▎ 摘　　要

Cobalt-doped magnetite/graphene nanocomposites (Co-MGNCs) were prepared by a facile one-pot electrochemical method. The morphology and composition of the synthesized products were characterized by X-ray photoelectron spectroscopy and field emission scanning electron microscopy techniques, which revealed that cobalt element was highly dispersed in the framework of graphene. For the first time, Co-MGNCs were demonstrated to own significant peroxidase-like activity, compared with graphene oxide and magnetic NPs. The as-prepared nanomaterials could effectively catalyze the reaction between 3,3,5,5-tetramethylbenzidine (TMB) and H2O2. Dopamine (DA) exhibits some reducibility due to the existence of a phenol hydroxyl group, which results in the consumption of H2O2 and causing the blue shallowing of the reaction solution between H2O2 and TMB. A visual, sensitive and simple colorimetric method based on Co-MGNCs as peroxidase mimetic was developed for detecting DA. Good linear relationships for DA were obtained from 0.5 to 50 mu M. The limit of detection (LOD) of the proposed method was calculated as 0.08 mu M and the relative standard deviation (RSD) was less than 4.0%. The visual method was successfully applied to DA detection in human serum samples.