Atomic structure of nanometer-sized amorphous TiO2

Hengzhong Zhang, Bin Chen, Jillian F. Banfield, Glenn A. Waychunas

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154 Citations (Scopus)

Abstract

Amorphous titania (TiO2) is an important precursor for synthesis of single-phase nanocrystalline anatase. We synthesized amorphous titania by hydrolysis of titanium ethoxide at the ice point. Transmission electron microscopy examination and nitrogen gas adsorption indicated that the particle size of the synthesized titania is ∼2 nm. Synchrotron wide-angle x-ray scattering (WAXS) was used to probe the atomic correlations in this amorphous sample. Atomic pair-distribution function (PDF) derived from Fourier transform of the WAXS data was used for reverse Monte Carlo (RMC) simulations of the atomic structure of the amorphous TiO2 nanoparticles. Molecular-dynamics simulations were used to generate input structures for the RMC. X-ray-absorption spectroscopy (XAS) simulations were used to screen candidate structures obtained from the RMC by comparing with experimental XAS data. The structure model that best describes both the WAXS and XAS data shows that amorphous TiO2 particles consist of a highly distorted shell and a small strained anataselike crystalline core. The average coordination number of Ti is 5.3 and most Ti-O bonds are populated around 1.940 Å. Relative to bulk TiO2, the reduction in the coordination number is primarily due to the truncation of the Ti-O octahedra at the amorphous nanoparticle surface and the shortening of the Ti-O bond length to the bond contraction in the distorted shell. The pre-existence of the anataselike core may be critical to the formation of single-phase nanocrystalline anatase in crystallization of amorphous TiO2 upon heating.

Original languageEnglish
Article number214106
Number of pages12
JournalPhysical Review B
Volume78
Issue number21
DOIs
Publication statusPublished - 1 Dec 2008
Externally publishedYes

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