Controlled derivatization of hydroxyl groups of graphene oxide in mild conditions

Abstract

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.

Strategies for the Controlled Covalent Double Functionalization of Graphene Oxide

“…The Boc‐monoprotected triethylene glycol (TEG) diamine 1 was mixed to a suspension of GO in DMF obtaining GO‐OE (OE stands for opening of epoxides) (Scheme ) . For the Williamson reaction, GO‐OE was mixed with the iodinated derivative 2 and K 2 CO 3 in DMF leading to GO‐OE‐W (W stands for Williamson reaction) . Potassium carbonate is commonly used to perform the Williamson reaction of phenol derivatives and it is mild enough to avoid reduction of GO .…”

Graphenic Materials for Biomedical Applications

“…Chemical modifications and the functionalization of GBMs are important methods for structural changes in GBM surface, which lead to an increase their solubility in biological systems and allow for tailoring of their interfacial and physicochemical characteristics, such as for the preparation of advanced functional GBMs [47,50]. There are two main groups of functionalization methods, namely, covalent and non-covalent functionalization.…”

“…However, the present oxygen-containing groups have high chemical reactivity. Therefore, it is difficult to control the functionalization process, since different reactions may occur simultaneously [50]. Generally, the process enhances solubility and the dispersion of Analytical methods, such as scanning and transmission electron microscopy (SEM and TEM), atomic force microscopy (AFM), infrared and/or Raman spectroscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry (ICP/MS), are the most useful tools for characterization [4,[38][39][40].…”

“…However, the present oxygen-containing groups have high chemical reactivity. Therefore, it is difficult to control the functionalization process, since different reactions may occur simultaneously [50]. Generally, the process enhances solubility and the dispersion of GBMs in different solvents, reduces aggregation, and also creates a gap between the conduction and valence bands, because the Fermi level is shifted either above or below the Dirac point [46,54].…”

Super tough graphene oxide reinforced polyetheretherketone for potential hard tissue repair applications

“…The benzene ring in PEEK is a carbon ring that consists of six sp 2 hybridized carbon atoms forming a plane hexagon, π electron is present in the perpendicular direction in the six-membered ring [52]. The angle between adjacent carbon atoms is 120° and the bond length is 1.4 Å.…”