Efficient Curing Sacrificial Agent-Induced Dual-Heterojunction Photoelectrochemical System for Highly Sensitive Immunoassay

A photoelectrochemical (PEC) biosensor is a very efficient and sensitive detection technology for the quick and effective conversion of light to electrical signals. However, the sensitivity and stability of the sensors are still unsatisfactory based on single-phase semiconductors or in the absence of sacrificial agents in the test solution. Herein, we present an efficient curing sacrificial agent-induced dual-heterojunction PEC system, which can detect the prostate-specific antigen (PSA) with high sensitivity. This PEC immune system was initially fabricated using single-walled carbon nanohorns (SWCNHs), p-type MoS₂, and n-type Ag₂S successively through a Schottky junction and p-n heterojunction on a glassy carbon electrode with electrodeposited gold nanoparticles. Then, the capture antibody (Ab1) was modified and the nonspecific binding sites were sealed off. Meanwhile, the ferrocene (Fc) solidified with hollow nanospheres of zinc ferrite (ZnFe₂O₄) served as a curing electronic sacrificial agent (Fc-ZnFe₂O₄). Next, the detection antibody labeled with Fc-ZnFe₂O₄ (Ab2-Fc-ZnFe₂O₄) was used as a bio-nanoprobe and captured by PSA and Ab1 via sandwich immunorecognition. Under white light, PEC signal amplification could be driven by the curing electronic sacrificial agent-induced dual-heterojunction to achieve the highly sensitive detection of the target. This proposed system exhibited excellent photocurrent performance within the working range from 1 fg·mL^-1 to 100 ng·mL^-1 at a low detection limit of 0.44 fg·mL^-1 (S/N = 3). The proposed strategy features high sensitivity, selectivity, and stability that provides a new opportunity for the development of biosensors in the PEC field.