Single-Walled Carbon Nanotubes-Copper Metal-Organic Framework Composite for the Sensitive Detection of Lead Ions in Aqueous Solutions

Abstract

Lead (Pb) is a hazardous heavy metal extensively employed in various industrial applications, often resulting in the presence of its ionic form (Pb2+) in water resources. Due to its profound toxicity to humans and the environment, the reliable detection and removal of Pb2+ ions from water are imperative. In this study, we have successfully synthesized a composite material consisting of single-walled carbon nanotubes (SWNTs) incorporated into a copper-based metal-organic framework (MOF) known as copper benzene tricarboxylate (CuBTC). This composite denoted as SWNTs@CuBTC, was synthesized via a solvothermal route. Comprehensive characterizations, including Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area analysis, and thermogravimetric analysis (TGA), were conducted to elucidate its structural and morphological properties. Electrochemical assessments, specifically cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were carried out to evaluate the electrochemical behaviour of the SWNTs@CuBTC composite. Subsequently, a sensor utilizing SWNTs@CuBTC was constructed by modifying glassy carbon electrodes (GCE) through a drop-casting technique. The sensing capabilities of this sensor were systematically examined using the differential pulse voltammetry (DPV) technique. Our sensor exhibited exceptional sensitivity towards Pb2+ ions, with a remarkable limit of detection (LOD) of 25 nM and a sensitivity of 0.1499 μA/nM, showcasing its potential for highly sensitive detection of Pb2+ ions in aqueous solutions.