Shaping Colloids for Self Assembly

本项目将探索和发展颗粒形状在胶体自组装中的作用。直到最近，用于胶体自组装的基本形状被限制为球体和棒状，这限制了胶体结构为fcc， bcc和一些简单的变体。在胶体晶体中无法达到原子和分子晶体所观察到的结构的丰富性，这一点在制造具有金刚石或类似对称性的光子胶体晶体的挑战中得到了明显的缓解，因为这样的晶体应该表现出完整的光子带隙。该项目将重点开发两种新的胶体系统：(1)锁-钥匙胶体和(2)立方胶体。这两组胶体都代表了对现有胶体的重大偏离，并导致了新的结构和新的相变类型。其目的是探索利用这些新的积木可以制造出的各种结构，并建立模型，捕捉控制它们形成的基本物理原理。耗尽相互作用将被用作控制相互作用强度和范围的主要手段。粒子的各向异性形状将被用来产生定向和特定的相互作用，这两者对于胶体科学来说都是相对较新的。一个相关的目标是开发精确控制由不同材料制成的胶体的相对位置的机制，从而增加它们制造有用的新材料的潜力，包括光子晶体、催化剂和太阳能电池。这项研究将支持一名涉及物理、化学和材料科学的跨学科科学博士生的教育。21世纪材料科学的核心目标是“自下而上”地制造纳米材料，而不是依靠传统的“自上而下”的方法。因此，他们的想法是制造纳米级组件，这些组件可以自底向上组装成复杂的有用材料，而不是像制造计算机芯片时通常采用的自上而下的方法那样，在大型物体上刻印小结构。在这种自下而上的方法中，小的纳米级组件携带着组装成所需结构所需的信息。该项目将探索纳米级物体自下而上自组装的策略，利用粒子形状作为粒子相互识别并融入更大结构设计的机制，就像拼图碎片拼在一起形成一幅大图一样。挑战是双重的，因为制造具有复杂形状的粒子的新技术将与指导其组装的设计方案一起开发。这些方法将有助于开发光开关和电路以及太阳能电池的新材料。该项目将支持研究生在这些先进技术方面的教育，为他们在先进科学技术领域的职业生涯提供支持。

Technical Abstract This project will explore and develop the role of particle shape in the self assembly of colloids. Until recently, the basic shapes used in colloidal self assembly have been limited to spheres and rods, which has limited colloidal structures to fcc, bcc, and a few simple variants. The inability to achieve the same richness of structures observed for atomic and molecular crystals in colloidal crystals has been brought into sharp relief by the challenge of making photonic colloidal crystals with the diamond or similar symmetries, as such crystals should exhibit full photonic band gaps. This project will focus on developing two new colloidal systems: (1) lock-and-key colloids and (2) cubic colloids. Both sets of colloids represent a significant departure from existing colloids and lead to new structures and new kinds of phase transitions. The aim is to explore the various kinds of structures that can be made using these new building blocks and to develop models that capture the basic physics controlling their formation. The depletion interaction will be used as the primary means of controlling the strength and range of the interaction. The anisotropic shapes of the particles will be exploited to generate directional and specific interactions, both of which are relatively new to colloidal science. A related goal is to develop mechanisms for precise control of the relative placement of colloids made from disparate materials, thus increasing their potential for making useful new materials, including photonic crystals, catalysts, and solar cells. The research will support the education of a PhD student in interdisciplinary science involving physics, chemistry, and materials science. Non-technical Abstract A central goal of 21st century materials science is to fabricate nanomaterials from the "bottom up" rather than relying on the traditional the "top down" approach. Thus, instead of imprinting small structures on large objects, as is typically done in top-down approaches for making computer chips, the idea is to make nanoscale components that assemble themselves from the bottom up into complex useful materials. In this bottom up approach, the small nanoscale components carry with them the information required for them to assemble into the desired structures. This project will explore strategies for bottom-up self-assembly of nanoscale objects using particle shape as the mechanism by which particles recognize each other and fit into a larger structural design, much as jigsaw puzzle pieces fit together to form a large picture. The challenge is two-fold in that new techniques to make particles with complex shapes will be developed along with design schemes for directing their assembly. These methods should be useful in developing new materials for optical switching and circuitry as well as for solar cells. This project will support the education of a graduate student in these advance techniques for careers in advanced science and technology.