Collaborative Research: Why Does Oxidation Improve Freezing? Using Laboratory Measurements and Molecular Simulations to Investigate Heterogeneous Ice Nucleation on Carbon Surfaces

合作研究：为什么氧化可以改善冷冻？

• 批准号: 1309601
• 负责人: Valeria Molinero
• 金额: $ 21.6万
• 依托单位: University of Utah
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1309601&HistoricalAwards=false
• 关键词: Collaborative; Research; Why; Does; Oxidation

The Environmental Chemical Sciences (ECS) program of the Division of Chemistry supports the collaborative research efforts of Sarah D. Brooks (Texas A&M University) and Valeria Molinero (University of Utah) to investigate the heterogeneous nucleation of ice on model organic surfaces and soot using an unprecedented combination of laboratory measurements and molecular simulations. The primary objective of this project is to evaluate which specific chemical and physical properties of carbonaceous surfaces modulate their ability to act as ice nuclei for water freezing. The second objective is to elucidate the heterogeneous mechanisms of formation of ice on these surfaces. Previous laboratory results suggest that oxidation processes representative of atmospheric aging improve the ice nucleating ability of aerosols, facilitating contact freezing at warmer temperatures. Oxidation, however, alters carbon surfaces not only by incorporation of hydrophilic groups but also through a modification of the nanostructure of the surface. Laboratory experiments will be conducted to determine the prerequisite temperature and relative humidity required for immersion and deposition freezing on hydrocarbon and oxidized hydrocarbon particles. Simulations will be used to determine the effect of nanostructure, chemical modifications, and hydrophilicity of the surface on the freezing temperatures, the heterogeneous mechanism of formation of ice, and the size and structure of the critical ice embryo. Abundant in the atmosphere due to anthropogenic and biogenic sources, carbonaceous particles display a wide range of effectiveness in promoting the nucleation of ice in clouds. This variability causes major uncertainties in predictions of the effect of aerosols on climate. The project will lead to an improved understanding of the phase of water in the atmosphere and assist in the parameterization of global climate models. A workshop to train high school teachers in the use of freely available molecular visualization software to develop classroom activities that complement and enhance the high-school curriculum will be developed at the University of Utah. The molecular visualization tools and the simulations that display the formation of ice will be incorporated into undergraduate courses taught by the PIs.

化学系的环境化学科学(ECS)项目支持德克萨斯农工大学的Sarah D.Brooks和犹他大学的Valeria Molineo的合作研究工作，利用前所未有的实验室测量和分子模拟相结合的方法来研究冰在模型有机表面和烟尘上的非均相成核。这个项目的主要目标是评估碳质表面的哪些特定的化学和物理性质调节了它们作为水冻结的冰核的能力。第二个目标是阐明在这些表面上形成冰的不均匀机制。以前的实验室结果表明，代表大气老化的氧化过程改善了气溶胶的冰核能力，促进了温度较高时的接触冻结。然而，氧化不仅通过加入亲水性基团改变碳表面，而且还通过修饰表面的纳米结构来改变碳表面。将进行实验室实验，以确定碳氢化合物和氧化碳氢化合物颗粒浸泡和沉积冻结所需的先决条件温度和相对湿度。模拟将被用来确定表面的纳米结构、化学修饰和亲水性对冻结温度的影响、冰形成的异质机制以及关键冰胚的大小和结构。由于人为和生物来源，碳质颗粒在大气中大量存在，在促进云中冰的成核方面表现出广泛的有效性。这种可变性导致对气溶胶对气候影响的预测存在重大不确定性。该项目将有助于更好地了解大气中水的相态，并有助于全球气候模型的参数化。犹他大学将举办一个讲习班，培训高中教师如何使用免费提供的分子可视化软件来开展补充和加强高中课程的课堂活动。显示冰形成的分子可视化工具和模拟将被纳入到PI教授的本科课程中。