Tracking the electrocatalytic activity of Au@Ag core–shell nanoparticles for nitrite oxidation via single-entity electrochemistry

Single-entity electrochemistry (SEE) has been extensively utilized for analyzing various substances, elucidating their mechanisms, and predicting particle behavior on electrode surfaces. In this paper, we propose a novel method for analyzing the electrochemical reactions between core–shell nanoparticles (NPs) and nitrite ions at the single-particle level. This method employs single Au@Ag core–shell NPs, nitrite ions (${\mathrm{NO}}_2^{-}$), and a carbon ultramicroelectrode (C-UME), utilizing the electrochemical oxidation of ${\mathrm{NO}}_2^{-}$ ions upon collision with individual core–shell nanoparticles on the C-UME surface. Au@Ag core–shell NPs with different ratios were synthesized to achieve the effective oxidation of ${\mathrm{NO}}_2^{-}$ ions, and their electrochemical properties were analyzed. Various parameters, such as applied potential and ${\mathrm{NO}}_2^{-}$ ion concentration, were adjusted in chronoamperometric experiments to analyze the resulting signals. This study is expected to significantly contribute to the analysis of oxidation/reduction, dispersion, and catalytic properties of various NPs, particularly core–shell NPs.