One-pot aqueous synthesis PbS quantum dots and their Hg2+ sensitive properties

In this study, we report the synthesis and stability of PbS quantum dots (QDs) using an aqueous route with L-Cysteine (L-Cys) as the capping molecule. The as-synthesized L-Cys-capped PbS QDs were characterized by high resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD), the results indicated that the QDs were about 4 nm in size and dispersed well with a rock salt crystalline structure, and there was L-Cys on the surface of QDs, which was confirmed by Fourier transform infrared (FT-IR) spectrometry. The influence of various experimental variables, including amounts of capping ligand, pH value and refluxing time, on the luminescent properties of the obtained QDs have been systematically investigated. The QDs exhibited optimal PL intensity when Pb: L-Cys: S = 1:2.2:0.3. In addition, the as-prepared QDs could be used as fluorescence probes to detect Hg2+ ions in aqueous media. The response of QDs fluorescence probes was linearly proportional to the concentration of Hg2+ ions ranging from 8 x 10(-9) to 2 x 10(-6) mol x L(-1) with a limit of detection of 2 x 10(-9) mol x L(-1). Furthermore, the method was successfully applied to the determine Hg2+ ions in different real samples.