Photocatalytic evaluation and characterization of TiO-riboflavin phosphate film: analysis of reactive oxygen species.

The effect of Riboflavin-5'-phosphate (RFPO) sensitization on photocatalytic properties of TiO film was studied. RFPO was adsorbed on film surface to investigate the photophysical properties of TiO upon blue-light photoexcitation. The film was characterized through scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and diffuse reflectance spectroscopy. The efficiency of the TiO/RFPO film was tested for pollutant elimination in aqueous media in a visible-light-driven system. The phenol paradigmatic model was employed in an aqueous solution as a contaminant target. TiO/RFPO sensitized photodegradation of phenol, which produces catechol, hydroquinone, and benzophenone, was monitored by absorption spectroscopy and HPLC. The results indicated that phenol degradation with TiO/RFPO film was due to the photogeneration of two reactive oxygen species, singlet molecular oxygen (O(Δ)) and superoxide radical anion (O) identified through specific detection techniques. The presence of O(Δ) is reported here for the first time as generated from a sensitized TiO film upon visible-light photoirradiation. Based on the photophysical determinations, a photocatalytic mechanism for TiO/RFPO was established.