Highly Selective and Sensitive Detection of Dopamine in the Presence of Excessive Ascorbic Acid Using Electrodes Modified with C-60-Functionalized Multiwalled Carbon Nanotube Films

Electrochemical detection of dopamine (DA) in the presence of a large excess of ascorbic acid (AA) was investigated with a novel all-carbon nanocomposite film of C-60-MWCNTs (C-60-functionalized multi-walled carbon nanotubes) using a bare MWCNTs film as control. Although both films can selectively detect DA from AA by separating their oxidation potentials, the C-60-MWCNTs film shows special selectivity and good sensitivity for detecting DA. On one hand, the C-60-MWCNTs composite film shows a higher activity for DA oxidation with enhanced peak current. On the other hand, the C-60-MWCNTs composite film effectively suppresses the oxidation of AA. Remarkably, it is found that the oxidation current of DA is over 2 times higher than that of AA even when the concentration of AA is about 3 to 4 orders of magnitude higher than that of DA. This offers a tremendous advantage for the simple and clean detection of DA free of the interfering AA signal in a real assay. Cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectrometry are used to characterize the C-60-MWCNTs composite film. These novel properties are interpreted to arise from the facile electron transfer between C-60 and MWCNTs in the C-60-MWCNTs nanocomposite film.