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Freedman MA, Huang Q, Pitta KR. Phase Transitions in Organic and Organic/Inorganic Aerosol Particles. Annu Rev Phys Chem 2024; 75:257-281. [PMID: 38382569 DOI: 10.1146/annurev-physchem-083122-115909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
The phase state of aerosol particles can impact numerous atmospheric processes, including new particle growth, heterogeneous chemistry, cloud condensation nucleus formation, and ice nucleation. In this article, the phase transitions of inorganic, organic, and organic/inorganic aerosol particles are discussed, with particular focus on liquid-liquid phase separation (LLPS). The physical chemistry that determines whether LLPS occurs, at what relative humidity it occurs, and the resultant particle morphology is explained using both theoretical and experimental methods. The known impacts of LLPS on aerosol processes in the atmosphere are discussed. Finally, potential evidence for LLPS from field and chamber studies is presented. By understanding the physical chemistry of the phase transitions of aerosol particles, we will acquire a better understanding of aerosol processes, which in turn impact human health and climate.
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Affiliation(s)
- Miriam Arak Freedman
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania, USA; ,
- Department of Meteorology and Atmospheric Science, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Qishen Huang
- Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, China;
| | - Kiran R Pitta
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania, USA; ,
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Huang Q, Pitta KR, Constantini K, Ott EJE, Zuend A, Freedman MA. Experimental phase diagram and its temporal evolution for submicron 2-methylglutaric acid and ammonium sulfate aerosol particles. Phys Chem Chem Phys 2024; 26:2887-2894. [PMID: 38054479 DOI: 10.1039/d3cp04411d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Liquid-liquid phase separation (LLPS) in aerosol particles is important for the climate system due to its potential to impact heterogeneous chemistry, cloud condensation nuclei, and new particle growth. Our group and others have shown a lower separation relative humidity for submicron particles, but whether the suppression is due to thermodynamics or kinetics is unclear. Herein, we characterize the experimental LLPS phase diagram of submicron 2-methylglutaric acid and ammonium sulfate aerosol particles and compare it to that of supermicron-sized particles. Surprisingly, as the equilibration time of submicron-sized aerosol particles was increased from 20 min to 60 min, the experimental phase diagram converges with the results for supermicron-sized particles. Our findings indicate that nucleation kinetics are responsible for the observed lower separation relative humidities in submicron aerosol particles. Therefore, experiments and models that investigate atmospheric processes of organic aerosol particles may need to consider the temporal evolution of aerosol LLPS.
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Affiliation(s)
- Qishen Huang
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
- Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Kiran R Pitta
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
| | - Kayla Constantini
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
| | - Emily-Jean E Ott
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
| | - Andreas Zuend
- Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, H3A 0B9, Canada
| | - Miriam Arak Freedman
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
- Department of Meteorology and Atmospheric Science, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Hu T, Brimblecombe P, Zhang Z, Song Y, Liu S, Zhu Y, Duan J, Cao J, Zhang D. Capillary rise induced salt deterioration on ancient wall paintings at the Mogao Grottoes. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 881:163476. [PMID: 37075995 DOI: 10.1016/j.scitotenv.2023.163476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 04/02/2023] [Accepted: 04/09/2023] [Indexed: 05/03/2023]
Abstract
Salt deterioration has been found to be a major threat to wall paintings at culture heritage sites in arid areas along the Silk Road. However, the routes of water migration that cause the efflorescence have not been identified, and consequently, effective preservation measures have not been developed. Our microanalysis, by interrogating 93,727 individual particles collected in a Mogao cave in Dunhuang, China, revealed that capillary rise of water in the earthen plasters drives the deterioration of wall paintings. The vertical distribution of chloride and sulfate particles in the salt efflorescence and their morphologies implied a migration of salts through capillary rise and subsequent crystal growth under environmental conditions exerts sufficient pressure to cause surface decay and loss. These results indicate that blocking the water capillary rise under the porous structures is likely the most effective route to prevent rapid deterioration of the ancient wall paintings. These salt transport and deterioration mechanisms in an arid environment, suggests that a wide range of management strategies and protective measures could be developed to effectively preserve heritage sites in arid regions, especially along the Silk Road.
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Affiliation(s)
- Tafeng Hu
- State Key Laboratory of Loess and Quaternary Geology, KLACP, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China.
| | - Peter Brimblecombe
- School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK; Department of Marine Environment and Engineering, National Sun Yat-sen University, Kaohsiung 804, Taiwan, China
| | - Zhengmo Zhang
- Conservation Institute, Dunhuang Academy, Dunhuang, 736200, China
| | - Yingpan Song
- State Key Laboratory of Loess and Quaternary Geology, KLACP, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China
| | - Suixin Liu
- State Key Laboratory of Loess and Quaternary Geology, KLACP, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China
| | - Yuqing Zhu
- State Key Laboratory of Loess and Quaternary Geology, KLACP, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China
| | - Jing Duan
- State Key Laboratory of Loess and Quaternary Geology, KLACP, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China
| | - Junji Cao
- Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
| | - Daizhou Zhang
- Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862-8502, Japan.
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Ohno PE, Brandão L, Rainone EM, Aruffo E, Wang J, Qin Y, Martin ST. Size Dependence of Liquid-Liquid Phase Separation by in Situ Study of Flowing Submicron Aerosol Particles. J Phys Chem A 2023; 127:2967-2974. [PMID: 36947002 DOI: 10.1021/acs.jpca.2c08224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023]
Abstract
Liquid-liquid phase separation (LLPS) of atmospheric particles impacts a range of atmospheric processes. Driven by thermodynamics, LLPS occurs in mixed organic-inorganic particles when high inorganic salt concentrations exclude organic compounds, which develop into a separate phase. The effect of particle size on the thermodynamic and kinetic drivers of LLPS, however, remains incompletely understood. Here, the size dependence was studied for the separation relative humidity (SRH) of LLPS. Submicron organic-inorganic aerosol particles of ammonium sulfate mixed with 1,2,6-hexanetriol and polyethylene glycol (PEG) were studied. In a flow configuration, upstream size selection was coupled to a downstream fluorescence aerosol flow tube (F-AFT) at 293 ± 1 K. For both mixed particle types, the SRH values for submicron particle diameters of 260-410 nm agreed with previous measurements reported in the literature for supermicron particles. For smaller particles, the SRH values decreased by approximately 5% RH for diameters of 130-260 nm for PEG-sulfate particles and of 70-190 nm for hexanetriol-sulfate particles. From these observations, the nucleation rate in the hexanetriol-sulfate system was constrained, implying an activation barrier to nucleation of +1.4 to +2.0 × 10-19 J at 70% RH and 293 K. Quantifying the activation barrier is an approach for predicting size-dependent LLPS in the atmosphere.
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Affiliation(s)
- Paul E Ohno
- School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
- Harvard University Center for the Environment, Cambridge, Massachusetts 02138, United States
| | - Lilliana Brandão
- School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Elizabeth M Rainone
- School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Eleonora Aruffo
- School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
- Department of Advanced Technologies in Medicine & Dentistry, University "G. d'Annunzio" of Chieti-Pescara, Chieti 66100, Italy
| | - Junfeng Wang
- School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Yiming Qin
- School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Scot T Martin
- School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
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Price CL, Preston TC, Davies JF. Hygroscopic Growth, Phase Morphology, and Optical Properties of Model Aqueous Brown Carbon Aerosol. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:3941-3951. [PMID: 35312301 DOI: 10.1021/acs.est.1c07356] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Brown carbon aerosol in the atmosphere contain light-absorbing chromophores that influence the optical scattering properties of the particles. These chromophores may be hydrophobic, such as PAHs, or water soluble, such as nitroaromatics, imidazoles, and other conjugated oxygen-rich molecules. Water-soluble chromophores are expected to exist in aqueous solution in the presence of sufficient water and will exhibit physical properties (e.g., size, refractive index, and phase morphology) that depend on the environmental relative humidity (RH). In this work, we characterize the RH-dependent properties of 4-nitrocatechol (4-NC) and its mixtures with ammonium sulfate, utilizing a single-particle levitation platform coupled with Mie resonance spectroscopy to probe the size, real part of the complex refractive index (RI), and phase morphology of individual micron-sized particles. We measure the hygroscopic growth properties of pure 4-NC and apply mixing rules to characterize the growth of mixtures with ammonium sulfate. We report the RI at 589 nm for these samples as a function of RH and explore the wavelength dependence of the RI at non-absorbing wavelengths. The real part of the RI at 589 nm was found to vary in the range 1.54-1.59 for pure 4-NC from 92.5 to 75% RH, with an estimated pure component RI of 1.70. The real part of the RI was also measured for mixtures of AS and 4-NC and ranged from 1.39 to 1.51 depending on the component ratio and RH. We went on to characterize phase transitions in mixed particles, identifying the onset RH of liquid-liquid phase separation (LLPS) and efflorescence transitions. Mixtures showed LLPS in the range of 85-76% RH depending on the molar ratio, while efflorescence typically fell between 22 and 42% RH. Finally, we characterized the imaginary part of the complex RI using an effective oscillator model to capture the wavelength-dependent absorption properties of the system.
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Affiliation(s)
- Chelsea L Price
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
| | - Thomas C Preston
- Department of Atmospheric and Oceanic Sciences and Department of Chemistry, McGill University, 805 Sherbrooke Street West, Montreal, Quebec H3A 0B9, Canada
| | - James F Davies
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
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Longnecker E, Metz L, Miller RS, Berke AE. Probing Liquid-Liquid Phase Separation in Secondary Organic Aerosol Mimicking Solutions Using Articulated Straws. ACS OMEGA 2021; 6:33436-33442. [PMID: 34926893 PMCID: PMC8674910 DOI: 10.1021/acsomega.1c04014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 11/18/2021] [Indexed: 06/14/2023]
Abstract
The presence or absence of liquid-liquid phase separation (LLPS) in aerosol particles containing oxidized organic species and inorganic salts affects particle morphology and influences uptake into, diffusion through, and reactivity within those particles. We report here an accessible method, similar to ice core analyses, using solutions that are relevant for both aerosol chemical systems and aqueous two-phase extraction systems and contain ammonium sulfate and one of eight alcohols (methanol, ethanol, 1-propanol, 2-propanol, 2-butaonol, 3-methyl-2-butanol, 1,2-propanediol, or 1,3-propanediol) frozen in articulated (bendable) straws to probe LLPS. For alcohols with negative octanol-water partitioning coefficient (K OW) values and O/C ratios ≥0.5, no LLPS occurs, while for alcohols with positive K OW values and O/C ratios ≤0.33, phase separation always occurs, both findings consistent with observations using different experimental techniques. When a third species, glyoxal, is added, the glyoxal stays in the aqueous phase, regardless of whether LLPS occurs. When phase separation occurs, the glyoxal forms a strong intermolecular interaction with the sulfate ion, red-shifting the ν3(SO4 2-) peak by 15 cm-1. These results provide evidence of chemical interactions within phase-separated systems that have implications for understanding chemical reactivity within those, and related, systems.
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Ott EJE, Kucinski TM, Dawson JN, Freedman MA. Use of Transmission Electron Microscopy for Analysis of Aerosol Particles and Strategies for Imaging Fragile Particles. Anal Chem 2021; 93:11347-11356. [PMID: 34370455 DOI: 10.1021/acs.analchem.0c05225] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
For over 25 years, transmission electron microscopy (TEM) has provided a method for the study of aerosol particles with sizes from below the optical diffraction limit to several microns, resolving the particles as well as smaller features. The wide use of this technique to study aerosol particles has contributed important insights about environmental aerosol particle samples and model atmospheric systems. TEM produces an image that is a 2D projection of aerosol particles that have been impacted onto grids and, through associated techniques and spectroscopies, can contribute additional information such as the determination of elemental composition, crystal structure, and 3D particle structures. Soot, mineral dust, and organic/inorganic particles have all been analyzed using TEM and spectroscopic techniques. TEM, however, has limitations that are important to understand when interpreting data including the ability of the electron beam to damage and thereby change the structure and shape of particles, especially in the case of particles composed of organic compounds and salts. In this paper, we concentrate on the breadth of studies that have used TEM as the primary analysis technique. Another focus is on common issues with TEM and cryogenic-TEM. Insights for new users on best practices for fragile particles, that is, particles that are easily susceptible to damage from the electron beam, with this technique are discussed. Tips for readers on interpreting and evaluating the quality and accuracy of TEM data in the literature are also provided and explained.
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Affiliation(s)
- Emily-Jean E Ott
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Theresa M Kucinski
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Joseph Nelson Dawson
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Miriam Arak Freedman
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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Kucinski TM, Ott EJE, Freedman MA. Dynamics of Liquid–Liquid Phase Separation in Submicrometer Aerosol. J Phys Chem A 2021; 125:4446-4453. [DOI: 10.1021/acs.jpca.1c01985] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Theresa M. Kucinski
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Emily-Jean E. Ott
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Miriam Arak Freedman
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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Freedman MA. Liquid-Liquid Phase Separation in Supermicrometer and Submicrometer Aerosol Particles. Acc Chem Res 2020; 53:1102-1110. [PMID: 32432453 DOI: 10.1021/acs.accounts.0c00093] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
ConspectusThe 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, submicrometer 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 in both supermicrometer and submicrometer 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 supermicrometer particles and cryogenic-transmission microscopy for submicrometer particles.This Account details our main results to date for the phase transitions of supermicrometer particles and the morphology of submicrometer aerosol. We have found that the relative humidity (RH) at which LLPS occurs (separation RH; SRH) is highly sensitive to the composition of the particles. For supermicrometer particles, SRH decreases as the pH is lowered to atmospherically relevant values. SRH also decreases when non-phase-separating organic compounds are added to the particles. For submicrometer particles, a size dependence of morphology is observed in systems that undergo LLPS in supermicrometer particles. In the limit of slow drying rates, particles <30 nm are homogeneous and larger particles are phase-separated. This size dependence of aerosol morphology arises because small particles cannot overcome the activation barrier needed to form a new phase when phase separation occurs by a nucleation and growth mechanism. The inhibition of LLPS in small particles is observed for mixtures of ammonium sulfate with single organic compounds as well as complex organics like α-pinene secondary organic matter. The morphology of particles affects activation diameters for the formation of cloud condensation nuclei. These results more generally have implications for aerosol properties that affect the climate system. In addition, LLPS is also widely studied in materials and biological chemistry, and our results could potentially translate to implications for these fields.
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Affiliation(s)
- Miriam Arak Freedman
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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