Sandwich-type signal-off photoelectrochemical immunosensor based on dual suppression effect of PbS quantum dots/Co3O4 polyhedron as signal amplification for procalcitonin detection.

• A sandwich-type signal off PEC sensor was constructed for PCT detection. • The photoactive matrix was Au NPs/BiOI NSs/B-TiO 2 NPs. • PbS/Co 3 O 4 was as a quenching signal label for signal amplification. • The PEC sensor exhibited a low detection limit of 0.02 pg/mL. A novel signal-off photoelectrochemical (PEC) immunosensor was proposed for procalcitonin (PCT) sensitive detection based on the Au nanoparticles/BiOI nanosheets/Black TiO 2 nanoparticles (Au NPs/BiOI NSs/B-TiO 2 NPs) as photoactive matrix and PbS quantum dots/Co 3 O 4 polyhedron (PbS/Co 3 O 4) as a quenching signal label for signal amplification. Concretely, BiOI NSs was fabricated by successive ionic layer absorption and reaction (SILAR) and formed the interlaced flake-like structure. Then Au NPs dropped on the BiOI NSs/B-TiO 2 NPs electrode forming Au NPs/BiOI NSs/B-TiO 2 NPs sensitization structure, which increased the utilization of visible light and accelerated electron transfer rate, resulting in a desirable PEC signal. PbS/Co 3 O 4 , an effective dual suppression signal quencher, was proposed for signal-off PEC immunosensor to weaken the photocurrent response because of the steric impedance, competitive absorption of light and competing consumption of electron donor. In this proposal, PCT was chosen to measure the performance of the suggested PEC immunosensor. Consequently, the fabricated PEC immunosensor showed a widely detection ranged from 0.1 pg/mL to 50 ng/mL and a low detection limit of 0.02 pg/mL (S/N = 3). What is more, the proposed PEC immunosensor possessed satisfactory selectivity, stability and reproducibility. [ABSTRACT FROM AUTHOR]