Pinecone shape hydroxypropyl-β-cyclodextrin on a film of multi-walled carbon nanotubes coated with gold particles for the simultaneous determination of tyrosine, guanine, adenine and thymine

A conductive composite film containing functionalized multi-walled carbon nanotubes (fMWCNTs), gold nanoparticles (Au) with hydroxypropyl-beta-cyclodextrin (HP beta CD) as catalysts have been synthesized on glassy carbon, gold and on indium tin oxide electrodes by potentiostatic methods. The presence of fMWCNTs and HP beta CD in the composite film enhances the active surface coverage concentration of Au by 397.0%. The presence of nanoparticles of gold catalyst in the film enhances the functional properties and produces an overall increase in the sensitivity of the modified electrodes. These modified electrodes exhibit promising electrocatalytic activity towards the oxidation of tyrosine (TYR), guanine (GU), adenine (AD) and thymine (THY) present in pH 7.4 aqueous solutions. Well separated voltammetric peaks are obtained between TYR and GU (80 mV), GU and AD (290 mV), AD and THY (185 mV) present in the analyte mixture. The sensitivity values of the composite films from cyclic voltammetry (CV) and semi derivative differential pulse voltammetry (DPV) show that, the composite film modified electrodes are efficient and they could be applied in biosensor devices. However, a detailed comparison between the sensitivities obtained using CV and semi derivative DPV shows that, the sensitivity obtained in semi derivative DPV technique is higher than CV. Electrochemical quartz crystal microbalance, scanning electrochemical microscope and scanning electron microscope techniques have been used for the electrochemical characterizations and surface morphology studies. (C) 2007 Elsevier Ltd. All rights reserved.