Voltammetric detection of potassium ferricyanide mediated by multi-walled carbon nanotube/titanium dioxide composite modified glassy carbon electrode

The MWCNT/TiO(2) composite was homogeneously coated on the surface of GCE and applied in the electrochemical determination of 0.1 mM potassium ferricyanide in 0.1 M Na(2)HPO(4) (pH 8.5). The redox couple of potassium ferricyanide with current enhancements of 3.0-3.1 folds was obtained using the MWCNT/TiO(2)/GCE when compared with unmodified GCE. A linear calibration plot showed a correlation coefficient of 0.999, with detection limits of 48.6 mu M ( 100 mV/s scan rate) and 1.1 mu M ( 5 mV/s scan rate) in the concentration ranges of 0.01-0.2 mM of potassium ferricyanide. High sensitivity responses of 77.6 mu A/mM for the anodic and of 68.9 mu A/mM for the cathodic peak currents were also obtained with an excellent correlation coefficient of 0.999. Based on plot of peak current against peak potential, the zero-current potentials were obtained as E(pa)(o)= 209 mV and E(pc)(o)= 189 mV. Diffusion coefficient was found as 1.52 x 10(-5) cm(2)/s from chronocoulometry study. The effect of temperature study was carried at 10 degrees C - 80 degrees C and activation energy obtained was 5.8-6 kJ/mol. The morphology of composite surface was examined by scanning electron microscopy.