Details of a Researcher - Einaga, Yasuaki

Papers - Einaga, Yasuaki

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PH sensing using boron doped diamond electrodes

Fierro Stéphane, Mitani Naoko, Comninellis Christos, Einaga Yasuaki

Physical Chemistry Chemical Physics 13 ( 37 ) 16795 - 16799 2011.10

ISSN 1463-9076

The boron doped diamond (BDD) electrode is presented as an appropriate candidate for next generation glass-free, highly stable and accurate pH sensors. The method used in this study is based on the potential change related to the hydrogen evolution reaction following a current step, which is pH dependent. Alkali cations in the solution have no influence on the accuracy of the pH calibration curve, which provides an advantage with respect to the conventional pH glass electrode. The unwanted influence of electrochemically active compounds in solution can be avoided by adjusting the current density applied during chronopotentiometric measurements. The accuracy of the pH measurements is due to the excellent stability as well as the wide potential window and low background current of BDD electrodes. This faculty was not observed when using conventional electrode materials. The efficacy of this new type of pH sensor has been tested using tap water as a typical real sample. © 2011 The Owner Societies.

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Phasic reward responses in the monkey striatum as detected by voltammetry with diamond microelectrodes

Yoshimi Kenji, Naya Yuuki, Mitani Naoko, Kato Taisuke, Inoue Masato, Natori Shihoko, Takahashi Toshimitu, Weitemier Adam, Nishikawa Natsuko, McHugh Thomas, Einaga Yasuaki, Kitazawa Shigeru

Neuroscience Research 71 ( 1 ) 49 - 62 2011.09

ISSN 0168-0102

Reward-induced burst firing of dopaminergic neurons has mainly been studied in the primate midbrain. Voltammetry allows high-speed detection of dopamine release in the projection area. Although voltammetry has revealed presynaptic modulation of dopamine release in the striatum, to date, reward-induced release in awakened brains has been recorded only in rodents. To make such recordings, it is possible to use conventional carbon fibres in monkey brains but the use of these fibres is limited by their physical fragility. In this study, constant-potential amperometry was applied to novel diamond microelectrodes for high-speed detection of dopamine. In primate brains during Pavlovian cue-reward trials, a sharp response to a reward cue was detected in the caudate of Japanese monkeys. Overall, this method allows measurements of monoamine release in specific target areas of large brains, the findings from which will expand the knowledge of reward responses obtained by unit recordings. © 2011 Elsevier Ireland Ltd and the Japan Neuroscience Society.

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Applications of Polycrystalline and Modified Functional Diamond Electrodes

Einaga Yasuaki, Fujishima Akira

109 - 131 2011.06

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Erratum

Ivandini Tribidasari A., Yamada Daisuke, Watanabe Takeshi, Matsuura Hiroaki, Nakano Nabuo, Fujishima Akira, Einaga Yasuaki

Journal of Electroanalytical Chemistry 655 ( 1 ) 96 2011.05

ISSN 1572-6657

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Electronic conductivity in Berlin green and Prussian blue

Pajerowski Daniel M., Watanabe Takeshi, Yamamoto Takashi, Einaga Yasuaki

Physical Review B - Condensed Matter and Materials Physics 83 ( 15 ) 2011.04

ISSN 1098-0121

We report the temperature dependent (100-300 K) conductivity of Berlin green and Prussian blue powders. The method of electronic conduction in vacuum dried Berlin green is identified as hopping of localized electrons and vacuum dried Prussian blue is reaffirmed as an insulator. The assignment of the conduction mechanism is based upon fits to the experimental data, and the different conductivities of the two samples can be understood in terms of both molecular and simple crystalline energy levels of the solids. © 2011 American Physical Society.

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Effect of the doping level on the biological stability of hydrogenated boron doped diamond electrodes

Trouillon Raphaël, O'Hare Danny, Einaga Yasuaki

Physical Chemistry Chemical Physics 13 ( 12 ) 5422 - 5429 2011.03

ISSN 1463-9076

Fouling of electrode surfaces by electrode reaction products or by biological spectator species is known to inactivate electrochemical sensors and thus limit their use in biological conditions. Here we present an investigation on the stability of boron doped diamond (BDD) electrodes with different levels of doping. Three different doping levels were used (0.1, 1 and 5% in the carbon phase). The highly doped (5%) BDD is of particular interest as it is here used for the first time for biological applications. Three different redox reactions were examined based on their electrode reaction characteristics: ruthenium(iii) hexaammine (outer sphere), ferrocyanide (suface dependent), dopamine (adsorption mediated). The effect of albumin at blood concentration was studied. All results were compared with glassy carbon. There were no significant differences for the outer sphere electrochemistry, but all the BDDs showed improved resistance to fouling for the ferrocyanide oxidation. The electrocatalytic activity of BBD towards dopamine oxidation increased with increased boron content. However, this appears to be due to a larger number of defect sites which also increases the vulnerability to fouling by albumin and by electrode reaction products and the 5% BDD had similar properties to glassy carbon in this regard. These results suggest that it is possible to optimise the BDD performance for specific applications and that the large potential window for BDD may be due, at least in part, to its relatively poor electrocatalytic activity. © the Owner Societies.

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Ferromagnetism of Pt nanoparticles induced by surface chemisorption

Sakamoto Yasuhiro, Oba Yojiro, Maki Hideyuki, Suda Masayuki, Einaga Yasuaki, Sato Tetsuya, Mizumaki Masaichiro, Kawamura Naomi, Suzuki Motohiro

Physical Review B - Condensed Matter and Materials Physics 83 ( 10 ) 2011.03

ISSN 1098-0121

The magnetic properties of different-sized Pt nanoparticles coated by alkanethiol molecules with different carbon chain lengths (1-octadecanethiol, 1-dodecanthiol, and 1-octanethiol) were systematically studied by means of magnetic measurement, x-ray magnetic circular dichroism (XMCD), x-ray absorption near-edge structure (XANES), and electron spin resonance (ESR). Furthermore, azobenzene-derivatized thiol coating of Pt nanoparticles was performed to detect the effect on magnetic characteristics of the geometrical transformation between cis and trans states induced by photoisomerization. All samples showed the ferromagnetism inherent in Pt. In all of the prepared particles Curie temperatures above 300 K were observed. The largest magnetization at 5 K was observed for the longest chain length of alkanethiol and the smallest particle size. The coercive force at 5 K increased as the chain length increased and the particle size decreased. The geometrical transformation of coated molecules barely affected the magnetization and coercive force. The increase in coercive force was accompanied by the enhanced contribution of the orbital magnetic moment. The origins of ferromagnetism and magnetic anisotropy in Pt nanoparticles are discussed in terms of the contribution from the coating molecules and downsizing effects. The appearance of ferromagnetism is mainly interpreted based on two mechanisms, i.e., the electronic band magnetism based on the Stoner criterion for ferromagnetism and the orbital ferromagnetism due to electrons captured in the atomiclike orbital on the particle surface. The chain-length and particle-size-dependent magnetic anisotropy is explained in terms of the change in angular momentum depending on the adsorption condition, especially the coverage ratio, of alkanethiol on the particle surface. This is consistent with the existence of orbital ferromagnetism in the Pt nanoparticle. © 2011 American Physical Society.

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Influence of doping level on the electrochemical oxidation of formic acid on boron doped diamond electrodes

Fierro Stéphane, Abe Kyoichi, Comninellis Christos, Einaga Yasuaki

Journal of the Electrochemical Society 158 ( 12 ) 2011

ISSN 0013-4651

The influence of the boron doping level in boron doped diamond electrodes (BDD) on the electro-generation of active intermediates (hydroxyl radicals and hydrogen peroxide) involved in the oxidation of organic compounds has been studied. It is shown that the boron doping level of diamond electrodes has no influence on the amount of hydroxyl radicals produced at the electrode surface in contrast with hydrogen peroxide, whose formation is favored by low boron doping levels. The influence of the boron doping level on the degradation of formic acid is also investigated. It is shown that lowly doped diamond films have a slight advantage; proving that hydrogen peroxide does not participate in the process. Moreover, the experimental results were compared with a theoretical model, which considers that the oxidation reaction is fast and controlled by mass transfer. All BDD electrodes showed a good agreement with the model independently of the boron doping level. However, the accuracy of the model tend to decrease with increasing boron content, which is probably due to the participation of active couples, which are known to be present at the surface of diamond films with high boron doping levels. © 2011 The Electrochemical Society.

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Highly sensitive detection of Cd² using boron doped diamond electrodes

Fierro Stéphane, Watanabe Takeshi, Akai Kazumi, Yamanuki Mikito, Einaga Yasuaki

Journal of the Electrochemical Society 158 ( 11 ) 2011

ISSN 0013-4651

The electrochemical detection of Cd² has been performed by anodic stripping voltammetry on boron doped diamond (BDD) electrodes. A new technique is proposed, which involves adding a known amount of copper to the sample to deposit an amalgam of Cd-Cu on the surface of the BDD electrode. This amalgam is then stripped during voltammetry measurements, allowing the generation of highly accurate calibration curves for Cd detection (r² 0.99) with a lower detection limit of 10 ppb. The conditions that are used for the anodic stripping voltammetry measurements have been optimized to avoid the deposition of cadmium and the appearance of the stripping peak related to copper. Real samples could contain a certain amount of copper, so the influence of small variations of Cu² concentration has been investigated and it was found that such variations have no influence on the accuracy of the calibration curve for Cd detection. The influence of other metals that could be dissolved in the sample has also been studied, and it was shown that lead and selenium have a negative influence on the technique. However, this negative interference can be eliminated by increasing the concentration of copper that is introduced in the sample. Furthermore, other species such as boron or chromium have no influence on the anodic stripping voltammetry measurements, so accurate calibration curves for Cd determination could be constructed in the presence of Pb, Se, B and Cr. © 2011 The Electrochemical Society.

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Surface modification of ferromagnetic L1o FePt nanoparticles using biotin avidin as biomolecular recognition probes

Indrianingsih Anastasia W., Suda Masayuki, Heta Yushi, Suzuki Koji, Einaga Yasuaki

Bulletin of the Chemical Society of Japan 84 ( 8 ) 873 - 877 2011

ISSN 0009-2673

Water-dispersible biotin-modified biofunctional ferromagnetic L1o FePt nanoparticles (NPs) have been synthesized by using a silica nanoreactor strategy. The coercivity field of the NPs was 16 kOe at room temperature, with a particle size of around 5.19 nm. Biotin-coated L1o FePt NPs were biocompatible in an aqueous environment and show site-specific interactions with avidin compounds that could potentially yield a new magnetic material for biological applications, such as for biomolecular recognition.© 2011 The Chemical Society of Japan.

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N,N'-bis(2-hydroxy-3-methoxybenzylidene)-1,3-diaminopropane dimeric 4f and 3d-4f heterodinuclear complexes

Wang Jing Hua, Yan Peng Fei, Li Guang Ming, Zhang Ju Wen, Chen Peng, Suda Masayuki, Einaga Yasuaki

Inorganica Chimica Acta 363 ( 14 ) 3706 - 3713 2010.11

ISSN 0020-1693

Three novel N,N′-bis(2-hydroxy-3-methoxybenzylidene)-1,3- diaminopropane dimeric lanthanide complexes, namely, [{H₂L}Sm(NO ₃)₃]₂·H₂O (1), [{H ₂L}Gd(NO₃)₃]₄·CH ₃OH (2), [{H₂L}Lu(NO₃)₃] ₄·H₂O (3) (H₂L = N,N′-bis(2- hydroxy-3-methoxybenzylidene)-1,3-diaminopropane) and three new N,N′-bis(2-hydroxy-3-methoxybenzylidene)-1,3-diaminopropane 3d-Gd heterodinuclear complexes, namely, [{LCo}(CH₃COO)(CH ₃COOH)Gd(NO₃)₂] (4), [{LNi(MeOH) ₂}Gd(NO₃)₃]·2MeOH (5) and [{(L)Zn(HNO₃)}Gd(NO₃)₃]·NO ₃·H₃O·MeOH (6) have been synthesized and isolated. X-ray crystallographical analysis reveals that complexes 1-3 are isomorphic with unique dimeric topology. Complexes 4-6 are of discrete 3d-4f dinuclear cores. Magnetic properties of complexes 2 and 4-6 are systematically investigated. Complexes 4 and 5 are ferromagnetic, while 2 and 6 are antiferromagnetic. © 2010 Elsevier B.V. All rights reserved.

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Diamond electrodes for electrochemical analysis

Einaga Yasuaki

Journal of Applied Electrochemistry 40 ( 10 ) 1807 - 1816 2010.10

ISSN 0021-891X

We have reported not only the above examples but also several additional examples of sensitive detection by BDD electrodes, such as uric acid [25], NADH [26], acids [27], toxic gases [28], etc. In fact, some of the examples are now in progress for the development of practical electrochemical sensor applications. Furthermore, in order to add other functions and improve the electrochemical properties, BDD electrodes with surfaces chemically modified by functional organic molecules are also actively being developed [29, 30]. Thus, it appears likely that, in the near future, electrochemical sensors using BDD can be applied for environmental analysis and medical analysis. © Springer Science+Business Media B.V. 2010.

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Electrochemical detection of tyrosine derivatives and protein tyrosine kinase activity using boron-doped diamond electrodes

Chiku Masanobu, Horisawa Kenichi, Doi Nobuhide, Yanagawa Hiroshi, Einaga Yasuaki

Biosensors and Bioelectronics 26 ( 1 ) 235 - 240 2010.09

ISSN 0956-5663

In this report, we determined protein tyrosine kinase (PTKs) activity in human epidermoid carcinoma cells (A431) by employing a novel electrochemical method using boron-doped diamond (BDD) electrodes that enables the electrochemical oxidation of tyrosine (Tyr), phosphorylated Tyr (Tyr-P) and sulfated Tyr (Tyr-S) in water-based solutions. Cyclic voltammetry for Tyr, Tyr-P and Tyr-S showed well-defined oxidation peaks at 0.8. V for Tyr, 1.4. V for Tyr-P and 1.7. V for Tyr-S, respectively. Very little work has been reported previously on the detection of Tyr-P and Tyr-S, probably due to their high oxidation potentials. We utilized electrochemical methods for the detection of kinase activity in connection with poly(Glu-Tyr) modified magnetic beads. Linear-sweep voltammograms for the electrochemical detection of PTKs activity were carried out using BDD electrodes consisting of peptide-modified magnetic beads. Without phosphorylation of the peptide-modified magnetic beads using PTKs, we observed clear oxidation peaks for Tyr oxidation and no significant electrochemical responses for Tyr-P oxidation at 1.4. V for the background. On the other hand, with phosphorylation of the beads using PTKs, the peak oxidation current at 1.4. V clearly increased, while the peak oxidation current for Tyr oxidation decreased. This indicates that PTKs activity could be successfully detected by using electrochemical methods employing BDD electrodes. This method was utilized for the in vitro kinase activity detection of human cell lysate, and the electrochemical measurements were compatible with the Enzyme-Linked ImmunoSorbent Assay based method. Our results indicate that the electrochemical method can be applied to real samples such as cell lysate. © 2010 Elsevier B.V.

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Fabrication of Cu-modified boron-doped diamond microband electrodes and their application for selective detection of glucose

Chiku Masanobu, Watanabe Takeshi, Einaga Yasuaki

Diamond and Related Materials 19 ( 7-9 ) 673 - 679 2010.07

ISSN 0925-9635

We describe a simple bench top method for fabricating boron-doped diamond (BDD) microband electrodes and copper-modified BDD microband electrodes. The method described here is inexpensive, robust, renewable, simple, and the BDD microband electrodes and the copper-modified BDD microband electrodes are very easy to fabricate. An advantage of the method is not only its simplicity but also the renewability. That is, even if the surface of the electrode is deactivated after an electrochemical reaction, it can be renewed by simply cutting off the end. As one of the example of application, we report on the selective detection of glucose in solution containing interference species such as Ascorbic acid (AA) and Uric acid (UA) by preparing Cu-modified BDD microband electrodes. Even in solutions containing 2 or 3 times the amount of interfering species compared to the glucose concentration, the Cu-modified BDD microband electrodes showed good selectivity and high durability. © 2010 Elsevier B.V. All rights reserved.

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Giant electric double-layer capacitance of heavily boron-doped diamond electrode

Watanabe Takeshi, Shimizu Tomoko K., Tateyama Yoshitaka, Kim Yousoo, Kawai Maki, Einaga Yasuaki

Diamond and Related Materials 19 ( 7-9 ) 772 - 777 2010.07

ISSN 0925-9635

The physical and electrochemical properties of boron-doped polycrystalline diamond electrodes, prepared with various B/C ratio, i.e., 0.1%, 0.5% (BDD-A), 1% (BDD-B), and 5% (BDD-C), were investigated. Electrochemical measurements of the heavily boron-doped films (BDD-C) showed giant electric double-layer capacitance and activity which is significantly larger than BDD-A and BDD-B as well as glassy carbon electrodes. However, interestingly, actual boron concentration of BDD-C was observed to be almost the same as that of BDD-B by secondary ion mass spectroscopy (SIMS) and glow discharge optical emission spectroscopy (GDOES) analysis. It is suggested that the large capacitance is due to a few sp²-bonded carbon impurities, which was observed only in BDD-C, although the amount of the sp²-bonded nondiamond species are very small. In the present work, the reason for the interesting electrochemical properties of heavily boron-doped diamond electrodes is discussed. Furthermore, dimensional stability of the electrodes was also confirmed by conducting harsh anodic treatment. © 2010 Elsevier B.V. All rights reserved.

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Development of amperometric arsine gas sensor using gold-modified diamond electrodes

Ivandini Tribidasari A., Yamada Daisuke, Watanabe Takeshi, Matsuura Hiroaki, Nakano Nabuo, Fujishima Akira, Einaga Yasuaki

Journal of Electroanalytical Chemistry 645 ( 1 ) 58 - 63 2010.06

ISSN 1572-6657

Amperometric gas sensor of arsine was developed using gold-modified diamond electrodes as the working electrodes. The detection method was conducted in high concentration of H₂SO₄. The reaction was declared based on two oxidation steps, involving oxidation of As^3- to As ⁰ at mild potential in strong acid, followed by electrochemical oxidation of As⁰ to As³⁺ at gold-based electrodes. Linear calibration curve was observed in the concentration range of 5-50 ppb (r ² = 0.985) with detection limit of ∼4.43 ppb (S/N = 3). Current decreasing of measurement was found ∼5.5% for 5 measurements. However, better stability was observed after the 5th measurement, indicated that the sensor could be applied for long time measurement. Investigation to several possible interference gasses, i.e. SO₂, H₂S, NO, NO ₂, CO, O₃ and H₂ indicated no significant interference of the gas to arsine measurements. © 2010 Elsevier B.V. All rights reserved.

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Controlled storage of ferrocene derivatives as redox-active molecules in dendrimers

Ochi Yousuke, Suzuki Mana, Imaoka Takane, Murata Masaki, Nishihara Hiroshi, Einaga Yasuaki, Yamamoto Kimihisa

Journal of the American Chemical Society 132 ( 14 ) 5061 - 5069 2010.04

ISSN 0002-7863

Dendritic polyphenylazomethines (DPA) could encapsulate ferroceniums by complexation of the electron-donating skeleton of the DPA imines. Upon addition of ferroceniums to a series of dendritic polyphenylazomethines (DPAGX, where X is the generation number, X = 1-4), the UV-vis spectra showed changes in a manner similar to that observed for the complexation of metal ions with DPAGX. Stepwise shifts in the isosbestic point were consistently observed with the number of imine groups in the first and second layers of the generation-4 dendrimer (DPAG4). DPAG2 and DPAG3 were also found to trap 6 equiv of ferroceniums. To investigate the complexation, UV-vis spectroscopy, ⁵⁷Fe MoÌssbauer spectroscopy, electrospray ionization-mass spectroscopy (ESI-MS), cyclic voltammetry (CV), and fluorescence spectroscopy were performed. We confirmed that neutral ferrocenes cannot complex with the imine group while ferroceniums can. Utilizing the redox property of ferrocenes, we were able to electrochemically control the encapsulation and release of ferrocenes into the DPA in a manner similar to redox-responsive proteins such as ferritin. In addition to ferrocenes, oligoferrocenes could also be trapped in the DPA. The biferrocene cation(1+) was particularly suitable for electrochemical switching due to its stable mixed valence condition. The terferrocene dication(2+) encapsulated into DPAG4 could be fabricated into a thin film, which exhibited the near-infrared absorption of an intervalence charge-transfer (IV-CT) band, pointing the way toward the use of such systems in material science. © 2010 American Chemical Society.

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Correlations between structure and magnetism of three N,N′-ethylene-bis(3-methoxysalicylideneimine) gadolinium complexes

Gao Ting, Yan Peng Fei, Li Guang Ming, Zhang Ju Wen, Sun Wen Bin, Suda Masayuki, Einaga Yasuaki

Solid State Sciences 12 ( 4 ) 597 - 604 2010.04

ISSN 1293-2558

Three Salen-like gadolinium complexes, namely, mononuclear (4f) complex [{H₂L}Gd(NO₃)₃] (1), heterodinuclear (3d-4f) complex [{LCu}Gd(NO₃)₃]·0.25H₂O (2) and dimeric heterotrinuclear (3d-4f-3d′) complex [{LCu}Gd(H₂O)₃{Fe(CN)₆}]₂·6H₂O (3) [H₂L = N,N′-ethylene-bis(3-methoxysalicylideneimine)] have been synthesized by stepwise reactions. X-ray diffraction analysis reveals that 1 is of a discrete structure in which H₂L coordinates to gadolinium ion through O₂O₂ moiety. Then, addition of Cu(Ac)₂·H₂O to the mononuclear lanthanide complex yields expected heterodinuclear (3d-4f) complexes [{LCu}Gd(NO₃)₃]. 3 features a unique 1D ladder-like topology structure through the intermolecular double links of Cu-N bonds. The measurement of variable-temperature magnetic susceptibility reveals that complex 1 exhibits antiferromagnetic interaction while 2 and 3 exhibit ferromagnetic interaction between spin carriers. The correlations between the structure and magnetism are described and discussed. © 2010.

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Anodic stripping voltammetry of zinc at boron-doped diamond electrodes in ammonia buffer solution

Langeloth Michael, Chiku Masanobu, Einaga Yasuaki

Electrochimica Acta 55 ( 8 ) 2824 - 2828 2010.03

ISSN 0013-4686

This paper describes the deposition of zinc(II) with anodic stripping voltammetry on the boron-doped diamond electrode. We illustrate the dependency of several parameters on the magnitude of the oxidation peak and try to optimize the method. The supporting electrolyte was found to influence the oxidation peak magnitude. Compared with acetic acid, the most frequently used supporting electrolyte, ammonia buffer solution leads to a four times higher signal. We assume that the formation of zinc complexes, primarily tetraaminezinc(II), are responsible for the better response. Further factors studied and assessed include buffer pH, buffer concentration, deposition potential, deposition time and scan rate. With the improved conditions, a final detection limit of 5 ppb was accomplished. © 2010 Elsevier Ltd. All rights reserved.

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Two-dimensional lanthanide-containing coordination Frameworks

Gao Ting, Li Guang Ming, Yan Peng Fei, Zhang Ju Wen, Sun Wen Bin, Suda Masayuki, Einaga Yasuaki

Zeitschrift fur Anorganische und Allgemeine Chemie 636 ( 3-4 ) 624 - 628 2010.03

ISSN 0044-2313

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