Theoretical Study of Local Surface Plasmon Resonances on a Dielectric-Ag Core-Shell Nanosphere Using the Discrete-Dipole Approximation Method

The local surface plasmon resonances（LSPRs） of dielectric-Ag core-shell nanospheres are studied by the discretedipole approximation method.The result shows that LSPRs are sensitive to the surrounding medium refractive index,which shows a clear red-shift with the increasing surrounding medium refractive index.A dielectric-Ag core-shell nanosphere exhibits a strong coupling between the core and shell plasmon resonance modes.LSPRs depend on the shell thickness and the composition of dielectric-core and metal-shell.LSPRs can be tuned over a longer wavelength range by changing the ratio of core to shell value.The lower energy mode ω;shows a red-shift with the increasing dielectric-core value and the inner core radius,while blue-shifted with the increasing outer shell thickness.The underlying mechanisms are analyzed with the plasmon hybridization theory and the phase retardation effect.