Upconversion spectroscopy and properties of NaYF4 doped with Er 3+, Tm3+ and/or Yb3+
Upconversion spectroscopy and properties of NaYF4 doped with Er 3+, Tm3+ and/or Yb3+
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DOI：
10.1016/j.jlumin.2005.03.011
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发表时间：
2006-03-01
影响因子：
3.6
通讯作者：
Güdel, HU
中科院分区：
文献类型：
--
作者：
Suyver, JF;Grimm, J;Güdel, HU
本文报道了掺Er ~（3+）、Tm ~（3+）和Yb ~（3+）的NaYF_4粉末的光谱研究。已知稀土掺杂的NaYF 4是非常有效的近红外到可见光上转换器。所有样品的概述发射光谱，并从这些上转换效率计算。本文首次给出了未掺杂NaYF_4的拉曼光谱，证明了NaYF_4的主要声子模位于300 ~ 400 cm（-1）之间。这些声子模式也是光学活性的，这一事实进一步证明了温度依赖的激发光谱。这些令人惊讶的低能量声子模式解释了稀土掺杂的NaYF 4样品的非常高的上转换效率。在NaErF 4样品中近似于70000 cm（-1）的激发光谱显示了大量的Er 3 + 4f激发，包括之前在激发光谱中没有观察到的杰出的F-2（2）（5/2）激发。从Er 3+，Yb 3+共掺杂NaYF 4样品的发射强度的低温功率依赖性，可以得出结论，在低温下的主导上转换机制是不同于在室温下的。从直接激发，对于所有样品，Yb 3 + F-2（5/2）-> F-2（7/2）、Er 3 + F-4（9/2）-> I-4（15/2）和Er 3 + S-4（3/2）-> I-4（15/2）发射的寿命被确定为温度的函数。在升高的温度下，观察到绿色寿命的显著降低，这与发光强度的同时猝灭相关。这种猝灭归因于两个邻近的Er 3+离子之间的交叉弛豫。(c)2005 Elsevier B. V.保留所有权利。
A spectroscopic investigation of NaYF4 powders doped with several different concentrations of Er3+, TM3+ and/or Yb3+ is described. Rare earth-doped NaYF4 is known to be a very efficient near-infrared to visible upconverter. The overview emission spectra for all samples are presented and from these the upconversion efficiency is calculated. Raman spectroscopy of undoped NaYF4 is presented here for the first time, demonstrating that the dominant phonon modes in NaYF4 lie between 300 and 400 cm(-1). The fact that these phonon modes are also the optically active ones is further demonstrated by temperature-dependent excitation spectroscopy. These surprisingly low-energy phonon modes explain the extraordinarily high upconversion efficiency of the rare earth-doped NaYF4 samples. Excitation spectroscopy lip to similar to 70000 cm(-1) in an NaErF4 sample reveals a multitude of Er3+ 4f excitations, including the illustrious F-2(2)(5/2) one that has not been observed in excitation spectroscopy before. From the low-temperature power-dependence of the emission intensities for an Er3+, Yb3+ codoped NaYF4 sample, it is concluded that the dominant upconversion mechanism at low temperature is a different one than at room temperature. From direct excitation, the lifetimes of the Yb3+ F-2(5/2) -> F-2(7/2), Er3+ F-4(9/2) -> I-4(15/2) and Er3+ S-4(3/2) -> I-4(15/2) emissions are determined as a function of temperature for all samples. At elevated temperatures, a significant decrease in the green lifetime is observed, which is correlated to a simultaneous quenching in the luminescence intensity. This quenching is ascribed to cross- relaxation between two nearby Er3+ ions. (c) 2005 Elsevier B.V. All rights reserved.