报告题目：3D imaging of the translational and rotational dynamics of colloids对胶体粒子平移和旋转动力学特性的三维成像研究
报告人：Prof. Andreas Zumbusch, Department of Chemistry, University of Konstanz, Germany
Abstract: Single particle tracking based on confocal fluorescence microscopy has revealed a wealth of details of the translational dynamics of spherical colloidal particles. To date, however, nearly no experimental on the rotational dynamics of colloids is available. We report results of 3D optical microscopy experiments in which translational and rotational colloid dynamics were simultaneously monitored. To this end, we employ polymer colloids with a differently labelled cores and shells.
For the investigation of spherical colloids, we produce particles containing two differently labelled fluorescent cores1. These rotational tracers can be combined with monodisperse host particles enclosing a single fluorescent core and chemical and physical properties identical to the tracers. This leads to a system of spherical colloids, in which rotation and translation of individual particles can be recorded simultaneously from dilute fluid to densely packed crystal. Our analysis shows that translation and rotation of colloidal particles are uncorrelated and decoupled for all volume fractions irrespective of the phase of the particle system.
Core/shell geometries also allow the tracking of translational and rotational motion of particles with anisotropic shapes, such as ellipsoids2,3. We introduce PMMA/PMMA core-shell ellipsoids with a spherical core and an elliptical shell labelled with different fluorescent dyes, which are well suited for confocal microscopy. The detection of each ellipsoid within the 3D image volume requires new image processing tools.4 We developed an algorithm which is able to detect each ellipsoid in position on subpixel accuracy and orientation within an accuracy of 5°. With this we are able to study a system of monodisperse ellipsoids over a wide range of volume fractions which show a glass transition at high volume fractions. As an outlook, we will discuss the implementation of optical tweezers for active manipulation of ellipsoidal colloids in dense suspensions.
 S. Schütter, J. Roller, A. Kick, J.-M. Meijer, A. Zumbusch, “Real-space imaging of translational and rotational dynamics of hard spheres from the fluid to the crystal“, Soft Matter, 13 (2017) 8240
 M. K. Klein, N. Klinkenberg, S. Schuetter, N. Saenger, Nicolai, P. Pfleiderer, A. Zumbusch, "Core-shell microparticles with ellipsoidal, fluorescent cores: Accessing rotational dynamics", Langmuir, 31 (2015) 2655
 M. K. Klein, N. R. S？nger, S. Schütter, P. Pfleiderer, A. Zumbusch, "Shape-tunable core-shell microparticles", Langmuir, 30 (2014) 12457
 J. Roller, P. Pfleiderer, J.-M. Meijer, A. Zumbusch "Detection and tracking of anisotropic core-shell colloids", J. Phys.: Cond. Matt., 30 (2018) 395903
Speaker: Professor Zumbusch has studied Chemistry and Physics at the Ludwig-Maximilians University in Munich, Germany and the Centre de Physique Moléculaire et Optique Hertzienne, CNRS, Bordeaux, France and is currently a Professor for Physical Chemistry at the University of Konstanz, Germany. His research interests include the development of single molecule fluorescence and label-free non-linear optical microscopy. Professor Zumbusch has pioneered both the development of single molecule fluorescence detection and CARS microscopy. He applies these techniques in biomedical imaging and in studies of intracellular transport, of post-translational protein modifications and of colloidal model systems.