Tailoring the morphology of CdSe nanocrystals by incorporation of Pb.

We have investigated the effects of Pb2+ addition on the morphological development of CdSe nanocrystals. We show that the addition of Pb ions in the initial precursor solution changed the morphology of CdSe nanocrystals to branched rods with high aspect ratio. The branched nanocrystals are mainly composed of wurzite phase grown along the [001] direction and the length of rods in each branched nanocrystal can be increased by increasing the amount of Pb2+ addition to accelerate the anisotropic growth of the nanocrystals. The luminescence, however, mostly arises from trap-related recombination and is significantly red-shifted by Pb2+ addition. Surface passivations of the branched nanocrystals with ZnS were proved to be effective in eliminating trap emission and enhancing band-edge emission, leading to a larger quantum yield.