Integrated studies of nanodroplet freezing

纳米液滴冷冻的综合研究

• 批准号: 1464924
• 负责人: Barbara Wyslouzil
• 金额: $ 47.5万
• 依托单位: Ohio State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1464924&HistoricalAwards=false
• 关键词: Integrated; studies; nanodroplet; freezing

With this award,the Chemical Structure, Dynamics and Mechanisms (CSDM-A) Program of the Division of Chemistry is funding Professor Barbara Wyslouzil at Ohio State University to pursue an integrated experimental and molecular modeling program exploring the physics of freezing. This includes determining the limits to which liquids can be supercooled, the transformation kinetics, and the structure of the emerging solid phase. The focus is on short chain-like molecules, i.e. n-alkanes and n-alcohols with less than 12 carbons, confined in nanodroplets. These chain molecules are the building blocks of materials as diverse as lipids, surfactants, and polymers. Freezing is a fundamental physical process that plays a central role in both industry and nature, such as in atmospheric aerosols. The freezing transitions will be quantitatively investigated with extremely well characterized samples under conditions that are far from equilibrium, and a powerful set of experimental tools probes conditions very close to the still idealized requirements of molecular simulations. Prof. Wyslouzil will also engage with high school students in her research and conduct public outreach in collaboration with the Steam Factory, an initiative at her institution to promote interdisciplinary collaboration across Science, Technology, Engineering, Arts, and Math.Prof. Wyslouzil and her research group will pursue the following specific experimental objectives: (1) measure liquid to solid nucleation rates as nanodroplets freeze, (2) explore the role of molecular structure on the relative importance of surface versus bulk freezing, and (3) further develop X-ray scattering techniques to follow this transformation directly. The objectives of the molecular modeling work are to (1) understand the driving force for surface freezing in chain-like molecules, and (2) calculate liquid-solid nucleation rates to compare directly to the measured values. Supersonic nozzle flows are to generate liquid droplets in highly non-equilibrium states with static pressure measurements to characterize the flow, spatially resolved small and wide angle X-ray scattering (SAXS/WAXS) to characterize the aerosol, and infrared spectroscopy to quantify the distribution of the condensable fraction among the vapor, liquid and solid states. Efforts to develop single nanodroplet/nanocrystal X-ray diffraction measurements to measure the structure of freezing clusters on a particle-by-particle basis using free electron lasers are to be extended. Molecular dynamics (MD) simulations are to directly test competing theories of surface freezing, and develop molecular level insight into homogeneous liquid-solid nucleation using available interaction potentials for both n-alcohols and n-alkanes at the united atom or all-atom level.

有了这个奖项，化学部的化学结构，动力学和机制（CSDM-A）计划资助俄亥俄州州立大学的Barbara Wyslouzil教授进行综合实验和分子建模计划，探索冻结的物理学。 这包括确定液体可以过冷的极限、相变动力学和出现的固相的结构。重点是短链状分子，即小于12个碳原子的正烷烃和正醇，限制在纳米液滴中。这些链状分子是脂质、表面活性剂和聚合物等多种材料的构建单元。冷冻是一种基本物理过程，在工业和自然界（例如大气气溶胶）中发挥着核心作用。冷冻转变将在远离平衡的条件下用非常好的表征样品进行定量研究，并且一组强大的实验工具探测非常接近分子模拟的理想化要求的条件。Wyslouzil教授还将与高中生一起参与她的研究，并与蒸汽工厂合作开展公共宣传，这是她所在机构的一项倡议，旨在促进科学，技术，工程，艺术和数学的跨学科合作。Wyslouzil教授和她的研究小组将追求以下具体实验目标：（1）测量纳米液滴冻结时液体到固体的成核速率，（2）探索分子结构对表面相对于本体冻结的相对重要性的作用，以及（3）进一步开发X射线散射技术以直接跟踪这种转变。分子模拟工作的目标是（1）了解链状分子表面冻结的驱动力，以及（2）计算液-固成核速率，以直接与测量值进行比较。超音速喷嘴流将产生处于高度非平衡状态的液滴，其中静压测量用于表征流，空间分辨小角和广角X射线散射（SAXS/WAXS）用于表征气溶胶，红外光谱用于量化可冷凝部分在蒸气、液体和固体状态之间的分布。努力开发单nanodrophe/nanodrophe X-射线衍射测量，以测量冻结集群的结构上一个粒子的基础上，使用自由电子激光器的扩展。分子动力学（MD）模拟是直接测试表面冻结的竞争理论，并在联合原子或全原子水平上使用正醇和正烷烃的可用相互作用势来发展对均匀液-固成核的分子水平洞察。

项目成果

How Cubic Can Ice Be?

• DOI: 10.1021/acs.jpclett.7b01142
• 发表时间: 2017-07-20
• 期刊: JOURNAL OF PHYSICAL CHEMISTRY LETTERS
• 影响因子: 5.7
• 作者: Amaya, Andrew J.;Pathak, Harshad;Wyslouzil, Barbara E.
• 通讯作者: Wyslouzil, Barbara E.