Selective Photooxidation of Valencene and Thymol with Nano-TiO 2 and O 2 as Oxidant.

The selective photocatalytic oxidation with O 2 as oxidant of valencene and thymol was evaluated using nanostructured TiO 2 under UV-Vis radiation at atmospheric conditions. The effect of the morphology and optical properties of TiO 2 nanotubes and aminate nanoparticles was studied. Different scavengers were used to detect the presence of positive holes (h + ), electrons (e - ), hydroxyl radicals (•OH), and the superoxide radical anion (O 2 - ) during the photooxidation reaction. Superoxide anion radical is the main oxidizing specie formed, which is responsible for the selective formation of nootkatone and thymoquinone using aminated TiO 2 nanoparticles under 400 nm radiation.