Evolution of the Raman Spectrum with the Chemical Composition of Graphene Oxide

Raman spectra of graphene oxides (GOs) with different chemical compositions and synthesized by oxidation of distinct starting materials were analyzed to relate the spectral features to structural properties. The chemical compositions of different graphene oxides were determined by X-ray photoelectron spectroscopy (XPS), and nanoplatelets were characterized by zeta potential (ζ) and dynamic light scattering (DLS) measurements. The results indicated that the chemical composition, size, and superficial charge of the nanoplatelets depend on the starting material. We found five reported bands (D, D′, G, D″, and D*) in the first-order Raman spectrum and three bands (2D, D + D′, and 2D′) in the second-order Raman spectrum that successfully interpret the Raman spectra between 1000 and 3500 cm–1. Analysis of the bands allowed linear correlations to be found between the maximum positions of the 2D and D + D′ bands and between the relative intensities of the D and G bands (ID/IG) and the Csp2 percentage. Moreover, our results demonstrate that the relative intensities of the D′ and D bands are in excellent agreement with the theoretical correlations and allow the type of defects produced during oxidation, namely, vacancies or sp3 hybridation, to be related to the size of the graphene oxide sheets.