Xu Joanna Xiuzhu, Liu Muqiong, Athukorale Sumudu, Zou Shengli, Zhang Dongmao
Department of Chemistry, Mississippi State University, Mississippi State, Mississippi 39762, United States.
Department of Chemistry, University of Central Florida, Orlando, Florida 32816, United States.
ACS Omega. 2019 Mar 4;4(3):4739-4747. doi: 10.1021/acsomega.8b03354. eCollection 2019 Mar 31.
Anisotropy and depolarization are two interconvertible parameters in fluorescence and light scattering spectroscopy that describe the polarization distribution of emitted and scattered photons generated with linearly polarized excitation light. Whereas anisotropy is more frequently used in fluorescence literature for studying association/dissociation of fluorophore-bearing reagents, depolarization is more popular in the light-scattering literature for investigating the effect of scatterers' geometries and chemical compositions. Presented herein is a combined computational and experimental study of the scattering and fluorescence depolarization enhancement induced by light scattering in turbid samples. The most important finding is that sample light scattering and fluorescence depolarization increases linearly with sample light-scattering extinction. Therefore, one can extrapolate the analyte-specific scattering and fluorescence depolarization through linear curve fitting of the sample light scattering and fluorescence depolarization as a function of the sample concentration or the path length of the sampling cuvettes. An example application of this linear extrapolation method is demonstrated for quantifying the fluorophore-specific fluorescence depolarization and consequently its anisotropy for an aggregation-induced-emission sample. This work should be important for a wide range of macromolecular, supramolecular, and nanoscale fluorescent materials that are often strong light scatterers due to their large sizes.
在荧光和光散射光谱学中，各向异性和去极化是两个可相互转换的参数，用于描述由线偏振激发光产生的发射光子和散射光子的偏振分布。虽然各向异性在荧光文献中更常用于研究含荧光团试剂的缔合/解离，但去极化在光散射文献中更常用于研究散射体几何形状和化学成分的影响。本文介绍了一项关于浑浊样品中光散射引起的散射和荧光去极化增强的计算与实验相结合的研究。最重要的发现是，样品光散射和荧光去极化随样品光散射消光呈线性增加。因此，通过将样品光散射和荧光去极化作为样品浓度或采样比色皿光程的函数进行线性曲线拟合，可以推断出特定分析物的散射和荧光去极化。本文展示了这种线性外推法在量化聚集诱导发光样品中荧光团特异性荧光去极化及其各向异性方面的一个应用实例。这项工作对于许多大分子、超分子和纳米级荧光材料来说应该很重要，这些材料由于尺寸较大，往往是强光散射体。
