Particle-electrode impacts: Evidencing partial versus complete oxidation via variable temperature studies

Correlated Anodic-Cathodic Nanocollision Events Reveal Redox Behaviors of Single Silver Nanoparticles

We reported a novel method to real-time monitor the redox behaviors of single Ag nanoparticles (AgNPs) at a Au ultramicroelectrode between oxidizing and reducing pulse potentials using the nanocollision electrochemical method. At fast pulse potentials, the instantaneous anodic-cathodic current transients of a single AgNP were observed for the electrooxidation of AgNP, followed by the electroreduction of the newborn silver oxide (AgO) NP in alkaline media via switching of redox potentials; however, only anodic oxidation signals of individual AgNPs were observed in neutral solution. Through this study, we have revealed the substantial different dynamic nanocollision electrochemical behaviors of single AgNPs on the electrode surface in various media. Our study offers a new view for clearly clarifying in situ tracking of the electron-transfer process of single NPs by correlating electrochemical oxidation and reduction behaviors with the complementary information.

Electrochemical impacts complement light scattering techniques for in situ nanoparticle sizing

We show that the electrochemical particle-impact technique (or 'nano-impacts') complements light scattering techniques for sizing both mono- and poly-disperse nanoparticles. It is found that established techniques - Dynamic Light Scattering (DLS) and Nanoparticle Tracking Analysis (NTA) - can accurately measure the diameters of '30 nm' silver particles assuming spherical shapes, but are unable to accurately size a smaller '20 nm' sample. In contrast, nano-impacts have a high accuracy (<5% error in effective diameters) and are able to size both individual '20 nm' and '30 nm' silver NPs in terms of the number of constituent atoms. Further study of a '20 nm and 30 nm' bimodal sample shows that the electrochemical technique resolves the two very similar sizes well, demonstrating accurate sizing regardless of particle size polydispersity, whereas due to inherent limitations of light scattering measurements this is not possible for DLS and NTA. Electrochemical sizing is concluded to offer significant attractions over light scattering methods.