Photoelectrochemical Immunosensor Based on a 1D Fe 2 O 3 /3D Cd-ZnIn 2.2 S y Heterostructure as a Sensing Platform for Ultrasensitive Detection of Neuron-Specific Enolase.

Lung cancer is a high-mortality cancer related to the concentration of neuron-specific enolase (NSE). In this work, a sandwich-type photoelectrochemical (PEC) immunosensor was constructed for ultrasensitive detection of NSE, which is based on iron trioxide/indium zinc cadmium sulfide (Fe 2 O 3 /Cd-ZnIn 2.2 S y ) as a sensing platform and Ag-modified polyaniline (Ag@PANI) as a signal amplification label. The 1D Fe 2 O 3 porous nanorods with a large specific surface area were synthesized by calcination of Fe-MIL-88A and etching of NaOH. To improve the photocurrent response, the 3D architecture Cd-ZnIn 2.2 S y was combined with the 1D Fe 2 O 3 porous nanorods to form a 1D Fe 2 O 3 /3D Cd-ZnIn 2.2 S y heterostructure. Specifically, the Fe 2 O 3 /Cd-ZnIn 2.2 S y heterostructure with a good energy level matching (the two can form a stepped energy level matching, which accelerates the transfer rate of electrons) can improve the separation efficiency of electron-hole pairs (e - /h + ) under visible light irradiation, which enhances the photocurrent response. Ag@PANI has a strong electron transport capability and can be used as a secondary antibody marker for the signal amplification of the immunosensor. The sensor exhibits a good linear detection range of 100 fg/mL to 100 ng/mL with a low detection limit of 33.5 fg/mL. Moreover, the constructed sandwich-type PEC immunosensor shows good performance and possesses excellent specificity, selectivity, and stability over a period of 4 weeks for NSE detection. With these excellent properties, the immunosensor can be extended to analyze and diagnose other disease biomarkers.