Synthesis of graphene oxide sheets with controlled sizes from sieved graphite flakes

Graphene oxide (GO) sheets with desired sizes and narrow size distribution were synthesized via a modified Hummers method by using sieved graphite flakes as the starting materials. This method outweighs previous post-synthesis fractionation methods in efficiency and scalability; thus it is more promising for large-scale synthesis of size-controlled GO. The as-prepared GO suspensions exhibited size-dependent liquid crystal behavior. The importance of hydrolysis step on exfoliation and preserving the sizes of GO sheets, and the removal of their sulfate species was also discussed. (C) 2016 Elsevier Ltd. All rights reserved.