Electrochemistry and Electrocatalysis of a Nafion/Nano‐CaCO3/Hb Film Modified Carbon Ionic Liquid Electrode Using BMIMPF6 as Binder

In this paper a room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) was used as binder for the construction of carbon ionic liquid electrode (CILE) and a new electrochemical biosensor was developed for determination of H2O2 by immobilization of hemoglobin (Hb) in the composite film of Nafion/nano-CaCO3 on the surface of CILE. The Hb modified electrode showed a pair of well-defined, quasi-reversible redox peaks with Epa and Epc as −0.265 V and −0.470 V (vs. SCE). The formal potential (E°′) was got by the midpoint of Epa and Epc as −0.368 V, which was the characteristic of Hb Fe(III)/Fe(II) redox couples. The peak to peak separation was 205 mV in pH 7.0 Britton–Robinson (B–R) buffer solution at the scan rate of 100 mV/s. The direct electrochemistry of Hb in the film was carefully investigated and the electrochemical parameters of Hb on the modified electrode were calculated as α=0.487 and ks=0.128 s−1. The Nafion/nano-CaCO3/Hb film electrode showed good electrocatalysis to the reduction of H2O2 in the linear range from 8.0 to 240.0 μmol/L and the detection limit as 5.0 μmol/L (3σ). The apparent Michaelis–Menten constant (KMapp) was estimated to be 65.7 μmol/L. UV-vis absorption spectroscopy and FT-IR spectroscopy showed that Hb in the Nafion/nano-CaCO3 composite film could retain its native structure.