The results of preparing and studying the properties of heteronanoparticles on the basis of the monodispersed spherical nanoparticles of silicon dioxide of 40, 120, and 350 nm in diameter and a shell of gold of 1 - 10 nm in thickness are presented. It is shown that the maximum in absorption spectra (plasmonic resonance) is determined by the ratio of the diameters of a dielectric core (nanoparticle SiO2) and a conductive (Au) shell. It has been established that heteronanoparticles SiO2/Au possess high catalytic activity in the decomposition reaction of peroxide which is determined by the amount of gold on the surface of a silicon core, and the size and structure of the surface of heteronanoparticles.