. Nanoparticles
Total three different types of commercial TiO2 NPs (referred as T1, T2 and T3) of known characteristics (Table 1) were used in this study. Samples T1 and T2 were of anatase crystal phase with 10–25 nm size and >99% purity. While sample T3 is mixture of anatase/rutile phase (∼80:20 wt %) with ∼21 nm size and >99.5% purity. The details of the nanoparticle characteristics as provided by the individual manufacturer were listed in Table 1. Aqueous suspensions of TiO2 NPs at 1 mg/mL concentration were prepared by sonication in water-bath (Model # FS30, Fisher Scientific, Waltham, MA, USA) for about 1 h at 23 °C using sterile deionized water. The suspensions were prepared fresh every time prior to each photocatalytic disinfection experiment.