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、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块体金属和合金的合成更加困难。传统的相图被用作指导块体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，因为纳米颗粒大大增加了比表面积和表面能。纳米相图作为常规相图的对应物是人们非常希望得到的。该项目旨在建立纳米相图，以指导纳米颗粒的合成，使用先进的实验表征和原子模拟。通过实验实时观察金属/合金纳米粒子的形成和生长过程，原子模拟为这些过程提供了理论上的理解。在纳米相图的指导下，合成了新形式的金属和合金纳米粒子。该项目增加了有关纳米颗粒形成过程的基础知识，并为合成一系列应用的新型纳米颗粒提供了一条新的途径。该项目的科学发现作为教育组成部分被纳入本科生和研究生课程。处于不同教育阶段的学生通过各种研究、教育和外展活动参与。技术概述许多金属纳米结构显示出与其块体形式不同的独特的物理和化学性质。以往的研究表明，这些金属纳米材料通常会形成在传统相图中不稳定的相。然而，目前还不能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努力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，并将其用于定性和定量地监测金属纳米颗粒在溶液中的成核和生长过程。用第一性原理计算了不同合成条件和不同长度尺度下纳米粒子的体积能、表面能和总能。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，并建立了纳米相图，以预测和指导金属纳米材料的合成。该项目的发现和结果在多个领域具有影响和影响，如固态化学、冶金和纳米技术。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.