L-Cysteine Modified Silver Nanoparticles: Mechanistic Insights for Trace Cadmium Detection in Water

Cadmium (Cd²⁺) pollution is a pressing environmental and public health issue due to its harmful effects and ability to persist in nature over time. This study developed a highly sensitive and selective colorimetric sensor using Lcysteine (LC) functionalized silver nanoparticles (AgNPs) for Cd²⁺ detection in water. The sensor achieved a detection limit (LOD) of ~2.70 ppb and a limit of quantification (LOQ) of 8.20 ppb, well below the WHO guideline for cadmium in drinking water. Selectivity tests against Sn²⁺, Hg²⁺, Fe³⁺, and Pb²⁺ showed minimal interference, confirming the sensor’s high specificity for Cd²⁺. UV-Vis spectroscopy and computational studies identified the thiol (-SH) group in L-cysteine as critical for binding Cd²⁺, with changes in absorbance and bond structure confirming Cd²⁺ detection. With a viscosity of ~1.25 mPa.s, the LC-AgNPs solution is suitable for printable sensors, offering a scalable, cost-effective method for real-time cadmium monitoring in resource-limited settings.