Direct electrochemistry of Hemoglobin immobilized on carbon paste electrode modified by carbon nanotubes

Direct electrochemical behaviors of Hemoglobin (Hb) adsorbed on carbon paste electrode modified by carbon nano-tubes(CNTs) were investigated. Hb-CNT-modified electrode showed a pair of well-defined and nearly reversible cyclic voltammetric peaks for HbhemeFe (III)/Fe (II) redox couple in phosphate buffered saline solution(pH = 7.0). The formal potential (E-01) was -0.160 V (vs SCE), which was almost independent of the scan rate. The number of electron transferred (n) was 1.021, suggesting about an electron transfer between the heme group of Hb and the electrode. The average apparent heterogeneous electron transfer rate constant (k(s)) obtained by fitting CV data for Hb on CNT-modified electrode was 0.0816 s(-1), greater than the value obtained from the same method for Hb with methylene blue as mediators. Hb-CNT-modified electrode showed a stable and significant catalytic activity for the electrochemical reduction of hydrogen peroxide, trichloroacetic acid and nitrobenzene.