Target-induced oxygen vacancy on the etching WO3 photoanode for in-situ amplified photoelectrochemical immunoassay.

Sluggish charge transfer and rapid electron-hole recombination severely limit the analytical performance of photoelectrochemical (PEC) immunoassays. This work presented a PEC immunosensing strategy that employed a target-induced enzyme-catalyzed reaction to in-situ generate oxygen vacancy (Ov) for amplifying the photocurrent detection of carcinoembryonic antigen (CEA). Concretely, ascorbic acid-2-phosphate (AAP) was catalyzed to produce ascorbic acid (AA) by alkaline phosphatase (ALP) in the presence of CEA. The generated AA could serve as a reducing agent to introduce oxygen vacancy (Ov) into the etching tungsten trioxide (E-WO3) photoanode, resulting in an Ov-enriched E-WO3 (E-WO3-Ov) photoanode. The formation of Ov allowed efficient introduction of defect levels into the energy band structure of E-WO3-Ov photoanode, resulting in high charge transfer and electron-hole separation efficiency for photocurrent amplification. Later, it was applied to fabricate a PEC immunosensor, thus enabling a wide linear range from 0.02 to 80 ng/mL and a low detection limit of 12.9 pg/mL. Overall, this work presented a promising sensing strategy for PEC immunosensors, expanding the scope of potential applications in bioassays and clinical diagnostics.