Enhanced simultaneous voltammetric detection of lead, copper, and mercury using a MIL-101(Cr)-(COOH)₂@MWCNTs modified...

Electrochemical methods, particularly those utilizing sensors, offer distinct advantages over classical analytical methods. They are cost-effective, compatible with mass fabrication, suitable for remote sensing, and can be designed as handheld analyzers. In this context, MIL-101(Cr)-(COOH)₂@MWCNTs was utilized for the first time as a modifier for GCE for the sensitive voltammetric detection of Pb(II), Cu(II), and Hg(II). The surface characteristics of the composite were examined using SEM, EDX, XRD, FTIR, and N₂ adsorption/desorption isotherms. The electrochemical behavior of the modified electrode was investigated using differential pulse anodic stripping voltammetry (DPASV).

The DPAS voltammograms of the composite modified electrode are characterized by a remarkable increase in the oxidation peak currents for Pb, Cu, and Hg, indicating that MIL-101(Cr)-(COOH)₂@MWCNTs composite significantly enhances the electrocatalytic response towards the oxidation of the studied heavy metals. The impact of various parameters, such as accumulation potential, accumulation time, amount of MOF, composite thickness, and supporting electrolyte concentration on the developed sensor's response, were investigated. The analytical performances were also investigated using DPASV. The optimized MIL-101(Cr)-(COOH)₂@MWCNTs/GCE-based sensor exhibited a linear range of 0.11-15.4 μM, 0.11-20.1 μM, and 0.06-20.1 μM, and lower limits of detection (LOD) of 0.08 μM, 0.09 μM, and 0.04 μM for Pb(II), Cu(II), and Hg(II), respectively.

This study introduces a novel MIL-101(Cr)-(COOH)₂@MWCNTs composite-modified GCE, offering exceptional sensitivity, selectivity, and repeatability for detecting Pb(II), Cu(II), and Hg(II). With broad analytical ranges, low detection limits, and successful application in real water samples, the work demonstrates significant potential for environmental heavy metal monitoring and pollution control.