Detection of Transient Nanoparticle Collision Events Using Electrochemiluminescence on a Closed Bipolar Microelectrode

The use of optical imaging and bipolar electrochemical arrays is a powerful approach for optically monitoring as well as spatially and temporally resolving heterogeneous electron-transfer processes. Previous studies, however, have been largely limited to the study of slower or steady-state redox processes. In this work, we use electrochemiluminescence (ECL) to demonstrate the ability to optically record transient collision events of single platinum nanoparticles on a carbon ultramicroelectrode (UME). The electrocatalytic signal of a Pt nanoparticle on a cathodic pole of a bipolar electrode is coupled to the ECL signal on the anodic pole generating a transient optical signal. Correlated amperometric (i-t) and ECL (count-t) traces are then compared to determine critical parameters which influence the accurate temporal resolution of these rapid events. Our results suggest that ECL can be an effective means for spatially and temporally resolving transient redox processes when used on arrays of closed bipolar electrodes.