Sol-gel derived poly(oxyethylene)/siloxane hybrids (di-urethanesils) doped with europium triflate, Eu(CF 3 SO 3 ) 3 , were examined by XRD, 13 C and 29 Si MAS NMR and FT-IR, FT-Raman, and photoluminescence spectroscopies. The host framework of these materials consists of a siliceous network grafted through urethane linkages to both ends of polymer chains with 6 oxyethylene repeat units. Xerogels with ∞ g n g 1 (where n is the molar ratio (OCH 2 CH 2 )/ Eu 3+ ) were analyzed. The compounds with n g 10 are amorphous. In samples with n e 5 crystalline Eu(CF 3 SO 3 ) 3 was detected. In the di-urethanesils with n g 10 the cations interact with the urethane carbonyl oxygen atoms. The complexation of the polyether chains to the cations is initiated at approximately n ) 10. At n e 10 both types of cation bonding situations occur. "Free" and weakly coordinated CF 3 SO 3ions exist in the whole range of salt concentrations analyzed. Ionic aggregates are formed in samples with n ) 5 and 1. For 200 g n g 20 the emission quantum yields range from 0.7 to 8.1%. The decrease in the quantum yield with the increase of the Eu 3+ concentration markedly depends on the activation of the energy transfer between the hybrid host's emitting centers and the cations, permitting, therefore, a fine-tuning of the emission chromaticity across the CIE (Commission Internationale d'E Ä clairage) diagram (e.g., (x, y) color coordinates from (0.19, 0.18) to (0.50, 0.49), for n ) 200 and 5, respectively).

Nd(3+)-based organic/inorganic hybrids have potential application in the field of integrated optics. Attractive sol-gel derived di-urea and di-urethane cross-linked poly(oxyethylene) (POE)/siloxane hybrids (di-ureasils and di-urethanesils, respectively) doped with neodymium triflate (Nd(CF(3)SO(3))(3)) were examined by Fourier transform mid-infrared (FT-IR), Raman (FT-Raman), (29)Si magic-angle spinning (MAS) nuclear magnetic resonance (NMR) and photoluminescence spectroscopies, and small-angle X-ray scattering (SAXS). The goals of this work were to determine which cation coordinating site of the host matrix (ether oxygen atoms or carbonyl oxygen atoms) is active in each of the materials analyzed, its influence on the nanostructure of the samples and its relation with the photoluminescence properties. The main conclusion derived from this study is that the hydrogen-bonded associations formed throughout the materials play a major role in the hybrids nanostructure and photoluminescence properties.