The chemical and structural analysis of graphene oxide with different degrees of oxidation
Graphene oxide (GO) with various degrees of oxidation was synthesized using a modified Hummers method. The formation of different types of oxygen containing functional groups in GO, and their influences on its structure were analyzed using X-ray diffraction (XRD), Fourier transform infra-red spectra, X-ray photoelectron spectra (XPS), zeta potential analysis and Raman spectroscopy. XRD studies showed a disruption of the graphitic AB stacking order during the increase in oxidation levels. XPS analysis revealed the formation of hydroxyl and carboxyl groups at lower oxidation levels and epoxide groups at higher oxidation levels. The influence of the oxidation degree on the properties of GO was evaluated by zeta potential analysis, which showed a linear increase in the zeta potential with increasing oxidation levels. Raman spectroscopy analysis revealed that increasing oxidation levels results in a transition from a crystalline to an amorphous structure. The electrochemical properties of GO is highly influenced by the variation in degree of oxidation. Our results suggest that the properties of GO can be tuned by varying the oxidation degree, which may pave the way to new developments in the GO-based applications.