Formation of tetrapod-shaped nanowires in the gas phase during the synthesis of ZnO nanostructures by carbothermal reduction.

We experimentally confirmed that charged ZnO nanoparticles were generated abundantly in the gas phase using a differential mobility analyzer (DMA). When they were size-selected by the DMA and captured on a grid for transmission electron microscopy, particles of 10 nm had a rod or tetrahedron shape, while particles larger than 10 nm tended to have a tetrapod shape. The tetrahedral particles seemed to be a seed for the growth of tetrapod nanowires.