Electrochemical characterization of cetyltrimethyl ammonium bromide modified carbon paste electrode and the application in the immobilization of DNA

A cetyltrimethyl ammonium bromide modified carbon paste electrode (CTAB/CPE) was developed in this work based on the surface modification method. The improved electrochemical response of K₄Fe(CN)₆ at this electrode indicated that CTAB could change the surface property of carbon paste electrodes (CPEs), which was demonstrated by the electrochemical impedance spectroscopy (EIS). In 0.1 mM Fe(CN)₆]^3−/4−, a low exchange current (i₀) of 2.72×10⁻⁷ A at bare CPE was observed while that at CTAB/CPE was 6.79×10⁻⁵ A. The effect of CTAB concentration on the electrode quality revealed that CTAB formed a compact monolayer on the electrode surface with high density of positive charges directed outside the electrode. This electrode showed strong accumulation ability toward Fe(CN)₆⁴⁻ and can also accumulate Co(phen)₃²⁺ by the adsorption of the organic ligands in the hydrophobic area of the monolayer. The electrode was applied to the immobilization of DNA, which was characterized by the isotherm adsorption of Co(phen)₃²⁺.