Direct electrochemistry and electrochemical catalysis of myoglobin–TiO2 coated multiwalled carbon nanotubes modified electrode

Abstract

TiO2 nanoparticles were homogeneously coated on multiwalled carbon nanotubes (MWCNTs) by hydrothermal deposition, and this nanocomposite might be a promising material for myoglobin (Mb) immobilization in view of its high biocompatibility and large surface. The glassy carbon (GC) electrode modified with Mb–TiO2/MWCNTs films exhibited a pair of well-defined, stable and nearly reversible cycle voltammetric peaks. The formal potential of Mb in TiO2/MWCNTs film was linearly varied in the range of pH 3–10 with a slope of 48.65 mV/pH, indicating that the electron transfer was accompanied by single proton transportation. The electron transfer between Mb and electrode surface, ks of 3.08 s−1, was greatly facilitated in the TiO2/MWCNTs film. The electrocatalytic reductions of hydrogen peroxide were also studied, and the apparent Michaelis–Menten constant is calculated to be 83.10 μM, which shows a large catalytic activity of Mb in the TiO2/MWCNTs film to H2O2. The modified GC electrode shows good analytical performance for amperometric determination of hydrogen peroxide. The resultant Mb–TiO2/MWCNTs modified glassy carbon electrode exhibited fast amperometric response to hydrogen peroxide reduction, long term life and excellent stability. Finally the activity of the sensor for nitric oxide reduction was also investigated.