Ultrasensitive photoelectrochemical immunosensor for the detection of amyloid β-protein based on SnO/SnS/AgS 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 AgS sensitized SnO/SnS nanocomposites. Specifically, SnO with flower-like porous nanostructure was innovatively applied in PEC immunosensor as a basal material. It could form a heterostructure with SnS, which brought about the sensitization of SnO and enhanced the separation of photogenerated electrons and holes. Moreover, AgS was in-situ growth on the surface of SnO/SnS, which further enhanced the photocurrent response significantly. Therefore, SnO/SnS/AgS 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 to 100 ng mL, with low limit of detection (0.17 pg mL) and limit of quantification (0.56 pg mL). 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.