Synthesis of Carbon Doped TiO₂ Quantum Dots for Photocatalytic Sterilization under the Visible Light Irradiation and the Mechanisms

In this article, the carbon doped TiO₂ (C-TiO₂) quantum dots (QDs) were prepared through the hydrothermal method and calcination. The size of the C-TiO₂ QDs is about 5.7 nm. The doping amount of carbon can be tuned by adjusting the volumes of the carbon source, ethylene glycol added. The carbon atoms are proved to be doped into the interstitial sites of TiO₂ lattice and induce the change of chemical states of Ti 2p and C 1s. The doping of carbon leads to the increasing photocatalytic sterilization of E. coli under the visible light irradiation. The survival rate of E. coli cells over C-TiO₂ is only 1.5 % after 6 h. The reactive oxygen species (ROS), such as hydroxyl radical and superoxide radical, are considered as the primary factors for the photocatalytic sterilization. Due to oxidative stress of the attack by ROS, the enzyme activity per cells increases for self-protection during the photocatalytic sterilization.