DFT-guided electronic modulation and interface engineering of nitrogen-rich carbon nitride nanotube arrays for enhanced electrochemical detection of metronidazole

Developing novel metal-free nanomaterials with high electrocatalytic activity is crucial for the sensitive electrochemical detection of trace metronidazole (MTZ) contaminant. Herein, we report a template-free, supramolecular self-assembly-driven hydrothermal-pyrolysis approach for the high-yield synthesis of nitrogen-rich g-C 3 N 4 nanotube arrays (gCN NTAs). This method affords nanotubes with an average diameter of 376.23 ± 151.18 nm, a nitrogen content of 74.37 at.% by XPS with a synthesis yield of 50.36%. TEM reveals a unique bilayer tubular structure with in-situ coral strip-like nanoarrays, thereby enhancing MTZ detection via aggregation-induced and local electric field effects. The gCN NTAs-based sensor exhibits a concentration-dependent signal-enhancement response toward MTZ, displaying linear ranges of 0.01-100 μM and 200-4000 μM, with correspondingly low limits of detection of 0.0168 and 0.0464 μM, limits of quantification of 0.0561 and 0.1546 μM, and high sensitivities of 0.2571 and 0.0932 μA/μM·cm 2 . In addition, it exhibits excellent selectivity, stability, and recovery rates in real samples. Density functional theory calculations show that N-doping reduces the HOMO-LUMO gap and enhances the local negative electrostatic potential. Adsorption energy and density of states analyses support that the formation of p-π conjugation lowers the reaction energy barrier, improving interfacial electron transfer. Biosafety evaluations validate the low cytotoxicity and high biocompatibility of gCN NTAs, highlighting their outstanding potential for diverse applications.