研究者詳細 - 仁科　勇太

論文 - 仁科　勇太

分割表示 219 件中 101 - 120 件目／全件表示 >>

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

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

Biosensors and Bioelectronics 165 2020年10月

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

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

DOI： 10.1016/j.bios.2020.112287

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

Yang Zhou, Yuta Nishina

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

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

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

DOI： 10.1039/d0na00327a

Is carboxylation an efficient method for graphene oxide functionalization?

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

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

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

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

DOI： 10.1039/d0na00561d

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

Rizwan Khan, Yuta Nishina

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

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

DOI： 10.1039/d0ta05489e

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

Yuta Nishina, Siegfried Eigler

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

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

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.

DOI： 10.1039/d0nr02164d

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

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

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

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

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

DOI： 10.1039/d0sc02422h

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

Muhammad Sohail Ahmad, Yuta Nishina

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

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

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

DOI： 10.1039/d0nr02984j

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

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

Carbon 160 204 - 210 2020年4月

掲載種別：研究論文（学術雑誌）

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

DOI： 10.1016/j.carbon.2019.11.094

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

Rizwan Khan, Ryo Nakagawa, Benoit Campeon, Yuta Nishina

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

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

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

DOI： 10.1021/acsami.9b21082

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

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

Carbon 158 356 - 363 2020年3月

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

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

DOI： 10.1016/j.carbon.2019.10.085

Structural optimization of alkylbenzenes as graphene dispersants

Shimpei Takeda, Yuta Nishina

Processes 8 ( 2 ) 2020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：MDPI

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

DOI： 10.3390/pr8020238

Functionalized Graphene Oxide Shields Tooth Dentin from Decalcification

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

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

掲載種別：研究論文（学術雑誌）

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

DOI： 10.1177/0022034519894583

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

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

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

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

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

DOI： 10.1002/anie.201913461

Robust sandwiched fluorinated graphene for highly reliable flexible electronics

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

Applied Surface Science 499 2020年1月

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

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

DOI： 10.1016/j.apsusc.2019.143839

Dehydrogenative Coupling of Toluene Promoted by Multi-Walled Carbon Nanotubes

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

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

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

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.].

DOI： 10.1007/s10562-019-02951-z

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

Yuki Hori, Koichiro Kubo, Yuta Nishina

Macromolecular Rapid Communications 42 ( 8 ) e2000577 2020年

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

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.

DOI： 10.1002/marc.202000577

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年11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：CELL PRESS

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.

DOI： 10.1016/j.celrep.2019.09.075

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

Muhammad Sohail Ahmad, Huixin He, Yuta Nishina

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

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

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

DOI： 10.1021/acs.orglett.9b02432

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

Ayano Satoh, Yuta Nishina

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

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

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

DOI： 10.1016/j.bmcl.2019.06.061

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：WILEY-V C H VERLAG GMBH

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.

DOI： 10.1002/celc.201901666

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