Infrared Spectral Signatures of Surface-Fluorinated Graphene: A Molecular Dynamics Study

Fluorination of graphene and other carbon nanostructures is used extensively as a tool for tuning graphene's mechanical, electronic, and optical properties, and as an intermediate step in graphene functionalization. However, by penetrating through graphene surfaces, fluorine atoms create defects that deteriorate the desired properties. Using molecular dynamics simulation, we predict distinct infrared (IR) signatures that can be used to detect fluorination patterns and defects. We show that two strong peaks around 1000 and 1500 cm(-1) in the IR signal in the graphene plane identify fluorine chains. Defects involving a single fluorine atom exhibit a clear IR peak at 800 cm(-1) originating from the wagging motion of the F-C(sp3) bond. A pair of neighboring fluorines produces a unique peak at 1150 cm(-1) arising as a result of the stretching vibration of the C(sp3) C(sp3) bond hosting the fluorines. The reported results provide straightforward and efficient means for spectroscopic characterization of fluorinated graphene and related materials.