CdS quantum-dots-modified CuBi2O4 nanorods as highly active and etchable photocathodic materials for sensitive photoelectrochemical immunoassay

Cathodic photoelectrochemical (PEC) analysis is highly favored for bioassays due to its excellent anti-interference ability toward reductive biomolecules, but it is still challenging to develop highly active photocathodic materials. Herein, CdS quantum dots (QDs) modified CuBi2O4 nanorods are proposed as highly active and etchable photocathodic materials for sensitive PEC immunoassay. After the growth of CdS QDs on CuBi2O4 nanorods, the cathodic photocurrent is greatly boosted because of the formation of p-n heterojunctions. CdS QDs can be etched by H2O2 due to the oxidization of S2- to SO42-, so CdS/CuBi2O4 can serve as an etchable photocathodic material. PEC immunoassay of carcinoembryonic antigen (CEA) is realized by using glucose oxidase (GOx)-conjugated immunomagnetic beads as labels, because H2O2 generated in the GOx-based enzymatic reaction can etch the photoactive material, leading to a decrease in photocurrent. A wide linear range is obtained in the range of 0.1–5 × 103 pg mL−1 with a low detection limit of 0.02 pg mL−1 for CEA detection.