Liu Jianing, Shen Tong, Yang Zhao Hua, Zhang Shu, Sun Guang Yu
School of Physics and Optoelectronic Engineering, Nanjing University of Information Science & Technology , Nanjing 210044, China.
Jiangsu Key Laboratory for Optoelectronic Detection of Atmosphere and Ocean, Nanjing University of Information Science & Technology , Nanjing 210044, China.
J Phys Chem Lett. 2017 Oct 5;8(19):4652-4658. doi: 10.1021/acs.jpclett.7b02096. Epub 2017 Sep 14.
Nucleation plays a decisive role in determining the crystal structure and size distribution; however, understanding of the fundamentals of nucleation is quite limited. In particular, it is unclear whether a nucleus forms spontaneously from solution via a single- or multiple-step process. Here we show how a binary mixture of charged colloidal spheres nucleates heterogeneously on a flat substrate by means of Bragg microscopy, laser diffraction, and laser microscopy. In contrast with the conventional one-step and two-step nucleation mechanisms, a novel pathway of multistep heterogeneous nucleation under certain experimental conditions is highlighted by four steps: initial homogeneous fluid → prenucleation clusters → preordered prenucleation clusters → intermediate ordered phase → final crystal. It is expected that the obtained results would be helpful in rationalizing the rich phase behavior exhibited by the binary mixture systems and in developing better and broadly applicable nucleation models as well as in designing defect-free single-crystal alloys.
成核作用在决定晶体结构和尺寸分布方面起着决定性作用；然而，对成核基本原理的理解相当有限。特别是，目前尚不清楚晶核是通过单步还是多步过程从溶液中自发形成的。在这里，我们展示了带电胶体球的二元混合物如何通过布拉格显微镜、激光衍射和激光显微镜在平坦基底上异质成核。与传统的一步和两步成核机制不同，在某些实验条件下，一种新的多步异质成核途径通过四个步骤得到突出：初始均相流体→预成核团簇→预有序预成核团簇→中间有序相→最终晶体。预计所获得的结果将有助于阐明二元混合体系所表现出的丰富相行为，有助于开发更好且广泛适用的成核模型，以及有助于设计无缺陷的单晶合金。
