Solid, Semisolid, and Liquid Phase States of Individual Submicrometer Particles Directly Probed Using Atomic Force Microscopy

Lee, Hansol D.; Ray, Kamal K.; Tivanski, Alexei V.

doi:10.1021/acs.analchem.7b02755

Cited by 43 publications

(137 citation statements)

References 50 publications

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“…Since then, AFM has been used, most often in tandem with other analysis techniques, to characterize aerosol mixing state in urban and marine‐influenced urban environments (Sobanska et al, ; Vester et al, ), as well as during Chinese wintertime haze events (Chen et al, ). More recently, AFM studies have incorporated more detailed analysis of specific properties, such as surface tension (Lee et al, , ) and hygroscopicity (Ghorai et al, ; Morris et al, ). An exciting advancement for AFM has been coupling with a scanning IR laser to conduct photothermal IR spectroscopy (Bondy et al, ; Kwon et al, ; Or et al, ).…”

Section: Measurement Techniques For Aerosol Mixing Statementioning

confidence: 99%

Aerosol Mixing State: Measurements, Modeling, and Impacts

Riemer

Ault

West

et al. 2019

Reviews of Geophysics

271

287

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Atmospheric aerosols are complex mixtures of different chemical species, and individual particles exist in many different shapes and morphologies. Together, these characteristics contribute to the aerosol mixing state. This review provides an overview of measurement techniques to probe aerosol mixing state, discusses how aerosol mixing state is represented in atmospheric models at different scales, and synthesizes our knowledge of aerosol mixing state's impact on climate‐relevant properties, such as cloud condensation and ice nucleating particle concentrations, and aerosol optical properties. We present these findings within a framework that defines aerosol mixing state along with appropriate mixing state metrics to quantify it. Future research directions are identified, with a focus on the need for integrating mixing state measurements and modeling.

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Section: Measurement Techniques For Aerosol Mixing Statementioning

confidence: 99%

Aerosol Mixing State: Measurements, Modeling, and Impacts

Riemer

Ault

West

et al. 2019

Reviews of Geophysics

271

287

View full text Add to dashboard Cite

show abstract

“…In these cases, the matrices contained only two species (one organic and water), which is very different from SOA matrices that contain thousands of different species (Nozière et al, 2015). In the future, researchers will likely continue to use viscosity data combined with the Stokes-Einstein relation to estimate diffusion rates of organics in SOA particles, because several techniques have been developed recently to measure the viscosities of SOA matrices and proxies of SOA matrices (Bateman et al, 2015;Grayson et al, 2016;Lee et al, 2017;Marsh et al, 2017;Price et al, 2015;Reid et al, 2018;Renbaum-Wolff et al, 2013a;Song et al, 2015;Zhang et al, 2015). As a result, the accuracy of the Stokes-Einstein relation for predicting diffusion rates of organics in SOA particles needs to be quantified.…”

Section: Introductionmentioning

confidence: 99%

Viscosities, diffusion coefficients, and mixing times of intrinsic fluorescent organic molecules in brown limonene secondary organic aerosol and tests of the Stokes–Einstein equation

et al. 2019

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Abstract. Viscosities and diffusion rates of organics within secondary organic aerosol (SOA) remain uncertain. Using the bead-mobility technique, we measured viscosities as a function of water activity (aw) of SOA generated by the ozonolysis of limonene followed by browning by exposure to NH3 (referred to as brown limonene SOA or brown LSOA). These measurements together with viscosity measurements reported in the literature show that the viscosity of brown LSOA increases by 3–5 orders of magnitude as the aw decreases from 0.9 to approximately 0.05. In addition, we measured diffusion coefficients of intrinsic fluorescent organic molecules within brown LSOA matrices using rectangular area fluorescence recovery after photobleaching. Based on the diffusion measurements, as the aw decreases from 0.9 to 0.33, the average diffusion coefficient of the intrinsic fluorescent organic molecules decreases from 5.5×10-9 to 7.1×10-13 cm2 s−1 and the mixing times of intrinsic fluorescent organic molecules within 200 nm brown LSOA particles increases from 0.002 to 14 s. These results suggest that the mixing times of large organics in the brown LSOA studied here are short (<1 h) for aw and temperatures often found in the planetary boundary layer (PBL). Since the diffusion coefficients and mixing times reported here correspond to SOA generated using a high mass loading (∼1000 µg m−3), biogenic SOA particles found in the atmosphere with mass loadings ≤10 µg m−3 are likely to have higher viscosities and longer mixing times (possibly 3 orders of magnitude longer). These new measurements of viscosity and diffusion were used to test the accuracy of the Stokes–Einstein relation for predicting diffusion rates of organics within brown LSOA matrices. The results show that the Stokes–Einstein equation gives accurate predictions of diffusion coefficients of large organics within brown LSOA matrices when the viscosity of the matrix is as high as 102 to 104 Pa s. These results have important implications for predicting diffusion and mixing within SOA particles in the atmosphere.

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“…(Prather et al, 2013;Jacobson, 2001;Vignati et al, 2010;de Leeuw et al, 2011;Wang et al, 2017) Typically existing as submicrometer-sized aerosols with inorganic core encased by organic shell (core-shell), their heterogeneous mixing states derive directly from the complex variety of organic, inorganic, and biological species in the SSML and ocean water. (Cochran et al, 2017;Ault et al, 2013) Nascent SSAs affect the Earth's climate and atmosphere through radiative forcing, directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation or ice nuclei (Lee et al, 2017b;Haywood and Boucher, 2000;Jacobson, 2001); however, their chemical and biological complexity that control the mixing state, hinder our ability to accurately predict their climate cooling abilities. (Lee et al, 2017b;Lee et al, 2017a) Thus, with relatively recent single particle methodology developments, characterizing the SSA-relevant aerosol chemical compositions and ensuing physicochemical properties can be performed through offline bulk ensemble and/or single particle techniques.…”

Section: Introductionmentioning

confidence: 99%

“…(Cochran et al, 2017;Ault et al, 2013) Nascent SSAs affect the Earth's climate and atmosphere through radiative forcing, directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation or ice nuclei (Lee et al, 2017b;Haywood and Boucher, 2000;Jacobson, 2001); however, their chemical and biological complexity that control the mixing state, hinder our ability to accurately predict their climate cooling abilities. (Lee et al, 2017b;Lee et al, 2017a) Thus, with relatively recent single particle methodology developments, characterizing the SSA-relevant aerosol chemical compositions and ensuing physicochemical properties can be performed through offline bulk ensemble and/or single particle techniques. (Laskina et al, 2015;Ault et al, 2013;Cochran et al, 2017;Estillore et al, 2017;Haywood and Boucher, 2000;Prather et al, 2013;Cochran et al, 2016;Morris et al, 2016;Fuentes et al, 2010;King et al, 2012;Schill et al, 2015;Morris et al, 2015;Schill and Tolbert, 2014;Jacobson, 2001;Collins et al, 2014;Guzman et al, 2012) Quantitative bulk ensemble techniques sample large particle numbers; however, they cannot provide individual particle specificity, which is crucial when studying submicrometer-sized aerosol particles that display large particle-to-particle variability.…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, AFM measurements can be performed under controlled relative humidity (RH), while producing high-resolution 3D height and phase images, and directly measuring viscoelastic properties of materials. (Lee et al, 2017a;Lee et al, 2017b) In this regard, simultaneous acquisition of the 3D height and phase images over individual particles can be used to quantify their mixing states, or organic volume fraction (OVF). OVF measurements require quantification of phase-separated organic component and the total particle volumes, which can be determined for individual particles using Eq.…”

Section: Introductionmentioning

confidence: 99%

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Dry versus wet? Implications on aerosol impaction and organic volume fraction

Lee

Kaluarachchi

Hasenecz

et al. 2018

Preprint

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Abstract. Understanding the impact of sea spray aerosols (SSA) on the climate and atmosphere requires quantitative knowledge of their chemical composition and mixing states. Furthermore, single particle measurements are needed to accurately represent large particle-to-particle variability. To quantify the mixing state, organic volume fraction (OVF), defined as the relative organic volume with respect to the total particle volume, is measured after generating and collecting aerosol particles, often using deposition impactors. In this process, the aerosol streams are either dried or kept wet prior to impacting on solid substrates. However, the atmospheric community has yet to establish how dry versus wet aerosol deposition influences the impacted particle morphologies and mixing states. Here, we apply complementary offline single particle atomic force microscopy (AFM) and bulk ensemble high performance liquid chromatography (HPLC) techniques to assess the effects of dry and wet deposition modes on the substrate-deposited aerosol particles' mixing states. Glucose and NaCl binary mixtures that form core-shell particle morphologies were studied as model systems, and the mixing states were quantified by measuring the OVF of individual particles using AFM and compared to the ensemble measured by HPLC. Dry deposited single particle OVF data positively deviated from the bulk HPLC data by up to 60 %. The positive deviation was attributed to significant spreading of the NaCl core upon impaction with the solid substrate, which is not readily evident in AFM imaging and leads to underestimation of the core volume. NaCl core spreading under impaction was confirmed by imaging dry deposited NaCl particles. This problem was circumvented by (a) performing wet deposition and thus bypassing the effects of the solid core spreading upon impaction and (b) performing a hydration-dehydration cycle on dry deposited particles to restructure the deformed NaCl core. Both approaches produced single particle OVF values that converge well with the bulk and expected OVF values, validating the methodology. These findings illustrate the importance of awareness in how conventional particle deposition methods may significantly alter the impacted particle morphologies and their mixing states. Our work can help improve quantification and predictions of chemical mixing states of atmospherically-relevant aerosols.

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Solid, Semisolid, and Liquid Phase States of Individual Submicrometer Particles Directly Probed Using Atomic Force Microscopy

Cited by 43 publications

References 50 publications

Aerosol Mixing State: Measurements, Modeling, and Impacts

Aerosol Mixing State: Measurements, Modeling, and Impacts

Viscosities, diffusion coefficients, and mixing times of intrinsic fluorescent organic molecules in brown limonene secondary organic aerosol and tests of the Stokes–Einstein equation

Dry versus wet? Implications on aerosol impaction and organic volume fraction

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