“…The dopant powders added to the Zn powders before thermal annealing are made of high purity Sn and Mg. Using conventional CVD, molecular beam epitaxy (MBE), and wet-chemistry growth techniques, these dopant elements have been found to influence many physical properties of the ZnO nanostructures, such as the electrical, magnetic, optical, and catalytic properties [ 25 , 26 , 27 ], as well as their morphology. S. K. Shina, in his work [ 23 ], observed that ZnO Sn-doped hierarchical nanorods had better responsiveness to ethanol and acetone vapors than the corresponding non-doped nanorods, due to the monocrystalline structure, increase in O-vacancy, and density of defect that accelerated and improved the effectiveness of the vapor diffusion process.…”