研究者詳細 - 竹岡　敬和

論文 - 竹岡　敬和

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Effect of supporting electrolyte concentration on the electrochemical reaction of redox-active surfactant micelles in aqueous solutions 査読有り

Y Takeoka, T Aoki, K Sanui, N Ogata, R Watanabe

JOURNAL OF ELECTROANALYTICAL CHEMISTRY 438 巻 ( 1-2 ) 頁： 153 - 158 1997年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

The effect of NaCl concentration on the redox potential of alpha-ferrocenylundecyl-omega-hydroxy-polyoxyethylene (FPEG) micelles has been studied in aqueous solutions. With increasing NaCl concentration, the anodic half-wave potentials E-1/2 of cyclic voltammograms of the aqueous solutions shift to higher potential, and the peak currents of the cyclic voltammograms decrease. The results are discussed in terms of thermodynamics of the micelle formation. An equation which interprets the correlation between the E-1/2, the salt concentration, diffusion coefficient of the micelle D-M, and the aggregation number m, has been derived. The changes in D-M and m with NaCl concentration do not explain the change in the value of E-1/2. The decrease in the equilibrium constant for the micelle-disruption K-d with increasing NaCl concentration affects the redox-potential of the FPEG micellar solutions. (C) 1997 Elsevier Science S.A.

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Cyclic voltammetric study of redox-active surfactant by hydrogel-modified electrode 査読有り

Y Takeoka, T Aoki, K Sanui, N Ogata, M Watanabe

POLYMER GELS AND NETWORKS 5 巻 ( 4 ) 頁： 369 - 383 1997年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCI LTD

The dissolved states of redox-active non-ionic surfactant (FPEG) in the swollen state of N-isopropyl acrylamide (NIPA) hydrogel have been studied by using a gel-modified electrode. The pronounced decrease in the peak current and the negative shift in the formal potential of CV at the gel-modified electrode, as compared with the normal GC electrode, was observed in the micelle-solution; this indicates that the diffusive FPEG molecules which form the micelle hardly penetrate into the NIPA gel. This result suggests that there exists all interaction between FPEG molecules and the NIFA gel in the vicinity of the surface of the NIPA gel in the micelle-solution. However, this also indicates that a small amount of FPEG molecules which can form micelles exist in the NIPA gel. (C) 1997 Elsevier Science Ltd.

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Cyclic voltammetric study of redox-active surfactant by gel-modified electrode 査読有り

Yukikazu Takeoka, Takashi Aoki, Kohei Sanui, Naoya Ogata, Masayoshi Watanabe

Polymer Gels and Networks 5 巻頁： 369-383 1997年

Effect of supporting electrolyte concentration on the electrochemical reaction of redox-active surfactant micelles in aqueous solutions 査読有り

Yukikazu Takeoka, Takashi Aoki, Kohei Sanui, Naoya Ogata, Masayoshi Watanabe

J.Electroanal.Chem. 438 巻頁： 153-158 1997年

Electrochemical studies of a redox-active surfactant. Correlation between electrochemical responses and dissolved states 査読有り

Y Takeoka, T Aoki, K Sanui, N Ogata, M Watanabe

LANGMUIR 12 巻 ( 2 ) 頁： 487 - 493 1996年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Electrochemical studies of a nonionic surfactant, alpha-(ferrocenylundecyl)-omega-hydroxy-oligo(ethylene oxide) (FPEG), have been conducted in 0.16 M NaCl aqueous solution at a glassy carbon electrode. The correlation between electrochemical responses and dissolved states has been examined in detail. Cyclic voltammograms (upsilon = 10 mV/s) of the FPEG solutions change with the concentration; below the critical micelle concentration (cmc), the voltammetric shape is of a typical surface-confined species, while above the cmc the diffusion-controlled waves are superimposed at the cathodic side of the surface waves, and far above the cmc the voltammetric shape is of a typical diffusion-controlled species. FPEG in the aqueous solutions adsorbs onto the glassy carbon electrode surface to form a monolayer because of its surface activity. The adsorption isotherm has been represented by the Frumkin isotherm, which includes the repulsive interaction between the adsorbed FPEG molecules. Above the cmc, FPEG forms micelles. Chronoamperometrically determined apparent diffusion coefficients of the micellar solutions decrease with increasing concentrations. This has been interpreted in terms of the change in the diffusion species by disruption of the micelles into monomers at the cmc in the concentration gradient in diffusion layers. Cyclic voltammetric peak potentials of the micellar solutions shift toward the anodic side with the concentration. This behavior has been explained as the electrochemical reaction coupled with a preceding disassembled reaction of the micelles.

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Electrochemical Studies of a Redox-active Surfactants. Correlation between Electrochemical Responses and Dissolved States 査読有り

Yukikazu Takeoka, Takashi Aoki, Kohei Sanui, Naoya Ogata, Masayoshi Watanabe

Langmuir 12 巻頁： 487-493 1996年

Relationships between Vascular Bundles of Panicle Neck Internode and Characters of Head under Different Planting Densities and Nitrogen Fertilizers Applied in Oryza sativa L.

Cui H., Takeoka Y., Jin R.

Japanese Journal of Crop Science 64 巻 ( 2 ) 頁： 216 - 220 1995年6月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Crop Science

Investigations were carried out on the characters of rachilets, grains and grain weight per panicle of the growing rice plant cv. Shimokita under different planting density and nitrogen fertilizer norm conditions during the maturity stage of growth. The large vascular bundle (LVB), and small vascular bundle (SVB) of the panicle neck internode (PNI) and partial different internode were examined under a microscope. Analysing the above date with various statistical methods, the change in LVB number of PNI and its relationship with rachilets, grains or grain weight were determined. The average numbers of LVB and SVB were 9.0 and 16.5, and the variable range were 5-13 and 11-22, respectively. The frequency distribution of these attributes in the 1st internode and itscoefficient variation was significantly larger that the other internodes. The number of LVB and SVB in PNI appeared to positively correlated; the former with the primary rachilets having a correlation coefficient (CC) of 0.894** and the latter with the secondary rachilets a CC of 0.764**. The LVB and SVB of the PNI exhibited a significantly higher positive correlation with the total grains at a CC of 0.955** and 0.850**, respectively. The number of LVB and SVB of the PNI increased with increasing nitrogen fertilizer norm. The number of LVB and SVB of the PNI decreased with increasing planting densities. © 1995, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.

DOI： 10.1626/jcs.64.216

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Scopus

ELECTROCHEMICAL CONTROL OF DRUG-RELEASE FROM REDOX-ACTIVE MICELLES 査読有り

Y TAKEOKA, T AOKI, K SANUI, N OGATA, M YOKOYAMA, T OKANO, Y SAKURAI, M WATANABE

JOURNAL OF CONTROLLED RELEASE 33 巻 ( 1 ) 頁： 79 - 87 1995年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Electrochemical control of drug release was demonstrated by redox-active micelles of non-ionic surfactants having a ferrocenyl moiety (FPEG). The surfactants formed micelles at the concentrations above the critical micelle concentration (CMC = 0.1 mM) in normal saline solutions when they existed as the reduced form (FPEG), whereas the micelles were disassembled into monomers when they existed as the oxidized form (FPEG(+)). This change was reversible and electrochemically controlled. The electroactivity of FPEG determined by cyclic voltammetry was quite sensitive to the aggregation states. Perylene, which was used as a model of hydrophobic drugs, could be solubilized in a 2 mM FPEG normal saline solution, however, it was hardly solubilized in a 2 mM FPEG(+) solution that was made by oxidation of the former solution. Quick and discrete response for releasing perylene from the redox active micelles was achieved by using controlled potential bulk electrolysis method.

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INTERACTION BETWEEN REDOX-ACTIVE NON IONIC SURFACTANT MICELLE AND POLY(ACRYLIC ACID) 査読有り

Y TAKEOKA, T AOKI, K SANUI, N OGATA, M WATANABE

KOBUNSHI RONBUNSHU 52 巻 ( 10 ) 頁： 657 - 661 1995年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：SOC POLYMER SCIENCE JAPAN

A non-ionic redox active surfactant, alpha-ferrocenylundecyl-omega-hydroxy-oligo(ethylene oxide), exhibits high ability to form polymer complexes with poly(acrylic acid) at a micelle forming concentration, in spite of the low molecular weight of the oligo(ethylene oxide) site. The fraction of carboxyls associated with ether oxygens (theta) between them has a high value (ca. 0.8) which is independent of the concentration of poly(acrylic acid). The complex formation seemed to be caused by hydrogen bonding and hydrophobic interactions. The complex formation influenced on electrochemical reactions of the redox active surfactant.

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Electrochemical control of drug release from redox-active micelles 査読有り

Yukikazu Takeoka, Takashi Aoki, Kohei Sanui, Naoya Ogata, Masayuki Yokoyama, Teruo Okano, Yasuhisa Sakurai, Masayoshi Watanabe

J. Controlled Release 33 巻頁： 79-87 1995年

Interaction between redox-active non-ionic surfactant micelle and poly(acrylic acid) 査読有り

Yukikazu Takeoka, Takashi Aoki, Kohei Sanui, Naoya Ogata, Masayoshi Watanabe

Kobunsi Ronbunshu 52 巻頁： 642-647 1995年

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