Preparation of Ce3+-Doped Inorganic-Organic Hybrid Materials Using Functionalized Silanes

Ce3+-doped, inorganic-organic hybrid monoliths were prepared from Si(OCH3)4, CH3 Si(OCH3)3, CeCl3 and various functionalized silanes (FSs) such as amino- (APTM), glycidyloxy- (GPTM), trifluoro- (TFTM) and chloro-(CPTM) silanes at 60°C by the sol-gel process. The functional groups of silane coupling agents coordinated with Ce3+ ions in the inorganic-organic materials. Ce3+-doped materials were transparent under the preparation conditions of FS/Ce3+ ratio of 100 and 1.0 × 10–4 mol/cm3 of Ce3+ concentration. Optical properties such as absorption spectra, emission spectra and fluorescence quantum yield for the Ce3+-doped hybrid materials were strongly affected by the Ce3+ ion environment. Emission spectra were observed for the Ce3+-doped materials below 400 nm. The emission intensities of the materials prepared from TFTM, CPTM and without FS were approximately 100 times as much as those of materials prepared from APTM and GPTM. The fluorescence quantum yield was highest (11%) for the material prepared from TFTM hybrid materials.     

Consecutive reactions of diethoxydimethylsilane and triethoxymethylsilane with methoxide ions in methanol solution

The consecutive reactions of (CH₃)₂Si(OC₂H₅)₂ and CH₃Si(OC₂H₅)₃ with methoxide ions were investigated in methanol solutions. The reverse transesterification reactions with ethoxide ions could be neglected in both cases since the concentration of ethoxide in methanol solution was assumed to be low due to the fast equilibrium reaction C₂H₅O^? + CH₃OH ? C₂H₅OH + CH₃O^?. The progress of the reactions was followed by monitoring the formation of ethanol with a Fourier-transform infrared spectrometer. All rate constants were determined at 295 K. The reactions between the dialkoxydimethylsilanes and methoxide ions were assumed to consist of two consecutive steps that can be represented by the net reaction; (CH₃)₂Si(OC₂H₅)₂ + 2CH₃O^? → (CH₃)₂Si(OCH₃)₂ + 2C₂H₅O^?. The two consecutive rate constants were established as 1.93 ± 0.12M^?1s^?1 and 1.00 ± 0.12M^?1s^?1, respectively. The consecutive rate constants for the reactions between the trialkoxymethylsilanes and methoxide ions can be written according to the total reaction; CH₃Si(OC₂H₅)₃ + 3CH₃O^? → CH₃Si(OCH₃)₃ + 3C₂H₅O^?. The three rate constants corresponding to each consecutive step were established as 1.12 ± 0.09 M^?1s^?1, 0.82 ± 0.10 M^?1s^?1, and 0.51 ± 0.06 M^?1s^?1, respectively. © 1995 John Wiley & Sons, Inc.     

Luminescent organic–inorganic hybrid materials based on lanthanide containing ionic liquids and sylilated β-diketone

In this work, we report the luminescent organic–inorganic hybrid materials prepared by hydrolysis and condensation of sylilated β-diketone under acid conditions in the presence of carboxyl-functionalized ionic liquid in which Eu³⁺ ions are coordinated to the oxygen atoms of carboxylate groups from the ionic liquids. The obtained materials were characterized with FT-IR, TG and photoluminescence spectroscopy. FT-IR spectra imply that Eu³⁺ ions are still coordinated to the ionic liquid in the hybrid materials. Excitation and emission spectra demonstrate that the energy transfer occurs from the β-diketone molecules covalently bonded with silica to Eu³⁺ ions. The Eu³⁺ (⁵D₀) quantum efficiency value of the hybrid materials has been estimated based on the emission spectrum and the value of lifetime. A large value of ratio (16.44) between the intensities of the ⁵D₀→⁷F₂ and ⁵D₀→⁷F₁ transition and high value of ⁵D₀ quantum efficiency (51.01%) are obtained.     

Geminal interactions in ClZ(CH3)2X molecules (Z = C, Si, Ge) according to ab initio calculations

The structure and electronic parameters of ClZ(CH₃)₂X molecules (Z = C, Si, Ge, X = CH₃, OCH₃) were calculated by the RHF/6–31G(d) and RHF/6–311G(d,p) methods with full geometry optimization; calculations of ClZ(CH₃)₂OCH₃ molecules were also performed by the RHF/6–31G(d) method with partial geometry optimization. The ³⁵Cl NQR frequencies calculated from the populations of less diffuse 3p constituents of valence p orbitals of chlorine [RHF/6–31G(d)] were in agreement with the experimental values. The ³⁵Cl NQR frequencies for molecules with X = OCH₃ are lower than those for molecules with X = CH₃ (the Z atom being the same), due mainly to direct through-field polarization of the Z-Cl bond, induced by the effect of unshared electron pair of the oxygen atom in the trans position with respect to that bond. The difference in the ³⁵Cl NQR frequencies decreases in going from Z = C to Z = Si, Ge, in parallel with variation of the Z-Cl bond polarization as the size of Z increases.     

Multi-step sol-gel process and its effect on the morphology of polyethylene oxide (PEO)/SiO2 anion-exchange hybrid materials

Polyethylene oxide (PEO)/SiO₂ anion-exchange hybrid materials were prepared through the sol-gel process of alkoxysilane functionalized PEO-1000 (PEO-[Si(OCH₃)₃]₂) and N-[3-(trimethoxysilyl)propyl] ethylene diamine (A-1120). The influence of the multi-step sol-gel processing procedure, i.e. the pre-hydrolysis of either of the two precursors on the homogeneity of the hybrid materials was investigated. Results showed that the sol-gel reaction of A-1120 and PEO-[Si(OCH₃)₃]₂ from the same time would result in hybrid materials with the highest homogeneity, and pre-hydrolysis of A-1120 or PEO-[Si(OCH₃)₃]₂ could only decrease the materials’ compatibility.     

A new promising phosphor, Na3La2(BO3)3:Ln (Ln=Eu, Tb)

We present an efficient way to search a host for ultraviolet (UV) phosphor from UV nonlinear optical (NLO) materials. With the guidance, Na₃La₂(BO₃)₃ (NLBO), as a promising NLO material with a broad transparency range and high damage threshold, was adopted as a host material for the first time. The lanthanide ions (Tb³⁺ and Eu³⁺)-doped NLBO phosphors have been synthesized by solid-state reaction. Luminescent properties of the Ln-doped (Ln=Tb³⁺, Eu³⁺) sodium lanthanum borate were investigated under UV ray excitation. The emission spectrum was employed to probe the local environments of Eu³⁺ ions in NLBO crystal. For red phosphor, NLBO:Eu, the measured dominating emission peak was at 613 nm, which is attributed to ⁵D₀-⁷F₂ transition of Eu³⁺. The luminescence indicates that the local symmetry of Eu³⁺ in NLBO crystal lattice has no inversion center. Optimum Eu³⁺ concentration of NLBO:Eu³⁺ under UV excitation with 395 nm wavelength is about 30 mol%. The green phosphor, NLBO:Tb, showed bright green emission at 543 with 252 nm excited light. The measured concentration quenching curve demonstrated that the maximum concentration of Tb³⁺ in NLBO was about 20%. The luminescence mechanism of Ln-doped NLBO (Tb³⁺ and Eu³⁺) was analyzed. The relative high quenching concentration was also discussed.     

Uniform Ln (Eu, Tb) doped NaLa(WO4)2 nanocrystals: Synthesis, characterization, and optical properties

Uniform shuttle-like Ln³⁺ (Eu³⁺, Tb³⁺) doped NaLa(WO₄)₂ nanocrystals have been solvothermally synthesized, and the size of the nanocrystals could be easily controlled by adjusting the volume ratio of ethylene glycol (EG) to water. Doped with 5 mol% Eu³⁺ and Tb³⁺ ions, the NaLa(WO₄)₂ nanocrystals showed strong red and green emissions with lifetimes of 0.8 and 1.40 ms, respectively. A high quenching concentration of 15 mol% was observed in Eu³⁺-doped NaLa(WO₄)₂ nanocrystals and 35 mol% in Tb³⁺-doped NaLa(WO₄)₂ nanocrystals. The emission intensity measurements of Eu³⁺-doped NaLa(WO₄)₂ with different sizes indicated that the emission intensity of shuttles with length of 300 nm in average was stronger than that of shuttles with length of 900 nm in average, but was weaker than that of needles with length of 4 and 9 μm in average.     

Sol–gel preparation and white up-conversion luminescence in rare-earth doped PbF<Subscript>2</Subscript> nanocrystals dissolved in silica glass

89.5(SiO₂)10(PbF₂)0.5(REF₃) silicate glasses have been prepared using room temperature sol–gel processing of Si(OCH₂CH₃)₄, Pb(CH₃COO)₂·3H₂O, RE(CH₃COO)₃·nH₂O and trifluoroacetic acid as a fluorinating agent, where RE stands for rare-earth ions, such as Yb³⁺, Er³⁺, Ho³⁺, Tm³⁺, or combinations of those ions. On heat treatment of these glasses at about 300–400 °C, the rare-earth doped spherical PbF₂ nanocrystals precipitate within SiO₂ glass matrix providing transparent nano-structured glass–ceramics, while the diameter of the nanocrystals can be set in the range from 5 to 25 nm by varying time and temperature of the heat treatment. The structural and photoluminescence studies confirm the incorporation of rare-earth ions into the PbF₂ nanocrystals and white and tuneable colour up-conversion luminescence has been detected in case of Yb³⁺-Er³⁺-Tm³⁺ and Yb³⁺-Ho³⁺-Tm³⁺ co-doped nanocrystals by varying dopant ratio and pump power.     

Thermal study in Eu3+-doped boehmite nanofibers and luminescence properties of the corresponding Eu3+:Al2O3

Eu³⁺-doped boehmite nanofiber materials with different Eu³⁺ concentrations were synthesized without any surfactant, and followed by a series of characterizations. It was found that the boehmite nanofibers became coarser with the increase of Eu³⁺ concentration, which resulted in a gradual decrease of their specific surface areas. Moreover, the thermal stability of the boehmite nanofibers was studied by thermogravimetry–differential scanning calorimetry. All materials showed the phase transition from γ-Al₂O₃ to other forms. Yet the transition temperature was increased with the increase of Eu³⁺ concentration. The Eu³⁺-doped boehmite nanofibers with the maximum Eu³⁺ concentrations showed the best thermal stability. Photoluminescence spectra showed that the 2 mol% of doping concentration of Eu³⁺ ions in Eu³⁺:Al₂O₃ nanofiber was optimum.     

Branched and dendritic metallo-carbosiloxanes with OCH2PPh2MLn end-grafted units

A straightforward method for the preparation of metallo carbosiloxanes of type Si(OCH₂CH₂CH₂SiMe₂[OCH₂PPh₂M(CO)_n])₄ (n = 3, M = Ni, 7a; n = 4, M = Fe, 7b; n = 5: M = Mo, 7c; M = W, 7d), Si(OCH₂CH₂CH₂SiMe[OCH₂PPh₂Ni(CO)₃]₂)₄ (8) and Me₂Si(OCH₂CH₂CH₂SiMe[OCH₂PPh₂Ni(CO)₃]₂)₂ (11) is described. The reaction of Si(OCH₂CH₂CH₂SiMeXCl)₄ (1: X = Me, 2: X = Cl) or Me₂Si(OCH₂CH₂CH₂SiMeCl₂)₂ (9) with HOCH₂PPh₂ (3) produces Si(OCH₂CH₂CH₂SiMe₂(OCH₂PPh₂))₄ (4), Si(OCH₂CH₂CH₂SiMe(OCH₂PPh₂)₂)₄ (5) or Me₂Si(OCH₂CH₂CH₂SiMe(OCH₂PPh₂)₂)₂ (10) in presence of DABCO. Treatment of the latter molecules with Ni(CO)₄ (6a), Fe₂(CO)₉ (6b), M(CO)₅(Thf) (6c: M = Mo; 6d: M = W), respectively, gives the title compounds 7a-7d, 8 and 11 in which the PPh₂ groups are datively bound to a 16-valence-electron metal carbonyl fragment.The formation of analytical pure and uniform branched and dendritic metallo carbosiloxanes is based on elemental analysis, and IR, ¹H, ¹³C{¹H}, ²⁹Si{¹H} and ³¹P{¹H} NMR spectroscopic studies. In addition, ESI-TOF mass spectrometric studies were carried out.     

Alternativ-Liganden. XXX [1] Neue Tripod-Liganden XM' (OCH2PMe2)n(CH2CH2PMe2)3−n (M' = Si; Ge; n = 0–3) für Käfigstrukturen

Alternative Ligands. XXX Novel Tripod Ligands XM' (OCH₂PMe₂)_n(CH₂CH₂PMe₂)_3?n (M' = Si, Ge; n = 0–3) for Cage Structures Attempts to prepare new tripod ligands XSi(OCH₂PMe₂)₃ [X = CF₃ ( 15 ), C₆F₅ ( 16 ), NMe₂ ( 17 ), Cl ( 18 ), F ( 19 ), H ( 20 ), OEt ( 21 ), OMe ( 22 )] prove to be unsuccessful in spite of using different pathways, because the groups X undergo following reactions giving insoluble solids (polyadducts) or form inseparable mixtures, e. g. (RO)_nSi(OCH₂PMe₂)_4?n (R = Me, Et). In many cases Si(OCH₂PMe₂)₄ ( 13 ) can be isolated from the reaction mixture. The syntheses of the ligands XSi(CH₂CH₂PMe₂)₃ [X = NMe₂ ( 6 ), Cl ( 7 ), F ( 8 ), OMe ( 9 ), Vi ( 12 )], Si(OCH₂PMe₂)₄ ( 13 ) und Me₃GeOCH₂PMe₂ ( 14 ) are successful. The compounds MeSi(OCH₂PMe₂)₂CH₂CH₂NMe₂ ( 10 ) and MeSi(OCH₂PMe₂)₂CH₂CH₂P(CF₃)₂ ( 11 ) with different donor groups are obtained in good yields. The preparative program includes the synthesis of the known representatives MeSi(OCH₂PMe₃)₃ ( 1 ), MeSi(OCH₂PMe₂)₂CH₂CH₂PMe₂ ( 2 ), MeSi(OCH₂PMe₂)(CH₂CH₂PMe₂)₂ ( 3 ), MeSi(CH₂CH₂PMe₂)₃ ( 4 ) and MeGe(OCH₂PMe₂)₃ ( 5 ). Important preparative steps are the substitution of M'Cl (M' = Si, Ge) by Me₂PCH₂O groups and the photochemically induced or base catalyzed addition of HNMe₂, HPMe₂ or HP(CF₃)₂ to SiVi functions. The novel compounds are characterized by analytical and spectroscopic (IR, NMR, MS) investigations.     

The preparation,characterization, photoelectrochemical and photocatalytic properties of lanthanide metal-ion-doped TiO2 nanoparticles

Lanthanide metal-ion-doped TiO₂ nanoparticles were prepared with hydrothermal method and characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma (ICP) and fluorescence spectrum. The results showed that a small part of metal ions entered into the lattice of TiO₂ and others adsorbed on the surface of TiO₂. The photoelectrochemical and photocatalytic properties of these lanthanide metal-ion-doped TiO₂ nanoparticles were investigated and the results showed that the photoresponse of Eu³⁺-, La³⁺-, Nd³⁺- and Pr³⁺-doped TiO₂ electrodes were much larger and that of Sm³⁺-doped TiO₂ electrode was a little larger than that of undoped TiO₂ electrode, indicating that the photogenerated carriers were separated more efficiently in Eu³⁺-, La³⁺-, Nd³⁺- and Pr³⁺-doped TiO₂ nanoparticles than in undoped TiO₂ nanoparticles. The photocatalytic degradation of rhodamine B (RB) was conducted in the suspension of lanthanide metal-ion-doped TiO₂ nanoparticles, and its first-order reaction rate constant (k) and average initial rate (r_ini) were significantly higher in the presence of Eu³⁺-, La³⁺-, Nd³⁺- and Pr³⁺-doped TiO₂ nanoparticles than those in the presence of undoped TiO₂ nanoparticles. The enhanced photocatalytic degradation rate of RB in the presence of Eu³⁺-, La³⁺-, Nd³⁺- and Pr³⁺-doped TiO₂ nanoparticles is attributed to increased charge separation in these systems. The effect of the content of La³⁺ on the reaction parameters (k and r_ini) was also investigated and the result showed that there was an optimal value (ca. 0.5%) of the content of La³⁺ to make the rate constant (k) and average initial rate (r_ini) reach the maxima.     

Dissoziative ionisierung von 2-trimethylsilyl-1-phenoxyethan. Nachweis des nicht-klassischen ethylen-trimethylsilanium-ions in der gasphase

The mass spectrometric investigation of specifically deuterium and ¹³C labelled 2-trimethylsilyl-l-phenoxyethanes proves that the dissociative ionization of β-silyl-substituted ethane derivatives (loss of PhO^?; p-CH₃C₆H₄O^?; and C₄H^?₉ from PhOCH₂CH₂SiMe₃, p-MeC₆H₄OCH₂CH₂SiMe₃ and CH₃CH₂CH(CH₃)CH₂-CH₂SiMe₃, respectively) yields the non-classical bridge ethylene trimethylsilanium ion and not the open-chain isomer. Other stable C₅H₁₃Si^+? ions, characterised by collisional activation mass spectrometry, are the dimethyl n-propyl silicenium ion and the l-trimethylsilyl ethyl cation, both generated from the molecular ions of CH₃CH₂CH₂Si(Cl)Me₂ and CH₃CH(Cl)SiMe₃ via unimolecular loss of Cl^?.     

Preparation and luminescence properties of green-light-emitting afterglow phosphor Ca8Mg(SiO4)4Cl2:Eu2+

Green-light-emitting long-lasting phosphorescence phosphor, Eu²⁺ activated calcium magnesium chlorosilicate Ca₈Mg(SiO₄)₄Cl₂, has been prepared by a modified solid-state reaction method using Ca₂SiO₄:Eu²⁺ as a precursor. Its properties have been discussed and analyzed utilizing XRD, photoluminescence, excited-state decay curve and long-lasting phosphorescence decay curve. Upon UV light excitation, the emission spectrum of Ca₈Mg(SiO₄)₄Cl₂:Eu²⁺ phosphor is composed of two separate bands centered at 425 nm and 505 nm, respectively. Furthermore, after irradiation by a 320-nm UV light for 3 min, the 2% Eu²⁺-doped Ca₈Mg(SiO₄)₄Cl₂ phosphor emits intense green-light-emitting afterglow from the 4f⁶5d¹→4f⁷ transition of Eu²⁺, and its afterglow can be seen with the naked eye in the dark clearly for more than 3 h after removal of the excitation source. The disappearance of the high-energy 425 nm band in the afterglow emission spectrum is explained by its different crystallographic sites. The afterglow decay curve of the Eu²⁺-doped Ca₈Mg(SiO₄)₄Cl₂ phosphor contains a fast decay component and another slow decay one. The possible mechanism of this long-lasting phosphorescence phosphor is also discussed based on the experimental results.     

Effect of Inorganic Components on Thermal Stability of Methylsiloxane-Based Inorganic/Orgnaic Hybrids

The thermal decomposition behavior of methylsiloxane-based inorganic/organic hybrids containing an inorganic component derived from metal alkoxides such as Si(OCH₃)₄, Al(O^sC₄H₉)₃, Ti(OⁱC₃H₇)₄ and Nb(OC₂H₅)₅ was investigated by means of thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The decomposition temperature of methyl groups in methylsiloxane-based inorganic/organic hybrids containing an inorganic component derived from metal alkoxides was higher than that in the methylsiloxane-based inorganic/organic hybrid prepared from only CH₃Si(OC₂H₅)₃. In particular, when incorporating Nb and Ti inorganic components, methyl groups in methylsiloxane-based inorganic/organic hybrids decomposed at about 100 and 200^∘C higher temperatures, respectively, than those in the methylsiloxane-based inorganic/organic hybrid prepared from only CH₃Si(OC₂H₅)₃. The incorporation of an inorganic component other than siloxane into methylsiloxane-based inorganic/organic hybrids was found to thermally stabilize the methyl groups of methylsiloxane networks.     

Hydrothermal synthesis and luminescence behavior of rare-earth-doped NaLa(WO4)2 powders

NaLa(WO₄)₂ powders doped with Eu³⁺, Nd³⁺, and Er³⁺ have been synthesized by a mild hydrothermal method and a crystal of exclusive scheelite phase could be obtained at low temperature. From the spectrum of Eu³⁺ it has been concluded that the dopant Eu³⁺ ion occupies a La³⁺ site and mainly takes the site with C₂ symmetry. The higher quenching concentration can be observed in the Eu³⁺-doped NaLa(WO₄)₂ powders. The Er³⁺- and Nd³⁺-doped NaLa(WO₄)₂ powders exhibit luminescence in the near infrared (Er³⁺ at 1550 nm, and Nd³⁺ at 1060 nm). The transition mechanism of the up-conversion luminescence of the Er³⁺-doped NaLa(WO₄)₂ powders can be ascribed to two photons absorption process.     

Characterization and properties of Eu3+-doped CdWO4 prepared by a hydrothermal method

Eu³⁺-doped CdWO₄ was prepared for the first time by a hydrothermal method. The structure, morphology, and luminescence of the Eu³⁺-doped CdWO₄ were characterized. TEM results revealed that the pure CdWO₄ was a nanorod with a width of about 50 nm. The photoluminescent properties of Eu³⁺-doped CdWO₄ complexes indicated energy transfer from WO₄ ^2? groups to Eu³⁺ and suggested effective doping of Eu³⁺ into the lattice of CdWO₄. The photocatalytic activity of CdWO₄ and Eu³⁺-doped CdWO₄ was investigated by the photodegradation of methyl orange (MO). Eu³⁺-doped CdWO₄ had enhanced photocatalytic activity in the photodegradation of MO. The hydroxyl radical was detected by the terephthalic acid photoluminescence (TA-PL) method, and the regular change revealed that the hydroxyl radical may be the active species.     

Crystal structure of Eu-doped M3MgSi2O8 (M: Ba, Sr, Ca) compounds and their emission properties

Emission properties of Eu²⁺-doped M₃MgSi₂O₈ (M: Ba, Sr, Ca) are discussed in terms of the crystal structure. When Ba²⁺ ions account for over one third of M²⁺ ions, M₃MgSi₂O₈ crystallizes in glaserite-type trigonal structure, while Ba-free compounds crystallize in merwinite-type monoclinic structure. Under UV excitation, the Eu²⁺-doped glaserite-type compounds exhibit an intense blue emission assigned to 5d-4f electron transition at about 435 nm, regardless of the molar ratio of Ba²⁺, Sr²⁺ and Ca²⁺ ions. By contrast, the Eu²⁺-doped merwinite-type compounds show an emission color sensitive to the ratio. A detailed analysis of the emission spectra reveals that the emission chromaticity for the Eu²⁺-doped M₃MgSi₂O₈ is composed of two emission peaks reflecting two different sites accommodating M²⁺ ion.     

Dynamic mechanical and dielectric properties of ORMOCER® incorporating functionalized poly(styrene) latexes

Organically modified aluminosilicate hybrid materials incorporating polystyrene and poly(styrene‐co‐hydroxypropyl acrylate) latexes, (3‐glycidyloxypropyl) trimethoxysilane, and aluminum sec‐butoxide [Al(O^sBu)₃] were synthesized by a sol–gel process. The bulk materials obtained were macroscopically homogeneous dispersions with good mechanical properties. Dynamic mechanical and dielectric analyses of these new hybrid materials as a function of the Al(O^sBu)₃ concentration and copolymer composition revealed a series of transitions that represented relaxation processes of the incorporated polymer (glass transition), ?Al? O? Si?, the ?Si? O? Si? part of the network, and segmental motion of unreacted ?Si? (CH₂)₃OCH₂CHCH₂O chains. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 860–867, 2001     

Molecular design of luminescent organic-inorganic hybrid materials activated by europium (III) ions

Luminescent hybrid materials consisting in rare-earth (Eu³⁺, Gd³⁺) organic complexes covalently attached to a silica-based network have been obtained by a sol–gel process. Four dicarboxylic acids with different aromatic subunits (dipicolinic acid, 4-phenyl-2,6-pyridinedicarboxylic acid, 4-(phenylethynyl)-2,6-pyridinedicarboxylic acid and 2,6-Bis(3-carboxy-1-pyrazolyl)pyridine) have been chosen as ligands for Ln³⁺ ions. They were grafted to 3-aminopropyltriethoxysilane (APTES) to give organically modified alkoxysilanes that were used as molecular precursors for the preparation of hybrid materials. Ln³⁺ first coordination sphere, composition of the siloxane matrix and connection between the organic and inorganic parts have been characterized by infrared spectroscopy, by ¹³C²⁹Si solid-state NMR as well as by elemental analyses. UV excitation in the organic component resulted in strong emission from Eu³⁺ ions due to an efficient ligand-to-metal energy transfer. As compared to reference organic molecules, hybrid samples exhibited similar emission properties under UV excitation in addition to mainly unchanged excited states lifetimes. However, by direct excitation of the Eu³⁺-⁵D₀ energy level, the presence of two different site distributions were evidenced in the four hybrid compounds. Emission features related to each of these site distributions and their respective attribution were investigated. Variations in the relative emission intensities were observed according to the nature of the organic chromophore. These variations were discussed in relation to the ATE (Absorption-Transfer-Emission) mechanism and to the relative energy positions of the ligand and the rare-earth ions respectively.