Jain Piyush, Vincent Olivier, Stroock Abraham D
Langmuir. 2019 Mar 19;35(11):3949-3962. doi: 10.1021/acs.langmuir.8b04307. Epub 2019 Mar 5.
Probing nanoconfined solutions in tortuous, mesoporous media is challenging because of pore size, complex pore connectivity, and the coexistence of multiple components and phases. Here, we use optical reflectance to experimentally investigate the wetting and drying of a mesoporous medium with ∼3-nm-diameter pores containing aqueous solutions of sodium chloride and lithium chloride. We show that the vapor activities (i.e., relative humidities) that correspond to optical features in the isotherms for solutions can be used to deduce the thermodynamic state of a nanoscopic solution that undergoes evaporation and crystallization upon drying and condensation and deliquescence when increasing the relative humidity. We emphasize specific equilibrium states of the system: the onset of draining during desorption and the end of filling during adsorption as well as percolation-induced scattering and crystallization. We find that theoretical arguments involving classical thermodynamics (a modified Kelvin-Laplace equation and classical nucleation theory) explain quantitatively the evolution of the optical features and thereby the state of the solution as a function of imposed vapor activity and solute concentration.
在曲折的介孔介质中探测纳米受限溶液具有挑战性，这是由于孔径、复杂的孔连通性以及多种组分和相的共存。在此，我们利用光反射率通过实验研究了一种具有约3纳米直径孔隙的介孔介质的润湿和干燥过程，该介质含有氯化钠和氯化锂的水溶液。我们表明，对应于溶液等温线中光学特征的蒸汽活度（即相对湿度）可用于推断纳米级溶液的热力学状态，该溶液在干燥时会经历蒸发和结晶，而在相对湿度增加时会发生冷凝和潮解。我们强调了系统的特定平衡状态：解吸过程中排水的开始、吸附过程中填充的结束以及渗流引起的散射和结晶。我们发现，涉及经典热力学（修正的开尔文 - 拉普拉斯方程和经典成核理论）的理论论证定量地解释了光学特征的演变，从而解释了溶液状态随施加的蒸汽活度和溶质浓度的变化。
