Small Is Different:  Shape-, Size-, and Composition-Dependent Properties of Some Colloidal Semiconductor Nanocrystals

As the size of material becomes equal to or falls below the nanometer length scale that characterizes the motion of its electrons and thus its properties, the latter become sensitive not only to the size but also to the shape and composition of the particles. In this Account, we describe the changes of some interesting properties in different colloidal semiconductor nanoparticles, such as the electronic relaxation rates as spherical nanoparticles change to nanorods, and the changes in the structure or size of very small nanoparticles upon adsorbing strongly bound molecules. We have also determined and explained the difference in the interfacial crossing rates of electrons and holes in a composite…