Journal of Sol-Gel Science and Technology 24, 155–165, 2002 c  2002 Kluwer Academic Publishers. Manufactured in The Netherlands. Optical Properties of Lanthanide Doped Hybrid Organic-Inorganic Materials ELOISA CORDONCILLO, PURIFICATION ESCRIBANO AND F. JAVIER GUAITA Departamento de Qu´ ımica Inorg´ anica y Org´ anica. Universitat Jaume I, 12080 Castell´ on, Spain CLOTILDE PHILIPPE, BRUNO VIANA AND CLEMENT SANCHEZ Laboratoire de Chimie de la Mati` ere Condens´ ee UMR CNRS 7574. Universit´ e Pierre et Marie Curie, 4 place Jussieu, 75252 Paris, France clems@ccr.jussieu.fr Received April 30, 2001; Accepted November 6, 2001 Abstract. Sol-gel matrices have been investigated for some years as potential matrices for rare earth luminescence. Sm 3+ , Eu 3+ , Dy 3+ , Er 3+ and Tm 3+ optical properties in siloxane-zirconium hybrid matrices prepared at room temperature have been investigated. Even if luminescence efficiency is governed by non-radiative relaxation linked to hydroxyl groups, in these matrices, rare earth fluorescence is always observed but lifetimes and quantum yields are dependent on the elaboration procedure. Eu 3+ is used as a probe of the local surrounding around the dopant and the emission and decay profiles measurements in rare earth doped and undoped matrices are presented. Keywords: hybrids, organic-inorganic, sol-gels, nanoparticules, rare-earth, emission 1. Introduction In the last decade, sol-gel technology has been widely used to prepare optical materials [1–4]. The advantages of the sol-gel method for preparation of optical materi- als are good uniformity of chemical compositions and less contamination from preparation processes. The chemical synthesis of gels is performed in organic solu- tion at lower temperatures than conventional chemical methods; organic components can therefore be easily preserved in an oxide gel matrix. Inorganic and organic components can be mixed at the nanometric scale, in virtually any ratio leading to hybrid organic-inorganic nanocomposites which are extremely versatile in their composition, processing and properties [5, 6]. In that case, the synthesis and characterization of organic- inorganic hybrid materials is a rapidly growing field or research opening a new design of new materials for different applications [6–9]. Our interest is focused on siloxane-based hybrid belonging to the so-called class II of the hybrid materials [10], i.e. where the or- ganic and inorganic compounds are linked by strong covalent bonding. The photophysical properties of rare earth ions are studied with a lot of interest because they are used as visible and near-IR radiation sources, some of them particularly important for solid state lasers, scintillators field, optical communication amplifiers, and the very large lamp market [11]. A particular attention has been paid to reduce the number of hydroxyl groups because the luminescence efficiency of rare earth ions in sol-gel host materials is currently limited by the presence of residual water and hydroxyl groups [12]. In addition, due to low solubil- ity of rare earth ions in the silicon matrices, clusteri- zation of rare earth ions will occur. Clustering results in concentration quenching of fluorescence due to non- radiative energy transfer between rare earth ions within the clusters [13–15]. This effect is undesirable because it leads to poor luminescence efficiency.