SDS capped CuS nanoparticles as selective turn-on sensor of Pb2+ in aqueous medium: a combined experimental and theoretical study

In environmental safety, lead (Pb²⁺) contamination in aquatic systems is a serious threat, responsible for high toxicity and bioaccumulation. According to the WHO, 10 ppb for Pb²⁺ is considered the limit in drinking water. Importantly, detecting Pb²⁺ concentrations in water samples with selective, sensitive, and cost-effective strategies remains imperative. In this context, a sodium dodecyl sulfate (SDS)-capped copper sulfide (CuS) nanoparticle-based fluorescence “turn-on” sensor was developed using a sol-gel method at room temperature. Furthermore, comprehensive characterization, including UV-Vis spectroscopy, FT-IR, XRD, HR-TEM, SAED, and EDX, was used to confirm crystallinity, surface functionalization, size, morphology, and elemental composition of the CuS nanoparticles. The developed CuS-SDS nanoparticles exhibited pronounced fluorescence enhancement upon interaction with Pb²⁺ ions at pH 7.2 and a negligible response toward other metals. In real-sample analysis, fluorescence titration studies showed a linear response to Pb²⁺ concentration with a high correlation coefficient (R² = 0.99). It was found that CuS NPs can detect Pb²⁺ in drinking water up to a limit of detection of 6.35 µM. However, the developed nanoscale sensor also demonstrated remarkable stability over a wide range of pH and temperature. Furthermore, practical applicability was investigated through real tap-water sample analysis, yielding accurate results. DFT and NTO analysis demonstrated that Pb²⁺ binding to sulfate groups of SDS suppresses photoinduced electron transfer, thereby restoring radiative recombination and enhancing fluorescence. Overall, the current study presented a selective nanoparticle-based fluorescence sensor to detect Pb²⁺ ions in real water samples.