Photosensitised Degradation of Organic Dyes by Visible Light Using Riboflavin Adsorbed on the Surface of TiO₂ Nanotubes

Visible light-assisted degradation of indigo carmine (IC), methylene blue (MB) and methyl orange (MO) aqueous solutions has been achieved on the surface of TiO₂ nanotube (NT) arrays impregnated with riboflavin (RF). Diluted RF water solutions in the presence of RF-TiO₂ NTs irradiated with UV light produced O₂, CO and CO₂ as main gas products. On the contrary, the same solutions irradiated with visible light evolved O₂ as a main product. This in situ O₂ generation under visible light absorption allows the degradation of the dyes without the necessity to bubble air or oxygen in the reaction system The photocatalytic degradation of MO, MB and IC can be described by a pseudo-first-order kinetic model obtaining ca. 100% degradation of MB, MO and IC in less than 3 h of visible light illumination. The results provided here are highly promising in view of various photocatalytic applications of the prepared RF-TiO₂ NTs catalysts by two environmentally friendly compounds in the degradation of pollutants using solar radiation.

sensitiser; titanium dioxide; riboflavin; nanotubes; visible light