Determination of hydrogen peroxide is rapidly becoming of practical importance in the clinical and environmental fields. The electrodes modified with different electron transfer mediators and enzymes have been used as sensor or biosensors for hydrogen peroxide detection. In this research the electrochemical behavior of thionin incorporated on multi-walled carbon nanotubes (MWNTs) modified GC electrode is investigated by cyclic voltammetery (CV) and choronoamperometry. The results indicate that thionine can be strongly adsorbed on the surface of the MWNT modified electrode to form an approximate monolayer film with the average surface concentration (F ) of thionine is about 2x 1010 mol cm2. MWCNTs can greatly promote the redox of thionin, on which a pair of well-defined and nearly reversible CV peaks for thionin redox couple was obtained in wide pH range. The formal potential of thionin adsorbed on MWCNTs modified glassy carbon electrode shifted negatively with an increasing in pH values with a slope of 64 mV/pH in the range 2-10, which is close to the expected Nernstian value of 59 mV for a two-electron, two-proton process. The transfer coefficient (El was calculated that 0.38 ,and heterogeneous electron transfer rate constant was 35 s in pH 7, indicating greatly facilated in the electron transfer between thionin and MWNTs adsorbed on the electrode surface. The high efficiency of the thionine-MWCNTs modified glassy carbon electrode towards the catalytic electroreduction of oxygen and hydrogen peroxide has been observed. Potential application of thionine-MWCNTs modified glassy carbon electrode as biosensor to monitor glucose is proposed when glucose —oxidase was attached at electrode surface.
