Ultrasensitive simultaneous detection of lead and cadmium in water using gold nanocluster-modified gold electrodes

Heavy metals (HMs) pose significant environmental risks due to their widespread presence. In particular, lead (Pb) and cadmium (Cd) can accumulate in the human body through prolonged exposure or bioaccumulation <i>via</i> the food chain, presenting substantial threats to human health and ecosystems. This study developed a novel electrochemical sensing platform for simultaneous detection of trace Pb²⁺ and Cd²⁺ using a bare gold electrode modified with gold nanoclusters (GNPs-Au) through a potentiostatic method. Through systematic optimization of deposition parameters including 2 mmol per L HAuCl₄, 0.2 V deposition potential, and 80 s deposition time, the modified electrode exhibited 7.2-fold increased surface area compared to the bare gold electrode, as confirmed by field emission scanning electron microscopy (FESEM) and electrochemical characterization. The enhanced surface area provided abundant electrochemical reaction sites, significantly improving detection sensitivity. Under optimal detection conditions comprising pH 3.3, -4 V enrichment potential, and 390 s enrichment time, the modified electrode demonstrated linear responses for Pb²⁺ and Cd²⁺ in the range of 1-250 μg L^-1 with a detection limit of 1 ng L^-1. The spike-recovery test yielded quantitative recoveries ranging from 90.86% to 113.47%. The interference experiment confirmed Cu²⁺ has a significant effect on the measurement. Moreover, the method successfully detected Pb²⁺ and Cd²⁺ in real water samples, with results showing minor errors compared to atomic absorption spectroscopy (AAS). These findings demonstrate the robust potential of GNPs-Au for trace heavy metal ion detection in environmental monitoring.