Opal-matrix nanocomposites containing metallic nanoparticles

Abstract

A method has been proposed for the fabrication of three dimensional photonic crystals based on ordered opal matrices (OMs), with pores containing iron group metal (M = Ni, Co, Fe) nanoparticles. The core of the method is the reduction of salts and oxides of these metals with supercritical isopropanol. The phase composition of OM/M composites depends on the composition of the starting salts (nitrates or chlo rides): the use of ferric chloride leads to the formation of nanoparticles of solid solutions based on nickel metal, α cobalt, or β cobalt (Ni-Fe and Co-Fe systems) in opal pores; with the corresponding nitrates, we obtain OM/NiCo (cubic solid solution), OM/Fe, OM/Ni 3 Fe, OM/NiFe, OM/CoFe, and OM/NiCoFe nanocomposites. We have measured broadband reflection spectra of the (111) surface of the photonic crystals using a fiber optic technique for taking reflection spectra. The intensity peak in the reflection (band gap) spectrum of the OM/M (M = Fe, Co, Ni) nanocomposites is shown to be shifted to longer wavelengths.