Electrochemical Detection of Colloidal Semiconductor Nanoparticles: From Single Nanoparticles to Aggregates

Our group develops electrochemical methods to study semiconductors in colloidal suspension to study photocatalytic processes of colloidal semiconducting nanoparticles (NPs). We have demonstrated the detection of individual anatase NPs interacting with an electrode by photoelectrochemical currents. The NPs are suspended in methanol under constant illumation and we present this as a model system of photocatalysis. However, under different experimental conditions, the photocatalytic currents go from steps to spikes. We have assigned the spike currents to aggregates. As illumination time increases, the current spikes also increase in size, consistent with the growth of agglomerates that can store a larger number of electrons. We propose that these interactions carry information about the photochemical process at the single agglomerate, and in turn, from the NPs that construct the aggregate. This seminar will present our advances towards measuring the particle by particle charge storage and the ability to allow electrons to flow across the NPs. We will also discuss the rate of photooxidation in the context of the agglomeration in solution and its implication on the detection of single NPs.