非稀土掺杂协同核壳包裹对氟化物纳米晶上转换发光性能的增强

为提高上转换纳米晶的发光效率,提出协同增强的策略,将核壳包裹和非稀土离子掺杂两种方式进行有效的结合,使上转换纳米晶的发光效率实现"1+12"的增强效果。以Na Gd F_4作为基质材料,Yb~(3+)和Er~(3+)分别作为敏化离子和发光离子,以Li~+离子和Na Gd F_4作为非稀土掺杂离子和包裹壳层来构建核/壳纳米结构,研究两种增强方式的协同作用对Na Gd F4∶Yb~(3+)/Er~(3+)纳米晶的上转换发光性能的影响。结果表明,Li+离子掺杂与包裹Na Gd F4壳层共同作用使得β-Na Gd F4∶Yb~(3+)/Er~(3+)纳米晶的上转换发光增强了39倍,明显优于单一方式的增强效果。通过一系列的优化实验结果发现,Li+离子的最佳掺杂摩尔分数为4%。基于以上实验结果,给出了非稀土离子掺杂核壳纳米晶协同增强上转换发光效率的机理。

Enhancment of Upconversion Luminescence of Lanthanide-doped Nanocrystals Through Non-lanthanide Ions Doping Core-shell Nanoarchitecture

In order to improve the luminescence efficiency of upconversion nanocrystals, a new strat-egy to significantly enhance upconversion emission was proposed based on coupling of non-lanthanide ions doping with the growth of an inert shell. As a proof-of-concept experiment, hexagonal NaGdF4∶Yb3+/Er3+, NaGdF4 and Li+ ions were chosen as luminescent core, inert shell and non-lanthanide ions, respectively. The results demonstrate that significant enhancement of 39 times fromβ-NaGdF4∶Yb3+/Er3+ nanocrystals is clearly observed under the synergistic effect, which is larger than the sum of separate enhancement from the Li+ doping and growth of an inert shell. By means of a series of experimental studies, the optimal doping mole fraction of Li+ ions in the core-shell nanocrystals is found to be about 4%. Moreover, the mechanism for the luminescent enhancement of upconversion nanocrystals has been discussed.