Ye Matthew, Hueckel Theodore, Gatenil Perapat P, Nagao Keisuke, Carter W Craig, Macfarlane Robert J
Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
ACS Nano. 2024 Jun 18;18(24):15970-15977. doi: 10.1021/acsnano.4c04192. Epub 2024 Jun 5.
Nanoparticle assembly is a material synthesis strategy that enables precise control of nanoscale structural features. Concepts from traditional crystal growth research have been tremendously useful in predicting and programming the unit cell symmetries of these assemblies, as their thermodynamically favored structures are often identical to atomic crystal analogues. However, these analogies have not yielded similar levels of influence in programming crystallite shapes, which are a consequence of both the thermodynamics and kinetics of crystal growth. Here, we demonstrate kinetic control of the colloidal crystal shape using nanoparticle building blocks that rapidly assemble over a broad range of concentrations, thereby producing well-defined crystal habits with symmetrically oriented dendritic protrusions and providing insight into the crystals' morphological evolution. Counterintuitively, these nonequilibrium crystal shapes actually become more common for colloidal crystals synthesized closer to equilibrium growth conditions. This deviation from typical crystal growth processes observed in atomic or molecular crystals is shown to be a function of the drastically different time scales of atomic and colloidal mass transport. Moreover, the particles are spherical with isotropic ligand grafts, and these kinetic crystal habits are achieved without the need for specifically shaped particle building blocks or external templating or shape-directing agents. Thus, this work provides generalizable design principles to expand the morphological diversity of nanoparticle superlattice crystal habits beyond the anhedral or equilibrium polyhedral shapes synthesized to date. Finally, we use this insight to synthesize crystallite shapes that have never before been observed, demonstrating the ability to both predict and program kinetically controlled superlattice morphologies.
纳米颗粒组装是一种材料合成策略，能够精确控制纳米级结构特征。传统晶体生长研究中的概念在预测和规划这些组装体的晶胞对称性方面非常有用，因为它们热力学上有利的结构通常与原子晶体类似物相同。然而，这些类比在规划微晶形状方面并未产生类似程度的影响，微晶形状是晶体生长的热力学和动力学共同作用的结果。在这里，我们展示了使用纳米颗粒构建块对胶体晶体形状进行动力学控制，这些构建块在很宽的浓度范围内快速组装，从而产生具有对称取向树枝状突起的明确晶体习性，并深入了解晶体的形态演变。与直觉相反，对于在更接近平衡生长条件下合成的胶体晶体，这些非平衡晶体形状实际上变得更为常见。这种与在原子或分子晶体中观察到的典型晶体生长过程的偏差表明，这是原子和胶体质量传输时间尺度截然不同的函数。此外，颗粒是具有各向同性配体接枝的球形，并且这些动力学晶体习性的实现无需特定形状的颗粒构建块或外部模板或形状导向剂。因此，这项工作提供了可推广的设计原则，以扩大纳米颗粒超晶格晶体习性的形态多样性，超越迄今为止合成的无定形或平衡多面体形状。最后，我们利用这一见解合成了前所未有的微晶形状，展示了预测和规划动力学控制的超晶格形态的能力。
