A label-free photoelectrochemical aptamer sensor based on in situ Ag2S quantum dot-sensitized BiOI/CdWO4 heterojunction for detection of ochratoxin A

Ochratoxin A (OTA) is a kind of mycotoxin. It widely exists in all kinds of mammals and has teratogenicity and cytotoxicity. In this paper, a label-free photoelectrochemical (PEC) aptamer sensor based on bismuth oxyiodide/cadmium tungstate (BiOI/CdWO4) was designed to detect OTA. The BiOI/CdWO4 heterojunction is an excellent optoelectronic active material with remarkable chemical stability. AgNO3 and Na2S were selected to grow in situ to form Ag2S quantum dots, which were sensitized to enhance the absorption of visible light and promote the generation of photocurrent. In this system, with the increasing of OTA concentration, the photoelectric signal intensity reduces as the specific binding with aptamer. When the concentration of OTA is between 0.01 ng/mL and 50.00 ng/mL, the linear equation is I (μA) = 48.95 – 10.276 lgc (cOTA, ng/mL), R2 = 99.281, and the detection limit is 0.823 pg/mL. The newly designed PEC aptamer sensor has exceptional stability, sensitivity, and reproducibility, making it capable of detecting OTA effectively and sensitively.