title: Lasting antibacterial activities of Ag-TiO2/Ag/a-TiO2 nanocomposite thin film photocatalysts under solar light irradiation.
abstract: Photodegradation of Escherichia coli bacteria in presence of Ag-TiO(2)/Ag/a-TiO(2) nanocomposite film with an effective storage of silver nanoparticles was investigated in the visible and the solar light irradiations. The nanocomposite film was synthesized by sol-gel deposition of 30 nm Ag-TiO(2) layer on approximately 200 nm anatase(a-)TiO(2) film previously doped by silver nanoparticles. Both Ag/a-TiO(2) and Ag-TiO(2)/Ag/a-TiO(2) films were transparent with a SPR absorption band at 412 nm. Depth profile X-ray photoelectron spectroscopy showed metallic silver nanoparticles with diameter of 30 nm and fcc crystalline structure were self-accumulated on the film surface at depth of 5 nm of the TiO(2) layer and also at the interface of the Ag-TiO(2) and a-TiO(2) films (at depth of 30 nm). Both OH(-) bounds and H(2)O contents were concentrated on the film surface and at the interface, as a profit in releasing more ionic (not metallic) silver nanoparticles. Antibacterial activity of the nanocomposite film against E. coli bacteria was 5.1 times stronger than activity of the a-TiO(2), in dark. Photo-antibacterial activity of the nanocomposite film exposed by the solar light was measured 1.35 and 6.90 times better than activity of the Ag/a-TiO(2) and a-TiO(2), respectively. The main mechanism for silver ion releasing was inter-diffusion of water and silver nanoparticles through pores of the TiO(2) layer. Durability of the nanocomposite film was at least 11 times higher than the Ag/a-TiO(2) film. Therefore, the Ag-TiO(2)/Ag/a-TiO(2) photocatalyst can be nominated as one of the effective and long-lasting antibacterial nanocomposite materials.
authors.affiliation: Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran, Iran. oakhavan@sharif.edu
authors.forename: O
authors.initials: O
authors.lastname: Akhavan
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D004926:Escherichia coli / Q000502:physiology; D008027:Light; D050296:Microbial Viability / Q000187:drug effects*; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D055668:Photochemical Processes; D011827:Radiation; D012834:Silver / Q000737:chemistry / Q000494:pharmacology*; D016082:Solar System; D014025:Titanium / Q000737:chemistry / Q000494:pharmacology*; D014961:X-Ray Diffraction
chemical_list: D000900:Anti-Bacterial Agents; C009495:titanium dioxide; D012834:Silver; D014025:Titanium