“…The UV emission band is related to near band-edge (NBE) emission of the ZnO NPs, and is attributed to the recombination of free excitons by exciton-exciton collision process [13,43]. Several authors have investigated the PL properties of ZnO nanostructures [13,[43][44][45][46][47][48][49]. Generally, visible emission in ZnO consists of blue, violet, green and yellow emission peaks, which is attributed to different intrinsic defects such as oxygen vacancies (Vo), zinc vacancies (V Zn ), oxygen interstitials (Oi), zinc interstitials (Zn i ) and oxygen antisites (O Zn ).…”