Synergistic Ag-polyaniline/MXene interfaces for enhanced electrochemical nitrate detection

A V₂CT_x MXene/Ag-doped polyaniline (VCX-PANI-Ag) nanocomposite was successfully synthesized and employed as the sensing interface on a screen-printed carbon electrode (SPCE) for electrochemical nitrate detection. The successful formation of the ternary nanocomposite was confirmed by XRD, FESEM, HRTEM, SAED, UV-Vis, and XPS, demonstrating the uniform integration of crystalline Ag nanoparticles with conductive polyaniline on VCX nanosheets. Owing to the synergistic effects of the conductive MXene framework, electrocatalytically active Ag nanoparticles, and the PANI network, the sensor exhibited two linear detection ranges of 0-2.2 mM and 2.2-12.2 mM, with detection limits of 0.0145 mM and 0.0276 mM, and sensitivities of 0.0871 and 0.0458 mA mM^-1 cm^-2, respectively. The sensor demonstrated excellent selectivity toward nitrate in the presence of Cl^-, NO₂^-, PO₄^3-, HCO₃^-, CH₃COO^-, Ca²⁺, Mg²⁺, K⁺, Na⁺, NH₄⁺, Fe³⁺, Fe²⁺, Mn²⁺, and Ni²⁺ and maintained stable electrochemical performance over 100 cyclic voltammetry cycles. Real-sample testing with tap water, lake water, and soil leachates produced spike-and-recovery values ranged from 50% to 97.5%, with an average RSD of 5.3%, underscoring the sensor's robustness, precision, and reproducibility under environmentally relevant conditions.