Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada.
College of Chemistry, Nankai University, Tianjin 300071, P. R. China.
J Phys Chem A. 2021 Apr 15;125(14):2954-2966. doi: 10.1021/acs.jpca.1c01522. Epub 2021 Apr 6.
Charged droplets have been associated with distinct chemical reactivity. It is assumed that the composition of the surface layer plays a critical role in enhancing the reaction rates in the droplets relative to their bulk solution counterparts. We use atomistic modeling to relate the localization of ions in the surface layer to their ejection propensity. We find that ion ejection takes place via a two-stage process. First, a conical protrusion emerges as a result of a global droplet deformation that is insensitive to the locations of the single ions. The ions are subsequently ejected as they enter the conical regions. The study provides mechanistic insight into the ion-evaporation mechanism, which can be used to revise the commonly used ion-evaporation models. We argue that atomistic molecular dynamics simulations of minute nanodrops do not sufficiently distinguish the ion-evaporation mechanism from a Rayleigh fission. We explain mass spectrometry data on the charge state of small globular proteins and the existence of supercharged droplet states that have been detected in experiments.
带电荷的液滴与独特的化学反应性有关。人们认为，表面层的组成在提高液滴相对于其本体溶液的反应速率方面起着关键作用。我们使用原子模拟来将表面层中离子的定位与其喷射倾向联系起来。我们发现，离子喷射是通过两个阶段的过程发生的。首先，由于全局液滴变形而出现一个锥形突起，而这种变形对单个离子的位置不敏感。随后，当离子进入锥形区域时，它们被喷射出来。该研究为离子蒸发机制提供了机械洞察力，可用于修正常用的离子蒸发模型。我们认为，对微小纳米液滴的原子分子动力学模拟并不能充分区分离子蒸发机制和瑞利分裂。我们解释了关于小球状蛋白质的电荷状态的质谱数据，以及实验中检测到的超荷电液滴状态的存在。
