Simultaneous electrochemical detection of multiple heavy metal cations using multi-walled carbon nanotubes...

Voltammetric sensing platforms based on screen-printed carbon electrodes (SPCEs) offer a promising solution for simultaneous detection of heavy metal ions, such as cadmium (Cd²⁺), lead (Pb²⁺), and copper (Cu²⁺), with high sensitivity, selectivity, and reliability. Surface modification with functional materials can substantially enhance the effective electroactive area, promote analyte pre-concentration, and facilitate electron-transfer kinetics. In this study, carboxylated multi-walled carbon nanotubes (HOOC-MWCNTs) functionalized with a ferrocenyl-containing triazole-complex (1,1-bis[[(4-ferrocenyl-1,2,3-triazole-1-yl-methyl)dimethylsilyl]ethyl]ferrocene) are proposed as electrode-modifier materials. The modified electrodes were characterized by Raman spectroscopy, energy-dispersive X-ray analysis, and scanning electron microscopy. Cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques were used to evaluate the electrochemical and sensing properties, respectively. CV measurements showed a significantly higher oxidation peak current and reduced peak-to-peak potential separation (ΔE _p) for Fc-triazole@HOOC-MWCNT@SPCE compared with the unmodified electrodes, indicating an increased electroactive surface area and improved electron-transfer kinetics. SWV measurements enabled the easy distinction of redox reactions at distinct characteristic potentials of different metal species. Hence, an effective sensing performance for Cd²⁺, Pb²⁺, and Cu²⁺ was achieved over the concentration range of 1 µM to 1000 µM, with limits of detection (LoDs) of 8.0 nM for Cd²⁺, 23.4 nM for Pb²⁺, and 23.6 nM for Cu²⁺. Selectivity, reproducibility, and stability were explored over a period of 20 days. The practical applicability of the modified electrode for determining the target cations in real water samples was demonstrated with reliable results.