Optical properties of γ-Fe2O3 nanoparticles dispersed on sol–gel silica spheres

Two types of γ-Fe2O3 nanoparticles, pure γ-Fe2O3 and γ-Fe2O3 dispersed on sol–gel silica spheres (γ-Fe2O3/SiO2) in thin film form were prepared by the sol–gel technique. Transmission electron microscopy, X-ray diffraction, optical transmittance and FTIR studies along with photoluminescence measurements were carried out for characterizing the samples. The X-ray diffraction patterns of both γ-Fe2O3 nanoparticles and γ-Fe2O3/SiO2 indicated their phase-pure forms which were supported by the FTIR spectra. The average sizes of the nanoparticles obtained from transmission electron microscopy studies were ∼4 nm for both types of samples. Optical transmittance studies indicated direct allowed transitions with two band gaps at ∼2.43 and 3.07 eV. Although both types of samples showed excitonic luminescence at ∼2.38 eV (at room temperature), the luminescence intensity of the γ-Fe2O3/SiO2 was higher than that of pure γ-Fe2O3.