Tailoring plasmonic properties of Ag-SiO2 nanorods and their surface-enhanced Raman scattering activities

Due to a wide range of applications, plasmonic properties of metal nanoparticles have been widely explored, while the understanding of plasmonic behaviors of dielectric-metal composites is still limited. Herein, as a proof of concept, the relationship between compositions and plasmonic behaviors of Ag-SiO2 composites was investigated considering their extensive utilization as SERS substrates. Ag-SiO2 nanorods with regulated compositions were fabricated via glancing angle co-deposition. By increasing Ag relative deposition rate, structure of Ag-SiO2 nanorods evolves from Ag nanoparticles embedded into SiO2 matrix to quasi-one-dimensional Ag structure, inducing plasmon resonance changes over a wide range and corresponding SERS activity variations. Plasmonic resonance resulted from individual Ag nanoparticle, coupling effect of Ag nanoparticles, and quasi-one-dimensional Ag nanorods can be observed successively as Ag content increases in Ag-SiO2 nanorods. Meanwhile, SERS performance of Ag-SiO2 corresponds well with their plasmon behaviors and the maximum SERS signal was obtained from Ag-SiO2 composites with quasi-one-dimensional Ag structure. With the optimization of plasmon and SERS performance of Ag-SiO2 nanorods, we demonstrated the potential use of Ag-SiO2 nanorods in real applications as SERS chemical sensors for the detection of melamine.