The elemental composition of GO was determined by using a home-built mass spectrometer with laser probe (LMS). The diameter of the crater for single laser impulse was 0.42-0.48 mm, and the depth was 1 ím. IR spectra were recorded using a Perkin-Elmer 325 instrument. XPS spectra were obtained using a Kratos Series 800 spectrometer with hî)1253.6 eV and an analyzing window of 4 6 mm2. The accuracy of the measured core level binding energies (Eb) was 0.1 eV. For LMS, IR, and XPS experiments, GO samples were prepared as films by drying a droplet of the sol in air at ambient temperature. X-ray powder diffraction (XRD) patterns were recorded with a DRON-1 instrument using Cu KR radiation. Prior to the
measurement, the GO sample was dried in a vacuum over P2O5
for 24 h.