American Association for Aerosol Research - Abstract Submission

AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA

Abstract View


Molecular Dynamics Simulations of Aqueous-Organic Binary and Ternary Nanodroplets

Fawaz Hrahsheh, GERALD WILEMSKI, Missouri University of Science and Technology, Rolla MO

     Abstract Number: 499
     Working Group: Aerosol Nucleation: From Clusters to Nanoparticles

Abstract
The structure of nanodroplets plays an important role in many natural and technological processes including particle nucleation and growth and aerosol formation in the atmosphere. Among other factors, chemical miscibility and surface tension strongly affect the structure of multicomponent nanodroplets at low temperature. Here, we investigate the structure of water/butanol, water/nonane, and water/butanol/nonane nanodroplets using molecular dynamics (MD) simulations. Each binary system has a bulk miscibility gap that strongly influences nanodroplet structure. Our MD results confirm several of our previous theoretical predictions of structures for binary nanodroplets using density functional theory and lattice Monte Carlo techniques: Core-shell and well-mixed structures are found for water/butanol nanodroplets, while nonspherical, phase-separated Russian Doll (RD) structures occur for water/nonane nanodroplets at all temperatures studied, 220K – 300K. In the ternary nanodroplets, butanol plays the role of a surfactant that forms a thin interface surrounding the aqueous region of the droplet. Depending on the nonane concentration, two types of structures were found. At high nonane levels, an onion-like, spherically symmetric structure occurs with nonane completely wetting the butanol interface that covers the inner aqueous core. When the nonane content is reduced below a critical level, the droplet consists of a lens shaped nonane region that only partially wets the spherical water/butanol core-shell giving rise to an overall nonspherical RD structure. These different structures may have a strong effect on the contribution of water to the ternary droplet growth rate.