Direct electrochemistry and electrocatalysis of hemoglobin on three-dimensional graphene modified carbon ionic liquid electrode

In this paper three-dimensional graphene (3D-GR) was directly formed on the surface of carbon ionic liquid electrode (CILE) by electrodeposition. By using 3D-GR/CILE as the substrate electrode, a new electrochemical biosensor was prepared by immobilization of hemoglobin (Hb) on the electrode surface with a chitosan film. Electrochemical investigation indicated that a pair of well-defined redox peaks appeared on cyclic voltammogram, indicating the realization of direct electron transfer of Hb with the underlying electrode. The result can be ascribed to the porous structure of 3D-GR with high conductivity and big surface area. Based on the electrochemical data, the electron transfer coefficient (α) and the apparent heterogeneous electron transfer rate constant (ks) were calculated to be 0.426 and 1.864 s−1, respectively. The modified electrode displayed good electrocatalytic activity to the reduction of trichloroacetic acid (TCA), and the catalytic reduction peak current had a good linear relationship to TCA concentration in the range from 0.4 to 26.0 mmol/L with the detection limit of 0.133 mmol/L (3σ). Therefore a new third-generation electrochemical Hb biosensor based on 3D-GR/CILE was constructed with good stability and reproducibility.