Direct Electrochemistry of Hemoglobin Immobilized on Hydrophilic Ionic Liquid-chitosan-ZrO2 Nanoparticles Composite Film with Carbon Ionic Liquid Electrode as the Platform

A stable composite film composed of 1-butyl-3-methyl-imidazolium tetrafluoroborate, chitosan, zirconia nanoparticles and the hemoglobin (Hb) was cast on the surface of an ionic liquid of an N-butylpyridinium hexafluorophosphate modified carbon paste electrode to fabricate a modified electrode. Scanning electron microscopy images of the modified electrode indicated that there was a dendritic structure on the modified electrode, and UV-Vis and FT-IR spectra showed that Hb in the composite film retained its native structure. Voltammetric experiments at the modified electrode showed that, in a pH 7.0 phosphate buffer solution, a pair of well-defined and quasi-reversible redox voltammetric peaks was obtained with the formal potential located at –0.216 V. The electrochemical parameters of Hb in the composite film were further carefully calculated: the electron-transfer rate constant was 0.52 s–1 and the charge transfer coefficient was 0.34. The catalytic reduction peak current had a linear relationship with the concentration of trichloroacetic acid (TCA) in the range from 0.2 to 10.3 mmol/L with a detection limit of 66.7 µmol/L. Therefore, the composite film as a novel matrix opened up a possibility for further study on the design of enzymatic biosensors with potential applications.