▎ 摘　　要

This paper presents a method for the preparation of a graphene-based hybrid composite film by electrodeposition of reduced graphene oxide and overoxidized electropolymerized polypyrrole onto a glassy carbon electrode (GCE) using cyclic voltammetry. The morphology of the hybrid composite film was characterized by scanning electron microscopy. The electrochemical activity of the modified GCE was studied by cyclic voltammetry using the negatively charged redox probe Fe(CN)(6)(3-) and the positively charged redox probe Ru(NH3)(6)(3+). The modified GCE displays excellent electrocatalytic activity for dopamine (DA) and uric acid (UA), but electrostatically repulses ascorbate anion under physiological pH conditions. The voltammetric response to DA is linear in the 2.0M to 160M concentration range even in the presence of 1.0mM ascorbic acid and 0.1mM of UA. The detection limit is 0.5M. The amperometric response to DA (best measured at 0.22V vs. Ag/AgCl) extends from 0.4M to 517M and has a 0.2M detection limit.