▎ 摘　　要

In the present work, for the first time, excellent activity and antifouling properties of reduced graphene oxide (rGO) nanosheets toward the oxidation of insulin at physiological pH were reported. Electrochemical oxidation of insulin at the surface of rGO, graphene oxide (GO) and graphite (G) were investigated and compared. Cyclic voltammetry and hydrodynamic amperometry were used to investigate the analytical characteristics of the rGO-modified GC (GC/rGO) electrode toward the oxidation of insulin. While the electrooxidation of insulin on the bare glassy carbon (GC) electrode, G and GO-modified GC electrodes led to the deactivation of the surface after a short period of time, the GC electrode coated with rGO revealed highly stable insulin oxidation current. The effect of various experimental parameters on the electrochemical oxidation of insulin was investigated using cyclic voltammetric technique. The amperometric response of the GC/rGO electrode toward insulin under the optimum conditions was found to be linear over the concentration range of 4-640 nM with a sensitivity of 7.1254 nA/nM and a detection limit of 350 pM. The modified electrode offers considerable advantages of simple and fast electrode preparation, low cost, fast response time, signal stability, high sensitivity and insulin determination at physiological pH. (C) 2016 Published by Elsevier B.V.