CdTe-MSA quantum dots prepared by a green hydrothermal route as highly selective ‘turn-off’ fluorescent nanosensors for Lead(II) detection in environmental water monitoring

In this study, water-dispersible CdTe quantum dots (QDs) capped with mercaptosuccinic acid (MSA) were synthesized via a green one-pot hydrothermal route and explored as efficient fluorescent probes for Pb2+ detection in aqueous media. The obtained QDs, with an average diameter of 3.4 nm, exhibited high colloidal stability, strong fluorescence, and a narrow emission profile. Remarkably, a selective fluorescence "turn-off" response was observed exclusively in the presence of Pb2+ ions, with no significant interference from other tested metal cations. Quantitative analysis using the Stern–Volmer model revealed a linear detection range of 0.2–4 µM R² = 0.9948 and a low detection limit of 72 nM. Taken with the Benesi–Hildebrand analysis, results confirmed a static quenching mechanism arising from strong Pb2+-carboxylate binding, followed by electron transfer and formation of a non-emissive ground-state complex. Adsorption experiments demonstrated that Pb2+ uptake follows pseudo-first-order kinetics and fits the Langmuir isotherm model, indicating monolayer adsorption on homogeneous active sites. Recovery tests in spiked real tap water samples achieved 95–109 % recoveries with RSD < 5 %, underscoring the probe's reliability under realistic conditions. These results highlight CdTe-MSA QDs as cost-effective, selective, and sensitive chemosensors with strong potential for environmental monitoring of lead contamination.