Permselectivity and High Sensitivity at Ultrathin Monolayers. Effect of Film Hydrophobicity
Permselectivity and High Sensitivity at Ultrathin Monolayers. Effect of Film Hydrophobicity
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DOI：
10.1021/ac00113a008
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发表时间：
1995-09
影响因子：
7.4
通讯作者：
Q. Cheng;A. Brajter-toth
中科院分区：
文献类型：
--
作者：
Q. Cheng;A. Brajter-toth
研究了单分子膜结构和溶液组成对自组装单分子膜电化学响应的影响。研究的单分子膜由硫辛酸（1，2-二硫戊环-3-戊酸）和1-hexanethethanol，其中不同程度的表面疏水性，通过这两个分子的共组装获得。在更亲水的硫辛酸单分子膜上，亲水性探针Fe（CN）6 3-和Ru（NH 3）6 3+获得了快速的动力学和高的电化学灵敏度。在亲水性单层电极上的选择透过性可以通过控制单层COOH头部基团的解离程度来实现。随着共吸附正己烷的增加，膜的疏水性增加，亲水性探针的动力学变慢。对于更疏水的儿茶酚胺和醌探针，较慢的动力学（较低的灵敏度），始终观察到在单层电极，独立的单层组合物。提出了一个简单的改进的斯特恩模型来表示探针响应，单层结构和电解质组成之间的关系。讨论了Donnan势在控制膜选择透过性中的作用，并讨论了单层稳定性和基底质量对单层电极响应的作用。
The effect of monolayer structure and solution composition on electrochemical response at ultrathin monolayers formed by self-assembly has been investigated. The monolayers studied consisted of thioctic acid (1,2-dithiolane-3-pentanoic acid) and 1-hexanethiol, where different degrees of surface hydrophobicity were obtained through the coassembly of these two molecules. On the more hydrophilic thioctic acid monolayers, fast kinetics and high electrochemical sensitivity were obtained for hydrophilic probes Fe(CN) 6 3- and Ru(NH3) 6 3+ . Permselectivity at the hydrophilic monolayer electrodes could be achieved by controlling the extent of dissociation of the monolayer COOH head groups. As the hydrophobicity of the film increased with the coadsorption of hexanethiol, the kinetics of the hydrophilic probes became slower. For more hydrophobic catecholamines and quinone probes, slower kinetics (lower sensitivity) were consistently observed at the monolayer electrodes, independent of the monolayer composition. A simple modified Stern model is proposed to represent the relationship between the probe response, the monolayer structure, and the electrolyte composition. The role of the Donnan potential in controlling film permselectivity is addressed, and the roles of monolayer stability and substrate quality on the monolayer electrode response are discussed.