Structure and Ultrafast Dynamics of White-Light-Emitting CdSe Nanocrystals
Structure and Ultrafast Dynamics of White-Light-Emitting CdSe Nanocrystals
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DOI：
10.1021/ja900529h
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发表时间：
2009-04-29
影响因子：
15
通讯作者：
Rosenthal, Sandra J.
中科院分区：
文献类型：
--
作者：
Bowers, Michael J., II;McBride, James R.;Rosenthal, Sandra J.
超小的CdSe纳米晶体的白光发射为实现固态照明提供了另一种方法，作为一种对消费者有吸引力的技术。不幸的是，它们极小的尺寸限制了传统方法的可行性。本文报道了它们的结构，这是使用像差校正的原子序数衬度扫描透射电子显微镜（Z-STEM）获得的第一个图像。Z-STEM具有亚埃的分辨率，是少数几种可用于直接成像的方法之一。最初的图像表明它们是晶体，直径约为四个晶格平面。除了结构之外，首次使用超快荧光上转换光谱在白光光谱的不同波长处测量激子动力学。这些数据表明，大量的陷阱状态负责的广谱发射。希望本文所提供的信息能为今后白光纳米晶体的开发和改进提供基础。
White-light emission from ultrasmall CdSe nanocrystals offers an alternative approach to the realization of solid-state lighting as an appealing technology for consumers. Unfortunately, their extremely small size limits the feasibility of traditional methods for nanocrystal characterization. This paper reports the first images of their structure, which were obtained using aberration-corrected atomic number contrast scanning transmission electron microscopy (Z-STEM). With subangstrom resolution, Z-STEM is one of the few available methods that can be used to directly image the nanocrystal's structure. The initial images suggest that they are crystalline and approximately four lattice planes in diameter. In addition to the structure, for the first time, the exciton dynamics were measured at different wavelengths of the white-light spectrum using ultrafast fluorescence upconversion spectroscopy. The data suggest that a myriad of trap states are responsible for the broad-spectrum emission. It is hoped that the information presented here will provide a foundation for the future development and improvement of white-light-emitting nanocrystals.