Remote Bactericidal Effect of Anatase TiO2 Photocatalytic Nanoparticles Annealed with Low-Temperature O2 Plasma

The remote bactericidal effect of TiO2 photocatalyst, i.e., the bactericidal effect away from the photocatalyst, was successfully achieved using a humidified airflow. The TiO2 photocatalyst used was anatase-type TiO2 nanoparticles(NPs)annealed with a low-temperature O-2 plasma. For comparison, anatase-type TiO2 NPs annealed in the air were used. The bacteria, Bacillus subtilis, were placed away from the TiO2 NPs. The plasma-assisted- annealed TiO2 NPs significantly inactivated 99% of the bacterial cells in 5 h, whereas the pristine and air-annealed TiO2 NPs inactivated 88- 90% of the bacterial cells. The remote bactericidal effect of plasmaassisted-annealed TiO2 NPs would be attributed to a larger amount of H2O2 molecules traveled by the airflow from the TiO2 NPs. The molecules were generated by chemically reacting more photoexcited carriers on the TiO2 surface with H2O and O-2 in the airflow. These photoexcited carriers originated from more oxygen- based species adsorbed and more oxygen vacancies introduced on the TiO2 surface by the plasma-assisted-annealing.