[en] The polyoxometalate (POM) anion of europium (III) decatungstate [EuW₁₀O₃₆]^9- exhibits great luminescence quantum yields of approximately 67% but suffers reduced red light emissions that are due to the low ⁵D₀→⁷F₂ transmissions. Fine tuning the microenvironment around [EuW₁₀O₃₆]^9- anion through intercalation into different compositions of layered double hydroxides (LDHs) materials, greatly enhances the ⁵D₀→⁷F₂ transmissions. The positive nanosheets in LDHs provide a conducive microenvironment for strong transitions of ⁵D₀→⁷F₂ to occur. The ratio I(⁵D₀→⁷F₂)/I(⁵D₀→⁷F₁) for the observed intensities vary from 0.44 for [EuW₁₀O₃₆]^9- ion to 14.08, 6.20, 1.75 and 1.59 in Mg₂Al-EuW₁₀O₃₆, LYbH-EuW₁₀O₃₆, Zn₂Al-EuW₁₀O₃₆ and LEuH-EuW₁₀O₃₆ materials respectively (Mg₂Al = magnesium aluminum LDHs, Zn₂Al = Zinc aluminum LDHs, LYbH = layered ytterbium hydroxide LDHs, and LEuH = layered europium hydroxide LDHs). As such, these materials can find a wide application in processes that require the red light luminescence.

[en] Powder FTIR spectra of the solid solution series vertical stroke (Ca_2-xEu_x)₄(OH)₈ vertical stroke [(Al_2+xSi_1-x)₄O₂₄]-SOD, 0 ≤ x ≤ 1, were taken at room temperature. All members, including the mineral bicchulite, vertical stroke Ca₈(OH)₈ vertical stroke [Al₈Si₄O₂₄]-SOD, have a sodalite-type structure. Spectra taken in the hydroxyl region (4000 - 3000 cm^-1) yield information related to the local structural states of the pseudo-cubane-like (Ca_2+xEu_2-x)(OH)₄-clusters, 0 ≤ x ≤ 2. Three different patterns of short range order could be identified. Depending on x, different concentrations of Ca₄(OH)₄, EuCa₃(OH)₄, and Eu₂Ca₂(OH)₄ clusters are found, whereas Eu₃Ca(OH)₄ or Eu₄(OH)₄ clusters are not observed. Hence, short range order is maintained such that each SOD cage of an all-alumina framework contains two Ca and two Eu per cluster. The positions of the framework stretching and bending modes shift linearly towards lower wavenumbers with increasing Al content. The shifts are correlated with changes of the framework geometry. Furthermore, Al rich samples show splitting of the stretching and bending modes. This is interpreted as the change of the local environment of Al due to the substitution of Eu³⁺ for Ca²⁺. With the use of deuteration experiments a more detailed assignment could be achieved, especially for the M-OH absorption bands. Finally, changes in the line shape, resulting from cation ordering, are studied by autocorrelation analysis. In particular, samples of intermediate composition show large broadening parameters, Δ_corr, suggesting high degrees of local structural heterogeneity. (orig.)

[en] Anisotropic structures, nanoneedles, and nanospindles of rare earth hydroxychloride (RE(OH)2Cl) and oxychloride (REOCl) (rare earth=Eu and Tb) were synthesized. The rare earth hydroxychloride nanostructures were formed via a thermally assisted hydrolysis of the rare-earth sesquioxide nanocrystals. The morphological evolution of the nanostructures was studied using high-resolution transmission electron microscopy and scanning electron microscopy, while the structural evolution was investigated using X-ray diffraction techniques. The thermal stability of the rare earth hydroxychlorides was investigated using thermogravimetric analysis. The rare earth oxychloride nanospindles were synthesized via a simple heat-treatment of rare earth hydroxychloride nanospindles

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[en] Two kinds of coumarin derivatives, 7-hydroxy coumarin and 7-hydroxy-4-methyl coumarin, were intercalated into the layered europium hydroxide by ion exchange reaction. The two organic compounds, despite with the same basic structure of benzopyrone but only varied substituent groups, demonstrated much different intercalation structures. The 7-hydroxy coumarin molecules may deposite on the external surface of the layers and 7-hydroxy-4-methyl coumarin molecules corresponded to a vertical mono-layered arrangement. In addition, co-intercalation of surfactant 1-octane sulfonic acid sodium with coumarin anions into layered europium hydroxide can enlarge the interlayer distance, both of the coumarin anions located vertically in the interlayer. The thermal stability of organics was enhanced after intercalation. The combination of the coumarin anions with the positively-charged layers generated hybrid materials exhibiting versatile luminescence properties. In solid state, the luminescence of the organics and Eu³⁺ were co-quenched for 7-hydroxy coumarin composites, but surfactant co-intercalated 7-hydroxy-4-methyl coumarin composite showed strong violet emission. In formamide, all of the composites displayed blue emission. The energy transfer between Eu³⁺ and organics and the change of microenvironment were proposed to account for the versatile luminescence properties. This work benefits the improvement of stability and fluorescence property of coumarin dyes and offers a beneficial approach to fabricate organic-inorganic hybrid materials with controllable structures and luminescence properties. - Graphical abstract: Intercalation of coumarin derivatives into LEuH forms organic-inorganic hybrid materials with versatile structures and luminescence properties, which benefits the improvement of stability and fluorescence property of such dyes.

[en] The narrowest inhomogenous optical linewidth ever seen in a solid was observed in Eu(OH)₃. This transition is quadratically enhanced in a magnetic field and the results are explained completely in terms of second order perturbation theory and the coupling of crystal-field energy levels. Optical coherent transients are reported here for the first time in this optically pure, stoichiometric material. The optical dephasing time, T₂, is shown to be greater than 2 microseconds for the ⁷F₀-⁵D₀ zero phonon transition. Hole burning, attributed to optical pumping of nuclear-quadrupole levels, was used to measure the quadrupole splitting in the excited, ⁵D₀ state. Due to the small magnetic moment, conventional magnetic resonance techniques failed to make this measurement in all Eu compounds. The new technique developed and used in these hole burning measurements yields the quadrupole coupling coefficients, absolute value P = 11.6 MHz and absolute value P = 4.5 MHz for the 153 isotope and the 151 isotope, respectively

No abstract available

[en] Full text: The Lanthanide hydrous oxides concentrate produced from monazite mineral of the Egyptian beach black sand deposits contains a considerable percent of samarium, europium and gadolinium as a group, which in turn represents a valuable concentration with respect to their international prices due to their scarcity and wide demand in modern industries. The rare earth elements, being chemically similar to one another, invariably occur together in the source minerals and behaves as a single chemical entity. The problem of separating them one from another for scientific purposes or industrial use has been one of the most challenging tasks of rare earth technology. The present work is directed to microdetermination of Sm, Eu and Gd in their acid solutions after complete separation and recovery using di-2-ethyl hexyl phosphoric acid diluted with kerosene (D2EHPA/KX) as a solvent for the extraction processes. Different acid solutions with different pH values for their stripping were utilised

[en] Europium as waste can produce a pollution problem in water that is in contact with it, what would has a heavy environmental impacts, because of the possibilities of diffusion of these wastes from their place of confinement or storage until the geo and biosphere. The solution of such problem requires of a lot of knowledge over the behavior of several chemical elements such as europium in aqueous solutions. In this work it was used a low ion force (0.02 M). The data set will allow extrapolate the hydrolytic behavior of europium in too much minors ion force media, such as the ground waters, including in ion force zero

No abstract available