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. Graphical abstract: [Figure not available: see fulltext.].