Preparation of a GdCaAl3O7 matrix by the non-hydrolytic sol-gel route

Due to their stable physical and chemical properties, inorganic matrices have been widely employed as hosts for lasers and phosphors. We have prepared a GdCaAl₃O₇ matrix by the non-hydrolytic sol-gel route and have investigated the influence of heating treatment on sample structure. Europium III chloride was added as a structural probe, and the structure was analyzed by thermal analyses (TG/DTA/DSC), X-ray diffraction (XRD), and photoluminescence (PL). The XRD analysis revealed that initial crystallization took place at 400 °C. The peaks corresponding to the GdCaAl₃O₇ and GdAlO₃ phases were observed at 800 and 1000 °C. PL data revealed the characteristic transition bands arising from the ⁵D₀→⁵F_J (J=0, 1, 2, 3, and 4) manifolds under maximum excitation at 275, 391 and 463 nm for all the samples. All the analyses gave evidence that this methodology leads to the formation of a GdCaAl₃O₇ phase.     

A Study on Some Europium(III) Supramolecules by Electrospray Mass Spectrometry

Electrospray mass spectrometry (ESMS) of a series of europium(III) supramolecules derived from tris(2-aminoethyl)amine (tren) and 2,6-diformyl-4-R-phenol (R = F, Cl, t-Butyl) is described. the peaks were assigned by both m / Z values and the isotope distributions. the ESMS are largely affected by the nature of the cryptates.     

Ligand-to-metal charge-transfer quenching of the Eu(D1) state in europium-doped tris(2,2,6,6-tetramethyl-3,5-heptanedionato)gadolinium (III)

Rate constants for the decay of the Eu³⁺(⁵D₁) state in dilute Eu³⁺-doped tris(2,2,6,6-tetramethyl-3,5-heptanedionato)gadolinium(III) are reported for a temperature range 50-315 K. A temperature-independent contribution of 1.3×10⁶ s⁻¹ is attributed to carbonyl mediated ⁵D₁→⁵D₀ relaxation. A temperature-dependent contribution, that has been parameterized as k_CT=Ae^−E_a/kT with E_a=2540±140 cm⁻¹ and A=1.3×10¹² s⁻¹ is attributed to quenching of ⁵D₁ by a low-lying ligand-to-metal charge-transfer state (CTS). The height of the activation barrier, E_a, relative to the previously reported height for charge-transfer quenching of the Eu³⁺(⁵D₀) state in the pure europium analog (J. Phys. Chem. 100 (1996) 9216) is discussed in terms of mechanistic implications. Specifically, these data strongly suggest that quenching of ⁵D₁ by the charge-transfer state is mediated by the ⁵D₀ state with a novel, indirect mechanism.     

Luminescent Eu(III) and Tb(III) Complexes: Developing Lanthanide Luminescent-Based Devices

This mini review gives some highlights of the work recently carried out in our research group in Dublin on the developments of lanthanide luminescent devices, where the future goal is to produce devices that can operate as sensors. A few examples demonstrate our design principles for targeting both anion and cations that are of biological or pharmaceutical relevance, where the recognition occurs in aqueous competitive media. We also discuss the possibility of developing mixed f-d metal complexes and conjugates that can be employed as novel supramolecular architectures.     

Photosensitized luminescence of thermostable polynuclear Eu(III) complexes

Tetranuclear europium(III) complexes, [Eu₄(μ-O)(L₁)₁₀] (L₁=2-hydroxy-4-octyloxybenzophenone,1) and [Eu₄(μ-O)(L₂)₁₀] (L₂=2-hydroxy-4-dodecyloxybenzophenone,2) were synthesized by the reaction of lanthanide nitrates with L₁ or L₂ in the presence of triethylamine in methanol. The photosensitized emission bands of the both Eu(III) complexes in THF-d₈ were observed around 579, 590, 615, 653, and 699 nm by the excitation of the ligands at 380 nm, whereas the emission from the mononuclear complex 3 containing ethanol molecules was almost quenched. The emission efficiencies were determined to be 3.1±0.1% for 1 and 3.9±0.1% for 2, respectively. The differential scanning calorimetry (DSC) measurements demonstrated that the decomposition points of 1 and 2 were 309 °C and 320 °C, respectively, indicating high thermostability of these complexes compared to the mononuclear Eu(III) complex 3 (250 °C). New strategy for designing stable rare earth compounds giving strong emission would be emphasized by introducing polynuclear complexes. Polynuclear complexes should open a wide range of molecular design for photosensitized luminescence and thermal stability.     

铕(Ⅲ)-苯甲酸衍生物配位化合物中Eu(Ⅲ)离子格位

以 2 ,3 二甲氧基苯甲酸 (2 ,3 HDMOBA)和 4 甲基苯甲酸 (p HMBA)为配体 ,合成了新的稀土配合物Eu(2 ,3 DMOBA) 3 和Eu(p MBA) 3 。在 77K下测定了高分辨激发光谱和时间分辨谱。配合物Eu(2 ,3 DMOBA) 3中Eu(Ⅲ )离子格位只有一种 ,配合物Eu(p MBA) 3 中确有化学环境类似的多种类型的Eu(Ⅲ )离子。     

A series of Eu(III) emitters with a novel triphenylamine-derived beta-diketone ligand

In this paper, a series of Eu(III)complexes with a novel triphenylamine-derived beta-diketone ligand are synthesized. Systematical research reveals that these Eu(III) complexes take an occasional antenna mechanism by transferring energy between singlet state of ligand and central Eu(III), which leads to much shortened excited state lifetimes of the corresponding Eu(III) complexes.     

三价铕离子配合物的激光光谱研究

利用高灵敏度的时间辨激光光谱技术研究了在配位场作用下Ｅｕ＾３＾＋的直接激发与发特性。Ｅｕ＾３＾＋的直接激发光谱（特别是７Ｆ０－５Ｄ０的超灵敏跃迁）及其发射光谱随不同的配合物的变化，同时观测到与配位对称性及配位强度有联系的７Ｆ１－５Ｄ０磁偶极跃 迁的分裂。在对７Ｆ０－５Ｄ０跃迁共振与非共振的１０ｐｓ激光脉冲的激励下，都可以立即观察到５Ｄ０－７ＦＪ（Ｊ＝２，３，４）的发射，说明Ｅｕ＾３＾＋的５Ｄ０能态     

Europium(III) Concentration Effect on the Spectroscopic and Photoluminescent Properties of BaMoO4:Eu

BaMoO₄:Eu (BEMO) powders were synthesized by the polymeric precursor method (PPM), heat treated at 800 °C for 2 h in a heating rate of 5 °C/min and characterized by powder X-ray diffraction patterns (XRD), Fourier Transform Infra-Red (FTIR) and Raman spectroscopy, besides room temperature Photoluminescence (PL) measurements. The emission spectra of BEMO samples under excitation of 394 nm present the characteristic Eu³⁺ transitions. The relative intensities of the Eu³⁺ emissions increase as the concentration of this ion increases from 0.01 to 0.075 mol, but the luminescence is drastically quenched for the Ba_0.855Eu_0.145MoO₄ sample. The one exponential decay curves of the Eu^{3+ 5}D₀→⁷F₂ transition, λ _exc = 394 nm and λ _em = 614 nm, provided the decay times of around 0.54 ms for all samples. It was observed a broadening of the Bragg reflections and Raman bands when the Eu⁺³ concentration increases as a consequence of a more disordered material. The presence of MoO₃ and Eu₂Mo₂O₇ as additional phases in the BEMO samples where observed when the Eu³⁺ concentration was 14.5 mol%.     

Eu(III) complexation of phenyltrisalanine and phenylbisalanine in aqueous solution studied by photoluminescence and UV spectroscopy

The Eu(III)-coordination of phenyltrisalanine (Pta) 1, in aqueous solution was investigated. The photoluminescence data suggested that the chelating effect of Pta places the metal ion on the face of the aromatic ring as proposed in 4. Furthermore, Eu(III) is usually used as a substitute for Ca(II) in spectroscopic studies and the formation of a 1:1 complex between Pta and Eu(III) indicated the possibility that Pta may be used as a Ca(II) binder. For comparison, phenylbisalanine (Pba) 2, was subjected to similar studies and was found to behave more like phenylalanine.     

Syntheses and electroluminescent properties of two europium ternary complexes Eu(DBM)3(PBO) and Eu(DBM)3(PBT)

Two europium complexes, Eu(DBM)₃(PBO) and Eu(DBM)₃(PBT) (DBM=dibenzoylmethanato, PBO=2-(2-pyridyl)benzoxazole, PBT=2-(2-pyridyl)benzothiazole), were prepared and used as emitting materials in organic electroluminescent (EL) devices. The devices with the structures ITO/TPD/Eu(DBM)₃(PBO) (or Eu(DBM)₃(PBT)/BCP/Alq₃/Mg:Ag/Ag emit red light originating from the europium complexes.     

A red europium (III) ternary complex for InGaN-based light-emitting diode

One kind of europium (III) ternary complex was synthesized, and its photoluminescence properties were investigated. This complex exhibits broad excitation band in near-UV range, and strong red emission which is due to the ⁵D₀–⁷F_j transitions of Eu³⁺ ions. The luminescence quantum yield for the Eu³⁺ complex is 0.17. Thermogravimetric analysis confirms a high thermal stability of the complex with a decomposition temperature of 344 °C. All the characteristics indicate that the Eu³⁺ complex is a highly efficient red phosphor suitable to be excited by near UV light. An intense red light-emitting diode was fabricated by combining the europium (III) ternary complex with a ~395 nm-emitting InGaN chip.     

Influences of compositions and ligands on photoluminescent properties of Eu(III) ions in composite europium complex/PMMA systems

Three kinds of europium complexes; Eu(phen)₂Cl₃(H₂O)₂, Eu(DN-bpy)phenCl₃(H₂O)₂ and Eu(DB-bpy)phenCl₃(H₂O)₂ (phen: 1,10-phenanthroline, DN-bpy: 4,4′-Dinonyl-2,2′-dipyridyl, DB-bpy: 4,4′-Di-tert-butyl-2,2′-dipyridyl) were prepared and then incorporated into polymethyl methacrylate (PMMA) matrix with different molar ratios of CO groups/Eu³⁺ ions. The final solid composites were formed by a self-assembly process among Eu³⁺ ion, the ligands and PMMA during the solvent evaporation process, and then the ligands re-coordinate to Eu(III). It was found that the ligands affect not only the emission properties of the pure complexes, but also the miscibility of the complexes and PMMA. More than one kind of symmetric sites of Eu³⁺ ions were formed in the composites due to the coordination of CO in PMMA to Eu³⁺ ions. The micro-environments of Eu(III) in the composites were changed with the compositions and the ligands, leading to the change in the crystalline structure, and consequently, the emission characteristics.     

XPS study of Eu(III) coordination compounds: Core levels binding energies in solid mixed-oxo-compounds EumXxOy

Literature is relatively sparse on XPS studies of europium compounds: it is essentially restricted to metallic compounds (EuM₅, in which M is a transition metal) or to simple oxides. While particular interest have been devoted to understanding physical phenomenon in the beginning of “shake-down” and “shake-up” satellites evidenced on core-level regions of the lanthanides, few information on absolute binding energies (BE) was available. This paper reports an XPS binding energy data base for europium(III) compounds, in which Eu cation have various chemical environments: simple oxide Eu₂O₃, Eu mixed oxides with organic oxalate, acetylacetonate or inorganic sulfate, nitrate, carbonate ligands. The values of core-level BE (O_1s, Eu_3d and Eu_4d) and the characteristics of shake-down satellites of Eu_3d are reported, and their variations are attributed to ionicity/covalency changes. Such interpretation was already published for Group A mixed oxides and zeolites. These data are needed for determining Eu(III) species sorbed onto minerals in the presence of various ligands in the framework of retention studies for assessing the safety of future nuclear waste disposals.     

Synthesis and luminescence of Eu(III) complexes with macrocyclic azacrown ethers and 1,10-phenanthroline

Complexes of Eu(III) with mixed macrocyclic azacrown ethers and 1,10-phenanthroline (phen) were synthesized and their luminescence properties measured. The specific azacrown ethers used were 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetate (TETA) and 1,4,8,12-tetraazacyclopentadecane ([15]aneN₄). The phen-coordinated complexes excited by UV light produced a very bright red emission via an intra-molecular energy transfer from phen to Eu(III). For [Eu(TETA)·(phen)·(H₂O)]⁻ and [Eu([15]aneN₄)·(phen)₂]³⁺, the quantum yields of sensitized luminescence were 8.4% and 7.8%, respectively, and were much greater than those from non-sensitized luminescence of 1.2% and 4.4%, respectively. The decay times of the corresponding phen-coordinated complexes, as measured at room temperature, were 1.6 and 0.6 ms, respectively, and were much longer than those of the phen-uncoordinated complexes of 0.3 and 0.2 ms, respectively.     

Fluorimetric Determination of Thyroxine Hormone with Eu(III)-(Pyridine-2,6-Dicarboxylate) Tris Complex

We describe a method for the determination of thyroxine (Thy) using its quenching effect on Eu(PDA)₃ ^3- tris complex fluorescence. The relative fluorescence intensities are measured at fixed _exc = 282 nm, _em = 615 nm by titrating the metal complex with Thy in piperazine buffer solution at pH 6.5. Data indicated an associative type of reaction of two molecules valid between 0.0 < R < 1.0, R being the mole ratio of Eu(PDA)₃ ^3- to Thy. Over this ratio and up to (R 1.0) collisional quenching of Eu(PDA)₃ ^3- complex ion emission is seen as a result of heavy atom effect, intermolecular energy transfer playing the main role. This is also confirmed by the Stern-Volmer equation. In optimized experimental conditions, the L- form of Thy is determined in a range of 15.5–551.6 g/ml (2.0 × 10^–5 – 7.1 × 10^–4 M) with relative error of ±1.17%.     

Spectroscopic Determination of Heparin Sodium Using Europium (III) as a Probe Ion

Abstract

A sensitive, rapid, accurate and precise procedure for the microdetermination of heparin sodium in bulk, in injection and in blood serum. The procedure was built around the fact that heparin possesses many active binding sites; carboxylic, hydroxylic, amino and sulphonated groups, which are strongly bound to Eu³⁺ ions. Such binding enhances the europium emission at 616 nm which is a forbidden transition. The emission of europium at 592 nm comes from a non hypersensitive transition and is not affected by the ligand which is bound to europium ions. The intensity ratio R, defined as I₅₉₂/I₆₁₆ was used to determine the amount of free and bound europium ions. There is a linear relationship between bound europium ions and heparin sodium within the concentration range 1–12 ug. mL^?1 (0.07–0.84 USP. IN). Reaction conditions were studied and percentage recoveries was 99.77 ± 1.68. The relative stability of the complex was 1.2E⁵ and the correlation coefficient was 0.99923. Heparin was isolated from serum using ECTEOLA-cellulose and Sephadex G25 columns. The method shows good agreement with an anilinonaphthalene-1-sulfonate (ANS) and protamine fluorometric method.     

EPR and luminescence studies of Eu(II) magnetically diluted in LiCl-KCl salt

High-temperature LiCl-KCl molten salt medium provides an efficient way to produce the paramagnetic Eu(II) ion to be magnetically diluted into a diamagnetic host medium. Eu(II) was formed by a dissolution and an auto-reduction processes in a high-temperature LiCl-KCl eutectic melt at 723 K by using Eu₂O₃ as a starting material. By using EPR and luminescence spectroscopic method, we studied the nature of the magnetically isolated paramagnetic Eu(II) ion diluted in a LiCl-KCl medium. With the aid of these spectroscopic tools, it was found that stable Eu(II) species was formed spontaneously at 723 K under anaerobic conditions. EPR and luminescence spectroscopy provided detailed information regarding the nature of the europium ion in a molten salt.     

Ordered luminescent nanohybrid thin films of Eu(BA)3Phen nanoparticle in polystyrene matrix from diblock copolymer self-assembly

A simple route for fabricating highly ordered luminescent thin films based on hybrid material of diblock copolymer and europium complex, assisted with self-organization of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer upon solvent annealing, is presented. PS-b-PEO self-organized into hexagonal patterns and europium complex of Eu(BA)₃Phen was selectively embedded in PS blocks after solvent annealing in benzene or benzene/water vapor. During benzene annealing, the orientation of the PEO cylindrical domains strongly depended on the Eu(BA)₃Phen concentration. In contrast, when the hybrid thin films were annealed in mixture of benzene and water vapor, high degree of orientation of the PEO cylindrical domains is more easily obtained, which is independent of Eu(BA)₃Phen concentration. Furthermore, preferential interaction of PEO domains with water induces a generation of nanopores in the hybrid thin film. Atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the long-range lateral order and phase composition of the hybrid thin films. The ordered nanohybrid thin films kept the fluorescence property of Eu(BA)₃Phen and showed a strong red emission under the 254 nm light's irradiation. The fluorescence property was confirmed by photoluminescence (PL) spectra.     

Synthesis and photophysical properties of novel polymeric Eu(III) complex with bicoordination ligand

A novel complex of Eu(III) with bicoordination ligand: 4,4′-bis[2-(2′-pyridyl) benzimidazol-yl]-biphenyl (Bmbp) has been synthesized. The structure of the ligand was characterized by ¹H NMR, FT-IR and UV-vis; Eu(III) complex was characterized by FT-IR, UV-vis, elemental analysis, conductivity measurements and gel-permeation chromatography (GPC). The luminescence properties were investigated by UV-vis and fluorescence spectra. The experimental results show that the complex contain more than one Eu(III) ion, the emission at 614 nm from the ⁵D₀→⁷F₂ electronic dipole transition is large enhanced, and the complex is excellent energy transfer from ligand to Eu³⁺in the solid state. Thermal property measurement and analysis show that it has a good thermal stability.