UV and visible light photocatalytic composite Pt and Au-TiO2 coatings have been deposited
on silicon and glass substrates at low temperature using a hybrid ECWR-PECVD/MS-PVD
process. Methylene blue, stearic acid, and sulfamethoxazole were used as dye, organic,
and antibiotic model pollutants, respectively, to demonstrate the efficiency of these
nanocomposite coatings for water decontamination or self-cleaning surfaces applications.
Raman investigations revealed the formation of anatase polymorph of TiO2 in all synthesized
coatings with a shifting of the main vibrational mode peak to higher wavenumber in
the case of Au-TiO2 coating, indicating an increase number of crystalline defects
within this coating. Because of the difference of the chemical potentials of each
of the investigated noble metals, the sputtered metal layers exhibit different morphology.
Pt sputtered atoms, with high surface adhesion, promote formation of a smooth 2D layer.
On the other hand, Au sputtered atoms with higher cohesive forces promote the formation
of 5-10 nm nanoparticles. As a result, the surface plasmon resonance phenomenon was
observed in the Au-TiO2 coatings. UV photoactivity of the nanocomposite coatings was
enhanced 1.5-3 times and 1.3 times for methylene blue and stearic acid, respectively,
thanks to the enhancement of electron trapping in the noble metal layer. This electron
trapping phenomenon is higher in the Pt-TiO2 coating because of its larger work function.
On the other hand, the enhancement of the visible photoactivity was more pronounced
(3 and 7 times for methylene blue and stearic acid, respectively) in the case of Au-TiO2
thanks to the surface plasmon resonance. Finally, these nanocomposite TiO2 coatings
exhibited also a good ability for the degradation of antibiotics usually found in
wastewater such as sulfamethoxazole. However, a complementary test have showed an
increase of the toxicity of the liquid medium after photocatalysis, which could be
due the presence of sulfamethoxazole's transformation byproducts.