Metal nanoparticles (NPs) have been of interest in many fields, often because of their large surface-to-volume ratio and size dependent optical properties. Most research on NPs has focused on ensemble-averaged properties, but there have been investigations of the electrochemical behavior of an immobilized single NP, despite the experimental difficulties of fixing, characterizing, and making measurements at the nm scale.
Researchers at The University of Texas at Austin have developed a unique method for detection of a single nanoparticle (IrOx specifically) collisions on a NaBH4-treated platinum ultramicroelectrode (UME). We observe single NP events through the enhanced current by electrocatalytic water oxidation, when IrOx contacts the electrode and transiently sticks to it. The overall current transient consists of repeated current spikes that return to the background level, superimposed on a current decay, rather than the staircase response seen where an NP sticks on the UME. Here each event produces a unique current spike (or “blip”). The frequency of the spikes was directly proportional to the particle concentration, and the peak current increased with the applied potential. The observed current is very sensitive to the material and surface state of the measuring electrode; a NaBH4-treated Pt UME was important in obtaining reproducible results.
Issued Patent: US 8,808,530, “Method and Apparatus for Electroacoustic Amplification on Pre-Oxidized Measuring Electrode”