Theoretical and experimental investigations of plasmonic properties of Ag nanosphere and SiO2/Ag core-shell nanostructure

Due to localized surface plasmon resonance (LSPR) properties of plasmonic nanostructures, the electric field is enhanced in their vicinity which is exploited for sensing. Here, the LSPR properties of an Ag nanosphere and a SiO2/Ag core-sell are theoretically studied and their characteristics are experimentally investigated. The theoretical study of the nanostructures showed one intensive plasmon mode whereas only SiO2/Ag core-shell showed the tunable plasmonic properties so that it can be tuned to the desired spectral region by changing core-shell design and the refractive index of the surrounding medium. Optimized SiO2/Ag core-shell showed significant LSPR sensitivity up to 523.6 nm/RIU. SiO2/Ag core-shells were prepared using modified Stober method. By controlling the reaction conditions, nanoparticles with the size of similar to 50 nm were fabricated without using a coupling agent, based on the mixture of silver ions in solution including water, ethanol and ammonia, for the direct synthesis of SiO2/Ag core-shells with no aggregation.