Titanium K-edge X-ray absorption near-edge structure (XANES) spectroscopy is used to examine the local Ti environments in the sol, gel, and xerogels of titanium oxide prepared by a sol-gel method. The xerogels were prepared by heat treatment at 200, 300, 400, 500, and 600 degrees C (denoted xero-200, xero-300, xero-400, xero-500, and xero-600), and the xerogels were doped with Fe(II), Ni(II), and Cu(II) ions (xero-Fe, xero-Ni, and xero-Cu). The local structures of the samples are compared using the pre- and post-edge features of the XANES spectra. Further analysis of the pre-edge features using Gaussian functions provides the energy and height of each peak, and the intensity ratios between peaks. Based on the resulting data, the samples can be classified into three groups: a weak Ti-Ti interaction group, an anatase-like structure group, and an anatase group. The sol, gel, xerogel, and xero-Ni are in the weak Ti-Ti interaction group, and the xero-200, xero-Fe, and xero-Cu are in the anatase-like structure group. The remaining samples are in the anatase group.

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Ni L-and Ti L-edge as well as Ti K-edge X-ray absorption experiments for TiO2 thin films and Ni-doped TiO2 thin films coated on glass plates were performed using synchrotron radiation to investigate the structures around Ni and Ti ions in the films. The obtained spectra were compared with the results of theoretical calculations. It has consequently been found that the spectral features were affected by a change in the oxidizing form of Ni ions due to hydrogen reduction, by the charge variation and/or slight orbital splitting of Ti ions, and by the magnitude of the interaction between the center Ti ion and neighboring Ti ions.

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