Cooperative surface-enhanced Raman spectroscopy enhancement in Au nanorod/SiO2 nanoparticle solutions

Abstract

Surface-enhanced Raman spectroscopy (SERS) signals in liquid state are significantly enhanced by utilizing cooperative interaction between metal surface plasmon and dielectric resonance. Raman signals from the diluted solutions are very weak even if they are amplified by SERS using Au nanorods. When SiO2 nanoparticles are added together with Au nanorods, however, Raman intensity increased by three order comparing with that of system containing only Au nanorods. Finite-difference time-domain simulations show that SiO2 nanoparticles exhibit dipolar electric resonance, which is strongly enhanced by interacting with the surface plasmon of Au nanorods. The size and concentration of SiO2 nanoparticles are optimized to 354 nm in diameter and 4.5 vol%. Under the optimized condition, SERS intensity decrease with concentration of analyte (rhodamine 6G or crystal violet) is much slower for the system containing both Au nanorods and SiO2 nanoparticles than that of the system containing only Au nanorods. The detection limit is 10(-10) M for both aqueous rhodamine 6G and crystal violet solutions.