Bactericidal Properties of Plasmonic Photocatalysts Composed of Noble Metal Nanoparticles on Faceted Anatase Titania.

Octahedral anatase particles (OAP) with eight equivalent {101} facets and decahedral anatase particles (DAP) with two additional {001} facets were modified with nanoparticles of noble metals (silver, copper, gold and platinum) by photodeposition, and applied for inactivation of Escherichia coli K12. XRD, DRS, XPS and STEM analyses confirmed the presence of noble metals nanoparticles (NPs) on the surface of faceted titania samples. Both OAP and DAP samples modified with silver and copper exhibited high bactericidal activities under visible light irradiation. It was also found that DAP under UV irradiation showed surprisingly high bactericidal activity, which could be attributed to efficient generation of reactive oxygen species, due to intrinsic properties of DAP, i.e., charge carriers' separation (migration of electrons and holes to {101} and {001} facets, respectively). However, an unexpected decrease in activity after DAP modification with gold and platinum NPs (mainly deposited on {101} facets) suggested that bacteria cells were directly decomposed on DAP surface. SEM images revealed that silver-modified samples caused severe damages of cell walls and membranes, due to antibacterial properties of silver (in the dark) and photocatalytic effect under visible and UV irradiation.