Fabrication and characterization of oxides.

Abstract

The aim of this work is the synthesis and characterization of ZnO, MgO, Mg: ZnO and Er: MgO for the photocatalytic activity under UV irradiation. The films were synthesized using the sol-gel method and were deposited via dip-coating technique and annealing at Ta = 500 °C; also for NPs preparation, we used the sol-gel method at room temperature; then were annealed at T = 950 °C. Structural, surface morphology and optical characterizations of the thin films and the NPs were studied as a function of the dopant concentration. All the prepared samples were evaluated the photocatalytic activity against methylene blue dye under UV irradiation at room temperature. Structural characterization via XRD showed the formation of hexagonal structure of ZnO for ZnO films, and the formation of MgO cubic structure for MgO films and NPs, while the NPs exhibited also a formation of Er2O3 cubic structure. EDX revealed that Mg had been incorporated into the ZnO, and Er has been also incorporated into MgO. Surface morphology via AFM showed that the RMS values increase with the increase of Mg dopant from 4.46 to 12.30 nm, and the ESEM images showed that the films had wrinkles morphology. While the surface morphology of MgO NPs via TEM revealed that the nanoparticles agglomerate in rounded shaped aggregates with nanometric grain size. Optical characterization revealed that Mg doping enlarged the optical band-gap from 3.28 to 3.40 eV and dropped the Urbach energy from 332 to 322 meV for ZnO films. While the bandgap energy of MgO thin films achieved a value of 4.08 eV lower than the bulk value of MgO 7.8 eV, and for MgO NPs the Er decrease the optical band-gap from 5.87 to 5.46 eV. Finally, photocatalytic activity proved that the addition of Mg and Er as dopants has promoted faster the MB dye degradation for ZnO and MgO, due to multiple factors such as the surface area.