Sol-gel technique for the generation of europium-doped mesoporous and dense thin films: A luminescent study

In this paper, a series of europium-activated titania mesoporous and dense thin films were prepared by sol-gel process. Structural characterizations show that high europium ion loadings can be incorporated into titanium dioxide walls without destroying the mesoporous arrangement. However, high europium content locks the titanium dioxide crystallization process. Upon 10% europium ions loading, mesoporous thin films are mainly amorphous, whereas dense ones are still partially crystallized. Eu³⁺ ion luminescence has been investigated by exciting through the semiconductor host lattice. Emission features reveal that europium ions adopt similar environments (nanocrystalline and glassy-like ones) in both dense and mesoporous thin films. Fluctuations of europium emission under continuous UV excitation have been observed. One observes that the effect strongly depends on the thin films’ crystalline character which is strongly related with the texturation and existence at the mesoscopic length scale.     

Bright Red Organic Electroluminescent Devices Based on a Soluble Rare Earth Complex Eu(TTA)_3 Phen

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Chelation of Na+ cations in nonaqueous solvents. Structural requirements and methodological considerations

Intrinsic formation constants for complexes of Na⁺ ions with a series of polyamines have been determined from²³Na NMR measurements in binary mixtures of tetrahydrofuran (THF) and amines. The results show in a totally unambiguous manner a regular decrease in the magnitude of the chelate effect with the number of atoms intervening between the nitrogen ligators. The key assumption, tetracoordination of the cation, is critically examined, and experimental evidence is adduced in its support.     

Electrothermal AAS studies of Sm, Eu, Dy, and Er separated from uranium

Summary Studies were conducted on the assay of Sm, Eu, Dy and Er separated from uranium using aqueous standards by electrothermal AAS with Massmann type graphite furnace. The working curves were found to be linear in the ranges Sm (1–10 g/ml), Eu (0.05–0.6 g/ml), Dy (0.1–0.8 g/ml) and Er (0.1–1.0 g/ml). The values obtained for synthetic samples agreed favourably with those obtained by emission spectrographic method. Experiments using pyrolytic carbon coated tubes with and without pretreatment by La, Ta and Y have shown an enhancement with treatment upto a maximum of 15% and improve the memory effect marginally. The effect of Ta treatment was found to be singularly useful in improving the general behaviour of Sm. The interference effects of lanthanides, other than the analyte, were found to be negligible. However, the presence of uranium was found to affect the absorbance. The absorbance of Eu was found to be nearly independent of uranium after an initial increase. On the other hand, the absorbance of other elements studied was found to drastically decrease after an initial enhancement. Detailed investigations of temperature dependence of absorbance were carried out using Eu, Dy and Er. The differences in the behaviour of these elements is attributed to probable differences in the modes of their atomization.

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Untersuchung von aus Uran abgetrenntem Samarium, Europium, Dysprosium und Erbium durch elektrothermische Atomabsorptions-Spektralphotometrie

Zusammenfassung Die Untersuchungen wurden mit Hilfe des Graphitrohrofens nach Maßmann durchgeführt. In folgenden Bereichen ergaben sich lineare Eichkurven: Sm 1–10 g/ml, Eu 0,05–0,6 g/ml, Dy 0,1–0,8 g/ml, Er 0,1-1,0 g/ml. Die aus synthetischen Proben erhaltenen Ergebnisse stimmten gut mit den durch Emissionsspektrographie erhaltenen überein. Versuche wurden mit Röhren mit pyrolytischen Kohlenstoffüberzug mit und ohne Vorbehandlung durch La, Ta und Y durchgeführt und ergaben eine bis 15%ige Steigerung durch die Behandlung sowie eine mäßige Besserung des Memoryeffektes. Eine Behandlung mit Ta war besonders für Sm vorteilhaft. Störungen durch andere Lanthanide waren vernachlässigbar. Uran beeinflußte jedoch die Absorption. Im Falle von Eu zeigte sich nach anfänglicher Zunahme fast eine Unabhängigkeit, während bei den anderen untersuchten Elementen nach anfänglicher Zunahme eine beträchtliche Abnahme auftrat. Mit Eu, Dy und Er wurde ebenfalls die Temperaturabhängigkeit der Absorption untersucht. Festgestellte Unterschiede im Verhalten werden auf unterschiedliche Atomisierung zurückgeführt.

     

Influence of ligands on the photoluminescent properties of Eu in europium β-diketonate/PMMA-doped systems

Three kinds of europium β-diketonates Eu(DBM)₃, Eu(BA)₃ and Eu(TTA)₃ (DBM: Dibenzoylmethane; BA: 1-Benzoylacetone; TTA: Thenoyltrifluoroacetone) were doped in poly(methyl methacrylate) (PMMA) matrix. The doped systems were studied by using photoluminescent (PL) spectroscopy, emission decay experiments and X-ray diffractometry. Eu(III) ions in the doped Eu(DBM)₃/PMMA systems have two distinct symmetric sites and the emission band changes greatly with the compositions. Eu(III) in the Eu(BA)₃/PMMA systems gives only one symmetric site in the doped systems and the emission band changes slightly with the compositions. Although two distinct symmetric sites of Eu(III) can be distinguished in the doped systems of Eu(TTA)₃/PMMA, the two sites have similar ⁵D₀ lifetimes and the luminescent spectra almost do not change with the compositions. XRD reveals that crystallites were formed in the doped Eu(DBM)₃/PMMA systems that have different crystalline structure from that of the chelate, and Eu(BA)₃ and Eu(TTA)₃ exist in amorphous state in the doped systems. The difference between the PL properties and structures of the doped systems for the three kinds of chelates should be attributed to different interactions between the chelate molecules and between the chelate and PMMA.     

Red Electroluminescence and Photoluminescence from Novel Binuclear Europium Complex with Squaric Acid Ligand

Organic electroluminescent devices (OELDs) have attracted much attention for several years because of their potential application in large area, multi-colored flat panel displays1-5. The green organic EL display using Alq3 as emitter was commercialized in 19976. However, red-emitting OELD with excellent properties has not been well developed. In order to realize practical full-color OELDs, it is considered very important to develop red and blue emitting materials with excellent propert…     

Electrochemical methylation of a chelate anionic NiI complex with methylcobaloxime. Partial modeling of the action mechanism of the active center of acetyl-CoA synthase

Electrochemically generated anions of Co and Ni chelate complexes can be alkylated with BuⁿBr, BuⁿI, and (dmgH)₂CoMe (dmgH is the dimethylglyoximate anion). Unlike the anionic Co complexes, the anionic Ni complex cannot be alkylated with BuⁿBr; however, it reacts with stronger alkylating agents (BuⁿI and (dmgH)₂CoMe). It is assumed that the electrochemical alkylation of the Ni complex with (dmgH)₂CoMe can serve as a model for alkylation occurring in biological synthesis of acetyl coenzyme A. Reactions of some Co chelate anions with BuⁿI can proceedvia the reduction of the latter. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 55–58, January, 2000.     

Tuning of nickel 2-phosphinophenolates - catalysts for oligomerization and polymerization of ethylene

This short personal account summarizes recent work concerning the syntheses and structural aspects of neutral and cationic (organo)nickel and (organo)palladium 2-phosphinophenol(ate) complexes and catalysts for the oligo- or polymerization of ethylene.     

Synthesis, structure and physicochemical characterization of a noncentrosymmetric, quaternary thiostannate: EuCu2SnS4

EuCu₂SnS₄ was prepared by a stoichiometric combination of the elements heated to 700 °C for 125 h. The structure was determined by single crystal X-ray diffraction methods. The compound crystallizes in the noncentrosymmetric, orthorhombic space group Ama2 with a=10.4793(1) Å, b=10.3610(2) Å, c=6.4015(1) Å, Z=4, R1=0.99% and wR2=2.37%. The structure type is that of SrCu₂GeSe₄. The structure can be described as a three-dimensional network built from near perfect SnS₄ and distorted CuS₄ tetrahedra together with EuS₈ square antiprisms. The dark red compound is a semiconductor with an optical bandgap of 1.85 eV.     

KZnF3：Eu的水热合成及其光谱性质

采用中温水热法合马了立方钙钛矿单相ＫＺｎＦ３及ＫＺｎＦ３：Ｅｕ，通过ＳＥＭ观察了产物形态．ＸＰＳ测定结果表明，产物含氧量不高。荧光光谱及ＥＳＲ谱表明，ＫＺｎＦ３：Ｅｕ体系中Ｅｕ＾２＋与Ｅｕ＾３＋共存，进一步讨论了不等价取代中的电荷补偿途径。