Intensity Of Eu3 Research Articles

Binuclear europium(III) pivalates with 4,7-diphenyl-1,10-phenanthroline: Controllable synthesis, unique structural transitions, and remarkable luminescence

Solution chemistry methods were developed, resulting in the controllable formation of complexes [(bath)2Eu2(piv)6]·2EtOH (1a·2EtOH), [(bath)2Eu2(piv)6]·1.5EtOH (1b·1.5EtOH), and [(bath)2Eu2(piv)6]·0.75H2O (1c·0.75H2O), where piv is (CH3)3CCO2− and bath is 4,7-diphenyl-1,10-phenanthroline. Polymorphs 1a, 1b, and 1c of the composition [(bath)2Eu2(piv)6] are produced by desolvation of the appropriate solvates. 1a·2EtOH, 1b·1.5EtOH, 1c·0.75H2O, 1a, 1b, and 1c were characterized by single-crystal X-ray diffraction (SC-XRD). 1a·2EtOH, 1b·1.5EtOH, and 1c·0.75H2O differ in the structural functions of µ2-piv anions and have different molecular and crystal structures. 1a·2EtOH contains two μ2-piv-κ2O,O′ anions and two μ2-piv-κ2O,O,O′ anions, whereas 1b·1.5EtOH and 1c·0.75H2O have four μ2-piv-κ2O,O′ anions. Single crystals of 1b·1.5EtOH (monoclinic, C2/c) and 1c·0.75H2O (monoclinic, I2/a) undergo reversible desolvation–solvation without structural changes. The unique feature of 1b and 1c is melting at high temperatures. The melting of 1b and its subsequent crystallization lead to the polymorphic transition from 1b to 1c. The latter is reversibly melt-crystallized. The unique feature of 1a·2EtOH is that it undergoes two 0D–0D single-crystal-to-single crystal (SCSC) transitions. The SCSC transition from 1a·2EtOH (triclinic, P1¯) to 1a (monoclinic, P21) is a result of desolvation is accompanied by a change in the crystal system. The most significant change during the temperature-induced SCSC polymorphic transition from 1a to 1c (monoclinic, I2/a) is the Eu–O bond cleavage resulting in different coordination geometries of Eu atoms in 1a and 1c. The overall quantum yield QLnL for 1a·2EtOH amounts to 62%. A comparison of the spectroscopic and photophysical data for the Eu complexes shows that the differences in the coordination geometries of the metal atoms in the Eu pivalates have no effect on intensity of Eu3+ ion luminescence. The results of the present study demonstrate that all complexes hold promise for the design of brightly emissive Eu3+-containing materials.

Luminescence properties of (Sr0.86Mg0.14)3(PO4)2:Eu2+,Mn2+ phosphors for LEDs application

To explore new emission-tunable phosphors for LEDs, a series of (Sr0.86Mg0.14)3(PO4)2:Eu2+,Mn2+ (SMP:Eu2+,Mn2+) phosphors were prepared by solid-state reaction method, and their photoluminescence properties were investigated. For Eu2+-single-doped SMP samples, two main emission bands located at 522 and 625 nm were found. The two bands could be attributed to different Eu2+ emission centers, and the excitation spectra as well as time-resolved photoluminescence spectra also verify this point. The optimal Eu2+ doping concentration in the SMP host was determined to be 0.2%. The excitation spectra of the typical SMP:0.2%Eu2+ reveal that broad excitation bands from 250 to 450 nm have been obtained, which can well match the NUV LED chip. By doping Mn2+ into the SMP:0.2%Eu2+ phosphor, the emission intensity of Eu2+ at 522 nm shows a fast decay owing to the energy transfer (ET) from Eu2+ to Mn2+, which could be interpreted by the change of the Eu2+ decay lifetime. As a result, the tunable emission was achieved. The corresponding ET mechanism was discussed and the ET efficiency was evaluated. Besides, the thermal quenching behavior of both SMP:0.2%Eu2+ and SMP:0.2%Eu2+,20%Mn2+ phosphors was also investigated.

Role of Li + ions on the luminescence properties in water dispersible mesoporous CaF 2 : Eu 3 + nanocrystals

Polyvinyl pyrrolidone- (PVP) and ethylene glycol- (EG) coated water dispersible mesoporous CaF2:Eu3+,Li+ nanocrystals were synthesized by a simple one-pot hydrothermal method. The role of Li+ ions on the morphology and spectra in the CaF2 nanocrystals have been reported. The synthesized nanocrystals were monodisperse with regular sphere-like shapes and exhibited obvious hollow mesoporous structure. The results from x-ray photoelectron spectroscopy determined the successful incorporation of Eu3+ ions and Li+ ions into the CaF2 host lattice. The excitation and emission intensity of Eu3+ enhanced with Li+ concentration until 7 mol.%. The nanocrystals could disperse in water for more than a month due to the EG and PVP molecules coated over the nanocrystals.

Simultaneous Quantification of Anticardiolipin IgG and IgM by Time Resolved Fluoroimmunoassay.

The autoimmune disease antiphospholipid syndrome (APS) is characterized by the presence of anticardiolipin antibodies (aCL), along with anti-β2-glycoprotein I (β2GPI) antibodies and lupus anticoagulant (LA). In this study, we developed a time-resolved fluoroimmunoassay (TRFIA) system for simultaneous quantification of aCL IgG and IgM. A 96-well microtiter plate precoated with the complex of cardiolipin from bovine heart and bovine β2GPI was incubated with the anticardiolipin IgG and IgM standard substance or serum, and the conjugate of Eu3+-labeled anti-human IgG and Sm3+-labeled anti-human IgM was pipetted to the wells to form a tipical double-antibody-sandwich immunoreactions; finally the fluorescent intensity of Eu3+ and Sm3+ was detected to reflect the quantity of anticardiolipin IgG and IgM. This assay showed a good relationship between fluorescence intensities and the concentration of anticardiolipin antibody(aCL) IgG and IgM, with a low-end sensitivity of 0.1 U/ml for IgG and 0.1 U/ml for IgM, respectively. The intra- and inter-assay coefficients of variation (CV) of the calibrators was 3.0% and 4.51% for IgG, and 2.76% and 4.45% for IgM. The average recovery was 100.38% for aCL IgG and 100.45% for aCL IgM. For serum samples, the results of our method showed a good correlation with those obtained with ELISA kit. Simultaneous detection of aCL-IgG and aCL-IgM in the same reaction well can optimize assay performance by avoiding potential influence of different reaction conditions-timing, and well-to-well difference in concentration and characteristics of cardiolipin antigen. The results of a combo aCL-IgG and aCL-IgM assay for the same sample are more consistent and more reliable. This dual-label time-resolved fluoroimmunoassay is sensitive for detecting aCL IgG and IgM across a wide concentration range with stable reagents and may assist in the clinical diagnosis of antiphospholipid syndrome.

The Role of Ligand Topology in the Decomplexation of Luminescent Lanthanide Complexes by Dipicolinic Acid

In this study, we present the aqueous solution behavior of two luminescent lanthanide antenna complexes (Eu3+ ⊂1, Dy3+ ⊂9) with different ligand topologies in the presence of dipicolinic acid (DPA, pyridine-2,6-dicarboxylic acid). Macrocyclic (1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid, DO3A, 9) and acyclic (1,4,7-triazaheptane-1,1,7,7-tetraacetic acid, DTTA, 1) ligands have been selected to form a ratiometric pair in which Dy3+ ⊂9 acts as a reference and Eu3+ ⊂1 acts as a probe for the recognition of DPA. The pair of luminescent complexes in water reveals the capability to work as a DPA luminescent sensor. The change of emission intensity of Eu3+ indicates the occurrence of a new sensitization path for the lanthanide cation through excitation of DPA. NMR evidence implies the presence of free 1 and mass spectrometry shows the formation of emitting [EuDPA2 ]- as a result of a ligand exchange reaction.

Effect of lithium excess on the LiAl_5O_8:Eu luminescent properties under VUV excitation

The influence of lithium excess and calcination temperature on the luminescence properties of the LiAl5O8:Eu under VUV excitation was investigated. The presence of both broad bands and sharp peaks in the VUV and X-ray emission spectra suggests the presence of Eu2+, even in absence of reducing atmosphere in the synthesis. The VUV excitation spectra indicated a band gap of 8.5 eV while the UV excited one showed the Eu3+ charge transfer transition starting at 3.9 eV. These values indicate that Eu2+ is stable in this host since its ground state is below the Fermi level of the host (ca. 4.1 eV). The relation between the intensity of Eu2+ and Eu3+ emissions showed that the reduction is favored at higher temperatures and lower Li content, leading to the proposition of a reduction mechanism based on the incorporation of charge compensation defects formed in the aliovalent doping of Eu3+ in Li+ sites.

Luminescent properties and energy transfer process of Sm3+-Eu3+ co-doped MY2(MoO4)4 (M=Ca, Sr and Ba) red-emitting phosphors

MY2(MoO4)4:Sm3+ and MY2(MoO4)4:xSm3+,yEu3+ (M=Ca, Sr and Ba) phosphors were successfully prepared using solid-state reaction route, and their luminescent properties and energy transfer process from Sm3+ to Eu3+ were systematically investigated. The results indicate that MY2(MoO4)4:Sm3+ phosphors can be effectively excited by 407 nm near UV light originating from the 6H5/2 → 4F7/2 transition of Sm3+, and exhibit a satisfactory red emission at 646 nm attributed to the 4G5/2 → 6H9/2 transition of Sm3+, in which the emission intensity of SrY2(MoO4)4:Sm3+ is the strongest among the MY2(MoO4)4:Sm3+ (M=Ca, Sr and Ba) phosphors. For Eu3+ co-doped MY2(MoO4)4:Sm3+ samples, with increasing Eu3+ doping content, the main emission peaks of Sm3+ (approximately 646 nm) are decreased, but the emission peaks and intensity of Eu3+ are increased while the maximum intensity of luminescence at the Eu3+ concentration 0.9. The introduction of Eu3+ in the MY2(MoO4)4:Sm3+ phosphors can remarkably generate a strong emission line at 616 nm, originating from the 5D0→7F2 transition of Eu3+ and Sm3+ (4G5/2) → Eu3+ (5D0) effective energy transfer process. The energy transfer mechanism from Sm3+ to Eu3+ was discussed in detail.

Solvothermal fabrication and luminescent properties of Eu2+/Gd3+ doped potassium magnesium fluoride

Abstract Phase-pure Gd-/Eu-doped and co-doped KMgF 3 phosphors are synthesized by solvothermal techniques at 200 °C for 5 days. The crystal structure, particle size and morphologies of the as-synthesized products are investigated by X-ray powder diffraction (XRD) and environment scanning electron microscopy (ESEM). The excitation and emission spectra of the rare earth ions doped KMgF 3 are measured by the fluorescence spectrophotometer and the effects of Gd 3+ ions molar fraction on the luminescence of Eu 2+ ions are discussed. In the co-doped Eu 2+ and Gd 3+ system, the emission intensity of Eu 2+ ion gradually increases with the increasing Gd 3+ concentration, and the enhancement of Eu 2+ fluorescence is due to an efficient energy transfer from Gd 3+ to Eu 2+ in the host. In addition, the mechanism of energy transfer has been discussed in detail. These results suggest that the phosphors of KMgF 3 : Gd 3+ , Eu 2+ would become promising short-wave laser materials.

Synthesis and Characterization of SiO2@Y2MoO6:Eu3+ Core-Shell Structured Spherical Phosphors by Sol-Gel Process.

SiO2@Y2MoO6:Eu3+ core-shell phosphors were prepared by the sol-gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as kinetic decays were used to characterize the resulting SiO2@Y2MoO6:Eu3+ core-shell phosphors. The XRD results demonstrated that the Y2MoO6:Eu3+ layers on the SiO2 spheres crystallized after being annealed at 700 °C and the crystallinity increased with raising the annealing temperature. The obtained core-shell phosphors have spherical shape with narrow size distribution (average size ca. 640 nm), non-agglomeration, and smooth surface. The thickness of the Y2MoO6:Eu3+ shells on the SiO2 cores could be easily tailored by varying the number of deposition cycles (70 nm for four deposition cycles). The Eul+ shows a strong PL emission (dominated by 5D0-7F2 red emission at 614 nm) under the excitation of 347 nm UV light. The PL intensity of Eu3+ increases with increasing the annealing temperature and the number of coating cycles.

Preparation and luminescence properties of color-tunable single-phased LaPO4:Eu3+/Tb3+ phosphors

A novel series of color-tunable single-phased phosphors La1–x–yPO4:xEu3+/yTb3+(x=0, 0.01, 0.02, 0.03, 0.04, 0.05; y=0, 0.05, 0.10, 0.15, 0.20) was synthesized via co-precipitation method with diammonium hydrogen phosphate as precipitant. The morphology, crystal structure and photoluminescence properties of the as-prepared samples were characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM) and fluorescence spectrophotometer. The results reveal that the as-synthesized samples calcined at 1100 °C display spherical morphology with uniform distribution. Upon excitation with 350 nm ultraviolet radiation, the LaPO4:Eu3+/Tb3+ phosphors showed a green light peaking at 543 nm assigned to the characteristic 5D4-7F5 emission of Tb3+ and a red light peaking at 591 nm corresponding to the characteristic 5D0-7F1 emission of Eu3+ simultaneously. For the Eu3+/Tb3+ co-activated phosphors, Tb3+ acts as an efficient sensitizer to enhance the emission intensity of Eu3+ ions. The energy transfer mechanism and the emission color tunability of LaPO4:Eu3+/Tb3+ have been studied. The results indicate that a color-tunable luminescence(from green to white to red) can be achieved by adjusting the Eu3+/Tb3+ doping ratio in the LaPO4 host matrix.

Synthesis and luminescence of spherical Y2O3:Eu3+ and Y2O3:Eu3+/Bi3+ particles

Y2O3:Eu3+ and Y2O3:Eu3+/Bi3+ particles with spherical morphology are synthesized by microwave-assistant hydrothermal process. The results show that cubic phase Y2O3:Eu3+ and Y2O3:Eu3+/Bi3+ particles with uniform size and spherical shape are obtained. The doping Eu3+ and Bi3+ ion have no influence on the phase and morphology of samples. In the hydrothermal process, the fast and homogeneous microwave heating benefits the formation of samples with uniform size and spherical shape. Both Y2O3:Eu3+ and Y2O3:Eu3+/Bi3+ show dominant red emission originating from the 5D0 → 7F2 transition of Eu3+. The codoping Bi3+ can enhance the intensity of Eu3+ emission.

BaLaF5, BaLaF5:Eu3+, BaLaF5:Eu3+/Tb3+ and BaLaF5:Eu3+@BaLaF5:Gd3+ core/shell nanoplates: hydrothermal synthesis, luminescence and magnetic properties

Well defined and photoluminescent BaLaF5:Eu3+, BaLaF5:Eu3+/Tb3+ and BaLaF5:Eu3+@BaLaF5:Gd3+ core/shell nanoplates were synthesized via facile hydrothermal method. X-ray powder diffraction, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy, Fourier transform infrared spectrum, photoluminescence, kinetics of luminescence decay and magnetic studies were used to characterize the structural, optical and magnetic properties of these nanoplates. TEM images show that these nanoplates have pseudo spherical shape with the average crystallite size of 14–21 nm. Down-conversion luminescent properties of doped BaLaF5 nanoplates were investigated and impact of core/shell formation and co-doping has been explored. The luminescent intensity and lifetime of Eu3+ in Eu3+/Tb3+ co-doped BaLaF5 nanoplates and BaLaF5:Eu3+@BaLaF5:Gd3+ core/shell nanoplates are enhanced with respect to the bare BaLaF5:Eu3+ nanoplates. Coating BaLaF5:Eu3+ core with BaLaF5:Gd3+ shell on the surface reduces defects on the surface of core and so the surface quenching is suppressed, thus reducing the efficiency of nonradiative decay pathways. In the case of Eu3+/Tb3+ co-doped BaLaF5 nanoplates, energy transfer process from Tb3+ to Eu3+ enhanced the luminescent intensity of Eu3+ ion. Also the Gd3+ doped BaLaF5 core/shell nanoplates exhibit weakly ferromagnetic interactions with coercivity value of 418.96 G at room temperature.

Composition-induced tunable white emission in Ce/Tb/Eu co-doped lithium–barium borophosphate glasses

Ce/Tb/Eu co-doped lithium–barium borophosphate glasses were successfully synthesized by melt quenching method. The structure and luminescence properties of glasses were characterized by Fourier transform infrared spectroscopy, photoluminescence spectra spectroscopy and colorimetric analysis. The influence of matrix composition on glass structure and photoluminescent properties was investigated in detail. The partial replacement of BaO for B2O3 changed the ratios of Ce3+/Ce4+ and Eu2+/Eu3+, and altered the glass structure, which affected the physical properties of the glass samples. The emission intensity of Ce3+, Eu2+ and Tb3+ decreased with increasing BaO content, but the intensity of Eu3+ increased continuously. Energy was transferred from Ce3+, Tb3+and Eu2+ to Eu3+ ions, which resulted in the enhancement of Eu3+ luminescence intensity. Meanwhile, the colors of Ce/Tb/Eu co-doped luminescent glasses changed from cold white to warm white by changing glass matrix composition. Possible mechanisms of the reduction for valence-variable rare earth ions were also discussed.

Optical Amines and Ammonia Sensors Based on Europium(III) Luminescent Complexes

The effect of amines and ammonia vapour on luminescence of Eu (III) complexes immobilized in different matrices has been investigated. It has been revealed that interaction of Eu (III) tris-dibenzoylmethanate with analyte vapour results in the increase of the intensity of Eu (III) luminescence. The mechanism of the effect of ammonia and amines vapours on intensification of the Eu (III) luminescence has been suggested using the data of IR, luminescence spectroscopy and quantum chemistry calculations.

Enhancement of Luminescence of YPO<sub>4</sub>:Eu<sup>3+</sup>,Yb<sup>3+</sup> Nanophosphor Synthesized by Hydrothermal Method

YPO4 nanowires (NWs) and nanoparticles (NPs) have been synthesized by hydrothermal methods respectively in the absence and presence of EDTA. The Eu3+ and Yb3+ codoped YPO4 NWs and NPs prepared directly from hydrothermal systems show efficient red down-conversion luminescence (DL) and upconversion luminescence (UL) at room temperature without further annealing process. EDTA plays a critical role in controlling the morphologies of YPO4 nanocrystals in hydrothermal systems and enhances both the DL and UL intensities of Eu3+ by the factor of 100%. Monodispersed Eu3+ and Yb3+ codoped YPO4 NPs will be a new candidate for application in infrared displays and biological labels.

Na+ induced electric-dipole dominated transition (5D0→7F2) of Eu3+ emission in AMgPO4:Eu3+ (A=Li+, Na+, K+) phosphors

A series of Eu3+ doped (AMgPO4)1.00−x:Eu3+x (A=Li+, Na+, K+) phosphors were prepared by the solid-state method. XRD results confirm that the samples contain mixture phases of crystals. Cation effect of Li+, Na+, K+ on the PL properties of (AMgPO4)1.00−x:Eu3+x phosphors is discussed. The results indicated that among the three cations, Na+ not only provides the most intensity of Eu3+ emission, but also produces electric-dipole dominated transition (5D0→7F2) and results to obtain the most red color. The optimized molar concentrations of Eu3+ for the three kinds of samples are 6, 8, 10%, which (NaMgPO4)0.92:Eu3+0.08 is a potential candidate as the red-emitting phosphor for UV-based white LED.

Preparation and Luminescence Properties of Eu<sup>3+</sup> Doped Niobium Silicate Glass Ceramics

niobium silicate glass with the mass composition of 35SiO2-25Nb2O5-20Na2O-10K2O- 7B2O3-3Eu2O3was synthesized by a traditional glass melting method. Glass ceramics containing Na2Nb8O21nanocrystals were prepared by heat treating the glass samples. The results of X-ray diffraction (XRD) indicated that the crystallite in the glass ceramics is Na2Nb8O21nanocrystals. The luminescence spectra showed the emission intensity of Eu3+doped glass ceramics was stronger than that of the glass matrix, and increased with the heat treatment temperature increasing..The transmittance of the glass ceramics can be up to 80% in the near-infrared light area.

Synthesis and Photoluminescence Properties of Monodisperse Spherical SiO<sub>2</sub>@Lu<sub>2</sub>O<sub>3</sub>: Eu<sup>3+</sup> Particles with Core-Shell Structure

Spherical submicron SiO2 particles have been coated with luminescent Lu2O3: Eu3+ layers by a Pechini sol-gel process, resulting in the formation of SiO2@Lu2O3: Eu3+ core-shell particles(300, 500 nm). The obtained core–shell phosphors have perfect spherical shape with narrow size distribution, smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (50 nm for four deposition cycles). Under the excitation of ultraviolet, the Eu3+ ion mainly shows its characteristic emissions in the core-shell particles from Lu2O3: Eu3+) shells. The PL intensity of Eu3+ increases with the number of coating cycles.

Synthesis, characterization, and photoluminescence of SrBPO5:R,Na+ (R = Eu3+, Tb3+) phosphor for solid state lighting

A series of phosphors SrBPO5:R,Na+ (R = Eu3+, Tb3+) were prepared by high-temperature solid-state synthesis, and their phase purity, morphology, IR spectra, and UV-Vis photoluminescence properties were investigated. The f-f transitions of Eu3+ and Tb3+ ions in the host lattice were assigned and discussed. The excitation and emission spectra indicate that SrBPO5:Eu3+,Na+ and SrBPO5:Tb3+,Na+ can be effectively excited by ultraviolet (394 and 370 nm), and exhibit reddish orange emission and yellowish green emission, respectively. The influence of the doping concentration on the relative emission intensity of Eu3+/Tb3+ was investigated, and the critical distance Rc was estimated in term of the concentration quenching data. The present study suggests SrBPO5:R,Na+ (R = Eu3+, Tb3+) phosphor can be a potential candidate as an UV-convertible phosphor for white light-emitting diodes (LEDs).

The Photoluminescence from (Eu, Yb) Co-Doped Silicon-Rich Si Oxides

We report on photoluminescence (PL) properties of europium (Eu) and ytterbium (Yb) co-doped silicon oxide films with different Si excess. After annealing the films in N2, strong PL were observed from Eu and Yb3+ ions and their intensities are correlated. The PL intensity of Eu is mainly from 3+ for no and relatively low temperature anneals (<900 °C) while the Eu2+ emission is dominating for annealing at 1000 °C or above in the co-doped Si-rich oxide films. Transmission electron microscopy shows amorphous (Eu, Yb, Si, O)-containing precipitates in the Si-rich oxide during 1000-1200 °C annealing and these precipitates are considered to be responsible for the Eu2+-related luminescence.