A signal-off type photoelectrochemical immunosensor for the ultrasensitive detection of procalcitonin: Ru(bpy)32+ and Bi2S3 co-sensitized ZnTiO3/TiO2 polyhedra as matrix and dual inhibition by SiO2/PDA-Au

A signal-off type photoelectrochemical (PEC) immunosensor based on Ru(hpy)(3)(2+) and Bi2S3 co-sensitized ZnTiO3/TiO2 polyhedra as matrix and SiO2 /PDA-Au as the label of second antibody was proposed for the ultrasensitive detection of procalcitonin (PCT). The hollow ZnTiO3/TiO2 polyhedra called zinc titanium composite hollow structures (ZTCHS) was prepared by hydrothermal method to enhance the utilization of visible light comparing with pure ZnTiO3 or TiO2 . The unique structure endowed large specific surface areas and satisfying load capacity to ZTCHS. Ru(hpy)(3)(2+) and Bi2S3 were utilized to co-sensitize ZTCHS to further strengthen the PEC performance of ZTCHS. It was interesting that the dual-inhibition effects of SiO2 /PDA-Au further enhanced the sensitivity of proposed PEC immunosensor. On the one hand, the steric hindrance of SiO2 /PDA effectively restricted electron transfer. On the other hand, Au nanoparticles could absorb visible light to compete with the matrix material. Based on the above aspects, the proposed signal-off type PEC immunosensor possessed a wide linear range from 0.0001 ng mL(-1) to 100 ng mL(-1) and low detection limit (about 0.03 pg mL(-1), S/N = 3), demonstrating the promising application of PEC immunosensor in analysis fields.