The bactericidal properties of TiO2 are attributed to the high redox potential of the surface species also known as ROS, such as hydroxyl radical (radical dotOH), superoxide radical (View the MathML source), hydrogen peroxide (H2O2) formed by photo-excitation. The type and the source of TiO2 plays an important role during bacterial inactivation because the rate of formation of ROS is a function of the particle size, crystalline phase, the isoelectric point, specific surface area of the nanostructure