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

Abstract

Abstract In this paper a carbon ionic liquid electrode (CILE) was fabricated by using ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF 6 ) 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 (Δ 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 (α) 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 × 10 −5 cm 2 /s. Under the selected conditions the oxidation peak current was in linear with DA concentration from 1.0 × 10 −5 to 6.0 × 10 −4 mol/L with the detection limit as 6.75 × 10 −6 mol/L (3σ)by differential pulse voltammetry. The proposed method showed good selectivity and was further applied to the DA injection samples determination with satisfactory results.