Optical Resonances of the Systems of Nanoparticles with a Metallic Shell

Characteristic features of the formation of the plasma resonance absorption spectra of double-layer nanoparticles with a dielectric core and metal shell were investigated theoretically and experimentally. Two peaks of the surface plasma resonances were observed with the example of an AgI–Ag system. The model of the conductivity electron free path limitation suggested by Kreibig for describing the dimensional dependence of the optical constants of homogeneous spherical metal nanoparticles was extended to the case where metal is concentrated in the shell of the particle. It is established that allowance for the dimensional effect leads to a decrease in plasma resonance absorption and expansion, with the two-peak band structure being preserved. The influence of the metal shell granularity and the degree of the polydispersity of particles on the spectral position, halfwidth, and absolute value of absorption resonances was investigated.