CAREER: Understanding Quasicrystalline Superstructures Formed from Pyramidal Nanocrystals

非技术概要：晶体材料的特点是具有规则的、重复的原子结构，而非晶态材料如玻璃是无序的。准晶体（QC）材料是不寻常的，因为它们是有序的，但不是周期性的，这使它们成为一个根本不同的材料类别，既不是晶体也不是玻璃。独特的结构赋予QC材料有趣的热、电、磁、光学和机械性能，使其适用于诸如不粘和隔热涂层或耐腐蚀性和极强的医疗设备和手术器械材料等应用。该奖项由材料研究部的固态和材料化学项目支持，可以研究由金字塔形纳米颗粒（纳米晶体）自组装的QC材料。该项目包括详细表征新的QC材料的结构和形成过程，并开发新的表征和生长方法，可能适用于研究其他软物质组装系统。这项研究提供了充分的基础和视觉兴趣，以及技术相关性，所有这些都纳入了PI的教育和推广活动。YouTube上没有行话、讲故事的电影被制作出来，并通过各种社交媒体平台进行推广。这些视频独特地利用了这一基础研究创造的美丽而引人注目的QC模式与现实世界的艺术、装饰和建筑设计之间的联系。此外，该项目还通过一年一度的STEM日向当地高中生提供支持。技术概述：本项目由材料研究部固体与材料化学项目支持，将金字塔形纳米晶体（nc）组装的准晶体（QC）超结构的教育和研究结合起来。将纳米结构自组装成新的上层结构是一种很有前途的方法，可以将纳米性质转移到宏观材料中，最终实现高效太阳能电池、低能耗照明和显示器，以及更敏感的生物传感器。为了实现这些机会，需要对NC上部结构的形成进行合理的控制。准晶体是有序的，但不是周期性的，因此不属于晶体或玻璃的分类。与传统的数控晶体超结构相比，数控QC超晶格（QC- sls）的研究还处于起步阶段。nc是如何组织成这些远距离有序的非周期格的，这仍然是一个悬而未决的问题；生产和表征这些独特材料的方法有限。为了解决这些问题，PI的团队首先合成了各向异性锥体nc，并将它们组装成QC上层结构。然后，利用原位和非原位实空间方法（电子显微镜和断层扫描）的组合，辅以互反空间测量（电子衍射和x射线散射），对这些材料进行表征。除了二维超晶格外，通过微流体生长的三维QC超晶体将使用一种新的超晶体学技术进行结构表征。总之，这些工具提供了有关这些结构的包装的精美细节，并指定了单个nc的相对方向。这些信息阐明了NC合成、上层建筑形成和改造如何共同创造QC上层建筑。这项研究的结果被整合到一系列针对年轻学生和成年人的推广活动中，这些活动旨在通过引人注目的视觉故事激发人们对科学和技术的兴趣。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-Technical Summary:Crystalline materials are characterized by a structure with a regular, repeating pattern of atoms, while amorphous materials such as glass are disordered. Quasicrystalline (QC) materials are unusual in that they are ordered but not periodic, making them a fundamentally different category of materials which is neither a crystal nor a glass. The unique structure gives QC materials intriguing thermal, electrical, magnetic, optical and mechanical properties, making them useful for applications such as non-stick and thermally insulating coatings or corrosive-resistant and extremely strong materials for medical devices and surgical instruments. This CAREER award, supported by the Solid State and Materials Chemistry program within the Division of Materials Research, enables study of QC materials self-assembled from pyramid-shaped nano-sized particles (nanocrystals). The project includes detailed characterization of new QC materials’ structures and formation processes and also develops new characterization and growth methods that may be applicable to studying other soft matter assembly systems. The research offers ample fundamental and visual interest, as well as technological relevance, all of which are integrated into the PI’s education and outreach activities. YouTube movies with a jargon-free, storytelling style are created and promoted through various social media platforms. These videos take unique advantage of the connection between the beautiful and eye-catching QC patterns created by this fundamental study and real-world art, decoration and architectural design. Additionally, the project supports outreach to local high school students through an annual STEM Day. Technical Summary:This CAREER project, supported by the Solid State and Materials Chemistry program within the Division of Materials Research, integrates education and research on quasicrystalline (QC) superstructures assembled from pyramid-shaped nanocrystals (NCs). Self-assembly of NCs into novel superstructures is a promising approach for transporting nanoscopic properties into macroscopic materials to eventually enable highly efficient solar cells, low-energy-consumption lighting and displays, and more sensitive biological sensors. To realize these opportunities requires rational control over the formation of NC superstructures. Quasicrystals are ordered but not periodic and as such defy classification as either a crystal or a glass. The study of NC QC superlattices (QC-SLs) is in its infancy compared to efforts on conventional NC crystalline superstructures. It remains an outstanding question how NCs organize into these long-range ordered yet aperiodic lattices; methods to produce and characterize these unique materials are limited. To address these issues, the PI's group first synthesizes anisotropic pyramidal NCs and assembles them into QC superstructures. These materials are then characterized using combinations of in situ and ex situ real space methods (electron microscopies and tomography) complemented by reciprocal space measurements (electron diffraction and X-ray scattering). In addition to 2D superlattices, 3D QC supercrystals grown via microfluidics will be structurally characterized using a new super-crystallography technique. Together, these tools provide exquisite detail concerning the packing of these structures and specify the relative orientation of individual NCs. Such information clarifies how NC synthesis, superstructure formation and transformation work together to create QC superstructures. Results generated in this research are integrated into a series of outreach activities that target younger students and adults alike with compelling, visual stories designed to provoke interest in science and technology.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.