Einaga, Yasuaki



Faculty of Science and Technology, Department of Chemistry (Yagami)



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Career 【 Display / hide

  • 1997.04

    理化学研究所 ,ジュニアリサーチアソシエイト

  • 1998.04

    日本学術振興会 ,特別研究員

  • 1999.11

    東京大学 ,助手

  • 2001.04

    慶應義塾大学理工学部化学科, 専任講師

  • 2003.04

    慶應義塾大学理工学部化学科, 助教授/准教授

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Academic Background 【 Display / hide

  • 1994.03

    The University of Tokyo, Faculty of Science

    University, Graduated

  • 1996.03

    The University of Tokyo, Graduate School, Division of Science, 化学専攻

    Graduate School, Completed, Master's course

  • 1999.03

    The University of Tokyo, Graduate School, Division of Science, 応用化学専攻

    Graduate School, Completed, Doctoral course

Academic Degrees 【 Display / hide

  • 博士(工学), The University of Tokyo, 1999.03


Research Areas 【 Display / hide

  • Nanotechnology/Materials / Functional solid state chemistry (Functional Material Chemistry)


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  • Low-interference norepinephrine signal on dopamine detection using nafion-coated boron doped diamond electrodes

    Irkham , Nasa K., Kurnia I., Hartati Y.W., Einaga Y.

    Biosensors and Bioelectronics (Biosensors and Bioelectronics)  220 2023.01

    ISSN  09565663

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    The detection of dopamine in the presence of norepinephrine using nafion-coated boron doped diamond (Nafion-BDD) electrodes was presented. An increase current signal for dopamine could be observed at around 0.75 V using Nafion-BDD, while a change in the current signal of norepinephrine that appears at similar potential was not observed. This might be due to electronegativity of the norepinephrine that is not positive enough to be attracted towards the nafion membrane, albeit neutral enough to pass through the membrane and undergo electrochemical oxidation. An optimization process including accumulation time of dopamine inside the nafion layer, solution of the pH, and nafion thickness was conducted to exploit the difference electrochemical behavior between those two catecholamines at the Nafion-BDD. Using an accumulation time of 300 s, solution pH of 7, and nafion thickness of 1.1 μm, dopamine's LOD was found to be 0.966 μM. Low-interference signal of norepinephrine to the dopamine could be observed with an excellent %recovery of dopamine in 5% range when the concentration of norepinephrine was 10 times lower compared to dopamine concentration.

  • Boron-Doped Diamond Electrodes: Fundamentals for Electrochemical Applications

    Einaga Y.

    Accounts of Chemical Research (Accounts of Chemical Research)  55 ( 24 ) 3605 - 3615 2022.12

    ISSN  00014842

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    ConspectusBoron-doped diamond (BDD) electrodes have emerged as next-generation electrode materials for various applications in electrochemistry such as electrochemical sensors, electrochemical organic synthesis, CO2 reduction, ozone water generation, electrochemiluminescence, etc. An optimal BDD electrode design is necessary to realize these applications. The electrochemical properties of BDD electrodes are determined by important parameters such as (1) surface termination, (2) surface orientation, and (3) boron doping level.In this Account, we discuss how these parameters contribute to the function of BDD electrodes. First, control of the surface termination (hydrogen/oxygen) is described. The electrochemical conditions such as the solution pH and the application potential were studied precisely. It was confirmed that an acidic solution and the application of negative potential accelerate hydrogenation, and the mechanism behind this is discussed. For oxygenation, we directly observed changes in surface functional groups by in situ attenuated total reflection infrared spectroscopy and electrochemical X-ray photoelectron spectroscopy measurements.Next, the difference in surface orientation was examined. We prepared homoepitaxial single-crystal diamond electrodes comprising (100) and (111) facets with similar boron concentrations and resistivities and evaluated their electrochemical properties. Experimental results and theoretical calculations revealed that (100)-oriented single-crystal BDD has a wider space charge layer than (111)-oriented BDD, resulting in a slower response. Furthermore, isolated single-crystal microparticles of BDD with exposed (100) and (111) crystal facets were grown, and we studied the electrochemical properties of the respective facets by combination with hopping-mode scanning electrochemical cell microscopy.We also systematically investigated how the boron concentration and sp2 species affect the electrochemical properties. The results showed that the appropriate composition (boron and sp2 species level) is dependent on the application. The transmission electron microscopy images and electron energy loss spectra of highly boron-doped BDD are shown, and the relationship between the composition and electrochemical properties is discussed. Finally, we investigated in detail the effect of the sp2 component on low-doped BDD. Surprisingly, although the sp2 component is usually expected to induce a narrowing of the potential window and an increase in the charging current, low-doped BDD showed the opposite trend depending on the degree of sp2 carbon.The results and discussion presented in this Account will hopefully promote a better understanding of the fundamentals of BDD electrodes and be useful for the optimal development of electrodes for future applications.

  • Boron-Doped Diamond as a Quasi-Reference Electrode

    Peng Z., Fiorani A., Akai K., Murata M., Otake A., Einaga Y.

    Analytical Chemistry (Analytical Chemistry)  94 ( 48 ) 16831 - 16837 2022.12

    ISSN  00032700

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    As a working electrode, boron-doped diamond (BDD) has been studied in detail in electrochemical processes because of its superior electrochemical properties. However, these characteristics have rarely been mentioned when BDD is used as a quasi-reference electrode (QRE). Herein, we conducted a systematic investigation on BDD electrodes, with different boron-doping levels (1 and 0.1%) and different surface terminations (hydrogen and oxygen) for their application as a QRE. A BDD electrode with 1% boron and a hydrogen-terminated surface achieved the best stability. Its open-circuit potential (OCP) exhibited less than 100 mV of potential drift over 6000 s and showed a minuscule half-wave potential difference (E1/2) of 0.0037 V in 0.1 mM K3[Fe(CN)6]/1 M KCl solution before and after the OCP measurement. Based on these observations, anions are found to contribute to the potential, which we preliminarily speculate as related to the capacitance caused by electrostatic adsorption on the positively charged hydrogen-terminated surface. The repeatability of measurement was verified through continuous cyclic voltammetry tests in 0.1 mM K3[Fe(CN)6]/1 M KCl, showing a maximum E1/2 difference of 0.042 V. The contribution of the redox couples was excluded, and the repeatability was considered to originate from its surface stability. Finally, a linear response of the optimized BDD as a QRE was validated (R2 > 0.99) by determination of free chlorine and dopamine concentrations, respectively. These results consolidate the existing fundamental research on BDD electrodes and promote the possibility of its application as a QRE in harsh environments or in vivo biological monitoring.

  • Electrochemical detection of triamterene in human urine using boron-doped diamond electrodes

    Ishii K., Ogata G., Einaga Y.

    Biosensors and Bioelectronics (Biosensors and Bioelectronics)  217 2022.12

    ISSN  09565663

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    Urine is one of the most used biological fluids for screening drug delivery and the resultant metabolites. In sports, the use of diuretics such as triamterene is considered a violation of anti-doping rules and is stipulated to be present at less than 79 nM in urine by the World Anti-Doping Agency (WADA). It is therefore important to develop effective rapid and low-cost tests for this diuretic. Here we apply electrochemical analysis using boron-doped diamond (BDD) electrodes, which have superior properties such as low background current, a wide potential window, and high resistance to deactivation. Since real urine samples show clear oxidation current peaks in the potential range more positive than 0.5 V (vs. Ag/AgCl) due to the presence of bio-components such as protein, uric acid, and ascorbic acid, to detect triamterene effectively, the electrochemical protocol was optimized towards a potential range where the other components have limited effect. Our results show that reduced triamterene exhibits an oxidation peak at 0.1 V (vs. Ag/AgCl) in 0.1 M phosphate buffer (PB) and at 0.2 V (vs. Ag/AgCl) in pooled human urine. The peak current value increased according to the triamterene concentration. The limit of detection (LOD) was 3.15 nM in the PB and 7.80 nM in pooled human urine. Finally, triamterene detection was attempted in individual urine samples. Triamterene was electrochemically detectable in individual urine samples, excluding urine samples containing an excess amount of ascorbic acid. The limit of detection (LOD) in individual urine samples was determined to be 20.8 nM.

  • Application of boron doped diamond electrodes to electrochemical gas sensor

    Triana Y., Ogata G., Einaga Y.

    Current Opinion in Electrochemistry (Current Opinion in Electrochemistry)  36 2022.12

    ISSN  24519103

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    Boron-doped diamond (BDD) electrodes have been attracting attention as superior electrode materials for electrochemical sensing applications. Here, we focused on applications of the BDD electrodes to electrochemical gas sensing especially dissolved gas in aqueous solution. This article discusses arsine, hydrogen sulfide, nitrogen dioxide gas for environmental sensing, and oxygen in the blood for biomedical sensing. The analytical performances suggest that BDD electrodes are more than adequate for determining the concentration of these gas species.

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Research Projects of Competitive Funds, etc. 【 Display / hide

  • 革新的sp3機能電極材料の創製


    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (A) , Principal investigator

  • 光制御可能な超伝導ナノ微粒子の創製


    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Principal investigator


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