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Glass transition temperatures of individual submicrometer atmospheric particles: direct measurement via heated atomic force microscopy probe

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dc.contributor.authorLei, Z.
dc.contributor.authorZhang, J.
dc.contributor.authorMueller, E.A.
dc.contributor.authorXiao, Y.
dc.contributor.authorKolozsvari, K.R.
dc.contributor.authorMcNeil, A.J.
dc.contributor.authorHoll, M.M.B.
dc.contributor.authorAult, A.P.
dc.date.issued2022
dc.descriptionData source: Supplementary information, https://doi.org/10.1021/acs.analchem.2c01979
dc.description.abstractThe phase (solid, semisolid, or liquid) of atmospheric aerosols is central to their ability to take up water or undergo heterogeneous reactions. In recent years, the unexpected prevalence of viscous organic particles has been shown through field measurements and global atmospheric modeling. The aerosol phase has been predicted using glass transition temperatures (Tg), which were estimated based on molecular weight, oxygen:carbon ratio, and chemical formulae of organic species present in atmospheric particles via studies of bulk materials. However, at the most important sizes for cloud nucleation (∼50–500 nm), particles are complex mixtures of numerous organic species, inorganic salts, and water with substantial particle-to-particle variability. To date, direct measurements of Tg have not been feasible for individual atmospheric particles. Herein, nanothermal analysis (NanoTA), which uses a resistively heated atomic force microscopy (AFM) probe, is combined with AFM photothermal infrared (AFM-PTIR) spectroscopy to determine the Tg and composition of individual particles down to 76 nm in diameter at ambient temperature and pressure. Laboratory-generated proxies for organic aerosol (sucrose, ouabain, raffinose, and maltoheptaose) had similar Tg values to bulk Tg values measured with differential scanning calorimetry (DSC) and the Tg predictions used in atmospheric models. Laboratory-generated phase-separated particles and ambient particles were analyzed with NanoTA + AFM-PTIR showing intraparticle variation in composition and Tg. These results demonstrate the potential for NanoTA + AFM-PTIR to increase our understanding of viscosity within submicrometer atmospheric particles with complex phases, morphologies, and compositions, which will enable improved modeling of aerosol impacts on clouds and climate.
dc.identifier.citationAnalytical Chemistry, 2022; 94(35):11973-11977
dc.identifier.doi10.1021/acs.analchem.2c01979
dc.identifier.issn0003-2700
dc.identifier.issn1520-6882
dc.identifier.urihttps://hdl.handle.net/11541.2/33813
dc.language.isoen
dc.publisherAmerican Chemical Society
dc.relation.fundingNational Science Foundation (NSF) CHE-1654149
dc.relation.fundingNSF CHE-1955000
dc.rightsCopyright 2022 American Chemical Society
dc.source.urihttps://doi.org/10.1021/acs.analchem.2c01979
dc.titleGlass transition temperatures of individual submicrometer atmospheric particles: direct measurement via heated atomic force microscopy probe
dc.typeJournal article
pubs.publication-statusPublished
ror.mmsid9916731219501831

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