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

Electrochemical sensing of many biomolecules has been achieved by measuring the redox current of H 2 O 2 , so the development of highly active catalysts toward H 2 O 2 electroreduction is strongly needed for sensitive biosensing. Herein, we report the high catalytic activity of Cu 2 S@Co 3 S 4 core-shell heterostructures toward H 2 O 2 electroreduction and their application in immunosensing. The synthesis of Cu 2 S@Co 3 S 4 core-shell heterostructures involves growth of amorphous Co(OH) 2 nanosheets on Cu 2 O nanocubes and one-step sulfuration of Cu 2 O@Co(OH) 2 by a hydrothermal method. Sulfuration of Cu 2 O@Co(OH) 2 results in great enhancement in electrocatalytic activity for H 2 O 2 reduction. Due to the great synergistic effect between Cu 2 S and Co 3 S 4 , the Cu 2 S@Co 3 S 4 heterostructures show higher electrocatalytic activity than Cu 2 S and Co 3 S 4 alone. Surface coating of polyethyleneimine (PEI) on Cu 2 S@Co 3 S 4 enables facile immobilization of antibody. A label-free electrochemical immunosensor using Cu 2 S@Co 3 S 4 @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 . • Cu 2 S@Co 3 S 4 heterostructures were explored as a highly active electrocatalyst toward H 2 O 2 reduction. • Sulfuration of Cu 2 O@Co(OH) 2 results in great enhancement in electrocatalytic activity for H 2 O 2 reduction. • Synergetic effects between Cu 2 S and Co 3 S 4 enable the high electrocatalytic activity of Cu 2 S@Co 3 S 4 . • A label-free electrochemical immunosensor was constructed using Cu 2 S@Co 3 S 4 as the electrode material. • The detection limit is as low as 0.6 pg mL −1 for immunosensing of alpha fetoprotein.