Influence of Fe Ions on the Optical Properties of Fe–ZnO Inverse Opals

Abstract

In this work we study the influence of Fe ions doping concentration on the optical properties of ZnO inverse opals. The ZnO inverse opals were obtained by impregnating the PMMA opal template with a zinc acetate solution. After the solidification of this solution in the void spaces of the synthetic PMMA and the thermal removal of the PMMA template, it remained a regular 3-D ordered porous ZnO solid which constitutes an inverse opal. The ZnO:Fe inverse opals were obtained following the same procedure but using zinc acetate and iron nitrate solutions instead. Scanning Electron Microscopy (SEM) images show the close-packed self-assembly of PMMA opals, the surface morphology of ZnO inverse opals formed by spherical void spaces of 295 nm diameter, and a discontinuous surface morphology of the ZnO:Fe inverse opals. The XRD diffractogram of ZnO inverse opals shows peaks characteristic of ZnO with wurtzite phase, and the micro-Raman spectrum shows phononic lines corresponding also to the same crystallographic structure. The energy band gap of ZnO and ZnO:Fe inverse opals were calculated from their absorption spectra giving the values of 3.2 and 2.4 eV, respectively.