Xiang Juan, Guo Jun, Zhou Feimeng
Institute of Surface Analysis and Biosensing, College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, PR China.
Anal Chem. 2006 Mar 1;78(5):1418-24. doi: 10.1021/ac051601h.
The combination of scanning electrochemical microscopy (SECM) with surface plasmon resonance (SPR) is described. By oxidizing ferrocenylalkanethiol self-assembled monolayer (SAM) with SECM-generated Ce4+, the coupled technique, SECM-SPR, is shown to be viable for determining local variations in thin film thickness. Factors (tip/substrate distance, tip potential scan rate, and solution composition change) affecting the SECM-SPR response and operation are also discussed. The approach was further extended to the determination of conformational changes of cytochrome c molecules attached electrostatically onto a negatively charged SAM during its reduction by the tip-generated methyl viologen monocation. The high sensitivity of the SPR equipped with a bicell detector facilitates the measurement of infinitesimal film thickness changes accompanying redox reactions, while the SECM provides a means to obviate the necessity of applying a potential to the SPR substrate, which tends to cause unwanted interferences and complications. The approach also affords an avenue for determining film thickness variations that are not subject to certain effects, such as the surface charge, the heterogeneity of the substrate, and the distance between the redox center of the immobilized molecule and the underlying substrate electrode.
本文描述了扫描电化学显微镜（SECM）与表面等离子体共振（SPR）的联用。通过用SECM产生的Ce4+氧化二茂铁基烷硫醇自组装单分子层（SAM），结果表明联用技术SECM-SPR可用于测定薄膜厚度的局部变化。还讨论了影响SECM-SPR响应和操作的因素（针尖/基底距离、针尖电位扫描速率和溶液组成变化）。该方法进一步扩展到测定细胞色素c分子在被针尖产生的甲基紫精单阳离子还原过程中静电附着在带负电的SAM上时的构象变化。配备双池检测器的SPR的高灵敏度有助于测量伴随氧化还原反应的微小薄膜厚度变化，而SECM提供了一种避免向SPR基底施加电位的方法，施加电位往往会导致不必要的干扰和复杂性。该方法还为确定不受某些影响（如表面电荷、基底的不均匀性以及固定化分子的氧化还原中心与下层基底电极之间的距离）的薄膜厚度变化提供了一条途径。
