Europium Salts Research Articles

Single-Bubble Sonoluminescence of Colloidal Suspensions of Europium(II) Salt Nanoparticles.

Colloidal suspensions of EuCl2, EuBr2, and EuSO4 nanoparticles (<50 nm) in dodecane and EuSO4 in 70% H2SO4 were synthesized. Moving single-bubble sonoluminescence (m-SBSL) spectra were obtained for a bubble performing radial oscillations in these suspensions and translational motions at the antinode of a standing ultrasonic wave with a frequency of about 27 kHz. In these spectra (at a spectral resolution of 10 nm), the sono-excited luminescence bands of the Eu2+ ion were detected for the first time, coinciding in the shape and position of the maxima (404, 413, and 377 nm for EuCl2, EuBr2, and EuSO4, respectively) with the bands of Eu2+ located in a crystalline environment in the photoluminescence spectra of nanoparticles of europium salts in suspensions. The detected sonoluminescence of Eu2+ arises due to the injection of nanoparticles into a bubble deformed during motion and excitation of a lanthanide ion at the periphery of the bubble volume during collisions of nanoparticles with charged particles, mainly electrons, coming from a hot nonequilibrium plasma, which periodically arises during bubble compression. Evidence for the excitation of the europium ion in the bubble is the absence of its luminescence bands in the SBSL spectra of the translationally immobile bubble, in which nanoparticles are unlikely to enter. The nanoparticles that enter the bubble also undergo decomposition in the plasma into fragments, in particular, with the formation of Eu, Eu+ in the excited state. The atomic lines of these fragments were recorded for the first time in the m-SBSL spectrum with a resolution of 1 nm for a suspension of EuSO4 nanoparticles in 70% H2SO4. The resulting m-SBSL spectra will add to the library of characteristic spectra of objects of sonoluminescent spectroscopic analysis and will make it possible to identify and determine the content of Eu or Eu2+ in these objects.

Effect of Glymo on the Morphological and Optical Properties of Eu3+-Doped Lu2SiO5 Films

Eu3+-(5% mol)-doped Lu2SiO5 optical quality films were prepared using the sol–gel method and dip-coating technique from lutetium and europium salts as the lanthanide precursors and tetraethyl orthosilicate (TEOS) as the silicon source. To increase the thickness of the films, 3-Glycidyloxypropyl trimethoxysilane (Glymo) was added as the rheological agent during sol formation. Structural, morphological, and luminescent properties were investigated for Lu2SiO5, Eu3+:Lu2SiO5, and Eu3+:Lu2SiO5/Glymo in order to obtain high quality in luminescent films. X-ray diffraction (XRD) results show that the incorporation of the Eu3+ ions do not affect the A-Type and B-Type monoclinic crystalline phase typical of Lu2SiO5, even after five dipping cycles on quartz substrates and a final annealing process at 1100 °C. The morphology and topography of the films were studied by SEM and AFM. These techniques revealed films without surfactant that were uniform with low rugosity while the film with surfactant presented porous hills and valleys with uneven high values of roughness. The photoluminescence spectrum of Eu3+:Lu2SiO5 films showed 2 broad emission peaks centered at 589 nm and 612 nm. The presence of Glymo in the system promoted the formation of residual Lu2Si2O7 compounds with the highest lifetime values compared with films without surfactant. The results of the films are promising for luminescent applications.

The interaction of triglycidyl phosphate with europium nitrate and properties of obtained metal-containing polymer

The interaction of phosphorus-containing epoxy trifunctional monomer – triglycidyl phosphate (TGPhT), with europium (III) nitrate hexahydrate is studied. A dissolution of europium salt added into TGPhT is occurred due to the interaction of the cation with phosphoryl groups and oxygen atoms of the epoxy ring, that is accompanied by the opening reaction and led to the formation of a polymer. The interaction of triepoxide with salt is investigated by FTIR-spectroscopy and differential scanning calorimetry (DSC). The thermal stability of the samples is determined by combined method of thermogravimetry and differential scanning calorimetry (TG/DSC), coupled with a quadrupole mass spectrometry to identify the gaseous products evolved during the thermal analysis of the samples. The kinetic parameters of the curing reaction are computed by using Thermokinetics software. The interaction of TGPhT with europium nitrate is suggested to occur through opening of epoxy rings in the presence of europium ions via the mechanism of cationic polymerization. The cured epoxy polymer exhibits luminescent properties.

New europium-doped carbon nanoparticles showing long-lifetime photoluminescence: Synthesis, characterization and application to the determination of tetracycline in waters

The growing appearance of antibiotic-resistant strains of microorganisms originated from the widespread use and ubiquitous presence of such drugs is a major concern in the world. The development of methodologies able to detect such substances at low concentration in real water samples is mandatory to overcome this problem. Europium(III) is known to form complexes with tetracycline (TC) with photoluminescent characteristics useful for TC determination.In the present work, we synthesized for the first time carbon nanoparticles (CN) showing delayed photoluminescence using a Europium(III) doping synthesis. The new material (PCNEu) was characterized both morphologically and spectroscopically, showing an analytical photoluminescent signal in presence of TC, arising from the 5D0→7F2 transition of europium, one hundred times higher than that of the europium salt alone in presence of the antibiotic. This enhancement is a consequence of the amplifying effect exerted by nanoparticle structure itself, leading to an efficient synergistic “antenna effect” in the system PCNEu - TC. The analytical signal is affected both by pH and the nature of the buffer used, and it allows the detection of tetracycline in waters with a limit of detection of 2.18 nM and recoveries between 90 and 110%. The analytical performance of the developed methodology enables having lower limits of detection than other luminescent and chemiluminescent reported methodologies.

Solvation-controlled emission of divalent europium salts

Coordination-environment-dependent tuning of luminescence of divalent europium is an emerging topic of research. While it has been extensively demonstrated in the solid state, recent reports indicate similar findings in solution, where emission properties were tuned by altering different ligands and counter anions. In the present study, we demonstrate that differences in solvation shells alter the luminescence properties of divalent europium. Steady-state emission measurements indicate that the emission maxima of EuII salts in dimethoxyethane is red-shifted compared to the maxima in tetrahydrofuran. This shifting was confirmed with three different EuII salts: EuI2, EuBr2, and Eu(OTf)2. UV–visible spectroscopic measurements indicate a marginal difference in absorption spectra of EuII salts in tetrahydrofuran and dimethoxyethane, ruling out the possibility that a difference in ground-state geometry is responsible for the solvation-induced emission shift. Time-dependent density functional theory studies further support this conclusion. Relaxation of the excited state in dimethoxyethane is a postulated mechanism behind the red-shifted emission. The current study demonstrates a straight-forward path toward tuning the emission properties of EuII without altering light absorption.

Luminescent Coatings Based on (3-Aminopropyl)triethoxysilane and Europium Complex β-Diketophosphazene.

The reaction of β-diketophosphazene with the europium (III) salt synthesized the corresponding metal complex which was structured with (3-aminopropyl)triethoxysilane and treated with dibenzoylmethane for additional coordination of europium atoms. The polymer thus obtained exhibits luminescence with a maximum of 615 nm, which is characteristic of europium. The polymer is thermally stable up to 300 °C, the coating based on it has a contact angle of 101°, and the adhesive strength of the coating to non-finished glass (according to ISO 2409: 2013) is 1 point.

Luminescent Complexes of Europium (III) with 2-(Phenylethynyl)-1,10-phenanthroline: The Role of the Counterions.

New antenna ligand, 2-(phenylethynyl)-1,10-phenanthroline (PEP), and its luminescent Eu (III) complexes, Eu(PEP)2Cl3 and Eu(PEP)2(NO3)3, are synthesized and characterized. The synthetic procedure applied is based on reacting of europium salts with ligand in hot acetonitrile solutions in molar ratio 1 to 2. The structure of the complexes is refined by X-ray diffraction based on the single crystals obtained. The compounds [Eu(PEP)2Cl3]·2CH3CN and [Eu(PEP)2(NO3)3]∙2CH3CN crystalize in monoclinic space group P21/n and P21/c, respectively, with two acetonitrile solvent molecules. Intra- and inter-ligand π-π stacking interactions are present in solid stat and are realized between the phenanthroline moieties, as well as between the substituents and the phenanthroline units. The optical properties of the complexes are investigated in solid state, acetonitrile and dichloromethane solution. Both compounds exhibit bright red luminescence caused by the organic ligand acting as antenna for sensitization of Eu (III) emission. The newly designed complexes differ in counter ions in the inner coordination sphere, which allows exploring their influence on the stability, molecular and supramolecular structure, fluorescent properties and symmetry of the Eu (III) ion. In addition, molecular simulations are performed in order to explain the observed experimental behavior of the complexes. The discovered structure-properties relationships give insight on the role of the counter ions in the molecular design of new Eu (III) based luminescent materials.

Synthesis and structural characterization of an air and water stable divalent Europium squarate prepared by in situ reduction

A new air and water stable divalent Europium squarate, [Eu(C4O4)(H2O)] (1), has been prepared and structurally characterized. 1 was synthesized by in situ reduction of a trivalent Europium salt using a Zinc amalgam and mild solvothermal heating. The resulting divalent Europium metal centers in 1 are both air and water stable. This demonstrates that this methodology does not require strict anaerobic conditions. A variation on the synthetic conditions used to prepare 1 (sans the Zinc amalgam) yielded two new series of trivalent lanthanide squarates, [Ln2(C4O4)2(C4O3OH)2(H2O)12] (Ln ​= ​La – Nd) (2) and [Ln2(C4O4)3(H2O)8] (Ln ​= ​Dy – Lu) (3), which have also been structurally and spectroscopically characterized. Single crystal X-ray diffraction analysis reveals that 1 crystallizes in the C2/m space group and is a 3D structure constructed from sheets of EuO7(H2O) polyhedra with an unusual triangular dodecahedral (CN ​= ​8) geometry, 2 crystallizes in the P1¯ space group and is a 0D structure constructed from LnO3(H2O)6 monocapped square antiprismatic (CN ​= ​9) metal centers, and 3 crystallizes in the P21/n space group and is a 2D sheet structure constructed from LnO4(H2O)4 square antiprismatic (CN ​= ​8) metal centers. In all structures, the squarate ligands bind to the metal centers with varying, and sometimes uncommon, coordination modes and denticities. Herein, the synthesis, structure, and solid-state UV–vis–NIR spectroscopy of 1, 2, and 3 are presented.

A detailed study on the synergistic corrosion inhibition impact of the Quercetin molecules and trivalent europium salt on mild steel; electrochemical/surface studies, DFT modeling, and MC/MD computer simulation

For the first time, Quercetin (3,3′,4′5,7-Pentahydroxyflavone) and Eu ions were used in 3.5 wt% NaCl solution for mild steel (MS) corrosion mitigation. Tafel outcomes demonstrated the effectiveness of Quercetin:Eu compounds in the corrosion inhibition of the steel samples via mixed-type mechanism. The EIS and Tafel results showed about 98% and 90% efficiencies during 48 h of MS exposure to 3.5 wt% NaCl solution containing 200:600 ppm Quercetin:Eu, respectively. Also, EIS measurements displayed that in the presence of 200:600 ppm Quercetin:Eu inhibitor, the total resistance reached 69,751 Ω·cm2 after 48 h of immersion. The Tafel curves indicated that the icorr diminished to 0.71 μA·cm−2 after 48 h of MS subjection to the electrolyte. The FE-SEM micrographs proved that after introducing 200:600 ppm Quercetin:Eu complex, a compact and almost smooth inhibitive layer covered the MS surface. Based on the AFM test results, the average roughness reached 96 nm after 200:600 ppm Quercetin:Eu complexes adsorption on the MS surface. Detection of 17 wt% Eu element on the protected metal surface clarified the successful Quercetin:Eu complex adsorption. The theoretical (i.e., DFT and MC/MD) results further ensured the Quercetin:Eu complexes adsorption on the metallic surface.

Crystallization of Diamond from Melts of Europium Salts

Diamond crystallization in melts of europium salts (Eu2(C2O4)3·10H2O, Eu2(CO3)3·3H2O, EuCl3, EuF3, EuF2) at 7.8 GPa and in a temperature range of 1800–2000 °C was studied for the first time. Diamond growth on seed crystals was realized at a temperature of 2000 °C. Spontaneous diamond nucleation at these parameters was observed only in an Eu oxalate melt. The maximum growth rate in the europium oxalate melt was 22.5 μm/h on the {100} faces and 12.5 μm/h on the {111} faces. The diamond formation intensity in the tested systems was found to decrease in the following sequence: Eu2(C2O4)3·10H2O &gt; Eu2(CO3)3·3H2O &gt; EuF3 &gt; EuF2 = EuCl3. Diamond crystallization occurred in the region of stable octahedral growth in melts of Eu3+ salts and in the region of cubo-octahedral growth in an EuF2 melt. The microrelief of faces was characterized by specific features, depending on the system composition and diamond growth rate. In parallel with diamond growth, the formation of metastable graphite in the form of independent crystals and inclusions in diamond was observed. From the spectroscopic characterization, it was found that diamonds synthesized from Eu oxalate contain relatively high concentrations of nitrogen (about 1000−1200 ppm) and show weak PL features due to inclusions of Eu-containing species.

Complex Formation of Europium(III) with Photoditazine According to Luminescence and IR Spectroscopy

Europium(III) complexation with photoditazine, a photosensitizer for photodynamic therapy, was studied using luminescence and IR spectroscopy. The luminescence spectra of europium–photoditazine solutions and solid complex show emission bands in the 400–700 nm range, typical of both Eu3+ complexes and photoditazine. It was shown that Eu3+ luminescence intensity in the red region increases upon complex formation with photoditazine. Since the luminescence bands of solutions at 400–700 nm overlap with photoditazine absorption bands, the addition of europium chloride enhances the excitation energy transfer to photoditazine. A medication comprising a europium salt and photoditazine as a photosensitizer could serve for the targeted delivery of light radiation to photoditazine at UV excitation, which would result in more efficient formation of reactive oxygen species and can be promising for external photodynamic therapy.

Solubilities of Folic Acid and Selected Synthesized Metal Folates

The synthesis scheme and properties of folates with compositions Li2C19H17N7O6 ∙ 5H2O, PbC19H17N7O6 ∙ 4H2O, CdC19H17N7O6 · 4H2O, and Eu2(C19H17N7O6)3 · 12H2O are described. The solubility constants KS are determined for lead(II), cadmium, europium(III) and folic acid C19H19N7O6 · 2H2O at an ionic strength I = 0.1. The contemplations on using soluble europium(III) salts to extract folic acid from solutions at pH ~6 in the form of poorly soluble europium folate (logKS = –24.68 ± 0.11), followed by regeneration of folic acid (by 99%) in an acidic medium, and on using folic acid or soluble sodium folate as an antidote of lead poisoning are presented.

Biphasic Sol-Gel Synthesis of Microstructured/Nanostructured YVO4:Eu3+ Materials and Their H2O2 Sensing Ability.

Microstructured/nanostructured YVO4:Eu3+ powders and films were synthesized through a biphasic sol–gel method, aiming at their application as H2O2 sensing materials based on the turn-off luminescence of Eu3+ ions. The synthesis was typically carried out at temperatures of 80 °C or lower by using organic solutions to dissolve vanadium alkoxide and aqueous solutions to dissolve yttrium and europium salts together with sodium carboxylates. The resultant crystalline YVO4:Eu3+ powders and films were characterized as containing micrometer-sized particles comprising primary nanoparticles with high specific surface areas. A comparative study was performed on the H2O2-responsive turn-off luminescence properties for the above samples and those synthesized by a single-phase sol–gel or a conventional solid-state reaction method. The results indicated that the microstructural feature of the samples from the biphasic sol–gel method was effective for detecting H2O2 through its adsorption on the particle surface and quenching of the Eu3+ luminescence. The film samples showed repeatable and quantitative turn-off luminescence, thereby demonstrating their suitability as solid-state H2O2 sensors.

(Invited) Differences in Emission Properties for Triboluminescent EuD4tea Synthesized Using Both Europium Nitrate or Europium Acetate

Europium tetrakis dibenzoylmethide triethylammonium (EuD4TEA) is one of the most intense triboluminescent (TL) materials currently known. Some time ago, the authors reported that the triboluminescent yield was increased by 82% by changing the starting europium salt from europium chloride to europium nitrate. Unfortunately, europium nitrate has been classified as a hazardous material that cannot be shipped by air, which limits the availability of manufacturers and increases the cost. In an effort to further reduce the synthesis cost of EuD4TEA, we explore the effects of europium acetate on the triboluminescent properties of EuD4TEA by comparing the triboluminescent yield. The photoluminescent spectra as well as crystal structure using an optical microscope will also be explored

Synthesis and structural characterization of dinuclear Zinc(II) and Europium(III) complexes based on a bis-hydrazone ligand

A C2-symmetrical N,O-Schiff base ligand containing two hydrazone units has been synthesized and structurally characterized. The solid state structure as determined by single-crystal X-ray diffraction analysis reveals the presence of both intramolecular and intermolecular hydrogen bonds which lead to the formation of a C1-symmetrical conformation as well as a novel one-dimensional (1-D) helical hydrogen-bonded network. The reactions of this bis-hydrazone ligand with zinc(II) and europium (III) salts under appropriate conditions resulted in dinuclear mono-ligand zinc and tri-ligand europium complexes, respectively. The complexes were characterized by NMR spectroscopies, mass spectrometry and elemental analysis. The zinc complex has been further structurally determined by X-ray crystallography. In its solid state structure, the ligand is doubly deprotonated incorporating two zinc(II) cores that are bridged with both phenol-O group and acetate counterions. The solution electronic absorption and emission properties were characterized for both the ligand and zinc complex.

Ab initio structure determination of [Eu5(C2H4O2)6(CH3CO2)3] n by X-ray powder diffraction

The compound [Eu5(C2H4O2)6(CH3CO2)3] n was synthesized by dissolving acetate europium salt in ethylene glycol solvent and heating under reflux for a short time. Its structure was solved ab initio from synchrotron powder diffraction data using optimization methods in direct space. The compound has a very large unit-cell volume of 23679 Å3 and the highest centred cubic symmetry space group, Ia{\bar 3}d (No. 230). The porous metal–organic framework structure is similar to those usually observed in zeolites, with pores volumes of 82 Å3, which is of potential interest for gas storage.

Synthesis and luminescence spectra of poly(methyl methacrylate)/CdS:Ln(III) composites

Cadmium sulfide was prepared by colloidal synthesis in methyl methacrylate (MMA). Europium and terbium salts were added to the colloidal solutions. Using MMA radical polymerization, we synthesized PMMA/CdS:Eu(III), PMMA/CdS:Tb(III), and PMMA/CdS:Eu(III):Tb(III) luminescent composites. Their luminescence is due to defects in the CdS crystals and the 5Dо → 7Fj and 5D4 → 7Fj electronic transitions of the Eu3+ and Tb3+ ions, respectively. It depends on the composition of the materials, complexation on the surface of the colloidal particles, heat treatment time during synthesis, excitation wavelength, and other factors.

Nanocrystalline EuVO4: synthesis, characterization, optical and photocatalytic properties

In this paper europium vanadate (EuVO4) nanoparticles were prepared via a sonochemical method based on the reaction between europium salt and ammonium metavanadate in water. Moreover, this method is free from any surfactant and organic solvents. The structural, morphological and optical properties of as-obtained products were characterized by techniques such as XRD, EDS, SEM, and UV–visible. The magnetic properties of as-prepared EuVO4 nanoparticles were also investigated with vibrating sample magnetometer. To evaluate the catalytic properties of nanocrystalline europium vanadium oxide, the photocatalytic degradation of methyl orange under ultraviolet light irradiation was carried out.

Counter anion and pH directed assembly of europium(III) compounds based on tetrazole containing carboxylic acids

Counter anion and pH play important roles in the self-assembly process of coordination compounds. Tetrazole carboxylate ligands are outstanding candidates for construction of coordination architectures. Four new compounds based on Htzpya, Hatzpa, Hpytza and europium(III) salts, namely mononuclear [Eu(tzpya)2(H2O)5]Cl·4H2O (1), binuclear [Eu2(atzpa)4(H2O)8](NO3)2·2H2O (2), one dimensional [Eu(pytza)3(H2O)2]n·2nH2O (3) and [Eu(pytza)2(H2O)4]nCln (4) were obtained, where Htzpya=3-(5-tetrazolyl)pyridine-1-acetic acid, Hatzpa=5-aminotetrazole-1-propanoic acid and Hpytza=5-(4-pyridyl) tetrazole-2-acetic acid. Different europium(III) salts EuX3·6H2O (X=Cl−, NO3−) and pH values were selected to investigate the influence of both the counter anions and the pH on the formation of such compounds. Furthermore, the luminescence properties of 1–4 in the solid state were also investigated at room temperature, showing both intraligand emission and characteristic peaks of Eu3+ for compounds 1–4.

Effects of Water on the Triboluminescent Properties of Europium Tetrakis Dibenzoylmethide Triethylammonium

Europium tetrakis dibenzoylmethide triethylammonium (EuD4TEA) is one of the most intense triboluminescent (TL) materials currently known. The authors have reported in 2011, that the intensity of emission can be enhanced by changing the starting europium salt from europium chloride to europium nitrate by 82%. While investigating the impact of solvents on the intensity of light emission, the authors in 2012, demonstrated that replacing anhydrous ethanol with laboratory grade ethanol showed no change in the observed TL results. However, changing the solvent from ethanol to acetone resulted in faster precipitation of the compound, and slow crystallization yielded larger crystals with higher intensity of triboluminescence. As a result of this research, this paper investigates the effect of solvent dilution using deionized water on the triboluminescent properties of EuD4TEA.