A photoelectrochemical aptasensor based on promising Z‑scheme for monitoring 3,3′,4,4′-tetrachlorobiphenyl in coral reef fish

A novel photoelectrochemical (PEC) aptasensor coupled with a Z‑scheme was developed to realize quantitative determination of 3,3′,4,4′-tetrachlorobiphenyl (PCB77) at a concentration of sub-picogram per liter. The PEC aptasensor was fabricated by immobilizing ZnSe/Ag 2 Se on indium-tin oxide (ITO) that could covalently bind sulfurized aptamer. Meanwhile, complementary DNA-functionalized CdTe units were used as the sensitizers, and these were immobilized on the aptamer to form Z‑scheme dual-photosystem (PS). The Z‑scheme PS based on both ZnSe/Ag 2 Se and CdTe would be provided with better photocatalytic activity than conventional heterojunctions , and improving the photo-to-current conversion efficiency without biased voltage. Following the process of hatching, PCB77 was captured via the aptamer on the PEC aptasensor, producing aptamer–PCB77 complexes with weak conductive performance. Using the photocurrent change as a response signal for the quantitative detection of PCB77, the detection limits of the proposed method were 0.05 pg L –1 and 0.22 ng L –1 for the linear ranges of 0.01–500 pg L –1 and 0.5–10 5 ng L –1 , respectively. Compared with other technologies, the PEC aptasensor is more flexible, sensitive, specific and rapid in the absence of biased voltage under visble light. The results presented herein can potentially help build a model for the detection of various polychlorinated biphenyls (PCBs) with stable chemical properties and insulation performances that can be used to study persistent organic pollutants (POPs) in marine organisms and in the analysis of environmental conditions.