Visible light-responsive enrofloxacin PEC aptasensor based on CN QDs sensitized Bi₄O₅Br₂ nanosheets

The excessive application of enrofloxacin (ENR) results in residues contaminating both food and the environment. Consequently, developing robust analytical methods for the selective detection of ENR is crucial. The photoelectrochemical (PEC) sensor has emerged as a highly sensitive analytical technique that has seen rapid development in recent years. The functioning of a PEC sensor relies on the reducing capacity of photogenerated electrons and the oxidizing capacity of photogenerated holes produced by the photoactive material. Bi₄O₅Br₂ demonstrates its potential in electrochemical detection, but faces inherent challenges, including swift electron-hole recombination and slow carrier migration, which hinder its catalytic activity.

In this study, we synthesized carbon nitride quantum dots doped with Bi₄O₅Br₂ (CN QDs/Bi₄O₅Br₂) through an in situ growth method, utilizing this composite as a photoactive material. The incorporation of CN QDs leads to a 17-fold increase in photocurrent compared to Bi₄O₅Br₂ alone. This enhancement is attributed not only to the improved separation of electron-hole pairs, facilitated by the CN QDs, which boosts photocatalytic activity, but also to the enlarged range of visible light absorption. We employed an ENR-specific aptamer as the recognition element, resulting in the construction of a high-performance photoelectrochemical aptasensor for ENR detection. The sensor exhibited a linear detection range of 1 × 10^-1 to 1 × 10⁶ ng mL^-1 and a detection limit of 0.033 ng mL^-1. The impressive performance of the CN QDs/Bi₄O₅Br₂ sensing platform demonstrates its potential application in detecting ENR concentrations in food, biomedical contexts, and environmental analyses.

Benefiting from the sensitization of CN QDs, CN QDs/Bi₄O₅Br₂ exhibited 17-fold PEC signal of pure Bi₄O₅Br₂. The presence of quantum dots in CN QDs/Bi₄O₅Br₂ facilitates rapid separation of electron-hole pairs, leading to significantly enhanced PEC activity and improved detection performance for ENR. This research convincingly illustrates that integrating CN QDs with Bi₄O₅Br₂ nanosheets could pave the way for designing more efficient bismuth-based semiconductor photoactive materials for sensing applications.