Optimization of the size and yield of graphene oxide sheets in the exfoliation step

In this paper we demonstrate that the yield and size of the graphene oxide sheets (GO) obtained by sonication of graphite oxide (GrO) can be optimized not only by selecting the appropriate exfoliation conditions but also as a function of the crystalline structure of the parent graphite. A larger crystal size in the parent graphite favors GrO exfoliation and yields larger sheets in shorter sonication times, independently of the oxygen content of the GrO. A maximum yield of GO is obtained in all cases, after which no further improvement is achieved and the size of the sheets decreases. (C) 2013 Elsevier Ltd. All rights reserved.