Voltammetric studies on surface-modified electrodes with functionalised carbon nanotubes under different dispersion conditions

Quantitative analysis was performed on voltammetric data obtained from surface-modified electrodes that were prepared with functionalised carbon nanotubes (fCNTs) consisting of functionalised single-walled carbon nanotubes (fSWCNTs) and functionalised multi-walled carbon nanotubes (fMWCNTs). In order to obtain the optimum coating procedure, the fCNTs were dispersed in individual solutions of N-methyl-2-pyrrolidone, N,N-dimethylformamide and ethanol (EtOH), and drop cast onto glassy carbon (GC) electrode surfaces to become the surface-modified electrodes. Different classes of surfactants (positive, negative and neutrally charged) at varying concentrations were tested in the bulk solution to see how they affected the dispersion properties of the fCNTs as well as how they influenced the experimental heterogeneous electron transfer rates (k⁰) measured via cyclic voltammograms (CVs) of the ferri-/ferrocyanide redox couple at the immersed film electrodes. The k⁰-values measured at the fSWCNT/GCE and fMWCNT/GCE film electrodes were compared and the results indicated that the type of fCNTs and the%wt of the fCNTs used in the dispersion did not affect the rates of heterogeneous electron transfer. The effect of increasing bulk surfactant concentration was examined to determine the optimum current responses with the lowest voltammetric peak-to-peak separation (ΔE_pp) values for the film electrodes. Thin layer diffusion and semi-infinite diffusion processes were found to be dominant at slow and fast scan rates, respectively.