Surface plasmon resonances in ellipsoidal bimetallic nanoparticles

The surface plasmon response of three-layered bimetallic nanoparticles embedded in a SiO2 host matrix is studied for different geometries. The analytical solution for the electromagnetic response in relation to the extinction cross section of the bimetallic nanoparticles is obtained by means of quasistatic theory. To show the extinction spectra of the three-layered bimetallic nanoparticles, we chose two different metals, namely, Ag and Au-Ag 50:50 alloy. The optical properties of the metals studied are described within the modified Drude-Sommerfcld model of the dielectric function with parameters accounting for the contribution of conduction electrons and interband transitions. We found that the position of the surface plasmon resonance depends on the dielectric function of the intermediate medium between the Au-Ag 50:50 alloy core and the Ag shell, the thickness of the Ag shell, the thickness of the intermediate medium, and the aspect ratio of the three-layered nanoparticles.