Enhancement of UV luminescence in Zn/ZnO nanocomposites synthesized by controlled thermal oxidation of Zn nano-octahedrals

Defect-free photoluminescence (PL) emission is always desirable for the practical applications of functional materials. The presence of metal nanostructures near the semiconductor can result in a reduction of defect emission, if present. Here, the enhancement of ultraviolet (UV) PL emission of Zn/ZnO nanocomposites (NCs) has been demonstrated with a corresponding reduction of defect-mediated PL emission. Zn/ZnO NCs have been synthesized by annealing of Zn nano-octahedral in the air (at 500 °C for 5 h). Annealing at 800 °C has been found to result in the complete oxidation of Zn and the formation of ZnO nanoparticles (NPs). UV and visible PL emissions have been observed from Zn nano-octahedral, Zn/ZnO NCs, and ZnO NPs. The observed PL emissions from Zn have been argued as due to transitions of electrons from sp band to the upper states of 3 d band. For ZnO the UV emission is due to near-band-edge emission of ZnO and visible PL emissions are due to the presence of defect states in ZnO. About 2.15-fold enhancement of UV PL emission of Zn/ZnO NCs has been argued as due to presence of metallic Zn in the Zn/ZnO NCs. Thus, the present study can open up a new avenue for Zn/ZnO NCs for possible applications in UV regions.