Synthesis Of Silver Nanowires And Photopluminescence Enhancement From Ag/ZnO Nanostructures

Ag nanowires have attracted more and more attention with their fascinating optical and electrical properties, and potential applications in nonlinear optics surface-enhanced Raman scattering and plasmonics. In this thesis, the synthesis process of Ag nanowires and the localized surface plasmon resonance coupling between Ag nanowires and ZnO quantum dots have been studied. The specific works are as follows:The uniform silver nanowires with an average diameter of180nm and length in the range of3-35μm had been synthesized by polyol chemical reduction methods. The obtained Ag nanowires are decahedron with fivefold twinned structure, bounded by five {100} side planes with <100> growth direction. Ag nanowires exhibit two localized surface plasmon resonant peaks (LSPR) at about338and385nm positions, both of them belong to the transverse plasmon modes of the Ag nanowires. There is a red shift in the maximum absorption peak when the sizes of Ag nanowires become larger. The Ag/ZnO composite structures were prepared by mixing Ag nanowires with ZnO quantum dots and coating on silicon substrate. The photoluminsence enhancement was observed in such composite structures as compared to the pure ZnO quantum dots. The enhancement ratio is30-fold for emission at345nm and12-fold for that at383nm. These enhancement emission positions coincide with the localized surface plasmon resonant absorption peaks of Ag nanowires, which indicate there are two localized surface plasmon resonant modes in Ag nanowires. In addition, the absorption peak of338nm red-shifts to343nm, and the intensity is enhanced more than the strength of the absorption peak at385nm. The red shift of the absorption peak at385nm is not obvious.The localized surface plasmon resonance coupling between Ag nanowires and ZnO films was investigated. The ZnO films were prepared by sol-gel method and the ultraviolet peak of ZnO films located at377nm. The enhancement ratio is2-fold for emission at378nm when the Ag nanowires solution were coated on the ZnO films, which indicates the resonance coupling between Ag nanowires and ZnO films is weak.The results show that the enhanced ultraviolet photoluminscence is observed from ZnO quantum dots aftter mixed with Ag nanowires. And these composite structures can be applied for light-emitting diodes, LEDs and other photonic devices, and the current works may give a new approach to design ZnO based nano light-emitting devices.