Controlled derivatization of hydroxyl groups of graphene oxide in mild conditions

Graphene oxide (GO) is constituted of various oxygen-containing functionalities, primarily epoxides and hydroxyl groups on the basal plane, with a very low amount of carbonyl, quinone, carboxylic acid, phenol, and lactone functions at the edges. The high chemical reactivity of these oxygenated groups makes functionalization difficult to control as different reactions can occur concomitantly. In this study we have investigated the reactivity of GO towards orthogonal reactions to selectively functionalize the hydroxyl groups, which are present in a high amount. We explored both the esterification and the Williamson reaction. Our strategies present the main advantage to occur in mild conditions, thus preserving the intrinsic properties of GO, whereas most reactions reported in literature require relatively harsh conditions, leading to (partial) reduction, and/or are not chemoselective. We have also extended our study to the ketones and examined their derivatization by the Wittig reaction. This work has allowed developing two facile methods for the covalent derivatization of the hydroxyl groups in mild conditions, while GO was not reactive towards the Wittig reaction, probably due to the low amount of ketones. Overall, this work leads to a better understanding of the reactivity of GO for controlled derivatization. This opens promising perspectives for multi-functionalization of GO in order to design graphene-based nanomaterials endowed of multiple properties.