Surface modification and physicochemical characterization of graphene oxide nano-composite sheets with ethaline as a green deep eutectic solvent

Functionalized graphene oxide nano-composite sheets have received recent attention for many important applications including energy harvesting and storage, conduction fibres and electronics. Different organic solvents have been used during the functionalization of graphene oxide nano-composite sheets; however, many conventional solvents present toxicity and environmental concerns. Deep eutectic solvents (DESs) have therefore been investigated as alternatives for the surface modification of carbon-based materials. This study investigates the use of Ethaline, a choline chloride-based deep eutectic solvent, for the surface modification of graphene oxide (GO). The synthesis and treatment were performed under relatively mild conditions, and the materials before and after treatment were characterized using FTIR spectroscopy, BET and BJH surface adsorption analysis, and field-emission scanning electron microscopy (FE-SEM) coupled with EDX and elemental mapping. The results show changes in the FTIR bands together with substantial changes in the measured textural properties and surface morphology after treatment. The presence and distribution of carbon, nitrogen, oxygen and chloride in the treated material are consistent with the presence of Ethaline-derived components on the GO surface. These findings are consistent with surface modification and interactions between Ethaline and oxygen-containing groups of GO; however, the available characterization does not by itself establish the exact bonding mechanism or confirm chemical reduction of GO. The Ethaline-treated GO therefore represents a promising modified carbon material, while further work is required to assess component-specific effects, solvent recovery, stability, possible release, and the oxidation state of the modified GO.