Size-Dependent Liquid–Liquid Phase Separation in Atmospherically Relevant Complex Systems

Kucinski, Theresa M.; Dawson, Joseph Nelson; Freedman, Miriam Arak

doi:10.1021/acs.jpclett.9b02532

Cited by 47 publications

(76 citation statements)

References 49 publications

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“…4). 67,69 In our initial publications, we observed that for intermediate solubility organic compounds such as succinic and pimelic acids mixed with ammonium sulfate, particles less than 170 nm and 270 nm, respectively, were homogeneous rather than phase separated (Fig. 4).…”

Section: Size Dependence Of Morphologymentioning

confidence: 94%

“…We have investigated whether systems that contain ammonium sulfate combined with mixtures of organic acids have size-dependent LLPS using cryo-TEM. 69 Organic-containing aerosol particles are often mixtures of hundreds of compounds, especially far from the source emission or in cases where gas phase compounds are oxidized to form organic compounds that partition to the particle phase. We have worked with a) mixtures of dicarboxylic acids, b) mixtures of approximately 10 organic compounds with a variety of functional groups and chemical structures, and c) secondary organic material generated from the ozonolysis of a-pinene.…”

Section: Size Dependence Of Llps In Atmospherically Relevant Organic ...mentioning

confidence: 99%

“…69 Phase separation into three liquid phases is rare and follows no trend with particle size. 69 We expect that separation into three liquid phases represents a kinetically trapped state of the particles, as the compounds used are sufficiently soluble in aqueous solution that we do not expect phase separation between more and less soluble components. The significance of this work is the indication that the size dependence of the morphology is relevant for atmospheric particles due to the use of complex mixtures in this study.…”

Section: Size Dependence Of Llps In Atmospherically Relevant Organic ...mentioning

confidence: 99%

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Liquid–Liquid Phase Separation in Supermicrometer and Submicrometer Aerosol Particles

Freedman

2020

Acc. Chem. Res.

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The interactions of aerosol particles with light and clouds are among the most uncertain aspects of anthropogenic climate forcings. The effects of aerosol particles on climate depend on their optical properties, heterogeneous chemistry, water uptake behavior, and ice nucleation activity. These properties in turn depend on aerosol physics and chemistry including composition, size, shape, internal structure (morphology), and phase state. The greatest numbers of particles are found at small, submicron sizes, and the properties of aerosol particles can differ on the nanoscale compared with measurements of bulk materials. As a result, our focus has been on characterizing the phase transitions of aerosol particles both in supermicron and submicron particles. The phase transition of particular interest for us has been liquid-liquid phase separation (LLPS), which occurs when components of a solution phase separate due to a difference in solubilities. For example, organic compounds can have limited solubility in salt solutions especially as the water content decreases, increasing the concentration of the salt solution, and causing phase separation between organic-rich and inorganic-rich phases. To characterize the systems of interest, we primarily use optical microscopy for supermicron particles and cryogenictransmission microscopy for submicron particles.

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Section: Size Dependence Of Morphologymentioning

confidence: 94%

Section: Size Dependence Of Llps In Atmospherically Relevant Organic ...mentioning

confidence: 99%

Section: Size Dependence Of Llps In Atmospherically Relevant Organic ...mentioning

confidence: 99%

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Liquid–Liquid Phase Separation in Supermicrometer and Submicrometer Aerosol Particles

Freedman

2020

Acc. Chem. Res.

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“…mixtures of SOA and SIA proxies (33). However, two liquid phases were reported in the majority of those experiments, and conditions favoring three liquid phases were unclear and not elucidated.…”

Section: Significancementioning

confidence: 96%

Coexistence of three liquid phases in individual atmospheric aerosol particles

Huang

Mahrt

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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Individual atmospheric particles can contain mixtures of primary organic aerosol (POA), secondary organic aerosol (SOA), and secondary inorganic aerosol (SIA). To predict the role of such complex multicomponent particles in air quality and climate, information on the number and types of phases present in the particles is needed. However, the phase behavior of such particles has not been studied in the laboratory, and as a result, remains poorly constrained. Here, we show that POA+SOA+SIA particles can contain three distinct liquid phases: a low-polarity organic-rich phase, a higher-polarity organic-rich phase, and an aqueous inorganic-rich phase. Based on our results, when the elemental oxygen-to-carbon (O:C) ratio of the SOA is less than 0.8, three liquid phases can coexist within the same particle over a wide relative humidity range. In contrast, when the O:C ratio of the SOA is greater than 0.8, three phases will not form. We also demonstrate, using thermodynamic and kinetic modeling, that the presence of three liquid phases in such particles impacts their equilibration timescale with the surrounding gas phase. Three phases will likely also impact their ability to act as nuclei for liquid cloud droplets, the reactivity of these particles, and the mechanism of SOA formation and growth in the atmosphere. These observations provide fundamental information necessary for improved predictions of air quality and aerosol indirect effects on climate.

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“… 50 − 53 The size-dependent aerosol composition results in highly variable and relative humidity (RH)-dependent water uptake, which, in turn, affects the phase state by changing the aerosol solute concentration and viscosity. 54 This is particularly true for sub-100 nm aerosols that are predominantly organic 39 and, thus, generally have lower water uptake. 17 , 33 , 55 …”

Section: Introductionmentioning

confidence: 99%

Probing the Water Uptake and Phase State of Individual Sucrose Nanoparticles Using Atomic Force Microscopy

Madawala

Lee

Kaluarachchi

et al. 2021

ACS Earth Space Chem.

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The effects of atmospheric aerosols on the climate and atmosphere of Earth can vary significantly depending upon their properties, including size, morphology, and phase state, all of which are influenced by varying relative humidity (RH) in the atmosphere. A significant fraction of atmospheric aerosols is below 100 nm in size. However, as a result of size limitations of conventional experimental techniques, how the particle-to-particle variability of the phase state of aerosols influences atmospheric processes is poorly understood. To address this issue, the atomic force microscopy (AFM) methodology that was previously established for sub-micrometer aerosols is extended to measure the water uptake and identify the phase state of individual sucrose nanoparticles. Quantified growth factors (GFs) of individual sucrose nanoparticles up to 60% RH were lower than expected values observed on the sub-micrometer sucrose particles. The effect could be attributed to the semisolid sucrose nanoparticle restructuring on a substrate. At RH > 60%, sucrose nanoparticles are liquid and GFs overlap well with the sub-micrometer particles and theoretical predictions. This suggests that quantification of GFs of nanoparticles may be inaccurate for the RH range where particles are semisolid but becomes accurate at elevated RH where particles are liquid. Despite this, however, the identified phase states of the nanoparticles were comparable to their sub-micrometer counterparts. The identified phase transitions between solid and semisolid and between semisolid and liquid for sucrose were at ∼18 and 60% RH, which are equivalent to viscosities of 10 11.2 and 10 2.5 Pa s, respectively. This work demonstrates that measurements of the phase state using AFM are applicable to nanosized particles, even when the substrate alters the shape of semisolid nanoparticles and alters the GF.

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Size-Dependent Liquid–Liquid Phase Separation in Atmospherically Relevant Complex Systems

Cited by 47 publications

References 49 publications

Liquid–Liquid Phase Separation in Supermicrometer and Submicrometer Aerosol Particles

Liquid–Liquid Phase Separation in Supermicrometer and Submicrometer Aerosol Particles

Coexistence of three liquid phases in individual atmospheric aerosol particles

Probing the Water Uptake and Phase State of Individual Sucrose Nanoparticles Using Atomic Force Microscopy

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