Effect of phase transition induced by annealing temperature on wettability, optical and photocatalytic properties of nanostructured iron oxide thin film

Nanostructured iron oxide thin films were prepared by sol-gel method and spin coating technique. The structural properties of samples were extracted from X-ray diffraction. The results indicated that the sample contained both maghemite (gamma-Fe2O3) and hematite (alpha-Fe2O3) phases at 300 A degrees C annealing temperature. The remainder of the maghemite phase transformed entirely to hematite by increasing annealing temperature from 300 to 500 A degrees C. Morphological analysis showed that roughness of surface increased by annealing temperature. Fractal dimension were calculated by two methods which for both of them, it increased by annealing temperature. According to the contact angle measurement, the hydrophilic behavior converts to hydrophobic feature by changing the maghemite phase to hematite. The transparency and band gap of films decreased by phase transition from gamma to alpha. Degradation of Rhodamine B and Methylene blue dyes with iron oxide were investigated. Increasing the annealing temperature enhanced the photocatalytic behavior due to the band gap narrowing induced by phase transition and alpha-Fe2O3 had the best photocatalytic degradation of MB which was reached to 95.4% in 120 min. under visible light irradiation. Whereas it exceeded than 98.6% for RhB in 135 min.