Abstract
AbstractThe SiO2/Ag core-shell structure is synthesized via surface decorated method and seed-mediated technique. The morphology of silver layers on silica spheres can be accurately controlled by adjusting the quantity of NaOH. The two different structures are (1) larger and isolated silver particles on the silica spheres; (2) ultrafine and uniform silver nanoparticles on the silica spheres.The morphology of the core-shell structure was observed by scanning electronic microscopy (SEM) and transmission electronic microscopy (TEM). Use HR-TEM and X-ray diffraction pattern (XRD) to identify the crystal plane of silver particles. Furthermore, the X-ray photoelectron spectroscopy (XPS) experiment exhibits the chemical shift of binding energy. The results indicated the electrons were transferred from Ag particles to SiO2 confirming the chemical absorption between the silver particles and silica spheres.The surface plasmon resonance (SPR) peak depended on the morphology of SiO2/Ag core-shell structure and was observed by ultraviolet / visible spectroscopy (UV-Vis) and TEM.The Mie scattering theory and the dipolar coupling effect of neighboring silver particles as a whole may serve as the mechanism of optical properties. Furthermore, the observed SPR band could be tailored as expected by the modeling of optical properties. By adjusting appropriate parameters: (1) various size and coating density of silver particles; (2) various thickness of silver shell, a core-shell structure models and optical modes corresponding to the experimental results can be designed.