Self-assembled graphene monoliths: properties, structures and their pH-dependent self-assembly behavior

Fabricating self-supporting, three dimensional graphene macroscopic structures from two dimensional graphene sheets by self-assembly has been an intriguing subject in exploring the performance of graphene structures for practical advanced applications. Monolithic graphene hydrogels (GHs) with quite good mechanical properties and excellent resilience were self-assembled from graphene oxide (GO) dispersions under hydrothermal conditions by changing the pH value. The structure-property relationships and the self-assembly behavior of GHs were investigated. It was found that the formation of GHs was pH-dependent. The charge state of carboxyl groups on the graphene was the key factor that influenced the balance of attraction and repulsion interactions of the GO and consequently determined the self-assembly behavior. Both the graphene molecular structure and colloidal interactions were correlated with the unique self-assembly behavior, which can be used to design graphene arrangements with various structures, functions and mechanical properties. This method is superior to the conventional method that adjusts the concentration and reduction time of the GO dispersion.