Blue green and UV emitting ZnO nanoparticles synthesized through a non-aqueous route

ZnO nanoparticles of size ∼15 nm were synthesized through a non-aqueous route. TEM images showed spherical particles and elongated structures in the as prepared and annealed samples. Photoluminescence spectra showed ultraviolet luminescence arising from free exciton, donor–acceptor pairs and its LO phonon replica and deep level luminescence in blue, green and yellow regions. Annealing lead to persistent blue emission and quenching of yellow and green emissions. The ratio of the intensities of ultraviolet photoluminescence to that of visible photoluminescence increased on annealing. MicroRaman spectrum of ZnO nanoparticles showed all the non-polar and polar Raman modes. Disorder activated Raman scattering resulted in the appearance of B1 silent modes in the Raman spectra which diminished on annealing. Surface defects in the nanoparticles are responsible for the quenching of green luminescence and appearance of new modes as a result of disorder activated Raman scattering.

► ZnO nanoparticles synthesized through non-aqueous route.
► On annealing UV and blue emission were persistent.
► Green and yellow emission quenched and Raman modes in (500–600 cm−1) disappeared.
► Surface defects responsible for luminescence quenching and disappearance of DARS.