CAREER: Understanding Quasicrystalline Superstructures Formed from Pyramidal Nanocrystals

非技术摘要：晶体材料的特点是具有规则、重复的原子图案的结构，而玻璃等非晶材料是无序的。 准晶（QC）材料的不同寻常之处在于它们是有序的但不是周期性的，这使得它们成为一种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材料令人着迷的热、电、磁、光学和机械性能，使其可用于不粘和隔热涂层或医疗设备和手术器械的耐腐蚀和极强材料等应用。 该职业奖由材料研究部的固态和材料化学项目支持，能够研究由金字塔形纳米颗粒（纳米晶体）自组装的QC材料。该项目包括新QC材料结构和形成过程的详细表征，还开发了可用于研究其他软物质组装系统的新表征和生长方法。该研究提供了充足的基础和视觉兴趣以及技术相关性，所有这些都融入了 PI 的教育和推广活动中。 YouTube 电影采用无行话、讲故事的风格，通过各种社交媒体平台制作和推广。 这些视频独特地利用了这项基础研究创建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，该项目还通过每年一度的 STEM 日来支持当地高中生的宣传活动。技术摘要：该职业项目由材料研究部的固态和材料化学项目支持，整合了由金字塔形纳米晶体 (NC) 组装而成的准晶 (QC) 超结构的教育和研究。将NC自组装成新型上层结构是将纳米级特性转移到宏观材料中的一种有前景的方法，最终可实现高效太阳能电池、低能耗照明和显示器以及更灵敏的生物传感器。要实现这些机会，需要对数控上层建筑的形成进行合理控制。准晶体是有序的，但不是周期性的，因此无法分类为晶体或玻璃。与传统 NC 晶体超结构的研究相比，NC QC 超晶格 (QC-SL) 的研究还处于起步阶段。 NC 如何组织成这些长程有序但非周期性的晶格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是有限的。为了解决这些问题，PI 的团队首先合成了各向异性金字塔形 NC，并将它们组装成 QC 上层结构。然后使用原位和非原位真实空间方法（电子显微镜和断层扫描）的组合并辅以倒易空间测量（电子衍射和 X 射线散射）来表征这些材料。除了 2D 超晶格之外，通过微流体生长的 3D QC 超晶体也将使用新的超晶体学技术进行结构表征。这些工具共同提供了有关这些结构的封装的精美细节，并指定了各个 NC 的相对方向。这些信息阐明了 NC 合成、上层结构形成和转换如何协同工作以创建 QC 上层结构。 这项研究产生的结果被纳入一系列针对年轻学生和成年人的外展活动中，通过引人入胜的视觉故事来激发人们对科学和技术的兴趣。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力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.