Direct electrochemistry of cytochrome c immobilized on a graphene oxide-carbon nanotube composite for picomolar detection of hydrogen peroxide

We describe the fabrication of an amperometric biosensor based on cytochrome c (Cyt c) immobilized graphene oxide-multiwalled carbon nanotube (GO-MWCNT) composite on a nano Au modified glassy carbon electrode for trace level detection of H2O2. Morphology and surface characterization of the nanocomposite reveal the successful formation of a highly conducting MWCNT network on the GO surface. Electrochemical impedance studies indicate a lower charge transfer resistance compared to the bare electrode. Cyclic voltammetry studies clearly demonstrate an enhanced direct electrochemistry of Cyt c with a high electron transfer rate constant (k s) value of 3.4 s-1. An amperometric H2O 2 biosensor has been fabricated with an excellent current sensitivity of 0.533 μA pM-1 cm-2 and a very low detection limit of 27.7 pM. The fabricated sensor shows exceptional selectivity to H 2O2 in the presence of a high concentration of some likely interferents. Moreover, the sensor exhibits high stability with appreciable repeatability and reproducibility. © 2014 the Partner Organisations.