研究者詳細 - 仁科　勇太

論文 - 仁科　勇太

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Chemical functionalization of graphitic nanocarbons

Nishina, Y.

Molecular Technology: Energy Innovation 4-4 2018年

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

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

CARBON 122 643 - 652 2017年10月

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

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

DOI： 10.1016/j.carbon.2017.07.016

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

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

CATALYSIS TODAY 291 124 - 132 2017年8月

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

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

DOI： 10.1016/j.cattod.2017.01.017

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

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

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

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

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

DOI： 10.1039/c7cc02337e

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

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

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

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

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

DOI： 10.1002/cssc.201700576

Surfactant modified graphene oxide laminates for filtration 査読

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

Carbon 116 240 - 245 2017年5月

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

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

DOI： 10.1016/j.carbon.2017.01.102

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

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

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

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

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

DOI： 10.1021/acs.chemmater.6b04807

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

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

SCIENTIFIC REPORTS 7 2017年3月

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

Single-walled carbon nanotubes (SWCNTs) are potentially strong optical absorbers with tunable absorption bands depending on their chiral indices (n, m). Their application for solar energy conversion is difficult because of the large binding energy (> 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.

DOI： 10.1038/srep43445

Nucleophilic fluoroalkylation/cyclization route to fluorinated phthalides 査読

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

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

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

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

DOI： 10.3762/bjoc.14.12

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

Hideyuki Suzuki, Yuta Nishina

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

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

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

DOI： 10.1246/bcsj.20160346

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

Muttaqin, Takahiro Nakamura, Yuta Nishina, Shunichi Sato

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

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

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

DOI： 10.1007/s10853-016-0368-8

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

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

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

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

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

DOI： 10.13005/ojc/330221

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

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

Chemical Communications 53 ( 63 ) 8890 - 8893 2017年

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

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

DOI： 10.1039/c7cc03910g

Deposition of an Ultraflat Graphene Oxide Nanosheet on Atomically Flat Substrates

Khan, M.Z.H., Shahed, S.M.F., Yuta, N., Komeda, T.

Journal of Electronic Materials 46 ( 7 ) 2017年

Formation and Characterization of Copper Nanocube-Decorated Reduced Graphene Oxide Film

Khan, M.Z.H., Rahman, M.A., Yasmin, P., Tareq, F.K., Yuta, N., Komeda, T., Jahan, R.A.

Journal of Nanomaterials 2017 2017年

ChemInform Abstract: Synthesis of 2-Arylphenol Derivatives Through a One-Pot Suzuki-Miyaura Coupling/Dehydrogenative Aromatization Sequence with Pd/C Catalysis

Kotaro Kikushima, Yuta Nishina

ChemInform 47 ( 2 ) 2016年7月

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

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

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

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

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

DOI： 10.15282/ijame.13.1.2016.2.0262

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

Kumika Morioku, Naoki Morimoto, Yasuo Takeuchi, Yuta Nishina

SCIENTIFIC REPORTS 6 2016年5月

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

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

DOI： 10.1038/srep25824

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

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

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

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

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

DOI： 10.1021/acs.orglett.6b00629

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

Naoki Morimoto, Takuya Kubo, Yuta Nishina

SCIENTIFIC REPORTS 6 2016年2月

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

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

DOI： 10.1038/srep21715

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