Colloidal PbTe-Au nanocrystal heterostructures

Colloidal PbTe nanocrystals are reacted with AuCl₃ in the presence of dodecylamine and tetraoctylammonium bromide in a toluene solution. At room temperature, only homogenous nucleation of isolated Au nanocrystals in solution is observed. At higher temperatures (i.e. 60 °C or higher) the gold ions/atoms are able to diffuse through the PbTe nanocrystals and to form one or more metallic gold regions inside them, while most of the remaining volume of each nanocrystal becomes amorphous. Longer reaction times lead to the growth of a single balloon-shaped Au domain attached via its apex to the surface of each nanocrystal. The structural and compositional quantification of the starting PbTe nanocrystals and of the various reaction products is often complicated by several reactive processes occurring during in situ analysis by electron microscopy. Evidences of the formation of a metastable Au₃Te compound are presented.