Shape control of PbSe nanocrystals using noble metal seed particles.

We demonstrate that the shape of PbSe nanocrystals can be controlled systematically by seeding their growth with noble metal nanoparticles (Au, Ag, or Pd) and varying the seed and precursor concentrations. Cylinders (quantum rods), cubes, crosses, stars, and branched structures were produced in high yield at 150 degrees C in reaction times of a few minutes. Although their absorption spectrum does not exhibit sharp features, the quantum rods exhibit significant photogeneration efficiency, enabling infrared sensitization of a polymeric photoconductive nanocomposite.