Carbonaceous glass electrode fabricated with L-cysteine incorporated C@Fe2O3 for the ultra-selective determination of toxic metal ions

A highly effective electrochemical sensor for detecting heavy metal ions (Cd²⁺ and Pb²⁺) was developed using a L-cysteine-functionalized carbon-doped Fe₂O₃ nanocomposite. The prepared nanocomposite was thoroughly characterized using XRD, UV–Visible spectroscopy, FTIR, and FESEM to evaluate its structural and morphological properties. The UV–Vis spectrum displayed an absorption band around 349 nm, confirming the synthesis of iron oxide nanoparticles. FESEM images revealed distinct spherical structures with minor aggregations, attributed to magnetic interactions between the carbon-doped iron oxide nanoparticles and L-cysteine molecules. XRD analysis showed well-defined peaks corresponding to the C@Fe₂O₃/L-Cys nanoparticles, indicating high purity and crystallinity of the prepared nanocomposite. The electrochemical characteristics of the modified electrodes were assessed using Cyclic Voltammetry, with potassium ferrocyanide serving as the standard redox probe. Several factors influencing sensitivity were systematically investigated to optimize the performance of the designed sensing element. These included parameters such as pH, deposition time, deposition potential, and the effect of the supporting medium. The proposed method enabled sensitive and reliable detection of hazardous metal ions, achieving remarkably low detection limits of 0.072 nM for Cd²⁺ and 0.065 nM for Pb²⁺. The exceptional sensitivity and selectivity for Cd²⁺ and Pb²⁺ detection can be attributed to the strong binding affinity of the C@Fe₂O₃/L-Cys nanocomposite with these target metal ions.