Department of Materials Science and Engineering, University of Illinois, Urbana, IL, 61801, USA.
Materials Research Laboratory, University of Illinois, Urbana, IL, 61801, USA.
Nat Commun. 2020 Sep 11;11(1):4555. doi: 10.1038/s41467-020-18363-2.
Development of the surface morphology and shape of crystalline nanostructures governs the functionality of various materials, ranging from phonon transport to biocompatibility. However, the kinetic pathways, following which such development occurs, have been largely unexplored due to the lack of real-space imaging at single particle resolution. Here, we use colloidal nanoparticles assembling into supracrystals as a model system, and pinpoint the key role of surface fluctuation in shaping supracrystals. Utilizing liquid-phase transmission electron microscopy, we map the spatiotemporal surface profiles of supracrystals, which follow a capillary wave theory. Based on this theory, we measure otherwise elusive interfacial properties such as interfacial stiffness and mobility, the former of which demonstrates a remarkable dependence on the exposed facet of the supracrystal. The facet of lower surface energy is favored, consistent with the Wulff construction rule. Our imaging-analysis framework can be applicable to other phenomena, such as electrodeposition, nucleation, and membrane deformation.
晶态纳米结构的表面形貌和形状的发展控制着各种材料的功能，从声子输运到生物相容性。然而，由于缺乏单粒子分辨率的实空间成像，这种发展的动力学途径在很大程度上仍未被探索。在这里，我们使用胶体纳米粒子组装成超晶体作为模型系统，并确定了表面波动在超晶体形成中的关键作用。利用液相透射电子显微镜，我们绘制了超晶体的时空表面轮廓，这些轮廓符合毛细波理论。基于这一理论，我们测量了其他难以捉摸的界面特性，如界面刚度和迁移率，前者显示出与超晶体暴露面的显著依赖性。具有较低表面能的面是有利的，这与 Wulff 构造规则一致。我们的成像分析框架可应用于其他现象，如电沉积、成核和膜变形。
