Oxygen-assisted unidirectional growth of CdSe nanorods using a low-temperature redox process

The role of oxygen in directing the low temperature (125 degrees C), redox-assisted, unidimensional and unidirectional growth of CdSe nanocrystals (NCs) was investigated. In the presence of oxygen, CdSe quantum dots grow selectively along their c axis with little to no change in their width. Reduction of oxygen in the growth medium results in three-dimensional growth. Moreover the one-dimensional growth was found to occur only from one of the two inequivalent polar (0001) facets, as supported by the seeded growth of Cd(x)Hg(1-x)Se onto CdSe seeds. This is in agreement with density functional theory simulations, which indicate that due to selective oxygen passivation growth can occur only along the [0001] direction. The ability to control seeded NC growth with respect to morphology and directionality opens new possibilities toward the low temperature synthesis of complex nanostructures.