Pt nanoclusters based on N, S co-doped graphene quantum dots as a smart probe for ultrasensitive Ag+ sensing

In this work, a simple strategy for the rapid detection of Ag + based on nitrogen, sulfur doped graphene quantum dots (N, S-GQDs) decorated platinum nanoclusters (PtNCs) was proposed for the first time. N, S-GQDs decorated PtNCs (N, S-GQDs@PtNCs) were prepared by a reduction method using ascorbic acid (AA) as reducing agent and N, S-GQDs as a stabilizer and morphology directing reagent, respectively. The N, S-GQDs@PtNCs have an excellent peroxidase activity, which could catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H 2 O 2 to lead to an obvious color change. However, Ag + could be reduced to Ag 0 by N,S-GQDs, and the Ag 0 covered the surface of N, S-GQDs@PtNCs causing its peroxidase activity to decrease. Ag + concentration could be quantified by measuring the maximum absorption signal at 652 nm for oxidized TMB with a wide linear range of 0.5–300.0 nM and a limit of detection (LOD) as low as 0.2 nM. In addition, satisfactory results were obtained for the detection of Ag + in actual water samples. The prepared colorimetric sensor had advantages such as simple operation, cost-effective, fast response, and visualization, and had great potential in detecting toxic Ag + in environmental.