| Project/Area Number |
16550073
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Analytical chemistry
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| Research Institution | Kobe University |
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Principal Investigator |
OSAKAI Toshiyuki Kobe University, Faculty of Science, Department of Chemistry, Associate Professor, 理学部, 助教授 (00194118)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2005: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2004: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Keywords | oil / water interface / electron transfer / scanning electrochemical microscopy / natural antioxidants / kinetics / reaction mechanism / Marcus theory / diffusion control / 抗酸化剤 / ボルフィリン錯体 / 反応層 |
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| Research Abstract |
Electron transfer at the oil/water interface is important for understanding electron transfer processes at biomembranes, which include respiratory electron transport reactions and synergistic antioxidant activities of natural antioxidants such as vitamin C and vitamin E. In this study scanning electrochemical microscopy (SECM) was employed to examine the reaction mechanisms of interfacial electron transfer reactions for biologically relevant compounds.
In the 2004 fiscal year, SECM was used to determine rate constants for the electron transfer between zinc tetraphenylporphyrin radical cation and natural antioxidants including ascorbic acid (vitamin C) and chlorogenic acid at nitrobenzene/water and benzene/water interfaces. The apparent rate constants determined were proportional to the square root of the antioxidant concentration. This dependence could not be elucidated in terms of either the "electron-transfer mechanism" due to heterogeneous electron transfer at the interface or the "ion-transfer mechanism" involving the distribution of the radical cation to the aqueous phase. However, the dependence could be well explained by a new mechanism, in which the electron transfer should occur in the oil phase after the partial distribution of the antioxidant to the oil phase.
In the 2005 fiscal year, SECM was employed to study the mechanism of heterogeneous (i.e., true) electron transfer at oil/water interfaces. The rate constants (κ) determined for the electron transfer between decamethylferrocene and hexacyanoferrate at oil/water interfaces depended on the Gibbs free energy (ΔG) of the electron transfer reaction, but did not show the parabolic dependence expected from the Marcus theory. There was an upper limit of the rate constant, which supported our previous theory in which the "microscopic" diffusion of redox species at the oil/water interface was taken into consideration.
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