Quantum Electronics Department, Institute of Physics "Gleb Wataghin", University of Campinas - UNICAMP, Campinas, São Paulo, Brazil.
Methods Mol Biol. 2020;2135:85-93. doi: 10.1007/978-1-0716-0463-2_4.
Colloidal quantum dots (QDs), due to their versatile optoelectronic properties, have been used in life science applications, especially in fluorescence-based techniques, for over two decades. A great variety of QD syntheses and conjugations are available, and tailoring these for the desired application requires a refined structural characterization. Life science applications rely on the interaction of QDs with biostructures; hence, the knowledge of the QD actual size (i.e., its hydrodynamic radius in the medium the experiment is being carried) and the size of their conjugates is paramount. Fluorescence correlation spectroscopy (FCS) is an optical technique that uses fluorophore light emission to measure its hydrodynamic radius, instead of relying on particle light scattering or crystalline structure, making it ideal for studying bioconjugated QDs in suspension. From the fluorescence intensity autocorrelation, FCS measures the diffusion coefficient of systems in a diluted sample and, by obtaining the diffusion coefficient, it is possible to calculate its hydrodynamic radius. In this chapter we describe the main aspects of the FCS technique and how to use it to calculate the hydrodynamic radius of QDs.
胶体量子点（QDs）由于其多功能的光电特性，已经在生命科学应用中得到了广泛应用，特别是在基于荧光的技术中，已经超过了二十年。有各种各样的 QD 合成和偶联方法，为了满足特定的应用需求，需要对其进行精细的结构表征。生命科学应用依赖于 QD 与生物结构的相互作用；因此，了解 QD 的实际尺寸（即在实验进行的介质中的流体力学半径）及其偶联物的尺寸至关重要。荧光相关光谱（FCS）是一种光学技术，它利用荧光体的光发射来测量其流体力学半径，而不是依赖于粒子光散射或晶体结构，因此非常适合研究悬浮液中的生物共轭 QD。从荧光强度自相关，FCS 可以测量稀释样品中系统的扩散系数，并且通过获得扩散系数，可以计算出其流体力学半径。在这一章中，我们将描述 FCS 技术的主要方面以及如何使用它来计算 QD 的流体力学半径。
