Direct Observation of the Reactivity of Electrons toward Gold Nanoparticles in Aqueous Solution

The catalytic activity of gold nanoparticles (AuNPs) has been widely acknowledged; however, Au NPs are considered to be highly inert as radiosensitizers in biological systems. This apparent discrepancy across different fields complicates the understanding of their interfacial reactivity, particularly in terms of electron transfer reactions. Here, we employ pulse radiolysis to determine the rate constants for the reactions of electrons with AuNPs in aqueous solution. Our investigation of AuNPs with different sizes and surface modifications demonstrates the potential influence of the AuNPs design on electron transfer reactions. These findings address long-standing mechanistic contradictions and underscore the significance of interfacial electron dynamics on AuNPs in both catalytic and biological processes.