Peng Hongshang, Huang Shihua, You Fangtian, Chang Jianjun, Lu Shaozhe, Cao Lin
Institute of Optoelectronic Technology, Beijing Jiaotong University, 100044 Beijing, China.
J Phys Chem B. 2005 Mar 31;109(12):5774-8. doi: 10.1021/jp0453414.
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.
通过凝胶热解法制备了平均尺寸为18纳米的La2O2S:Eu3+纳米晶体（NCs）。颗粒形态为六边形。首先通过5D0 --> 7F1区域的时间分辨光谱检测表面Eu3+离子。由于表面Eu3+离子占据的位点对称性较低，在体晶体中双重简并的5D0 --> 7F1(E)线发生分裂，荧光寿命变短。激光选择性激发结果表明Eu3+位点对称性的降低似乎是突然的，这意味着合成的La2O2S:Eu3+ NCs可能具有La2O2S/La2O(2-x)S(1+x)核壳结构，且壳层并非处于无序状态而是相当纯净的状态。
