Graphene Oxide Sheets in Solvents: To Crumple or Not To Crumple?

Some earlier studies suggested that graphene oxide (GO) sheets adopt a crumpled configuration in water, similar to the shape of a paper ball, which turns into an even more compact, collapsed form upon addition of a poor solvent due to enhanced intrasheet affinity. Although those results have been debated in studies concerning membrane configurations, they are now often used to justify the existence of folds and wrinkles in solution-processed GO-based structures. This has led to a misconception that wrinkled and crumpled features may be intrinsic to solution processing and unavoidable. Here, we connect this problem to experimental observations of the liquid crystallinity of GO dispersions, which clearly show that the sheets are neither crumpled nor collapsed, with or without poor solvent. The sheets can simply fold flat or restack to hide their surfaces from poor solvent, without incurring the energetic cost of severe deformations to crumple.