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

Adam Milsom, Adam M. Squires, Christopher Brasnett, William N. Sharratt, Annela M. Seddon, Christian Pfrang*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

1 Citation (Scopus)
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Abstract

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.

Original languageEnglish
Pages (from-to)1642-1650
Number of pages9
JournalEnvironmental Science: Atmospheres
Volume3
Issue number11
DOIs
Publication statusPublished - 26-Sept-2023

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