Dynamics of Liquid–Liquid Phase Separation\nin Submicrometer Aerosol

Abstract

Nanoscale\nmaterials, when compared to their bulk components, possess\nunique properties. In particular, shifts in phase transitions can\noccur for submicrometer particles. For instance, small particles do\nnot undergo the process of liquid–liquid phase separation (LLPS).\nLLPS has applications in emulsions such as Janus particles, controllable\nmorphology to create drug-rich phases during drug delivery, and is\noften observed in atmospheric aqueous aerosol particles. In atmospheric\nparticles, LLPS is tracked as a function of particle water activity,\nwhich is equivalent to the relative humidity (RH) at equilibrium.\nWe probed three organic/inorganic aerosol systems in the range of\nRH over which phase separation occurs (SRH). Our findings indicate\nthat SRH for submicrometer aerosol particles is lower than for micrometer-sized\ndroplets. These findings show that it may be necessary to update the\nrepresentation of phase transitions in aerosol particles in climate\nmodels. The vast majority of organic/inorganic aerosol particles have\nsubmicrometer diameters, and a decrease in SRH for submicrometer particles\nindicates that the current estimation of phase-separated aerosols\nmay be overestimated. Furthermore, understanding the properties of\nLLPS at the nanoscale can provide key parameters to describe these\nsystems and may lead to better control of phase separation in submicrometer\nparticles.