Crystallization is a universal phenomenon underpinning many industrial and natural processes and is fundamental to chemistry and materials science. However, microscopic crystallization pathways of nanoparticle superlattices have been seldom studied mainly owing to the difficulty of real-time observation of individual self-assembling nanoparticles in solution. Here, using in situ electron microscopy, we directly image the full self-assembly pathway from dispersed nanoparticles into ordered superlattices in nonaqueous solution. We show that electron-beam irradiation controls nanoparticle mobility, and the solvent composition largely dictates interparticle interactions and assembly behaviors. We uncover a multistep crystallization pathway consisting of four distinct stages through multi-order-parameter analysis and visualize the formation, migration, and annihilation of multiple types of defects in nanoparticle superlattices. These findings open the door for achieving independent control over imaging conditions and nanoparticle assembly conditions and will enable further study of the microscopic kinetics of assembly and phase transition in nanocolloidal systems.

中文翻译：

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非水溶液中动态纳米粒子超晶格的多步结晶

结晶是支撑许多工业和自然过程的普遍现象，是化学和材料科学的基础。然而，由于难以实时观察溶液中单个自组装纳米粒子，因此很少研究纳米粒子超晶格的微观结晶途径。在这里，使用原位电子显微镜，我们直接成像从分散的纳米粒子到非水溶液中有序超晶格的完整自组装途径。我们表明，电子束辐照控制纳米粒子的移动性，溶剂组成在很大程度上决定了粒子间的相互作用和组装行为。我们通过多阶参数分析揭示了一个由四个不同阶段组成的多步结晶途径，并可视化了形成、迁移、并消除纳米粒子超晶格中的多种缺陷。这些发现为实现对成像条件和纳米粒子组装条件的独立控制打开了大门，并将有助于进一步研究纳米胶体系统中组装和相变的微观动力学。