Palmitic Acid on Salt Subphases and in Mixed Monolayers of Cerebrosides: Application to Atmospheric Aerosol Chemistry
Palmitic Acid on Salt Subphases and in Mixed Monolayers of Cerebrosides: Application to Atmospheric Aerosol Chemistry
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DOI：
10.3390/atmos4040315
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发表时间：
2013-12-01
期刊：
影响因子：
2.9
通讯作者：
Allen, Heather C.
中科院分区：
文献类型：
--
作者：
Adams, Ellen M.;Allen, Heather C.
棕榈酸 (PA) 已被发现是海洋气溶胶的主要成分，通常用于研究含有机物的大气气溶胶，因此在此用作代理系统。使用表面压力面积等温线 (pi-A)、布鲁斯特角显微镜 (BAM) 和振动和频发生 (VSFG) 来观察超纯水、CaCl2 和 MgCl2 水溶液以及人造海水 (ASW) 亚相薄膜压缩过程中的 PA 单分子层。 pi-A 等温线表明盐亚相改变了 PA 的相行为，BAM 进一步揭示了与纯水相比，单层发生了冷凝。 VSFG 光谱和 BAM 图像显示 Mg2+ 和 Ca2+ 诱导 PA 酰基链有序化，并且确定 Mg2+ 与单层的相互作用弱于 Ca2+。 pi-A 等温线和 BAM 也用于监测 PA 和脑苷脂（一种简单的糖脂）的混合单层。结果表明，PA 对脑苷脂单层也有缩合作用。热力学分析表明两种组分之间存在吸引相互作用；这可能是由于半乳糖和羰基头基的氢键作用所致。塌陷结构的 BAM 图像显示，PA 和脑苷脂的混合单层在所有表面压力下均可混溶。这些结果表明，有机涂层气溶胶的表面形态受到水核和有机膜本身化学成分的影响。
Palmitic acid (PA) has been found to be a major constituent in marine aerosols, and is commonly used to investigate organic containing atmospheric aerosols, and is therefore used here as a proxy system. Surface pressure-area isotherms (pi-A), Brewster angle microscopy (BAM), and vibrational sum frequency generation (VSFG) were used to observe a PA monolayer during film compression on subphases of ultrapure water, CaCl2 and MgCl2 aqueous solutions, and artificial seawater (ASW). pi-A isotherms indicate that salt subphases alter the phase behavior of PA, and BAM further reveals that a condensation of the monolayer occurs when compared to pure water. VSFG spectra and BAM images show that Mg2+ and Ca2+ induce ordering of the PA acyl chains, and it was determined that the interaction of Mg2+ with the monolayer is weaker than Ca2+. pi-A isotherms and BAM were also used to monitor mixed monolayers of PA and cerebroside, a simple glycolipid. Results reveal that PA also has a condensing effect on the cerebroside monolayer. Thermodynamic analysis indicates that attractive interactions between the two components exist; this may be due to hydrogen bonding of the galactose and carbonyl headgroups. BAM images of the collapse structures show that mixed monolayers of PA and cerebroside are miscible at all surface pressures. These results suggest that the surface morphology of organic-coated aerosols is influenced by the chemical composition of the aqueous core and the organic film itself.