Ultrasensitive photoelectrochemical immunosensor for the detection of amyloid β-protein based on SnO2/SnS2/Ag2S nanocomposites.

An ultrasensitive label-free photoelectrochemical (PEC) immunosensor with high visible-light activity was developed for quantitative detection of amyloid β-protein (Aβ) by cross-linking anti-Aβ antibody onto the Ag2S sensitized SnO2/SnS2 nanocomposites. Specifically, SnO2 with flower-like porous nanostructure was innovatively applied in PEC immunosensor as a basal material. It could form a heterostructure with SnS2, which brought about the sensitization of SnO2 and enhanced the separation of photogenerated electrons and holes. Moreover, Ag2S was in-situ growth on the surface of SnO2/SnS2, which further enhanced the photocurrent response significantly. Therefore, SnO2/SnS2/Ag2S could form stepwise band-edge structure, which benefited the light harvesting and provided a good foundation for sensor construction and detection. Under optimal conditions, the PEC immunosensor was used to detect the content of Aβ and exhibited a wide linear concentration range from 0.5 pg mL-1 to 100 ng mL-1, with low limit of detection (0.17 pg mL-1) and limit of quantification (0.56 pg mL-1). Additionally, the designed PEC immunosensor exhibited good reproducibility, specificity, and stability which may find potential applications in the biosensor, biomedicine, clinical diagnosis, photocatalysis and other related fields.