Substrate mediated dissolution of redox active nanoparticles; electron transfer over long distances

Reflective dark field microscopy is used to observe the decrease in the light scattered from Ag nanoparticles immobilised on differing solid substrates. The nanoparticles are exposed to solutions containing halide ions, both at open circuit and under potentiostatic control, leading to the loss of the nanomaterial. By coupling optical and electrochemical techniques the physical origin of this transformation is demonstrated to be the electrochemical dissolution of the metal nanoparticles driven by electron transfer to ultra-trace dissolved oxygen. The dissolution kinetics of the surface-supported metal nanoparticles is compared on four substrate materials (i.e., glass, indium titanium oxide, glassy carbon and platinum) with different electrical conductivity. The three conductive substrates catalyse the redox-driven dissolution of Ag nanoparticles with the electrons transferred from the nanoparticles, via the macroscopic electrode to the dioxygen electron acceptor.