Facile synthesis l-cysteine capped CdS:Eu quantum dots and their Hg2+ sensitive properties

- l-Cys CdS:Eu QDs were first successfully synthesized in aqueous solution.
- The synthesized l-Cys CdS:Eu QDs exhibit higher photoluminescent intensity and bright a strong yellow emission.
- The as-prepared QDs could be used as fluorescence probes to detect Hg2+ ions in aqueous media.

This paper described a facile aqueous route to prepare CdS: Eu quantum dots (QDs) with strong yellow emission using l-cysteine (l-Cys) as the capping ligands. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) confirm that the CdS:Eu QDs have a cubic structure with good crystallinity, the average diameter of the CdS:Eu QDs is about 8 nm. The traces of groups adsorbed on CdS:Eu QDs were confirmed via FT-IR spectra. In addition, the synthesis parameters including the concentration of doped Eu3+ ions, the pH value and the reaction time have influence on the optical properties of CdS:Eu QDs. The as-prepared l-Cys capped CdS:Eu QDs were used as a fluorescence probe to detect Hg2+ ions in aqueous media based on fluorescence quenching. The response of l-Cys capped CdS:Eu QDs as a fluorescence probe was linearly proportional to the concentration of Hg2+ ions in the range of 5 × 10−6 to 1 × 10−3 mol L−1 with a limit of detection of 2 × 10−6 mol L−1.