Multi-walled carbon nanotubes with poly(methylene blue) composite film for the enhancement and separation of electroanalytical responses of catecholamine and ascorbic acid

A novel conductive composite film containing multi-walled carbon nanotubes (MWCNTs) with poly(methylene blue) (PMB) has been synthesized on glassy carbon electrode (GCE), gold and indium tin oxide electrodes by potentiostatic methods. The presence of MWCNTs in the composite film enhance the surface coverage concentration (Γ) of PMB, increased the electron transfer rate constant (Ks) by 44.53% and decreased the degradation of PMB during the cycling. The composite film exhibits a promising higher electrocatalytic activity towards the oxidation of ascorbic acid (AA), epinephrine (EP) and dopamine (DA) present in pH 7.4 aqueous solution. The presence of PMB in the composite film enhances the functional properties and overall increase in the sensitivity of the composite film modified electrodes. Both, the cyclic voltammetry (CV) and square wave voltammetry (SWV) have been used for the measurement of electroanalytical properties of analytes by means of composite film modified electrodes. In CV, well-separated voltammetric peaks have been obtained at the composite film modified GCEs for AA–EP and AA–DA mixture with a peak separation of 144.36 and 164.00 mV, respectively. The detection limit values obtained are equivalent to the concentrations found in physiological conditions. Similar sensitivity values have been observed in CV and semi-derivative SWV. Further, the electrochemical quartz crystal microbalance and scanning electron microscopy have been used to reveal the enhancements in functional properties and surface morphology of the composite film.