Electronic structure of titania aerogels from soft x-ray absorption spectroscopy

The electronic structure of TiO₂ aerogels is studied by soft x-ray absorption near-edge structure (XANES) spectroscopy. High-resolution O K-edge and Ti L2,3-edge XANES spectra of aerogels are compared with those of rutile, anatase, and unrelaxed amorphous phases of full-density TiO₂. Results show that all the main spectroscopic features of aerogels, reflecting the element-specific partial density of empty electronic states and correlation effects, can be attributed to the absence of long-range order in stoichiometric amorphous TiO₂. Based on these results, we discuss the effects of short- and long-range order on the electronic structure of TiO₂.