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Published on: September 9, 2022
Curvature-dependent adsorption of surfactants in water nanodroplets and nanobubbles
Fabio Staniscia1, Matej Kanduč1
1Department of Theoretical Physics, Jožef Stefan Institute, Jamova 39, Ljubljana, SI-1000, Slovenia.
Hypothesis:
Surfactants, molecules that readily adsorb to liquid interfaces and reduce surface tension, are paramount to numerous natural and technological processes: from cloud formation and climate modeling to the stability and reactivity of nanodroplets and nanobubbles. While surfactant adsorption at planar interfaces has been well-studied, their behavior at curved interfaces remains much less understood. Since curvature modifies interfacial thermodynamic properties, we hypothesize that it will also affect surfactant adsorption.
Simulations:
To test this hypothesis, we perform molecular dynamics simulations of short-chain surfactants at water-vapor interfaces with varying curvature, examining droplets, bubbles, and planar interfaces.
Findings:
The outcomes reveal a systematic dependence of adsorption on curvature, which is enhanced at droplet interfaces and reduced at bubble interfaces, with the effect becoming more pronounced for surfactants with longer alkyl tails. We attribute this curvature-dependent behavior to two key mechanisms: Laplace pressure and curvature-dependent surface tension. The breakdown of these contributions allows us to obtain a quantitative understanding and to predict the influence of curvature on adsorption.
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