Heterogeneous Nucleation and Crystal Growth in Colloidal Model Systems Studied by Confocal Microscopy

虽然晶体的成核和生长是一个具有基础和技术重要性的长期研究课题，但在微观层面上成核过程的细节仍然知之甚少。这既适用于块体中的(“均匀”)形核，也适用于表面附近的(“非均质”)形核。微米级胶体粒子悬浮液由于易于在所有相关的时间和长度尺度上通过常规或共聚焦显微镜观察，可能控制粒子间的相互作用，以及最近可利用的工具如光学或磁钳方便地操纵单个粒子的位置，因此已成为此类单粒子水平研究的有价值的模型系统。该项目的主要目标是详细地了解靠近AT、弯曲、粗糙和结构化表面的异质晶体成核，这些表面既可以加速成核，也可以抑制成核。我们将集中讨论对成核过程最感兴趣的晶体前体和临界晶核的性质。我们将在指数和密度匹配的有机溶剂中使用聚甲基丙烯酸甲酯胶体，它们相互作用就像略带电荷的硬球。在共聚焦显微镜下观察到晶核的形状、大小和对称性将由光学多钳子和随后的结晶过程产生。我们还计划研究由不同尺寸、电荷和混合比的颗粒组成的二元系统，重点是分离和晶体生长之间的相互作用。

While nucleation and growth of crystals is a longstanding research topic of fundamental and technological importance details of the nucleation process on a microscopic level are still poorly understood. This holds both for ("homogeneous") nucleation in the bulk and for ("heterogeneous") nucleation near surfaces. Suspensions of micron-sized colloidal particles have become valuable model systems for such studies on the single-particle level because of the ease of their observation by conventional or confocal microscopy at all relevant time and length scales, the possible control the interparticle interaction and the recent availability of tools such as optical or magnetic tweezers to conveniently manipulate individual particle positions.The main goal of this project is to reach a detailed understanding of heterogeneous crystal nucleation close to at, curved, rough, and structured surfaces that can either accelerate or suppress nucleation. We will focus on the properties of crystal precursors and critical crystal nuclei which are of prime interest for the nucleation process. We will use polymethylmethacrylate colloids in a index and density matched organic solvent which interact like slightly charged hard spheres. Crystal nuclei of controlled shape, size and symmetry will be generated by an optical multitweezer and the subsequent processes during crystallization observed by confocal microscopy. We also plan to study binary systems composed of particles with different sizes, charges and mixing ratios, with emphasis on the interplay between demixing and crystal growth.