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Transparent TiO 2 films with a high photodegradation activity towards an azo dye in aqueous solut... more Transparent TiO 2 films with a high photodegradation activity towards an azo dye in aqueous solution were prepared by sol–gel processing. Films on soda–lime glass supports protected with a thin silica barrier layer exhibited better crystallization and monodisperse nanoparticles, higher absorption of light below 370 nm, and higher photocatalytic activity than those films deposited on bare glass supports proving the detrimental effect of interdiffused sodium ions on the development of the anatase nanostructure. The effect of substrate was more pronounced in thinner films (300 nm) than in thicker ones (1200 nm), which were achieved by adding a template (i.e. Pluronic F127) to the sol.
Titanium dioxide has become the material of choice for hydrophilic photocatalytic surfaces and th... more Titanium dioxide has become the material of choice for hydrophilic photocatalytic surfaces and the sol-gel technique has emerged as one of the most promising techniques for growing TiO 2 thin films. This chapter describes our sol-gel preparation and utilization of thin titania films on glass substrates as catalysts for photodegradation of organic pollutants, such as azo dyes and pesticides in aqueous solutions. The good photoefficiency of the as-prepared films relies on their high contact surface area and nanocrystalline structure, which facilitates efficient photoinduced electron-hole pair generation. Transparent TiO 2-anatase films on soda-lime glass supports were produced by two different sol-gel processing routes: (i) dip coating from alcoholic sols containing surfactants and followed by heat treatment at 500°C; (ii) dip coating from aqueous sols after extended refluxing treatment and followed by heating at ~100°C. In both cases the starting precursor was titanium alkoxide and the final coating consisted of a dominant anatase crystalline phase. In case of the high-temperature processing route, the detrimental effect of interdiffused sodium ions from the glass substrate during heat treatment was prevented by depositing a thin silica barrier layer prior to titania deposition. The intermediate barrier layer was not needed in case of the low-temperature processing route, where the crystallization of anatase has been already promoted during the formation of the sol. X-ray absorption spectroscopy and X-ray diffraction were applied to determine the structure development at different stages from the precursor solution to the solid thin film. Surface morphology, characterized by monodispersed or joint nanoparticles and variable roughness, was investigated with atomic force microscopy, while the surface and in-depth composition of films were analyzed by X-ray photoelectron spectroscopy. A photocatalytic activity of the as-prepared films was studied in two different tailor-made photoreactors filled with an aqueous solution of certain pollutant. In case of an azo dye, the films were immersed in its colored solution and photobleaching was followed in-situ with the help of UV-VIS spectroscopy. The degradation of the pesticide was monitored by HPLC analysis and its mineralization by ionic chromatography. The insecticide thiacloprid was stable under irradiation (wavelength range 310-400 nm) in the absence of TiO 2 films during 8 hours long period, whereas in the presence of best-performing titania films the half time of the parent molecule was typically 15 minutes. The titania catalyst can be easily removed from the solution, which is one of the principal advantages of using the immobilized films as catalysts rather than powders.
In this study we have focused on 3,5,6-trichloro-2-pyridinol (TCP), degradation product of chlorp... more In this study we have focused on 3,5,6-trichloro-2-pyridinol (TCP), degradation product of chlorpyrifos. Photolysis experiments were conducted in order to elucidate its degradation mechanism. Identification of products was performed using the LC-MS technique. To evaluate the mineralization efficiency, TiO 2 photocatalytic study was performed. Under photolytic experimental conditions, the concentration of TCP after 120 min of irradiation reached 5.9 ± 1.5% of the initial concentration, while chloride concentration reached approximately 73% of total chloride concentration. The TOC measurements after 120 min of photocatalytic degradation experiment revealed high mineralization rate, i.e. 53.6 ± 1.9%, while chloride concentration reached 26.6 mg L À1 what means almost quantitative transformation of organic chlorine into chloride. TIC chromatogram (ESI, negative ion mode) of the reaction mixture after 30 min of irradiation revealed the presence of several peaks. One of them has already been reported previously. Two other products have been identified in this study for the first time. They have been formed by radical attack of the reactive OH species on the carbonyl group followed by the corresponding NeC or CeC bond cleavages and recyclization with formation of the pyrrol structures substituted with carboxylic groups. Both deprotonated molecules easily lose CO 2 in ESI conditions.
Transparent TiO 2 films with a high photodegradation activity towards an azo dye in aqueous solut... more Transparent TiO 2 films with a high photodegradation activity towards an azo dye in aqueous solution were prepared by sol–gel processing. Films on soda–lime glass supports protected with a thin silica barrier layer exhibited better crystallization and monodisperse nanoparticles, higher absorption of light below 370 nm, and higher photocatalytic activity than those films deposited on bare glass supports proving the detrimental effect of interdiffused sodium ions on the development of the anatase nanostructure. The effect of substrate was more pronounced in thinner films (300 nm) than in thicker ones (1200 nm), which were achieved by adding a template (i.e. Pluronic F127) to the sol.
Titanium dioxide has become the material of choice for hydrophilic photocatalytic surfaces and th... more Titanium dioxide has become the material of choice for hydrophilic photocatalytic surfaces and the sol-gel technique has emerged as one of the most promising techniques for growing TiO 2 thin films. This chapter describes our sol-gel preparation and utilization of thin titania films on glass substrates as catalysts for photodegradation of organic pollutants, such as azo dyes and pesticides in aqueous solutions. The good photoefficiency of the as-prepared films relies on their high contact surface area and nanocrystalline structure, which facilitates efficient photoinduced electron-hole pair generation. Transparent TiO 2-anatase films on soda-lime glass supports were produced by two different sol-gel processing routes: (i) dip coating from alcoholic sols containing surfactants and followed by heat treatment at 500°C; (ii) dip coating from aqueous sols after extended refluxing treatment and followed by heating at ~100°C. In both cases the starting precursor was titanium alkoxide and the final coating consisted of a dominant anatase crystalline phase. In case of the high-temperature processing route, the detrimental effect of interdiffused sodium ions from the glass substrate during heat treatment was prevented by depositing a thin silica barrier layer prior to titania deposition. The intermediate barrier layer was not needed in case of the low-temperature processing route, where the crystallization of anatase has been already promoted during the formation of the sol. X-ray absorption spectroscopy and X-ray diffraction were applied to determine the structure development at different stages from the precursor solution to the solid thin film. Surface morphology, characterized by monodispersed or joint nanoparticles and variable roughness, was investigated with atomic force microscopy, while the surface and in-depth composition of films were analyzed by X-ray photoelectron spectroscopy. A photocatalytic activity of the as-prepared films was studied in two different tailor-made photoreactors filled with an aqueous solution of certain pollutant. In case of an azo dye, the films were immersed in its colored solution and photobleaching was followed in-situ with the help of UV-VIS spectroscopy. The degradation of the pesticide was monitored by HPLC analysis and its mineralization by ionic chromatography. The insecticide thiacloprid was stable under irradiation (wavelength range 310-400 nm) in the absence of TiO 2 films during 8 hours long period, whereas in the presence of best-performing titania films the half time of the parent molecule was typically 15 minutes. The titania catalyst can be easily removed from the solution, which is one of the principal advantages of using the immobilized films as catalysts rather than powders.
In this study we have focused on 3,5,6-trichloro-2-pyridinol (TCP), degradation product of chlorp... more In this study we have focused on 3,5,6-trichloro-2-pyridinol (TCP), degradation product of chlorpyrifos. Photolysis experiments were conducted in order to elucidate its degradation mechanism. Identification of products was performed using the LC-MS technique. To evaluate the mineralization efficiency, TiO 2 photocatalytic study was performed. Under photolytic experimental conditions, the concentration of TCP after 120 min of irradiation reached 5.9 ± 1.5% of the initial concentration, while chloride concentration reached approximately 73% of total chloride concentration. The TOC measurements after 120 min of photocatalytic degradation experiment revealed high mineralization rate, i.e. 53.6 ± 1.9%, while chloride concentration reached 26.6 mg L À1 what means almost quantitative transformation of organic chlorine into chloride. TIC chromatogram (ESI, negative ion mode) of the reaction mixture after 30 min of irradiation revealed the presence of several peaks. One of them has already been reported previously. Two other products have been identified in this study for the first time. They have been formed by radical attack of the reactive OH species on the carbonyl group followed by the corresponding NeC or CeC bond cleavages and recyclization with formation of the pyrrol structures substituted with carboxylic groups. Both deprotonated molecules easily lose CO 2 in ESI conditions.