▎ 摘　　要

The authors describe a voltammetric immunosensor with antibody immobilized on a glassy carbon electrode (GCE) modified with N-doped graphene (N-GS), electro-deposited gold nanoparticles (AuNPs) and chitosan (Chit). The preparation is simple and the thickness of the electrodeposited films can be well controlled. Due to the specific advantages of N-GS, AuNPs and Chit, the electrode has a large specific surface, improved conductivity, high stability. A new label-free immunosensor for the model antigen (alpha fetoprotein, AFP) detection was then designed by employing N-GS-AuNP-Chit as the antibody immobilization and signal amplification platform. Differential pulse voltammetry and electrochemical impedance spectroscopy were used for the characterization of the stepwise assembly process. Under the optimized conditions, at a typical working potential of +0.20 V (vs. SCE), and by using hexacyanoferrate as an electrochemical probe, the immunosensor has a detection limit as low as 1.6 pg mL(-1) and a linear analytical range that extends from 5 pg mL(-1) to 50 ng mL(-1). AFP was quantified in spiked human serum samples with acceptable precision.