Liquid-liquid phase separation (LLPS) in atmospheric aerosol particles involves the formation of a liquid-liquid interface and influences climate and air-quality through processes including solar radiation scattering and cloud nucleation. Surface and interfacial tensions control particle morphology in LLPS particles and at small particle sizes may prevent LLPS altogether. Despite the importance of LLPS, direct measurements of the phase behavior of submicron aerosol particles have remained challenging and knowledge gaps remain regarding the structure, composition, and energetics of the associated liquid-liquid interfaces. Here, we detail detection of LLPS in submicron aerosol particles by insertion of a solvatochromic probe molecule. Subsequent detection of particle fluorescence allows the determination of the separation relative humidity at which LLPS occurs for several mixed organic/inorganic particle systems. We highlight the importance of further size- and chemistry-dependent measurements to quantify the role of liquid-liquid interfaces in determining phase behavior in atmospheric particles.

Liquid-liquid phase separation and interface formation in submicron aerosol particles

ACS Fall 2021

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