Preparation and surface effect analysis of trivalent europium-doped nanocrystalline La2O2S.
La2O2S:Eu3+ nanocrystals (NCs) with a mean size of 18 nm are prepared by gel thermolysis. The morphology of the particles is hexagonal. The surface Eu3+ ions are first detected by time-resolved spectra in the 5D0 --> 7F1 region. Because the symmetry of the sites occupied by surface Eu3+ ions is lower, the 5D0 --> 7F1(E) line, which is doubly degenerate in the bulk crystal, is split, and the fluorescence lifetime becomes shorter. The results of the laser-selective excitation indicate that the degradation of the site symmetry of Eu3+ seems to be abrupt, which means the as-synthesized La2O2S:Eu3+ NCs might be of the La2O2S/La2O(2-x)S(1+x)core-shell structure and the shell are not in a disordered state but a rather pure one.
Peng
Hongshang
H
Institute of Optoelectronic Technology, Beijing Jiaotong University, 100044 Beijing, China. hillphs@sina.com
Huang
Shihua
S
You
Fangtian
F
Chang
Jianjun
J
Lu
Shaozhe
S
Cao
Lin
L