Abstract

We report in this study on the direct electron transfer for hemoglobin (IIb) entrapped in cationic didodecyldimethylammonium bromide (DDAB) surfactant films cast on vitreous-carbon electrodes, in neutral aqueous solution. This was achieved by using for the first time the electrochemical impedance spectroscopy (EIS) measurements. This allows providing further insights in the electrical properties of these biofilms. The electroassisted catalytic reduction of molecular oxygen by the entrapped Hb, in neutral aqueous solution was also investigated. A catalytic current was observed close to the Fe(III)/Fe(II) redox potential of the immobilized Hb, and the intensity of the voltammetric cathodic peak (measured by cyclic voltammetry) is directly proportional to oxygen partial pressure. The influence of oxygen partial pressure on the impedance response of the films was also analyzed. The obtained results emphasizes the fact that the total charge transfer resistance of the modified electrode decreases with increasing oxygen partial pressure. A preliminary explanation of such an observation is discussed.