Imaging Local Electrochemical Current via Surface Plasmon Resonance

An Electrochemical Landscape Electrochemical detection is an analytical method that has been used for a wide range of purposes, including trace chemical analysis, glucose and neurotransmitter monitoring, DNA and protein detection, and electrocatalysis. Scanning electrochemical microscopy maps changes in the local electrochemical current along a surface in a serial way, but serial probing can disrupt the process under study. Shan et al. (p. 1363) show that optical measurements of surface plasmon resonances can be used as a less disruptive way of determining the concentration of electrochemically active species on gold-coated glass slides and their current density. This method can be used for a wide range of applications from analyzing DNA and protein microarrays and enzyme-amplified biosensors to probing the activities of cells. The concentration of electrochemically active species on a gold electrode provides a local measurement of current density. We demonstrated an electrochemical microscopy technique based on the detection of variations in local electrochemical current from optical signals arising from surface plasmon resonance. It enables local electrochemical measurements (such as voltammetry and amperometry) with high spatial resolution and sensitivity, because the signal varies with current density rather than current. The imaging technique is noninvasive, scanning-free, and fast, and it constitutes a powerful tool for studying heterogeneous surface reactions and for analyzing trace chemicals.