Theoretical calculations of electron energy-loss near-edge structure (ELNES) and x-ray absorption near-edge structure (XANES) of selected wide-gap materials including TiO 2 , AlN, GaN, InN, ZnO, and their polymorphs are performed using a first-principles method. Calculations of 39 K and L 3 ͑L 2,3 ͒ edges are made using large supercells containing 72 to 128 atoms. A core hole is included in the final state, and the matrix elements of the electric dipole transition between the ground state and the final state are computed. Structures of some metastable crystals are optimized by a plane-wave basis pseudopotential method. Spectral differences in ELNES and XANES among polymorphs are quantitatively reproduced in this way. The origin of the spectral differences is pursued from the viewpoint of chemical bondings. Crystallographic orientation dependence of ELNES and XANES is also examined both by experiment and theory. The dependence is found to be much larger in K edges than that in L 3 ͑L 2,3 ͒ edges.

Formation energies of neutral and charged oxygen vacancies in MgO, ZnO, Al 2 O 3 , In 2 O 3 and SnO 2 have been calculated by a first principles plane-wave pseudopotential method. Two kinds of polymorphs, i.e., an ordinary phase and a high-pressure or an hypothetical negative pressure phase, have been chosen in order to see the effects of crystal structure. Supercells composed of 54 to 96 atoms were employed, and structural relaxation around the vacancy within second nearest neighbor distances was taken into account. Defect levels were obtained from the difference in total energies of the neutral and charged supercells that contain a vacancy. Ionization energies of the vacancy were calculated as the difference in the bottom of the conduction band and the defect levels. They are found to be proportional to band-gaps with a factor of approximately 0.5, which are prohibitively large for the n-type conduction.

Graphite oxide (GO) and its constituent layers (i.e., graphene oxide) display a broad range of functional groups and, as such, continue to attract significant attention for use in numerous applications. GO is commonly prepared using the "Hummers method" or a variant thereof where graphite is treated with KMnO4 and various additives in H2SO4. Despite its omnipresence, the underlying chemistry of such oxidation reactions is not well understood and typically afford results that are irreproducible and, in some cases, unsafe. To overcome these limitations, the oxidation of graphite under Hummers-type conditions was monitored over time using in situ X-ray diffraction (XRD) and in situ X-ray absorption near edge structure (XANES) analyses with synchrotron radiation. In conjunction with other atomic absorption spectroscopy, UV-Vis spectroscopy and elemental analysis measurements, the underlying mechanism of the oxidation reaction was elucidated and the reaction conditions were optimized. Ultimately, methodology for reproducibly preparing GO on large scales using only graphite, H2SO4, and KMnO4 was developed and successfully adapted for use in continuous flow systems. Although graphite oxide (GO) has been known for more than 150 years, its individual layers, often termed graphene oxide, have recently gained extraordinary attention for potential use in a broad range of applications. 1-8 The attraction is due, in part, to the material's high chemical potential, which stems from the myriad functional groups decorated on its surface. GO is typically prepared by treating graphite with a strong oxidizer followed by exfoliation, and many variations

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