Revealing the Hemispherical Shielding Effect of SiO(2)@Ag Composite Nanospheres to Improve the Surface Enhanced Raman Scattering Performance

Many studies widely used SiO(2)@Ag composite nanospheres for surface enhanced Raman scattering (SERS), which mainly contributes to electromagnetic enhancement. In addition to experiments, previous simulations mostly adopted a two-dimensional model in SERS research, resulting in the three-dimensional information being folded and masked. In this paper, we adopted the three-dimensional model to simulate the electric field distribution of SiO(2)@Ag composite nanospheres. It is found that when the Ag nanoparticles are distributed densely on the surface of SiO(2) nanospheres, light cannot pass through the upper hemisphere due to the local surface plasmon resonance (LSPR) of the Ag nanoparticles, resulting in the upper hemisphere shielding effect; and if there are no Ag nanoparticles distributed densely on the surface of SiO(2) nanospheres, the strong LSPR cannot be formed, so the incident light will be guided downward through the whispering gallery mode of the spherical structure. At the same time, we designed relevant experiments to synthesize SiO(2)@Ag composite nanosphere as SERS substrate and used Rhodamine 6G as a probe molecule to study its SERS performance. This design achieved a significant SERS effect, and is very consistent with our simulation results.