Realizing Ultralow Concentration Gelation of Graphene Oxide with Artificial Interfaces

Understanding the chemistry in the gelation (interfacial assembly) of graphene oxide (GO) is very essential for the practical uses of graphene-based materials. Herein, with the designed artificial interfaces due to the introduction of water-miscible isopropanol, the gelation of GO is achieved in water at an ultralow concentration (0.1 mg mL^-1 , the lowest ever-reported) with a solvothermal treatment. Intrinsically, with a lower intercalation energy, water shows much stronger attraction with GO than isopropanol, inducing a microphase separation in the miscible mixture of isopropanol and water. In the solvothermal process, the partially reduced GO sheets interact with each other along the water-isopropanol interface and assemble into interconnected frameworks. In general, the formation of the artificial interface results in locally concentrated GO in the water phase, which is the final driving force for the gelation at ultralow concentration. Thus, the threshold for the GO gelation concentration is dependent upon the water fraction in the mixture and water acts as the spacer to facilitate the gelation and final control of the resulting materials microstructure. This study enriches interface/gelation chemistry of GO and indicates a practical way for precise structural control and scale-up preparation of graphene-based materials.