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Direct Electrochemistry of Hemoglobin Immobilized in the Sodium Alginate and SiO₂ Nanoparticles Bionanocomposite Film on a Carbon Ionic Liquid Electrode

W. Sun*, D. Wang, Z. Zhai, R. Gao and K. Jiao

Key Laboratory of Eco-Chemical Engineering of Ministry of Education, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, Shandong, P.R. China

In this paper a carbon ionic liquid electrode (CILE) was fabricated by using a room temperature ionic liquid of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF₆) as binder. By using the CILE as basal electrode, the hemoglobin (Hb) molecule was immobilized on the surface of CILE with a sodium alginate (SA) hydrogel and SiO₂ nanoparticles organic-inorganic composite material. The direct electrochemical behaviors of Hb in the bionanocomposite film were further studied in a pH 7.0 Britton-Robinson (B-R) buffer solution. A pair of well-defined quasi-reversible cyclic voltammetric peaks of Hb was obtained on SA/nano-SiO₂/Hb/CILE with the formal potential (E⁰') at -0.355 V (vs. SCE), which was the characteristic of heme Fe(III)/Fe(II) redox couples. The formal potential of Hb Fe(III)/Fe(II) couple shifted negatively with increasing pH of solution with a slope of -45.2 mV/pH, which indicated that a one electron transfer accompanied with one proton transportation. The immobilized Hb showed good electrocatalytic manner to the reduction of trichloroacetic acid (TCA).

Keywords: 1-Butyl-3-methylimidazolium hexafluorophosphate, Hemoglobin, Direct electron transfer, Carbon paste electrode, SiO₂ nanoparticle