Acoustic levitation with polarising optical microscopy (AL-POM): water uptake in a nanostructured atmospheric aerosol proxy

Milsom, A. ORCID: https://orcid.org/0000-0003-3875-9015, Squires, A. M. ORCID: https://orcid.org/0000-0003-1396-467X, Brasnett, C. ORCID: https://orcid.org/0000-0001-9235-1673, Sharratt, W. N. ORCID: https://orcid.org/0000-0003-2148-8423, Seddon, A. M. ORCID: https://orcid.org/0000-0002-5794-8500 and Pfrang, C. ORCID: https://orcid.org/0000-0001-9023-5281 (2023) Acoustic levitation with polarising optical microscopy (AL-POM): water uptake in a nanostructured atmospheric aerosol proxy. Environmental Science: Atmospheres, 3 (11). pp. 1579-1686. ISSN 2634-3606 doi: 10.1039/d3ea00083d

Abstract/Summary

Laboratory studies on levitated particles of atmospheric aerosol proxies have provided significant contributions to our understanding of aerosol processes. We present an experimental method combining acoustic levitation with polarising optical microscopy (AL-POM) to probe optically birefringent particles, such as the nanostructured surfactant atmospheric aerosol proxy studied here. Birefringent particles were subjected to a step increase in humidity. A decrease in birefringence was measured over time as a result of a nanostructure change, confirmed by complementary synchrotron X-ray scattering. A multi-layer water uptake model was created and fitted to the experimental data, revealing a water diffusion coefficient increase by ca. 5–6 orders of magnitude upon phase transition. This has implications for the timescale of water uptake in surfactant-containing aerosols and their atmospheric lifetimes. This experimental setup has strong potential to be used in conjunction with other levitation methods and in different contexts concerning birefringent materials such as crystallisation.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/113644
Identification Number/DOI	10.1039/d3ea00083d
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Uncontrolled Keywords	Pollution, Environmental Chemistry, Chemistry (miscellaneous), Analytical Chemistry
Publisher	Royal Society of Chemistry (RSC)
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