Branched Heterostructured Semiconductor Nanocrystals with Various Branch Orders via a Facet-to-Facet Linking Process.

Branched heterostructured semiconductor nanoparticles such as core seeded tetrapods and octapods offer properties not seen in their spherical core-shell counterparts, but are challenging to synthesize with a large diversity of branch numbers via heterogeneous nucleation and growth processes alone. This work describes a process to facet-link matchstick-like Ag2S-tipped ZnS nanorods via their Ag2S tips, producing branched Ag2S-centered ZnS nanoparticles such as bipods, tripods, and in general multipods with 4 to 16 ZnS arms as a function of reaction time. The angle between nanorods in the bipods and tripods is found to be close to 120°, resulting in unexpected bent and trigonal planar geometry, respectively. This is attributed to the exposed facets of the monoclinic Ag2S tips, their relative chemical reactivities, and their atomic composition. The formation of particles with an increasing number of branches takes place in a stepwise manner, thus making the facet-linking approach a facile synthesis route to systematically obtaining a diverse set of branched heterostructured semiconductor nanoparticles with a well-defined number of branches.