High quality, low oxygen content and biocompatible graphene nanosheets obtained by anodic exfoliation of different graphite types

Anodic exfoliation of graphite has emerged as an attractive method to access graphene nanosheets in large quantities, but oxidation reactions associated to this process compromise the structural quality of the resulting materials. Here, we demonstrate that the type of starting graphite material impacts the oxygen and defect content of anodically exfoliated graphenes obtained thereof. We investigated highly oriented pyrolytic graphite (HOPG) as well as graphite foil, flakes and powder as electrode in the anodic process. Importantly, materials with low levels of oxidation and disorder (similar to those typically achieved with cathodic exfoliation approaches) could be attained through proper choice of the graphite electrode. Specifically, using graphite foil afforded nanosheets of higher quality than that of HOPG-derived nanosheets. This discrepancy was interpreted to arise from the structural peculiarities of the former, where the presence of folds, voids and wrinkles would make its exfoliation process to be less reliant on oxidation reactions. Furthermore, cell viability tests carried out with murine fibroblasts on thin graphene films suggested that the anodically exfoliated graphenes investigated here (possessing low or high oxidation levels) are highly biocompatible. Overall, control upon the extent of oxidation and disorder should expand the scope of anodically exfoliated graphenes in prospective applications. (C) 2015 Elsevier Ltd. All rights reserved.