Wet chemical synthesis of ZnO nanocrystals: dependence of growth and morphology on the solvent composition

摘要

Zinc oxide (ZnO) nanocrystals were prepared using a wet chemical route starting from zinc acetate dihydrate dissolved in pure ethanol, pure water, and mixtures of ethanol and water. X-ray diffraction (XRD) studies along with thermogravimetric analyses results show that ZnO begins to crystallize at a temperature lower than 100 ℃ in a starting solution having 1:4 ethanol-water volume ratio. For other starting solutions, ZnO forms above 150 ℃. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies confirm the formation of nanoparticles of size ～ 15-20 nm and XRD analysis shows that the particles crystallize in the wurtzite structure. SEM and TEM studies show that ZnO particles grown in pure ethanol, pure water and in ethanol-water mixtures (other than the 1:4 mixture) have similar morphology, with the nanocrystals forming randomly grouped clusters. In the case of 1:4 solvent, however, the morphology is different, ZnO in this case growing in the form of chain like structures which appear like rods. Room temperature photoluminescence spectra exhibit a strong emission band in the red region probably caused by transitions between deep levels involving zinc interstitials.