Emission Intensity Of Eu3 Research Articles

Tunable emission from LiBaBO3 :Eu3+ ;Bi3+ phosphor for solid-state lighting.

Europium (Eu3+ ) and bismuth (Bi3+ ) co-activated LiBaBO3 powder phosphors were synthesized by a solid-state reaction and the structure, particle morphology, optical and photoluminescent properties were investigated. X-Ray diffraction patterns of the LiBaBO3 phosphors crystallized in a pure monoclinic phase, i.e. there were no secondary phases due to either incidental impurities or undecomposed starting materials. Scanning electron microscopy images showed that the powders were made up of fluffy needle-like particles that were randomly aligned. The band-gap of the LiBaBO3 host was estimated to be 3.33eV from the UV/vis absorption data. Blue emission was observed from the LiBaBO3 host, which is ascribed to self-activation of the host matrix. In addition, greenish-blue (493nm) and red (613nm) emissions were observed from europium-doped samples and were attributed to the emissions of Eu2+ and Eu3+ , respectively. Furthermore, after codoping with Bi3+ , the emission intensity of Eu3+ located at 613nm was significantly enhanced. From the Commission Internationale de I'Eclairage (CIE) color coordinates, white emission was observed from LiBa1-x BO3 :xEu3+ (x=0.020 and 0.025) phosphor powders with color coordinates of x=0.368, y=0.378 and x=0.376, y=0.366, respectively.

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.

New insight into the structure evolution and site preferential occupancy of Na2Ba6(Si2O7)(SiO4)2:Eu2+ phosphor by cation substitution effect

A series of single-phased Na2Ba5.99-x(Si2O7)(SiO4)2:0.01Eu2+, xMg2+ and Na2Ba5.99-y(Si2O7)(SiO4)2:0.01Eu2+, yZn2+ phosphors have been successfully prepared via the solid-state reaction. Structural refinement, luminescence property, color tuning and thermally stability were systematically investigated. The as-prepared Na2Ba6(Si2O7)(SiO4)2:0.01Eu2+ phosphor showed broad excitation bands from 250 nm to 450 nm and presented wide emission bands under 365 nm excitation, which could be decomposed by Gaussian fitting into three peaks corresponding to different Eu luminous centers named Eu1, Eu2 and Eu3. By substituting Mg2+ or Zn2+ for Ba2+, the relative intensities of Eu1, Eu2 and Eu3 emission bands changed gradually. Combined with the variation tendencies of BaO bond lengths by Rietveld refinement, the possible mechanism of the luminescence transformation of Eu2+ ion was the preferential occupancy of Eu2+ at different crystallographic sites. In addition, the introduction of Mg2+ ion expressed more obvious improvement on the thermal quenching behaviors of Eu2+ than Zn2+ ion in this matrix. The emission intensities of Eu2 and Eu3 could be enhanced from 63.2% to 82.7% and 35.1%–46.8% at 373 K compared to the initial intensity when Mg2+ concentration was 0.10. Generally, this work sheds some new lights on the design and structure explanation of preferential occupancy at different crystallographic sites in phosphors.

Hydrothermal synthesis of NaLa(WO4)2:Eu3+ octahedrons and tunable luminescence by changing Eu3+ concentration and excitation wavelength

NaLa(WO4)2:Eu3+ phosphors with different Eu3+ concentrations have been synthesized by a hydrothermal method. The phase is confirmed by XRD analysis, which shows a pure-phase NaLa(WO4)2 XRD pattern for all of NaLa(WO4)2:Eu3+ phosphors. The SEM and TEM images indicate that all of NaLa(WO4)2:Eu3+ phosphors have a octahedral morphology. These suggest that the Eu3+ doping has no influence on the structure and growth of NaLa(WO4)4 particles. By monitoring the emission of Eu3+ at 615 nm, NaLa(WO4)2:Eu3+ phosphors show excitation bands originating from both host and Eu3+ ions. Under the excitation at 271 nm corresponding to WO42− groups, emission bands coming from the 1A1 → 3T1 transition with the WO42− groups and the 5D0 → 7Fj (j = 0, 1, 2, 3 and 4) transitions of Eu3+ are observed. The emission intensity relating to WO42− groups decreases with increasing Eu3+ concentration. But emission intensities of Eu3+ increase firstly and then decreases because of concentration quenching effect. Under the excitation at 395 nm corresponding to 7F0 → 5L6 transition of Eu3+, only characteristic Eu3+ emission bands can be observed. The results of this work suggest that tunable luminescence can be obtained for Eu3+ doped NaLa(WO4)2 phosphors by changing Eu3+ concentration and excitation wavelength.

The first principles calculation and temperature-sensitive luminescence behavior of optimized red phosphor Mg2Al4Si5O18: Eu3+

Eu3+ doped Mg2Al4Si5O18 phosphors were prepared by the solid-state reaction. The first principles calculation, XRD, diffuse reflection spectra, photoluminescence spectra and thermal quenching are carried out to investigate the electron structure, crystal structure, photoluminescence and thermal properties. The calculation results show that Mg2Al4Si5O18 possesses the direct band gap of about 5.1eV. With the introduction of Eu3+, the energy gap becomes obviously smaller due to the discontinuity of exchange-correlation energy. Between HOMOs and LOMOs, a series of f orbitals of Eu3+ can be observed, which is the essential condition to realize the efficient 4f–4f transitions of Eu3+. The experimental results indicate that the samples can efficiently absorb the UV-light and emit the red light with the highest peak at 614nm. With the co-doping of Bi3+ as sensitizer, the emission intensity of Eu3+ increases by about 49% due to the energy transfer between Bi3+ and Eu3+. With the introduction of Li+/Na+/K+ as charge compensators, the emission intensities of Mg2Al4Si5O18: Eu3+ are enhanced by about 22%, 18% and 5%. With the temperature increase, the emission intensity of all samples, especially the Bi3+ doped samples, dramatically declines, which reveals two important effects: one is that the Eu3+ emission is very sensitive to temperature, and other is that the complex energy transfer process among the excited and ground states of Eu3+, Bi3+ or host absorption occurs. To explain the degradation, the mechanism based on the configurational coordinate diagram is proposed and this model could be helpful for the understanding of the energy transfer mechanism among the various energy levels in the process of temperature change.

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.

Energy transfer and dissipation processes studied using photoluminescence of Eu3 + ions doped in epitaxial ZnO films

Photoluminescence from Eu3+ ions initiated by band-to-band excitations of ZnO host crystals was investigated in epitaxial films grown on sapphire C-planes. Emissions from Eu3+ ions were only observed when the films were deposited under H2O vapor gas flow. The maximum emission intensities were three times as large as those of films deposited on Si substrates. Close correlation between the emission intensities of Eu3+ ions and disorder in the host crystal lattice was evidenced by X-ray diffraction, which indicates that non-radiative energy dissipation channels determine the lifetime of the excited states, and high crystallinity is essential for intense emissions. In addition, the emission intensities from ZnO defects and Eu3+ ions exhibited a similar dependence on annealing temperature, suggesting the relevance of defect-mediated energy transfer from ZnO to Eu3+ ions. The excitation energy is shared among band-edge emissions, defect emissions, and emissions from Eu3+ ions, and these emissions compete with one another. In particular, the overlap of the Eu3+ emission energies on the red defect emission band facilitates efficient energy transfer from the ZnO crystals. Hydrogen atoms released from H2O will prevent Eu3+ ions from being bonded to excess oxygen atoms and/or promote substitution of Zn2+ sites with Eu3+ ions.

Quadruple-stranded Eu-helicate assembled from bis-β-diketonate: Its stability towards metal ions

Herein, we reported the synthesis and investigation of highly luminescent quadruple-stranded helicate (C6H16N)4[Eu2(MBDA)4]2 ·3C4H10O·4C2H3N(1-Eu)[H2MBDA=N-methyl-4,4′-bis(4,4,4-trifluoro-1,3-dioxobutyl)diphenylamine] for its stability toward metal ions in the solution. The material was characterized via X-ray crystallographic technique, Fourier transform infrared(FTIR) spectroscopy and electrospray ionization quadrupole time-offlight(ESI-TOF) mass spectrometry. The results on the luminescence quantum yields clearly demonstrate that the ligand can effectively sensitize the luminescence of the Eu3+ ions(Φ overall=15%). Upon the addition of different metal ions(i. e., Ag+, Cd2+, Zn2+, Fe3+, Al3+ and Ni2+) to the CH3CN solution of compound 1-Eu, the emission intensities of Eu3+ ions at 612 nm were affected to some extent, which could be attributed to the presence of ion exchanges between Eu3+ ions and the metals ions, and the result was confirmed by ESI-TOF mass spectrometry.

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.

Low voltage cathode-luminescent properties of Zn co-doped Y2O3:Eu red phosphor

Zn co-doped and undoped Y2O3-Eu red phosphor was prepared by citric acid gel method and it was investigated to know its cathodoluminesecent properties at low voltage excitation (<2kVs). In this connection the cathodoluminescence (CL) spectra of Zn co-doped and undoped phosphors were taken and they showed various line emissions along with a sharp red emission at 611nm, irrespective of Zn concentration, due to 5D0–7F2 transitions from Eu luminescent center. It was found that the incorporation of Zn could significantly enhance the CL emission intensity of Eu at about 33% when compared with Zn undoped phosphor. It was also found the Zn co-doping could not alter the crystal structure whereas it could change the morphology of the particles. The promising results revealed the possible application of this phosphor materials as red phosphor for field emission displays [FEDs].

Temperature dependence of luminescence spectra in europium doped Ga2O3 film

Europium doped Ga2O3 films were deposited on sapphire substrates by using pulsed laser deposition. The influences of substrate temperature on structural and optical properties have been systematically investigated by means of X-ray diffraction and photoluminescence. High quality single (−201) oriented Ga2O3 film can be obtained at substrate temperature of 400°C. The emission intensity of Eu3+ decreased solely with elevated temperature by using 325nm light, while it had a maximum value at a certain temperature under 488nm light. Both of the experimental data were well fitted by the luminescence dynamic equation models, suggesting that the variation of the emission intensity may be attributed to the thermal activated distribution of electrons among 7Fj and thermal quenching effect.

Substantial enhancement of red emission intensity by embedding Eu-doped GaN into a microcavity

We investigate resonantly excited photoluminescence from a Eu,O-codoped GaN layer embedded into a microcavity, consisting of an AlGaN/GaN distributed Bragg reflector and a Ag reflecting mirror. The microcavity is responsible for a 18.6-fold increase of the Eu emission intensity at ∼10K, and a 21-fold increase at room temperature. We systematically investigate the origin of this enhancement, and we conclude that it is due to the combination of several effects including, the lifetime shortening of the Eu emission, the strain-induced piezoelectric effect, and the increased extraction and excitation field efficiencies. This study paves the way for an alternative method to enhance the photoluminescence intensity in rare-earth doped semiconductor structures.

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.

Efficient sensitization of Eu2+/Mn2+ emissions by Ce3+ doping in NaMgPO4 host under UV excitation

A series of Ce3+/Eu2+/Mn2+-tridoped NaMgPO4 phosphors were synthesized using the combustion-assisted synthesis method. The luminescence properties and energy transfer from Ce3+/Eu2+ to Mn2+ in NaMgPO4 host have been studied. Co-doping Ce3+/Mn2+ is proved to be an ineffective approach to enhance the red emission of Mn2+, while effective energy transfer from Eu2+ to Mn2+ occurs in NaMgPO4:Eu2+,Mn2+ due to good spectrum overlap between the emission band of NaMgPO4:Eu2+ and the excitation band of NaMgPO4:Eu2+,Mn2+. NaMgPO4:Eu2+,Mn2+ phosphor shows a blue emission centered at 442 and a red emission peaking at 635 nm, which could be ascribed to the allowed 5d–4f transition of Eu2+ ions and the 4T1(4G)–6A1(6S) transition of Mn2+ ions, respectively. Co-doping Ce3+ ions can greatly enhance both the emission intensities of Eu2+ and Mn2+ ions, which is attributed to an efficient Ce3+ → Eu2+ → Mn2+ energy transfer and an increase in the number of luminescent centers (Eu2+) on Ce doping.

Effect of K+ ions on the photoluminescence properties of Ca4.75(PO4)3Cl: 0.05Eu2+, 0.2Mn2+ phosphors

K+ ions were incorporated into Ca4.75(PO4)3Cl: 0.05Eu2+, 0.2Mn2+ Phosphors, which has a significant effect on the photoluminescence properties of phosphors. With increasing the K+ concentration (x value) in Ca4.75−xKx(PO4)3Cl: 0.05Eu2+, 0.2Mn2+ (x=0-0.15), the emission intensity of Eu2+ increases and reaches its maximum value at the x=0.1, and then decreases for the higher K+ concentrations, which can be explained by charge compensations and crystal lattice strain relaxing. The results show a potential for increasing the emission intensity of Ca4.75(PO4)3Cl: 0.05Eu2+, 0.2Mn2+ phosphors by properly doping K+ ions.

Effects of substitution of BaF2 for GdF3 on optical properties of dense oxyfluoride borogermanate scintillating glasses

Eu3+-activated B2O3-GeO2-37Gd2O3-3Eu2O3-(15–x)GdF3-xBaF2 (0≤x≤15) scintillating glasses with the density of 6.1–6.3 g/cm3 were synthesized by a melt-quenching method. The substitution of BaF2 for expensive GdF3 in oxyfluoride borogermanate glasses slightly decreased the glass density within 3.0%. Their optical properties were characterized by transmittance, photoluminescence (excitation and emission), and X-ray excited luminescence (XEL) spectra in detail. The emission intensity of Eu3+ ions increased with the elevated x values. The Eu–O covalancey nature and the local environment of Eu3+ ions were evaluated by Judd-Ofelt results. It was found that the covalency property of Eu–O bond increased with increasing x values.

Luminescent LuVO4:Ln3+ (Ln = Eu, Sm, Dy, Er) hollow porous spheres for encapsulation of biomolecules

In this study, LuVO4:Ln3+ (Ln=Eu, Sm, Dy, Er) hollow porous spheres, synthesized via self-sacrificing templated route, are developed for enzyme immobilization and protein adsorption. The four LuVO4 hollow spheres with diameter of 180nm, 280nm, 370nm and 480nm were obtained. The size of LuVO4 hollow sphere is dependent on Lu(OH)CO3 template. Upon excitation by UV light, hollow LuVO4:Ln3+ (Ln=Eu, Sm, Dy, Er) spheres exhibit red (Eu3+), orange (Sm3+), yellow-green (Dy3+), and green (Er3+) emissions. The good biocompatibility of sample is validated by MTT assay. Due to structure feature and size of obtained sample, the rapid encapsulation of biomolecules within samples has been achieved. Furthermore, the hollow spheres show different biomolecules adsorption capacities at different buffer solution pH values. The release behaviors of two kinds of biomolecules (lysozyme and bovine serum albumin) are also investigated. LuVO4 hollow spheres are suitable carriers for biomolecules. The emission intensity of Eu3+ in the LuVO4:Eu3+ varies with the released amount of LYZ. This enables the monitoring of release process by the change in the luminescence intensity.

Sonochemical synthesis of hierarchical SrWO4:Eu3+/Bi3+ superstructures and tunable luminescence

Hierarchical 3D SrWO4:Eu3+/Bi3+ superstructures were synthesized by the sonochemical process. The SrWO4:Eu3+/Bi3+ phosphors were characterized by XRD, FTIR, SEM, and fluorescence spectrophotometer. The XRD and FTIR results indicated that the samples have the pure tetragonal phase. The SEM images showed that the samples have hierarchical structure composing of lots of similar nanosheets with the thickness of about 20 nm and the width in the range of 0.3–1.5 μm. Under the excitation of 266 nm, SrWO4:Eu3+/Bi3+ phosphors showed characteristic emission bands originating from the 5D0 → 7FJ (J = 1, 2, 3 and 4) transitions of Eu3+ ions. The codoped Bi3+ ions highly enhanced the emission intensity of Eu3+, suggesting the efficient energy transfer between Bi3+ and Eu3+. The energy transfer from Bi3+ to Eu3+ was mainly through exchange interaction which is located at the nearest neighbour lattices.

Synthesis and luminescence properties of highly uniform SiO2@LaPO4:Eu3+ core–shell phosphors

Abstract SiO 2 @LaPO 4 :Eu 3+ core–shell phosphors have been successfully synthesized by a one-step and economical wet-chemical route at low temperature. The as-obtained products were characterized by means of photoluminescence spectroscopy (PL), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). The SEM, EDS and XPS analysis indicate that SiO 2 @LaPO 4 :Eu 3+ core–shell phosphors can only be synthesized in a pH range of 8–11 and the possible mechanism has been proposed. The XRD results demonstrate that the structure of LaPO 4 :Eu 3+ layers is transferred into monoclinic phase from hexagonal phase after annealing at 800 °C for 2 h. The SiO 2 @LaPO 4 :Eu 3+ phosphors show strong orange–red luminescence under ultraviolet excitation. The relative emission intensity of Eu 3+ increases with increasing the annealing temperature and the number of coating cycles, and the optimum concentration for Eu 3+ was determined to be 5 mol% of La 3+ in SiO 2 @LaPO 4 phosphors.