All-solid-state metal-mediated Z-scheme photoelectrochemical immunoassay with enhanced photoexcited charge-separation for monitoring of prostate-specific antigen.

An all-solid-state metal-mediated Z-scheme photoelectrochemical (PEC) immunoassay was designed for sensitive detection of prostate-specific antigen (PSA) by using WO-Au-CdS nanocomposite as photoactive material and copper ion (Cu) as an inhibitor. The Z-scheme PEC system comprising of CdS nanoparticle (photosystem I; PS I), WO nanorod (photosystem II; PS II) and gold nanoparticle (Au NP; solid electron mediator) was reasonably established by a simple and green synthetic method. As an important part of Z-scheme system, the sandwiched gold nanoparticles between electron donor materials and hole provider materials could accelerate electron transfer from positive conduction band (CB) of WO to negative valence band (VB) of CdS, thus resulting in high-efficient separation of the carriers. In the presence of target PSA, a sandwiched immunoreaction was executed between capture antibody-coated microplate and CuO nanoparticle-labeled detection antibody. Thereafter, CuO nano labels were dissolved into Cu ions under acidic condition to decrease the photocurrent of Z-scheme WO-Au-CdS thanks to the formation of exciton trapping center of CuS (x = 1,2) on the surface. Under optimum conditions, Z-scheme PEC immunoassay exhibited good photocurrents toward target PSA within a linear range of 0.01-50 ng mL at a limit of detection of 1.8 pg mL. Moreover, the Z-scheme PEC immunoassay had high selectivity and accuracy. Importantly, this method provides a new horizon for detection of disease-related biomarkers with high sensitivity.