Highly fluorescent CdTe/ZnSe quantum dot-based "turn-off" sensor for the on-site rapid detection of Lead ions in aqueous medium.

Lead (Pb) is a heavy metal known for its adverse effects on both human health and the environment. In recent years, the industrial utilization of Pb has surged, underscoring the imperative need for efficient measurement methods. In this study, a rapid and simple photochemical method was used to synthesize thioglycolic acid (TGA)-stabilized CdTe/ZnSe core-shell quantum dots (QDs). These CdTe/ZnSe QDs emit vibrant green fluorescence and exhibit remarkable quenching in the presence of Pb ions. This property enables the development of an on-site on/off sensor without the necessity of additional modifications. The proposed sensor possesses an outstanding sensitivity to Pb, with a detection limit and linear range of 31.8 nM and 50 nM-10 µM, respectively. Importantly, the selectivity of this fluorescence-based sensor was validated by analyzing various positively and negatively charged ions. Furthermore, the developed sensor showed reliable performance against real river, agricultural, and tap water, as confirmed by Inductively Coupled Plasma (ICP) analysis. Additionally, CdTe/ZnSe QDs immobilized on glass slides were successfully employed for on-site water sample analysis, providing a versatile solution for environmental monitoring.