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Greffage de complexes de terres rares luminescents sur silicium cristallin et silicium nano-cristallin pour la détection de NO en phase gazeuse

Abstract : This thesis is about the synthesis and characterization of luminescent nanostructures doped with rare earth ions that can be used as sensor for gases such as nitrogen monoxide (NO). Crystalline silicon, which is used as a substrate here, is a poor light emitter because of its indirect gap. It is challenging for the microelectronic and optical telecommunications industries to obtain optical properties, including emission, from this material. Thanks to quantum confinement in silicon nanostructures, a radiative emission can be obtained at room temperature. A possible way to enhance these properties is to modify the surface in such a way that it becomes optically active. In this work, complexes containing luminescent elements as lanthanides were grafted on the silicon surface. These elements are very interesting for optical applications because the wavelength of their emission peaks is almost independent of the environment and an emission from the blue to the near infrared can be obtained, depending on the rare earth. To produce inorganic/organic hybrid materials, different steps were developed and optimized during this work. So as to attach the rare-earth based complexes to the silicon surface, that surface is oxidized in order to generate reactive groups like silanols. A second required step is the functionalization of the surface by an aminosilane (APTES) which enables to link the silica surface and the complexes. To fix the optically active ions, it is necessary to complex the lanthanide ions with a ligand (DOTAGA) that can react with the ammine group to create a covalent bound of the complex. In this work, it is shown that the synthesized lanthanide complexes (Tb, Eu, Ce, Yb and Nd) are optically active and that after grafting on the silicon surface, Tb, Eu and Ce based complexes have a strong luminescence while Yb and Nd based complexes are weakly active. The same type of results are obtained when the complexes are grafted on porous silicon. Moreover, the effect of the environment, in particular a nitrogen oxide one, is studied on these samples in order to check whether they can be used as NO sensors.
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Submitted on : Friday, October 23, 2020 - 2:54:29 PM
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Kathleen Toussaint. Greffage de complexes de terres rares luminescents sur silicium cristallin et silicium nano-cristallin pour la détection de NO en phase gazeuse. Physique [physics]. Université de Lorraine, 2020. Français. ⟨NNT : 2020LORR0107⟩. ⟨tel-02976596⟩



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