On the Calculation of Optical Characteristics and Dimensional Shifts of Surface Plasmons of Spherical Bimetallic Nanoparticles

Abstract

Formulas of efficient relaxation time are obtained for the cases when the free length of electrons is less or comparable with the characteristic dimensions of metallic regions. The frequency dispersion of optical characteristics of spherical bimetallic particles is calculated near plasma resonance in the absence of quantum-size effects. Retaining the style of common description of metallic particles based on the Mie–Drude theories, the frequency dependence of electric dipole polarizability of a two-layered metallic nanosphere was analyzed. The appearance of two polarizability maxima is the result of a difference in core and shell metals. The calculations are conducted for the following particles immersed into teflon: Au@Ag, Ag@Au, Au@Pt, Pt@Au, and Pt@Pd. It is demonstrated that the optical characteristics of bimetallic particles can be controlled by means of changing their composition and volumetric metal content. Cross-sections of absorption and scattering, as well as optical radiation efficiency of the particles in a wide spectrum range are calculated. Possible temperature of bimetallic particles at the absorption of an electromagnetic wave (for the photothermal therapy of malignant tumors) is estimated.