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, C-13 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 C=C 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. (C) 2004 Elsevier Ltd. All rights reserved.