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-Fe ₂O₃/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/SiO ₂ was higher than that of pure γ-Fe₂O₃.