Oxidative modification of multi-wall carbon nanotubes for the electrochemical detection of dopamine

Multi-wall carbon nanotubes (MWCNTs) with different degrees of oxidation were prepared by a wet chemical oxidation method. Their morphology and chemical composition were characterized by infrared spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. The oxidized MWCNTs were coated on glassy carbon for use as electrodes and their electrocatalytic oxidation activities for dopamine, ascorbic acid and uric acid were investigated by cyclic voltammetry and differential pulse voltammetry in order to evaluate their performance for selective dopamine detection. Results indicated that the electrocatalytic oxidation activities are dependent on both the electron transfer resistance of the graphitic layers and the electrostatic attraction between dopamine and carboxyl groups on the MWCNTs. Optimized MWCNTs with an appropriate content of carboxyl groups and nearly complete graphitic layers have a wide linear response current range for dopamine contents from 2 to 100 μM, and can be used for the selective detection of dopamine in the presence of ascorbic acid and uric acid.