Study of the adsorption kinetics of thiol-derivatized porphyrin on the surface of gold electrode

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• 作者：Guofang Zuo ; Xiuhui Liu ; Jiandong Yang ; Xiujuan Li ; Xiaoquan Lu ; ^{luxq@nwnu.edu.cn}
• 关键词：Adsorption kinetics ; Thiol-derivatized porphyrins ; Electrochemistry ; Self-assembled monolayer
• 刊名：Journal of Electroanalytical Chemistry
• 出版年：2007
• 出版时间：15 July 2007
• 年：2007
• 卷：605
• 期：2
• 页码：81-88
• 全文大小：225 K

文摘

The adsorption kinetics of thiol-derivatized porphyrins (abbreviated as H₂TPPO(CH₂)_nSH, where n = 3, 4, 6, 9, 10 and 12) on gold electrode have been investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) and the intention was to study the effect of alkyl chain length and terminal group on the process of forming SAMs. The time dependence on surface coverage supported that the adsorption of H₂TPPO(CH₂)_nSH molecules typically processes with a two-step adsorption consisting of a fast initial adsorption and a following slow reorganization. The equilibrium constant (K) for the adsorption and the Gibbs free energy (¦¤G_ads) of SAMs were evaluated based on the Frumkin isotherm and the interaction factor between adsorbate¨Cadsorbate molecules was also discussed. The adsorption processes at the initial step could be satisfactorily described by simple Langmuir adsorption kinetics, irrespective of alkyl chain length of adsorbate molecule. Based on Langmuir kinetics, the adsorption rate constant was determined at the initial step for the formation of all H₂TPPO(CH₂)_nSH¨CSAMs studied in this work. The rate constant value was found to decrease with increasing alkyl chain length and the unique structure of porphyrin moiety as a large terminal group had a great influence on the initial adsorption kinetics compared with that of n-alkanethiol on gold.