研究者詳細 - 山本　崇史

論文 - 山本　崇史

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Designing Molecularly Imprinted Polymer-Modified Boron-Doped Diamond Electrodes for Highly Selective Electrochemical Drug Sensors

Kanako Ishii, Genki Ogata, Takashi Yamamoto, Shuyi Sun, Hiroshi Shiigi, Yasuaki Einaga

ACS Sensors （ACS Publications） 9 （ 3 ） 1611 - 1619 2024年03月

研究論文（学術雑誌）, 共著, 査読有り

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An Electrochemical Diagnosis of Urinary Tract Infection Using Boron-doped Diamond Electrodes

Ziping Zhang, Genki Ogata, Kai Asai, Takashi Yamamoto, Yasuaki Einaga

ACS Sensors （ACS Publications） 8 （ 11 ） 4245 - 4252 2023年11月

研究論文（学術雑誌）, 共著, 査読有り

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Selective Electro-Oxidation of Cumene Utilizing a Flow Reactor Equipped with Diamond Electrodes

Shogo Nihongi, Riyako Matsuoka, Tsuyoshi Saitoh, Yasuaki Einaga, Takashi Yamamoto

Current Research in Green and Sustainable Chemistry （ELSEVIER） 7 100378 2023年10月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

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Spin Manipulation in a Metal-Organic Layer through Mechanical Exfoliation for Highly Selective CO₂ Photoreduction

Dayu Wu, Hua-Qing Yin, Zeshi Wang, Mingren Zhou, Chengfeng Yu, Jing Wu, Huixian Miao, Takashi Yamamoto, Wenjiang Zhaxi, Zetao Huang, Luying Liu, Wei Huang, Wenhui Zhong, Yasuaki Einaga, Jun Jiang, Zhi-Ming Zhang

Angewandte Chemie International Edition （Wiley-VCH GmbH） 62 （ 18 ） e202301925 2023年04月

研究論文（学術雑誌）, 共著, 責任著者, 査読有り

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Amine-Functionalized Diamond Electrode for Boosting CO₂ Reduction to CO

Tatsuhiko Mikami, Takashi Yamamoto, Mai Tomisaki, Yasuaki Einaga

ACS Sustainable Chemistry & Engineering （American Chemical Society） 10 （ 45 ） 14685 - 14692 2022年11月

研究論文（学術雑誌）, 共著, 責任著者, 査読有り

Carbon capture, utilization, and storage (CCUS) have been attracting much attention as an initiative to achieve carbon neutrality. In the capture and storage strategy, amines are widely used for highly efficient separation and capturing of CO₂ since amines react with CO₂ to form carbamates. In the utilization strategy, CO₂ electroreduction is a promising method to convert CO₂ into value-added compounds because reaction conditions are relatively mild and easily controlled. In this work, toward combining CO₂ capture and storage technologies and CO₂ electroreduction, we focused on amine modification of the electrode surface, in which boron-doped diamond (BDD) was chosen as a sustainable electrode material. CO₂ electroreduction using the amine-modified BDD was performed, and an applied potential dependence of the product selectivity was examined. In situ attenuated total reflectance-infrared measurements showed that the peak intensity of the stretching vibration of the carbonyl group at around 1640 cm^-1 decreased as applied potentials became more negative. The effect of amine modification of the BDD surface lies in the formation of a C-N bond during CO₂ electroreduction, resulting in the enhancement of the selectivity of CO production up to 8 times compared to the unmodified BDD.

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Electro-conversion of cumene into acetophenone using boron-doped diamond electrodes

Mana Kitano, Tsuyoshi Saitoh, Shigeru Nishiyama, Yasuaki Einaga, Takashi Yamamoto

Beilstein Journal of Organic Chemistry （Beilstein-Institut） 18 1154 - 1158 2022年09月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

A straightforward electro-conversion of cumene into acetophenone has been reported using boron-doped diamond (BDD) electrodes.This particular conversion is driven by the addition reaction of a cathodically generated hydroperoxide anion to an anodically generated cumyl cation, where the BDD’s wide potential window enables the direct anodic oxidation of cumene into the cumyl cation. Since electricity is directly employed as the oxidizing and reducing reagents, the present protocol is easy to use, suitable for scale-up, and inherently safe.

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Anodic Oxidation of Phenols: A Key Step for the Synthesis of Natural Products

Takashi Yamamoto, Tsuyoshi Saitoh, Yasuaki Einaga, Shigeru Nishiyama

2021年09月

研究論文（学術雑誌）, 共著, 筆頭著者, 責任著者, 査読有り

Fabrication and electrochemical properties of boron-doped SiC

Kazuki Uchiyama, Takashi Yamamoto, Yasuaki Einaga

Carbon （Carbon） 174 240 - 247 2021年04月

責任著者, 査読有り, ISSN 0008-6223

Silicon carbide (SiC) has excellent properties such as chemical and physical stability, biocompatibility, and high thermal conductivity. However, electrical conductivity of SiC is not high enough for electrochemical applications, which has been a major challenge. Here, in order to improve the conductivity, we prepared boron-doped SiC (SiC:B) and evaluated the electrochemical properties. SiC and SiC:B were fabricated by a microwave plasma chemical vapor deposition method. Structural characterization revealed that the main phase of SiC:B is 3C–SiC where the concentration of doped boron could be controlled by tuning the growth conditions. Electrochemical properties were evaluated by cyclic voltammetry measurements, indicating that the reactivity and sensitivity of the SiC:B electrode was comparable of that of the glassy carbon electrode.

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Weak Antilocalization and Spin Hall Effect in Pt Films Doped with Molecular Spin

Wataru Iwamoto, Takashi Yamamoto, Kaname Tsuchii, Yuya Tazaki, Akio Asami, Hiroki Hayashi, Yasuaki Einaga, Kazuya Ando

ACS Applied Electronic Materials （American Chemical Society (ACS)） 2 （ 7 ） 2098 - 2103 2020年07月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 2637-6113

© 2020 American Chemical Society. A high degree of tunability and versatility of organic chemistry has paved the way toward molecular engineering of electronic and spintronic devices. Here, we report molecular spin doping of a Pt film, the key material in spin orbitronics. The molecular spin doping using a monolayer of a metal terpyridine complex allows to control the interaction between the conduction electrons and localized magnetic moments in the Pt film. The interaction was probed by measuring the weak antilocalization, which demonstrates enhanced magnetic impurity scattering induced by the molecular spin doping. By measuring the spin-orbit torque generated by Pt doped with molecular spins, we found that the spin Hall effect is robust against the magnetic impurity scattering, showing that the significant spin-orbit coupling dominates the charge-to-spin conversion in Pt. These results demonstrate that the molecular spin doping paves the way to explore spin-orbitronics phenomena.

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Surface Rashba-Edelstein Spin-Orbit Torque Revealed by Molecular Self-Assembly

S. Haku, A. Ishikawa, A. Musha, H. Nakayama, T. Yamamoto, K. Ando

Physical Review Applied （Physical Review Applied） 13 （ 4 ） 044069 2020年04月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 2331-7019

© 2020 American Physical Society. © 2020 American Physical Society. We report the observation of a spin-orbit torque (SOT) originating from the surface Rashba-Edelstein effect. We find that the SOT in a prototypical spin-orbitronic system, a Pt/Co bilayer, can be manipulated by molecular self-assembly on the Pt surface. This provides evidence that the Rashba spin-orbit coupling at the Pt surface generates a sizable SOT, which is hidden by the strong bulk and interface spin-orbit coupling. We show that the molecular tuning of the surface Rashba-Edelstein SOT is consistent with density-functional-theory calculations. These results illustrate the crucial role of the surface spin-orbit coupling in the SOT generation, which alters the landscape of metallic spin-orbitronic devices.

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Avian Influenza Virus Detection by Optimized Peptide Termination on a Boron-Doped Diamond Electrode

Teruhiko Matsubara, Michiko Ujie, Takashi Yamamoto, Yasuaki Einaga, Tomo Daidoji, Takaaki Nakaya, Toshinori Sato

ACS Sensors （American Chemical Society (ACS)） 5 （ 2 ） 431 - 439 2020年02月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 2379-3694

Copyright © 2020 American Chemical Society. The development of a simple detection method with high sensitivity is essential for the diagnosis and surveillance of infectious diseases. Previously, we constructed a sensitive biosensor for the detection of pathological human influenza viruses using a boron-doped diamond electrode terminated with a sialyloligosaccharide receptor-mimic peptide that could bind to hemagglutinins involved in viral infection. Circulation of influenza induced by the avian virus in humans has become a major public health concern, and methods for the detection of avian viruses are urgently needed. Here, peptide density and dendrimer generation terminated on the electrode altered the efficiency of viral binding to the electrode surface, thus significantly enhancing charge-transfer resistance measured by electrochemical impedance spectroscopy. The peptide-terminated electrodes exhibited an excellent detection limit of less than one plaque-forming unit of seasonal H1N1 and H3N2 viruses. Furthermore, the improved electrode was detectable for avian viruses isolated from H5N3, H7N1, and H9N2, showing the potential for the detection of all subtypes of influenza A virus, including new subtypes. The peptide-based electrochemical architecture provided a promising approach to biosensors for ultrasensitive detection of pathogenic microorganisms.

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Enhancement of coercivity of self-assembled stacking of ferrimagnetic and antiferromagnetic nanocubes

Keisuke Sawano, Keishi Tsukiyama, Makoto Shimizu, Mihiro Takasaki, Yuya Oaki, Takashi Yamamoto, Yasuaki Einaga, Christian Jenewein, Helmut Cölfen, Hideo Kaiju, Tetsuya Sato, Hiroaki Imai

Nanoscale （Royal Society of Chemistry (RSC)） 12 （ 14 ） 7792 - 7796 2020年

研究論文（学術雑誌）, 共著, 査読有り, ISSN 2040-3364

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An electrochemical aptamer-based sensor prepared by utilizing the strong interaction between a DNA aptamer and diamond.

Asai K, Yamamoto T, Nagashima S, Ogata G, Hibino H, Einaga Y

The Analyst （Analyst） 145 （ 2 ） 544 - 549 2019年11月

共著, 査読有り, ISSN 0003-2654

© 2020 The Royal Society of Chemistry. Stable and continuous biosensing of electroactive species in vivo has been achieved by using boron-doped diamond (BDD) electrodes owing to their outstanding electrochemical properties. However, the present problem in biosensing using BDD electrodes is how to specifically measure/detect the target molecules, including electrochemically inactive species. A possible solution is to fabricate an electrochemical aptamer-based (E-AB) sensor using a BDD electrode. In a preliminary investigation, we found that DNA aptamers strongly adsorb on the BDD surface and the aptamer-adsorbed BDD apparently worked as an E-AB sensor. The present study reports the performance of the aptamer-adsorbed BDD electrode as an E-AB sensor. Doxorubicin (DOX), a widely used chemotherapeutic, was chosen as a target molecule. The sensor could be prepared by just dipping BDD in an aptamer solution for only 30 min, and the electrochemical signals were dependent on the DOX concentration. The adsorption of DNA was strong enough for continuous measurements and even a sonication treatment. Such behaviors were not observed when using gold and glassy carbon electrodes. In a kinetic measurement, distortion by a sluggish response was observed for both association and dissociation phases, indicating that the interaction between DOX and the aptamer involves several kinetic processes. By fitting to a Langmuir isotherm, a limit of detection of 49 nM and a maximum detectable concentration of 2.3 μM were obtained. Although the sensitivity was lower than those of the well-established E-AB sensors of gold, the values are within a drug's therapeutic range. Overall, the present work demonstrates that a DNA aptamer and a BDD electrode is an effective combination for an E-AB sensor with stable sensitivity, and a wide variety of DNA aptamers can be applied without any special treatment.

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Observation of Proton Transfer Coupled Spin Transition and Trapping of Photoinduced Metastable Proton Transfer State in an Fe(II) Complex.

Nakanishi T, Hori Y, Sato H, Wu SQ, Okazawa A, Kojima N, Yamamoto T, Einaga Y, Hayami S, Horie Y, Okajima H, Sakamoto A, Shiota Y, Yoshizawa K, Sato O

Journal of the American Chemical Society （Journal of the American Chemical Society） 141 （ 36 ） 14384 - 14393 2019年08月

共著, 査読有り, ISSN 0002-7863

An important technique to realize novel electron- and/or proton-based functionalities is to use a proton-electron coupling mechanism. When either a proton or electron is excited, the other one is modulated, producing synergistic functions. However, although compounds with proton-coupled electron transfer have been synthesized, crystalline molecular compounds that exhibit proton-transfer-coupled spin-transition (PCST) behavior have not been reported. Here, we report the first example of a PCST Fe(II) complex, wherein the proton lies on the N of hydrazone and pyridine moieties in the ligand at high-spin and low-spin Fe(II), respectively. When the Fe(II) complex is irradiated with light, intramolecular proton transfer occurs from pyridine to hydrazone in conjunction with the photoinduced spin transition via the PCST mechanism. Because the light-induced excited high-spin state is trapped at low temperatures in the Fe(II) complex-a phenomenon known as the light-induced excited-spin-state trapping effect-the light-induced proton-transfer state, wherein the proton lies on the N of hydrazone, is also trapped as a metastable state. The proton transfer was accomplished within 50 ps at 190 K. The bistable nature of the proton position, where the position can be switched by light irradiation, is useful for modulating proton-based functionalities in molecular devices.

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Influence of the Nature of Boron-Doped Diamond Anodes on the Dehydrogenative Phenol-Phenol Cross-Coupling

Gleede B., Yamamoto T., Nakahara K., Botz A., Graßl T., Neuber R., Matthée T., Einaga Y., Schuhmann W., Waldvogel S.

ChemElectroChem （ChemElectroChem） 6 （ 10 ） 2771 - 2776 2019年05月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 2196-0216

© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Boron-doped diamond (BDD) represents a powerful and innovative electrode material. In particular, in combination with fluorinated solvents such as 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), the system exhibits the largest known electrochemical window of approximately 5 V in protic media. Furthermore, the anodic treatment allows the direct formation of oxyl radicals, which are known to exhibit specific reactivity. The electrochemical dehydrogenative phenol-phenol cross-coupling is a versatile and useful transformation to non-symmetric biphenols. This electro-organic conversion can be divided into two regimes: initial oxidation at the anode and the electrolyte-controlled follow-up reaction. This work intends to provide an answer about the influence of BDD electrodes on oxidation reactions in electrosynthesis. Depending on the electro-organic transformation, the support material of BDD, its boron content, and its fabrication method have a significant influence on the electrosynthetic efficiency.

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Thermoresponsive, Freezing-Resistant Smart Windows with Adjustable Transition Temperature Made from Hydroxypropyl Cellulose and Glycerol

Nakamura C., Yamamoto T., Manabe K., Nakamura T., Einaga Y., Shiratori S.

Industrial and Engineering Chemistry Research （Industrial and Engineering Chemistry Research） 58 （ 16 ） 6424 - 6428 2019年04月

共著, ISSN 08885885

© 2019 American Chemical Society. A thermoresponsive smart window that can switch its transmittance to control heating from sunlight is attracting great attention. Such windows made from a hydrogel of a thermoresponsive polymer such as poly(N-isopropylacrylamide) (PNIPAm) or hydroxypropyl cellulose (HPC) have been successful and can switch their transmittance at room temperature. However, such hydrogels occasionally freeze in cold places, degrading their transmittance. Thus, a thermoresponsive hydrogel that can be used in various geographical regions is desired. Here, we produced a thermoresponsive smart window with freezing resistance made from HPC and glycerol. We could adjust its switching temperature by simply changing the amount of added glycerol, letting us easily change it to room temperature for practical use. These smart windows show high cyclic performance, freezing resistance, and heat shielding, demonstrating great potential.

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Oxidative Cleavage of the Acyl-Carbon Bond in Phenylacetone with Electrogenerated Superoxide Anions

Zhang, Y., Sugai, T., Yamamoto, T., Yamamoto, N., Kutsumura, N., Einaga, Y., Nishiyama, S., Saitoh, T., Nagase, H.

ChemElectroChem （ChemElectroChem） 6 （ 16 ） 4194 - 4198 2019年

共著, 査読有り, ISSN 2196-0216

© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim An oxidative cleavage reaction of the acyl−carbon bond in phenylacetone derivatives under cathodic reduction is reported. This particular transformation is driven by the cathodic reduction of dissolved molecular oxygen to superoxide anions. Various cathode materials were examined, and we discovered that boron-doped diamond (BDD) enables highly efficient molecular conversion, owing to BDD's outstanding electrochemical property for utilizing the small amounts of molecular oxygen effectively. The scope of the reaction is broad and can be applied to a variety of substrates, ranging from ketones to esters and amides. As an electric current is directly employed to generate the superoxide anion, the reaction is metal- and catalyst-free. Electro-organic synthesis using the carbon-based BDD electrode thus provides access to sustainable molecular transformations.

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In situ spectroscopic study on the surface hydroxylation of diamond electrodes

Kasahara S., Ogose T., Ikemiya N., Yamamoto T., Natsui K., Yokota Y., Wong R., Iizuka S., Hoshi N., Tateyama Y., Kim Y., Nakamura M., Einaga Y.

Analytical Chemistry （Analytical Chemistry） 91 （ 8 ） 4980 - 4986 2019年

研究論文（学術雑誌）, 共著, ISSN 00032700

© 2019 American Chemical Society. Carbon-based materials are regarded as an environmentally benign alternative to the conventional metal electrode used in electrochemistry from the viewpoint of sustainable chemistry. Among various carbon electrode materials, boron-doped diamond (BDD) exhibits superior electrochemical properties. However, it is still uncertain how surface chemical species of BDD influence the electrochemical performance, because of the difficulty in characterizing the surface species. Here, we have developed in situ spectroscopic measurement systems on BDD electrodes, i.e., in situ attenuated total reflection infrared spectroscopy (ATR-IR) and electrochemical X-ray photoelectron spectroscopy (EC-XPS). ATR-IR studies at a controlled electrode potential confirmed selective surface hydroxylation. EC-XPS studies confirmed deprotonation of C-OH groups at the BDD/electrolyte interface. These findings should be important not only for better understanding of BDD's fundamentals but also for a variety of applications.

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High-temperature cooperative spin crossover transitions and single-crystal reflection spectra of [Fe^III(qsal)₂](CH₃OSO₃) and related compounds

Takahashi K., Yamamoto K., Yamamoto T., Einaga Y., Shiota Y., Yoshizawa K., Mori H.

Crystals （Crystals） 9 （ 2 ） 2019年

共著, ISSN 2073-4352

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. New Fe(III) compounds from qsal ligand, [Fe(qsal) 2 ](CH 3 OSO 3 ) (1) and [Fe(qsal) 2 ](CH 3 SO 3 )·CH 3 OH (3), along with known compound, [Fe(qsal) 2 ](CF 3 SO 3 ) (2), were obtained as large well-shaped crystals (Hqsal = N-(8-quinolyl)salicylaldimine). The compounds 1 and 2 were in the low-spin (LS) state at 300 K and exhibited a cooperative spin crossover (SCO) transition with a thermal hysteresis loop at higher temperatures, whereas 3 was in the high-spin (HS) state below 300 K. The optical conductivity spectra for 1 and 3 were calculated from the single-crystal reflection spectra, which were, to the best of our knowledge, the first optical conductivity spectra of SCO compounds. The absorption bands for the LS and HS [Fe(qsal) 2 ] cations were assigned by time-dependent density functional theory calculations. The crystal structures of 1 and 2 consisted of a common one-dimensional (1D) array of the [Fe(qsal) 2 ] cation, whereas that of 3 had an unusual 1D arrangement by π-stacking interactions which has never been reported. The crystal structures in the high-temperature phases for 1 and 2 indicate that large structural changes were triggered by the motion of counter anions. The comparison of the crystal structures of the known [Fe(qsal) 2 ] compounds suggests the significant role of a large non-spherical counter-anion or solvate molecule for the total lattice energy gain in the crystal of a charged complex.

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Electrochemical Pinacol Coupling of Acetophenone Using Boron-Doped Diamond Electrode

Nakahara K., Naba K., Saitoh T., Sugai T., Obata R., Nishiyama S., Einaga Y., Yamamoto T.

ChemElectroChem （ChemElectroChem） 6 （ 16 ） 4153 - 4157 2019年

共著, ISSN 2196-0216

© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim An electrochemical pinacol coupling reaction of acetophenone using a boron-doped diamond (BDD) electrode has been reported. This transformation is driven by the one-electron reduction of acetophenone on the BDD cathode, followed by an intermolecular radical coupling. Owing to the BDD's outstanding electrochemical properties, the pinacol-type compound has been obtained in good conversion yield. The roles of a supporting electrolyte and solvent were addressed; (1) lithium ions contribute to increase in the reactivity of the radical intermediate. (2) Addition of water promotes the electron transfer process at the BDD surface. The reaction is relatively tolerant to para-substituted acetophenone derivatives. Since electric current is directly employed as reducing reagents to generate a radical intermediate, the reaction is metal-free, sustainable, and inherently safe.

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山本 崇史

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論文 - 山本　崇史