Anisotropic Arm Growth In Unconventional Semiconductor Cdse/Cds Nanotetrapod Synthesis Using Core/Shell Cdse/Cds As Seeds

Anisotropic semiconductor CdSe/CdS tetrapods exhibit unique dimension-dependent quantum confinement and efficient charge separation/transport along the arms, making them useful in a wide range of optoelectronic applications. Traditionally, the CdSe/CdS tetrapods were produced by anisotropic CdS growth on the zinc blende CdSe core, induced by ligands that selectively bind to specific facets of CdSe. In this work, we report an unconventional method to grow CdSe/CdS nanotetrapods using wurtzite CdSe/CdS core/shell nanocrystals as seeds, without the aid of selective-binding ligands. The CdS layer thickness in the seeds and the Cd and S precursor concentrations have a significant impact on the morphology of CdS growth. The tetrapods we obtained have one arm much longer than the other three. Through a detailed transmission electron microscopy study, we found the anisotropic arms resulted from the stacking faults occurred in the growth, which induced a local phase change from wurtzite to zinc blende at one end of the CdSe/CdS nanocrystal. This special crystal growth mechanism can be applied to other seed-mediated methods to produce anisotropic nanostructures.