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长期的研究课题的基础和技术的重要性，在微观层面上的成核过程的细节仍然知之甚少。这适用于本体中的（"均质"）成核和表面附近的（"非均质"）成核。微米级胶体颗粒的悬浮液已经成为单颗粒水平上进行此类研究的有价值的模型系统，因为它们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进行观察，控制粒子间相互作用的可能性以及最近可用的工具，如光学或磁性镊子，可以方便地操纵单个粒子的位置。本项目的主要目标是达到异质晶体成核的详细了解接近at，弯曲，粗糙，和结构化的表面，可以加速或抑制成核。我们将集中在晶体前体和临界晶核的性质，这是最感兴趣的成核过程。我们将在折射率和密度匹配的有机溶剂中使用聚甲基丙烯酸甲酯胶体，其相互作用像轻微带电的硬球。控制的形状，大小和对称性的晶核将产生的光学多镊子和后续过程中的结晶共聚焦显微镜观察。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，重点是分层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.