Abstract

For the first time, the study of the effect of length and degree of oxidation of multi-walled carbon nanotubes (CNTs) on the electroanalytical DNA sensing properties of modified glassy carbon electrodes (GCEs) is reported. GCE/CNT electrodes were prepared using chitosan (CHI) as a dispersing agent. Short (S-NCs) and long (L-NCs) carbon nanotubes, as well as unoxidized and 3 or 6 hour oxidized samples were used. Cyclic voltammetry indicated that S-NCs exhibited larger capacitance values than L-NCs, and that these values increased when the CNTs were oxidized. Using Scanning Electrochemical Microscopy (SECM), an increase in the surface homogeneity was determined when oxidized CNTs were used as electrode modifiers. dsDNA electrooxidation showed the highest response using GCEs/CHI-L-NCs, and a clear decrease in the current intensity was observed when the oxidation time was increased. This result correlates with the higher BET surface area of L-NCs. In conclusion, the electrochemical performance of GCE/CNT electrodes against DNA increase when the length of CNTs is higher and decrease at higher oxidation state.