MWCNTs-CoP hybrids for dual-signal electrochemical immunosensing of carcinoembryonic antigen based on overall water splitting.

Abstract Great efforts have been made to search for highly active catalysts toward electrochemical water splitting, but double-signal immunosensors have not been reported based on bifunctional water splitting electrocatalysts. We report here a dual-signal electrochemical immunosensor for detecting carcinoembryonic antigen (CEA) using multi-wall carbon nanotubes (MWCNTs)-cobalt phosphide (CoP) as an electrocatalytic label. The preparation of MWCNTs-CoP involves the growth of Co3O4 nanoparticles on MWCNTs and low-temperature phosphatization of Co3O4 nanoparticles. The MWCNTs-CoP catalyst shows excellent electrocatalytic activities in a neutral medium toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), enabling MWCNTs-CoP as the electrocatalytic label for sensitive immunosensing. The linear range of the sandwich-type immunosensor for detecting CEA based on the HER signal is from 10−4–100 ng mL−1, whereas a linear range for detecting CEA based on the OER signal is achieved from 10−4 to 10 ng mL−1. The detection limits for detecting CEA using HER and OER signals are 10 and 12 fg mL−1, respectively. This work can provide a new double-signal immunosensing platform based on a bifunctional water splitting electrocatalyst.