Interfacial directed assembly and attachment of interconnected nanoparticle networks

纳米颗粒是直径大约是人类头发宽度的千分之一的颗粒。 该奖项支持研究纳米颗粒如何组装并附着在流体表面。 这一过程与一些细粉末如何在静止的水面上形成一层漂浮物没有什么不同。 由于化学的最新进展，具有可编程大小、形状和组成的纳米颗粒构建块已经变得可用。将这些构建块相互连接形成“薄片”可以产生具有新兴特性的新材料和设备，这些特性引起了科学家和工程师的兴趣。不幸的是，组装说明尚未提供。该项目将通过实验和计算机模型的结合来缩小这一知识差距。 这种协同方法将揭示积木自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，这些构建块组装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，并可能导致新的纳米结构材料的开发。研究生将接受先进的实验和建模方法的广泛培训，并为本科生提供研究机会。 还将为当地的K-12项目开发互动学习模块。胶体纳米粒子在流体界面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。在合成具有精确定义形状的多面体纳米颗粒构建块及其自组装成高度有序的超结构方面已经取得了显着的进展。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超结构之间的有趣的协同作用。利用可编程对称的超结构为通过设计创造具有特性的材料提供了新的机会。这项工作的主要目标是达到一个更好的理解的基本动力学和热力学因素的相互作用的自组装和定向附着。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流体界面处的纳米颗粒取向以及颗粒之间的相互作用。在液-液界面处的纳米颗粒取向和随后的定向附接是界面能、多颗粒相互作用的性质和界面纳米颗粒扩散的耦合动力学、从纳米颗粒表面的配体位移和相邻纳米颗粒通过相互暴露的刻面的外延融合的复杂函数。描述纳米颗粒组装体如何转变为外延连接的超结构的机制提出了一个有趣的未解决的科学问题，竞争性假设将通过实验和模拟相结合的方式进行测试。事实上，这提供了将原位X射线结构分析与多尺度建模紧密结合的挑战和机会。该提案提出了一种假设驱动的协作方法，其两个目标旨在了解：（1）特定的纳米颗粒超晶格多晶型物如何在流体界面处组装，以及（2）定向附着如何将组装的超晶格转变成外延连接的准超晶格。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准。

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.