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Publication abstract: To elucidate the intricate role the sea surface microlayer (SML) and sea spray aerosols (SSA) play in the climate, understanding the chemical complexity of the SML and how it affects the physical-chemical properties of the microlayer and SSA are important to investigate. While the surface tension of the SML has been studied previously using conventional experimental tools, accurate measurements must be localized to the thickness of the air-liquid interface of the SML. Here we explore the atomic force microscopy (AFM) capabilities to quantify the surface tension of aqueous solution droplets with (sub)micrometer indentation depths into the interface. Sample droplets of hexanoic acid at molar concentrations ranging from 0.1 mM to 80 mM and SML from a recent wave flume study were investigated. A constant radius AFM nanoneedle was used to probe through ca. 200 µL droplets with 0.3 - 1.2 µm indentation depths. As a comparison, the surface tension of bulk samples was also measured using a conventional force tensiometer. The data for the hexanoic acid show an excellent overlap between the AFM and force tensiometer surface tension measurements. For the surface tension measurements of the SML however, the measured values from the AFM were lower than the force tensiometer, which was attributed to the presence of thin multilayers of surfactant surface films on the air-liquid interface of SML and the high sensitivity of the AFM methodology. Overall, the study confirmed the accuracy of the AFM method to quantify the surface tension of aqueous solutions over a wide range of concentrations for surface-active organic compounds. The methodology can be further used to reveal small, yet important, differences in the surface tension of complex air-liquid interfaces. Research Data Curation Program, UC San Diego, La Jolla, 92093-0175 (https://lib.ucsd.edu/rdcp) Kaluarachchi, Chathuri P.; Lee, Hansol D.; Lan, Yiling; Lansakara, Thiranjeewa; Tivanski, Alexei V. (2021). Data from: Surface Tension Measurements of Aqueous Liquid-Air Interfaces Probed with Microscopic Indentation. In Center for Aerosol Impacts on Chemistry of the Environment (CAICE) Collection. UC San Diego Library Digital Collections. https://doi.org/10.6075/J0ZW1JGC This package contains an explanatory readme file and the data used to generate surface tension measurements of hexanoic acid samples and SML using AFM nanoneedle method, and bulk tensiometer method.
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