Collision and Oxidation of Silver Nanoparticles on a Gold Nanoband Electrode

We report the use of gold nanoband electrodes ranging from 60 to 180 nm in width to study collision and oxidation of single Ag nanoparticles (NPs). The use of nanoscale electrodes has enabled the observation of unique single-NP collision responses indicating a strong electrode size effect when the critical dimension of the electrode (the bandwidth) is reduced to that of NPs. In addition to multipeak events, NP collision on a nanoband electrode displays reduced collision frequency, significantly higher probability of single peak events, and fewer subpeaks. More importantly, the average charge transferred in a single-peak event is about 50% less than that of the first subpeak of a multipeak event. The reduced charge of single-peak collisions and the more frequent appearance on nanoelectrodes are strong evidence that NPs start to behave differently at the electrode/solution interface when the size of the electrode is reduced to be comparable to that of the NPs. The reduced charge is likely due to a weaker particle electrode interaction when the particle collides on the edge of the nanoband electrode. Random walk numerical simulation was used to further understand the electrode size effect in single-particle collision and oxidation. The simulated results are in good agreement with the experiments. A detailed analysis of the collision signal reveals that a Ag NP is more likely to diffuse away after making its initial contact with a nanoband electrode, due to the electrode's smaller critical dimension and a possible strong edge effect from the negatively charged silicon nitride/oxide. This study offers a deeper insight into the dynamic collision behavior of metal NPs on the electrode surface.