Synthesis and Characterization of Rare Earth Complexes

Rare earth (Eu³⁺) single nuclear chelated with α-methacrylic acid and 1, 10-phenanthroline, as well as the heteronuclear chelated of Eu³⁺ and La³⁺ ions, were synthesized. The composition and structure of the rare earth complexes were confirmed by IR, SEM and XRD. The thermal analysis indicated that the heat-stability was improved. Moreover, the fluorescence spectra proved that the complexes had good fluorescence property. The results showed that it was convenient to synthesize series of europium chelate. The complexes exhibited characteristic fluorescence of europium. ion. The sensitization of La³⁺ could enhance the fluorescence emission intensity of Eu³⁺ ion.     

Synthesis,photoluminescence properties and thermal investigation by TG-MS of RE(DAS)_3·xH_2O(RE=Eu~(3+),Tb~(3+))

Rare earth(Ⅲ) diphenyl-4-amine sulfonates(RE(DAS)_3·xH_2O,RE=Eu~(3+),Tb~(3+))phosphors were synthesized by precursor method from barium diphenyl-4-amine sulfonate and rare earth sulfates.FTIR,TG/DSC coupled to mass spectrometry(TG/DSC/MS),X-ray powder diffraction(XPD),scanning electron microscopy(SEM) and photo luminesce nce(PL) spectroscopy were utilized to structurally and morphologically characterize the samples.Thermal decomposition of Eu(DAS)_3·7H_2O and Tb(DAS)_3·2H_2O at 973 K under dynamic air atmosphere results in crystalline Eu_2O_2SO_4 and Tb_2O_2SO_4 materials,respectively.Accordingly,MS spectra reveal the liberation of thermal decomposition products of precursors,largely as CO_2,NO_2 and SO_2 gases.The diphenyl-4-amine sulfonate(DAS) ligand demonstrats a good stabilizing property for Eu~(3+) and Tb~(3+) ions.The Eu(DAS)_3·7H_2O and Tb(DAS)_3·2H_2O compounds display efficient red and green emissions,under UV excitation,arising from the ~5D_0→~7F_J(J=0-4) and ~5D_4→~7F_J(J=0-6) transitions of the Eu~(3+) and Tb~(3+) ions,respectively.     

Nanocomposites of CsPbBr3 perovskite quantum dots embedded in Gd2O3:Eu3+ hollow spheres for LEDs application

Gd₂O₃:Eu³⁺@CsPbBr₃ quantum dots (QDs) mesoporous hollow nanocomposites with good luminescent properties and high stability were built. Among which, the hollow Gd₂O₃:Eu³⁺ spheres and CsPbBr₃ QDs were prepared by urea homogeneous precipitation and hot-injection method, respectively. Finally, the Gd₂O₃:Eu³⁺@CsPbBr₃ QDs shell–core compounds were constructed through mechanical stirring. The structure, morphology, stability and luminescent properties were studied by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry/thermogravity (DSC/TG), X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence excitation/photoluminescence (PLE/PL) and life decay tools. Compared to the original CsPbBr₃ QDs, Gd₂O₃:Eu³⁺@CsPbBr₃ QDs display better photostability, thermal stability and current stability. The resulting Gd₂O₃:Eu³⁺@CsPbBr₃ QDs composite exhibits good yellow emission. The Gd₂O₃:Eu³⁺@CsPbBr₃ QDs mixed silicone resin was directly coated on the blue LED chip, then the w-LED device with the color coordinate of (0.31, 0.32) was successfully assembled. The Gd₂O₃:Eu³⁺@CsPbBr₃ QDs compounds with excellent luminescent properties and stability are expected to be widely used in lighting and display areas.     

Preparation and photoluminescence enhancement of Li＋ and Eu3＋ co-doped YPO4 hollow microspheres

Li+ and Eu3+ co-doped YPO4 hollow microspheres were successfully synthesized by a sacrificial template method using polystyrene (PS) as template. Techniques of X-ray diffraction (XRD), scanning electron microscopy (SEM), as well as transmission electron microscopy (TEM) were employed to characterize the as-synthesized sample. Furthermore, the photoluminescence (PL) characterization of the Li+ and Eu3+ co-doped YPO4 microsphere was carried out and the effects of the doping concentration of Li+ and Eu3+ active center concentration as well as calcination temperature on the PL properties were studied in detail. The results showed that the incorporation of Li+ ions into the YPO4 :Eu3+ lattice could induce a remarkable improvement of the PL intensity. The highest emission intensity was observed with the compound of 5%Li+ and 5%Eu3+ co-doped YPO4 , whose brightness was increased by a factor of more than 2.2 in comparison with that of the YPO4 :5%Eu3+.     

Structural and photoluminescence studies of Eu3+ doped zinc oxide nanorods prepared by precipitation method

Trivalent europium doped zinc oxide (ZnO:Eu3+) nanocrystals were synthesized via room temperature chemical co-precipitation and they were systematically characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and photoluminescence (PL) spectroscopy. The as-synthesized samples were found to have hexagonal wurtzite coexisted with the intermediate Zn5(OH)8Cl2·H2O phase, while the single hexagonal phase was facilitated due to the calcinations. The as obtained samples were broadly composed of nanoflakes while the highly crystalline nanorods were formed due to low temperature annealing of the as-synthesized samples. The crystallite size of the nanoflakes and nanorods (40-90 nm) were extracted from the XRD pattern which was found to be consistent with scanning electron microscopy (SEM) measurements. The photolumi-nescence (PL) spectra of nanophosphors showed bright red and orange emissions at 618 and 594 nm respectively with efficient broad blue green emission spectrum due to ZnO lattice. Further, a good energy transfer process from ZnO host to Eu3+ was observed in PL emission and excitation spectra of Eu3+ doped ZnO ions. In all, the present nanophosphors were found to have great potentiality for bio-applications.     

Synthesis and luminescence properties of SrAleO4：Eue＋,Dy3＋ hollow microspheres via a solvothermal co-precipitation method

SrAl2O4:Eu2+,Dy3+ hollow microspheres were successfully prepared through a facile and mild solvothermal co-precipitation combining with a postcalcining process.The structure and particle morphology were investigated by X-ray diffraction(XRD),scanning and transmission electron microscopy(SEM and TEM)pictures,respectively.The mechanism for the formation of spherical SrAl2O4:Eu2+,Dy3+ phosphor was preliminary presented.After being irradiated with ultraviolet(UV)light,the spherical phosphor emitted long-lasting green phosphorescence.Both the photoluminescence(PL)spectra and luminance decay,compared with that of commercial bulky powders,revealed that the phosphors had efficient luminescent and long lasting properties.It was considered that the SrAl2O4:Eu2+,Dy3+ hollow microspheres had promising long-lasting phosphorescence with potential scale-dependent applications in photonic devices.     

Eu2＋ and Dy3＋ codoped （Ca,Sr）7（SiO3）6Cl2 highly efficient yellow phosphor

Eu2+ and Dy3+ codoped(Ca,Sr)7(SiO3)6Cl2 yellow phosphors were successfully synthesized by self-flux method. The structure, morphology and photoluminescence properties were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM) and photoluminescence spectra. The as-prepared phosphor showed a broad emission spectrum centered at 550 nm for Eu2+single-doped phosphor, while located at 548–544 nm for the Eu2+, Dy3+ codoped samples under excitation at 380 nm light. The emission intensity was greatly improved when Dy3+ was doped into the(Ca,Sr)7(SiO3)6Cl2:Eu2+ system. The composition-optimized sample with 3 mol.% of Dy3+ and constant 10 mol.% of Eu2+ exhibited a 220% PL enhancement compared to the phosphor with 10 mol.% Eu2+ single-doped. Meanwhile, it was found that the quantum efficiency of phosphor namely(Ca,Sr)7(SiO3)6Cl2:3 mol.% Dy3+, 10 mol.% Eu2+ could get up to 24.6%. The synthesized yellow-emitting(Ca,Sr)7(SiO3)6Cl2:Dy3+,Eu2+ is a promising candidate as high-efficiency yellow phosphor for NUV-excited white LEDs.     

Photoluminescent properties of Eu3＋ and Tb3＋ codoped Gd2O3 nanowires and bulk materials

In this paper, the Gd2O3：Eu3＋,Tb3＋phosphors with different doping concentrations of Eu3＋and Tb3＋ions were prepared by a hydrothermal method for nanocrystals and the solid-phase method for microcrystals. The interaction of the doped ions with different concentrations and the luminescent properties of the nanocrystals and microcrystals were studied systematically. Their structure and morphology of Gd2O3：Eu3＋,Tb3＋phosphors were analyzed by means of X-ray powder diffraction （XRD）, transmission electron mi-croscopy （TEM） and scanning electron microscopy （SEM）. The photoluminescence （PL） properties of Gd2O3：Eu3＋,Tb3＋phosphors were also systematically investigated. The results indicated that when the concentration of doped Eu3＋was fixed at 1 mol.%, the emis-sion intensity of Eu3＋ions was degenerating with Tb3＋content increasing, while when the Tb3＋content was fixed at 1 mol.%, the emission intensity of Tb3＋ions reached a maximum when the concentration of Eu3＋was 2 mol.%, implying that the energy transfer from Eu3＋to Tb3＋took place. In addition, Tb3＋could inspire blue-green light and the Eu3＋could inspire red light. Therefore co-doping systems by controlling the doping concentration and the hosts are the potential white emission materials.     

Dual-functionalization based on combination of quercetin compound and rare earth nanoparticle

While the nanoparticles like La2O3 and other rare earth oxides were believed to be able to provide effective scavenging hydroxyl radical.Quercetin,a hydrophobic agent,showed some potential antibacterial activity.The present work successfully performed the surface modification of rare earth nanoparticle using facile and general strategy.In specific,the hydrophobic quercetin was grafted on the rare earth nanoparticle through the coupling with silane.The surface modified nanoparticle was characterized by Fourier-transform infrared(FTIR),thermogravimetric analysis(TGA),and scanning electron microscopy(SEM).The surface modification helped to retain both the scavenging hydroxyl radical property of rare earth nanoparticle and the antibacterial activity of quercetin.This dual-function properties showed potential for application in the development of biomedicine such as antioxidant,anti-inflammatory,antibacterial and anticancer.     

Combustion synthesis,characterization and luminescence properties of barium aluminate phosphor

The blue-green emitting Eu2+ and Nd3+ doped polycrystalline barium aluminate(BaAl2O4:Eu2+,Nd3+) phosphor, was prepared by a solution-combustion method at 500 oC without a post-annealing process. The characteristic variation in the structural and luminescence properties of the as-prepared samples was evaluated with regards to a change in the Ba/Al molar ratio from 0.1:1 to 1.4:1. The morphologies and the phase structures of the products were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS), while the optical properties were investigated using ultra-violet(UV) and photoluminescence(PL) spectroscopy, respectively. The XRD and TEM results revealed that the average crystallite size of the BaAl2O4:Eu2+,Nd3+ phosphor was about 70 nm. The broad-band UV-excited luminescence of the phosphors was observed at λmax=500 nm due to transitions from the 4f65d1 to the 4f7 configuration of the Eu2+ ion. The PL results indicated that the main peaks in the emission and excitation spectrum of phosphor particles slightly shifted to the short wavelength due to the changes in the crystal field due to the structure changes caused by the variation in the quantity of the Ba ions in the host lattice.     

Synthesis,structure and luminescent properties of a new Vernier phase Lu7O6F9 doped by Eu^3＋ as potential scintillator with unique lath tube architecture

To explore novel nano-scintillator with a controllable architecture, pure and Eu3+ doped lutetium oxyfluoride(Lu7O6F9) powder were synthesized by combining mild hydrothermal method and solid state calcination approach. The products were all pure orthorhombic Vernier phase demonstrated by X-ray powder diffraction(XRD). The detailed crystal structure was also studied by Reitveld refinement. Lath-like microcrystals composed of nanoparticles with unique hollow tube of the products were supported by the images of scanning electron microscopy(SEM) and transmission electron microscopy(TEM). Excited by X-ray with W as the target, the pure product showed intense broad emission with the peak at about 400 nm suitable for modern photoelectric multiplier tube(PMT), while the Eu3+ doped sample transferred the incident energy to Eu3+ ions and gave strong 5D0→7Fj(j=0, 1, 2 and 4) emission, which fitted for imaging and labeling measurements. From the luminescent properties, both pure and Eu3+-doped products are potential excellent scintillator for X-ray imaging and other high energy detectors, and the pure product is also a good host candidate for rare earth doping.     

Synthesis and characterization of needle-like BaAleO4：Eu,Dy phosphor via hydrothermal-homogeneous precipitation method

A needle-like Eu2+ and Dy3+ co-doped BaAl2O4 long-lasting phosphor was synthesized via a hydrothermal-homogeneous precipitation method assisted by cetyl trimethyl ammonium bromide(CTAB) as a template.The crystal structure,morphology and optical properties of the composites were characterized.XRD results showed that the single-phase BaAl2O4 was formed at 900 ℃ in an active carbon atmosphere,which was much lower than that prepared by traditional solid-state reaction method.Scanning electron microscopy(SEM) and transmission electron microscopy(TEM) observation revealed that the precursor had well-dispersed distribution and showed needle-like morphology with the average diameter of about 100 nm and the length up to 1 μm.The final product,BaAl2O4:Eu2+,Dy3+ phosphor,inherited the needle-like shape from precursor via adding the surfactant CTAB.After irradiation by ultraviolet radiation with 355 nm for 5 min,the phosphors emitted bluish green color long-lasting phosphorescence corresponding to the typical emission of Eu2+ ion.Both the photoluminescence spectra and luminance decay revealed that the phosphor had efficient luminescent and long-lasting properties.     

White light emission of Eu^3＋/Ag co-doped Y2Si2O7

The Eu3+/Ag co-doped rare earth disilicate Y2Si2O7 microcrystal was synthesized by sol-gel method. Through controlling the thermal treatment process of Y2Si2O7:Eu3+/Ag precursor, various phases(amorphous, α, β, γ, δ) were prepared. White light emission was observed under UV light excitation in the samples heavily doped with Ag. The white light was realized by combining the intense red emission of Eu3+, the green emission attributed to the very small molecule-like, non-plasmonic Ag particles(ML-Ag-particles), and the blue emission due to Ag ions. Results demonstrated that Eu3+/Ag co-doped Y2Si2O7 microcrystal could be potentially applied as white light emission phosphors for UV LED chips.     

Fabrication and photoluminescent characteristics of one-dimensional La202S：Eu3＋ nanocrystals

One-dimensional La2O2S:Eu3+ nanowires(NWs) were fabricated with a simple hydrothermal method.The structures were characterized by X-ray diffraction and transmission electron microscopy(TEM).The photoluminescent properties including excitation and emission spectra were studied.The results indicated that in excitation spectra there existed charge transfer(CT) absorption of both O2-→Eu3+ and S2-→Eu3+,and f-f transitions absorption in NWs and corresponding sub-meter materials(SMs).The relative intensity of CT absorption of O2-→Eu3+ to S2-→Eu3+ in both samples clearly changed.The strong yellow and red emissions of Eu3+ ions in NWs were observed.     

Synthesis and luminescence properties of a novel red-emitting phosphor SrCaSiO_4：Eu~（3＋） for ultraviolet white light-emitting diodes

A novel red phosphor based on Eu3+-activated SrCaSiO4 was successfully synthesized by conventional solid state reaction method and the photoluminescence properties were investigated. X-ray diffraction (XRD) patterns indicated that SrCaSiO4:Eu3+ phosphors belong to orthorhombic crystal system (space group=Pmnb). The photoluminescence (PL) excitation spectrum showed broad-band absorption and the strongest excitation peak at 397 nm contributed to the 7F0→5L6 transition which matched well with the emission of a...     

Optical and electrical conductivity properties of rare earth elements (Sm,Y, La,Er) co-doped CeO2

In this research, un-doped CeO₂ and Ce_0.85La_0.10M_0.05O₂ (M: Sm, Er, Y) compounds were synthesized by hydrothermal method and the multi-functional properties are reported. Oxygen defects were created with the additives of rare earth ions. The electrical and luminescence behaviors of the synthesized compounds were investigated in accord with the types of additives. The synthesized products were characterized by X-ray diffraction (XRD) analysis, Brunauer–Emmett–Teller (BET) measurement, UV–vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and electrochemical impedance spectroscopic (EIS). All synthesized compounds are found to be nano-structured and have cubic phase. The total conductivity of all samples was calculated. Hence, the total conductivity of un-doped CeO₂, Ce_0.85La_0.10Y_0.05O₂, Ce_0.85La_0.10Er_0.05O₂ and Ce_0.85La_0.10Sm_0.05O₂ is found to be 2.07 × 10^?10, 5.70 × 10^?4, 1.0 × 10^?3 and 0.0747 S/cm, respectively. Also, bandgap energy (E_g) of these samples calculated from UV visible absorption spectra is discussed, and the optical results show variation between 3.2 and 2.15 eV. Additionally, the luminescence properties of the compounds were investigated and different emissions occur depending on the additive type. Accordingly, photoluminescent emission spectra of Ce_0.85La_0.10Y_0.05O₂, Ce_0.85La_0.10Er_0.05O₂ and Ce_0.85La_0.10Sm_0.05O₂ phosphors indicate that these phosphors have red, green and orange-red colors, respectively.     

Effect of rare earths on viscosity and thermal expansion of soda-lime-silicate glass

Viscosity of soda-lime-silicate glass doped with rare earth oxides (Pr₆O₁₁, Eu₂O₃, Yb₂O₃) was investigated by the rotating crucible viscometer, the melting temperature and activation energy for viscous flow of the studied melt were derived on the basis of the Arrhenius Equation, the coefficient of thermal expansion, glass transition temperature and dilatometric softening temperature were also determined with dilatometry, in order to reveal the effects of rare earth elements on the behavior of soda-lime-silicate glass. The results showed that introduction of rare earth oxides decreased the viscosity of soda-lime-silicate glass and melting temperature of corresponding melt, increased coefficient of thermal expansion of soda-lime-silicate glass. The glass transition temperature, dilatometric softening temperature, and melting temperature of soda-lime-silicate glass doped with rare earth oxides increased with increasing cationic field strength of corresponding rare earth ions.     

Photoluminescence properties of Ca-doped BaMg Al10O17）：Eu2＋,Mn2＋ blue phosphor using BaF2 and CaF2 as co-flux

Ca-doped Ba Mg Al10O17：Eu2＋,Mn2＋（BAM） blue phosphors were synthesized by flux assisted solid-state reaction method using Ca F2 and Ba F2 as co-flux.Good dispersity and particle size homogenization of hexagonal pure phase BAM were obtained by sintering at 1400 ℃.The effects of the Ca2＋ ions content on the structure, morphology and photoluminescence properties of the phosphors were studied.The results indicated that the incorporation of Ca could decrease the lattice constant, improve the homogeneity and dispersity and enhance the photoluminescence（PL） intensity of the phosphor effectively.The optimum Ba0.86Ca0.04Mg0.97Al10O17：0.1Eu2＋,0.03Mn2＋ PL intensity was enhanced for about 30% and relative brightness was improved about 4%.Furthermore, the synthesized BAM and commercial BAM phosphors were annealed for 30 min at 600 oC in air.The Ca-doped phosphors had stronger emission intensity, higher brightness and better chromaticity stability than that of the commercial phosphor.These results indicated that Ca-doped blue phosphors had good potential applications in the commercial tricolor fluorescent lamps as well as in other display and lamps.     

Photoluminescence studies of Eu2+-Yb3+ co-doped BaMgAl10O17 phosphor synthesized by the combustion method

BaMgAl10O17:Eu2+,Yb3+ was investigated as a possible quantum cutting system to enhance solar cells efficiency. Phosphors were synthesized by combustion method and composed of nanorods. Photoluminescence spectra showed that Eu in the sample was reduced to bi-valence while Yb remained trivalence. Through a cooperative energy transfer process, the obtained powders exhibited both blue emission of Eu2+ (around 450 nm) and near infrared emission of Yb3+ (around 1020 nm) under broad band excitation (250-410 nm) originating from 4f→5d transition of Eu2+. Energy transfer phenomenon between the sensitizer Eu2+ and the activator Yb3+ was investigated via the lumines-cent spectra and the decay curves of Eu2+ with different Yb3+ concentrations. Results indicated that energy transfer efficiency from Eu2+ to Yb3+ was not high. The poor efficiency can be explained by the long distance between rare earth ions.     

Preparation,structure, luminescence properties of europium doped zinc spinel structure green-emitting phosphor ZnAl2O4:Eu2+

The Zn_(1-x)Al_2 O_4:xEu~(2+) phosphor powders were synthesized by the solid-state reaction method.The synthesis temperature for ZnAl_2 O_4 was optimized,whereas the phase structure,TEM images,photoluminescence(PL) properties,the concentration quenching mechanism,the fluorescence decay curves,as well as the CIE chromaticity coordinates of the samples were investigated in details.Under the excitation at 379 nm,the phosphor exhibits an asymmetric broad-band green emission with a peak at 532 nm,which is ascribed to the 5 d-4 f transition of Eu2+.When the doping concentration of Eu2+ ions is 0.01,the luminescence intensity of the sample reaches the maximum value.It is further proved that the exchange interaction results in the concentration quenching of Eu2+ in the Zn_(1-x)Al_2 O_4:xEu~(2+) phosphor powders.The thermal quenching property of ZnAl_2 O_4:Eu~(2+)phosphor was investigated and the quantum efficiency(QE) values of the selected Zn_(0.99)Al_2 O_4:0.01 Eu~(2+) phosphor was measured and determined as 54.85%.The lifetime of the optimized sample Zn_(0.99)Al_2 O_4:0.01 Eu~(2+) is 3.0852 μs and the CIE coordinate of the sample was calculated as(0.3323,0.5538) with high-color-purity green emission.All properties indicate that the green-emitting ZnAl_2 O_4:Eu~(2+) phosphor powder has potential application in white LEDs.