Wüest M. 51 Wykes M. 82 Yamaguchi M. 17 Ybarra G. 129 Yubero F ...

JUNE 28 WEDNESDAY AFTERNOON
RIVA-TF-WeA-P.2 PHOTOCATALYTIC DEGRADATION OF COMMERCIAL DYES
USED IN THE TEXTILE INDUSTRY BY THE DEPOSITION TiO 2 THIN FILMS ON
GLASS SUBSTRATES. S.M. Marques 1 , C.J. Tavares 1 , V. Teixeira 1 , J.O. Carneiro 1 , A.J. Fernandes
2 .
1 Departamento de Física, Universidade do Minho, 4800-058 Guimarães, Portugal.
2 Departamento de Física, Universidade de Aveiro, 3810-193 Aveiro, Portugal
ctavares@fisica.uminho.pt
The interest in nanoparticle photocatalytic titania (TiO 2 ) thin films has been increasing over the last
few years, due to the self-cleaning nature of these coatings. They have been used on industrial applications,
mainly due their ability to degrade pollutants dissolved in water. Titania acts as a photocatylist
for the dissociation of organic impurities on a particular surface, such as glass. The driving
force behind this photocatalisation is simply ultraviolet (UV) light and atmospheric oxygen. The thin
films of titania were deposited by unbalanced reactive magnetron sputtering, from a high purity Ti
target in an Ar/O 2 atmosphere, with an argon flow rate of 60 sccm (working gas) and a variable oxygen
flow rate in he range of 1.5-9 sccm (reactive gas). Due to the fact that the deposition temperature
is rather low (≈ 200ºC), the titanium dioxide particles that nucleate on the substrate do not have sufficient
energy and mobility to crystallise in a regular lattice, such as Brookite, Anatase or Rutile. In
order to achieve this thermodynamical equilibrium and enhance the composition between the crystallographic
phases, after deposition the samples were thermally annealed in a high vacuum furnace at
different temperatures, 300ºC, 400ºC and 500ºC for 2 hours. In order to comprehend the underlying
structure, X-ray diffraction measurements were then preformed in these heat treated samples and the
composition of the films was study by Rutherford Backscattering spectroscopy (RBS). We also estimated
the thickness of the films made with different flow rates of oxygen and with different times of
deposition, using the Swanepoel’s method for the calculation of the optical properties of the coatings.
The photocatalytic behaviour of the titania coatings was assessed by combined ultra-violet irradiation
and absorption measurements of particular dyes. The observed photo-decomposition of the
aqueous solution (organic pollutants) was measured in the UV/Vis Spectrum by the decrease of the
maximum absorbance with irradiation time. The colour of the dye becomes colourless during this
process, hence indicating that the chemical oxidation-reduction mechanisms abound on the surface
of the titania films. As pollutants, we used dyes that are currently used in the textile industry, as it is
the case of the reactive dye “RED 41”.
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