Updated on 2022/08/21

写真a

 
NISHINA Yuta
 
Organization
Research Core for Interdisciplinary Sciences Associate Professor
Position
Associate Professor
Profile

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)

External link

Degree

  • PhD ( Okayama University )

Research Interests

  • Materials chemistry

  • Organic chemistry

  • Catalysis

  • Carbon

Research Areas

  • Nanotechnology/Materials / Structural organic chemistry and physical organic chemistry

  • Nanotechnology/Materials / Organic functional materials

  • Life Science / Bioorganic chemistry

  • Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Catalyst and resource chemical process

  • Nanotechnology/Materials / Functional solid state chemistry

Research History

  • 岡山大学 異分野融合先端研究コア

    2018.10

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  • 岡山大学 異分野融合先端研究コア 准教授

    2014.3 - 2018.10

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  • Okayama University   Assistant Professor

    2010.4 - 2014.3

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Committee Memberships

  • 高分子学会   「高分子」 編集委員  

    2020.4   

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  • 炭素材料学会   「炭素」 編集委員  

    2020.4   

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Papers

  • Optimizing the structure and molecular weight of polymers for graphene dispersants

    Shimpei Takeda, Yuta Nishina

    POLYMER JOURNAL   2022.8

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SPRINGERNATURE  

    Graphene is an allotrope of carbon consisting of a single-atom-thick honeycomb lattice nanostructure. Among the various preparation methods for graphene, the liquid-phase exfoliation of graphite is mass-producible and cost-effective. To facilitate the exfoliation of graphite in organic solvents, polymers can be employed as dispersants. We synthesized polymer dispersants with various monomer ratios and molecular weights and investigated the efficient acquisition of graphene from graphite. Graphene with a uniform thickness was obtained when graphite was exfoliated using an optimized polymer dispersant. The optimized polymer enabled a high yield and concentration of graphene using liquid-phase exfoliation.

    DOI: 10.1038/s41428-022-00684-2

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  • Growth of ZIF-8 Nanoparticles In Situ on Graphene Oxide Nanosheets: A Multifunctional Nanoplatform for Combined Ion-Interference and Photothermal Therapy

    Chunxu Lv, Wenyan Kang, Shuo Liu, Pishan Yang, Yuta Nishina, Shaohua Ge, Alberto Bianco, Baojin Ma

    ACS NANO   16 ( 7 )   11428 - 11443   2022.7

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER CHEMICAL SOC  

    The regulation of intracellular ions' overload to interrupt normal bioprocesses and cause cell death has been developed as an efficient strategy (named as ion-interference therapy/IIT) to treat cancer. In this study, we design a multifunctional nanoplatform (called BSArGO@ZIF-8 NSs) by in situ growth of metal organic framework nanoparticles (ZIF-8 NPs) onto the graphene oxide (GO) surface, subsequently reduced by ascorbic acid and modified by bovine serum albumin. This nanocomplex causes the intracellular overload of Zn2+, an increase of reactive oxygen species (ROS), and exerts a broad-spectrum lethality to different kinds of cancer cells. BSArGO@ZIF-8 NSs can promote cell apoptosis by initiating bim (a pro-apoptotic protein)-mediated mitochondrial apoptotic events, up-regulating PUMA/ NOXA expression, and down-regulating the level of Bid/p53AIP1. Meanwhile, Zn2+ excess triggers cellular dysfunction and mitochondria damage by activating the autophagy signaling pathways and disturbing the intracellular environmental homeo-stasis. Combined with the photothermal effect of reduced GO (rGO), BSArGO@ZIF-8 NSs mediated ion-interference and photothermal combined therapy leads to effective apoptosis and inhibits cell proliferation and angiogenesis, bringing a higher efficacy in tumor suppression in vivo. This designed Zn-based multifunctional nanoplatform will allow promoting further the development of IIT and the corresponding combined cancer therapy strategy.

    DOI: 10.1021/acsnano.2c05532

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  • Combined Photothermal and Photodynamic Therapy for Cancer Treatment Using a Multifunctional Graphene Oxide

    Shi Guo, Zhengmei Song, Ding-Kun Ji, Giacomo Reina, Jean-Daniel Fauny, Yuta Nishina, Cecilia Menard-Moyon, Alberto Bianco

    PHARMACEUTICS   14 ( 7 )   2022.7

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:MDPI  

    Graphene oxide (GO) is one of the most studied nanomaterials in many fields, including the biomedical field. Most of the nanomaterials developed for drug delivery and phototherapies are based on noncovalent approaches that lead to an unspecific release of physisorbed molecules in complex biological environments. Therefore, preparing covalently functionalized GO using straightforward and versatile methods is highly valuable. Phototherapies, including photothermal therapy (PTT) and photodynamic therapy (PDT), have shown great potential as effective therapeutic approaches against cancer. To overcome the limits of a single method, the combination of PTT and PDT can lead to a combined effect with a higher therapeutic efficiency. In this work, we prepare a folic acid (FA) and chlorin e6 (Ce6) double-functionalized GO for combined targeted PTT/PDT. This conjugate can penetrate rapidly into cancer cells and macrophages. A combined effect of PTT and PDT is observed, leading to a higher killing efficiency toward different types of cells involved in cancer and other diseases. Our work provides a simple protocol to prepare multifunctional platforms for the treatment of various diseases.

    DOI: 10.3390/pharmaceutics14071365

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  • Nanocellulose Paper Semiconductor with a 3D Network Structure and Its Nano–Micro–Macro Trans-Scale Design

    Hirotaka Koga, Kazuki Nagashima, Koichi Suematsu, Tsunaki Takahashi, Luting Zhu, Daiki Fukushima, Yintong Huang, Ryo Nakagawa, Jiangyang Liu, Kojiro Uetani, Masaya Nogi, Takeshi Yanagida, Yuta Nishina

    ACS Nano   16 ( 6 )   8630 - 8640   2022.6

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Chemical Society (ACS)  

    Semiconducting nanomaterials with 3D network structures exhibit various fascinating properties such as electrical conduction, high permeability, and large surface areas, which are beneficial for adsorption, separation, and sensing applications. However, research on these materials is substantially restricted by the limited trans-scalability of their structural design and tunability of electrical conductivity. To overcome this challenge, a pyrolyzed cellulose nanofiber paper (CNP) semiconductor with a 3D network structure is proposed. Its nano-micro-macro trans-scale structural design is achieved by a combination of iodine-mediated morphology-retaining pyrolysis with spatially controlled drying of a cellulose nanofiber dispersion and paper-crafting techniques, such as microembossing, origami, and kirigami. The electrical conduction of this semiconductor is widely and systematically tuned, via the temperature-controlled progressive pyrolysis of CNP, from insulating (10(12) Omega cm) to quasimetallic (10(-2) Omega cm), which considerably exceeds that attained in other previously reported nanomaterials with 3D networks. The pyrolyzed CNP semiconductor provides not only the tailorable functionality for applications ranging from water-vapor-selective sensors to enzymatic biofuel cell electrodes but also the designability of macroscopic device configurations for stretchable and wearable applications. This study provides a pathway to realize structurally and functionally designable semiconducting nanomaterials and all-nanocellulose semiconducting technology for diverse electronics.

    DOI: 10.1021/acsnano.1c10728

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  • Graphene Oxide-Based Multi-Component Antimicrobial Hydrogels

    Mohammed Zahedul Islam Nizami, Benoit Denis Louis Campeon, Akira Satoh, Yuta Nishina

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   95 ( 5 )   713 - 720   2022.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:CHEMICAL SOC JAPAN  

    Graphene oxide (GO)-based hydrogel composed of magnesium oxide (MgO) and povidone-iodine (PVP-I) is synthesized. GO in the hydrogel plays two roles; gelator by self-assembling and carrier for MgO and PVP-L MgO particles act as cross-linking initiators and fillers that increase the cohesion and adhesion strengths of the hydrogels. Besides, MgO promotes antibacterial activities and regulates cellular activities over the lifetime of the hydrogel. In addition, PVP-I slowly releases free iodine from the hydrogel, exhibiting germicidal activity over time. A combination of GO, MgO, and PVP-I in the hydrogel exhibit improved electrical conductivity, fluid uptake ability, water retention capacity, water vapor transmission rate, and integrity value. Furthermore, the hydrogel has shown antimicrobial properties against Staphylococcus aureus. These findings are unique and indicate that GO-based hydrogel could be a promising material for biomedical application, especially for the treatment of pathological and surgical wounds.

    DOI: 10.1246/bcsj.20220017

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  • Surface Functionalities of Graphene Oxide with Varying Flake Size

    Yee Yee Khine, Xiaojun Ren, Dewei Chu, Yuta Nishina, Tobias Foller, Rakesh Joshi

    INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH   61 ( 19 )   6531 - 6536   2022.5

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    The size of graphene oxide (GO) flakes may change the chemical composition on the surface, thereby altering its intrinsic properties. The current work explored the variations of surface moieties with four different sizes: 0.3, 0.7, 20, and 42 mu m(2), which were obtained with morphological integrity under controlled fabrication technique. On the basis of comprehensive analyses, slight variations in the composition of each chemical moiety were observed. At the same time, slight fluctuations were found for both edge-to-basal plane (E/B) and carbon-to-oxygen (C/O) ratios with increasing flake size.

    DOI: 10.1021/acs.iecr.2c00748

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  • Synergic effect of graphene oxide and boron nitride on the mechanical properties of polyimide composite films

    Yi Kai Cheng, Benoit Denis Louis Campeon, Seiji Obata, Yuta Nishina

    NANOSCALE ADVANCES   4 ( 10 )   2339 - 2345   2022.5

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    The addition of two-dimensional (2D) materials into polymers can improve their mechanical properties. In particular, graphene oxide (GO) and hexagonal boron nitride (h-BN) are expected to be potential nanoplatelet additives for polymers. Interactions between such nanoplatelets and polymers are effective in improving the above properties. However, no report has investigated the effect of using two types of nanoplatelets that have good interaction with polymers. In this study, we fabricated polyimide (PI) films that contain two types of nanoplatelets, amine-functionalized h-BN (BN<INF>NH<INF>2</INF></INF>) and GO. We have elucidated that the critical ratio and the content of BN<INF>NH<INF>2</INF></INF> and GO within PI govern the films' mechanical properties. When the BN<INF>NH<INF>2</INF></INF>/GO weight ratio was 52 : 1 and their content was 1 wt% in the PI film, the tensile modulus and tensile strength were increased by 155.2 MPa and 4.2 GPa compared with the pristine PI film.

    DOI: 10.1039/d2na00078d

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  • Grafting redox-active molecules on graphene oxide through a diamine linker: length optimization for electron transfer

    Rizwan Khan, Yuta Nishina

    DALTON TRANSACTIONS   51 ( 5 )   1874 - 1878   2022.2

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    A redox-active molecule is grafted on graphene oxide (GO) via successive reactions. In the first step, GO is modified with diamine, which acts as a linker for the redox-active molecule. In the second step, the redox-active molecule is attached to the amino group of the linker by amide bond formation. Through these processes GO is partially reduced, enhancing its electrochemical properties. The structure of the functionalized GO is characterized by XPS, TGA, FTIR, and CV, and applied for electrodes in supercapacitors (SCs). The distance and direction of the redox-active molecule on the electrode affect the SC performance; ethylene diamine is the most promising linker to efficiently transfer electrons from the redox-active molecule to the electrode surface.

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  • Uniform coating of magnesium oxide crystal with reduced graphene oxide achieves moisture barrier performance

    Akinori Saito, Seiji Obata, Yuta Nishina

    Applied Surface Science   573   2022.1

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    Magnesium oxide (MgO) has high thermal conductivity while keeping insulation; thus, MgO is attractive material as a filler for thermosetting or thermoplastic resins. However, MgO readily hydrates with water or moisture. Thus, the surface of MgO is coated with organic or inorganic substances. We focused on graphene oxide (GO) as a surface coating agent. It has a 2-dimensional thin sheet structure, oxygen functional groups on the surface, and negative zeta-potential. Typically, GO has been used as a support material for metal nanoparticles. In this research, GO was coated on MgO micro-crystal surface to improve the surface character of MgO. The negatively charged GO and the positively charged MgO were combined with strong interaction. 0.5 wt% GO coated MgO showed excellent moisture resistance compared to organic substances coating. Coating of MgO with GO or reduced GO (rGO) is effective to overcome the weaknesses of MgO. Due to the hydrophilicity and high thermal conductivity of rGO, MgO/rGO composite can be a filler for high moisture resistance and thermal conductivity.

    DOI: 10.1016/j.apsusc.2021.151483

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  • Oxidation-degree-dependent moisture-induced actuation of a graphene oxide film

    Waka Nakanishi, Yoshihiro Yamauchi, Yuta Nishina, Masafumi Yoshio, Masayuki Takeuchi

    RSC ADVANCES   12 ( 6 )   3372 - 3379   2022.1

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    Multilayered films prepared from graphene oxide (GO) subjected to a single oxidation process (1GO) can actuate in response to moisture, whereas those prepared from GO subjected to two oxidation processes (2GO) lose this ability. To elucidate the origin of this difference, the structures and properties of various multilayered films and their contents were analyzed. According to atomic force microscopy images, the lateral size of the GO monolayer in 2GO (2.0 +/- 0.4 mu m) was smaller than that in 1GO (3.2 +/- 0.4 mu m), although this size difference did not affect actuation. Scanning electron microscopy images of the cross sections of both films showed fine multilayered structures and X-ray diffraction measurements showed the moisture sensitive reversible change in the interlayer distances for both films. Both films adsorbed 30 wt% moisture in 60 s with different water contents at the bottom moist sides and top air sides of the films. Nanoindentation experiments showed hardness values (1GO: 156 +/- 67 MPa; 2GO: 189 +/- 97 MPa) and elastic modulus values (1GO: 4.7 +/- 1.7 GPa; 2GO: 5.8 +/- 3.2 GPa) typical of GO, with no substantial difference between the films. On the contrary, the 1GO film bent when subjected to a weight equal to its own weight, whereas the 2GO film did not. Such differences in the macroscopic hardness of GO films can affect their moisture-induced actuation ability.

    DOI: 10.1039/d1ra07773b

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  • Design of a graphene oxide-BODIPY conjugate for glutathione depletion and photodynamic therapy

    Giacomo Reina, Amalia Ruiz, Barbara Richichi, Giacomo Biagiotti, Gina E. Giacomazzo, Lucas Jacquemin, Yuta Nishina, Cecilia Menard-Moyon, Wafa T. Al-Jamal, Alberto Bianco

    2D MATERIALS   9 ( 1 )   2022.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing Ltd  

    Boron dipyrromethene derivates (BODIPYs) are promising photosensitisers (PSs) for cancer treatment using photodynamic therapy (PDT). This study investigates the functionalisation of graphene oxide (GO) with a BODIPY derivate for glutathione (GSH) depletion and PDT. The functionalisation of GO with a 3,5-dichloro-8-(4-boronophenyl) BODIPY via a diol derivatisation with the phenyl boronic acid moiety at the meso position of the BODIPY core, allowed to preserve the intrinsic properties of GO. We demonstrated that both chlorine atoms were substituted by GSH in the presence of glutathione transferase (GST), inducing a relevant bathochromic shift in the absorption/emission features and thus generating the active PS. Ex vitro assessment using cell lysates containing cytoplasmatic GST revealed the intracellular catalytic mechanism for the nucleophilic substitution of the GO-BODIPY adduct with GSH. Confocal microscopy studies showed important differences in the cellular uptake of free BODIPY and GO-BODIPY and revealed the coexistence of GO-BODIPY, GO-BODIPY-GS, and GO-BODIPY-GS(2) species inside vesicles and in the cytoplasm of the cells after 24 h of incubation. In vitro biocompatibility and safety of GO and GO-BODIPY were evaluated in 2D and 3D models of prostate adenocarcinoma cells (PC-3), where no toxicity was observed up to 100 mu g ml(-1) of GO/GO-BODIPY in all treated groups 24 h post-treatment (cell viability > 90%). Only a slight decrease to 80% at 100 mu g ml(-1) was observed after 48 h of incubation. We demonstrated the efficacy of a GO adduct containing an alpha-chlorine-substituted BODIPY for the simultaneous depletion of intracellular GSH and the photogeneration of reactive oxygen species using a halogen white light source (5.4 mW cm(-2)) with a maximum in the range of 500-800 nm, which significantly reduced cell viability (<50%) after irradiation. Our study provides a new vision on how to apply BODIPY derivates and potentiate the toxicity of PDT in prostate and other types of cancer.

    DOI: 10.1088/2053-1583/ac4572

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  • Synthesis of microporous polymers with exposed C60 surfaces by polyesterification of fullerenol

    Hirotomo Nishihara, Akio Harigaya, Alberto Castro-Muñiz, Mao Ohwada, Takashi Kyotani, Yuta Nishina

    Chemical Communications   58 ( 50 )   7086 - 7089   2022

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    Fullerene-based microporous polymers synthesized by polyesterification of fullerenol possess excellent stability against solvents and exposed C60 surfaces confirmed by enhanced hydrogen spillover.

    DOI: 10.1039/d2cc00728b

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  • 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 )   2021.12

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:NATURE RESEARCH  

    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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  • Bulk-scale synthesis of randomly stacked graphene with high crystallinity

    Zizhao Xu, Shingo Nakamura, Taiki Inoue, Yuta Nishina, Yoshihiro Kobayashi

    CARBON   185   368 - 375   2021.11

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:PERGAMON-ELSEVIER SCIENCE LTD  

    Since the strong interlayer interaction of AB-stacked graphene in bulk form degrades the superior property of single-layer graphene, formation of randomly stacked graphene is required to apply the high performances of graphene to macroscopic devices. However, conventional methods to obtain bulk-scale graphene suffer from a low crystallinity and/or the formation of a thermodynamically stable AB-stacked structure. This study develops a novel approach to produce bulk-scale graphene with a high crystallinity and high fractions of random stacking by utilizing the porous morphology of a graphene oxide sponge and an ultrahigh temperature treatment of 1500-1800 degrees C with ethanol vapor. Raman spectroscopy indicates that the obtained bulk-scale graphene sponge possesses a high crystallinity and a high fraction of random stacking of 80%. The large difference in the random-stacking ratio between the sponge and the aggregate samples confirms the importance of accessibility of ethanol-derived species into the internal area. By investigating the effect of treatment temperature, a higher random-stacking ratio is obtained at 1500 degrees C. Moreover, the AB-stacking fraction was reduced to less than 10% by introducing cellulose nanofiber as a spacer to prevent direct stacking of graphene. The proposed method is effective for large-scale production of high-performance bulk-scale graphene. (C) 2021 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.carbon.2021.09.034

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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   2021.10

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    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   2021.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER ADVANCED TECHNOLOGY  

    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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  • Grafting chelating groups on 2D carbon for selective heavy metal adsorption

    Risa Shibahara, Kazuhide Kamiya, Yuta Nishina

    NANOSCALE ADVANCES   3 ( 20 )   5823 - 5829   2021.10

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    Iminodiacetic acid (IDA) is a tridentate ligand, which can capture metal ions by forming two fused five-membered chelate rings. In this study, we fixed IDA moieties onto a two-dimensional nanocarbon, graphene oxide (GO), to obtain materials with high and selective adsorption of metal ions. The synthesis conditions for the GO-IDA composites were optimized, then their structures were characterized by infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and CHN elemental analysis. In addition, the heavy-metal removal efficiency and selectivity of the GO-IDA composites with different length alkyl linkers between the GO and IDA were investigated. An aqueous solution containing 10 metal ions (Al, As, B, Cd, Cr, Cu, Mn, Pb, Se, and Zn) was used as a model for contaminated water at pH 7, and the interactions of the ions with GO-IDA were in the order of Cu > Pb > As > B > Zn > Al approximate to Se. The interaction between Cu and GO-IDA was confirmed by XPS and extended X-ray absorption fine structure (EXAFS), which showed that Cu was coordinated to IDA.

    DOI: 10.1039/d1na00435b

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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   2021.9

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    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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  • Enabling the fast lithium storage of large-scalable gamma-Fe2O3/Carbon nanoarchitecture anode material with an ultralong cycle life

    Sadeeq Ullah, Benoit D. L. Campeon, Shumaila Ibraheem, Ghulam Yasin, Rajesh Pathak, Yuta Nishina, Tuan Anh Nguyen, Yassine Slimani, Qipeng Yuan

    JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY   101   379 - 386   2021.9

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    Two-dimensional (2D) materials are generally expected to have superior lithium-ion (LIBs) performances compare with their bulk counterpart as they display superior specific surface area. In this context, the development of 2D maghemite would be of great interest owing to its high theoretical specific capacity, natural abundance, and relatively low cost and toxicity; however, maghemite do not have a layered crystalline structure. Herein, to overcome this hindrance, gamma-Fe2O3 has been enclosed within a 2D carbon matrix via a simple and facile synthesis strategy based on the complexation of ethylene glycol with aqueous iron species by hydrolysis and condensation reactions followed by its carbonization. As obtained 2D carbon gamma-Fe2O3 nanosheet composite (C-EG-Fe) is composed of 41.3 wt.% carbon and 10.2 wt.% Fe. When used as anode materials in LIBs, C-EG-Fe demonstrated the enhanced initial discharge capacity of 1589 mAh g(-1) at 100 mA g(-1), and outstanding ultralong cycling performance with the significant stable capacity of 700 mAh g(-1) and 230 mAh g(-1) at the higher current rate of 0.5 A g(-1) and 10 A g(-1) for more than 300 and 6000 cycles, respectively. These results enable a promising avenue to design the large-scale production of 2D C-EG-Fe sheets-based nanostructured anode materials for next-generation LIBs for largescale energy storage applications. (C) 2021 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

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  • Insights into carbon nanotube-assisted electro-oxidation of polycyclic aromatic hydrocarbons for mediated bioelectrocatalysis

    Paulo Henrique M. Buzzetti, Pierre-Yves Blanchard, Emerson Marcelo Girotto, Yuta Nishina, Serge Cosnier, Alan Le Goff, Michael Holzinger

    CHEMICAL COMMUNICATIONS   57 ( 71 )   8957 - 8960   2021.9

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    A series of polycyclic aromatics, naphthalene, phenanthrene, perylene, pyrene, 1-pyrenebutyric acid N-hydroxysuccinimide ester (pyrene NHS) and coronene, were immobilized via pi stacking on carbon nanotube (CNT) electrodes and electro-oxidized in aqueous solutions. The obtained quinones were characterized and evaluated for the mediated electron transfer with FAD dependent glucose dehydrogenase during catalytic glucose oxidation.

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  • High valence states of Pd supported on ferroelectric BaTiO3 driven by electric polarization

    Tasuku Yoshida, Jun Kano, Masaichiro Mizumaki, Yusuke Tamenori, Kiyofumi Nitta, Kazuo Kato, Satoshi Hinokuma, Norihiro Oshime, Satoshi Hirose, Hitoshi Mikami, Naoshi Ikeda, Tatsuo Fujii, Yuta Nishina, Tomoko Okubo

    Applied Physics Letters   119 ( 9 )   092904 - 092904   2021.8

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    At a metal-ferroelectric junction, it has been considered that the electric polarization of the ferroelectric material can affect the electronic structure of the neighboring metal. Here, we demonstrate that the valence state of Pd can be shifted to the unstable high value of 4+ by the electric field of electric polarization in ferroelectric BaTiO3. Study of the absorption fine structure of both hard and soft x rays revealed the existence of Pd4+ states on the surface of Pd oxide nanoparticles. The positions of Pd and oxygen atoms are shifted in opposite directions by the electric field due to the electric polarization of ferroelectric BaTiO3. The atomic displacement of Pd and O forms a zigzag structure, in which the coordination number of Pd atoms is changed from four to six, producing a quadrivalent state. This report presents experimental evidence that ferroelectric polarization can control the electronic states of neighboring metal atoms, and we suggest that using the ferroelectric support effect may produce a new type of catalyst.

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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 )   2021.7

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    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.

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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   2021.7

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    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.

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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   2021.6

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    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.

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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   2021.6

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    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.

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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   2021.5

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    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.

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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   2021.4

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    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.

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  • REDOX ACTIVITY OF GRAPHENE OXIDE ANALOGUES IN ORGANIC REACTIONS

    Yuta Nishina

    CARBON   175   606 - 606   2021.4

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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   2021.3

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    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.

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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   2021.3

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    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

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  • Electrochemical Production of Graphene Analogs from Various Graphite Materials

    Masato Komoda, Yuta Nishina

    CHEMISTRY LETTERS   50 ( 3 )   503 - 509   2021.3

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    Oxidation of graphite is widely recognized as a promising method for large-scale production of graphene-like materials. Chemical oxidation of graphite has been developed for more than 100 years, while electrochemical oxidation has attracted attention over the last 10 years as a simple, safe, and controllable production method for graphene. This review summarizes the electrochemical production of graphene analogs focusing on the electrochemical conditions and form of starting graphite that affect the properties of the products. Electrochemical treatment of graphite by direct current has been applied to various graphite, such as HOPG, graphite rod, graphite foil, and powdered graphite, and generates deeply oxidized graphene materials. On the other hand, treatments with alternative current generate low oxygen content products. Therefore, the electrochemical treatment of graphite provides an option for the controlled production of graphene-like materials.

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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 )   2021.2

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    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.

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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   2021.2

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    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.

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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   2021.2

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    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

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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   2021.1

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    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.

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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   2021.1

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    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.

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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   2020.12

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    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.

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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   2020.12

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    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   2020.11

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    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 International journal

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

    Nanoscale   12 ( 42 )   21780 - 21787   2020.11

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    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   2020.11

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    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.

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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   2020.10

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    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

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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   2020.10

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    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.

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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   2020.9

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    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

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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   2020.7

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    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.

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  • Chemical and electrochemical synthesis of graphene oxide-a generalized view International journal

    Yuta Nishina, Siegfried Eigler

    Nanoscale   12 ( 24 )   12731 - 12740   2020.6

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    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 Reviewed

    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   2020.6

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    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.

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  • Graphene-based carbocatalysts for carbon-carbon bond formation International journal

    Muhammad Sohail Ahmad, Yuta Nishina

    Nanoscale   12 ( 23 )   12210 - 12227   2020.6

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    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.

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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   2020.4

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    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.

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  • A Simple and Robust Functionalization of Graphene for Advanced Energy Devices International journal

    Rizwan Khan, Ryo Nakagawa, Benoit Campeon, Yuta Nishina

    ACS Applied Materials and Interfaces   12 ( 11 )   12736 - 12742   2020.3

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    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.

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

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

    Carbon   158   356 - 363   2020.3

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    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

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  • Structural optimization of alkylbenzenes as graphene dispersants

    Shimpei Takeda, Yuta Nishina

    Processes   8 ( 2 )   2020.2

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    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.

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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   2020.2

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    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 International journal

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

    Angewandte Chemie - International Edition   59 ( 4 )   1542 - 1547   2020.1

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    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.

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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   2020.1

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    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

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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   2020.1

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    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 International journal

    Yuki Hori, Koichiro Kubo, Yuta Nishina

    Macromolecular Rapid Communications   42 ( 8 )   e2000577   2020

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    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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  • Dorsal-to-Ventral Cortical Expansion Is Physically Primed by Ventral Streaming of Early Embryonic Preplate Neurons

    Kanako Saito, Mayumi Okamoto, Yuto Watanabe, Namiko Noguchi, Arata Nagasaka, Yuta Nishina, Tomoyasu Shinoda, Akira Sakakibara, Takaki Miyata

    CELL REPORTS   29 ( 6 )   1555 - +   2019.11

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    Despite recent studies elucidating the molecular mechanisms underlying cortical patterning and map formation, very little is known about how the embryonic pallium expands ventrally to form the future cortex and the nature of the underlying force-generating events. We find that neurons born at embryonic day 10 (E10) in the mouse dorsal pallium ventrally stream until E13, thereby superficially spreading the preplate, and then constitute the subplate from E14. From E11 to E12, the preplate neurons migrate, exerting pulling and pushing forces at the process and the soma, respectively. At E13, they are morphologically heterogeneous, with similar to 40% possessing corticofugal axons, which are found to be in tension. Ablation of these E10-born neurons attenuates both deflection of radial glial fibers (by E13) and extension of the cortical plate (by E14), which should occur ventrally, and subsequently shrinks the postnatal neocortical map dorsally. Thus, the preplate stream physically primes neocortical expansion and arealization.

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  • Selective Hydrogenation by Carbocatalyst: The Role of Radicals. International journal

    Muhammad Sohail Ahmad, Huixin He, Yuta Nishina

    Organic letters   21 ( 20 )   8164 - 8168   2019.10

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    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.

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

    Ayano Satoh, Yuta Nishina

    BIOORGANIC & MEDICINAL CHEMISTRY LETTERS   29 ( 19 )   2019.10

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    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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  • Electrosynthesis of Pyrenediones on Carbon Nanotube Electrodes for Efficient Electron Transfer with FAD-dependent Glucose Dehydrogenase in Biofuel Cell Anodes

    Pierre-Yves Blanchard, Paulo Henrique M. Buzzetti, Bridget Davies, Yannig Nedellec, Emerson Marcelo Girotto, Andrew J. Gross, Alan Le Goff, Yuta Nishina, Serge Cosnier, Michael Holzinger

    CHEMELECTROCHEM   6 ( 20 )   5242 - 5247   2019.10

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    A particularly efficient redox mediator for electron transfer between FAD-dependent glucose dehydrogenase (FAD-GDH) and carbon nanotube (CNT) based electrodes can be obtained via electrosynthetic oxidation of pyrene in aqueous buffer solution. H-1-NMR spectroscopic studies reveal the formation of a 2 : 1 mixture of 1,6-pyrenedione and 1,8-pyrenedione at the electrode. The formed pyrenedione exhibits a well-defined surface-bound redox system at -0.1 V vs. SCE and provides excellent electron transfer kinetics with this enzyme. Furthermore, the pi-system of pyrenedione allows improved stacking behavior with the CNT walls, leading to enhanced stabilities compared to commonly used mediators like naphthoquinone. The electrosynthesis of pyrenedione for catalytic glucose oxidation is optimal at pH 2 using cyclic voltammetry or chronoamerometry. It is envisioned that the electrosynthetic methodology can be expanded to form different redox mediators for a series of enzymes.

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  • Selective Reduction Mechanism of Graphene Oxide Driven by the Photon Mode versus the Thermal Mode. Reviewed International journal

    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   2019.9

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    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.

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

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

    ADVANCED FUNCTIONAL MATERIALS   29 ( 39 )   2019.9

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    The design of multifunctional materials able to both selectively deliver a drug into cells in a targeted manner and display an enhanced propensity for biodegradation is an important goal. Here, graphene oxide (GO) is functionalized with the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) known to interact with the formyl peptide receptor, which is expressed in different cancer cells, including cervical carcinoma cells. This study highlights the ability of GOfMLP for targeted drug delivery and cancer cell killing and the subsequent degradation capacity of the hybrid. Biodegradation is assessed via Raman spectroscopy and transmission electron microscopy. The results show that GOfMLP is susceptible to faster myeloperoxidase-mediated degradation. The hybrid material, but not GO, is capable of inducing neutrophil degranulation with subsequent degradation, being the first study showing inducible neutrophil degradation by the nanomaterial itself with no prior activation of the cells. In addition, confocal imaging and flow cytometry using HeLa cells demonstrate that GOfMLP is able to deliver the chemotherapeutic agent doxorubicin faster into cells, inducing higher levels of apoptosis, when compared to nonfunctionalized GO. The results reveal that GOfMLP is a promising carrier able to efficiently deliver anticancer drugs, being endowed with the ability to induce its own biodegradation.

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  • Ir-Catalyzed Reduction of Carbonyl Compounds Using Biogenetic Alcohols

    Yuta Nishina

    INORGANICS   7 ( 9 )   2019.9

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    Biomass has gained great attention as an alternative to fuel-derived chemicals. This report concerns new catalytic systems consisting of [IrCp*Cl-2](2) (Cp*: Pentamethylcyclopentadienyl) for the reduction of aldehyde and biogenetic alcohols as hydrogen sources. [IrCp*Cl-2](2) has been used as a transfer hydrogenation catalyst using fossil fuel-derived alcohols as hydrogen sources in the presence of a base. In contrast, our system does not require any base, and the reaction can proceed in water. Various types of biogenetic alcohols can be used as hydrogen sources, such as monosaccharides, oligosaccharides, and glycerol. Aromatic and aliphatic aldehydes, as well as ketones, were successfully reduced to the corresponding alcohols in the present system.

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

    Ohno Kohji, Zhao Chenzhou, Nishina Yuta

    LANGMUIR   35 ( 33 )   10900 - 10909   2019.8

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    Given the specificity of the structure and function of graphene oxide (GO), hybridization with a variety of compounds will further extend its applications. To that end, we examined a new method for introducing a polymer brush onto the GO surface. In this method, GO was surface-modified with 2-((3-((2-bromo-2-methylpropanoyl)oxy)propyl)thio)ethylamine hydrochloride, which is a newly synthesized compound that contains an initiating group for atom transfer radical polymerization (ATRP) and an amino group for reacting with the epoxy groups on the GO surface. The ATRP-initiator-functionalized GO was then used as a substrate for the surface-initiated ATRP of methyl methacrylate (MMA), which produced graft polymers of poly(MMA) (PMMA) with targeted molecular weights and narrow molecular weight distributions; the average graft density was similar to 0.06 chains/nm(2). Because of their high dispersibilities and structural anisotropies, the PMMA-brush-decorated GOs formed lyotropic liquid crystals in their suspensions. In addition, similar suspensions with relatively high hybrid concentrations exhibited structural color that depended on the concentration.

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

    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   2019.7

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    © 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.

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  • Bipolar anodic electrochemical exfoliation of graphite powders Reviewed

    Hideki Hashimoto, Yusuke Muramatsu, Yuta Nishina, Hidetaka Asoh

    Electrochemistry Communications   104   2019.7

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    © 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.

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

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

    NATURE COMMUNICATIONS   10   2019.6

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    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.

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

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

    ACS APPLIED MATERIALS & INTERFACES   11 ( 8 )   7695 - 7702   2019.2

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    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.

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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

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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 Reviewed

    Kinoshita Hiroshi, Suzuki Kyoko, Suzuki Tsutomu, Nishina Yuta

    DIAMOND AND RELATED MATERIALS   90   101 - 108   2018.11

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    The tribological properties of oxidized wood-derived nanocarbons (oWNCs), which have the same surface chemical composition as graphene oxide (GO), were investigated as additives in water-based lubricants using a sintered tungsten carbide ball and a stainless steel flat plate with a reciprocating sliding configuration. WNCs were synthesized from four kinds of Japanese wood powder by metal-catalyzed carbonization, and were strongly oxidized by a modified Hummer's method. The four oWNCs have aggregated chain-like nanostructures and maintain graphitic layers. In addition, the four oWNCs were well-dispersed in water due to their high level of oxidation. The four oWNC aqueous dispersions improved lubrication. In particular, the aqueous dispersion of the oWNC derived from Japanese cedar (J. Cedar) wood powder showed a very low friction coefficient and formed a thick tribofilm on the plate surface. The most distinctive properties of the J. Cedar oWNC, compared to the other oWNCs, were the small primary and secondary particle sizes, which were much smaller than those of the other oWNCs. The small-sized J. Cedar oWNC may possibly enter the frictional interface, preventing direct contact between the ball and plate surfaces and forming a tribofilm.

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

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

    Microbiological Research   215   29 - 35   2018.10

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    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.

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

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

    JOURNAL OF CATALYSIS   365   344 - 350   2018.9

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    Transition metal catalyzed carbon-carbon bond formation reactions have become important transformations in organic synthesis. In this study, we have explored a general strategy of transition metal free carbocatalytic carbon-hydrogen (C-H) functionalization. A carbon-based catalyst bearing nitrogen functional groups can facilitate the C-H functionalization of unactivated arenes to obtain biaryl products. We propose the active sites on the catalyst by analyzing its chemical composition before and after reaction, in-situ FT-IR, in-situ electron spin resonance (ESR), and density function theory calculation. As a result, stable NH groups and radicals were found to be effective for the reaction, providing high recyclability of the catalyst. The present methodology offers a diverse substrate scope without any dry or inert conditions, thus opening the door for an alternative to the conventional metal-based coupling reactions. (C) 2018 Elsevier Inc. All rights reserved.

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  • New insertion support device assisted the accurate placement of tunneled cuffed catheter: First experience of 10 cases

    Toshiaki Ohara, Kazufumi Sakurama, Satoshi Hiramatsu, Toshimasa Karai, Toshiaki Sato, Yuta Nishina

    JOURNAL OF VASCULAR ACCESS   19 ( 5 )   501 - 505   2018.9

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    Introduction: The tunneled cuffed catheter is used in hemodialysis patients for whom an arteriovenous fistula or arteriovenous graft is not suitable or for bridging usage of them. Accurate placement of a tunneled cuffed catheter is necessary for safe hemodialysis, but placement is sometimes difficult because of individual body differences. We developed a new device to support accurate placement of the tunneled cuffed catheter. In this study, we report our first clinical experience of the device.Methods: We made the device by expanded polytetrafluoroethylene with some special processes. The processes enable it to maintain plasticity and temporary shape in the autoclaved condition. The device is laid on the surface of the patient's body to mark the root of the catheter with a felt-tipped marker before catheterization. That enables us to know the accurate catheter root and tunneled cuffed catheter exit site on the body surface. Ten patients underwent tunneled cuffed catheter insertion according to the marking.Case description: The mean age was 71.3 +/- 12.8 years. The tunneled cuffed catheter was safely placed according to the marking in all patients, and all catheter tips were placed in the right atrium. The mean verification tip location difference before and after catheterization was 0.70 +/- 0.48 cm. This result indicated that the device could assist in inserting a catheter accurately within an error of 1.18 cm. The tunneled cuffed catheters were patent in all the cases, without replacement and complications until the end of bridging use or during the observation period.Conclusion: Our newly developed insertion support device enhances safety and prevents catheter waste during replacement.

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

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

    Materials Chemistry and Physics   212   149 - 154   2018.6

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    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.

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

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

    NANOSCALE   10 ( 13 )   5965 - 5974   2018.4

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    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.

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

    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

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    We have developed a combined approach of metaheuristic optimization algorithms (MOA), such as the genetic algorithm, with an ab-initio materials simulation engine. Concurrent run of the ab-initio calculations with each different parameter set selected by the MOA searches the optimum condition within a given input-parameter space. Using this methodology, the optimum dopant and its position/structure at a graphene edge are found to be a multiple N-atoms doping at graphitic sites, which predicts to lead to better charging/discharging performance when it is used as an anode material of Li-ion battery.

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

    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

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    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.

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

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

    CARBON   122   643 - 652   2017.10

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    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.

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

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

    CATALYSIS TODAY   291   124 - 132   2017.8

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    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.

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

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

    CHEMICAL COMMUNICATIONS   53 ( 53 )   7226 - 7229   2017.7

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    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.

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

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

    CHEMSUSCHEM   10 ( 12 )   2560 - 2565   2017.6

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    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.

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  • Surfactant modified graphene oxide laminates for filtration Reviewed

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

    Carbon   116   240 - 245   2017.5

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    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.

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

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

    CHEMISTRY OF MATERIALS   29 ( 5 )   2150 - 2156   2017.3

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

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

    SCIENTIFIC REPORTS   7   2017.3

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    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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  • Nucleophilic fluoroalkylation/cyclization route to fluorinated phthalides Reviewed

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

    Beilstein Journal of Organic Chemistry   14   182 - 186   2017.1

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    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 Reviewed

    Hideyuki Suzuki, Yuta Nishina

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   90 ( 1 )   74 - 78   2017.1

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    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.

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

    Muttaqin, Takahiro Nakamura, Yuta Nishina, Shunichi Sato

    JOURNAL OF MATERIALS SCIENCE   52 ( 2 )   749 - 759   2017.1

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    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.

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

    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

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    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.

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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 Reviewed

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

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

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    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.

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

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

    International Journal of Automotive and Mechanical Engineering   13 ( 1 )   3150 - 3156   2016.6

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    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.

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

    Kumika Morioku, Naoki Morimoto, Yasuo Takeuchi, Yuta Nishina

    SCIENTIFIC REPORTS   6   2016.5

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    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.

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

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

    ORGANIC LETTERS   18 ( 9 )   2020 - 2023   2016.5

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    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.

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

    Naoki Morimoto, Takuya Kubo, Yuta Nishina

    SCIENTIFIC REPORTS   6   2016.2

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    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.

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

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

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   89 ( 1 )   67 - 73   2016.1

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    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.

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

    Naoki Morimoto, Yasuo Takeuchi, Yuta Nishina

    CHEMISTRY LETTERS   45 ( 1 )   21 - 23   2016.1

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    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.

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  • Oxidation and reduction of graphitic materials for physical and chemical property control

    Nishina Yuta

    TANSO   2016 ( 271 )   15 - 24   2016

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    Oxidation of graphite produces graphite oxide and/or graphene oxide, both of which are abbreviated "GO". The preparation methods of these materials have been described by Brodie, Staudenmaier, and Hummers. Graphene oxide is widely recognized as a promising material in various fields, but its structure and composition has still not been fully controlled. In this article, general strategies to control the structure, particle size, and oxidation degree of graphene-like materials are introduced with emphasis on the oxidation of graphite by KMnO4 in H2SO4 (oGO) and the reduction of highly oxidized graphene oxide by hydrazine (rGO). Even though the oxygen content is the same, oGO and rGO have different properties, such as adsorption ability, oxidation ability, and electronic conductivity, because of differences in the persisting graphitic structure and defects. These results can be used as a guideline for the production of tailor-made GO. The current method of GO preparation is also discussed.

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

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

    GREEN CHEMISTRY   18 ( 4 )   1117 - 1124   2016

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    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.

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

    Hiroshi Kinoshita, Yuta Nishina

    Tribology Online   11 ( 2 )   235 - 241   2016

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    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.

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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 Reviewed

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

    6TH NANOSCIENCE AND NANOTECHNOLOGY SYMPOSIUM (NNS2015)   1710   2016

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    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.

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  • Photoinduced Structural Dynamics from sp3 to sp2 Hybridization in Graphene Oxide

    Hada Masaki, Nishina Yuta, Hayashi Yasuhiko, Tokunaga Tomoharu, Koshihara Shin-ya, Ichiyanagi Kohei, Nozawa Shunsuke, Adachi Shin'ichi, Katayama Ikufumi, Suzuki Takayuki, Minami Yasuo, Takeda Jun

    Meeting Abstracts of the Physical Society of Japan   71   1279 - 1279   2016

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

    Kotaro Kikushima, Yuta Nishina

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY   2015 ( 26 )   5864 - 5868   2015.9

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    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.

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

    Nishina Yuta, Morimoto Naoki, Morioku Kumika

    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY   250   2015.8

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

    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   2015.7

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    Gold nanoparticles (AuNPs) were synthesized easily using bottom-up method in aqueous extract of air-dried P. obtusifulia R. Br. leaves without elevated temperature. The appearance of surface plasmon resonance (SPR) peak at 549.5 nm in UV-Vis spectrometry analysis give the early evidence of the AuNPs in the solution. The particles shape was in spherical form and the average size of obtaining amps is 90, 25 nm. The AuNPs was stable for several days and also sensitive toward Pb(OAc)(2) solution.

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

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

    CHEMICAL COMMUNICATIONS   51 ( 27 )   5883 - 5886   2015

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

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

    CHEMICAL COMMUNICATIONS   51 ( 27 )   5883 - 5886   2015

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    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 Reviewed

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

    RSC ADVANCES   5 ( 26 )   20376 - 20385   2015

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    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.

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

    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

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

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

    MECHANICAL ENGINEERING JOURNAL   2 ( 6 )   2015

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    High-performance lubricating additives are desired in order to improve the properties of lubricating fluids. Recently, carbon nanomaterials such as fullerenes, carbon nanotubes, and carbon onions have been studied as lubricating additives for water and lubricating oils. However, the costs of these carbon nanomaterials are too high for practical use. On the other hand, graphene oxide (GO) is a carbon nanomaterial that consists of single atom thick sheets that possess a large number of oxygen functional groups. Since GO is synthesized from graphite using a chemical liquid process, the cost of GO is significantly lower than other carbon nanomaterials. In this study, the application and tribological properties of GO monolayer sheets as additives in water and poly-alpha olefin (PAO) were investigated. The dependence of the friction coefficient of GO-water dispersions on GO concentration (0.01-1.0 mass %) was investigated. In particular, GO-water dispersions with a concentration of less than 0.1 mass % demonstrated low friction coefficients. In this study, GO was simply dispersed in PAO using surfactant and intermediary solvents without the need for drying treatments. We found that the use of anionic surfactants in the GO-PAO dispersions was better than cationic surfactants in terms of the degree of wear observed. Specifically, GO-PAO dispersions that used an anionic surfactant with a GO concentration of 4 mass % had the smallest wear in this study. Moreover, friction coefficients were not decreased by the addition of GO in PAO. Finally, we found that intermediary solvents did not affect lubrication.

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  • Polycyclic N-Heterocyclic Compounds 76: Synthesis and Antiplatelet Evaluation of 2,4-Disubstituted 5,6-Dihydro[1]benzofuro[3',2':2,3]oxepino[4,5-d]pyrimidines Reviewed

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

    JOURNAL OF HETEROCYCLIC CHEMISTRY   51 ( 3 )   661 - 668   2014.5

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    Reaction of several Vilsmeier reagents with 5-amino-2,3-dihydro[1]benzofuro[3,2-b]oxepin-4-carbonitrile gave tetracyclic 2-substituted 4-chloro-5,6-dihydro[1] benzofuro[3',2':2,3]oxepino[4,5-d]pyrimidines. The structure of one of these, the 4-chloro-2-phenyl derivative, was confirmed by X-ray crystallography. Treatment of the 4-chloro derivatives with simple amines as nucleophile afforded 2-substituted 4-amino derivatives. A pentacyclic compound was also obtained by dehydrative ring closure. These products were evaluated for antiplatelet activity, and some showed potency comparable with that of aspirin.

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

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

    CARBON   66   720 - 723   2014.1

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    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.

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

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

    NANOSCALE   6 ( 12 )   6501 - 6505   2014

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    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.

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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 Reviewed

    Akinori Saito, Shun-Ichi Yamamoto, Yuta Nishina

    RSC Advances   4 ( 104 )   59835 - 59838   2014

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

    Yuta Nishina

    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN   71 ( 12 )   1307 - 1308   2013.12

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    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.

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

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

    Catalysis Science and Technology   3 ( 10 )   2550 - 2554   2013.10

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    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.

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

    Yuta Nishina, Bunsho Ohtani, Kotaro Kikushima

    BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY   9   1663 - 1667   2013.8

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    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.

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

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

    MATERIALS LETTERS   97   181 - 183   2013.4

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    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.

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

    Naoki Morimoto, Yasuo Takeuchi, Yuta Nishina

    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL   368   31 - 37   2013.3

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    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.

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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 Reviewed

    Kotaro Kikushima, Yuta Nishina

    RSC ADVANCES   3 ( 43 )   20150 - 20156   2013

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    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.

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  • Palladium on graphene: the in situ generation of a catalyst for the chemoselective reduction of alpha,beta-unsaturated carbonyl compounds Reviewed

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

    RSC ADVANCES   3 ( 36 )   15608 - 15612   2013

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    Palladium-supported graphene oxide has been successfully applied as a catalyst precursor for the selective reduction of alpha,beta-unsaturated carbonyl compounds. Pd nanoparticles were formed during the course of the reduction with only negligible leaching of the Pd species into the reaction mixture.

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

    Yuta Nishina, Junya Morita, Bunsho Ohtani

    RSC ADVANCES   3 ( 7 )   2158 - 2162   2013

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    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.

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  • Crystal and Fine Structural Transformations of Heat-Treated Biogenic Manganese Oxide Reviewed

    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) - 99   2013

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    In the natural aquatic environment, there are various types of biogenic manganese oxide (BMO) precipitates which are produced by manganese oxidizing microorganisms, at ambient temperature, atmosphere and neutral pH.BMO is a very interesting and useful functional material because of its unique property; hollow globule shape formed by nanosheets, large surface area and photocatalytic characteristics. In this study, thermally-processed BMO at 100 − 1000 °C was analyzed by XRD, XANES, SEM, TEM and nitrogen adsorption method to reveal the effects of heat-treatment on its crystal structure, Mn valence state, globule morphology, microstructure, pore size distribution and specific surface area. In the result, morphology of BMO is maintained below 800 °C, while nanosheets composing BMO were changed into nanoparticles at 600 °C. The crystal structure was transformed from birnessite into hausmannite (Mn3O4) at 600 °C. The specific surface area was increased by heat-treatment between 300 and 500 °C. In cases of artificial manganese oxides, such changes of crystal structure and specific surface area were not observed, and combustion of organic materials produced by microorganisms in BMO probably has a large effect on them.

    DOI: 10.2497/jjspm.60.92

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

    Kensuke Okuda, Takashi Hirota, Yuta Nishina, Hiroyuki Ishida

    Acta Crystallographica Section E: Structure Reports Online   68 ( 11 )   o3252 - +   2012.11

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    In the title compound, C14FH13ClN2O, the fused hydropyrimidine ring adopts an envelope conformation with one of the methylene C atoms at the flap. The three-membered ring is approximately perpendicular to the attached isoquinoline ring system, with a dihedral angle of 89.44(11)°. In the crystal, molecules are linked by a weak C-H⋯π interaction, forming a helical chain along the c axis.

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

    Kensuke Okuda, Takashi Hirota, Yuta Nishina, Hiroyuki Ishida

    Acta Crystallographica Section E: Structure Reports Online   68 ( 9 )   o2819 - +   2012.9

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    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.

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

    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   2012.9

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    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.

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

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

    MATERIALS LETTERS   81   88 - 91   2012.8

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    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.

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

    Yuta Nishina, Junya Miyata

    SYNTHESIS-STUTTGART   44 ( 16 )   2607 - 2613   2012.8

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    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.

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

    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   2012.7

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    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.

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

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

    TETRAHEDRON   68 ( 29 )   5730 - 5737   2012.7

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    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.

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  • Arrangement and Dispersion of Rh and Pt Atoms on Graphene Oxide Sheets Reviewed

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

    CHEMISTRY LETTERS   41 ( 7 )   680 - 682   2012.7

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    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.

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  • 酸化薄片化黒鉛及びその製造方法 Reviewed

    仁科勇太

    特願2012-083453,岡山大学   2012

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

    Yuta Nishina, Junya Miyata, Ryo Kawai, Kazuma Gotoh

    RSC ADVANCES   2 ( 25 )   9380 - 9382   2012

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    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.

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

    Yuta Nishina, Keishi Takami

    GREEN CHEMISTRY   14 ( 9 )   2380 - 2383   2012

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    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.

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

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

    RSC ADVANCES   2 ( 16 )   6420 - 6423   2012

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    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.

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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 Reviewed

    仁科勇太

    特願2012-029061,岡山大学   2012

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  • 臭素化触媒及びその製造方法 Reviewed

    仁科勇太

    特願2011-263954,岡山大学   2011.12

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

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

    SYNLETT   17 ( 17 )   2585 - 2589   2011.10

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    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.

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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 Reviewed

    仁科勇太

    PCT/JP2011/74795,岡山大学   2011.10

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

    Yuta Nishina, Tatsuya Kida, Tomonari Ureshino

    ORGANIC LETTERS   13 ( 15 )   3960 - 3963   2011.8

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    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).

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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 Reviewed

    仁科勇太

    特願2011-008026号,岡山大学   2011.1

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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 Reviewed

    仁科勇太

    特願2010-288035号 岡山大学   2010.12

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  • Synthesis of Functionalized Pentacenes from Isobenzofurans Derived from C-H Bond Activation Reviewed

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

    ORGANIC LETTERS   12 ( 22 )   5287 - 5289   2010.11

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    The synthesis of unsymmetric functionalized pentacenes from 1,4-anthraquinones and functionalized isobenzofurans, which were prepared by transformation via C H bond activation, was successfully accomplished. Examples of the synthesis of pentacenes with functional groups at the 5-position are still rare. These obtained functionalized pentacenes are highly soluble in hexane, toluene, and THF.

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

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

    ORGANIC LETTERS   11 ( 12 )   2711 - 2714   2009.6

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    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).

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  • Reactions and Mechanistic Studies of Rhenium-Catalyzed Insertion of alpha,beta-Unsaturated Carbonyl Compounds into a C-H Bond Reviewed

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

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   81 ( 11 )   1393 - 1401   2008.11

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    A rhenium complex, [ReBr(CO)(3)(thf)](2), catalyzes the insertion of alpha,beta-unsaturated carboryl compounds into a C-H bond of aromatic compounds having nitrogen-containing directing groups. In this reaction, Re-2(CO)(10) call also be used as a catalyst. When imines are employed as the aromatic substrates, sequential cyclization proceeds and indene derivatives are obtained in good to excellent yields. This reactivity is ill contrast to those of ruthenium and rhodium complexes, which are usually used as catalysts in the insertion reactions of unsaturated molecules into a C-H bond. Investigations oil the reaction mechanism indicate that the rhenium catalyst promotes C-H bond activation of aromatic compounds, the insertion of alpha,beta-unsaturated carbonyl compounds into a Re-C bond, and intramolecular nucleophilic cyclization followed by reductive elimination and the elimination of an amine.

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

    Yoichiro Kuninobu, Yuta Nishina, Takashi Matsuki, Kazuhiko Takai

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   130 ( 43 )   14062 - +   2008.10

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    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 Reviewed

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

    TETRAHEDRON   64 ( 26 )   5974 - 5981   2008.6

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    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 Reviewed

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

    PURE AND APPLIED CHEMISTRY   80 ( 5 )   1149 - 1154   2008.5

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    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 Reviewed

    Yoichiro Kuninobu, Yuta Nishina, Kazuhiko Takai

    TETRAHEDRON   63 ( 35 )   8463 - 8468   2007.8

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    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 Reviewed

    Yoichiro Kuninobu, Yuta Nishina, Takahiro Takeuchi, Kazuhiko Takai

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

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:WILEY-BLACKWELL  

    DOI: 10.1002/ani3.200702256

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  • From Newcomer

    Nishina Y.

    TANSO   2017 ( 279 )   156 - 156   2007

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    DOI: 10.7209/tanso.2017.156

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

    Yoichiro Kuninobu, Yuta Nishina, Chie Nakagawa, Kazuhiko Takai

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   128 ( 38 )   12376 - 12377   2006.9

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    DOI: 10.1021/ja065643e

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

    Yoichiro Kuninobu, Yuta Nishina, Kazuhiko Takai

    ORGANIC LETTERS   8 ( 13 )   2891 - 2893   2006.6

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    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 Reviewed

    Y Kuninobu, Y Nishina, M Shoitho, K Takai

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

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:WILEY-V C H VERLAG GMBH  

    DOI: 10.1002/anie.200503627

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Books

  • Engineering Materials for Stem Cell Regeneration

    Mohammed Zahedul, Islam Nizami, Yuta Nishina( Role: Joint author ,  Recent Advances in Stem Cells for Dental Tissue Engineering)

    Springer  2021.9 

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  • グラフェンから広がる二次元物質の新技術と応用―世界の動向、CVD合成、転写積層、量子物性、センサ・デバイス、THz応用

    仁科勇太, 小幡誠司( Role: Contributor ,  酸化グラフェンの合成と還元)

    エヌティーエス  2020.3  ( ISBN:4860436636

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  • Molecular Technology: Synthesis Innovation

    Yuta Nishina( Role: Contributor ,  Chemical functionalization of graphitic nanocarbon)

    2019.8 

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  • Molecular Technology: Energy Innovation

    Yuta Nishina( Role: Contributor ,  Molecular Design of Glucose Biofuel Cell Electrodes)

    Wiley-VCH  2018.10 

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  • Nanocarbons for Energy Conversion

    Yuta Nishina(Improved synthesis of graphene-like materials and their application)

    Springer  2018.8 

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  • 炭素材料の研究開発動向2018

    仁科勇太( Role: Contributor ,  ナノカーボンの作製・機能創出・利用)

    CPC研究会  2018.6 

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  • 電気化学・インピーダンス測定のデータ解析手法と事例集

    仁科勇太( Role: Contributor ,  グラフェンを負極材に利用したリチウムイオン電池の評価事例)

    技術情報協会  2018.1 

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  • 高耐熱・高放熱部材の性能向上と熱対策技術

    仁科勇太( Role: Contributor ,  グラフェン類と高分子の複合体の調製法と熱伝導性材料への応用)

    技術情報協会  2017.1 

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  • カーボンナノチューブ・グラフェンの応用研究最前線

    仁科勇太( Role: Contributor ,  酸化グラフェンの大量合成)

    エヌティーエス  2016.9 

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  • 酸化グラフェンの機能と応用

    仁科勇太( Role: Contributor ,  酸化グラフェンの合成)

    シーエムシー出版  2016.4 

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  • GRAPHENE SCIENCE HANDBOOK

    Yuta Nishina, Naoki Morimoto( Role: Contributor ,  Facile Preparation of Graphene Oxide and Its Metal Composite Materials toward Application for Catalysts in Organic Reactions)

    Taylor & Francis  2016.4 

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  • グラフェン・コンポジット

    仁科勇太( Role: Contributor ,  酸化グラフェンの合成方法とサイズ・酸化度の制御)

    S&T出版  2014.7 

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  • グラフェン・コンポジット

    仁科勇太, 齋藤彰範( Role: Contributor ,  金属-酸化グラフェン複合体の作製と触媒作用)

    S&T出版  2014.7 

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  • 触媒の設計・反応制御 事例集

    仁科勇太, 菊嶌孝太郎(金属-グラフェン複合体の触媒としての応用)

    技術情報協会  2013.1 

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MISC

  • Coordination chemistry for innovative carbon-related materials

    Ryota Sakamoto, Ryojun Toyoda, Guan Jingyan, Yuta Nishina, Kazuhide Kamiya, Hirotomo Nishihara, Tomoki Ogoshi

    Coordination Chemistry Reviews   466   2022.9

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    With the emergence of energy and environmental problems and the deepening of devices to solve these problems, the demand for carbon materials is increasing and higher performance is required. While a variety of scientific knowledge has been poured into the creation of innovative carbon materials, coordination chemistry also makes a significant contribution to the creation of innovative carbon materials, especially for metal-containing carbon materials. In this review, we summarize the new carbon and related materials opened up by complex chemistry. In the first chapter, the prospect of this review is mentioned as an introduction. There are various methods for synthesizing carbon materials mediated by complex chemistry, and these are listed in Chapter 2. In Chapter 3, we summarize the various applications of coordination-chemistry-based carbon materials. In Chapter 4, we discuss the potential of conductive molecular frameworks as new materials that can replace or surpass carbon materials. Chapter 5 summarizes this review and presents the future challenges and prospects of coordination-chemistry-based carbon and related materials.

    DOI: 10.1016/j.ccr.2022.214577

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

    Rizwan Khan, Yuta Nishina

    Nanoscale   13 ( 1 )   36 - 50   2021.1

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    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   2020.6

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    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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  • Fusion of Nanocellulose and Electronic Materials for Green Flexible Electronics

    古賀大尚, 長島一樹, 高橋綱己, 仁科勇太

    電子情報通信学会技術研究報告   119 ( 389(OME2019 59-64) )   2020

  • 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   2019.3

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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   2018.6

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  • 異分野融合による紙のリノベーション研究

    コガ ヒロタカ, ナガシマ カズキ, ニシナ ユウタ

    53 ( 6 )   391 - 394   2018.6

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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   2017.2

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  • Can Graphene Work as a Superior Support Material in Catalysis?

    58 ( 4 )   214 - 217   2016.8

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  • Preparation Method of Metal/Graphene (Oxide) Composites and Application for Catalysts

    57 ( 6 )   328 - 333   2015.12

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  • Graphene Oxide Lubricant Additive in Water

    44 ( 2 )   8 - 15   2015.2

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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

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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

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    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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  • Efficient Preparation Method of Graphene Oxide and its Structure Control

    65 ( 2 )   134 - 139   2014.2

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  • Tribological property of water dispersion of single-layered graphene oxide

    木之下博, ALIAS A.A., 仁科勇太, 藤井正浩

    日本機械学会機素潤滑設計部門講演会講演論文集   14th (Web)   2014

  • J111014 The Effect of Friction Reduction by Water Dispersed Graphene Oxide : Influence of Sliding Material

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

    Mechanical Engineering Congress, Japan   2013   "J111014 - 1"-"J111014-4"   2013.9

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    The problems of oil lubricants in waste and maintenance management are crucial for cost and environment. Water with less harmful to environment is suitable as a candidate lubricant to replace oil lubricants. However, water is lack of viscosity, which leads to high friction and severe wear between the sliding materials. Graphene Oxide (GO) is single layer graphite with oxygen functional groups and easy to be dispersed in water. In this study, the effect of friction reduction by water dispersed GO has been evaluated with different sliding materials. The friction coefficients between SUS304 substrate vs. SUS304 ball and SUS304 substrate vs. tungsten carbide (WC) ball were approximately 0.05. Severe wear was apparent on the SUS304 ball surface slid in the GO dispersion; however, only small wear was observed on the WC ball surface after friction test in the GO dispersion.

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  • 微生物由来マンガン酸化物の機能探索-磁性流体を用いた磁性の付与-

    木村倫康, 橋本英樹, SAFARIK Ivo, 仁科勇太, 宮田直幸, 中西真, 藤井達生, 高田潤

    粉体粉末冶金協会講演概要集   2012   2012

  • 微生物由来マンガン酸化物のキャラクタリゼーションと固体触媒への応用

    木村倫康, 橋本英樹, 仁科勇太, 宮田直幸, 古谷充章, 中西真, 藤井達生, 高田潤

    粉体粉末冶金協会講演概要集   2012   2012

  • マンガン酸化細菌が作るマンガン酸化物~その基礎・応用研究~(2)炭化水素ハロゲン化触媒特性について

    仁科勇太, 橋本英樹, 木村倫康, 宮田直幸, 大谷文章, 高田潤

    日本化学会講演予稿集   92nd ( 1 )   2012

  • マンガン酸化細菌が作るマンガン酸化物~その基礎・応用研究~(1)形態的・構造的特徴について

    木村倫康, 橋本英樹, 宮田直幸, 古谷充章, 仁科勇太, 中西真, 藤井達生, 高田潤

    日本化学会講演予稿集   92nd ( 1 )   2012

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Industrial property rights

  • 酸化グラフェン被覆酸化マグネシウム粒子及びその製造方法

    齋藤 彰範, 仁科 勇太

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    Applicant:タテホ化学工業株式会社

    Application no:特願2019-222727  Date applied:2019.12.10

    Announcement no:特開2021-091570  Date announced:2021.6.17

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  • 酸化還元性電子輸送体及び電極

    辻村 清也, 仁科 勇太

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    Applicant:株式会社仁科マテリアル

    Application no:特願2019-194744  Date applied:2019.10.2

    Announcement no:特開2021-061224  Date announced:2021.4.15

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  • 植物病害防除剤及び植物病害の防除方法

    一瀬 勇規, 澤井 拓, オンビロ シゴンベ ゲオフレイ, 能年 義輝, 仁科 勇太, 松井 英譲

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    Applicant:国立大学法人 岡山大学

    Application no:特願2019-037966  Date applied:2019.3.1

    Announcement no:特開2019-151631  Date announced:2019.9.12

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  • 電気二重層キャパシタ

    高井 充, 仁科 勇太, 人見 篤志, 伊藤 秀毅, 檜 圭憲

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    Applicant:TDK株式会社

    Application no:特願2019-027721  Date applied:2019.2.19

    Announcement no:特開2020-136487  Date announced:2020.8.31

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  • 炭素ナノ構造体の生成方法及び炭素ナノ構造体

    池田 直, 仁科 勇太, 狩野 旬, 青柳 佑海人, 藤原 孝将, 森 正和

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    Applicant:国立大学法人 岡山大学

    Application no:特願2018-222786  Date applied:2018.11.28

    Announcement no:特開2019-099989  Date announced:2019.6.24

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  • 水処理用薬剤および水処理方法

    菅原 広, 中村 勇規, 吉川 浩, 仁科 勇太

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    Applicant:オルガノ株式会社

    Application no:特願2018-046785  Date applied:2018.3.14

    Announcement no:特開2019-155292  Date announced:2019.9.19

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  • 接着剤組成物の製造方法および接着剤組成物

    熊本 拓朗, 村上 康之, 仁科 勇太

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    Applicant:日本ゼオン株式会社

    Application no:特願2017-072146  Date applied:2017.3.31

    Announcement no:特開2018-172557  Date announced:2018.11.8

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  • 水性媒体用流動抵抗低減剤組成物

    仁科 勇太, 小方 聡, 栃木 弘, 神田 信

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    Applicant:国立大学法人 岡山大学

    Application no:特願2016-213110  Date applied:2016.10.31

    Announcement no:特開2018-070785  Date announced:2018.5.10

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  • 直鎖炭化水素の製造方法

    仁科 勇太, 池田 俊徳, 門前 雅之

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    Applicant:国立大学法人 岡山大学

    Application no:特願2016-145069  Date applied:2016.7.25

    Announcement no:特開2018-016545  Date announced:2018.2.1

    Patent/Registration no:特許第6464512号  Date registered:2019.1.18 

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  • アゾ化合物の製造方法

    山本 俊一, 赤田 充生, 仁科 勇太

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    Applicant:株式会社仁科マテリアル

    Application no:特願2016-140953  Date applied:2016.7.17

    Announcement no:特開2018-008920  Date announced:2018.1.18

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  • 酸化黒鉛の製造方法

    小野 博信, 鴻巣 修, 郷田 隼, 佐藤 裕一, 仁科 勇太

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    Applicant:株式会社日本触媒

    Application no:特願2016-044584  Date applied:2016.3.8

    Announcement no:特開2017-160070  Date announced:2017.9.14

    Patent/Registration no:特許第6592384号  Date registered:2019.9.27 

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  • 多孔性ポリマーの製造方法

    仁科 勇太, 西原 洋知, 京谷 隆, 大和田 真生, 針谷 明夫

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    Applicant:国立大学法人東北大学

    Application no:特願2016-022476  Date applied:2016.2.9

    Announcement no:特開2017-141335  Date announced:2017.8.17

    Patent/Registration no:特許第6864877号  Date registered:2021.4.7 

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  • 硫黄含有酸化グラフェン又は硫黄含有グラフェン及びその製造方法

    西尾 直高, 大塚 喜弘, 堤 聖晴, 仁科 勇太

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    Applicant:株式会社ダイセル

    Application no:特願2016-008543  Date applied:2016.1.20

    Announcement no:特開2017-128472  Date announced:2017.7.27

    Patent/Registration no:特許第6691782号  Date registered:2020.4.15 

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  • 木質系炭素原子含有物の製造方法及び木質系炭素原子含有物を含有した潤滑剤

    木之下 博, 仁科 勇太, 鈴木 勉, 鈴木 京子

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    Applicant:国立大学法人北見工業大学

    Application no:特願2015-249257  Date applied:2015.12.22

    Announcement no:特開2017-114702  Date announced:2017.6.29

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  • 芳香族化合物を酸化的カップリングさせる方法

    仁科 勇太, 森奥 久実加

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    Applicant:国立大学法人 岡山大学

    Application no:特願2015-153716  Date applied:2015.8.3

    Announcement no:特開2017-031106  Date announced:2017.2.9

    Patent/Registration no:特許第6646295号  Date registered:2020.1.15 

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  • 炭素-金属複合体

    仁科 勇太, 小野 博信

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    Applicant:株式会社仁科マテリアル

    Application no:特願2015-047409  Date applied:2015.3.10

    Announcement no:特開2016-166113  Date announced:2016.9.15

    Patent/Registration no:特許第6476019号  Date registered:2019.2.8 

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  • 水系潤滑液組成物

    木之下 博, 仁科 勇太, 栃木 弘, 神田 信, 渡辺 佳久

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    Applicant:国立大学法人 岡山大学

    Application no:特願2014-235013  Date applied:2014.11.19

    Announcement no:特開2016-098279  Date announced:2016.5.30

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  • 潤滑油組成物

    木之下 博, 仁科 勇太, 栃木 弘, 熊谷 恭大, 渡辺 佳久

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    Applicant:国立大学法人 岡山大学

    Application no:特願2014-199132  Date applied:2014.9.29

    Announcement no:特開2016-069482  Date announced:2016.5.9

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  • 潤滑油及びその製造方法

    木之下 博, 仁科 勇太

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    Applicant:国立大学法人 岡山大学

    Application no:特願2014-172774  Date applied:2014.8.27

    Announcement no:特開2016-047875  Date announced:2016.4.7

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  • 導電性繊維の製造方法、シート状電極の製造方法、導電性繊維、及びシート状電極

    古賀 大尚, 菅沼 克昭, 能木 雅也, 外村 英嗣, 仁科 勇太

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    Applicant:国立大学法人大阪大学

    Application no:特願2014-106142  Date applied:2014.5.22

    Announcement no:特開2015-221947  Date announced:2015.12.10

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  • 水系潤滑剤

    木之下 博, 仁科 勇太

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    Applicant:国立大学法人 岡山大学

    Application no:JP2014063398  Date applied:2014.5.20

    Publication no:WO2014-189065  Date published:20141127

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  • 細胞死抑制剤及びその製造方法

    佐藤 あやの, 仁科 勇太

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    Applicant:国立大学法人 岡山大学

    Application no:特願2015-504347  Date applied:2014.3.5

    Publication no:WO2014-136808  Date published:2014912

    Patent/Registration no:特許第6263815号  Date registered:2018.1.5 

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  • 細胞死抑制剤及び新規化合物

    佐藤 あやの, 仁科 勇太

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    Applicant:国立大学法人 岡山大学

    Application no:特願2015-504346  Date applied:2014.3.5

    Publication no:WO2014-136807  Date published:2014912

    Patent/Registration no:特許第6263814号  Date registered:2018.1.5 

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  • 酸化黒鉛の製造方法及び酸化黒鉛

    仁科 勇太

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    Applicant:仁科 勇太

    Application no:特願2014-036086  Date applied:2014.2.26

    Announcement no:特開2015-160766  Date announced:2015.9.7

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  • 酸化グラフェンに金属を担持させる方法及び金属-酸化グラフェン複合体の製造方法

    仁科 勇太

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    Applicant:国立大学法人 岡山大学

    Application no:特願2014-535610  Date applied:2013.9.13

    Patent/Registration no:特許第6116016号  Date registered:2017.3.31 

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  • 酸化グラフェンに金属を担持させる方法及びこの方法で作成した金属-酸化グラフェン複合体

    仁科 勇太

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    Applicant:国立大学法人 岡山大学

    Application no:JP2013074937  Date applied:2013.9.13

    Publication no:WO2014-042259  Date published:2014320

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  • 金属を担持した薄片状の酸化黒鉛及びその作製方法

    後藤 和馬, 仁科 勇太, 石田 祐之, 橋本 英樹, 藤井 英司

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    Applicant:岡山県

    Application no:特願2013-014821  Date applied:2013.1.29

    Announcement no:特開2014-144892  Date announced:2014.8.14

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  • ハロゲン化触媒及びその製造方法

    仁科 勇太, 高見 佳志

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    Applicant:国立大学法人 岡山大学

    Application no:JP2012080866  Date applied:2012.11.29

    Publication no:WO2013-081034  Date published:201366

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  • 酸化薄片化黒鉛及びその製造方法

    仁科 勇太

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    Applicant:国立大学法人 岡山大学

    Application no:特願2012-083453  Date applied:2012.4.2

    Announcement no:特開2013-212948  Date announced:2013.10.17

    Patent/Registration no:特許第5098064号  Date registered:2012.10.5 

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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

    仁科 勇太, 團野 瑛章

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    Applicant:国立大学法人 岡山大学

    Application no:特願2012-029061  Date applied:2012.2.14

    Announcement no:特開2013-166088  Date announced:2013.8.29

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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

    仁科 勇太, 橋本 英樹, 高田 潤

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    Applicant:国立大学法人 岡山大学

    Application no:特願2012-553562  Date applied:2011.10.27

    Publication no:WO2012-098746  Date published:2012726

    Patent/Registration no:特許第5863676号  Date registered:2016.1.8 

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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

    仁科 勇太, 高井 和彦, 森田 惇也

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    Applicant:国立大学法人 岡山大学

    Application no:特願2012-549663  Date applied:2011.8.17

    Announcement no:特開2012-086159  Date announced:2012.5.10

    Publication no:WO2012-086259  Date published:2012628

    Patent/Registration no:特許第5854405号  Date registered:2015.12.18 

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Research Projects

  • Development of sediment microbial fuel cells for improvement of water quality and reduction in greenhouse gas emissions in agricultural drainage canals

    Grant number:22H02458  2022.04 - 2025.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    前田 守弘, 仁科 勇太, 赤尾 聡史, 諸泉 利嗣

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    Grant amount:\17420000 ( Direct expense: \13400000 、 Indirect expense:\4020000 )

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  • Exploration of functional carbon materials that selectively interact with molecules and ions in water

    Grant number:22H04548  2022.04 - 2024.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    仁科 勇太

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    Grant amount:\4680000 ( Direct expense: \3600000 、 Indirect expense:\1080000 )

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  • 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

    Grant number:21H01763  2021.04 - 2024.03

    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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    Grant amount:\17420000 ( Direct expense: \13400000 、 Indirect expense:\4020000 )

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  • Ultrafast 3D structural dynamics for exploration of photoresponsive materials

    Grant number:20H01832  2020.04 - 2023.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    羽田 真毅, 仁科 勇太, 恩田 健, 大村 訓史

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    Grant amount:\18330000 ( Direct expense: \14100000 、 Indirect expense:\4230000 )

    本研究提案では、フェムト秒からピコ秒の時間幅を持つパルス電子線を用いた斜入射型の時間分解電子線回折装置を構築し、既存の透過型の時間分解電子線回折装置と組み合わせることで、時間一次元、空間三次元の超高速構造ダイナミクスの可視化技術を創出する。そして、本技術を活用して、無機物質、有機分子、炭素材料など多彩な物質の非平衡状態の構造変化と機能との関係を世界に先駆けて展開し、非平衡超高速構造変化と機能の関係解明のための次世代の超高速三次元構造ダイナミクス観測の科学技術基盤を開拓する。
    2020年度は、斜入射型の時間分解電子線回折装置を構築するとともに、既存の透過型の時間分解電子線回折装置を用いて、カーボンナノチューブのナノスケールで生じるフォノン振動とマクロな熱伝導の関連性を解明することができ、Carbon誌に論文が掲載された。超高速時間分解電子線回折法では、物質の局所的な構造を追うことが特異とされてきたが、本研究はこのナノ特性をバルクの物性と結び付けた学術的な価値の高い研究である。さらに共同研究者と超高速時間分解電子線回折法に関するレビュー論文をAccounts of Chemical Research誌に掲載することができ、今後の超高速時間分解電子線回折法に関する研究の指針を示すことができた。さらに、超高速時間分解電子線回折法により酸化グラフェンのz軸方向のダイナミクス計測(グラフェンの二層化の構造ダイナミクス)にも成功しており、現在論文を投稿中である。

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  • Development of functional carbon materials that selectively interact with molecules and ions in water

    Grant number:20H05224  2020.04 - 2022.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    仁科 勇太

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    Grant amount:\4940000 ( Direct expense: \3800000 、 Indirect expense:\1140000 )

    本研究では,分子認識可能な機能部位を炭素材料に付与し,水中に含まれる分子またはイオンと選択的に相互作用または除去する材料に展開した。本領域の発展に貢献すべく,A01班が創出する機能性高分子と炭素の複合体,および無機多孔質材料と炭素の複合体の作製を検討した。さらに,機能開拓班(A03班)への橋渡しをスムーズに行えるように,材料の評価および基礎物性評価を実施した。有機合成と炭素材料の両軸で研究を実施することにより,新規な水圏機能材料を創出した。
    具体的には,炭素材料を水圏機能材料として応用すべく水との相互作用を高めるために,親水性官能基を付与した。黒鉛やナノダイヤの酸化条件を変えることにより,酸素含有量を5~50%の範囲で制御し,カルボキシ基を豊富に含むものやヒドロキシ基・エポキシ基を豊富に含むものを作り分けた。また,これら酸素官能基を足掛かりとして,機能性分子を炭素材料上に導入した。合成した機能化炭素材料を用いて,水中の重金属の除去率を評価した。イミノ二酢酸を酸化グラフェン上に固定化した材料が,重金属を選択的に除去できることを見いだした。また,イミノ二酢酸と酸化グラフェンの間にリンカーとなるアルキル鎖をはさむと,その効率が向上した。アルキル鎖の長さの最適化も行い,その妥当性をDFT計算にて検証した。DFT計算を駆使し,イミノ二酢酸の構造を変えることにより,有用な金属を回収するための素材を開発している。

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  • Metal-free and heterogeneous catalysts

    Grant number:19H02718  2019.04 - 2022.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    仁科 勇太

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    Grant amount:\17160000 ( Direct expense: \13200000 、 Indirect expense:\3960000 )

    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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  • Improvement of heat transfer and friction coefficient by graphene oxide nanosheet suspensions

    Grant number:19K04196  2019.04 - 2022.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    小方 聡, 仁科 勇太

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    Grant amount:\4420000 ( Direct expense: \3400000 、 Indirect expense:\1020000 )

    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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  • Molecular design of electrodes for biofuel cells

    Grant number:17K18992  2017.06 - 2019.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Research (Exploratory)  Grant-in-Aid for Challenging Research (Exploratory)

    Nishina Yuta

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    Grant amount:\6500000 ( Direct expense: \5000000 、 Indirect expense:\1500000 )

    We achieved the following 3 tasks.
    1) Development of mediator molecules that efficiently transfer electrons from enzymes, 2) Establishment of techniques to immobilize enzymes and mediator molecules on electrodes, 3) Establishment of techniques to increase the amount of enzymes and mediator molecules per unit area

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  • Establishment of dispersion technique of graphene oxide in lubricating oils, and its synergistic effect with other additives and low temperature operation

    Grant number:17H03165  2017.04 - 2020.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    KINOSHITA Hiroshi

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    Grant amount:\17160000 ( Direct expense: \13200000 、 Indirect expense:\3960000 )

    Graphene oxides were reduced by heating or using a dispersant, and then they were added to the lubricating oil. In heat dispersion, the friction coefficient was lower than that without addition, however it did not depend on the dispersion temperature. Wear was lower than without addition, and the lower the heating temperature, the lower the wear. Using the dispersant, a friction coefficient was lower than that without the addition, however it did not depend on the concentration of the dispersant. Wear was smaller than that without the addition when the concentration of the dispersant was low. In particular, High lubricity of graphene oxide was observed even at low temperatures. It was also found that the friction force becomes very low when graphene oxide was used in combination with ZnDTP.

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  • Synthesis of novel nanocarbon materials by ultrahigh temperature process under reactive environment

    Grant number:17H02745  2017.04 - 2020.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    Kobayashi Yoshihiro

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    Grant amount:\18330000 ( Direct expense: \14100000 、 Indirect expense:\4230000 )

    We have developed a thermal process for synthesizing low-defect/turbostratic/multilayer graphene thin films, which are nanocarbon structures with excellent two-dimensional physical properties comparable to single-layer graphene, by a thermal process at ultrahigh temperature under reactive atmosphere. The physical superiority originated from the turbostratic structure was verified from optical and electrical properties. Turbostratic multilayer graphene was synthesized by direct growth on template graphene, in addition to use graphene oxide as starting material. The interaction between graphene layers was controlled by inserting cellulose nanofibers and nanodiamonds between the layers, and it is effective for revealing the monolayer-like properties. Carrier transport properties such as mobility and conductivity were significantly improved, owing to the monolayer-like property caused from the turbostratic stacking and shielding of environmental effects by multilayer structure.

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  • Development of ultrahigh rate lithium ion battery via polarization assist incorporation into electrodes

    Grant number:16K14094  2016.04 - 2018.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research  Grant-in-Aid for Challenging Exploratory Research

    Teranishi Takashi

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    Grant amount:\3770000 ( Direct expense: \2900000 、 Indirect expense:\870000 )

    There is huge demand for lithium ion battery with ultrahigh rate capability. We aim to simultaneously incorporate polarization assist architecture into both cathode and anode electrodes, in attempt to activate interfacial charge transfer. LiCoO2 modified with BaTiO3 is utilized as cathode, while the graphene oxides, rGO, and nitridized rGO are employed for anode active material for assembling full cells. In fact, modified electrodes exhibit significantly greater power density; discharge capacity of modified sample at 5th cycle at 10C rate is ca. 15 times as high as conventional electrodes, i.e., bare LCO/Graphite. The result implies the polarization assist architecture incorporated into both cathodes and anodes effectively improves the power density of lithium ion batteries.

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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

    Grant number:16H00915  2016.04 - 2018.03

    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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    Grant amount:\4680000 ( Direct expense: \3600000 、 Indirect expense:\1080000 )

    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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  • International supports of atomic layered materials and promoting the collaborated research

    Grant number:15K21722  2015.11 - 2019.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    Saito Riichiro, NISHINA yuta, YANAGI kazuhiro, KAWANO yukio

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    Grant amount:\45890000 ( Direct expense: \35300000 、 Indirect expense:\10590000 )

    Atomic layered materials, which are the thinnest material in the nature, have shown unique and significant properties and thus the research of the atomic layered materials are very active in the world for recent decades. In particular, hexagonal boron nitride (h-BN) is an important atomically-flat materials which can produce only in Japan. In this project, we support the supply of hBN samples internationally to enhance the international collaboration, which is very efficient for promoting the activity not only domestic but also international research. Further, sending or inviting many young researchers for the international collaborating research on atomic layer materials by this project, we encourage young scientists to establish a new network of the research. This is an important results of the project for our continuing the research for the next generation.

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  • Inhibition of fatigue fractures using graphene oxide as innovative lubricant additive

    Grant number:15K13858  2015.04 - 2017.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research  Grant-in-Aid for Challenging Exploratory Research

    KINOSHITA HIROSHI, FUJII Masahiro, NISHINA Yuta

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    Grant amount:\3900000 ( Direct expense: \3000000 、 Indirect expense:\900000 )

    In order to prevent fatigue fractures by repeated stress, hardness of contact materials have been increased. However it is not sufficient. In this study, we carried out to improve fatigue life using dispersing graphene oxide in lubricating oil. Dispersion methods of graphene oxide in lubricating oil and rolling tester with minimum lubricating oils were developed. Improvement of fatigue life was achieved by the dispersing graphene oxide in the lubricating oil. However, formation of tribofilm which seems to greatly improve fatigue life was not achieved. In the future, in order to achieve further improvement of fatigue life, we will discover dispersants that will improve formation of tribofilms.

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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

    Grant number:15F15074  2015

    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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    Grant amount:\1200000 ( Direct expense: \1200000 )

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  • Characterization of golgins in secretion and Golgi

    Grant number:26440055  2014.04 - 2018.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    Satoh Ayano, Nishino Kunihiko, Nishino Mitsuko, Nishina Yuta, Yu Sidney

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    Grant amount:\5070000 ( Direct expense: \3900000 、 Indirect expense:\1170000 )

    We have shown that secretion increases and the structure of the Golgi changes when knocking down giantin, which is one of the Golgin protein group. In this research project, to clarify the molecular mechanisms underlying this phenomenon as the ultimate goal, the structure of the Golgi was analyzed in detail using electron beam tomography and the like. Also, during this time, we discovered a novel small molecule involved in secretion regulation, so we performed the characterization of new molecules, as well.

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  • Development of graphene oxide as new tailor-made lubricating additives

    Grant number:26289028  2014.04 - 2018.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    Kinoshita Hiroshi

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    Grant amount:\15470000 ( Direct expense: \11900000 、 Indirect expense:\3570000 )

    Graphene oxide (GO) has one layer of graphite structure with a size of over several μm. In addition, GO has many oxygen functional groups. In this study, tribological properties of GO dispersions in water, ionic liquid, and lubricating oil. The very low friction coefficient obtained by GO water dispersion can be achieved by the synergetic effect of the formation of the tribofilm and the presence of GO on the sliding surface. When GO was dispersed in ionic liquid, a slight effect of reducing friction coefficient was observed. In addition, corrosion wear of ionic liquid friction was suppressed by adding GO in ionic liquid, but the sliding wear was increased in increasing concentration of GO. When GO was added to lubricating oil, lubricating property was improved as GO was dispersed in lubricating oil using anionic surfactant.

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  • 酸化グラフェンの欠陥を有機分子で修復する

    Grant number:26107528  2014.04 - 2016.03

    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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    Grant amount:\4810000 ( Direct expense: \3700000 、 Indirect expense:\1110000 )

    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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  • Preparation of high-performance catalysts by oxidation state control of Pd on GO

    Grant number:25870457  2013.04 - 2015.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)  Grant-in-Aid for Young Scientists (B)

    NISHINA Yuta

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    Grant amount:\4420000 ( Direct expense: \3400000 、 Indirect expense:\1020000 )

    Graphene oxide (GO) is a two-dimensional sheet of sp2-hybridized carbon. Due to its extraordinary thermal, mechanical, and electrical properties, GO has attracted much interest. Pd/GO, a composite of Pd nanoparticle and exfoliated graphene, was used as a catalyst in organic reactions. In Suzuki-Miyaura cross coupling reaction, Pd/GO showed high reusability without aggregation of Pd nanoparticle.

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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

    Grant number:08J06785  2008 - 2009

    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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    Grant amount:\1200000 ( Direct expense: \1200000 )

    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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