The luminescent properties of ZnO nanoparticles, prepared using the wet chemical method, were investigated. The nanoparticles (5 to 10nm) had an hexagonal wurtzite structure, and the room-temperature photoluminescence spectrum exhibited a broad visible luminescence band and insignificant near-bandgap emissions. The broad green luminescence predominated at both room and boiled-off liquid-N temperatures, while the ultra-violet band-edge emission was strongly quenched. The as-prepared nanoparticles had a residual intermediate compound on their surface, in the form of an acetate group. This acted as a source of defect centers for the emission of green luminescence. A trace amount of zinc hydroxide was observed in one of the samples and was found to enhance further the intensity of the green luminescence. Raman scattering studies of nanoparticles indicated that the acetate/hydroxyl groups were loosely bound to the surface and were not present in the interior of the ZnO structure.

Effect of Surface Defects on the Visible Emission from ZnO Nanoparticles. Yadav, H.K., Sreenivas, K., Gupta, V., Singh, S.P., Katiyar, R.S.: Journals of Materials Research, 2007, 22[9], 2404-9