Self-crosslinking of graphene oxide sheets by dehydration

Graphene oxide (GO) sheets have attracted increasingly high inter-est due to their relative ease of synthesis and water processability for a wide range of applications. Understanding how the sheets interact with each other is a crucial and foundational piece of knowl-edge guiding the production, processing, and use of GO in many applications. Here, we report that dehydration, such as by vacuum drying, triggers irreversible self-crosslinking of GO sheets and dras-tically alters their solution processability. Dehydrated GO films maintain structural integrity in water, and they can no longer redis-perse as single layers even after agitation. At the bilayer level, dehy-dration fixes the stacked GO sheets together and prevents them from dissociation after sonication. Spectroscopical studies support the formation of new ester bonds, suggesting a condensation-ester-ification reaction between GO sheets. This new insight about a fundamental property of GO sheets should have broad implications in how the material should be processed and used.