Characteristics and microstructure of aqueous colloidal dispersions of graphite oxide

A highly oxidized graphite oxide was synthesized from natural graphite powder by oxidation with KMnO4 in concentrated H2SO4 followed by hydrolysis, washing and centrifugation. Concentrated gel-like colloidal dispersions were obtained. The corresponding filtrates, supernatants, GO dispersions, and solid GO films obtained from them, were investigated by various chemical analyses, small angle X-ray scattering, X-ray diffraction, light scattering (LS), Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, 13C Nuclear Magnetic Resonance and Thermo-Gravimetric Analysis. The spectroscopic analysis shows besides the common peaks assigned to water molecules, hydroxyl and carboxyl groups, elimination of CC bonds due to strong oxidation and presence of bands assigned to sulfate. Data of Gas Chromatography/Mass Spectrometry experiments confirm the presence in GO of water and an abundance of carboxyl groups. Scattering measurements confirm that the structure of the GO colloids consists of plate-like objects, mostly containing only a few layers, with a small population of thicker aggregates. SEM images of cross sections of dried GO film, obtained by freeze fracture, demonstrate that a continuous film-like structure was successfully achieved by elimination of water localized within exfoliated GO particles in the swelled GO aqueous colloidal dispersions.