Humidity-dependent surface tension measurements of individual inorganic and organic submicrometre liquid particles
Humidity-dependent surface tension measurements of individual inorganic and organic submicrometre liquid particles
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DOI：
10.1039/c4sc03716b
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发表时间：
2015-01-01
期刊：
影响因子：
8.4
通讯作者：
Tivanski, Alexei V.
中科院分区：
文献类型：
--
作者：
Morris, Holly S.;Grassian, Vicki H.;Tivanski, Alexei V.
表面张力是液体的一个重要性质，对于大体积样品很容易测量。然而，对于尺寸小于1微米的液滴，目前没有报告测量。在这项研究中，原子力显微镜（AFM）和力谱已被用来测量单个亚微米大小的液滴在环境压力和控制相对湿度（RH）的表面张力。由于大气气溶胶的表面张力是理解气溶胶气候效应的关键因素，因此研究了三种大气相关系统（NaCl、丙二酸和谷氨酸）。单颗粒AFM测量成功地实现了在直径为200至500 nm的潮解颗粒的表面张力的测量。潮解颗粒在高RH下持续吸水，这改变了液滴的浓度和表面张力。因此，测量作为RH的函数的表面张力。基于原子力显微镜的表面张力测量接近预测值的基础上散装测量和活动的这三个化学系统。在浓缩的有机酸液滴中的非理想行为被认为是重要的，并且是在本体溶液预测和AFM数据之间观察到差异的原因。因此，这些测量对于改进大气气候模型至关重要，因为由于仪器的限制，迄今为止无法进行直接测量。
Surface tension, an important property of liquids, is easily measured for bulk samples. However, for droplets smaller than one micron in size, there are currently no reported measurements. In this study, atomic force microscopy (AFM) and force spectroscopy have been utilized to measure surface tension of individual submicron sized droplets at ambient pressure and controlled relative humidity (RH). Since the surface tension of atmospheric aerosols is a key factor in understanding aerosol climate effects, three atmospherically relevant systems (NaCl, malonic and glutaric acids) were studied. Single particle AFM measurements were successfully implemented in measuring the surface tension of deliquesced particles on the order of 200 to 500 nm in diameter. Deliquesced particles continuously uptake water at high RH, which changes the concentration and surface tension of the droplets. Therefore, surface tension as a function of RH was measured. AFM based surface tension measurements are close to predicted values based on bulk measurements and activities of these three chemical systems. Non-ideal behaviour in concentrated organic acid droplets is thought to be important and the reason for differences observed between bulk solution predictions and AFM data. Consequently, these measurements are crucial in order to improve atmospheric climate models as direct measurements hitherto have been previously inaccessible due to instrument limitations.