The effect of local dielectric environment on the resonance light scattering of Au–Ag bimetallic nanotube

In this study, electrodynamic calculations were used to investigate the resonance light-scattering (RLS) properties of dielectric–Au–Ag double nanotube. It has been found that the scattering spectrum exhibits at most three pronounced RLS peaks in the visible region, and the RLS band number could be fine tuned by changing the dielectric constant of the inner dielectric wire. The outer dielectric surrounding also greatly affects the intensity and wavelength position of the RLS. The RLS with the longest wavelength (denoted as peak3) is always enhanced with the increase of the outer surrounding dielectric constant, i.e., ε₄. Whereas the ε₄-dependent scattering intensity change of RLS at middle wavelength becomes non-monotonous when the Ag-coating thickness is much smaller than that of Au wall. On the contrary, the ε₄-dependent scattering intensity change of RLS at shorter wavelength becomes non-monotonous when the Ag-coating thickness is much larger than that of Au wall. Although peak3 has a longer wavelength when the inner wire dielectric constant ε₁ has a large value, the ε₄-dependent wavelength shift has been decreased; as the wavelength shift has been decreased, ε₁ is increased. Similarly, although peak3 has a longer wavelength when the Ag coating has a small thickness, the ε₄-dependent wavelength shift has been decreased as the Ag-coating thickness is decreased. These calculating results about local dielectric environment-dependent RLS present a potential for design and fabrication of optical refractive index nanosensors based on light scattering.