Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland.
J Phys Chem A. 2021 May 6;125(17):3528-3548. doi: 10.1021/acs.jpca.1c00202. Epub 2021 Mar 19.
The uptake of water vapor by various organic aerosols is important in a number of applications ranging from medical delivery of pharmaceutical aerosols to cloud formation in the atmosphere. The coefficient that describes the probability that the impinging gas-phase molecule sticks to the surface of interest is called the mass accommodation coefficient, α. Despite the importance of this coefficient for the description of water uptake kinetics, accurate values are still lacking for many systems. In this Feature Article, we present various experimental techniques that have been evoked in the literature to study the interfacial transport of water and discuss the corresponding strengths and limitations. This includes our recently developed technique called photothermal single-particle spectroscopy (PSPS). The PSPS technique allows for a retrieval of α values from three independent, yet simultaneous measurements operating close to equilibrium, providing a robust assessment of interfacial mass transport. We review the currently available data for α for water on various organics and discuss the few studies that address the temperature and relative humidity dependence of α for water on organics. The knowledge of the latter, for example, is crucial to assess the water uptake kinetics of organic aerosols in the Earth's atmosphere. Finally, we argue that PSPS might also be a viable method to better restrict the α value for water on liquid water.
各种有机气溶胶对水蒸气的吸收在许多应用中很重要，从药物气溶胶的医学输送到大气中的云形成。描述撞击气相分子粘到感兴趣表面的概率的系数称为质量容纳系数，α。尽管该系数对于描述水吸收动力学很重要，但许多系统仍然缺乏准确的值。在这篇专题文章中，我们介绍了文献中提出的各种实验技术，以研究水的界面输运，并讨论了相应的优缺点。这包括我们最近开发的称为光热单颗粒光谱（PSPS）的技术。PSPS 技术允许从三个独立但同时进行的接近平衡的测量中检索 α 值，从而对界面质量传输进行稳健评估。我们回顾了各种有机物上水的 α 值的现有数据，并讨论了少数研究有机物上水的 α 值对温度和相对湿度的依赖性的研究。例如，后者的知识对于评估地球大气中有机气溶胶的水吸收动力学至关重要。最后，我们认为 PSPS 也可能是一种可行的方法，可以更好地限制水在液态水上的 α 值。
