Colorimetric assay of Hg2+ based on the inhibition of peroxidase mimetic activity of gold nanoclusters induced by Hg2+

Abstract

In this paper, we report a highly sensitive and selective colorimetric assay for Hg²⁺ detection in aqueous solutions. Bovine serum albumin–gold nanoclusters (BSA–AuNCs) were prepared and used as a mimetic peroxidase to catalyze the 3,3′,5,5′-tetramethylbenzidine (TMB)–H₂O₂ system. In the absence of Hg²⁺, the AuNCs catalyze the reaction between TMB and H₂O₂, leading to a color change from colorless to blue. In the presence of Hg²⁺, owing to high-affinity metallophilic interactions between Hg²⁺ and Au⁺ on the surface of the AuNCs, Hg²⁺ can decrease the catalytic ability of the AuNCs, resulting in a decreased color change. The color changes in varying degrees depending on the concentration of Hg²⁺. The method shows low detection limits for Hg²⁺: 3.0 nM in deionized water and 3.5 nM in lake water.