12 research outputs found
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
Singlet oxygen generation in the presence of titanium dioxide materials used as sunscreens in suntan lotions
Photocatalytic activity of 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
Photosensitized films on polymers : titania-polymer interactions and visible light induced photoactivity
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
New insight into singlet oxygen generation at surface modified nanocrystalline : the effect of near-infrared irradiation
Photocatalytic activity of 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