Electroactive endohedral metallofullerene film electrodes in aqueous solutions

The aqueous electrochemistry of Dy@C82 films and membrane films of didodecyldimethylammonium bromide (DDAB) encapsulated with Dy@C82 has been studied systematically. The redox responses of the Dy@C82 films depend strongly on the supporting electrolytes. In the aqueous solution of tetrabutylammonium bromide, we obtained four cathodic waves at 0.040, −0.40, −1.04, and −1.35 V, and one oxidation wave at +0.31 V. For the membrane films of Dy@C82–DDAB film, however, the well-defined redox responses in water are relatively independent of the supporting electrolytes because of the encapsulation and fine dispersion of Dy@C82 in the DDAB membrane. Reversible reduction and oxidation waves were obtained even in the pH 7.0 buffer solution containing KCl, which is associated with the charge balance of the DDAB ions with the ions of Dy@C82. It was found that Dy@C82 in the DDAB membrane promotes the encapsulation of hemoglobin (Hb) and Hb can catalyze the reduction of Dy@C82. Significantly enhanced electrocatalytic reduction of O2 by Hb in the presence of Dy@C82 has also been demonstrated. Here Dy@C82 acts an electron-transfer mediator, which points to the potential application of metallofullerenes in biochemical sensing.