Large-scale synthesis of zinc oxide rose-like structures and their optical properties

Zinc oxide (ZnO) rose-like structures, which are composed of several or tens of nanoplates, have been successfully synthesized on a large scale through the hydrothermal decomposed method. The influences of the pH and the concentration of the reaction precursors on the morphology, orientation and density of the obtained ZnO nanocrystals were investigated. It was found that the pH and the concentration significantly affected the morphology, orientation and density of the as-grown ZnO nanostructures. The obtained zinc oxide rose-like structures were investigated by X-ray diffraction, energy-dispersive X-ray fluorescence, field emission scanning electron microscopy, transmission electron microscopy (TEM), selected area electron diffraction and photoluminescence. The possible growth mechanism of the rose-like structures was briefly discussed. This facile low-cost controllable growth procedure should promise us a future large-scale synthesis of ZnO nanostructures for many important applications in nano-/micro-scale devices. Room-temperature photoluminescence spectra from the ZnO rose- and daisy-like nanostructures reveal similar photoluminescence features: a strong UV emission peak at about 378 nm and a weak green emission band at ∼500 nm. The strong UV photoluminescence and the weak green emission indicate the good crystallization quality of the rose-like nanostructures.