Electrochemical reactions in subfemtoliter-droplets studied with plasmonics-based electrochemical current microscopy.

We report on a plasmonics-based electrochemical current imaging of redox reactions in aqueous droplets with diameters varying from a few hundred nanometers (tens of attoliter in volume) to a few micrometers. The imaging technique allows us to obtain cyclic voltammograms of multiple droplets on a gold electrode simultaneously and to examine the local redox reactions within a droplet. The results are supported by numerical simulations. The work demonstrates a new capability of studying electrochemistry in microdroplets, which offers an opportunity to understand electrochemical reactions within a small confined volume.