Electrocatalytic reduction of H2O2 and oxygen on the surface of thionin incorporated onto MWCNTs modified glassy carbon electrode:: Application to glucose detection

A new H2O2 enzymeless sensor has been fabricated by incorporation of thionin onto multiwall carbon nanotubes (MWCNTs) modified glassy carbon electrode. First 50 mu L of acetone solution containing dispersed MWCNTs was pipetted onto the surface of GC electrode, then, after solvent evaporations, the MWCNTs modified GC electrode was immersed into an aqueous solution of thionin (electroless deposition) for a short period of time < 5 - 50 s. The adsorbed thin film of thionin was found to facilitate the reduction of hydrogen peroxide in the absence of peroxidase enzyme. Also the modified electrode shows excellent catalytic activity for oxygen reduction at reduced overpotential. The rotating modified electrode shows excellent analytical performance for amperometric determination of hydrogen peroxide, at reduced overpotentials. Typical calibration at - 0.3 V vs. reference electrode, Ag/AgCl/3 M KCI, shows a detection limit of 0.38 mu M, a sensitivity of 11.5 nA/mu M and a liner range from 20 mu M to 3.0 mM of hydrogen peroxide. The glucose biosensor was fabricated by covering a thin film of sol- gel composite containing glucose oxides on the surface of thionin/MWCNTs modified GC electrode. The biosensor can be used successfully for selective detection of glucose based on the decreasing of cathodic peak current of oxygen. The detection limit, sensitivity and liner calibration rang were 1 mu M, 18.3 mu A/mM and 10 mu M - 6.0 mM, respectively. In addition biosensor can reach 90% of steady currents in about 3.0 s and interference effect of the electroactive existing species (ascorbic acid- uric acid and acetaminophen) is eliminated. The usefulness of biosensor for direct glucose quantification in human blood serum matrix is also discussed. This sensor can be used as an amperometric detector for monitoring oxidase based biosensors.