Hollow Co3O4 nanospheres for the direct electrochemistry and electrocatalysis of hemoglobin with an ionic liquid as an enhancer

Hollow Co3O4 nanospheres were synthesized through a solvothermal route and applied to fabricate a redox protein-based sensing platform. Hemoglobin (Hb) was selected as the model protein to investigate the electrocatalytic properties of the composite film composed of hollow Co3O4 nanospheres, ionic liquid (IL) 1-butyl-3-methyl-imidazolium tetrafluoroborate ([BMIM]BF4) and Nafion, with a carbon ionic liquid electrode (CILE) as the substrate electrode. UV-vis absorption and FT-IR spectra results indicate that Hb remained in its native structure in the composite film. The results of cyclic voltammograms show that Hb entrapped in the composite film exhibited an excellent direct electrochemistry, and retained its biocatalytic activity toward the electro-reduction of trichloroacetic acid (TCA), with a linear range from 1.0 to 20.0 mmol L-1. The results could be attributed to the synergistic effect of hollow Co3O4 nanospheres and IL in the composite film, which provided a specific microenvironment to keep the native structure of Hb and promote the electron transfer rate of Hb. The fabricated biosensor displays high sensitivity, good reproducibility and long-term stability.