Surface Energy Engineering in the Solvothermal Deoxidation of Graphene Oxide



A route to achieving high yields of monodisperse, deeply deoxidized graphene oxide (GO) in solution is presented. It overcomes many of the problems of dispersibility and inefficient reduction of GO in solvothermal deoxidation that are usually observed, despite the previous use of strong reducing agents (e.g. Fe2+, S or hydrazine). It is shown that the incomplete deoxidation is most likely due to agglomeration/self-assembly of partially reduced GO, which also creates poor dispersibility. GO deoxidation is found to be highly sensitive to the solvent surface energy and, through experiments and empirical calculations, tuning the solvent surface energy to around 85.6 mJ/m2 (at 100 °C) leads to fully deoxidized GO. These calculations also allow appropriate solvent surface energies to be calculated for other temperatures for deep deoxidation of GO. This approach makes solvothermal deoxidation of GO a potential route to large scale, economic production of highly disperse monolayered graphene.