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Surfactant Partitioning Dynamics in Freshly Generated Aerosol Droplets
Alison Bain1,2, Lara Lalemi1, Nathan Croll Dawes1
1School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K.
Journal of the American Chemical Society
|June 1, 2024
Summary
Aerosol droplet interfaces take milliseconds to reach equilibrium, impacting chemical reactions. Understanding surfactant behavior in these microcompartments is key to explaining accelerated chemistry.
Area of Science:
- Interfacial science
- Physical chemistry
- Atmospheric chemistry
Background:
- Aerosol droplets are microcompartments where interfacial processes significantly influence reactivity due to high surface-area-to-volume ratios.
- Unusual chemical kinetics observed in droplets necessitate a deeper understanding of their dynamic surface properties.
- Current knowledge of microscopic droplet interfaces lags behind that of bulk processes.
Purpose of the Study:
- To quantitatively measure dynamic surface tensions of aerosol droplets.
- To investigate the kinetics of surfactant partitioning to the droplet-air interface.
- To understand the time-dependence of interfacial surfactant concentration in microdroplets.
Main Methods:
- Utilized stroboscopic imaging to observe dynamic surface tensions of 14-25 μm radius droplets.
- Employed droplets containing strong surfactants: sodium dodecyl sulfate and octyl-β-D-thioglucopyranoside.
- Interpreted experimental results using a kinetic model tailored for high surface-area-to-volume ratios.
Main Results:
- Demonstrated that aerosol droplet interfaces require up to many milliseconds to reach equilibrium.
- Provided insights into surfactant diffusion and adsorption kinetics at the droplet-air interface.
- Quantified the time-dependent interfacial surfactant concentration.
Conclusions:
- Microscopic droplet interfaces exhibit slow equilibration dynamics, taking milliseconds to stabilize.
- These slow interfacial dynamics are crucial for explaining accelerated chemical reactions observed in aerosol droplets.
- Future studies of microcompartment chemistry must consider these time scales for accurate mechanistic interpretation.
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