Real-space and Real-time Study of Two-dimensional Colloidal Quasicrystals

准晶是介于晶相和无序相之间的结构。它们表现出一些类似于晶体的性质，但它们不具有晶体的周期结构。准晶可以与光以独特的方式相互作用，并显示出丰富的光学性质，这在晶体或完全无序的材料中没有表现出来。虽然原子准晶主要是金属合金，但在由纳米颗粒、胶束和聚合物制成的软材料中也发现了合成准晶。然而，无论是天然的还是合成的准晶，都是由光学显微镜无法直接观察到的太小的单元组成的。因此，充分了解准晶的形成和稳定性已被证明是具有挑战性的。该项目的目标是从大到足以用光学显微镜观察的单组分微粒建造二维准晶。这些微粒将在外加交变电场的作用下组装成准晶。将详细观察微粒子的形成过程，并将实验与数值模拟进行比较，以了解准晶形成的动力学。该项目的结果将解决关于准晶形成的基本问题，如长程但非周期有序如何出现和演化，以及是什么稳定了低温和高温准晶。这项研究将与各种教育和外展努力相结合，包括一项鼓励阅读困难儿童参与科学和工程的活动。该项目的目标是从尺寸与可见光波长相当的颗粒中组装出二维十二方准晶体。由于颗粒的大小，用光学显微镜可以直接观察到准晶的动态形成。这为解决与软物质形成准晶有关的基本问题提供了一种工具。不同材料的胶体微球通过外加电场和几何约束相结合，可以组装出高质量的大尺寸二维准晶。所有粒子的坐标将被可视化为时间的函数，稳定胶体准晶的潜在驱动力将被确定，成核和生长机制将被识别。互补的蒙特卡罗模拟和布朗动力学模拟将并行进行，以解释实验观测结果。最后，将测量组装的准晶在可见光和近红外光谱中的光子性质。这个项目将提供一个机会来寻找在广泛的长度范围内统一软物质准晶形成的物理原理。这个奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为是值得支持的。

Quasicrystals are structures that lie between crystalline and disordered phases. They exhibit some properties similar to those of crystals, but they do not have the periodic structure of crystals. Quasicrystals can interact with light in unique ways and exhibit rich optical properties that are not manifested in crystals or in completely disordered materials. Although atomic quasicrystals are predominantly metallic alloys, synthetic quasicrystals have also been found in soft materials made from nanoparticles, micelles, and polymers. However, both natural and synthetic quasicrystals are built from units that are too small to be directly observed by optical microscopy. As a result, it has proven challenging to fully understand the formation and stability of quasicrystals. The goal of this project is to build two-dimensional quasicrystals from single-component microparticles that are large enough to observe with optical microscopy. The assembly of the microparticles into quasicrystals will be driven using applied alternating current electric fields. The formation of the Microparticles will be observed in detail and the experiments will be compared with numerical simulations to understand the dynamics of quasicrystal formation. Results of the project will address fundamental questions about quasicrystal formation, such as how the long-range but non-periodic order emerges and evolves and what stabilizes low and high temperature quasicrystals. The research will be integrated with a variety of educational and outreach efforts, including an activity to encourage participation of children with dyslexia in science and engineering. The objective of this project is to assemble two-dimensional dodecagonal quasicrystals from particles whose sizes are comparable to the wavelengths of visible light. Owing to the size of the particles, the dynamic formation of quasicrystals can be observed directly with optical microscopy. This provides a tool to address fundamental issues related to quasicrystal formation from soft matter. Large high-quality two-dimensional quasicrystals will be assembled from colloidal microspheres of different materials by combining externally applied fields with geometric confinement. The coordinates of all particles will be visualized as a function of time, the underlying driving forces that stabilize colloidal quasicrystals will be determined, and nucleation and growth mechanisms will be identified. Complementary Monte Carlo and Brownian Dynamics simulations will be performed in parallel to interpret experimental observations. Finally, the photonic properties of the assembled quasicrystals in both visible and near-infrared light spectra will be measured. This project will offer an opportunity to search for physical principles that unify the formation of soft-matter quasicrystals over a broad range of length scales.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.