2021/10/21 更新

写真a

ニシナ ユウタ
仁科 勇太
NISHINA Yuta
所属
異分野融合先端研究コア 准教授
職名
准教授
プロフィール

略歴
1984年5月 岡山県生まれ

学歴
2003年4月 岡山大学工学部物質応用化学科 入学
2007年3月 岡山大学大学院自然科学研究科博士前期課程 修了
2010年3月 岡山大学大学院自然科学研究科博士後期課程 修了(工学博士)

職歴
平成20年4月-平成22年3月 日本学術振興会特別研究員(DC2)
平成22年4月-平成26年3月 岡山大学異分野融合先端研究コア 助教(特任)
平成23年1月-平成23年2月 フロリダ州立大学化学科 客員研究員(兼任)
平成23年12月-平成24年1月 南洋理工大学化学生物学科 客員教授(兼任)
平成25年10月-平成29年3月 JSTさきがけ 研究員(兼任)
平成26年4月-平成30年9月 岡山大学異分野融合先端研究コア 准教授
平成29年4月-平成31年3月 大阪大学産業科学研究所 招聘准教授(兼任)
平成30年10月-現在 岡山大学異分野融合先端研究コア 研究教授
平成31年4月-令和2年3月 大阪大学産業科学研究所 招聘教授(兼任)

外部リンク

学位

  • 博士(工学) ( 岡山大学 )

研究キーワード

  • 材料化学

  • 有機化学

  • 触媒

  • カーボン

研究分野

  • ものづくり技術(機械・電気電子・化学工学) / 触媒プロセス、資源化学プロセス

  • ナノテク・材料 / 機能物性化学

  • ライフサイエンス / 生物有機化学

  • ナノテク・材料 / 構造有機化学、物理有機化学

  • ナノテク・材料 / 有機機能材料

経歴

  • 岡山大学 異分野融合先端研究コア   研究教授

    2018年10月 - 現在

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  • 岡山大学 異分野融合先端研究コア 准教授

    2014年3月 - 2018年10月

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  • 岡山大学 異分野融合先端研究コア   助教

    2010年4月 - 2014年3月

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委員歴

  • 高分子学会   「高分子」 編集委員  

    2020年4月 - 現在   

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  • 炭素材料学会   「炭素」 編集委員  

    2020年4月 - 現在   

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論文

  • The carbonization of aromatic molecules with three-dimensional structures affords carbon materials with controlled pore sizes at the Ångstrom-level

    Tomoki Ogoshi, Yuma Sakatsume, Katsuto Onishi, Rui Tang, Kazuma Takahashi, Hirotomo Nishihara, Yuta Nishina, Benoît D.L. Campéon, Takahiro Kakuta, Tada Aki Yamagishi

    Communications Chemistry   4 ( 1 )   2021年12月

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    掲載種別:研究論文(学術雑誌)  

    Carbon materials with controlled pore sizes at the nanometer level have been obtained by template methods, chemical vapor desorption, and extraction of metals from carbides. However, to produce porous carbons with controlled pore sizes at the Ångstrom-level, syntheses that are simple, versatile, and reproducible are desired. Here, we report a synthetic method to prepare porous carbon materials with pore sizes that can be precisely controlled at the Ångstrom-level. Heating first induces thermal polymerization of selected three-dimensional aromatic molecules as the carbon sources, further heating results in extremely high carbonization yields (>86%). The porous carbon obtained from a tetrabiphenylmethane structure has a larger pore size (4.40 Å) than those from a spirobifluorene (4.07 Å) or a tetraphenylmethane precursor (4.05 Å). The porous carbon obtained from tetraphenylmethane is applied as an anode material for sodium-ion battery.

    DOI: 10.1038/s42004-021-00515-0

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  • Tracking the light-driven layer stacking of graphene oxide

    Masaki Hada, Satoshi Ohmura, Yuki Yamamoto, Yoshiya Kishibe, Wataru Yajima, Ryo Shikata, Tomohiro Iguchi, Keishi Akada, Shoji Yoshida, Jun ichi Fujita, Shin ya Koshihara, Yuta Nishina

    Carbon   183   612 - 619   2021年10月

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    掲載種別:研究論文(学術雑誌)  

    Layer stacking of two-dimensional (2D) materials, such as graphene and transition metal dichalcogenides, is critical for controlling their physical and transport properties. By exploiting a specific stacking order, the electronic band structures of such 2D materials can be tuned, from which unusual and exotic properties may emerge. Graphene oxide (GO) undergoes layer stacking along with its photo- and thermal-induced reduction process; however, the underlying mechanism and dynamics during its layer stacking have not been revealed. In this study, we demonstrate time-resolved electron diffraction for monitoring the structural dynamics during the layer stacking of GO induced by ultraviolet photoexcitation. The experimental results accompanied by the density functional theory calculations reveal that AB stacking of graphitic domains of GO layers coincides within ∼40 ps with photoinduced removal of the epoxy-oxygen from the basal plane of GO via the strong interactions between the GO layers.

    DOI: 10.1016/j.carbon.2021.07.058

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  • Disposable electrochemical glucose sensor based on water-soluble quinone-based mediators with flavin adenine dinucleotide-dependent glucose dehydrogenase

    Jannatul Morshed, Ryo Nakagawa, Motaher M. Hossain, Yuta Nishina, Seiya Tsujimura

    Biosensors and Bioelectronics   189   2021年10月

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    掲載種別:研究論文(学術雑誌)  

    Glucose level measurement is essential for the point-of-care diagnosis, primarily for persons with diabetes. A disposable electrochemical glucose sensor is constructed using flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) and redox mediator for electron transfer from the enzyme to the electrode surface. Ideally, a suitable mediator should have high water solubility, high kinetic constant, high stability, and redox potential between −0.2 and 0.1 V vs. Ag|AgCl|sat. KCl. We designed and synthesized two new quinone-based water-soluble mediators: quinoline-5,8-dione (QD) and isoquinoline-5,8-dione (IQD). The formal potentials for both QD and IQD at pH 7.0 were −0.07 V vs. Ag|AgCl|sat. KCl. The logarithms of the electron exchange rate constants (k2/(M−1 s−1)) between QD/IQD and FAD-GDH were 7.7 ± 0.1 and 7.4 ± 0.1 for QD and IQD, respectively, which are the highest value among the water-soluble mediators for FAD-GDH reported to date. Disposable amperometric glucose sensors were fabricated by dropping FAD-GDH and QD or IQD onto a test strip. The sensor achieved a linear response up to glucose concentrations of 55.5 mM. The linear response was obtained even when the mediator loading was low (0.5 nmol/strip); loading was only 0.2 mol% of glucose. The results proved that the response current was primarily controlled by glucose diffusion. In addition, the sensor using QD exhibited high stability over 3 months at room temperature.

    DOI: 10.1016/j.bios.2021.113357

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  • Covalent double functionalization of graphene oxide for proton conductive and redox-active functions

    Rizwan Khan, Keita Miyagawa, Alberto Bianco, Yuta Nishina

    Applied Materials Today   24   2021年9月

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    掲載種別:研究論文(学術雑誌)  

    The covalent double functionalization of graphene oxide (GO) is an effective approach to tune the properties of graphene-like materials. The first step is the ring-opening reaction of epoxides by amines, followed by the second step consisting on the nucleophilic addition reaction of GO hydroxyl groups to an α,β-unsaturated carbonyl compound. The benefit of doubly functionalized GO is to possess different functions, confirmed by measuring proton conductivity and supercapacitor performance. The proton conductivity can be improved by introducing sulfonic acid and redox-active functional groups on GO, while the capacitance for supercapacitor can be increased by introducing two distinct redox-active molecules. The current study evidences that a double functionalization allow to design a multifunctional GO platform as an electrolyte membrane for fuel cells and/or an electrode material for supercapacitors.

    DOI: 10.1016/j.apmt.2021.101120

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  • Simulating the redox potentials of unexplored phenazine derivatives as electron mediators for biofuel cells

    Ryo Nakagawa, Yuta Nishina

    JPhys Energy   3 ( 3 )   2021年7月

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    掲載種別:研究論文(学術雑誌)  

    In this research, we aimed to establish a guideline for designing electron mediators suitable for biofuel cells. A redox potential simulator was fabricated by combining density functional theory calculation and experiment, allowing us to select molecules with appropriate redox potentials efficiently. Previously, mediators have been developed depending on the trials and errors; thus, our strategy will speed up the development of biofuel cells with outstanding performances.

    DOI: 10.1088/2515-7655/abebc8

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  • Constructing monolithic sulfur cathodes with multifunctional N,P dual-doped carbon nanocages to achieve high-areal-capacity lithium-sulfur batteries

    Lingyu Du, Xiongcan Deng, Xueyi Cheng, Liwei Liu, Qiang Wu, Lijun Yang, Xizhang Wang, Yuta Nishina, Zheng Hu

    FlatChem   28   2021年7月

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    掲載種別:研究論文(学術雑誌)  

    Despite the great progress achieved, lithium-sulfur (Li-S) batteries still suffer unsatisfactory performance at high sulfur loading (>5 mg cm−2), which results from the impeded kinetics in charge transfer and polysulfides conversion with increasing electrode thickness. Herein, we have constructed a high-sulfur-loading monolithic cathode by in-situ reducing graphene oxide (GO) in the aqueous solution with dispersed sulfur-filled N,P dual-doped carbon nanocages (NPCNC). The Li-S battery with the areal sulfur loading of 6 mg cm−2 exhibits a high areal capacity of 6.7 mAh cm−2 and a retention of 4.2 mAh cm−2 after 250 cycles. The excellent performance is attributed to the synergism of the facilitated charge transfer and alleviated polysulfide diffusion by the reduced GO-framed 3D network, and the suppressed shuttle and polarization effects by the confinement and electrocatalysis of NPCNC. In addition, the monolithic sulfur electrode is free from binder, conductive agent and current collector, much beneficial to gravimetric performance. This study demonstrates an efficient strategy to increase the areal performance of Li-S batteries.

    DOI: 10.1016/j.flatc.2021.100253

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  • A glutathione responsive nanoplatform made of reduced graphene oxide and MnO<inf>2</inf> nanoparticles for photothermal and chemodynamic combined therapy

    Baojin Ma, Yuta Nishina, Alberto Bianco

    Carbon   178   783 - 791   2021年6月

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    掲載種別:研究論文(学術雑誌)  

    Based on the specific tumor microenvironment, characterized by an overproduction of H2O2 and a high glutathione (GSH) concentration, the cascade reactions of nanomaterials, capable of mediating GSH depletion and reactive oxygen species (ROS) generation, have become a popular strategy to increase cancer therapy efficiency. In this study, we exploited reduced graphene oxide (rGO), one of the most promising graphene-based materials, in combination with manganese dioxide nanoparticles (MnO2 NPs) to design a multifunctional nanoplatform (rGO@MnO2) for efficient photothermal/chemodynamic combined therapies. MnO2 NPs were anchored onto the surface of rGO nanosheets (rGO NSs). MnO2 NPs oxidize intracellular GSH, and the generated Mn2+ ions converted H2O2 into HO[rad] by Fenton reaction. Meanwhile, rGO NSs mediated photothermal therapy (PTT) could further kill cancer cells. High temperature caused by photothermal conversion increased Fenton reaction rate, which enhanced the efficiency of MnO2 NPs mediated chemodynamic therapy (CDT). Importantly, thanks to the enhanced cell uptake of MnO2 NPs favored by the delivery properties of rGO, rGO@MnO2 possessed higher lethality to cancer cells. The decrease in the nanomaterials’ effective dose would further improve biosecurity and reduce cost. Therefore, rGO@MnO2 have great potential in cancer therapy by exploiting the synergistic effect of PTT and photothermal/delivery effect enhanced CDT.

    DOI: 10.1016/j.carbon.2021.03.065

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  • High-sorption terpyridine-graphene oxide hybrid for the efficient removal of heavy metal ions from wastewater

    Dawid Pakulski, Adam Gorczyński, Dawid Marcinkowski, Włodzimierz Czepa, Tomasz Chudziak, Samanta Witomska, Yuta Nishina, Violetta Patroniak, Artur Ciesielski, Paolo Samorì

    Nanoscale   13 ( 23 )   10490 - 10499   2021年6月

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    掲載種別:研究論文(学術雑誌)  

    Pollution of wastewater with heavy metal-ions represents one of the most severe environmental problems associated with societal development. To overcome this issue, the design of new, highly efficient systems capable of removing such toxic species, hence to purify water, is of paramount importance for public health and environmental protection. In this work, novel sorption hybrid materials were developed to enable high-performance adsorption of heavy metal ions. Towards this end, graphene oxide (GO) exhibiting various C/O ratios has been functionalized with ad hoc receptors, i.e. terpyridine ligands. The maximum adsorption capacity of highly oxidized/terpyridine hybrids towards Ni(ii), Zn(ii) and Co(ii) was achieved at pH = 6 and 25 °C reaching values of 462, 421 and 336 mg g-1, respectively, being the highest reported in the literature for pristine GO and GO-based sorbents. Moreover, the uptake experiments showed that heavy metal ion adsorption on GO-Tpy and GOh-Tpy is strongly dependent on pH in the range from 2 to 10, as a result of the modulation of interactions at the supramolecular level. Moreover, the ionic strength was found to be independent of heavy metal ion adsorption on GO-Tpy and GOh-Tpy. Under ambient conditions, adsorption capacity values increase with the degree of oxidation of GO because dipolar oxygen units can both interact with heavy-metal ions via dipole-dipole and/or ionic interactions and enable bonding of more covalently anchored terpyridine units. Both adsorption isotherms and kinetics studies revealed that the uptake of the heavy metal ions occurs at a monolayer coverage, mostly controlled by the strong surface complexation with the oxygen of GO and nitrogen-containing groups of terpyridine. Furthermore, selectivity of the hybrid was confirmed by selective sorption of the above heavy metal ions from mixtures involving alkali (Na(i), K(i)) and alkaline Earth (Mg(ii), Ca(ii)) metal ions due to the chelating properties of the terpyridine subunits, as demonstrated with municipal drinking (tap) water samples. Our findings provide unambiguous evidence for the potential of chemical tailoring of GO-based materials with N-heterocyclic ligands as sorbent materials for highly efficient wastewater purification.

    DOI: 10.1039/d1nr02255e

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  • Fiber-crafted biofuel cell bracelet for wearable electronics

    Sijie Yin, Xiaohan Liu, Tatsuya Kaji, Yuta Nishina, Takeo Miyake

    Biosensors and Bioelectronics   179   2021年5月

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    掲載種別:研究論文(学術雑誌)  

    Wearable devices that generate power using sweat have garnered much attention in the field of skin electronics. These devices require high performance with a small volume and low production rate of sweat by living organisms. Here we demonstrate a high-power biofuel cell bracelet based on the lactate in human sweat. The biofuel cell was developed by using a lactate oxidase/osmium-based mediator/carbon nanotube fiber for lactate oxidation and a bilirubin oxidase/carbon nanotube fiber for oxygen reduction; the fibers were woven into a hydrophilic supportive textile for sweat storage. The storage textile was sandwiched between a hydrophobic textile for sweat absorption from the skin and a hydrophilic textile for water evaporation to improve sweat collection. The performance of the layered cell was 74 μW at 0.39 V in 20 mM artificial sweat lactate, and its performance was maintained at over 80% for 12 h. Furthermore, we demonstrated a series-connection between anode/cathode fibers by tying them up to wrap the bracelet-type biofuel cell on the wrist. The booster six-cell bracelet generated power at 2.0 V that is sufficient for operating digital wrist watches.

    DOI: 10.1016/j.bios.2021.113107

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  • Biodegradation of graphene materials catalyzed by human eosinophil peroxidase

    Rajendra Kurapati, Cristina Martìn, Vincenzo Palermo, Yuta Nishina, Alberto Bianco

    Faraday Discussions   227   189 - 203   2021年4月

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    掲載種別:研究論文(学術雑誌)  

    Understanding the biodegradability of graphene materials by the action of oxidative enzymes secreted by immune cells is essential for developing applicable biomedical products based on these materials. Herein, we demonstrate the biodegradation of graphene oxide (GO) by recombinant eosinophil peroxidase (EPO) enzyme extracted from human eosinophils in the presence of a low concentration of hydrogen peroxide and NaBr. We compared the degradation capability of the enzyme on three different GO samples containing different degrees of oxygen functional groups on their graphenic lattices. EPO succeeded in degrading the three tested GO samples within 90 h treatment. Raman spectroscopy and transmission electron microscopy analyses provided clear-cut evidence for the biodegradation of GO by EPO catalysis. Our results provide more insight into a better understanding of the biodegradation of graphene materials, helping the design of future biomedical products based on these carbon nanomaterials.

    DOI: 10.1039/c9fd00094a

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  • High-density monolithic pellets of double-sided graphene fragments based on zeolite-templated carbon

    Atsushi Gabe, Mohammed Ouzzine, Erin E. Taylor, Nicholas P. Stadie, Naoki Uchiyama, Tomomi Kanai, Yuta Nishina, Hideki Tanaka, Zheng Ze Pan, Takashi Kyotani, Hirotomo Nishihara

    Journal of Materials Chemistry A   9 ( 12 )   7503 - 7507   2021年3月

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    掲載種別:研究論文(学術雑誌)  

    High-density and highly porous graphene-based pellets that exhibit an anomalous gas densification property have been fabricated by using zeolite-templated carbon (ZTC) as the major component and reduced graphene oxide (rGO) as a pure carbon binder. The unique structure of each ZTC particle consists of double-sided graphene fragments connected in a periodic, three-dimensional framework. The graphene-like sheets of rGO strongly connect the ZTC particles upon hot-pressingviathe generation of a large amount of unpaired electron spins, yielding monolithic pellets with exceptional mechanical toughness. The uniaxial pressing applied to the isotropic ordered framework of ZTC during pelletization leads to unique anisotropic structures. The so-obtained pellets represent a high density packing of graphene nanofragments with high volumetric surface area that exhibits high volumetric H2storage at room temperature.

    DOI: 10.1039/d0ta11625d

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  • Enhanced photocatalytic activity and stability of TiO<inf>2</inf>/graphene oxide composites coatings by electrophoresis deposition

    Sujun Guan, Liang Hao, Hiroyuki Yoshida, Takaomi Itoi, Yanling Cheng, Satoshi Seki, Yuta Nishina, Yun Lu

    Materials Letters   286   2021年3月

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    掲載種別:研究論文(学術雑誌)  

    To enhanced photocatalytic activity and stability of titania (TiO ) coatings, graphene oxide (GO) forms on the surface of TiO coatings is fabricated by electrophoretic deposition (EPD). The results show the effect of EPD time on the formed hydroxyl groups from GO is significant, especially the controllable amount of GO by adjusting EPD time. The change in surface morphology of the GO on TiO coatings is obvious, showing an increased amount of GO. Owing to the effect of charge transfer between TiO and GO, the TiO /GO composites coatings exhibit excellent and stable photocatalytic activity. Notably, the cycle result of the sample after ultrasonic cleaning every 10 min reveal that the combination of TiO and GO is satisfactory. 2 2 2 2 2 2

    DOI: 10.1016/j.matlet.2020.129258

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  • Light reflectance and photoelectron yield spectroscopy enable acceptor level measurement in p-type Ba<inf>1-x</inf>TiO<inf>3</inf>semiconductor

    Saya Fujii, Jun Kano, Norihiro Oshime, Tohru Higuchi, Yuta Nishina, Tatsuo Fujii, Naoshi Ikeda, Hiromi Ota

    Journal of Applied Physics   129 ( 8 )   2021年2月

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    掲載種別:研究論文(学術雑誌)  

    We report the band structure of Ba-deficient BaTiO3 as a p-type semiconductor, studied by a combination of light reflectance and photoelectron yield spectroscopy. Two acceptor levels were observed at the tail of a valence band. As the quantity of Ba vacancies increased, the density of state of the two acceptor levels also increased. The levels of the conduction band minimum and the valence band maximum shifted far away from the vacuum level, but the bandgap seems to be independent of Ba deficient concentration. For classical semiconductors such as Si and GaAs, the observation of impurity levels is restricted to low temperatures (∼20 K) owing to their narrow bandgaps. Oxide semiconductors have now been demonstrated with wide bandgaps and acceptor levels, at normal operating temperatures, which could lead to new device designs in the future.

    DOI: 10.1063/5.0033761

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  • Exploring Structures and Dynamics of Molecular Assemblies: Ultrafast Time-Resolved Electron Diffraction Measurements

    Masaki Hada, Yuta Nishina, Takashi Kato

    Accounts of Chemical Research   54 ( 3 )   731 - 743   2021年2月

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    掲載種別:研究論文(学術雑誌)  

    ConspectusMolecular assemblies have been widely applied to functional soft materials in a variety of fields. Liquid crystal is one of the representative molecular soft materials in which weak intermolecular interactions induce its dynamic molecular behavior under external stimuli, such as electric and magnetic fields, photoirradiation, and thermal treatment. It is important to understand molecular behavior and motion in the liquid-crystalline (LC) states at the picosecond level for further functionalization of liquid crystals and molecular assembled materials. For investigation of assembled structures of the materials on the nanometer scale, X-ray diffraction (XRD) measurements have been a powerful tool. Despite the dynamic nature of the assembled materials, however, time resolution of XRD is limited to millisecond due to the response speed of the detector, which hampered real-time observation of the dynamics of the molecular assembly. For further understanding of the dynamic behavior of functional molecules and improvement of performance for their applications, the insights of faster dynamics on the micro-, nano-, pico-, and even femtosecond time scales are required. In this context, the interdisciplinary approaches of the emerging fields of materials chemistry and ultrafast science will open up new aspects of molecular science and technology. These approaches may lead to more effective design of new functional materials, which enables us to control molecular behaviors and motions.The development of ultrashort pulsed X-ray and electron sources has resulted in the visualization of the key structural dynamics on the femto-to picosecond time scale not only in isolated molecules but also in assembled molecules, such as in the LC, crystal, and amorphous phases. We focus on ultrafast phenomena in molecular assemblies induced by photoexcitation. Ultrafast time-resolved electron diffraction measurements are sensitive to the molecular periodicity under photoexcitation, and thus the methodologies directly provide the ultrafast photoinduced molecular dynamic arrangements.In this Account, we describe ultrafast structural dynamics of molecules in the LC phases observed by time-resolved electron diffraction measurements. Photoinduced conformational changes of LC molecules is shown as the example, which is the first observation of LC molecule using time-resolved electron diffraction. It is important to understand the correlation between the conformational or configurational changes induced in a photoirradiated single molecule and the oriented collective motions of molecular assemblies induced by intermolecular interaction. We also show observation of collective motions of azobenzene LC molecules. The collective motions are initiated from photoreaction in a single molecule and are subsequently amplified by the steric interaction with its neighboring molecules.One remaining challenge is to create the platform of materials and sample preparations for time-resolved electron diffraction experiments, which can only be achieved by the interdisciplinary fusion of the fields of materials chemistry and ultrafast science. Time-resolved electron diffraction is a powerful tool for structural investigation of molecular materials with a dynamic nature, whose adaptability goes beyond that of more complex assemblies of carbon nanomaterials. This methodology will extend the possibility to investigate motions of a variety of molecular self-assemblies on a larger scale, for example, to understand responses of biomolecular assemblies and intermolecular chemical reactions.

    DOI: 10.1021/acs.accounts.0c00576

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  • Co and Ni assisted CdS@g-C<inf>3</inf>N<inf>4</inf> nanohybrid: A photocatalytic system for efficient hydrogen evolution reaction

    Jamal Abdul Nasir, Noor Islam, Zia ur Rehman, Ian S. Butler, Akhtar Munir, Yuta Nishina

    Materials Chemistry and Physics   259   2021年2月

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    掲載種別:研究論文(学術雑誌)  

    Although the green production of H through water splitting has prompted the search for solar energy harvesting materials, this still remains an ongoing challenge in the field. We report here a novel and cost-effective photocatalytic system, Co and Ni assisted CdS-NRs/g-C N nanohybrid, with the potential to significantly accelerate the solar-assisted water-splitting reaction. In this system, the co-catalysts (Co and Ni) are selectively incorporated as redox mediators to impart electrons and holes away from CdS-NRs/g-C N . As a result, an excellent H production rate of 11376 μmol g h , turnover number (TON) of 1945 (after 24 h), and external quantum yield (EQY) of 4.4% were obtained at 420 nm and under mild reaction conditions. In addition, when the reaction media was tested in the absence of co-catalysts, a notable decrease in activity was observed indicating the promising role of Ni and Co as cocatalysts. The process of redox shuttle proceeds without adding sacrificial reagents, and relies entirely on the employed cocatalysts to competently separate the oxidation and reduction steps. It is anticipated that this unique cocatalysts-supported nanohybrid can create a synergistic effect between the cocatalysts and the CdS-NRs/g-C N heterojunction, providing more active sites to the catalytic system for the subsequent water splitting redox reaction. The experimental results reveal that the selective and optimum use of dual cocatalysts can be a promising approach to trigger both the production of H and improve the stability of the photocatalytic system for overall water splitting. 2 3 4 3 4 2 3 4 2 −1 −1

    DOI: 10.1016/j.matchemphys.2020.124140

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  • Reaction between Graphene Oxide and Intracellular Glutathione Affects Cell Viability and Proliferation

    Baojin Ma, Shi Guo, Yuta Nishina, Alberto Bianco

    ACS Applied Materials and Interfaces   13 ( 3 )   3528 - 3535   2021年1月

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    掲載種別:研究論文(学術雑誌)  

    Graphene oxide (GO) is currently developed for biomedical applications as a promising nanoplatform for drug delivery, phototherapy, and biosensing. As a consequence, its safety and cytotoxicity issues have attracted extensive attention. It has been demonstrated that GO causes an increase of intracellular oxidative stress, likely leading to its cytotoxicity and inhibition of cell proliferation. Being one of the main reductive intracellular substances, glutathione (GSH) is vital in the regulation of the oxidative stress level to maintain normal cellular functions. In this study, we found that GSH could be oxidized to GSSG by GO, leading to the formation of reduced GO (rGO). GSH depletion affects the intracellular reductive/oxidative balance, provoking the increase of the reactive oxygen species level, sequentially inhibiting cell viability and proliferation. Therefore, the reaction between GO and GSH provides a new perspective to explain the origin of GO cytotoxicity.

    DOI: 10.1021/acsami.0c17523

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  • Pure electric and magnetic fields applied to reduced graphene oxide for defect repair and oxygen removal

    Takeshi Miyata, Syun Gohda, Takashi Fujii, Hironobu Ono, Hibiki Itoh, Yuta Nishina, Keiichiro Kashimura

    Carbon   171   10 - 15   2021年1月

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    掲載種別:研究論文(学術雑誌)  

    The rapid repair of graphene oxide (GO) was demonstrated using a microwave cavity resonator that separates pure electric and magnetic fields from microwaves. Reduced graphene oxide (rGO), a high-quality graphene-like material, was obtained using our method. Raman spectroscopy of rGO after microwave treatment revealed that the D band intensity decreased as the temperature increased, while the G and G′ band intensities increased with increasing temperature. Furthermore, the cavity resonator provided better defect repair and oxygen removal from GO than conventional heating, and the microwave magnetic field yielded better quality rGO than the microwave electric field. Microwave heating removed surface impurities and repaired defects in GO more effectively than conventional heating, while suppressing graphitisation. These findings provide guidelines for the microwave-assisted reduction of GO for the fast and large-scale production of graphene.

    DOI: 10.1016/j.carbon.2020.08.044

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

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

    RSC Advances   11 ( 2 )   838 - 846   2020年12月

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    掲載種別:研究論文(学術雑誌)  

    In this study, porous boron nitride (p-BN) with hexagonal phase boron nitride (h-BN) pore walls was synthesized using high-temperature calcination. Negligible variation in pore-wall structure can be observed in powder X-ray diffraction (XRD) profiles and infrared (IR) spectra. However, a highly stable p-BN with a stable pore structure even at 973 K under the oxidative conditions is obtained when synthesized at higher than 1573 K under nitrogen gas flow. For p-BN, this stability is obtained by generating h-BN microcrystals. Nitrogen adsorption-desorption isotherms at 77 K provide type-IV features and typical adsorption-desorption hysteresis, which suggests micropore and mesopore formation. Moreover, adsorption-desorption isotherms of Ar at 87 K are measured and compared with those of nitrogen. The relative adsorbed amount of nitrogen (i.e., the amount of nitrogen normalized by that of Ar at each relative pressure or adsorption potential value) on p-BN is considerably larger than that on microporous carbon at low-pressure regions, which suggests the existence of strong adsorption sites on the p-BN surface. In fact, the relative number of adsorbed nitrogen molecules to that of Ar on p-BN is, at most, 150%-200% larger than that on microporous carbon for the same adsorption potential state. Furthermore, additional adsorption enhancement to nitrogen between P/P0 = 10-5 and 10-3 can be observed for p-BN treated at 1673 K, which suggests the uniformly adsorbed layer formation of nitrogen molecules in the vicinity of a basal planar surface. Thus, unlike typical nanoporous sp2 carbons, p-BN materials have the potential to enhance adsorption for certain gas species because of their unique surface state.

    DOI: 10.1039/d0ra08437a

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  • Sophisticated rGO synthesis and pre-lithiation unlocking full-cell lithium-ion battery high-rate performances

    Benoît Denis Louis Campéon, Yumi Yoshikawa, Takashi Teranishi, Yuta Nishina

    Electrochimica Acta   363   2020年12月

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    掲載種別:研究論文(学術雑誌)  

    For the application to portable devices and storage of renewable energies, high-performance lithium-ion batteries are in great demand. To this end, the development of high-performance electrode materials has been actively investigated. However, even if new materials exhibit high performance in a simple evaluation, namely half-cell tests, it is often impossible to obtain satisfactory performance with an actual battery (full cell). In this study, the structure of graphene analogs is modified in various ways to change crystallinity, disorder, oxygen content, electrical conductivity, and specific surface area. These graphene analogs are evaluated as negative electrodes for lithium-ion batteries, and we found reduced graphene oxide prepared by combination of chemical reduction and thermal treatment was the optimum. In addition, a full cell is fabricated by combining it with LiCoO modified with BaTiO , which is applicable to high-speed charge–discharge cathode material developed in our previous research. In general, pre-lithiation is performed for the anode when assembling full cells. In this study, we optimized a "direct pre-lithiation" method in which the electrode and lithium foil were in direct contact before assembling a full cell, and created a lithium-ion battery with an output of 293 Wh kg at 8,658 W kg . 2 3 −1 −1

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  • Diazonium Electrografting vs. Physical Adsorption of Azure A at Carbon Nanotubes for Mediated Glucose Oxidation with FAD-GDH

    Andrew J. Gross, Shunya Tanaka, Clara Colomies, Fabien Giroud, Yuta Nishina, Serge Cosnier, Seiya Tsujimura, Michael Holzinger

    ChemElectroChem   7 ( 22 )   4543 - 4549   2020年11月

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    掲載種別:研究論文(学術雑誌)  

    The electrochemical reduction of aryldiazonium salts is a versatile and direct route to obtain robust covalently modified electrodes. We report here a comparative study of Azure A modified carbon nanotube electrodes prepared by diazonium electrografting and by physical adsorption for bioelectrocatalytic glucose oxidation with fungal FAD-glucose dehydrogenase from Aspergillus sp. The electrografted and adsorbed electrodes exhibited different reversible electroactivity consistent with polymer-type and monomer-type phenothiazine surface assemblies, respectively. The electrografted Azure A electrodes exhibited superior mediated bioelectrocatalysis compared to the adsorbed Azure A electrodes. A more than 10-fold higher catalytic current up to 2 mA cm at 0.2 V vs. Ag/AgCl together with a similarly low onset potential of −0.05 V vs. Ag/AgCl was observed at the electrografted electrodes. Faster estimated electron transfer kinetics and a +200 mV potential shift for the polymer-type redox couple vs. the adsorbed monomer-type couple underlines the favourable driving force for mediated electron transfer with the buried FAD active site for the diazonium-derived bioelectrode. −2

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  • Iron nanoparticle templates for constructing 3D graphene framework with enhanced performance in sodium-ion batteries 国際誌

    Benoît D.L. Campéon, Chen Wang, Yuta Nishina

    Nanoscale   12 ( 42 )   21780 - 21787   2020年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    This study examines the synthesis and electrochemical performance of three-dimensional graphene for Li-ion batteries and Na-ion batteries. The in situ formation of iron hydroxide nanoparticles (Fe(OH)x NPs) of various weights on the surface of graphene oxide, followed by thermal treatment at elevated temperature and washing using hydrochloric acid, furnished 3D graphene. The characterization studies confirmed the prevention of graphene layer stacking by over 90% compared with thermal treatment without Fe(OH)x. The electrochemical performance of the 3D graphene was evaluated as a counter electrode for lithium metal and sodium metal in a half-cell configuration. This material showed good performances with a charging capacity of 507 mA h g-1 at 372 mA g-1 in Li-ion batteries and 252 mA h g-1 at 100 mA g-1 in Na-ion batteries, which is 1.4 and 1.9 times higher, respectively, than the graphene prepared without Fe(OH)x templates.

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  • Analyzing dynamic chemical states of palladium supported on graphene oxide by X-ray absorption fine structure under oxidative and reductive environments

    Masahiro Kunisu, Jumpei Yahiro, Naoki Morimoto, Yuta Nishina

    Chemistry Letters   49 ( 11 )   1337 - 1340   2020年11月

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    掲載種別:研究論文(学術雑誌)  

    The chemical state of Pd supported on reduced graphene oxide (rGO) changed dynamically and sensitively between Pd0 and Pd2+ by switching atmosphere between H2 and O2. In contrast, Pd supported on graphene oxide (GO) did not show such dynamic redox properties. The catalytic activity in dehydrogenation and hydrogenation reactions also depended on the oxygen content of GO.

    DOI: 10.1246/CL.200529

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  • A needle-type biofuel cell using enzyme/mediator/carbon nanotube composite fibers for wearable electronics

    Sijie Yin, Xiaohan Liu, Yuka Kobayashi, Yuta Nishina, Ryo Nakagawa, Ryoji Yanai, Kazuhiro Kimura, Takeo Miyake

    Biosensors and Bioelectronics   165   2020年10月

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    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 ADVANCED TECHNOLOGY  

    To realize direct power generation from biofuels in natural organisms, we demonstrate a needle-type biofuel cell (BFC) using enzyme/mediator/carbon nanotube (CNT) composite fibers with the structure Osmium-based polymer/CNT/glucose oxidase/Os-based polymer/CNT. The composite fibers performed a high current density (10 mA/cm ) in 5 mM artificial blood glucose. Owing to their hydrophilicity, they also provided sufficient ionic conductivity between the needle-type anode and the gas-diffusion cathode. When the tip of the anodic needle was inserted into natural specimens of grape, kiwifruit, and apple, the assembled BFC generated powers of 55, 44, and 33 μW from glucose, respectively. In addition, the power generated from the blood glucose in mouse heart was 16.3 μW at 0.29 V. The lifetime of the BFC was improved by coating an anti-fouling polymer 2-methacryloyloxyethyl phosphorylcholine (MPC) on the anodic electrode, and sealing the cathodic hydrogel chamber with medical tape to minimize the water evaporation without compromising the oxygen permeability. 2

    DOI: 10.1016/j.bios.2020.112287

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  • Bottom-up synthesis of nitrogen-doped nanocarbons by a combination of metal catalysis and a solution plasma process

    Yang Zhou, Yuta Nishina

    Nanoscale Advances   2 ( 10 )   4417 - 4420   2020年10月

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    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  

    We aimed to develop the bottom-up synthesis of nanocarbons with specific functions from molecules without any leaving group, halogen atom and boronic acid, by employing a metal catalyst under solution plasma irradiation. Pyridine was used as a source of carbon. In the presence of a Pd catalyst, the plasma treatment enabled the synthesis of N-doped carbons with a pyridinic configuration, which worked as an active catalytic site for the oxygen reduction reaction.

    DOI: 10.1039/d0na00327a

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  • Is carboxylation an efficient method for graphene oxide functionalization?

    Shi Guo, Jésus Raya, Dingkun Ji, Yuta Nishina, Cécilia Ménard-Moyon, Alberto Bianco

    Nanoscale Advances   2 ( 9 )   4085 - 4092   2020年9月

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    掲載種別:研究論文(学術雑誌)  

    Graphene oxide (GO) is one of the most popular materials applied in different research areas thanks to its unique properties. The application of GO requires well-designed protocols to introduce different functionalities on its surface, exploiting the oxygenated groups already present. Due to the complex and unstable chemical environment on the GO surface, it is recommended to perform the functionalization under mild conditions. The carboxylation of GO is a widely used method to introduce additional carboxylic acids, which could be further modified through amidation or esterification reactions. The strategy already reported in the literature requires harsh conditions (excess amount of sodium hydroxide). GO is readily reduced under basic conditions, but the reduction of GO during the carboxylation is barely studied. In this work, we performed the carboxylation using chloroacetic acid with different amounts of sodium hydroxide and characterized the functionalized GO with various techniques. The carboxylated GO was exploited to develop a double functionalization approach combining an epoxide ring opening reaction and an amidation. The results showed that strong basic conditions were necessary to derivatize GO. Nevertheless, these conditions resulted in a partial reduction of GO and some functionalities on GO were removed during the reaction, thus reducing the total efficiency of the functionalization in comparison to an epoxide ring opening reaction, indicating that carboxylation is not an efficient approach for the functionalization of GO. This journal is

    DOI: 10.1039/d0na00561d

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  • Grafting conductive polymers on graphene oxide through cross-linker: A stepwise approach

    Rizwan Khan, Yuta Nishina

    Journal of Materials Chemistry A   8 ( 27 )   13718 - 13724   2020年7月

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    掲載種別:研究論文(学術雑誌)  

    A three-step reaction furnished a composite of graphene and a conductive polymer. In the first step, graphene oxide was modified with a diamine, which acted as a linker for polymer attachment. In the second step, an initiating site was attached to the free amine of the linker. Finally, a polymer was grown from the initiation site, and graphene oxide was reduced during polymer growth. The method does not require any catalyst, acid, or reducing agent, furnishing the graphene-polymer composite in a straightforward procedure. Various instrumental techniques, including step-by-step AFM analysis, were used to characterize the structure of the products in each step and confirm the covalent functionalization among graphene oxide, cross-linker, and polymer. The average surface height was sequentially increased after each step, indicating the success of the sequential reactions. The graphene-polymer composite showed excellent electrochemical performance and stability compared with a composite prepared by physical mixing of graphene and polymer.

    DOI: 10.1039/d0ta05489e

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  • Chemical and electrochemical synthesis of graphene oxide-a generalized view 国際誌

    Yuta Nishina, Siegfried Eigler

    Nanoscale   12 ( 24 )   12731 - 12740   2020年6月

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    記述言語:英語  

    Graphene oxide (GO) is a water soluble carbon material in general, suitable for applications in electronics, the environment, and biomedicine. GO is produced by oxidation of abundantly available graphite, turning black graphite into water-dispersible single layers of functionalized graphene-related materials. Therefore, oxidation gives chemicals access to the complete surface area of GO. These fundamentals have led to a rich chemistry of GO. Here, we review the progress made in controlling the synthesis of GO, introduce the current structural models used to explain the phenomena and present versatile strategies to functionalize the surface of GO. Finally, an outlook is given for future directions.

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  • Carbon-rich materials with three-dimensional ordering at the angstrom level 査読

    Shixin Fa, Masanori Yamamoto, Hirotomo Nishihara, Hirotomo Nishihara, Ryota Sakamoto, Kazuhide Kamiya, Kazuhide Kamiya, Yuta Nishina, Tomoki Ogoshi, Tomoki Ogoshi

    Chemical Science   11 ( 23 )   5866 - 5873   2020年6月

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    出版者・発行元:Royal Society of Chemistry (RSC)  

    Carbon-rich materials, which contain over 90% carbon, have been mainly synthesized by the carbonization of organic compounds. However, in many cases, their original molecular and ordered structures are decomposed by the carbonization process, which results in a failure to retain their original three-dimensional (3D) ordering at the angstrom level. Recently, we successfully produced carbon-rich materials that are able to retain their 3D ordering at the angstrom level even after the calcination of organic porous pillar[6]arene supramolecular assemblies and cyclic porphyrin dimer assemblies. Other new pathways to prepare carbon-rich materials with 3D ordering at the angstrom level are the controlled polymerization of designed monomers and redox reaction of graph. Electrocatalytic application using these materials is described.

    DOI: 10.1039/d0sc02422h

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  • Graphene-based carbocatalysts for carbon-carbon bond formation 国際誌

    Muhammad Sohail Ahmad, Yuta Nishina

    Nanoscale   12 ( 23 )   12210 - 12227   2020年6月

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    記述言語:英語  

    Organic transformations are usually catalyzed by metal-based catalysts. In contrast, metal-free catalysts have attracted considerable attention from the viewpoint of sustainability and safety. Among the studies in metal-free catalysis, graphene-based materials have been introduced in the reactions that are usually catalyzed by transition metal catalysts. This review covers the literature (up to the beginning of April 2020) on the use of graphene and its derivatives as carbocatalysts for C-C bond-forming reactions, which are one of the fundamental reactions in organic syntheses. Besides, mechanistic studies are included for the rational understanding of the catalysis. Graphene has significant potential in the field of metal-free catalysis because of the fine-tunable potential of the structure, high stability and durability, and no metal contamination, making it a next-generation candidate material in catalysis.

    DOI: 10.1039/d0nr02984j

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  • Tailoring the interaction between graphene oxide and antibacterial pyridinium salts by terminal functional groups

    R. Fujii, K. Okubo, S. Takashiba, A. Bianco, Y. Nishina

    Carbon   160   204 - 210   2020年4月

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    掲載種別:研究論文(学術雑誌)  

    Nanocarbons, especially two-dimensional carbons, have received considerable attention due to their unique structure and physical and chemical properties, which make them promising candidate materials for biomedical applications. In this study, we focus on graphene oxide (GO), which has many oxygenated functional groups and high affinity with water and biomaterials, and the synthesis of GO complexes with antibacterial agents, like cetylpyridinium chloride (CPC) and its derivatives. We found that the sustained release of CPCs from GO can be controlled by changing the terminal functional group of CPC. The prepared GO-CPC complexes were subjected to antibacterial tests against S. mutans. CPC with the carboxy group was degraded by the oxidizing property of GO, resulting in the loss of antibacterial properties. On the other hand, the other CPC derivatives were released from GO and showed antibacterial activities. Finally, we propose a new mechanism describing how GO and CPC form a functional complex, and how CPC is released from this complex. These findings will lead to pioneering the carbon-based functional antibacterial agents designed at the molecular level.

    DOI: 10.1016/j.carbon.2019.11.094

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  • A Simple and Robust Functionalization of Graphene for Advanced Energy Devices 国際誌

    Rizwan Khan, Ryo Nakagawa, Benoit Campeon, Yuta Nishina

    ACS Applied Materials and Interfaces   12 ( 11 )   12736 - 12742   2020年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Efficient and selective methods for graphene functionalization are needed because they allow tuning of the graphene surface and electronic properties. To date, graphene has been functionalized using ionic bonds, π-πinteractions, and covalent bonds. Graphene derivatives based on these methods have been used in various applications, but a new functionalization strategy that improves the properties of graphene is still needed. Herein, a new concept for graphene functionalization using halogenated graphene has been developed, in which brominated graphene is successfully functionalized by heteroatom-containing molecules to form onium bonds, such as pyridinium or ammonium. The counterion bromide is replaced with other anions, such as sulfate, by treating with sulfuric acid while retaining the molecules, which demonstrates the durable properties of onium bonding. To emphasize the advantages of this strategy for graphene functionalization, the performance for energy-related applications, such as biofuel cells, supercapacitors, and Li-ion batteries, is evaluated after introducing redox-active moieties onto graphene through onium bonding. This new graphene functionalization concept will provide a new approach to the design of tailor-made materials with targeted functions.

    DOI: 10.1021/acsami.9b21082

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  • Non-destructive, uniform, and scalable electrochemical functionalization and exfoliation of graphite 査読

    Benoît D.L. Campéon, Mitsuo Akada, Muhammed S. Ahmad, Yasushi Nishikawa, Kazuma Gotoh, Yuta Nishina

    Carbon   158   356 - 363   2020年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Exfoliation of graphite through functionalization is a promising technique to produce two-dimensional (2D) nanocarbons on a large scale. Due to the high stability of graphite, a conventional functionalization of graphite has been performed in harsh conditions, such as in concentrated sulfuric acid. Therefore, environmental and safety have been problems for scaling up the operation. In contrast, the electrochemical functionalization of a graphite electrode has recently attracted considerable attention because it does not require oxidants or sulfuric acid. However, 2D carbons produced through the existing electrochemical method are generally lacking in quality, due to the non-uniform destruction of the intermediately functionalized graphite. This paper reports a method for the non-destructive functionalization of graphite using HBF diluted by water or methanol as an electrolyte. It is confirmed that the choice of solvents and electrochemical conditions enabled fine control over the functionalization degree and the type of functional groups on 2D carbons. Compared to chemically generated 2D carbons, the electrochemically generated 2D carbon exhibits similar or better physical and chemical properties when used in lithium-ion battery electrodes and water purification membranes. This electrochemical method is also applicable to a continuous flow system, thus promising the mass production of 2D carbons for future industrialization. 4

    DOI: 10.1016/j.carbon.2019.10.085

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  • Structural optimization of alkylbenzenes as graphene dispersants

    Shimpei Takeda, Yuta Nishina

    Processes   8 ( 2 )   2020年2月

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    掲載種別:研究論文(学術雑誌)  

    Among the several methods of producing graphene, the liquid-phase exfoliation of graphite is attractive because of a simple and easy procedure, being expected for mass production. The dispersibility of graphene can be improved by adding a dispersant molecule that interacts with graphene, but the appropriate molecular design has not been proposed. In this study, we focused on aromatic compounds with alkyl chains as dispersing agents. We synthesized a series of alkyl aromatic compounds and evaluated their performance as a dispersant for graphene. The results suggest that the alkyl chain length and solubility in the solvent play a vital role in graphene dispersion.

    DOI: 10.3390/pr8020238

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  • Functionalized Graphene Oxide Shields Tooth Dentin from Decalcification

    M. Z.I. Nizami, Y. Nishina, T. Yamamoto, Y. Shinoda-Ito, S. Takashiba

    Journal of Dental Research   99 ( 2 )   182 - 188   2020年2月

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    掲載種別:研究論文(学術雑誌)  

    This in vitro study assessed the efficacy of functionalized graphene oxide (f-GO) nanocomposites on the decalcification of dentin, because dental caries of the root surface is becoming one of the new problems in aged society. Hydroxyapatite plates (HAP) and dentin slices were coated with f-GO nanocomposites by comparing them to silver diamine fluoride as a positive control, then treated with decalcification solutions such as ethylenediaminetetraacetic acid and citrate at 37°C for 24 h. Scanning electron microscopy (SEM) revealed significant protection of the surface morphology of HAP and dentin. On the other hand, a cariogenic Streptococcus mutans growth was inhibited by f-GO nanocomposites. In addition, cytotoxicity of them to epithelial cells was much less than that of povidone-iodine, which is commonly used for oral disinfectant. We synthesized 5 different f-GO nanocomposites such as GO–silver (Ag), GO-Ag–calcium fluoride (CaF ), GO-CaF , GO-zinc, and GO–tricalcium phosphate (Ca (PO ) ). They were standardized by evaluating under SEM, transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetry analysis (TGA), and Raman spectra after being synthesized in an aseptic technique. The abilities of GO-Ag, GO-Ag-CaF , and GO-CaF nanocomposites were most preventive for decalcification. In addition, GO-Ag and GO-Ag-CaF almost completely inhibited S. mutans growth. However, they did not exhibit cytotoxicity to epithelial cells except at the highest concentration (0.1 w/v%) of GO-Ag and GO-Ag-CaF . Furthermore, these f-GO nanocomposites exhibited less or no discoloration of dentin, although commonly used silver diamine fluoride causes discoloration of dentin to black. Thus, these f-GO nanocomposites are useful to protect dental caries on the tooth root that becomes a social problem in aged society. 2 2 3 4 2 2 2 2 2

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  • A Flexible Method for Covalent Double Functionalization of Graphene Oxide 国際誌

    Shi Guo, Yuta Nishina, Alberto Bianco, Cécilia Ménard-Moyon

    Angewandte Chemie - International Edition   59 ( 4 )   1542 - 1547   2020年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A method for the double functionalization of graphene oxide (GO) under mild alkaline conditions has been developed. Two functional groups were covalently linked to GO in two steps: the first group was attached by an epoxide ring-opening reaction and the second, bearing an amine function, was covalently conjugated to benzoquinone attached to the GO. The doubly functionalized GO was characterized by several techniques, confirming the sequential covalent modification of the GO surface with two different functional groups. This method is straightforward and the reaction conditions are mild, allowing preservation of the structure and properties of GO. This strategy could be exploited to prepare multifunctional GO conjugates with potential applications in many fields ranging from materials science to biomedicine.

    DOI: 10.1002/anie.201913461

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  • Robust sandwiched fluorinated graphene for highly reliable flexible electronics

    Mamina Sahoo, Jer Chyi Wang, Yuta Nishina, Zhiwei Liu, Jong Shing Bow, Chao Sung Lai

    Applied Surface Science   499   2020年1月

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    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  

    The high sensitivity of graphene to the surface condition of the gate dielectric layer and its poor van der Waals adhesion with a flexible substrate result in interfacial sliding and fracturing of graphene at low strains, making the successful utilization of pristine graphene (PG) in flexible electronics challenging. Here, we report a facile method for the fabrication of flexible graphene field effect transistors (F-GFETs) using sandwiched fluorinated graphene (FG). The “FG-PG-FG” sandwich structure shows a high optical transparency (>94%) with an average carrier mobility above 340 cm /V·s, higher than that obtained when GO and Ion gel were used as gate dielectric materials on F-GFETs and a relatively low gate leakage current of ~160 pA. Furthermore, we observed a high mechanical stability, retaining >88% of the original current output against bending deformation of up to 6 mm and >77% after 200 bending cycles by applying a tensile strain of 1.56%, compared to the control sample. This improved performance is attributed to the fact that the sandwiched FG provides a good dielectric environment by tuning the C/F ratio, which tightly fixes the PG under strain. These findings provide a new route for the future development of graphene-based flexible electronics. 2

    DOI: 10.1016/j.apsusc.2019.143839

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  • Dehydrogenative Coupling of Toluene Promoted by Multi-Walled Carbon Nanotubes

    Soliman I. El-Hout, Yang Zhou, Jun Kano, Yoshiaki Uchida, Yuta Nishina

    Catalysis Letters   150 ( 1 )   256 - 262   2020年1月

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    掲載種別:研究論文(学術雑誌)  

    Abstract: We report here the formation of carbon–carbon bonds via carbon-hydrogen bond activation catalysed by multi-walled carbon nanotubes (mwcnts), the catalytic activity of which is influenced by nanocarbon morphology and structure. Control of nanocarbon defects and edges allows the realisation of a high-performance carbon-based catalyst that can replace its metal-based counterparts. Graphic Abstract: [Figure not available: see fulltext.].

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  • Unveiling the Mechanism of Polymer Grafting on Graphene for Functional Composites: The Behavior of Radicals 国際誌

    Yuki Hori, Koichiro Kubo, Yuta Nishina

    Macromolecular Rapid Communications   42 ( 8 )   e2000577   2020年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Polymer–graphene composites have attracted significant attention; however, their formation mechanisms are a focus of debate. This work tries to clarify how grafting occurs on graphene by electron spin resonance techniques. As a result, two pathways are found. One passes through the radicals formed by cleaving C-O bonds on graphene are transferred to monomers, then grafting and polymerization proceed. Another mechanism passes through the oxy-radicals, which react with monomers in solution and finally react with carbon radicals on graphene. Based on the mechanism, various types of polymer–graphene composites are prepared, and applied to electrical conductive sheets, basic catalysts, and acidic catalysts.

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  • Selective Hydrogenation by Carbocatalyst: The Role of Radicals. 国際誌

    Muhammad Sohail Ahmad, Huixin He, Yuta Nishina

    Organic letters   21 ( 20 )   8164 - 8168   2019年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The selective hydrogenation of the nitro moiety is a difficult task in the presence of other reducible functional groups such as alkenes or alkynes. We show that the carbon-based (metal-free) catalyst can be used to selectively reduce substituted nitro groups using H2 as a reducing agent, providing a great potential to replace noble-metal catalysts and contributing to simple and greener strategies for organic synthesis.

    DOI: 10.1021/acs.orglett.9b02432

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  • High-throughput screening of bioactive compounds via new catalytic reaction in the pooled mixture 査読

    Ayano Satoh, Yuta Nishina

    BIOORGANIC & MEDICINAL CHEMISTRY LETTERS   29 ( 19 )   2019年10月

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    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  

    To increase the chances of finding new candidate molecules with medicinal properties, while expending less resource and effort, the present study used pooled substrates as starting materials. A bisindole compound that showed inhibitory activity was then isolated from the mixture, and the activity was improved by optimizing the substituents on the indole skeleton.

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  • Selective Reduction Mechanism of Graphene Oxide Driven by the Photon Mode versus the Thermal Mode. 査読 国際誌

    Masaki Hada, Kiyoshi Miyata, Satoshi Ohmura, Yusuke Arashida, Kohei Ichiyanagi, Ikufumi Katayama, Takayuki Suzuki, Wang Chen, Shota Mizote, Takayoshi Sawa, Takayoshi Yokoya, Toshio Seki, Jiro Matsuo, Tomoharu Tokunaga, Chihiro Itoh, Kenji Tsuruta, Ryo Fukaya, Shunsuke Nozawa, Shin-Ichi Adachi, Jun Takeda, Ken Onda, Shin-Ya Koshihara, Yasuhiko Hayashi, Yuta Nishina

    ACS nano   13 ( 9 )   10103 - 10112   2019年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A two-dimensional nanocarbon, graphene, has attracted substantial interest due to its excellent properties. The reduction of graphene oxide (GO) has been investigated for the mass production of graphene used in practical applications. Different reduction processes produce different properties in graphene, affecting the performance of the final materials or devices. Therefore, an understanding of the mechanisms of GO reduction is important for controlling the properties of functional two-dimensional systems. Here, we determined the average structure of reduced GO prepared via heating and photoexcitation and clearly distinguished their reduction mechanisms using ultrafast time-resolved electron diffraction, time-resolved infrared vibrational spectroscopy, and time-dependent density functional theory calculations. The oxygen atoms of epoxy groups are selectively removed from the basal plane of GO by photoexcitation (photon mode), in stark contrast to the behavior observed for the thermal reduction of hydroxyl and epoxy groups (thermal mode). The difference originates from the selective excitation of epoxy bonds via an electronic transition due to their antibonding character. This work will enable the preparation of the optimum GO for the intended applications and expands the application scope of two-dimensional systems.

    DOI: 10.1021/acsnano.9b03060

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  • A Biodegradable Multifunctional Graphene Oxide Platform for Targeted Cancer Therapy 査読

    Martin Cristina, Ruiz Amalia, Keshavan Sandeep, Reina Giacomo, Murera Diane, Nishina Yuta, Fadeel Bengt, Bianco Alberto

    ADVANCED FUNCTIONAL MATERIALS   29 ( 39 )   2019年9月

  • Polymer-Brush-Decorated Graphene Oxide: Precision Synthesis and Liquid-Crystal Formation 査読

    Ohno Kohji, Zhao Chenzhou, Nishina Yuta

    LANGMUIR   35 ( 33 )   10900 - 10909   2019年8月

  • Influence of pressure of nitrogen gas on structure and thermoelectric properties of acid-treated PEDOT:PSS films 査読

    May Thu Zar Myint, Hirotaka Inoue, Susumu Ichimura, Takeshi Nishikawa, Yuta Nishina, Aung Ko Ko Kyaw, Yasuhiko Hayashi

    Journal of Materials Science: Materials in Electronics   30 ( 14 )   13534 - 13542   2019年7月

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    掲載種別:研究論文(学術雑誌)  

    © 2019, Springer Science+Business Media, LLC, part of Springer Nature. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most commonly investigated conductive polymer due to its unique thermoelectric properties. Several post treatments using various acids have been reported to improve the thermoelectric properties of PEDOT:PSS. In most articles, however, only the role of acids on the structure and thermoelectric properties of PEDOT:PSS were reported. In this article, we report the major role of the pressure of nitrogen gas (N2) on the structure and thermoelectric properties of PEDOT:PSS after treatment with various acids at optimized temperatures. After treatment with acids followed by N2 gas-passing, electrical conductivity enhances significantly. Therefore, N2 gas-passing after acid treatments results in higher thermoelectric properties than other traditional acid treatment methods. The enhancement in electrical conductivity is attributed to the removal of insulating PSS and the conformational change of the PEDOT chain. Furthermore, the pressure of N2 is responsible for the additional conformation of PEDOT chain, favoring the linear orientation of the PEDOT structure and resulting in an improvement of the electrical conductivity.

    DOI: 10.1007/s10854-019-01721-2

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  • Bipolar anodic electrochemical exfoliation of graphite powders 査読

    Hideki Hashimoto, Yusuke Muramatsu, Yuta Nishina, Hidetaka Asoh

    Electrochemistry Communications   104   2019年7月

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    掲載種別:研究論文(学術雑誌)  

    © 2019 The Authors The electrochemical exfoliation of graphite has attracted considerable attention as a method for large-scale, rapid production of graphene and graphene oxide (GO). As exfoliation typically requires direct electrical contact, and is limited by the shape and/or size of the starting graphite, treatment of small graphite particles and powders, the typical form available commercially, is extremely difficult. In this study, GO nanosheets were successfully prepared from small graphite particles and powders by a bipolar electrochemical process. Graphite samples were placed between two platinum feeder electrodes, and a constant current was applied between the feeder electrodes using dilute sulfuric acid as the electrolyte. Optical microscopy, atomic force microscopy, X-ray diffractometry, Raman spectroscopy, and X-ray photoelectron spectroscopy were employed to examine the samples obtained after electrolysis. The results obtained from these analyses confirmed that anodic electrochemical exfoliation occurs in the graphite samples, and the exfoliated samples are basically highly crystalline GO nanosheets with a low degree of oxidation (C/O = 3.6–5.3). This simple electrochemical method is extremely useful for preparing large amounts of graphene and GO from small particles of graphite.

    DOI: 10.1016/j.elecom.2019.06.001

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  • Force-driven reversible liquid-gas phase transition mediated by elastic nanosponges 査読

    Nomura, Keita, Nishihara, Hirotomo, Yamamoto, Masanori, Gabe, Atsushi, Ito, Masashi, Uchimura, Masanobu, Nishina, Yuta, Tanaka, Hideki, Miyahara, Minoru T., Kyotani, Takashi

    NATURE COMMUNICATIONS   10   2019年6月

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

    Nano-confined spaces in nanoporous materials enable anomalous physicochemical phenomena. While most nanoporous materials including metal-organic frameworks are mechanically hard, graphene-based nanoporous materials possess significant elasticity and behave as nanosponges that enable the force-driven liquid-gas phase transition of guest molecules. In this work, we demonstrate force-driven liquid-gas phase transition mediated by nanosponges, which may be suitable in high-efficiency heat management. Compression and free-expansion of the nanosponge afford cooling upon evaporation and heating upon condensation, respectively, which are opposite to the force-driven solid-solid phase transition in shape-memory metals. The present mechanism can be applied to green refrigerants such as H2O and alcohols, and the available latent heat is at least as high as 192 kJ kg(-1). Cooling systems using such nanosponges can potentially achieve high coefficients of performance by decreasing the Young's modulus of the nanosponge.

    DOI: 10.1038/s41467-019-10511-7

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  • "Ultramixing": A Simple and Effective Method To Obtain Controlled and Stable Dispersions of Graphene Oxide in Cell Culture Media 査読

    Giacomo Reina, Amalia Ruiz, Diane Murera, Yuta Nishina, Alberto Bianco

    ACS APPLIED MATERIALS & INTERFACES   11 ( 8 )   7695 - 7702   2019年2月

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    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 last decade has seen an increase in the application of graphene oxide (GO) in the biomedical field. GO has been successfully exploited for its ability to deliver many kinds of drugs into target cells. However, GO toxicity assessment is still controversial. Several studies have demonstrated that GO protein coating is crucial to alleviate the material's toxicity. Besides, coronation leads to the formation of big agglomerates, reducing the cellular uptake of the material and thus its therapeutic efficiency. In this work, we propose a simple and efficient method based on rapid (ultra-turrax, UT) mixing to control protein corona formation. Using the UT protocol, we were able to reduce GO agglomeration in the presence of proteins and obtain stable GO dispersions in cell culture media. By labelling GO with luminescent nanoparticles (quantum dots), we studied the GO internalization kinetic and efficiency. Comparing the "classic" and UT protocols, we found that the latter allows faster and more efficient internalization both in macrophages and HeLa cells without affecting cell viability. We believe that the use of UT protocol will be interesting and suitable for the preparation of next-generation GO-based drug-delivery platforms.

    DOI: 10.1021/acsami.8b18304

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  • Electrical conductivity and optical bandgap of carbonized cellulose nanofiber papers

    D. Fukushima, K. Nagashima, T. Takahashi, T. Yanagida, Y. Nishina, K. Uetani, M. Nogi, H. Koga

    2019年1月

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  • Tribological properties of oxidized wood-derived nanocarbons with same surface chemical composition as graphene oxide for additives in water-based lubricants 査読

    Kinoshita Hiroshi, Suzuki Kyoko, Suzuki Tsutomu, Nishina Yuta

    DIAMOND AND RELATED MATERIALS   90   101 - 108   2018年11月

  • Specific growth inhibitors of Ralstonia solanacearum, Xanthomonas oryzae pv. oryzae, X. campestris pv. campestris, and Clavibacter michiganensis subsp. michiganensis 査読

    Geofrey Sing'ombe Ombiro, Taku Sawai, Yoshiteru Noutoshi, Yuta Nishina, Hidenori Matsui, Mikihiro Yamamoto, Kazuhiro Toyoda, Yuki Ichinose

    Microbiological Research   215   29 - 35   2018年10月

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    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 GmbH  

    Plant pathogenic bacteria cause huge yield losses in crops globally. Therefore, finding effective bactericides to these pathogens is an immediate challenge. In this study, we sought compounds that specifically inhibit the growth of Ralstonia solanacearum. As a result, we identified one promising compound, 1-(4-bromophenyl)-6-methoxy-2,3,4,9-tetrahydro-1H-β-carboline, which inhibited the growth of R. solanacearum (Rs1002) from a pilot library of 376 chemicals provided from RIKEN. We further obtained its structural analogues and assessed their ability to inhibit Rs1002 growth. Then we identified five compounds, named ralhibitins A to E, that specifically inhibit growth of Rs1002 at &gt
    5 μg/ml final concentration. The most effective compounds, ralhibitins A, C, and E completely inhibited the growth of Rs1002 at 1.25 μg/ml. In addition, ralhibitins A to E inhibited growth of Xanthomonas oryzae pv. oryzae but not the other bacteria tested at a final concentration of 10 μg/ml. Whereas, ralhibitin E, besides inhibiting R. solanacearum and X. oryzae pv. oryzae, completely inhibited the growth of X. campestris pv. campestris and the Gram-positive bacterium Clavibacter michiganensis subsp. michiganensis at 10 μg/ml. Growth inhibition by these compounds was stable at pH 6–9 and after autoclaving. Because Rs1002 grew in the culture medium in which ralhibitins were incubated with the ralhibitin-insensitive bacteria, the unaffected bacteria may be able to inactivate the inhibitory effect of ralhibitins. These results suggest that ralhibitins might be potential lead compounds for the specific control of phytopathogenic bacteria.

    DOI: 10.1016/j.micres.2018.06.005

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  • Investigation of active sites for C-H functionalization on carbon-based catalyst: Effect of nitrogen-containing functional groups and radicals 査読

    Ahmad Muhammad Sohail, Suzuki Hideyuki, Wang Chen, Zhao Min, Nishina Yuta

    JOURNAL OF CATALYSIS   365   344 - 350   2018年9月

  • 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

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    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

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  • Graphene oxide size and oxidation degree govern its supramolecular interactions with siRNA 査読

    Giacomo Reina, Ngoc Do Quyen Chau, Yuta Nishina, Alberto Bianco

    NANOSCALE   10 ( 13 )   5965 - 5974   2018年4月

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    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  

    Several studies have demonstrated the ability of graphene oxide (GO) to efficiently adsorb small-interfering RNA (siRNA) on its surface and to transport it into cells. However, studies on whether and how siRNA interacts with GO are still inconclusive. In this context, understanding the interaction between GO and siRNA is fundamental to design new efficient gene silencing tools. In this work, the interactions between GO and siRNA molecules were systematically investigated. We focused on how the GO size, oxygenated groups present on the surface and chemical functionalization affect the double helix siRNA structure, using gel electrophoresis, UV-Vis spectroscopy, fluorescence resonance energy transfer (FRET) and circular dichroism (CD). We found that the siRNA secondary structure was clearly altered by the interaction with GO flakes. In addition, we were able to correlate the double strand damage with the size and the oxygenated groups present on the GO sheets. Finally, we demonstrated that GO functionalized with low molecular weight polyethyleneimine (PEI, 800 Da) is able to protect siRNA from structural modifications. We believed that this research effort will improve our understanding of the behavior of GO/siRNA complexes, and thus facilitate the design of appropriate bio/nanointerfaces and new efficient gene silencing systems.

    DOI: 10.1039/c8nr00333e

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  • Metaheuristic Ab Initio Optimum Search for Doping Effects in Nanocarbons 査読

    Tsuruta Kenji, Mitani Keiichi, Al Asad, Md. Abdullah, Nishina Yuta, Gotoh Kazuma, Ishikawa Atsushi

    THERMEC 2018: 10TH INTERNATIONAL CONFERENCE ON PROCESSING AND MANUFACTURING OF ADVANCED MATERIALS   941   2356 - 2359   2018年

  • Simultaneous improvement in electrical conductivity and Seebeck coefficient of PEDOT:PSS by N-2 pressure-induced nitric acid treatment 査読

    May Thu Zar Myint, Masaki Hada, Hirotaka Inoue, Tatsuki Marui, Takeshi Nishikawa, Yuta Nishina, Susumu Ichimura, Masayoshi Umeno, Aung Ko Ko Kyaw, Yasuhiko Hayashi

    RSC ADVANCES   8 ( 64 )   36563 - 36570   2018年

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    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  

    As a thermoelectric (TE) material suited to applications for recycling waste-heat into electricity through the Seebeck effect, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonic acid) (PEDOT:PSS) is of great interest. Our research demonstrates a comprehensive study of different post-treatment methods with nitric acid (HNO3) to enhance the thermoelectric properties of PEDOT:PSS. The optimum conditions are obtained when PEDOT:PSS is treated with HNO3 for 10 min at room temperature followed by passing nitrogen gas (N-2) with a pressure of 0.2 MPa. Upon this treatment, PEDOT:PSS changes from semiconductor-like behaviour to metal-like behaviour, with a simultaneous enhancement in the electrical conductivity and Seebeck coefficient at elevated temperature, resulting in an increase in the thermoelectric power factor from 0.0818 to 94.3 W m(-1) K-2 at 150 degrees C. The improvement in the TE properties is ascribed to the combined effects of phase segregation and conformational change of the PEDOT due to the weakened coulombic attraction between PEDOT and PSS chains by nitric acid as well as the pressure of the N-2 gas as a mechanical means.

    DOI: 10.1039/c8ra06094k

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  • Elucidation of siRNA complexation efficiency by graphene oxide and reduced graphene oxide 査読

    Ngoc Do Quyen Chau, Giacomo Reina, Jesus Raya, Isabella Anna Vacchi, Cecilia Menard-Moyon, Yuta Nishina, Alberto Bianco

    CARBON   122   643 - 652   2017年10月

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    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  

    Gene therapy has attracted tremendous attention as a promising method for the treatment of many diseases. Graphene oxide (GO), the oxidized form of graphene, is showing lot of potential in this field. Indeed, the polar GO oxygenated functional groups make this material highly hydrophilic, leading to a good dispersibility in water. Until now, the interaction of small interference RNA (siRNA) with graphene materials has not been elucidated. The main goal of this work was to develop a novel platform to complex siRNA molecules and to rationalize the supramolecular interactions between GO surface and the double strand RNA. Our study focused first on green and facile methods such as hydrothermal or vitamin C treatments to prepare graphene oxides at various percentage of oxygen. Epoxidation was also explored to reintroduce epoxide groups on reduced GO for further functionalization. Subsequently, we performed the covalent functionalization of GO with triethyleneglycoldiamine (TEG) and with low molecular weight polyethyleneimine (PEI) via the epoxy ring opening reaction. Finally, by gel electrophoresis, we were able to correlate the GO complexation ability with the graphene surface chemistry. In addition, ozonated GO functionalized with PEI showed a high complexing capacity for siRNA, proving to be a promising candidate for gene silencing. (C) 2017 The Authors. Published by Elsevier Ltd.

    DOI: 10.1016/j.carbon.2017.07.016

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  • Effects of preparation method on the properties of cobalt supported beta-zeolite catalysts for Fischer-Tropsch synthesis 査読

    Manami Nakanishi, Md. Azhar Uddin, Yoshiei Kato, Yuta Nishina, Abdul Muaz Hapipi

    CATALYSIS TODAY   291   124 - 132   2017年8月

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    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 effect of preparation method on the properties of Co supported beta-zeolite catalysts was examined in this study. Co-supported beta-zeolite catalysts (20wt.% Co as Ca3O4) were prepared by impregnation (IMP20), incipient wetness (IW20), physical mixing (PHY20) and precipitation (PCT20) methods and were characterized by various methods including N-2 adsorption (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H-2 thermal programmed reduction (H-2-TPR), and transmission electron microscopy (TEM). Fischer-Tropsch (FT) synthesis was carried out over these catalysts at 230 degrees C and 1 MPa in a fixed-bed flow-type reactor. XPS and H-2-TPR analyses suggest that the catalysts can be ranked in terms of metal-support interactions: PCT20&gt;IMP20 congruent to IW20&gt;PHY20. On the other hand, based on reducibility, the catalysts were ordered as follows: PHY20&gt;IMP20 congruent to IW20&gt;PCT20. The catalytic activity and product selectivity during FT synthesis were also found to depend on the catalyst preparation method. The catalyst prepared by the incipient wetness method exhibited the highest CO conversion with high liquid production, whereas the physically mixed catalyst showed the lowest CO conversion. All the catalysts produced gasoline-range liquid hydrocarbons (C-5 -C-11) mainly and the selectivity towards i-paraffins was more than 60% in the case of the catalyst prepared by precipitation. Furthermore, the composition of liquid products produced over catalysts prepared by the impregnation and incipient wetness methods were similar to each other. Thus, the results of the study clearly show that the physico-chemical properties of the catalysts as well as catalytic activities and product selectivity during the FT reaction strongly depend on the catalyst preparation method. (C) 2017 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.cattod.2017.01.017

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  • Carbocatalytic reductive coupling reactions via electron transfer from graphene to aryldiazonium salt 査読

    Naoki Morimoto, Kumika Morioku, Hideyuki Suzuki, Yumi Nakai, Yuta Nishina

    CHEMICAL COMMUNICATIONS   53 ( 53 )   7226 - 7229   2017年7月

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    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 reductive coupling reaction using two-dimensional nanocarbon, i.e., reduced graphene oxide (rGO), as a carbocatalyst and/or a reaction initiator was developed. The radical species on the rGO played an important role in the coupling reaction.

    DOI: 10.1039/c7cc02337e

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  • Renewable Wood Pulp Paper Reactor with Hierarchical Micro/Nanopores for Continuous-Flow Nanocatalysis 査読

    Hirotaka Koga, Naoko Namba, Tsukasa Takahashi, Masaya Nogi, Yuta Nishina

    CHEMSUSCHEM   10 ( 12 )   2560 - 2565   2017年6月

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    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  

    Continuous-flow nanocatalysis based on metal nanoparticle catalyst-anchored flow reactors has recently provided an excellent platform for effective chemical manufacturing. However, there has been limited progress in porous structure design and recycling systems for metal nanoparticle-anchored flow reactors to create more efficient and sustainable catalytic processes. In this study, traditional paper is used for a highly efficient, recyclable, and even renewable flow reactor by tailoring the ultrastructures of wood pulp. The "paper reactor" offers hierarchically interconnected micro-and nanoscale pores, which can act as convective-flow and rapid-diffusion channels, respectively, for efficient access of reactants to metal nanoparticle catalysts. In continuous-flow, aqueous, room-temperature catalytic reduction of 4-nitrophenol to 4-aminophenol, a gold nanoparticle (AuNP)-anchored paper reactor with hierarchical micro/nanopores provided higher reaction efficiency than state-of-the-art AuNP-anchored flow reactors. Inspired by traditional paper materials, successful recycling and renewal of AuNP-anchored paper reactors were also demonstrated while high reaction efficiency was maintained.

    DOI: 10.1002/cssc.201700576

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  • Surfactant modified graphene oxide laminates for filtration 査読

    B. Lian, J. Deng, G. Leslie, H. Bustamante, V. Sahajwalla, Y. Nishina, R. K. Joshi

    Carbon   116   240 - 245   2017年5月

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    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  

    We have used a cationic surfactant cetyltrimethylammonium bromide (C16TAB) to increase the interlayer spacing between laminates in graphene oxide (GO) membranes for higher water flux. The addition of C16TAB to the GO membrane increased the permeability without compromising the ability to completely reject sucrose molecules. Species larger than sucrose can still permeate through modified GO membranes nearly with same rate as in the case of pure GO membranes. We speculate that interaction of C16TAB surfactant with sucrose molecules could be responsible for the selective rejection of sucrose. The selective rejection of sucrose, which is a common draw in forward osmosis (FO) process, suggests that surfactant modified GO membranes have the potential to improve the efficiency of the FO process.

    DOI: 10.1016/j.carbon.2017.01.102

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  • SWCNT Photocatalyst for Hydrogen Production from Water upon Photoexcitation of (8,3) SWCNT at 680-nm Light 査読

    Noritake Murakami, Yuto Tango, Hideaki Miyake, Tomoyuki Tajima, Yuta Nishina, Wataru Kurashige, Yuichi Negishi, Yutaka Takaguchi

    SCIENTIFIC REPORTS   7   2017年3月

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

    Single-walled carbon nanotubes (SWCNTs) are potentially strong optical absorbers with tunable absorption bands depending on their chiral indices (n, m). Their application for solar energy conversion is difficult because of the large binding energy (&gt; 100 meV) of electron-hole pairs, known as excitons, produced by optical absorption. Recent development of photovoltaic devices based on SWCNTs as light-absorbing components have shown that the creation of heterojunctions by pairing chirality-controlled SWCNTs with C-60 is the key for high power conversion efficiency. In contrast to thin film devices, photocatalytic reactions in a dispersion/solution system triggered by the photoexcitation of SWCNTs have never been reported due to the difficulty of the construction of a well-ordered surface on SWCNTs. Here, we show a clear-cut example of a SWCNT photocatalyst producing H-2 from water. Self-organization of a fullerodendron on the SWCNT core affords water-dispersible coaxial nanowires possessing SWCNT/C-60 heterojunctions, of which a dendron shell can act as support of a co-catalyst for H-2 evolution. Because the band offset between the LUMO levels of (8, 3) SWCNT and C-60 satisfactorily exceeds the exciton binding energy to allow efficient exciton dissociation, the (8, 3) SWCNT/fullerodendron coaxial photocatalyst shows H-2-evolving activity (QY = 0.015) upon 680-nm illumination, which is E-22 absorption of (8, 3) SWCNT.

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  • Real-Time, in Situ Monitoring of the Oxidation of Graphite: Lessons Learned 査読

    Naoki Morimoto, Hideyuki Suzuki, Yasuo Takeuchi, Shogo Kawaguchi, Masahiro Kunisu, Christopher W. Bielawski, Yuta Nishina

    CHEMISTRY OF MATERIALS   29 ( 5 )   2150 - 2156   2017年3月

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    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  

    Graphite oxide (GO) and its constituent layers (i.e., graphene oxide) display a broad range of functional groups and, as such, have attracted significant attention for use in numerous applications. GO is commonly prepared using the "Hummers method" or a variant thereof in which graphite is treated with KMnO4 and various additives in H2SO4. Despite its omnipresence, the underlying chemistry of such oxidation reactions is not well understood and typically affords results that are irreproducible and, in some cases, unsafe. To overcome these limitations, the oxidation of graphite under Hummers-type conditions was monitored over time using in situ X-ray diffraction and in situ X-ray absorption near edge structure analyses with synchrotron radiation. In conjunction with other atomic absorption spectroscopy, UV vis spectroscopy and elemental analysis measurements, the underlying mechanism of the oxidation reaction was elucidated, and the reaction conditions were optimized. Ultimately, the methodology for reproducibly preparing GO on large scales using only graphite, H2SO4 and KMnO4 was developed and successfully adapted for use in continuous flow systems.

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  • Nucleophilic fluoroalkylation/cyclization route to fluorinated phthalides 査読

    Masanori Inaba, Tatsuya Sakai, Shun Shinada, Tsuyuka Sugiishi, Yuta Nishina, Norio Shibata, Hideki Amii

    Beilstein Journal of Organic Chemistry   14   182 - 186   2017年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Beilstein-Institut Zur Forderung der Chemischen Wissenschaften  

    Discribed in this article is a versatile and practical method for the synthesis of C3-perfluoroalkyl-substituted phthalides in a one-pot manner. Upon treatment of KF or triethylamine, 2-cyanobenzaldehyde reacted with (perfluoroalkyl)trimethylsilanes via nucleophilic addition and subsequent intramolecular cyclization to give perfluoroalkylphthalides in good yields.

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  • Preparation of Manganese/Graphite Oxide Composite Using Permanganate and Graphite: Application as Catalyst in Bromination of Hydrocarbons 査読

    Hideyuki Suzuki, Yuta Nishina

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   90 ( 1 )   74 - 78   2017年1月

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    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  

    A highly efficient one-pot preparation of manganese/graphite oxide (MnOX/GO) composite from graphite and KMnO4 is described. Hummers preparation method of GO requires a stoichiometric amount of KMnO4, as a result, the method produces a large amount of reduced Mn species. The Mn residue generally is a waste, therefore, we envisioned converting it to value-added materials. A MnOX/GO composite was prepared in one-pot by treating the unpurified GO with aqueous KOH. The composite was characterized by XRD, XAFS, SEM and TEM. Among various applications of the MnO(X/)GO composite, we applied it as a recyclable catalyst for bromination of saturated hydrocarbons, one of the most basic but important chemical transformations. The MnOX/GO composite is expected to be an efficient catalyst because of the high surface area and high accessibility of substrates derived from the 2-dimensional sheet structure. When the reaction of a saturated hydrocarbon and Br-2 in the presence of catalytic MnOX/GO was performed under fluorescent light irradiation, a brominated product was formed in high yield in a short reaction time. GO could strongly bind with Mn to prevent elution to the liquid phase, enabling the high recyclability.

    DOI: 10.1246/bcsj.20160346

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  • Chemical surface modification of graphene oxide by femtosecond laser pulse irradiation in aqueous suspensions 査読

    Muttaqin, Takahiro Nakamura, Yuta Nishina, Shunichi Sato

    JOURNAL OF MATERIALS SCIENCE   52 ( 2 )   749 - 759   2017年1月

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    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  

    Reduction of graphene oxide (GO) by femtosecond laser pulse irradiation of an aqueous suspension was studied. Different laser parameters such as laser fluence and irradiation time were scanned to obtain the optimum reduced graphene oxide (rGO) with fewer defect sites and lower electrical resistivity. The fabricated rGO samples were characterized using several techniques such as X-ray diffraction, UV-Visible absorption spectrometry, Raman spectroscopy, X-ray photoelectron spectroscopy, and others. The XRD profiles of rGO revealed that the interplanar spacing between carbon layers significantly decreased to 3.51 , which is close to that of pristine graphite. Furthermore, the intensity ratio of D and G bands of rGO measured by Raman spectroscopy was more than 20 % smaller than that of GO, indicating the enhancement of sp(2) domains. It is noted that the defect sites and the disorder carbon double bond networks on the basal graphene plane were relatively decreased after reduction. In addition, the electrical resistivity of rGO significantly decreased to 3.3 Omega center dot cm under the optimum condition. From these results, femtosecond laser can be used as a suitable tool for GO reduction because it is a simple, controllable, and flexible method for getting highly reduced graphene oxide.

    DOI: 10.1007/s10853-016-0368-8

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  • Use of aqueous extract of Pseuderanthemum acuminatissimum Radlk leaves to mediate the synthesis of gold nanoparticles and their anti eschericia coli activity 査読

    S. Salprima Yudha, Totok Eka Suharto, Eka Angasa, Yuta Nishina, Zulfikri Achid Mardlia, Sipriyadi

    Oriental Journal of Chemistry   32 ( 2 )   745 - 751   2017年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Oriental Scientific Publishing Company  

    This research provides a new route to obtain gold nanoparticles (AuNPs) using an aqueous extract of air-dried Pseuderanthemum acuminatissimum Radlk leaves. The extract was used as a reducing agent in the formation of metallic gold from gold ions, and acted as a stabilizer of the obtained AuNPs in the reaction mixture. The formation of AuNPs in aqueous extract of P. acuminatissimum Radlk leaves was validated by change in color and the appearance of surface plasmone resonance (SPR) peak at 552 nm. The average size of the gold nanoparticles was 63 nm, and irregular shapes were observed in the reaction mixture. Fourier transform infrared spectroscopy (FT-IR) reveals the presence of organic compound containing hydroxyl functional groups in the air-dried P. acuminatissimum Radlk leaves, which predicted to be the most responsible for the reduction of gold ions to form metallic gold. The antibacterial properties of the gold nanoparticles were studied using Escherichia coli (ATCC 8739 TM∗) strain
    the AuNPs significantly inhibited the growth of E. coli indicated by a slight increase in the size of the inhibition zone as the volume of added nanocolloid was increased. Therefore, the present study indicated the promising of green synthesis of AuNPs using biological agents and as a potential material to inhibit the bacterial growth.

    DOI: 10.13005/ojc/330221

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  • Tuning the redox potential of Vitamin K3 derivatives by oxidative functionalization using a Ag(i)/GO catalyst 査読

    S. I. El-Hout, H. Suzuki, S. M. El-Sheikh, H. M.A. Hassan, F. A. Harraz, I. A. Ibrahim, E. A. El-Sharkawy, S. Tsujimura, M. Holzinger, Y. Nishina

    Chemical Communications   53 ( 63 )   8890 - 8893   2017年

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    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  

    We propose herein initial results to develop optimum redox mediators by the combination of computational simulation and catalytic functionalization of the core structure of vitamin K3. We aim to correlate the calculated energy value of the LUMO of different vitamin K3 derivatives with their actual redox potential. For this, we optimized the catalytic alkylation of 1,4-naphthoquinones with a designed Ag(i)/GO catalyst and synthesized a series of molecules.

    DOI: 10.1039/c7cc03910g

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  • Dependence of ph level on tribological effect of graphene oxide as an additive in water lubrication 査読

    A. A. Alias, H. Kinoshita, Y. Nishina, M. Fujii

    International Journal of Automotive and Mechanical Engineering   13 ( 1 )   3150 - 3156   2016年6月

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

    A study of the effectiveness of graphene oxides (GO) dispersed in water as a lubricant additive between tungsten carbide (WC) pin against stainless steel (SUS304) plate was carried out. A 0.1 wt.% GO was prepared and used as a lubricant under an applied load of 3 N for 20,000 friction cycles of reciprocating tribological testing. The results show that a GO dispersion with pH 3 provided the lowest friction coefficient, which was approximately 0.05. Worn areas on the wear track of the SUS304 flat plate and WC ball surface were also small. The increasing pH obviously affected the tribological properties, where the friction coefficient increased to approximately 0.10-0.20 in the steady state for pH 5, pH 7 and pH 9. Meanwhile, a GO dispersion with pH 10 was not able to provide good tribological properties for the tested materials. The observations on microscopic images revealed the formation of tribofilms on the wear tracks for low pH. The tribofilms caused reduction of the friction force and protected the plates from severe wear during the sliding tests.

    DOI: 10.15282/ijame.13.1.2016.2.0262

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  • Concurrent Formation of Carbon-Carbon Bonds and Functionalized Graphene by Oxidative Carbon-Hydrogen Coupling Reaction 査読

    Kumika Morioku, Naoki Morimoto, Yasuo Takeuchi, Yuta Nishina

    SCIENTIFIC REPORTS   6   2016年5月

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

    Oxidative C-H coupling reactions were conducted using graphene oxide (GO) as an oxidant. GO showed high selectivity compared with commonly used oxidants such as (diacetoxyiodo) benzene and 2,3-dichloro-5,6-dicyano-p-benzoquinone. A mechanistic study revealed that radical species contributed to the reaction. After the oxidative coupling reaction, GO was reduced to form a material that shows electron conductivity and high specific capacitance. Therefore, this system could concurrently achieve two important reactions: C-C bond formation via C-H transformation and production of functionalized graphene.

    DOI: 10.1038/srep25824

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  • Lewis Acid and Fluoroalcohol Mediated Nucleophilic Addition to the C2 Position of Indoles 査読

    Naoki Morimoto, Kumika Morioku, Hideyuki Suzuk, Yasuo Takeuchi, Yuta Nishina

    ORGANIC LETTERS   18 ( 9 )   2020 - 2023   2016年5月

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    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  

    Indole readily undergoes nucleophilic substitution at the C3 site, and many indole derivatives have been functionalized using this property. Indole also forms indolium, which allows electrophilic addition in acidic conditions, but current examples have been limited to intramolecular reactions. C2 site-selective nucleophilic addition to indole derivatives using fluoroalcohol and a Lewis acid was developed.

    DOI: 10.1021/acs.orglett.6b00629

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  • Tailoring the Oxygen Content of Graphite and Reduced Graphene Oxide for Specific Applications 査読

    Naoki Morimoto, Takuya Kubo, Yuta Nishina

    SCIENTIFIC REPORTS   6   2016年2月

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

    Graphene oxide (GO) is widely recognized as a promising material in a variety of fields, but its structure and composition has yet to be fully controlled. We have developed general strategies to control the oxidation degree of graphene-like materials via two methods: oxidation of graphite by KMnO4 in H2SO4 (oGO), and reduction of highly oxidized GO by hydrazine (rGO). Even though the oxygen content may be the same, oGO and rGO have different properties, for example the adsorption ability, oxidation ability, and electron conductivity. These differences in property arise from the difference in the underlying graphitic structure and the type of defect present. Our results can be used as a guideline for the production of tailor-made graphitic carbons. As an example, we show that rGO with 23.1 wt% oxygen showed the best performance as an electrode of an electric double-layer capacitor.

    DOI: 10.1038/srep21715

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  • Hydrosilane-Assisted Formation of Metal Nanoparticles on Graphene Oxide 査読

    Akinori Saito, Hiroshi Kinoshita, Ken-ichi Shimizu, Yuta Nishina

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   89 ( 1 )   67 - 73   2016年1月

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    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  

    Metal nanoparticles were formed on graphene oxide by a deposition process with hydrosilane, giving thin layer metal graphene oxide (metal/GO) composites. The particle size and catalytic activity could be controlled by varying the hydrosilane amount. Hydrosilane prevented the aggregation of GO layers by surface functionalization via silane coupling reaction. The metal/GO composites were evaluated as catalysts in hydrosilane oxidation.

    DOI: 10.1246/bcsj.20150331

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  • Carbon-catalyzed Dehydrogenation of Indolines: Detection of Active Intermediate and Exploration of High-performance Catalyst 査読

    Naoki Morimoto, Yasuo Takeuchi, Yuta Nishina

    CHEMISTRY LETTERS   45 ( 1 )   21 - 23   2016年1月

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    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  

    Metal-free oxidation of indoline using molecular oxygen as an oxidant was investigated. Among various carbon-based catalysts, we found that reduced graphene oxide (rGO) was the most active. Superoxide radical was formed in the course of the reaction. Although graphene oxide (GO) did not function as a catalyst, rGO could be recycled at least 5 times without any structural change.

    DOI: 10.1246/cl.150905

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  • The Scaevola frutescen (Mill.) Krause Dried-Leaves Extract as a Potential Natural Reduction System for Synthesis of Gold Nanoparticles and Their Evaluation for Antibacterial of Eschericia coli 査読

    Salprima S. Yudha, Eka Angasa, Totok Eka Suharto, Yuta Nishina, Zulfikri Achid Mardlia, Sipriyadi

    6TH NANOSCIENCE AND NANOTECHNOLOGY SYMPOSIUM (NNS2015)   1710   2016年

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    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:AMER INST PHYSICS  

    Many reports recently show that some plant and animal extracts were useful to prepare some desired materials. In line with the statement, this report will present a bioresources candidate that can be used for green preparation of gold nanoparticles. The Scaevola fruteschen (Mill.) Krause was obtained from Enggano island, Bengkulu Province, Indonesia. The current research include synthesis, characterization and application study of the obtained nanoparticles in their original medium/reduction system as antibacterial agent of Escherichia coli. Besides that, the interaction study of the nanoparticles solution with Pb2+ ions was also studied. The results, shows that the present reduction system (aqueous extract of the plant leaves) successfully reduced gold (III) ions to gold metals as shown by new peak at 544 nm in spectrophotometry analysis. The average nanopartiles size was 96 nm based on Particles Size Analyzer (PSA) result. The stability study revealed that the nanoparticles solution was not stable in the persence of Pb(OAc)(2) at high concentration. The nanoparticles were effective enough toward E. coli as shown by inhibition zone that indicates the degree of sensitivity of bacteria to nanoparticles.

    DOI: 10.1063/1.4941483

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  • Fast, scalable, and eco-friendly fabrication of an energy storage paper electrode 査読

    Hirotaka Koga, Hidetsugu Tonomura, Masaya Nogi, Katsuaki Suganuma, Yuta Nishina

    GREEN CHEMISTRY   18 ( 4 )   1117 - 1124   2016年

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    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  

    Recent progress in portable and wearable electronics has promoted a growing demand for high-performance and flexible energy-storage devices that are abundant and affordable. Because reduced graphene oxide (rGO), originating from inexpensive graphite, serves as a higher-performance energy-storage electrode than conventional activated carbons and carbon nanotubes, research and development of rGO/polymer composite electrodes for flexible supercapacitors have become a center of attraction. However, the fabrication of rGO-based flexible electrodes frequently requires a long time with high-temperature treatment or toxic chemical treatment, resulting in the lack of scalability and eco-friendliness. Here we show a fast, scalable, and environment-compatible route to fabricate a high-performance rGO/cellulose paper supercapacitor electrode. Single-layer graphene oxide (GO) sheets and recycled waste pulp fibers were successfully fabricated into a paper composite by a well-established scalable papermaking process, followed by a room-temperature, additive-free, and millisecond-timescale flash reduction process. The as-prepared rGO/paper electrode had a high specific capacitance, up to 212 F g(-1), for an all paper-based flexible supercapacitor, comparable to those of state-of-the-art rGO-based electrodes, while dramatically decreasing the reduction time of GO from the conventional hour timescale to milliseconds. This work will pave the way for green, flexible, and mass-producible energy-storage paper in future wearable electronics.

    DOI: 10.1039/c5gc01949d

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  • Investigations on tribological mechanisms of graphene oxide and oxidized wood-derived nanocarbons as water-based lubricating additives 査読

    Hiroshi Kinoshita, Yuta Nishina

    Tribology Online   11 ( 2 )   235 - 241   2016年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japanese Society of Tribologists  

    Graphene oxide (GO) contains graphitic single-layered sheets, while oxidized wood-based nanocarbon (oWNC) is composed of graphitic nanoshells. Since both materials are thoroughly oxidized with many oxygen-containing functional groups, both GOs and oWNCs form stable dispersions in water. We found that lubrication by dispersions of GOs and oWNCs in water resulted in very low friction coefficients below 0.04 with only slight plate surface wear using a steel plate and tungsten carbide ball. After lubrication, thick tribofilms are formed on the sliding surfaces, which would decrease the friction. In this study, in order to clarify the tribological mechanisms that result in such low friction coefficients, we have performed tribological tests and analyzed the tribofilms formed by dispersions of GO in water using confocal laser scanning microscopy (CLSM) with an optical data storage system, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The GO tribofilm is composed of many carbons and some oxygen, derived from the disordered and aggregated GO sheets. The GO tribofilm have higher hardness and hydrophilic properties than the steel plates, which would provide low friction and wear. It is found that both the GO tribofilm and GOs are necessary to achieve the lowest possible coefficient of friction. It is likely that the oWNC tribofilm has similar friction and wear decreasing effects to that of the GO dispersion.

    DOI: 10.2474/trol.11.235

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  • Synthesis of 2-Arylphenol Derivatives through a One-Pot Suzuki-Miyaura Coupling/Dehydrogenative Aromatization Sequence with Pd/C Catalysis 査読

    Kotaro Kikushima, Yuta Nishina

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY   ( 26 )   5864 - 5868   2015年9月

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    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  

    One-pot synthesis of 2-arylphenols starting from 2-iodo-2-cyclohexen-1-one and arylboronic acids through sequential Suzuki-Miyaura coupling/dehydrogenative aromatization with Pd/C catalysis has been developed. A range of arylboronic acids serve as substrates, including those containing electron-donating or electron-withdrawing groups. Additionally, one-pot synthesis of di- or trisubstituted phenols bearing a phenyl group at the ortho position are also generated by using 2-iodo-2-cyclohexen-1-one derivatives as substrate. In the present method, commercially available and easily removable Pd/C was employed as a catalyst without any ligands. The operationally simple procedure and accessible conditions were used to provide modified phenols as the sole product in moderate to high yields.

    DOI: 10.1002/ejoc.201500723

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  • Metal free C-H coupling of aromatic compounds by graphene oxide activated by acidic additives 査読

    Nishina Yuta, Morimoto Naoki, Morioku Kumika

    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY   250   2015年8月

  • Production of Gold Nanoparticles (AuNPs) from Chloroaurate Ions Using Aqueous Extract Of Air-Dried Premna obtusifulia Leaves 査読

    Yudha Salprima S, Angasa Eka, Suharto Totok Eka, Nishina Yuta, Mardlia Zulfikri Achid

    RESEARCH JOURNAL OF PHARMACEUTICAL BIOLOGICAL AND CHEMICAL SCIENCES   6 ( 4 )   1802 - 1806   2015年7月

  • Tribological properties of graphene oxide as a lubricating additive in water and lubricating oils 査読

    Kinoshita Hiroshi, Ono Hideki, Alias Aidil Azli, Nishina Yuta, Fujii Masahiro

    MECHANICAL ENGINEERING JOURNAL   2 ( 6 )   2015年

  • Highly durable carbon-supported Pt catalysts prepared by hydrosilane-assisted nanoparticle deposition and surface functionalization 査読

    Akinori Saito, Hiromi Tsuji, Iwao Shimoyama, Ken-ichi Shimizu, Yuta Nishina

    CHEMICAL COMMUNICATIONS   51 ( 27 )   5883 - 5886   2015年

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    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  

    Hydrosilane enabled the formation of Pt nanoparticles and the silane functionalization of a carbon support material in one pot. The metal/Si-modified carbon composites are highly durable during catalytic methane oxidation.

    DOI: 10.1039/c4cc10298c

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  • Highly durable carbon-supported Pt catalysts prepared by hydrosilane-assisted nanoparticle deposition and surface functionalization 査読

    Akinori Saito, Hiromi Tsuji, Iwao Shimoyama, Ken-ichi Shimizu, Yuta Nishina

    CHEMICAL COMMUNICATIONS   51 ( 27 )   5883 - 5886   2015年

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    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  

    Hydrosilane enabled the formation of Pt nanoparticles and the silane functionalization of a carbon support material in one pot. The metal/Si-modified carbon composites are highly durable during catalytic methane oxidation.

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  • Facile identification of the critical content of multi-layer graphene oxide for epoxy composite with optimal thermal properties 査読

    Tianle Zhou, Shijo Nagao, Tohru Sugahara, Hirotaka Koga, Masaya Nogi, Katsuaki Suganuma, Thi Thi Nge, Yuta Nishina

    RSC ADVANCES   5 ( 26 )   20376 - 20385   2015年

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    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  

    Multi-layer graphene oxide (MGO) has attracted considerable interest in conductive polymer composites. However, in most cases the optimal MGO content is determined using a complex procedure. Avoiding the complicated work of processing polymerized samples followed by testing various properties, here a facile strategy is proposed to directly identify the critical MGO content among formulations for epoxy composites with optimal thermal properties, simply by monitoring the "unusual" nonlinear MGO content-dependent cure behaviors, as well as the "unusual" pattern of double-peak curing curves. The formation mechanism of the double-peak pattern was explored, with emphasis on studying the epoxy/MGO reaction using a modified Shrinking Core Model. The optimal content determined in this work 2 wt% MGO) was verified by the thermal properties (thermal conductivity, structural thermal stability and coefficient of thermal expansion) of MGO/epoxy composites. Based on the inherent relationship between the effect of MGO percolating chains on the thermal polymerization behavior and the resulting thermal properties, this strategy can be easily extended to different kinds of conductive MGO/polymer composites.

    DOI: 10.1039/c4ra15881d

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  • Targeted kinetic strategy for improving the thermal conductivity of epoxy composite containing percolating multi-layer graphene oxide chains 査読

    Zhou T, Koga H, Nogi M, Sugahara T, Nagao S, Nge T. T, Suganuma K, Cui H-W, Liu F, Nishina Y

    Express Polymer Letters   9 ( 7 )   608 - 623   2015年

  • Polycyclic N-Heterocyclic Compounds 75: Synthesis and Anti-platelet Evaluation of 2,4-Disubstituted 5,6-Dihydro[1]benzofuro[3’,2’:2,3]oxepino[4,5-d]pyrimidines 査読

    Okuda Kensuke, Takano Jun-ichi, Hirota Takashi, Sasaki Kenji, Nishina Yuta, Ishida Hiroyuki

    JOURNAL OF HETEROCYCLIC CHEMISTRY   51 ( 3 )   661 - 668   2014年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/jhet.1539

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  • Tribological properties of monolayer graphene oxide sheets as water-based lubricant additives 査読

    Hiroshi Kinoshita, Yuta Nishina, Aidil Azli Alias, Masahiro Fujii

    CARBON   66   720 - 723   2014年1月

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    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  

    Application and tribological properties of graphene oxide (GO) monolayer sheets as additives in water-based lubricants were investigated. The lubricating fluids were applied to a sintered tungsten carbide ball and stainless steel flat plate. It was found that adding GO particles into water improved lubrication and provided a very low friction coefficient of approximately 0.05 with no obvious surface wear after 60,000 cycles of friction testing. GO adsorption occurred on the lubricated surfaces of both the ball and flat plate, suggesting GO sheets may behave as protective coatings. (C) 2013 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.carbon.2013.08.045

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  • Fine tuning of the sheet distance of graphene oxide that affects the activity and substrate selectivity of a Pd/graphene oxide catalyst in the Heck reaction 査読

    Akinori Saito, Shun-Ichi Yamamoto, Yuta Nishina

    RSC Advances   4 ( 104 )   59835 - 59838   2014年

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    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  

    The interlayer distance of graphene oxide (GO) in a Pd/GO composite could be tuned using cationic surfactants. The distance becomes larger when a large surfactant is used. The catalytic activity in Heck reactions dramatically improved using the surfactant-modified Pd/GO catalyst. Substrate selectivity could also be improved by adjusting the size of the surfactant to increase accessibility of substrates to the active catalytic centre.

    DOI: 10.1039/c4ra10512e

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  • Facile preparation of Pd nanoparticles supported on single-layer graphene oxide and application for the Suzuki-Miyaura cross-coupling reaction 査読

    Shun-ichi Yamamoto, Hiroshi Kinoshita, Hideki Hashimoto, Yuta Nishina

    NANOSCALE   6 ( 12 )   6501 - 6505   2014年

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    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  

    Pd nanoparticles supported on single layer graphene oxide (Pd-slGO) were prepared by gentle heating of palladium(II) acetate (Pd(OAc)(2)) and GO in ethanol that served as a mild reductant of the Pd precursor. Pd-slGO showed a high catalytic performance (TON and TOF = 237 000) in the Suzuki-Miyaura cross-coupling reaction.

    DOI: 10.1039/c4nr00715h

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  • Application of Heterogeneous Catalysts for Organic Synthesis by Controlling the Oxidation State of Metal Species 査読

    Yuta Nishina

    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN   71 ( 12 )   1307 - 1308   2013年12月

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    記述言語:日本語   出版者・発行元:SOC SYNTHETIC ORGANIC CHEM JPN  

    One of the important research topics in the synthesis of pharmaceuticals and fine chemicals is to convert homogeneous reactions to heterogeneous versions by immobilization of metal species on polymer or inorganic supports. The oxidation state of the metal species can affect the character and reactivity of the catalyst. Recently, chemists have gained excellent techniques to control particle size and oxidation state of metal species, which has led to the development of new heterogeneous catalysts for organic reactions.

    DOI: 10.5059/yukigoseikyokaishi.71.1307

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  • Nanocrystalline magnesium oxide-stabilized palladium(0): The Heck reaction of heteroaryl bromides in the absence of additional ligands and base 査読

    Mannepalli Lakshmi Kantam, Police Vishnuvardhan Redddy, Pottabathula Srinivas, Akula Venugopal, Suresh Bhargava, Yuta Nishina

    Catalysis Science and Technology   3 ( 10 )   2550 - 2554   2013年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    An efficient and user-friendly protocol has been realized for the Heck reaction of heteroaryl bromides by using a reusable nanocrystalline magnesium oxide-stabilized palladium(0) catalyst without the aid of additional ligands and base. Dimethylamine generated under in situ conditions by the decomposition of DMF serves as the base in this reaction. The catalyst was reused with consistent activity up to four cycles. © 2013 The Royal Society of Chemistry.

    DOI: 10.1039/c3cy00404j

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  • Bromination of hydrocarbons with CBr4, initiated by light-emitting diode irradiation 査読

    Yuta Nishina, Bunsho Ohtani, Kotaro Kikushima

    BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY   9   1663 - 1667   2013年8月

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

    The bromination of hydrocarbons with CBr4 as a bromine source, induced by light-emitting diode (LED) irradiation, has been developed. Monobromides were synthesized with high efficiency without the need for any additives, catalysts, heating, or inert conditions. Action and absorption spectra suggest that CBr4 absorbs light to give active species for the bromination. The generation of CHBr3 was confirmed by NMR spectroscopy and GC-MS spectrometry analysis, indicating that the present bromination involves the homolytic cleavage of a C-Br bond in CBr4 followed by radical abstraction of a hydrogen atom from a hydrocarbon.

    DOI: 10.3762/bjoc.9.190

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  • Green synthesis of silver nanoparticles using aqueous rinds extract of Brucea javanica (L.) Merr at ambient temperature 査読

    Salprima S. Yudha, Doni Notriawan, Eka Angasa, Totok Eka Suharto, John Hendri, Yuta Nishina

    MATERIALS LETTERS   97   181 - 183   2013年4月

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    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  

    Aqueous rinds extract of Brucea javanica (L.) Merr has been used as the medium/reducing system for the formation of silver nanoparticles colloids. A solution of 0.01 N AgNO3 (1 ml) was added to the rind extracts (4 ml) at room temperature, and the formation of silver nanoparticles was observed using ultraviolet-visible spectrophotometer. The shape and size of the nanoparticles have been characterized using Transmission Electron Microscope (TEM) analysis. The experimental results show that the silver nanoparticles are formed easily in the extract at ambient temperature. The resulting nanoparticles were in the spherical form and the average size of the nanoparticles was about 38.00 +/- 14.00 nm. (C) 2013 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.matlet.2013.01.114

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  • Ionic amino acids: Application as organocatalysts in the aza-Michael reaction 査読

    Naoki Morimoto, Yasuo Takeuchi, Yuta Nishina

    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL   368   31 - 37   2013年3月

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    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 ethyl methyl imidazolium salts of amino acids, [emiml[AA], have been used as catalysts in the aza-Michael reaction. Furthermore, when chiral amino acids were used, a stereoselective reaction was achieved. The mechanism of the transformation was verified by the detection of a key intermediate by electrospray ionization mass spectroscopy (ESI-MS). (C) 2012 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.molcata.2012.11.012

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  • 微生物が作るマンガン酸化物の加熱処理による結晶構造と微細構造の変化 査読

    木村倫康, 橋本英樹, 宮田直幸, 仁科勇太, 草野圭弘, 池田靖訓, 中西真, 藤井達生, IVO Safarik, IVO Safarik, MIRKA Safarikova, 高田潤

    粉体および粉末冶金   60 ( 3 )   92-99 (J-STAGE)   2013年

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    記述言語:日本語  

    DOI: 10.2497/jjspm.60.92

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  • Copper-catalyzed oxidative aromatization of 2-cyclohexen-1-ones to phenols in the presence of catalytic hydrogen bromide under molecular oxygen 査読

    Kotaro Kikushima, Yuta Nishina

    RSC ADVANCES   3 ( 43 )   20150 - 20156   2013年

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    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  

    Catalytic oxidative aromatization has been achieved using 2-cyclohexen-1-ones to obtain phenol derivatives in the presence of a catalytic amount of copper salt and aqueous HBr under molecular oxygen. The amount of HBr was successfully reduced to a catalytic quantity, and the other additive such as a ligand and an oxidant as well as inert conditions were unnecessary. Various mono-, di-, and trisubstituted phenols with substituents at the desired positions could be synthesized under cheap and simple conditions. An oxidative aromatization/bromination sequence was also demonstrated to obtain bromophenols with excess HBr.

    DOI: 10.1039/c3ra43071e

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  • Palladium on graphene: the in situ generation of a catalyst for the chemoselective reduction of α,ß-unsaturated carbonyl compounds 査読

    Morimoto Naoki, Yamamoto Shun-ichi, Takeuchi Yasuo, Nishina Yuta

    RSC ADVANCES   3 ( 36 )   15608 - 15612   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1039/c3ra42150c

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  • Direct bromination of hydrocarbons catalyzed by Li2MnO3 under oxygen and photo-irradiation conditions 査読

    Yuta Nishina, Junya Morita, Bunsho Ohtani

    RSC ADVANCES   3 ( 7 )   2158 - 2162   2013年

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    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 method for the direct bromination of hydrocarbons with Br-2 using a ubiquitous and inexpensive catalyst is highly desirable. Herein, we report the selective mono-bromination of hydrocarbons in good yield using Li2MnO3 as a catalyst under irradiation with a fluorescent room light. This new catalyst can be recycled. The effect of light was investigated using action spectra, which revealed that the reaction occurred on the surface of the catalyst.

    DOI: 10.1039/c2ra22197g

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  • 10′-Chloro-3′,4′-dihydro-2′H-spiro[cyclopropane-1,7'(6'H)-pyrimido[2,1- a]isoquinolin]-6′-one 査読

    68 ( 11 )   o3252   2012年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1107/S1600536812044261

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  • 3-(2-Oxo-2,3,4,5-tetrahydrofuran-3-yl)-1-benzofuran-2-carbonitrile 査読

    Kensuke Okuda, Takashi Hirota, Yuta Nishina, Hiroyuki Ishida

    Acta Crystallographica Section E: Structure Reports Online   68 ( 9 )   o2819   2012年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The asymmetric unit of the title compound, C13H 9NO3, consists of two crystallographically independent molecules. In each molecule, the tetra-hydro-furan (THF) ring adopts an envelope conformation with one of the methyl-ene C atoms positioned at the flap. The dihedral angles between the mean plane of the THF and the benzofuran ring system are 70.85 (5) and 89.59 (6)°. In the crystal, molecules are stacked in a column along the a-axis direction through C - H⋯O hydrogen bonds, with columns further linked by C - H⋯N and C - H⋯O interactions.

    DOI: 10.1107/S1600536812036835

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  • Novel Plant Immune-Priming Compounds Identified via High-Throughput Chemical Screening Target Salicylic Acid Glucosyltransferases in Arabidopsis 査読

    Yoshiteru Noutoshi, Masateru Okazaki, Tatsuya Kida, Yuta Nishina, Yoshihiko Morishita, Takumi Ogawa, Hideyuki Suzuki, Daisuke Shibata, Yusuke Jikumaru, Atsushi Hanada, Yuji Kamiya, Ken Shirasu

    PLANT CELL   24 ( 9 )   3795 - 3804   2012年9月

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    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 SOC PLANT BIOLOGISTS  

    Plant activators are compounds, such as analogs of the defense hormone salicylic acid (SA), that protect plants from pathogens by activating the plant immune system. Although some plant activators have been widely used in agriculture, the molecular mechanisms of immune induction are largely unknown. Using a newly established high-throughput screening procedure that screens for compounds that specifically potentiate pathogen-activated cell death in Arabidopsis thaliana cultured suspension cells, we identified five compounds that prime the immune response. These compounds enhanced disease resistance against pathogenic Pseudomonas bacteria in Arabidopsis plants. Pretreatments increased the accumulation of endogenous SA, but reduced its metabolite, SA-O-beta-D-glucoside. Inducing compounds inhibited two SA glucosyltransferases (SAGTs) in vitro. Double knockout plants that lack both SAGTs consistently exhibited enhanced disease resistance. Our results demonstrate that manipulation of the active free SA pool via SA-inactivating enzymes can be a useful strategy for fortifying plant disease resistance and may identify useful crop protectants.

    DOI: 10.1105/tpc.112.098343

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  • Characterization of hybrid composite membrane based polymer/precursor/SiO2 査読

    Uma Thanganathan, Yuta Nishina, Kunio Kimura, Satoshi Hayakawa, Rambabu Bobba

    MATERIALS LETTERS   81   88 - 91   2012年8月

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    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  

    New class of hybrid composite was synthesized via sol-gel process with the combination of poly(vinyl alcohol) (PVA), TEOS, 3-glycidyloxypropyltrimethoxysilane (GPTMS) reacted with the cross-linking agent glutaraldehyde. The composites demonstrated a maximum high proton conductivity of 1.7 x 10(-2) S cm(-1) at 140 degrees C and a relative humidity of 50% RH. The swelling ratio was calculated in dry and wet conditions, and the composites were found capable of swelling. The structural formation of the composites was studied by techniques such as FTIR, TGA and impedance spectroscopy, and it was concluded that these PVA-SiO2/GPTMS/GA composite membranes exhibited excellent thermal, mechanical and conductivity properties. (C) 2012 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.matlet.2012.04.023

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  • Hydrothiolation and Intramolecular Cyclization Sequence for the Synthesis of 1,3-Oxathiine Frameworks 査読

    Yuta Nishina, Junya Miyata

    SYNTHESIS-STUTTGART   44 ( 16 )   2607 - 2613   2012年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:GEORG THIEME VERLAG KG  

    1,3-Oxathiine frameworks can be prepared via the sequential addition and intramolecular cyclization of thiosalicylic acid onto alkynes. A substituent on the alkyne and the presence of a palladium catalyst can allow product regioselectivity control. This strategy is applicable to the synthesis of heterocycles comprising sulfur and oxygen atoms, namely 3,1-benzoxathiines, without any unwanted byproduct.

    DOI: 10.1055/s-0032-1316563

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  • Ruthenium/magnesium-lanthanum mixed oxide: An efficient reusable catalyst for oxidation of alcohols by using molecular oxygen 査読

    M. Lakshmi Kantam, R. Sudarshan Reddy, Ujjwal Pal, M. Sudhakar, A. Venugopal, K. Jeeva Ratnam, F. Figueras, Venkat Reddy Chintareddy, Yuta Nishina

    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL   359   1 - 7   2012年7月

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    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  

    An efficient method for the oxidation of benzylic and secondary aromatic alcohols into their corresponding aldehydes or ketones has been achieved by using ruthenium supported magnesium lanthanum mixed oxide as a heterogeneous catalyst in toluene, with molecular oxygen as the sole oxidant. This catalyst can also be operated in solvent free conditions at 393 K and reused for five cycles with consistent yield and selectivity. (C)2012 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.molcata.2012.03.013

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  • Catalytic guanylation of aliphatic, aromatic, heterocyclic primary and secondary amines using nanocrystalline zinc(II) oxide 査読

    M. Lakshmi Kantam, S. Priyadarshini, P. J. Amal Joseph, P. Srinivas, A. Vinu, K. J. Klabunde, Yuta Nishina

    TETRAHEDRON   68 ( 29 )   5730 - 5737   2012年7月

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    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  

    Nanocrystalline ZnO was found to be a highly efficient heterogeneous catalyst for the guanylation of amines with various carbodiimides to afford N,N',N ''-trisubstituted guanidines in excellent yields. Structurally divergent aliphatic, aromatic, heterocyclic primary and secondary amines were converted to the corresponding N,N',N ''-trisubstituted guanidines using optimal conditions. The catalyst was easy to handle even under atmospheric conditions and can be easily recovered by centrifugation and reused for five cycles with consistent activity. (C) 2012 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tet.2012.05.044

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  • 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

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    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

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  • 酸化薄片化黒鉛及びその製造方法 査読

    仁科勇太

    特願2012-083453,岡山大学   2012年

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  • Recyclable Pd-graphene catalyst: mechanistic insights into heterogeneous and homogeneous catalysis 査読

    Yuta Nishina, Junya Miyata, Ryo Kawai, Kazuma Gotoh

    RSC ADVANCES   2 ( 25 )   9380 - 9382   2012年

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    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  

    Pd-graphene, a composite of Pd nanoparticles and exfoliated graphene, was used as a catalyst in organic reactions. In the Suzuki-Miyaura cross-coupling reaction, Pd-graphene showed high reusability without aggregation of Pd nanoparticles. The intermediates of the reaction in the liquid phase, Ph-Pd-Br and Ph-Pd-OH, were detected by ESI-MS.

    DOI: 10.1039/c2ra21185h

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  • Bromination of aromatic compounds using an Fe2O3/zeolite catalyst 査読

    Yuta Nishina, Keishi Takami

    GREEN CHEMISTRY   14 ( 9 )   2380 - 2383   2012年

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    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 catalytic bromination of non-activated aromatic compounds has been achieved using an Fe2O3/zeolite catalyst system. FeBr3 was identified as the catalytic species, formed in situ from HBr and Fe2O3. The catalyst was easy-to-handle and cost effective and could also be recycled. The reaction system was also amenable to the one-pot sequential bromination/C-C bond formation of benzene.

    DOI: 10.1039/c2gc35821b

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  • Biogenic manganese oxide: effective new catalyst for direct bromination of hydrocarbons 査読

    Yuta Nishina, Hideki Hashimoto, Noriyasu Kimura, Naoyuki Miyata, Tatsuo Fujii, Bunsho Ohtani, Jun Takada

    RSC ADVANCES   2 ( 16 )   6420 - 6423   2012年

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    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  

    Nano- and micro-architectural manganese oxide produced by microorganisms catalyses the selective monobromination of hydrocarbons in excellent yield under irradiation of fluorescent room light. The knowledge gained from investigating natural materials will lead to unprecedented catalyst designing toward efficient organic reactions.

    DOI: 10.1039/c2ra20896b

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  • 炭化水素の酸化触媒および炭化水素酸化物の製造方法 査読

    仁科勇太

    特願2012-029061,岡山大学   2012年

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  • 臭素化触媒及びその製造方法 査読

    仁科勇太

    特願2011-263954,岡山大学   2011年12月

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  • ハロゲン化触媒及びハロゲン化合物の製造方法 査読

    仁科勇太

    PCT/JP2011/74795,岡山大学   2011年10月

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  • Synthesis of Multisubstituted Cyclopentadienes from Cyclopentenones Prepared via Catalytic Double Aldol Condensation and Nazarov Reaction Sequence 査読

    Yuta Nishina, Tomohiro Tatsuzaki, Ayano Tsubakihara, Yoichiro Kuninobu, Kazuhiko Takai

    SYNLETT   17 ( 17 )   2585 - 2589   2011年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:GEORG THIEME VERLAG KG  

    The rhenium-catalyzed synthesis of cyclopentenone derivatives via double aldol condensation and successive Nazarov reaction is described. The cyclopentenones were converted to the corresponding cyclopentadienes using organolithium reagents. Cyclopentadienes with four different substituents could be synthesized by stepwise double aldol condensation using a ketone and two types of aldehydes, followed by treatment with an organolithium reagent.

    DOI: 10.1055/s-0030-1260324

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  • Facile Sc(OTf)(3)-Catalyzed Generation and Successive Aromatization of Isobenzofuran from o-Dicarbonylbenzenes 査読

    Yuta Nishina, Tatsuya Kida, Tomonari Ureshino

    ORGANIC LETTERS   13 ( 15 )   3960 - 3963   2011年8月

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    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  

    Isobenzofuran can be prepared from o-phthalaldehyde using hydrosilane. The formed isobenzofuran Is trapped by an alkene via a Diels-Alder reaction. Further dehydration proceeds to furnish the conjugated aromatic compound. This multistep reaction was promoted by catalytic amounts of Sc(OTf)(3).

    DOI: 10.1021/ol201479p

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  • ハロゲン化触媒およびハロゲン化合物の製造方法 査読

    仁科勇太

    特願2011-008026号,岡山大学   2011年1月

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  • ハロゲン化触媒及びハロゲン化合物の製造方法 査読

    仁科勇太

    特願2010-288035号 岡山大学   2010年12月

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  • Synthesis of Functionalized Pentacenes from Isobenzofurans Derived from C−H Bond Activation 査読

    Kuninobu Yoichiro, Seiki Takayuki, Kanamaru Shunsuke, Nishina Yuta, Takai Kazuhiko

    ORGANIC LETTERS   12 ( 22 )   5287 - 5289   2010年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1021/ol102349r

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  • Rhenium-Catalyzed Insertion of Nonpolar and Polar Unsaturated Molecules into an Olefinic C-H Bond 査読

    Yoichiro Kuninobu, Yasuo Fujii, Takashi Matsuki, Yuta Nishina, Kazuhiko Takai

    ORGANIC LETTERS   11 ( 12 )   2711 - 2714   2009年6月

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    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  

    Treatment of olefins bearing a directing group with alpha,beta-unsaturated carbonyl compounds, alkynes, or aldehydes in the presence of a catalytic amount of a rhenium complex, [ReBr(CO)(3)(thf)](2) gave gamma,delta-unsaturated carbonyl compounds, dienes, and allyl silyl ethers, respectively. This reaction proceeds via C-H bond activation, insertion of unsaturated molecules into the formed rhenium-carbon bond, and then reductive elimination (or transmetalation in the case of aldehydes).

    DOI: 10.1021/ol900962v

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  • Reactions and Mechanistic Studies of Rhenium-Catalyzed Insertion of α,β-Unsaturated Carbonyl Compounds into a C-H Bond 査読

    Kuninobu Yoichiro, Nishina Yuta, Okaguchi Kayo, Shouho Makoto, Takai Kazuhiko

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   81 ( 11 )   1393 - 1401   2008年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1246/bcsj.81.1393

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  • Synthesis of Cp-Re Complexes via Olefinic C-H Activation and Successive Formation of Cyclopentadienes 査読

    Yoichiro Kuninobu, Yuta Nishina, Takashi Matsuki, Kazuhiko Takai

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   130 ( 43 )   14062 - +   2008年10月

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    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  

    Treatment of an a,p-unsaturated ketimine with an alpha,beta-unsaturated carbonyl compound in the presence of a rhenium complex, Re-2(CO)(10), gave a cyclopentadienyl-rhenium complex. This reaction proceeds via rhenium-catalyzed C-H bond activation of an olefinic C-H bond, insertion of an alpha,beta-unsaturated carbonyl compound into a Re-C bond of the alkenylrhenium intermediate, intramolecular nucleophilic cyclization, reductive elimination, elimination of aniline to give a cyclopentadiene derivative, followed by the formation of a cyclopentadienyl-rhenium complex from the cyclopentadiene derivative and the rhenium complex.

    DOI: 10.1021/ja805921f

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  • Hydroarylation of acetylenes, acrylates, and isocyanates with heteroaromatic compounds under rhenium catalysis 査読

    Yoichiro Kuninobu, Kou Kikuchi, Yukimi Tokunaga, Yuta Nishina, Kazuhiko Takai

    TETRAHEDRON   64 ( 26 )   5974 - 5981   2008年6月

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    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  

    With the aid of a directing group, an imine moiety, heteroaromatic compounds add to acetylenes in the presence of a catalytic amount of [ReBr(CO)(3)(THF)](2) at the adjacent position of the directing group regioselectively to give hydroarylation of the acetylenes in good to excellent yields. Similarly, heteroaromatic compounds react with acrylates and isocyanates to give the corresponding hydroarylation products under rhenium catalysis. (C) 2008 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tet.2008.01.145

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  • Rhenium-catalyzed synthesis of indene derivatives via C-H bond activation 査読

    Yoichiro Kuninobu, Yuta Nishina, Atsushi Kawata, Makoto Shouho, Kazuhiko Takai

    PURE AND APPLIED CHEMISTRY   80 ( 5 )   1149 - 1154   2008年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:INT UNION PURE APPLIED CHEMISTRY  

    Rhenium complex, [ReBr(CO)(3)(thf)](2)-catalyzed reactions between aromatic imines and either acetylenes or alpha,beta-unsaturated carbonyl compounds gave indene derivatives in good to excellent yields. These reactions proceed via C-H bond activation, insertion of acetylenes or alpha,beta-unsaturated carbonyl compounds, intramolecular nucleophilic cyclization, and reductive elimination. Indene derivatives were also obtained from aromatic ketones and alpha,beta-unsaturated carbonyl compounds in the presence of catalytic amounts of the rhenium complex and p-anisidine. Sequential ruthenium-catalyzed hydroamination of aromatic acetylenes with anilines, and rhenium-catalyzed reactions of the formed aromatic ketimines with alpha,beta-unsaturated carbonyl compounds also provided indene derivatives.

    DOI: 10.1351/pac200880051149

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  • Rhenium-catalyzed synthesis of naphthalene derivatives via insertion of aldehydes into a C-H bond 査読

    Yoichiro Kuninobu, Yuta Nishina, Kazuhiko Takai

    TETRAHEDRON   63 ( 35 )   8463 - 8468   2007年8月

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    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  

    Arhenium complex, [ReBr(CO)(3)(THF)](2), catalyzed reactions of aromatic ketimines and aldehydes with dienophiles, followed by dehydration, to give naphthalene derivatives in good to excellent yields. This reaction proceeds via C-H bond activation, insertion of an aldehyde, intramolecular nucleophilic cyclization, reductive elimination, elimination of aniline and Diels-Alder reaction. After dehydration, naphthalene derivatives were formed. (c) 2007 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tet.2007.05.083

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  • Manganese-catalyzed insertion of aldehydes into a C-H bond 査読

    Yoichiro Kuninobu, Yuta Nishina, Takahiro Takeuchi, Kazuhiko Takai

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   46 ( 34 )   6518 - 6520   2007年

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    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-BLACKWELL  

    DOI: 10.1002/ani3.200702256

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  • Rhenium-catalyzed insertion of aldehyde into a C-H bond: Synthesis of isobenzofuran derivatives 査読

    Yoichiro Kuninobu, Yuta Nishina, Chie Nakagawa, Kazuhiko Takai

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   128 ( 38 )   12376 - 12377   2006年9月

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    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  

    DOI: 10.1021/ja065643e

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  • Sequential ruthenium-catalyzed hydroamination and rhenium-catalyzed C-H bond activation leading to indene derivatives 査読

    Yoichiro Kuninobu, Yuta Nishina, Kazuhiko Takai

    ORGANIC LETTERS   8 ( 13 )   2891 - 2893   2006年6月

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    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  

    Formal [3+2] annulation of arylacetylenes and alpha,beta-unsaturated carbonyl compounds is achieved in a one-pot reaction by successive treatment of the acetylenes with aniline and a catalytic amount of Ru-3(CO)(12) and NH4PF6 and C-H bond activation catalyzed by [ReBr(CO)(3)(thf)](2). The result suggests that the second rhenium-catalyzed indene formation is not disturbed by the first catalyst system.

    DOI: 10.1021/ol0611292

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  • Rhenium- and aniline-catalyzed one-pot annulation of aromatic ketones and alpha,beta-unsaturated esters initiated by C-H bond activation 査読

    Y Kuninobu, Y Nishina, M Shoitho, K Takai

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   45 ( 17 )   2766 - 2768   2006年

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    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  

    DOI: 10.1002/anie.200503627

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MISC

  • Covalent functionalization of carbon materials with redox-active organic molecules for energy storage

    Rizwan Khan, Yuta Nishina

    Nanoscale   13 ( 1 )   36 - 50   2021年1月

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    掲載種別:書評論文,書評,文献紹介等  

    Carbon-based materials (CBMs) have shown great versatility because they can be chemically combined with other materials for various applications. Chemical modification of CBMs can be achieved via covalent or non-covalent interactions. Non-covalent interactions are weak and fragile, causing structural change and molecule dissociation. Therefore, in this review, we summarize the covalent modification of CBMs via organic chemistry techniques, aiming at forming more robust and stable CBMs. Besides, their application as electrode materials in energy storage systems is also within the scope of this review. Covalent binding of redox-active organic molecules with CBMs improves the transfer rate of electrons and prevents the dissolution of redox-active molecules, resulting in good conductivity and cycle life. Numerous papers on the functionalization of CBMs have been published to date, but some of them lack scientific evidence and are unable to understand from chemistry viewpoint. Reliable articles with adequate evidence are summarized in this review from a synthetic chemistry viewpoint.

    DOI: 10.1039/d0nr07500k

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  • Graphene oxide: A new direction in dentistry

    Mohammed Zahedul Islam Nizami, Shogo Takashiba, Yuta Nishina

    Applied Materials Today   19   2020年6月

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    掲載種別:書評論文,書評,文献紹介等  

    This inclusive review summarizes the recent advances in the application of graphene oxide (GO) and functionalized GO in oral and dental research. GO possesses several extraordinary physical, chemical, optical, electrical, and mechanical properties. Because of its high surface area and oxygenated functional groups, GO exhibits excellent interaction ability with metals and ions as well as organic species. The current review reveals that GO has been used to produce a variety of functionalized nanocomposites, scaffolds, and advanced nanoparticle carriers. Accordingly, GO shows potential in a variety of research fields, such as tissue engineering, materials engineering, biomaterials, and drug delivery, indicating that the application of GO to biomedicine is particularly promising. More specifically, the recent application of GO in dentistry has provided outstanding results in antimicrobial action, regenerative dentistry, bone tissue engineering, drug delivery, physicomechanical property enhancement of dental biomaterials, and oral cancer treatment. The biocompatibilities of GO and its nanocomposites make them potential units in bone regeneration, osseointegration, and cell proliferation. Furthermore, its antibiofilm and antiadhesion properties have inspired researchers to develop GO for biofilm and caries prevention, as well as implant surface modification and as a quorum sensing inhibitor. This updated review is wide-ranging and provides a useful source for additional information on GO and its composites in dental research and applications.

    DOI: 10.1016/j.apmt.2020.100576

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  • 木材ナノセルロースペーパーの炭素化と電気特性遷移

    福島大喜, 吉田由紀, 上谷幸治郎, 能木雅也, 古賀大尚, 仁科勇太, 高橋綱己, 長島一樹, 柳田剛

    日本木材学会大会研究発表要旨集(完全版)(CD-ROM)   69th   ROMBUNNO.Z14‐02‐1545   2019年3月

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    記述言語:日本語  

    J-GLOBAL

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  • イノベーション創出を目指す異分野融合研究アライアンス 異分野融合による紙のリノベーション研究

    古賀大尚, 長島一樹, 仁科勇太

    セラミックス   53 ( 6 )   391‐394   2018年6月

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    記述言語:日本語  

    J-GLOBAL

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  • リサイクル可能な固定化触媒ペーパーリアクターの開発

    古賀大尚, 高橋司, 能木雅也, 仁科勇太

    日本木材学会大会研究発表要旨集(完全版)(CD-ROM)   67th   ROMBUNNO.K17‐05‐1515   2017年2月

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    記述言語:日本語  

    J-GLOBAL

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  • Graphene oxide: The new membrane material

    R. K. Joshi, S. Alwarappan, M. Yoshimura, V. Sahajwalla, Y. Nishina

    Applied Materials Today   1 ( 1 )   1 - 12   2015年

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    記述言語:英語   掲載種別:書評論文,書評,文献紹介等   出版者・発行元:Elsevier Ltd  

    A perfect molecular level separating unit for any kind of species to be filtered is on very high demand. In recent years, graphene oxide has emerged as an important material which can filter ions and molecules. This is an emerging field of research which has drawn extensive attention after the work by Nair et al. [1]. Following their work, various research groups started working in this area in last three years. Herein, we briefly review the recent development on graphene oxide membranes. This review is a summary of some very recent results and contributions made so far in this emerging research field. We have discussed recently developed mechanisms and models to understand the transport through GO based membranes. This review begins with a basic background on membrane technology followed by discussion related to developments of carbon materials based membrane technology. At the end we summarize advantages and disadvantages of membranes based on graphene oxide and discuss their future prospective.

    DOI: 10.1016/j.apmt.2015.06.002

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  • Anti-wear effect of graphene oxide in lubrication by fluorine-containing ionic liquid for steel

    Hiroshi KINOSHITA, Masahiro KONDO, Yuta NISHINA, Masahiro FUJII

    Tribology Online   10 ( 1 )   91 - 95   2015年

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共同研究・競争的資金等の研究

  • 3次元積層グラフェンの層間カップリング抑制による新規ナノ炭素構造体創成

    研究課題/領域番号:21H01763  2021年04月 - 2024年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    小林 慶裕, 仁科 勇太

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    配分額:17420000円 ( 直接経費:13400000円 、 間接経費:4020000円 )

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  • 動的機能を有する物質開拓のための超高速三次元構造ダイナミクス

    研究課題/領域番号:20H01832  2020年04月 - 2023年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    羽田 真毅, 仁科 勇太, 恩田 健, 大村 訓史

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    配分額:18330000円 ( 直接経費:14100000円 、 間接経費:4230000円 )

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  • 水中の分子・イオンと選択的に相互作用する機能性炭素材料の開発

    研究課題/領域番号:20H05224  2020年04月 - 2022年03月

    日本学術振興会  科学研究費助成事業 新学術領域研究(研究領域提案型)  新学術領域研究(研究領域提案型)

    仁科 勇太

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    配分額:4940000円 ( 直接経費:3800000円 、 間接経費:1140000円 )

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  • メタルフリー固体触媒の開発

    研究課題/領域番号:19H02718  2019年04月 - 2022年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    仁科 勇太

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    配分額:17160000円 ( 直接経費:13200000円 、 間接経費:3960000円 )

    カーボンを触媒として利用する有機合成反応の開発は,2010年頃に研究が展開された新しい分野である。そのため,反応メカニズムや活性点に関して未解明な点が多く,カーボン触媒の開発は試行錯誤に頼っていた。本研究では,カーボンやそのモデルとなる低分子に対して化学修飾により官能基やラジカルを付与して触媒性能を評価することにより,触媒活性が発現するメカニズムを解明した。
    本年度は,グラフェンに窒素元素をドープするとともに,ラジカルの量を増やしたカーボン触媒を創出し,ニトロ基の還元反応に適用した。従来のパラジウム触媒や白金触媒とは異なる選択性を示し,炭素触媒特有の性質が明らかとなった。
    また,トルエンが脱水素カップリングする反応においても,ラジカルが寄与している可能性を提示した。この反応においては,ラマンスペクトルにより,高結晶性の炭素ではなく,欠陥を多く有する炭素材料が優れた触媒活性を有することが分かった。また,炭素触媒の構造を模した分子を用いて反応性を評価することにより,トランスアルケンが触媒活性に寄与していることも示した。

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  • 酸化グラフェンナノシート懸濁液による摩擦抵抗と熱伝達の同時向上

    研究課題/領域番号:19K04196  2019年04月 - 2022年03月

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    小方 聡, 仁科 勇太

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    配分額:4420000円 ( 直接経費:3400000円 、 間接経費:1020000円 )

    本研究では抵抗低減と熱伝達率向上を同時達成することを目的として,酸化グラフェンナノシート懸濁液の流動抵抗および熱伝達性能を実験的に明らかにする.2019年度においては,高出力のシリンジポンプを自作し高濃度懸濁液で高レイノルズ数域まで測定出来る装置を作製し実験を行った.具体的には,0.1 wt%,0.3 wt%,0.5 wt%の酸化グラフェンナノシート懸濁液を用いて,円管内圧力損失測定および熱伝達率測定を行った.比較のため二酸化チタン0.5 wt%懸濁液およびPeo 15 ppm水溶液でも同様の実験を行った.本研究の結果,本酸化グラフェンナノシート懸濁液は乱流域で蒸留水と比較して管摩擦係数が最大36.5%低減する抵抗減少効果を明らかにした.この効果はレイノルズ数の増加に伴い極大値を示した後,一定値となる挙動を示した.一方,抵抗減少効果が生じるレイノルズ数範囲で酸化グラフェンナノシート懸濁液のヌセルト数は10‐20 %上昇し伝熱性能が向上することが分かった.この伝熱性能は本レイノルズ数範囲では濃度およびレイノルズ数の増加とともに上昇した.比較のために行った二酸化チタン懸濁液およびPeo水溶液においては,従来から指摘されているように抵抗低減と熱伝達向上を両立させることは不可能であった.熱伝達率と抵抗低減の相関から,本研究で用いた酸化グラフェンナノシート懸濁液はこれらの特性を伴に有していることが明らかにされた.これらの結果は,本研究で初めて明らかにされ,工学的・工業的に意義があることと言える.

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  • バイオ燃料電池用電極の分子デザイン

    研究課題/領域番号:17K18992  2017年06月 - 2019年03月

    日本学術振興会  科学研究費助成事業 挑戦的研究(萌芽)  挑戦的研究(萌芽)

    仁科 勇太, 辻村 清也, 冨永 昌人

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    配分額:6500000円 ( 直接経費:5000000円 、 間接経費:1500000円 )

    酵素を用いるバイオ燃料電池は中性条件下で作動するため,人工臓器の電源など生体内に埋め込んで使用することが可能なデバイスへの応用が期待されている。長期間にわたりエネルギーを供給できるバイオ燃料電池を開発することが望まれているが,実用化に耐えうる安定性と発電能力を有するものは開発されていない。本研究では,1)酵素からの電子移動を効率よく行うメディエーター分子の開発,2)酵素やメディエーター分子を電極に固定化する技術の確立,3)単位面積当たりの酵素やメディエーター分子の量を増やす技術の確立の3つのTaskを達成した。

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  • 酸化グラフェンの潤滑油への分散技術の確立と他添加剤との相乗効果および低温動作

    研究課題/領域番号:17H03165  2017年04月 - 2020年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    木之下 博, 仁科 勇太, 松本 直浩

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    配分額:17160000円 ( 直接経費:13200000円 、 間接経費:3960000円 )

    本申請者らは酸化グラフェンの“分散水”が,室温,鉄系材料の摩擦で摩擦係数0.05の極低摩擦,ほぼゼロ摩耗になることを見出した.鉄系・室温でこのような高潤滑性能の添加剤は存在しない.本研究では実用化を目指し,酸化グラフェンのアルキル化を最適化して,合成潤滑油への分散で高い潤滑性を実現し,他添加剤との混合添加の影響などを詳しく調べ,さらに低温でも潤滑効果を達成する研究を行う.
    本研究では,化学修飾と加熱還元の2通りの方法で疎水化を行い,これらを用い0℃以下の低温で往復摺動摩擦実験を行った.化学修飾による方法では,分散剤であるアルキルアミンの添加量が酸化グラフェンに対し等量もしくは4倍の程度の少ない添加量ほど良好な潤滑特性が得られた.逆に添加量が多いと摩擦はそれほど悪化しなかったが,摩耗は無添加のPAOよりも大きくなった.加熱による方法では全ての加熱温度域で無添加のPAOよりも摩耗が低減された.また,加熱温度が低いほど摩耗が低減し,加熱温度が高くなるにつれて摩耗低減効果が薄くなっていった.いずれの分散方法でも酸化グラフェンの極性を減じる効果が小さい時に,潤滑性向上効果が高くなる傾向であった.これは酸化グラフェンの酸素官能基が多いほど,酸化グラフェンの金属表面への吸着性が高くなるためだと思われる.ただ,酸化グラフェンの極性が高いほど分散性は悪化するので実用化の観点から望ましい事でない.
    また,本年度から境界潤滑になる往復摺動タイプの摩擦試験に加えて,混合および流体潤滑状態にもなるブロックオンリングタイプの摩擦試験機でも摩擦実験を行った.まだ実験数が少なくて明確な結果は得られていないが,往復摺動摩擦試験と同様な傾向は得られている.また一般的に潤滑油に用いられているZnDTPとの相乗効果については,ZnDTPの摩耗低減効果を阻害しなく,摩擦条件によっては相乗効果も認められた.

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  • 反応性雰囲気での超高温プロセスによる新奇ナノ炭素構造体の創成

    研究課題/領域番号:17H02745  2017年04月 - 2020年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    小林 慶裕, 仁科 勇太

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    配分額:18330000円 ( 直接経費:14100000円 、 間接経費:4230000円 )

    超高温・反応性雰囲気での熱プロセスにより、単層グラフェンに匹敵する優れた2次元物性を示すナノ炭素構造体である低欠陥・乱層・多層グラフェン薄膜を合成する手法を開発し、乱層構造に由来する物性的な優位性を検証した。グラフェン薄膜合成には、当初計画していた酸化グラフェンからの作製に加え、テンプレートグラフェン上への直接成長の両面からアプローチした。セルロースナノファイバやナノダイヤモンドをグラフェン層間に挿入するプロセスにより層間相互作用を制御し、単層性の顕在化に有効であること示した。乱層・多層薄膜での単層性の発現や環境効果の遮蔽により、移動度や伝導度などキャリア輸送特性の著しい向上を見出した。

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  • 正負極分極アシストによる超高速充放電Liイオン電池の実現

    研究課題/領域番号:16K14094  2016年04月 - 2018年03月

    日本学術振興会  科学研究費助成事業 挑戦的萌芽研究  挑戦的萌芽研究

    寺西 貴志, 仁科 勇太, 岸本 昭, 林 秀考

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    配分額:3770000円 ( 直接経費:2900000円 、 間接経費:870000円 )

    秒単位での超高速充放電が可能なLiイオン電池の開発が求められている.本研究は正負両極に分極アシスト機構を同時導入することで界面電荷移動の活性を相乗効果的に高めることを目的とした.正極にチタン酸バリウムBaTiO3を液相法により担持したLiCoO2を,負極は酸化グラフェンrGOおよびそれを窒化したN-rGOを作製し,全電池評価を行った.結果,正極BTO-LCO/負極rGOにおいて,改質前の試料(未処理LCO/グラファイト)に対して,10Cレート・5サイクル目で約15倍もの容量改善があった.正負極に導入した分極アシスト機構により,Liイオン電池の出力特性を劇的に改善できることが明らかとなった.

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  • 各種用途に適した酸化グラフェンおよびグラフェンの合成

    研究課題/領域番号:16H00915  2016年04月 - 2018年03月

    日本学術振興会  科学研究費助成事業 新学術領域研究(研究領域提案型)  新学術領域研究(研究領域提案型)

    仁科 勇太

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    配分額:4680000円 ( 直接経費:3600000円 、 間接経費:1080000円 )

    グラフェンに期待される応用は非常に幅広い。要求される性能に応じて、サイズや表面の官能基および欠陥を変える必要がある。本研究では、酸化グラフェンに着目した。酸化グラフェンを還元するとグラフェンに似た材料が得られるためである。また、酸化グラフェンは量産化に適しており、将来的な実用化に適した材料であることも、酸化グラフェンを用いるモチベーションとなっている。酸化グラフェンからグラフェンを作製するためには、酸化グラフェンの化学状態や還元手法を選ぶ必要がある。溶液中の酸化グラフェンをそのまま還元すれば、酸化グラフェンどうしが凝集してしまう。グラフェン膜を形成したい場合には、基板上に酸化グラフェン膜を形成し、その場で還元することが好ましい。また、化学還元法では、還元剤の一部がグラフェン骨格内にドーピングされたり、吸着したりする。さらに、高温でアルコール蒸気に曝すと、還元が進行しつつ欠陥が修復される。また、用途に応じて酸化グラフェンの配向を変える方法を確立し、その物性を評価した。こうして作製した、さまざまな酸素含有量や配向性を有する酸化グラフェンを共同研究先に提供し、用途開拓を行った。リチウムイオン電池、潤滑添加剤、触媒などの従来の用途に加え、本年は遺伝子治療に適用が期待されているsiRNA複合体の作製にも成功した。国内外の多くの研究者との協力関係を構築することにも成功し、さらに酸化グラフェンの量産化への道も開拓することができた。

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  • 原子層物質の国際的提供と共同研究の推進

    研究課題/領域番号:15K21722  2015年11月 - 2019年03月

    日本学術振興会  科学研究費助成事業 新学術領域研究(研究領域提案型)  新学術領域研究(研究領域提案型)

    齋藤 理一郎, 楠 美智子, 依光 英樹, 長汐 晃輔, 長田 俊人, 塚越 一仁, 上野 啓司, 越野 幹人, 若林 克法, 町田 友樹, 坂本 良太, 仁科 勇太, 柳 和宏, 河野 行雄

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    配分額:45890000円 ( 直接経費:35300000円 、 間接経費:10590000円 )

    究極に薄い物質は、1原子層からなる物質である。近年1原子層だけからなる、2次元物質(または原子層物質)が、従来の3次元の物質に比べて顕著で有用な特性を示すことから活発に研究が行われている。その中で、六方窒化ホウ素(hBN) の原子層試料は日本でしか合成することができないので、世界的に提供する必要がある。本国際共同研究加速基金では、このhBNやそのほかの原子層物質を国際的に提供することをサポートした。これによって国際共同研究を促進し、内外の原子層科学の分野の推進に大きく貢献した。また、多くの若手を派遣、招聘することにより、若手研究者の育成にも大きな成果を得た。

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  • 革新的潤滑添加剤である酸化グラフェンを用いた歯車のピッチング損傷の抑止

    研究課題/領域番号:15K13858  2015年04月 - 2017年03月

    日本学術振興会  科学研究費助成事業 挑戦的萌芽研究  挑戦的萌芽研究

    木之下 博, 藤井 正浩, 仁科 勇太, 大宮 祐也, 藤井 正浩

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    配分額:3900000円 ( 直接経費:3000000円 、 間接経費:900000円 )

    繰り返し応力による疲労破壊を抑制するために,接触材料の高硬度化が行われているが十分でない.本研究では,酸化グラフェンを潤滑油に分散させて,疲労寿命を向上させることを目的とする.そのため,酸化グラフェンの潤滑油への分散方法の検討,転動試験機の作製,転動試験を行った.転動試験の結果,酸化グラフェンを分散させることによって疲労寿命の向上が達成された.ただ,疲労寿命を大幅に向上させると思われるトライボフィルムの形成は達成されなかった.今後は,トライボフィルムが向上されるような分散剤を見出し,さらなる疲労寿命の向上を目指す.

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  • 金属-酸化グラフェン複合体触媒を用いる生物由来化合物の水中での化学変換

    研究課題/領域番号:15F15074  2015年

    日本学術振興会  科学研究費助成事業 特別研究員奨励費  特別研究員奨励費

    仁科 勇太, VERMA SANNY

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    配分額:1200000円 ( 直接経費:1200000円 )

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  • 細胞内輸送の高効率化とゴルジ体構造変化に関わるゴルジンタンパク質の機能解析

    研究課題/領域番号:26440055  2014年04月 - 2018年03月

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    佐藤 あやの, 西野 邦彦, 西野 美都子, 仁科 勇太

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    配分額:5070000円 ( 直接経費:3900000円 、 間接経費:1170000円 )

    これまでに、ゴルジンタンパク質群のひとつであるgiantinをノックダウンすると分泌が上がること、ゴルジ体の構造に変化が起こることを示した。本研究課題では、この現象に関わる分子機構を明らかにすることを最終的な目的とし、電子線トモグラフィーなどを用いゴルジ体の構造を詳細に解析した。また、この間、分泌調節に関わる新規小分子を発見したため、新規分子の特徴付けを合わせて行なった。本研究課題の期間は終了したが、引き続き、これらの解析や新規分子のターゲットの探索を行う予定である。

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  • 全く新しいデザイン潤滑添加剤である酸化グラフェンの開拓

    研究課題/領域番号:26289028  2014年04月 - 2018年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    木之下 博, 仁科 勇太

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    配分額:15470000円 ( 直接経費:11900000円 、 間接経費:3570000円 )

    酸化グラフェンは, 1層のグラファイト構造でサイズは数μm以上に達する.特異な点として,非常に多くの酸素官能基を有する.本研究では、酸化グラフェンを水、イオン液体、潤滑油に分散してトライボロジー特性を調べた.その結果,水分散で得られた非常に低い摩擦係数は、トライボフィルムの形成と摺動面に酸化グラフェンが存在することとの協調効果で達成されることが示唆された.イオン液体に分散した時は,若干の摩擦係数低減効果が見られた.さらに添加によってイオン液の腐食摩耗は抑えられたが,酸化グラフェンの添加濃度が高いと摩耗が大きくなった.潤滑油への添加ではアニオン系界面活性剤を用いることで潤滑性が向上した.

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  • 酸化グラフェンの欠陥を有機分子で修復する

    研究課題/領域番号:26107528  2014年04月 - 2016年03月

    日本学術振興会  科学研究費助成事業 新学術領域研究(研究領域提案型)  新学術領域研究(研究領域提案型)

    仁科 勇太

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    配分額:4810000円 ( 直接経費:3700000円 、 間接経費:1110000円 )

    酸化グラフェン(Graphene Oxide, GO)は、溶液中の化学プロセスで大量合成が可能なため、実用化が最も近いナノカーボン材料の一つであると期待されている。この性質は、既存の化学工場の設備を活用できるという特徴を持っている。また、合成に必要な黒鉛は、安価かつ大量に入手可能な材料で、資源枯渇、自然環境への影響が小さいという特徴がある。現在、GOは、電極、触媒、水浄化、放熱、樹脂補強材、潤滑剤などのさまざまな用途が見込まれている。しかし、GOは濃硫酸中で強力な酸化剤を用いて合成するため、その製造条件の設定が難しく、安全かつ効率的に大量合成する方法が確立されていない。これまで我々は、GOを安全かつ大量に製造する技術を開発し、さまざまな用途への実用化に向けて、研究を進めてきた。
    GOの性質は,用いる黒鉛の種類や形状・サイズにより大きく変化する。GOの性質を変える本質を解明することは,学術面のみならず品質の保証や再現性の確保の観点においても重要である。GOを化学修飾したり,酸化・還元をメカニズムに基づき行うことで,再現性良く望みのGOを合成することに成功した。

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  • パラジウム-グラフェン複合体:価数制御による高機能触媒の創出

    研究課題/領域番号:25870457  2013年04月 - 2015年03月

    日本学術振興会  科学研究費助成事業 若手研究(B)  若手研究(B)

    仁科 勇太

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    配分額:4420000円 ( 直接経費:3400000円 、 間接経費:1020000円 )

    酸化グラフェン(Graphene Oxide, GO)は,安価かつ大量に存在する黒鉛を化学的酸化することにより溶液中で合成可能であり,層の厚みを炭素1原子の単層にすることができ,さらに他の材料(高分子や金属ナノ粒子等)との複合化が容易である.我々は,GOの効率的合成法を開発し,金属-GO複合体および金属-グラフェン複合体を調製する方法へと展開した.さらに,金属-GO複合体を用いる高活性かつ高選択的な触媒反応を開発した.

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  • 7族元素を用いるC-H結合活性化を基盤とする有機合成反応の開発

    研究課題/領域番号:08J06785  2008年 - 2009年

    日本学術振興会  科学研究費助成事業 特別研究員奨励費  特別研究員奨励費

    仁科 勇太

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    配分額:1200000円 ( 直接経費:1200000円 )

    単純な有機化合物から複雑な化合物を合成するには、数段階にわたる炭素-炭素結合(C-C結合)形成と官能基変換を組み合わせることになるため、効率の高い合成反応の開発が望まれている。有機ハロゲン化合物を用いる反応では、あらかじめ基質分子内にハロゲン原子(X)の導入が必要であり、反応後にそのハロゲンが不要な塩として副生する。これに対し、有機化合物中に多く存在する炭素-水素結合(C-H結合)から直接にC-C結合が形成できれば、C-H結合を一旦、C-X結合などに変換する必要がなく、反応ステップ数も減るとともに、当然ながら反応のあとにハロゲン塩が副生しない。C-H結合活性化反応の適用限界を拡げることは、有機合成において、重要なことである。
    本研究では、有機合成の触媒として使われることが少なかった7族元素の触媒作用を明らかにし、新しいコンセプトに基づいて反応開発を行なった。その結果、C-H結合活性化反応の適用範囲を拡げ、実用的で一般的な合成手法へと展開することができた。具体的には、これまではベンゼン環上のC-H結合活性化が大部分を占めていたが、本研究ではそれをアルケンのC-H結合活性化へと展開した。C-H結合へ挿入する分子も極性をもたないアルキンからアルデヒドのような分極したものまで、幅広い基質で適用できる反応条件を見いだすことができた。さらに現在は、より一般的な基質であるアルカンのC-H結合を直接変換する反応の開発を行なっている。従来、有機合成の原料として認識されていなかった炭化水素を用いた効率的な反応につながる可能性を秘めている。

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