Measurement of the Hydrodynamic Radius of Quantum Dots by Fluorescence Correlation Spectroscopy Excluding Blinking
Measurement of the Hydrodynamic Radius of Quantum Dots by Fluorescence Correlation Spectroscopy Excluding Blinking
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DOI：
10.1021/jp512214p
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发表时间：
2015-03-19
影响因子：
3.3
通讯作者：
Cesar, C. L.
中科院分区：
文献类型：
--
作者：
de Thomaz, A. A.;Almeida, D. B.;Cesar, C. L.
量子点（QD）最重要的特性之一是它们的尺寸。它们的大小将决定光学性质，并在胶体介质中决定它们的相互作用范围。用于测量QD尺寸的最常见的技术是透射电子显微镜（TEM）和X射线衍射。然而，这些技术要求样品在真空下干燥。通过这种方式，任何流体动力学信息都被排除在外，并且制备过程甚至可以改变QD的大小。荧光相关光谱（FCS）是一种具有单分子灵敏度的光学技术，能够提取量子点的流体动力学半径（HR）。FCS的主要缺点是闪烁现象改变了相关函数，这意味着量子点的表观尺寸比实际尺寸小。在这项工作中，我们开发了一种排除FCS闪烁的方法并测量了胶体量子点的HR。我们比较了我们的结果与TEM图像，并通过FCS得到的HR高于TEM测量的半径。我们将这种差异归因于在TEM图像中看不到的QD的帽层。
One of the most important properties of quantum dots (QDs) is their size. Their size will determine optical properties and in a colloidal medium their range of interaction. The most common techniques used to measure QD size are transmission electron microscopy (TEM) and X-ray diffraction. However, these techniques demand the sample to be dried and under a vacuum. This way any hydrodynamic information is excluded and the preparation process may alter even the size of the QDs. Fluorescence correlation spectroscopy (FCS) is an optical technique with single molecule sensitivity capable of extracting the hydrodynamic radius (HR) of the QDs. The main drawback of FCS is the blinking phenomenon that alters the correlation function implicating in a QD apparent size smaller than it really is. In this work, we developed a method to exclude blinking of the FCS and measured the HR of colloidal QDs. We compared our results with TEM images, and the HR obtained by FCS is higher than the radius measured by TEM. We attribute this difference to the cap layer of the QD that cannot be seen in the TEM images.