Iron-doped photocatalytic TiO2 sputtered coatings on plastics for self-cleaning applications

Titanium dioxide is among the few semiconductors that have good chemical/photochemical stabilities and high oxidation power. However, its relatively high band gap makes it only effective when exposed under UV light. It has been found that the addition of transition metals to TiO2 can improve the photocatalytic activity by UV irradiation and extend its use in the visible region of the electromagnetic spectrum. In this work, the reactive magnetron sputtering method was used to prepare pure and Fe-doped titanium dioxide thin films. The films were deposited onto microscope glass slides and polycarbonate plates at different total pressures and iron-doping concentrations. The morphology of the films was analysed by atomic force microscopy (AFM) and their structure by X-ray diffraction (XRD). The effect of Fe-doping and total sputtering pressure on the photocatalytic activity, was evaluated by measuring the degradation rates of the rhodamine-B (RhB) dye under UV irradiation. The experimental results show that the deposited TiO2 films on the glass substrate were of the anatase phase with a 〈0 0 4〉 preferred orientation. On contrary, for TiO2 films deposited on the polycarbonate substrate only an amorphous structure was obtained. The crystallite sizes of the films were 4.1 and 7.1 nm for TiO2 films deposited at total sputtering pressures of 0.4 and 0.5 Pa, respectively. The iron doped films resulted in the light absorbance shifting to the visible range of the electromagnetic spectrum. In general, iron doping led to a decrease in the photocatalytic activity of TiO2 films deposited on both substrates. However, the highest photodegradation rates were obtained for films deposited on the polymer substrate under the lower total pressure of 0.4 Pa.