Fig. 3
FDTD simulation results for the intensity trend along with the change of spacing. a Ag nanoparticles coated with 5 nm SiO2, the distance between Ag@SiO2 nanostructures is 14 nm. b Distance between Ag@SiO2 nanostructures is 10 nm. c Distance between Ag@SiO2 nanostructures is 4 nm. d Distance between Ag@SiO2 nanostructures is 0 nm. e Ag nanoparticles coated with 20 nm SiO2; here, we denoted the distance between Ag@SiO2 nanostructures as −16 nm. f Variation of the SERS intensity along with the spacing between nanoparticles