Giavazzi Fabio, Haro-Pérez Catalina, Cerbino Roberto
Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli Studi di Milano, via F.lli Cervi 93, 20090 Segrate, Italy.
J Phys Condens Matter. 2016 May 18;28(19):195201. doi: 10.1088/0953-8984/28/19/195201. Epub 2016 Apr 19.
We probe the roto-translational Brownian motion of optically anisotropic particles suspended in water with a simple and straightforward optical microscopy experiment that does not require positional or rotational particle tracking. We acquire a movie of the suspension placed between two polarizing elements and we extract the translational diffusion coefficient D T and the rotational diffusion coefficient D R from the analysis of the temporal correlation properties of the spatial Fourier modes of the intensity fluctuations in the movie. Our method is successfully tested with a dilute suspension of birefringent spherical colloidal particles obtained by polymerizing an emulsion of droplets of liquid crystal in a nematic phase, whose roto-translational dynamics is found to be well described by theory. The simplicity of our approach makes our method a viable alternative to particle tracking and depolarized dynamic light scattering.
我们通过一个简单直接的光学显微镜实验来探究悬浮在水中的光学各向异性粒子的旋转平移布朗运动，该实验无需对粒子进行位置或旋转跟踪。我们获取了置于两个偏振元件之间的悬浮液的影片，并通过分析影片中强度涨落的空间傅里叶模式的时间相关特性，提取出平移扩散系数(D_T)和旋转扩散系数(D_R)。我们的方法已成功应用于通过聚合向列相液晶液滴乳液得到的双折射球形胶体粒子的稀悬浮液，其旋转平移动力学被发现与理论描述相符。我们方法的简单性使其成为粒子跟踪和去偏振动态光散射的可行替代方法。
