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.