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Décoration de réseaux linéaires de défauts smectiques par des nanoparticules d'or

Abstract : We create thin smectic films of topological defects, linearly oriented along a unique direction, on top of rubbed polymer substrate, thanks to our knowledge develop on crystalline substrate. First we can study the influence of the substrate on defects structure, and perform X-Rays diffraction in combining transmission and reflexion setup. Second by mixing the liquid crystal with gold nanoparticles (NPs), we provide anisotropy to the NPs self-assembly and to their optical properties, tunable under light polarization. At low NPs concentration, we create chains of individual nanoparticles trapped within smectic dislocations, parallel to each other and aligned along the defects. Inside a chain, depending on concentration NPs can be isolated or electromagnetically coupled. At high enough concentration , this leads to anisotropic properties of the collective localized surface plasmon resonance as large as 40 nm. Then the linear assembly turn into two dimensional organization of the GNPs, with dense packing along the defects and an anisotropy of the optical properties remains.Concerning pure liquid crystal matrix, we are strengthening the hypothesis of a structure made of a rotating grain boundary but with an eccentric curvature center.We identify two areas being able to trap the NPs: a preferential site should be one dislocation close to the substrate, without disorder induced by the presence of the NPs; a second site should be an assembly of dislocation localized on top of the rotating grain boundary close to the air interface, which reconstructs depending on the NPs concentration. This directed assembly of NPs opens the route for various hybrid system with NPs of larger size and anisotropic shape, in order to enhanced the anisotropic effect of their assemblies.
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Submitted on : Saturday, December 14, 2013 - 12:49:25 PM
Last modification on : Saturday, January 15, 2022 - 3:44:41 AM
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  • HAL Id : tel-00918722, version 1


Coursault Delphine. Décoration de réseaux linéaires de défauts smectiques par des nanoparticules d'or. Matière Molle [cond-mat.soft]. Université Pierre et Marie Curie - Paris VI, 2013. Français. ⟨NNT : 2013PA066080⟩. ⟨tel-00918722⟩



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