2005 Fiscal Year Final Research Report Summary
Studies on rapid molecular diffusion and charge propagation in a quasi-solid of nanostructured polymers
| Project/Area Number |
15550101
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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 |
Polymer chemistry
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| Research Institution | Ibaraki University |
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Principal Investigator |
KANEKO Masao Ibaraki University, College of Science, Professor, 理学部, 教授 (90109794)
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| Project Period (FY) |
2003 – 2005
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| Keywords | Polysaccharide solid / Solid state electrochemistry / Diffusion coefficient of molecules / Ionic conduction / Alternating current impedance spectroscopy / Redox molecules / Cyclic voltammogram / Dye-sensitized solar cell |
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| Research Abstract |
A quasi solid composed of double helical nanoheterostructured polysaccharide network involving excess water was prepared by heating an aqueous solution of the polysaccharide utilizing microwave irradiation and by the following cooling and solidification. The solid was prepared in the presence of various redox molecules and before cooling down three electrodes (working, counter, and reference) were soaked in the hot solution to prepare a solid involving redox compound installed with three electrodes. Thus, solid state electrochemical measurements were for the first time realized. The ionic conductivity, electrochemical reactivity and diffusion coefficient of molecules in the solid were analyzed by cyclic voltammetry and alternating current impedance spectroscopy. It was shown that electrochemical reactions and molecular diffusion depend on the polysaccharide concentration and the redox compound structure in the solid, so that the behavior was analyzed in relevance to the charge propagat
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ion mechanism through the redox molecules.
As for the polymers, agarose, carageenan, agar, etc. were used. Ionic conductivity by various ions was measured. As for the redox molecules to study molecular diffusion, Ru(bpy)_3^<2+> with sensitizing ability, various metal complexes with various catalysis function (cyano complexes, ammine complexes, Prussian Blue, etc.), and methylviologen were used. Fundamental data of ion diffusion and ionic conductivity were accumulated. It was clarified that conductivity by small ions is the same as in an aqueous solution. Alternating current impedance spectroscopy exhibited interesting results that the resistance for charge transfer and double layer capacitance on the electrode surface is larger than those in an aqueous solution, but that the resistance for charge transport decreases with the increase of the polysaccharide concentration. By utilizing these solids photosensor of humidity was fabricated. The solid was successfully applied to solidify the organic liquid electrolyte solution in a dye-sensitized solar cell, giving almost similar conversion efficiency for the solid type cell as a liquid type one. Less
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