Direct Electron Transfer Of Glucose Oxidase Anode

The distance between the internal activity center FAD to outside surface of glucose oxidase enzyme is 11A, which is too long to transfer electron. Direct electronic transfer is sorpposed to be the most ideal resoltion of transforming electron from FAD to electrode for Gox fuel cell or sensor. It enhance the output power of biofuel cell and response of sensor,which can be significant for new energy battery.This paper focus on multi-walled carbon nanotubes modified enzyme electrode and phenothiazine polymer modified enzyme electrode, expecting realizing direct electron tranfer. Fisr, multi-walled carbon nanotubes modified enzyme electrode was detected in phosphate buffer solution and glucose solution;then, phenothiazine dye was voltalized polymer onto multi-walled carbon nanotubes modified enzyme electrode to enhance direct electron transfer. As the experiments indicate that multi-walled carbon nanotubes can be used to realize direct electron tranfer from FAD to electrode in phosphate buffered saline but not in glucose solution during glucose was oxidased. Furthermore metal impurities contained in multi-walled carbon nanotubes were discovered related to direct electron transfer of glucose oxidase immobilized onto the surface of multi-walled carbon nanotubes modified glassy carbon electrode. The trdox peaks disappear after carbon nanotubes were reflowed 24h in nitric acid and re-appear after a mount of metal impurities(such as Ni,NiO,Co,CoO,Fe,Fe2O3) were added into washed-carbon nanotubes, and 6.4% metal impurities contained in multi-walled carbon nanotubes infect mostly. When 20 mmol/L glucose was added into phosphate buffered saline every 50 s at-0.375 V, the current and the concentration of glucose between 0.25～1.75mmol/L is linear relationship.Phenothiazine polymer show only redox peak of polyer without the oxidase peak of glucose.They all indicate that direct electron transfer can not be realized during glucose was oxidased by these mathods.Not only the multi-walled carbon nanotubes modified enzyme electrode but also the phenothiazine polymer and multi-walled carbon nanotubes modified enzyme electrode can not realize direct electron transfer during glucose was oxidased.The phenothiazine dye need modified and electronegative, aggregated to a net structure conducting polymer for direct electron transfer.