A photoelectrochemical immunosensor based on Z-scheme CdS composite heterojunction for aflatoxin B1.

Aflatoxin B1 (AFB1) is a highly toxic fungal contaminant widely found in agricultural products. It causes serious harm to human health and the environment. Thus, a fast and sensitive detection approach is urgently needed to prevent AFB1-contaminated products from entering the market effectively. A photoelectrochemical (PEC) immunosensor was developed based on tungsten trioxide/cadmium sulfide core/shell coated with a composite layer consisting of polydopamine and loaded gold nanoparticles (WO/CdS@PDA/Au) for AFB1 detection. CdS formed a heterojunction with WO, which improved the photoelectric performance. The coated PDA reducing CdS toxicity was demonstrated by biological experiment of Bacillus subtilis. PDA and Au NPs promoted electron transfer between the semiconductors, being beneficial promoting the photoelectron transfer. Additionally, the antibodies were immobilized on WO/CdS@PDA/Au via the reactive quinones on the surface of the PDA and electrostatic adsorption from Au NPs. The WO/CdS@PDA/Au composite as a Z-scheme heterojunction possessed high performance of photocurrent response, and the photoproduced electron/hole transfer path was speculated by electrons spin-resonance spectroscopy technique. Under the optimum experimental conditions, the PEC immunosensor showed a wide linear detection range from 0.05 to 100 ng mL for AFB1, indicating that the immunosensor has a bright application prospect.