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Lookup NU author(s): Dr Terry Egerton
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This paper uses measurements of adsorption and vibrational spectra (DRIFTS, ATR, and Raman) to characterize TiO2 (rutile) nanoparticles that have been surface treated with aluminum and stearate, "aluminum stearate". From these measurements, we have developed a model of titania particles covered by patches of "alumina". Vibrational spectra, particularly the spectra of the carboxylate headgroups, show that the stearate then adsorbs on both the titania and the alumina. Surprisingly, the distribution of the stearate between alumina and titania is sensitive to the presence of water. As the water content decreases, the relative amounts of stearate on titania, rather than alumina, increase, and this increase is accompanied by a less ordered structuring of the stearate tails, as evidenced by a shift of the C-H stretching bands to higher frequencies and a broadening of the 1296 cm -1 Raman band. This effect is consistent with earlier observations that the presence of water reduced the bonding of stearate headgroups to the surface of titania. We have also shown that the dispersion in C 12-C15 alkyl benzoate of aluminum stearate coated titania is sensitive to the presence of small amounts, ∼4%, of water. Finally, we have demonstrated that surface stearate, like surface alumina, reduces the rate of phototocatalytic oxidation of 2-propanol. A 7% stearate coating reduces acetone formation by a factor of 4. There is no evidence from these studies that, during the oxidation experiment, 2-propanol displaces stearate from the titania surface. © 2005 American Chemical Society.
Author(s): Egerton TA, Everall NJ, Tooley IR
Publication type: Article
Publication status: Published
Journal: Langmuir
Year: 2005
Volume: 21
Issue: 7
Pages: 3172-3178
Print publication date: 29/03/2005
ISSN (print): 0743-7463
ISSN (electronic): 1520-5827
Publisher: American Chemical Society
URL: http://dx.doi.org/10.1021/la047390d
DOI: 10.1021/la047390d
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