Preparation of a glassy carbon electrode modified with reduced graphene oxide and overoxidized electropolymerized polypyrrole, and its application to the determination of dopamine in the presence of ascorbic acid and uric acid

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)₆³⁻ and the positively charged redox probe Ru(NH₃)₆³⁺. 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 2.0 μM to 160 μM concentration range even in the presence of 1.0 mM ascorbic acid and 0.1 mM of UA. The detection limit is 0.5 μM. The amperometric response to DA (best measured at 0.22 V vs. Ag/AgCl) extends from 0.4 μM to 517 μM and has a 0.2 μM detection limit. [Figure not available: see fulltext.].