In this paper, a new electron mediator modified graphene oxide (GO) was firstly prepared by covalently grafted (4-ferrocenylethyne) phenylamine (FEPA) onto the surface of GO. The successful attachment of FEPA onto GO sheets was demonstrated by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-vis spectroscopy, thermogravimetric analysis (TGA) and electrochemical experiments. The as prepared FEPA modified GO (FEPA-GO) proved to be a novel hybrid composite with highly enhanced conductivity and compatibility. Combined the FEPA-GO with chitosan (CS) to fabricate the modified glassy carbon electrode (GCE), a highly sensitive amperometric nitrite sensor was successfully constructed. The electrochemical oxidation current of nitrite on the CS/FEPA-GO/GCE was largely enhanced, which may result from the catalysis effect of the FEPA-GO. With this novel sensor, the oxidation peak currents were linearly dependent on the nitrite concentrations in the range of 0.3-3100 mu mol L-1 with the detection limit of 0.1 mu mol L-1. Modification of FEPA on GO held great promise to enhance the electrochemical performance of GO and will pay a new way for fabricating newly ferrocene functionalized graphene-based electrochemical biosensors. (c) 2013 Elsevier Ltd. All rights reserved.