Efficient synthesis of amine-functionalized graphene oxide by ultrasound-assisted reactions and density functional theory mechanistic insight

Herein described is a facile preparation protocol by which amino-alcohol derivatives of graphene oxide (GO) can be conveniently synthesized in high yield and short time by an ultrasound treatment of ethanol-graphite-oxide suspensions and amines. Linear primary amines of different chain length rapidly react with graphite oxides prepared from powder and flakes, leading to the formation of GO amino-alcohol derivatives. Characterization of the amine-modified materials by XRD, TGA, FTIR, and Raman spectroscopy demonstrates the proposed derivatization; the findings are corroborated by SEM and TEM observations. Additionally, quantum-chemical investigations shed additional light on the reaction, suggesting an alcohol-accelerated S N 2 mechanism where the initial step, the simultaneous formation of a C–N bond (GO-amine) and rupture of an epoxide bond in GO, is rate-determining. Energy barriers lower than 8 kcal/mol are estimated, which can be overcome with the energy supplied by the sonotrode tip (ca. 2 kcal) and the use of ethanol to facilitate it.