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 (H2O2) 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 (Na3SPO3) to hydrogen sulfide (H2S), which can react with Bi3+ in the BiNPs@h-BiOBr photoelectrode to generate bismuth sulfide (Bi2S3), 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.