Ascorbic Acid Induced the Improved Oxygen Vacancy Defects of Bi4O5Br2 and Its Application on Photoelectrochemical Detection of DNA Demethylase MBD2 with Improved Detection Sensitivity

Abstract Oxygen vacancy defects (OVs) are one of the main strategies for nanomaterials modification to improve the photoactivity, but current methods for fabricating OVs are usually complicated and harsh. It is important to develop simple, rapid, safe, and mild methods to fabricate OVs. By studying the effects of different weak reducing agents, the concentration of the reducing agent and the reaction time on fabrication of OVs, it is found that L ‐ascorbic acid (AA) gently and rapidly induces the increase of OVs in Bi 4 O 5 Br 2 at room temperature. The increased OVs not only improve the adsorption of visible light, but also enhance the photocurrent response. Based on this, the preparation of OVs in Bi 4 O 5 Br 2 is employed to the development of a photoelectrochemical biosensor for the detection of DNA demethylase of methyl‐CpG binding domain protein 2 (MBD2). The biosensor shows a wide linear range of 0.1–400 ng mL −1 and a detection limit as low as 0.03 ng mL −1 (3σ). In addition, the effect of plasticizers on MBD2 activity is evaluated using this sensor. This work not only provides a novel method to prepare OVs in bismuth rich materials, but also explores a new novel evaluation tool for studying the ecotoxicological effects of contaminants.