Collaborative Research: Guiding synthesis of nanoparticles with nanometric phase diagram and in situ X-ray diffraction

金属纳米结构被广泛应用于许多重要的应用中，例如催化剂、能量存储和生物医学工程。金属纳米结构的合成比块体金属和合金的合成更困难。传统的相图被用作指导块状金属和合金的合成和加工的路线图，但它们不适用于纳米颗粒，因为纳米颗粒具有显著增加的表面积和表面能。纳米相图作为常规相图的对应物是非常需要的。本计画旨在利用先进的实验表征与原子模型建立奈米级相图，以指导奈米粒子的合成。实验进行观察金属/合金纳米颗粒的形成和生长在真实的时间，和原子模型提供这些过程的理论理解。新型金属和合金纳米粒子的合成是由新的纳米相图指导的。该项目增加了有关纳米颗粒形成过程的基础知识，并为一系列应用提供了合成新型纳米颗粒的新途径。该项目的科学成果作为教育内容纳入本科和研究生课程。不同教育阶段的学生通过各种研究，教育和推广活动参与。许多金属纳米结构显示出不同于其本体形式的独特物理和化学性质。以往的研究表明，这些金属纳米材料经常形成在传统相图中不稳定的相。然而，目前还没有完全理解为什么会发生这种情况，以及在什么情况下会发生这种情况。该项目旨在通过一种结合计算和实验研究工作的新方法来回答这些基本问题。发展了最先进的原位X射线表征技术，并用于定性和定量地监测溶液中金属纳米颗粒的成核和生长过程。 第一性原理计算被用来评估在不同的合成条件下，在不同的长度尺度的纳米粒子的体积，表面和总能量。通过计算和实验相结合的方法，揭示了金属纳米结构的形成机理，建立了金属纳米结构的纳米相图，预测和指导了金属纳米材料的合成。该项目的发现和成果在固态化学、冶金和纳米技术等多个领域产生了影响和意义。该奖项反映了NSF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 SummaryMetallic nanostructures are widely used in many important applications, such as catalysts, energy storage and biomedical engineering. The synthesis of metallic nanostructures is more difficult than that of bulk metals and alloys. Conventional phase diagrams are used as road maps to guide the synthesis and processing of bulk metals and alloys, but they are not suitable for nanoparticles, which have drastically increased surface area and surface energy. Nanometric phase diagrams as the counterpart of conventional phase diagram is highly desired. This project aims to establish nanometric phase diagrams for guiding synthesis of nanoparticles using advanced experimental characterizations and atomistic modeling. Experiments are conducted to observe the formation and growth of metal/alloy nanoparticles in real time, and atomistic modeling provides theoretical understanding of these processes. The synthesis of new forms of metal and alloy nanoparticles is guided by the novel nanometric phase diagrams. This project adds to the fundamental knowledge about the formation process of nanoparticles, and provides a new avenue of synthesizing novel nanoparticles for a range of applications. The scientific findings from this project are integrated as education components into undergraduate and graduate courses. Students at different stages of education participate through a variety of research, education, and outreach activities. Technical SummaryMany metallic nanostructures show unique physical and chemical properties that are different from their bulk forms. Previous researches have demonstrated that these metallic nanomaterials often form phases that are not stable in conventional phase diagram. However, it is not yet fully understood why this can happen and in what condition this would happen. This project aims to answer these fundamental questions via a novel approach combining computational and experimental research efforts. State-of-the-art in situ X-ray characterization techniques are developed and employed to monitor the nucleation and growth processes of metallic nanoparticles in solutions, both qualitatively and quantitatively. First principles computations are used to evaluate the bulk, surface and total energies of nanoparticles in different synthesis conditions and at different length scales. By coupling computational and experimental investigations, the formation mechanisms of metallic nanostructures are revealed and the nanometric phase diagrams are established to predict and guide the syntheses of metallic nanomaterials. The findings and outcome of this project have impacts and implications in multiple fields, such as solid state chemistry, metallurgy, and nanotechnology.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.