Photoelectrochemical immunosensor based on CdSe@BiVO4 Co-sensitized TiO2 for carcinoembryonic antigen.

The fast and accurate detection of Carcinoembryonic Antigen (CEA) plays an important role in clinical cancer treatment and therapy. An ultrasensitive photoelectrochemical (PEC) immunosensor for the detection of CEA was constructed using CdSe@BiVO4 co-sensitized TiO2 nanorods as photoactive materials. TiO2 nanorods were assembled on the FTO modified electrode to immobilize capture antibodies. With a sandwich immunoassay format, CEA and signal antibodies labelled CdSe@BiVO4 were introduced in sequence via specific immunoreaction, and the ultrahigh sensitivity of this immunoassay results from the following three aspects. Firstly, the co-sensitization of BiVO4 and CdSe extends the absorption range of TiO2 from ultraviolet region to visible light region, which can adequately utilize the light energy; Secondly, the effective matching of energy levels among TiO2, CdSe and BiVO4 accelerates the separation and transfer of photogenerated electron-hole pairs and significantly improves the PEC performance; Finally, the introduced Au evidently expedites the interfacial electron transfer from TiO2 to FTO electrode, further resulting in noticeably increased photocurrent. Based on multiple signal amplification strategy, a largely linear detection range from 0.01 ng mL-1 to 50 ng mL-1 with a low detection limit (0.5 pg mL-1) were obtained. In addition, the prepared immunosensor with attractive properties provides a promising platform for PEC detection.