Talreja-Muthreja Tanya, Linnow Kirsten, Enke Dirk, Steiger Michael
University of Hamburg, Department of Chemistry, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany.
University of Leipzig, Faculty of Chemistry and Mineralogy, Linnéstr. 3, 04103 Leipzig, Germany.
Langmuir. 2022 Sep 13;38(36):10963-10974. doi: 10.1021/acs.langmuir.2c01309. Epub 2022 Aug 29.
The deliquescence behavior of salt nanocrystals is different from that of bulk crystals. Here, we report the first systematic measurements of the deliquescence relative humidity (DRH) of sodium chloride crystals confined in various nanoporous silica materials with pore diameters ranging from 8 to 89 nm. Deliquescence humidities were determined by water vapor sorption measurements. In comparison to the DRH of bulk NaCl crystals (75.3% RH), the DRH decreases from 73 to 58% as the pore size decreases from 89 to 8 nm. In contrast, according to literature data, the DRH of NaCl aerosol nanoparticles increases with decreasing crystal size. A thermodynamic model approach, based on the combined use of an ion-interaction model, the Laplace equation, and the Kelvin equation, is used to calculate the influence of the confinement in nanopores on the solid-liquid and liquid-vapor phase equilibria. These calculations reveal that the main reason for the decrease in the DRH in nanopores is the concave curvature of the liquid-vapor interface that is formed during deliquescence. The same model approach shows that the increase in DRH of nanosized aerosol particles is due to the convex curvature of the liquid-vapor interface, whereas the effect of increases in solubility with decreasing crystal size is small.
盐纳米晶体的潮解行为与块状晶体不同。在此，我们报告了首次对限制在孔径范围为8至89纳米的各种纳米多孔二氧化硅材料中的氯化钠晶体的潮解相对湿度（DRH）进行的系统测量。潮解湿度通过水蒸气吸附测量来确定。与块状氯化钠晶体的DRH（75.3%相对湿度）相比，随着孔径从89纳米减小到8纳米，DRH从73%降至58%。相比之下，根据文献数据，氯化钠气溶胶纳米颗粒的DRH随着晶体尺寸的减小而增加。基于离子相互作用模型、拉普拉斯方程和开尔文方程的联合使用的热力学模型方法，用于计算纳米孔中的限制对固 - 液和液 - 气平衡的影响。这些计算表明，纳米孔中DRH降低的主要原因是潮解过程中形成的液 - 气界面的凹曲率。相同的模型方法表明，纳米级气溶胶颗粒的DRH增加是由于液 - 气界面的凸曲率，而随着晶体尺寸减小溶解度增加的影响较小。
