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Oral Sessions
Day 2, June 23（Mon.） 14:25-14:40
Room A (Maesato West)
- 2A-O2-1425
Ion behavior in the Evaporating Charged Droplets Generated by Electrospray Ionization
(POSTECH)
Seongjae Jang, Minsu Kim, oJongcheol Seo
Charged droplets generated during electrospray ionization (ESI) provide a unique environment for molecular confinement, where rapid solvent evaporation drives non-equilibrium behaviors distinct from bulk solutions. Investigating ion dynamics in these charged micro-/nanodroplets offers new insights into chemical processes at fluctuating air-liquid interfaces.
Our group has explored the behavior of iodide (I–) ions at (i) the air-liquid interface and (ii) the solute-liquid interface in evaporating charged droplets using ion mobility spectrometry-mass spectrometry (IMS-MS). We observed that ion emissions at the interface (ion emission mechanism, IEM) predominantly yield small cluster ions (n < 3), with a strong preference for iodides over other halides. This preference diminishes for larger clusters (n > 4), which likely form via the charged residue mechanism (CRM). Additionally, we found that compact native protein ions selectively bind multiple iodides, unlike denatured proteins, which show no binding.
Molecular dynamics simulations corroborate these experimental findings, confirming iodide's strong interfacial affinity as the primary driver of its distinct behavior. Our study provides critical insights into ion surface propensity, ion transport across interfaces, and biomolecular ion structures in droplets.