Papers - Einaga, Yasuaki

Cathodic reductive coupling of methyl cinnamate on boron-doped diamond electrodes and synthesis of new neolignan-type products

Kojima Taiki, Obata Rika, Saito Tsuyoshi, Einaga Yasuaki, Nishiyama Shigeru

Beilstein Journal of Organic Chemistry 11   200 - 203 2015.02

ISSN  1860-5397

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<p>The electroreduction reaction of methyl cinnamate on a boron-doped diamond (BDD) electrode was investigated. The hydrodimer, dimethyl 3,4-diphenylhexanedioate (racemate/meso = 74:26), was obtained in 85% yield as the major product, along with small amounts of cyclic methyl 5-oxo-2,3-diphenylcyclopentane-1-carboxylate. Two new neolignan-type products were synthesized from the hydrodimer.</p>

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Photochromism-induced amplification of critical current density in superconducting boron-doped diamond with an azobenzene molecular layer

Natsui Keisuke, Yamamoto Takashi, Akahori Miku, Einaga Yasuaki

ACS Applied Materials and Interfaces 7 ( 1 ) 887 - 894 2015.01

ISSN  1944-8244

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<p>A key issue in molecular electronics is the control of electronic states by optical stimuli, which enables fast and high-density data storage and temporal-spatial control over molecular processes. In this article, we report preparation of a photoswitchable superconductor using a heavily boron-doped diamond (BDD) with a photochromic azobenzene (AZ) molecular layer. BDDs electrode properties allow for electrochemical immobilization, followed by copper(I)-catalyzed alkyne-azide cycloaddition (a click reaction). Superconducting properties were examined with magnetic and electrical transport measurements, such as field-dependent isothermal magnetization, temperature-dependent resistance, and the low-temperature voltage-current response. These measurements revealed reversible amplification of the critical current density by 55% upon photoisomerization. This effect is explained as the reversible photoisomerization of AZ inducing an inhomogeneous electron distribution along the BDD surface that renormalizes the surface pinning contribution to the critical current.</p>

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Electrochemical properties of phosphorus doped diamond

Mukuda Yu, Watanabe Takeshi, Ueda Akihiko, Nishibayashi Yoshiki, Einaga Yasuaki

Electrochimica Acta 179   599 - 603 2015.01

ISSN  0013-4686

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<p>The electrochemical properties of an n-type phosphorus doped diamond (PDD) electrode were investigated and compared with a p-type boron doped diamond (BDD) electrode. The Mott-Schottky plots in 0.1 M HClO₄ are reported and related to the energy band diagram of electrochemically pretreated BDD and PDD. These results revealed that the band position of anodically pretreated PDD corresponded to the one of anodically pretreated BDD. Moreover, it was found the flat-band potential of the anodically pretreated PDD decreased by ca. 1 V after cathodically pretreatment. The cyclic voltammetries for Ru(NH₃)₆
^3+/2+ showed that electrochemical behaviors of PDD and BDD were entirely different in possible direction for charge transfer across the electrode-electrolyte inaterface. In addition, less n-type diode-like behavior was observed at the cathodically pretreated PDD than the anodically pretreated PDD. These results point out the importance of the surface chemistry controlled by electrochemical pretreatments.</p>

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Development of μtas for high-throughput screening of nad(p)-dependent oxidoreductases

Shimokihara Shota, Shitara Shunya, Oyobiki Ryo, Watanabe Takeshi, Einaga Yasuaki, Matsumoto Yoshinori, Fujiwara Kei, Horisawa Kenichi, Doi Nobuhide

  1302 - 1304 2015

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<p>Although oxidoreductases are widely used in many applications, such as biosensors and biofuel cells, improvements in the function of existing oxidoreductases or the discovery of novel oxidoreductases with greater activity is desired. To increase the activity of oxidoreductases by directed evolution, a powerful screening technique for oxidoreductases is required. In this study, we developed a microfluidic total analysis system for high-throughput screening of NAD(P)-dependent oxidoreductases. This system comprises three microfluidic devices: an encapsulating device, a NADH measuring device, and a magnetic beads sorting device. We demonstrated the utility of each part of the system.</p>

Antiferromagnetic transition in a novel star-shaped high-spin Fe(III) tetranuclear cluster from a mononuclear coordination anion featuring π-extended schiff base ligands

Takahashi Kazuyuki, Kawamukai Kiko, Mochida Tomoyuki, Sakurai Takahiro, Ohta Hitoshi, Yamamoto Takashi, Einaga Yasuaki, Mori Hatsumi, Shimura Yasuyuki, Sakakibara Toshiro, Fujisawa Takumi, Yamaguchi Akira, Sumiyama Akihiko

Chemistry Letters 44 ( 6 ) 840 - 842 2015

ISSN  0366-7022

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<p>A novel star-shaped high-spin Fe(III) tetranuclear cluster was unexpectedly obtained by the reaction of an [Fe&lt;sup&gt;III&lt;/sup&gt;(phsal)&lt;inf&gt;2&lt;/inf&gt;]&lt;sup&gt;-&lt;/sup&gt; anion with an Fe(II) coordination cation (H&lt;inf&gt;2&lt;/inf&gt;phsal: N-(2- hydroxyphenyl)salicylaldimine). Despite a star-shaped Fe(III) tetranuclear structure similar to reported Fe(III) single molecule magnets, the present compound exhibited a bulk antiferromagnetic transition at 0.6K due to a magnetic exchange coupling through intercluster π-stacking interactions.</p>

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Advances in electrochemical biosensing using boron doped diamond microelectrode

Fierro Stéphane, Einaga Yasuaki

Topics in Applied Physics 121   295 - 318 2015

ISSN  0303-4216

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<p>The development of boron doped diamond (BDD) as electrode material lead to significant improvement toward optimal sensitivity, reproducibility and stability during the in vivo monitoring of electroactive species. The most recent developments in the field of biosensing using BDD electrodes, namely the fabrication of the sensor and application in monitoring of dopamine and glutathione, are described in this chapter.</p>

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Yeast-based biochemical oxygen demand sensors using goldmodified boron-doped diamond electrodes

Ivandini Tribidasari A., Harmesa [No Value], Saepudin Endang, Einaga Yasuaki

Analytical Sciences 31 ( 7 ) 643 - 649 2015

ISSN  0910-6340

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<p>A gold nanoparticle modified boron-doped diamond electrode was developed as a transducer for biochemical oxygen demand (BOD) measurements. Rhodotorula mucilaginosa UICC Y-181 was immobilized in a sodium alginate matrix, and used as a biosensing agent. Cyclic voltammetry was applied to study the oxygen reduction reaction at the electrode, while amperometry was employed to detect oxygen, which was not consumed by the microorganisms. The optimum waiting time of 25 min was observed using 1-mm thickness of yeast film. A comparison against the system with free yeast cells shows less sensitivity of the current responses with a linear dynamic range (R&lt;sup&gt;2&lt;/sup&gt; = 0.99) of from 0.10 mM to 0.90 mM glucose (equivalent to 10 - 90 mg/L BOD) with an estimated limit of detection of 1.90 mg/L BOD. However, a better stability of the current responses could be achieved with an RSD of 3.35%. Moreover, less influence from the presence of copper ions was observed. The results indicate that the yeast-immobilized BOD sensors is more suitable to be applied in a real condition.</p>

Magnetic enzymatic platform for organophosphate pesticide detection using boron-doped diamond electrodes

Pino Flavio, Ivandini Tribidasari A., Nakata Kazuya, Fujishima Akira, Merkoçi Arben, Einaga Yasuaki

Analytical Sciences 31 ( 10 ) 1061 - 1068 2015

ISSN  0910-6340

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<p>A simple and reliable enzymatic system for organophosporus pesticide detection was successfully developed, by exploiting the synergy between the magnetic beads collection capacity and the outstanding electrochemistry property of boron-doped diamond electrodes. The determination of an organophosphate pesticide, chlorpyrifos (CPF), was performed based on the inhibition system of the enzyme acetylcholinesterase bonded to magnetic beads through a biotin-streptavidin complex system. A better sensitivity was found for a system with magnetic beads in the concentration range of 10^-9 to 10^-5 M. The estimated limits of detection based on IC₁₀ (10% acetylcholinesterase (AChE) inhibition) have been detected and optimized to be 5.7 × 10^-10 M CPF. Spiked samples of water of Yokohama (Japan) have been measured to validate the efficiency of the enzymatic system. The results suggested that the use of magnetic beads to immobilize biomolecules or biosensing agents is suitable to maintain the superiority of BDD electrodes.</p>

Toward high-throughput screening of NAD(P)-dependent oxidoreductases using boron-doped diamond microelectrodes and microfluidic devices

Oyobiki Ryo, Kato Taisuke, Katayama Michinobu, Sugitani Ai, Watanabe Takeshi, Einaga Yasuaki, Matsumoto Yoshinori, Horisawa Kenichi, Doi Nobuhide

Analytical Chemistry 86 ( 19 ) 9570 - 9575 2014.10

ISSN  0003-2700

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<p>Although oxidoreductases are widely used in many applications, such as biosensors and biofuel cells, improvements in the function of existing oxidoreductases or the discovery of novel oxidoreductases with greater activities is desired. To increase the activity of oxidoreductases by directed evolution, a powerful screening technique for oxidoreductases is required. In this study, we demonstrate the utility of boron-doped diamond (BDD) microelectrodes for quantitative and potentially high-throughput measurement of the activity of NAD(P)-dependent oxidoreductases. We first confirmed that BDD microelectrodes can quantify the activity of low concentrations (10-100 pM) of glucose-6-phosphate dehydrogenase and alcohol dehydrogenase with a measuring time of 1 ms per sample. In addition, we found that poisoning of BDD microelectrodes can be repressed by optimizing the pH and by adding l-arginine to the enzyme solution as an antiaggregation agent. Finally, we fabricated a microfluidic device containing a BDD electrode for the first time and observed the elevation of the oxidation current of NADH with increasing flow rate. These results imply that the combination of a BDD microelectrode and microfluidics can be used for high-throughput screening of an oxidoreductase library containing a large number (&gt;10⁶) of samples, each with a small (nanoliter) sample volume.</p>

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A double-QM/MM method for investigating donor-acceptor electron-transfer reactions in solution

Futera Zdenek, Sodeyama Keitaro, Burda Jaroslav V., Einaga Yasuaki, Tateyama Yoshitaka

Physical Chemistry Chemical Physics 16 ( 36 ) 19530 - 19539 2014.09

ISSN  1463-9076

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<p>We developed a double-quantum mechanical/molecular mechanical (d-QM/MM) method for investigation of full outer-sphere electron transfer (ET) processes between a donor and an acceptor (DA) in condensed matter. In the d-QM/MM method, which employs the novel concept of multiple QM regions, one can easily specify the number of electrons, spin states and appropriate exchange-correlation treatment in each QM region, which is especially important in the cases of ET involving transition metal sites. We investigated Fe^2+/3+ self-exchange and Fe³⁺ + Ru²⁺ → Fe²⁺ + Ru³⁺ in aqueous solution as model reactions, and demonstrated that the d-QM/MM method gives reasonable accuracy for the redox potential, reorganization free energy and electronic coupling. In particular, the DA distance dependencies of those quantities are clearly shown at the density functional theory hybrid functional level. The present d-QM/MM method allows us to explore the intermediate DA distance region, important for long-range ET phenomena observed in electrochemistry (on the solid-liquid interfaces) and biochemistry, which cannot be dealt by the half-reaction scheme with the conventional QM/MM. © 2014 The Owner Societies.</p>

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First principles calculation study on surfaces and water interfaces of boron-doped diamond

Futera Zdenek, Watanabe Takeshi, Einaga Yasuaki, Tateyama Yoshitaka

Journal of Physical Chemistry C 118 ( 38 ) 22040 - 22052 2014.09

ISSN  1932-7447

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<p>We investigated water interfaces of boron-doped diamond (BDD) terminated by hydrogen, oxygen, and hydroxyl groups by using density functional theory (DFT)-based molecular dynamics to elucidate the electrochemical behaviors of the as-grown and oxidized BDD electrodes. The reversible outer-sphere electron transfer on the as-grown electrode and the irreversibility on the oxidized electrode, observed in the experiment, are well explained by the BDD band position and subsurface band bending, which depend on the termination and interfacial dipoles. The reductive character of the H-terminated BDD is found, while the interface covered by the carbonyl oxygen is clearly oxidative. The redox character of the hydroxyl termination depends on the lateral hydrogen bonding network among the termination groups and is rather oxidative at the water interface. We also examined the preference of the boron position in the diamond and the stability of boron pairs and clusters. It is suggested that the wide distribution of the single boron dopants is crucial to the BDD conductivity, against the tendency of clustering. These results give novel atomistic aspects of the termination and the boron doping effects on the BDD electrodes, which is useful for further exploration of the efficient electrochemical applications of BDD.</p>

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Direct determination of chemical oxygen demand by anodic decomposition of organic compounds at a diamond electrode

Kondo Takeshi, Tamura Yusuke, Hoshino Masaki, Watanabe Takeshi, Aikawa Tatsuo, Yuasa Makoto, Einaga Yasuaki

Analytical Chemistry 86 ( 16 ) 8066 - 8072 2014.08

ISSN  0003-2700

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<p>Chemical oxygen demand (COD) was measured directly with a simple electrochemical method using a boron-doped diamond (BDD) electrode. By applying a highly positive potential (+2.5 V vs Ag/AgCl) to an aqueous electrolyte containing potassium hydrogen phthalate, glucose, and lactic acid or sodium dodecylbenzenesulfonate using a BDD electrode, an anodic current corresponding to the electrolytic decomposition of these organic compounds was observed. No such current was seen on glassy carbon or platinum electrodes due to a significant background current caused by the oxygen evolution reaction. The electric charge for the anodic current observed at the BDD electrode was found to be consistent with the theoretical charge required for the electrolytic decomposition of the organic compounds to CO₂ and was used to calculate COD. This analysis was performed by a simple I-t measurement at constant potential using a BDD electrode, and no calibration was needed. This new simple indicator, "ECOD" (electrochemical oxygen demand), will be useful for continuous monitoring of industrial wastewater with low protein concentrations and on-site instant analysis of natural water with a BDD electrode-based portable ECOD meter. © 2014 American Chemical Society.</p>

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Electrochemical Application of Diamond Electrodes

Einaga Yasuaki

  493 - 512 2014.03

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<p>This chapter gives a brief review of recent developments on the applications of boron-doped diamond (BDD) electrodes. Specifically, electrochemical applications of BDD electrodes for water treatment, ozone generation, organic synthesis, and electrochemical analysis. Additionally several recent examples of recent developments for electrochemical analysis are introduced. © 2014 Elsevier Ltd. All rights reserved.</p>

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Synergistic spin transition between spin crossover and spin-peierls-like singlet formation in the halogen-bonded molecular hybrid system

Fukuroi Kappei, Takahashi Kazuyuki, Mochida Tomoyuki, Sakurai Takahiro, Ohta Hitoshi, Yamamoto Takashi, Einaga Yasuaki, Mori Hatsumi

Angewandte Chemie - International Edition 53 ( 7 ) 1983 - 1986 2014.02

ISSN  1433-7851

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<p>To introduce halogen-bond interactions between a cation and an anion, a novel Fe^III complex from iodine-substituted ligands involving a paramagnetic nickel dithiolene anion was prepared and characterized. The compound exhibited the synergy between a spin-crossover transition and a spin-Peierls-like singlet formation. The halogen-bond interactions between the iodine and the sulfur atoms stabilized the paramagnetic state of π-spins and played a crucial role in the synergistic magnetic transition between d- and π-spins. In addition, the compound showed the light-induced excited spin state trapping effect. Something to get crossover: An Fe^III complex with iodine-substituted ligands involving a paramagnetic nickel dithiolene anion shows a synergy between a spin-crossover transition and a spin-Peierls-like singlet formation. The halogen-bond interactions between the iodine and the sulfur atoms stabilized the paramagnetic state of π-spins and played a significant role in the synergistic magnetic transition between d- and π-spins. Copyright © 2014 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.</p>

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High-yield electrochemical production of formaldehyde from CO₂ and seawater

Nakata Kazuya, Ozaki Takuya, Terashima Chiaki, Fujishima Akira, Einaga Yasuaki

Angewandte Chemie - International Edition 53 ( 3 ) 871 - 874 2014

ISSN  1433-7851

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<p>The catalytic, electrocatalytic, or photocatalytic conversion of CO ₂ into useful chemicals in high yield for industrial applications has so far proven difficult. Herein, we present our work on the electrochemical reduction of CO₂ in seawater using a boron-doped diamond (BDD) electrode under ambient conditions to produce formaldehyde. This method overcomes the usual limitation of the low yield of higher-order products, and also reduces the generation of H₂. In comparison with other electrode materials, BDD electrodes have a wide potential window and high electrochemical stability, and, moreover, exhibit very high Faradaic efficiency (74 %) for the production of formaldehyde, using either methanol, aqueous NaCl, or seawater as the electrolyte. The high Faradaic efficiency is attributed to the sp ³-bonded carbon of the BDD. Our results have wide ranging implications for the efficient and cost-effective conversion of CO₂. Boron is a diamond's best friend: A boron-doped diamond (BDD) electrode exhibited very high Faradaic efficiency (74 %) for the production of formaldehyde using either methanol, aqueous NaCl, or seawater as the electrolyte at room temperature and ambient pressure. Copyright © 2014 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.</p>

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Diamond electrodes

Einaga Yasuaki, Foord John S., Swain Greg M.

MRS Bulletin 39 ( 6 ) 525 - 532 2014

ISSN  0883-7694

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<p>Boron-doped diamond electrodes have attracted increasing interest from researchers due to their outstanding properties for electroanalysis and other electrochemical applications. Material quality and availability have come a long way since the initial reports on the basic electrochemical properties back in the late 1980s and early 1990s. In this review, we highlight how diamond electrochemistry has diversified and matured in recent years in terms of the understanding of structure-property relationships and the development of new applications of materials in electroanalytical chemistry. © Materials Research Society 2014.</p>

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Synthesis of biodiesel using a two-compartments electrochemical cell

Shibano Shuhei, Ivandini Tribidasari A., Terashima Chiaki, Nakata Kazuya, Einaga Yasuaki

Chemistry Letters 43 ( 8 ) 1292 - 1293 2014

ISSN  0366-7022

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<p>An electrochemical method was developed for biodiesel, i.e., fatty acid methyl ester (FAME), production. A twocompartment cell completed with a cation-exchange separating membrane was utilized to minimize recombination between protons and hydroxide or methoxide ions, which leads to the low product yield. In addition to the product yield increase, the method was found to reduce the requirement of organic salt to be only in the cathode chamber. Electrolysis at low voltage (4.6 V) resulting high product yield (ca. 94% in 2 h) at Pt as well as a boron-doped diamond (BDD) electrode as the cathode, suggested the system was free from the dependence on electrode types.</p>

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Tailored design of boron-doped diamond electrodes for various electrochemical applications with boron-doping level and sp²-bonded carbon impurities

Watanabe Takeshi, Honda Yuki, Kanda Kazuhiro, Einaga Yasuaki

Physica Status Solidi (A) Applications and Materials Science 211 ( 12 ) 2709 - 2717 2014

ISSN  1862-6300

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<p>The effects of sp2-bonded carbon impurities on the electrochemical properties of boron-doped diamond were investigated in moderately ([B] &lt; 10²⁰cm^-3) and heavily ([B] &gt; 10²¹cm^-3) boron doping levels. Significant influences of sp2-bonded carbon impurities, which show glassy carbon-like electrochemical properties after anodic oxidation, were observed in heavily boron-doped diamond. This indicated that the significant effects of enhanced adsorption properties were possibly caused by surface relaxation of the strains induced by heavy boron doping and sp²-bonded carbon impurities. On the other hand, their durability was still similar to diamond electrodes rather than glassy-carbon electrodes because of the low fraction of sp²-bonded carbon impurities. Such "active" diamond electrodes are much less suitable for wastewater treatment than ordinary diamond electrodes due to a different oxygenevolution mechanism. On the other hand, "active" BDD electrodes have a much higher efficiency for electrochemical ozone production than other BDD electrodes. The electrode properties of BDD can be designed by controlling the boron doping level and introducing the sp²-bonded carbon impurities. The guidelines proposed in this study can be used effectively to design electrodes according to their individual application, such as for use as electrochemical sensors, in wastewater treatment or electrochemical ozone production.</p>

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Electrochemical detection of hydrogen peroxide at platinum-modified diamond electrodes for an application in melamine strip tests

Rismetov Bakhadir, Ivandini Tribidasari A., Saepudin Endang, Einaga Yasuaki

Diamond and Related Materials 48   88 - 95 2014

ISSN  0925-9635

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<p>Electrochemical detection of hydrogen peroxide (H₂O₂) at a platinum-deposited boron doped diamond was studied for an application in melamine strip test. Deposition of Pt particles at a boron-doped diamond surface was performed using cyclic voltammetry method. The method was also used for electrochemical measurements. The oxidation-reduction peak currents of H ₂O₂ at + 0.6 V and - 0.1 V (vs. Ag/AgCl), respectively were found to be linear in the concentration range of 0.05-20 mM (R² = 0.99). Linearity was also observed to be dependent on horseradish peroxidase (HRP) concentration in the constant concentration of H₂O₂. The method was then applied in immunochromatographic strip test for melamine detection to determine the activity of HRP labeled at melamine antibody. Taking an assumption that the activity of HRP was equivalent to melamine concentration, linearity of the current responses to the concentrations of standard melamine solutions in the range of 5-100 μg/ml could be achieved. Limit of detection of 0.51 μg/ml was estimated. The obtained results demonstrated that the designed biosensor for detection of H₂O₂ could be applied for the quantitative and selective detection of melamine. © 2014 Elsevier B.V.</p>

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Cathodic pretreatment improves the resistance of boron-doped diamond electrodes to dopamine fouling

Trouillon Raphaël, Einaga Yasuaki, Gijs Martin A M

Electrochemistry Communications 47   92 - 95 2014

ISSN  1388-2481

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<p>The resistance of cathodically and anodically treated boron-doped diamond electrodes to dopamine fouling was investigated. It was found, using cyclic voltammetry and electrochemical impedance spectroscopy, that the cathodic preparation offers an increased resistance to fouling, in addition to an enhanced electrochemical response. © 2014 Elsevier B.V.</p>

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