A simple label-free photoelectrochemical immunosensor for highly sensitive detection of aflatoxin B1 based on CdS–Fe3O4 magnetic nanocomposites

A simple label-free photoelectrochemical (PEC) platform was developed based on magnetic CdS–Fe3O4 nanocomposites and used for detection of aflatoxin B1 (AFB1). CdS quantum dots (QDs) were successfully assembled on mesoporous Fe3O4 NPs via covalent binding and employed as the photoactive materials on the surface of screen-printed electrode (SPE). H2O2 was employed as a sacrificial electron donor for scavenge photo-generated holes in the valence band of CdS QDs. Anti-aflatoxin B1 (anti-AFB1) was conjugated onto CdS–Fe3O4 nanocomposites modified SPE by using the classic EDC coupling reactions between the carboxy group (–COOH) groups on the surfaces of the TGA capped CdS QDs and the amino group (–NH2) groups of the antibody (Ab). The concentrations of AFB1 were measured through the decreased photocurrent resulting from the increased steric hindrances due to the formation of the immunocomplex. Under the optimal conditions, the PEC biosensor for AFB1 determination exhibited a linear range from 0.01 ng mL−1 to 80 ng mL−1 with a detection limit of 5.0 pg mL−1. Besides, the PEC biosensor has been applied in the corn samples detection. The proposed PEC biosensor is simple, sensitive, fast and stable, which opens up a new promising PEC platform for other small molecules analysis.