Hydrothermal synthesis of ZnO nanobundles controlled by PEO–PPO–PEO block copolymers

Homocentric ZnO nanobundles with pyramidlike and hexagonal prism shapes were synthesized in colloidal systems formed by PEO–PPO–PEO amphiphilic block copolymers. The prism- and pyramidlike ZnO crystals were produced by L64 and F68, respectively, which may be attributed to the different growth rates of various crystal facets. It was proposed that the two processes for crystallization, including nucleation and crystal growth, happened in the macromolecular micelles under hydrothermal conditions. The room-temperature photoluminescence spectra of the ZnO products showed sharp ultraviolet emission located around 390 nm originating from the radiative recombination of free excitons. The sharp emission, with a half-maximum of about 8 nm, gave a powerful attestation that the sample was of high crystal quality, which was consistent with the SEM and TEM observations. The single ultraviolet emission is important for the application of ZnO-based materials in the electronic and photonic realms.

The supersaturated Zn(OH)2−4 solution enwrapped in macromolecular micelles first nucleated under hydrothermal conditions. Many tiny ZnO crystal nuclei were restricted in the hydrophobic core. The epitaxial growth of these ZnO nuclei along (0001) direction resulted in the formation of ZnO homocentrical bundle structures.Figure optionsDownload as PowerPoint slide