Investigation of Some Physical Properties of Cobalt Doped MoO3 Nanofilms and Their Effects on the Degradation of the Methylene Blue Solution under UV Illumination

Abstract—Pristine and Cobalt (Co)-doped MoO3 nanofilms were synthesized on glass substrates using the spray pyrolysis method. The nanometric pristine MoO3 films were prepared from the 10 -2 M.L -1 solution of ammonium molybdate tetrahydrate [(NH4)6Mo7O24,4H2O] in distilled water. Co-doping at 0.5, 0.75 and 1% was obtained by adding cobalt (II) chloride hexahydrate (Cl2CoH12O6) in the pristine solution. The structure and the morphology of the films were investigated by X-ray diffraction and atomic force microscopy. Two pronounced (020) and (040) peaks corresponding to the orthorhombic structure phase of α-MoO3 were detected. The AFM observations showed the formation of micro-plates parallel to the surface plane with a roughness ranging from 33 nm to 54 nm. Optical properties were investigated through reflectance, transmittance and photoluminescence measurements. The optical band gap, the Urbach energy and the refractive index were deduced from these measurements. The presence of oxygen vacancies were revealed from the interband transitions in the blue and green domains. Co-doped MoO3 nanofilms showed ferromagnetic behavior. Photocatalytic degradation of aqueous solution of methylene blue (MB) under UV irradiation in the presence of Co-MoO3 nanofilms has been carried out using UV-visible spectrometer by monitoring the absorption of the solution of MB. The intensity of the absorption peak recorded toward 660 nm was deceased with the increase of the UV-illumination time and the color of the initial MB solution was drastically degraded.