Diffuse layer properties of thiol-modified gold electrodes probed by direct force measurements
Diffuse layer properties of thiol-modified gold electrodes probed by direct force measurements
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DOI：
10.1021/la700987u
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发表时间：
2007-08-14
期刊：
影响因子：
3.9
通讯作者：
Papastavrou, Georg
中科院分区：
文献类型：
--
作者：
Rentsch, Samuel;Siegenthaler, Hans;Papastavrou, Georg
修饰金电极在恒电位控制下的扩散层特性已通过直接力测量确定。这些测量是使用由附着在原子力显微镜悬臂上的二氧化硅颗粒组成的胶体探针进行的。金电极通过不同厚度的自组装单分子层（SAM）进行修饰。此外，单层的末端官能团也发生了变化。相互作用力分布已适合非线性泊松-玻尔兹曼方程的完整解。通过考虑表面之间的电荷调节，获得了力分布的准确定量描述。研究了从这些拟合中获得的扩散层电势与施加到金电极上的电势的关系。已针对不同厚度和表面终端的各种 SAM 确定了 SAM 的电容和零电荷电势 (pzc)。通过我们的直接力测量获得的值与经典电化学技术报告的值一致。 SAM 的电容主要取决于单层的厚度及其晶体结构。已发现不同官能团的 pzc 存在显着差异。这些变化与终止 SAM 的官能团的偶极矩有关。我们的数据与离子吸附一致，但这种效应似乎不如裸金电极明显。
The diffuse layer properties of modified gold electrodes under potentiostatic control have been determined by direct force measurements. These measurements have been performed with a colloidal probe consisting of a silica particle attached to the cantilever of an atomic force microscope. The gold electrodes were modified by self-assembled monolayers (SAMs) of different thickness. Additionally, the terminating functional groups of the monolayer have been varied. The interaction force profiles have been fit to the full solutions of the nonlinear Poisson -Boltzmann equation. An accurate quantitative description of the force profiles has been obtained by taking charge regulation between the surfaces into account. The diffuse layer potentials obtained from these fits were studied in dependence of the potential applied to the gold electrode. The capacitance of the SAM and the potential of zero charge (pzc) have been determined for various SAMs of different thickness and surface termination. The values obtained by our direct force measurements are in agreement with the ones reported by classical electrochemical techniques. The capacitance of the SAM depends primarily on the thickness of the monolayer and its crystalline structure. Pronounced differences in the pzc for the different functional groups have been found. These changes are related to the dipole moment of the functional group terminating the SAM. Our data are in agreement with ion adsorption, but this effect seems to be less pronounced than for bare gold electrodes.