Visible-light driven label-free photoelectrochemical immunosensor based on TiO2/S-BiVO4@Ag2S nanocomposites for sensitive detection OTA.

A label-free photoelectrochemical (PEC) platform with high visible-light activity for quantitative detection of the ochratoxin A (OTA) was developed by assembly of Ag2S nanoparticles (NPs) sensitized on titanium dioxide/red blood cell-like shape bismuth vanadate (TiO2/S-BiVO4) electrode via layer-by-layer (LBL) strategy. In this protocol, ascorbic acid was used as an efficient electron donor for scavenging photo-generated holes and inhibiting light driven electron-hole pair recombination. TiO2 has good photoelectric activity and large surface area. The S-BiVO4 with porous structure surfaces can contribute to the high photocurrent intensity under visible-light irradiation. Moreover, the Ag2S NPs were in-situ growth on surfaces of thioglycolic acid modified S-BiVO4, which enhanced photocurrent response and further improved the photocurrent conversion efficiency. Under optimal conditions, the PEC immunosensor exhibited a wide linear concentration range from 5pgmL-1 to 750ngmL-1, with a low detection limit of 1.7pgmL-1 (S/N = 3) for OTA. Additionally, the designed immunosensor was performed with good stability, reproducibility and selectivity, thus opening up a new promising PEC platform for some other small molecules analysis.