Sol-gel synthesis and photoluminescence of LaPO_4:Eu^(3+) nanorods

Monoclinic LaPO4 nanostructures with uniform rod shape have been successfully synthesized by a simple sol-gel method.The procedure involves formation of homogeneous,transparent,metal-citrate-EDTA gel precursors,followed by calcination to promote thermal decomposition of the gel precursors to yield the LaPO4 nanoparticles.Their morphologies and structures were characterized by XRD,TEM,TG-DSC and HRTEM.The results indicate that single monoclinic phase LaPO4 nanorods are readily obtained at 800 ℃ within 3 h.Furthermore,photoluminescence(PL) characterization of the Eu3+-doped LaPO4 nanocrystals was carried out.The effects of calcination temperatures and Eu3+ doping content on the PL properties were elaborated in detail.Room-temperature photoluminescence(PL) characterization reveals that the optical brightness as well as the intensity ratio of 5D0-7F1 to 5D0-7F2 is highly dependent on the calcination temperature,and the Eu0.05La0.95PO4 nanophosphor shows the relatively promising PL performance with the most intense emission.

Effect of rare earth Eu on anti-passivation of metal oxide anode coating

The anti passivation effect of metal oxide anode coating doped with rare earth element Eu was discussed. The morphology and the composition distribution of the metal oxide coating anode before and after electrolysis were studied by SEM and EDX analyses. The results show that the erosion of the electrolyte at the defects is the main cause for the failure of the coating. The erosion rate of the electrolyte is anisotropic. In area with high density of defects, the erosion rate is very fast and the failure of the coating is very quick. Moreover, the life time of the coating is prolonged by the doping of Eu. [

Structure and Luminescence Properties of Eu^(3+) Doped SiO_2 Glass Synthesized by Sol-Gel Process

Under different annealing temperatures, Eu 3+ doped SiO 2 gel and glass were prepared by sol gel method, and the structure and luminescent properties were studied with excitation spectra, emission spectra, IR and DTA TG. The results show that the fluorescent intensity tends to get stable when concentration of Eu 3+ doped is above 1 86 % (mass fraction) most water absorbed by the gel was removed at 300 ℃, and that the emission spectrum of Eu 3+ , with peaks at 614, 588, 577 nm, is due to 5D 0→ 7F 2, 5D 0→ 7F 1, 5D 0→ 7F 0 transitions, and the excitation peaks at 318, 362, 380, 393, 412 and 462 nm were observed. These results illustrate that the temperature range of 300～500 ℃ is critical for the structure conversion from gel to glass, and the fluorescence is strongly quenched by water.

Properties of Local Structure Surrounding Eu^(3+)Ion in Various Niobate-Silicate Glasses

A Series of niobate silicate glasses doped with Eu 3+ ions were prepared. The emission, phonon side band spectra, fluorescence line narrowing spectroscopy and fluorescence lifetimes in these glasses were studied. The intensity parameters and crystal field parameter of Eu 3+ were obtained. The results indicate that the intensity ratio of the electric dipole to magnetic dipole transition and the intensity parameter Ω 2 increase with the increasing concentration of Nb 2O 5, indicating that the symmetry becomes lower, the Eu O bonds become stronger and the covalency of Eu O bond increases. The value of B 20 decreases with the increasing concentration of Nb 2O 5, indicating that the distance between the Eu 3+ ion and oxygen decreases and the Eu O bond becomes strong, corresponding to the results of the former. As the concentration of Nb 2O 5 increases, the electron phonon coupling becomes stronger, thus the nonradiative transition rate of 5D 0 becomes larger and the lifetime of 5D 0 becomes shorter.

Nanosized complex fluorides based on Eu^(3+) doped Sr_2LnF_7(Ln=La, Gd)

A simple co-precipitation approach taking place between Ln3＋, Sr2＋ cations and F anions, led to the formation of nanocrystalline Eu3＋ doped Sr2LnF7 （Ln-La and Gd） complex fluorides. The reaction was carried out in the presence of polyeth- ylene glycol, PEG 6000 as a surfactant/surface modifier, providing small size and homogeneity of the products. The synthesized compounds were composed of small nanoparticles with an average size of 15 nm. All obtained Eu3＋ doped compounds exhibited an intensive red luminescence. In the case of gadolinium based compounds, the energy transfer phenomena could be observed from Gd3＋ ions to Eu3＋ ions. In order to study the structure and morphology of the synthesized fluorides, powder X-ray diffraction （XRD） and transmission electron microscopy （TEM） measurements were performed. Also FT-IR spectra of the products were re- corded, revealing the presence of PEG molecules on the nanoparticles suN＇ace. A spectrofluorometry technique was applied to examine optical properties of the synthesized nanoparticles. Excitation and emission spectra as well as luminescence decay curves were measured and analysed. The performed analysis revealed a red luminescence, typical for the Eu3＋ ion situated in the inorganic, highly symmetric matrix. Concentration quenching phenomena and lifetimes shortening, together with an increasing of the Eu3＋ doping level, were observed and discussed. Judd-Ofelt analysis was also performed for all doped samples, in order to support the registered spectroscopic data and examine in details structural and optoelectronic properties of the synthesized nanomaterials.

A new oxyapatite red phosphor Eu^(3+)-doped Ca_(3)Y_(7)(BO_(4))(SiO_(4))_(5)O:Synthesis,structure and luminescence properties

A series of new oxyapatite red phosphors Ca_(3) Y_(7)(BO_(4)) (SiO_(4))_(5) O doped with different concentrations of Eu^(3+)were successfully synthesized by high temperature solid state method.The X-ray diffraction(XRD)Rietveld refinement results show that the structure of the phosphor belongs to space group P6_(3)/m and Eu^(3+)ion replaces Y^(3+)ion.The emission spectrum consists of the characteristic emission peaks corresponding to Eu^(3+)under the excitation of 274 nm and the dominant emission peak is at 614 nm(^(5)D_(0)→^(7)F_(2) of Eu^(3+)).The concentration quenching effect occurs and the optimized Eu^(3+)concentration is 4.0 mol%.The energy level diagram for luminous mechanism is also given and the non-radiative energy transfer mechanism between Eu^(3+)is mainly exchange interaction.The CIE coordinate is close to the ideal red light and the color purity is higher than 99.79%.Moreover,the phosphor exhibits moderate thermal stability because the photoluminescence intensity at 423 K is still maintained at higher than 78.97%of that at room temperature.The internal quantum efficiency of Ca_(3) Y_(7)(BO_(4)) (SiO_(4))_(5) O:4.0 mol%Eu^(3+)phosphor is 58.2%.A red light emitting diode(LED)device based on it can emit bright red light.The CCT values of the device are basically unchanged when driven by various bias current.The results show that Ca_(3) Y_(7)(BO_(4)) (SiO_(4))_(5) O:Eu^(3+)is a new type of oxyapatite red fluorescent material with good comprehensive performances.

Production, characterization, and luminescent properties of Eu3+ doped yttrium niobate-tantalate films

Monoclinic yttrium tantalate (M'-YTaO4,M'-YTO),and two different kinds of yttrium niobium-tantalate (M'-YTao.85Nbo.15O4 (M'-YTNO) and Eu3+ doped M'-YTao.85Nbo.15O4 (M'-YTNO∶Eu3+)) were produced by sol-gel method and grown on single crystalline Si (100) substrate by spin coating approach.Structural properties and thermal behaviours of the films were characterized by means of X-ray diffraction (XRD),atomic force microscopy (AFM),scanning electron microscopy (SEM),and thermogravimetry and differential thermal analysis (TG-DTA).Systematic Steady-state photoluminescence and lifetime measurements in a series of yttrium niobium-tantalate with varying amounts of Eu3+ were presented.The photoluminescence spectra of the films exhibited strong blue (380-400 nm) and red (614 nm) emissions upon ultraviolet excitation.Emission intensities were strongly dependent on the host lattice composition and film morphology.1.5％ Eu3+ doped films exhibited the brightest luminescence and long lifetime extending to 1.22 ms when excited at 254 nm.To the best of our knowledge,this is the first attempt in the production of M'-YTO,M'-YTNO,and M'-YTNO∶Eu3+ films on single crystalline Si (100) substrate via sol-gel spin coating.

Electrospinning Synthesis and Photoluminescence Properties of SnO2：xEu3＋ Nanofibers

NnO2：xEu3＋（x=O, 1%, 3%, 5%, molar fraction） fibers were synthesized by electrospinning technology. The size of the as-prepared fibers is relatively uniform and the average diameter is about 200 nm with a large draw ratio. The as-prepared Eu3＋ doped SnO2 nanofibers have a rutile structure and consist of crystallitc grains with an average size of about 10 nm. A slight red shift of the A1gand Bag vibration modes and an additional peak at 288 nm were observed in the Raman spectra of the nanofibers. The energies of bandgaps of the SnO2 nanofiber with Eu doping of 1% and 3% are 2.64 eV, and the energy of bandgap is 2.94 eV with Eu doping of 5%（molar fraction）. There is only orange emission（5D0→7F1 magnetic dipole transition） for Eu doped SnO2 nanofibers, and no red emission could be observed. The orange emission upon indirect excitation splits into three peaks and the peak intensity at the excitation wavelength of 275 nm is higher than that at the excitation wavelength of 488 nm.

Concentration and annealing effect on PL properties of sol-gel derived SiO_2-Y_2O_3:Eu^(3+) nanocomposites

An improved sol-gel method was employed to prepare Eu3+ ions doped SiO2-Y2O3 nanocomposites.Systematic study was carried out on the effect of post-annealing treatment on photoluminescence(PL) properties of the samples under various europium ions doping concentrations.X-ray diffraction(XRD) patterns indicated that the samples showed an amorphous matrix structure,and the scanning electron microscopy(SEM) pictures showed that the samples presented a nano size(from 21 to 42 nm) granular-stack structure after hi...

Growth and optical properties of Dy^(3+)/Eu^(3+) co-doped NaYF_4 single crystals with cubic lattice for white LED application

Dy3+/Eu3+ co-doped cubic lattice Na YF4 single crystal with high quality in the size of ~Φ1.0 cm×10.0 cm was grown by an improved Bridgman method using potassium fluoride(KF) as assistant flux. X-ray diffraction(XRD), absorption spectra, excitation spectra and emission spectra are measured to investigate the phase and luminescent properties of the crystal. The effects of excitation wavelength and concentrations of Dy3+ and Eu3+ ions on the luminescent characteristics are analyzed. The Na YF4 single crystal with the doping molar concentrations of 1.205% Dy3+ and 0.366% Eu3+ exhibits an excellent white light emission with chromaticity coordinates of x=0.321, y=0.332. It indicates that the Dy3+/Eu3+ co-doped cubic lattice Na YF4 single crystal can be a potential luminescent material for the ultraviolet(UV) light excited white light emitting diode(w-LED).

Luminescence properties of tunable red-green emitting phosphor Ba2Ca(BO3)2：Eu3＋,Tb3＋

A series of Eu^(3+) or Tb^(3+) doped Ba_2Ca(BO_3)_2 phosphors were synthesized by a high temperature solid state method, and the luminescence properties are investigated. Ba_2Ca(BO_3)_2:Tb^(3+) can show an obvious green emission, and the peak locates at 551 nm, which corresponds to the 5D34→7F5 transition of Tb^(3+). Ba_2Ca(BO_3)_2:Eu+ can present the characteristic emission of Eu^(3+), and the peak locates at 600 nm, which is ascribed to the 5D70→F2 transition of Eu^(3+). In order to achieve the emission-tunable phosphors, the Eu^(3+)/Tb^(3+) co-doped Ba_2Ca(BO_3)_2 are synthesized. When tuning the Eu^(3+) or Tb^(3+) concentration, Ba_2Ca(BO_3)_2:Eu^(3+), Tb^(3+) can both show the tunable emission, which may be induced by the energy transfer from Tb^(3+) to Eu^(3+).

Synthesis of luminescent KY_3F_(10) nanopowder multi-doped with lanthanide ions by a co-precipitation method

A series of KY3F10 nanophosphors doped with Gd3＋, Ce3＋ and Eu3＋ ions were obtained with the use of a co-precipitation method. The resulting products were white precipitates, consisting of spherical particles with diameter about 150-200 nm, which was confirmed using transmission electron microscopy （TEM） technique. Powder X-ray diffraction （XRD） and energy dispersive X-ray analysis （EDX） measurements confirmed appropriate structures of the nanoparticles obtained. Spectroscopic properties of the prod- ucts were examined on the basis of the measured excitation/emission spectra and luminescence decay curves. The synthesized sam- ples showed orange-red luminescence, characteristic for Eu3＋ ions. The reaction process was performed in required alkaline pH ad- justed with the use of ethylenediaminetetraacetic acid （EDTA） and potassium hydroxide. The samples containing large amounts of Gd3＋ dooant ions exhibited a tendencv to form nroducts with different momhologies.

Combustion synthesis, characterization and luminescence properties of barium aluminate phosphor

The blue-green emitting Eu2＋ and Nd3＋ doped polycrystalline barium aluminate （BaAI204：Eu2＋,Nd3＋） phosphor, was prepared by a solution-combustion method at 500 ℃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/A1 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 urn. The broad-band UV-excited luminescence of the phosphors was observed at 2max=500 um due to transitions from the 4f^65d1 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.

Gain enhancement of terahertz surface plasmon in electrically pumped multilayer graphene

We propose a surface plasmon(SP) structure in electrically pumped multiple graphene-layer(MGL), and calculate the functions of dynamic conductivity and absorption coefficient. Meanwhile, the dependences of absorption coefficient on different factors are simulated. SP can get gain when absorption coefficient is negative, and the SP gain can be enhanced by lowering temperature, applying high bias voltage and choosing the graphene with proper layer number and long momentum relaxation time. The study on SP gain is hopeful to be used in amplifiers and graphene-based plasmon devices.