Surface Characteristics that Drive Heterogeneous Ice Nucleation

在化学系环境化学科学项目的支持下，米里亚姆·弗里德曼教授和她在宾夕法尼亚州立大学的研究生和本科生将研究大气颗粒或气溶胶的冻结行为。气溶胶催化大气中云的形成，云可以由液态水、冰或这些相的混合物组成。云中的冰粒可以通过将水滴冻结在零下38摄氏度以下而形成，或者在温度较高的情况下，冰可以在冰核粒子(INP)的表面形成。粒子是如何在分子水平上使冰成核的，目前还不是很清楚。为了研究促进冰核形成过程的表面特征，该项目中使用的方法是使用表面可以无限调整和探测的材料。该项目的目标是提供一个框架，以了解哪些表面特征对冰核形成是重要的，以及这些不同特征的相对重要性。该项目对大气科学家开发云形成模型具有重要意义。此外，物理化学界对这个项目很感兴趣，因为它涉及相变、催化和表面。冰核实验是纳入本科生研究人员的理想选择，通常会导致与本科生合著者发表论文。这些研究的结果将被纳入本科课程讲课。从事这项工作的学生还将参与与家庭的公共宣传以及对更广泛社区成员的继续教育。该项目以无机系统以及有机和生物系统的冰核行为为特征。矿物、有机和生物成冰颗粒(INP)在结构如何决定成冰行为方面有相似之处。对于无机体系，官能团的作用和表面组成将使用功能化的金纳米颗粒、多孔的金属硅酸盐和尖晶石来表征。在有机和生物系统方面，本项目旨在通过对原始和陈年微塑料、成冰细菌及其分离蛋白以及不同水解度的聚乙烯醇/聚乙酸乙烯酯的研究，来表征氢键在冰核形成中的作用。实验将主要使用浸泡冻结进行，这是大气中冰核形成的主要途径。这一奖项反映了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。

With support from the Environmental Chemical Sciences Program in the Division of Chemistry, Professor Miriam Freedman and her graduate and undergraduate students at Pennsylvania State University will study the freezing behavior of atmospheric particles, or aerosols. Aerosols catalyze the formation of clouds in the atmosphere, which can be composed of liquid water, ice, or a mixture of these phases. Ice particles in clouds can form by the freezing of aqueous droplets below -38 degrees C, or ice can form on the surface of an ice-nucleating particle (INP) at warmer temperatures. How particles nucleate ice on a molecular level is not well understood. To investigate the surface features that promote the ice nucleation process, the approach used in this project is to work with materials in which the surface can be infinitely tuned and probed. The goal of this project is to provide a framework for understanding which surface features are important for ice nucleation and the relative importance of these different features. This project is important for atmospheric scientists developing models of cloud formation. In addition, this project is of interest to the physical chemistry community because it deals with phase transitions, catalysis, and surfaces. Ice nucleation experiments are ideal for the inclusion of undergraduate researchers, often leading to publications with undergraduate coauthors. Results from these studies will be incorporated into undergraduate course lectures. Students performing this work will also be engaged in public outreach to families as well as continuing education for members of the wider community.This project characterizes the ice nucleation behavior of inorganic systems as well as organic and biological systems. Similarities are hypothesized between mineral, organic, and biological ice nucleating particles (INPs) in terms of how structure determines the ice nucleation behavior. For inorganic systems, the role of functional groups and surface composition will be characterized using functionalized gold nanoparticles, porous metalosilicates, and spinels. In terms of organic and biological systems, this project aims to characterize the role of hydrogen bonding on ice nucleation through studies of virgin and aged microplastics, ice-nucleating bacteria and their isolated proteins, and poly(vinyl alcohol)/poly(vinyl acetate) with different degrees of hydrolysis. Experiments will be performed primarily using immersion freezing, which is a dominant pathway for ice nucleation in the atmosphere.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.