研究者詳細 - 大久保　貴広

論文 - 大久保　貴広

分割表示 128 件中 1 - 20 件目／全件表示 >>

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

Web of Science

researchmap

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)

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

DOI： 10.1039/d0ra08437a

researchmap

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

Web of Science

researchmap

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

Web of Science

researchmap

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

Web of Science

researchmap

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

researchmap

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

researchmap

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

researchmap

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

Web of Science

researchmap

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})

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.

DOI： 10.1039/D0TA09944A

researchmap

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})

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.

DOI： 10.1039/D0QI01112F

researchmap

　前のページ - 次のページ　

<大久保 貴広>

論文 - 大久保 貴広

<大久保　貴広>

論文 - 大久保　貴広