The PL spectra of the ZnO nanorods have a weak band ultraviolet (UV) PL band at about 380 nm, attributed to an exciton-related activity [30] and a relatively strong visible (green/yellow) emission band at around 550 nm, due to the point defects, such as oxygen vacancies or Zn interstitials which act as donors at levels located below the conduction band edge [29,31–33].