Colloquium: Dr. Steve Erwin, U.S Naval Research Laboratory

The various mechanisms that control the growth of nanocrystals are
surprisingly difficult to investigate because they occupy a position
awkwardly intermediate between molecules and solids - the regimes for which traditional experimental and theoretical methods work well. Two case studies illustrate these difficulties as we address some
unresolved questions about nanocrystal growth. (1) We propose an
explanation for "cation exchange" reactions in nanocrystals -
reactions that take place orders of magnitude faster than in their
macroscopic counterparts. (2) We propose and demonstrate a
mechanism to explain why certain crystallographically isotropic
materials grow into highly anisotropic "nanoplatelet" shapes.