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

Abstract

ZnO nanoparticles of size ∼15nm 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.