Photophysics of the triple state of metal complexes of 9-anthracenecarboxylic acid

The triplet-triplet (T-T) absorption spectra and the T-T absorption decay kinetics are measured for solutions of 9-anthracenecarboxylic acid (ACA) and its complexes with metal ions (Cd³⁺ and Ln³⁺=Y³⁺, La³⁺, Ce³⁺, Eu³⁺, Gd³⁺, and Tb³⁺) in dimethylsulfoxide (DMSO) by the methods of flashlamp and laser pulse photolysis. The rate constants k _T of intracomplex quenching of the triplet state are measured for ACA complexes with ions Gd³⁺, Ce³⁺, Tb³⁺, and Eu³⁺. Larger values of k _T in complexes of ACA with paramagnetic ions Ce³⁺, Tb³⁺, and Eu³⁺, which have low-lying energy levels, compared to the values of k _T for complexes with other ligands (pyrene-3-sulfonate, pyrene-1,3,6,8-tetrasulfonate, and benzo[ghi]perylene-1,2-dicarboxylate) were explained by the lower energy of the triplet state of ACA (14400 cm^?1). For a complex with a paramagnetic ion Gd³⁺, which has no low-lying energy levels, the value of k _T is close to that measured by us earlier for the inner-sphere complex of pyrene-1,3,6,8-tetrasulfonate with the same ion. These results confirm our earlier assumption about the inner-sphere complexing of ACA with Ln³⁺ ions in DMSO.     

Eu/Tb ions co-doped white light luminescence Y2O3 phosphors

Y₂O₃:Eu³⁺, Tb³⁺ phosphors with white emission are prepared with different doping concentration of Eu³⁺ and Tb³⁺ ions and synthesizing temperatures from 750 to 950 °C by the co-precipitation method. The resulted phosphors were characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. The results of XRD indicate that the crystallinity of the synthesized samples increases with enhancing the firing temperature. The photoluminescence spectra indicate the Eu³⁺ and Tb³⁺ co-doped Y₂O₃ phosphors show five main emission peaks: three at 590, 611 and 629 nm originate from Eu³⁺ and two at 481 and 541 nm originate from Tb³⁺, under excitation of 250-320 nm irradition. The white light luminescence color could be changed by varying the excitation wavelength. Different concentrations of Eu³⁺ and Tb³⁺ ions were induced into the Y₂O₃ lattice and the energy transfer from Tb³⁺→Eu³⁺ ions in these phosphors was found. The Commission International de l’Eclairage (CIE) chromaticity shows that the Y₂O₃:Eu³⁺, Tb³⁺ phosphors can obtain an intense white emission.     

Intramolecular Energy Transfer and Co-luminescence Effect in Rare Earth Ions (La, Y, Gd and Tb) Doped with Eu3+ β-diketone Complexes

In this paper, Eu³⁺ β-diketone Complexes with the two ligands 1-(2-naphthoyl)-3, 3, 3-trifluoroacetonate (TFNB) and 2’2-bipyridine (bpy) have been synthesized. Furthermore, we reported a systematical study of the co-fluorescence effect of Eu(TFNB)₃bpy doped with inert rare earth ions (La³⁺, Gd³⁺ and Y³⁺) and luminescence ion Tb³⁺. The co-luminescence effect can be found by studying the luminescence spectra of the doped complexes, which means that the existence of the other rare earth ions (La³⁺, Y³⁺, Gd³⁺ and Tb³⁺) can enhance the luminescence intensity of the central Eu³⁺, which may be due to the intramolecular energy transfer between rare earth ions and Eu³⁺. The efficient intramolecular energy transfer in all the complexes mainly occurs between the ligand TFNB and the central Eu³⁺. Full characterization and detail studies of luminescence properties of all these synthesized materials were investigated in relation to co-fluorescence effect between the central Eu³⁺ and other inert ions. Further investigation into the luminescence properties of all the complexes show that the characteristic luminescence of the corresponding Eu³⁺ through the intramolecular energy transfers from the ligand to the central Eu³⁺. Meantime, the differences in luminescence intensity of the ⁵D₀→⁷F₂ transition, in the ⁵D₀ lifetimes and in the ⁵D₀ luminescence quantum efficiency among all the synthesized materials confirm that the doped complex Eu_0.5Tb_0.5(TFNB)₃bpy exhibits higher ⁵D₀ luminescence quantum efficiency and longer lifetime than the pure Eu(TFNB)₃bpy complex and other materials.     

Sensitized luminescence of Eu and Tb macrocyclic complexes bearing benzophenone antennae

Sensitized luminescence behavior of lanthanide (Ln=Eu³⁺, Tb³⁺) macrocyclic cyclen (1,4,7,10-tetraazacyclododecane) complexes bearing one or four benzophenone (BP) moieties as antenna (LnL1 and LnL4) has been studied in water. Despite higher molar extinction coefficient of EuL4 owing to four antennae, it shows only one-thirtieth the luminescence intensity of EuL1. Energy level of triplet excited-state of BP antenna (E_T) is only a few kJ mol⁻¹ higher than that of ⁵D₂ excited-state of Eu³⁺, thus promoting a back energy transfer (BET) from ⁵D₂ of Eu³⁺ to ground-state BP antennae. On EuL4 bearing four antennae, BET occurs more rapidly than that on EuL1, thus exhibiting much weaker luminescence. For Tb complexes, the energy gap between E_T of BP antenna and ⁵D₄ excited state of Tb³⁺ is large enough (>13 kJ mol⁻¹), such that practically no BET occurs. The luminescence intensity of TbL4 is, however, lower (two-third) than that of TbL1. Time-resolved luminescence measurement reveals that hydration number of Tb³⁺ within TbL4 is twice that within TbL1. This is because the structural distortion of ligands on TbL4, caused by an intramolecular dipole-dipole interaction among the BP antennae, allows coordination of higher number of H₂O molecules to Tb³⁺, thus leading to a strong Tb luminescence quenching via O-H oscillators.     

Sensitized luminescence properties of dinuclear lanthanide macrocyclic complexes bearing a benzophenone antenna

Dinuclear lanthanide (Ln=Tb³⁺ or Eu³⁺) complexes (Ln₂L2) of two octadentate macrocyclic polyaminopolycarboxylic ligands connected through a benzophenone (BP) moiety (L2) have been synthesized. Sensitized luminescence properties of Ln₂L2 in water have been studied in comparison to those of BP-conjugated mononuclear Ln complexes (LnL1). The luminescence intensity of Tb₂L2 is lower than that of TbL1 because of lower triplet quantum yield of the BP moiety. In contrast, Eu₂L2 shows higher intensity than EuL1. For both Eu complexes, energy level of triplet excited-state BP (³BP*) is only 3 kJ mol⁻¹ higher than that of ⁵D₂ excited-state of Eu³⁺. The ⁵D₂ state formed by a triplet-energy transfer (TET) from ³BP* is therefore deactivated by a back energy transfer (BET) to the ground-state BP, resulting in low luminescence intensity of EuL1. In contrast, within Eu₂L2, TET from ³BP* to ⁵D₀ state of two Eu³⁺ ions is accelerated, thus leading to higher luminescence intensity. Another notable feature of Eu₂L2 is the luminescence quantum yield independent of its concentration. In contrast, for EuL1 system, an intermolecular BET occurs from ⁵D₂ state of Eu³⁺ to the ground-state BP conjugated to another EuL1 complex, resulting in a yield decrease with the concentration increase.     

Energy transfer and photoextinction from Ln to Tb and Eu in aqueous chloride solutions

Energy transfer and photoextinction from Ln³⁺ to Tb³⁺ and Eu³⁺ in aqueous chloride solutions were studied by absorption, emission and excitation spectra. The energy gaps below the luminescent terms of Gd³⁺, Tb³⁺ and Eu³⁺ are spanned by 10, 5 and 4 quanta, respectively, of the highest energy vibration in aqueous solution, and luminescence is observed in each case. This is not so for other Ln³⁺ where nonradiative deactivation dominates over luminescence. It was verified that only Gd³⁺ could transfer energy to Tb³⁺ and Eu³⁺ ions in aqueous or acid solutions. The ions Pr³⁺, Nd³⁺, Sm³⁺, Dy³⁺, Ho³⁺ and Er³⁺ exhibited strong competitive absorption at certain wavelengths, resulting in the photoextinction of Tb³⁺ and Eu³⁺ emission.     

Lanthanide-cored fluorinated dendrimer complexes: synthesis and luminescence characterization

Eu³⁺-, Tb³⁺- and Er³⁺-cored dendrimer complexes were prepared by self-assembly of three fluorinated dendrons, each with a carboxylate anion focal point, around the lanthanide ion. Energy transfer from the peripheral fluorinated phenyl moieties of the dendrons to the lanthanide cation was evidenced spectroscopically for Eu³⁺- and Tb³⁺-cored dendrimer complexes in solution. The excitation of perfluorinated aromatic groups was found to decay with ca. 0.7 ns and a longer decay time 10-13 ns was related to the coordination at the Ln³⁺ focal point. Luminescence from the lanthanide core decays with lifetime in the range 1-1.5 ms over a wide concentration range (μM-mM), similar to the luminescence decay time of the corresponding acetate ion complexes in D₂O. The main quenching mechanism of the lanthanide emission appears to be due to vibrations among surrounding C-H bonds of the intermediate shell of the flexible dendrimer scaffold. Antenna effect and energy harvesting from the surface of the dendrimer and transfer to the core was the main mechanism for luminescecnce in the dendrimer complexes with lanthanide cations.     

Photophysical Properties of Lanthanide Hybrids Covalently Bonded To Functionalized MCM-41 by Modified Aromatic Carboxylic Acids

MCM-41 mesoporous silica has been functionalized with aromatic carboxylic acids salicylic acid (Sal) and 2-hydroxyl-3-methylbenzoic acid (HMBA) through co-condensation approach of tetraethoxysilane (TEOS) in the presence of the cetyltrimethylammonium bromide (CTAB) surfactant as a template. Organic ligands salicylic acid or 2-hydroxyl-3-methylbenzoic acid grafted to the coupling agent 3-(triethoxysilyl)-propyl isocyanate (TEPIC) was used as the precursor for the preparation of an organic–inorganic hybrid materials. Novel organic–inorganic mesoporous luminescent hybrid containing Ln³⁺ (Tb³⁺, Eu³⁺) complexes covalently attached to the functionalized ordered mesoporous MCM-41, which were designated as Ln-Sal-MCM-41 and Ln-HMBA-MCM-41, respectively, were obtained by sol–gel process. The luminescence properties of these resulting materials were characterized in detail, and the results reveal that luminescent mesoporous materials have high surface area, uniformity in the mesopore structure and good crystallinity. Moreover, the mesoporous material covalently bonded Tb³⁺ complex (Tb-Sal-MCM-41 and Tb-HMBA-MCM-41) exhibit the stronger characteristic emission of Tb³⁺ and longer lifetime than the corresponding Eu-containg materials Eu-Sal-MCM-41 and Eu-HMBA-MCM-41 due to the triplet state energy of modified organic ligands Sal-TEPIC and HMBA-TEPIC match with the emissive energy level of Tb³⁺ very well. In addition, the luminescence lifetime and emission quantum efficiency of ⁵D₀ Eu³⁺ excited state also indicates the efficient intramolecular energy transfer process in Tb-SAL-MCM-41 and Tb-HMBA-MCM-41.     

Photoluminescence investigations of Zn2SiO4 co-doped with Eu and Tb ions

Zinc silicate phosphors co-doped with Eu³⁺ ions and also with both Eu³⁺ and Tb³⁺ ions were prepared by high temperature solid state reaction in air or reducing atmosphere. The luminescence characteristics of the prepared phosphors were investigated. While in the samples prepared in air, Eu³⁺ emission was found to be dominant over Tb³⁺ emission, in the samples prepared in reducing atmosphere, intense Eu²⁺ emission at 448 nm was found to be predominant over narrow Tb³⁺ emission. Luminescence studies showed that Eu³⁺ ions occupy asymmetric sites in Zn₂SiO₄ lattice. The intense f-f absorption peak of Eu³⁺ at 395 nm observed in these phosphors suggests their potential as red emitting phosphors for near ultra-violet light emitting diodes.     

Photoinduced energy transfer from the triplet state of naphthalene moiety in the Tb/Eu complexes of a specially designed naphthalene cryptand

The paper reports time-resolved emission and energy transfer (ET) studies of metal ion complexes of a specially designed rigid macrocyclic naphthalene cryptand (L) under different conditions. Complex formation of L with Li⁺ and H⁺ causes an appreciable increase in singlet state quantum yield and lifetime of L implying photoinduced electron transfer (PET) from the cryptand moiety to naphthalene unit in the free L. The system exhibits photoinduced ET at 77 K in its Tb³⁺ and Eu³⁺ complexes with either NO₃⁻¹ or Cl⁻¹ as counter-anion. The extent of ET is higher for the Tb³⁺ complex as compared to that for the Eu³⁺ complex. In both Tb³⁺ and Eu³⁺ complex, the NO₃⁻¹ ions influence the relative orientation of donor (L) and acceptor (Ln³⁺) more in favour of ET than the Cl⁻¹ ions. The rate constants for the ET from the naphthalene moiety of L to the acceptor (Ln³⁺) have been evaluated at 77 K. The results suggest ET from the triplet state of naphthalene using an exchange mechanism. The ground state geometries of the system L and its complexes with Li⁺, Cs⁺ and Tb³⁺ have been determined using DFT methods to interpret our results.     

Energy transfer from benzoic acid to lanthanide ions in benzoic acid-functionalized lanthanide-doped CaF2 nanoparticles

The preparation of benzoic acid-functionalized CaF₂:Ln³⁺ (Ln = Eu or Tb) nanoparticles and their sensitized luminescence are described in this report. First, to achieve sufficient proof for energy transfer from benzoic acid (BA) to lanthanide ions doped in nanoparticles, we employ Eu³⁺ as the microscopic probe and investigate the luminescent spectra of benzoic acid-functionalized CaF₂:Eu³⁺ (BA-CaF₂:Eu³⁺) nanoparticles. Next, to further reveal the difference between sensitized luminescence and common luminescence for Eu³⁺ doped in CaF₂ nanoparticles, we study the emission spectra of BA-CaF₂:Eu³⁺ nanoparticles excited at 286 nm and 397 nm, respectively. Finally, we analyze and compare the luminescent spectra of BA-CaF₂:Tb³⁺ and CaF₂:Ce³⁺, Tb³⁺ nanoparticles in detail. Our results indicate that both Eu³⁺ and Tb³⁺ doped in CaF₂ nanoparticles can be efficiently sensitized through benzoic acid.     

Effect of Eu,Tb codoping on the luminescent properties of Y2O3 nanorods

Red-emitting Y₂O₃:Eu³⁺ and green-emitting Y₂O₃:Tb³⁺ and Y₂O₃:Eu³⁺, Tb³⁺ nanorods were synthesized by hydrothermal method. Their structure and micromorphology have been analyzed by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The photoluminescence (PL) property of Y₂O₃:Eu³⁺,Tb³⁺ phosphor was investigated. In the same host (Y₂O₃), upon excitation with ultraviolet (UV) irradiation, it is shown that there are strong emissions at around 610 and 545 nm corresponding to the forced electric dipole ⁵D₀-⁷F₂ transition of Eu³⁺ and ⁵D₄-⁷F₅ transition of Tb³⁺, respectively. Different qualities of Eu³⁺and Tb³⁺ ions are induced into the Y₂O₃ lattice. From the excitation spectrum, we speculate that there exists energy transfer from Tb³⁺ to Eu³⁺ ions .The emission color of powders reveals regular change in the separation of light emission. These powders can meet with the request of optical display material for different colors or can be potentially used as labels for biological molecules.     

On the Luminescence of Ce<Superscript>3+</Superscript>, Eu<Superscript>3+</Superscript>, and Tb<Superscript>3+</Superscript> in Novel Borate LiSr<Subscript>4</Subscript>(BO<Subscript>3</Subscript>)<Subscript>3</Subscript>

This paper reports on the photoluminescence (PL) and time-resolved properties of Ce³⁺, Eu³⁺, and Tb³⁺ in novel LiSr₄(BO₃)₃ powder phosphors. Ce³⁺ shows an emission band peaking at 420 nm under 350-nm UV excitation. Energy transfer from Ce³⁺ to Mn²⁺ takes place in the co-doped samples. Eu³⁺ shows red emission under near UV excitation. LiSr₄(BO₃)₃:Eu³⁺ phosphor could be a suitable candidate for phosphor-converted solid state lighting. The luminescence lifetime is 2.13 ms for Eu³⁺ in LiSr₄(BO₃)₃:0.001Eu³⁺. As Eu³⁺ concentration increasing, the decay curves deviate from exponential behavior. Tb³⁺ shows the strongest ⁵D₄→⁷ F₅ emission line at 540 nm. Decay curves of ⁵D₄→⁷ F₅ and ⁵D₃→⁷ F₅ emission with different Tb³⁺ concentrations were also measured. Cross-relaxation process is discussed based on the decay curves.     

Optical properties of red, green and blue emitting rare earth benzenetricarboxylate compounds

Red, blue and green emitting rare earth compounds (RE³⁺=Eu³⁺, Gd³⁺ and Tb³⁺) containing the benzenetricarboxylate ligands (BTC) [hemimellitic (EMA), trimellitic (TLA) and trimesic (TMA)] were synthesized and characterized by elemental analysis, complexometric titration, X-ray diffraction patterns, thermogravimetric analysis and infrared spectroscopy. The complexes presented the following formula: [RE(EMA)(H₂O)₂], [RE(TLA)(H₂O)₄] and [RE(TMA)(H₂O)₆], except for Tb-TMA compound, which was obtained only as anhydrous. Phosphorescence data of Gd³⁺-(BTC) complexes showed that the triplet states (T) of the BTC³⁻ anions have energy higher than the main emitting states of the Eu³⁺ (⁵D₀) and Tb³⁺ (⁵D₄), indicating that BTC ligands can act as intramolecular energy donors for these metal ions. The high values of experimental intensity parameters (Ω₂) of Eu³⁺-(BTC) complexes indicate that the europium ion is in a highly polarizable chemical environment. Based on the luminescence spectra, the energy transfer from the T state of BTC ligands to the excited ⁵D₀ and ⁵D₄ levels of the Eu³⁺ and Tb³⁺ ions is discussed. The emission quantum efficiencies (η) of the ⁵D₀ emitting level of the Eu³⁺ ion have been also determined. In the case of the Tb³⁺ ion, the photoluminescence data show the high emission intensity of the characteristic transitions ⁵D₄→⁷F_J (J=0-6), indicating that the BTC ligands are good sensitizers. The RE³⁺-(BTC) complexes act as efficient light conversion molecular devices (LCMDs) and can be used as tricolor luminescent materials.     

A cross-relaxation mechanism of fluorescence quenching in complexes of lanthanide ions with organic ligands

For the first time, direct experimental evidence of a new mechanism for the quenching of fluorescence of organic ligands (L) in complex compounds with lanthanide ions (Ln³⁺) is obtained. By analogy with the mechanism of luminescence quenching upon pair interactions of Ln³⁺ ions in inorganic systems, this mechanism is called the cross-relaxation mechanism. The experiments are performed with complexes of Tb³⁺ with dianions of halogen-substituted fluoresceins (HSFs): 4,5-dibromo-and 4,5-diiodofluorescein, eosin B, eosin, erythrosin, and Rose Bengal in dimethyl sulfoxide. In accordance with this mechanism—exchange energy transfer, L^2?(*S ₁), Tb³⁺(⁷ F ₆)→L^2?(T ₁), Tb³⁺(⁷ F _{5, 4}), allowed by the spin selection rules—an increase in the quantum yield of formation of the triplet state (Φ_T) of a ligand L^2? and a decrease in the quantum yield of fluorescence (Φ_fl) are found to take place upon complexation. The efficiency of this process amounts to ～1 in accordance with the equality Φ_fl+Φ_T=1, valid for solutions of HSFs. The possibility of other processes leading to a similar effect, specifically, recharging of the system (as for complexes of HSFs with Eu³⁺ and ³⁺) is considered. An example of inductive resonance interactions in complexes of HSFs with Pr³⁺ is given. The manifestation of equilibrium between outer-sphere and inner-sphere complexes in the photophysics of complexes of metals with HSFs is discussed.

     

Spectroscopic Study on the Photophysical Properties of Lanthanide Complexes with Long Chain Mono-Docosyl Phthalate

Ortho phthalic anhydride was modified with long chain alcohol (1-docosanol) to its corresponding monodocosyl phthalate (22-Phth). Subsequently, three novel lanthanide (Eu³⁺, Tb³⁺, and Dy³⁺) complexes with the long chain monodocosyl phthalate were synthesized and characterized by elemental analysis and Infrared spectra. The photophysical properties of these complexes were studied in detail with ultraviolet-visible absorption spectra, low temperature phosphorescence spectra and fluorescent spectra. The triplet state energy of 22-Phth was determined to be around 25,000 cm⁻¹ from the maximum phosphorescent peak at 400 nm, suggesting 22-Phth is suitable for the sensitization of the luminescence of Eu³⁺, Tb³⁺, and Dy³⁺. The fluorescence excitation and emission spectra for these lanthanide complexes of the three ligands take agreement with the above predict from energy match principle.     

Influence of electric field on photoluminescence of lanthanide-doped nematic liquid crystal

Highly resolved luminescence and luminescence excitation spectra of recently synthesized LnL₃bpy complexes, where Ln=Eu³⁺, Tb³⁺, bpy=2,2′- bipyridyne and L=phosphoroazo derivative of β-diketone: CCl₃C(O)NP(O)(OCH₃)₂, in solid state and dissolved in nematic liquid crystal 6CHBT [4-(isothiocyanatophenyl)-1-(trans-4-hexyl)cyclohexane] were measured. The photoluminescence intensity of the complexes dissolved in 6CHBT was found to exhibit a strong dependence on the electric field. The mechanism of the effect and reason of its asymmetry with respect to the sign of electric field are discussed in the paper. Luminescence decay time in various environments and experimental quantum yields of the luminescence of these compounds in CDCl₃ and CHCl₃ solutions were measured.     

Effect of symmetric substitution on the phenyl groups of Eu-dibenzoyl methane complexes on their luminescence properties

Complexes of Eu³⁺ ion and ligands like dibenzoylmethane (DBM) as well as flouro- and methoxy-substituted DBMs have been prepared and characterized. Peak maxima and line shapes of the π-π^* transitions arising from the ligands in these complexes were very sensitive to the nature of the substituents attached to the phenyl groups of DBM. Symmetric substitution at both the phenyl groups led to improved luminescence in terms of higher quantum yields of emission and longer lifetime of the excited state (⁵D₀) of Eu³⁺ ions. Effective averaging/cancellation of the dipole-dipole interactions in symmetrically substituted ligands and the associated decrease in the extent of quenching were responsible for the improved luminescence from such complexes.     

Solvothermal synthesis and luminescence properties of the novel aluminum garnet phosphors for WLED applications

The color rendering index (CRI) and structural stability of cerium doped yttrium aluminum garnet (YAG:Ce) based phosphors have been enhanced by replacing Y³⁺ ions by larger radius ions (Tb³⁺, Gd³⁺, Eu³⁺, and Sm³⁺) at the dodecahedral site and replacing Al³⁺ ions by larger ones (Ga³⁺, Y³⁺, Tb³⁺, Gd³⁺, and Sm³⁺) at the octahedral site. These aluminum garnet crystalline powders were prepared by solvothermal reaction method at 300 °C for 48 h. The lattice constant values of synthetic aluminum garnet crystalline powders are larger than that of YAG and the emission wavelength of Ce³⁺ ion of these samples is longer than that of YAG:Ce. FESEM and TEM studies revealed that the Ln₃Ga₂Al₃O₁₂ and Ln₃Al₂Al₃O₁₂ crystalline powders have 3-dimensional star-like morphology with submicron size and good crystallinity, while, Ln₃(LnAl)Al₃O₁₂ garnet crystalline powders were cubic crystalline phases and shaped as cubes with the round edge having an approximate diameter of about 200–400 nm. All the prepared powders were grown along (100) direction and crystallized into single crystal. Also, the effects of treatment time and reaction temperature on the structure of aluminum garnet crystalline powders have been investigated.     

Preparation and luminescence properties of hybrid materials containing lanthanide complexes covalently bonded to a terpyridine-functionalized silica matrix

New kinds of organic-inorganic hybrid materials consisting of lanthanide (Er³⁺, Eu³⁺, and Tb³⁺) complexes covalently bonded to a silica-based network have been obtained by a sol-gel approach. A new versatile compound containing terpyridine has been synthesized by 4′-p-aminophenyl-2,2′:6′,2″-terpyridine and 3-(triethoxysilyl)propyl isocyanate, which is used as the a ligand of lanthanide ions and also the siloxane network precursor. The obtained hybrid materials were characterized by FT-IR, TGA, DSC, near-infrared, and visible spectrofluorometer, as well as decay analysis. For the Hybrid-Er and Hybrid-Eu, excitation at the ligand absorption wavelength resulted in the typical near-IR luminescence (centered at around 1.54 μm) resulting from the ⁴I_13/2-⁴I_15/2 transition of Er³⁺ ions and strong visible region emission of the Eu³⁺ ions (⁵D₀-⁷F_J), which contributed to the efficient energy transfer from the ligands to the lanthanide ions. However, we have not found strong emission for the Hybrid-Tb. This indicated that the energy transfer did not take place in this system. A model of indirect excitation mechanism to explain the phenomenon was also suggested.