The prospective application of luminescence to imaging devices is shown using a combination of color-tunable and patternable mechanoluminescent materials. A white light source is demonstrated by using an alternative color tuning method, induced under high vibration conditions. As the implementation is fairly straightforward, it is expected that the present results will find a number of potential uses in current industrial applications.
A series of novel CVD films of titanium(IV) oxide of different thicknesses, spanning the range 10-91 nm, are prepared on quartz, via the reaction of titanium(IV) chloride and ethyl acetate, using a CVD technique. The films are clear, mechanically robust and comprise thin layer of nanocrystalline anatase titania of different thicknesses that absorb UV light. The UV-Visible spectral profiles of all the CVD TiO2 films of different thickness are the same and obey Lambert's law (absorbance is porportional to film thickness). A plot of the reciprocal length for the TiO2 coating versus wavelength is reported. The photocatalytic activity of each film to mediate the destruction of a thin layer of stearic acid is investigated. The rate depends directly upon the fraction of light absorbed and the apparent quantum yield for the overall process is 0.00035, which appears low compared with that for sol-gel TiO2 films.
An ink is described which, when printed or coated onto a photocatalyst film, changes colour irreversibly and rapidly upon UV activation of the photocatalyst film and at a rate commensurate with its activity.
The results of a detailed characterization study of a novel UV-activated colorimetric oxygen indicator
are described. The indicator uses nanoparticles of titania to photosensitize the reduction of methylene
blue by triethanolamine in a polymer encapsulation medium, using UVA light. Upon UV irradiation, the
indicator bleaches and remains in this colorless state in the dark, unless and until it is exposed to oxygen,
whereupon its original color is restored. The indicator is reusable and irreversible. The rate of color
recovery is proportional to the level of oxygen present. A layer of PET (poly(ethylene terephthalate)), of
thickness b, placed on top of the indicator film slows down its response, and the 90% recovery time is
proportional to b.
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