▎ 摘　　要

We report a facile strategy to prepare nitrogen functionalized reduced graphene oxide (NRGO) by using ammonia plasma treatment of reduced graphene oxide (RGO) synthesized via a chemical method. The chemical composition of NRGO and its morphology was studied extensively by various surface probing techniques such as Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and Raman spectroscopy. Electrochemical investigations were performed using various redox probes such as potassium ferricyanide and hexaammineruthenium (III) chloride indicated a large electroactive surface area of NRGO and fast electron transfer. Meanwhile the direct electron transfer of hemoglobin (Hb) immobilized on NRGO was confirmed by a reduction peak that appeared on the cyclic voltammogram. Further, the electron transfer coefficient (alpha) and heterogeneous electron transfer rate constant (ks) for Hb at the NRGO were calculated to be 0.43 and 1.05 s(-1) respectively. Moreover, the GCE/NRGO/Hb modified electrode was employed for the determination of nitrite over the linear range from 5 to 300 nM with a limit of detection of 1.3 nM. Our results suggest that NRGO is a potential candidate for the electrochemical sensing of nitrite. (C) 2017 Elsevier B.V. All rights reserved.