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Composite PVA/ZnO-nanorods fibers, synthesized through co-axial flux extrusion exhibit higher anisotropic photonic properties, both in absorption and emission, as a result of the collective alignment of the ZnO nanorods along the main axis of the PVA fiber. This photonic anisotropy is triggered by a synergistic interaction between the PVA matrix, stretched above Tg, and cooled down under strain. Compared with non-elongated fibers that present an isotropic emission, composite fibers previously submitted to a tensile stress absorb selectively UV emission when the polarized laser beam is parallel to the main axis of the fiber. In addition, their photoluminescence is also anisotropic, with a waveguide behavior along the fiber’s main axis.
Polyvinyl alcohol/Poly-aniline/Vanadium Oxide nanocomposite-based macroscopic fibers have been generated by using a redox reaction addressed while performing an extrusion shaping process. The resulting composites have been thoroughly characterized via a large set of techniques such as SEM, SAXS, XRD and FTIR, in order to determine aniline effects over final materials' structures and properties. Thus, the perturbation of the preferential orientation of the V2O5 nano-ribbons toward the fiber main axis, induced by aniline Red-ox intercalation, has been observed. Also, the partial reduction of V5+ species to V4+ ones, due to the strongly oxidizing character of the first ones toward aniline, has been revealed by Electron Spin Resonance (ESR). Moreover, these fibers are able to detect 5 ppm of ethanol within 3-5 seconds at 42 °C, and possess a toughness of 12 J.g-1.
Using both β-diketone and malonamide organosilane derivatives and silica Si-HIPE macro-mesocellular foams (acronym refers to the High Internal Phase Emulsion process), organically modified silicates (ORMOSILs) with chelating functionality have been synthesized. The organic functionalities have been anchored to the silica porous networks by both a two-steps grafting method, relating to grafted gOrgano-Si(HIPE), and a one-step co-condensation process, relating to Organo-Si(HIPE). The loading of monoliths by lanthanides was performed by impregnation of an europium (III) salt in solution, leading to a new Eu3+@(g)Organo-Si(HIPE) hybrid foams series. The resulting materials have been thoroughly characterized via a large set of techniques such as SEM, TEM, SAXS, mercury intrusion porosimetry, nitrogen adsorption, FTIR and 29Si CP MAS NMR. Luminescence behavior of this Eu3+@Organo-Si(HIPE) series was also studied and the effects of environment and europium concentration will be discussed.
Upon extrusion process, first vanadium oxide macroscopic fibers have been obtained. They are associated to longitudinal Young modulus from 15 to 25 GPa and depict strong high scale textural anisotropy as observed through cross-polarized microscopy. TEM observations and SAXS experiments reveal that those macroscopic fibers are made of nanoscopic ribbons associated to preferential orientation parallel to the macroscopic fiber main axis, while XRD and NMR investigations reveal a microstructure close to the V2O5.1.8H2O xerogels. These fibers can detect down to 0.1 ppm of ethanol within 16 seconds at 40°C.
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