A novel signal on-off type photoelectrochemical (PEC) biosensing system was designed for sensitive detection of carcinoembryonic antigen (CEA) based on tin disulfide nanosheets loaded on reduced graphene cxide (SnS2-GR) as the photoactive material and gold nanoparticles coated on reduced graphene oxide-functionalized copper sulfide (Au@CuS-GR) for signal amplification. It's the first time for SnS2-GR was exploited as a sensing matrix. Here, the photocurrent signals of SnS2 were amplified attributed to the sensitization effect of graphene. As signal amplifier, Au@CuS-GR could quench the photocurrents of SnS2-GR not only through the p-n type semiconductor quenching effect as well as the steric hindrance effect, but also as peroxidase mimetics to catalyze the oxidation of 4-Chloro-1-naphthol (4-CN) to produce insoluble product on the electrode surface. Based on the multiple signal amplification ability of Au@CuS-GR, CEA was detected sensitively with a linear range from 0.1 pg mL-1 to 10 ng mL-1 and limit of detection down to 59.9 fg mL-1 (S/N = 3). Meanwhile, the PEC biosensor displayed excellent performance in the assay of human serum sample, showing good application prospects for various target analysis.
