Fluctuating Structure of Aqueous Organic Nanodroplets
Supercooled and nano-confined water occurs frequently as nanometer-sized aqueousorganic aerosol droplets that are ubiquitous in the atmosphere and in many industrial processes. Nanodroplet structure is important because it influences droplet growth and evaporation rates, heterogeneous reaction rates, and radiative properties. We used classical molecular dynamic simulations to study the structure of binary water-nonane and ternary water-butanol-nonane nanodroplets for several temperatures and droplet sizes. We found that nonspherical, phase-separated Russian Doll (RD) structures occur for water/nonane nanodroplets at all temperatures studied, 220K-300K. The RD structure consists of a nearly spherical water droplet partially wetted by a convex lens of nonane. We then studied the effects of butanol on the wetting of the water/butanol core-shell droplet by the nonane lens. At low concentrations, butanol acts as a surfactant to significantly enhance the wetability of the water droplet by nonane. At 250 K, with sufficient butanol and nonane, perfect wetting (thin film formation by nonane) occurs. Perfect wetting also occurs at higher temperatures, 270 K to 300 K, but this wetting state is progressively destabilized at higher temperature. All of the nanodroplets studied undergo distinct transitions between partial dewetting and perfect wetting states due to isothermal fluctuations in the local distribution of butanol on the surface of the water core. These fluctuations favor the wetted state at lower temperatures and the dewetted state at higher temperatures.
F. Hrahsheh and G. Wilemski, "Fluctuating Structure of Aqueous Organic Nanodroplets," AIP Conference Proceedings, vol. 1527, pp. 63-66, American Institute of Physics (AIP), Jun 2013.
The definitive version is available at http://dx.doi.org/10.1063/1.4803204
19th International Conference on Nucleation and Atmospheric Aerosols (2013: Jun. 23-28, Fort Collins, CO)
Keywords and Phrases
Contact angle; Molecular dynamics; Nanodroplets; Nucleation
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Article - Conference proceedings
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