Luminescence Spectra Of Eu Research Articles

Probing the coordination of europium(III) in a functionalized ionic liquid using luminescence spectroscopy

In view of the ever increasing attention on the rare earth recovery by functionalized ionic liquids (FILs), an attempt was made using luminescence spectroscopy to understand the detailed extraction and complexation behavior of europium(III) using a renowned phosphonium based functionalized ionic liquid, trihexyltetradecylphoshonium bis(2,4,4-trimethylpentyl)phosphinate ([P66614][C16H34PO2]) dissolved in 1,3-diisopropyl benzene (DIPB). Europium(III) complexation with [P66614][C16H34PO2] was investigated by luminescence spectroscopy by changing various extraction parameters such as aqueous phase acidity, concentration of the ionic liquid extractant, initial Eu(III) concentration and initial nitrate ion concentration. The peak intensity decreases gradually with increasing the acidity of the aqueous phase from pH 3 to 0.5 M nitric acid and the peak shape for 5D0 → 7F2 transition changes completely at 0.5 M nitric acid. Increase in the concentration of the ionic liquid and the initial metal ion in the aqueous phase increases the peak intensity of the hypersensitive transition and hence the asymmetry ratio (AR). The advantages of [P66614][C16H34PO2] were explored by comparing the emission intensity of the extracted Eu(III) in [P66614][C16H34PO2] phase with that of the organic phase containing the mixture of the precursors used for the synthesis of FIL and organic phase containing Cyanex 272 dissolved in DIPB phase. The emission profiles of Eu(III) extracted in different organic phases follows the order: [P66614][C16H34PO2] > [P66614][NO3] + 0.05 M Cyanex 272 > Cyanex 272 irrespective of the aqueous phase nitric acid concentration. The nature of Eu(III) coordination during the complex formation was ascertained from the decay profiles of Eu(III) emission. The luminescence spectra of Eu(III) were recorded in chloride medium and the results were compared with the nitrate medium.

Reddish-Orange Luminescence from BaF2:Eu3+ Fluoride Nanocrystals Dispersed in Sol-Gel Materials.

Nanocrystalline transparent BaF2:Eu3+ glass-ceramic materials emitting reddish-orange light were fabricated using a low-temperature sol-gel method. Several experimental techniques were used to verify structural transformation from precursor xerogels to sol-gel glass-ceramic materials containing fluoride nanocrystals. Thermal degradation of xerogels was analyzed by thermogravimetric analysis (TG) and differential scanning calorimetry method (DSC). The presence of BaF2 nanocrystals dispersed in sol-gel materials was confirmed by the X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). In order to detect structural changes in silica network during annealing process, the infrared spectroscopy (IR-ATR) was carried out. In particular, luminescence spectra of Eu3+ and their decays were examined in detail. Some spectroscopic parameters of Eu3+ ions in glass-ceramics containing BaF2 nanocrystals were determined and compared to the values obtained for precursor xerogels. It was observed, that the intensities of two main red and orange emission bands corresponding to the 5D0→7F2 electric-dipole transition (ED) and the 5D0→7F1 magnetic-dipole (MD) transition are changed significantly during transformation from xerogels to nanocrystalline BaF2:Eu3+ glass-ceramic materials. The luminescence decay analysis clearly indicates that the measured lifetime 5D0 (Eu3+) considerably enhanced in nanocrystalline BaF2:Eu3+ glass-ceramic materials compared to precursor xerogels. The evident changes in luminescence spectra and their decays suggest the successful migration of Eu3+ ions from amorphous silica network to low-phonon BaF2 nanocrystals.

Monodispersed Spherical Nanoparticles GdxSiyOz:Eu3+ for Magnetic Resonance Tomography and Optical Imaging

The melt method is used for synthesizing monodispersed spherical silica nanoparticles Gdx-SiyOz:Eu3+. The particle diameter is 450 nm, and the standard deviation does not exceed 5%. The nanoparticles have a line luminescence spectrum with a dominant band at 614 nm. The effect of a constant magnetic field up to 15 T on the intensity and shape of the luminescence spectra of Eu3+ ions is studied. It is shown that the obtained material has a stable photoluminescence, the intensity of which does not depend on the magnetic field in the entire studied range. The synthesized nanoparticles GdxSiyOz : Eu3+ are promising for use as a contrast agent for magnetic resonance tomography and luminescent marker.

Synthesis and Luminescent Properties of Europium(III, II) Phosphates

Nanosized europium phosphates Eu3PO7, Eu(PO3)3, and Eu(PO3)3: Eu2+ have been prepared by low-temperature extraction-pyrolytic method. Optimal temperature and time of precursor pyrolysis for preparing luminophor containing europium in different oxidation states have been determined. Phosphate luminophore based on Eu3+ exhibit intense red luminescence with λmax ∼ 600–650 nm. Luminescence spectra of Eu(PO3)3: Eu2+ are characterized by emission bands in the region 400–700 nm typical for both Eu3+ (the bands of 5D0–7Fj(j = 0, 1, 2) transitions), and Eu2+ (the band of 4f65d → 8S7/2 transition). Luminescence-exciting wavelengths provide different contribution to the radiation intensity of both Eu2+ and Eu3+.

Complexation of Eu(III) in a Completely Incinerable Ionic Liquid System: A Luminescence Spectroscopy Approach

AbstractLuminescence study of europium(III) ion has been carried out in a completely incenerable (CHON based) ionic liquid system. The ionic liquid used in the study was trioctylmethylammonium nitrate ([N1888][NO3] while the extractant used was N,N‐dioctyl‐2‐hydroxyacetamide (DOHyA). The complexation of europium(III) in such type of ionic liquid system and its elaboration by luminescence study is highlighted for the first time in this paper. The luminescence behaviour of europium(III) was ascertained as a function of various parameters, such as aqueous phase acidity, extractant concentration, initial metal ion concentration, types of ionic liquid diluents etc. The luminescence intensity of Eu(III) was remarkably high in the ionic liquid medium at all aqueous phase acidity (0.1 M to 5 M HNO3) as compared to that of in aqueous phase. The luminescence lifetime of Eu(III) in this complex is in the range of 360 μs – 550 μs which is quite higher than that of aqueous phase (107 μs ‐ 130 μs), suggesting the luminescence enhancement is a result of reduction in non‐radiative decay channels in ionic liquid medium. The emission peak of Eu(III) in DOHyA was compared with that of DOMeA (N,N‐dioctyl‐2‐methoxyacetamide) in ionic liquid medium in order to highlight the presence of –OH group in DOHyA. The luminescence spectra of Eu(III) was also investigated by changing the type of aqueous phase acidity from nitrate ion to chloride ion and the results are detailed in the paper.

Eu3+-Doped Wide Band Gap Zn2SnO4 Semiconductor Nanoparticles: Structure and Luminescence

Nanocrystalline Zn2SnO4 powders doped with Eu3+ ions were synthesized via a mechanochemical solid-state reaction method followed by postannealing in air at 1200 °C. X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and Raman and photoluminescence (PL) spectroscopies provide convincing evidence for the incorporation of Eu3+ ions into the host matrix on noncentrosymmetric sites of the cubic inverse spinel lattice. Microstructural analysis shows that the crystalline grain size decreases with the addition of Eu3+. Formation of a nanocrystalline Eu2Sn2O7 secondary phase is also observed. Luminescence spectra of Eu3+-doped samples show several emissions, including narrow-band magnetic dipole emission at 595 nm and electric dipole emission at 615 nm of the Eu3+ ions. Excitation spectra and lifetime measurements suggest that Eu3+ ions are incorporated at only one symmetry site. According to the crystal field theory, it is assumed that Eu3+ ions participate at octahedral sites of Zn2+ or Sn4+ under a weak cr...

Luminescent properties of Ln3+ doped tellurite glasses containing AlF3

The low-phonon energy tellurite glasses TeO2-BaO-Bi2O3 and TeO2-BaO-Bi2O3-AlF3 triply doped with Eu3+, Tb3+, Tm3+ ions in two different molar ratios were synthesized using melt-quenching technique. Their structure and luminescence properties were widely investigated by X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR) and Photoluminescence Spectroscopy (PL). The luminescence spectra of Eu3+, Tb3+, Tm3+ co-doped glasses show apart of the bands corresponding to the 4f-4f transitions of lanthanide ions also band corresponding to glass matrix. AlF3 doping increases emission intensity, although to improve overall emission color further studies on molar composition of samples and the molar ratio of the components should be carried out.

Synthesis and Characterization of Eu<sup>3+</sup> Doped CaO-Nb<sub>2</sub>O<sub>5</sub>-SiO<sub>2</sub> Glass-Ceramics

The glass-ceramics containing nanocrystalline CaNb2O6phase in the 35%SiO2-25%Nb2O5-20%CaO-15BaO-5%Eu2O3(wt%) glass system were prepared by the melt-quench technique followed by a two-stage controlled heat treatment. Samples were characterized by differential thermal analysis, X-ray diffraction, scanning electron microscope, spectrophotometer and fluorescence spectrophotometer. The results shown that glass ceramic phase is CaNb2O6, grain size is about 30 nm, The two-stage controlled heat treatment is beneficial to control of the number and size of grains, thus affecting the transparency of glass ceramic and luminescence properties. The transmittance of the glass ceramics can be up to 80% in the near-infrared light area. The luminescence spectra of Eu3+-doped glass and glass–ceramics were recorded at 394 nm excitation wavelength and the luminescence intensity is found to be increased with heat-treatment time due to increase in crystallinity. Fluorescence spectrum showed 4 emission peak, which located in the 578 nm (5D0-7F0), 592 nm (5D0-7F1), 615 nm (5D0-7F2) and 654 nm (5D0-7F3), Eu3 +emission peak intensity in the glass ceramic sample were greater than the substrate glass.

Synthesis and Characterization of Eu<sup>3+</sup>-Doped Transparent Glass-Ceramics Containing Nanocrystalline AlNbO<sub>4</sub>

The transparent glass-ceramics containing nanocrystalline AlNbO4 phase in the 25Al2O3-27Nb2O5-40SiO2-7Na2O-2Eu2O3(wt%) glass were prepared by the melt-quench technique followed by a two-stage controlled heat treatment. Crystalline phase were indentified using X-ray diffraction (XRD) which AlNbO4 phase was found. Scanning electron microscopy (SEM) was used to image the crystalline phase morphologies. The luminescence spectra of Eu3+-doped glass and glass-ceramics were recorded at 393 nm exciation wavelength and the luminescence intensity is found to be increase with heat-treatment time due to increase in crystallinity. The high intensity ratio of 5D0-7F2 to 5D0-7F1 indicates that the Eu3+-doped nanocrystalline AlNbO4 glass-ceramics are promising candidate materials as red-light source.

Rare earths in lead-free oxyfluoride germanate glasses

Spectroscopic properties of rare earths in lead-free oxyfluoride germanate glasses were studied. The absorption and luminescence spectra of Eu3+, Pr3+ and Er3+ ions were examined as a function of BaF2 concentration and several spectroscopic parameters for rare earths were determined. The ratio of integrated luminescence intensity of the 5D0→7F2 transition to that of the 5D0→7F1 transition of Eu3+ decrease significantly with increasing BaF2 content. The absorption (Er3+) and emission (Pr3+) ‘hypersensitive transitions’ of rare earths are shifted in direction to shorter wavelengths with increasing BaF2 content in glass composition. Emission spectra and their decays corresponding to the main 4I13/2→4I15/2 laser transition of Er3+ were also analyzed. Quite long-lived NIR luminescence of Er3+ is observed for lead-free glass samples with low BaF2 concentration.

Luminescence spectra of Eu(III/II)-doped LaAlO3 powders prepared by a solid-state reaction of Eu(III)-doped LaCO3OH and Al2O3

Lanthanum aluminate (LaAlO3) powder was prepared by a solid-state reaction of lanthanum(III) hydroxycarbonate (LaCO3OH) and nanosized δ-alumina (δ-Al2O3) powders at elevated temperatures. The conversion of LaCO3OH into LaAlO3 was monitored by powder X-ray diffraction and 27Al magic-angle spinning nuclear magnetic resonance spectroscopy. The latter tool was useful for the detection of unreacted Al2O3 in final products. The formation temperature of LaAlO3 was reduced using metal fluorides as an additive. The luminescence spectra of Eu(III)-doped LaAlO3 (LaAlO3:Eu3+) powders obtained by calcination of a mixture of LaCO3OH:Eu3+ and nanosized δ-Al2O3 were compared with those of LaAlO3:Eu3+ powders obtained by other synthesis methods. The LaCO3OH:Eu3+–Al2O3 reaction system was preferable to the La2O3–Eu2O3–Al2O3 reaction system because LaAlO3:Eu3+/2+ powders exhibited stronger emission peaks.

Spectroscopic characterization and the coordination behavior of isonicotinamide with lanthanide ions

The coordination of amide groups to metal ions is important because it may be involved in the interactions between metal ions and proteins. The synthesis and characterization of nine novel lanthanide–isonicotinamide (ina) complexes, including LaCl3, PrCl3, NdCl3, SmCl3, EuCl3, GdCl3, TbCl3, ErCl3 and PrBr3 complexes are reported. The structures of these complexes in the solid state have been characterized by X-ray single crystal diffraction, FTIR, FIR, THz and Luminescence spectroscopy. Isonicotinamide has only one coordination mode in four structures as O-monodentate ligand to coordinate to metal ions, but four kinds of topological structures are observed for lanthanide–isonicotinamide complexes, including LnCl3⋅(C6H6N2O)2⋅4H2O (La, Pr, Nd and Sm), EuCl3⋅(C6H6N2O)2⋅7H2O, LnCl3⋅(C6H6N2O)2⋅6H2O (Gd, Tb and Er) and PrBr3⋅(C6H6N2O)2⋅7H2O. Chloride ions can coordinate to metal ions or hydrogen-bonded. FTIR spectra indicate the formation of four kinds of lanthanide–ina complexes, the extensive hydrogen bond networks after complexation and the coordinations and the changes of the conformation of the ligand. FIR and THz spectra also confirm the formation of lanthanide ion–ina complexes. Luminescence spectra of Eu and Tb-ina complexes have the characteristics of Eu and Tb ions.

Synthesis and Characterization of Eu3+ -Doped Transparent Glass-ceramics Containing Nanocrystalline SrII NbIV O3

The glass–ceramics containing a rarely achievable nanocrystalline SrIINbIVO3 phase in the 53.75SiO2–18.25K2O–9Bi2O3–9SrO–9Nb2O5–0.5CeO2–0.5Eu2O3 (mol%) glass system were prepared by the melt-quench technique followed by a two-stage controlled heat treatment. The unusual oxidation state of Nb in SrIINbIVO3 crystal is 4+ and upon heat treatment of the samples at lower temperature of 500°C for several hours, the glass composition and chemical environment around Nb ions played a key role for the formation of SrIINbIVO3 in the glass–ceramics. The microstructure of the glass–ceramics was studied using TEM and FESEM. The TEM images advocate 10–40 nm crystallite size of SrIINbIVO3. FTIR study confirms that all the samples consist of SiO4, BiO3, BiO6, and NbO6 structural units. The refractive index at different wavelengths was found to vary in the range 1.7105–1.7905 and increase with increase in heat-treatment time. The luminescence spectra of Eu3+-doped glass and glass–ceramics were recorded at 465 nm excitation wavelength and the luminescence intensity is found to be increased with heat-treatment time due to increase in crystallinity. The high intensity ratio of 5D0→7F2 to 5D0→7F1 indicates that the Eu3+-doped nanocrystalline SrIINbIVO3 glass–ceramics are promising candidate materials as red-light source.

Factors influencing the luminescence intensity of europium(III) complexes prepared via synergistic extraction

The excitation and luminescence spectra of Eu(III) extracted with pivaloyltrifluoroacetone (HA) and/or 2,2′-bipyridyl (B) into CHCl3 were measured. The data were compared to those obtained in an HA/CHCl3 solution into which EuA3 or EuA3B was dissolved. The results are summarized as follows: (1) The degree of HA influence on the luminescence intensity differs in the two systems; in the HA/CHCl3-dissolved EuA3, the intensity abruptly decreases when the HA concentration exceeds approximately 10−2M, depending on EuA3 concentration. The data measuring the size of the dominant species in the CHCl3 containing EuA3 and HA via DLS indicate that the abrupt concentration quenching is due to the formation of aggregate consisting of EuA3 and HA. However, in the solvent-extracted sample, the luminescence intensity is not influenced by the HA concentration, even at 0.1M HA. This difference can be explained by the difference in water content. (2) In the synergistic extraction of Eu(III) with HA and B, the intensity is not substantially influenced by HA. The effect of HA on the luminescence intensity in the B/CHCl3-dissolved EuA3 is larger than that obtained via solvent extraction. These results suggest that synergistic extraction could be an efficient method for preparing the phosphor in solution and that, when using luminescence intensity to determine Eu(III) concentration, one should be careful for the other materials, such as HA, that are involved in the solution and serve as reference materials.

Synthesis, luminescence properties of Eu(III) and Tb(III) complexes with a novel aromatic carboxylic acid and their interactions with bovine serum albumin

A novel aromatic carboxylic acid ligand (L) was synthesized and its corresponding Eu(III) and Tb(III) complexes, Na3EuLCl3·2H2O (EuL) and Na3TbLCl3·3H2O (TbL), were successfully prepared. L and its corresponding complexes were characterized by means of MS, elemental analysis, IR, 1H NMR and TG. The luminescence spectra of Eu(III) and Tb(III) complexes were investigated and the results showed that L was an efficient sensitizer for Eu(III) and Tb(III) luminescence. The interactions of L, EuL and TbL with bovine serum albumin (BSA) have been investigated through fluorescence spectroscopy under physiological conditions. The Stern–Volmer analysis indicated that the fluorescence quenching of BSA by L, EuL and TbL was resulted from static mechanism, and the binding constants (Ka) were 2.22×104, 1.33×105 and 4.27×105 at 300K, respectively. The binding sites (n) and the corresponding thermodynamic parameters ΔH, ΔS, and ΔG were calculated at different temperatures. According to the theoretical and experimental results, van der Waals interactions and hydrogen bonds were found to play major roles in the binding reaction. Furthermore, UV–Vis absorption spectroscopy and synchronous fluorescence spectra indicated that the conformation of BSA was changed. The results obtained in the work can help understand the action mode between L and its corresponding Eu(III) and Tb(III) complexes with BSA, and they are also expected to provide important information of designs of new inspired drugs based on Eu and Tb.

Synthesis and characterization of rhombohedral- and tetragonal-lanthanum oxyfluoride powders

Rhombohedral- and tetragonal-lanthanum oxyfluoride (LaOF) powders were prepared by thermal decomposition of lanthanum(III) carbonate fluoride (LaFCO3) powders that had been obtained from boiling an aqueous solution containing lanthanum(III) salt, fluoride ion (F−), and urea. The conversion process of LaFCO3 to LaOF was monitored by thermogravimetry, powder X-ray diffraction, and 19F magic-angle spinning nuclear magnetic resonance spectroscopy. The crystal structure (rhombohedral, tetragonal) of LaOF depended on the mole ratio of F− to La3+ ions in the preparation of LaFCO3, and tetragonal-LaOF was completely transformed into rhombohedral-LaOF at 1000°C. The difference in crystal structures was reflected in the intensity of the 5D0→7F0 transition peak in the luminescence spectra of Eu3+-doped LaOF powders.

Double Perovskite Structure: A Vibrational and Luminescence Investigation Providing a Perspective on Crystal Field Strength

The luminescence spectra of Eu(3+) doped in a series of double perovskite lattices Ba(2)LnMO(6) (Ln = Y, Gd; M = Nb, Ta) have been recorded at room temperature and 10 K. Together with FT-IR and FT-Raman spectra and aided by DFT vibrational energy calculations, assignments have been made for the crystal field levels of the (5)D(J) (J = 0,1) and (7)F(J) (J = 0-2) multiplets. The luminescence spectra are consistent with monoclinic symmetry of these systems. The crystal field parameters from the fitting of the energy level data set of Ba(2)YNbO(6):Eu(3+) enable the crystal field strength to be calculated, and the order of magnitude is Cl(-) < O(2-) < F(-) for the EuX(6)(n-) (n = 6 for halogen, 9 for oxide) moieties. For these systems, an empirical linear relationship between crystal field strength and electronegativity of ligand X has been found. By contrast, the nephelauxetic series from the depression of the Slater parameter F(2) is Cl(-) ≈ O(2-) > F(-) > free ion for these systems.

Eu(III), Tb(III) complexes with novel ligands containing pyridine-2,6-dicarboxylic acid unit: Synthesis, characterization, fluorescence properties and application in biological imaging

Three novel ligands containing pyridine-2,6-dicarboxylic acid unit, trans-4 -(4′-methoxystyryl) pyridine-2,6-dicarboxylic acid, trans-4-(4′-(dimethylamino)styryl)pyridine-2,6-dicarboxylic acid, and trans-4-(4′-(diphenylamino)styryl)pyridine-2,6-dicarboxylic acid were synthesized and their complexes with Eu(III), Tb(III) ions were successfully prepared. The ligands and the corresponding metal complexes were characterized by means of MS, elemental analysis, IR, 1H NMR and TG–DTA. The luminescence spectra of Eu(III) and Tb(III) complexes in solid state were studied. The strong luminescence emitting peaks at 615 nm for Eu(III) and 545 nm for Tb(III) can be observed. The applications in cell imaging of the europium and terbium complexes were investigated.

Synthesis and spectral characteristics of Sr 2Y 8(SiO 4) 6O 2: Eu polycrystals

Spectral-luminescent characteristics of Sr 2Y 8(SiO 4) 6O 2: Eu powder crystal phosphor with the apatite structure and high-intensity luminescence of Eu 3+ ions have been studied. The charge state of europium in the samples has been characterized by means of X-ray L 3-adsorption spectroscopy. It was established that Eu 3+ forms two types of optical centers. Besides, luminescence of Eu 2+ions was found. Reduction Eu 3+→Eu 2+ was considered, which may be due to V Sr ∥ vacancy formation in the 4 f crystal lattice position and to negative charge transfer by this vacancy to two Eu Y 3 + ions. Thus, in the silicate lattice there exist inhomogeneously distributed oxygen-deficient centers, which are responsible for nonradiative transfer of excitation energy to Eu 3+ and Eu 2+ ions. To study electron-vibrational interactions in the crystal phosphor samples, their IR and Raman spectra were examined. In the luminescence spectrum of Eu 2+, a series of low-intensity bands caused by interaction of the 4 f 65 d state of Eu 2+ with silicate lattice vibrations was observed.

Polymer composite P3HT:Eu 3+ doped La 2O 3 nanoparticles as a down-converter material to improve the solar spectrum energy

Europium-doped La 2O 3 nanocrystalline powders with sizes in the range of 50–200 nm have been obtained by the modified sol–gel Pechini method. These nanocrystals have been deagglomerated using sonication for 3 h and have been dispersed into a semiconductor P3HT polymeric matrix. We studied and analysed the spectroscopic properties of the trivalent europium in the hexagonal La 2O 3 nanocrystals dispersed in the polymer. The luminescence spectrum of Eu 3+ in these nanocrystals is dominated by the 5D 0 → 7F 2 transition with a maximum intensity peak located at 626 nm. We observed that P3HT absorbs part of the light emitted by the nanoparticles. These properties look promising for using this material as a down-converter material in solar cells.