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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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2
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Bain A, Chan MN, Bzdek BR. Physical properties of short chain aqueous organosulfate aerosol. ENVIRONMENTAL SCIENCE: ATMOSPHERES 2023; 3:1365-1373. [PMID: 38013727 PMCID: PMC10500313 DOI: 10.1039/d3ea00088e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 08/08/2023] [Indexed: 11/29/2023]
Abstract
Organosulfates comprise up to 30% of the organic fraction of aerosol. Organosulfate aerosol physical properties, such as water activity, density, refractive index, and surface tension, are key to predicting their impact on global climate. However, current understanding of these properties is limited. Here, we measure the physical properties of aqueous solutions containing sodium methyl or ethyl sulfate and parameterise the data as a function of solute concentration. The experimental data are compared to available literature data for organosulfates, as well as salts (sodium sulfate and sodium bisulfate) and organics (short alkyl chain length alcohols and carboxylic acids) to determine if the physical properties of organosulfates can be approximated by molecules of similar functionality. With the exception of water activity, we find that organosulfates have intermediate physical properties between those of the salts and short alkyl chain organics. This work highlights the importance of measuring and developing models for the physical properties of abundant atmospheric organosulfates in order to better describe aerosol's impact on climate.
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Affiliation(s)
- Alison Bain
- School of Chemistry, University of Bristol Bristol UK
| | - Man Nin Chan
- Earth System Science Programme, Faculty of Science, The Chinese University of Hong Kong Hong Kong China
- The Institute of Environment, Energy and Sustainability, The Chinese University of Hong Kong Hong Kong China
| | - Bryan R Bzdek
- School of Chemistry, University of Bristol Bristol UK
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3
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Tong YK, Liu Y, Meng X, Wang J, Zhao D, Wu Z, Ye A. The relative humidity-dependent viscosity of single quasi aerosol particles and possible implications for atmospheric aerosol chemistry. Phys Chem Chem Phys 2022; 24:10514-10523. [PMID: 35441631 DOI: 10.1039/d2cp00740a] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Viscosity is a fundamental physicochemical property of aerosol particles that influences chemical evolution, mass transfer rates, particle formation, etc. and also changes with ambient relative humidity (RH). However, the viscosity of real individual aerosol particles still remains less understood. Here, we developed a novel optical system based on dual optical tweezers to measure the viscosity of single suspending aerosol droplets under different RH conditions. In our experiment, a pair of quasi atmospheric aerosol droplets composed of organic and inorganic chemical substances were trapped and levitated by dual laser beams, respectively, and then collided and coalesced. The backscattering light signals and bright-field images of the dynamic coalescence process were recorded to infer the morphological relaxation time and the diameter of the composited droplet. Then, the viscosity of the droplet was calculated based on these measured values. The ambient RH of the aerosol droplets was controlled by varying the relative flow rates of dry and humidified nitrogen gas in a self-developed aerosol chamber. The viscosities of single aqueous droplets nebulized with solutes of sucrose, various sulfates and nitrates, and organic/inorganic mixtures were measured over the atmospheric RH range. Besides, the viscosities of the proxies of actual ambient aerosols in Beijing were investigated, which reasonably interpreted the aerosol chemistry transforming from sulfate dominating to nitrate dominating at the PM10 (particulate matter with an aerodynamic diameter of less than 10 μm) level in the last decade in Beijing. Furthermore, the hygroscopicity of droplets with a solute of organic/inorganic mixtures was researched to obtain a deep insight into the relationship between the viscosity and mass transfer process. Hence, we provide a robust approach for investigating the viscosity and hygroscopicity of the actual individual liquid PM10 aerosols.
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Affiliation(s)
- Yu-Kai Tong
- Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
| | - Yaoyao Liu
- Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
| | - Xiangxinyue Meng
- State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
| | - Jie Wang
- Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
| | - Dongping Zhao
- Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
| | - Zhijun Wu
- State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
| | - Anpei Ye
- Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China.
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4
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McGrory MR, Shepherd RH, King MD, Davidson N, Pope FD, Watson IM, Grainger RG, Jones AC, Ward AD. Mie scattering from optically levitated mixed sulfuric acid-silica core-shell aerosols: observation of core-shell morphology for atmospheric science. Phys Chem Chem Phys 2022; 24:5813-5822. [PMID: 35226003 DOI: 10.1039/d1cp04068e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Sulfuric acid is shown to form a core-shell particle on a micron-sized, optically-trapped spherical silica bead. The refractive indices of the silica and sulfuric acid, along with the shell thickness and bead radius were determined by reproducing Mie scattered optical white light as a function of wavelength in Mie spectroscopy. Micron-sized silica aerosols (silica beads were used as a proxy for atmospheric silica minerals) were levitated in a mist of sulfuric acid particles; continuous collection of Mie spectra throughout the collision of sulfuric acid aerosols with the optically trapped silica aerosol demonstrated that the resulting aerosol particle had a core-shell morphology. Contrastingly, the collision of aqueous sulfuric acid aerosols with optically trapped polystyrene aerosol resulted in a partially coated system. The light scattering from the optically levitated aerosols was successfully modelled to determine the diameter of the core aerosol (±0.003 μm), the shell thickness (±0.0003 μm) and the refractive index (±0.007). The experiment demonstrated that the presence of a thin film rapidly changed the light scattering of the original aerosol. When a 1.964 μm diameter silica aerosol was covered with a film of sulfuric acid 0.287 μm thick, the wavelength dependent Mie peak positions resembled sulfuric acid. Thus mineral aerosol advected into the stratosphere would likely be coated with sulfuric acid, with a core-shell morphology, and its light scattering properties would be effectively indistinguishable from a homogenous sulfuric acid aerosol if the film thickness was greater than a few 100 s of nm for UV-visible wavelengths.
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Affiliation(s)
- Megan R McGrory
- Central Laser Facility, Research Complex, STFC Rutherford Appleton Laboratory, Oxford, OX11 0FA, UK. .,Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
| | - Rosalie H Shepherd
- Central Laser Facility, Research Complex, STFC Rutherford Appleton Laboratory, Oxford, OX11 0FA, UK. .,Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
| | - Martin D King
- Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
| | - Nicholas Davidson
- School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
| | - Francis D Pope
- School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
| | - I Matthew Watson
- School of Earth Science, University of Bristol, Wills Memorial Building, Bristol, BS8 1RJ, UK
| | - Roy G Grainger
- National Centre for Earth Observation, Atmospheric, Oceanic and Planetary Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
| | - Anthony C Jones
- Met Office, Fitzroy Road, Exeter, EX1 3PB, UK.,College of Engineering Maths and Physical Sciences, University of Exeter, Exeter, EX4 4PY, UK
| | - Andrew D Ward
- Central Laser Facility, Research Complex, STFC Rutherford Appleton Laboratory, Oxford, OX11 0FA, UK.
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5
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Hardy DA, Archer J, Lemaitre P, Vehring R, Reid JP, Walker JS. High time resolution measurements of droplet evaporation kinetics and particle crystallisation. Phys Chem Chem Phys 2021; 23:18568-18579. [PMID: 34612393 DOI: 10.1039/d1cp02840e] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A refined technique for observing the complete evaporation behaviour of free-falling droplets, from droplet generation to complete solvent evaporation, with ultra-high time resolution is introduced and benchmarked. High-resolution phase-delay stroboscopic imaging is employed to simultaneously resolve the evolving droplet morphology, geometric and aerodynamic diameters, throughout the evaporative lifetime with a user-controlled < μs timescale. This allows rapid, complex morphological changes, such as crystallisation events, to be clearly observed and the corresponding mechanisms to be inferred. The dried particles are sampled for offline SEM analysis and the observed morphologies compared to the inflight imaging. Density changes can be calculated directly from the deviation between the geometric and aerodynamic diameters. The full capabilities of the new technique are demonstrated by examination of the different evaporation behaviours and crystallisation mechanisms for aqueous sodium chloride droplets evaporating under different ambient relative humidity (RH) conditions. The crystallisation window, defined as the time taken from initial to complete crystallisation, is shown to be RH dependent, extending from 0.03 s at 20% RH and 0.13 s at 40% RH. The different crystallisation mechanisms observed during the experiments are also clearly reflected in the final structure of the dry particles, with multi-crystal structures produced at low RH compared to single-crystal structures at higher RH. It is anticipated that this technique will unlock measurements which explore the evaporation behaviour and crystallisation mechanisms for rapid, complex droplet drying events, and with increasingly non-ideal solutions, relevant to industrial applications.
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Affiliation(s)
- D A Hardy
- School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK.
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6
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Ingram S, Rovelli G, Song YC, Topping D, Dutcher CS, Liu S, Nandy L, Shiraiwa M, Reid JP. Accurate Prediction of Organic Aerosol Evaporation Using Kinetic Multilayer Modeling and the Stokes-Einstein Equation. J Phys Chem A 2021; 125:3444-3456. [PMID: 33861595 DOI: 10.1021/acs.jpca.1c00986] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Organic aerosol can adopt a wide range of viscosities, from liquid to glass, depending on the local humidity. In highly viscous droplets, the evaporation rates of organic components are suppressed to varying degrees, yet water evaporation remains fast. Here, we examine the coevaporation of semivolatile organic compounds (SVOCs), along with their solvating water, from aerosol particles levitated in a humidity-controlled environment. To better replicate the composition of secondary aerosol, nonvolatile organics were also present, creating a three-component diffusion problem. Kinetic modeling reproduced the evaporation accurately when the SVOCs were assumed to obey the Stokes-Einstein relation, and water was not. Crucially, our methodology uses previously collected data to constrain the time-dependent viscosity, as well as water diffusion coefficients, allowing it to be predictive rather than postdictive. Throughout the study, evaporation rates were found to decrease as SVOCs deplete from the particle, suggesting path function type behavior.
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Affiliation(s)
- Stephen Ingram
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Grazia Rovelli
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Young-Chul Song
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - David Topping
- Department of Earth and Environmental Sciences, University of Manchester, Oxford Rd, Manchester M13 9PL, U.K
| | - Cari S Dutcher
- Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, Minnesota 55455, United States.,Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Avenue SE, Minneapolis, Minnesota 55455, United States
| | - Shihao Liu
- Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, Minnesota 55455, United States
| | - Lucy Nandy
- Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, Minnesota 55455, United States
| | - Manabu Shiraiwa
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Jonathan P Reid
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
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7
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Modeling of the Refractive Index for the Systems MX+H2O, M2X+H2O, H3BO3+MX+H2O, and H3BO3+M2X+H2O. M = K+, Na+, or Li+ and X = Cl− or SO42−. Processes (Basel) 2021. [DOI: 10.3390/pr9030525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The modeling of the refractive index for binary aqueous solutions of boric acid, sodium chloride, potassium chloride, sodium sulfate, lithium sulfate, and potassium sulfate, as well as ternary aqueous solutions of boric acid in the presence of sodium sulfate, lithium sulfate, or potassium chloride, is reported. The refraction index was represented by molar refraction. It was described as the sum of solutes’ partial molar refraction and solvent molar refraction. The solutes’ partial molar refraction was estimated from the molar refraction of the binary solutions. The excess molar refraction for these systems was described with the equation of Wang et al. The polarizability of the solutes present in the studied systems was estimated using the Lorenz–Lorenz relation. The results showed the model is appropriate for describing the systems studied; the interactions of boric acid, sodium, potassium, lithium, chloride, and sulfate ions with water molecules are relevant to explain the molar refraction and refractive index, and those for the binary systems of lithium chloride and sodium chloride are also relevant the ion–ion interactions. The model is robust and presents estimation capabilities within and beyond the concentrations and temperature range studied. Therefore, the outcomes represent valuable information to understand and follow the industrial processing of natural brines.
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8
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Otero Fernandez M, Thomas RJ, Oswin H, Haddrell AE, Reid JP. Transformative Approach To Investigate the Microphysical Factors Influencing Airborne Transmission of Pathogens. Appl Environ Microbiol 2020; 86:e01543-20. [PMID: 32978136 PMCID: PMC7657628 DOI: 10.1128/aem.01543-20] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 09/17/2020] [Indexed: 01/06/2023] Open
Abstract
Emerging outbreaks of airborne pathogenic infections worldwide, such as the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, have raised the need to understand parameters affecting the airborne survival of microbes in order to develop measures for effective infection control. We report a novel experimental strategy, TAMBAS (tandem approach for microphysical and biological assessment of airborne microorganism survival), to explore the synergistic interactions between the physicochemical and biological processes that impact airborne microbe survival in aerosol droplets. This innovative approach provides a unique and detailed understanding of the processes taking place from aerosol droplet generation through to equilibration and viability decay in the local environment, elucidating decay mechanisms not previously described. The impact of evaporation kinetics, solute hygroscopicity and concentration, particle morphology, and equilibrium particle size on airborne survival are reported, using Escherichia coli MRE162 as a benchmark system. For this system, we report that (i) particle crystallization does not directly impact microbe longevity, (ii) bacteria act as crystallization nuclei during droplet drying and equilibration, and (iii) the kinetics of size and compositional change appear to have a larger effect on microbe longevity than the equilibrium solute concentration.IMPORTANCE A transformative approach to identify the physicochemical processes that impact the biological decay rates of bacteria in aerosol droplets is described. It is shown that the evaporation process and changes in the phase and morphology of the aerosol particle during evaporation impact microorganism viability. The equilibrium droplet size was found to affect airborne bacterial viability. Furthermore, the presence of Escherichia coli MRE162 in a droplet does not affect aerosol growth/evaporation but influences the dynamic behavior of the aerosol by processing the culture medium prior to aerosolization, affecting the hygroscopicity of the culture medium; this highlights the importance of the inorganic and organic chemical composition within the aerosolized droplets that impact hygroscopicity. Bacteria also act as crystallization nuclei. The novel approach and data have implications for increased mechanistic understanding of aerosol survival and infectivity in bioaerosol studies spanning the medical, veterinary, farming, and agricultural fields, including the role of microorganisms in atmospheric processing and cloud formation.
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Affiliation(s)
| | - Richard J Thomas
- Defence Science Technology Laboratory (DSTL), Porton Down, Salisbury, United Kingdom
| | - Henry Oswin
- School of Chemistry, University of Bristol, Bristol, United Kingdom
| | - Allen E Haddrell
- School of Chemistry, University of Bristol, Bristol, United Kingdom
| | - Jonathan P Reid
- School of Chemistry, University of Bristol, Bristol, United Kingdom
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9
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Davidson NM, Gallimore PJ, Bateman B, Ward AD, Botchway SW, Kalberer M, Kuimova MK, Pope FD. Measurement of the fluorescence lifetime of GFP in high refractive index levitated droplets using FLIM. Phys Chem Chem Phys 2020; 22:14704-14711. [PMID: 32573569 DOI: 10.1039/c9cp06395a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Green fluorescent protein (GFP) is a widely used fluorescent probe in the life sciences and biosciences due to its high quantum yield and extinction coefficient, and its ability to bind to biological systems of interest. This study measures the fluorescence lifetime of GFP in sucrose/water solutions of known molarity in order to determine the refractive index dependent lifetime of GFP. A range of refractive indices from 1.43-1.53 were probed by levitating micron sized droplets composed of water/sucrose/GFP in an optical trap under well-constrained conditions of relative humidity. This setup allows for the first reported measurements of the fluorescence lifetime of GFP at refractive indices greater than 1.46. The results obtained at refractive indices less than 1.46 show good agreement with previous studies. Further experiments that trapped droplets of deionised water containing GFP allowed the hygroscopic properties of GFP to be measured. GFP is found to be mildly hygroscopic by mass, but the high ratio of molecular masses of GFP to water (ca. 1500 : 1) signifies that water uptake is large on a per-mole basis. Hygroscopic properties are verified using brightfield microscope imaging, of GFP droplets at low and high relative humidity, by measuring the humidity dependent droplet size. In addition, this experiment allowed the refractive index of pure GFP to be estimated for the first time (1.72 ± 0.07). This work provides reference data for future experiments involving GFP, especially for those conducted in high refractive index media. The work also demonstrates that GFP can be used as a probe for aerosol studies, which require determination of the refractive index of the aerosol of any shape.
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Affiliation(s)
- N M Davidson
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
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10
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Day CPF, Miloserdov A, Wildish-Jones K, Pearson E, Carruthers AE. Quantifying the hygroscopic properties of cyclodextrin containing aerosol for drug delivery to the lungs. Phys Chem Chem Phys 2020; 22:11327-11336. [PMID: 32406900 DOI: 10.1039/d0cp01385d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Aerosol dynamics is important to quantify in drug delivery to the lungs with the aim of delivering therapeutics to a target location and optimising drug efficacy. The macrocycle (2-hydroxypropyl)-β-cyclodextrin (2-HP-β-CD) is thought to alleviate symptoms associated with neurodegenerative diseases when inhaled but the hygroscopic response is not well understood. Here we measure the hygroscopic growth of individual aqueous aerosol containing 2-HP-β-CD in optical tweezers through analysis of morphology-dependent resonances arising in Raman spectra. Droplets are analysed in the size range of 3-5 μm in radius. The evolving radius and refractive index of each droplet are measured in response to change in relative humidity from 98-20% to determine mass and radius based hygroscopic growth factors, and compared with dynamic vapour sorption measurements. Bulk solution refractive index and density measurements were used in accordance with the self-consistent Lorenz-Lorentz rule to determine melt solute and droplet properties. The refractive index of 2-HP-β-CD was determined to be 1.520 ± 0.002 with a density of 1.389 ± 0.005 g cm-3. To our knowledge, we show the first aerosol measurements of 2-HP-β-CD and determine hygroscopicity. By quantifying the hygroscopic growth and physicochemical properties of 2-HP-β-CD, the impact of aerosol dynamics can be accounted for in tailoring drug formulations and informing models used to predict drug deposition patterns within the respiratory system.
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Affiliation(s)
- C P F Day
- Chemistry, School of Natural and Environmental Sciences, Bedson Building, Newcastle University, Newcastle Upon Tyne, NE1 7RU, UK.
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11
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Abstract
Atmospheric aerosol particles cool Earth’s climate by serving as cloud droplet seeds. This cooling effect represents both the single most uncertain and the largest negative radiative forcing. Cloud droplet activation is strongly influenced by aerosol particle surface tension, which in climate models is assumed equivalent to that of pure water. We directly measure the surface tensions of surfactant-coated, high surface-to-volume ratio droplets, demonstrating that their surface tensions are significantly lower than pure water but do not match the surface tension of the solution from which they were produced and depend on finite droplet size. These results suggest surfactants could potentially significantly modify radiative forcing and highlight the need for a better understanding of atmospheric surfactant concentrations and properties. Surface tension influences the fraction of atmospheric particles that become cloud droplets. Although surfactants are an important component of aerosol mass, the surface tension of activating aerosol particles is still unresolved, with most climate models assuming activating particles have a surface tension equal to that of water. By studying picoliter droplet coalescence, we demonstrate that surfactants can significantly reduce the surface tension of finite-sized droplets below the value for water, consistent with recent field measurements. Significantly, this surface tension reduction is droplet size-dependent and does not correspond exactly to the macroscopic solution value. A fully independent monolayer partitioning model confirms the observed finite-size-dependent surface tension arises from the high surface-to-volume ratio in finite-sized droplets and enables predictions of aerosol hygroscopic growth. This model, constrained by the laboratory measurements, is consistent with a reduction in critical supersaturation for activation, potentially substantially increasing cloud droplet number concentration and modifying radiative cooling relative to current estimates assuming a water surface tension. The results highlight the need for improved constraints on the identities, properties, and concentrations of atmospheric aerosol surfactants in multiple environments and are broadly applicable to any discipline where finite volume effects are operative, such as studies of the competition between reaction rates within the bulk and at the surface of confined volumes and explorations of the influence of surfactants on dried particle morphology from spray driers.
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12
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Bain A, Preston TC. The wavelength-dependent optical properties of weakly absorbing aqueous aerosol particles. Chem Commun (Camb) 2020; 56:8928-8931. [DOI: 10.1039/d0cc02737e] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A model for calculating the wavelength-dependent refractive index of multicomponent mixtures is presented and applied to aqueous systems in the atmosphere and oceans.
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Affiliation(s)
- Alison Bain
- Department of Atmospheric and Oceanic Sciences and Department of Chemistry
- McGill University
- Montreal
- Canada
| | - Thomas C. Preston
- Department of Atmospheric and Oceanic Sciences and Department of Chemistry
- McGill University
- Montreal
- Canada
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13
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Rovelli G, Song YC, Maclean AM, Topping DO, Bertram AK, Reid JP. Comparison of Approaches for Measuring and Predicting the Viscosity of Ternary Component Aerosol Particles. Anal Chem 2019; 91:5074-5082. [PMID: 30921513 DOI: 10.1021/acs.analchem.8b05353] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Measurements of the water activity-dependent viscosity of aerosol particles from two techniques are compared, specifically from the coalescence of two droplets in holographic optical tweezers (HOT) and poke-and-flow experiments on particles deposited onto a glass substrate. These new data are also compared with the fitting of dimer coagulation, isolation, and coalescence (DCIC) measurements. The aerosol system considered in this work are ternary mixtures of sucrose-citric acid-water and sucrose-NaNO3-water, at varying solute mass ratios. Results from HOT and poke-and-flow are in excellent agreement over their overlapping range of applicability (∼103-107 Pa s); fitted curves from DCIC data show variable agreement with the other two techniques because of the sensitivity of the applied modeling framework to the representation of water content in the particles. Further, two modeling approaches for the predictions of the water activity-dependent viscosity of these ternary systems are evaluated. We show that it is possible to represent their viscosity with relatively simple mixing rules applied to the subcooled viscosity values of each component or to the viscosity of the corresponding binary mixtures.
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Affiliation(s)
- Grazia Rovelli
- School of Chemistry , University of Bristol , Bristol BS8 1TS , U.K
| | - Young-Chul Song
- School of Chemistry , University of Bristol , Bristol BS8 1TS , U.K
| | - Adrian M Maclean
- Department of Chemistry , University of British Columbia , Vancouver , BC V6T 1Z1 , Canada
| | - David O Topping
- School of Earth, Atmospheric and Environmental Science , University of Manchester , Manchester M13 9PL , U.K
| | - Allan K Bertram
- Department of Chemistry , University of British Columbia , Vancouver , BC V6T 1Z1 , Canada
| | - Jonathan P Reid
- School of Chemistry , University of Bristol , Bristol BS8 1TS , U.K
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14
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Marsh A, Rovelli G, Miles REH, Reid JP. Complexity of Measuring and Representing the Hygroscopicity of Mixed Component Aerosol. J Phys Chem A 2019; 123:1648-1660. [PMID: 30707027 DOI: 10.1021/acs.jpca.8b11623] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The validation of approaches to predict the hygroscopicity of complex mixtures of organic components in aerosol is important for understanding the hygroscopic response of organic aerosol in the atmosphere. We report new measurements of the hygroscopicity of mixtures of dicarboxylic acids and amino acids using a comparative kinetic electrodynamic balance (CK-EDB) approach, inferring the equilibrium water content of the aerosol from close to a saturation relative humidity (100%) down to 80%. We show that the solution densities and refractive indices of the mixtures can be estimated with an accuracy of better than ±2% using the molar refractive index mixing rule and densities and refractive indices for the individual binary organic-aqueous solutions. Further, we show that the often-used mass-, volume-, and mole-weighted mixing rules to estimate the hygroscopicity parameter κ can overestimate the hygroscopic parameter by a factor of as much as 3, highlighting the need to understand the specific nonideal interactions that may arise synergistically in mixtures and cannot be represented by simple models. Indeed, in some extreme cases the hygroscopicity of a multicomponent mixture can be very close to that for the least hygroscopic component. For mixtures of similar components for which no additional synergistic interactions need be considered, the hygroscopicity of the mixed component aerosol can be estimated with high accuracy from the hygroscopic response of the binary aqueous-organic aerosol. In conclusion, we suggest that the hygroscopicity of multicomponent organic aerosol can be highly nonadditive and that simple correlations of hygroscopicity with composition may often misrepresent the level of complexity essential to interpreting aerosol hygroscopicity.
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Affiliation(s)
- Aleksandra Marsh
- School of Chemistry , University of Bristol , Cantock's Close , Bristol BS8 1TS , U.K
| | - Grazia Rovelli
- School of Chemistry , University of Bristol , Cantock's Close , Bristol BS8 1TS , U.K
| | - Rachael E H Miles
- School of Chemistry , University of Bristol , Cantock's Close , Bristol BS8 1TS , U.K
| | - Jonathan P Reid
- School of Chemistry , University of Bristol , Cantock's Close , Bristol BS8 1TS , U.K
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15
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Gregson FKA, Robinson JF, Miles REH, Royall CP, Reid JP. Drying Kinetics of Salt Solution Droplets: Water Evaporation Rates and Crystallization. J Phys Chem B 2018; 123:266-276. [DOI: 10.1021/acs.jpcb.8b09584] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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16
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Marsh A, Rovelli G, Song YC, Pereira KL, Willoughby RE, Bzdek BR, Hamilton JF, Orr-Ewing AJ, Topping DO, Reid JP. Accurate representations of the physicochemical properties of atmospheric aerosols: when are laboratory measurements of value? Faraday Discuss 2018; 200:639-661. [PMID: 28574570 DOI: 10.1039/c7fd00008a] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Laboratory studies can provide important insights into the processes that occur at the scale of individual particles in ambient aerosol. We examine the accuracies of measurements of core physicochemical properties of aerosols that can be made in single particle studies and explore the impact of these properties on the microscopic processes that occur in ambient aerosol. Presenting new measurements, we examine here the refinements in our understanding of aerosol hygroscopicity, surface tension, viscosity and optical properties that can be gained from detailed laboratory measurements for complex mixtures through to surrogates for secondary organic atmospheric aerosols.
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17
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Bouteloup R, Mathieu D. Improved model for the refractive index: application to potential components of ambient aerosol. Phys Chem Chem Phys 2018; 20:22017-22026. [PMID: 30110027 DOI: 10.1039/c8cp02701c] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Understanding the impact of atmospheric aerosols on the global radiative balance requires knowing the refractive index (RI) of their components. Currently available methods to estimate this property from molecular structure are mostly empirical and exhibit significant errors (>10%). This work reports a more physically sound model leading to predictions within ±5% from experiment. The root mean square relative error is <1% for general organic compounds, and <2% for oxygen-rich compounds of special interest in aerosol chemistry. In this approach, the RI is obtained from the Lorentz-Lorenz equation. The molar volume and polarizability required as input are obtained from the addition of a so-called geometrical fragment (GF) associated with every non-hydrogen atom in the molecule. The value of this GF method to the study of ambient aerosol is demonstrated through extensive validation and application to compounds that may be present in aerosol droplets. In so doing, insight is provided into the origin of significant errors previously noted using earlier methods. Moreover, it is demonstrated that reference values of the refractive index reported in widely used compilations should be considered with caution. Finally, a Python script is provided as supplementary information for easy use of the present model to estimate molar volume and refractive index for any molecule.
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18
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Marshall FH, Berkemeier T, Shiraiwa M, Nandy L, Ohm PB, Dutcher CS, Reid JP. Influence of particle viscosity on mass transfer and heterogeneous ozonolysis kinetics in aqueous–sucrose–maleic acid aerosol. Phys Chem Chem Phys 2018; 20:15560-15573. [DOI: 10.1039/c8cp01666f] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ozonolysis kinetics of viscous aerosol particles containing maleic acid are studied. Kinetic fits are constrained by measured particle viscosities.
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Affiliation(s)
| | - Thomas Berkemeier
- School of Chemical & Biomolecular Engineering
- Georgia Institute of Technology
- Atlanta
- USA
| | | | - Lucy Nandy
- Department of Mechanical Engineering
- University of Minnesota
- Minneapolis
- USA
| | - Peter B. Ohm
- Department of Mechanical Engineering
- University of Minnesota
- Minneapolis
- USA
| | - Cari S. Dutcher
- Department of Mechanical Engineering
- University of Minnesota
- Minneapolis
- USA
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19
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Cai C, Marsh A, Zhang YH, Reid JP. Group Contribution Approach To Predict the Refractive Index of Pure Organic Components in Ambient Organic Aerosol. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:9683-9690. [PMID: 28753320 DOI: 10.1021/acs.est.7b01756] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We introduce and assess a group contribution scheme by which the refractive index (RI) (λ = 589 nm) of nonabsorbing components common to secondary organic aerosols can be predicted from the molecular formula and chemical functionality. The group contribution method is based on representative values of ratios of the molecular polarizability and molar volume of different functional groups derived from data for a training set of 234 compounds. The training set consists of 106 nonaromatic compounds common to atmospheric aerosols, 64 aromatic compounds, and 64 compounds containing halogens; a separate group contribution model is provided for each of these three classes of compound. The resulting predictive model reproduces the RIs of compounds in the training set with mean errors of ±0.58, ±0.36, and ±0.30% for the nonaromatic, aromatic, and halogen-containing compounds, respectively. We then evaluate predictions from the group contribution model for compounds with no previously reported RI, comparing values with predictions from previous treatments and with measurements from single aerosol particle experiments. We illustrate how such comparisons can be used to further refine the predictive model. We suggest that the accuracy of this model is already sufficient to better constrain the optical properties of organic aerosol of known composition.
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Affiliation(s)
- Chen Cai
- School of Chemistry, University of Bristol , Bristol BS8 1TS, United Kingdom
- The Institute for Chemical Physics, Beijing Institute of Technology , Beijing 100081, People's Republic of China
| | - Aleksandra Marsh
- School of Chemistry, University of Bristol , Bristol BS8 1TS, United Kingdom
| | - Yun-Hong Zhang
- The Institute for Chemical Physics, Beijing Institute of Technology , Beijing 100081, People's Republic of China
| | - Jonathan P Reid
- School of Chemistry, University of Bristol , Bristol BS8 1TS, United Kingdom
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20
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Willoughby RE, Cotterell MI, Lin H, Orr-Ewing AJ, Reid JP. Measurements of the Imaginary Component of the Refractive Index of Weakly Absorbing Single Aerosol Particles. J Phys Chem A 2017; 121:5700-5710. [DOI: 10.1021/acs.jpca.7b05418] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Rose E. Willoughby
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
| | - Michael I. Cotterell
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
- College
for Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, United Kingdom
- Aerosol
Observation Based Research, Met Office, Exeter EX1 3PB, United Kingdom
| | - Hongze Lin
- College
of Optical Science and Engineering, Zhejiang University, Hangzhou 310058, China
| | - Andrew J. Orr-Ewing
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
| | - Jonathan P. Reid
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
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21
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Haddrell AE, Miles REH, Bzdek BR, Reid JP, Hopkins RJ, Walker JS. Coalescence Sampling and Analysis of Aerosols using Aerosol Optical Tweezers. Anal Chem 2017; 89:2345-2352. [DOI: 10.1021/acs.analchem.6b03979] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Allen E. Haddrell
- School
of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | | | - Bryan R. Bzdek
- School
of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - Jonathan P. Reid
- School
of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - Rebecca J. Hopkins
- Defence Science and Technology Laboratory (DSTL), Porton Down, Salisbury SP4 0JQ, United Kingdom
| | - Jim S. Walker
- Bristol Industrial and Research Associates Ltd (BIRAL), Unit 8 Harbour Road Trading Estate, Portishead, Bristol BS20 7BL, United Kingdom
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22
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Ingram S, Cai C, Song YC, Glowacki DR, Topping DO, O’Meara S, Reid JP. Characterising the evaporation kinetics of water and semi-volatile organic compounds from viscous multicomponent organic aerosol particles. Phys Chem Chem Phys 2017; 19:31634-31646. [DOI: 10.1039/c7cp05172g] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Here we present methods to simultaneously investigate diffusivities and volatilities in studies of evolving single aerosol particle size and composition.
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Affiliation(s)
- Stephen Ingram
- School of Chemistry
- University of Bristol
- Bristol BS8 1TS
- UK
| | - Chen Cai
- Department of Atmospheric and Oceanic Sciences
- School of Physics
- Peking University
- Beijing 100871
- China
| | | | - David R. Glowacki
- School of Chemistry
- University of Bristol
- Bristol BS8 1TS
- UK
- Department of Computer Science
| | - David O. Topping
- School of Earth and Atmospheric Sciences
- University of Manchester
- Manchester M13 9PL
- UK
| | - Simon O’Meara
- School of Earth and Atmospheric Sciences
- University of Manchester
- Manchester M13 9PL
- UK
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23
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Boyer HC, Bzdek BR, Reid JP, Dutcher CS. Statistical Thermodynamic Model for Surface Tension of Organic and Inorganic Aqueous Mixtures. J Phys Chem A 2016; 121:198-205. [DOI: 10.1021/acs.jpca.6b10057] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hallie C. Boyer
- Department
of Mechanical Engineering, University of Minnesota, Twin Cities, Minneapolis, Minnesota 55455, United States
| | - Bryan R. Bzdek
- School
of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - Jonathan P. Reid
- School
of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - Cari S. Dutcher
- Department
of Mechanical Engineering, University of Minnesota, Twin Cities, Minneapolis, Minnesota 55455, United States
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24
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Song YC, Haddrell AE, Bzdek BR, Reid JP, Bannan T, Topping DO, Percival C, Cai C. Measurements and Predictions of Binary Component Aerosol Particle Viscosity. J Phys Chem A 2016; 120:8123-8137. [DOI: 10.1021/acs.jpca.6b07835] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Young Chul Song
- School
of Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom
| | - Allen E. Haddrell
- School
of Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom
| | - Bryan R. Bzdek
- School
of Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom
| | - Jonathan P. Reid
- School
of Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom
| | - Thomas Bannan
- School
of Earth, Atmospheric and Environmental Science, University of Manchester, Manchester, M13 9PL, United Kingdom
| | - David O. Topping
- School
of Earth, Atmospheric and Environmental Science, University of Manchester, Manchester, M13 9PL, United Kingdom
- National
Centre for Atmospheric Science, University of Manchester, Manchester, M13 9PL, United Kingdom
| | - Carl Percival
- School
of Earth, Atmospheric and Environmental Science, University of Manchester, Manchester, M13 9PL, United Kingdom
| | - Chen Cai
- The
Institute of Chemical Physics, Key Laboratory of Cluster Science, Beijing Institute of Technology, Beijing 100081, People’s Republic of China
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