▎ 摘　　要

We have demonstrated electrochemical detection of reduced graphene oxide (rGO) nanoparticles on an ultramicroelectrode (UME) in aqueous solution using rGO collision events. The collision phenomena are detected by monitoring a current-time transient. To attract the rGO to the UME surface, a positive electric field was developed near the UME using a redox reaction. As model systems, ferrocenemethanol and ferrocyanide oxidation reactions were adopted. Amperometric current measurements showed a staircase current response after attachment of rGO on the UME surface. The magnitude of the staircase current is given by the stepwise increase in current, which can provide insight into the size distribution of the rGO colliding with the UME. In the presence of higher concentrations of rGO, multiple collision events happened sequentially on the UME. In this case, an increasing current trend, rather than a single staircase current, was observed. The overall current increment for a given time is a measure of the concentration of rGO in solution. By using this method, charged conductive materials in an aqueous solution can be sensitively detected and/or accumulated.