Anisotropic growth of PbSe nanocrystals on Au-Fe₃O₄ hybrid nanoparticles

A technique to grow PbSe nanocrystals with different morphologies on Au-Fe₃O₄ binary hybrid nanoparticles was investigated. When these nanoparticles were used to seed growth of PbSe, the semiconductor was found to be nucleating only on the Au portion. The evolution of PbSe size and morphology was observed through transmission electron microscopy (TEM) imaging of particles sampled at different times during the course of the reaction. The observation at an intermediate seed concentration and an initial reaction temperature of ca. 125°C, showed an induction period during which no PbSe nanocrystals. Examinations of TEM showed that the lattice planes are always oriented perpendicular to the growth direction, in both the simple rods and the branched structures. Seeding with binary particles has significant advantages over pure metal seeding, even when single-component anisotropic PbSe nanocrystals are the desired product.