Catalytic synthesis and structural characteristics of high-quality tetrapod-like ZnO nanocrystals by a modified vapor transport process

High-quality tetrapod-like ZnO (T-ZnO) nanocrystals were synthesized by a modified vapor transport process. NiO nanocrystals were prepared on a Si substrate as a catalyst. High-yield zinc vapor was produced by a carbothermal reduction of zinc carbonate to promote the synthesis of T-ZnO nanocrystals. The as-grown T-ZnO nanocrystals are assembled by four hexagonal prismatic nanorods, whose diameters and lengths are 80-100 and 600-1000 nm, respectively. In the center of a T-ZnO nanocrystal, a tetrahedral core and several irregular patches were found among the nanorods. As a whole, T-ZnO nanocrystals are preferentially arranged along the (001) direction of ZnO. The photoluminescence spectrum of T-ZnO nanocrystals showed two emission bands, a strong ultraviolet emission at around 390 nm and a weak blue emission at 440 nm. The green light emission that is related to the existence of the defects in ZnO crystals cannot be distinguished. It implies that the high crystal integrity of T-ZnO nanocrystals has been obtained. The process reported here is demonstrated as an effective candidate for synthesizing ZnO three-dimensional nanocrystals.