Luminescence Properties of Rare-Earth Ions in Organic-Inorganic Hybrid Mesostructured Thin Films
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Luminescence Properties of Rare-Earth Ions in Organic-Inorganic Hybrid Mesostructured Thin Films Anne-Christine Franville, Bruce Dunn1 and Jeffrey I. Zink2 Laboratoire des Matériaux Inorganiques, UMR-CNRS 6002, Université Blaise Pascal and ENSCCF, 24 Av. des Landais, 63174 Aubière Cedex, FRANCE. 1 Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095-1595. 2 Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 900951569. ABSTRACT This paper describes the preparation of hybrid surfactant-templated thin films functionalized with rare-earth (Eu3+ and Tb3+) organic complexes. 2-D hexagonally ordered films are obtained by a one-pot synthesis process based on an acid-catalyzed approach. Ln3+ ions are coordinated to bis-silylated ligands that co-polymerize with TEOS, which enables one to incorporate the fluorescent centers within the silica framework. Luminescent properties of the organic-inorganic mesostructured films are discussed and compared to those of amorphous samples with similar composition. INTRODUCTION Organic-inorganic hybrid materials incorporating optically active organic moieties have been widely studied in the past decade because these systems are able to combine the unique properties of the organic part (high fluorescence yields, fast photochromic responses, NLO properties, etc..) and the good thermal and photochemical stability of the inorganic backbone [1,2]. The introduction of luminescent species into hierarchically ordered materials is currently under active investigation for advanced optical applications. Indeed, the mesoscopic ordering exhibiting by M41S type materials is attractive to provide well-defined microenvironments around the dopant molecules, to produce size-confined structures, to avoid concentration quenching by dimers formation or to modify the light propagation properties [3,4]. Functionalization of ordered mesoporous silica materials can be achieved by postdoping techniques or by a one-pot synthesis process. The latter enables to better control the loading and the distribution of the organic component within the host architecture. The one-pot synthesis route uses a sol-gel based co-assembly process between the surfactant molecules, TEOS and organically modified alkoxysilanes (see [5] for a recent review). This way, the organic molecules are covalently attached to the templated silica network and their location in the final materials depends on the number of anchoring Si(OEt)3 groups on the organoalkoxysilane moieties. On the other hand, mesoscopically ordered thin films can be obtained by an evaporation-induced selfassembly process under acidic conditions [6]. However, very few studies have yet reported on the formation of mesostructured organosilica films [7-9]. The aim of this study is to prepare hybrid mesostructured thin films incorporating luminescent rare-earth complexes. These complexes are covalently grafted to silica by means of bis-silylated ligands, which enable one to put the emitting species inside
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