Direct electrochemistry and electrocatalysis of hemoglobin on chitosan-room temperature ionic liquid-TiO2-graphene nanocomposite film modified electrode

TiO2-graphene nanocomposite was prepared by hydrolysis of titanium isopropoxide in colloidal suspension of graphene oxide and in situ hydrothermal treatment. The direct electrochemistry and electrocatalysis of hemoglobin in room temperature ionic liquid 1-Butyl-3-methylimidazolium hexafluorophosphate, chitosan and TiO2-graphene nanocomposite modified glassy carbon electrode were investigated. The biosensor was examined by using UV-vis spectroscopy, scanning electron microscopy and electrochemical methods. The results indicated that hemoglobin remained its bioactivity on the modified electrode, showing a couple of well-defined and quasi-reversible redox peaks, corresponding to hemoglobin FeIII/FeII couple. The kinetic parameters for the electrode reaction, such as the formal potential (Eo'), the electron transfer rate constant (ks), the apparent coverage (Γ), and Michaelis–Menten constant (Km) were evaluated. The biosensor showed good electrochemical responses to the reduction of H2O2 in the ranges of 1–1170 μM. The detection limit was 0.3 μM (S/N = 3). The properties of this composite film, together with the bioelectrochemical catalytic activity, could make them useful in the development of bioelectronic devices, and investigation of electrochemistry of other heme proteins at functional interface.

► An electrochemical sensor based on TiO2-graphene/chitosan/[bmim]PF6 composite film is developed for hemoglobin studied.
► The sensor shows good electrocatalytic responses to H2O2 in the ranges of 1–1170 μM with the detection limit of 0.3 μM.
► The formal potential, electron transfer rate constant, apparent coverage, and Michaelies–Menten constant were evaluated.