The Effect of Organic Diluent on the Extraction of Eu(III) by HEH[EHP]

ABSTRACT

Because there are fewer tools available to probe the interactions therein, the effect of the fundamental chemistry of the organic diluent on solvent extraction equilibria has been under-characterized relative to the aqueous. As a result, diluents for solvent extraction are often selected for an application not for their utility as a medium for reaction, but for other (often equally) important reasons (like low flammability). To begin to improve this imbalance in the science, twenty different diluents have been used in a study of the extraction of radiotracer ^152/154Eu³⁺ from dilute nitric acid solutions using the extractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]). To increase the utility of the study and to honor the memory of Professor Jan Rydberg, this investigation was conducted by a cadre of comparatively inexperienced separation scientists (who are as a result no longer inexperienced separation scientists) as a radioanalytical chemistry and solvent extraction educational exercise. Slope analysis was used to determine the apparent stoichiometry of the extracted metal complex. The results discussed in the following indicate that, while the pH dependence exhibits the expected three H⁺ exchanged per metal ion extracted, the extractant dependence suggests that the number of protonated extractant molecules in the extracted complex changes with the organic diluent. The experimentally observed “extractant dependency” ranges from 2.5 to 3.0 dimer equivalent molecules per extracted metal ion. Ironically, in the diluents exhibiting the highest apparent M:(HA)₃ stoichiometry, HEH[EHP] extracts Eu³⁺ less efficiently. Europium luminescence spectroscopy was used to probe for changes in the first coordination sphere of the complex in different diluents. A model and conceptual framework for understanding these observations is described.     

Unveiling the presence of mixed oxidation states of Europium in Li7+δEuxLa3−δZr2−δO12−δ garnet and its impact on the Li-ion conductivity

Recently, lanthanides have been employed by researchers to examine their impact on the structure and properties of Li₇La₃Zr₂O₁₂ (LLZO) garnets. In this regard, we developed Europium oxide (Eu₂O₃) doped LLZO (Li_7+δEu_xLa_3−δZr_2−δO_12−δ) solid electrolyte which demonstrates a cubic phase with the symmetry of Iad (No.230) at room temperature. In this investigation, different concentrations of Eu ranging from 0.1 to 0.6 atoms per formula unit (pfu) were doped into Li₇La₃Zr₂O₁₂ to evaluate the impact of Eu on the stability of the cubic phase and thereby the ionic conductivity. The results unveiled that upon doping Eu³⁺ ions, the Eu²⁺ state is also formed and is then self-doped into the structure in which Rietveld refinement coupled with XPS, EPR, and solid-state NMR suggests that Eu³⁺ ions most probably partially occupy Zr⁴⁺ (16a) site, the Eu²⁺ ions occupy La³⁺ (24d) site, and the Li⁺ ions occupy two different sites (24d and 96h). It was further found that such a site preference induces distortion at LaO₈ polyhedrons opening up the neck for Li-ions diffusion, thereby enhancing the ionic conductivity. Moreover, it was revealed that Li-ions probably hop from 96h to 24d and then to 96h site to generate the Li-ion movement. Overall, by introducing Eu ions into the LLZO structure, an enhanced bulk ionic conductivity of 0.30 × 10⁻³ S/cm at 298 K with a minimum electronic conductivity of 2.547 × 10⁻⁹ S/cm at 298 K was achieved.     

Low temperature thermoluminescence properties of Eu and R doped CaAl2O4

The thermoluminescence (TL) of calcium aluminate persistent luminescence materials doped with Eu²⁺ and co-doped with R³⁺ ions were studied between 20 and 325 K. The basic material, CaAl₂O₄:Eu²⁺, showed three TL bands between 150 and 300 K in the glow curve. Changing the R³⁺ co-dopant to the adjacent element in the rare earth series affects significantly the thermoluminescence intensity and even the position of the glow curve maximum. The physical effect seemed to be removing the traps since the La³⁺, Y³⁺, and Lu³⁺ ions suppressed the thermoluminescence. The Pr³⁺, Ho³⁺, and Dy³⁺ co-doping enhanced mainly the low temperature traps and these materials have an intense but relatively short persistent luminescence at room temperature. The Nd³⁺ and Tm³⁺ ions enhanced the TL bands close to room temperature and are thus the most suitable co-dopants to induce intense and long persistent luminescence. The quenching of the thermoluminescence by Sm³⁺ was concluded to be due to the presence of Sm²⁺ that removes totally the traps.     

Photoluminescence of transparent glass-ceramics based on ZnO nanocrystals and co-doped with Eu3+, Yb3+ ions

Glasses of the K₂OZnOAl₂O₃SiO₂ system co-doped with Eu₂O₃ and Yb₂O₃ were prepared by the melt-quenching technique. Transparent zincite (ZnO) glass–ceramics were obtained by secondary heat-treatments at 680–860 °C. At 860 °C, traces of Eu oxyapatite appeared in addition to ZnO nanocrystals. The average crystal size obtained from the X-ray diffraction data was found to range between 14 and 35 nm. Absorption spectra of the initial glasses are composed of an absorption edge and absorption bands due to electronic transitions of Eu³⁺ ions. With heat-treatment, the absorption edge pronouncedly shifts to the visible spectral range. The luminescence properties of the glass and glass-ceramics were studied by measuring their excitation and emission spectra at 300, 78, and 4.2 K. Strong red emission of Eu³⁺ ions dominated by the ⁵D₀–⁷F₂ (612 nm) electric dipole transition was detected. Changes in the luminescence properties of the Eu³⁺-related excitation and emission bands were observed after heat-treatments at 680 °C and 860 °C. The ZnO nanocrystals showed both broad luminescence (400–850 nm) and free-exciton emission near 3.3 eV at room temperature. The upconversion luminescence spectrum of the initial glass was obtained under excitation of the 976 nm laser source.     

Luminescent Eu(III) hybrid sensors for in situ copper detection

In this work we used the sol-gel technique to develop luminescent Eu(III) transparent films deposited on glass slides to build for sensor devices capable of monitoring transition metal ions in aqueous solutions. The films were obtained from a bis(trialkoxysilyl) organic precursor synthesized from the amide of the 2,6-pyridinedicarboxylic acid (DPA) with aminopropyltriethoxysilane (APTES) in the presence or absence of cetyl trimethyl ammonium bromide (CTAB) surfactant as templating agent and triethylethoxysilane (TEOS) as crosslinker. These sensor devices were used to perform in situ quenching experiments by Cu(II), Fe(III), Co(II) and Ni(II) ions. The results indicate that the templated films allow the detection and quantification of these metals down to ppb levels by means of the values of the Stern-Volmer constants. In particular, it was shown that Cu(II) acts as an extremely efficient quencher (K_SV = 3.5 × 10⁵ M⁻¹) when compared with the results obtained for the other metals, opening the possibility to use these devices as potential Cu(II) sensors for actual applications in aqueous media.     

螯合—中性萃取剂对铕的协同萃取

本文进一步研究了螯合－中性协同萃取体系：１－苯基－３－甲基－４－（２′－氯苯甲酰基）吡唑酮－５（ＰＭＣＢＰ）分别与三辛基氧膦（ＴＯＰＯ）、二辛基亚砜（ＤＯＳＯ）、二环己基亚砜（ＤＣｙＨＳＯ）和磷酸三丁酯（ＴＢＰ）的二甲苯溶液从盐酸介质中对铕（Ⅲ）的萃取．实验结果表明均有明显的协同应采用斜率法测定了协萃配合物的组成为：ＥｕＡ２·Ｃｌ·Ｂ（ＨＡ＝ＰＭＣＢＰ，Ｂ＝ＴＯＰＯ，ＤＯＳＯ，ＤＣｙＨＳＯ，ＴＢＰ）．中性萃取剂的协萃能力是：ＴＯＰＯ＞ＤＯＳＯ＞ＤＣｙＨＳＯ＞ＴＢＰ．计算了它们的萃取平衡常数，并且讨论了协萃机理     

Lanthanide tetrafluorobenzoates as emitters for OLEDs: New approach for host selection

Brightly luminescent and highly soluble lanthanide tetrafluorobenzoates, as well as their mixed ligand complexes, were synthesized and thoroughly characterized. The low charge carrier mobility hampered their use in OLED, but this problem was overcome by a thoughtful selection of host material. The organic molecules acted both as ligands in the complex and as the host material, leading to zero increase in the Stokes shift.     

Structural and photophysical properties of lanthanide complexes with N-(diphenylphosphoryl)-4-methylbenzenesulfonamide

Lanthanide complexes with N-(diphenylphosphoryl)-4-methylbenzenesulfonamide (HPMSP) as new sensitizers of visible luminescence were obtained. The series of stable lanthanide complexes Na[Ln(PMSP)₄], where Ln = Eu³⁺, Gd³⁺, Tb³⁺ were characterized by X-ray diffraction, IR, absorption, emission, and excitation spectra at 295 and 77 K as well as luminescence decay times and intrinsic emission quantum yields. The Tb complex, exhibiting relatively efficient ligand-to-metal energy transfer and strong metal-centred emission, is a promising candidate for effective UV-to-visible energy converters. Temperature dependent quenching of sensitized ⁵D₀ europium emission and presence of ⁵D₁ emission are discussed.     

Facile Synthesis of Amine-Functionalized Eu3+-Doped La(OH)3 Nanophosphors for Bioimaging

Here, we report a straightforward synthesis process to produce colloidal Eu³⁺-activated nanophosphors (NPs) for use as bioimaging probes. In this procedure, poly(ethylene glycol) serves as a high-boiling point solvent allowing for nanoscale particle formation as well as a convenient medium for solvent exchange and subsequent surface modification. The La(OH)₃:Eu³⁺ NPs produced by this process were ~3.5 nm in diameter as determined by transmission electron microscopy. The NP surface was coated with aminopropyltriethoxysilane to provide chemical functionality for attachment of biological ligands, improve chemical stability and prevent surface quenching of luminescent centers. Photoluminescence spectroscopy of the NPs displayed emission peaks at 597 and 615 nm (λ_ex = 280 nm). The red emission, due to ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transitions, was linear with concentration as observed by imaging with a conventional bioimaging system. To demonstrate the feasibility of these NPs to serve as optical probes in biological applications, an in vitro experiment was performed with HeLa cells. NP emission was observed in the cells by fluorescence microscopy. In addition, the NPs displayed no cytotoxicity over the course of a 48-h MTT cell viability assay. These results suggest that La(OH)₃:Eu³⁺ NPs possess the potential to serve as a luminescent bioimaging probe.     

A reliable and sensitive time-resolved fluorescent immunochromatographic assay (TRFICA) for ochratoxin A in agro-products

Immunochromatographic assays (ICAs) are considered as a suitable diagnostic tool for the detection of mycotoxins. Mycotoxins and especially, ochratoxin A are analytes with more demanding sensitivity requirements. To enhance the sensitivity of current immunochromatographic assays for ochratoxin A (OTA), a novel sensitive ICA was developed in this study. In the assay, microspheres enclosing fluorescent europium (III) [Eu(III)] nanoparticles (EuNPs) were used as a label for OTA monoclonal antibody (OTA-mAb) conjugation. Accordingly, assay was called time-resolved fluorescent immunochromatographic assay (TRFICA). The test strip was composed of three parts: a sample pad, nitrocellulose membrane and an absorbent pad. As for detection, a proper concentration of conjugated microspheres was pipetted into the microtube and sample extract was added to it. Then the strip was inserted into the tube and the fluid flow along the strip. The TRFICA results were obtained in 8 min and read by a portable TRFICA strip reader. The established method allows quantitative determination of OTA with limit of detection as low as 1.0 μg kg⁻¹ in the samples. For validation, spiked samples including wheat, maize, soybean and rice were respectively assayed by TRFICA and a standard high performance liquid chromatography equipped with a fluorescence detector (HPLC-FLD), and good agreement of results was obtained between two methods.