Local ordering of dimethylformamide around graphene oxide

Neutron scattering with isotopic substitution and high-energy X-ray scattering have been used to evaluate the ordering of the polar solvent, dimethylformamide (DMF), around the surface of dispersed graphene oxide (GO) nanosheets. Empirical potential structural refinement (EPSR) has been used to model the interaction of this technically important material with the solvent. In reciprocal space, both neutron and X-ray scattering patterns show significant differences between the GO solution and the solvent. In real space, these differences in structure persist to at least 5 Å from the GO surface, and some changes to the solvent structure are discernible to 10 Å. EPSR modelling of the solvent interaction was undertaken using a supercell generated from the GO surface, extended in the z-direction and filled with DMF molecules. Two different GO surfaces were used: one with a random distribution of epoxide and hydroxide functional groups and one in which the arrangement was semi-ordered. There is no apparent influence of the arrangement of the functional groups on the modelled structure. The z-dependent distribution functions indicate that the oxygen atoms within the DMF molecule are closest to the nanosheet surface, implying that the solvent ordering reflects a small positive charge to the GO surface. This article is part of the theme issue 'Surfaces, interfaces and heterogeneous catalysis'.