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Issue 6, 2011
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XANES and XPS investigations of (TiO2)x(SiO2)1−x: the contribution of final-state relaxation to shifts in absorption and binding energies

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Abstract

The (TiO2)x(SiO2)1−x system (0 ≤ x ≤ 0.33) was synthesized by the sol–gel method and investigated by X-ray absorption near-edge spectroscopy (XANES) and X-ray photoelectron spectroscopy (XPS). The use of both hard (Ti K-edge) and soft (Ti L-edge) X-rays provides a useful way to monitor changes in the bulk and surface, respectively, of these amorphous materials. The average CN of both bulk-Ti and surface-Ti increases with greater x in the chemical formula, due to the larger ionic radius of Ti. Comparison of Ti K- and L-edge spectra of annealed samples revealed that Ti atoms at the surface have a higher average CN than in the bulk, likely due to the presence of surface hydroxide and water groups that can coordinate to the Ti centres. The O K-edge, Ti L-edge, and Si L-edge XANES absorption energies showed little to no change with Ti content, while the O 1s, Ti 2p, and Si 2p XPS BEs were found to decrease with increasing Ti content due to nearest-neighbour and next-nearest-neighbour effects, which lead to increased final-state relaxation. The degree of final-state relaxation is more significant than previously believed for these amorphous powders.

Graphical abstract: XANES and XPS investigations of (TiO2)x(SiO2)1−x: the contribution of final-state relaxation to shifts in absorption and binding energies

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Publication details

The article was received on 13 Oct 2010, accepted on 12 Nov 2010 and first published on 07 Dec 2010


Article type: Paper
DOI: 10.1039/C0JM03464A
Citation: J. Mater. Chem., 2011,21, 1829-1836
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    XANES and XPS investigations of (TiO2)x(SiO2)1−x: the contribution of final-state relaxation to shifts in absorption and binding energies

    M. W. Gaultois and A. P. Grosvenor, J. Mater. Chem., 2011, 21, 1829
    DOI: 10.1039/C0JM03464A

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