In this study, two kinds of mesoporous materials were prepared. The first was a silica mesostructure grown within a porous aluminium oxide membrane columnar material (hybrid-AOM). This was prepared using a sol-gel technique with Pluronic P123 triblock copolymer as the structure-directing agent and tetraethyl orthosilicate as the inorganic source. The hybrid-AOM had a similar pore size distribution to that of as-prepared SBA-15 but showed an amorphous character, as demonstrated by nitrogen adsorption and SAXRD. The second type of material was a continuous mesoporous silica thin film, prepared by the dip-coating technique using Pluronic F127 triblock copolymer as the structure-directing agent and the same silica source as hybrid-AOM. The film, which was self-assembled on substrates such as indium tin oxide (ITO), glass and gold, exhibited long-range ordered mesostructures after several treatments and aging. Grazing incidence small-angle X-ray scattering method (GISAXS) showed that the thin film contracted in a direction perpendicular to the substrate after drying and surfactant removal.Removal of the surfactant template from both materials in order to create porous silica was achieved by calcination, ethanol extraction and peroxide-Fe treatments. Calcination was found to be the best method to remove surfactant from both mesostructures (hybrid-AOM and thin film). However, this was found to cause cracking and crumpling of the hybrid-AOM with the evaporated gold being easily peeled off after calcination. Ethanol extraction was thus applied where calcination was not suitable. The surfactant removal was confirmed using an infrared spectroscopy and the structure was confirmed after extraction using 1D X-ray diffraction (XRD). The surface morphology, porosity and crystallinity of the mesostructures prepared were characterized by nitrogen adsorption, scanning electron microscopy and small angle XRD. To form modified electrodes, the hybrid-AOM template was coated by evaporation with pure gold on one side, whilst the mesostructured thin film was grown on either gold or ITO. The permeability of the void space for both hybrid and thin film samples was calculated from the cyclic voltammetry response of a neutral probe (FcMeOH). Cationic ([Ru(bpy)3]2+) and anionic (I-) electroactive species were used to observe the electrochemical response under different pH regimes. FcMeOH was also used to study the effect of KCl concentration on the silica surface charge. Gold and platinum were electrochemically deposited using mesoporous silica as a template.

Solubility-based membrane separation, in which the more soluble species preferentially permeates across the membrane, has attracted considerable recent attention due to both economic and environmental concerns. This solubility-selective mode is particularly attractive over a diffusivity-selective mode in applications in which the heavier species are present in dilute concentrations. Examples include the recovery of volatile organic components (VOCs) from effluent streams and the removal of higher hydrocarbons from natural gas. Recently, nanocomposites have shown great promise as possible membrane materials for solubility-selective separations. The chemical derivatization of inorganic mesoporous substrates has been explored to synthesize organic-inorganic nanocomposite membranes. The most exciting feature of this approach is that it enables the rational engineering of membrane nano-architecture with independent control over the free volume and chemistry to create membranes with highly customizable permselectivity properties. In this study, we synthesized the organic-inorganic nanocomposite membranes by decorating the surfaces of commercially available mesoporous alumina substrates, and surfactant-templated highly ordered mesoporous silicate thin films placed on commercially available macroporous inorganic substrates, with a selective organic material that is physically or chemically anchored to the porous surfaces. Hyperbranched melamine-based dendrimers, with nanometer dimension and chemical composition designed to target certain components, were used as filling agents. We evaluated these membranes for several environmentally relevant separations, such as the recovery of the higher hydrocarbon from air and the removal of trace VOCs from air or water, while exploring the impact of organic oligomer size, chemistry, and surface coverage, as well as substrate pore size and structure, on membrane performance. First, we did a model study to verify the feasibility of dendrimer growth inside mesopores by using ordered mesoporous silica. Alumina-ordered mesoporous silica (alumina-OMS) hybrid membranes were prepared as new inorganic porous substrates. Finally, we synthesized dendrimer-ceramic nanocomposite membranes by growing several generations of melamine-based dendrimers with diverse functional groups directly off the commercial alumina membranes. Composite membranes show very high propane/nitrogen selectivity up to 70.

Ce travail de thèse porte sur l’élaboration et la caractérisation optique et structurale de films de silice ou de titane mésostructurés porteurs de nanoparticules d’argent. Il s’intéresse également aux propriétés photochromiques des films à base de titane. Pour ce travail, des films mésoporeux de SiO2, et de TiO2, amorphe ou anatase, ont été synthétisés par voie sol-gel et caractérisés. Après leur imprégnation par des ions métalliques, trois protocoles de réduction ont été utilisés. La croissance thermique favorise la coalescence des nanoparticules; des bâtonnets d’argent sont obtenus dans les films de silice hexagonaux 2D alors que des agglomérats se forment en surface et dans l’épaisseur des films de TiO2 présentant des pores sphériques. La réduction chimique permet une croissance rapide des nanoparticules d’argent dans les pores; des bâtonnets et sphères de taille et forme contrôlées sont obtenus dans les films de SiO2 et de TiO2, respectivement. La croissance optique des nanoparticules d’argent par photoréduction est aussi un procédé rapide; des nanoparticules avec une plus large distribution de taille que leurs similaires chimiques sont obtenues dans les films de TiO2, mais seulement quelques nanoparticules dans la matrice SiO2 en raison de sa faible réponse à l’UV. L’étude du comportement photochromique des nanoparticules d’argent déposées dans des films de TiO2 a démontré l’influence de la répartition initiale des nanoparticules et de l’intensité incidente sur la couleur du film. Un blanchiment du film optique ou chimique est observé après insolation avec une lumière monochromatique puissante, et un comportement multiphotochromique pour de faibles intensités lumineuses / This study is focused on the elaboration, and the optical and structural characterization of mesostructured silica and titania films incorporating silver nanoparticles. It also deals with the photochromic properties of titania films. For that purpose, mesoporous thin films of silica and amorphous or anatase titania were produced using sol-gel method and characterized. After soaking in a metal salt solution, three kinds of reduction processes were explored. The thermal route promotes coalescence of nanoparticles; silver nanorods are obtained in 2D hexagonal silica films, whereas aggregates are formed on the surface and in the thickness of titania films having spherical pores. Chemical reduction leads to a rapid growth of silver nanoparticles in the pores: silver nanorods and spheres with a controlled size and shape are obtained in the silica and the titania films, respectively. Optical growth of silver nanoparticles by photoreduction is also a fast process: nanoparticles with a larger size distribution than the chemically reduced films are obtained in the titania matrix, but few nanoparticles are obtained in the silica matrix due to their low response to the UV light. The photochromic behavior study of silver nanoparticles deposited in amorphous or anatase titania films shows the influence of the initial nanoparticle distribution inside the film and the irradiance intensities on the photo-induced color changes. A bleaching of the optically and chemically reduced film can be observed after irradiation with monochromatic visible light at high intensities and multiphotochromic behavior at low irradiance values