Electrochemical sensing of dopamine at the surface of a dopamine grafted graphene oxide/poly(methylene blue) composite modified electrode

Abstract

The simultaneous electrochemical reduction of graphene oxide (GO) and oxidative polymerization of methylene blue yielding a polymer composite on a glassy carbon electrode surface is demonstrated. The stability of the reduced graphene oxide (ERG)/poly(methylene blue) (PMB) composite in buffer solution is also studied in detail. Interestingly, methylene blue initially forms a radical cation, which donates an electron to GO, then GO undergoes reduction and during the subsequent cycles, it forms the polymer composite through covalent interactions between simultaneously reduced GO and oxidized methylene blue. The formation of the polymer composite is characterized using electrochemical impedance spectroscopy, laser Raman spectroscopy, SEM and UV-Visible absorption studies. Dopamine is a neurotransmitter with primary amine and phenolic functional groups. The electrografting of dopamine onto an ERG/PMB composite modified electrode is carried out and is evaluated by FT-IR and XPS studies and the electrochemical stability of the grafted dopamine is demonstrated using CV studies. Differential pulse voltammetry studies reveal that the modified electrode shows a high selectivity and sensitivity towards the detection of dopamine in the presence of ascorbic acid (AA) and uric acid (UA) with a detection limit of 1.03 × 10⁻⁶ mol L⁻¹ from a calibration curve with a linear range of 0.96 × 10⁻⁶ mol L⁻¹ to 7.68 × 10⁻⁶ mol L⁻¹. Hence, this dopamine grafted on polymer composite modified electrode provides an attractive platform for the selective sensing of dopamine in the presence of interferents.