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Choczynski JM, Shokoor B, Salazar J, Zuend A, Davies JF. Probing the evaporation dynamics of semi-volatile organic compounds to reveal the thermodynamics of liquid-liquid phase separated aerosol. Chem Sci 2024; 15:2963-2974. [PMID: 38404378 PMCID: PMC10882461 DOI: 10.1039/d3sc05164a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 01/16/2024] [Indexed: 02/27/2024] Open
Abstract
Liquid-liquid phase separation (LLPS) is a thermodynamically driven process that occurs in mixtures of low miscibility material. LLPS is an important process in chemical, biological, and environmental systems. In atmospheric chemistry, LLPS in aerosol containing internally-mixed organic and inorganic particles has been an area of significant interest, with particles separating to form organic-rich and aqueous phases on dehydration. This alters the optical properties of the particles, has been connected to changes in the cloud nucleation ability of the aerosol, and potentially changes the reactivity of particles towards gas-phase oxidants. Although the chemical systems that undergo LLPS have become quite well-characterized, the properties and processes of LLPS particles are quite poorly understood. In this work, we characterize LLPS in aerosol particles containing ammonium sulfate and triethylene glycol (3EG), a semi-volatile organic molecule. We explore the relative humidity (RH) conditions under which LLPS occurs and characterize the rate of evaporation of 3EG from well-mixed and LLPS particles as a function of RH. We show that the evaporation rates vary with RH due to changes in chemical activity, however no clear change in the dynamics following LLPS are observed. We interpret our observations using a thermodynamic model (AIOMFAC) coupled with an evaporation model and show that a significant increase in the activity coefficient of 3EG as the RH decreases, required for LLPS to occur, obscures a clear step-change in the evaporation rates following LLPS. By characterizing the evaporation rates, we estimate the composition of the organic-rich phase and compare our results to thermodynamic predictions. This study is the first to explore the connection between LLPS and the chemical evolution of aerosol particles via the evaporation of semi-volatile organic material. Ultimately, we reveal that the thermodynamics of non-ideal mixing are primarily responsible for the controlling both the rate of evaporation and the onset of LLPS, with LLPS itself having limited impact on the rate of evaporation in a fluid system. These results have significant implications for understanding and predicting the lifetime of aerosol particles, their effect on cloud formation, and the chemical evolution of multiphase systems by particle-gas partitioning and heterogeneous reactions.
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Affiliation(s)
- Jack M Choczynski
- Department of Chemistry, University of California Riverside Riverside CA USA
| | - Bilal Shokoor
- Department of Chemistry, University of California Riverside Riverside CA USA
| | - Jorge Salazar
- Department of Chemistry, University of California Riverside Riverside CA USA
| | - Andreas Zuend
- Department of Atmospheric and Oceanic Sciences, McGill University Montreal Quebec Canada
| | - James F Davies
- Department of Chemistry, University of California Riverside Riverside CA USA
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Wallace BJ, Mongeau ML, Zuend A, Preston TC. Impact of pH on Gas-Particle Partitioning of Semi-Volatile Organics in Multicomponent Aerosol. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:16974-16988. [PMID: 37885068 DOI: 10.1021/acs.est.3c02894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
The partitioning of semivolatile organic compounds (SVOCs) between the condensed and gas phases can have significant implications for the properties of aerosol particles. In addition to affecting size and composition, this partitioning can alter radiative properties and impact cloud activation processes. We present measurements and model predictions on how activity and pH influence the evaporation of SVOCs from particles to the gas phase, specifically investigating aqueous inorganic particles containing dicarboxylic acids (DCAs). The aerosols are studied at the single-particle level by using optical trapping and cavity-enhanced Raman spectroscopy. Optical resonances in the spectra enable precise size tracking, while vibrational bands allow real-time monitoring of pH. Results are compared to a Maxwell-type model that accounts for volatile and nonvolatile solutes in aqueous droplets that are held at a constant relative humidity. The aerosol inorganic-organic mixture functional group activity coefficients thermodynamic model and Debye-Hückel theory are both used to calculate the activities of the species present in the droplet. For DCAs, we find that the evaporation rate is highly sensitive to the particle pH. For acidity changes of approximately 1.5 pH units, we observe a shift from a volatile system to one that is completely nonvolatile. We also observe that the pH itself is not constant during evaporation; it increases as DCAs evaporate, slowing the rate of evaporation until it eventually ceases. Whether a DCA evaporates or remains a stable component of the droplet is determined by the difference between the lowest pKa of the DCA and the pH of the droplet.
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Affiliation(s)
- Brandon J Wallace
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Michel Laforest Mongeau
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Andreas Zuend
- Department of Atmospheric and Oceanic Sciences, McGill University, 805 Sherbrooke Street West, Montreal, Quebec, Canada H3A 0B9
| | - Thomas C Preston
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
- Department of Atmospheric and Oceanic Sciences, McGill University, 805 Sherbrooke Street West, Montreal, Quebec, Canada H3A 0B9
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Kaur Kohli R, Salas S, Shokoor B, Price CL, Davies JF. Chemically Resolved Evaporation Dynamics of Dicarboxylic Acid Mixtures in Solid Particles. Anal Chem 2023. [PMID: 37490783 DOI: 10.1021/acs.analchem.3c02475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
The evaporation rate and corresponding vapor pressure of dicarboxylic acids have been the subject of numerous scientific studies over the years, with reported values spanning several orders of magnitude. Recent work has identified the importance of considering the phase state of the material during evaporation, likely accounting for some of the variability in measured vapor pressures. In the homologous series of dicarboxylic acids, the phase state under dry conditions may be crystalline or amorphous, with particles of odd-carbon-numbered acids exhibiting tendencies to remain amorphous and spherical. Although measurements of vapor pressures for pure components make up most of the available literature data, for many applications, these compounds are not present in isolation. Additionally, many systems containing a semi-volatile material exist in a solid state, especially under dry and low relative humidity conditions. In this work, we explore the evaporation of compounds present in mixed solid-state particles. Specifically, we use single particle levitation coupled with mass spectrometry to measure the evolving composition of solid particles containing mixtures of glutaric acid and succinic acid, glutaric acid and adipic acid, and malonic acid and succinic acid. Under dry conditions, these systems exhibit non-spherical geometries consistent with crystallization of one or both components into an organic crystal. Our measurements allow the evaporation of each component in the mixture to be characterized independently and effective vapor pressures of the pure components to be inferred. The resulting vapor pressures are compared against pure component vapor pressures. We demonstrate that these mixtures exhibit thermodynamic ideality but can be influenced by limited diffusion in the solid phase. These are the first results in the literature that explore the thermodynamic and kinetic factors that control the evaporative evolution of mixed solid-state particles.
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Affiliation(s)
- Ravleen Kaur Kohli
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
| | - Stephanie Salas
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
| | - Bilal Shokoor
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
| | - Chelsea L Price
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
| | - James F Davies
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
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Rafferty A, Vennes B, Bain A, Preston TC. Optical trapping and light scattering in atmospheric aerosol science. Phys Chem Chem Phys 2023; 25:7066-7089. [PMID: 36852581 DOI: 10.1039/d2cp05301b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Aerosol particles are ubiquitous in the atmosphere, and currently contribute a large uncertainty to climate models. Part of the endeavour to reduce this uncertainty takes the form of improving our understanding of aerosol at the microphysical level, thus enabling chemical and physical processes to be more accurately represented in larger scale models. In addition to modeling efforts, there is a need to develop new instruments and methodologies to interrogate the physicochemical properties of aerosol. This perspective presents the development, theory, and application of optical trapping, a powerful tool for single particle investigations of aerosol. After providing an overview of the role of aerosol in Earth's atmosphere and the microphysics of these particles, we present a brief history of optical trapping and a more detailed look at its application to aerosol particles. We also compare optical trapping to other single particle techniques. Understanding the interaction of light with single particles is essential for interpreting experimental measurements. In the final part of this perspective, we provide the relevant formalism for understanding both elastic and inelastic light scattering for single particles. The developments discussed here go beyond Mie theory and include both how particle and beam shape affect spectra. Throughout the entirety of this work, we highlight numerous references and examples, mostly from the last decade, of the application of optical trapping to systems that are relevant to the atmospheric aerosol.
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Affiliation(s)
| | - Benjamin Vennes
- Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, Canada.
| | - Alison Bain
- School of Chemistry, University of Bristol, Bristol, UK
| | - Thomas C Preston
- Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, Canada. .,Department of Chemistry, McGill University, Montreal, Quebec, Canada
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Price CL, Kaur Kohli R, Shokoor B, Davies JF. Connecting the Phase State and Volatility of Dicarboxylic Acids at Elevated Temperatures. J Phys Chem A 2022; 126:6963-6972. [PMID: 36150212 DOI: 10.1021/acs.jpca.2c04546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The partitioning of semivolatile organic molecules between condensed phases and the vapor phase has broad application across a range of scientific disciplines, with significant impacts in atmospheric chemistry for regulating the evolving composition of aerosol particles. Vapor partitioning depends on the molecular interactions and phase state of the condensed material and shows a well-established dependence on temperature. The phase state of solid organic material is not always well-defined, and many examples can be found for the formation of amorphous subcooled liquid states rather than crystalline solids. This can lead to significant changes to vapor equilibrium processes by modifying the thermodynamics and kinetics of evaporation. Here, we explore the influence of phase state on the evaporation dynamics of a series of straight-chain dicarboxylic acids across a range of above-ambient temperatures. These molecules show an odd/even alteration in some of their properties based on the number of carbon atoms that may be connected to their phase state under dry conditions. Using a newly developed linear-quadrupole electrodynamic balance, we levitate single particles containing the sample and expose them to dry conditions across a range of temperatures (ambient to ∼350 K). Using the rate of evaporation measured from the change in the size or relative mass, we derive the vapor pressure and enthalpy of vaporization. Light scattering data allows for unambiguous identification of the phase of the particles (crystal vs amorphous) allowing the vapor equilibrium properties to be attributed to a particular state. This work highlights a new experimental method for characterizing vapor pressures of low volatility substances and extends the temperature range of available data for the vapor pressure of terminal dicarboxylic acids. These measurements show that crystalline and subcooled liquid states persist at elevated temperatures and provide a direct comparison between subcooled and crystal phases under the same experimental conditions.
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Affiliation(s)
- Chelsea L Price
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
| | - Ravleen Kaur Kohli
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
| | - Bilal Shokoor
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
| | - James F Davies
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
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Willis MD, Wilson KR. Coupled Interfacial and Bulk Kinetics Govern the Timescales of Multiphase Ozonolysis Reactions. J Phys Chem A 2022; 126:4991-5010. [PMID: 35863113 DOI: 10.1021/acs.jpca.2c03059] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Chemical transformations in aerosols impact the lifetime of particle phase species, the fate of atmospheric pollutants, and both climate- and health-relevant aerosol properties. Timescales for multiphase reactions of ozone in atmospheric aqueous phases are governed by coupled kinetic processes between the gas phase, the particle interface, and its bulk, which respond dynamically to reactive consumption of O3. However, models of atmospheric aerosol reactivity often do not account for the coupled nature of multiphase processes. To examine these dynamics, we use new and prior experimental observations of aqueous droplet reaction kinetics, including three systems with a range of surface affinities and ozonolysis rate coefficients (trans-aconitic acid (C6H6O6), maleic acid (C4H4O4), and sodium nitrite (NaNO2)). Using literature rate coefficients and thermodynamic properties, we constrain a simple two-compartment stochastic kinetic model which resolves the interface from the particle bulk and represents O3 partitioning, diffusion, and reaction as a coupled kinetic system. Our kinetic model accurately predicts decay kinetics across all three systems, demonstrating that both the thermodynamic properties of O3 and the coupled kinetic and diffusion processes are key to making accurate predictions. An enhanced concentration of adsorbed O3, compared to gas and bulk phases is rapidly maintained and remains constant even as O3 is consumed by reaction. Multiphase systems dynamically seek to achieve equilibrium in response to reactive O3 loss, but this is hampered at solute concentrations relevant to aqueous aerosol by the rate of O3 arrival in the bulk by diffusion. As a result, bulk-phase O3 becomes depleted from its Henry's law solubility. This bulk-phase O3 depletion limits reaction timescales for relatively slow-reacting organic solutes with low interfacial affinity (i.e., trans-aconitic and maleic acids, with krxn ≈ 103-104 M-1 s-1), which is in contrast to fast-reacting solutes with higher surface affinity (i.e., nitrite, with krxn ≈ 105 M-1 s-1) where surface reactions strongly impact the observed decay kinetics.
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Affiliation(s)
- Megan D Willis
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Kevin R Wilson
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, United States
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Kaur Kohli R, Van Berkel GJ, Davies JF. An Open Port Sampling Interface for the Chemical Characterization of Levitated Microparticles. Anal Chem 2022; 94:3441-3445. [PMID: 35167275 DOI: 10.1021/acs.analchem.1c05550] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Several studies have reported ionization methods to classify the chemical composition of levitated particles held in an electrodynamic balance using mass spectrometry (MS). These methods include electrospray-based paper spray (PS) ionization, plasma discharge ionization, and direct analysis in real-time (DART) ionization, with each showing advantages and disadvantages. Our recent work demonstrated that PS ionization could yield accurate data for the chemical evolution of mixed component particles undergoing evaporation. However, measurements were performed using an internal standard to account for and correct the inherent variability in the PS ionization source. Here, we explore a new electrospray-based method coupled to particle levitation-the Open Port Sampling Interface (OPSI), which provides many advantages over the PS method, with few disadvantages. In this application note we report experiments in which micron-sized particles, containing analytes such as citric acid, maleic acid, and tetraethylene glycol, were levitated and optically probed to determine their size and mass. Subsequent transfer of individual levitated particles into the OPSI allowed for the ionization and mass spectrometry analysis of these particles. We discuss the stability and reproducibility of MS measurements, demonstrate effective quantitation in both positive and negative mode, and determine the sensitivity of the OPSI to a range of analyte mass present in levitated particles. Importantly, we show stability of the OPSI over >6 h without the need for normalizing signal variations with an internal standard in the sample, demonstrating robust application of the OPSI to measurements over extended periods of time.
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Affiliation(s)
- Ravleen Kaur Kohli
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
| | | | - James F Davies
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
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Müller M, Mishra A, Berkemeier T, Hausammann E, Peter T, Krieger UK. Electrodynamic balance–mass spectrometry reveals impact of oxidant concentration on product composition in the ozonolysis of oleic acid. Phys Chem Chem Phys 2022; 24:27086-27104. [DOI: 10.1039/d2cp03289a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Electrodynamic balance–mass spectrometry measurements reveal how the ozone concentration influences the product composition of oleic acid aerosol droplets.
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Affiliation(s)
- Marcel Müller
- Institute for Atmospheric and Climate Science, ETH Zurich, Universitätstrasse 16, 8092 Zurich, Switzerland
| | - Ashmi Mishra
- Multiphase Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
| | - Thomas Berkemeier
- Multiphase Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
| | - Edwin Hausammann
- Institute for Atmospheric and Climate Science, ETH Zurich, Universitätstrasse 16, 8092 Zurich, Switzerland
| | - Thomas Peter
- Institute for Atmospheric and Climate Science, ETH Zurich, Universitätstrasse 16, 8092 Zurich, Switzerland
| | - Ulrich K. Krieger
- Institute for Atmospheric and Climate Science, ETH Zurich, Universitätstrasse 16, 8092 Zurich, Switzerland
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Li Z, Meng Y, Nie H, Gu R, Wang X, Xiao D. The unique physical shading pattern of Rayleigh scattering for the generally improved detection of scattering particles. Analyst 2022; 147:2361-2368. [DOI: 10.1039/d2an00488g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A facile physical shading method, based on the Rayleigh scattering pattern, exhibited excellent performance detection because of its reduced background noise.
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Affiliation(s)
- Zhihui Li
- College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
| | - Yan Meng
- Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu 610064, P. R. China
| | - Hongyu Nie
- College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
| | - Rongmeng Gu
- College of Chemical Engineering, Sichuan University, Chengdu 610064, P. R. China
| | - Xiaokun Wang
- College of Chemical Engineering, Sichuan University, Chengdu 610064, P. R. China
| | - Dan Xiao
- College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
- Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu 610064, P. R. China
- College of Chemical Engineering, Sichuan University, Chengdu 610064, P. R. China
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