Significance of a Noble Metal Nanolayer on the UV and Visible Light Photocatalytic Activity of Anatase TiO₂ Thin Films Grown from a Scalable PECVD/PVD Approach

Abstract

UV and visible light photocatalytic composite Pt and Au-TiO 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 TiO in all synthesized coatings with a shifting of the main vibrational mode peak to higher wavenumber in the case of Au-TiO 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-TiO 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-TiO 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-TiO thanks to the surface plasmon resonance. Finally, these nanocomposite TiO 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.

Transparent anti-fogging and self-cleaning TiO2/SiO2 thin films on polymer substrates using atmospheric plasma

“…HMDSO flow), the positions of the Ti 2p 1/2 and Ti 2p 3/2 peaks, observed at 464.5 eV and 458.8 eV (Fig. 4b ), respectively, is characteristic of TiO 2 bondings This value is very close to that of pure TiO 2 generally reported 8 , 15 , 19 , 20 , indicating that Ti is predominantly involved in Ti-O-Ti bonding. Nevertheless, Ti-O-Si bonding can not be excluded as the peak shows a significant full width at half maximum (FWHM) of 1.5 eV.…”

Morphology- and Crystalline Composition-Governed Activity of Titania-Based Photocatalysts: Overview and Perspective

“…Although well-organized titania nanostructures might be easily obtained by a convenient hydrothermal method, such as nanowires (1D), nanotubes (1D), and faceted NPs (0D), other methods are used for the preparation of 2D titania nanostructures since titania films are usually deposited on some supports, such as glass, polyvinyl chloride, and quartz. Therefore, chemical vapor deposition (CVD) [152], plasma-enhanced chemical vapor deposition (PECVD) [153], dc-sputtering [154], anodization (exemplary shown in Figure 11 as "mesopores") [155] and successive-ionic-layeradsorption-and-reaction (SILAR) [156] methods have been proposed for the preparation of 2D titania photocatalysts. However, hydrothermal methods have been also used for the preparation of titania nanoplates (shown in Figure 13) for application as sensors to detect toxic gases [157].…”

Experimental and theoretical analysis of tool life between plasma enhanced CVD and PVD multilayer nanocoated cutting tools

“…Muthuraja et al [13] conducted experiments on PECVD-Chromium diamonds like carbon (Cr-DLC) coated nozzle needle surface and revealed that it is to wear protective. Baba et al [14] investigated the PECVD-PVD hybrid nanocoatings of TiO 2 on the cutting tool and revealed that the deposition of surface coating is suitable for only self-cleaning surfaces. Asha et al [15] explain that when HCHCr alloy steel machined by multilayer coated carbide inserts the tool life is increased.…”