Characterization of the pH of Organic/Inorganic Aerosol Using Ratiometric Fluorescence Imaging

化学系的环境化学科学项目资助了Miriam Freedman教授，该项目主要研究气溶胶的酸度。气溶胶颗粒的这一特性影响大气中的化学反应以及人类健康。根据气溶胶颗粒和气相分子的组成，可以利用模型估计气溶胶颗粒的酸度。这些模型预测气溶胶颗粒是高酸性的，但结果因使用的模型而异。该项目旨在利用碳量子点开发一种新的气溶胶酸度直接测量方法。使用这种方法将使探索海洋和大陆环境中高酸度气溶胶颗粒的分子起源成为可能。探测器的进一步发展将使大气化学研究或对高酸性样品感兴趣的其他领域的应用成为可能。该项目具有技术转让的潜力，为本科生和研究生提供培训，并通过外联活动支持向公众传播。为了研究气溶胶颗粒的酸度，本项目将使用碳量子点的比例荧光成像。目前，Freedman研究小组已经开发出一种覆盖pH值范围为0 - 3.5的探针。为了确定大陆和海洋气溶胶高酸度的来源，将对含盐有机化合物模式系统的pH值进行表征。硫酸铵将用于模拟大陆气溶胶，氯化钠将用于模拟海洋气溶胶。所选择的有机化合物应与特定类型的气溶胶相关，并具有一定范围的pKa值，从单一有机化合物到混合物的一系列组成复杂性，以及一系列表面活性。为了进一步开发探针，该项目旨在增加可测量的pH范围，纳入内部标准，并将探针沉积在基板上。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Environmental Chemical Sciences Program in the Division of Chemistry funds Professor Miriam Freedman for this project which is focused on the acidity of aerosols. This property of aerosol particles impacts chemical reactions in the atmosphere as well as human health. Based on the composition of aerosol particles and gas-phase molecules, the acidity of aerosol particles can be estimated using models. These models predict that aerosol particles are highly acidic, but results differ depending on the model used. This project aims to develop a novel direct measure of aerosol acidity using carbon quantum dots. Using this approach will make it possible to explore the molecular origins of the high acidity of aerosol particles for both marine and continental environments. Further development of the probes will enable applications in atmospheric chemistry studies or in other fields where highly acidic samples are of interest. This project has potential for technology transfer, provides training for undergraduate and graduate students, and supports dissemination to the public through outreach events.To study the acidity of aerosol particles, this project will use ratiometric fluorescence imaging of carbon quantum dots. Currently, the Freedman research group has developed a probe that covers the pH range of 0 – 3.5. To determine the origins of the high acidity of continental and marine aerosol, the pH of model systems of organic compounds with salts will be characterized. Ammonium sulfate will be used for model continental aerosol and sodium chloride will be used for model marine aerosol. The organic compounds are chosen to be relevant for the specific type of aerosol as well as to have a range of pKa values, a range of complexities in composition from single organic compounds to mixtures, and a range of surface activities. To develop the probe further, the project aims to increase the pH range that can be measured, incorporate an internal standard, and deposit the probe on substrates.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.