Abstract Long chain fatty acids and alcohols are low volatile species in continental and marine aerosols. We established a surface film model by Langmuir trough to investigate the interfacial properties of sea salts droplets coated by surface active molecules—stearic acid (SA), oleic acid (OA), 1-octadecanol (C18OH) and their mixtures. The aim of this work was to verify the impact of the head group, saturation degree, mixing ratio of different surfactants on miscibility and stability between these compounds in monolayers at the air–water interface. Compared to the organic-coated water droplets, the surface properties of mixed fatty acid and alcohol-coated aqueous sea salt particles are substantially different. Mixed SA/C18OH monolayers are less stable than pure SA or C18OH monolayer at high surface pressure. From the point of view of the geometry, steric hindrance of unsaturated chain is the crucial factor in loose packing of OA monolayer. The negative values of excess mixing areas (ΔAex) for OA/C18OH monolayer on artificial seawater result from the attractive interaction between tail groups. The maximum negative value of excess Gibbs free energies (ΔGex) appears at the equimolecular OA and C18OH. Surface pressure−area (π–A) isotherm combined with equilibrium spreading pressure (ESP) confirms that the tightly packed monolayer formed by C18OH molecules can minimize water evaporation rate of the potential droplet. Different surface properties of organic films coated on aqueous aerosol must have a significant impact on interaction droplet growth. The interactions between fatty acid and alcohol at the air-water interface provide an insight into the nucleation and growth mechanism of droplets covered by film-forming species.

中文翻译：

---

水气溶胶表面低挥发性化合物混合物有机膜模型的建立

摘要 长链脂肪酸和醇是大陆和海洋气溶胶中的低挥发性物质。我们通过 Langmuir 槽建立了表面膜模型，以研究由表面活性分子 - 硬脂酸 (SA)、油酸 (OA)、1-十八醇 (C18OH) 及其混合物包覆的海盐液滴的界面特性。这项工作的目的是验证头基、饱和度、不同表面活性剂的混合比对这些化合物在气水界面单层中的混溶性和稳定性的影响。与有机包覆的水滴相比，混合脂肪酸和醇包覆的水性海盐颗粒的表面性质有很大不同。在高表面压力下，混合的 SA/C18OH 单层比纯 SA 或 C18OH 单层稳定性差。从几何的角度来看，不饱和链的空间位阻是OA单层松散堆积的关键因素。人工海水上 OA/C18OH 单层的过量混合面积 (ΔAex) 的负值是由于尾基团之间的吸引力相互作用造成的。过量吉布斯自由能 (ΔGex) 的最大负值出现在等分子 OA 和 C18OH 处。表面压力-面积 (π-A) 等温线与平衡扩散压力 (ESP) 相结合，证实由 C18OH 分子形成的紧密堆积的单层可以最大限度地降低潜在液滴的水分蒸发率。涂覆在水性气溶胶上的有机薄膜的不同表面特性必须对相互作用的液滴生长产生显着影响。