Luminescence properties of europium (III) cryptates trapped in sol-gel glass

The Lanthanide complexes Eu-2.2.1 and Eu-2.2.2 were synthesized and then incorporated into silica based transparent organic-inorganic hybrid material by the sol-gel method as an example of how doped xerogel materials are emerging as an important means of producing new materials. The produced gels were diagnosed to monitor emission spectra of the luminescent trivalent europium (Eu³⁺) complexes; emissions were compared to those for gels containing uncomplexed Eu³⁺. Results of the experiments (emission and lifetimes) concerning the coordination sphere composition showed that a cryptand ligand with aromatic groups (short range effect) and the hydrophobic gel host (long range effect) settle efficient action in the antenna effect and isolate the central ion from efficient quenchers, as e.g. water molecules. Each ligand imposed a distinct splitting pattern on the europium emission bands that helps identify them.     

Study of the luminescence of tris(2-thenoyltrifluoroacetonato)lanthanide(III) complexes covalently linked to 1,10-phenanthroline-functionalized hybrid sol-gel glasses

The solubility and uniform distribution of lanthanide complexes in sol-gel glasses can be improved by covalently linking the complexes to the sol-gel matrix. In this study, several lanthanide β-diketonate complexes (Ln=Nd, Sm, Eu, Tb, Er, Yb) were immobilized on a 1,10-phenanthroline functionalized sol-gel glass. For the europium(III) complex, a sol-gel material of diethoxydimethylsilane (DEDMS) with polymer-like properties was derived. For the other lanthanide complexes, the sol-gel glass was prepared by using a matrix of tetramethoxysilane (TMOS) and DEDMS. Both systems were prepared under neutral reaction conditions. High-resolution emission and excitation spectra were recorded. The luminescence lifetimes were measured.     

New Insights into Optoelectronic Features of Eu(III) Complexes with Heterocyclic Ligand for Advanced Optical Applications

Our present technological society needs the assistance of lanthanide luminescence in almost every field to meet the global energy demands. In present research work we have synthesized five (one binary and four ternary) 5-(4-methylphenyl)-2- furoic acid based Eu(III) complexes with ancillary ligands, namely, aqua (H₂O), neocuproine (neo), 2, 2’-bipyridyl (bipy), bathophenanthroline (batho) and 1, 10-phenanthroline (phen). The spectroscopic analysis and photophysical features are characterized by the use of different investigative techniques. All the findings obtained from EDAX, elemental (CHN) analysis, FT-IR, NMR, UV–visible spectroscopy declared the coordination of ligand binding sites with the europium ion. These Eu(III) complexes possess good thermal stability and excellent optoelectronic features as predicted with the help of TGA and PL analysis. Diffuse reflectance spectral studies confirm their applications in the wide band gap semiconductors. The Judd–Ofelt analysis and monoexponential behavior of lifetime reveals the existence of asymmetric and single local environment around europium ion. All the complexes show sharp red emission validated by CIE color coordinates, color purity, asymmetric ratio and CCT values. SEM analysis tells that the bulk of these complexes comprised of spherical shaped particles with uniform distribution.

     

Luminescent europium(III) and terbium(III) nicotinate complexes covalently linked to a 1,10-phenanthroline functionalised sol-gel glass

Sol-gel glasses with covalently linked lanthanide complexes are luminescent materials which can be processed at ambient temperatures, which have a good solubility and uniform distribution of the complexes in the host matrix. In this study, a luminescent terbium(III) complex was covalently coupled to an organic-inorganic hybrid material prepared by the sol-gel process. This was realised by use of nicotinate groups as the ligands for the terbium(III) ion. The [Tb(C₅H₄NCO₂)₃(phen)(H₂O)₂] complex was immobilised on the sol-gel glass matrix and showed a green photoluminescence upon irradiation with ultraviolet light. The nicotinate groups act as an antenna to absorb the incident light and channel the excitation energy to the terbium(III) ion. The sol-gel glass was also prepared for the corresponding europium(III) complex. In this case, excitation of the europium(III) ion was possible via both the nicotinate ligands and the 1,10-phenanthroline ligands. High-resolution luminescence and excitation spectra were recorded and the radiative lifetimes were measured.     

Photophysical Properties of Luminescent Quaternary Lanthanide Molecular Hybrid Systems with Chemical Bonds from the Cooperative Design and Assembly of Structure and Function

Two long chain aliphatic acyl chlorides (dodecanoyl chloride (C₁₀H₁₉OCl, abbreviated as DC) and stearoyl chloride (C₁₈H₃₅Ocl, abbreviated as SC)) were modified by means of the amidation reaction with crosslinking molecules (N-aminopropyl-triethoxylsiliane, (APES, H₂N(CH₂)₃Si(OC₂H₅)₃)) and afford two kinds of structural molecular bridge DC (SC)− APES with double reactivity. Subsequently, according to the principle of coordination chemistry, ternary lanthanide (terbium and europium) molecular complex systems with two molecular bridges DC (SC)− APES and 1,10-phenanthroline (phen) of were successfully assembled. Then the modified molecular bridges behave as structural ligands to form the covalent bond Si− O network with matrix precursor (tetraethoxysilane, TEOS) through a sol-gel process (cohydrolysis and copolycondensation process), resulting in a novel quaternary molecular hybrid material (so called as phen-Tb(Eu)−DC(SC)− APES) with strong chemical bonds (N− Tb(Eu)− O coordination bonds and Si− O covalent bonds). And phen behaves as functional ligand to sensitize the luminescence of terbium or europium ions through the effective intramolecular energy transfer process, which gives rise to the characteristic emission of metal ion.     

Eu2+掺杂硼硅酸镁玻璃的发光性能

利用高温固相法合成了Eu2+掺杂的新型蓝色硼硅酸盐发光玻璃,讨论了不同掺杂浓度下硼硅酸镁玻璃体系中Eu-O键共价性的变化以及氧原子周围不同配位环境对MgO-SiO2-B2O3玻璃发光性能的影响.利用X射线衍射仪和荧光光谱仪对该玻璃体系进行了结构表征和性能测试.在紫外-可见光激发下,Eu2+掺杂硼硅酸镁玻璃的荧光发射光谱...     

Spectroscopic study of sulforhodamine 640-doped sol-gel silica

The sol-gel process is a technique which provides a low-temperature route for the preparation of organic dye-doped porous silica glass. Extended UV transmission was observed for HCl-catalysed sol-gel silica. Properties of a solute may differ greatly between a free solution and that solution confined in pores of a sol-gel glass. Absorption and fluorescence properties of sulforhodamine 640-doped silica samples prepared by sol-gel process were investigated. In the TEOS-derived gel, the emission of the dye does not shift during aging but exhibits a large change during drying. The emission maximum of sulforhodamine 640 blue shifts was discussed as a function of increasing rigidity of the surrounding matrix.     

稀土配合物掺杂凝胶的原位光声光谱研究及其共发光效应

采用溶胶-凝胶方法,制备了Ln(Sal)₃·H₂O(Ln3+∶La3+, Nd3+, Tb3+; Sal: 水杨酸) 稀土配合物掺杂的二氧化硅凝胶样品。首次采用光声光谱对稀土配合物在凝胶中的形成进行研究。结果表明,经110 ℃热处理后,Tb3+, La3+和Nd3+配合物掺杂的凝胶样品在配体吸收处的光声强度依次明显增强;而对仅在室温陈化、干燥的湿凝胶样品,其配体吸收处的光声强度几乎完全相同。研究发现,未经适当的热处理过程凝胶样品中稀土配合物尚不能形成。结合荧光光谱,分析了凝胶中稀土离子配位环境的变化和稀土配合物的形成。首次发现了稀土芳香羧酸配合物掺杂凝胶的共发光效应,考察Tb_0.8Gd_0.2(Sal)₃·H₂O和Tb_0.8Nd_0.2(Sal)₃·H₂O配合物掺杂的凝胶样品,发现Gd3+离子的引入了增强了凝胶样品中Tb3+的发光效率,而Nd3+离子的引入明显减弱了凝胶中Tb3+的发光,并对共发光效应可能的机理进行了讨论。     

A new Eu(III)/Tb(III) binuclear coordination compound with crown ethers and bridging 4,4′-dipyridyl

A new Eu(III)/Tb(III) binuclear coordination compound with red and yellow emissions in solution and solid state, respectively, has been prepared. The lanthanide (Ln) ions are coordinated to crown ethers (C) and bridged by a dipyridyl (dipy) ligand. Ln/C and Ln/C/dipy complexes were also synthesized as precursors for the bimetallic compounds. The homo- and heterobimetallic Ln(III) complexes were characterized by elemental analysis as well as infra-red, absorption (UV-visible) and emission spectroscopies. The heterobimetallic complex geometry was predicted using the Sparkle/AM1 model and suggested to a chemical environment of very low symmetry around the lanthanide ions (C₁), in agreement with the luminescence spectrum. The Eu(III) and Tb(III) complexes display intense red and green emissions, respectively, in the solid state at room temperature.     

Micro-Meter Size Organogelator with Tri-Color Luminescence (Blue, Green and Red) Activated by Dy3+, Tb3+ and Eu3+ ions

The preparation of a novel type of low-molecular-weight amphiphilic organogelator bearing three long 14-alkyl chains and hydrophilic oligo(oxyethylene) groups was described. Ultra-violet absorption and fluorescence spectra give evidence of the energy transfer between organic ligands to lanthanide ions. Characteristic green, blue and red luminescence of the organogels were obtained and interesting emission properties of terbium, dysprosium and europium ions were unexpectedly observed at the first time during the order-disorder phase transition point (29 °C).     

Luminescent molecular hybrid system derived from 2-furancarboxylic acid and silylated monomer coordinated to rare earth ions

In this study, silica-based organic-inorganic hybrids were prepared by the sol-gel method. Tetraethoxysilane (abbreviated as TEOS) and a kind of monomer (abbreviated as FA-APES) derived from modified 2-furancarboxylic acid (abbreviated as FA) with (3-aminopropyl)triethoxysilane (abbreviated as APES) were used as the inorganic and organic fragments, respectively. Coordination reaction between lanthanides (europium and terbium ions) and CO group of the monomer happened simultaneously. And after days of aging process the resultant materials showed characteristic luminescence of lanthanides. The enhancement of luminescence can be seen by the comparison with simply doped lanthanide hybrid systems. And it can be explained by the coordination ability of the organic counterpart. IR, NMR, UV-vis absorption, low-temperature phosphorescence spectroscopy and fluorescence spectroscopy were applied to characterize and the above spectroscopic data revealed that the triplet state energy of organic ligand matches with the emissive energy level of lanthanides (especially of Tb³⁺).     

新型稀土铕,铽β-二酮配合物的合成与荧光性质

采用克莱森缩合反应合成了一种新型的β-二酮化合物1-(4-氨基苯)-4,4,4-三氟丁烷-1,3-二酮(p-NBFA).以其为第一配体,邻菲咯啉(phen)为第二配体,合成出新型Eu(Ⅲ),Tb(Ⅲ)三元配合物.通过元素分析确定了配合物的组成为Eu(p-NBFA)3phen和Tb(p-NBFA)3phen.红外光谱的分...     

Rare Earth Centered Hybrid Materials: Tb<Superscript>3+</Superscript> Covalently Bonded with La<Superscript>3+</Superscript>, Gd<Superscript>3+</Superscript>, Y<Superscript>3+</Superscript> Through Sulfonamide Bridge and Luminescence Enhancement

The organic ligand 5-sulfosalicylic acid (SSA) is grafted by (3-aminopropyl) triethoxysilane (APTES) to achieve functionalized sulfonamide bridge (SSA-Si) which can both coordinate to Ln³⁺ to form luminescent center and link inorganic Si-O network through hydrolysis and condensation reaction with tetraethoxysilane (TEOS). Thus the organic–inorganic hybrid is obtained with sol-gel method. The organic polymer poly-methyl methacrylate (PMMA) acts as another precursor is prepared through the direct addition polymerization of MMA monomer in the presence of the initiator BPO (benzoyl peroxide). The two kinds of precursors are coordinated to the Ln³⁺ simultaneously to form organic–inorganic-polymeric hybrids which contain both inorganic Si-O-Si net and organic periodic C–C chains. In these complicated compounds we intercalate different ratios of Tb³⁺ and inert lanthanide ion (La³⁺, Gd³⁺, Y³⁺) and find that the introduction of the inert lanthanide ions can enhance the luminescence intensity. This enhancement phenomenon is called co-luminescence effect which is studied by emission spectra in this paper.     

含铕配合物荧光纳米纤维的制备及光学性质的研究

通过静电纺丝技术,将发光良好的稀土配合物Eu(DBM)₃·H₂O和Eu(DBM)₄·CPC纳米微粒复合到水溶性的聚乙烯基吡咯烷酮中,制备了具有稀土铕离子红色特性荧光的聚合物纳米纤维。通过对稀土配合物以及聚合物纳米纤维样品扫描电镜和透射电镜的测试,发现当稀土配合物复合到聚合物纳米纤维中后,由于与聚乙烯基吡咯烷酮乙醇溶解性良好,其微观结构发生了变化,得到了50～100 nm左右的比较均匀的线状结构。同时,通过对稀土配合物以及聚合物纳米纤维样品的荧光激发、发射光谱及荧光寿命进行研究,表明稀土配合物在聚合物纳米纤维中比其在粉末状有更高的发光强度及更长的荧光寿命,其原因在于高分子纳米纤维为稀土配合物提供了较稳定的化学环境。     

Structural Investigation and Photoluminescent Properties of Gadolinium(III), Europium(III) and Terbium(III) 3-Mercaptopropionate Complexes

This work reports on the synthesis, crystallographic determination and spectroscopic characterization of gadolinium(III), terbium(III) and europium(III) 3-mercaptopropionate complexes, aqua-tris(3-mercaptopropionate)lanthanide(III) - [Ln(mpa)₃(H₂O)]. The Judd-Ofelt intensity parameters were experimentally determined from emission spectrum of the [Eu(mpa)₃(H₂O)]complex and they were also calculated from crystallographic data. The complexes are coordination polymers, where the units of each complex are linked together by carboxylate groups leading to an unidimensional and parallel chains that by chemical interactions form a tridimensional framework. The emission spectrum profile of the [Eu(mpa)₃(H₂O)] complex is discussed based on point symmetry of the europium(III) ion, that explains the bands splitting observed in its emission spectrum. Photoluminescent analysis of the [Gd(mpa)₃(H₂O)] complex show no efficient ligand excitation but an intense charge transfer band. The excitation spectra of the [Eu(mpa)₃(H₂O)] and [Tb(mpa)₃(H₂O)] complexes do not show evidence of energy transfer from the ligand to the excited levels of these trivalent ions. Therefore the emission bands are originated only by direct f-f intraconfigurational excitation of the lantanide(III) ions.     

Variation in the Luminescence Lifetimes of Eucl3·nH2O(N=0,L,2,3,6)

Eu³⁺ ion emission spectra and luminescence lifetimes were investigated for EuCl₃ -nH₂O (n=0,1,2,3,6). Each compound exhibited a characteristic set of emission bands and a specific luminescence lifetime. The number of water molecules and chloride ions coordinated to the Eu³⁺ ion in these materials was estimated from the observed lifetimes, spectroscopic implications, and expected lanthanide coordination numbers. Approximation of the observed luminescence decay constant for each material was possible through the use of arithmetic terms associated with both the complexed water molecules and the complexed chloride ions which make up the inner-coordination sphere of the Eu³⁺ ion.     

Sensitization of Europium Luminescence in Complexes with Thiaprophenic Acid

The sensitized luminescence of europium ion in complexes with thiaprophenic acid has been investigated. It is shown that the luminescence intensity of the Eu (III) increases by 10⁷ times as the result of intramolecular energy transfer from ligand to lanthanide ion. The luminescence properties of the complex have been studied in solutions and a highly sensitive luminescence method for the determination of thiaprophenic acid has been developed.     

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.     

Three-dimensional memory effect in fluorescent photosensitive glass activated by europium and cerium

The persistent extinction of fluorescence emission of Eu(3+) in glasses activated with europium and cerium is reported for the first time to the authors' knowledge. The glass samples containing Eu(3+) and Ce(3+) were initially colorless and transparent and exhibited intense emission peaks at 592 and 612 nm assigned to the (5)D(0)-(7)F(1, 2) transitions of Eu(3+). The complete extinction of the Eu(3+)-ion emission was obtained as an effect of multipulse excimer-UV-laser (lambda = 248 nm, tau(FWHM) >/= 20 ns) irradiation of the glass samples. Fluorescence microscopy, M?ssbauer spectrometry, and electron spin resonance were applied for investigation of the modifications induced by the laser treatment. As a decisive proof of the extinction of fluorescence we succeeded in recording three-dimensional fluorescent photographic patterns within the activated samples.     

Effect of C-H bonds on the quenching of luminescent lanthanide chelates

The quenching of europium(III) and terbium(III) chelate luminescence by high-energy C-H vibrational manifolds was studied with two types of stable chelates, i.e., a seven-dentate phenylethynylpyridine derivative and a nine-dentate terpyridine derivative. The replacement of C-H bonds by C-D bonds in the chelating parts of the ligands had a clear positive effect on Eu³⁺ luminescence but a negligible effect on Tb²⁺ luminescence. In aqueous solution, however, the positive effect was undetectable, if the chelating ligand did not create complete shielding of the ion against aqueous quenching. In chelates, where the coordination of water molecules to the inner sphere is prevented, the residual quenching through C-H vibrational quanta can be avoided by replacement of all C-H bonds in the vicinity of the emitting ion by C-D bonds.