Facile synthesis of N-acetyl-l-cysteine capped ZnS quantum dots as an eco-friendly fluorescence sensor for Hg2+

This paper described an investigation of a novel eco-friendly fluorescence sensor for Hg2+ ions based on N-acetyl-l-cysteine (NAC)-capped ZnS quantum dots (QDs) in aqueous solution. By using safe and low-cost materials, ZnS QDs modified by NAC were easily synthesized in aqueous medium via a one-step method. The quantitative detection of Hg2+ ions was developed based on fluorescence quenching of ZnS QDs with high sensitivity and selectivity. Under optimal conditions, its response was linearly proportional to the concentration of Hg2+ ions in a range from 0 to 2.4 × 10−6 mol L−1 with a detection limit of 5.0 × 10−9 mol L−1. Most of common physiologically relevant cations and anions did not interfere with the detection of Hg2+. The proposed method was applied to the trace determination of Hg2+ ions in water samples. The possible quenching mechanism was also examined by fluorescence and UV–vis absorption spectra.