Développement de nanoémetteurs polarisés pour leur application comme sondes d'orientation

Abstract : Luminescent nanoparticles have been studied for their applications in lighting devices or as probes in biology. Among these nanoparticles, the anisotropic crystals doped with lanthanides ions emit linearly polarized light. The relation between the polarized directions and the crystallographic axis of the nanocrystals allow determining their 3D orientation, which could be an asset to track objects or to characterize flows.The purposes of this thesis were to investigate the origin of the polarized light of nanorods of lanthanum phosphate doped with europium ions (LaPO4:Eu) and to apply this polarized light to determine their orientation.First, nanorods of LaPO4:Eu are synthesized and aligned to prepare oriented films. The phase transition of the LaPO4 matrix is investigated, from the hexagonal to the monoclinic structure. The luminescence is used to track precisely the transition and show the presence of structural defects. Then the polarized spectra are observed. The polarization degrees of the monoclinic phase are higher than those of the hexagonal one. The sensitivity of the polarization with the dielectric medium is also shown.Then, the polarized light is used to determine the orientation of the nanorods. The knowledge of the polarized spectra along he nanorods axis and perpendicularly to it is used to calculate the order parameter of disoriented nanorods in a microfluidic channel and then to estimate the shear rate of the flow. Our study allows quantifying the conditions in which the nanorods can be used as probes to measure the local shear rate.
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  • HAL Id : tel-01917562, version 1

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Elodie Chaudan. Développement de nanoémetteurs polarisés pour leur application comme sondes d'orientation. Matériaux. Université Paris-Saclay, 2018. Français. ⟨NNT : 2018SACLX063⟩. ⟨tel-01917562⟩

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