Confinement on energy transfer between luminescent centers in nanocrystals
Confinement on energy transfer between luminescent centers in nanocrystals
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DOI：
10.1063/1.1614865
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发表时间：
2003-11-01
影响因子：
3.2
通讯作者：
Niedbala, RS
中科院分区：
文献类型：
--
作者：
Chen, XY;Zhuang, HZ;Niedbala, RS
纳米晶体中光学中心的发光动力学与声子态密度（PDOS）密切相关，这与块体材料的光子态密度有很大不同。结果表明，纳米晶体中的能量传递（ET）受到离散PDOS以及直接尺寸限制的限制。利用激光光谱实验和计算机模拟研究了Y（2）O（2）S纳米晶体中Er（3+）（4）S（3/2）态荧光衰减的温度、浓度和尺寸依赖性。一组微观速率方程，管理的激发概率P（i）（t）的演变迭代求解使用Monte Carlo方法。基于一个五参数的理论模型的ET模拟结果与实验结果吻合较好。结果表明，Er（3+）：Y（2）O（2）S纳米晶体中声子辅助的电子转移过程对295 K下的荧光衰减有部分贡献，而在5 K下的贡献可以忽略不计。对于应用，由于纳米荧光粉中缺乏低频声子模式和受限的激发迁移，对ET的纳米限制效应可能会显著降低敏化或上转换发光的效率。(C)2003年，美国物理学会。
The luminescence dynamics of optical centers in nanocrystals depends critically on the phonon density of states (PDOS), which is quite distinct from that of bulk materials. It is shown that energy transfer (ET) in nanocrystals is confined by discrete PDOS as well as direct size restriction. Temperature-, concentration-, and size-dependence of the fluorescence decay from the (4)S(3/2) state of Er(3+) in Y(2)O(2)S nanocrystals have been investigated using laser spectroscopic experiments and computational simulations. A set of microscopic rate equations that govern the evolution of the excitation probability P(i)(t) are solved iteratively using a Monte Carlo method. The simulations of ET based on a theoretical model with five parameters are in good agreement with the experimental results. It is shown that phonon-assisted ET processes in Er(3+):Y(2)O(2)S nanocrystals contribute partly to the fluorescence decay at 295 K, and is negligible at 5 K. For applications, the nanoconfinement effects on ET may significantly reduce the efficiency of sensitized or upconversion luminescence due to the lack of low-frequency phonon modes and restricted excitation migration in nanophosphors. (C) 2003 American Institute of Physics.