Hemin molecules were immobilized onto chemically converted graphene (CCG) sheets through it-it stacking interaction to form a CCG-hemin composite. The composite modified electrode exhibited much higher electrochemical stability and stronger catalytic activity than those of hemin modified electrode. The potentials of dioxygen (O(2)) and hydrogen peroxide (H(2)O(2)) reduction reactions at CCG-hemin electrode were measured to be about 0.16 and 0.14 V higher than those at hemin electrode, respectively. Thus, this composite can be used for the fabrication of high-performance electrochemical sensors of O(2) and H(2)O(2). (C) 2011 Elsevier B.V. All rights reserved.