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Elaboration et caractérisation de phases cristal liquides de suspensions de rutile (TiO2). Propriétés physiques anisotropes

Abstract : TiO2 rutile nanorods of average length L = 160 +/- 40 nm and average diameter D = 15 +/- 5 nm have been synthesized through a seed-mediated growth process by TiCl4 hydrolysis in concentrated acidic solution, inspired of a Chimie Douce method. These nanorods were dispersed in water to yield stable (aggregation-free) colloidal aqueous suspensions. At volume fractions phy > 3%, the suspensions spontaneously display a phase separation into an isotropic liquid phase and a liquid-crystalline phase identified as nematic by X-ray scattering. At phy > 12 %, the suspensions form a nematic single phase, with large order parameter, S = 0.75 +/- 0.05.
Very well aligned rutile films on glass substrate were produced by spin-coating and their photocatalytic properties were examined by monitoring the decomposition of methylene blue under UV-light. We found that UV-light polarized along the quadratic axis of the rutile nanorods was most efficient for this photocatalytic reaction.
Some experiments of conduction have been performed. TiO2 rutile is a semi conductor with, for the bulk, a gap of around 3 eV. As in the photocatalytic studies, the polarized UV-light has a huge influence on the charge transport. A Schottky diode behaviour has been observed and explained. Irradiation in the visible spectrum has been shown to have no consequence on the properties of conduction. Rutile films have been also characterized to estimate the correction for the gap of anisotropic nanoparticles. Finally, a thermal study and a comparison with a monocrystal have been done.
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Contributor : Arnaud Dessombz <>
Submitted on : Monday, January 19, 2009 - 7:30:55 PM
Last modification on : Thursday, December 10, 2020 - 11:09:02 AM
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  • HAL Id : tel-00354476, version 1


Arnaud Dessombz. Elaboration et caractérisation de phases cristal liquides de suspensions de rutile (TiO2). Propriétés physiques anisotropes. Analyse de données, Statistiques et Probabilités []. Université Paris Sud - Paris XI, 2008. Français. ⟨tel-00354476⟩



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