Ca-MOF-Polymer Modified Thin-Film Electrode for Detection of Toxic Cadmium (Cd²⁺) in Biofluid and Environmental Fluid

Competitive adsorption of Cd2+ on the cell leads different diseases like kidney damage and osteoporosis. It is crucial for Cd2+ intake that ambient and biofluid supplies of Cd2+ be contained. For this, Calcium based Metal Organic Framework (Ca-MOF) was developed by hydrothermal methods using bidendate 1,4-benzene dicarboxylic acid (BDC) and Calcium derived from biowaste chicken egg shells. Lower binding efficiency of Cd2+ with the undoped MOF is improved by complexing it with polyaniline (PANI) to generate Ca-MOF-PANI which provide amine functional groups. These are characterized by Cyclic Voltammetry (CV), Ultra-violet Visible (UV-vis) spectroscopy, Scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) spectroscopy. Electrochemical sensing showed an irreversible oxidation peak for Cd2+ at -0.75 V. The Ca-MOF-PANI showed higher Cd2+ sensing than the CaCO3, Ca-MOF and PANI modified electrodes and confirmed by UV-vis studies. The sensor showed lowest detection limit (LOD) of 138 nM (25.3 ppb) with linearity range 0.1-2000 mu M, respectively, high selectivity in presence of potential interferences, good reproducibility, stability, and repeatability features. Real sample analysis using urine and water samples indicates good signal recoveries ranged from 93.0% to 112.0%.