Application of CuS-functionalized ZnO nanoflakes for a paper-based photoelectrochemical immunoassay using an in situ electron donor producing strategy.

Copper sulfide (CuS), an excellent photoactive material, is introduced into a paper-based photoelectrochemical (PEC) immunosensor for the first time using an in situ electron donor producing approach. ZnO nanoflakes (ZNF) with a large surface area are first electrodeposited onto a gold-paper electrode, and then functionalized with CuS via a simple hydrothermal and ion exchange method. The recombination process of electron–hole pairs in CuS is prevented since the energy levels between ZnO and CuS are matched well, resulting in a high PEC performance. The glucose oxidase (GOx) and signal antibodies co-labeled nanoporous gold (NPG) is then introduced into the immunosensor via sandwich immunoreactions. On the basis of the catalytic chemistry of GOx to produce in situ H2O2 for electron donation, an enhanced photocurrent was achieved. By coupling the brilliant properties of CuS/ZNF, a modified gold-paper electrode with amplified electron donor production through NPG, a sensitive PEC immunosensor for carcinoembryonic antigen (CEA) analysis is proposed. The immunosensor displayed a linear response to CEA in the range from 2 pg mL−1 to 100 ng mL−1 with a relatively low detection limit of 0.7 pg mL−1. The proposed immunosensor exhibited good performance, which has a promising prospect in clinical diagnosis. [ABSTRACT FROM AUTHOR]