Visible light induced photocatalytic inactivation of bacteria by modified titanium dioxide films on organic polymers

Commercially available polypropylene foil was pretreated with a low temperature oxygen plasma and covered with a thin fi lm of nanocrystalline titanium dioxide by dip coating. The fi lms were then photos- ensitized by titanium( IV ) surface charge transfer complexes formed by impregnation with catechol. The photoactivity of the coatings up to 460 nm was con fi rmed by photoelectrochemical measurements. The photoinactivation of Escherichia coli and Staphylococcus aureus was evaluated by a glass adhesion test based on ISO 27447:2009(E) in the presence of visible light. The coating showed good antimicrobial activity induced by light from a light-emitting diode (405 nm), in particular towards E. coli ATCC 25922 strain. Adaptation of ISO 27447:2009(E) to assess bacterial photoinactivation by photocatalytic coatings will allow this procedure to be applied for the comparison of photoactivity under a range of irradiation conditions

Photocatalytic activity of TiO2TiO_2 films on Si support prepared by atomic layer deposition

TiO2 films were deposited on the native oxide covered Si(1 0 0) with ALD method. The films were grown applying various numbers of deposition cycles at different temperatures. The resulting coatings possessed different thickness, crystallinity, morphology and roughness. The photocatalytic activity of the films has been studied in the presence of terephthalic acid, Azur B and two herbicides: 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid. Coatings deposited at 350 °C (anatase–rutile composites) show the highest activity in the process of TA oxidation (the highest efficiency of hydroxyl radical generation). The influence of film thickness on photoactivity is more complex and depends on the mechanism of processes to be photocatalysed

On Oxygen Activation at Rutile- and Anatase-TiO2

The rutile form of titanium dioxide (r-TiO2) usually shows a photocatalytic activity lower than that of anatase-TiO2 (a-TiO2). Nevertheless, there are numerous examples of sometimes unexpectedly high activity of r-TiO2. This material may appear to be particularly useful when a noncomplete and selective photocatalytic oxidation of organic substrates is required. On the basis of literature examples and our own studies, we compare the photocatalytic activities of r-TiO2, a-TiO2, and r-TiO2/a-TiO2 composites. Because of a significantly better oxygen adsorption at the surface of r-TiO2 and a lower redox potential of the excited electron, more efficient O2•– production takes place at the surface of rutile. As a consequence, generation of 1O2 (involving O2 reduction and the subsequent oxidation of superoxide) and reduction of H2O2 to OH– and HO• are also favored with this material. Therefore, r-TiO2 can be considered to be a particularly good photocatalyst for activation of molecular oxygen. On the other hand, a-TiO2 appears to be a stronger oxidant. In its presence, efficient HO• generation (the result of water or surface hydroxyl group oxidation) and oxidation of H2O2 to O2•– are observed

Photocatalytic activity of TiO2TiO_2 modified with hexafluorometallates : fine tuning of redox properties by redox-innocent anions

A group of selected hexa fl uorometallates ([AlF 6 ] 3 − , [TiF 6 ] 2 − , [ZrF 6 ] 2 − , and [SiF 6 ] 2 − ) has been adsorbed at the surface of titanium dioxide. Such modi fi cation in fl uenced the electronic and chemical properties of TiO 2 , as well as its photoactivity. The modi fi cation with [TiF 6 ] 2 − inhibited the e ffi ciency of OH • production but enhanced the generation of photocurrent and singlet oxygen. The results of modi fi cations with [ZrF 6 ] 2 − were the opposite generation of 1 O 2 was not observed in this case and photocurrents were lower; however, due to a better OH • production, degradation of herbicides was faster