Photocatalytic Degradation of β-carotene with TiO 2 and Transition Metal Ions Doped TiO 2 under Visible Light Irradiation

Abstract

β-carotene, one of the carotenoids, was photodegraded under visible light irradiation by using pure TiO 2 and M-TiO 2 (M= metal; Ag, Fe, Ru). The photocatalysts were prepared by a sol-gel method and incipient wetness impregnation method, and investigated by means of X-ray diffraction and scanning electron microscopy for characterization. The effects of photocatalyst and oxygen content were investigated, which was based on the absorbance at 450 nm of photodegradation of β-carotene as the main index. The study of photocatalytic activity indicated that Ag-doped TiO 2 showed higher photocatalytic activity than other photocatalysts. And also a quick decrease of β-carotene in the presence of oxygen was observed. β-cyclocitral, 5,6-epoxy-β-ionone and dihydroactinidiolide, the main photocatalytic degradation products of β-carotene were confirmed by gas chromatograph-mass spectrometer (GC-MS) analysis. All these degradation products can be used for fragrance and flavoring agents, such as cigarette flavoring ingredients.