CAREER: Molecular Studies of Phase Separations and Internal Structure in Individual Particles

在这个由化学系环境化学科学项目资助的项目中，密歇根大学的安德鲁·奥尔特教授正在研究大气中单个颗粒的特性。这些颗粒会影响云的形成和性质以及健康。使用的工具是先进的显微镜和光谱表征。具体来说，该项目重点关注最近在大气中观察到的两相（有机和水相）颗粒和粘性/玻璃状颗粒，其形成和性质尚不清楚。了解这些颗粒如何根据关键大气变量（例如相对湿度和温度）发生变化，将提高我们预测它们在大气中的形成、性质和丰度的能力。该项目通过在密封环境反应池中与两台显微镜、拉曼显微光谱仪和红外原子力显微镜（AFM-IR）相结合进行一系列实验室研究，重点研究混合有机/无机颗粒的基本性质。这些研究使用了一系列模型系统（例如硫酸铵和二羧酸），以及更复杂的混合物、室内产生的颗粒和来自大气的颗粒。研究人员探究单个颗粒内的差异，以了解物理和化学特性的微观变化。特别令人感兴趣的是作为粒径函数的相分离，以及相分离颗粒的微环境中的酸度和反应性。一项名为底特律研究实习暑期体验 (D-RISE) 的外展计划正在扩大。它使参与者能够开展互动活动，例如大气中的颗粒物，并在下一学年向同学展示。除了吸引项目参与者之外，这还扩大了底特律高中科学领域代表性不足的群体对科学研究的接触。玻璃态和相分离气溶胶研究的更广泛影响是了解这些颗粒是否吸收水并使云滴成核，这对于云的形成和性质非常重要，以及它们是否与大气中的重要气体发生反应。

In this project, funded by the Environmental Chemical Sciences program of the Chemistry Division, Professor Andrew Ault of the University of Michigan is studying the properties of individual particles in the atmosphere. These particles can impact cloud formation and properties, as well as health. The tools used are advanced microscopic and spectroscopic characterization. Specifically, the project focuses on particles with two phases (organic and aqueous) and viscous/glassy particles recently observed in the atmosphere whose formation and properties are not well understood. Understanding how these particles change based on key atmospheric variables such as relative humidity and temperature will improve our ability to predict their formation, properties, and abundance in the atmosphere.This project focuses on the fundamental properties of mixed organic/inorganic particles through a series of laboratory studies in sealed environmental reaction cells coupled to two microscopes, a Raman microspectrometer and an atomic force microscopy with infrared (AFM-IR). The studies use a series of model systems (such as ammonium sulfate and dicarboxylic acids), as well a more complex mixtures, chamber-generated particles and particles from the atmosphere. The researchers probe differences within individual particles to understand microscopic changes in physical and chemical properties. Of particular interest are phase separations as a function of particle size, and acidity and reactivity in the microenvironments of phase-separated particles. An outreach program, the Detroit Research Internship Summer Experience (D-RISE), is being expanded. It enables participants to develop interactive activities, such as on particulate matter in the atmosphere, that are presented to classmates the following academic year. In addition to engaging the program participants, this also expands exposure to scientific research to underrepresented groups in the sciences at Detroit high schools. The broader impact of the studies of glassy and phase-separated aerosol are to understand if these particles take up water and nucleate cloud droplets, which is important for cloud formation and properties, as well as if they react with important gases in the atmosphere.