Biosynthesized ZnO/Co₃O₄ Nanocomposite-Modified Electrode for Electrocatalytic Lead Detection and Quantification

This study employed square wave stripping voltammetry to detect Pb²⁺ using a modified electrode made from a watermelon peel extract-assisted ZnO/Co₃O₄ nanocomposite. The as-prepared nanomaterials' physicochemical and electrochemical characterizations were elucidated using thermogravimetric analysis and differential thermal analysis (TGA/DTA), X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), scanning electron microscopy-energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy (TEM), high-resolution transmission electron microscopy, selected area electron diffraction, Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy techniques. The electrochemical sensing capability of ZnO nanoparticles (NPs) was enhanced by creating a ZnO/Co₃O₄ nanocomposite, which improved the conductivity of the ZnO NPs through the incorporation of Co₃O₄. The peel extract aided in creating a ZnO/Co₃O₄ nanocomposite-modified electrode that offers more active sites for the detection and quantification of Pb²⁺. Before the detection and quantification of Pb²⁺, experimental variables, such as the deposition potential and deposition time, were optimized. The suggested limit of detection and limit of quantification were determined to be 0.03923 μmol/L and 0.131 μmol/L, respectively, in the concentration range of 0.371-0.405 μmol/L. The prepared nanosensor demonstrated sensitivity and simplicity, making it suitable for various environmental analyses.