Chemical Bond Modification upon Phase Transformation of TiO2 Nanoribbons Revealed by Nanoscale X ray Linear Dichroism

Titanium dioxide in the TiO2 amp; 8722;B phase, which can be stabilized in nanoparticle form, is a promising anode material for lithium ion batteries. Here the structural and electronic changes between nanoribbons in TiO2 amp; 8722;B and the thermodynamic stable anatase phase are studied using nanoscale X ray absorption spectroscopy and first principles calculations. The oxygen K edge spectra of the two phases display marked differences which are very well reproduced in the calculations. Strong linear dichroism is observed in single nanoribbons, reflecting preferential O 2p to Ti 3d bond orientation in the low symmetry crystal structures. A simple bond counting model is developed which semiquantitatively accounts for the major dichroic effect. It is shown that the crystal orientation of the nanoparticles can be inferred from the dichroic spectr