Production of photocatalytically active titania layers: A comparison of plasma processes and coating properties

• Published in: Surface & coatings technology 2013-07, Vol.227, p.2-9
• Main Authors: Moser, Eva Maria, Chappuis, Sidney, Olleros, Javier
• Format: Article
• Language: English
• Subjects: Applied sciences; Carbon; Coating; Cross-disciplinary physics: materials science; rheology; Doping; Exact sciences and technology; Materials science; Metals. Metallurgy; Methods of deposition of films and coatings; film growth and epitaxy; Methylene blue; PECVD; Photocatalysis; Photocatalytic activity; Physical vapor deposition; Physics; Production techniques; PVD; Surface treatment; Surface treatments; Thin films; Titania; Titanium dioxide; Ultraviolet
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2013.01.050

The deposition of photocatalytically active titania layers at ambient temperature was developed using the reactive dc magnetron sputtering (PVD) and the plasma enhanced metal organic chemical vapour deposition (PE-MOCVD) method at reduced and at atmospheric pressure. An increase of the photo-activity in the near ultraviolet and blue light irradiation was achieved by doping the titania layers using the elements nitrogen and/or carbon. Investigation of the chemical and structural features of the titania layers produced at similar experimental conditions was carried out by X-ray photoelectron spectroscopy, atomic force microscopy, FTIR, and Raman. The optical energy bandgap and photocatalytic activity at 365/428nm for various titania layers were analysed using ellipsometry and the methylene blue dye bleaching according to ISO 10678:2010, respectively. The reduction of the aqueous methylene blue solution was similar for the two categories of titania layers. However, the photo-induced properties such as the mineralization of stearic acid for investigating anti-fingerprint effects evidenced a weaker interaction between the hydrophobic PE-MOCVD titania surfaces than for the hydrophilic and rougher PVD produced titania layers when irradiated under ultraviolet. The observed differences were related to the chemical and structural features since the hydrophobic PE-MOCVD produced titania layers were mostly amorphous and nitrogen/carbon incorporation into TiO2 led to an enhanced photocatalytic ability by a factor of two regarding the dye tests, whereas the energy bandgap remained at about 3.2eV. However, the energy bandgap was red-shifted by doping the hydrophilic and partly crystalline PVD titania layers, but decremented the anatase domains and reduced the wettability of the surface. Substitutional and interstitial doping of nitrogen and carbon was evidenced by XPS and an additional benefit regarding the adhesion and abrasion resistance was observed for the tailored doping of titania layers. ► High photocatalytic activity despite low crystallinity and high amount of doping ► Different surface properties exhibit impact onto functional features. ► Comparison of normed test of methylene blue with mineralisation of stearic acid