Electrochemical (EC) impacts of single nanoparticles (NPs) on an ultramicroelectrode are coupled with optics to identify chemical processes at the level of individual NPs. While the EC signals characterize the charge transfer process, the optical monitoring gives a complementary picture of the transport and chemical transformation of the NPs. This is illustrated in the case of electrodissolution of Ag NPs. In the simplest case, the optically monitored dissolution of individual NPs is synchronized with individual EC spikes. Optics then validates in situ the concept of EC nanoimpacts for sizing and counting of NPs. Chemical complexity is introduced by using a precipitating agent, SCN(-), which tunes the overall electrodissolution kinetics. Particularly, the charge transfer and dissolution steps occur sequentially as the synchronicity between the EC and optical signals is lost. This demonstrates the level of complexity that can be revealed from such electrochemistry/optics coupling.

Transport-reaction processes at individual Ag nanoparticles (NPs) are studied using electrochemistry coupled with in situ 3D light scattering microscopy. Electrochemistry is used to trigger a (i) diffusiophoretic transport mode capable of accelerating and preconcentrating NPs toward an electrode and (ii) subsequent diffusion-controlled oxidation of NPs. Individual NP dissolution rate, analyzed using optical modeling, suggests the intervention of insoluble products. New insights into diverse NPs behaviors highlight the strength of coupled optical-electrochemical 3D microscopies for single-NP studies.