Titanium dioxide (TiO 2 ) thin films were prepared using a sol-gel process and applying between two and five coating layers onto the surface of borosilicate glass slides and 304 stainless steel sheets. The physical properties of the multilayer TiO 2 thin films on both of the substrates under the same fabrication process were systematically compared. Our results indicate that the crystalline phase structure of the prepared TiO 2 thin film was entirely composed of anatase with an optical band gap of 3?27 eV. The grain sizes of the TiO 2 crystals in the films on the glass slides and the stainless steel sheets were in the ranges of 15-100 nm and 20-250 nm respectively. The results suggested that at least three layers of coating were required to produce the TiO 2 thin film with the desired range of properties. IntroductionTitanium dioxide (TiO 2 ) is a photocatalyst that has been extensively used due to its good photocatalytic activity, relatively low toxicity and low production cost. The applications of TiO 2 can be found in various practices including the sterilisation and disinfection of microorganism s (especially bacteria and viruses), as well as the treatment and purification of water and air. 1-5 One of the most widely used methods to fabricate TiO 2 nanoparticles is the sol-gel technique. 5-8 This coating technique has been applied to various materials, such as metal, plastic, silicon and polymer. [9][10][11] In this research, we fabricated TiO 2 thin films using a simplified sol-gel technique modified from Eshaghi et al. 5 This was achieved by hydrolysing the sol solution at room temperature, using different solvents for the sol-gel preparation, modifying the calcination temperature scheme for the multilayer coating and reducing the stirring time and dip coating speed. A wide range of the thin films' physical properties were also systematically compared and reported for the different amounts of coating layers. The main objective of this article is to provide information for selecting the optimum number of layers of TiO 2 thin film for a photocatalytic process based on their physical properties. Experimental Preparation of TiO 2 thin filmsTwo different substrates were used in this study: borosilicate glass slides (25?4676?261?2 mm) and stainless steel sheets (40?0685?060?3 mm). The TiO 2 thin films were prepared with an acid catalysed sol-gel dip coating process using titanium tetraisopropoxide {Ti[OCH(CH 3 ) 2 ] 4 (TTIP)} as a precursor. In this study, the sol solution was prepared by the hydrolysis of TTIP under acidic conditions at room temperature. The TTIP was mixed with isopropanol at a volume ratio of 1 : 15. The pH of the solutions was adjusted to 2-3 using concentrated hydrochloric acid. The solutions were stirred at room temperature in a closed chamber with a constant flush of N 2 gas for 1 h and then left at room temperature in a closed vessel for 24 h to transform the sol to gel before being ready to use.The thin films were developed on the surfaces by dip coating the sol-gel solutions at a speed ...
This research investigates the photocatalytic decolourisation of two selected dyes using multiple thin film coatings (three, four and five layers) of a TiO 2 photocatalyst under a low intensity ultraviolet A (UVA) light source. The TiO 2 photocatalyst was prepared using a simplified sol-gel process, and the decolourisation efficiencies of the two experimental dyes, indigo carmine and reactive black 5, were studied. The kinetics of the photocatalytic decolourisation reactions under low intensity UVA were described by a pseudofirst order kinetic model, and the photocatalytic kinetic rate constants were reported. An increase in the number of coating layers contributed to the TiO 2 photocatalyst's smaller grain size, higher surface area and narrower optical band gap. The findings also revealed a positive relationship between the number of TiO 2 coating layers and the efficiencies and kinetics of dye decolourisation in the experimental photocatalytic process. In addition, the TiO 2 thin film photocatalyst induced high photocatalytic activity, even under low intensity UVA light.
This experimental research comparatively investigates the Escherichia coli (E. coli) bacterial inactivation of the TiO 2 photocatalytic thin films fabricated by the sol-gel dip-coating (SG) and low-temperature spray-coating (SP) techniques, with low-intensity (12 μW·cm . Moreover, the essential physical characteristics of the SG-TiO 2 and SP-TiO 2 photocatalytic thin films were determined prior to the experimental bacterial inactivation. The findings showed that both photocatalytic thin films possessed the ideal physical characteristics, especially the SP-TiO 2 thin film. In addition, the viable cell counts, the cell morphology, and the bioluminescence-based adenosine triphosphate (ATP) indicated that both SG-TiO 2 and SP-TiO 2 thin films under UVA could effectively inhibit the proliferation of the E. coli cells in both NB and 0.85% NaCl.
Titanium dioxide (TiO 2) and ferric-doped TiO 2 (Fe-TiO 2) thin films were synthesized on the surface of 304 stainless steel sheets using a simplified sol-gel preparation method. The Fe-TiO 2 thin films were prepared with weight-to-volume ratios of Fe 3+ /TiO 2 of 0.3%, 0.5%, and 0.7%, respectively. The crystalline phase structures of the prepared TiO 2 and Fe-TiO 2 thin films were entirely anatase. The measured optical band gaps of the TiO 2 , 0.3% Fe-TiO 2 , 0.5% Fe-TiO 2 , and 0.7% Fe-TiO 2 thin films were 3.27, 3.28, 3.22, and 2.82 eV, respectively. The grain sizes and other physical properties of the prepared thin films were also reported. The kinetics of the photocatalytic processes under a UV-LED light source could be explained by the Langmuir-Hinshelwood kinetic model with the specific rates of 2.00 × 10 −3 , 4.00 × 10 −3 , 5.00 × 10 −3 , and 7.00 × 10 −3 min −1 mW −1 , for TiO 2 , 0.3% Fe-TiO 2 , 0.5% Fe-TiO 2 , and 0.7% Fe-TiO 2 , respectively. An increase in Fe 3+ dopant concentration could enhance the photocatalytic activity of toluene decomposition as a result of lower optical band gaps, smaller grain size, and higher surface area.
SiO2-TiO2 nanocomposites were synthesized by the sol-gel method with different SiO2 contents (0.125, 0.25, 0.50 and 0.75%wt). The characteristics of prepared samples were obtained from x-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), UV–visible spectrophotometer, and Brunauer Emmett and Teller (BET) surface area analyzer. SiO2-TiO2 nanocomposites have higher UV absorption capability and a higher specific surface area compared to pure TiO2, resulting in improved dye degradation by photocatalytic activity. The results show that the dye degradation efficiency of 0.5SiO2-TiO2 is higher than pure TiO2. It can degrade the dye up to 96.91% within 2 h, while TiO2 was able to degrade dye at 88.62%.
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