Long persistent and photostimulated luminescence properties of Sr2Al2SiO7：Eu2＋/Tm3＋ phosphors A series of Sr2Al2SiO7 phosphors with fixed Eu2+ concentration and various Tm3+ concentrations were synthesized via a high temperature solid state reaction. The structure and luminescence properties of the samples were characterized by X-ray powder diffraction(XRD), photoluminescence(PL) spectra, decay curves, thermoluminescence(TL) glow curves as well as the photostimulated luminescence(PSL) spectra. Sr2Al2 Si O7:Eu2+,Tm3+ phosphors exhibited strong green phosphorescence and photostimulated luminescence originating from 4f65d1–4f7 transition of Eu2+ after ultraviolet light stimulation. Deep traps were found by analyses on the phosphorescence decays and thermoluminescence spectra. It was also found that with increasing the time interval between UV excitation turn-off and stimulation turn-on, the photostimulated luminescence became stronger. This phenomenon resulted from the fact that the captured electron was retrapped by the deep traps. Compared with the Tm3+-free sample, it was found that the PSL intensity was strongly enhanced in Tm3+ codoping samples.
Tunable luminescence of Ce3＋/Li＋,Eu2＋ co-doped Ca4（PO4）2O phosphor for white light emitting diodes Phosphors Ca4(PO4)2O:Ce3+/Li+,Eu2+ were prepared by solid state reaction successfully, and characterized by X-ray diffraction, UV-Vis spectrometer and photoluminescence spectrometry. The as-prepared phosphors exhibited strong absorption in the UV-visible region and dual-emission bands centered at approximately 460 and 630 nm. Energy transfer from Ce3+ to Eu2+ was also observed. By varying the excitation wavelength, these new phosphors exhibited tunable emissions from blue to white and then to yellow, making them potential candidates as UV-convertible phosphors for white light emitting diodes.
Synthesis and luminescence properties of white-light-emitting phosphor SraGdNa（PO4）3F：Dy3＋ Novel Sr3Gd(1–x)DyxNa(PO4)3F(SGNP:x Dy3+, x=0.01, 0.03, 0.05, 0.07, 0.09, 0.11) phosphors were synthesized by a conventional solid-state reaction method at different compositions. The X-ray diffraction results confirmed that the as-prepared samples were pure phase. The phosphor had two intense emission bands centering at 481 and 574 nm which could be attributed to the 4F9/2→6H15/2 transition and the 4F9/2→6H13/2 transition, respectively. The chromaticity coordinates(x, y) of this phosphor were calculated to be(0.3054, 0.3354) located on the region of white light region when excited at 350 nm. The concentration quenching mechanism of Dy3+ was ascribed to the dipole-dipole interaction. The current research suggested that the phosphors might be potential application in the w-LEDs.
Synthesis and luminescence properties of bluish-green emitting K2MgSiaO8：Eu2＋ phosphor Eu2+-doped K2 Mg Si3O8 phosphors were synthesized by conventional solid-state reaction method. The phase formation of as-prepared samples was characterized by X-ray powder diffraction. The luminescence properties were investigated by the photoluminescence excitation and emission spectra, decay curve and CIE coordinates. The phosphor showed bluish-green emission centered at 460 nm under the excitation of UV and near UV light with the wavelength range of 250–430 nm. Two Eu2+ emission centers existed in the K2 Mg Si3O8:Eu2+ phosphor according to the luminescence spectra and the decay curves. The critical quenching concentration of Eu2+ doping was determined to be 3.0 mol.% and the concentration quenching mechanism was dipole-dipole interactions between Eu2+ ions. These results suggested that K2 Mg Si3O8:Eu2+ was a potential bluish-green phosphor candidate for white UV-LED.
Effects of Eu3＋ and Dy3＋ doping or co-doping on optical and structural properties of BaB2Si2O8 phosphor for white LED applications A series of Eu3+ and Dy3+ doped/co-doped as well as un-doped BaB2Si2O8 phosphors were synthesized via solid state reaction method. The PL result showed typical blue and green emission from Dy3+ and red emission from Eu3+. The f-f transitions involving the lanthanide ions along with dopant site occupancy were discussed thoroughly. Phonon assisted energy transfer process was observed from Eu3+ to Dy3+, which enhanced the emissions of Dy3+. Combinations of the emissions from Eu3+ and Dy3+ showed a possible white to red tuneable emission on the CIE diagram. The white warmth emissions of the phosphor were revealed to be adjustable through designing the dopant concentration and excitation wavelengths. An unusual energy transfer that originated from Eu3+ to Dy3+ was also discovered and the energy transfer mechanism was discussed. Proposed energy transfer mechanism was investigated using luminescence decay lifetime. All the phosphor exhibited efficient excitation in the UV range which matched well with the emissions from Ga N-based LED chips. This presented the Ba B2Si2O8 phosphor as a promising candidate for white LED applications. The effects of doping on the structural properties and the optical band gap of Ba B2Si2O8 phosphor were also discussed in this study.
Preparation, structure and luminescence properties of deep red phosphors SrSiNe：Eu2＋ This paper reported a novel synthetic route to Eu2+ doped SrSiN2 deep red phosphors for white light-emitting diodes. A series of single-phased and high-efficiency Sr Si N2:Eu2+ red phosphors were synthesized based on this method. Their structure, morphology, luminescence, quantum efficiency(QE) and thermal quenching properties were investigated and compared with those of Sr Si N2: Eu2+ prepared by the conventional route. It was found that the addition of a small amount of Si3N4 could promote the formation of Sr Si N2 from Sr2Si5N8 phase. A highly uniform rod-shaped morphology was obtained based on this method. The X-ray powder diffraction and the Rietveld refinement analysis identified the preferential crystalline orientation growth. Under the blue light excitation, Eu2+ doped Sr Si N2 phosphors showed excellent optical properties. Compared with those prepared by the conventional approaches, the external QE of Sr Si N2:Eu2+ phosphor was greatly improved, allowing it a promising phosphor for white LEDs.
Photoluminescence of Tb-doped MgAI-LDHs depending on phase transition caused by annealing
A novel visible-light Nd-doped CdTe photocatalyst for degradation of Reactive Red 43： Synthesis, characterization, and photocatalytic properties Novel high-efficiency visible-light-sensitive Nd-doped Cd Te nanoparticles were prepared with various doping concentrations of neodymium ion by a facile hydrothermal method. The reaction products were analyzed via X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), photoelectron spectroscopy(XPS), and UV-Vis diffuse reflectance spectroscopy techniques. Red shift was seen in the absorption band edge peak in the UV-Vis absorbance spectrum with increasing Nd content. The XRD and XPS results confirmed that Nd ions successfully replaced Cd atoms and were incorporated into the crystal lattice of Cd Te. SEM and TEM images indicated spherical structure and high crystallinity. Even at a very low Nd/Cd Te molar ratio of 2 mol.%, Nd doping could greatly enhance the photocatalytic activity of Cd Te. The photocatalytic activity of Nd-doped Cd Te nanoparticles was evaluated by monitoring the decolorization of RRed 43 in aqueous solution under visible-light irradiation. The color removal efficiency of Nd0.08Cd0.92 Te and pure Cd Te were 83.14% and 14.32% after 100 min of treatment, respectively. Among different amounts of the doping agent, 8 mol.% Nd indicated the highest decolorization. The presence of radical scavengers such as Cl-, CO32-, SO42-, and buthanol was found to reduce the decolorization efficiency.
Copper-cerium oxides supported on carbon nanomaterial for preferential oxidation of carbon monoxide The CuxO-Ce [email protected], CuxO-Ce O2/MWCNTs-Co and CuxO-Ce O2/MWCNTs-Ni catalysts were prepared by the impregnation method and characterized by transmission electron microscopy, scanning electron microscopy, X-ray powder diffraction, H2-temperature programmed reduction and N2 adsorption-desorption techniques. It was found that the Fe nanoparticles were encapsulated into the multi-layered carbon nanospheres(CNSs). However, the multi-wall carbon nanotubes(MWCNTS) were generated on the Co/Al2O3 and Ni/Al2O3 precursor. The addition of carbon nanomaterial as supports could improve structural properties and low-temperature activity of the Cu O-Ce O2 catalyst, and save the used amount of metal catalysts in the temperature range with high selectivity for CO oxidation. The copper-cerium oxides supported on carbon nanomaterial had good resistence to H2 O and CO2.
Effect of niobium addition on magnetization reversal behavior for SmCo-based magnets with TbCu7-type structure The effect of Nb addition on the microstructure and magnetic properties of nanocrystalline Sm(CobalNbxZr0.02)7 permanent magnet were investigated. The magnetization reversal behavior for ball milled Sm(CobalNbxZr0.02)7 samples with high coercivity was investigated by analyzing hysteresis curves and recoil loops of demagnetization curves. Nb addition proved to result in relevant improvement in the magnetic properties, especially in the coercivity Hc. It was shown that the magnetic properties of Sm(CobalNbxZr0.02)7 nanocrystalline magnets were improved by an additional 0.06 at.% Nb. In particular, Hc was improved from 602 to 786 k A/m at room temperature. The maximum value of the integrated recoil loops area for 0.06 at.% Nb-doped samples of 1.81 k J/m3 was much lower than that of the Nb-free sample, which could be explained by a smaller recoverable portion of the magnetization remaining in the Nb-doped sample when the applied field was below the coercivity Hc. The nucleation field Hn for irreversible magnetization reversal of the magnetically hard phase were calculated by analyzed in terms of the ΔMirrev-H curve and the Kondorsky model.
First-principles study of the electronic structure of a superstoichiometric rare earth dihydride GdH2.25
Effect of solution pH value changes on fluorescence intensity of magnetic-luminescent [email protected]：Eu3＋ nanoparticles In this paper, bifunctional [email protected]:Eu3+ core-shell nanoparticles with both magnetic and fluorescent properties were synthesized through a urea homogeneous precipitation(UHP) method. Particular emphasis was placed on investigating the influence of the solution p H value on the photoluminescence of the core-shell nanocomposites. It showed that the samples treated at the solution of p H=3.0 had the highest luminescence due to the enhanced crystallinity and size uniformity of nanoparticles. The [email protected]:Eu3+ nanocomposites exhibited an almost spherical shape with a mean diameter of 60 nm, and had strong red emissions of Eu3+ at 612 nm as well as good magnetization with the saturation magnetization of 1.29 emu/g. It thus indicated that the core-shell nanocomposites investigated has great potential in biomedical applications.
Adsorption of rare earth ions using carbonized polydopamine nano carbon shells Herein we reported the structure effects of carbon nano-shells prepared by the carbonization of polydopamine for the adsorption of rare earth elements(REEs) for the first time. Solid carbon spheres, 60 nm carbon shells and 500 nm carbon shells were prepared and evaluated for adsorption and desorption of REEs. The adsorption performance of carbon nano-shells for REEs was far superior to the solid carbon spheres. In addition, the effect of acidity on the adsorption and desorption properties was discussed. The good adsorption performance of the carbon nano-shells could be attributed to their pore structure, specific surface area, and the presence of both amine and carbonyl groups from the grafted dopamine.
Enhancing extraction ability by rational design of phosphoryl functionalized ionic liquids and mechanistic investigation on neodymium （III） extraction Four ionic liquids(ILs): 3-(diethoxyphosphoryl)propyl triphenylphosphinium hexafluorophosphate [Ph3PC3P(OEt)2][PF6](IL-1), 3-(ethoxyphenylphosphoryl)propyl triphenylphosphinium hexafluorophosphate [Ph3PC3PPh(OEt)][PF6](IL-2), 3-(diphenylphosphoryl)propyl triphenylphosphinium hexafluorophosphate [Ph3PC3P(Ph)2][PF6](IL-3), and 3-(diethoxyphosphoryl)propyl triphenylphosphinium bis(trifluoromethanesulfonyl)imide [Ph3PC3P(OEt)2][NTf2](IL-4) were synthesized and characterized by IR and 31 P, 1H, 13 C NMR spectroscopy. The liquid-liquid extraction of neodymium(III) by these phosphorus functionalized ionic liquids(PFILs) diluted with common room temperature ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C6mim][NTf2] was studied. The extraction percentage of Nd(III) was measured as a function of various parameters, such as the initial p H of aqueous phase, equilibrium time, temperature, and concentration of PFIL extractant. The influence of the nature of diluents and salting-out reagents on extraction was also investigated. The results indicated that the extraction process was exothermical and the extraction percentage of Nd(III) by IL-1 was the highest among the PFILs investigated. A possible metal complexation mechanism was proposed for the present PFIL/IL extraction system. And the loaded Nd(III) ions by PFIL could be stripped completely from the ionic liquid phase by 1 mol/L nitric acid.
Solvent extraction-sepacation of La（Ⅲ）, Eu（Ⅲ） and Er（Ⅲ） ions from aqueous chloride medium using carbamoyl-carboxylic acid extractants N,N-dibutyldiglycol amic acid(HLI) and N,N-dioctyldiglycol amic acid(HLII) were synthesized and characterized by conventional spectroscopic methods. These molecules were examined as extractants for extraction-separation of La(III), Eu(III) and Er(III), as representative ions of light, middle and heavy rare earths, from aqueous chloride solutions. The analysis of the extraction equilibria revealed that the extracted species of lanthanum and europium ions by both of the extractants had a 1:3 metal to ligand ratio. It was suggested that erbium ions were extracted into the organic phase via the formation of Er(LI or II)2Cl complexes. The effect of the organic diluents on the extraction-separation efficiency of the studied rare earths by HLI and HLII was investigated by comparing the results obtained in dichloromethane and carbon tetrachloride. Regardless to the diluent used, the order of selectivity presented by the investigated extractants was Er(III)>Eu(III)>La(III). It is noteworthy that, a significant enhancement in separation of the studied rare earths by the extractants was achieved in their competitive extraction experiments with respect to that obtained in single component extraction experiments. Applicability of the extractants for the removal of rare earth ions from spent Ni-MH batteries was tested by removal of La(III), Eu(III) and Er(III) ions from simulated leach solution of such batteries.
Removal of trivalent samarium from aqueous solutions by activated biochar derived from cactus fibres 从水的答案关于三价的钐(Sm (III )) 的吸着从仙人掌属植物 Ficus Indica 获得的激活的 biochar 纤维的效率被批实验调查。各种各样的物理化学的参数的效果(例如 pH，起始的金属集中，离子的力量，温度和接触时间) 在 Sm (III ) 上，吸附被学习，表面种类被 FTIR 光谱学描绘在以前并且在 lanthanide 吸着以后。试验性的结果证明激活的 biochar 纤维在酸的答案为 Sm (III ) 拥有了非凡的吸着能力(q 最大 =90 g/kg， pH 3.0 ) 并且近中立的答案(q 最大 =350 g/kg， pH 6.5 ) 。这与表面被归因于钐建筑群的形成羧基的一半，在简历吸着剂的薄片状的结构上的高密度可得到。
First-principles investigation of mechanical and electronic properties of LaAg5 Laves phase under pressure The effects of applied pressure on the structural, mechanical, and electronic properties of LaAg5 compound were investigated employing the first-principles method based on the density functional theory. The mechanical results demonstrated that bulk modulus, shear modulus and Young’s modulus presented the linearly increasing dependences on the external pressure; the B/G and Poisson’s ratio indicated that La Ag5 compound was a ductile material with central forces in interatomic under pressure from 0 to 40 GPa; the universal anisotropic index was performed to investigate the elastic anisotropic of La Ag5. Additionally, the pressure dependence of the density of states and Mulliken charge were also discussed. The bonding characterization in La Ag5 was composed of metallic, covalent and ionic. The metallic component was derived from free-electron transferring from Ag-s and Ag-d to Ag-p, and from La-s to La-d. The ionic component was due to the charge movement from La to Ag. The covalent was owing to Ag-p-La-d bonding hybridization and Ag-s-Ag-p in the Ag atomic chains. The covalent and ionic bonds were stronger under pressure but there was no significant change in metallic nature.
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