• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.23-28
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• 1999

Au fine particles dispersed $TiO_{2}$ film was prepared on silica glass substrate by sol-gel dipping and firing process. The $TiO_{2}$ films were fabricated from the system of titanium tetraisopropoxide-EtOH-HCl-$H_{2}O$-hydrogen tetrachloroaurat (III) tetrahydrate. The conditions for the formation of clear solution and dissolving high concentration of Au compound were examined. Photoreduction process was adopted to control the size of gold metal particles. Phase evolution of matrix $TiO_{2}$ and variation of Au particle with UV irradiation were investigated by XRD, SEM, TEM and UV-visible spectrophotometer. The effect of CPCl (Cetylpyridinium chloride monohydrate) as a dispersion agent was evaluated.

• Analytical Science and Technology
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• v.13 no.2
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• pp.234-240
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• 2000

The efficiency of Photocatalytic Oxidation Process were investigated for the treatment of Aquatic Humic Substances (AHS). In UV-only system, pH 7-9 was the optimum pH range for TOC removal, and alkali range was the optimum pH for absorbance decrease. In UV/$TiO_2$ system, the optimum $TiO_2$ dosage was 50ppm and over 50ppm of $TiO_2$ dosage was not effective for removal of AHS. In UV/$H_2O_2$ system, optimum $H_2O_2$ dosage was 20mM, when over 20mM dosage, removal of TOC (Total Organic Carbon) and absorbance was decreased. Radical scavenger affected on the photo-oxidation of AHS. Removal rate of TOC and absorbance was decreased by addition of carbonate ions and TOC removal was more effected than that of absorbance.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.E1
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• pp.19-26
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• 2006

The decomposition of gaseous $CH_3CHO$ was investigated by metal loaded $TiO_2$ (pure $TiO_2,\;Pt/TiO_2,\;Pd/TiO_2,\;Mn/TiO_2\;and\;Ag/TiO_2$) with $UV/TiO_2$ process and $UV/TiO_2/O_3$ process at room temperature and atmospheric pressure. Metal loaded $TiO_2$ was prepared by photodeposition. Decomposition of $CH_3CHO$ was carried out in a flow-type photochemical reaction system using three 10W black light lamps ($300{\sim}400nm$) as a light source. The experimental results showed that the degradation rate of $CH_3CHO$ was increased with Pt and Ag on $TiO_2$ compared to pure $TiO_2$, but decreased with depositing Pd and Mn on pure $TiO_2$. The considerable increase in the degradation efficiency of the $CH_3CHO$ was found by a combination of photocatalysis and ozonation as compared to only by ozonation or photocatalysis. Loading of Pt on $TiO_2$ promoted conversion of gaseous ozone. The degradation rate of gaseous $CH_3CHO$ decreased with an increase of water vapor in the feed stream for the both $UV/TiO_2\;and\;UV/TiO_2/O_3$ processes. The pure $TiO_2$ was more affected by the water vapor than Pt loaded $TiO_2$.

• Korean Journal of Materials Research
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• v.26 no.2
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• pp.73-78
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• 2016

$TiO_2$ nanoparticles were synthesized by a sol-gel process using titanium tetra isopropoxide as a precursor at room temperature. Ag-doped $TiO_2$ nanoparticles were prepared by photoreduction of $AgNO_3$ on $TiO_2$ under UV light irradiation and calcinated at $400^{\circ}C$. Ag-doped $TiO_2$ nanoparticles were characterized for their structural and morphological properties by X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The photocatalytic properties of the $TiO_2$ and Ag-doped $TiO_2$ nanoparticles were evaluated according to the degree of photocatalytic degradation of gaseous benzene under UV and visible light irradiation. To estimate the rate of photolysis under UV (${\lambda}=365nm$) and visible (${\lambda}{\geq}410nm$) light, the residual concentration of benzene was monitored by gas chromatography (GC). Both undoped/doped nanoparticles showed about 80 % of photolysis of benzene under UV light. However, under visible light irradiation Ag-doped $TiO_2$ nanoparticles exhibited a photocatalytic reaction toward the photodegradation of benzene more efficient than that of bare $TiO_2$. The enhanced photocatalytic reaction of Ag-doped $TiO_2$ nanoparticles is attributed to the decrease in the activation energy and to the existence of Ag in the $TiO_2$ host lattice, which increases the absorption capacity in the visible region by acting as an electron trapper and promotes charge separation of the photoinduced electrons ($e^-$) and holes ($h^+$). The use of Ag-doped $TiO_2$ nanoparticles preserved the option of an environmentally benign photocatalytic reaction using visible light; These particles can be applicable to environmental cleaning applications.

• Journal of Industrial Technology
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• v.27 no.A
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• pp.15-18
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• 2007

This study investigated disinfection effect by general water purifier and water purifier with UV light disinfection. The results are as follows : (i) The general bacteria existed plentifully in a storage tank before treatment (ii) Water treated in water purifier did not meet the water treatment regulation standard since the presence of bacteria, whereas with UV light application the regulation standard is totally satisfied. (iii) Photocatalytic disinfection process with UV light in the presence of $TiO_2$ more effectively killed general bacteria than UV light only.

• Korean Journal of Materials Research
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• v.28 no.11
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• pp.620-626
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• 2018

Highly self-cleaning thin films of $TiO_2-SiO_2$ co-doped with Ag and F are prepared by the sol-gel method. The asprepared thin films consist of bottom $SiO_2$ and top $TiO_2$ layers which are modified by doping with F, Ag and F-Ag elements. XRD analysis confirms that the prepared thin film is a crystalline anatase phase. UV-vis spectra show that the light absorption of $Ag-F-TiO_2/SiO_2$ thin films is tuned in the visible region. The self-cleaning properties of the prepared films are evaluated by a water contact angle measurement under UV light irradiation. The photocatalytic performances of the thin films are studied using methylene blue dye under both UV and visible light irradiation. The $Ag-F-TiO_2/SiO_2$ thin films exhibit higher photocatalytic activity under both UV and visible light compared with other samples of pure $TiO_2$, Ag-doped $TiO_2$, and F-doped $TiO_2$ films.

• Journal of Environmental Science International
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• v.13 no.1
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• pp.41-45
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• 2004

In this study, The decomposition of gas-phase Benzene and Toluene, Xylene in air streams by direct UV Photolysis, UV/TiO$_2$ and UV/TiO$_2$/A.C process was studied. The experiments were carried out under various UV light intensities and initial concentrations of B.T.X to investigate and compare the removal efficiency of the pollutant. B.T.X was determined by GC-FID of gas samples taken from the a glass sampling bulb which was located at reactor inlet and outlet by gas-tight syringe. From this study, the results indicate that UV/TiO$_2$/A.C system (photooxidation-photocatalytic oxidation-adsorption process) is ideal for treatment of B.T.X from the small workplace. Although the results needs more verifications, the methodology seems to be reasonable and can be applied for various workplace (laundry, gas station et al.).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.726-732
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• 2007

We fabricated UV absorption functional $10{\sim}50nm-TiO_{2-x}/quartz$ structures layer using ALD (atomic layer deposition) method. We deposited $10nm-TiO_{2-x}$ layer on quartz substrate using ALD, and film thickness was determined by an ellipsometer. The others specimen thickness was controlled by ALD time lineally. We characterized controlling phase UV and visible optical property using an X-ray difractometer, a UV-VIS-IR spectrometer and a digital camera. $ALD-TiO_{2-x}$ layers were non-stoichiometric $TiO_{2-x}$ form and amorphous phases comparing with bulk $TiO_2$. While the conventional bulk $TiO_2$ had band gap of $3.0{\sim}3.2eV$ resulting in absorption edges at 380 nm and 415 nm, $ALD-TiO_{2-x}$ layers showed absorption edges at 197 nm and 250 nm. Therefore, our nano-thick $ALD-TiO_{2-x}$ was able to absorb shorter UV region and showed excellent transmittance in visible region. Our result implies that our newly proposed nano-thick $TiO_{2-x}$ using ALD process may improve transmittance in visible rays and be able to absorb shorter UV light effectively.

• Journal of Environmental Science International
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• v.13 no.3
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• pp.289-295
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• 2004

The objective of this study is to delineate removal efficiency of the MTBE in solution by $TiO_2$ photocatalytic degradation as a function of the following different experimental conditions: Initial concentration of MTBE, air flow rate in solution, $H_2O_2$ dosage and pH of the solution. Photodegradation rate was increased with decreasing initial concentration of MTBE. The removal efficiency was 82% after 180 min in the case of MTBE concentration of 100 mg/L but 100% after 180 min in the case of 20 mg/L. Removal efficiency was increased with increasing pH, $H_2O_2$ dosage and air flow rate in solution.

• Journal of Environmental Science International
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• v.15 no.7
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• pp.677-688
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• 2006

Currently, the application of $TiO_2$ photocatalyst has been focused on purification and treatment of wastewater. However, the use of conventional $TiO_2$ slurry photocatalyst results in disadvantage of stirring during the reaction and of separation after the reaction. And the usage of artificial UV lamp has made the cost of photocatalyst treatment system high. Consequently, we studied that solar light/$TiO_2$ film system was designed and developed in order to examine disinfection characteristics of sewage wastewater treatment. The optimum conditions for disinfection such as solar light intensity, characteristic of sewage wastewater, amounts of $TiO_2$ and comparison of solar ligth/$TiO_2$ systems with UV light/$TiO_2$ system was examined. The results are as follows: (1) photocatalytic disinfection process with solar light in the presence of $TiO_2$ film more effectively killed total coliform (TC) than solar light or $TiO_2$ film absorption only. (2) The survival ratio of TC and residual ratio of organic material (BOD, CODcr) decreased with remain resistant material. (3) The survival ratio of TC and residual ratio of organic material (BOD, CODcr) decreased with the increase of amounts of $TiO_2$. (4) TC survival ratio decreased linearly with increasing UV light intensity. (5) The disinfection effect of solar light/$TiO_2$ slurry system decreased more than UV light/$TiO_2$ film systems. (6) The disinfection reaction followed first-order kinetics. We suggest that solar light instead of using artificial UV light was conducted to investigate the applicability of alternative energy source in the disinfection of TC and the degradation of organic material.