Synthesis, optical properties and modeling of silver core-silver oxide shell nanostructures in silica films

Sol−gel silica films containing silver ions were annealed in a rich−hydrogen atmosphere and subsequently in a rich−oxygen atmosphere. High resolution transmission electronic microscopy measurements shown unusual core−shell structures of silver−silver oxide nanoparticles in these films. The optical properties of these nanostructures exhibited red shift and damping in the UV-vis spectra. In order to calculate the optical properties were used the Mie theory using two approaches. The first one, corresponding to the core−shell model that includes a refractive index of the shell (ns) different to the one of the host matrix (nm). While in the second approach, we replaced in the Mie theory the refractive index of the environment (silica) by a local refractive index (nl) depending on the thickness of the silver oxide shell. Both calculations given the same results because they are equivalents