Nonlinear Dependences of Optical Properties of Spherical Core–Shell Silver–Gold and Gold–Silver Nanoparticles on Their Parameters

Abstract

Modeling of nonlinear optical properties of spherical core–shell gold–silver and silver–gold nanoparticles (NPs) placed in water was carried out on the base of extended Mie theory. Efficiency cross sections of absorption σ abs, scattering σ sca, and extinction σ ext of radiation with wavelengths λ = 400 and 532 nm for core–shell NPs with constant core radii r 00 = 5, 10, 20, and 40 nm and in the range of relative radii r 1/r 00 = 1–8 were calculated (r 1 is the radius of shell). Dependences of optical properties of gold–silver and silver–gold NPs on increasing of core radius r 0 in the range 0 − r 1 under condition r 1 = const and increasing of r 0 under r 1 − r 0 = const were investigated. Results show the nonlinear behavior of optical properties of core–shell gold–silver and silver–gold NPs on radiation wavelengths (optical indexes of metals), different core and shell radii, and their correlation, on relative NP radii r 1/r 00. An increase and decrease of absorption, scattering, and extinction efficiency cross sections of core–shell NPs with changing of wavelengths, core and shell radii, and relative NP radii r 1/r 00 are established. These dependences can be used for experimental investigation of the interesting first stages of shell formation on core and optical determination of core–shell NP parameters.