Antimicrobial properties of highly efficient photocatalytic TiO₂ nanotubes

A rapid chlorine-based electrochemical anodization method resulted in the production of free-standing bundles of titania (TiO₂) nanotubes with high-aspect ratio (up to 100μm long and about 20nm in diameter). XRD and Raman spectroscopy revealed the presence of partially crystalline amorphous titania nanostructures modified with surface hydroxyl groups. Photocatalytic antimicrobial properties of these nanotubes have been investigated using Escherichia coli and Staphylococcus aureus and compared with a commercial reference sample, Evonic-Degussa P25. Titania nanotubes were found to be highly efficient in inactivating both E. coli (97.53%) and S. aureus (99.94%) in under 24h of UV irradiation. On the other hand, commercial Evonik Degussa P-25 titania nanoparticles and control samples did not reveal antimicrobial properties for the same amount of time under either light or dark conditions. These results indicate that along with material properties, the high-aspect ratio nanotube architecture, surface hydroxyls, physicochemical properties of TiO₂ nanotubes as well as experimental conditions of the biological investigations play a significant role in the antibacterial activity.