Surface Enrichment in Nanodroplet Aerosols

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Barbara Wyslouzil is supported by a grant from the Theoretical and Computational Chemistry Program to continue her experimental research on nucleation of aerosol particles. The goal of the proposed work is to use small angle neutron scattering (SANS) to look for structure in multicomponent nanometer sized liquid droplets in an aerosol. Wyslouzil will be looking for surface enrichment in multicomponent droplets which she anticipates have internal structures on the nanometer length scale. She has already perfected a supersonic nozzle design that produces aerosol droplets of uniform size and has tested the feasibility of using SANS for performing depth profiling experiments. During the next phase of this research program, Wyslouzil plans to address three tasks: 1) conduct experiments with binary nanodroplets to determine their composition and structure; 2) improve her ability to conduct SANS measurements from aerosols; and 3) refine the data analysis procedures and modeling for interpreting the SANS experimental data. Multicomponent, nanometer-sized aerosol particles are produced by nucleation and condensation in many industrial and natural settings. Fine refractory particles form in combustion and metallurgical processes while sulfuric acid - water droplets are produced in stack gases, volcanic plumes, and as a byproduct of photochemical reactions in the atmosphere. The surface composition of these particles can strongly affect heterogeneous reactions, growth and evaporation kinetics, and the accomodation of trace gaseous species. Wyslouzil's research will contribute to our basic understanding of such phenomena.