Homogeneous and transparent sulfur and nitrogen (S, N)-codoped TiO2 nanocrystalline thin films were
deposited on glass substrates by sol gel dip coating method using thiourea (Tu) as a source of sulfur
and nitrogen. The surface structure of the films was modified by addition of different concentrations
of polyethylene glycol (PEG) into the TiO2 sol. The equal powders of pure and modified TiO2 were also
prepared to compare of their photocatalytic activity with films.
The films and powders were characterized by different techniques like diffuse reflectance UV–Vis
spectroscopy (DRS), X-ray diffraction (XRD) and scanning electron microscopy equipped with energy
dispersive X-ray microanalysis (SEM-EDX).
DRS exhibited a shift in optical absorption wavelength to visible region and XRD analysis showed that
only the anatase TiO2 formed in both of film and powder. The photocatalytic activity was evaluated
by the degradation of methyl orange (MO) as a model. The modified TiO2 films and powders showed
excellent visible-light photocatalytic ability for the degradation of MO under both irradiation of visible
and sun light. So that, up to 96% MO can be decomposed in sun light only within 3 h in the presence of a
modified TiO2 film consist of Tu/TiO2 molar ratio of 0.45 and 0.9 g PEG. On the other hand, MO solution
was discolored completely under sun light in 75 min in the presence of the modified TiO2 powder.