Quantum chemical investigation of epoxide and ether groups in graphene oxide and their vibrational spectra

Abstract

We present a detailed analysis of the factors influencing the formation of epoxide and ether groups in graphene nanoflakes using conventional density functional theory (DFT), the density-functional tight-binding (DFTB) method, π-Hückel theory, and graph theoretical invariants. The relative thermodynamic stability associated with the chemisorption of oxygen atoms at various positions on hexagonal graphene flakes (HGFs) of D(6h)-symmetry is determined by two factors - viz. the disruption of the π-conjugation of the HGF and the geometrical deformation of the HGF structure. The thermodynamically most stable structure is achieved when the former factor is minimized, and the latter factor is simultaneously maximized. Infrared (IR) spectra computed using DFT and DFTB reveal a close correlation between the relative thermodynamic stabilities of the oxidized HGF structures and their IR spectral activities. The most stable oxidized structures exhibit significant IR activity between 600 and 1800 cm(-1), whereas less stable oxidized structures exhibit little to no activity in this region. In contrast, Raman spectra are found to be less informative in this respect.

Combined Effects of Functional Groups, Lattice Defects, and Edges in the Infrared Spectra of Graphene Oxide

“…Models of the structure of graphene oxide based on density functional theory (DFT) 6,9,[30][31][32][33][34][35][36][37][38][39][40] have been used to generate tables of functional group IR absorption band assignments for graphene oxide and its derivatives (see Table S1 and S2 in the Supporting Information (SI)).…”

Exploration of the Binding Properties of the Azo Dye Pollutants with Nitrogen‐Doped Graphene Oxide by Computational Modeling for Wastewater Treatment Improvement

“…The structure of NGO was created manually, therefore, the mentioned structure was optimized with the B3LYP/6–31G(d) level of theory (Figure ). The B3LYP method is a well–known approach for the optimizing the substituted graphene structures ,. As it is clear from Figure , the final optimized structure is not flat and the nitrogen– and oxygen‐containing functional groups altered the final structure from the flat structure of graphene to a twisted one.…”

Polarised infrared microspectroscopy of edge-oriented graphene oxide papers

“…This observation is consistent with the grazing/normal incidence (polarised) data of Mattson et al [21] where the narrow 1425 cm -1 band was much stronger. The absorbance around 1425 cm -1 has generally been assigned to edge carboxyls [21,26,29,33,34] but in several cases specifically the O-H deformation mode [26,33] and in others the C-O stretch [29]. The confusion here is understandable as the narrow band is near the peak of the broader band and a natural choice for assigning the global peak position in that region.…”