Fabrication and nonlinear optical investigations of SiO2@Ag core-shell nanoparticles

Abstract

SiO2@Ag core-shell nanoparticles were successfully prepared by a facile and simplified synthesis strategy. Initially, the SiO2 nanospheres were synthesized without functionalization using any silanols. Subsequently, by higher loading of Ag particles onto SiO2 nanospheres, positively charged Ag(NH3)2+ ions were treated with negatively charged SiO2 surface followed by a reduction reaction to obtain SiO2@Ag core-shell nanoparticles. The resultant Ag nanoparticles exhibit a strong absorption band at 410nm over the amorphous SiO2 nanospheres. FTIR spectroscopy evidenced the presence of amine and nitro compounds in the products and revealed that the SiO2 surface is mostly filled with Ag NPs. The crystal structure and chemical composition were examined by Powder XRD analysis and X-ray photoelectron spectroscopy respectively. The FESEM micrographs visualized the successful formation of SiO2@Ag core-shell NPs and EDS analysis confirmed the higher loading of Ag NPs. The optical nonlinearity was examined by z-scan measurement at the excitation wavelength of 632.8nm using a continuous wave red He-Ne laser.