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

金属纳米结构在催化剂、储能和生物医学工程等领域有着广泛的应用。金属纳米结构的合成比大块金属和合金的合成更困难。传统的相图被用作指导大块金属和合金的合成和加工的路线图，但它们不适合纳米颗粒，因为纳米颗粒的表面积和表面能大大增加。纳米相图作为传统相图的对应物是非常需要的。本项目旨在利用先进的实验表征和原子模型建立纳米相图，指导纳米颗粒的合成。通过实验实时观察金属/合金纳米颗粒的形成和生长，原子模型为这些过程提供了理论理解。新形式的金属和合金纳米颗粒的合成是由新的纳米相图指导的。该项目增加了纳米颗粒形成过程的基础知识，并为合成具有广泛应用价值的新型纳米颗粒提供了新的途径。这个项目的科学发现作为教育的组成部分被整合到本科和研究生课程中。不同教育阶段的学生通过各种研究、教育和推广活动参与。许多金属纳米结构表现出独特的物理和化学性质，不同于它们的体积形式。以往的研究表明，这些金属纳米材料经常形成在常规相图中不稳定的相。然而，目前还不完全清楚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的新方法来回答这些基本问题。最先进的原位x射线表征技术被开发并用于监测金属纳米颗粒在溶液中的成核和生长过程，包括定性和定量。采用第一性原理计算方法对不同合成条件和不同长度尺度下纳米颗粒的体积、表面和总能进行了计算。通过计算和实验相结合的研究，揭示了金属纳米结构的形成机理，建立了纳米相图，预测和指导了金属纳米材料的合成。这个项目的发现和结果在多个领域都有影响和启示，如固态化学、冶金和纳米技术。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 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.