Zinc and Molybdenum Co-Doped BiVO₄ Nanoarray for Photoelectrochemical Diethylstilbestrol Analysis Based on the Dual-Competitive System of Manganese Hexacyanoferrate Hydrate Nanocubes

This study proposes a competitive photoelectrochemical (PEC) immunosensor for detecting diethylstilbestrol (DES). The PEC sensing platform uses a zinc and molybdenum codoped BiVO4 nanoarray ((Zn,Mo):BiVO4) as the photoactive matrix and manganese hexacyanoferrate hydrate loading silicon dioxide layer composite nanocubes (MHCF@SiO2 NCs) as the signal quencher. The (Zn,Mo):BiVO4 nanoarray demonstrated brilliant PEC behavior, by virtue of the local electric field formed by the codoped Zn and Mo. This doping accelerated the electron transfer and improved the photoelectric conversion efficiency in BiVO4 nanoarray under visible light. Furthermore, the nanoarray structure with its large surface area provided abundant binding sites for the immune response. As the MHCF@SiO2 NCs-anti-DES competitively bonded with either free DES or bovine serum albumin conjugated DES (BSA-DES), hydrogen peroxide (H2O2) as electron donor was competitively consumed and meanwhile steric resistance blocked electrons transfer. For the above reasons, the photocurrent signal was reduced. Thus, the standard sample free DES was accurately detected, and the fabricated PEC immunosensor displayed an outstanding photocurrent response from 0.1 pg/mL to 50 ng/mL with a detection limit of 0.05 pg/mL. Simultaneously, the acceptable stability, selectivity, and reproducibility of the designed dual-competitive sensing platform suggest its applicability to small molecule detection.