Thiourea functionalized CdSe/CdS quantum dots as a fluorescent sensor for mercury ion detection

CdSe/CdS quantum dots (QDs) functionalized by thiourea (TU) were synthesized and used as a fluorescent sensor for mercury ion detection. The TU-functionalized QDs were prepared by bonding TU via electrostatic interaction to the core/shell CdSe/CdS QDs after capping with thioglycolic acid (TGA). It was observed that the fluorescence of the functionalized QDs was quenched upon the addition of Hg²⁺. The quantitative detection of Hg²⁺ with this fluorescent sensor could be conducted based on the linear relationship between the extent of quenching and the concentration of Hg²⁺ added in the range of 1-300 mg L^-1. A detection limit of 0.56 mg L^-1 was achieved. The sensor showed superior selectivity for Hg²⁺ and was successfully applied to the determination of mercury in environmental samples with satisfactory results.