Direct electron transfer and electrocatalysis of horseradish peroxidase immobilized in gemini surfactant - Ionic liquid composite film on glassy carbon electrode

A novel composite material comprised of gemini surfactant (i.e. dodecyl-alpha,omega-bis (dimethylcetylammonium bromide), C-16-C-12-C-16) and hydrophobic room temperature ionic liquid (i.e. 1-octyl-3-methylimidazolium hexafluorophate, OMIMPF6) has been fabricated. This composite material suits for the immobilization of horseradish peroxides (HRP). The ultraviolet-visible spectra and reflectance absorption infrared spectra of the HRP immobilized in the C-16-C-12-C-16-OMIMPF6 material are almost the same as those of native HRP. When it is coated on a glassy carbon (GC) electrode, the resulting electrode C-16-C-12-C-16-OMIMPF6-HRP/GC exhibits a pair of well-defined, stable and reversible voltammetric peaks in 0.10 M pH 7 phosphate buffer solutions. When the hydrophobic action of ionic liquid and gemini surfactant used increases, more immobilized HRP can undergo electrochemical reaction and the voltammetric peaks become larger. In addition, the C-16-C-12-C-16-OMIMPF6-HRP/GC electrode shows good catalytic response to dissolved oxygen and H2O2. The cathodic peak current of the electrode is linear to H2O2 concentration in the range of 5.82 mu M to 388 mu M. The apparent Michaelis-Menten constant is estimated to be 0.159 mM. The electrode has good stability and reproducibility. Hence, the composite material has potential applications in fabricating biosensors and bioelectronics. (C) 2007 Elsevier B.V. All rights reserved.