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ABSTRACT: Three-dimensionally ordered macroporous (3DOM) ZrO2:Eu3+ (0.5%, 1%, 2% and 5%) were successfully prepared using a polystyrene (PS) colloidal crystal template in combination with a sol-gel method. The structure, morphology, porosity, and optical properties of the materials were well characterized by X-ray diffraction (XRD), Field emission scanning electron micrograph (FESEM), N2 adsorption, and photoluminescence (PL) spectra. The results indicated that the closely packed material exhibited three-dimensional ordering of pores and a strong red 5D0 → 7F2 transitions under charge transfer excitation. Strong PL and abundant porosity are of particular interest and give this multifunctional material future potential.
Journal of Nanoscience and Nanotechnology 08/2010; 10(9):5874-5878. · 1.56 Impact Factor
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ABSTRACT: In order to improve photoluminescence properties, terbium complex Tb(acac)3phen (acacacetylacetone, phen-1,10-phenanthroline) was incorporated into polystyrene (PS), polyvinylpyrrolidone (PVP), and polymethylmethacrylate (PMMA) matrixes and electrospun into various aligned composite fibers. Their morphology, structure and photoluminescence properties were systematically characterized and studied. The results demonstrated that under the ultraviolet (UV) light exposure, the emission intensity for 5D4 --> 7F(J) of Tb3+ in the composite fibers considerably increased, while it was greatly quenched in the pure complex, implying remarkably improved photostability in the composites. The composite fibers also demonstrated much better temperature stability of photoluminescence over the pure complex.
Journal of Nanoscience and Nanotechnology 03/2010; 10(3):2070-6. · 1.56 Impact Factor
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ABSTRACT: Luminescence enhancement and quenching of Eu(TTA)(3) x 2 H(2)O complex in DMF (N,N-dimethylformamide) solution containing silver nanoparticles were observed, which depended on the concentrations of both europium complex and silver nanoparticles. Their origins were discussed based on absorption spectra, excitation and emission spectra, and luminescent decay dynamics. The results indicated that when the concentration of Eu complex was high enough, strong interaction among complex molecules occurred. The presence of Ag nanoparticles definitely decreased the interaction among complex molecules. In the solution containing Ag nanoparticles the electronic-dipole transition rate of (5)D(0)-(7)F(2) increased due to enhanced local field surrounding Eu(3+) ions, while the nonradiative transition rate from (5)D(0) decreased owing to decreased resonant energy transfer among europium complex molecules. These two factors lead to the luminescence enhancement of europium complex. As to the luminescent quenching, was attributed to absorption competition between Ag nanoparticles and europium complex at excited wavelength.
The Journal of chemical physics 09/2009; 131(5):054506. · 3.09 Impact Factor
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ABSTRACT: Three-dimensionally ordered macroporous (3DOM) ZrO2:Eu3+ inverse opal materials prepared by polystyrene (PS) colloidal crystal templating, using the sol−gel method, were successfully fabricated. Their crystal structure, morphology, and photoluminescence (PL) properties and the effect of the photonic stop-band on the spontaneous emission of Eu3+ ions were studied and compared with those of the nonporous sample. In the 3DOM ZrO2:Eu3+, significant suppression for the 5D0-7F1 transition peaking at 590 nm was observed, which was in good agreement with the photonic band gap calculated (586 nm). After grinding the 3D ZrO2:Eu3+ inverse opal material, the suppression of emission was restored due to the disappearance of the photonic band gap. In the 3DOM ZrO2:Eu3+, the luminescent lifetime of 5D0-7FJ depended strongly on emission wavelengths, which was mainly attributed to the appearance of different Eu3+ centers. In the 3DOM ZrO2:Eu3+, three symmetry sites for Eu3+ were identified by site-selective excitation, differing from the nonporous sample, in which only one site was identified.
04/2009;
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ABSTRACT: The effects of size and europium concentration on photoluminescence properties of La2O2S: Eu3+ nanocrystals (20 nm) and the corresponding bulk were studied. The results indicate that in nanocrystals, the absorption edge largely shifted to blue in comparison to the bulk, which was mainly attributed to the variation of phonon-excitation relaxation. Two excitation bands were observed, located at 250 and 330 nm, respectively, corresponding to the charge transfer (CT) transitions of Eu−O and Eu−S. Relative to the CT transition of Eu−O, that of Eu−S increased greatly with europium concentration. The dependence of photoluminescence intensity on concentration showed that in the nanocrystals and the bulk, Eu3+ ions had two different quenching mechanisms, respectively, the exchange interaction and electric dipole−dipole interaction.
11/2008;
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ABSTRACT: PbWO4: Er3+,Yb3+ nanocrystals (100 nm) were prepared by the hydrothermal method at different pH values (pH = 4, 7, and 9). Their structure and luminescence properties under 978-nm laser-diode excitation were studied. The results indicate that the practical ratio of W to Pb in the nanocrystals and the doping concentration of Yb3+ depended strongly on the pH value due to structure change. In upconversion, red (4F9/2→4I15/2) and green (2H11/2,4S3/2→4I15/2) emissions were observed, both of which occurred via a two-photon populating process. Biexponential upconversion dynamics were observed, which was attributed to luminescence centers surrounded by different local environments. The intensity ratio of 2H11/2→4I15/2 to4S3/2→4I15/2 (RHS) was explored to reveal the local thermal effect under the exposure of the laser diode, showing that the temperature at the exposed spot increased linearly with respect to excitation power density and Yb3+ concentration.
11/2008;
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ABSTRACT: Upconversion (UC) white light hybrid thin films containing Ln(3+)-tridoped (Yb3+, Er3+ and Tm3+) NaYF4 nanoparticles and poly(vinyl pyrrolidone) (PVP, M(w) approximately 1300000) were prepared by a spin-coating method and characterized by X-ray diffraction (XRD), field emission scanning electron micrograph (FE-SEM) and Fourier transform infrared spectra (FT-IR). White light was generated by two different lanthanide ions, Er3+ (red and green) and Tm3+ (blue) under excitation by a 980-nm laser diode. Due to the modification of PVP to the UC populating processes, the color stability of the white light in the hybrid films was remarkably improved.
Journal of Nanoscience and Nanotechnology 09/2008; 8(8):3921-5. · 1.56 Impact Factor
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Huihui Liu,
Hongwei Song,
Suwen Li,
Xinguang Ren,
Shaozhe Lu,
Hongquan Yu,
Guohui Pan, Hui Zhang,
Lanying Hu,
Qilin Dai,
Ruifei Qin,
Jihong Yu,
Guangmei Wang,
Jiuxing Jiang
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ABSTRACT: To modify the photoluminescence properties the Eu(DBM)3bath complexes were encapsulated into the sub-nanometer pores of aluminosilicates zeolites L and Y and characterized by X-ray diffraction (XRD), transmission electron micrographs (TEM), Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible (UV-vis) absorption spectra. The luminescent properties of the encapsulated composites (Eu-L and Eu-Y) were systematically studied. The results indicate that in both the two composites the crystal-field symmetry becomes lower, as a consequence, the 5D0-7F2 electronic-dipole transition relative to the 5D0-7F1 magnetic-dipole transition of Eu3+ increases in contrast to the pure complexes. The outer quantum efficiency of the Eu3+ emission and the photostability of Eu3+ are both improved considerably. The adsorption of water in the composites has influence on the thermostability and decay dynamics of the Eu3+ emission. In the composite Eu-L, which contains less water the thermostability of luminescence is improved considerably and the lifetime becomes longer in comparison to the pure complexes. Overall, zeolite L is a more ideal host material for modification of lanthanide complexes.
Journal of Nanoscience and Nanotechnology 09/2008; 8(8):3959-66. · 1.56 Impact Factor
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ABSTRACT: The europium complex Eu(TTA)3(TPPO)2 (TTA = thenoyltrifluoroacetone, TPPO = triphenylphosphine oxide) was incorporated into poly(methyl methacrylate) (PMMA, Mw ≈ 350 000), polystyrene (PS, Mw ≈ 250 000), poly(vinyl pyrrolidone) (PVP, Mw ≈ 1 300 000) matrixes and electrospun into various composite fibers. The thermal stability of these composite fibers is better than that of the pure europium complex. Their photoluminescence properties were studied in comparison to those of the pure complex. The results indicate that, in all of the composite fibers, the excitation bands of the ligands split into different components because of the distorted crystal field, which reduces the degree to which the 5D0−7F0 transition is parity-forbidden. In addition, the thermal stability of the photoluminescence of Eu3+ in the composite fibers is considerably improved over that of the pure complex. Also, the Eu(TTA)3(TPPO)2/PS composite fibers exhibit better photostability upon exposure to ultraviolet light. In the Eu(TTA)3(TPPO)2/PS composite, blue and green band emissions caused by fluorescent impurities appear and, together with the red emissions of Eu3+, produce white light, which might have a potential application in white light-emitting diodes (LEDs).
05/2008;
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ABSTRACT: One-dimensional nanosized phosphors demonstrate special structural and photoluminescence properties, which have application potential in some optical fields. In this article, we present our recent progress on preparation and luminescence properties of some one-dimensional rare earth compounds and complexes, the core-shell oxide nanowires prepared by a two-step hydrothermal route, the nanowires of some inorganic compounds doped with rare earths and rare earth complexes/PVP composites prepared by the electrospinning method, and the rare earth complexes in the SBA-15 mesoporous molecule sieves. In these systems, some novel or improved photoluminescence properties are observed such as improved luminescence quantum yield, thermal stability and/or photostability, and depressed thermal effect in upconversion luminescence.
Journal of Nanoscience and Nanotechnology 04/2008; 8(3):1316-25. · 1.56 Impact Factor
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ABSTRACT: This paper describes a procedure based on electrospinning for generating europium-doped yttrium vanadate (YVO4:Eu3+) nanofibers with diameters ranging from 30 to 50 nm. The YVO4:Eu3+ nanofibers were obtained through calcining precursory nanofibers, which were prepared through the electrospinning method. Suitable electrospinning parameters, such as concentration of PVP in solution, spinneret tip-to-collector plate distance (TCD), and applied voltage between spinneret and collector plate, are used to obtain thinner and more uniform precursory nanofibers of YVO4:Eu3+, which is important for preparing smaller diameter pure YVO4:Eu3+ nanofibers. The luminescent properties of the YVO4:Eu3+ nanofibers including excitation and emission spectra and fluorescence lifetime were studied. The excitation spectrum shows a broad band extending from 200 to 350 nm, which corresponds to the strong vanadate absorption in YVO4:Eu3+. The emission spectrum is dominated by the red 5D0 --> 7F2 hypersensitive transition of Eu3+. The fluorescence lifetime of Eu3+ 5D0 --> 7F2 (619 nm) is determined to be 493 micros at room temperature, which is basically in accordance with that in the bulk (521 micros).
Journal of Nanoscience and Nanotechnology 03/2008; 8(3):1432-6. · 1.56 Impact Factor
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ABSTRACT: CdWO4:Eu3+ nanocrystals were prepared by the hydrothermal method at different pH values (pH = 4, 7.5, and 10) and annealed at different temperatures. Their structural and photoluminescence properties were systemically studied. The studies on electron spin resonance and Fourier-transfer infrared absorption spectra demonstrated that at least two kinds of surface defects were involved, the surface dangling bonds of transition metals and the surface adsorption of the OH− and CO32− groups. The surface adsorption in the pH = 10 sample increased considerably, which led the surface dangling bonds to decrease and even to disappear. Due to the existence of surface defect states, especially the surface dangling bonds, tungstates at two symmetry sites were formed, the normal site and the perturbed site locating at/near the surface. The former tungstates located at high energy side ( ∼ 290 nm) in the excitation bands and emitted blue-green photons, while the latter located at low energy ( ∼ 340 nm) and emitted red photons. They can both effectively transfer the energies to Eu3+ ions, generating red 5D0-7FJ transitions. As the nanocrystalline powders were annealed, colorations appeared and evolved with temperature, while the surface dangling bonds and surface adsorption gradually disappeared. The defect states had great and complicated influence on luminescence efficiency, luminescent stability, and temperature-stability of tunstates and Eu3+ ions.
Journal of Applied Physics 09/2007; 102(5):054311-054311-8. · 2.17 Impact Factor
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Hui Zhang,
Hongwei Song,
Hongquan Yu,
Xue Bai,
Suwen Li,
Guohui Pan,
Qilin Dai,
Tie Wang,
Wenlian Li,
Shaozhe Lu,
Xinguang Ren,
Haifeng Zhao
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ABSTRACT: Composite fibers of poly(vinyl pyrrolidone) (PVP, Mw ≈ 1 300 000) and europium complex Eu(BA)3(TPPO)2 (BA =1-benzoylacetone; TPPO = triphenylphosphine oxide) with strong photoluminescence were prepared by electrospinning. Their luminescent properties were studied in comparison to that of the pure complex. The results indicate that due to decreased symmetry in the composites the excitation bands are split into two different components, peaking at 246 and 336 nm, respectively, while the ratio of the electronic dipole 5D0-7F2 transitions to the magnetic dipole 5D0-7F1 ones in the emission spectra becomes a little larger. The room temperature fluorescence lifetime for the 5D0 level becomes shorter due to increased radiative and nonradiative transition rates. The temperature dependence of photoluminescence was investigated under 325-nm excitation. It is interesting to observe that in the composite fiber the total emission intensity of the Eu3+ ions changes little below 150 K, while in the pure complex the intensity decreases monotonically with increasing temperature. In addition, the composite fibers exhibit better photostability exposed to ultraviolet lights. These novel luminescent composite fibers have potential application in nanodevices.
04/2007;
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Suwen Li,
Hongwei Song,
Wenlian Li,
Xinguang Ren,
Shaozhe Lu,
Guohui Pan,
Libo Fan,
Hongquan Yu, Hui Zhang,
Ruifei Qin,
Qilin Dai,
Tie Wang
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ABSTRACT: Ternary terbium complexes were fully encapsulated and uniformly distributed into the channels of unmodified and modified mesoporous molecule sieves of SBA-15 and characterized by transmission electron micrographs (TEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-vis) absorption spectra, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and elemental analysis. The luminescent properties for the encapsulated complexes were systematically studied in contrast to the pure complexes, including excitation and emission spectra, fluorescence dynamics, photostability under UV exposure, and the temperature dependence of intensity and lifetime. The results indicate that the excitation bands assigned to the pi-pi* electron transition of the ligands for Tb complexes encapsulated in SBA-15 were split into different components due to decreased symmetry and disappeared at long wavelengths. Owing to suppressed vibration transitions, the outer quantum efficiency of the 5D4-7FJ (J = 0-5) emissions was enhanced largely in comparison to the pure complexes. In addition, the photostability and thermostability of the emissions were also improved considerably.
The Journal of Physical Chemistry B 12/2006; 110(46):23164-9. · 3.70 Impact Factor
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ABSTRACT: Y2O3:Eu3+ inverse opal films were fabricated by the self-assembly technique, which had a lattice parameter of ∼260 nm and a photonic stop band at 520 nm. Near the center of the photonic stop band, both the emission intensity and the spontaneous transition rate of 5D1–7F1 transitions were modified. At the band gap edge, no obvious change was observed for the 5D0–7FJ spontaneous transition rate, however, the emission intensity of 5D0–7FJ (J = 0, 1) was depressed in contrast to the 5D0–7F2, which improved the color purity of the red emission.Graphical abstractView high quality image (172K)Highlights► Y2O3:Eu3+inverse opal films were fabricated. ► Both the emission intensity and the spontaneous transition was modified. ► The color purity of the red emission was improved due to the inverse opal structure.
Chemical Physics Letters 509:33-36. · 2.34 Impact Factor
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ABSTRACT: The ZnO@ZnWO4:Eu3+ core–shell composites were prepared by a two-step hydrothermal method and the photoluminescence properties of the composites were studied in contrast to the corresponding hexagonal ZnO and monoclinic ZnWO4: Eu3+ nanocrystals prepared by the one-step hydrothermal method. The results demonstrate that in the nanocomposites the Eu3+ ions in the ZnWO4 phase occupy two symmetry sites, one a well-crystalline inner site and one a disordered surface site; while in the ZnWO4: Eu3+ nanocrystals, the local environments surrounding Eu3+ ions are relatively disordered for both the inner and the surface sites. This indicates that in the composites, the crystallinity of the ZnWO4 becomes better, which have positive influence on the improvement of photoluminescence. The temperature stabilities for both the emissions of ZnO and Eu3+ ions are improved in contrast to the pure ZnO or ZnWO4:Eu3+ nanocrystals.
Journal of Luminescence. 128(7):1205-1210.
