Chemical Makeup and Hydrophilic Behavior of Graphene Oxide Nanoribbons after Low-Temperature Fluorination

Here we investigated the fluorination of graphene oxide nanoribbons (GONRs) using H₂ and F₂ gases at low temperature, below 200°C, with the purpose of elucidating their structure and predicting a fluorination mechanism. The importance of this study is the understanding of how fluorine functional groups are incorporated in complex structures, such as GONRs, as a function of temperature. The insight provided herein can potentially help engineer application-oriented materials for several research and industrial sectors. Direct ¹³C pulse magic angle spinning (MAS) nuclear magnetic resonance (NMR) confirmed the presence of epoxy, hydroxyl, ester and ketone carbonyl, tertiary alkyl fluorides, as well as graphitic sp²-hybridized carbon. Moreover, ¹⁹F-¹³C cross-polarization MAS NMR with ¹H and ¹⁹F decoupling confirmed the presence of secondary alkyl fluoride (CF₂) groups in the fluorinated graphene oxide nanoribbon (FGONR) structures fluorinated above 50°C. First-principles density functional theory calculations gained insight into the atomic arrangement of the most dominant chemical groups. The fluorinated GONRs present atomic fluorine percentages in the range of 6-35. Interestingly, the FGONRs synthesized up to 100°C, with 6-19% of atomic fluorine, exhibit colloidal similar stability in aqueous environments when compared to GONRs. This colloidal stability is important because it is not common for materials with up to 19% fluorine to have a high degree of hydrophilicity.