Hydroxyl-assisted anion layer modulation in a (BiO)₂OHCl/MWCNT composite for sensitive electrochemical detection of Cd2+ and Pb2+

Hydroxyl-rich surface (BiO)₂OHCl/MWCNT enhances heavy metals accumulation via coordination. • Anion modulation (OH − /Cl − ) optimizes internal electronics for faster charge transfer. • Conductive MWCNT network further accelerates interfacial electron transfer. • LODs of 0.23 μg/L Pb 2+ and 0.41 μg/L Cd 2+ with 96–104% recovery in seawater samples. The escalating contamination of aquatic ecosystems by toxic heavy metal ions Cd 2+ and Pb 2+ necessitates reliable monitoring solutions. Herein, a glassy carbon electrode modified with a hydroxylated bismuth oxychloride/multi-walled carbon nanotube ((BiO)₂OHCl/MWCNT) nanocomposite is presented for the simultaneous detection of Cd 2+ and Pb 2+ . The material was synthesized via a one-step alkaline hydrothermal assembly, which ensures the uniform dispersion of MWCNTs to establish a conductive network for electron transport. The hydroxyl-induced anion-layer modulation optimizes the internal electronic environment to accelerate interfacial charge transfer. Concurrently, surface hydroxyl groups provide specific coordination interactions, improving the adsorption affinity and accumulation efficiency of the target metal ions. Under optimized conditions in sodium acetate-acetic acid buffer (pH 5.0), the sensor exhibits linear detection ranges of 10–300 μg/L for both Cd 2+ and Pb 2+ , with limits of detection (LOD) of 0.226 μg/L and 0.412 μg/L (S/N = 3), respectively. The proposed sensor exhibits good repeatability, reproducibility, and anti-interference capability, and was successfully applied to the analysis of spiked seawater samples. Download: Download high-res image (189KB) Download: Download full-size image