Europium Salts Research Articles

Faster Synthesis of Beta-Diketonate Ternary Europium Complexes: Elapsed Times & Reaction Yields.

β-diketonates are customary bidentate ligands in highly luminescent ternary europium complexes, such as Eu(β-diketonate)3(L)2, where L stands for a nonionic ligand. Usually, the syntheses of these complexes start by adding, to an europium salt such as EuCl3(H2O)6, three equivalents of β-diketonate ligands to form the complexes Eu(β-diketonate)3(H2O)2. The nonionic ligands are subsequently added to form the target complexes Eu(β-diketonate)3(L)2. However, the Eu(β-diketonate)3(H2O)2 intermediates are frequently both difficult and slow to purify by recrystallization, a step which usually takes a long time, varying from days to several weeks, depending on the chosen β-diketonate. In this article, we advance a novel synthetic technique which does not use Eu(β-diketonate)3(H2O)2 as an intermediate. Instead, we start by adding 4 equivalents of a monodentate nonionic ligand L straight to EuCl3(H2O)6 to form a new intermediate: EuCl3(L)4(H2O)n, with n being either 3 or 4. The advantage is that these intermediates can now be easily, quickly, and efficiently purified. The β-diketonates are then carefully added to this intermediate to form the target complexes Eu(β-diketonate)3(L)2. For the cases studied, the 20-day average elapsed time reduced to 10 days for the faster synthesis, together with an improvement in the overall yield from 42% to 69%.

Eu³⁺-based bridged silsesquioxanes for transparent luminescent solar concentrators.

The sol-gel preparation of a bridged silsesquioxane containing europium(III) salts and 2-thenoyltrifluoroacetone has been achieved from a new ethane tetracarboxamide-based organosilane. Free-standing films with thicknesses up to 440 μm and maximum absolute quantum yield (q) of 0.34 ± 0.03 (excitation at 320 nm) were prepared by the drop cast method, while thin films (∼200-400 nm) spin-coated on glass substrates led to highly luminescent coatings with q = 0.60 ± 0.02 (excitation at 345 nm). The thin films were tested as planar luminescent solar concentrators and the optimized device displays an optical conversion efficiency of 12.3% in the absorbing spectral region of the active layer (300-380 nm).

Magnetic luminescent material based on silver doped lanthanum manganite and europium salts with 1,10-phenanthroline

Coordination compounds of europium(iii) with 1,10-phenanthroline Eu(phen)2(NO3)3 and [Eu(phen)(OAc)3)]2 were tested as luminescent layers adsorbed on the surface of magnetic powder La0.8Ag0.1MnO3+δ. The luminescent and magnetic characteristics of the obtained magnetic luminescent material were studied.

The electronic properties of mixed valence hydrated europium chloride thin film.

We investigate the electronic properties of a model mixed-valence hydrated chloride europium salt by means of high resolution photoemission spectroscopy (HRPES) and resonant photoemission spectroscopy (RESPES) at the Eu 3d → 4f and 4d → 4f transitions. From the HRPES spectra, we have determined that the two europium oxidation states are homogeneously distributed in the bulk and that the hydrated salt film is exempt from surface mixed valence transition. From the RESPES spectra, the well separated resonant contributions characteristic of divalent and trivalent europium species (4f(6) and 4f(7) final states, respectively) are accurately extracted and quantitatively determined from the resonant features measured at the two edges. The partial absorption yield spectra, obtained by integrating the photoemission intensity in the valence-band region, can be well reproduced by atomic multiplet calculation at the M(4,5) (3d-4f) absorption edge and by an asymmetric Fano-like shape profile at the N(4,5) (4d-4f) absorption edge. The ratio of Eu(2+) and Eu(3+) species measured at the two absorption edges matches with the composition of the mixed valence europium salt as determined chemically. We have demonstrated that the observed spectroscopic features of the mixed valence salt are attributed to the mixed-valence ground state rather than surface valence transition. HRPES and RESPES spectra provide reference spectra for the study of europium salts and their derivatives.

Eu-MOFs with 2-(4-carboxyphenyl)imidazo[4,5-f]-1,10-phenanthroline and ditopic carboxylates as coligands: synthesis, structure, high thermostability, and luminescence properties.

Hydrothermal reactions of europium(III) salt with 2-(4-carboxyphenyl)imidazo[4,5-f]-1,10-phenanthroline and dicarboxylic acid as coligands-benzene-1,4-dicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 2,5-dibromoterephthalic acid, and naphthalene-1,4-dicarboxylic acid-lead to four europium fluorescent materials (1-4). Structural analyses reveal that 1-4 have binuclear 3D metal-organic frameworks with different channels, void volumes, and conjugated structures tuned by ditopic carboxylates. There are no latticed and coordinated water molecules occurring in 1-3, while the free water molecules fill in 1D channels of 4. 4' was readily obtained via water removal of 4. Thermal analyses of all compounds show the high thermal stability of the main framework up to 450 °C. Optical studies indicate that 1-4 and 4' show the characteristic red luminescence emission of the Eu(III) ion in the visible regions at room temperature. On the basis of emission spectra, their luminescence lifetimes were determined. In particular, compound 4' shows a longer lifetime (τ = 0.942 ms) and significantly enhanced quantum yield (39%) compared with those of 1 (11%, 0.770 ms), 2 (4%, 0.414 ms), 3 (18%, 0.807 ms), and 4 (26%, 0.858 ms).

Reverse lyotropic liquid crystals from europium nitrate and P123 with enhanced luminescence efficiency.

Fabrication of lyotropic aggregates containing the lanthanide ions is becoming a preferable way to prepare novel functional materials. Here, the lyotropic liquid crystals (LLCs) of reverse hexagonal, reverse bicontinuous cubic, and lamellar phases have been constructed in sequence directly from the mixtures of Eu(NO3)3·6H2O and Pluronic P123 amphiphilc block copolymer with increasing the salt proportion. Their phase types and structural characteristics were analyzed using polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS) measurements. The driving forces of reverse LLC phase formation were investigated using Fourier-transformed infrared spectroscopy (FTIR) and rheological measurements. The hydrated europium salt was found to act not only as a solvent here, but also as the bridge to form hydrogen bonding between coordinated water molecules and PEO blocks, which played a key role in the reverse LLCs formation. Compared to those in aqueous solutions and solid state, the enhanced luminescence quantum yields and prolonged excited state lifetimes were observed in two europium containing reverse mesophases. The luminescence quenching effect of lanthanide ions was efficiently suppressed, probably due to the substitution of coordinated water molecules by oxyethyl groups of P123 and ordered phase structures of LLCs, where the coordinated europium ions were confined and isolated by PEO blocks. The optimum luminescence performance was then found to exist in the reverse hexagonal phase. The obtained results on such lanthanide-induced reverse LLCs should be referable for designing new luminescent soft materials construction to expand their application fields.

Mechanochemistry with metallosupramolecular polymers.

The transduction of mechanical force into useful chemical reactions is an emerging design approach to impart soft materials with new functions. Here, we report that mechanochemical transductions can be achieved in metallosupramolecular polymers. We show that both reversible and irreversible reactions are possible and useful to create mechanically responsive materials that display new functions. The metallopolymer studied was a cross-linked network assembled from a europium salt and a telechelic poly(ethylene-co-butylene) with 2,6-bis(1'-methylbenzimidazolyl)pyridine (Mebip) ligands at the termini. The Eu(3+) complexes serve both as mechanically responsive binding motifs and as built-in optical probes that can monitor the extent of (dis)assembly due to their characteristic photoluminescent properties. Indeed, dose-dependent and reversible metal-ligand dissociation occurs upon exposure to ultrasound in solution. The absence of ultrasound-induced dissociation of a low-molecular weight model complex and in-depth studies of temperature effects confirm that the dissociation is indeed the result of mechanical activation. The influence of the strength of the metal-ligand interactions on the mechanically induced dissociation was also explored. Metallopolymers in which the Mebip ligands were substituted with more strongly coordinating dipicolinate (dpa) ligands do not dissociate upon exposure to ultrasound. Finally, we show that mechanochemical transduction in metallosupramolecular polymers is also possible in the solid state. We demonstrate mending of damaged objects through ultrasound as well as mechanochromic behavior based on metal-exchange reactions in metallopolymers imbibed with an auxiliary metal salt.

Influence of various anions (Cl−, NO3−, and CH3COO−) of europium salts on the thermal decomposition behavior of Eu3+-modified 1,8-naphthalic anhydride hybrid mesoporous silica

Hybrid bimodal mesoporous silica grafted 1,8-naphthalic anhydride (NA) as a luminescent tracer was modified by Eu3+ ions, whereas the influence of the interaction between europium salts with various anions (Cl−, NO3−, and CH3COO−) and NA molecules grafted onto the mesopores on their thermal decomposition behaviors and kinetic properties were studied in detail in accordance with the thermogravimetric analyzer (TGA) profiles obtained at different heating rates under flowing N2 atmosphere. Meanwhile, Kissinger and Flynn–Wall–Ozawa algorithms were used to calculate the apparent activation energies of Eu3+-modified NA existing in the mesoporous channels and therefore the thermal decomposition mechanism was discussed on the basis of the Coats-Redfern method. Moreover, XRD, TEM, N2 adsorption–desorption isotherms and FT-IR techniques were employed to analyze the structural characteristics and textural properties of the resultant samples.

Eu3+-modification of luminescent hybrid bimodal mesoporous silicas with various anions (NO3−, CH3COO−, and Cl−)

In order to enhance the intensity of luminescent hybrid bimodal mesoporous silica (LHMS), the rare earth Eu3+ ion was employed as an enhancer to modify 1,8-naphthalic anhydride (NA) molecules. The modified LHMS were prepared with various anions of europium salts including Cl−, NO3−, and CH3COO−. The structure and photoluminescence properties of the obtained samples were characterized by XRD, TEM, N2-adsorption/desorption, FT-IR, TGA, ICP-OES, and PL measurements. The results showed that the bimodal mesoporous system of BMMs could be preserved after functionalization via grafted Eu3+-modified NA molecules onto mesoporous matrix. However, the structure parameters and textural properties of resultant LHMS series were obviously influenced by the anions volume. Meanwhile, the luminescent performances of LHMS series were seriously impacted by both of the binding force between Eu3+ and various anions and steric hindrance of the anions, resulting in the intensity of emission peak of obtained LHMS series declining as following order: LHMS-EN (NO3−) > LHMS-EA (CH3COO−) > LHMS-EC (Cl−). Finally, the related mechanism was discussed in-depth.

Colloidal and transparent opal-matrix nanocomposites filled with europium-doped silica sols

Three-dimensional ordered opal-matrix composites filled with europium-doped silica sols have been produced using methods of colloid chemistry. According to elemental analysis data, the Eu concentration in the nanocomposites was ∼30 ppm. A uniform europium distribution over the tetrahedral and octahedral pores of the 3D opal matrix was ensured by repeatedly filling the opal pores with silica sols doped with europium salts or europium oxide. Varying high-temperature annealing conditions, one can control the microstructure of 3D ordered nanocomposites, producing opaline and transparent photonic crystals. The microstructure of opal photonic crystals has the form of an ordered fcc lattice of amorphous silica spheres, whose tetrahedral and octahedral pores are filled with mesoporous europium-doped glass. Partial sintering of the silica spheres and mesoporous glass in transparent photonic crystals results in a periodic arrangement of quantum dots enriched in Eu-doped silica.

Yolk–shell structured Y2O3:Eu3+ phosphor powders with enhanced photoluminescence properties prepared by spray pyrolysis

Highly crystalline Y2O3:Eu3+ yolk–shell phosphor powders with enhanced photoluminescence intensity are successfully prepared by spray pyrolysis. The Y2O3:Eu3+ yolk–shell powder is formed directly from each droplet containing yttrium and europium salts and sucrose inside a hot-wall reactor that is maintained at 900 °C. The yolk–shell structure of the phosphor powder is maintained even at a high post-treatment temperature of 1200 °C, exhibiting the maximum photoluminescence intensity. For comparison, a spherical shape Y2O3:Eu3+ phosphor powder is also prepared by the same procedure but without sucrose during spray pyrolysis. The photoluminescence intensity of the Y2O3:Eu3+ yolk–shell powder is 171% of that of the spherical shape phosphor powder at a post-treatment temperature of 1200 °C. The morphological advantage of a yolk–shell phosphor powder with a core@void@shell configuration inducing higher absorption of excitation light in the structure is attributed to multiple light-reflecting and light-scattering in the interstitial void between the core and the shell.

Luminescent Materials of Europium(III) Coordinated by a Terpyridine‐Functionalized Poly(Ionic Liquid)

AbstractA new poly(ionic liquid) (Terpy‐PIL) carrying a terpyridine group in each repeating unit of the polymer architecture was readily prepared by polymerization of the monomer (Terpy‐IL), which was initiated by azobis(isobutyronitrile) (AIBN). The obtained poly(ionic liquid) can coordinate and sensitize europium(III) ions through numerous chelating terpyridine moieties, which are linked to the polymer chains. A red‐emitting luminescent material was obtained by the complexation of europium(III) salts with Terpy‐PIL, and the luminescence is due to an energy transfer from the terpyridine moieties to Eu3+ ions. The luminescence performance of the luminescent material based on Terpy‐PIL, for example the 5D0 quantum efficiency and the decay time, is much higher than that of the luminescent material prepared from the monomer Terpy‐IL, which can be ascribed to the confinement of the europium(III)–terpyridine complexes to the polymer architecture.

Spectral engineering of optical fiber preforms through active nanoparticle doping

Europium doped alkaline earth fluoride [Eu:AEF2 (AE = Ca, Sr, Ba)] nanoparticles were synthesized and systematically incorporated into the core of modified chemical vapor deposition (MCVD)-derived silica-based preforms by solution doping. The resulting preforms were examined to determine the impact of the nanoparticles chemistry on the spectroscopic behavior of the glass. The dominant existence of Eu3+ was demonstrated in all preforms, which is in contrast to conventional solution doped preforms employing dissolved europium salts where Eu2+ is primarily observed. Raman spectroscopy and fluorescence lifetime measurements indicated that the nanoparticles composition is effective in controlling, at a local chemical and structural level, the spectroscopic properties of active dopants in optical fiber glasses. Further, there is a systematic and marked increase in radiative lifetime, τ, of the Eu3+ emission that follows the cationic mass; τCa < τSr < τBa with the BaF2-derived sample yielding a 37% lengthening of the lifetime over the CaF2-derived one. Such nanoscale control of what otherwise is silica glass could be useful for realizing property-enhanced and tailored spectroscopic performance from otherwise “standard” materials, e.g., vapor-derived silica, in next generation optical fibers.

Effects of dietary Europium complex and Europium(III) on cultured pearl colour in the pearl oysterPinctada martensii

In the present study, through a transmission experiment, the effects of europium complex and Eu3+ on the pearl colour in the pearl oyster Pinctada martensii were evaluated. Europium complex and europium salt were respectively enriched by dietary green algae platymonas subcordiformi, and their toxicity to algae were analysed by the 96-h acute toxic experiment. Then, the green algae enriched europium complex and europium salt were respectively fed pearl oysters for 2 months, and the surface microstructures of cultured pearls were presented with scanning electron microscopy (SEM) and atomic force microscope(AFM). The results show that toxicity of europium complex to algae is much lower than Eu3+ from lowest no observable effect concentration LNOEC values and 96h-EC50 values and two compounds can modify pearl structure and optimize pearl colour from SEM and AFM images. Taken together, our results, for the first time, show that rare earth complex can improve the pearl quality. This study provides an innovative approach for additional investigation of the influence of rare earth elements on pearls.

Functionalized Nanoporous Thin Films from Metallo-Supramolecular Diblock Copolymers

A polystyrene-[Ni(2+)]-poly(ethylene oxide) metallo-supramolecular block copolymer (PS-[Ni(2+)]-PEO), where -[ is a terpyridine, is used to create nanoporous thin films with free terpyridine ligands homogenously distributed on the pore walls. The PS-[Ni(2+)]-PEO block copolymer is synthesized by a two step assembly process, and is then self-assembled into a thin film in order to obtain PEO cylinders oriented perpendicularly to the film surface. The supramolecular junction is opened by exposing the film to an excess of a competing ligand, and the free PEO block is then rinsed away by a selective solvent. The presence of the terpyridines on the pore walls is evidenced by fluorescence spectroscopy after formation of a fluorescent complex with an europium salt.

Development of polymeric sensing films based on a tridentate bis(phosphinic amide)-phosphine oxide for detecting europium(iii) in water

A novel europium(III) membrane luminescence sensor based on a tridentate bis(phosphinic amide)-phosphine oxide, PhPO(C(6)H(4)POPhN(CH(CH(3))(2))(2))(2) (1), is described. The new luminescent complex, [Eu(1)(2)]Cl(3)2, which is formed between europium(III) and ligand 1 and has a 1 : 2 stoichiometry, has been evaluated in solution. It has the excellent spectroscopic and chemical characteristics that make it appropriate for sensing film applications. All the parameters (polymer, plasticizer, ligand and ionic additive) that can affect the sensitivity and selectivity of the membrane sensor and instrumental conditions have been carefully optimized. The best sensing response (λ(exc) = 229.04 nm, λ(em) = 616.02 nm) was observed for 33.4 : 65.1 : 1.5 (%, w/w) PVC : DOS : 1. The sensing film shows a good response time (10 min) and a very good selectivity toward europium(III) with respect to other lanthanides(III) ions, such as La, Sm, Tb and Yb. The newly-developed sensing film has a linear range from 1.6 × 10(-7) to 5.0 × 10(-6) mol L(-1) for Eu ions with a very low detection limit (4.8 × 10(-8) mol L(-1)) and good sensitivity (9.41 × 10(-7) a.u. mol(-1) L(-1)) to europium. Complexes of [Eu(1)(2)]Cl(3) (2) and [Eu(1)]Cl(3) (4) were isolated by mixing ligand 1 with Eu(Cl(3))·6H(2)O in acetonitrile at room temperature in ligand : metal molar ratios of 1 : 2 and 1 : 1, respectively. The 1 : 1 derivative is the product of thermodynamic control when a molar ratio of ligand to europium salt of 1 : 1 is used. The new compounds have been characterized in both the solid form (IR, MS-TOF, elemental analysis, TGA and X-ray diffraction) and in solution (multinuclear magnetic resonance). In both europium complexes, the ligand acts as a tridentate chelate. Thermogravimetric (TG) studies demonstrated that neither complex 2 or 4 possess any water molecules directly bound to the lanthanide metal, which corroborates the X-ray structure. The investigation of the solution behaviour of the Y(III) complexes with pulsed gradient spin-echo (PGSE) NMR diffusion measurements showed that average structures with 1 : 1 and 1 : 2 stoichiometries are retained in acetonitrile solutions.

Construction of [EuZn(glycinate)(oxalate)2(H2O)2]n: An unusual heterometallic 3D 3d–4f coordination framework generated by in situ glycinate synthesis

Abstract The 3D heterometallic 3d–4f coordination polymer, [EuZn(gly)(ox)2(H2O)2]n, 1, (gly = glycinate, ox = oxalate), was the product of the hydrothermal synthesis of glycinate from the reaction of tetrazole-1-acetic acid, sodium oxalate, zinc and europium salts in the presence of a trace quantity of nitric acid. Coordination polymer 1 exhibits an unusual 3D heterometallic coordination framework that is built up by heterometallic dinuclear EuZn secondary building units and mixed ox and gly linkers in a uninodal 6-connected vme {33.43.58.6} net. The solid-state photoluminescence and lifetime characteristics of 1 reveal intense red luminescence.

Sensitization of Lanthanoid Luminescence by Organic and Inorganic Ligands in Lanthanoid-Organic-Polyoxometalates

The reaction of terbium and europium salts with the lacunary polyxometalate (POM) [As(2)W(19)O(67)(H(2)O)](14-) and 2-picolinic acid (picH) affords the ternary lanthanoid-organic-polyoxometalate (Ln-org-POM) complexes [Tb(2)(pic)(H(2)O)(2)(B-β-AsW(8)O(30))(2)(WO(2)(pic))(3)](10-) (1), [Tb(8)(pic)(6)(H(2)O)(22)(B-β-AsW(8)O(30))(4)(WO(2)(pic))(6)](12-) (2), and [Eu(8)(pic)(6)(H(2)O)(22)(B-β-AsW(8)O(30))(4)(WO(2)(pic))(6)](12-) (3). A detailed synthetic investigation has established the conditions required to isolate pure bulk samples of the three complexes as the mixed salts H(0.5)K(8.5)Na[1]·30H(2)O, K(4)Li(4)H(4)[2]·58H(2)O, and Eu(1.66)K(7)[3]·54H(2)O, each of which has been characterized by single crystal X-ray diffraction. Complexes 2 and 3 are isostructural and can be considered to be composed of two molecules of 1 linked through an inversion center with four additional picolinate-chelated lanthanoid centers. When irradiated with a laboratory UV lamp at room temperature, compounds K(4)Li(4)H(4)[2]·58H(2)O and Eu(1.66)K(7)[3]·54H(2)O visibly luminesce green and red, respectively, while compound H(0.5)K(8.5)Na[1]·30H(2)O is not luminescent. A variable temperature photophysical investigation of the three compounds has revealed that both the organic picolinate ligands and the inorganic POM ligands sensitize the lanthanoid(III) luminescence, following excitation with UV light. However, considerably different temperature dependencies are observed for Tb(III) versus Eu(III) through the two distinct sensitization pathways.

Functional novel polymer electrolytes containing europium picrate

Novel polymer electrolytes based on either di-ureasil ormolytes or gelatin and containing europium picrate [Eu(pic)3] were prepared, characterised and compared by conductivity measurements, thermal analysis and electrochemical stability, X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopies. Small electrochromic devices (ECDs) with gelatin–europium salt optimised composition were assembled and characterised. The obtained results confirmed that these materials may perform as satisfactory multifunctional component layers in the field of ECD based devices.

Ultraweak emission of the Eu(III) ions in cathodic generated electrochemiluminescence

High voltage cathodic generated electrochemiluminescence (ECL) of selected systems generating weak photon emission was studied. The investigated systems contained europium salts, and co-reactants: H 2O 2 and K 2S 2O 8. During the cathodic pulse polarization of an oxide-covered working aluminum electrode, hot electrons in metal may enter the conduction band of water through the oxide layer/solution interface and turn into hydrated electron after salvation. The ECL intensity and spectra was measured though a suitable cut-off filters, with a photon counting unit attached to a PC computer. On the basis of the analysis of the spectra in particular systems, emitters were identified and simplified scheme of the processes was proposed. The Eu(III)-specific electro generated luminescence is produced via several parallel mechanisms, which usually involve a type of the co-reactant, oxidation state changes of europium ions in aqueous solution and the influence of working electrode surface emission.