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1. Fluorescence Aerosol Flow Tube Spectroscopy to Detect Liquid–Liquid Phase Separation

   https://doi.org/10.1021/acsearthspacechem.1c00061  

   Ohno, Paul E.; Qin, Yiming; Ye, Jianhuai; Wang, Junfeng; Bertram, Allan K.; Martin, Scot T. (May 2021, ACS Earth and Space Chemistry)
2. Single Liquid Aerosol Microparticle Electrochemistry on a Suspended Ionic Liquid Film

   https://doi.org/10.1002/smll.202308637  

   Krushinski, Lynn E.; Vannoy, Kathryn J.; Dick, Jeffrey E. (February 2024, Small)

   Abstract Liquid aerosols are ubiquitous in nature, and several tools exist to quantify their physicochemical properties. As a measurement science technique, electrochemistry has not played a large role in aerosol analysis because electrochemistry in air is rather difficult. Here, a remarkably simple method is demonstrated to capture and electroanalyze single liquid aerosol particles with radii on the order of single micrometers. An electrochemical cell is constructed by a microwire (cylindrical working electrode) traversing a film of ionic liquid (1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl)imide) that is suspended within a wire loop (reference/counter electrode). An ionic liquid is chosen because the low vapor pressure preserves the film over weeks, vastly improving suspended film electroanalysis. The resultant high surface area allows the suspended ionic liquid cell to act as an aerosol net. Given the hydrophobic nature of the ionic liquid, aqueous aerosol particles do not coalesce into the film. When the liquid aerosols collide with the sufficiently biased microwire (creating a complex boundary: aerosol|wire|ionic liquid|air), the electrochemistry within a single liquid aerosol particle can be interrogated in real‐time. The ability to achieve liquid aerosol size distributions for aerosols over 1 µm in radius is demonstrated. 

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3. Liquid–Liquid Phase Separation Can Drive Aerosol Droplet Growth in Supersaturated Regimes

   https://doi.org/10.1021/acsenvironau.3c00015  

   Malek, Kotiba; Gohil, Kanishk; Olonimoyo, Esther A.; Ferdousi-Rokib, Nahin; Huang, Qishen; Pitta, Kiran R.; Nandy, Lucy; Voss, Katelyn A.; Raymond, Timothy M.; Dutcher, Dabrina D.; et al (September 2023, ACS Environmental Au)
4. Aerosol Optical Tweezers Constrain the Morphology Evolution of Liquid-Liquid Phase-Separated Atmospheric Particles

   https://doi.org/10.1016/j.chempr.2019.10.018  

   Gorkowski, Kyle; Donahue, Neil M.; Sullivan, Ryan C. (January 2020, Chem)
5. Liquid–liquid phase separation and viscosity within secondary organic aerosol generated from diesel fuel vapors

   https://doi.org/10.5194/acp-19-12515-2019  

   Song, Mijung; Maclean, Adrian M.; Huang, Yuanzhou; Smith, Natalie R.; Blair, Sandra L.; Laskin, Julia; Laskin, Alexander; DeRieux, Wing-Sy Wong; Li, Ying; Shiraiwa, Manabu; et al (January 2019, Atmospheric Chemistry and Physics)

   Abstract. Information on liquid–liquid phase separation (LLPS) and viscosity (ordiffusion) within secondary organic aerosol (SOA) is needed to improvepredictions of particle size, mass, reactivity, and cloud nucleatingproperties in the atmosphere. Here we report on LLPS and viscosities withinSOA generated by the photooxidation of diesel fuel vapors. Diesel fuelcontains a wide range of volatile organic compounds, and SOA generated bythe photooxidation of diesel fuel vapors may be a good proxy for SOA fromanthropogenic emissions. In our experiments, LLPS occurred over the relativehumidity (RH) range of ∼70 % to ∼100 %,resulting in an organic-rich outer phase and a water-rich inner phase. Theseresults may have implications for predicting the cloud nucleating propertiesof anthropogenic SOA since the presence of an organic-rich outer phase athigh-RH values can lower the supersaturation with respect to water requiredfor cloud droplet formation. At ≤10 % RH, the viscosity was ≥1×108 Pa s, which corresponds to roughly the viscosity of tarpitch. At 38 %–50 % RH, the viscosity was in the range of 1×108 to 3×105 Pa s. These measured viscosities areconsistent with predictions based on oxygen to carbon elemental ratio (O:C)and molar mass as well as predictions based on the number of carbon,hydrogen, and oxygen atoms. Based on the measured viscosities and theStokes–Einstein relation, at ≤10 % RH diffusion coefficients oforganics within diesel fuel SOA is ≤5.4×10-17 cm2 s−1 and the mixing time of organics within 200 nm diesel fuel SOAparticles (τmixing) is 50 h. These small diffusion coefficientsand large mixing times may be important in laboratory experiments, where SOAis often generated and studied using low-RH conditions and on timescales ofminutes to hours. At 38 %–50 % RH, the calculated organic diffusioncoefficients are in the range of 5.4×10-17 to 1.8×10-13 cm2 s−1 and calculated τmixing values arein the range of ∼0.01 h to ∼50 h. These valuesprovide important constraints for the physicochemical properties ofanthropogenic SOA. 

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