Application of a g-C ₃ N ₄ @nZVI/CNTs Modified Carbon Paste Electrode for Uric Acid Detection in Spiked Urine Samples

A carbon paste electrode (CPE) based on a g-C 3 N 4 @nZVI/CNT nanocomposite was fabricated via chemical reduction and subsequently evaluated towards electrochemical detection of uric acid (UA) via differential pulse voltammetry (DPV). During synthesis, graphitic carbon nitride (g-C 3 N 4 ) serves as a durable substrate with extensive surface area promoting the homogeneous distribution of nano zero-valent iron (nZVI) particles. Carbon nanotubes (CNTs) were incorporated into the composite to enhance electrical conductivity and mechanical stability. The subsequent nanocomposite was characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy, confirming the successful integration of g-C 3 N 4 , nZVI, and CNTs with well-dispersed iron nanoparticles on the g-C 3 N 4 matrix. The resulting g-C 3 N 4 @nZVI/CNT-modified CPE demonstrated superior electrochemical sensitivity toward UA as evidenced by a pronounced increase in peak current during DPV analysis compared to bare and individually modified electrodes. Under optimized conditions, the sensor exhibited a linear response of 2.0–100.0 μM and detection limit of 1.7 μM. The electrode maintained high selectivity in the presence of common interferants with good repeatability and long-term operational stability. These findings highlight the synergistic interaction among g-C 3 N 4 , nZVI, and CNTs in boosting electron transfer and catalytic activity, making this composite a promising, cost-effective, and scalable solution for sensitive UA detection in clinical diagnostics and environmental monitoring.