Electrochemical Behavior of a Gold Electrode Modified with SWNTs/DDAB Films and Its Electrocatalytic Activity Towards Ascorbic Acid

A film of single-wall carbon nanotubes (SWNTs) and didodecyldimethylammonium bromide (DDAB) is prepared by casting a solution of SWNTs and DDAB onto the surface of a gold electrode. The electrochemical behavior of the film is investigated by electrochemical impedance spectroscopy and cyclic voltammetry. In a 0.10 M phosphate buffer solution of pH 7.0, the film-modified electrode gives a pair of redox peaks in cyclic voltamograms, with the anodic and cathodic peak potentials of 0.095 and 0.042 V. The peak currents change linearly with the scan rate at 30–500 mV/s. The modified electrode has an excellent electrocatalytic activity towards the oxidation of ascorbic acid (AA). The catalysis currents are proportional to the AA concentration in the range of 5.0 × 10^?4 to 3.2 × 10^?2 M. The linear-regression equation is i (µA) = 1.2079 + 1.3987 × 10³c_AA (M), with a correlation coefficient of 0.9995. The detection limit is 2.2 × 10^?4 M (signal-to-noise ratio of 3). The Michaelis-Menten constant (K_m) is 1.0 × 10^?4 M by the Lineweaver-Burk equation.