Iron oxide thin films have been deposited over fused quartz substrate by simple metal organic deposition from Fe-(III) acetylacetonate as the organic precursor. The decomposition of Fe-acetylacetonate is characterised by its distinct transition temperatures and thermogravimetric loss rates, which have been measured by thermal gravimetric analysis. As-deposited films were sintered in the temperature range 365-800 degreesC and the structural changes of the iron oxide thin films as they transform into different crystalline phases have been studied by X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible absorption spectroscopy and scanning electron microscopy techniques. Mainly amorphous gamma -Fe2O3, is formed at an annealing temperature of approximately 365-400 degreesC which transforms to alpha -Fe2O3 phase with a further increase (600-800 degreesC) in sintering temperature. The film sintered at 800 degreesC consists of mainly crystalline alpha -Fe2O3 phase, which shows photocatalytic degradation of an oxygenated aqueous solution of phenol upon visible light illumination.