Date

2014

Author

Altıntaş Yıldırım, Özlem

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Zinc oxide (ZnO) nanostructures have attracted considerable attention in many electrical, optoelectronic and magnetic applications due to their unique properties originating form characteristic wide band gap and large exciton binding energy of ZnO. Electrical, optical and magnetic properties of ZnO nanostructures strongly depend on their size and morphology. Therefore, there has been a strong interest in the synthesis of ZnO nanostructures with well-controlled size and shape. These synthesis approaches should allow morphological control and size modification for the resultant ZnO nanostructures. Meanwhile, simple experimental conditions without any sophisticate equipment requirements are critical for achieving economically feasible and large-scale production. The main objective of this study was to establish such synthesis routes for obtaining ZnO nanostructures. This study focuses on two main topics: (i) investigation of solution based synthesis methods for size and morphology controlled ZnO nanostructures and (ii) investigation of functional properties of ZnO nanostructures with silver (Ag) and copper (Cu) incorporation. Synthesis of pure ZnO nanostructures was carried out using two different generic aqueous routes; microemulsion and precipitation. In microemulsion technique, ZnO nanoparticles were synthesized by using sodium bis(2-ethylhexyl) vi sulfosuccinate:glycerol:n-heptane microemulsion system. The formation of ZnO nanoparticles was achieved after calcination of microemulsion products in air at various temperatures. Size and morphology of the nanostructures were controlled with applying different microemulsion formulations and calcination temperatures. Synthesis of ZnO nanoparticles was also achieved by low temperature precipitation method due to intrinsic yield problem of microemulsion approach. The precipitation system was formed using zinc acetate dihydrate as zinc source, ethylene glycol or water as solvent, and polyvinyl pyrrolidone as chelating agent. The size and shape of the ZnO nanoparticles were manipulated by the choice of precipitation temperature, amount of the chelating agent and type of the solvent, which essentially change the nature of adsorption events between ZnO crystals and organic molecules leading to changes in nucleation and growth events during precipitation. The precipitation method was further expanded in order to realize chemical modifications of ZnO nanostructures for tailoring their functional properties. Both Ag and Cu doped ZnO (ZnO:Ag and ZnO:Cu) nanoparticles were synthesized by room temperature precipitation method without any subsequent thermal treatment. A rigorous structural analyses Rietveld and electron microscopy techniques have been performed on these chemically modified particles to explain the nature and mechanism of metal doping in ZnO crystal lattice. In addition, the effect of metal ion doping on the functional properties, such as photocatalytic activity (for ZnO:Ag) and room temperature ferromagnetism (for ZnO:Cu) have been demonstrated.

Subject Keywords

Zinc oxide., Copper oxide., Emulsions., Nanoparticles

URI

http://etd.lib.metu.edu.tr/upload/12618340/index.pdf
https://hdl.handle.net/11511/24319

Collections

Graduate School of Natural and Applied Sciences, Thesis