Dipartimento di Fisica, Sapienza-Università di Roma, Piazzale A. Moro 2, 00185 Roma, Italy.
Nat Commun. 2012 Jul 24;3:975. doi: 10.1038/ncomms1968.
Colloidal particles have the right size to form ordered structures with periodicities comparable to the wavelength of visible light. The tantalizing colours of precious opals and the colour of some species of birds are examples of polycrystalline colloidal structures found in nature. Driven by the demands of several emergent technologies, efforts have been made to develop efficient, self-assembly-based methodologies for generating colloidal single crystals with well-defined morphologies. Somewhat unfortunately, these efforts are often frustrated by the formation of structures lacking long-range order. Here we show that the rational design of patch shape and symmetry can drive patchy colloids to crystallize in a single, selected morphology by structurally eliminating undesired polymorphs. We provide a proof of this concept through the numerical investigation of triblock Janus colloids. One particular choice of patch symmetry yields, via spontaneous crystallization, a pure tetrastack lattice, a structure with attractive photonic properties, whereas another one results in a colloidal clathrate-like structure, in both cases without any interfering polymorphs.
胶体粒子的大小合适，可以与可见光波长相当的周期性形成有序结构。珍贵蛋白石的诱人色彩和某些鸟类的颜色就是自然界中多晶胶体结构的例子。受到几种新兴技术的需求的推动，人们已经努力开发有效的、基于自组装的方法，以生成具有良好形貌的胶体单晶。有些不幸的是，这些努力常常因形成缺乏长程有序的结构而受挫。在这里，我们表明，通过合理设计补丁形状和对称性，可以通过结构消除不需要的多晶型物，使具有各向异性的胶体在单一的、选定的形态中结晶。我们通过对三嵌段 Janus 胶体的数值研究证明了这一概念。通过选择特定的补丁对称性，通过自发结晶，可以得到纯的 tetrastack 晶格，这是一种具有吸引力的光子特性的结构，而另一种则得到胶体笼状结构，在这两种情况下都没有任何干扰的多晶型物。
