Hybrid composite materials containing magnetic iron oxide nanoparticles
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Hybrid composite materials containing magnetic iron oxide nanoparticles Corinne Chanéac, Elisabeth Tronc and Jean-Pierre Jolivet Laboratoire de Chimie de la Matière Condensée, UMR-CNRS 7574, Université Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris Cedex 05, France
ABSTRACT Hybrid magnetic composites made up of calibrated maghemite nanoparticles well dispersed in an epoxide resin were obtained by polymerization of the resin inside stable organosols of maghemite. The sol stability was ensured by ligand adsorption onto the particle surface. Studies of phenylphosphonic acid adsorption are presented. They show a strong interaction between PPA ions and hydroxyl groups of particle surface and through bridging ≡Fe2O2POΦ species. Infrared and Mössbauer spectroscopies as well as quasi- elastic light scattering and transmission electron microscopy were used to characterize the materials. INTRODUCTION Technological developments require more and more elaborated materials and send for new synthesis strategies. Sol-gel chemistry currently contributes to the elaboration of inorganicorganic hybrid materials [1,2]. Such materials where the inorganic phase consists of metal oxide nanoparticles are interesting in various areas (optical and electrical properties, biological activity, quantum confinement effects, magnetic effects…) [3,4]. In general, the particles are formed by an in-situ reaction during or after the matrix polymerization. Composites can also be obtained using preformed particles. In previous studies [5], we showed that composites could be obtained by polymerization of silica inside an aqueous sol of maghemite particles, under the control of the particle/solvent interactions. To obtain hybrid nanocomposite, the formation of a kinetically stable organosol where the organic matrix will be polymerized is require in order to adapt the characteristics of the particle surface to those of the organic medium. The coupling agent should be a molecule with a hydrophobic tail (e.g. alkyl or vinyl chains, phenyl group) and a complexing head (e.g. carboxylate, sulfonate or phosphonate) [6]. We present studies of the adsorption of phenylphosphonic acid, ΦPO(OH)2, on nanometric maghemite. We also report the preparation and the characterization of organosols, and of hybrid magnetic materials, epoxide resin-based. EXPERIMENTAL SECTION The synthesis of hybrid materials involves three stages : i) Synthesis of maghemite aqueous sols : Maghemite, γ-Fe2O3, particles with mean size of 9.0 and 4.7 nm were obtained by oxidizing magnetite [7]. Calibrated Fe3O4 nanoparticles were prepared as previously described [8], by precipitating an aqueous mixture of FeCl2 (1 mol.L-1) and Fe(NO3)3 (2 mol.L-1). Oxidation was achieved by treatment in perchloric acid (3 mol.L-1). The FeII ions released in solution were eliminated after centrifugation. The treatments were repeated until the FeII/FeIII ratio in the solid was ca. 0.01. After the last separation, the particles were dispersed in pure water giving a stable sol of γ-Fe2O3 particles ([FeIII]=1 mol.
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