Effect of hydroxide ion concentration on the evolution of nanostructures and structure correlated luminescence of ZnO nanopowders

Abstract Low dimensional nanostructures such as 1-D nanoneedles, 2-D nanoplates, and 3-D agglomerated nanospheres have been synthesized by controllable direct precipitation method and tuning of low dimensional structure correlated surface defect state induced luminescence emission from bluish green to bluish white has been studied. Change in concentration of OH − ions in precursors tune the morphology from 3-D to 1-D nanostructures. At low concentration of OH − , coalescence process dominates leading to formation of agglomerated nano-spheres while at intermediate and high concentration of OH − , growth along c-axis is heavily suppressed by adsorption of OH − ion over (0001) plane leading to nanoplate formation or by capping of (0001) plane by low energy surface { 01 1 ¯ 0 } leading to the formation of nano-needle. Thus, the concentration of OH − ions in precursor tunes the aspect ratio of nanostructures based on adsorption of OH − ions on the polar surface (0001). Nanostructures correlated defect state emission based on available surface for impurity adsorption leading to introduction of surface defect states is established by a change in emission profile of the samples after prolonged storage. The samples were exposed to high energy UV radiation before the storage. Theoretical electroluminescence emission efficiency reveals the effect of structure correlated photoluminescence of ZnO nanopowders on possible device performance if ZnO nanopowders are used for device fabrication. Concentration of OH − ions, dimension of nanostructures, formation of surface defect states and storage of ZnO nanopowders should be optimized to achieve maximum luminescence efficiency for consideration of optoelectronic applications.