Synthesis and characterization of tailored zinc oxide nanostructures and their engineered nanocomposites

Nanosized ZnO particles were synthesized using a simple thermal decomposition and an electrochemical deposition method. The mean crystallite sizes and other structural properties were estimated at various experimental conditions using x-ray diffraction techniques and transmission electron microscopy analysis. The qualitative microstrain of nanosized ZnO particles obtained from the Williamson-Hall plot was inversely proportional to the crystallite size. The slight quantum confinement effect was identified by the shift of the absorption edge. Several factors are considered to contribute to the characteristics and the mechanisms of the various visible emissions in nanosized ZnO particles. The efficiency and position of visible emission peaks were dependent on the particle size. Green emission of nanosized ZnO particles was enhanced dramatically without significant weight loss of ZnO crystals using rapid heating and quenching treatment under forming gas ambient.; ZnO nanorods were synthesized using a hydrothermal method and a vapor-solid growth method. The as-synthesized ZnO nanorods exhibited higher luminescence efficiency than as-synthesized ZnO particles. The morphology and photoluminescence of as-synthesized ZnO nanorods were controlled by the precursor concentration.; A dense amorphous silica film was deposited onto the surface of ZnO nanostructures using sodium silicate and hydrochloric acid solution. The presence and uniformity of the silica coating layer were confirmed by various analytical tools. Because of the presence of the passive silica coating layer, the thermal stability of nanorods under forming gas and chemical stability of nanoparticles in acid solutions was dramatically improved.; A novel electrochemical deposition coating method was developed to encapsulate the surface of ZnS:Ag particulates with nanosized ZnO particles. The ZnO nanoparticle layer on the surface of ZnS:Ag phosphors has been investigated using various characterization techniques. This ZnO coating layer contributed to the improvement of the cathodoluminescent lifetime of ZnS:Ag phosphors.; ZnO nanorods grown on ZnS:Ag thin films using the hydrothermal method has been investigated for use as blue and green composite phosphors. The as-synthesized nanocomposite exhibited predominant blue luminescence emitted from ZnS:Ag phosphor. However, a balance of visible luminescence between blue and green emission was achieved using rapid heating and quenching treatments under forming gas ambient.