Synthesis And Characterization Of ZnO/Ag(Au) Composite Nanoparticles

Semiconductor nanoparticles, also known as quantum dots (QDs) have attracted considerable interest in biological and medical community because of their unique properties. As a new generation of compound semiconductor, Nanometer zinc oxide is the functional material with manifold excellent performances and widespread applications. The steady and high intensity of ZnO resonant multi-phonon singals can be prospectively used in biology molecular labeling and detection.In this thesis, we synthesized ZnO/Ag and ZnO/Au composite nanoparticles by reducing metallic ions on the surface of the ZnO nanocrystals which acted as seeds. Utilizing Ag and Au nanoparticles as the SERS-active substrate we achieved SERS signals. The microstructure and optical properties of the composite nanoparticles were investigated. The results are given as follows:1. ZnO nanocrystals were prepared by the sol-gel methods. ZnO/Ag and ZnO/Au composite nanoparticles were separately synthesized by reducing Ag⁺ or Au³⁺ on the surface of ZnO nanocrystals.2. Ag(Au) capped ZnO did not changed its hexagonal wurtzite structure. The surface plasmon absorption band of Ag growing on ZnO nanocrystals shifts toward lower energy, which indicated that the interaction between Ag and ZnO exists. We observed SERS signals and first reported a typical resonant sixfold-phonon process within ZnO/Ag composite nanoparticles.3. SERS was also observed in ZnO/Au composite nanoparticles. Spectra indicated Metallic gold spreadly growing around ZnO nanocrystals. TEM and XPS shows there was a complicated interface between Au and ZnO nanoparticles, which was maybe Zn and Au alloy.