Synergistic electrocatalysis of Cu2S@Co3S4 core-shell heterostructures toward H2O2 reduction and their application for sensitive immunosensing of alpha fetoprotein

Abstract

Electrochemical sensing of many biomolecules has been achieved by measuring the redox current of H2O2, so the development of highly active catalysts toward H2O2 electroreduction is strongly needed for sensitive biosensing. Herein, we report the high catalytic activity of Cu2S@Co3S4 core-shell heterostructures toward H2O2 electroreduction and their application in immunosensing. The synthesis of Cu2S@Co3S4 core-shell heterostructures involves growth of amorphous Co(OH)2 nanosheets on Cu2O nanocubes and one-step sulfuration of Cu2O@Co(OH)2 by a hydrothermal method. Sulfuration of Cu2O@Co(OH)2 results in great enhancement in electrocatalytic activity for H2O2 reduction. Due to the great synergistic effect between Cu2S and Co3S4, the Cu2S@Co3S4 heterostructures show higher electrocatalytic activity than Cu2S and Co3S4 alone. Surface coating of polyethyleneimine (PEI) on Cu2S@Co3S4 enables facile immobilization of antibody. A label-free electrochemical immunosensor using Cu2S@Co3S4@PEI as the electrode material possesses a wide linear range for detecting alpha fetoprotein from 1 pg mL−1 to 100 ng mL−1, with a detection limit as low as 0.6 pg mL−1.