Application of Multi-walled Carbon Nanotube Modified Carbon Ionic Liquid Electrode for the Voltammetric: Detection of Dopamine

In this paper a carbon ionic liquid electrode (CILE) was fabricated by using ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) as the binder. Then a Nafion and multi-walled carbon nanotubes (MWCNTs) composite material was further cast on the CILE surface to get a modified electrode denoted as Nafion-MWCNTs/CILE. The fabricated electrode showed strong electrocatalytic ability to the oxidation of dopamine (DA) with a pair of well-defined redox peaks appeared. Compared with other electrodes the redox peak currents increased with the decrease of the peak-to-peak separation (Delta E-p), and the result was attributed to the specific properties of MWCNTs and its interaction with imidazolium ion present on the CILE surface. The electrochemical parameters of DA on the Nafion-MWCNTs/CILE were calculated with the electron transfer coefficient (alpha) as 0.433, the electron transfer number (n) as 1.1, the apparent heterogeneous electron transfer rate constant (k(s)) as 0.774 s(-1) and the diffusion coefficient (D) as 3.05 x 10(-5) cm(2)/s. Under the selected conditions the oxidation peak current was in linear with DA concentration from 1.0 x 10(-5) to 6.0 x 10(-4) mol/L with the detection limit as 6.75 x 10(-6) mol/L (3 sigma) by differential pulse voltammetry. The proposed method showed good selectivity and was further applied to the DA injection samples determination with satisfactory results.