A Common Mechanism Underlies the Dark Fraction Formation and Fluorescence Blinking of Quantum Dots
A Common Mechanism Underlies the Dark Fraction Formation and Fluorescence Blinking of Quantum Dots
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DOI：
10.1021/nn800684z
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发表时间：
2009-05-01
期刊：
影响因子：
17.1
通讯作者：
Heyes, Colin D.
中科院分区：
文献类型：
--
作者：
Durisic, Nela;Wiseman, Paul W.;Heyes, Colin D.
已知 CdSe 量子点 (QD) 表现出幂律闪烁动力学和暗分数。仍然缺乏对这些特性的机械起源的完整描述。我们表明，QD 环境 pH 值的变化会系统地改变暗部分和闪烁统计数据。随着 pH 值降低，“开启”时间变短，“关闭”时间变长，并且永久暗分数增加。在暗分数增加之前，单个 OD 的发射强度会降低。有趣的是，当量子点从暴露于空气的环境进入水性环境时，描述闪烁的概率分布函数的形式发生了变化。这些结果用于提出 H+ 离子的耦合作用，通过该作用，它们首先降低发射态的强度，并影响 QD 在“开”和“关”状态之间切换的概率，并最终将 OD 捕获在永久“关”状态。我们讨论并扩展了两个理论眨眼模型，以解释 H+ 离子的影响，并强调它们控制眨眼的扩散控制机制的共同原理。
CdSe quantum dots (QDs) are known to exhibit both power-law blinking dynamics and a dark fraction. A complete description of the mechanistic origins of these properties is still lacking. We show that a change in the pH of the QD environment systematically changes both the dark fraction and the blinking statistics. As pH is lowered, shorter "on" times and longer "off" times, as well as an increase in the permanent dark fraction, are observed. The increase in the dark fraction is preceded by a decrease in the emission intensity of a single OD. Interestingly, the form of the probability distribution function describing blinking changes when the QDs are taken from an air-exposed environment into an aqueous one. These results are used to propose a coupled role for H+ ions by which they first reduce the intensity of the emitting state as well as affect the probabilities of the QD to switch between "on" and "off" states and eventually trap the OD in a permanent "off" state. We discuss and extend two theoretical blinking models to account for the effect of H+ ions as well as to highlight their common principle of a diffusion-controlled mechanism governing blinking.