Halide Ion-Induced Switching of Gold Nanozyme Activity Based on Au-X Interactions

The influence of halide ion on the peroxidase activity of protein-modified gold nanoparticles (AuNPs) has been explored, based on the Au-X interaction directed binding of halide ion to AuNPs. Due to different Au-X interactions, halide has been demonstrated to display different switching behaviors to the catalytic activity of protein-modified AuNPs. Presented is the finding that iodide can rapidly inhibit the enzyme activity of CM-AuNP nanozyme effectively. Iodide-mediated irreversible inhibition is due not to I^--induced aggregation of AuNP but to the Au-I bond-induced blocking of active sites of AuNP nanozyme. I^- switching efficiency was found to be strongly dependent on the surface density of modifiers and the intrinsic property of the modifier. Similar to iodide, bromide can also inhibit the enzyme activity effectively, but its inhibition behavior is reversible. Due to the weak Au-Cl interaction, chloride has no influence on the enzyme activity of CM-AuNP at low ion concentration and exhibits weak activity inhibition at high ion concentration. Fluoride shows no influence on the activity of gold nanozyme due to the absence of Au-F interaction. Our results have improved a profound understanding of anion-mediated AuNP nanozyme activity because of their interfacial interaction and provided guidance in the further utilization of nanozyme in numerous areas.