Ionic Liquid-hemoglobin-carbon Paste Composite Bioelectrode and Its Electrocatalytic Activity

A new carbon ionic liquid paste bioelectrode was fabricated by mixing hemoglobin (Hb) with graphite powder, ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF(4)) and liquid paraffin homogeneously. Nafion film was cast on the electrode surface to improve the stability of bioelectrode. Direct electrochemistry of Hb in the bioelectrode was carefully investigated. Cyclic voltammetric results indicated that a pair of well-defined and quasi-reversible electrochemical responses appeared in pH 7.0 phosphate buffer solution (PBS), indicating that direct electron transfer of Hb was realized in the modified electrode. The formal potential (E(0)') was calculated as -0.316 V (vs. SCE), which was the typical characteristic of the electrochemical reaction of heme Fe(III)/Fe(II) redox couple. Based on the cyclic voltammetric results the electrochemical parameters of the electrode reaction were calculated. This bioelectrode showed high electrocatalytic activity towards the reduction of trichloroacetic acid (TCA) with good stability and reproducibility.