Interfacial directed assembly and attachment of interconnected nanoparticle networks

纳米粒子的直径大约是人类头发宽度的千分之一。该奖项支持研究纳米颗粒如何在流体表面组装和附着。这个过程与一些细粉末如何形成一层漂浮在静止水面上的过程没有什么不同。由于化学的最新进展，具有可编程大小、形状和组成的纳米粒子构建块已经成为可能。将这些积木相互连接形成“薄片”，可以产生具有新兴特性的新型材料和设备，这引起了科学家和工程师的兴趣。不幸的是，汇编指令还不可用。这个项目将通过实验和计算机模型的结合来弥补这一知识差距。这种协同方法将揭示构建块自我组装和附着机制的关键细节。因此，结果将导致设计新的构建块的策略，这些构建块可以组合成具有最小缺陷的理想模式。该项目将产生具有科学和社会重要性的新知识，并可能导致新型纳米结构材料的发展。研究生将在先进的实验和建模方法方面接受广泛的培训，并为本科生提供研究机会。还将为当地K-12课程开发互动学习模块。胶体纳米颗粒在流体界面上的自组装和定向附着的结合提出了科学上有趣和技术上重要的研究挑战。在具有精确定义形状的多面体纳米颗粒构建块的合成和它们的自组装成高度有序的上层结构方面取得了显著的进展。最近的进展揭示了界面自组装和定向外延连接成有序和连接的上层结构之间有趣的协同作用。具有可编程对称性的上层结构为创造具有设计属性的材料提供了新的机会。这项工作的主要目的是为了更好地理解控制自组装和定向附着相互作用的基本动力学和热力学因素。研究人员假设，预测和创建具有可编程结构的耦合组件的关键在于理解和控制纳米颗粒在流体界面上的取向以及颗粒之间的相互作用。纳米颗粒在液-液界面上的取向和随后的定向附着是界面能、多粒子相互作用的性质以及界面纳米颗粒扩散、配体从纳米颗粒表面位移和相邻纳米颗粒通过相互暴露面的外延融合的耦合动力学的复杂函数。描述纳米粒子组装如何转变为外延连接的上层结构的机制是一个有趣的未解决的科学问题，相互竞争的假设将通过实验和模拟的结合来验证。事实上，这为将原位x射线结构分析与多尺度建模紧密结合提供了挑战和机遇。该提案提出了一种假设驱动的协作方法，其两个目标旨在理解：(1)特定纳米颗粒超晶格多晶如何在流体界面上组装；(2)定向附着如何将组装的超晶格转变为外延连接的准二维固体。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。

Nanoparticles are particles with diameters roughly one thousandth the width of a human hair. This award supports research to investigate how nanoparticles assemble and attach at the surface of a fluid. The process is not unlike how some fine powders can form a layer that floats on top of the surface of quiescent water. Nanoparticle building blocks with programmable size, shape, and composition have become available thanks to recent advances in chemistry. Connecting these building blocks to each other to form "sheets" can give rise to new classes of materials and devices with emergent properties that have intrigued scientists and engineers alike. Unfortunately, assembly instructions are not yet available. This project will close this knowledge gap with a combination of experiments and computer models. This synergistic approach will unveil key details of the mechanism by which the building blocks self-assemble and attach. Hence, the results will lead to strategies to design new building blocks that assemble into desirable patterns with minimal defects. This project will produce new knowledge of scientific and societal importance and may lead to the development of new nanostructured materials. Graduate students will receive extensive training in advanced experimental and modeling approaches, and research opportunities will be provided for undergraduates. Interactive learning modules for local K-12 programs will also be developed.The combination of self-assembly and directed attachment of colloidal nanoparticles at fluid interfaces presents scientifically interesting and technologically important research challenges. Remarkable strides have been made in the synthesis of polyhedral nanoparticle building blocks with precisely defined shapes and their self-assembly into highly ordered superstructures. Recent advances have revealed intriguing synergies between interfacial self-assembly and directed epitaxial attachment into ordered and connected superstructures. Access to superstructures with programmable symmetry opens new opportunities to create materials with properties by design. The main goal of this work is to attain a better understanding of the basic kinetic and thermodynamic factors governing the interplay of self-assembly and directed-attachment. The investigators hypothesize that the key to predicting and creating coupled assemblies with programmable structures lies in understanding and controlling the nanoparticle orientation at the fluid interface as well as the interactions among particles. The nanoparticle orientation at the liquid-liquid interface and subsequent directed attachment is a complex function of the interfacial energies, the nature of multi-particle interactions and the coupled dynamics of interfacial nanoparticle diffusion, ligand displacement from the nanoparticle surface and epitaxial fusion of adjacent nanoparticles through mutually exposed facets. The mechanism describing how the nanoparticle assembly transforms into an epitaxially connected superstructure presents an interesting unresolved scientific question, and competing hypotheses will be tested via a combination of experiments and simulations. In fact, this provides both a challenge and an opportunity to closely integrate in-situ X-ray structure analysis with multi-scale modeling. The proposal presents a hypothesis-driven collaborative approach with two objectives that aim to understand: (1) how specific nanoparticle superlattice polymorphs assemble at fluid interfaces and (2) how directed attachment can transform the assembled superlattice into an epitaxially connected quasi-2D solid.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.