Rapid and Scalable Wire-bar Strategy for Coating of TiO2 Thin-films: Effect of Post-Annealing Temperatures on Structures and Catalytic Dye-Degradation

Abstract

Titanium dioxide (TiO 2 ) thin films were rapidly coated on Corning glass substrates from the precursor solution using the wire-bar technique at the room temperature and then post-annealed at 400, 500 and 600 • C for 1 h under atmospheric conditions. The structural, morphological, optical, wettability and photocatalytic properties of the films were studied. X-ray diffraction analysis confirmed the formation of an anatase TiO 2 structure irrespective of the post-annealing temperatures. The optical transparency of the films in the visible range was measured to be > 70%. A water contact angle (WCA) of~0 • was observed for TiO 2 thin-film, post-annealed at 400 • C and 500 • C. However, WCA of 40.3 • was observed for post-annealed at 600 • C. The photocatalytic dye-degradation using post-annealed thin-film was investigated indicating a steady improvement in the dye-degradation percentage (from 24.3 to 29.4%) with the increase of post-annealing temperature. The demonstrated TiO 2 thin-films deposited by wire-bar coating technique showed promises for the manufacturing of large-area cost-effective self-cleaning window glass.Molecules 2020, 25, 1683 2 of 13 sheeting water and the later by rolling water droplets that carries away dirt [8]. The superhydrophilic and superhydrophobic properties are attractive in self-cleaning applications and are commonly evaluated based on the water contact angles (WCAs) with the material/surface. WCAs of <5 • and >150 • are called superhydrophilic and superhydrophobic materials respectively [8]. The superhydrophilic material when employed on a substrate/surface leads to the formation of uniform thin layer of water upon contact and gradually carries away dust particles from the surface [9]. In contrast, hydrophobic surfaces accumulate small water droplets, leading to deterioration of transparency [7,9]. In the current context, TiO 2 thin layers are capable of photocatalytically degrading the organic pollutants present on glass and tiles and irregular shapes on solid surfaces when irradiated with UV light or sun light [8,9]. The decomposed organic pollutant or dirt can be washed away by sheeting water without the need of additional mechanical cleaning due to its superhydrophilic nature [7,8]. Recently, the scope of superhydrophilic and photocatalytic TiO 2 thin-films has been widened to air purification for the effective decomposition (and the subsequent removal) of nitrogen oxide (NO x ), formaldehyde, benzene and other volatile organic compounds (VOCs) [10][11][12]. The air purification processes convert toxic gases to harmless compounds like nitrate ions that are ultimately washed into the soil and help to fertilize plants [10]. The unique wettability and non-toxic properties of TiO 2 materials are also employed in biomedical applications where surface wettability can play an important role in protein adsorption, cell adhesion and proliferation [9]. Moreover, the antibacterial, self-cleaning, and anti-odour properties of TiO 2 films deposited on fibres, textile, cotton, etc. also allow thi...

Porous V2O5/TiO2 Nanoheterostructure Films with Enhanced Visible-Light Photocatalytic Performance Prepared by the Sparking Method

“…Titanium dioxide (TiO 2 ) is a widely used photocatalyst because of its low cost, environmental friendliness, and stable photocatalytic reaction [ 1 , 2 ]. There are three forms of TiO 2 phases (anatase, rutile, and brookite), in which the anatase phase has higher photocatalytic activity than both the rutile and brookite phases.…”

Annealing synchronizes the 70 S ribosome into a minimum-energy conformation

“…Full annealing consists of tandem heating and cooling steps. Cooling rate and annealing temperature are usually two critical elements for homogenization of metals, alloys, and semiconductors ( 22 , 23 ). In metallurgy, the annealing temperature is usually 30 °C to 50 °C greater than the upper critical temperature of metals ( 24 ).…”

Annealing synchronizes the 70S ribosome into a minimum-energy conformation

“…Full annealing consists of two tandem heating and cooling steps. Cooling rate and annealing temperature are usually two critical elements for homogenization of metals, alloys, and semiconductors (22, 23). In metallurgy, the annealing temperature is usually 30°C to 50°C greater than the upper critical temperature of metals (24).…”