Growth of Variable Aspect Ratio ZnO Nanorods by Solochemical Processing

In this work, variable aspect ratio (length divided by diameter) zinc oxide nanorods were synthesized through a simple solochemical method by reacting a Zn2+ precursor with sodium hydroxide at low reaction temperatures. The analysis of the X-ray diffraction data indicated that the samples had hexagonal wurtzite structure and nanometric size crystallites. The transmission electron microscopy (TEM) images of the products prepared at 60 and 80 °C exhibited rod-like architecture, showing that the reaction temperature did not affect the ZnO morphology. The average aspect ratio of the ZnO nanorods decreased from 3.4 to 2.4 when the reaction temperature was raised from 60 to 80 °C. The samples presented a blue shift in the excitonic absorption compared to ZnO bulk that increased alongside with reaction temperature. In addition, this research investigated the results obtained by varying the concentration of zinc chloride solution. At the same temperature, it could be verified that when the zinc concentration was increased, the diameter of the ZnO nanorods also slightly increased, and much shorter nanorods were achieved, especially in the reactions performed at 50 and 70 °C. Finally, the growth mechanism of the ZnO nanostructures was proposed based on the results obtained by changing the zinc precursor concentration and reaction temperature.