Photocatalytic disinfection of phytopathogenic bacteria by dye-sensitized TiO2 thin film activated by visible light

Synthetic pesticides have been used to control plant diseases or pests for a long time. The public has been affected by many problems such as environmental pollution and health issues from synthetic pesticide use in agriculture. It has consequently become necessary to develop alternative methods for the control of plant diseases. The TiO2 photocatalyst technique has potential for agricultural application because it will not form dangerous compounds. However, UV is only about 3% of the light existing in the solar spectrum. This limits TiO2 photocatalytic disinfection application under visible light irradiation. Our current research emphasizes the improvement of TiO2 thin film photocatalytic efficiency under visible light (λ > 400 nm) by doping a novel photosensitive dye (5, 10, 15, 20-tetraphenyl-21H, 23H-porphine nickel, TPPN) using the sol–gel method. These results showed that the TiO2 thin film doped with 200 μM of TPPN had high indigo dye photodegrading efficiency. The inhibition rates of TiO2/TPPN thin film illuminated by visible light against phytopathogenic bacteria including Enterobacter cloacae SM1, Erwinia carotovora subsp. carotovora 3 and E. carotovora subsp. carotovora 7 which induced severe soft/basal rot disease in vegetable crops were all more than 90%. These evidence suggest that the TiO2/TPPN thin film under visible light irradiation has the potential for direct application to plant protection in irrigation water systems.