Qin Weiping

Synthesis and upconversion luminescence of LaF3 : Yb3+, Er3+/SiO2 core/shell microcrystals

Abstract LaF 3 : Yb 3+ , Er 3+ microcrystals were synthesized by a hydrothermal method, and then, the LaF 3 : Yb 3+ , Er 3+ microcrystals were coated with silica. Phase identification of LaF 3 : Yb 3+ , Er 3+ and LaF 3 : Yb 3+ , Er 3+ /SiO 2 was performed via XRD. The TEM image showed that the size of LaF 3 : Yb 3+ Er 3+ was 150 nm and LaF 3 : Yb 3+ , Er 3+ /SiO 2 presented clearly a core/shell structure with 20 nm shell thickness. The upconversion spectra of LaF 3 : Yb 3+ , Er 3+ and LaF 3 : Yb 3+ , Er 3+ /SiO 2 in solid state and in ethanol were studied with a 980 nm diode laser as the excitation source. The upconversion spectra showed that the silica shell had little effect on the properties of fluorescence of the LaF 3 : Yb 3+ , Er 3+ microcrystals. At the same time, the green luminescence photo of LaF 3 : Yb 3+ , Er 3+ /SiO 2 in the PBS buffer was obtained, which indicated that the LaF 3 : Yb 3+ , Er 3+ /SiO 2 could be used in biological applications.

Laser-induced filling and thermal filling of spectral holes in BaFCl0.5Br0.5:Sm2+

Laser-induced filling and temperature cycling experiments were conducted in the sample BaFCl0.5Br0.5:Sm2+. Under laser irradiation, the decay curve of the hole area is composed of a fast component and a slow component. In the temperature cycling curve, there are a slow decrease of the hole area from 77 to 200 K and a rapid drop above 300 K. The decay of the hole area with time at 77 k and 313 K follow a logarithmic law. Analysis of these results shows that there are two kinds of traps which govern hole burning and filling processes in the sample. One is related to some impurities or defects. Another is related to Sm3+ ions. The distribution of the potential well of the latter, produced by substitutional disorder, can be described by a two-level-system model.