Oxygen Vacancy-Engineered Hierarchical BiNPs@h-BiOBr Composites Synergized with an MB-Assisted Enzymatic Modulation Strategy for Cathodic Photoelectrochemical Sensing of Penicillin G

Penicillin antibiotic accumulation, especially in the food matrix, can give rise to antibiotic resistance risks and allergic reactions in the body, posing great adverse impacts on human health. A cathodic photoelectrochemical (PEC) sensor has demonstrated great advantages in analytical detection because of its high sensitivity and strong anti-interference capability. Herein, an efficient cathodic PEC sensor was presented based on oxygen vacancy (OV)-engineered hierarchical BiNPs@h-BiOBr composites and a magnetic bead (MB)-assisted enzymatic modulation strategy. The few-layered nanoflake-assembled hierarchical bismuth oxybromide (h-BiOBr) structure was formed by a mild halogenation reaction with a Bi-based metal–organic framework (Bi-MOF) as a template. Further introducing plasma Bi nanoparticles (BiNPs) and rich OVs on h-BiOBr effectively extended the spectral absorption range and enhanced photogenerated charge separation and transfer efficiency, thereby producing an amplified cathodic PEC response under hydrogen peroxide (H 2 O 2 ) as electron acceptors. Taking penicillin G (PG) as the model target, an MB-assisted enzymatic hydrolysis reaction was triggered based on the target–aptamer recognition to convert sodium thiophosphate (Na 3 SPO 3 ) to hydrogen sulfide (H 2 S), which can react with Bi 3+ in the BiNPs@h-BiOBr photoelectrode to generate bismuth sulfide (Bi 2 S 3 ), inducing an obvious PEC signal suppression. Using this mechanism, the proposed PEC sensor demonstrated ultrasensitive determination of PG with a low detection limit of 23 fg/mL, along with admirable anti-interference capability, reproducibility, and stability. Furthermore, it was successfully used to detect PG in multiple animal-derived foods with satisfactory recoveries, providing a valuable tool for antibiotic contamination assessment toward food safety.