High performance photoelectrochemical immunosensing platform based on front-illuminated Mo:BiVO₄ photoelectrodes for...

The outstanding photoactive materials are the imperative for the construction of a front-illuminated photoelectrochemical (PEC) biosensor, which is crucial step for improving the detection sensitivity. Yet, the weak and unstable initial PEC signals of the photoelectrodes have limited evidently the detection performance. Herein, a front-illuminated "on-off" PEC immunosensor was constructed based on Mo:BiVO₄ as photoactive matrix and Au/CeO₂ as signal quencher for sensitive detection of procalcitonin (PCT). Systematic studies reveal that the Mo doped BiVO₄ can increase the charge carrier density of BiVO₄, leading to much higher initial signal under front illumination than back illumination. Moreover, Mo:BiVO₄ was directly grown on conducting substrates, which effectively overcomes the loose combination of sensing substrate ensuring good electrical contact and continuity. Upon coupling with Au/CeO₂ as signal quencher, the initial photocurrent signal can be significantly quenched. As a result, the proposed PEC immunosensor presents a wide linear range from 10 fg mL^-1 to 50 ng mL^-1 with a detection limit of 2.45 fg mL^-1. Impressively, this study will open a new avenue for the construction of highly efficient and stable photoelectrode, as well as extend the application of PEC biosensor for biomarkers detection in early disease diagnosis.