LAUSR

A method is described here for the quickly (<30 s) accurate determination of Cr(VI) (Cr2O72−), based on fluorescent probes gold nanodots (AuNDs, excitation/emission peaks at 395/604 nm) coated with glutathione (GSH). The fluorescence of the AuNDs responses linearly to Cr(VI) concentrations, ranging widely from 1 nM to 10 mM with detection limit as low as 0.35 nM. At the same time, the AuNDs is demonstrated highly selective for Cr(VI) detection over other acid group ions and metal ions without any masking reagent. These make probability for practical use. The quenching mechanism is investigated deeply via fluorescent lifetime, XPS and TEM analysis. Different from most reported quenching explanation of aggregation derived from charge attraction, these results verify the redox reaction between Cr2O72− and sulfhydryl (–S) of GSH. The Au(I)–S bonds of AuNDs broke, accompanies with the oxidation of–S to form S–S bonds. As a result, AuNDs cross linked to each other. In the end, the fluorescence quenched. Attractively, the present study provides a new strategy for pollutant detection, such as from harmful Cr(VI) of Cr2O72− to nontoxic Cr(III).