Thèse Année : 2024

Orientation Tomography in Liquid Crystals & Shearmetry in Hydrovoltaic Systems by Spectroscopy of Polarized Luminescence of LaPO4 : Eu Nanorods

Orientation Tomography in Liquid Crystals & Shearmetry in Hydrovoltaic Systems by Spectroscopy of Polarized Luminescence of LaPO4 : Eu Nanorods

Résumé

Suspension of LaPO4:Eu nanorods exhibit liquid crystalline behavior and were previously shown to spontaneously self-assemble into complex structures. Moreover, their large aspect ratio makes them easily aligned under external forces, which we explore for the in situ characterization of flow shear in hydrovoltaic systems.The first objective of this thesis was to further develop the existing methodology for the orientation tomography utilizing the polarized luminescence originating from the europium dopant. This required the implementation of a confocal micro-spectroscopy platform with high spatial resolution and the formulation of a theoretical framework.The improved methodology was then applied to study the liquid crystal assemblies and their evolution over time. Numerical modeling was explored to investigate the role of the different volume and surface forces in establishing the experimentally observed structures.Finally, the previously demonstrated shearmetry technique was further developed to account for the non-Newtonian behavior of the nanorod suspensions. As an application for the technique, we aimed to characterize the effect on shear stresses on the electrochemical response of a hydrovoltaic system. To achieve this, a microfluidic hydrovoltaic device had to be created.Altogether, this thesis highlights the versatility of luminescent LaPO4 nanorods and their applications.
Suspension of LaPO4:Eu nanorods exhibit liquid crystalline behavior and were previously shown to spontaneously self-assemble into complex structures. Moreover, their large aspect ratio makes them easily aligned under external forces, which we explore for the in situ characterization of flow shear in hydrovoltaic systems.The first objective of this thesis was to further develop the existing methodology for the orientation tomography utilizing the polarized luminescence originating from the europium dopant. This required the implementation of a confocal micro-spectroscopy platform with high spatial resolution and the formulation of a theoretical framework.The improved methodology was then applied to study the liquid crystal assemblies and their evolution over time. Numerical modeling was explored to investigate the role of the different volume and surface forces in establishing the experimentally observed structures.Finally, the previously demonstrated shearmetry technique was further developed to account for the non-Newtonian behavior of the nanorod suspensions. As an application for the technique, we aimed to characterize the effect on shear stresses on the electrochemical response of a hydrovoltaic system. To achieve this, a microfluidic hydrovoltaic device had to be created.Altogether, this thesis highlights the versatility of luminescent LaPO4 nanorods and their applications.
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Dates et versions

tel-04922569 , version 1 (31-01-2025)

Identifiants

  • HAL Id : tel-04922569 , version 1

Citer

Lilian Magermans. Orientation Tomography in Liquid Crystals & Shearmetry in Hydrovoltaic Systems by Spectroscopy of Polarized Luminescence of LaPO4 : Eu Nanorods. Other. Institut Polytechnique de Paris, 2024. English. ⟨NNT : 2024IPPAX088⟩. ⟨tel-04922569⟩
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