Zinc oxide nanoparticles: A study of defect level blue–green emission

Systematic investigation of the structural, morphological and optical properties of hexylamine capped zinc oxide (ZnO) nanoparticles is presented. Optical properties indicate the presence of sufficient amount of surface defects. These defects in highly dispersed ZnO nanoparticles have been studied by annealing the nanoparticles in air at various temperatures and recording the photoluminescence spectra. The annealing temperature was found to strongly influence the UV band edge emission and the blue–green defect level emission (DLE). At low annealing temperatures an increase in UV emission with temperatures is observed and this emission is proposed to be a result of desorption of surface adsorbed water and hydroxyl groups. The DLE of the synthesized sample is likely due to the presence of oxygen vacancies on the surface resulting in green emission.

► Monodispersed nanoparticles were successfully synthesized by wet chemical method.
► Hexylamine is found to be an effective capping agent.
► The defect-level blue–green emission is attributed to the presence of oxygen vacancies.