Effect of surface activation on charge and mass transfer rates of the hexacyanoferrate(III)/(II) redox probe at fibrinogen-modified carbon paste electrodes

The electron transfer and mass transport properties of fibrinogen-modified carbon paste surfaces, following preliminary activation for various duration, has been studied using cyclic voltammetry (CV) and chronoamperomety. Activation was carried out by subjecting the surface, exposed to a solution-containing oxidant species, to positive polarization of increasing duration. Modification was subsequently achieved following spontaneous adsorption of fibrinogen on exposure to a solution containing the protein. To investigate the electrochemical properties of this surface, the variations in the charge-transfer and mass-transport kinetics of hexacyanoferrate(III)/(II) ions, used as a redox probe, were analyzed separately. The results showed the favorable effect of activation on electrocatalysis and charge-transport properties through the coating. Relative to pretreated bare surfaces, however, the presence of fibrinogen induced opposed variations, thus explaining unchanged CV peak currents. These features were essentially attributed to morphological changes promoted by activation in the protein layer.