Studies of structural disorder of self-assembled thiol monolayers on gold by cyclic voltammetry and ac impedance
Studies of structural disorder of self-assembled thiol monolayers on gold by cyclic voltammetry and ac impedance
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DOI：
10.1016/s0022-0728(98)00470-7
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发表时间：
1999-03-19
影响因子：
4.5
通讯作者：
Zhong, B
中科院分区：
文献类型：
--
作者：
Diao, P;Jiang, DL;Zhong, B
用循环伏安法和电化学阻抗谱研究了十八烷基吡啶在金表面的自组装。CV实验表明，在金上组装良好的硫醇单分子膜基本上没有针孔缺陷。通过比较表观电子转移速率常数，这是从CV实验中获得的膜覆盖的Au电极，与理论上的，这是通过假设电子隧道穿过的无折叠位点单层的存在，得到支持硫醇单分子层中的“折叠”位点。用经验关系Z = R-3 + 1/[σ（j ω）（α）]描述惰性电解液中的薄膜包覆Au，并由α值估计单层结构的无序度。论证了具有恒相位元件特性的理想极化电极的导纳平面图是一个圆弧，可以用它来确定极化率。交流阻抗实验结果表明，a在初始吸附时间后急剧增加，并缓慢接近其最终值。这是由于在Au电极上的烷基乙醇胺吸附动力学中，快速吸附步骤之后是缓慢的结晶过程。对于在金上良好组装的硫醇单层，a可以接近0.99，这意味着塌陷位点的数量不大，单层Au电极的表面相当光滑。(C)1999年Elsevier Science S.A. All rights reserved.
Self-assembly of octadecyl mercaptan on gold has been investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV experiments show that well-assembled thiol monolayers on gold are essentially free of pinhole defects. Support for the existence of 'collapsed' sites in thiol monolayers is obtained by comparing the apparent electron transfer rate constant, which is obtained from CV experiments at a film covered Au electrode, with the theoretical one, which is calculated by assuming electrons tunnel across the collapsed-site-free monolayer. The empirical relationship Z = R-3 + 1/[sigma(j omega)(alpha)] is used to describe the film coated Au in inert electrolyte and the degree of disorder of the monolayer structure is estimated from the a value. It is demonstrated that the admittance plane plot of an ideally polarizable electrode with constant phase element behavior is a circular are which can be used to determine a. Results of EIS experiments show that a increases sharply after the initial adsorption time and approaches its final value slowly. This is attributed to the rapid adsorption step followed by a slow crystallization process in the kinetics of alkanethiol adsorption onto the Au electrode. For a well-assembled thiol monolayer on gold, a can approach 0.99, which means that the number of collapsed sites is not large and the surface of the monolayer Au electrode is rather smooth. (C) 1999 Elsevier Science S.A. All rights reserved.