Simon Bulou

Photocatalytic Anatase TiO2 Thin Films on Polymer Optical Fiber Using Atmospheric-Pressure Plasma

Due to the undeniable industrial advantages of low-temperature atmospheric-pressure plasma processes, such as low cost, low temperature, easy implementation, and in-line process capabilities, they have become the most promising next-generation candidate system for replacing thermal chemical vapor deposition or wet chemical processes for the deposition of functional coatings. In the work detailed in this article, photocatalytic anatase TiO2 thin films were deposited at a low temperature on polymer optical fibers using an atmospheric-pressure plasma process. This method overcomes the challenge of forming crystalline transition metal oxide coatings on polymer substrates by using a dry and up-scalable method. The careful selection of the plasma source and the titanium precursor, i.e., titanium ethoxide with a short alkoxy group, allowed the deposition of well-adherent, dense, and crystalline TiO2 coatings at low substrate temperature. Raman and XRD investigations showed that the addition of oxygen to the precursors carrier gas resulted in a further increase of the films crystallinity. Furthermore, the films deposited in the presence of oxygen exhibited a better photocatalytic activity toward methylene blue degradation assumedly due to their higher amount of photoactive {101} facets.

a-SiC x N y thin films deposited by a microwave plasma assisted C VD process using a CH 4 /N 2 /Ar/HMDSN mixture: methane rat e effect

Amorphous silicon carbonitride thin films were deposited using a microwave plasma assisted chemical vapour deposition process fed with a mixture of methane, nitrogen, argon and hexamethyldisilazane (Si2C6H19N). Effects of the methane rate on thin films composition, n anostructuration and characteristics are investigated by means of various techniques such as X-ray Photoelectron Spectroscopy, Fourier Transform Infrared Spectroscopy, Transmission Electron Microscopy and UV-Visible absorption. The raise of the methane rate results in less organic, denser films and in an increase of refractive index.

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

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 sulfamethoxazoles transformation byproducts.

Transparent anti-fogging and self-cleaning TiO 2 /SiO 2 thin films on polymer substrates using atmospheric plasma

Transparent anti-fogging and self-cleaning coatings are of great interest for many applications, including solar panels, windshields and displays or lenses to be used in humid environments. In this paper, we report on the simultaneous synthesis, at atmospheric pressure, of anatase TiO2 nanoparticles and low-temperature, high-rate deposition of anatase TiO2/SiO2 nanocomposite coatings. These coatings exhibit durable super-hydrophilic and photocatalytic properties. The strategy followed relies on concomitant and separated injections of titania, i.e. titanium isopropoxide, and silica, i.e. hexamethyldisiloxane, precursors in the stream of a blown-arc discharge to form transparent anti-fogging and self-cleaning anatase TiO2/SiO2 nanocomposite coatings on polymer substrates.