Myoglobin/Sol−Gel Film Modified Electrode: Direct Electrochemistry and Electrochemical Catalysis

Direct electrochemical and electrocatalytic behavior of myoglobin (Mb) immobilized on carbon paste electrode (CPE) by a silica sol−gel film derived from tetraethyl orthosilicate was investigated for the first time. Mb/sol−gel film modified electrodes show a pair of well-defined and nearly reversible cyclic voltammetric peaks for the Mb Fe(III)/Fe(II) redox couple at about −0.298 V (vs Ag/AgCl) in a pH 7.0 phosphate buffer solution. The formal potential of the Mb heme Fe(III)/Fe(II) couple shifted linearly with pH with a slope of 52.4 mV/pH, denoting that an electron transfer accompanies single-proton transportation. An FTIR and UV−vis spectroscopy study confirms that the secondary structure of Mb immobilized on an electrode by a sol−gel film still maintains the original arrangement. The immobilized Mb displays the features of a peroxidase and acts in an electrocatalytic manner in the reduction of oxygen, trichloroacetic acid (TCA), and nitrite. In comparison to other electrodes, the chemically modified el...