Upconversion luminescence enhancement in Yb3+/Tm3+-codoped Lu2O3 nanocrystals induced by doping with Li+ ions.
Upconversion luminescence enhancement in Yb3+/Tm3+-codoped Lu2O3 nanocrystals induced by doping with Li+ ions.
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DOI：
10.1166/jnn.2011.5232
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发表时间：
2011-11
影响因子：
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通讯作者：
Li Li-Li;Wei Xiantao;C. Xueqin;Deng Kaimo;Chen Qihong;Cheng Yonghu;Gu Changxin;Yin Min
中科院分区：
文献类型：
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作者：
Li Li-Li;Wei Xiantao;C. Xueqin;Deng Kaimo;Chen Qihong;Cheng Yonghu;Gu Changxin;Yin Min
采用Sol-Gel法制备了掺杂2%Yb3+、0.5%Tm3+以及不同Li+掺杂浓度(0、3、5、7、10、12、15摩尔%)的Lu_2O_3纳米晶。研究了不同Li+掺杂浓度对Lu2O3：2%Yb3+，0.5%Tm3+纳米晶的结构、形貌和上转换发光强度的影响。用X射线衍射仪、场发射扫描电子显微镜、傅立叶变换红外光谱、拉曼光谱和上转换光谱对所制备的纳米晶进行了系统的表征。结果表明，所有的纳米晶都能很容易地转化为纯的立方相Lu2O3，显示出良好的结晶性。实验结果表明，掺Li~(2+)：2%Yb~(3+)，0.5%Tm~(3+)纳米晶可以显著提高上转换发光强度。在980 nm激光激发下观察到强蓝光(490 Nm)和弱红光(653 Nm)发射，分别归因于Tm3+离子的1G4-->；3H6和1G4-->；3F4跃迁。基于稳态速率方程的简单分析和与功率相关的研究都表明，1G4能级可以由三步能量转移(ET)过程填充。上转换发光的增强是由于Tm~(3+)离子周围局域场对称性的改变、OH-基团数目的减少以及Li~(++)离子引起的纳米晶尺寸增大的结果。
Lutetium oxide (Lu2O3) nanocrystals doped with 2%Yb3+, 0.5%Tm3+, and various doping concentrations of Li+ (0, 3, 5, 7, 10, 12, and 15 mol%) were prepared by the sol-gel method. The dependence on different doping concentrations of Li+ ions of the structure, morphology, and the upconversion emission intensity of the Lu2O3:2%Yb3+, 0.5%Tm3+ nanocrystals was investigated. The obtained Lu2O3 nanocrystals were systematically characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), Fourier transformed infrared (FT-IR) spectra, Raman spectra, and upconversion spectra measurements. It was found that all the nanocrystals can be readily indexed to pure cubic phase of Lu2O3, indicating good crystallinity. The experimental results show that Li+ doping in Lu2O3:2%Yb3+, 0.5%Tm3+ nanocrystals can greatly enhance the upconversion emission intensity. The strong blue (490 nm) and the weak red (653 nm) emissions from the prepared nanocrystals were observed under 980 nm laser excitation, and attributed to the 1G4 --> 3H6 and 1G4 --> 3F4 transitions of Tm3+ ions, respectively. An simple analysis based on steady-state rate equations and a power-dependent study both indicate that the 1G4 levels can be populated by three-step energy transfer (ET) processes. The enhancement of the upconversion luminescence was suggested to be the consequence of the modification of the local field symmetry around the Tm3+ ion, reduced number of OH- groups, and the enlarged nanocrystal size induced by the Li+ ions.