Eu3+ ion-doped LaPO4 nanowires or nanorods have been successfully synthesized by a simple hydrothermal method. The influence of varying the hydrothermal
and subsequent sintering conditions on the morphology and structure of the LaPO4 host has been investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). For comparison, the Eu3+ ions were also doped into monoclinic monazite LaPO4 nanoparticles and perovskite LaAlO3 nanoparticles. The relative intensities of the emission lines of the LaPO4:Eu3+ nanosystems were essentially independent of their shape. The optimal doping concentrations in the monoclinic LaPO4 and perovskite LaAlO3 nanosystems were determined to be about 5.0 and 3.5 mol%, respectively. Under appropriate UV-radiation, the red light emitted
from LaAlO3:Eu3+ (3.5 mol%) was brighter than that from LaPO4:Eu3+ (5.0 mol%) nanomaterial, resulting from differences in their spin-orbit couplings and covalence, which indicates that the
nanoscale LaAlO3 is a promising host material for rare earth ions.
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Supported by the National Natural Science Foundation of China (Grant Nos. 20873039 & 90606001), Hunan Provincial Natural Science
Foundation (No. 07jj4002), and the Students Innovation Training Fund of Hunan University 相似文献
Properties of the quantum-cutting phosphors are dependent on various factors such as dopant concentration, crystallinity, homogeneity, particle size and surface morphology. Effective control of the above parameters can enhance the quantum-cutting ability of the phosphor material. Nano-sized particles of Y2O3:Tb3+,Yb3+ were prepared with a solution-based co-precipitation method and subsequent calcination. Effective control of the reaction parameters and doping concentration helped to produce uniform nanostructures with high quantum-cutting efficiency up to 181.1 %. The energy transfer mechanism between Tb3+ and Yb3+ was studied by considering their spectroscopic properties and time-resolved spectroscopy. The high efficiency and small particle size of the quantum-cutting phosphor Y2O3:Tb3+,Yb3+ make it a suitable candidate for its application in solar cells. 相似文献
Eu, Dy co-doped strontium aluminate nanophosphors were prepared by the combustion synthesis method. Their structure and morphology were investigated by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy. According to the XRD and the TEM analysis, the average crystallite size was found to be in the nanometer range. The phase structure of the prepared nanophosphor is consistent with a standard monoclinic phase with a space group P21. The prepared SrAl2O4:Eu2+, Dy3+ nanophosphor emitted green light with a peak at 510 nm showing blue shift, which is due to the reduction in the particle size. Two distinct peaks were observed in the ML intensity versus time curve. The two peaks in ML indicate the presence of charge transfer in an ML process. 相似文献
In3+-doped BiVO4 nanoparticles with enhanced visible light activity have been successfully synthesized by a hydrothermal method. The synthesized materials were characterized by X-ray diffraction, Raman, X-ray photoelectron spectroscopy, scanning electron microscopy, BET surface areas analysis, and ultraviolet–visible diffuse reflectance spectra. In comparison with pure BiVO4, the In3+-doped BiVO4 displayed greater photocatalytic activity in the degradation of methyl blue under visible light illumination. All samples possessed a single monoclinic structure. The introduction of In ions resulted in structural distortion and the decreased band gap energy, producing more electrons and holes for photocatalytic reaction. In the meantime, the doping In ions entails a red shift in the absorption edge and an increase in the intensity of light absorption. The best photocatalytic performance was obtained with the BiVO4 sample containing 5.0 mol% In ions. 相似文献
The details of the mechanism of persistent luminescence were probed by investigating the trap level structure of Sr2MgSi2O7:Eu2+,R3+ materials (R: Y, La-Lu, excluding Pm and Eu) with thermoluminescence (TL) measurements and Density Functional Theory (DFT)
calculations. The TL results indicated that the shallowest traps for each Sr2MgSi2O7:Eu2+,R3+ material above room temperature were always ca. 0.7 eV corresponding to a strong TL maximum at ca. 90 °C. This main trap
energy was only slightly modified by the different co-dopants, which, in contrast, had a significant effect on the depths
of the deeper traps. The combined results of the trap level energies obtained from the experimental data and DFT calculations
suggest that the main trap responsible for the persistent luminescence of the Sr2MgSi2O7:Eu2+,R3+ materials is created by charge compensation lattice defects, identified tentatively as oxygen vacancies, induced by the R3+ co-dopants. 相似文献
Ion-exchange modification of MF-4SK perfluorosulfonic membranes with Eu3+ and Tb3+ cations was realized. The state of cations in the membrane was studied by X-ray photoelectron spectroscopy. Special features of the luminescence of the resulting systems point to preferential excitation energy transfer from europium to terbium. 相似文献
Perfluorosulfonic membranes were modified by terbium(III) polypyridyl complexes by ionexchange sorption of cations followed by addition of ligands. The luminescence sensitization degree is compared with the state of ligands in the grafted complexes. In the case of the terbium(III) 4,7-diphenylphenanthroline complex, strong blue luminescence of the ligand is observed, along with radiation transitions of the cation. The character of luminescence quenching in modified membranes in a wet medium is determined by the ability of ligands to prevent terbium from adsorbing water molecules. 相似文献
In this study, we analyze the effect of Tb3+ concentration on the structural and optical properties of CaF2 terbium-doped thin films deposited on soda-lime glass substrates with an indium tin oxide (ITO)-sputtered coating by means of electrochemical processes. Compositional results showed that thin films have excess of F, which is believed to be the source for defect formation. XRD results showed not only shifting and widening of the CaF2 peaks as a function of [Tb3+] increase in the electrolitic solution but also an additional peak when high [Tb3+] are used, promoting thus the formation of secondary phases such as NaTbF4. According to photoluminescence (PL) results, when using UV excitation (λ?=?325 nm), CaF2:Tb3+ thin films presented green emission (5D4?→?7FJ, where J?=?6, 5, 4, 3, 2, 1, 0). Besides, PL studies not only allowed us to establish the quenching for Tb3+ concentration in the CaF2 matrix, but they also showed that there are no changes in intensity or peak position attributed to the presence of cubic NaTbF4 because its emission coincides with that of CaF2 terbium-doped thin films.
Graphical abstract Increase of [Tb3+] in the CaF2 solution and the presence of Na+ promotes a competition effect between CaF2:Tb3+ and NaTbF4 phases under equal deposition conditions
Novel luminescent bio-based hydrogels comprising cellulose and Y4Si2O7N2:Ce4+ (YC) were prepared in an alkali/urea aqueous system using epichlorohydrin as a cross-linker. The structure, characteristics and properties of the hydrogels were investigated by various techniques, including FTIR spectroscopy, wideangle X-ray diffraction, scanning electron microscopy, etc. The results showed that when the content of YC was less than 0.05 g, the YC particles were tightly embedded in the macro porous of cellulose matrix, which not only supplied cavities for YC immobilization, but also supplied the pore wall to protect the structure and character of YC. Hence, the cellulose–YC hybrid hydrogels exhibited strong cyan fluorescence under a UV lamp. However, excess of YC particles were enshrouded in the cellulose matrix resulted in smaller pores, weaker fluorescence intensity, lower swelling ratio and higher mechanical properties. 相似文献
The compounds AMMgE(PO4)3 (A = Na, K, Rb, Cs; M = Sr, Pb, Ba; E = Ti, Zr) were synthesized by the sol–gel procedure followed by heat treatment and studied by X-ray diffraction, differential thermal and electron microprobe analysis, and IR spectroscopy. The phosphates crystallize in the kosnarite (KZr2(PO4)3, space group \(R\bar 3\)) and langbeinite (K2Mg2(SO4)3, space group P213) structural types. The structure of KPbMgTi(PO4)3 was refined by full-profile analysis (space group P213, Z = 4, a = 9.8540(3) Å, V = 956.83(4) Å3). The structure is formed by a framework of vertex-sharing MgO6 and TiO6 octahedra and PO4 tetrahedra. The K and Pb atoms fully occupy the extra-framework cavities and are coordinated to nine oxygen atoms. A variable-temperature X-ray diffraction study of KPbMgTi(PO4)3 showed that the compound expands isotropically and refer to medium-expansion class (linear thermal expansion coefficients αa = αb = αc = 8 × 10–6°C–1). The number of stretching and bending modes of the PO4 tetrahedron observed in the IR spectra is in agreement with that predicted by the factor group analysis of vibrations for space groups \(R\bar 3\) and P213. A structural transition from the cubic langbeinite to the rhombohedral kosnarite was found for CsSrMgZr(PO4)3. In the morphotropic series of ASrMgZr(PO4)3 (A = Na, K, Rb, Cs) the kosnarite–langbeinite transition occurs upon the Na → K replacement. The effect of the sizes and electronegativities of cations combined in AMMgE(PO4)3 on the change of the structural type was analyzed. 相似文献
CaAl2O4:Eu2+, Nd3+@TiO2 composite powders were synthesized by a sol–gel method under mild conditions (i.e. low temperature and ambient pressure).
The as-prepared powders were characterized by transmission electron microscopy (TEM) and analyzed by X-ray diffraction (XRD).
The photocatalytic behavior of the TiO2-base surfaces was evaluated by the degradation of nitrogen monoxide gas. It suggested that CaAl2O4:Eu2+, Nd3+@TiO2 composite powders were composed of anatase titania and that CaAl2O4:Eu2+, Nd3+. TiO2 particles were deposited on the surface of CaAl2O4:Eu2+, Nd3+ to form uniform film. CaAl2O4:Eu2+, Nd3+@TiO2 composite powders exhibited higher photocatalytic activity compared with pure TiO2 under visible light. And the result also clearly indicated that the long afterglow phosphor absorbed and stored lights for
the TiO2 to remain photocatalytic activity in the dark. 相似文献
The inorganic ceramic compounds based on the CeO2 belong into the group of high-temperature pigments. The pigments have been prepared by the classical dry process (i.e. solid-state
reaction) in the temperature range from 1,300 to 1,600 °C and by the coprecipitation at the three different temperatures:
400, 600 and 1,100 °C. The principal of these pigments makes the host lattice of the CeO2, which is doped by terbium ions. This incorporation of the doped ions leads to obtaining of the interesting dark orange colour
after application into ceramic glaze. The aim of our research was to improve and optimize the synthesis conditions of these
pigments. The samples were submitted to thermal analysis (TG–DTA) for determination of the temperature interval of the pigment
formation and the thermal stability of pigments. The compounds were also measured from the point of view of their colouring,
structure and particle size distribution. 相似文献
Eu2+/Dy3+-codoped BaAl2O4 phosphors were prepared by conventional solid-state reaction with boric acid flux. The effects of boric acid on structural and luminescent properties of BaAl2O4:(Eu2+, Dy3+) were investigated. The crystallinity of BaAl2O4 improved with increasing amount of H3BO3. Incorporation of Eu2+ and Dy3+ ions into effective lattice sites was promoted by H3BO3 addition. As a result, Eu2+ emission in BaAl2O4 was greatly enhanced by H3BO3, and the duration of persistent luminescence increased with the amount of H3BO3. However, the decay lifetime of persistent luminescence was not strongly influenced by the amount of H3BO3. 相似文献
The intermetallic cerium compounds Ce3-Pd3Bi4, CePdBi, and CePd2Zn3 were synthesized from the elements in sealed tantalum ampoules in an induction furnace. The compounds were characterized by X-ray powder and single crystal diffraction: CeCo3B2 type (ordered version of CaCu5), P6/mmm, a = 538.4(4), c = 427.7(4) pm, wR2 = 0.0540, 115 F2 values, 9 variables for CePd2Zn3 and Y3Au3Sb4 type, I\({\bar 4}\)3d, a = 1005.2(2) pm, wR2 = 0.0402, 264 F2 values, 9 variables for Ce3Pd3Bi4, and MgAgAs type, a = 681.8(1) pm for CePdBi. The bismuthide structures are build up from three-dimensional networks of corner-sharing PdBi4 tetrahedra with Pd–Bi distances of 281 (Ce3Pd3Bi4) and 296?pm (CePdBi), respectively. The cerium atoms are located in larger voids of coordination number 12 (Ce3Pd3Bi4) and 10 (CePdBi). In CePd2Zn3 the cerium atoms fill larger channels within the three-dimensional [Pd2Zn3] network with 18 (6 Pd + 12 Zn) nearest neighbors. The three compounds contain stable trivalent cerium with experimental magnetic moments of μeff = 2.70(2), 2.48(1), and 2.49(1) μB/Ce atom for CePd2Zn3, Ce3Pd3Bi4, and CePdBi, respectively. Susceptibility and specific heat data gave no hint for magnetic ordering down to 2.1?K. 相似文献
La3+-doped BiPO4 photocatalysts were prepared via a hydrothermal process. Their morphologies, structures, and light absorption properties were evaluated. A small amount of La-doping (optimized at 2 mol %) could significantly improve the activity of BiPO4 in the degradation of methylene blue under ultraviolet irradiation. After five recycles, the La3+-doped BiPO4 did not exhibit any apparent loss in activity, confirming its stability despite recycling. 相似文献
Rhombohedral hexametavanadates K4Sr(VO3)6, K4Ba(VO3)6, Rb4 Ba(VO3)6, and Cs4Ba(VO3)6 melt incongruently in the temperature range of 491 to 600°C. Cooling of peritectic melts yields mixtures of compounds typical
of M2+O-M2+O-V2O5 systems, far from equilibrium and depending on the cooling kinetics. The vanadate Cs4Ba(VO3)6 undergoes reversible polymorphic transformation at 360°C. All compounds show broad-band luminescence with a maximum of the
luminescence spectrum at 490–590 nm with three types of excitation. The vanadates K4Sr(VO3)6 and Rb4Ba(VO3)6 show the highest luminescence intensity at room temperature. The latter is also most efficient at liquid nitrogen temperatures.
The luminescence spectra depend on the excitation of vanadates. Three hypotheses were put forward to interpret this finding.
The nature of luminescence is attributed to the relaxation of electronic excitation in [VO4]3− structural tetrahedra present in the vanadates. The performance characteristics of luminophores were determined. These luminophores
may be promising as X-ray luminescent screens, radioluminescence indicators, and light-emitting diode devices. 相似文献
A method for the preparation of nanoand submicron spherical particles of magnetite which form agglomerates was described. At varying the reaction conditions, the particles of -50—200 nm were obtained and characterized by scanning electron microscopy, IR-spectroscopy, X-ray analysis, thermogravimetric analysis and differential scanning calorimetry. The scheme (zero approach) of the magnetite formation in the studied system was proposed. The investigation of magnetic properties proved that the obtained particles related to the hard magnetic materials. Curie temperature for the particles with different sizes was detected. 相似文献
The cerium complex bound to the derivative of oligoDNA has been synthesized successfully that can hydrolyze DNA with sequence-specificity.
The synthesized derivative of oligoDNA, 5′-EDTA-P-10 mers ODN, was demonstrated by HPLC. The fluorescence spectrum of Tb3+ was detected after its interaction with the hybrid of 10-mers ODN and 26-mers ODN and the results show that the artificial
endo-enzyme can recognize and combine firmly with the substrate DNA. The electrophorogram shows that the cerium-oligoDNA hybrid
can specifically hydrolyze its substrate DNA and the cleavage site of this hydrolysis reaction is also discussed. This artificial
nuclease can be widely used in molecular biology and genetic engineering as one kind of endo-enzyme. 相似文献
Zinc gallate (ZnGa2O4) nanopowders doped with Cr3+ (1?mo%) were synthesized by the citric acid assisted sol–gel method. The influence of annealing temperature, structural, morphological, and optical properties of ZnGa2O4: Cr3+ (1?mol%) nanosized particles were investigated. The X-ray diffraction (XRD) spectra indicated that the nanoparticles are cubic in structure and the annealing temperature did not influence any c in structure. The average crystallite size of ZnGa2O4: Cr3+ nanoparticles were observed to increase from 11.85 to 30.88?nm as the annealing temperature increased from 600 to 1000?°C. The scanning electron microscopy (SEM) showed nearly spherical nanostructures that change in size with annealing temperature. The high resolution transmission electron microscope (HR-TEM) images show well resolved lattice fringes which is an indications of highly crystalline samples. Ultraviolet–visible (UV–Vis) measurement show decrease in reflectance in visible region and energy band gap was found to decrease with annealing temperature. The photoluminescence (PL) intensity was found to be maximum for sample annealed at high temperature (1000?°C) and least with sample annealed at low temperature (600?°C). An increase in annealing temperature leads significantly increment in PL intensity. The degree of crystallinity also increased with annealing temperature from XRD, SEM, and HR-TEM analysis. The photoluminescence lifetimes, particle size, and emission spectra are comparable with reports on bioimaging applications.
Fluorescence and spectral hole burning properties of Eu3+ ions were studied in nanocrystals-precipitated SnO2-SiO2 glasses. The glasses were prepared to contain various amount of Eu2O3 using the sol-gel method, in which SnO2 nanocrystals were precipitated by heating in air. In the glasses containing Eu2O3 less than 1%, the Eu3+ ions were preferentially doped in the SnO2 nanocrystals and their fluorescence intensities were enhanced by the energy transfer due to the recombination of electrons
and holes excited in SnO2 crystals. The SnO2 nanocrystals-precipitated glasses exhibited the persistent spectral holes with the depth of ∼25% of the total fluorescence
intensities of the Eu3+ ions. With the increasing Eu2O3 concentration, the amount of SnO2 nanocrystals decreased and the Sn4+ ions formed the random glass structure together with the silica network. This structure change induced the fluorescence intensities
and the hole depth to decrease. 相似文献