Enhanced electrochemical sensing of dopamine based on carboxylic acid functionalized multi-walled carbon nanotubes/poly(toluidine blue) composite

A highly sensitive and simple electrochemical method was developed for detection of dopamine (DA) based on carboxylic acid functionalized multi-walled carbon nanotubes (MWCNTs-COOH) and electrochemically synthesized polymer of toluidine blue (Poly(TB)) composite film modified glassy carbon electrode (GCE) (abbreviated as MWCNTs-COOH/Poly(TB)/GCE). The physicochemical and electrochemical characterizations were evaluated using FT-IR spectroscopy, field emission scanning electron microscope (FE-SEM) and electrochemical impedance spectroscopy (EIS). Further, the possible electrochemical polymerization mechanism of toluidine blue was proposed. The EIS responses confirmed that the least charge transfer rate at the composite film modified GCE. The developed MWCNTs-COOH/Poly(TB)/GCE demonstrated superior sensitivity towards DA over that of the other modified electrodes in a physiological pH. Under optimal experimental conditions, the limit of detection (LOD) was found to be 10.39 nM (3S/m) in the linear dynamic range from 1 to 300 mu M. The modified electrode exhibited good stability, repeatability, reproducibility and also selectivity over the commonly interfering species. Finally, the developed method was applied for real sample analysis and this can be further extendable as a sensing platform for clinical laboratory applications.