Effect of Yb3+ codoping on the upconversion emission in nanocrystalline Y2O3:Er3+
Effect of Yb3+ codoping on the upconversion emission in nanocrystalline Y2O3:Er3+
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DOI：
10.1021/jp0218692
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发表时间：
2003-02-06
影响因子：
3.3
通讯作者：
Bettinelli, M
中科院分区：
文献类型：
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作者：
Vetrone, F;Boyer, JC;Bettinelli, M
报道了Y_2O_3：Er ~（3+），Yb ~（3+）纳米晶和体相样品在488 nm处的Stokes发射。研究了两种纳米晶样品，一种是通过推进剂合成产生的，另一种是通过湿法合成产生的。在大块和纳米晶样品中观察到Er 3+离子的绿色、红色和NIR发射。在488 nm激发后，在块体和纳米晶样品中也观察到来自F-2（5/2）-> F-2（7/2）Yb 3+跃迁的发射，从而表明存在从Er 3+到Yb 3+的能量转移过程。归因于Yb 3+发射的峰在纳米晶材料中强度小得多，这表明能量转移过程在这种材料中不容易发生，因为其表面上吸附的CO2和H2O具有固有的高声子能量。在用978 nm激发后，在所研究的样品中证明了绿色和红色反斯托克斯发光。增强的红色发射中观察到的散装和纳米晶体样品，虽然在纳米晶体Y2 O3：Er 3+，Yb 3+的程度要大得多。红色发射的增强是由于以下形式的离子对过程：（F-4（7/2），I-4（11/2））->（F-4（9/2），F-4（9/2）），其直接填充F-4（9/2）状态。然而，这一过程不能解释块体和纳米晶样品之间的红色增强幅度的巨大差异。发现声子辅助的能量转移过程是有效的，这也填充了F-4（9/2）态。该过程更容易在纳米晶体材料中发生，因为来自吸附的碳酸根和氢氧根离子的大振动量子可以容易地桥接能量的失配。
The Stokes emission of nanocrystalline and bulk Y2O3:Er3+, Yb3+ following 488 nm were reported. Two nanocrystalline samples were studied, one produced via propellant synthesis and the other via wet synthesis. Green, red, and NIR emission from the Er3+ ion was observed in both bulk and nanocrystalline samples. Emission from the F-2(5/2) --> F-2(7/2) Yb3+ transition was also observed in the bulk and nanocrystalline samples following 488 nm excitation, thereby signifying the presence of an energy transfer process from Er3+ to Yb3+. The peaks attributed to Yb3+ emission were much less intense in the nanocrystalline material, indicating that the energy transfer process occurs less readily in this material because of the inherent high phonon energies from the adsorbed CO2 and H2O on their surface. Following excitation with 978 nm, green and red anti-Stokes luminescence was evidenced in the samples under investigation. An enhancement of the red emission is observed in both bulk and nanocrystalline samples, although to a much greater degree in nanocrystalline Y2O3:Er3+, Yb3+. The enhancement of the red emission was shown to occur due to an ion-pair process of the form: (F-4(7/2), I-4(11/2)) --> (F-4(9/2), F-4(9/2)), which directly populates the F-4(9/2) state. However, this process cannot account for the drastic difference in the magnitude of the red enhancement between bulk and nanocrystalline samples A phonon-assisted energy transfer process was found to be operative, which also populates the F-4(9/2) state. This process occurs more readily in the nanocrystalline material as the large vibrational quanta from the adsorbed carbonate and hydroxyl ions can easily bridge the mismatch in energy.