Accounting for changes in particle charge, dry mass and composition occurring during studies of single levitated particles

Allen E. Haddrell, James F. Davies, Akihiro Yabushita, Jonathan P. Reid

研究成果: Contribution to journalArticle査読

15 被引用数 (Scopus)

抄録

The most used instrument in single particle hygroscopic analysis over the past thirty years has been the electrodynamic balance (EDB). Two general assumptions are made in hygroscopic studies involving the EDB. First, it is assumed that the net charge on the droplet is invariant over the time scale required to record a hygroscopic growth cycle. Second, it is assumed that the composition of the droplet is constant (aside from the addition and removal of water). In this study, we demonstrate that these assumptions cannot always be made and may indeed prove incorrect. The presence of net charge in the humidified vapor phase reduces the total net charge retained by the droplet over prolonged levitation periods. The gradual reduction in charge limits the reproducibility of hygroscopicity measurements made on repeated RH cycles with a single particle, or prolonged experiments in which the particle is held at a high relative humidity. Further, two contrasting examples of the influence of changes in chemical composition changes are reported. In the first, simple acid-base chemistry in the droplet leads to the irreversible removal of gaseous ammonia from a droplet containing an ammonium salt on a time scale that is shorter than the hygroscopicity measurement. In the second example, the net charge on the droplet (<100 fC) is high enough to drive redox chemistry within the droplet. This is demonstrated by the reduction of iodic acid in a droplet made solely of iodic acid and water to form iodine and an iodate salt.

本文言語英語
ページ(範囲)9941-9953
ページ数13
ジャーナルJournal of Physical Chemistry A
116
40
DOI
出版ステータス出版済み - 10 11 2012
外部発表はい

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry

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