Colorimetric detections of iodide and mercuric ions based on a regulation of an Enzyme-Like activity from gold nanoclusters

A simple colorimetric method was developed for sensitive and selective detections of I- and Hg2+. Histidine stabilized gold nanoclusters (His-AuNCs) were synthesized and catalyzed the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to a blue product. As a strong ligand toward gold, iodide (I-) attached to the surface of the His-AuNCs and significantly enhanced the oxidase-like activity of the His-AuNCs. Based on this enhancement, a sensitive colorimetric response toward I- was obtained. Furthermore, the strong interaction between Hg2+ and I- was adopted for an indirect Hg2+ detection. Under the optimal conditions, the platform presented high selectivity for the determinations of I- and Hg2+ in the ranges 0.02-1 µM and 0.05-0.8 µM, with detection limits as 3.3 nM and 8 nM respectively. This colorimetric assay was successfully applied for analysis of real samples.