Amorphous and Crystalline Mesoporous Materials Prepared Via Evaporation
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Amorphous and crystalline mesoporous materials prepared via evaporation David Grosso, Florence Cagnol, Aurélie Coupé, Niki Baccile, Cédric Boissière, Galo J. de A. A. Soler-Illia, Eduardo Crepaldi, and, Clément Sanchez. Laboratoire Chimie de la Matière Condensée, UPMC - CNRS, 4 place Jussieu, 75252 Paris, France. ABSTRACT Because of the increasing interest in nanoscale technologies, many groups have taken part in the recent development of nanostructured materials that may be preserved in a robust form for designed applications. Amongst the various possible synthesis paths, the Evaporation Induced Self Assembly (EISA), leading to surfactant templated materials in the shape of thin films (liquid deposition), spheres (spray-drying) or monolith (slowevaporation), is one of the most promising since it enables to control morphologies and allows keeping the stoichiometry in non-volatile species homogeneously distributed in the final materials. The elaboration of the desired mesoporous materials passes by the control of the three steps involved in such a process: The control on the precursor chemical reactivity in the initial solution, the control of all processing parameters during evaporation and the control during consolidation by thermal decomposition of the organic phase and the potential crystallisation of the inorganic network. Through the use of complementary in-situ experiments and conventional characterisation techniques (NMR, 2D-SAXS, interferometry, TEM, ellipsometry, N2-BET), the present paper recalls the top-to-bottom studies of the EISA process applied to two different systems (SiO2 and TiO2) as thin films and spherical sub-micronic particles. In addition, the preparation of ordered mesoporous pure anatase thin films stable up to 700°C will be presented in details at the end of this work. INTRODUCTION Porous oxide materials in forms of films, fibres, powders, monoliths or macrospheres are widely used in various domains. This arises from the combination between accessible porosity, high surface area, and the wide physico-chemical properties that can offer solid matter. However, a precise control of the porosity during synthesis remained a challenge up to the last decade where the template process was introduced [1]. This latter technique combines the sol-gel chemistry and the structuring effect of surfactant in solution where the surfactant micelles dimensionality and self assembly into mesophases dictate the final structure. By carefully adjusting chemical composition, the conditions of self-assembly processing, and the treatment conditions, several porous structures were reproducibly stabilised (e.g. disordered, 2D, 3D and lamellar) with pore size distribution ranging from 2 to 10 nm. Through the Evaporation Induced Self Assembly (EISA) method [2], it is now possible to synthesis SiO2 [3], TiO2 [4,5], ZrO2 [6,5], VO2 [7] and Al2O3 [8] and other mixed oxides such as Y2O3- ZrO2 and CeO2-ZrO2 [9] based mesoporous films by dip-coating that will find application in sensing, optoelectronic, optics and phot
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