読

Akira Oda, Takahiro Ohkubo, Takashi Yumura, Hisayoshi Kobayashi, Yasushige Kuroda

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 ( 36 ) 25105 - 25114 2017年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC CHEMISTRY

Understanding the exact position and the detailed role of the Al array in zeolites is essential for elucidating the origin of unique properties that can be derived from the metal-ion exchanged in zeolite samples and for designing zeolite materials with high efficiency in catalytic and adsorption processes. In this work, we investigate, for the first time, the important role of the Al array in the reactivity observed on the metal-ion exchanged in zeolites on the basis of the calculation method by utilizing the spontaneous heterolytic cleavage of H-2 observed experimentally on the Zn2+-ion exchanged in MFI-type zeolites (Zn2+-MFI) as the model reaction. In the case of calculation, two main types of models for considering the Al positions in MFI-type zeolites were adopted: in the first type, the Al atoms with appropriate distances are aligned in the circumferential direction of the straight channel (abbreviated as a circumferentially arrayed Al-Al site); in the second type, the nearest neighbouring Al atoms with appropriate distances are directed toward the straight channel axis (abbreviated as a channel directionally arrayed Al-Al site). Results indicated that the Al-array direction governs the reactivity of Zn2+-MFI. The former type of array well explains the experimental fact that spontaneous and irreversible heterolysis of H-2 takes place on Zn2+-MFI, even at room temperature, whereas the latter type of array is less reactive; high activation energy is required for the heterolytic cleavage of H-2 (ca. > 70 kJ mol(-1)). A detailed analysis of the geometric and electronic structures of a series of Zn2+-MFI models with various Al-array directions clarified the following facts: the circumferentially arrayed Al-Al site induces an inevitable environment around the Zn2+ site, with the simultaneous existence of both a Lewis acid point (coordinatively unsaturated and distorted Zn2+) and a Lewis base point (the lattice oxygen atom juxtaposed with exchanged Zn2+, which participates in the activation of H-2: O-jL). It is the circumferentially arrayed Al-Al atoms that confer acidic and basic nature on the metal ion and the lattice oxygen atom (OjL), and ultimately trigger the heterolytic dissociation of H-2, even at 300 K.

DOI： 10.1039/c7cp02669b

Identification of a Stable Zn-II-Oxyl Species Produced in an MFI Zeolite and Its Reversible Reactivity with O-2 at Room Temperature 査読

Akira Oda, Takahiro Ohkubo, Takashi Yumura, Hisayoshi Kobayashi, Yasushige Kuroda

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 56 ( 33 ) 9715 - 9718 2017年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-V C H VERLAG GMBH

Although a terminal oxyl species bound to certain metal ions is believed to be the intermediate for various oxidation reactions, such as O-O bond generation in photosystem II (PSII), such systems have not been characterized. Herein, we report a stable Zn-II-oxyl species induced by an MFI-type zeolite lattice and its reversible reactivity with O-2 at room temperature. Its intriguing characteristics were confirmed by in situ spectroscopic studies in combination with quantum-chemical calculations, namely analyses of the vibronic Franck-Condon progressions and the ESR signal features of both Zn-II-oxyl and Zn-II-ozonide species formed during this reversible process. Molecular orbital analyses revealed that the reversible reaction between a ZnII-oxyl species and an O-2 molecule proceeds via a radical O-O coupling-decoupling mechanism; the unpaired electron of the oxyl species plays a pivotal role in the O-O bond generation process.

DOI： 10.1002/anie.201702570

Tubular nitrogen-doped TiO2 samples with efficient photocatalytic properties based on long-lived charge separation under visible-light irradiation: synthesis, characterization and reactivity 査読

Yoshikazu Hirose, Atsushi Itadani, Takahiro Ohkubo, Hideki Hashimoto, Jun Takada, Shigeharu Kittaka, Yasushige Kuroda

DALTON TRANSACTIONS 46 ( 13 ) 4435 - 4451 2017年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC CHEMISTRY

A nitrogen-doped TiO2 sample was prepared at 413 K by direct hydrothermal treatment of titanium isopropoxide in an aqueous solution of NH3. This new material has a large specific surface area of ca. 220 m(2) g(-1) because of its tubular structure and it exhibits a prominent absorption feature in the region between 400 and 650 nm. It responds strongly to light in the visible region, which is key to its potential performance as a photocatalyst that may improve the efficiency for utilization of solar energy. Actually, this sample exhibits very efficient activity in the decomposition of CH3COOH under visible light among the samples prepared. This effective photocatalysis of the present sample was substantiated by characteristic spectroscopic features, such as: (1) an optical absorption band with lambda > 400 nm because of the doped nitrogen species; (2) the formation of EPR-active, long-lived N-. and O(2)(-)species, as well as N-2(-) species, under visible-light irradiation in the O-2 or N-2 adsorption process at 300 K by way of the monovalent nitrogen ions in the bulk (both substitutional and interstitial); (3) the existence of IR-active O-2 species adsorbed on the nitrogen-doped TiO2 sample even without light irradiation; and (4) an XPS N-1s band around 399.6 eV that is assignable to the N- species. The amounts of N-. and O-2(-) species formed in the nitrogen-doped TiO2 sample under visible-light irradiation correlated well with the levels of reactivity observed in the decomposition of CH3COOH on the samples with varying amounts and types of doped nitrogen species. We conclude that the photoactive N-. and O-2(-) species created in the present sample are responsible for the decomposition of organic materials assisted by visible light irradiation. These features may be attributable to the interface between the sample's tubular structure and anatase with poor crystallinity, which probably causes the resistance to the recombination of electron-hole pairs formed by irradiation.

DOI： 10.1039/c6dt04914a

微生物由来鞘状酸化鉄を利用した多孔質炭素材料および炭素－酸化鉄複合材料の作製査読

西村維心, 後藤和馬, 日浦登和, 川村仁美, 橋本英樹, 松本修治, 高田潤, 粕壁隆敏, 西原洋知, 後藤秀徳, 大久保貴広, 石田祐之

炭素 280 188 - 197 2017年

Material Exhibiting Efficient CO2 Adsorption at Room Temperature for Concentrations Lower Than 1000 ppm: Elucidation of the State of Barium Ion Exchanged in an MFI-Type Zeolite 査読

Atsushi Itadani, Akira Oda, Hiroe Torigoe, Takahiro Ohkubo, Mineo Sato, Hisayoshi Kobayashi, Yasushige Kuroda

ACS APPLIED MATERIALS & INTERFACES 8 ( 13 ) 8821 - 8833 2016年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Carbon dioxide (CO2) gas is well-known as a greenhouse gas that leads to global warming. Many efforts have been made to capture CO2 from coal-fired power plants, as well as to reduce the amounts of excess CO2 in the atmosphere to around 400 ppm. However, this is not a simple task, particularly in the lower pressure region than 1000 ppm. This is because the CO2 molecule is chemically stable and has a relatively low reactivity. In the present study, the CO2 adsorption at room temperature on MFI-type zeolites exchanged with alkaline-earth-metal ions, with focus on CO2 concentrations <1000 ppm, was investigated both experimentally and by calculation. These materials exhibited a particularly efficient adsorption capability for CO2, compared with other presented samples, such as the sodium-form and transition-metal ion-exchanged MFI-type zeolites. Ethyne (C2H2) was used as a probe molecule. Analyses were carried out with IR spectroscopy and X-ray absorption, and provided significant information regarding the presence of the M2+-O2--M2+ (M2+: alkaline-earth-metal ion) species formed in the samples. It was subsequently determined that this species acts as a highly efficient site for CO2 adsorption at room temperature under very low pressure, compared to a single M2+ species. A further advantage is that this material can be easily regenerated by a treatment, e.g., through the application of the temperature swing adsorption process, at relatively low temperatures (300-473 K).

DOI： 10.1021/acsami.6b00909

Possibility of Copper-Ion-Exchanged MFI-Type Zeolite as C-H Bond Activation Material for Propane and the Driving Force for Activation 査読

Atsushi Itadani, Yusuke Sogawa, Akira Oda, Takahiro Ohkubo, Takashi Yumura, Hisayoshi Kobayashi, Mineo Sato, Yasushige Kuroda

JOURNAL OF PHYSICAL CHEMISTRY C 119 ( 37 ) 21483 - 21496 2015年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

The dehydrogenation of propane (C3H8) utilizing solid catalysts is expected to be a promising method for producing propene (C3H6) selectively and economically. Propene is useful as a raw material to produce other valuable materials. To push forward the dehydrogenation reaction of C3H8, it is essential to find catalysts that work effectively in the activation of the C-H bonds in C3H8. To this end, we investigated the interaction of C3H8 with the copper-ion-exchanged MFI-type zeolite (CuMFI) at room temperature. The C3H8 adsorption properties of CuMFI were remarkable, compared with those of the sodium-form MFI-type zeolite (NaMFI); CuMFI exhibited irreversible adsorption, even at room temperature, whereas NaMFI exhibited reversible adsorption. Correspondingly, the CuMFI had an adsorption energy of 110 kJ mol(-1) in the initial adsorption region, whereas the NaMFI had an adsorption energy of 50 kJ mol(-1). Furthermore, a peculiar feature was observed in the appearance of the characteristic infrared (IR) absorption bands at 2740, 2659, and 2624 cm(-1) and, particularly, the band that appeared at 2555 cm(-1). They were noticeably shifted toward the lower wavenumber side, compared with the C-H vibration bands for a gaseous C3H8 molecule. This was a result of the interaction of C3H8 with the Cu+ ions formed in CuMFI. The application of density functional theory calculations to the model, comprising the interaction between the dual-Cue site in CuMFI and C3H8, well explains the observation of the appearance of these four types of bands toward the lower wavenumber side and also the adsorption energy. The cause is the dominant contribution of the back-donation from Cu+ to C3H8, rather than the donation from C3H8 to Cu+, which results in a weakening of the C-H bonds in the C3H8 molecule. The Cu site taking a dimeric structure, not various types of single-Cu+ sites, plays a key role in activating C3H8 effectively, even at around 300 K. Results of this study should contribute to not only understanding the critical role of the dimeric Cu+ species in MFI but also developing new materials with superior activity in the activation of the C-H bond in alkanes.

DOI： 10.1021/acs.jpcc.5b05577

Synthesis of an unexpected [Zn-2](2+) species utilizing an MFI-type zeolite as a nano-reaction pot and its manipulation with light and heat 査読

Akira Oda, Takahiro Ohkubo, Takashi Yumura, Hisayoshi Kobayashi, Yasushige Kuroda

DALTON TRANSACTIONS 44 ( 21 ) 10038 - 10047 2015年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC CHEMISTRY

Compared with mercury, the existence of [Zn-2](2+) species is rare. We succeeded in preparing a stable [Zn-2](2+) species by utilizing an MFI-type zeolite as a nano-reaction pot, which was confirmed using XAFS spectroscopy: the bands at R = 2.35 angstrom due to the Zn+-Zn+ scattering and at 9660.7 eV due to the 1s-sigma* (the anti-bonding orbital comprised of the 4s-4s orbital) transition of the [Zn-2](2+) species. This species also gives the characteristic band around 42 000 cm(-1) due to its sigma-sigma* transition. Furthermore, UV-irradiation corresponding to the sigma-sigma* transition causes the bond dissociation, forming two unprecedented Zn+ ions, and detached Zn+ ions were recombined through heat-treatment at 573 K: [Zn+-Zn+] reversible arrow 2Zn(+). These processes were reproduced by applying the DFT calculation method to the assumed triplet, sigma(alpha)-sigma*(alpha), structure formed on the M7-S2 site with the specific Al array in the MFI-type zeolite. Research into the specific field using zeolites to synthesize "ultra-state ions" is very promising.

DOI： 10.1039/c5dt01088h

An Important Factor in CH4 Activation by Zn Ion in Comparison with Mg Ion in MFI: The Superior Electron-Accepting Nature of Zn2+ 査読

Akira Oda, Hiroe Torigoe, Atsushi Itadani, Takahiro Ohkubo, Takashi Yumura, Hisayoshi Kobayashi, Yasushige Kuroda

JOURNAL OF PHYSICAL CHEMISTRY C 118 ( 28 ) 15234 - 15241 2014年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

We present clear IR and density functional theory (DFT) evidence demonstrating that the electron-accepting nature of Zn2+ ion exchanged in MFI-type zeolite (ZnMFI) plays a dominant role in CH4 activation. The IR study revealed that the heterolytic dissociation of CH4 takes place on the Zn2+ ion exchanged in MFI under a CH4 atmosphere even near room temperature, whereas a similar reaction scarcely occurred on Mg2+ ion exchanged in MFI, although the ionic radius and charge of Mg2+ are almost the same as those of Zn2+. These data indicate that the dissociation reaction of CH4 on Zn2+ in MFI is facilitated not only by the electrostatic interaction but also by the electron-transfer interaction. This interpretation was clearly evidenced by the observed v(1) mode of the C-H symmetric stretching vibration, i.e., a larger band shift toward lower wavenumbers, for the molecular CH4 adsorbed on ZnMFI, compared with those for a gaseous CH4 molecule. Additional experiments were also performed by the IR method utilizing CO as a probe molecule that has an electron-donating nature. All experimental data presented were successfully explained in terms of the superior electron-accepting nature of Zn2+ exchanged in MFI. Furthermore, the DFT calculation method completely explained all experimental data by adopting the M7S2 model, which was truncated from the ZnMFI structure; the electron-accepting nature is dominant in the heterolytic activation of CH4 in the Zn2+ ion in MFI in comparison with that of Mg2+ exchanged at the same site. We have thus shown that the electron-transfer interaction between Zn2+ and CH4 plays a key role in the heterolytic CH4 activation process: the sigma donation from the sigma(C-H) orbital of CH4 toward the Zn 4s orbital through overlapping with each orbital.

DOI： 10.1021/jp5013413

Biosynthesis of elliptical hematite microparticles and their photocatalytic performance 査読

B. Ahmmad, K. Kanomata, F. Hirose, J. Kurawaki, T. Ohkubo

Rangsit Journal of Arts and Sciences 4 ( 1 ) 31 - 38 2014年

Success in Making Zn+ from Atomic Zn-0 Encapsulated in an MFI-Type Zeolite with UV Light Irradiation 査読

Akira Oda, Hiroe Torigoe, Atsushi Itadani, Takahiro Ohkubo, Takashi Yumura, Hisayoshi Kobayashi, Yasushige Kuroda

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 135 ( 49 ) 18481 - 18489 2013年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

For the first time, the paramagnetic Zn+ species was prepared successfully by the excitation with ultraviolet light in the region ascribed to the absorption band resulting from the 4s-4p transition of an atomic Zn-0 species encapsulated in an MFI-type zeolite. The formed species gives a specific electron spin resonance band at g = 1.998 and also peculiar absorption bands around 38,000 and 32,500 cm(-1) which originate from 4s-4p transitions due to the Zn+ species with paramagnetic nature that is formed in MFI. The transformation process (Zn-0 -> Zn+) was explained by considering the mechanism via the excited triplet state (P-3) caused by the intersystem crossing from the excited singlet state produced through the excitation of the 4s-4p transition of an atomic Zn-0 species grafted in MFI by UV light. The transformation process was well reproduced with the aid of a density functional theory calculation. The thus-formed Zn+ species which has the doublet spin state exhibits characteristic reaction nature at room temperature for an O-2 molecule having a triplet spin state in the ground state, forming an eta(1) type of Zn2+-O-2(-) species. These features clearly indicate the peculiar reactivity of Zn+ in MFI, whereas Zn-0-(H+)(2)MFI hardly reacts with O-2 at room temperature. The bonding nature of [Zn2+-O-2(-)] species was also evidenced by ESR measurements and was also discussed on the basis of the results obtained through DFT calculations.

DOI： 10.1021/ja4077342

Mechanism of CH4 activation on a monomeric Zn2+-ion exchanged in MFI-Type zeolite with a specific Al arrangement: Similarity to the activation site for H2 査読

Akira Oda, Hiroe Torigoe, Atsushi Itadani, Takahiro Ohkubo, Takashi Yumura, Hisayoshi Kobayashi, Yasushige Kuroda

Journal of Physical Chemistry C 117 ( 38 ) 19525 - 19534 2013年9月

記述言語：英語掲載種別：研究論文（学術雑誌）

In this work, we used both experimental and density functional theory (DFT) calculation methods to examine the mechanism of CH4 activation taking place on the Zn2+ ion exchanged MFI-type zeolite (ZnMFI). The heterolytic dissociation of CH4 on ZnMFI around 300 K was observed experimentally, causing the appearance of IR bands at 3615, 2930, and 2892 cm-1. The first band can be assigned to the OH stretching vibration associated with the formation of the Brønsted acid site and the latter to the C-H stretching modes ascribable to the -[ZnCH3]+ species. Combining the IR spectroscopy with a DFT calculation, it is apparent that the heterolytic C-H bond dissociation of CH4 has an activation energy of 15 kJ mol-1 and takes place on a monomeric Zn2+ at the M7S2 site. The M7S2 site has a specific Al arrangement in MFI and exhibits a pronounced reactivity for the H-H bond cleavage of H2, even at room temperature. In addition, to our knowledge, we are the first to succeed in explaining the dissociation process of CH4 by applying natural bond orbital (NBO) and interaction localized orbital (ILO) analyses to the present system
the donation interaction from the CH4-σ(C- H) orbital to the Zn-4s orbital triggers the cleavage of the C-H bond of CH 4 under mild conditions. © 2013 American Chemical Society.

DOI： 10.1021/jp4065517

Further evidence for the existence of a dual-Cu+ site in MFI working as the efficient site for C2H6 adsorption at room temperature 査読

Atsushi Itadani, Yusuke Sogawa, Akira Oda, Hiroe Torigoe, Takahiro Ohkubo, Yasushige Kuroda

Langmuir 29 ( 31 ) 9727 - 9733 2013年8月

記述言語：英語掲載種別：研究論文（学術雑誌）

We have recently clarified the following point: a dual-type site, which is composed of a pair of monovalent copper ions (Cu+) formed in a copper-ion-exchanged MFI-type zeolite (CuMFI), functions as the active center for strong ethane (C2H6) adsorption even at room temperature rather than a single-type site composed of a Cu+ ion. However, the character of the dual-Cu+ site in a CuMFI is not yet fully understood. In this study, we have elucidated the nature of the active sites for C2H6 based on infrared (IR) and calorimetric data. On the basis of the results obtained, we came to the conclusion that the dual-Cu+ site composed of Cu+ ions giving the adsorption energy of 100 kJ mol-1 and the absorption band at 2151 cm -1 for carbon monoxide (used as a probe molecule) at room temperature functions as an adsorption site for C2H6. We also evaluated, for the first time, the interaction between the dual-Cu+ site and C2H6 energetically, by the direct measurement of heat of adsorption. The value of 67 kJ mol-1 that we recorded was higher than that for the single-Cu+ site in this sample and also for other samples, such as NaMFI and HMFI. © 2013 American Chemical Society.

DOI： 10.1021/la4018568

Highly compressed nanosolution restricted in cylindrical carbon nanospaces 査読

Masayasu Nishi, Takahiro Ohkubo, Kazuma Tsurusaki, Atsushi Itadani, Bashir Ahmmad, Koki Urita, Isamu Moriguchi, Shigeharu Kittaka, Yasushige Kuroda

Nanoscale 5 ( 5 ) 2080 - 2088 2013年3月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

We shed light on the specific hydration structure around a zinc ion of nanosolution restricted in a cylindrical micropore of single-wall carbon nanotube (SWNT) by comparison with the structure restricted in a cylindrical mesopore of multi-wall carbon nanotube (MWNT) and that of bulk aqueous solution. The average micropore width of open-pore SWNT was 0.87 nm which is equivalent to the size of a hydrated zinc ion having 6-hydrated water molecules. We could impregnate the zinc ions into the micropore of SWNT with negligible amounts of ion-exchanged species on surface functional groups by the appropriate oxidation followed by heat treatment under an inert condition. The results of X-ray absorption fine structure (XAFS) spectra confirmed that the proportion of dissolved species in nanospaces against the total adsorbed amounts of zinc ions on the open-pore SWNT and MWNT were 44 and 61%, respectively, indicating the formation of a dehydrated structure in narrower nanospaces. The structure parameters obtained by the analysis of XAFS spectra also indicate that the dehydrated and highly compressed hydration structure can be stably formed inside the cylindrical micropore of SWNT where the structure is different from that inside the slit-shaped micropore whose pore width is less than 1 nm. Such a unique structure needs not only a narrow micropore geometry which is equivalent to the size of a hydrated ion but also the cylindrical nature of the pore. © 2013 The Royal Society of Chemistry.

DOI： 10.1039/c2nr33681b

Green synthesis of mesoporous hematite (alpha-Fe2O3) nanoparticles and their photocatalytic activity 査読

Bashir Ahmmad, Kwati Leonard, Md Shariful Islam, Junichi Kurawaki, Manickavachagam Muruganandham, Takahiro Ohkubo, Yasushige Kuroda

ADVANCED POWDER TECHNOLOGY 24 ( 1 ) 160 - 167 2013年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

A green synthesis method for the preparation of mesoporous alpha-Fe2O3 nanoparticles has been developed using the extract of green tea (camellia sinensis) leaves. This simple and one-step method can suitably be scaled up for large-scale synthesis. The as-prepared mesoporous nanoparticles were characterized by SEM, TEM, XRD, XPS, Raman, UV-visible spectroscopy and N-2 adsorption analysis. The nanoparticles were highly pure and well crystallized with an average particle size of 60 nm. The photocatalytic activity of nanoparticles was evaluated by the amount of hydroxyl radical formation under visible light irradiation detected by fluorescence spectroscopy. The as-prepared alpha-Fe2O3 showed two times higher activity than commercial alpha-Fe2O3 in term of hydroxyl radical formation and enhanced performance in a photoelectrochemical cell. Also, a plausible mechanism for the formation of mesoporous alpha-Fe2O3 has been suggested. (C) 2012 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

DOI： 10.1016/j.apt.2012.04.005

TiO2/TaON- and TiO2/BiOI-based solid-state solar cells 査読

Bashir Ahmmad, Junichi Kurawaki, Takahiro Ohkubo, Fumihiko Hirose

Journal of Energy Engineering 139 ( 4 ) 338 - 342 2013年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：American Society of Civil Engineers (ASCE)

A three-phase solid-state solar cell (SSSC) has been developed successfully using TaON nanoparticles or BiOI microspheres as a sensitizer material over a TiO2 film and CuI as a hole collector. Stable current (I sc)-voltage (Voc) curves are found under ultraviolet UV visible light irradiation with an efficiency of 0.15% and 0.10% for TaON- and BiOI-based solar cells, respectively. The observed photocurrents in SSSCs are approximately 10 and 48 times higher than those in wet-type solar cells (WSCs) based on TaON and BiOI, respectively. A plausible mechanism of charge transfer and hole filling is discussed in terms of the band gap energy and band position of the semiconductor materials. © 2013 American Society of Civil Engineers.

DOI： 10.1061/(ASCE)EY.1943-7897.0000130

Photosensitized hydrogen evolution from water using single-walled carbon nanotube/fullerodendron/Pt(II) coaxial nanohybrids 査読

Yukari Sasada, Tomoyuki Tajima, Takaaki Wada, Tetsuya Uchida, Masayasu Nishi, Takahiro Ohkubo, Yutaka Takaguchi

NEW JOURNAL OF CHEMISTRY 37 ( 12 ) 4214 - 4219 2013年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC CHEMISTRY

Direct incorporation of a Pt(II) complex into the shell of SWCNT/fullerodendron coaxial nanohybrids produces a new coaxial nanowire, SWCNT/fullerodendron/Pt(II), that shows efficient photocatalytic activity for hydrogen evolution from water (Phi = 0.16 upon irradiation at 450 +/- 5 nm) without any aid of electron relay such as methyl viologen.

DOI： 10.1039/c3nj00790a

Template-free fabrication of a cylindrical macropore array in SnO2 査読

Yushi Ozawa, Tomoyuki Tajima, Masayasu Nishi, Takahiro Ohkubo, Yutaka Takaguchi

RSC ADVANCES 3 ( 45 ) 22949 - 22952 2013年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC CHEMISTRY

A simple sol-gel condensation of tin(IV) tert-butoxide led to the formation of meso/macroporous membranes. SEM observation clearly shows the cylindrical macropore array, of which mean pore diameter is controllable between 200 and 800 nm. The existence of slit-shaped mesopores (12 nm) was confirmed by a N-2 adsorption-desorption experiment.

DOI： 10.1039/c3ra43642j

Structure of hydrated cobalt ions confined in the nanospace of single-walled carbon nanotubes 査読

Bashir Ahmmad, Masayasu Nishi, Fumihiko Hirose, Takahiro Ohkubo, Yasushige Kuroda

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 15 ( 21 ) 8264 - 8270 2013年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC CHEMISTRY

The structure of hydrated Co ions confined in the nanospace of single-walled carbon nanotubes (SWNTs) has been studied using the X-ray absorption fine structure (XAFS) technique. Water adsorption isotherms on Co-impregnated SWNTs indicate a high affinity of Co ions to water molecules. The results of XAFS analysis provided the information on the proportion of dissolved species in nanospaces against the total amount of cobalt ions adsorbed on the open-pored SWNT. The structural information of the first shell around a Co ion was expressed in terms of the hydration number, Co-O distance and Debye-Waller factor. The actual coordination number and the interatomic distance of Co-O for the dissolved species were remarkably reduced compared to the bulk aqueous solution indicating the dehydration of water molecules from Co ions and a compact hydrated structure in the micropore of SWNTs.

DOI： 10.1039/c3cp50181g

Arrangement and Dispersion of Rh and Pt Atoms on Graphene Oxide Sheets 査読

Kazuma Gotoh, Hideki Hashimoto, Ryo Kawai, Yuta Nishina, Eiji Fujii, Takahiro Ohkubo, Atsushi Itadani, Yasushige Kuroda, Hiroyuki Ishida

CHEMISTRY LETTERS 41 ( 7 ) 680 - 682 2012年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CHEMICAL SOC JAPAN

Hybrid materials of ultimately minimized metal particles, namely, isolated atoms or subnano-sized particles, on thermally exfoliated graphene oxide sheets were produced using cation-exchanged highly oxidized graphite as a precursor. Rh atoms on graphene sheets arrange with a regular spacing of 0.50 or 0.45 nm and form square or rectangular grid patterns, whereas isolated Pt atoms disperse on graphene sheets randomly.

DOI： 10.1246/cl.2012.680

Dual-Copper Catalytic Site Formed in CuMFI Zeolite Makes Effective Activation of Ethane Possible Even at Room Temperature 査読

Atsushi Itadani, Hiroe Torigoe, Takashi Yumura, Takahiro Ohkubo, Hisayoshi Kobayashi, Yasushige Kuroda

JOURNAL OF PHYSICAL CHEMISTRY C 116 ( 19 ) 10680 - 10691 2012年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

The role of dual-cation sites in zeolites has received a renaissance in chemistry and industry directed toward fixation and activation of various gases; such sites may be expected to be more efficient than a single-cation site. We aimed to clarify the real active centers in the copper-ion-exchanged MFI-type zeolite (CuMFI) for ethane (C2H6). A peculiar feature was found in the appearance of the characteristic IR bands at 2644 and 2582 cm(-1) when C2H6 was adsorbed on Cu+ formed in CuMFI. The existence of dual species composed of two Cu+ ions bridging C2H6 was clearly indicated by extended X-ray absorption fine structure (EXAFS) data. Density functional theory calculations gave clear evidence that the two IR bands are distinctly due to C2H6 adsorbed on the dual-Cu+ site and not on a single site; this agrees with the EXAFS data. These data lead us to conclude that the dual-Cu+ site in the CuMFI sample is indispensable for efficient activation of C2H6 through the simultaneous interaction of C2H6 with two Cu+ ions.

DOI： 10.1021/jp3022858

Water-initiated ordering around a copper ion of copper acetate confined in slit-shaped carbon micropores 査読

Takahiro Ohkubo, Yutaro Takehara, Yasushige Kuroda

MICROPOROUS AND MESOPOROUS MATERIALS 154 82 - 86 2012年5月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Physical or chemical properties of hydrated ions confined in solid nanospaces are not substantially understood, although they are indispensable for the development of new science and technology. We study the local structure around a Cu2+ of copper acetate restricted in slit-shaped micropore of two kinds of activated carbon fibers (ACFs) by X-ray absorption fine structure (XAFS) technique. The results indicate that the highly dispersed copper acetate on the surface of ACFs can be partially dissolved after the adsorption of water. Also, when we adsorb water to copper acetate-deposited ACFs, the Cu-Cu distance of the dinuclear species of copper acetate becomes longer with the ordering of the Cu-Cu bond because of the reduction of the number of the bridging carboxylate inside the micropore. In addition, the results of EXAFS spectra suggest that water molecules can play an important role for the ordering of the specific dinuclear complex of copper acetate formed in the micropore even though the number of bridging carboxylate which can stabilize the dinuclear structure is decreased by the adsorption of water. (C) 2011 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.micromeso.2011.09.011

Unprecedented Reversible Redox Process in the ZnMFI-H-2 System Involving Formation of Stable Atomic Zn-0 査読

Akira Oda, Hiroe Torigoe, Atsushi Itadani, Takahiro Ohkubo, Takashi Yumura, Hisayoshi Kobayashi, Yasushige Kuroda

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 51 ( 31 ) 7719 - 7723 2012年

Visible-Light-Derived Photocatalyst Based on TiO2-delta N delta with a Tubular Structure 査読

Yoshikazu Hirose, Toshinori Mori, Yuka Morishita, Atsushi Itadani, Takayuki Kudoh, Takahiro Ohkubo, Tomoko Matsuda, Shigeharu Kittaka, Yasushige Kuroda

INORGANIC CHEMISTRY 50 ( 20 ) 9948 - 9957 2011年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

We succeeded in achieving visible-light responsiveness on a tubular TiO2 sample through the treatment of a tubular TiO2 that has a large surface area with an aqueous solution of ammonia or triethylamine at room temperature and subsequent calcination at 623 K, which produced a nitrided tubular TiO2 sample. It was found that the ease of nitridation is dependent on the surface states; washing the tubular TiO2 sample with an aqueous acidic solution is very effective and indispensable. This treatment causes the appearance of acidic sites on the tubular TiO2, which was proved by the following experiments: NH3 temperature-programmed desorption and two types of organic reactions exploiting the acid properties. The prepared samples, TiO2-delta N delta, efficiently absorb light in the visible region, and they exhibit a prominent feature for the decomposition of methylene blue in an aqueous solution at 300 K under irradiation with visible light, indicating the achievement of visible-light responsiveness on the tubular TiO2 sample. This type of tubular TiO2-delta N delta sample has merit in the sense that it has a large surface area and a characteristic high transparency for enabling photocatalytic reactions because it has a tubular structure and is composed of thin walls.

DOI： 10.1021/ic200424v

Actual Structure of Dissolved Zinc Ion Restricted in Less Than 1 Nanometer Micropores of Carbon 査読

Takahiro Ohkubo, Masayasu Nishi, Yasushige Kuroda

JOURNAL OF PHYSICAL CHEMISTRY C 115 ( 30 ) 14954 - 14959 2011年8月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

The structures and properties of hydrated ions confined in solid nanospaces are not substantially understood, although they are indispensable for the development of new devices such as electrical double-layer capacitors. We describe the hydration structure around a Zn2+ restricted in slit-shaped micropores of two kinds of activated carbon fibers (ACF) by the analysis of X-ray absorption fine structure (XAFS) spectra. The proportion of dissolved species against the total adsorbed amounts of Zn2+ on ACF was decreased with the reduction of the average micropore width of ACF. We could trace the actual structure of "nanosolution" around a Zn2+ restricted in less than 1 nm pore by extended XAFS (EXAFS) spectra with applying these values. Our results strongly indicate that the dehydrated structure can be stably formed inside the micropore whose pore size is less than the total diameter of the symmetrically hydrated ion, where the dehydrated ions can be stabilized by the strong potential well of the micropore.

DOI： 10.1021/jp2043653

Exfoliated graphene sheets decorated with metal/metal oxide nanoparticles: Simple preparation from cation exchanged graphite oxide 査読

Kazuma Gotoh, Taro Kinumoto, Eiji Fujii, Aki Yamamoto, Hideki Hashimoto, Takahiro Ohkubo, Atsushi Itadani, Yasushige Kuroda, Hiroyuki Ishida

CARBON 49 ( 4 ) 1118 - 1125 2011年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

We produced carbon hybrid materials of graphene sheets decorated with metal or metal oxide nanoparticles of gold, silver, copper, cobalt, or nickel from cation exchanged graphite oxide. Measurements using powder X-ray diffraction, transmission electron microscopy, and X-ray absorption spectra revealed that the Au and Ag in the materials (Au-Gr and Ag-Gr) existed on graphene sheets as metal nanoparticles, whereas Cu and Co in the materials (Cu-Gr and Co-Gr) existed as a metal oxide. Most Ni particles in Ni-Gr were metal, but the surfaces of large particles were partly oxidized, producing a core-shell structure. The Ag-Gr sample showed a catalytic activity for the oxygen reduction reaction in 1.0 M KOH aq. under an oxygen atmosphere. Ag-Gr is superior as a cathode in alkaline fuel cells, which should not be disturbed by the methanol cross-over problem from the anode. We established an effective approach to prepare a series of graphene-nanoparticle composite materials using heat treatment. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.carbon.2010.11.017

Template-Free Synthesis of Self-Assembled Co3O4 Micro/Nanocrystals 査読

R. Amutha, S. Akilandeswari, M. Muruganandham, Mika Sillanpaa, Bashir Ahmmad, Takahiro Ohkubo

JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 11 ( 4 ) 3171 - 3179 2011年4月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER SCIENTIFIC PUBLISHERS

In this article, we have reported the fabrication of various morphological porous Co3O4 by thermal decomposition of cobalt oxalate at open atmospheric conditions. Uniform cobalt oxalate microrods and microneedles were synthesized without using any surfactants or templates in large scale. The cobalt oxalate preparation method was played a crucial role on the crystal structure and its morphology. The as prepared cobalt oxalates and its corresponding cobalt oxides were characterized by using the thermogravimetric analysis, X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM) and nitrogen adsorption analysis. The XRD results indicated that the orthorhombic and monoclinic cobalt oxalates were formed in different experimental conditions. The influence of preparation method of cobalt oxalates and cobalt precursors on the final morphology has been investigated. The M-H loop of the Co3O4 porous microrods and microneedles showed the presence of paramagnetic properties at room temperatures. A plausible mechanism of both cobalt oxalates and Co3O4 formation was proposed based on the experimental results.

DOI： 10.1166/jnn.2011.3848

Structural optimization of arranged carbon nanotubes for hydrogen storage by grand canonical Monte Carlo simulation 査読

Daiki Minami, Takahiro Ohkubo, Yasushige Kuroda, Kenichi Sakai, Hideki Sakai, Masahiko Abe

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 35 ( 22 ) 12398 - 12404 2010年11月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

We revealed the arrangement of single wall carbon nanotube (SWNT) which is suitable for the adsorption of hydrogen by means of grand canonical Monte Carlo (GCMC) simulation with simple cylindrical model Here, we calculated the amount of adsorbed hydrogen with triangular lattice (TL) and square lattice (SL) model for the bundle structure with venous kinds of tube diameters (D) and inter axis distances (R(a)) Our results indicate that any arrangements having smaller R(a) are not suitable for the storage of hydrogen and the adsorption amount of hydrogen can be achieved the target value (6 wt % and 45 kg m(-3)) proposed by Department of Energy (DOE) in United States by SWNTs having larger R(a) at 77 K and 1 MPa Furthermore these results show that the best arrangement of SWNTs for the adsorption of hydrogen at this condition is TL structure having R(a) = 2 159 nm and D = 1 227 nm (C) 2010 Professor T Nejat Veziroglu Published by Elsevier Ltd All rights reserved

DOI： 10.1016/j.ijhydene.2010.08.082

Direct Information on Structure and Energetic Features of Cu+-Xe Species Formed in MFI-Type Zeolite at Room Temperature 査読

Hiroe Torigoe, Toshinori Mori, Kazuhiko Fujie, Takahiro Ohkubo, Atsushi Itadani, Kazuma Gotoh, Hiroyuki Ishida, Hiroki Yamashita, Takashi Yumura, Hisayoshi Kobayashi, Yasushige Kuroda

JOURNAL OF PHYSICAL CHEMISTRY LETTERS 1 ( 18 ) 2642 - 2650 2010年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

The interacted species of Xe with metal ions that are stable at room temperature are not known and are a subject of interest for fundamental chemistry We have,experimentally found a new and stable Xe species, XeCu+, which was formed it room temperature in a copper ion exchanged MFI-type zeolite. The presence of a prominent interaction between Cu+ in MFI and Xe, which has a covalent nature, was for the first time evidenced from experimental in situ synchrotron X-ray absorption fine structure and heat of adsorption measurements; the Cu+-Xe bond length of 2.45 angstrom and the bonding energy of ca. 60 kJ mol(-1). The bonding nature between Xe and Cu+ in the MFI zeolite was discussed utilizing density functional theory; the observed significant stabilization comes from the d(Cu+ in MFI)-p(Xe) orbital interaction. These new findings may pave a new way to developing fundamental chemistry of Xe compounds.

DOI： 10.1021/jz100838c

その他リンク： http://orcid.org/0000-0001-5907-3683

Existence of dual species composed of Cu+ in CuMFI being bridged by C2H2 査読

Atsushi Itadani, Takashi Yumura, Takahiro Ohkubo, Hisayoshi Kobayashi, Yasushige Kuroda

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 12 ( 24 ) 6455 - 6465 2010年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC CHEMISTRY

The interaction of ethyne (C2H2), as well as of carbon dioxide (CO2), with copper-ion-exchanged MFI zeolite (CuMFI) at room temperature was examined. It was found that CuMFI preferentially adsorbs C2H2, while this material does not respond to CO2. To clarify the specificity of CuMFI, a combination of various experimental techniques and theoretical calculations was adopted. Distinctive interaction energies of 140 and 110 kJ mol(-1) were clearly observed at the initial stage of C2H2 adsorption on CuMFI, suggesting the presence of two types of adsorbed C2H2. Two distinct IR bands at 1620 and 1814 cm(-1) appeared, which were assigned to the CRC stretching vibration modes of C2H2 differing in their adsorbed state. Both photoluminescence and X-ray absorption spectra showed that cuprous ions (Cu+) in CuMFI act as efficient sites for a marked C2H2 adsorption. From the analysis of the latter spectra and the calculational results based on the density functional theory, the formation of dual Cu+center dot center dot center dot(C2H2)center dot center dot center dot Cu+ complexes was indicated for the first time for CuMFI, and such a special configuration of the Cu+ sites contributed to the extremely strong adsorption of C2H2. In contrast, it was necessary for the linear CO2 molecule to take a bent structure to be adsorbed on Cu+ in CuMFI. It was concluded that the difference in the adsorption response of Cu+ in CuMFI towards C2H2 and CO2 is due to the chemistry between the nature of electron donation of Cu+ and the hybrid orbitals of the respective molecules. This work promotes further understanding of the states of active centres in CuMFI for C2H2 activation, as well as for N-2 fixation.

DOI： 10.1039/c000967a

その他リンク： http://orcid.org/0000-0001-5907-3683

Formation mechanism of powder emulsion; evaluating hydrophobic interaction between solid particles at the ari/water interface 査読

K. Igarashi, H. Maruyama, T. Ohkubo, K. Sakai, N. Naito, H. Sakai, M. Abe

材料技術 28 ( 1 ) 8 - 13 2010年

Potential for C-H Activation in CH4 Utilizing a CuMFI-Type Zeolite as a Catalyst 査読

Atsushi Itadani, Hiroyuki Sugiyama, Masashi Tanaka, Takahiro Ohkubo, Takashi Yumura, Hisayoshi Kobayashi, Yasushige Kuroda

JOURNAL OF PHYSICAL CHEMISTRY C 113 ( 17 ) 7213 - 7222 2009年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

We have found that a copper ion-exchanged MFI (Mobil Five)-type zeolite, having an ion exchange capacity of 112% (CuMFI-112), exhibits a specific interaction with CH4, even at room temperature. The observed properties are very remarkable compared with those found in the adsorbed amount of sodium ion-exchanged MFI and in the interaction with the sodium ion in MFI as well as in the adsorbed amounts for other types of copper ion-exchanged zeolites. The specificity of Cu+ in MFI is clearly evident. The most remarkable feature of the present system is the distinct appearance of infrared bands (IR) at 2661 and 2619 cm(-1) due to adsorbed CH4 at 300 K and the change in the X-ray absorption fine structure spectra of CuMFI before and after CH4 adsorption at 300 K, indicating the existence of substantial and specific interaction in this system. In addition, calculations based on the density functional theory were carried out by utilizing a Cu-AlSi91O151H66 cluster model, which is made up of a 10-membered ring of CuMFI. As a result, the calculations gave absorption bands that can be explained reasonably by the observed novel IR bands, indicating the existence of two types of eta(2)(H, H)-type interactions between Cu+ and CH4: (1) hydrogen interacted with a Cu cation coordinating to two oxygen atoms near an intersection of straight and sinusoidal channels, and (2) hydrogen interacted with a Cu cation located above a 5-membered ring on a wall of a straight channel. The nature of such bonding can be described by the formation of Cu-C bonds, which causes the deformation the T-d structure of CH4. Such interaction results in a weakening of the C-H bond and thus a lower frequency shift of the C-H bond interacting with Cu+.

DOI： 10.1021/jp807008t

その他リンク： http://orcid.org/0000-0001-5907-3683

Evaluating the formation of powder emulsion on the basis of the fractal properties of nano-ordered solid particles 査読

K. Igarashi, H. Maruyama, T. Ohkubo, K. Sakai, H. Sakai, M. Abe

材料技術 27 ( 1 ) 6 - 13 2009年

カチオン性シランカップリング剤で処理した基板上への酸化チタン薄膜の調製と光触媒特性査読

河野浩輝, 柴田裕史, 大久保貴広, 酒井俊郎, 酒井健一, 酒井秀樹, 阿部正彦

材料技術 26 ( 3 ) 147 - 153 2008年5月

Adsorption and micellization behavior of novel gluconamide-type gemini surfactants 査読

Kenichi Sakai, Shin Umezawa, Mamoru Tamura, Yuichiro Takamatsu, Koji Tsuchiya, Kanjiro Torigoe, Takahiro Ohkubo, Tomokazu Yoshimura, Kunio Esumi, Hideki Sakai, Masahiko Abe

JOURNAL OF COLLOID AND INTERFACE SCIENCE 318 ( 2 ) 440 - 448 2008年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE

The adsorption and micellization behavior of novel sugar-based gemini surfactants (N,N'-dialkyl-N,N'-digluconamide ethylenediamine, Glu(n)-2-Glu(n), where n is the hydrocarbon chain length of 8, 10 and 12) has been studied on the basis of static/dynamic surface tension, fluorescence, dynamic light scattering (DLS) and cryogenic transmission electron microscope (cryo-TEM) data. The static surface tension of the aqueous Glu(n)-2-Glu(n) solutions measured at the critical micelle concentration (cmc) is observed to be significantly lower than that of the corresponding monomeric surfactants. This suggests that the gemini surfactants, newly synthesized in the current study, are able to form a closely packed monolayer film at the air/aqueous solution interface. The greater ability in the molecular association is supported by the remarkably (approximately 100-200 times) lower cmc of the gemini surfactants compared with the corresponding monomeric ones. With a combination of the fluorescence and DLS data, a structural transformation of the Glu(n)-2-Glu(n) micelles is suggested to occur with an increase in the concentration. The cryo-TEM measurements clearly confirm the formation of worm-like micelles of Glu(12)-2-Glu(12) at the concentration well above the cmc. (C) 2007 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcis.2007.10.039

カチオン／アニオン界面活性剤混合系を利用したチタニア／界面活性剤複合粒子の調製とナノ構造制御査読

酒井秀樹, 河野浩輝, 萩原英輝, 小倉卓, 柴田裕史, 酒井健一, 大久保貴広, 阿部正彦

J. Jpn. Soc. Colour Mater. 81 ( 9 ) 325 - 330 2008年

記述言語：日本語出版者・発行元：Japan Society of Colour Material

カチオン界面活性剤とアニオン界面活性剤の混合水溶液中で形成されるナノサイズの分子集合体の存在下で酸化硫酸チタンの加水分解・重縮合反応を行うことにより, ナノサイズの規則的構造を有するチタニア／界面活性剤複合粒子を調製した。また, 界面活性剤の混合比を変化させることにより規則構造の間隔および形態制御を試みた。カチオン界面活性剤にセチルトリメチルアンモニウムブロミド (CTAB), アニオン界面活性剤にソディウムオクチルサルフェイト (SOS) を用いたところ, SOSの混合比が小さいときにはヘキサゴナル型の規則構造を有する粒子が得られ, 規則構造の周期はSOS混合比の増大とともに増加した。一方, ある混合比を超えるとラメラ型の規則構造へと変化し, 規則構造の周期は逆に減少することがわかった。また, アニオン界面活性剤としてSOSの替わりにソディウムドデシルサルフェイト (SDS) またはソディウムオクタノエート (SO) を用いた際にも同様の傾向が観測されたが, 規則構造周期の絶対値ならびに相変化組成は界面活性剤種により変化した。以上の結果より, カチオン／アニオン界面活性剤混合比の変化により規則的構造の周期および形態をオングストロームオーダーで精密に制御できることがわかった。

DOI： 10.4011/shikizai.81.325

その他リンク： https://jlc.jst.go.jp/DN/JALC/00319065301?from=CiNii

Photo-isomerization of spiropyran-modified cationic surfactants 査読

Hideki Sakai, Hiroatsu Ebana, Kenichi Sakai, Koji Tsuchiya, Takahiro Ohkubo, Masahiko Abe

JOURNAL OF COLLOID AND INTERFACE SCIENCE 316 ( 2 ) 1027 - 1030 2007年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE

Photo-induced isomerization of a newly synthesized surfactant,1'(6-trimethylammoniododecyl)-3',3'-dimethyl-6-nitrospiro-(2H-1-benzopyran-2,2'-indoline) bromide (SP-Me-12), has been characterized on the basis of the UV-vis absorption spectra and the surface tension data. Visible light (lambda > 420 nm) incident on the aqueous solution of SP-Me-12 results in the isomerization from the merocyanine (MC) form to the spiropyran (SP) form; this structural change was confirmed by a complete disappearance of a characteristic absorption peak of the MC form. When the surfactant solution is stored in the dark, the isomerized SP form reverts to the original MC form, however, the reverse isomerization rate is observed to be considerably slower than that seen for visible light irradiation (from the MC form to the SP form). A reversible change in the surface tension of the aqueous surfactant solution is observed for the photo-induced isomerization: the surface tension measured below the critical aggregation concentration decreases as a result of the visible light irradiation and it is gradually reversed to the original level during the equilibration in the dark. (C) 2007 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcis.2007.08.042

Phase behavior of mixed solution of a glycerin-modified cationic surfactant and an anionic surfactant 査読

Koji Tsuchiya, Jun Ishikake, Tae Seong Kim, Takahiro Ohkubo, Hideki Sakai, Masahiko Abe

JOURNAL OF COLLOID AND INTERFACE SCIENCE 312 ( 1 ) 139 - 145 2007年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE

The phase behavior of mixed solution of newly synthesized monoglycerylcetyldimethylammonium chloride (MGCA) and sodium octyl sulfate (SOS) in water was investigated by cryo-transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS), differential scanning calorimetry (DSC), and fluorescence polarizing for evaluation of the microviscosity of bilayers. No precipitate was observed in the mixed solution except at concentrations below 20 mM over all mixing ratios, and stable vesicles were formed in a considerably wide range of mixing ratio, even at the equimolar ratio. Vesicles formed in aqueous 1/1 MGCA/SOS mixture were found to exhibit no phase transition, and fluorescence polarizing measurements showed that the vesicle bilayers have a high fluidity. This flexibility allows the bilayers to have a spontaneous curvature, and thus vesicles rather than flat lamellae can be stabilized in the mixture even at the equimolar ratio. In addition, because the glycerin group of MGCA interacts strongly with water, the hydration repulsion contributes to prevent the bilayers consisting of MGCA and SOS from adhering and floccuiating even though the charge neutralization between MGCA and SOS occurs at the equimolar ratio. (c) 2006 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcis.2006.07.075

Synthesis of highly-ordered mesoporous silica particles using mixed cationic and anionic surfactants as templates 査読

Takahiro Ohkubo, Taku Ogura, Hideki Sakai, Masahiko Abe

JOURNAL OF COLLOID AND INTERFACE SCIENCE 312 ( 1 ) 42 - 46 2007年8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）出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE

We applied a molecular assembly formed in an aqueous surfactant mixture of cationic cetyltrimethylammonium bromide (CTAB) and anionic sodium octylsulfate (SOS) as templates of mesoporous silica materials. The hexagonal pore size can be controlled between 3.22 and 3.66 nm with the mixed surfactant system. In addition, we could observe the lamellar structure of the mixed surfactants with precursor molecules, which strongly shows the possibility of precise control of both the pore size and the structure of pores by changing the mixing ratio of surfactants. Moreover, use of the cationic surfactant having longer hydrophobic chain like stearyltrimethyl ammonium bromide (STAB) caused the increase in dloo space and shifted the point of phase transition from hexagonal phase to lamellar phase to lower concentration of SOS. (c) 2007 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcis.2007.02.043

Preparation of petaloid microspheres of basic magnesium carbonate 査読

Takahiro Ohkubo, Sei Suzuki, Kohei Mitsuhashi, Taku Ogura, Shinichi Iwanaga, Hideki Sakai, Masumi Koishi, Masahiko Abe

LANGMUIR 23 ( 11 ) 5872 - 5874 2007年5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）出版者・発行元：AMER CHEMICAL SOC

The synthesis of basic magnesium carbonate was examined under ultrasonic irradiation and was performed by the soda ash method using magnesium sulfate and sodium carbonate as starting materials. The particulate product was evaluated using SEM observations. Ultrasonic irradiation in the preparation of basic magnesium carbonate was found to give fine petaloid microspheres of about 3 mu m in primary particle size.

DOI： 10.1021/la7002782

RBM band shift-evidenced dispersion mechanism of single-wall carbon nanotube bundles with NaDDBS 査読

Shigenori Utsumi, Mamiko Kanamaru, Hiroaki Honda, Hirofumi Kanoh, Hideki Tanaka, Takahiro Ohkubo, Hideki Sakai, Masahiko Abe, Katsumi Kaneko

JOURNAL OF COLLOID AND INTERFACE SCIENCE 308 ( 1 ) 276 - 284 2007年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE

The dispersion process of single-wall carbon nanotube (SWNT) by using sodium dodecylbenzene sulfortate (NaDDBS) was studied by means of surface tension measurements, ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), and transmission electron spectroscopy (TEM). The critical micelle concentration (CMC) and the concentration where the surface tension begins to drop increase by the presence of SWNT. The isotherm of NaDDBS amount adsorbed on SWNT shows the plateau region at 0.2-6 mM and the saturated region above 40 mM. The external surface of SWNT bundle is fully covered with adsorbed NaDDBS at the plateau region, showing that SWNTs can be dispersed with the bundle form. On the other hand, SWNTs are dispersed in individual tubes at the saturated region, where the adsorption amount corresponds to coating of individual tube surfaces with NaDDBS. This dispersion state was confirmed by SEM and TEM observations. The effect of the dispersion state of SWNTs on radial breathing mode in Raman spectrum gave inherent peak shifts, being the in situ evidences on the g step-wise dispersion mechanism of the SWNT bundle to the individual tubes. (c) 2006 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcis.2006.12.041

Adsorption and aggregation properties of amino acid-based N-alkyl cysteine monomeric and N,N '-dialkyl cystine gemini surfactants 査読

Tomokazu Yoshimura, Ayako Sakato, Koji Tsuchiya, Takahiro Ohkubo, Hideki Sakai, Masahiko Abe, Kunio Esumi

JOURNAL OF COLLOID AND INTERFACE SCIENCE 308 ( 2 ) 466 - 473 2007年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE

An amino acid-based gemini surfactant derived from cystine (2C(n)Cys, where n represents the hydrocarbon chain lengths of 8, 10, and 12) was synthesized by reacting cystine with n-alkyl bromide, and its adsorption and aggregation properties were characterized by measurements of equilibrium and dynamic surface tension and dynamic light scattering. The properties of 2CnCys were compared with those of an amino acid-based monomeric surfactant derived from cysteine (C(n)Cys). For n = 8 and 10, when compared to C(n)Cys, 2C(n)Cys exhibited excellent surface activities, such as a lower critical micelle concentration (cmc), greater efficiency in lowering the surface tension of water, and smaller area occupied per molecule. Adsorption rate at air/water interface decreased with an increase in hydrocarbon chain length, chain number, and concentration of respective compounds. Further, the kinetics were discussed using the monomer diffusion coefficient obtained from short and long time scales in dynamic surface tension plots. In addition, the aggregation properties of 2C(n)Cys for n = 8 and 10 differed from those in the case of n = 12. In other words, relatively larger micelles with diameters of approximately 7 nm were formed by 2C(n)Cys for n = 8 and 10 in comparison to those formed by C(n)Cys (2-3 nm). On the other hand, for a 0.832 mmol dm(-3) 2C(12)Cys solution, the aggregation structure investigated by cryogenic transmission electron microscopy (cryo-TEM) and small-angle neutron scattering (SANS) revealed the coexistence of small unilamellar vesicles and small rods. (c) 2006 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcis.2006.11.038

Cationic surfactant changes the morphology of DNA molecules 査読

Hisanori Nakanishi, Koji Tsuchiya, Takahiro Okubo, Hideki Sakai, Masahiko Abe

LANGMUIR 23 ( 2 ) 345 - 347 2007年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

The effect of cetyltrimethylammonium bromide (CTAB), a cationic surfactant, was investigated on the aggregated form of DNA molecules in water at a given temperature. CTAB caused changes in the aggregated form of DNA molecules from loosely packed spherical to rodlike through toroidal one with increasing concentration below the critical micelle concentration (CMC). The change was suggested to arise from the ion complex formation between CTAB and DNA molecules due to the electrostatic interaction, thereby reducing the surface charge and solubility in water of the latter.

DOI： 10.1021/la051443p

その他リンク： http://orcid.org/0000-0001-5907-3683

Synthesis and properties of a microtube photocatalyst with photoactive inner surface and inert outer surface 査読

Kohei Mitsuhashi, Naoki Tagami, Katsuyuki Tanabe, Sei Suzuki, Shinichi Iwanaga, Takahiro Ohkubo, Hideki Sakai, Masumi Koishi, Masahiko Abe

JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY 185 ( 2-3 ) 133 - 139 2007年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

Synthesis of a photocatalyst with a novel particle form, its photoactivity, and the degradation of polyvinyl alcohol containing the photocatalyst were studied in detail. A microtube photocatalyst with titanium dioxide particles supported on the inner surface of the microtube was synthesized by adding fine titanium dioxide particles in the formation process of basic magnesium carbonate microtube. The photoactivity of the microtube photocatalyst was confirmed from the decomposition of 2-propanol under blacklight irradiation. Moreover, the microtube photocatalyst was found to cause no degradation of polyvinyl alcohol, whereas, it decomposed 2-propanol with its photoactivity when impregnated in a polyvinyl alcohol foam. This fact was considered to be derived from the unique structure of the microtube photocatalyst, which has a photoactive inner surface with titanium dioxide and an inert outer surface of basic magnesium carbonate. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jphotochem.2006.04.047

Preparation of tiny biodegradable capsules using electrocapillary emulsification 査読

Masahiko Abe, Ai Nakayama, Tamotsu Kondo, Hiroshi Morishita, Koji Tsuchiya, Shigenori Utsumi, Takahiro Ohkubo, Hideki Sakai

JOURNAL OF MICROENCAPSULATION 24 ( 8 ) 777 - 786 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：TAYLOR & FRANCIS LTD

Conditions for preparing tiny biodegradable capsules were examined using electrocapillary emulsification that allows one to prepare monodisperse emulsions with ease by applying a DC potential between oil and water phases without mechanical agitation. The results obtained showed that a 1:4 mixture of polysorbate 80 (TO-10), a hydrophilic non-ionic surfactant, and sorbitan monooleate (SO-10), an oleophilic surfactant, is appropriate as the surfactant to be added to oil phase, cyclohexane is acceptable as the oil phase and 1000 V is optimum as the DC potential to be applied. The capsules prepared had sizes ranging from 100 - 300 nm and a surface roughness of similar to 10nm and degraded in model intestinal juice more easily and rapidly than in model gastric juice. In addition, the capsules containing lactoferrin, an anti-carcinogenic protein, were found to keep 12.5% of the protein used in encapsulation without losing its activity.

DOI： 10.1080/02652040701644752

両親媒性マイクロチューブによって安定化されたPickeringエマルションの調製査読

鈴木生, 三觜幸平, 瓦吹亮, 岩永真一, 大久保貴広, 酒井秀樹, 小石眞澄, 阿部正彦

材料技術 25 ( 4 ) 153 - 159 2007年

W/O型エマルションの水相中への着色剤分散剤の添加効果査読

奥田貞直, 大久保貴広, 酒井秀樹, 阿部正彦

材料技術 25 ( 4 ) 160 - 169 2007年

Room temperature synthesis of crystalline mesostructured titania particles using Gemini-type surfactants as templates 査読

M. Abe, H. Shibata, K. Tsubone, H. Mihara, T. Sakai, K. Torigoe, S. Dai, T. Ohkubo, S. Utsumi, K. Sakamoto, M. Matsumoto, H. Sakai

色材協会誌 80 ( 11 ) 450 - 452 2007年

疎水内表面と親水外表面を有する両親媒性マイクロチューブの調製と特製査読

三觜幸平, 瓦吹亮, 鈴木生, 岩永真一, 大久保貴広, 酒井秀樹, 小石眞純, 阿部正彦

材料技術 25 ( 3 ) 127 - 134 2007年

Adsorption and aggregation properties of heterogemini surfactants containing a quaternary ammonium salt and a sugar moiety 査読

Kanae Nyuta, Tomokazu Yoshimura, Koji Tsuchiya, Takahiro Ohkubo, Hideki Sakai, Masahiko Abe, Kunio Esumi

LANGMUIR 22 ( 22 ) 9187 - 9191 2006年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

A novel heterogemini surfactant comprising two hydrocarbon chains and two different hydrophilic groups such as a quaternary ammonium cation and gluconamide nonion N,N-dimethyl-N-[2-(N'-alkyl-N'-gluconamide)ethyl]-1-alkylammonium bromides (2C(n)AmGlu, where n represents hydrocarbon chain lengths of 8, 10, 12, and 14) was synthesized by reacting N,N-dimethylethylenediamine with alkyl bromide, followed by a reaction with 1,5-D(+)gluconolactone. The adsorption properties of 2C(n)AmGlu were characterized by surface tension measurements made using the Wilhelmy plate method, and their aggregation properties were investigated by dynamic light scattering and cryogenic transmission electron microscopy techniques. The relationship between the hydrocarbon chain length and the logarithm of the critical micelle concentration (cmc) for 2C(n)AmGlu exhibited a linear decrease when the chain length was increased up to 12 and then a departure from linearity at n = 14. The surface tension reached 24-26 mN m(-1) at each cmc, indicating high efficiency in lowering the surface tension of water. Furthermore, it was found that the structure of the aggregate formed for 2CnAmGlu in solution was influenced by the hydrocarbon chain length; that is, for n = 10 and 12, micelles with a hydrodynamic radius of 2-5 nm were formed, whereas vesicles were also observed for n = 14.

DOI： 10.1021/la061688h

Polymerizable cationic gemini surfactant 査読

Masahiko Abe, Kazuyuki Tsubone, Takaaki Koike, Koji Tsuchiya, Takahiro Ohkubo, Hideki Sakai

LANGMUIR 22 ( 20 ) 8293 - 8297 2006年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

A polymerizable cationic gemini surfactant, [CH(2)dC(CH3) COO(CH2)(11)N+ CH3)(2)CH2]2 center dot 2Br(-), 1 has been synthesized and its basic interfacial properties were investigated (in water and in the presence of 0.05 M NaBr). For comparison, the properties of monomeric surfactant corresponding to 1, CH(2)dC(CH3) COO(CH2)(11)N+(CH3)(3)center dot Br-, 2, were also investigated. Parameters studied include cmc (critical micelle concentration), C-20 (required to reduce the surface tension of the solvent by 20 mN/m), gamma(cmc) (the surface tension at the cmc), cmc (the maximum surface excess concentration at the air/water interface), A(min) (the minimum area per surfacatant molecule at the air/water interface), and cmc/C-20 ratio (a measure of the tendency to form micelles relative to adsorb at the air/water interface). For the polymerizable gemini surfactant, 1, the methacryloxy groups at the terminal of each hydrophobic group in a molecule have no contact with the air/water interface in the monolayer, whereas for the corresponding monomeric surfactant, 2, the methacryloxy group contacts at the interface forming a looped configuration like a bolaamphiphile. Polymerized micelles of the gemini surfactant are fairly small monodisperse and spherical particles with a mean diameter of 3 nm.

DOI： 10.1021/la060156y

Preparation and photocatalytic activity of titania particulate film with mesostructured silica as binder 査読

Hirobumi Shibata, Takahiro Ohkubo, Hiroki Kohno, Pramoch Rangsunvigit, Hideki Sakai, Masahiko Abe

JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY 181 ( 2-3 ) 357 - 362 2006年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

TiO2 (titania) particulate films with mesostructured silica (SiO2) as binder were prepared by drying glass substrate coated with an aqueous mixture of titania. particles, tetramethoxysilane (TMOS) and cetyltrimetylammonium bromide (CTAB) at appropriate temperature. X-ray diffraction (XRD) and IR absorption measurements on the obtained films revealed the formation of titania particles/silica composite thin film. XRD patterns at low angle region on these films indicated silica binder has well-ordered lamellar type mesostructure. These films show characteristic properties on both high absorption ability and photocatalytic activity to oxidative degradation of gaseous 2-propanol. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jphotochem.2005.12.018

孔版印刷に及ぼすW/O型エマルション中の着色剤の存在位置査読

奥田貞直, 大久保貴広, 酒井秀樹, 阿部正彦

MATERIALS TECHNOLOGY 24 ( 4 ) 222 - 230 2006年7月

Preparation and formation mechanism of mesoporous titania particles having crystalline wall 査読

H Shibata, H Mihara, T MLikai, T Ogura, H Kohno, T Ohkubo, H Sakait, M Abe

CHEMISTRY OF MATERIALS 18 ( 9 ) 2256 - 2260 2006年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Mesoporous titania particles having anatase-type crystalline wall were prepared using a low-temperature crystallization technique. Crystalline mesoporous titania was obtained through the sol-gel process of titanium oxysulfate sulfuric acid hydrate (TiOSO4 center dot xH(2)SO(4)center dot xH(2)O) at 333 K in the presence of cetyltrimethylammonium bromide (C16TAB), a cationic surfactant. The mesoporous titania with hexagonal structure was formed according to the following mechanism. Nuclei of ultrafine titanium hydroxide oxide (TiO(OH)(2)) were formed from TiOSO4 on the periphery of the surface of cationic C16TAB micelles at the rimary stage of sol-gel reaction. Then, heat treatment at 333 K induced the transformation of the particle wall from TiO(OH)(2) to anatase nanocrystal, which resulted in the formation of mesoporous titania with a crystalline wall. Moreover, the presence of bromide ion (Br-), the counterion of C16TAB, was shown to suppress the collapse of mesostructure by retarding the transition from anatase to rutile.

DOI： 10.1021/cm0524042

Preparation of highly dispersed core/shell-type titania nanocapsules containing a single Ag nanoparticle 査読

H Sakai, T Kanda, H Shibata, T Ohkubo, M Abe

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 128 ( 15 ) 4944 - 4945 2006年4月

Preparation of highly dispersed core/shell-type titania nanocapsules containing a single Ag nanoparticle 査読

H Sakai, T Kanda, H Shibata, T Ohkubo, M Abe

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 128 ( 15 ) 4944 - 4945 2006年4月

Preparation of Nanocapsules with Alginate/Polylysine Complex Wall 査読

Masahiko Abe, Kensuke Tanaka, Ai Nakayama, Tamotsu Kondo, Koji Tsuchiya, Veerapat Tantayakom, Takahiro Ohkubo, Hideki Sakai

Journal of Oleo Science 55 ( 12 ) 615 - 621 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）

This paper deals with a novel preparation method of nanocapsules with alginate/polylysine complex wall. The preparation method consisted of the following steps: dispersion of an aqueous sodium alginate solution into cyclohexane to give a W/O emulsion, preparation of calcium alginate gel beads by adding the emulsion into a calcium aerosol OT solution in cyclohexane, and alginate/polylysine complex wall formation on the surface of calcium alginate beads by adding the beads into an aqueous poly-L-lysine solution. The size of alginate/polylysine complex capsules thus prepared was found to be 100-500 nm. Moreover, an attempt was made to prepare much smaller capsules using a laboratory-made apparatus for electrocapillary emulsification and the capsule size could be reduced to about 40 nm. © 2006, Japan Oil Chemists' Society. All rights reserved.

DOI： 10.5650/jos.55.615

FT-IR and NMR Study on Concentration-Dependent Vesicle-Micelle Transition in CTAB/SOS/D2O Ternary System 査読

H. Nakanishi, K. Tsuchiya, T. Ohkubo, H. Sakai, M. Abe

材料技術 24 ( 1 ) 20 - 26 2006年

Pore-size control of carbon nanospace with ultrasonic irradiation

T. Ohkubo, R. Hori, K. Tsuchiya, H. Sakai, M. Abe

2006 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2006 Technical Proceedings 1 162 - 165 2006年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

In this study, we examined the micropore-size control on activated carbons by ultrasonic irradiation with various conditions. Pitch-based activated carbon fiber (ACF) was used for the sample having relatively uniform micropores whose micropore size was determined as 1.15 nm from the measurement of nitrogen adsorption isotherm at 77 K and high-resolution αs-plot analysis. Also, the ultrasonic irradiations to ACF were carried out in the water bath with various irradiation times and at three irradiation frequencies (40 kHz, 200 kHz, and 1 MHz). The results indicate that we can decrease the pore volume and average pore widths of ACFs with longer irradiation time. Also, we examined the dependence of ultrasonic frequencies on micropore-size control. The average pore width of ACF irradiated by 40 kHz was decreased over 10% from the original one. This result suggests that the nanospaces of ACF are collapsed as a result of sonication. Besides, larger pores, are more easily collapsed selectively.

Preparation of mesoporous titania particles with photocatalytic activity under visible-light irradiation 査読

H Shibata, T Mukai, T Akita, T Ohkubo, H Sakai, M Abe

CHEMISTRY LETTERS 34 ( 12 ) 1696 - 1697 2005年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CHEMICAL SOC JAPAN

Novel visible light-responsive photocatalytic mesoporous titania particles were prepared using the sol-gel reaction of titanium oxysulfate sulfuric acid hydrate TiOSO(4)(.)xH(2)SO(4)(.) xH(2)O in aqueous solution in the presence of lyotropic cetyltrimethylammonium bromide (CTAB) liquid crystal as template. The absorption threshold of the calcined particles shifted toward the longer wavelength side and they showed a photocatalytic activity in the oxidation of gaseous 2-propanol under visible light (> 440 nm) irradiation.

DOI： 10.1246/cl.2005.1696

その他リンク： http://orcid.org/0000-0001-5907-3683

Direct synthesis of mesoporous titania particles having a crystalline wall 査読

H Shibata, T Ogura, T Mukai, T Ohkubo, H Sakai, M Abe

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 127 ( 47 ) 16396 - 16397 2005年11月

Photoinduced reversible change of fluid viscosity 査読

H Sakai, Y Orihara, H Kodashima, A Matsumura, T Ohkubo, K Tsuchiya, M Abe

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 127 ( 39 ) 13454 - 13455 2005年10月

Membrane properties of cationic liposomes composed of dipalmitoylphosphatidylcholine and dipalmityldimethylammonium bromide 査読

S Yokoyama, A Inagaki, T Imura, T Ohkubo, N Tsubaki, H Sakai, M Abe

COLLOIDS AND SURFACES B-BIOINTERFACES 44 ( 4 ) 204 - 210 2005年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Cationic liposomes composed of dipalmitoylphosphatidylcholine (DPPC) and dipalmityldimethylammmonium bromide (DPAB) were prepared by the Bangham method and the effect of DPAB on the membrane properties was examined in terms of liposomal shape, particle size, trapping efficiency, surface potential and dispersibility. The dispersibility of the mixed DPPC/DPAB liposomes (the mole fraction of DPAB (X-DPAB) >= 0.05) was excellent and the dispersibility was maintained for 6 months, since the zeta-potential of the mixed liposomes was approximately +40 mV. The trapping efficiency of the mixed DPPC/DPAB liposomes (X-DPAB = 0.05) was 10 times greater than that of the DPPC liposomes, and the value was largest among the mixed liposomes (X-DPAB = 0-1.0). Freeze-fracture electron micrographs indicated that the shape of the mixed DPPC/DPAB liposomes (XDPAB = 0.05) was that of large unilamellar vesicles (LUVs) with a diameter of approximately 2 mu m, while the shape of the DPPC liposomes was that of multilamellar vesicles (MLVs). The mixed liposomes had, therefore, a high trapping efficiency. Furthermore, the shape of the mixed DPPC/DPAB liposomes (X-DPAB = 0.75) was also that of LUVs with a diameter of approximately mu m and these had a high trapping efficiency. Whereas, the particle size (500 nm) of the mixed DPPC/DPAB liposomes (X-DPAB = 0.25) was smaller than that of the former and had the minimum trapping efficiency. The phase transition temperature of the liposomal bilayer membranes indicated a maximum value at 0.25-0.30 mole fractions of DPAB. These facts were considered to be due to the fact that DPPC and DPAB, whose molar ratio was 7.5:2.5, were tightly packed in the liposomal bilayer membranes and that the curvature of the liposomal particle was resultantly large. Nevertheless, LUVs having a high trapping efficiency were easily obtained by mixing a small amount of DPAB with the DPPC. (c) 2005 Published by Elsevier B.V.

DOI： 10.1016/j.colsurfb.2005.01.005

その他リンク： http://orcid.org/0000-0001-5907-3683

Preparation of ZrB 2 and HfB 2 by metallothermic reduction of ZrO 2, ZrSiO 4, and HfO 2 査読

Takahiro Ohkubo, Tetsuo Ono, Katsuhiro Nishiyama, Susumu Niwa, Hideki Sakai, Masumi Koishi, Masahiko Abe

Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy 52 ( 9 ) 664 - 669 2005年9月

担当区分：筆頭著者記述言語：日本語掲載種別：研究論文（学術雑誌）

ZrB 2 and HfB 2 were prepared by metallothermic reduction (MTR) of ZrO 2, ZrSiO 4, and HfO 2 with Mg or Mg and MgO mixtures. We understood that the theory of function-building fine particle preparation was able to be applied to synthesize nano-atomized fine particles of ZrB 2. ZrB 2 can also be obtained directly from mixture of ZrSiO 4, B 2O 3, and Mg by MTR method. This sample has no borides such as silicon boride except for ZrB 2. Therefore, this result shows the possibility to obtain ZrB 2 easily from natural source. In addition, HfB 2 can also be synthesized by MTR method using HfO 2 which was calcined over 750°C.

DOI： 10.2497/jjspm.52.664

その他リンク： http://orcid.org/0000-0001-5907-3683

Bドープによる可視光応答型TiO2の調製とその光物性査読

大久保貴広, 秋田隆仁, 柴田裕史, 丹羽進, 西山勝廣, 酒井秀樹, 阿部正彦

粉体および粉末冶金 52 ( 7 ) 495 - 499 2005年7月

金属熱還元法を用いた窒素ドープ型酸化チタンの調製とその光物性査読

大久保貴広, 秋田隆仁, 柴田裕史, 丹羽進, 西山勝廣, 酒井秀樹, 阿部正彦

粉体および粉末冶金 52 ( 7 ) 489 - 494 2005年7月

Synthesis of Microtubes with a Surface of “House of Cards” Structure via Needlelike Particles and Control of Their Pore Size 査読

K. Mitsuhashi, N. Tagami, K. Tanabe, T. Ohkubo, H. Sakai, M. Koishi, M. Abe

Langmuir 21 ( 8 ) 3659 - 3663 2005年4月

Novel approach for the preparation of metal containing mesoporous silica using solubilization of fatty acid salt 査読

A Yamaguchi, M Yokoyama, T Ogura, K Oyaizu, M Yuasa, T Ohkubo, H Sakai, M Abe

CHEMISTRY LETTERS 34 ( 3 ) 346 - 347 2005年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CHEMICAL SOC JAPAN

We have prepared copper-containing mesoporous silica (Cu/MS) using solubilization of copper oleate in nonionic surfactant aggregates. The amount of copper loading in calcined Cu/MS corresponded to the amount of copper oleate solubilized in surfactant aggregates of the mixed solution.

DOI： 10.1246/cl.2005.346

Nanospace molecular science and adsorption 査読

K Kaneko, T Ohba, T Ohkubo, S Utsumi, H Kanoh, M Yudasaka, S Iijima

ADSORPTION-JOURNAL OF THE INTERNATIONAL ADSORPTION SOCIETY 11 21 - 28 2005年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER

The relationships between the enhanced interaction potential and intensive confinement effect of slit-shaped and cylindrical nanospaces are shown. The structures of water molecules and aqueous ions confined in nanospaces of activated carbon fiber (ACF) and single wall carbon nanohorn (SWNH)s were studied by adsorption, in situ small angle X-ray scattering(SAXS), GCMC simulation, and EXAFS spectroscopy. Water molecules are associated with each other to form the clusters, being stabilized in the carbon nanospaces. This stabilization mechanism of water in carbon nanospaces were evidenced by the interaction potential calculation, GCMC simulation, and the density fluctuation analysis of in situ SAXS. The Ornstein-Zernike analysis of in situ SAXS profiles lead to the conclusion that the critical size of water clusters for predominant water adsorption in hydrophobic carbon nanospaces is about 0.5 nm corresponding to the octomer to decamer. The adsorption hysteresis of water adsorption isotherm of nanoporous carbon was interpreted by the cluster growth, which is confirmed by the density fluctuation analysis. The Rb and Br ions confined in the carbon nanospaces were examined by EXAFS spectroscopy. The remarkable decreases in the hydration number and the water-Rb ion distance of the solution confined in the nanospaces were observed. In particular, the hydration number of the Rb ion in the nanospaces of SWNH is less than 3, being much smaller than the hydration number (6) of the bulk solution. The electrical double layer structure in the nanospaces should be quite different from that in the bulk solution.

DOI： 10.1007/s10450-005-5893-8

ミセル電解法による無機薄膜の作成査読

今村仁, 吉岡浩也, 土屋好司, 中野智, 大久保貴広, 岡部慎也, 酒井秀樹, 二瓶好正, 阿部正彦

材料技術 23 27 - 35 2005年

Stearylamine Changes the Liposomal Shape from MLVs to LUVs 査読

Shoko Yokoyama, Akiko Inagaki, Koji Tsuchiya, Hideki Sakai, Tomohiro Imura, Takahiro Ohkubo, Nobuyuki Tsubaki, Masahiko Abe

Journal of Oleo Science 54 ( 4 ) 251 - 254 2005年

記述言語：英語掲載種別：研究論文（学術雑誌）

The shape of mixed dipalmitoylphosphatidylcholine (DPPC)/stearylamine (SA) liposomes prepared by the Bangham method was examined using freeze-fracture electron microscopy. The shape of the mixed DPPC/SA liposomes (XSA = 0.05) was not that of multilamellar vesicles (MLVs) but large unilamellar vesicles (LUVs) with a diameter of approximately 1.0 μm. These facts overthrow the preconceived idea that the shape of the DPPC/SA liposomes prepared by the Bangham method is that of MLVs. The trapping efficiency of the mixed DPPC/SA liposomes (XSA = 0.05) was ten times greater than that of the DPPC liposomes, since the DPPC liposomes were MLVs. The data of the DSC peak for the DPPC/SA liposomes also indicated that the shape of the DPPC/SA liposomes is that of LUVs. We emphasize that the shape of the DPPC liposomes changes from that of MLVs to LUVs by the mixing of a small amount of SA into the DPPC liposomes. © 2005, Japan Oil Chemists' Society. All rights reserved.

DOI： 10.5650/jos.54.251

その他リンク： http://orcid.org/0000-0001-5907-3683

Mechanism of Concentration-Dependent Vesicle-Micelle Transition in Aqueous Mixture of Cationic and Anionic Surfactants 査読

Hisanori Nakanishi, Koji Tsuchiya, Takahiro Ohkubo, Hideki Sakai, Masahiko Abe

Journal of Oleo Science 54 ( 8 ) 443 - 451 2005年

記述言語：英語掲載種別：研究論文（学術雑誌）

The phase behavior of aqueous mixed solution of cationic cetyltrimethyl-ammonium bromide (CTAB) and anionic sodium octylsulfate was studied focusing on the concentration-dependent vesicle-micelle transition. Dynamic light scattering measurements and freeze fracture TEM observations showed that the phase transition occurs in two steps depending on the total surfactant concentration. Equilibrium vesicles (V) formed in dilute solution was shown to transform to micelles (M) through a micelle/ small unilamellar vesicle (M + V) coexisting state. The concentration at which the transition from V to M + V occurs on the SOS-rich side lies around the CMC of pure SOS (120 mM). Moreover, electroconductivity and FT-IR measurements revealed that the phase transition is accompanied by a decrease in the degree of counter ion dissociation from surfactant molecules. Based on these experimental findings, the cause of the phase transition was discussed. © 2005, Japan Oil Chemists' Society. All rights reserved.

DOI： 10.5650/jos.54.443

その他リンク： http://orcid.org/0000-0001-5907-3683

Effect of Alkyl Chain Length of Phosphatidylcholine on the Membrane Properties of Cationic Liposomes 査読

A. Inagaki, K. Tsuchiya, H. Sakai, T. Imura, T. Ohkubo, N. Tsubaki, S. Yokoyama, M. Abe

材料技術 23 107 - 110 2005年

Phase Behavior of Mixed Solutions of a Cationic Surfactant with a Ferrocenyl Group and an Anionic Surfactant: Surface Chemical and Electrochemical Approaches 査読

H. Imamura, K. Tsuchiya, Y. Kondo, N. Yoshino, T. Ohkubo, H. Sakai, M. Abe

J. Oleo Sci. 54 ( 3 ) 125 - 134 2005年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japan Oil Chemists' Society

The phase behavior of mixed solutions of (11-ferrocenyl)undecyltrimethyl-ammonium bromide (FTMA⁺), a redox-active cationic surfactant, and sodium dodecylbenzenesulfonate (SDBS), an anionic surfactant, was investigated in detail, and the mechanisms of spontaneous vesicle formation and the control of reversible formation of vesicles through the redox reaction of FTMA⁺ in the mixed system were also examined. Differential interference optical microscopic observations, particle size measurements, and trapping efficiency measurements revealed that various types of aggregates including mixed micelles, vesicles, and liquid crystals are formed in the system depending on the mixing ratio of FTMA⁺ and SDBS. Ultracentrifugal measurements showed that the composition of bimolecular membranes composed of FTMA⁺ and SDBS differs from the initial surfactant mixing ratio and changes depending on the initial mixing ratio. Surface tension measurements indicated an important contribution of the formation of a pseudo-double chain-type complex through the electrostatic interaction between FTMA⁺ and SDBS to spontaneous vesicle formation. In addition, the existence of a benzyl group in the anionic surfactant was suggested to be important for the pseudo-double chain-type surfactant to take the orientation favorable to vesicle formation.<br>

DOI： 10.5650/jos.54.125

その他リンク： https://jlc.jst.go.jp/DN/JALC/00245616486?from=CiNii

EXAFS study of electrolytic nanosolution confined in interstitial nanospaces of single-wall carbon nanohorn colloids 査読

T. Ohkubo, Y. Hattori, H. Kanoh, T. Konishi, H. Sakai, M. Abe, D. Kasuya, M. Yudasaka, S. Iijima, T. Fujikawa, K. Kaneko

Physica Scripta T T115 685 - 687 2005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）出版者・発行元：IOP PUBLISHING LTD

The structure of RbBr aqueous solution confined in the interstitial nanospaces of single-wall carbon nanohorn (SWNH) assemblies was elucidated by using extended x-ray absorption fine structure (EXAFS) technique. The decrease of hydration number around a Rb ion is clearly observed. The EXAFS analysis indicates that the highly distorted and dehydrated structure around ions of aqueous solution confined in the nanospace (nanosolution: NSN) to form quasi one-dimensional structure in the interstitial nanospaces of SWNH assemblies. This unique hydration structures formed in nanospaces of SWNH is quite different from that not only of the bulk aqueous solution, but also confined in the slit-shaped nanospaces of activated carbon fiber (ACF). © Physica Scripta 2005.

DOI： 10.1238/Physica.Topical.115a00685

その他リンク： http://orcid.org/0000-0001-5907-3683

機能構築微粒子調製法によるTiB2のナノ微細化査読

大久保貴広, 西山勝廣, 小野哲央, 丹羽進, 河野通, 酒井秀樹, 小石真純, 阿部正彦

粉体および粉末冶金 52 ( 1 ) 3 - 9 2005年

Preparation and Characterization of Nonionic Surfactant Vesicles Using Supercritical Carbon Dioxide 査読

K. Ri, S. Yamaguchi, P. Wongtrakul, S. Hashimoto, K. Otake, T. Ohkubo, H. Sakai, M. Abe

材料技術 23 340 - 347 2005年

Effects of Dialkyldimethylammonium Bromides on the Membrane Properties of Cationic Liposomes 査読

Akiko Inagaki, Koji Tsuchiya, Hideki Sakai, Tomohiro Imura, Takahiro Ohkubo, Nobuyuki Tsubaki, Shoko Yokoyama, Masahiko Abe

Journal of Oleo Science 54 ( 7 ) 383 - 388 2005年

記述言語：英語掲載種別：研究論文（学術雑誌）

Cationic liposomes composed of dipalmitoylphosphatidylcholine (DPPC) and dialkyldimethylammonium bromides (DLAB, DMAB, DPAB or DSAB) were prepared by the Bangham method, and the effect of the alkyl chain length of dialkyldimethylammonium bromide on the membrane properties of the liposomes was examined in terms of the trapping efficiency liposomal shape and phase transition temperature. Furthermore, the effect of stearylamine (SA) on the liposomal membrane properties was also investigated. Large unilamellar vesicles (LUVs) with a diameter of approximately 1.0 ~ 1.5 μm were formed by mixing small amounts of cationic substances, not only dialkyldimethylammonium bromides, but also SA. The trapping efficiency of the mixed liposomes was greater than that of the DPPC liposomes since the DPPC liposomes were multilamellar vesicles. The maximum trapping efficiency of the mixed liposomes was obtained at 0.05 mole fractions of the cationic substances. Furthermore, dialkyldimethylammmonium bromides with longer alkyl chains, DSAB, DPAB and DMAB, formed cationic substance-rich liposomes with DPPC, and they had the second maximum trapping efficiency at 0.75 ~ 0.9 mole fractions of cationic substance. © 2005, Japan Oil Chemists' Society. All rights reserved.

DOI： 10.5650/jos.54.383

その他リンク： http://orcid.org/0000-0001-5907-3683

EXAFS Study of Electrolytic Nanosolution Confined in Interstitial Nanospaces of SingleWall Carbon Nanohorn Colloids 査読

T. Ohkubo, Y. Hattori, H. Kanoh, T. Konishi, H. Sakai, M. Abe, D. Kasuya, M. Yudasaka, S. Iijima, T. Fujikawa, K. Kaneko

Physica Scripta 685 - 685 2005年

Cluster-associated filling of water in hydrophobic carbon micropores 査読

T Kimura, H Kanoh, T Kanda, T Ohkubo, Y Hattori, Y Higaonna, R Denoyel, K Kaneko

JOURNAL OF PHYSICAL CHEMISTRY B 108 ( 37 ) 14043 - 14048 2004年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

The pore-wall chemistry of activated carbon fiber (ACF) was controlled by heating in Ar and H-2. The ACF structures were characterized from various levels, and interaction of water vapor with the micropores of ACF was directly measured by calorimetry. Two kinds of pitch-based ACFs with different pore widths (w) (P5, w = 0.7 nm, and P20, w = 1.0 nm) were used. P20 was treated at 1273 K in a gas flow of Ar or H-2 for 1 h to modify its surface properties. Adsorption isotherms of water on the two ACFs at 303 K showed different features, which are possibly caused by the pore width difference. The surface modification by the heat treatment of P20 changed its pore structure, leading to different water adsorption behavior. The mechanisms of water adsorption and desorption can be discussed through the differential or integral heat of water adsorption or desorption. Water adsorbs on the functional groups located at the surface of P20 with an adsorption heat comparable to the heat of condensation at relatively low P/P-0, causing the cluster formation of water molecules. The removal of such functional groups by heat treatment decreases the adsorption heat at low pressure. The differential heat abruptly increases at filling in all cases, indicating a structural formation of water from a clustered form to a highly ordered form.

DOI： 10.1021/jp048934n

その他リンク： http://orcid.org/0000-0001-5907-3683

Control of particle alignment in water by an alternating electric field 査読

M Abe, A Yamamoto, M Orita, T Ohkubo, H Sakai, N Momozawa

LANGMUIR 20 ( 17 ) 7021 - 7026 2004年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

We attempted to align a large number of silica particles dispersed in aqueous solution by controlling the alternating electric field between the two electrodes (400 mum apart). Relatively large particles (9.9 mum) were found to align forming strings in the direction parallel to the electric field while relatively small particles (2.0 and 4.9 mum) were observed to align making stripes in the direction perpendicular to the field. The number of stripes formed by particles between the electrodes increased with increasing frequency of the alternating field. This peculiar perpendicular particle alignment appeared when the contribution to particle alignment of electroosmotic flow exceeded that of dielectric polarization and the osmotic flow was found to be stronger around the particles than in the vicinity of the electrode surface.

DOI： 10.1021/la0490801

Three-dimensional arrangements of polystyrene latex particles with a hyperbolic quadruple electrode system 査読

M Abe, M Orita, H Yamazaki, S Tsukamoto, Y Teshima, T Sakai, T Ohkubo, N Momozawa, H Sakai

LANGMUIR 20 ( 12 ) 5046 - 5051 2004年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

An attempt was made to arrange polystyrene latex particles (2, 5, and 10,mum in diameter) dispersed in aqueous media making use of their dielectrophoresis and electrophoresis with a hyperbolic quadruple electrode system. Application of a high-frequency ac field enabled the particles to arrange themselves between the electrodes forming a particle monolayer due to the negative dielectrophoretic force. Simultaneous application of high-frequency ac and dc fields caused the particles to gather in the region surrounded by the electrodes to form particle multilayers. Appropriate choice of the way of applying an electric field thus allowed the reversible control of particle arrangements (monolayer, multilayer, dispersion). Reapplication of an ac field to the particle layers produced highly dense particle multilayers.

DOI： 10.1021/la036465v

Solution Properties of Sulfate-Type Fluoro-Hybrid Anionic Surfactants with a Benzene Ring in Their Molecules 査読

Chengxu Sun, Haruhiko Miyazawa, Yukishige Kondo, Norio Yoshino, Koki Abe, Masanobu Sagisaka, Boonyarach Kitiyanan, Takahiro Ohkubo, Hideki Sakai, Masahiko Abe

Journal of Oleo Science 53 ( 8 ) 371 - 376 2004年

記述言語：英語掲載種別：研究論文（学術雑誌）

Two novel sulfate-type fluoro-hybrid anionic surfactants with a bezene ring in their molecules, F8H3OS and F6H5OS, were synthesized and their solution properties were investigated. Both of the hybrid surfactants were found to show an outstanding surface and interfacial tension lowering ability. F8H3OS formed compact micelles with small aggregation numbers and the micelles coagulated with increase in the surfactant concentration, while F6H5OS formed micelles at its low concentration and the micelles were transformed into vesicles at high concentrations of the surfactant. © 2004, Japan Oil Chemists' Society. All rights reserved.

DOI： 10.5650/jos.53.371

その他リンク： http://orcid.org/0000-0001-5907-3683

Control of viscoelasticity using redox reaction 査読

Tsuchiya, K, Orihara, Y, Kondo, Y, Yoshino, N, Ohkubo, T, Sakai, H, Abe, M

Journal of the American Chemical Society 126 ( 39 ) 12282 - 12283 2004年

Synthesis and Photochemical Properties of Cationic Surfactant Having a Spiropyran Group 査読

C. Sun, K. Arimitsu, K. Abe, T. Ohkubo, T. Yamashita, H. Sakai, M. Abe

材料技術 22 ( 6 ) 229 - 237 2004年

Electrically Controlled Two-Dimensional Cluster Formation of Polystyrene Particles and Cluster Fixation with Adsorbed Polyelectrolyte 査読

Hiroyuki Yamazaki, Masanori Orita, Toshio Sakai, Takahiro Ohkubo, Hideki Sakai, Takashi Yamashita, Tohru Kohno, Masahiko Abe

Journal of Oleo Science 53 ( 9 ) 437 - 444 2004年

記述言語：英語掲載種別：研究論文（学術雑誌）

An attempt was made to orderly arrange a large number of polystyrene particles dispersed in aqueous medium on the electrode surface and fix the formed particle arrangement. The measuring cell used consisted of two transparent indium tin electrodes 500 μm apart from each other in the vertical direction. The gap between the electrodes was filled with a dispersion of polystyrene particles (5 μm size) and the behavior of the particles in electric fields applied between the electrodes was on-site observed with an optical microscope. Simultaneous application of DC and AC fields caused polystyrene particles to form single-layered clusters each consisting of several tens particles on the lower electrode. Densely arranged clusters were formed for the particles with polyallylamine hydrochloride (PAH), a cationic polyelectrolyte, adsorbed on their surface upon application of DC and AC fields and the clusters formed remained unbroken after removal of the fields. No cluster formation was observed, however, for the particles after adsorbing the cationic polyelectrolyte and then poly (sodium styrenesulfonate) (PSS), an anionic polyelectrolyte. These findings suggested that particle arrangement and its fixation of polystyrene particles are appreciably affected by polyelectrolyte adsorption. © 2004, Japan Oil Chemists' Society. All rights reserved.

DOI： 10.5650/jos.53.437

その他リンク： http://orcid.org/0000-0001-5907-3683

Ordered Arrangement of Polystyrene Latex Particles Conducted by Electrophoresis and Dielectrophoresis 査読

Hideki Sakai, Masanori Orita, Hiroyuki Yamazaki, Toshio Sakai, Nobuyuki Momozawa, Takahiro Ohkubo, Masahiko Abe

Journal of Oleo Science 53 ( 7 ) 355 - 362 2004年

記述言語：英語掲載種別：研究論文（学術雑誌）

Polystyrene latex particles in 5 μm diameter were arranged one-, two- and three-dimensionally by electrophoresis and dielectrophoresis using the following electrodes, plate-plate electrode, plate-needle electrode and hyperbolic quadruple electrode. Application of an AC field brought about a one dimensional latex particle arrangement, resulting a pearl chain, by dielectrophoretic force on using the plate-plate electrode. Particle arrangement could be tuned by changing AC bias frequecy when using the plate-needle electrode. With the hyperbolic quadruple electrode, particles could be closely packed in a two-dimensional arrangement with application of the AC field. Simultaneous application of high frequency AC and DC fields resulted in arrangement in the region surrounded by the electrodes with consequent particle multilayer formation. Reversible control of particle arrangement (dispersion, monolayer, and multilayer) can thus be carried out through appropriate choice of electrode and mode of electric field application. © 2004, Japan Oil Chemists' Society. All rights reserved.

DOI： 10.5650/jos.53.355

その他リンク： http://orcid.org/0000-0001-5907-3683

Structural anomalies of Rb and Br ionic nanosolutions in hydrophobic slit-shaped solid space as revealed by the EXAFS technique 査読

T Ohkubo, Y Hattori, H Kanoh, T Konishi, T Fujikawa, K Kaneko

JOURNAL OF PHYSICAL CHEMISTRY B 107 ( 49 ) 13616 - 13622 2003年12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）出版者・発行元：AMER CHEMICAL SOC

The hydration structure of RbBr electrolytic solutions confined in slit-shaped nanospaces of carbon was determined with the extended X-ray absorption fine structure (EXAFS) technique and related analysis. The nitrogen adsorption isotherms at 77 K were measured to evaluate the porosity of RbBr-deposited carbon samples. The EXAFS results indicate that the electrolytic solution confined in hydrophobic nanospaces has a restricted hydration structure depending on the average pore width of the nanospaces. Also the asymmetric-field effect of slit-pore geometry on the formation of unique hydration structures of ions in nanospaces was unveiled with the analysis of EXAFS spectra. A marked decrease of the hydration number around a Rb ion was observed in slit-shaped nanospaces, indicating the compressed hydration structure around a Rb ion restricted in slit-shaped nanospaces. The distorted hydration structure around a Br ion in the slit-shaped pore of 0.7 nm was formed to increase the hydration number, though partially dehydrated structure can be formed in a 1.1 nm pore. The cluster-mediated ordered structure of water molecules can play an important role in forming a dehydrated structure around a Br ion confined in the 1.1-nm pore.

DOI： 10.1021/jp0343685

Growth of Highly-Oriented Silica Nanotubes of Mica Substrate 査読

Hideki Sakai, Ryoko Takubo, Takahiro Ohkubo, Aritomo Yamaguchi, Toshiaki Kakihara, Masahiko Abe

Journal of the Japan Society of Colour Material 76 ( 12 ) 476 - 479 2003年

Nanosolution as a new turn of nanoconfinement for fluids 査読

T Ohkubo, H Kanoh, K Kaneko

AUSTRALIAN JOURNAL OF CHEMISTRY 56 ( 10 ) 1013 - 1016 2003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）出版者・発行元：C S I R O PUBLISHING

Towards the goal of nanoscale molecular systems, littlework has been undertaken on ionic solutions at the nanoscale ('nanosolution', NSN). Functional nanoporous materials can be applied to confine, and thereby allow study of molecular assemblies and NSNs; electrically neutral hydrophobic pores reveal a particularly marked confinement effect. This article summarizes the properties and structures of molecules confined within nanospaces and the pioneering work on the distorted and partially dehydrated structures of NSNs.

DOI： 10.1071/CH03109

その他リンク： http://orcid.org/0000-0001-5907-3683

Pore structures of ZSM-5 synthesized in the mesopore spaces of a carbon aerogel 査読

YS Tao, H Tanaka, T Ohkubo, H Kanoh, K Kaneko

ADSORPTION SCIENCE & TECHNOLOGY 21 ( 2 ) 199 - 203 2003年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：MULTI SCIENCE PUBL CO LTD

A mesoporous ZSM-5 monolith several millimetres in size has been synthesized employing the template method and using a carbon aerogel with uniform mesopores. Measurement of the pore-size distribution using nitrogen adsorption showed a bimodal pore system of mesopores and micropores whose average pore widths were 8 nm and 0.51 nm, and whose volumes were 0.09 cm(3)/g and 0.34 cm(3)/g, respectively.

DOI： 10.1260/026361703769013925

Structure of ultra-thin RbBr "solution" in carbon nanospace 査読

T Ohkubo, H Kanoh, Y Hattori, T Konishi, K Kaneko

NANOTECHNOLOGY IN MESOSTRUCTURED MATERIALS 146 61 - 64 2003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）出版者・発行元：ELSEVIER SCIENCE BV

The hydration structure of RbBr electrolytic solution confined in carbon nanospaces was determined with EXAFS technique and related analyses. The analytical results indicate that the electrolytes confined in hydrophobic nanospaces have an incomplete dehydration structure, because of an intensive restriction and cluster formation of adsorbed water molecules in the nanospaces.

DOI： 10.1016/S0167-2991(03)80327-0

その他リンク： http://orcid.org/0000-0001-5907-3683

Restricted hydration structures of Rb and Br ions confined in slit-shaped carbon nanospace 査読

T Ohkubo, T Konishi, Y Hattori, H Kanoh, T Fujikawa, K Kaneko

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 124 ( 40 ) 11860 - 11861 2002年10月

Hydrogen-bond change-associated gas adsorption in inorganic-organic hybrid microporous crystals 査読

S Onishi, T Ohmori, T Ohkubo, H Noguchi, L Di, Y Hanzawa, H Kanoh, K Kaneko

APPLIED SURFACE SCIENCE 196 ( 1-4 ) 81 - 88 2002年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

CO2 is almost vertically adsorbed and desorbed at 0.0106-0.0073 relative pressure at 273 K, respectively, on the preevacuated Cu-complex. crystals which have no open micropores from the crystallographic structures. These vertical adsorption and desorption steps are named gate effects. Here, guest water molecules are evolved during the pre-evacuation at 373 K and the crystal structure with X-ray diffraction examination does not change due to pre-evacuation. The X-ray diffraction patterns also show no change before and after the steps. The adsorption/desorption gate effects and the remarkable hysteresis are explained in terms of the molecular valve model stemming from the reorientation of the bending vibration of the hydrogen bonding. This model can explain the observed hysteresis in the gate effect; the spring constant difference of the molecular valve for desorption and adsorption is estimated to be a similar order to that of the hydrogen bond in bulk ice. (C) 2002 Elsevier Science B.V All rights reserved.

DOI： 10.1016/S0169-4332(02)00048-X

Adsorption properties of templated mesoporous carbon (CMK-1) for nitrogen and supercritical methane - Experiment and GCMC simulation 査読

Takahiro Ohkubo, Jin Miyawaki, Katsumi Kaneko, Ryong Ryoo, Nigel A. Seaton

Journal of Physical Chemistry B 106 ( 25 ) 6523 - 6528 2002年6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）出版者・発行元：AMER CHEMICAL SOC

Nitrogen adsorption isotherms at 77 K and high pressure adsorption of supercritical methane at 303 K were measured on mesoporous carbon (CMK-1) prepared from the templating of MCM-48. These experimental isotherms were simulated with grand canonical Monte Carlo (GCMC) simulation using the rod-aligned slitlike pore (RSP) model. This RSP model gives good agreement with the experimental nitrogen adsorption isotherm in the low-pressure region, while it describes well the observed methane isotherm. The isothermal compressibility of the adsorbed methane at 303 K was calculated from the experimental and simulated isotherms. The isothermal compressibility of the adsorbed methane shows the intermediate state between the supercritical and liquid phase. This indicates that the adsorbed layer of supercritical methane is highly compressed by the strong interaction potential from the pore walls.

DOI： 10.1021/jp0200369

Oriented structures of alcohol hidden in carbon micropores with ERDF analysis 査読

T Ohkubo, K Kaneko

COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS 187 177 - 185 2001年8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）出版者・発行元：ELSEVIER SCIENCE BV

The X-ray diffraction (XRD) of alcohol molecules such as methanol, ethanol, and I-propanol confined in slit-shaped graphitic micropores of activated carbon fibers (ACFs) having different pore widths was measured at 303 K. The effect of the pore width on the molecular assembly structure of alcohol in the micropores was examined. The XRD patterns were analyzed by use of the electron radial distribution function (ERDF) analysis. The adsorbed density of alcohol in micropores of 1.1 nm in width was close to the solid density, while that in micropores of 0.7 nm in width was smaller than the liquid density. The ERDF of alcohol adsorbed in the 0.7 nm micropores showed a highly ordered structure compared with the 1.1 nm micropores, which is completely different from the adsorbed density results. It was presumed that alcohol molecules are hydrogen-bonded to form a layered structure, which is fit for the slit-shaped micropore. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0927-7757(01)00627-6

High-temperature treatment effect of microporous carbon on ordered structure of confined SO2 査読

T Ohkubo, CM Yang, E Raymundo-Pinero, Linares-Solano, K Kaneko

CHEMICAL PHYSICS LETTERS 329 ( 1-2 ) 71 - 75 2000年10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）出版者・発行元：ELSEVIER SCIENCE BV

The X-ray diffraction (XRD) of SO2 molecules adsorbed in micropores of activated carbon fiber (ACF) was measured at 303 K. Effect of pore width and high-temperature treatment (HTT) of ACF on the XRD of SO2 in micropores were examined. The HTT gave rise to a more dipole-oriented structure of SO2 molecules in micropores of 1.1 nm width, whereas the opposite effect was observed in micropores of 0.7 nm. The intensified image potential of an SO2 molecule for the heat-treated graphitic pore wall should stabilize the dipole-oriented structure in the case of 1.1 nm micropores, while the heat-treatment provides defective structures in the narrow micropore system. The presence of O-2 stabilized the dipole-oriented structure of SO2 molecules in the micropore. (C) 2000 Elsevier Science B.V.

DOI： 10.1016/S0009-2614(00)00973-8

In situ X-ray diffraction studies on micropore filling 査読

T. Iiyama, T. Ohkubo, K. Kaneko

Membrane Science and Technology 6 ( C ) 35 - 66 2000年

記述言語：英語掲載種別：研究論文（学術雑誌）

The molecular level picture of micropore filling mechanism in carbon micropores was summarized and the necessity of the structural study on molecules confined in carbon micropores with in situ X-ray diffraction is described. The detailed explanation of in situ X-ray diffraction technique for adsorption studies is given. The effectiveness of the in situ X-ray diffraction for elucidation of structures of molecules filled in micropore is shown for CCl4, water, and alcohol molecules. In situ X-ray diffraction studies shows the presence of organized structure inherent to an adsorbate molecule, although only adsorption measurement cannot distinguish the molecular state different from the bulk liquid. © 2000 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0927-5193(00)80004-2

その他リンク： http://orcid.org/0000-0001-5907-3683

Confined state of alcohol in carbon micropores as revealed by in situ X-ray diffraction 査読

T Ohkubo, T Iiyama, T Suzuki, K Kaneko

CHARACTERIZATION OF POROUS SOLIDS V 128 411 - 419 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）出版者・発行元：ELSEVIER SCIENCE BV

The X-ray diffraction (XRD) of ethanol and methanol molecules confined in carbon micropores was measured at 303 K. The effect of the pore width in the range of 0.7-1.1 nm on the molecular assembly structure of ethanol and methanol in the micropores was examined. The XRD patterns were analyzed by use of the electron radial distribution function (ERDF) analysis. The density of alcohol molecular assemblies in micropores was determined by using ethanol or methanol adsorption at 303 K and nitrogen adsorption at 77 K. The density of alcohol molecular assemblies in pores of 1.1 nm was close to the solid density of alcohol, whereas that in micropores of 0.7 nm was almost equal tr, the bulk liquid density. However the amplitudes of the ERDFs of alcohol in both micropores were much greater than that of bulk liquid, indicating that the serious confinement in micropores gives rise to their solid-like ordering even at 303 K.

その他リンク： http://orcid.org/0000-0001-5907-3683

Cluster mediated filling of water and alcohol on microporous carbon alloys 査読

K Kaneko, CM Yang, T Ohkubo, T Kimura, T Iiyama, H Touhara

ADSORPTION SCIENCE AND TECHNOLOGY 1 - 5 2000年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：WORLD SCIENTIFIC PUBL CO PTE LTD

Adsorption isotherms of water and ethanol on fluorinated, nitrogen-alloyed, and pristine pitch-based activated carbon fiber(ACF)s were measured in order to elucidate water adsorption mechanism in hydrophobic micropores. States of alloyed fluorine and nitrogen atoms were examined by XPS. Fluorine atoms are bound by covalent bonding, while the presence of the pyridinic nitrogen was observed. Fluorination of ACF lowered the adsorptivity for water and ethanol. On the contrary, the nitrogen alloying enhanced the adsorptivity for ethanol. The adsorption states of water and ethanol in micropores of ACF were examined by use of in situ X-ray diffraction. The electron radial distribution function (ERDF)s from X-ray diffraction patterns showed that water and ethanol molecules form highly ordered structures in micropores at the saturated filling. The in situ small angle X-ray scattering (SAXS) of water-adsorbed ACF indicated the presence of different physical processes upon adsorption and desorption, which can be associated with the adsorption hysteresis. These integrated information on water and ethanol adsorption on F or N-alloyed and pristine ACFs were summarized to understand the cluster-mediated filling of water in hydrophobic micropores.

Organized structures of methanol in carbon nanospaces at 303 K studies with in situ X-ray diffraction 査読

T Ohkubo, T Iiyama, K Kaneko

CHEMICAL PHYSICS LETTERS 312 ( 2-4 ) 191 - 195 1999年10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）出版者・発行元：ELSEVIER SCIENCE BV

The X-ray diffraction of methanol molecules confined in carbon micropores having different pore widths (micropore widths, 0.7 and 1.1 nm) was measured at 303 K and the structural results were compared with those of ethanol, The methanol molecules confined in micropores of 0.7 nm have a more solid-like ordered structure than in 1.1 nm. The nearest-neighbor Peak of the electron radial distribution function of confined methanol did not shift from that of bulk methanol, but the amplitude was much greater than that of bulk methanol. These results were different from those of confined ethanol. Methanol molecules confined in carbon micropores have a rigid organized structure even at 303 K. However, no remarkable orientation effect, as in confined ethanol, was observed. (C) 1999 Published by Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0009-2614(99)01001-5

Pore-width-dependent ordering of C2H5OH molecules confined in graphitic slit nanospaces 査読

T Ohkubo, T Iiyama, K Nishikawa, T Suzuki, K Kaneko

JOURNAL OF PHYSICAL CHEMISTRY B 103 ( 11 ) 1859 - 1863 1999年3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）出版者・発行元：AMER CHEMICAL SOC

The X-ray diffraction (XRD) of C2H5OH molecules confined in slit-shaped graphitic micropores of activated carbon fibers having different pore widths was measured at 303 K. The effect of the pore width in the range 0.7-1.1 nm on the molecular assembly structure of C2H5OH in the micropores was examined. The XRD patterns were analyzed by use of the electron radial distribution function (ERDF) analysis. The densities of C2H5OH molecular assemblies in micropores were determined by C2H5OH adsorption at 303 K and N-2 adsorption at 77 K. The density of C2H5OH molecular assemblies in the 0.9 and 1.1 nm pores was close to the solid density of C2H5OH. The ERDFs showed that the first and second nearest-neighbor peaks shift to a shorter distance with a decrease of the pore width while their peak heights increase. These changes of the ERDFs coincided very well with the adsorbed density of C2H5OH, indicating that the serious confinement by the micropores gives rise to the solidlike ordering even at 303 K.

DOI： 10.1021/jp984261v

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