Revealing the diverse electrochemistry of nanoparticles with scanning electrochemical cell microscopy

The next generation of electroactive materials will depend on advanced nanomaterials, such as nanoparticles (NPs), for improved function and reduced cost. As such, the development of structure-function relationships for these NPs has become a prime focus for researchers from many fields, including materials science, catalysis, energy storage, photovoltaics, environmental/biomedical sensing, etc. The technique of scanning electrochemical cell microscopy (SECCM) has naturally positioned itself as a premier experimental methodology for the investigation of electroactive NPs, due to its unique capability to encapsulate individual, spatially distinct entities, and to apply a potential to (and measure the resulting current of) single-NPs. Over the course of conducting these single-NP investigations, a number of unexpected (i.e. rarely-reported) results have been collected, including fluctuating current responses, and carrying of the NP by the SECCM probe, hypothesised to be due to insufficient NP-surface interaction. Additionally, locations with measurable electrochemical activity have been found to contain no associated NP, and conversely locations with no activity have been found to contain NPs. Through presenting and discussing these findings, this article seeks to highlight complications in single-NP SECCM experiments, particularly those arising from issues with sample preparation.