Influence of Molten Salt on Luminescent Intensity and Particle Size of Y_2O_3:Eu^(3+) Phosphor

The Y-Eu oxalate precursor was prepared with a homogeneous precipitation method. And the additives, Na2CO3, S, NaCl or their combination, were introduced into the precursor to prepare Y2O3 ：Eu^3＋ red phosphors at 1000 1300 ℃ for 2 h. The effect of molten salts on particle size and luminescent intensity was studied. The experimental results showed that the complex molten salt （Na：CO3 ＋ S ＋ NaCl） was conductive to enhance the luminescent intensity of Y2O3 ：Eu^3＋. The emission intensity of the phosphor prepared with these additives at 1300 ℃ was about 45% higher than that of the one prepared without molten salt, and about 11% higher than that of the corresponding commercial phosphor. Meanwhile, the particle size of Y2O3 ：Eu^3＋ phosphor was controlled effectively with the molten salt.

Synthesis and Properties of Eu_(3+) Activated Strontium Molybdate Phosphor

In order to prepare fluorescent material for white Light Emitting Diodes （LEDs）, a new Eu^3＋ activated molybdate phosphor SrMoO4 was fabricated with solid-state method. X-ray diffraction （XRD） showed that the doping of trivalent europium ion reduced the lattice parameters. The excitation and emission spectra indicated that this phosphor could be excited effectively by the visible light, and then emitted red light with the peaks located at 616 and 624 nm. The influence of Eu^3＋ concentration on the luminescent properties of Eu^3＋ doped SrMoO4 was investigated and the 25% （mole fraction） was the appropriate molar concentration. The reaction time and temperature had obvious effect on the luminescent properties. The luminescent intensity reached the strongest when it was sintered at 800 ℃ for 3 h.

Co-luminescence properties of terbium ions–benzoic acid–phen complexes doped with europium ions

Series of complexes Eux Tb1-x(BA)3phen(0.01 B x B 0.50)were synthesized by co-precipitation method,BA was used as the carboxylic acid ligand and 1,10-phenanthroline was used as the electrically neutral ligand.The samples were characterized by means of X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),thermal gravimetric analyses and differential scanning calorimetry(TG–DSC),ultraviolet and visible spectrophotometer absorption spectra,and photoluminescence spectra to study the structure,the energy absorption,the thermal,and luminescent properties of the rare earth complexes.The results show that the series rare earth organic complexes are well crystallized and show high thermal stability.The luminescent intensity of europium ion in the complexes increases as terbium ion transfers the absorbed energy to europium ion in the complexes.The emission of terbium ion at 545 nm is not quenched by europium ion but increases with the content of europium ion decreasing.When the x value is 0.01,the fluorescence intensity reaches the maximum as well as the emission intensity of terbium ions at 545 nm and europium ions at614 nm are almost equal.It realizes the co-luminescence phenomenon of terbium ion and europium ion.The series rare earth organic complexes with different colors can be obtained by adjusting the ratio of terbium ion and europium ion.

Photoluminescence Characterization of NASICON Material

Besides gas sensitivity,NASICON (Na super ion conductor) material has luminescence characterization.In this paper,the photoluminescence properties of NASICON and doped-NASICON material are investigated.The NASICON material was synthesized by conventional sol-gel process,and doped with Er_2O_3,Tm_2O_3,Dy_2O_3,CsCl by 1%,3%,5% (mass ratio),respectively.The ultraviolet light (325 nm,He-Cd laser) excited luminescent emissions of the resulted powders are recorded vs.wavelength in the 330 nm to 650 nm range.The main peak of the pure NASICON is found at the wavelength of 474 nm (blue light),the transition energy is 2.616 eV.The luminescent intensity is weakened obviously after doping with Er_2O_3 and Tm_2O_3,but is increased after doping with Dy_2O_3 and 3% CsCl.

Experimental optimum design and luminescence properties of NaY(Gd)(MoO_4)_2:Er^(3+)phosphors

Three-factor orthogonal design（OD） of Er3＋/Gd3＋/T（calcination temperature） is used to optimize the luminescent intensity of Na Y（Gd）（MoO4）2：Er3＋phosphor.Firstly,the uniform design（UD） is introduced to explore the doping concentration range of Er3＋/Gd3＋.Then OD and range analysis are performed based on the results of UD to obtain the primary and secondary sequence and the best combination of Er3＋,Gd3＋,and T within the experimental range.The optimum sample is prepared by the high temperature solid state method.Photoluminescence excitation and emission spectra of the optimum sample are detected.The intense green emissions（530 nm and 550 nm） are observed which originate from Er3＋2H11/2→4I15/2and4S3/2→4I15/2,respectively.Thermal effect is investigated in the optimum NaY（Gd3＋）（MoO4）2：Er3＋phosphors,and the green emission intensity decreases as temperature increases.

Photoluminescence properties of Y_(0.75-x)Gd_xAl_(0.10)BO_3:Eu_(0.10)^(3+),0.05R^(3+)(R= Sc,Bi) (0.00 ≤ x ≤ 0.45)

Y0.75-xGdxAl0.10BO3：Eu0.10^3＋,0.05R^3＋（R=Sc,Bi）（0.00≤x≤0.45）powder samples are prepared by solid-state reaction and their luminescence properties are investigated. With the replacement of Y^3＋ ions by Sc^3＋ （or Bi^3＋）and Gd^3＋ ions in （Y,Al）BO3：Eu,the intensities of emission at 254 and 147 nm are remarkably improved, because Sc^3＋ inos can absorb UV light and transfer the energy to Eu^3＋ ions efficiently. Moreover, Gd^3＋ and Bi^3＋ ions act as an intermediate ＂bridge＂ between the sensitizer and the activator （Eu^3＋） in energy transfer to produce light in the （Y, Gd）BO3：Bi^3＋, Eu^3＋ system more effectively. After doping an appropriate concentration of Gd^3＋ into Y0.50Gd0.25Al0.10BO3：Eu0.01^3＋,Bi0.05^3＋,the emission intensity reaches its maximum, which is nearly 110% compared with the red commercial phosphor （Y,Gd）BO3：Eu and better chromaticity coordinates （0.650, 0.350） are obtained.

Synthesis,Structure and Photoluminescence of a New Ir Complex Based on Pyridine-2,3-dicarboxylic Acid

A new complex Ir（ppy）2（Hpda）（Hppy=2-phenylpyridine, H2pda=pyridine-2,3-dicarboxylic acid） has been synthesized and characterized. According to single-crystal X-ray diffraction analyses, the title complex crystallizes in the monoclinic system, space group P21/n with a=8.5708（10）, b=22.685（2）, c=12.5722（15） , β=96.19（1）°, V=2430.2（5） 3, C（29）H（20）N3O4 Ir, Mr=666.22, Z=4, Dc=1.833 g/cm3, F（000）=1304, μ=5.54 mm（-1）, λ（Mo Kα）=0.71073 , GOOF=1.02, the final R=0.049 and w R=0.119 for 4680 independent reflections with Rint=0.069. The title complex is of mononuclear structure. Intermolecular C–H···O hydrogen bonds and π-π stacking interactions result in the formation of a 3D supramolecular network. Photoluminescent spectra show that one intense emission band with the maximum of 516 nm can be observed in the title complex.

Effect of calcinations temperature on the luminescence intensity and fluorescent lifetime of Tb^(3+)-doped hydroxyapatite(Tb-HA)nanocrystallines

Hydroxyapatite luminescent nanocrystallines doped with 6 mol.%Tb^(3+)(Tb-HA)were prepared via chemical deposition method and calcined at different temperature,and the effects of calcinations temperature on the luminescence intensity and fluorescent lifetime were studied.TEM image of Tb-HA revealed that the shape of nanocrystallines changed from needle-like to short rod-like and sphere-like with the increase of calcinations temperature;while the particles sizes decreased from 190 nm to 110 nm.the crystallinity degree increased.the typical emission peaks attributed to Tb^(3+) ions were observed in emission spectra of 6 mol.%Tb-HA under 378 nm excitation.the luminescent intensity of Tb-HA,which showed the fluorescence quenching,firstly enhanced and then decreased at 700℃;while the fluorescent lifetime increased firstly and then decreased after 600℃.Furthermore,the ratio of intensity between 545 nm and 490 nm corresponding to electric-dipole and magnetic-dipole transition(I_(R):I_(O))increases firstly and then decreases,which revealed that the proportion of substitute type and site of Ca^(2+) ions by Tb^(3+) ions were helpful to realize the substitute process and functional structure design.

Enhancement of structure stability and luminescence intensity of LiYF_4:Ln^(3+)nanocrystals

LiYF_4 nanocrystals with tetragonal structure were adopted as the host materials for the phosphors and scintillators owing to the low phonon energy and high optical transparency. LiYF_4：Ln^（3＋）（Ce^（3＋）,Eu^（3＋）） nanocrystals were fabricated by solvothermal method. Under UV excitation, they could emit visible light. In order to improve the luminescence intensity, the method of co-doping LiYF_4 nanocrystals with Sc was adopted. Sc^（3＋） ions could reduce the lattice expansion caused by the doping of Ce^（3＋） or Eu^（3＋） whose ionic radius was larger than Y^（3＋）. Crystal structure of Li（Y,Sc）F_4：Ln^（3＋） kept much more stable and the luminescence intensity could be significantly enhanced when the concentration of Sc was a moderate value. Thermoluminescence was employed to analyze the electron traps in Li（Y,Sc）F_4：Ce^（3＋）. Results suggested that the suppression of the generation of electron traps with the co-doping of Sc contributed to the enhancement of luminescence intensity of LiYF_4：Ce^（3＋）.

Upconversion luminescence and optical thermometry behaviors of Yb^(3+)and Ho^(3+)co‑doped GYTO crystal

Optical thermometry based on the upconversion(UC)luminescence intensity ratio(LIR)has attracted considerable attention because of its feasibility for achievement of accurate non-contact temperature measurement.Compared with traditional UC phosphors,optical thermometry based on UC single crystals can achieve faster response and higher sensitivity due to the stability and high thermal conductivity of the single crystals.In this study,a high-quality 5 at%Yb^(3+)and 1 at%Ho^(3+)co-doped Gd_(0.74)Y_(0.2)TaO_(4)single crystal was grown by the Czochralski(Cz)method,and the structure of the as-grown crystal was characterized.Importantly,the UC luminescent properties and optical thermometry behaviors of this crystal were revealed.Under 980 nm wavelength excitation,green and red UC luminescence lines at 550 and 650 nm and corresponding to the^(5)F_(4)/^(5)S_(2)→^(5)I_(8)and^(5)F_(5)→^(5)I_(8)transitions of Ho^(3+),respectively,were observed.The green and red UC emissions involved a two-photon mechanism,as evidenced by the analysis of power-dependent UC emission spectra.The temperature-dependent UC emission spectra were measured in the temperature range of 330–660 K to assess the optical temperature sensing behavior.At 660 K,the maximum relative sensing sensitivity(S_(r))was determined to be 0.0037 K^(−1).These results highlight the signifcant potential of Yb,Ho:GYTO single crystal for optical temperature sensors.

Self-polymerization of Eu(TTA)_3AA in rubber and their fluorescence effect

A simple europium complex,Eu（TTA）3 AA（TTA=4,4,4-trifluoro-1-（2-thienyl）-1,3-butanedione,AA=acrylic acid） was synthesized by a simple solution method.Then,two kinds of rubber matrix,nitrile-butadiene rubber（NBR） and silicone rubber（SiR） were used as the substrate for Eu（TTA）3 AA to prepare fluorescence composites.The neat Eu（TTA）3 AA complex showed the ability of self-polymerization when it was heated at 145 °C.It was found that the fluorescence intensity of the neat Eu（TTA）3 AA decreased over 70% when the polymerization time was over 25 min at 145 °C.The results also revealed that the polymerizated Eu（TTA）3 AA could be dispersed in nano-scale in two matrices and the luminescent intensities decreased 52% in NBR matrix,and 95% in SiR matrix compared with two relative compounds without crosslinking.To optimize the luminescence intensity of the composites,the Eu（TTA）3 AA polymerization kinetic process in matrix was investigated in detail by controlling the temperature,the crosslinking agent,etc.The results showed that the peroxide could accelerate Eu（TTA）3 AA self-polymerization in the rubber matrix,and therefore improved the dispersion,but not be helpful for the luminescence intensity enhancement.In addition,the relatively higher luminescence intensity in Eu（TTA）3 AA/NBR in comparison to that of Eu（TTA）3 AA/SiR might contribute to the interaction between nitrile group（–CN） in NBR and Eu-complexes,suggesting that the luminescence intensity of the composites also depended on the matrix characteristics.