Synthesis of ZnO nanoparticles at room temperature with enhanced ultra‐violet photoluminescence

Abstract

ZnO nanoparticles (NPs) have attracted a lot of attention due to the possibility of their applications in different fields including optoelectronics, photonics, biosensing, catalytic, etc. Most of the applications require devices made of good quality of NPs. However, synthesis of device grade NPs is always challenging. Here, improvement of crystalline quality of the ZnO NPs has been demonstrated with a very simple procedure. ZnO NPs of average crystallite size of ~11.5 nm with optical band gap of ~3.44 eV have been synthesized in room temperature following the co-precipitation method by either varying the concentration of KOH or time of synthesis. For both the cases, change in average size of NPs has not been found to change significantly. This is mainly because the required heat energy to grow the size has not been provided externally. However, the increase of concentration of KOH or time of preparation has been found to improve the quality of the ZnO crystallites. The improvement of crystalline quality has been argued as due to the availability of enough KOH or the time to repair the defects on the surface of the NPs. Improvement of crystalline quality has been found to result in an enhancement of intensity of the ultraviolet (UV) photoluminescence (PL) emission band over the visible PL emission band of ZnO. The defect mediated visible PL emission is always considered as loss. The enhancement is ~2-fold. Such large enhancement can be utilized for the fabrication of optoelectronic devices and others based on ZnO NPs synthesized at room temperature.