Nano-confinement of supercooled water occurs frequently as aqueous-organic aerosol nanodroplets that are ubiquitous in the atmosphere and in many industrial processes such as natural gas refining. The structure of these nanodroplets is important because it influences droplets growth and evaporation rates, nucleation rates, and radiative properties. We used classical molecular dynamic simulations to study the structures of binary water-butanol nanodroplets for several temperatures and droplet sizes. Water-butanol cross-interactions are calculated using a LJ potential with non-bonded specific parameters adjusted to reproduce experimentally observed mutual binary solubility of equilibrium water-butanol at 295 K. To compare with the results of the density functional theory (DFT) of aqueous-organic nanodroplets [<i>Phys. Chem. Chem. Phys.</i>, <b>8</b>, 1266-1270 (2006)], we focus on T=250 K. Our simulations shows three different structures according to the butanol concentrations. For low concentrations, we observe a core-shell (CS) structure where a butanol shell completely wets a rich water core. For high concentrations, perfect well-mixed (WM) structure occurs as the water and the butanol become highly miscible. For intermediate concentrations of butanol, we find a distinct phase separated (Russian Doll)-Shell (RDS) structure for water/butanol nanodroplets. This RDS structure consists of a nearly spherical rich water droplet partially wetted by a well-mixed water/butanol convex lens (RD) and this lens-on-sphere structure is coated by a thin shell of butanol. Moreover, we study the stability of our RDS structure for higher temperatures.

Confined phase separation of aqueous-organic nanodroplets

253rd National Meeting (2017)

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