Self-crosslinking of graphene oxide sheets by dehydration

•GO sheets can covalently self-crosslink upon dehydration •Dehydration triggers esterification between neighboring sheets •Self-crosslinking greatly alters the processability of GO materials Graphene oxide (GO) sheets have attracted increasingly high interest 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 knowledge 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 drastically alters their solution processability. Dehydrated GO films maintain structural integrity in water, and they can no longer redisperse as single layers even after agitation. At the bilayer level, dehydration 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-esterification 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. Graphene oxide (GO) sheets have attracted increasingly high interest 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 knowledge 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 drastically alters their solution processability. Dehydrated GO films maintain structural integrity in water, and they can no longer redisperse as single layers even after agitation. At the bilayer level, dehydration 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-esterification 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.