Luminescence tuning of upconversion nanocrystals.
Luminescence tuning of upconversion nanocrystals.
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DOI：
10.1002/chem.200903099
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发表时间：
2010-04
期刊：
影响因子：
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通讯作者：
Guofeng Wang;Q. Peng;Yadong Li
中科院分区：
文献类型：
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作者：
Guofeng Wang;Q. Peng;Yadong Li
通过三掺杂不同电子结构的Ln（3+）离子，成功实现了β-NaYF（4）纳米棒在980 nm激发下的上转换发光调谐。研究了Ce（3+）离子对NaYF（4）：Yb（3+）/Ho（3+）和Gd（3+）离子对NaYF（4）：Yb（3+）/Tm（3+）（Er（3+））的影响。在NaYF（4）中观察到Ho（3+）离子的（5）G（5）->（5）I（7）和（5）F（2）/（3）K（8）->（5）I（8）跃迁以及Ce（3+）离子的5d->4f跃迁。Yb（3+）/Ho（3+）纳米棒，而且随着Ce（3+）浓度的增加，（5）F（5）->（5）I（8）的强度相对于（5）S（2）/（5）F（4）->（5）I（8）增加，这可以归因于（5）I（6）（Ho）+（2）F（5/2）（Ce）→（5）I（7）（Ho）+（2）F（7/2）（Ce）和（5）S（2）/（5）F（4）（Ho）+（2）F（5/2）（Ce）→（5）F（5）（Ho）+（2）F（7/2）（Ce）。有趣的是，随着泵浦功率密度的增加，NaYF（4）：Yb（3+）/Ho（3+）纳米棒的发光始终由（5）S（2）/（5）F（4）→（5）I（8）跃迁主导，而Ce（3+）三掺杂的NaYF（4）：Yb（3+）/Ho（3+）纳米棒的发光依次由（5）S（2）/（5）F（4）→（5）I（8）和（5）G（5）→（5）I（7）跃迁主导。这些意见进行了讨论的基础上的速率方程模型。此外，Gd（3+）三掺杂的NaYF（4）：Yb（3+）/Tm（3+）（Er（3+））纳米棒在980 nm激发下可以发射从紫外到近红外的上转换发光。观察到Gd（3+）离子的（6）P（5/2）→（8）S（7/2）（约306 nm）和（6）P（7/2）→（8）S（7/2）（约311 nm）跃迁。除了上述的发光特性外，这些Gd（3+）三掺杂纳米棒在室温下也表现出顺磁性行为，在2 K或5 K下表现出超顺磁性行为。
Upconversion luminescence tuning of beta-NaYF(4) nanorods under 980 nm excitation has successfully been achieved by tridoping with Ln(3+) ions with different electronic structures. The effects of Ce(3+) ions on NaYF(4):Yb(3+)/Ho(3+) as well as Gd(3+) ions on NaYF(4):Yb(3+)/Tm(3+)(Er(3+)) have been studied in detail. By tridoping with Ce(3+) ions, not only were unusual (5)G(5)-->(5)I(7) and (5)F(2)/(3)K(8)-->(5)I(8) transitions from Ho(3+) ions and 5d-->4f transitions from Ce(3+) ions observed in NaYF(4):Yb(3+)/Ho(3+) nanorods, but also an increase in the intensity of (5)F(5)-->(5)I(8) relative to (5)S(2)/(5)F(4)-->(5)I(8) with increasing Ce(3+) concentration, which can be attributed to efficient energy transfers of (5)I(6) (Ho)+(2)F(5/2) (Ce)-->(5)I(7) (Ho)+(2)F(7/2) (Ce) and (5)S(2)/(5)F(4) (Ho)+(2)F(5/2) (Ce)-->(5)F(5) (Ho)+(2)F(7/2) (Ce). Interestingly, with increasing pump power density, the luminescence of NaYF(4):Yb(3+)/Ho(3+) nanorods is always dominated by the (5)S(2)/(5)F(4)-->(5)I(8) transition, whereas the luminescence of Ce(3+)-tridoped NaYF(4):Yb(3+)/Ho(3+) nanorods is dominated by the (5)S(2)/(5)F(4)-->(5)I(8) and (5)G(5)-->(5)I(7) transitions in turn. These observations are discussed on the basis of a rate equation model. Furthermore, Gd(3+)-tridoped NaYF(4):Yb(3+)/Tm(3+)(Er(3+)) nanorods can emit multicolor upconversion emissions spanning from the UV to the near-infrared under 980 nm excitation. (6)P(5/2)-->(8)S(7/2) ( approximately 306 nm) and (6)P(7/2)-->(8)S(7/2) ( approximately 311 nm) transitions from Gd(3+) ions were observed. In addition to the aforementioned luminescence properties, these Gd(3+)-tridoped nanorods also exhibit paramagnetic behavior at room temperature and superparamagnetic behavior at 2 or 5 K.