Graphene Oxide Films Obtained by Vacuum Filtration: X-Ray Diffraction Evidence of Crystalline Reorganization

In this study, films of graphene oxide and chemically or thermally reduced graphene oxide were produced by a simple vacuum filtration method and submitted to a thorough characterization by X-ray diffraction (XRD), Raman and infrared spectroscopies, field-emission scanning electron microscopy, transmission electron microscopy, atomic force microscopy, confocal microscopy, and contact angle measurements. Graphene oxide (GO) was produced from graphite by the modified Hummers method and thereafter reduced with NaBH4 or by heating under argon in a tubular furnace. The films were produced from aqueous solutions by vacuum filtration on a cellulose membrane. Graphite presents two characteristic XRD peaks corresponding to d=0.34 nm and d=0.17 nm. After oxidation, only a peak at d=0.84 nm is found for powder GO, confirming the insertion of oxygen groups with an increase in the interplanar distance of graphene nanoplatelets. However, for GO films, other unexpected peaks are observed at d=0.63 nm, d=0.52 nm, and d=0.48 nm. After reduction, both chemical and thermal, the peak at 0.84 nm disappears, while those corresponding to interplanar distances of 0.63 nm, 0.52 nm, and 0.48 nm are still present. The other characterizations confirm the production and chemical composition of GO and reduced GO films. The results indicate the combination of crystalline regions with different interplanar distances, suggesting the ordering of graphene/graphene oxide intercalated sheets.