US EPA

3860365 

Journal Article 

Ab Initio Study of the Vibrational Signatures for the Covalent Functionalization of Graphene 

Abuelela, AM; Farag, RS; Mohamed, TA; Prezhdo, OV 

2013 

Yes 

Journal of Physical Chemistry C
ISSN: 1932-7447
EISSN: 1932-7455 

117 

38 

19489-19498 

10.1021/jp405819b 

WOS:000330162500027 

The present work reports a theoretical study of the infrared (IR) and Raman spectra of chemical structures that are useful for the description of the surface chemistry of carbon materials. There has been a recent demand in materials science and surface functionalization to couple organic entities with sp(2) carbon nanostructures. A slab model of single-layer graphene with its edges terminated by hydrogen atoms containing 82 atoms per unit cell was used in our study. The organic coupling agent, perfluorophenylazide (PFPA), was used according to a recent experiment [Liu, L.-H.; et al.et al. Nano Lett. 2010, 10, 3754]. Two ab initio DFT functionals, B3LYP and omega B97XD, were adopted to calculate the IR and Raman spectra. The computational approach was tested by comparing the calculated IR spectra to those obtained experimentally for various reference compounds. The vibrational features were probed before and after the reaction, and the changes, arising in both PFPA and graphene spectra as a result of the coupling, were identified. B3LYP gave better agreement with the experimental results than omega B97XD for frequency calculations. The stretch modes of the azide group, as well as the fingerprint feature of the CF2 axial stretching vibrations, were used to probe the reaction, and the results were in good agreement with the experimental observations. Special attention was paid to the elucidation of the origins of the G-, D-, and D'-bands in the Raman spectra of graphene. Finally, the predicted assignments were employed to interpret the IR and Raman spectra obtained experimentally for functionalized graphenes.