L.-L. Wang

Changchun University of Technology, Huinan, Jilin Sheng, China

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Publications (6)2.29 Total impact

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    ABSTRACT: Ba2YF7:xYb(3+),0.02Er(3+) nanocrystals with different Yb3+ concentration (x = 0.2, 0.4, 0.6, 0.8, 0.98) were synthesized via a solvothermal method. Their X-ray diffraction patterns reveal that all the samples are cubic phase without phase change at arbitrary Yb3+ concentration. Upon excitation of 980 nm laser, these nanocrystals display upconversion emission in the green and red spectral regions. The relative emission intensity at these two regions can be tuned by Yb3+ concentration. To investigate the effect of Yb3+ ion, the decay times of 650 nm emission were measured and analyzed. Ba2YF7:0.6Yb(3+),0.02Er(3+) nanocrystals have the longest lifetime and highest emission interisity among all the samples. We concluded the lifetime of F-4(9/2) level has an effect on its own population and intensity ratio of red and green emission. Our results show Yb3+ ion can tune the upconversion emission and improve upconverison emission intensity. (C) 2013 Elsevier Ltd. All rights reserved.
    Full-text · Article · Jun 2013 · Materials Research Bulletin
  • C.-F. He · G.-S. Qin · D. Zhao · X.-H. Chuai · L.-L. Wang · W.-P. Qin
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    ABSTRACT: The up-conversion luminescence of Yb/Er co-doped 56ZrF4-28BaF2-2.5LnF3 -4AlF3-7NaF pumped by a 980 nm laser was studied and rich fluorescence lines were observed. It is shown that the peaks at 318.8, 380.6, 408.6, 453, 523, 545.5, 625.2, 653.8, 700.8 and 840.2 nm correspond to the transitions of 2P3/2→4I15/2, 4G11/2→4I15/2, 2H9/2→4I15/2, 4F5/2→4I15/2, 2H11/2→4I15/2, 4S3/2→4I15/2, 4F5/2→4I13/2, 4F9/2→4I15/2, 2H9/2→4I11/2 and 4S3/2→4I13/2, respectively. The concentrations influence of Yb and Er on the luminescence characteristics were described. The monotonically increasing up-conversion emission of Er3+ with the increase of Er3+ concentration was also observed. Furthermore, up-conversion mechanism was investigated in detail and it is attributed to the effective resonant energy transfer from Yb3+ to Er3+ ions in such system. The results provide a potential material for short wavelength up-conversion phosphor.
    No preview · Article · Jul 2011 · Guangxue Jingmi Gongcheng/Optics and Precision Engineering
  • H. Chen · X.-H. Chuai · L.-L. Wang · X.-S. Zhai · T. Jiang · D. Zhao · W.-P. Qin
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    ABSTRACT: Water soluble NaYF4:20%Yb, 0.5%Tm upconversion nanoparticles(UCNPs) were prepared by a facile solvothermal approach using polyvinylpyrrolidone (PVP) as the surfactant. X-ray diffraction (XRD) analyses showed that the UCNPs were pure cubic phase NaYF4 nanocrystals. The size and morphology of the UCNPs were characterized by a scanning electron microscopy (SEM). The SEM images proved that almost all the UCNPs were nanospheres with the size of ~40 nm. The UCNPs could be well dispersed in water to form a clearly transparent solution which could be kept for at least two days and there was no obvious precipitation. Pumped with 980-nm diode laser, the solution presented bright naked eye-visible violet/blue upconversion luminescence and the upconversion mechanism of the UCNPs was also given in this paper. These results showed that the UCNPs had potential applications in biological field as luminescence labeling probes.
    No preview · Article · Aug 2010
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    ABSTRACT: 300 nm Eu(DBM)3 Phen/SiO2 Colloidal hybrid sphere were synthesized by modified Stöber method. The silica spheres were self-assembled into 3D ordered crystal structure with 5 mm thick and over relative large areas (12 cm2) via sedimentation. The scanning electron microscopy (SEM) images indicate that the cubic-close-packed structure extends almost all of the layers along the direction perpendicular to the surface of the bottom of the beaker and the close-packed order extends throughout the colloidal crystal. Furthermore, elemental analysis of silica spheres by EDAX establishes that the fluorescent molecules contained in the SiO2 colloidal spheres. Under 355 nm continuous excitation, the ordered structure exhibits characteristic emission of trivalent europium ions.
    Full-text · Article · May 2008 · Chinese Journal of Luminescence
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    ABSTRACT: Tb(Asprin)3,Phen/SiO2, nanospheres were synthesized by a microemulsion method. They have a uniform diameter of ∼ 40 nm, and show the characteristic fluorescence of Tb3+ ions. TEM imaging indicated that the hybrid nanospheres are core/shell structure with fine spherical surfaces and Tb (Asprin)3 Phen has been successfully enveloped in the SiO2 spheres as chromophores cores. IR absorption spectra and photoluminescence spectra propose that the hybrid nanoparticles are promising materials for biological application.
    Full-text · Article · May 2008 · Chinese Journal of Luminescence
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    ABSTRACT: In this paper, discrete Yb3+-Tm3+ co-doped LaF3 nanoparticles with controlled chemical composition, and size distribution were readily synthesized using reverse micelles with microemulsions as confined reaction media. The morphology of the final product was characterized by the FESEM and HRTEM images. When the solid sample disperses in the ethanol without ultrasonic treatment, it is maize cob-like aggregator. The average diameter and length of the maize cob are about 110 and 575 nm, respectively. We suggested that the nanoparticles assemble into well-defined superstructures arising from the solvent evaporation, molecular cross-linking or interaction from surfactant molecules attached to specific nanoparticles crystal faces. After ultrasonic treatment for 30 min, the maize cob-like aggregator turns into a lot of nanoparticles owing to ultrasonic breach above a series of factors. The HRTEM image taken from individual nanoparticles indicates the crystalline nature, and the interplanar spacing of ∼ 0.366 mn corresponding to the [002] planes of pure hexagonal phase LaF., The TEM image of the samples annealed at 300 °C for 30 minutes displays the average diameter of NCs increased to about 35 nm and is in good agreement with XRD result. In addition, the NCs exhibit nearly monodisperse property, which is in favor of optimizing luminescence of the sample. 0The nanoparticles present a bright blue upconversion luminescence under the 978 nm excitation from a laser diode, which provides a promising upconversion phosphor for optoelectronic or biological applications.
    Full-text · Article · Apr 2008 · Chinese Journal of Luminescence