The photocatalytic properties of titanium dioxide are well known and have many applications including the removal of organic contaminants and production of self-cleaning glass. There is an increasing interest in the application of the photocatalytic properties of TiO(2) for disinfection of surfaces, air and water. Reviews of the applications of photocatalysis in disinfection (Gamage and Zhang 2010; Chong et al., Wat Res 44(10):2997-3027, 2010) and of modelling of TiO(2) action have recently been published (Dalrymple et al. , Appl Catal B 98(1-2):27-38, 2010). In this review, we give an overview of the effects of photoactivated TiO(2) on microorganisms. The activity has been shown to be capable of killing a wide range of Gram-negative and Gram-positive bacteria, filamentous and unicellular fungi, algae, protozoa, mammalian viruses and bacteriophage. Resting stages, particularly bacterial endospores, fungal spores and protozoan cysts, are generally more resistant than the vegetative forms, possibly due to the increased cell wall thickness. The killing mechanism involves degradation of the cell wall and cytoplasmic membrane due to the production of reactive oxygen species such as hydroxyl radicals and hydrogen peroxide. This initially leads to leakage of cellular contents then cell lysis and may be followed by complete mineralisation of the organism. Killing is most efficient when there is close contact between the organisms and the TiO(2) catalyst. The killing activity is enhanced by the presence of other antimicrobial agents such as Cu and Ag.

TiO 2 coated surfaces are increasingly studied for their ability to inactivate microorganisms.The activity of glass coated with thin films of TiO 2 , CuO and hybrid CuO/TiO 2 prepared by atmospheric Chemical Vapour Deposition (Ap-CVD) and TiO 2 prepared by a sol-gel process was investigated using the inactivation of bacteriophage T4 as a model for inactivation of viruses. The chemical oxidising activity was also determined by measuring stearic acid oxidation. The results showed that the rate of inactivation of bacteriophage T4 increased with increasing chemical oxidising activity with the maximum rate obtained on highly active sol-gel preparations. However these were delicate and easily damaged unlike the Ap-CVD coatings. Inactivation rates were highest on CuO and CuO/TiO 2 which had the lowest chemical oxidising activities. The inactivation of T4 was higher than that of Escherichia coli on low activity surfaces. The combination of photocatalysis and toxicity of copper acted synergistically to inactivate bacteriophage T4 and retained some selfcleaning activity. The presence of phosphate ions slowed inactivation but NaCl had no effect. The results show that TiO 2 /CuO coated surfaces are highly antiviral and may have applications in the food and healthcare industries.

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This paper describes the growth and testing of highly active biocidal films based on photocatalytically active films ofTiO2, grown by thermal CVD, functionally and structurally modified by deposition of nanostructured silver via a novel flame assisted combination CVD process. The resulting composite films are shown to be highly durable, highly photocatalytically active and are also shown to possess strong antibacterial behaviour. The deposition control, arising from the described approach, offers the potential to control the film nanostructure, which is proposed to be crucial in determining the photo and bioactivity of the combined film structure, and the transparency of the composite films. Furthermore, we show that the resultant films are active to a range of organisms, including Gram-negative and Gram-positive bacteria, and viruses. The very high-biocidal activity is above that expected from the concentrations of silver present, and this is discussed in terms of nanostructure of the titania/silver surface. These properties are especially significant when combined with the well-known durability of CVD deposited thin films, offering new opportunities for enhanced application in areas where biocidal surface functionality is sought.

The article reports on structure, mechanical, optical, photocatalytic and biocidal properties of Ti–Ag–O films. The Ti–Ag–O films were reactively sputter-deposited from a composed Ti/Ag target at different partial pressures of oxygen on unheated glass substrate held on floating potentialUfl. It was found that addition of ~2 at.% of Ag into TiO2film has no negative influence on UV-induced hydrophilicity of TiO2film. Thick (~1,500 nm) TiO2/Ag films containing (200) anatase phase exhibit the best hydrophilicity with water droplet contact angle (WDCA) lower than 10° after UV irradiation for 20 min. Thick (~1,500 nm) TiO2/Ag films exhibited a better UV-induced hydrophilicity compared to that of thinner (~700 nm) TiO2/Ag films. Further it was found that hydrophilic TiO2/Ag films exhibit a strong biocidal effect under both the visible light and the UV irradiation with 100% killing efficiency ofEscherichia coliATCC 10536 after UV irradiation for 20 min. Reported results show that single layer of TiO2with Ag distributed in its whole volume exhibits, after UV irradiation, simultaneously two functions: (1) excellent hydrophilicity with WDCA < 10° and (2) strong power to killE. colieven under visible light due to direct toxicity of Ag.