pointed out that the differences in particle size, surface area and charge among different varieties of TiO2 in powder affect the photocatalytic efficiency. In current study, though sample T1 and T2 have similar size distribution (10–25 nm), T2 has showed more bactericidal activity compared to sample T1 under similar test conditions. This difference could be attributed to the high particle specific surface area (SSA) of T2 (200–240 m2/g) compared to T1 (50–150 m2/g). Increasing the particle surface area provides high relative OH− ion coverages for hydroxyl radical (OH·) formation which is an important ROS responsible for photocatalytic disinfection. In contrast, sample T3 with mixed phase of anatase (∼80%) and rutile (∼20%), an average particle size of ∼21 nm and relatively low SSA (35–65 m2/g) have showed highest bactericidal activity than T1 and T2.