Comparative Studies on Electrocatalytic Activities of Electrochemically and Chemically Reduced Graphene Oxide Noncovalently Modified with Tetrathiafulvalene for Glucose Biosensing

Graphene, a two-dimensional nanomaterial, constitutes a new carbon comprising layers of carbon atoms arranged in six-membered rings [1]. It has attracted intense attention due to its unique electronic, thermal and mechanical properties. Graphene possesses a high ratio of surface area, a good conductivity and mechanical properties comparable with (or even better) than carbon nanotubes. Owing to its inert chemical property and highly hydrophobic surface, graphene is considered as an ideal support for redox mediators via π-π stacking interactions [2].

Many chemical methods have been developed for the preparation of graphene, such as epitaxial growth on silicon carbide and chemical reduction of graphene oxide (GO). As the oxidized form of graphene, GO could be easily obtained via a simple chemical processing of graphite. GO contains a range of reactive oxygen containing functional groups, which endows it water solubility and possibility for further biological applications. However, excess of oxygen may break the sp²structure of graphene, as a result deteriorate its conductivity.

In the present work, we have exploited unique characteristics of reduced graphene oxide (GO) (obtained by electrochemical treatments (ERGO) and chemical treatments with hydrazine (CRGO)) to construct the efficient anodic glucose oxidase based bioelectrocatalytic systems of potential utility for biofuel cells and biosensors. A noncovalent modification method of ERGO and CRGO conducting support with a mediator, tetrathiafulvalene (TTF), and the bioelectrocatalytic activities of ERGO-TTF and CRGO-TTF composites with immobilized glucose oxidase toward the oxidation of glucose have been demonstrated.

The presence of TTF is expected to facilitate an effective flow of electrons from the redox centers of glucose oxidase to the glassy carbon electrode [3]. TTF and its derivatives constitute a group of redox molecules that were successfully used as redox mediators in enzyme electrochemistry. Due to the existence of hydrophilic cation-exchange domains within Nafion deposits on graphene, capable of retaining soluble TTF⁺, the overall stability of the our bioelectrocatalytic film has increased. As before, reduced graphene oxide have supported transport of electrons within the bio-electrocatalytic film. On the whole, combination of TTF-graphene and glucose oxidase within the film (deposited onto glassy carbon electrode substrate) has produced a catalytic system capable of effective oxidation of glucose in 0.1 M phosphate buffer (pH=8.0). The formation, morphology, and electrocatalytic reactivity of our bioelectrocatalytic films containing of TTF-modified graphene were examined using cyclic voltammetry, rotating disk voltammetry, FTIR spectroscopy, transmission and scanning electrochemical microscopy.

References:

[1] A. K. Geim, K. S. Novoselov, Nat. Mater., 6 (2007) 183.

[2] S. Stankovich, D. A. Dikin, G. H. B. Dommett, K. M. Kohlhaas, E. J. Zimney, E. A. Stach, R. D. Piner, S. T. Nguyen, R. S. Ruoff, Nature, 442 (2006) 282.

[3] B. Kowalewska, P. J. Kulesza, Electroanalysis, 21 (2009) 351.