Nanoparticle-mediated evaporation at liquid-vapor interfaces

X Yong and SY Qin and TJ Singler, EXTREME MECHANICS LETTERS, 7, 90-103 (2016).

DOI: 10.1016/j.eml.2016.04.001

Advancing solution-based additive manufacturing of functional materials demands a fundamental understanding of how nanoparticles straddling a liquid-vapor interface influence evaporation. Using many-body dissipative particle dynamics, we model evaporation at liquid-vapor interfaces with adsorbed nanoparticles. We quantitatively characterize the interfacial mechanics and the nanoparticle-mediated evaporation, using a particle-free interface as the reference system. We demonstrate that particle-particle interactions are critical for surface tension reduction induced by nanoparticles. The comparison of evaporation rates measured for different surface coverages with partially-wetted nanoparticles shows that the interface-bound nanoparticles can suppress evaporation through reducing the accessible interfacial area. We also observe reduced evaporation rates when the wettability of nanoparticles is varied from hydrophilic to hydrophobic while the surface coverage is kept approximately constant. This behavior suggests that obstruction in the evaporation path of escaping vapor beads can also inhibit net evaporation. The results also indicate the interfacial mechanics has no direct correlation with evaporation. Further analysis of the evaporation suppression provides important insight that the retardation effect of surface-covering nanoparticles depends on ambient conditions and highlights that the nanoparticle monolayers modulate evaporation in a similar manner as insoluble surfactant monolayers. (C) 2016 Elsevier Ltd. All rights reserved.

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