Dosimetry characteristics of NaLi2PO4:Tb3+ OSLD phosphor

Journal of Radioanalytical and Nuclear Chemistry - NaLi2PO4:Tb3+ phosphor material was prepared by solid state diffusion method using NaH2PO4 and LiOH. The CW-OSL sensitivity of the material...     

A red-emitting Ca8MgLa(PO4)7:Ce3+,Mn2+ phosphor for UV-based white LEDs application

Ca(8)MgLa(PO(4))(7):Ce(3+),Mn(2+) phosphors have been prepared by a conventional solid state reaction under a weak reductive atmosphere. The crystal structure and photoluminescent properties were investigated. It was found that the red emission at 640nm originated from the (4)T(1)((4)G)→(6)A(1)((6)S) transition of Mn(2+) increases dramatically by a factor of 6.4 with the optimum Ce(3+) co-doping. The energy transfer from Ce(3+) to Mn(2+) was proposed to be resonance-type via an electric dipole-dipole mechanism and the energy transfer efficiency was also calculated by the relative emission intensity. With the broadband ultraviolet (UV) absorption of Ce(3+) and the suitable color coordinates, Ca(8)MgLa(PO(4))(7):Ce(3+),Mn(2+) phosphors might be a promising candidate as red phosphors in the field of UV-based white light-emitting diodes.     

Synthesis and characterization of novel blue emitting Na2CaSiO4:Ce3+ phosphor

The blue phosphors Na_(2?x)Ca_(1?x)SiO₄:xCe³⁺ were synthesized by the sol–gel method and their luminescence characteristics were investigated for the first time. Structural information about prepared samples is obtained by analyzing the XRD patterns and SEM micrographs. The photoluminescence (PL) excitation spectra indicate that the Na_(2?x)Ca_(1?x)SiO₄:xCe³⁺ phosphors can be effectively excited by ultraviolet (360 nm) light. The PL emission spectra exhibit tunable blue broadband emission with the dominant wavelength of 427–447 nm under excitation of 360 nm by controlling the doping concentration of Ce³⁺. The concentration quenching effect for Ce³⁺ was found at the optimum doping concentration of 4 mol%. The Commission Internationale de l’Eclairage 1931 chromaticity coordinates of Na_1.96Ca_0.96SiO₄:0.04Ce³⁺ are (0.1447, 0.0787), which are better color purity compared to the commercial Eu²⁺-doped BaMgAl₁₀O₁₇ phosphor. Na_1.96Ca_0.96SiO₄:0.04Ce³⁺ composition shows intense blue emission (peak wavelength, 439 nm) with relative intensity versus commercial BaMgAl₁₀O₁₇:Eu²⁺ blue phosphor (Nichia) 65 and 158 % under 254 and 365 nm excitation, respectively. All the results indicate that Na_(2?x)Ca_(1?x)SiO₄:xCe³⁺ phosphors are potential candidate as a blue emitting phosphor for UV-converting white light-emitting diodes.     

Studies of EPR parameters for Mn5+ -doped Li3PO4 and Li3VO4 crystals

The EPR parameters (zero-field splitting D and g factors g parallel, g perpendicular) of Mn5+ -doped Li3PO4 and Li3VO4 crystals are calculated from the complete high-order perturbation formulas based on a molecular orbital scheme for a 3d2 ion in tetragonal MX4 clusters. These formulas include not only the contribution coming from crystal-field excitations, but also that arising from charge-transfer excitations (which is discarded in crystal field theory). The calculated results are in reasonable agreement with the observed values. The contributions to EPR parameters coming from the charge-transfer excitations are comparable with those arising from the crystal-field excitations. It appears that for a high valence state 3dn ion in crystals, the reasonable explanations of EPR parameters should take the contributions due to both crystal-field and charge-transfer excitations into account.     

NH4H2PO4掺杂改性纳米TiO2的光催化性能

利用钛酸丁酯水解浸渍方法制备了几种不同浓度NH4H2PO4掺杂改性的TiO2纳米复合粉体材料并作了XRD、BET等表征。以正己烷的气相光催化氧化降解为探针反应研究了NH4H2PO4掺杂TiO2催化剂的光催化活性。并和未掺杂TiO2及商品TiO2 Degussa P-25作了比较．结果表明。掺杂NH4H2PO4能够显著地细化TiO2的晶粒度。增大TiO2的比表面积。同时，适量掺杂NH4H2PO4对TiO2的光催化活性也有较大的促进作用。     

Photoluminescence characterization of Ca10Na(PO4)7:Eu3+ red-emitting phosphor

Eu3+-doped Ca10Na(PO4)7 phosphors were successfully synthesized by solid-state reaction techniques. Their structures and photoluminescence characteristics were carefully studied. An efficient red emission under near-ultraviolet excitation is observed. The maximum intensity of luminescence was observed at the Eu3+ concentration around 9 mol%. The quadrupole-quadrupole interaction between Eu3+ ions is the dominant mechanism for concentration quenching of fluorescence emission from Eu3+ ions in Ca10-xNa(PO4)7:xEu3+. Due to the excitation spectrum is well coupled with near UV light, Ca10-xNa(PO4)7:xEu3+ phosphors have potential application as red phosphors in near UV chip-based white light emitting diodes.     

Synthesis, characterization and photoluminescence properties of Ce3+-doped ZnO-nanophosphors

The present study involves the synthesis of Ce³⁺ doped ZnO nanophosphors by the zinc nitrate and cerium nitrate co-precipitation method. The synthesized nanophosphors were characterized with respect to their crystal structure, crystal morphology, particle size and photoluminescence (PL) properties using X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive X-ray (EDX), transmission electron microscopy (TEM)/Energy-dispersive X-ray spectroscopy (EDS) and PL-spectroscopy respectively. XRD results revealed that ZnO nanophosphors are single phase and cubic type structures. Further, PL spectra of ZnO:Ce³⁺ nanophosphors showed green emission because of the charge transfer at single occupied oxygen vacancies with ZnO holes and red emission due to the cerium ion transitions. Intensity and fine structure of the Ce³⁺ luminescence and its temperature dependence are strongly influenced by the doping conditions. The formation of ZnO:Ce³⁺ nanophosphors was confirmed by Fourier transform infrared (FTIR) and XRD spectra.     

A tunable single-component warm white-light Sr3Y(PO4)3:Eu2+,Mn2+ phosphor for white-light emitting diodes

The photoluminescence properties and energy transfer of the Eu(2+) and Mn(2+) co-doped Sr(3)Y(PO(4))(3) phosphors are investigated in detail. Two main emission bands attributed to the Eu(2+) and Mn(2+) ions are observed under UV light excitation via an efficient energy transfer process. When the Eu(2+) doping content is fixed, the emission chromaticity can be varied by simply adjusting the content of Mn(2+). The study of the behavior as a function of doping concentration indicates that the warm white-light can be obtained in a single host lattice. Furthermore, the analysis of the fluorescence decay curves based on the Inokuti-Hirayama theoretical model reveals that the dipole-quadrupole interaction is mainly responsible for the energy transfer mechanism from the Eu(2+) to Mn(2+) ions in the Sr(3)Y(PO(4))(3) phosphor. The developed phosphor exhibits a strong absorption in UV spectral region and white-light emission which may find utility as a single-component white-light-emitting UV-convertible phosphor in white LED devices.     

Energy transfer characteristics of the hydrogen peroxide induced Ce3+-Ce4+ mixture

Luminescence of Ce3+ in the hydrogen peroxide induced sulfuric acid solutions was observed to be quenched by Ce4+ ions in the solution by energy transfer due to electric dipole interaction between Ce3+ and Ce4+. A systematic investigation of the energy transfer characteristics of Ce3+-Ce4+ mixture has been made by measuring the absorption, luminescence and excitation spectra at room temperature. The effect of the concentration of Ce3+ on the energy transfer process has been also studied and the critical transfer distance (Ro) has been calculated considering F?rster type interaction between the ions and found to be 8.7 A for the mixture of 1 x 10(-4) mol 1(-1) Ce3+ and 3 x 10(-4) mol l(-1) Ce4+.     

A novel Sr3Y(PO4)3-based white light-emitting phosphor

The Sr₃Y(PO₄)₃:0.05Sm³⁺, Sr₃Y(PO₄)₃:0.005Tb³⁺, and Sr₃Y(PO₄)₃:0.005Tb³⁺, 0.05Sm³⁺ phosphors were synthesized using a conventional solid-state reaction technique at high temperature and their photoluminescence properties under ultraviolet (UV) excitation were studied. We observed the UV sensitization of Sm³⁺ emission (565, 600, and 648 nm) by Tb³⁺ in Sr₃Y(PO₄)₃:0.005Tb³⁺, 0.05Sm³⁺, that leads to a white light emission with the CIE coordinate (0.367, 0.312) of Sr₃Y(PO₄)₃:0.005Tb³⁺, 0.05Sm³⁺ phosphor under UV excitation. The emission is a result of partial energy transfer from Tb³⁺ to Sm³⁺, which is discussed in detail in terms of the corresponding excitation and emission spectra.     

Ce3+、Tb3+离子及Ce3+-Tb3+离子对在Sr4Si3O8Cl4基质中发光的研究

研究了Ce³⁺、Tb³⁺、离子及Ce³⁺-Tb³⁺离子对在Sr₄Si₃O₈Cl₄基质中的发射光谱和激发光谱。初步讨论了Ce³⁺、Tb³⁺离子之间发光敏化的机理。     

新型Ce3+掺杂亚磷酸锰开放骨架材料的合成与荧光性质

通过高通量实验方法制备了一系列新型的Ce³⁺离子掺杂亚磷酸锰(NH₄)₄[Mn_4-xCe_x(HPO₃)₆](简称JIS-10∶xCe³⁺) 无机开放骨架材料. 通过粉末X射线衍射(PXRD)谱图、 扫描电子显微镜(SEM)、 微量元素能谱(EDS)、 X射线光电子能谱(XPS)、 傅里叶变换红外(FTIR)光谱和光致发光(PL)光谱等手段对该材料进行了表征, 并研究了Ce³⁺离子掺杂浓度、 反应温度和时间对晶体相变和发光性能的影响. 结果表明, 在波长260 nm的光激发下, Ce³⁺离子在500 nm处有1个绿光发射带而Mn²⁺离子在590 nm处有1个黄光发射带. 调变JIS-10∶xCe³⁺材料中Ce³⁺离子的掺杂浓度发现, 当x=0.06^{时, 即Ce3+离子的掺杂浓度较低时, 样品的发射颜色为黄绿色, 其CIE坐标为(0.38, 0.48); 当Ce3+离子的掺杂浓度增加时, 绿色发光带的增长快于黄色发光带的增长, 从而调整发射颜色; 在x=1.33时观察到最强的发射, 浓度过高发生浓度猝灭.}     

Spectroscopic characteristics of Sm3+-doped alkali fluorophosphate glasses

Optical absorption, luminescence and lifetime measurements of Sm(3+)-doped alkali fluorophosphate glasses with molar compositions of 50(NaPO(3))(6)+10TeO(2)+20AlF(3)+19RF+1Sm(2)O(3) (R=Li, Na and K) are described. The variation of optical properties with glass composition plays a dominant role in the determination of efficient laser materials. From the experimental oscillator strengths of f-f electric dipole transitions, the phenomenological Judd-Ofelt parameters have been evaluated and are used to evaluate radiative parameters such as radiative transition probabilities (A(R)), branching ratios (beta(R)), lifetimes (tau(R)) and integrated absorption cross-section (sigma(a)) for various excited levels. The predicted values of tau(R) and beta(R) from the (4)G(5/2) excited level to its lower levels are compared with the experimentally measured values. Stimulated emission cross-sections (sigma(e)) were also determined for (4)G(5/2)-->(6)H(J) (J=5/2, 7/2, 9/2 and 11/2) emission transitions. From the emission transitions of Sm(3+) in these alkali tellurofluorophosphate glasses certain potential laser transitions have been identified.     

Tagging of avidin immobilized beads with biotinylated YAG:Ce3+ nanocrystal phosphor

YAG:Ce³⁺ nanoparticles 9.5 ± 1.2 nm in diameter have been synthesized from aluminium isopropoxide and acetates of yttrium and cerium in 1,4-butanediol (1,4-BD) by autoclave treatment at 300 °C for 2 h. After replacing 1,4-BD by ultrapure water, NH₂ groups were introduced on the surface of YAG:Ce³⁺ nanoparticles by addition of 3-aminopropyltrimethoxysilane then biotinylation with sulfo-NHS-LC-biotin. We demonstrated that avidin immobilized beads are tagged by biotinylated YAG:Ce³⁺ nanoparticles by the selective avidin-biotin interaction, furnishing a green fluorescent image on excitation with blue light. This result indicates that YAG:Ce³⁺ nanoparticle phosphors have much potential in biological applications.     

掺三价铈离子四偏磷酸盐NaLn(PO3)4 (Ln=La, Gd)的真空紫外光谱研究

用高温固相法合成了NaLn（PO3）4：1．0％（原子分数）Ce^3＋（Ln=La,Gd）两种粉末发光材料,在合肥国家同步辐射实验室（NSRL）测得两种样品中Ce^3＋的真空紫外光谱。根据真空紫外光谱图,得到了两种稀土偏磷酸盐中所掺Ce^3＋离子5d轨道的能级分裂图。结合NaLa（PO3）4和NaGd（PO3）4的单晶结构数据,发现随着Ln-O平均键长的减小,Ce^3＋离子5d轨道的晶场劈裂（εcfs）、重心位移（εc）和总的红移（total redshilt,D）均增大。根据配体极化模型,计算了两种化合物中掺杂Ce^3＋离子的有效平均键长（Reff）和光谱极化率（αsp）,发现随着平均键长Rav（Ln—O）变短,Ce^3＋离子的光谱极化率（αsp）也随之减小。     

K3Ga2(PO4)3 and Na3Ga(PO4)2

The structures of tripotassium digallium tris(phosphate), K₃Ga₂(PO₄)₃, and trisodium gallium bis(phosphate), Na₃Ga(PO₄)₂, have different irregular one‐dimensional alkali ion‐containing channels along the a axis of the orthorhombic and triclinic unit cells, respectively. The anionic subsystems consist of vortex‐linked PO₄ tetrahedra and GaO₄ tetrahedra or GaO₅ trigonal bipyramids in the first and second structure, respectively.     

Promising oxonitridosilicate phosphor host Sr3Si2O4N2: synthesis, structure, and luminescence properties activated by Eu2+ and Ce3+/Li+ for pc-LEDs

A novel oxonitridosilicate phosphor host Sr(3)Si(2)O(4)N(2) was synthesized in N(2)/H(2) (6%) atmosphere by solid state reaction at high temperature using SrCO(3), SiO(2), and Si(3)N(4) as starting materials. The crystal structure was determined by a Rietveld analysis on powder X-ray and neutron diffraction data. Sr(3)Si(2)O(4)N(2) crystallizes in cubic symmetry with space group Pa ?3, Z = 24, and cell parameter a = 15.6593(1) ?. The structure of Sr(3)Si(2)O(4)N(2) is constructed by isolated and highly corrugated 12 rings which are composed of 12 vertex-sharing [SiO(2)N(2)] tetrahedra with bridging N and terminal O to form three-dimensional tunnels to accommodate the Sr(2+) ions. The calculated band structure shows that Sr(3)Si(2)O(4)N(2) is an indirect semiconductor with a band gap ≈ 2.84 eV, which is close to the experimental value ≈ 2.71 eV from linear extrapolation of the diffuse reflection spectrum. Sr(3-x)Si(2)O(4)N(2):xEu(2+) shows a typical emission band peaking at ~600 nm under 460 nm excitation, which perfectly matches the emission of blue InGaN light-emitting diodes. For Ce(3+)/Li(+)-codoped Sr(3)Si(2)O(4)N(2), one excitation band is in the UV range (280-350 nm) and the other in the UV blue range (380-420 nm), which matches emission of near-UV light-emitting diodes. Emission of Sr(3-2x)Si(2)O(4)N(2):xCe(3+),xLi(+) shows a asymmetric broad band peaking at ~520 nm. The long-wavelength excitation and emission of Eu(2+) and Ce(3+)/Li(+)-doped Sr(3)Si(2)O(4)N(2) make them attractive for applications in phosphor-converted white light-emitting diodes.     

Tunable full-color-emitting Ca3Sc2Si3O12:Ce3+, Mn2+ phosphor via charge compensation and energy transfer

A tunable full-color-emitting Ca(3)Sc(2)Si(3)O(12):Ce(3+), Mn(2+) (CSS:Ce(3+),Mn(2+)) phosphor is obtained by addition of doped ions as charge compensation. White LEDs with high R(a) (> 90) are achieved using the single CSS:Ce(3+),Mn(2+) phosphor.     

Photoluminescence enhancement of PEG-modified YAG:Ce3+ nanocrystal phosphor prepared by glycothermal method

Y3Al5O12:Ce3+ (YAG:Ce3+) nanocrystals were synthesized in 1,4-butylene glycol (BG) with and without poly(ethylene glycol) (PEG) by the glycothermal method. The internal quantum efficiency of the photoluminescence (PL) corresponding to the 5d --> 4f transition of Ce3+ in the YAG:Ce3+ nanocrystal increased from 21.3 to 37.9% by addition of PEG, while no appreciable change in the primary particle size, the crystallite size, and the lattice distortion was recognized by transmission electron microscopy and X-ray diffractometry. The thermogravimetry-differential thermal analysis, Fourier transform infrared absorption spectroscopy and 1H --> 13C cross-polarization magic angle spinning nuclear magnetic resonance (CP-MAS NMR) confirmed the preferential coordination of PEG to the YAG:Ce3+ nanocrystal. 27Al single-pulse excitation MAS NMR reveals that the ratio of the 4-fold coordination site to the 6-fold coordination site increased from 0.53 to 0.72 by addition of PEG. We conclude that the surface modification of the YAG:Ce3+ nanocrystal by PEG induces the surface passivation, the prevention of the oxidation of Ce3+ to Ce4+, the promotion of the incorporation of Ce3+ into YAG and the local structural rearrangement, resulting in the PL enhancement.     

Luminescence and microstructures of Eu(3+)-doped Ca9LiGd(2/3)(PO4)7

A red-emitting phosphor, Eu(3+)-doped Ca(9)LiGd(2/3)(PO(4))(7), was synthesized by the conventional high-temperature solid-state reaction. X-ray powder diffraction (XRD) analyses confirmed the pure crystalline phase of Whitlockite-type structure. The excitation spectra of Eu(3+) doped Ca(9)LiGd(2/3)(PO(4))(7) were measured in the VUV and UV region indicating an efficient energy transfer process from the host and Gd(3+) to Eu(3+) ions. Upon excitation with VUV and UV radiation, the phosphor showed strong red emission around 611 nm corresponding to the forced electric dipole (5)D(0)→(7)F(2) transition of Eu(3+) ions. The VUV- and UV-excited luminescence spectra of Ca(9)LiGd(2/3)(PO(4))(7):Eu(3+) together with the dependence of the integrated emission intensities on the doping levels were investigated. The Eu(3+) ions were investigated by a tunable laser as an excitation source. The excitation spectra of (7)F(0)→(5)D(0) transitions suggest that there are two families of inequivalent sites for Eu(3+) in this host. The concentration quenching and crystallographic site-occupancy of Eu(3+) ions in Ca(9)LiGd(2/3)(PO(4))(7) host were discussed on the basis of the site selective excitation and emission spectra, the luminescence decay and its crystal structure.