Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA.
Carl Zeiss Microscopy Inc., Pleasanton, CA, 94588, USA.
Small. 2020 Feb;16(8):e1906146. doi: 10.1002/smll.201906146. Epub 2020 Jan 23.
A method for the solidification of metallic alloys involving spiral self-organization is presented as a new strategy for producing large-area chiral patterns with emergent structural and optical properties, with attention to the underlying mechanism and dynamics. This study reports the discovery of a new growth mode for metastable, two-phase spiral patterns from a liquid metal. Crystallization proceeds via a non-classical, two-step pathway consisting of the initial formation of a polytetrahedral seed crystal, followed by ordering of two solid phases that nucleate heterogeneously on the seed and grow in a strongly coupled fashion. Crystallographic defects within the seed provide a template for spiral self-organization. These observations demonstrate the ubiquity of defect-mediated growth in multi-phase materials and establish a pathway toward bottom-up synthesis of chiral materials with an inter-phase spacing comparable to the wavelength of infrared light. Given that liquids often possess polytetrahedral short-range order, our results are applicable to many systems undergoing multi-step crystallization.
提出了一种涉及螺旋自组织的金属合金固化方法，作为一种生产具有新兴结构和光学性能的大面积手性图案的新策略，关注其潜在的机制和动力学。本研究报告了从液态金属中发现的一种亚稳、两相螺旋图案的新生长模式。结晶通过一个非经典的两步途径进行，包括初始形成多面体种子晶体，然后是在种子上异质成核并以强耦合方式生长的两种固体相的有序化。种子内的晶体学缺陷为螺旋自组织提供了模板。这些观察结果证明了缺陷介导的多相材料生长的普遍性，并为使用与红外光波长相当的相间间距的手性材料的自下而上合成建立了途径。鉴于液体通常具有多面体短程有序，我们的结果适用于许多经历多步结晶的系统。
