Shape controlled synthesis and photoluminescence properties of Eu3+-doped REVO4 nanophosphors

Eu3+-doped REVO4 nanphosphors were controllably synthesized by an EDTA-mediated hydrothermal method at 180 degrees C using RE(NO3)3 and Na3VO4 as precursors. The obtained products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectra (XPS), and photoluminescence spectroscopy (PL). The XRD results showed that the products were pure tetragonal structure and no other impurity phase appeared. The PL studies demonstrated Eu3+ ions doping effectively enhanced luminescent properties of LaxRE(1-x)VO4 and YxRE(1-x)VO4 nanoparticles, but EU3+ ions doping did not enhance luminescent properties of CexRE(1-x)VO4 (x not equal 0) nanoparticles. The prepared phosphors showed well-defined red luminescence due to radiative transitions from 5D0 to 7F(J) (J = 1,2) levels of Eu3+ ions, respectively. Furthermore, we reported Eu3+-doped CexRE(1-x)VO4 (x not equal 0) phases represented a new class of optically inactive materials.     

ZnO:Sb3+纳米粉的制备及发光性能的研究

采用共沉淀法制备了六方纤锌矿结构的Sb3+掺杂ZnO纳米荧光粉,并系统研究了不同Sb3+掺杂浓度、不同煅烧温度和时间对其发光性能的影响.借助于XRD、SEM、荧光光度计等测试手段对粉体的相组成、形貌及其光致发光性能进行了表征.结果表明:掺杂Sb3+样品的粒度小于未掺杂样品的粒度,当Sb3+掺杂浓度小于3％时,ZnO:S...     

Optical temperature sensor using Eu3+-doped fluoride glass

A thermooptical temperature sensor suitable for low temperatures is proposed. Eu3+-doped fluoride glass can be used as a thermooptical transducer, since its optical absorption intensity for the (7)F1-(7)F6 transition, which occurs at 2.2 microm, is modulated by temperature. Temperature resolving power is confirmed to be 0.5 K in the 77-150 K range using a Eu 3+-doped fluoride fiber. The applicable temperature range and resolving power are varied with the doping content of the Eu3+ ion.     

Eu3+ concentration effect on luminescence properties of YAG:Eu3+ nanoparticles

Nanocrystalline Eu³⁺-doped YAG powders were prepared by modified Pechini method. The structural properties were investigated with XRD, SEM and Raman spectroscopy. XRD pattern indicated that the phase-pure YAG:Eu³⁺ crystallites were obtained without the formation of any other phases. Raman spectrum revealed good homogeneity and crystallinity of synthesized nanopowders. The luminescent properties were studied by measurement of excitation and emission spectra, quantum yields and decay curves. The effect of Eu³⁺ concentration on ⁵D₀ level lifetime was studied. The processes resulting in the relaxation of excited state (⁵D₀ level) were discussed and the probabilities of radiative and nonradiative processes were calculated using the model of f–f transition intensities. It was found that the observed shortening of ⁵D₀ level lifetime with Eu concentration is caused by increase of nonradiative process probability.     

Hydrothermal synthesis and luminescent properties of GdVO4 : Eu3+ nanophosphors

Eu³⁺-doped GdVO₄ has been synthesised via hydrothermal method by altering the hydrothermal temperature, reaction time and surfactant. The microstructure and morphology information of the phosphors were investigated via the techniques of X-ray powder diffraction and scanning electronic microscopy, which show that the phosphors wear tetragonal phase and the products present various regular morphologies under different reaction conditions such as bulk and nanoparticle. Moreover, the morphologies of the products have been controlled by altering reaction temperature. In addition, the surfactant was also included to control the morphologies of the products and the phosphors present different morphologies. All the phosphors exhibit the characteristic fluorescence of Eu ion (⁵D₀ → ⁷F₂ and ⁵D₀ → ⁷F₂). The electric dipole transition ⁵D₀ → ⁷F₂ of Eu³⁺ is dominant indicating that most sites of Eu³⁺ ions in GdVO₄ have no inversion centre. Furthermore, we found that the reaction time and the morphologies have great influence on optical properties.     

Fluorescence properties of Eu3+-doped alumino silicate glasses

Alumino silicate glasses of a very broad range of molar compositions doped with 1 ⋅ 10²⁰ Eu³⁺ cm⁻³ (about 0.2 mol% Eu₂O₃) were prepared. As network modifier oxides Li₂O, Na₂O, K₂O, MgO, CaO, SrO, BaO, ZnO, PbO, Y₂O₃ and La₂O₃ have been used. All glasses show relatively broad fluorescence excitation and emission spectra. For most glasses only a weak effect of the glass composition on the excitation and emission spectra is observed. Although the glasses should be structurally similar, notable differences are found for the fluorescence lifetimes. These increase steadily with decreasing mean atomic weight, decreasing refractive index and decreasing optical basicity of the glasses, which may be explained by local field effects. An exception from this rule are the strontium, barium and potassium containing glasses, which show significantly increased fluorescence lifetimes despite of their high refractive index, optical basicity and molecular weight. The non mono-exponential fluorescence decay curves as well as the fluorescence spectra indicate a massive change in the local surroundings of the doped rare earth ions for these glasses.     

Preparation and luminescent properties of doped with Eu3+ ions YVO4 nanophosphors

YVO₄:Eu³⁺ nanophosphors were prepared by a sol–gel method. The structure and luminescent properties of YVO₄:Eu³⁺ nanophosphors are characterized by XRD and luminescent spectrophotometer. There are excellent luminescent properties for YVO₄:Eu³⁺ nanophosphors. The nanophosphors are applied in bioapplications field.     

Preparation and luminescent properties of Eu3+-doped zinc sulfide nanocrystals

The preparation and luminescent properties of Eu³⁺-doped zinc sulfide nanocrystal were investigated. The best reactive conditions were determined, such as the concentration of reactants, the kinds and amount of the surfactants, the reaction temperature and reaction time, the pH, the flowing speed and pressure of reactive gases. The crystal structure of the nanocrystal powders was tested by X-ray diffraction (XRD). The emission and excitation spectra of ZnS:Eu were characterized by fluorescent divide spectroscopy (FDS). The luminescent sites and their strength as a function of doping Eu³⁺ ions are discussed.     

Structural and luminescent properties of Eu3+-doped GdSrAl3O7 nanophosphor

Eu³⁺-doped GdSrAl₃O₇ nanophosphor with promising luminescent properties has been synthesized by low-temperature solution combustion synthesis. The structural properties examined by X-ray diffractometer, scanning electron microscopy, and transmission electron microscopy showed that pure tetragonal GdSrAl₃O₇: Eu³⁺ red nanophosphor having narrow size distribution in 50–55 nm range could be readily obtained at low temperature 550 °C. The photoluminescent excitation and emission spectra, life time, and concentration effect were studied in detail. Under excitation at 266 nm, Eu³⁺-doped GdSrAl₃O₇ nanophosphor revealed weak green emission and strong red emission attributed to ⁵D₁ → ⁷F_1–2 and ⁵D₀ → ⁷F_0–3 transitions of Eu³⁺ ion, respectively in the region of 525–700 nm. The red emission from ⁵D₀ → ⁷F₂ transition at 616 nm exhibits the highest intensity under the optimized concentration of 10 mol% after which the quenching mechanism became relevant. Quenching behavior of the europium in the GdSrAl₃O₇ host was explained by nonradiative cross-relaxation phenomenon. Moreover, Eu³⁺-doped GdSrAl₃O₇ nanophosphor can generate light from orange to deeper red by properly tuning the concentration of europium ions based on the energy transfer principle.     

Study on preparation and luminescent properties of Eu3+-doped LaAlO3 and GdAlO3

Eu³⁺-doped trigonal LaAlO₃ and orthorhombic GdAlO₃ phosphors have been successfully synthesized by sol–gel method. The crystallization processes of the phosphors have been characterized by X-ray diffraction (XRD) and thermogravimetry-differential scanning calorimetry (TG-DSC). The optical properties of these phosphors were investigated using the photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The influences of the different structures and bonding of the hosts on the luminescence performance of Eu³⁺ ion-doped LaAlO₃ and GdAlO₃ were investigated in detail based on chemical bond theory. Under appropriate UV-radiation, the reddish orange light emitted from GdAlO₃:Eu³⁺ was brighter than that from LaAlO₃:Eu³⁺. Such a brightly luminescent phosphor could be considered as an ideal optical material for the development of new optical display systems.     

Influence of the Eu3+ dosage concentration on luminescence properties of YPO4:Eu3+ microspheres

In this study, YPO₄:Eu³⁺ microspheres with different Eu³⁺ dosage concentration were fabricated by a facile hydrothermal route at 200 °C for 10 h in the presence of citric acid. The YPO₄:Eu³⁺ samples were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and luminescence spectroscopy. The XRD results reveal that the YPO₄:Eu³⁺ samples presented a tetragonal structure. The TEM and SEM observations demonstrate that the YPO₄:Eu³⁺ samples with uniform sphere-like morphologies can be obtained at 200 °C for 10 h. The sizes of samples are in the range of 2–2.2 μm. The room temperature luminescence properties of YPO₄:Eu³⁺ samples were studied using an excitation wavelength of 227 nm. The emission spectrum displays the bands associated to the ⁵D₀ → ⁷F_J (J = 1, 2 and 4) electronic transitions characteristics of the Eu³⁺ cations at different positions. The influence of Eu³⁺ dosage concentration on luminescence properties of YPO₄:Eu³⁺ microspheres were studied carefully.     

Study on luminescent properties of Eu3+ doped new type yttrium tungsten oxide nanophosphors

In this paper, a novel nanophosphor, Y10W2O21:Eu, was synthesized through co-precipitation which is a simple and low-costing method. The structure and morphology of the nanocrystal samples were characterized by using XRD and FE-SEM. The emission spectra, excitation spectra and fluorescence decay curves were measured. J-O parameters, quantum efficiencies of Eu3+ 5D0 energy level, color coordinates and Huang-Rhys factor of Y10W2O21:Eu nanophosphors were calculated. The results indicate that EU3+ 5D0-7F2 red luminescence at 610 nm can be effectively excited by 394 nm near-UV light and 464 nm blue light in Y10W2O21 host, which is similar to the familiar Eu3+ doped tungstate phosphors (e.g., Gd2(WO4)3:Eu, CaWO4:Eu). Besides, compared with the other types of tungstate phosphors, a less expensive tungsten was used, which can effectively reduce cost. Therefore, the Y10W2O21:Eu red nanophosphors may have a potential application for white LED.     

Up-conversion luminescence properties of Y2O2S:Yb3+,Er3+ nanophosphors

Up-converting yttrium oxysulfide nanomaterials doped with ytterbium and erbium (Y₂O₂S:Yb³⁺,Er³⁺) were prepared with the flux method. The precursor oxide materials were prepared using the combustion synthesis. The morphology of the oxysulfides was characterized with transmission electron microscopy (TEM). The particle size distribution was 10–110 nm, depending on the heating temperature. According to the X-ray powder diffraction (XPD), the crystal structure was found hexagonal and the particle sizes estimated with the Scherrer equation agreeded with the TEM images. Upon the 970 nm infrared (IR) laser excitation, the materials yield moderate green ((²H_11/2, ⁴S_3/2) → ⁴I_15/2 transition) and strong red (⁴F_9/2 → ⁴I_15/2) luminescence. The green luminescence was enhanced with respect to the red one by an increase in both the crystallite size and erbium concentration due to the cross-relaxation (CR) processes. The most intense up-conversion luminescence was achieved with x_Yb and x_Er equal to 0.10 and 0.005, respectively. Above these concentrations, concentration quenching occurred.     

Photophysical properties of Eu3+ and Tb3+-doped ZnAl2O4 phosphors obtained by combustion reaction

Europium- and terbium-doped zinc aluminate oxide nanocrystals with a spinel structure were successfully prepared by a combustion method, using urea as fuel. The samples thus obtained were characterized by X-ray diffraction, scanning electron microscopy and luminescence spectroscopy. X-ray diffraction results confirmed the formation of ZnAl₂O₄ spinel phase and a minor amount of ZnO. Our SEM results revealed agglomerates in the shape of irregular plates composed of nanoparticles with dispersed points of second phase in the surface. Powders containing Eu³⁺ and Tb³⁺ ions displayed red and green photoluminescence, respectively.     

Y2O3:Eu3+ core-in-multi-hollow microspheres: facile synthesis and luminescence properties

Y2O3:Eu3+ core-in-multi-hollow microspheres were synthesized via a facile hydrothermal method in the presence of glucose followed by a subsequent heat-treatment process. X-ray diffraction (XRD) pattern shows that the as-obtained hollow spheres are cubic phase of Y2O3. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images indicate that the samples are three layer hollow spheres with a diameter of 2-4 microm and the outermost wall thickness of 100 nm, the size of the inner core is about 300-400 nm, and the sub-outer wall thickness is about 100 nm. X-ray energy dispersive spectrum (EDS) shows that the samples are composed of Y, Eu and O. Photoluminescence spectra show that the hollow spheres have a strong characteristic red emission corresponding to the 5D0 - 7F2 transition of Eu3+ ions under ultraviolet excitation. This method can be used to synthesize other rare earth oxide hollow luminescent materials.