Observation of Local Redox Events at Individual Au Nanoparticles Using Electrogenerated Chemiluminescence Microscopy

Au nanoparticles (NPs) are known to be able to enhance the oxidation of tripropylamine (TrPA) and the generation of electrogenerated chemiluminescence (ECL) from Ru(bpy)(3)(2+) when TrPA is used as a coreactant. Local redox activities of single Au NPs can therefore be investigated using the combined methods of voltammetry and ECL imaging. Our study shows that ECL generation at individual Au NPs increases with particle size (diameters from 30 to 300 nm) and is affected by the local chemical and charge transfer environment of the NPs. Such an ECL detection scheme can allow one to study the local redox activities of single nanoparticles with improved spatial resolution. ECL at single Au NPs shows slight temporal variations in intensity attributed to the oxidation and reconstruction of small clusters on the Au surface during ECL generation. Quantitative agreement between calculations and experiment concerning the effect of particle size and electrode potential on spatial and transient ECL profiles is presented.