Liposome-Mediated In Situ Formation of Ag₃PO₄/AgBr/Br-CN Ternary Nanostructures on Photoanodes for Photoelectrochemical Immunoassay

A dual-photoelectrode self-powered photoelectrochemical (PEC) biosensing system for protein was proposed based on the liposome-assisted signal amplification strategy. The dual-photoelectrode self-powered device was constructed by integrating Ag 3 PO 4 with bromine-doped g-C 3 N 4 (Ag 3 PO 4 /Br-CN) as a photoanode and CuInS 2 as a photocathode synchronously. Ag nanoparticle (AgNP)-encapsulated liposomes as tags were labeled on the target protein through a sandwich immunoreaction implemented in a 96-well plate. The AgNP-encapsulated liposomes were used to generate the signal regulator Ag + for PEC detection. In the presence of Ag +, the reaction between Ag + and Ag 3 PO 4 /Br-CN occurred to form Ag 3 PO 4 /AgBr/Br-CN ternary heterostructures. The compact contact and the matchable band-edge levels of Ag 3 PO 4, AgBr, and Br-CN in the ternary heterostructures broaden the light absorption range and efficiently restrain the electron–hole recombination of the photoanode, producing an enhanced photocurrent response. The large loading capacity of liposomes, the fine performance of the formed ternary heterostructures, and the well-designed dual-photoelectrode self-powered PEC device endows the biosensing system with high sensitivity for protein detection. Using prostate-specific antigens as model proteins, the biosensing system exhibited a low detection limit of 3.4 × 10 –13 g mL –1 with a linear range of 1.0 × 10 –12 g mL –1 to 5.0 × 10 –8 g mL –1 . The marriage of the self-powered system with the liposome-assisted strategy not only represented a generic method for protein detection but also provided a path to fulfill the requirement of high sensitivity in PEC analysis.