Einaga, Yasuaki

写真a

Affiliation

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

Position

Professor

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Career 【 Display / hide 】

  • 1997.04
    -
    1998.03

    理化学研究所 ,ジュニアリサーチアソシエイト

  • 1998.04
    -
    1999.11

    日本学術振興会 ,特別研究員

  • 1999.11
    -
    2001.03

    東京大学 ,助手

  • 2001.04
    -
    2003.03

    慶應義塾大学理工学部化学科, 専任講師

  • 2003.04
    -
    2011.03

    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

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Academic Degrees 【 Display / hide 】

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

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Research Areas 【 Display / hide 】

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

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Books 【 Display / hide 】

  • Diamond Electrodes: Fundamentals and Applications

    Einaga Y., Diamond Electrodes: Fundamentals and Applications, 2022.01

    　View Summary

    This book introduces the recent development in Japan of diamond electrodes, which has attracted much attention in the world. For example, electrochemical sensors using diamond electrodes are now being utilized commercially. Newly developing applications such as electrochemical organic synthesis including CO2 reduction are also expected to form an important future technology. Those emerging applications to various fields which are receiving increasing attention are described in detail here. This book is useful not only for students who would like to begin their study of diamond electrodes but also for industries that are exploring novel electrochemical applications.

  • Electrogenerated Chemiluminescence at Diamond Electrode

    Irkham , Fiorani A., Einaga Y., Diamond Electrodes: Fundamentals and Applications, 2022.01

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    Electrogenerated chemiluminescence (also known as electrochemiluminescence and abbreviated ECL) is a complex phenomenon of luminescence triggered by electrochemical reactions where the heterogeneous electron transfer, then ECL as consequence, is affected by the electrode materials which is crucial in the signal development and intensity. Among electrode materials, doped diamond electrodes are still underdeveloped for ECL application especially compared to the more commons noble metals and other carbon-based. After a brief and general introduction on electrochemiluminescence, this chapter will focus on several studies and developments of doped diamond electrodes by taking advantage on its own unique properties as the electrode for ECL.

  • Electrochemical Properties of BDD Electrodes by Surface Control

    Einaga Y., Kasahara S., Natsui K., Diamond Electrodes: Fundamentals and Applications, 2022.01

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    Boron-doped diamond (BDD) has attracted much attention as a promising electrode material, because it has excellent electrochemical properties such as a wide potential window and low background current. It is known that the electrochemical properties of BDD electrodes are very sensitive to the surface termination such as to whether it is hydrogen- or oxygen-terminated. Especially for electrochemical sensor application, pretreating BDD electrodes by cathodic reduction (CR) to hydrogenate the surface has been widely used to achieve high sensitivity. However, little is known about the effects of the CR treatment conditions on surface hydrogenation. In this chapter, at first, a systematic study of CR treatments in order that we can achieve effective surface hydrogenation is discussed. Also, direct observation of surface hydroxylation by anodic oxidation was reported. 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). Furthermore, surface modification by functional molecules to introduce specific functions is also discussed. As examples, photochemical modification method via UV irradiation and electrochemical modification method are introduced. These surface control and modification should be important not only for better understanding of BDD’s fundamentals but also for a variety of applications.

  • Electrochemical CO<inf>2</inf> Reduction

    Tomisaki M., Einaga Y., Diamond Electrodes: Fundamentals and Applications, 2022.01

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    BDD electrode was utilized as the cathode for the electrochemical CO2 reduction due to its high hydrogen overpotential and high stability. Electroreduction of CO2 is one of the ways to convert CO2 into useful compounds which can be used in industrial fields and can be used as fuels. The efficiency or selectivity for the production of CO2 reduction products can be affected by electrode materials and electrolysis conditions. BDD electrode is inert, so formic acid production was predominant. However, we could also produce various kinds of products from CO2 by optimizing the electrode itself or electrolysis conditions. Many kinds of BDD electrodes were used such as BDD electrodes with various boron doping level, BDD electrodes with sp2 carbon impurities and BDD electrodes modified with metal particles electrochemically. Electrolysis conditions were also optimized such as the applied potential, applied current, catholyte and anolyte. In this chapter, the electrochemical CO2 reduction using BDD electrodes or using metal-modified BDD electrodes was described.

  • In Vivo Real-Time Measurement of Drugs

    Ogata G., Sawamura S., Asai K., Kusuhara H., Einaga Y., Hibino H., Diamond Electrodes: Fundamentals and Applications, 2022.01

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    Drugs play a key role in the treatment of patients with various diseases. A compound, when administered systemically, shows differential spatial and temporal distribution patterns not only in the body but also within each organ. In response to an increase or decrease in local concentrations in the organ, the activity of the cell population expressing the drug’s target protein(s) changes over time. Therefore, real time, simultaneous detection of kinetics of the drug and its pharmacological effects in in vivo microenvironments is essential for evaluating the efficacy of medicines. Although such challenging dual-mode measurement has not yet been addressed by any conventional methods, it has been successfully achieved via a microsensing system that we recently developed. The system consists of two different sensors: A needle-type boron-doped diamond microelectrode for monitoring the drug and a glass microelectrode for tracking electrophysiological activity of the target cells. This state-of-the-art approach is applicable to various drugs in terms of “local” pharmacokinetic and pharmacodynamic assays in vivo and may contribute to the development of next-generation therapeutic interventions.

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Papers 【 Display / hide 】

  • Fabrication of three-dimensional boron-doped diamond electrodes on SiC scaffolds

    Otake A., Diaz-Herrezuelo I., Uchiyama K., Fiorani A., Belmonte M., Einaga Y.

    Diamond and Related Materials (Diamond and Related Materials)  146 2024.06

    ISSN  09259635

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    Three-dimensional (3D) architected electrode materials are expected to exhibit advantageous properties such as enlarged surface area, increased mass transfer, enhanced adsorption and more active sites exposed. In this paper, boron-doped diamond (BDD) electrodes on 3D printed patterned silicon carbide (SiC) scaffolds have been fabricated using chemical vapor deposition (CVD). The stabilization of the plasma sphere by using clamshell type CVD reactor, introducing the outer protecting plate, the optimization of CVD parameters, and the design of 3D-SiC scaffolds improved the sp3/sp2 ratio, uniformity and growth rate of BDD. 3D-BDD electrodes exhibit enough electrical conductivity for electrochemical applications. The preliminary test for electrochemical carbon dioxide reduction (CO2R) has showed the potential advantages of this type of 3D structured BDD electrodes.

  • Fabrication of polycrystalline phosphorus-doped diamond electrodes from red phosphorus

    Moriguchi T., Tomisaki M., Sato S., Nakamura J., Yamada H., Einaga Y.

    Physical Chemistry Chemical Physics (Physical Chemistry Chemical Physics)  26 ( 20 ) 14825 - 14831 2024.05

    ISSN  14639076

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    Polycrystalline phosphorus-doped diamond was fabricated by the quartz-tube-type microwave plasma-assisted chemical vapor deposition method. Significantly, red phosphorus was used as a source of phosphorous, instead of PH3. Phosphorus-doped diamond electrodes with hydrogen-terminated and oxygen-terminated surfaces were investigated for the redox reactions of K3[Fe(CN)6] and [Ru(NH3)6]Cl3. The carrier concentration was estimated as 2.1-5.3 × 1018 cm−3 from electrochemical impedance measurements. Polycrystalline phosphorus-doped diamond shows great promise as chemical electrode materials.

  • Green Synthesis of Ceria Nanoparticles from Cassava Tubers for Electrochemical Aptasensor Detection of SARS-CoV-2 on a Screen-Printed Carbon Electrode

    Zakiyyah S.N., Irkham N., Einaga Y., Gultom N.S., Fauzia R.P., Kadja G.T.M., Gaffar S., Ozsoz M., Hartati Y.W.

    ACS Applied Bio Materials (ACS Applied Bio Materials)  7 ( 4 ) 2488 - 2498 2024.04

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    Green synthesis approaches for making nanosized ceria using starch from cassava as template molecules to control the particle size are reported. The results of the green synthesis of ceria with an optimum calcination temperature of 800 °C shows a size distribution of each particle of less than 30 nm with an average size of 9.68 nm, while the ratio of Ce3+ to Ce4+ was 25.6%. The green-synthesized nanoceria are applied to increase the sensitivity and attach biomolecules to the electrode surface of the electrochemical aptasensor system for coronavirus disease (COVID-19). The response of the aptasensor to the receptor binding domain of the virus was determined with the potassium ferricyanide redox system. The screen-printed carbon electrode that has been modified with green-synthesized nanoceria shows 1.43 times higher conductivity than the bare electrode, while those modified with commercial ceria increase only 1.18 times. Using an optimized parameter for preparing the aptasensors, the detection and quantification limits were 1.94 and 5.87 ng·mL-1, and the accuracy and precision values were 98.5 and 89.1%. These results show that green-synthesized ceria could be a promising approach for fabricating an electrochemical aptasensor.

  • Modification of boron-doped diamond electrode with polyaniline and gold particles to enhance the electrochemiluminescence of luminol for the detection of reactive oxygen species (hydrogen peroxide and hypochlorite)

    Rahmawati I., Fiorani A., Sanjaya A.R., Irkham , Du J., Saepudin E., Einaga Y., Ivandini T.A.

    Diamond and Related Materials (Diamond and Related Materials)  144 2024.04

    ISSN  09259635

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    A luminol electrochemiluminescence (ECL)-based sensor for reactive oxygen species (ROS), including H2O2 and hypochlorite was developed using gold particles-modified on polyaniline‑boron doped diamond electrode (Au-PANI/BDD). The gold particles were incorporated onto the surface of boron-doped diamond (BDD) electrode to enhance the electrochemiluminescence of luminol, while the polyaniline was used to provide better attachment of the gold particles on the surface of BDD electrode. The uniform distribution of gold particles on the PANI/BDD surface was verified through FE-SEM EDX analysis with an approximately weight percentage of 45.6 % (w/w). The modified electrode exhibited a remarkable five-fold increase in ECL intensity compared to the unmodified BDD, resulting in higher sensitivity. Furthermore, the sensor's performance was successfully demonstrated for H2O2 concentrations ranged linearly from 1 to 100 μM (R2 ≥ 0.99) with a low detection limit of 0.81 μM, and for hypochlorite concentrations from 1 to 20 μM (R2 ≥ 0.99) with a detection limit as low as 0.51 μM. Additionally, excellent repeatability and stability of the signals was also observed over 7 days. Furthermore, successful application in detecting H2O2 and hypochlorite in real sample highlights its promising potential as an ROS sensor.

  • Sluggish Electron Transfer of Oxygen-Terminated Moderately Boron-Doped Diamond Electrode Induced by Large Interfacial Capacitance between a Diamond and Silicon Interface

    Otake A., Nishida T., Ohmagari S., Einaga Y.

    JACS Au (JACS Au)  4 ( 3 ) 1184 - 1193 2024.03

    　View Summary

    Boron-doped diamond (BDD) has tremendous potential for use as an electrode material with outstanding characteristics. The substrate material of BDD can affect the electrochemical properties of BDD electrodes due to the different junction structures of BDD and the substrate materials. However, the BDD/substrate interfacial properties have not been clarified. In this study, the electrochemical behavior of BDD electrodes with different boron-doping levels (0.1% and 1.0% B/C ratios) synthesized on Si, W, Nb, and Mo substrates was investigated. Potential band diagrams of the BDD/substrate interface were proposed to explain different junction structures and electrochemical behaviors. Oxygen-terminated BDD with moderate boron-doping levels exhibited sluggish electron transfer induced by the large capacitance generated at the BDD/Si interface. These findings provide a fundamental understanding of diamond electrochemistry and insight into the selection of suitable substrate materials for practical applications of BDD electrodes.

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Papers, etc., Registered in KOARA 【 Display / hide 】

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Reviews, Commentaries, etc. 【 Display / hide 】

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

  • 電解発生活性化学種の利用による新物質変換系の構築

    2023.04
    -
    2026.03

    基盤研究(A), Principal investigator

  • 革新的sp3機能電極材料の創製

    2019.04
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    2022.03

    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

    2016.04
    -
    2019.03

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

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Courses Taught 【 Display / hide 】

  • SEMINAR IN CHEMISTRY

    2025

  • NANO SCALE SCIENCE JOINT SEMINAR

    2025

  • MATERIAL DESIGN SCIENCE JOINT SEMINAR

    2025

  • LABORATORIES IN CHEMISTRY 1

    2025

  • LABORATORIES IN BASIC CHEMISTRY

    2025

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