Fluorescence intermittency in single cadmium selenide nanocrystals
Fluorescence intermittency in single cadmium selenide nanocrystals
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DOI：
10.1038/383802a0
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发表时间：
1996-10-31
期刊：
影响因子：
64.8
通讯作者：
Brus, LE
中科院分区：
文献类型：
--
作者：
Nirmal, M;Dabbousi, BO;Brus, LE
半导体纳米晶体提供了一个机会，研究的演变，一个系统的大小增加，从分子尺度（1，2）庞大的材料性能。此外，它们强烈的尺寸依赖性光学性质使它们成为光电器件中的可调谐光吸收器和发射器，如发光二极管（3，4）和量子点激光器（5，6），以及生物系统的光学探针（7）。在这里，我们表明，从单一的荧光纳米晶体的硒化镉连续激发下的光发射打开和关闭间歇性的特征时间尺度约为0.5秒。从许多纳米晶体的系综测量中，这种不稳定性并不明显。当硫化锌的钝化、高带隙壳层包裹住发光层时，对激发强度的依赖性和开/关时间的变化（8，9）表明发光的突然关闭是由发光层的光电离引起的。因此，对单个纳米晶体的光谱测量可以揭示它们的光物理学的迄今未知的方面。
SEMICONDUCTOR nanocrystals offer the opportunity to study the evolution of hulk materials properties as the size of a system increases from the molecular scale(1,2). In addition, their strongly size-dependent optical properties render them attractive candidates as tunable light absorbers and emitters in optoelectronic devices such as light-emitting diodes(3,4) and quantum-dot lasers(5,6), and as optical probes of biological systems(7). Here we show that light emission from single fluorescing nanocrystals of cadmium selenide under continuous excitation turns on and off intermittently with a characteristic timescale of about 0.5 seconds. This intermittency is not apparent from ensemble measurements on many nanocrystals. The dependence on excitation intensity and the change in on/off times when a passivating, high-bandgap shell of zinc sulphide encapsulates the nanocrystal(8,9) suggests that the abrupt turning off of luminescence is caused by photoionization of the nanocrystal. Thus spectroscopic measurements on single nanocrystals can reveal hitherto unknown aspects of their photophysics.