Photothermal and colorimetric dual-readout silver ions determination utilizing the oxidase-mimicking activity of MnO2 nanosheets

Accurate and sensitive sensing of silver ions (Ag+) is meaningful to environmental safety and human health. However, many of the analytical methods for Ag+ usually rely on large analytical instruments for quantitative reading. Herein, we report a portable assay for Ag+ based on the excellent colorimetric and photothermal properties of a dye 3,3′,5,5′-tetramethylbenzidine (TMB). As an oxidase-like activity nanomaterial, MnO2 nanosheets (NSs) were employed to catalyze the oxidation of TMB into oxTMB. Nevertheless, the reduction of MnO2 NSs by glutathione (GSH) could minimize the catalytic ability of the MnO2 NSs. In this approach, the specific interaction of Ag+ and GSH was utilized to suppress this reduction process. According to this principle, Ag+ concentrations could be transformed to temperature and color signals. So that, Ag+ could be identified with naked-eyes, and also sensitive determined with a portable thermometer. The proposed sensor exhibited a high selectivity, making it a sensitive, portable, and accurate new Ag+ detection system.