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

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.