Ultrasensitive label-free photoelectrochemical immunosensor for the detection of amyloid β-protein based on Zn:SnO2/SnS2-Au nanocomposites

In this work, an ultrasensitive label-free photoelectrochemical (PEC) immunosensor was designed for the detection of amyloid beta-protein (A beta). Specifically, Zn:SnO2/SnS2 nanocomposites were successfully synthesized by a simple one-pot hydrothermal method and used to build the immunosensor. The combination of SnS2 and SnO2 with matching energy levels promoted the layer-by-layer transfer of photogenerated charges, reduced the recombination efficiency of photogenerated electron, and enhanced the photoelectric conversion efficiency. Meanwhile, the addition of Zn ions introduced a trap level, which hindered the reduction of electrons, and the recombination of electron-hole pairs, improved the photocurrent response significantly. On the other hand, Au nanoparticles (NPs) were reduced in situ on the surface of Zn:SnO2/SnS2, thus anti-A beta can form a gold amine bond with Au NPs. Therefore, Zn:SnO2/SnS2-Au could be a good substrate material for A beta immunosensor, which provides a good basis for early detection of Alzheimer's disease. Under certain experimental conditions, the constructed PEC immunosensor exhibited a broad linear range from 0.1 pg.mL(-1) to 100 ng.mL(-1) with a detection limit as low as 0.05 pg.mL(-1) (S/N = 3). It is worth mentioning that the PEC immunosensor presented good stability, reproducibility and selectivity. Meanwhile, it provided a novel platform to analyze other biomarkers.