Excitation-wavelength dependence of fluorescence intermittency in CdSe nanorods.
Excitation-wavelength dependence of fluorescence intermittency in CdSe nanorods.
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DOI：
10.1021/nn800421g
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发表时间：
2008-09
期刊：
影响因子：
17.1
通讯作者：
K. Knappenberger;Daryl B. Wong;W. Xu;A. Schwartzberg;A. Wolcott;J. Zhang;S. Leone
中科院分区：
文献类型：
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作者：
K. Knappenberger;Daryl B. Wong;W. Xu;A. Schwartzberg;A. Wolcott;J. Zhang;S. Leone
研究了激发波长和包埋介质对4 nm×20 nm硒化镉(CdSe)纳米棒荧光闪烁统计的影响。光子反聚束(PAB)实验证实了单个CdSe纳米棒的非经典发射，其辐射寿命为26+/-13 ns。闪烁数据显示的行为可以分为两类：在带隙能量附近的激发和在带隙以上能量超过240 meV的激发。在带隙能量下的激发(或=560 nm)会在“开”和“关”事件的分布中产生更明显的“开”时间概率，而那些激发超过带隙240 meV或更多(或=560 nm)的激发产生的“开”时间概率要低200倍，其持续时间超过4 S。“关”时间统计也对激发波长很敏感，显示出类似的但相反相关的效应。为了更好地了解激发波长的依赖关系，我们获得了单个纳米棒的荧光测量，这些纳米棒既沉积在裸显微镜盖片上，又包埋在1-乙基-3-甲基咪唑双(三氟甲基磺酰基)亚胺室温离子液体(RTIL)中。只有当激发能量超过240 meV阈值时，嵌入RTIL介质才会对合成的荧光统计产生显著影响。这一结果可以用进入非发射陷阱态的阈值来解释，该阈值归因于在较高的光子激发能量下热电荷载流子的自陷。
The influence of excitation wavelength and embedding media on fluorescence blinking statistics of 4 nm x 20 nm cadmium selenide (CdSe) nanorods is investigated. Photon antibunching (PAB) experiments confirm nonclassical emission from single CdSe nanorods that exhibit a radiative lifetime of 26 +/- 13 ns. The blinking data show behaviors that can be categorized into two classes: excitation near the energy of the band gap and at energies exceeding 240 meV above the band gap. Excitation at the band gap energy (lambda >or= 560 nm) results in more pronounced "on" time probabilities in the distribution of "on" and "off" events, while those resulting from excitation exceeding the band gap by 240 meV or more (lambda <or= 560 nm) are 200 times less likely to display continuous "on" fluorescence persisting beyond 4 s. The "off" time statistics are also sensitive to the excitation wavelength, showing a similar, but inversely correlated, effect. To understand better the excitation-wavelength dependence, fluorescence measurements are obtained for single nanorods deposited both on a bare microscope coverslip and embedded in 1-ethyl-3-methylimidizolium bis(trifluoromethylsulfonyl)imide room-temperature ionic liquid (RTIL). The embedding RTIL medium has a significant influence on the resultant fluorescence statistics only when the excitation energy exceeds the 240 meV threshold. The results are explained by a threshold to access nonemissive trap states, attributed to self-trapping of hot charge carriers at the higher photon excitation energies.