Journal of Alloys and Compounds 374 (2004) 74–78 Eu 3+ doped polyphosphate–aminosilane organic–inorganic hybrids F.A. Dias Filho a , S.J.L. Ribeiro a,∗ , R.R. Gonçalves a , Y. Messaddeq a , L.D. Carlos b , V. de Zea Bermudez c , J. Rocha d a Institute of Chemistry—UNESP, CP 355, Araraquara SP-14801-970, Brazil b Department of Physics, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal c Department of Chemistry CQ–VR, University of Trás-os-Montes and Alto Douro, 5001-911 Vila Real, Portugal d Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal Abstract The preparation and characterization of new Eu 3+ doped polyphosphate–aminosilane hybrids xerogels is reported. Eu 3+ 5 D 0 emission quantum efficiency ranges from 0.41 to 0.54 depending on the Si/P ratio. These rather high values are due to the substitution of phosphate and amino groups for water in the Eu 3+ coordination shell. Raman and 29 Si and 13 C CP–MAS NMR results suggest that no strong interaction exists between the polyphosphate and the siloxane parts. Not fully condensed siloxane colloidal domains seem to be homogeneously distributed in the polyphosphate network. Good optical quality and favorable Eu 3+ spectroscopic characteristics suggest these new hybrids as good hosts for lanthanide ions in optical devices. © 2003 Published by Elsevier B.V. Keywords: Organic–inorganic hybrids; Sol–gel; Europium; Polyphosphate; Luminescence 1. Introduction Organic–inorganic hybrids have emerged as potential hosts in different technological fields ranging from electro- chemistry, biology, mechanics, ceramics, electronics to pho- tonics [1–4]. In general, the main interest in these molecular scale composite materials basically derives from the possi- bility of tailoring the properties of novel multi-functional advanced materials through a combination, at the nano- size level, of organic and inorganic components in a single material. Concerning the preparation of rare earth doped materials the hybrid concept can be used to tailor some desired spec- troscopic characteristics, bringing together some interesting characteristics of the individual components of the compos- ite materials. In this way new Eu 3+ doped materials have been largely studied. Enhanced visible emission under UV excitation may be obtained for instance since: a high UV absorption cross section; an efficient intra-molecular energy transfer; and high quantum efficiency for the emitting level are provided [5,6]. ∗ Corresponding author. Fax: +55-16-2227932. E-mail address: sidney@iq.unesp.br (S.J.L. Ribeiro). We have recently studied the interesting behavior of Eu 3+ polyphosphate aqueous solutions [7]. Polyphosphate chains existing in water can encapsulate Eu 3+ ions protecting them against the well known deleterious effects of OH oscillators on the emission efficiencies. In water (europium chloride so- lution, pH ≈ 5) the emission quantum efficiency η (taken as the ratio between the experimental, k EXP , and purely radia- tive, k RAD , decay rates: η = k RAD /k EXP ) for the Eu 3+ 5 D 0 excited state is 0.04 showing that the experimental decay is mainly governed by non-radiative processes through OH oscilators. In polyphosphate solutions η increases to about 0.20 due to the coordination of polyphosphate chains to the Eu 3+ . In fact the number of water molecules in the Eu 3+ co- ordination shell that can also be obtained from decay times [8] is between 8 and 9 in water. This number decreases to around 1 in polyphoshate solutions due to substitution of phosphate groups to water molecules at the Eu 3+ first coordination shell [7]. Considering the utilization of Eu 3+ polyphosphate solutions as a precursor in the preparation of luminescent materials for example a major drawback is the hygroscopicity of the resulting material. In this work we present some results on new organic– inorganic hybrids prepared by the interaction in water between polyphosphate and aminosilanes. 3-aminopropyl- triethoxisilane was considered in a previous work together 0925-8388/$ – see front matter © 2003 Published by Elsevier B.V. doi:10.1016/j.jallcom.2003.11.066