Investigation of interactions between a NLO-dye and metal alkoxide precursors of hybrid materials
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Investigation of interactions between a NLO-dye and metal alkoxide precursors of hybrid materials Bénédicte Lebeau1 and Clément Sanchez2 1 Laboratoire de Matériaux Minéraux, CNRS UMR 7016, ENSCMu, UHA, 3 rue Alfred Werner, 68093 Mulhouse cedex, France 2 Laboratoire de Chimie de la Matière Condensée, CNRS UMR 7574, UPMC, 4 place Jussieu, 75252 Paris cedex 05, France ABSTRACT Interactions between the dye Red 17 (4-(amino-N,N-diethanol)-2-methyl-4’-nitroazobenzene) having nonlinear optical (NLO) properties and metallo-organic sol-gel precursors M(OR)n (M = Ti, Zr, Si and Sn; R = CnH2n+1) have been investigated by means of UV-VIS spectrophotometry and liquid state NMR (1H, 29Si and 119Sn) techniques. The presence of titanium, zirconium or tin alkoxides make strong modifications in the UV-VIS absorption spectrum of the Red 17 in solution. On the contrary, when the Red 17 is grafted to alkoxysilyl groups, only minor changes were observed. The resulting bathochromic shift of about 30 nm observed with transition metal or tin alkoxides was found to be due to Lewis acid-base type interactions between the Red 17 and the metallic centre. INTRODUCTION The concept of hybrid, organic-inorganic, nanocomposites made via soft inorganic chemistry processes such as sol-gel, has widely contributed to the development of new materials in various application fields such as optics, electronics, protection coatings...[1] Optics is one of the area that has widely benefited of the recent expansion of hybrid materials [2]. The main strategy consists in embedding organic dyes within inorganic or hybrid organic/inorganic matrix. Optical studies performed on organic/inorganic nanocomposites have evolved towards different objectives : investigate the fundamental spectroscopy of the dye molecule isolated in the sol-gel environment, study dye energy transfer in solid matrices, use luminescent molecules as probes of the sol-gel process and finally develop materials with specific optical properties based on the properties of organic or inorganic chromophores. From these studies it was clearly observed that the properties of hybrid materials do not depend only on both organic and inorganic components but also on the interface between both phases, which can be used to tune many properties [2]. In this article we report on the modifications of the optical properties of the (NLO) dye (4(amino-N,N-diethanol)-2-methyl-4’-nitroazobenzene), named Red 17, induced by interactions with different organic solvents and metallo-organic sol-gel precursors M(OR)n (M = Ti, Zr, Si and Sn; R = CnH2n+1). Because of its very efficient quadratic hyperpolarizability (β(0) (Red 17) = 55.10-30 esu), the Red 17 is a suitable dye to be embedded within sol-gel matrices to produce hybrid, organic-inorganic, optical devices with NLO properties [3]. In such materials, strong interactions between the dye and the host matrix are required to optimize the dye loading and to maintain the dye anisotropic alignment. However, the optical efficiency of the Red 17-doped solgel material depends
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