Molecular insights into the dispersion stability of graphene oxide in mixed solvents: Theoretical simulations and experimental verification

Improving the dispersion stability of graphene oxide (GO) suspensions is of great importance in many potential applications of GO, such as GO-based laminated membranes used for separation, printable electronics, and aqueous liquid crystals. Molecular dynamics (MD) simulations and quantum chemistry (QC) calculations along with complementary experiments were performed to study the dispersion stability of GO in the mixtures of water and polar organic solvents (dimethyl sulfoxide (DMSO), ethanol, and acetone). GO exhibits better dispersion stability in a solvent mixture than in pure water. The MD simulations uncover the underlying mechanism that mixed solvent layers are formed steadily on the surface of GO sheets and screen the interactions between them. QC calculations reveal that both DMSO and water form hydrogen bonds with the oxidized regions of GO. X-ray diffraction experiments confirm that the GO sheets are intercalated by DMSO and water molecules. Furthermore, the optimal ratio of the organic solvent to water is determined to achieve the best dispersion stability of GO through MD simulations. And such ratio is also verified by ultraviolet absorption spectral experiments. Thus, our findings provide a facile method to prepare GO suspensions with high dispersion stability.