Spinel Cobalt-Copper Sulfide Nanoparticle-Based Electrochemical Sensor for Ultrasensitive Detection of Toxic Cu ²⁺ and Hg ²⁺ Ions

Heavy metal ions, such as copper (Cu 2+ ) and mercury (Hg 2+ ), pose severe risks to human health and the environment even at trace levels, necessitating the development of sensitive and reliable detection methods. Here, we present a highly selective and sensitive electrochemical sensor based on modified carbon paste electrode with a spinel cobalt-copper sulfide nanoparticles (CuCo 2 S 4 NPs/CPE) for the simultaneous determination of Cu 2+ and Hg 2+ ions. The fabricated CuCo 2 S 4 NPs was characterized using Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray techniques, confirming its structural and functional advantages. Under optimized conditions, the sensor demonstrated excellent electrochemical response toward Cu 2+ and Hg 2+ ions using differential pulse voltammetry, achieving low detection limits of 0.18 nM for Cu 2+ and 0.15 nM for Hg 2+ , with high selectivity against interfering ions. Synergistic interaction between cobalt and copper in the sulfide matrix enhances electron transfer kinetics, catalytic activity, and adsorption capacity, leading to improved sensing performance. The sensor also exhibited good reproducibility, stability, and applicability in real water samples, showcasing its potential for environmental monitoring and biomedical analysis. This study provides a promising strategy for developing advanced electrochemical platforms for heavy metal ion detection with high sensitivity and reliability.