Luminescence of Eu3+ and Eu2+ in the new BaLnB9O16 borates (Ln = rare earth)

The luminescence of Eu³⁺ in the borates BaLnB₉O₁₆ (Ln = La, Gd and Y) has been investigated. Under UV excitation the Eu³⁺-activated lanthanum and gadolinium compounds show a bright red luminescence at room temperature, whereas the Eu³⁺-activated yttrium borate is characterized by a red-orange luminescence which indicates a change in the symmetry of the rare earth ion sites. As a consequence of the high energy of the charge transfer band the Eu³⁺ emission has a high efficiency under 253.7 nm excitation, a characteristic favorable for lighting applications. The sensitization of the Eu³⁺ emission by Bi³⁺ has been examined. Energy transfer from Bi³⁺ to Eu³⁺ is observed, but in presence of bismuth the efficiency of excitation through the Eu³⁺ charge transfer band is reduced. The luminescence of Eu²⁺ has also been studied. Eu²⁺-activated BaGdB₉O₁₆ shows an intense blue emission band under UV excitation.     

Luminescence of Sm2+ in strontium haloborates

The luminescence properties of Sm²⁺ in Sr₂B₅O₉R (R=Cl, Br) have been studied and compared with those in SrB₄O₇. In the range from 80 to 300 K the emission of Sm²⁺ in Sr₂B₅O₉R is predominantly due to the 4f⁵5d → 4f⁶ transition, while SrB₄O₇ : Sm²⁺ shows a very efficient emission of the 4f⁶ → 4f⁶ type. Differences in the luminescence of Sm²⁺ in the strontium haloborates and tetraborate are discussed.     

VUV sensitization of Mn2+ emission by Tb3+ in strontium aluminate phosphor

The luminescence properties of green emitting strontium aluminate phosphor SrAl₁₂O₁₉ doped and co-doped with Mn²⁺ and Tb³⁺ were studied using synchrotron radiation. It is shown that Tb³⁺, exhibiting a strong absorption band in the vacuum-ultraviolet (VUV), provides sensitisation of Mn²⁺ emission in this host. The observed sensitisation effect of the Tb–Mn pair can be used for improving the efficiency of VUV phosphors.     

Defect stabilization in ZnO nanorods by Mg2+ doping

Luminescent ZnO and Zn0.95Mg0.05O nanorods with length around 0.5 to 3 microm and diameter 100-150 nm were prepared by a facile solvothermal method. On hydriding at room temperature, a change of morphology from nanorods with aspect ratio 5-10 to particles of sizes 100 nm has been observed in both ZnO and Zn0.95Mg0.05O. While hydrided Zn0.95Mg0.05O showed an enhanced defect related green emission, the same got suppressed in hydrided ZnO. Even though it is observed that zinc vacancies are present in both as prepared ZnO and Zn0.95Mg0.05O, luminescence studies indicate that zinc vacancies get stabilized in Zn0.95Mg0.05O on hydrogenation.     

Accommodation of niobium and cerium variable valence cations in the crystal lattice of the Ln 2 3+ Ti 2 4+ O7 (Ln = Dy, Yb) pyrochlores

We have studied the accommodation of niobium and cerium variable valence cations in the Ln ₂ ³⁺ Ti ₂ ⁴⁺ O₇ (3+/4+) (Ln = Dy, Yb) pyrochlores in air and in a 5% H₂ + 95% Ar reducing atmosphere. The (Dy_0.8Ca_0.1Ce_0.1)₂Ti₂O_{7 ? δ} and (Yb_0.8Tb_0.1Ca_0.1)₂[Ti_1?x Nb _x ]₂O_{7 ? δ} (x = 0–0.3) oxygen ion conducting solid solutions were synthesized through coprecipitation followed by heat treatment in air for 4 h at temperatures of 1400 and 1550°C, respectively. According to X-ray photoelectron spectroscopy (XPS) data, the valence state of the niobium in the (Yb_0.8Tb_0.1Ca_0.1)₂[Ti_1?x Nb _x ]₂O_{7 ? δ} (x = 0.05, 0.1) solid solutions is 4+ and, hence, isovalent niobium substitution for titanium takes place. During synthesis in air, the titanium sublattice of the (Yb_0.8Tb_0.1Ca_0.1)₂[Ti_1?x Nb _x ]₂O_{7 ? δ} pyrochlores is stable when the Nb⁴⁺ content does not exceed 10% (x = 0.1). According to conductivity data for the high-conductivity material (Yb_0.8Tb_0.1Ca_0.1)₂[Ti_0.95Nb_0.05]₂O_6.9 at low oxygen partial pressures, there is no reduction of pentavalent niobium and no increase in electronic conductivity, which is supported by XPS results that only Nb⁴⁺ is present in the solid solution. In pyrochlore-like (Dy_0.8Ca_0.1Ce_0.1)₂Ti₂O_{7 ? δ} synthesized in air at 1400°C, the dysprosium site contains both tri- and tetravalent cerium, as supported by conductivity measurements under reducing conditions. The Ce⁴⁺ + e → Ce³⁺ reduction process led to a change in the color and disintegration of the sample when the oxygen partial pressure was reduced. In the 3+/4+ A₂B₂O₇ pyrochlores, variable valence cations on the A site (eightfold coordination) more readily participate in redox processes than do those on the B site (sixfold coordination).     

Study on UV excitation properties of Y2O3:Ln3+ (Ln = Eu3+ or Tb3+) luminescent nanomaterials

Y2O3:Ln3+ (Ln = Eu or Tb) nanocrystals with different Ln3+ doping concentrations and average sizes were prepared by chemical self-combustion. The corresponding bulk materials with various doping concentrations were obtained by annealing the nanomaterials at high temperature. The emission spectra, excitation spectra, and X-ray diffraction spectra were used in this study. It was found that the charge transfer band of Y2O3:Eu3+ red-shifted as particle size decreased, and the charge transfer band in the 5-nm particles obviously broadened toward the long wavelength. It was also found that the profile of excitation spectra corresponding to the 4f5d (4f8 --> 4f(7)5d1) transition changed a lot with the variation of the particle size. The dependence of the excitation spectra of Y2O3:Ln3+ on particle size was investigated.     

蓝色长余辉发光材料Sr2MgSi2O7:Eu2+,Ln3+的合成和性质

采用凝胶-燃烧法合成了系列稀土掺杂的Sr2MgSi2O7:Eu2 0.02,Ln3 0.04(Ln=La,Ce,Nd,Sm,Gd,Tb,Dy,Ho,Er,Tm)蓝色长余辉发光材料,用X射线粉末衍射(XRD)、扫描电镜(SEM)、荧光分光光度计等对合成产物进行了分析和表征.结果表明:掺杂了不同稀土离子的Sr2MgSi2O7:Eu2 ,Ln3 的晶体结构均为四方晶系结构;其激发、发射光谱的峰形、峰位基本无变化,激发光谱为一宽带,最大激发峰位于402nm处,次激发峰位于415nm处,与高温固相法制得的样品相比,激发峰发生了明显的红移;发射光谱也为一宽带,最大发射峰位于468nm附近,是由典型的Eu2 的4f5d-4f跃迁导致的,不同之处在于其激发光谱、发射光谱强度与余辉性质有所差别,其中Dy3 是最理想的共掺杂稀土离子,Sr2MgSi2O7:Eu2 ,Dy3 的亮度最高、余辉时间最长,可达5h以上;而Sr2MgSi2O7:Eu2 ,Sm3 的发光强度最低,余辉时间最短.     

Efficient stabilization of Cu+ ions in phosphate glasses via reduction of Cu2+ by Sn2+ during ambient atmosphere melting

Glasses containing substantial amounts of well-dispersed luminescent Cu⁺ ions are attractive materials for applications in solid-state lighting, photonic waveguides, and solar cells. Thus far, coming across a simple yet effective method for the preparation of such has remained elusive given the instability of Cu⁺ relative to Cu²⁺, especially for syntheses carried out under the oxidizing air atmosphere. In this work, high concentrations of monovalent copper ions are shown to be successfully incorporated in a high-solubility phosphate glass matrix by a simple melt-quench method. The traditional Cu²⁺ spectrophotometric analysis commonly utilized for liquid solutions is proposed herein for the solid-state material to estimate the reduction efficiency of Cu²⁺ during the material preparation process. Reproducibly, the use of relatively large quantities of copper(II) oxide with equal amounts of reducing agent tin(II) oxide (up to 20 mol%), together with the use of sucrose to assist as antioxidant during melting in air atmosphere, yields high-reduction efficiencies estimated at 98 %. Along with the optical absorption analysis, photoluminescence spectroscopy is employed in evaluating the emission properties of the glasses in connection to the Cu⁺ ions. Further, solid-state ³¹P nuclear magnetic resonance spectroscopy reveals the structural features of the glasses that support the remarkable stabilization of the Cu⁺ ions.     

Structure and electrical conductivity of Ln2+x Hf2−x O7−x/2 (Ln = Sm-Tb; x = 0, 0.096)

Data are presented on the evolution of the pyrochlore structure in the Ln_2+x Hf_2?x O_7?δ (Ln = Sm, Eu; x = 0.096) solid solutions and Ln₂Hf₂O₇ (Ln = Gd, Tb) compounds prepared from mechanically activated oxide mixtures. Sm_2.096Hf_1.904O_6.952 is shown to undergo pyrochlore-disordered pyrochlore-pyrochlore (P-P1-P) phase transformations in the temperature range 1200–1670°C. The former transformation leads to a rise in 840°C conductivity from 10^?4 to 3 × 10^?3 S/cm in the samples synthesized at 1600°C, and the latter leads to a drop in 840°C conductivity to 6 × 10^?4 S/cm in the samples synthesized at 1670°C. The reduction in the conductivity of Sm_2.096Hf_1.904O_6.952 is accompanied by the disappearance of the assumed superstructure. In the range 1300–1670°C, Eu_2+x Hf_2?x O_7?δ (x = 0.096) and Ln₂Hf₂O₇ (Ln = Gd, Tb) have a disordered pyrochlore structure. The highest 840°C conductivity is offered by Eu_2.096Hf_1.904O_6.952, Gd₂Hf₂O₇, and Tb₂Hf₂O₇ synthesized at 1670°C: 7.5 × 10^?3, 5 × 10^?3, and 2.5 × 10^?2 S/cm, respectively.     

Upconversion nanotubes with tunable fluorescence properties based on Gd2 O2 S:Ln3+ (Ln3+ = Yb3+, Er3+) and derivatives for photodynamic therapy

In this study, Gd₂ O₂ S:Ln³⁺ (Ln³⁺  = Yb³⁺, Er³⁺) upconversion nanotubes (UCNTs) were synthesised by using Gd(OH)₃ :Ln³⁺ (Ln³⁺  = Yb³⁺, Er³⁺) nanotubes as the template. The luminescent and biological properties of Gd₂ O₂ S:Ln³⁺ (Ln³⁺  = Yb³⁺, Er³⁺) UCNTs, along with photodynamic therapy (PDT) applications of the Gd₂ O₂ S:8%Yb³⁺, 2%Er³⁺ UCNT–Ce6 (chlorin e6) nanocomposites, were systematically studied. The resultant UCNTs showed excellent biocompatibility with human retinal pigment cells (ARPE‐19) even after a prolonged incubation time of 72 h, and could be used as luminescent probes. Microscopic imaging revealed that the UCNTs existed mainly in cytoplasm. PDT studies on the Gd₂ O₂ S:8%Yb³⁺, 2%Er³⁺ UCNT–Ce6 nanocomposites indicate that the growth of the tumour (cell) could be inhibited dramatically when it was injected (incubated) with Gd₂ O₂ S:8%Yb³⁺, 2%Er³⁺ UCNT–Ce6 nanocomposites under the irradiation of 980 nm laser.Inspec keywords: biomedical materials, nanofabrication, tumours, cellular biophysics, nanomedicine, eye, biomedical optical imaging, nanocomposites, gadolinium compounds, ytterbium, photodynamic therapy, fluorescence, erbium, laser beam effectsOther keywords: luminescent properties, biological properties, photodynamic therapy applications, UCNT–Ce6 nanocomposites, upconversion nanotubes, tunable fluorescence properties, biocompatibility, human retinal pigment cells, microscopic imaging, PDT studies, tumour, laser irradiation, wavelength 980.0 nm, time 72.0 hour, Gd₂ O₂ S:Yb,Er     

Luminescence properties of Ce3+ and Tb3+ in a new family of boron-rich alkaline earth rare earth borates

A novel family of borates formulated MLnB₉O₁₆ (M = SrorBa, Ln = rareearth), is reported. Under UV excitation BaLaB₉O₁₆:Ce³⁺ shows an emission band peaking at 350 nm. Its quantum efficiency is almost independent of Ce concentration. Energy transfer from Ce³⁺ to Tb³⁺ is efficient for the composition BaCe_1−xTb_xB₉O₁₆ when x exceeds 0.3, owing to the overlap of the Ce³⁺ emission band with the most intense f-f Tb³⁺ absorption lines. The Tb³⁺ emission sensitized by Ce³⁺ shows a very intense green color; its stability in a mercury vapor lamp has been checked.     

掺锶对羟磷灰石细胞毒性的影响

探讨掺锶对羟磷灰石细胞毒性的影响.合成含锶量分别为1%、5%、10%、100%的锶磷灰石陶瓷,应用MTT法及流式细胞仪法评价其细胞毒性,以纯羟磷灰石和空白培养液作对照.各实验组细胞毒性评级均为0级或1级,无明显细胞毒性,但随着掺锶量的增加细胞毒性有增大趋势;流式细胞仪法证实,锶羟磷灰石无显著细胞毒性.锶磷灰石没有明显细胞毒性,掺锶对羟磷灰石细胞毒性影响较小,锶磷灰石可能具有良好的生物相容性.     

Phosphors based on NaZr2(PO4)3-type calcium and strontium phosphates activated with Eu2+ and Sm3+

Ca_0.5Zr₂(PO₄)₃:Eu²⁺, Sr_0.5Zr₂(PO₄)₃:Eu²⁺, and Ca_0.5Zr₂(PO₄)₃:Eu²⁺, Sm³⁺ orthophosphates prepared through precipitation using sol-gel processes are analogs of NaZr₂(PO₄)₃ (NZP) and crystallize in space group R $\bar 3$ . Their crystallographic parameters determined by X-ray diffraction are consistent with the interatomic distances extracted from EXAFS data. Their luminescence spectra obtained under excitation in the range 300?C400 nm contain emission bands between 425 and 525 nm. Substitution of the larger sized cations Eu²⁺ and Sm³⁺ for Ca²⁺ shifts the emission bands to shorter wavelengths and reduces their width because of the decrease in the effect of the crystal field. Analysis of the spectra indicates that Eu²⁺ occupies two types of crystallographic sites (independent interstitial sites of different sizes and shapes in the NZP framework structure). Codoping with Eu and Sm has ensured luminescence with chromaticity coordinates approaching those of white light: (x = 0.27, y = 0.34).     

Electrical properties of Ln2Mo2O7 pyrochlores (Ln=SmYb,Y)

Cubic oxide pyrochlores, Ln₂Mo₂O₇, Ln=SmYb,Y, (Nd_1?xA_x), A=Er and Yb; 0 < x < 1.0, have been synthesized and electrical properties were examined in the range 77-600K. Semiconductor behavior is observed for Ln=EuYb, Y but the resistivity and E_a are low. Sm₂Mo₂O₇ and Nd_1?xYb_xMo₂O₇ (0.05 ≤ x ≤ 0.1) exhibit semimetallic or metallic behavior. The mechanism of conduction in these compounds is explained on the basis of band model proposed by Sleight et al.     

Ln(Ln=Gd3+,Cu+,Sm3+,Dy3+)助激活的Ca8Mg(SiO4)4Cl2:Eu2+荧光粉的光谱特性和Eu2+的格位计算

采用高温固相法合成了掺杂Ln(Ln=Gd3+,Cu+,Sm3+,Dy3+)作助激活离子的氯硅酸镁钙荧光粉.通过X射线衍射(XRD)对Ca8Mg(SiO4)4Cl2:Eu2+,Ln进行了表征.结果表明Ln的共掺杂并没有影响基质晶体的面心立方结构.所合成的荧光粉发射峰值位于507nm的绿光区.激发光谱在330~430nm之间均有较强吸收,与紫光InGaN芯片(395nm)相匹配.掺杂Ln作助激活荆增强了荧光粉的发光强度.借助Uitert经验公式计算出Eu2+在Ca8Mg(SiO4)4Cl2基质中占据八配位Ca(Ⅱ)格位.     

燃烧法合成铕镝掺杂铝酸锶长余辉发光材料的研究

以尿素和硝酸盐溶液为反应介质 ,在 6 0 0℃下用燃烧法一次制备出了Eu2 ,Dy3 掺杂的铝酸锶 (SrAl2 O4 )磷光体。用SEM、XRD研究了所得磷光材料的形态、粒度和物相组成 ,用荧光分光光度计测定了磷光材料的发光性能。结果表明 ,SrAl2 O4 ∶Eu2 ,Dy3 磷光材料的晶体结构属于单斜晶系结构。制备产物在 5 2 0nm处有很强的发射峰 ,它的激发光谱是激发峰峰值 2 90nm的宽带激发。制备产物的形貌呈疏松多孔状 ,晶粒形状为针状 ,长度有 2 0 0nm左右 ,直径在 80nm以下。并探讨了该材料发光性能的影响因素     

Synthesis of LaF3: Yb3+ ,Ln3+ nanoparticles with improved upconversion luminescence

Yb³⁺/Er³⁺ and Yb³⁺/Tm³⁺ co-doped LaF₃ nanoparticles with upconversion luminescence properties were prepared via the co-precipitation method, followed by heat treatment at different temperatures in the range of 180°C to 600°C. We investigated the influence of heat treatment temperatures on the size, morphology, and upconversion luminescence intensity of the nanoparticles. Significant increases of the particle size and upconversion luminescence intensity of the nanoparticles were observed with increasing heat treatment temperature. The upconversion mechanism of the LaF₃:Yb³⁺,Er³⁺ and LaF₃:Yb³⁺,Tm³⁺ nanoparticles was also discussed.     

Self-assembled peanut-like Ln3+ (Ln = Tb, Sm, Eu) doped NaLa(WO4)2: phase control and its relevance to luminescence modification

Ln3+ (Ln = Tb, Sm, Eu) doped NaLa(WO4)2 peanuts were successfully self-assembled by a facile EDTA assisted hydrothermal treatment. EDTA played critical roles in the phase and morphology control, which regulated the phase transformation from monoclinic La2(WO4)3 flowers to tetrahedral NaLa(WO4)2 peanuts. La2(WO4)3:Tb3+ exhibited two broad excitation bands at 280 and 340 nm, which are related to the normal and perturb sites of WO4(2-). However, the excitation band for NaLa(WO4)2:Tb3+ shifted to near ultraviolet region and showed only one broad excitation band originating from perturb sites. Under ultraviolet excitation, La2(WO4)3:Tb3+ displayed green light and NaLa(WO4)2:Tb3+ showed blue-green light consisting of WO4(2-) self-activated blue emission and the characteristic Tb3+ emission. It can be clearly seen that the blue emission of WO4(2-) was not sufficiently quenched in NaLa(WO4)2 as that in La2(WO4)3, because the distortions of crystalline lattice for NaLa(WO4)2 may alter the energy migration processes. When doping with Sm3+ and Eu3+, NaLa(WO4)2 peanuts exhibited white color emission which may find practical applications in solid state lighting devices.     

Excitation and spectral dependence of the rise and decay time responses of Eu2+- and Dy3+-doped strontium aluminates

Journal of Materials Science: Materials in Electronics - In this paper, we study the phosphorescence rise and decay time responses of Eu2+- and Dy3+-doped strontium aluminates prepared by different...