Photocatalytic evaluation and characterization of TiO2-riboflavin phosphate film: analysis of reactive oxygen species.

ABSTRACT

The effect of Riboflavin-5'-phosphate (RFPO4) sensitization on photocatalytic properties of TiO2 film was studied. RFPO4 was adsorbed on film surface to investigate the photophysical properties of TiO2 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 TiO2/RFPO4 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. TiO2/RFPO4 sensitized photodegradation of phenol, which produces catechol, hydroquinone, and benzophenone, was monitored by absorption spectroscopy and HPLC. The results indicated that phenol degradation with TiO2/RFPO4 film was due to the photogeneration of two reactive oxygen species, singlet molecular oxygen (O2(1Δg)) and superoxide radical anion (O2·-) identified through specific detection techniques. The presence of O2(1Δg) is reported here for the first time as generated from a sensitized TiO2 film upon visible-light photoirradiation. Based on the photophysical determinations, a photocatalytic mechanism for TiO2/RFPO4 was established.