インジゴテトラスルホン酸イオンの電子移動速度に対する4-アミノチオフェノール単分子膜のプロトネーションの効果

抄録

Electron transfer of indigotetrasulfonate ion at 4-aminothiophenol (ATP) monolayer-modified electrode was examined in the pH range of 2 to 6 by cyclic voltammetry and ac impedance spectroscopy. By changing up the pH of electrolyte from 2 to 6, the redox process of indigotetrasulfonate becomes reversible in the presence of ATP monolayer-modified electrode. While the electron-transfer rate constant of indigotetrasulfonate for bare gold was decreased from 2.5×10⁻³ cms⁻¹ at pH 2 to 4.7×10⁻⁵ cms⁻¹ at pH 6, that for ATP monolayer-modified electrode was increased from 3.2×10⁻⁵ cms⁻¹ to 1.6×10⁻² cms⁻¹. Reversible redox reaction of indigotetrasulfonate were also observed at cystamine and 4-mercaptopyridine modified electrodes at pH 6, but were not observed at 3-mercaptopropanesulfonic acid, 1-butanthiol and 4-hydoroxythiophenol at pH 6. Our results suggest that the electron transfer rate of indigotetrasulfonate ion is controlled by a specific interaction between the amine groups of the thiol monolayer and indigotetrasulfonate ion.