Nanostructured PEDOT/g-C3N4 Composite-Based Ion-Imprinted Electrochemical Sensor for Sensitive Cd(II) Detection

Cadmium (Cd 2+ ), among the most hazardous heavy-metal pollutants, enters ecosystems through both natural processes and anthropogenic activities. This study developed an electrochemical sensor using a two-dimensional nanomaterialcomposite strategy, which synergistically integrates ion-imprinted poly(3,4-ethylenedioxythiophene) (IIP-PEDOT) with graphite carbon nitride (g-C 3 N 4 ) nanomaterials for ultrasensitive Cd 2+ detection. First, the IIP film was fabricated via electropolymerization of EDOT monomers on a g-C 3 N 4 -modified screen-printed carbon electrode (SPCE), leveraging hydrophobic interactions and π–π conjugation effects between EDOT molecules and g-C 3 N 4 nanosheets. Subsequently, density functional theory (DFT) simulations elucidated the energy changes of the polymerization-complex structure formed by Cd 2+ with functional monomers, while also clarifying the coordination binding mechanisms between metal ions and recognition sites within imprinted cavities. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were systematically employed to characterize the morphological features and chemical composition of the IIP-PEDOT/g-C 3 N 4 nanocomposite material, validating the uniform dispersion of PEDOT polymer chains on the g-C 3 N 4 nanocarrier and confirming the stability of interfacial interactions. Experimental results demonstrated that the sensor exhibited superior selective Cd 2+ recognition capability with a remarkably low detection limit of 75 ng/L (0.67 nM) across a linear range of 0.01–10 μM, substantially outperforming EU drinking-water regulatory thresholds (approximately 45 μM), reflecting the superiority of the sensor. Furthermore, biological validation based on mouse-exposure models confirmed that the sensor could accurately reflect Cd 2+ accumulation levels in blood, liver, and kidney tissues. Additionally, the sensor demonstrates outstanding detection capabilities in the human blood environment, suggesting promising clinical biosample analysis applications. In brief, this IIP-PEDOT/g-C 3 N 4 nanocomposite sensing platform offers a cost-effective, rapid, and field-deployable solution for monitoring Cd 2+ contamination in environmental and biomedical matrices.