Photoelectrochemical interface mediated by S-scheme charge transfer and p-n heterojunction: Ultrasensitive detection of the emerging contaminant ornidazole.

Ornidazole (ONZ) is a widely used nitroimidazole-class antibiotic whose environmental persistence due to misuse intensifies antimicrobial resistance and accelerates pathogen evolution, posing serious risks to human health and ecological safety. To address this issue, we developed a novel photoelectrochemical (PEC) sensor for ultrasensitive ONZ detection based on a p-n heterojunction between pseudobrookite-type oxide MgTi2O5 and the metal-organic framework (MOF) Cu-BTC. Density functional theory (DFT) calculations corroborate the favorable band structure of the heterojunction. The built-in electric field and S-scheme charge transfer at the interface enable efficient separation of photogenerated carriers, yielding an ultralow detection limit of 0.65 pM, a wide linear range from 1 pM - 10 nM (R2 = 0.9992), and excellent anti-interference, selectivity, stability and reproducibility. The sensor achieved 98.43% - 103.62% recovery in real samples including commercial capsules, tablets, and environmental water, demonstrating high practical reliability. This work presents a cost-effective, portable, and high-performance platform for ONZ monitoring and offers new insights into advanced PEC sensor design for antibiotic pollution detection.