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.