Combining Sol-Gel Chemistry and Extrusion Process Toward Generating First Vanadium Oxide Macroscopic Fibers
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Combining Sol-Gel Chemistry and Extrusion Process Toward Generating First Vanadium Oxide Macroscopic Fibers L. Biette1, H. Serier1, F. Carn1, M.-F. Achard1, N. Steunou2, J. Livage2 and R. Backov1,* 1 Centre de Recherche Paul Pascal CNRS UPR 8641, 115 Ave Albert Schweitzer, 33600 Pessac, France ; 2 Laboratoire de Chimie de la Matière Condensée, UMR-7574 CNRS, 4 Place Jussieu, Université Pierre et Marie Curie, Paris CEDEX 05, France. [email protected] ABSTRACT 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. INTRODUCTION There is today a strong emerging and competitive field of inorganic morphosynthesis that is strongly related to the newly concepts of “chemistry of shapes” or synthesis over “all length scales” [1]. To address those concepts and reach hierarchical architectures, mineralization can be promoted at different length scales taking advantage from nature specific construction skills [2]. In this general context, three main strategies can be employed. One can make the use of metastable thermodynamic systems (emulsions [3], reverse emulsions [4] or air-liquid foams [5]) as a macroscopic pattern, while generating mesotexturation using lyotropic mesophases. Within a second route the mesoscopic supramolecular templating effect extends to higher length scales, with the advantage, for instance, to forward the molecular chirality toward the high scale shaping [6]. Also, it is possible to use preformed micro-organism [7] or preexisting colloidal opal-like organic textures[8]. Particularly, it has been demonstrated recently that hierarchical systems can be reached playing with carbon particles high aspect ratio (strong anisotropy) where organization at higher length scales is obtained through extrusion processes [9]. Taking benefit of an extrusion strategy applied to vanadium oxide gels, we generate for the first time macroscopic vanadium oxide fibers associated to a strong intrinsic one dimensional organization of vanadium oxide nanoscopic ribbon subunits. Final macroscopic fibers depict good selectivity, sensitivity and stability.
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EXPERIMENTAL DETAILS Syntheses Dowex 50WX2-100 ion exchange resin and sodium metavanadate (90%) were purchased from Aldrich. Synthesis of V2O5.nH2O gels was performed by the ion exchange method [10-12]. A solution of a sodium metavanadate (NaVO3) precursor of concentration 0.1 mol/L is passed through a proton exchange resin (DOWEX-W-hydrogen, strongly acidic cation, 2% cross-linking 50-100 mesh).
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