Simulations of the Surface Plasmon Resonances of Au@Ag Core-Shell Nanocubes: Effect of Core-Shell Size Ratio

Abstract

This paper reports a systematic investigation on the optical properties of Au@Ag core-shell nanocubes as a function of the core-shell size ratio with the boundary element method (BEM).The absorption cross sections (nm2) for different light wavelengths are calculated using the full Maxwell equations. Also, the related field enhancements for Au@Ag core-shell nanocubes with an incoming plane wave with a polarization along the x-axis are computed. The surface charge at the resonance wavelength of 400 nm and then the electric fields outside and inside the core-shell nanocubes are mapped. A comparison of plasmonic modes between Au@Ag core-shell and single Ag nanocubes shows that there are minor differences between their responses where the surface plasmonic resonance peak position remains constant with varying the core-shell nanocubes ratio up to 50% in most cases under consideration. However, the maximum values of absorption cross sections increase with increasing the core-shell sizes ratio up to core-shell size ratio equal to 50%. The core-shell size ratio dependence of optical properties described here can be utilized in designing plasmonic nanostructures for applications in biosensors, nonlinear spectroscopy, near-field lithography and plasmonic solar cells.