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

The unidirectional electric field derived from the p-n heterojunction accelerates carrier migration. • The S-scheme interfacial charge transfer pathway expedites the separation of electron-hole pairs. • Carrier transfer trends are corroborated by density functional theory calculations. • Demonstrates reliable detection of ornidazole in real-world samples. 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 MgTi 2 O 5 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 (R 2  = 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. Construction of a MgTi 2 O 5 /Cu-BTC p-n heterojunction sensing interface for ultrasensitive PEC detection of ONZ in pharmaceuticals and environmental water samples. Download: Download high-res image (166KB) Download: Download full-size image