Graphene oxide in aqueous and nonaqueous media: Dispersion behaviour and solution chemistry

Graphene oxide (GO) is a unique two-dimensional (2D) material with interesting physical/chemical properties. GO can be considered as a 2D amphiphilic conjugated polymer, consisting of hydrophilic oxygenated groups and hydrophobic conjugated graphitic domains. The diverse chemical groups endow GO with high chemical activity to react with other molecules and form new species with graphitic framework. In addition, the amphiphilic properties of GO sheets provide them the abilities to self-assemble into three-dimensional (3D) structure or reduced GO (rGO) gels with porous microstructures. The precondition of these promising properties of GO is its excellent solution-like dispersibility in aqueous or nonaqueous media. These liquid media facilitate the exfoliation of GO into single-layer sheets and provide the exfoliated GO sheets with specific chemical environment for functionalization and/or processing. Therefore, it is essential to understand the solution-based chemical behaviour of GO, which is important for better application of GO. In this review, we outline the solution-based chemistry of GO mainly in terms of molecular structure, dispersibility in solvents, solution properties and related processing of GO sheets. This review aims to systematically present physical/chemical behaviours of GO in solvents including aqueous and nonaqueous solvents, which is helpful for better understanding and application of GO materials. (C) 2019 Elsevier Ltd. All rights reserved.