In this research a novel osmium complex was used as electrocatalyst for electroreduction of oxygen and H2O2 in physiological pH solutions. Electroless deposition at a short period of time (60 s), was used for strong and irreversible adsorption of 1,4,8,12-tetraazacyclotetradecane osmium(III) chloride (Os(III)LCl2) ClO4 onto single-walled carbon nanotubes (SWCNTs) modified GC electrode. The modified electrode shows a pair of well defined and reversible redox couple, Os(IV)/Os(III) at wide pH range (1 – 8). The glucose biosensor was fabricated by covering a thin film of glucose oxidase onto CNTs/Os-complex modified electrode. The biosensor can be used successfully for selective detection of glucose based on the decreasing of cathodic peak current of oxygen. The fabricated biosensor shows high sensitivity, 826.3 nA mM1cm2, low detection limit, 56 nM, fast response time <3 s and wide calibration range 1.0 mM– 1.0 mM. The biosensor has been successfully applied to determination of glucose in human plasma. Because of relative low applied potential, the interference from electroactive existing species was minimized, which improved the selectivity of the biosensor. The apparent Michaelis-Menten constant of GOx on the nanocomposite, 0.91 mM, exhibits excellent bioelectrocatalytic activity of immobilized enzyme toward glucose oxidation. Excellent electrochemical reversibility, high stability, technically simple and possibility of preparation at short period of time are of great advantages of this glucose biosensor.
