Controlled Synthesis of CdSe Tetrapods with High Morphological Uniformity by the Persistent Kinetic Growth and the Halide-Mediated Phase Transformation

We report scalable controlled synthesis of CdSe tetrapods with high morphological uniformity based on the continuous precursor injection (CPI) approach with halide ligands. The CPI approach involves the successive injection of precursors into the seed solution at a controlled rate so that the reaction condition remains in the kinetic growth regime. To initiate the successful development of tetrapod structure, the controlled amount of halide ligands are added during the reaction, which triggered the formation of wurtzite arms on {111}-facets of the zincblende seeds. The formation of the wurtzite phase is responsible for the halide-mediated displacement of oleate ligands, destabilizing the embryonic CdSe phase on the zincblende seeds enabling the phase transformation to more stable wurtzite phase on the hexagonal {111}-facets. On the basis of these halide-mediated phase transformation of CdSe nanocrystals and the persistent kinetic growth induced by the CPI approach, well-defined CdSe tetrapods with controlled arm length and diameter have been produced in large quantity.