Derivitization of Pristine Graphene with Well-Defined Chemical Functionalities

Abstract

Covalent functionalization of pristine graphene poses considerable challenges due to the lack of reactive functional groups. Herein, we report a simple and general method to covalently functionalize pristine graphene with well-defined chemical functionalities. It is a solution-based process where solvent-exfoliated graphene was treated with perfluorophenylazide (PFPA) by photochemical or thermal activation. Graphene with well-defined chemical functionalities was synthesized and the resulting materials were soluble in organic solvents or water depending on the nature of the functional group on PFPA. KeywordsGraphene; Azides; Covalent functionalization; Photochemistry Graphene, a material having a two-dimensional atomic layer of sp 2 carbon, has emerged as a nanoscale material with a wide range of unique properties. [1][2][3] In order to realize the many potential applications that graphene can offer, the availability of graphene with well-defined and controllable surface and interface properties is of critical importance. Despite the numerous studies on the properties and potentials of graphene, robust methods for producing chemically functionalized graphene are still lacking. 4,5 The most common method for the covalent functionalization of graphene employs graphene oxide (GO), 6 which is prepared by treating graphite particles with strong acids. 7 The oxidation process produces various oxygen-containing species, the nature and density of which are difficult to control.Covalent functionalization of pristine graphene poses considerable challenges due to its lack of reactive functional groups. Herein, we report a simple and general method for the covalent functionalization of pristine graphene. The approach is based on perfluorophenylazide (PFPA), 8,9 which upon photochemical or thermal activation, is converted to the highly reactive singlet perfluorophenylnitrene that can subsequently undergo C=C addition reactions with the sp 2 C network in graphene to form the aziridine adduct. We have confirmed the covalent bond formation between PFPA and graphene using X-ray photoelectron spectroscopy. 10,11 By controlling the functional group on the PFPA (Scheme 1), graphene with well-defined chemical functionalities can be prepared in a single step using a simple solution-based process.* To whom correspondence should be addressed. yanm@pdx.edu. PFPAs bearing alkyl (1), ethylene oxide (2), and perfluoroalkyl groups (3) (Scheme 1) were synthesized and used in this study (see Supporting Information for detailed synthesis and characterization of the compounds). These functional groups were chosen to impact the solubility and surface energy of the resulting graphene. Pristine graphene was prepared by exfoliating graphite in o-dichlorobenzene (DCB), a procedure that has been shown to produce graphene flakes in high yield. 12 Sonication of graphite in DCB followed by centrifugation gave a well-dispersed graphene solution, which was collected and used in the subsequent reactions. These graphene flakes consisted primarily of ...

Chemical functionalization of graphene oxide for improving mechanical and thermal properties of polyurethane composites

“…One feasible and effective strategy to promote the reinforcement of composites is through chemical functionalization of nanofillers [20][21][22]. Among chemical functionalization methods, grafting molecules and/or polymer chains onto the surface of graphene sheets was studied for many polymers [23][24][25].…”

Controlled Covalent Functionalization of Thermally Reduced Graphene Oxide To Generate Defined Bifunctional 2D Nanomaterials

“…The functionalization of graphene under ambient conditions by perfluoroazides as precursors of the highly reactive nitrenes has been explored to overcome this drawback 13. The mild reaction conditions and well‐defined functionality provide superior efficiency and simplicity compared to common methods for the functionalization of nitrenes 17, 18. In addition to efficiency and simplicity, a universal and affordable functionalization method should also involve readily available starting materials and provide reactive functional groups for flexible post‐modification.…”

Janus graphene from asymmetric two-dimensional chemistry

“…Physisorption of chemical species on graphene would provide a facile way to alter its electronic properties 12 , however, covalent chemical modification shows a great advantage in achieving permanent stabilisation for long-term usage 13 . Previous attempts towards fundamental research on covalent functionalisation of graphene mainly involved the development of new modification strategies (for example, hydrogenation [14][15][16][17] , fluorination [18][19][20] , chlorination 21,22 , diazotization [23][24][25][26][27] and other cycloaddition reactions [28][29][30][31] ), covalent addition of edge and defects 27,32 , fabrication of chemical superlattices 26,33 and quantum effects in graphene modification 17,34 . Of the various significant research activities on graphene chemistry that have been conducted, nearly no work to date has been focused on the asymmetric chemistry of this ideal 2D atomic crystal via covalently attaching different functional groups on its two faces simultaneously.…”