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Departmental Colloquium

Coated Nanoparticles in Solution and at Interfaces  
Guest Speaker
Dr. Gary S. Grest  
Guest Affiliation
Sandia National Laboratories  
David Landau  
Thursday, February 23, 2012 4:00 pm - 5:00 pm  
Physics 202  

Among the most prevalent ways to control the assembly and integration of nanoparticles is to coat them with organic molecules whose specific functionalized groups modifies their inter particle interactions as well as the interaction of nanoparticles with their surrounding, while retaining their inherent properties. While it is often assumed that uniformly coating spherical nanoparticles with short organic will lead to symmetric nanoparticles, I will show using explicit-atom molecular dynamics simulations of model nanoparticles that the high curvature of small nanoparticle and the relatively short dimensions of the coating can produce highly asymmetric coating arrangements. In solution geometric properties dictate when a coating’s spherical symmetry will be unstable and that the chain end group and the solvent play a secondary role in determining the properties of surface patterns. At the water-vapor interface the anisotropic nanoparticle coatings seen in bulk solvents are reinforced by interactions at the interface. The coatings are significantly distorted and oriented by the surface and depend strongly on the amount of free volume provided by the geometry, end group, and solvent properties. At an interface any inhomogeneity or asymmetry tends to orient with the surface so as to minimize free energy. These asymmetric and oriented coatings are expected to have a dramatic effect on the interactions between nanoparticles and can influence the structures of aggregated nanoparticles which self-assemble in the bulk and at surfaces