Effect of annealing temperature and pH on morphology and optical property of highly dispersible ZnO nanoparticles

Highly dispersible zinc oxide nanoparticles were produced in large quantity via a simple solution method. The effect of temperature and pH impact on as-prepared ZnO nanoparticles with respect to the morphological and optical characteristics has been investigated. The average particle size of ZnO nanoparticles increased with increasing annealing temperature. A sharp UV band-edge emission was observed in as-prepared ZnO nanoparticles with negligibly less intense deep level emission. However, upon annealing at high temperature in air, UV band-edge emission disappears with an evolution of a broad deep level emission in photoluminescence spectra. Similarly, by adjusting the pH of reaction medium from 4 to pH = 8 using ammonium hydroxide solution, particle size gets bigger and bigger leads to red-shift in UV band-edge emission and an appearance of deep level emission peak. At pH = 8, well resolved sharp X-ray diffraction peaks were observed with lower FWHM values due to higher crystallite sizes.