• Environmental Engineering Research
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• v.16 no.2
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• pp.81-90
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• 2011

Different weight percentages of Ag, Pt, and Au doped nano $TiO_2$ were synthesized using the acetic acid hydrolyzed sol-gel method. The crystallite phase, surface morphology combined with elemental composition and light absorption properties of the doped nano $TiO_2$ were comprehensively examined using X-ray diffraction (XRD), $N_2$ sorption analysis, transmission electron microscopic (TEM), energy dispersive X-ray, and DRS UV-vis analysis. The doping of noble metals stabilized the anatase phase, without conversion to rutile phase. The formation of gold nano particles in Au doped nano $TiO_2$ was confirmed from the XRD patterns for gold. The specific surface area was found to be in the range 50 to 85 $m^2$/g. TEM images confirmed the formation a hexagonal plate like morphology of nano $TiO_2$. The photocatalytic activity of doped nano $TiO_2$ was evaluated using 4-chlorophenol as the model pollutant. Au doped (0.5 wt %) nano $TiO_2$ was found to exhibit higher photocatalytic activity than the other noble metal doped nano $TiO_2$, pure nano $TiO_2$ and commercial $TiO_2$ (Degussa P-25). This enhanced photocatalytic activity was due to the cathodic influence of gold in suppressing the electron-hole recombination during the reaction.

• International Journal of Highway Engineering
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• v.19 no.1
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• pp.53-62
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• 2017

PURPOSES : This research was a fundamental study on the application of an integral $TiO_2$ solution to asphalt concrete pavement. The integral $TiO_2$ solution was produced in pilot production equipment; application of the integral $TiO_2$ solution to asphalt pavement was conducted to examine the pollution-reducing capability of photocatalytic compounds such as $TiO_2$. The photocatalytic $TiO_2$ reacted with air pollutants, converting them into small amounts of relatively benign molecules. METHODS : In this study, laboratory experiments were conducted using five various testing methods. Tensile strength ratio (TSR) and British pendulum test (BPT) were conducted in order to evaluate the properties of asphalt pavement subsequent to the integral $TiO_2$ solution coating. In addition, methylene blue testing, a measurement of nitrate on the coated pavement, and nitrogen oxide (NOx) reduction testing were conducted in order to evaluate photocatalytic reaction. Lastly, a UV-A lamp was used as a light source for photocatalytic reactions. RESULTS : Test results indicated no change in the properties of asphalt pavement following the integral $TiO_2$ solution coating. In order to evaluate the performance of asphalt pavement as a function of $TiO_2$, the moisture susceptibility and skid resistance were investigated. The moisture susceptibility and skid resistance satisfied there quirements related to pavement quality and safety specification. Furthermore, the effects of reduction of air pollution were significantly improved as determined via the methylene blue test and NOx reduction test. The $TiO_2$-paved asphalt specimen exhibited approximately 43% reduction of NOx. CONCLUSIONS : This study has suggested that applying $TiO_2$ rarely impacts asphalt pavement performance measures such as moisture susceptibility and skid resistance, and that its application may be a better means of reducing air pollution. Further studies, such as proper $TiO_2$ dosage rates and compatibility with various pavement types, are required to broaden and generalize its application.

• Bulletin of the Korean Chemical Society
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• v.30 no.8
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• pp.1738-1742
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• 2009

Nanocrystalline Zn$Fe_2O_4$ oxide-semiconductor with spinel structure was synthesized by the polymerized complex (PC) method and investigated for its photocatalytic and photoelectric properties. The observation of a highly pure phase and a lower crystallization temperature in Zn$Fe_2O_4$ made by PC method is in total contrast to that was observed in Zn$Fe_2O_4$ prepared by the conventional solid-state reaction (SSR) method. The band gap of the nanocrystalline Zn$Fe_2O_4$ determined by UV-DRS was 1.90 eV (653 nm). The photocatalytic activity of Zn$Fe_2O_4$ prepared by PC method as investigated by the photo-decomposition of isopropyl alcohol (IPA) under visible light (${\geq}$ 420 nm) was much higher than that of the Zn$Fe_2O_4$ prepared by SSR as well as Ti$O_{2-x}N_x$. High photocatalytic activity of Zn$Fe_2O_4$ prepared by PC method was mainly due to its surface area, crystallinity and the dispersity of platinum metal over Zn$Fe_2O_4$.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.54-54
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• 2010

Zinc oxide is metal oxide semiconductor with the 3.37 eV bandgap energy. Zinc oxide is very attractive materials for many application fields. Zinc Oxide has many advantages such as high conductivity and good transmittance in visible region. Also it is cheaper than other semiconductor materials such as indium tin oxide (ITO). Therefore, ZnO is alternative material for ITO. ZnO is attracting attention for its application to transparent conductive oxide (TCO) films, surface acoustic wave (SAW), films bulk acoustic resonator (FBAR), piezoelectric materials, gas-sensing, solar cells and photocatalyst. In this study, we synthesized ZnO nanoparticles and defined their physical and chemical properties. Also we studied about the application of ZnO nanoparticles as a photocatalyst and try to find a enhancement photocatalytic activity of ZnO nanorticles.. We synthesized ZnO nanoparticles using spray-pyrolysis method and defined the physical and optical properties of ZnO nanoparticles in experiment I. When the ZnO are exposed to UV light, reduction and oxidation(REDOX) reaction will occur on the ZnO surface and generate ${O_2}^-$ and OH radicals. These powerful oxidizing agents are proven to be effective in decomposition of the harmful organic materials and convert them into $CO_2$ and $H_2O$. Therefore, we investigated that the photocatalytic activity was increased through the surface modification of synthesized ZnO nanoparticles. In experiment II, we studied on the stability of ZnO nanoparticles in water. It is well known that ZnO is unstable in water in comparison with $TiO_2$. $Zn(OH)_2$ was formed at the ZnO surface and ZnO become inactive as a photocatalyst when ZnO is present in the solution. Therefore, we prepared synthesized ZnO nanoparticles that were immersed in the water and dried in the oven. After that, we measured photocatalytic activities of prepared samples and find the cause of their photocatalytic activity changes.

• Membrane Journal
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• v.6 no.2
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• pp.101-108
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• 1996

The oxidation/degradation efficiency of formic acid through the photoelectrochemical reaction has been investigated as a basic research in order to develope the process for degrading toxic organic compounds dissolved in water. A $TiO_{2}$ photoelectro-membrane reactor for purification of water, in which filtration as well as photoelectrocatalytic oxidation of organic compounds could be carried out simultaneously, was developed. Porous $SnO_{2}$ tubes prepared by slip casting and commercial porous stainless steel tubes, being electrically conductive, were used as not only supports but also working electrodes. The UV light with the wavelength of 365 nm was applied as a light source for photocatalytic reactions. The photoelectrocatatytic composite membranes were prepared by coating the support surface with the $TiO_{2}$ sol of pH 1.45. The oxidation efficiency of formic acid increased with the reaction time and the applied voltage, but was almost independent of the solution flux. The results showed that more than 90% of formic acid could he dograded at 27V using the $TiO_{2}$/stainless steel composite membrane, while about 77% in case of the $TiO_{2}/SnO_{2}$ Composite membrane. It was also concluded that the oxidation efficiencies of formic acid could be significantly improved by about 6~7 times by the photoelectrochemical reaction in comparison with those by the photocatalytic reaction only.

• Journal of Sensor Science and Technology
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• v.29 no.2
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• pp.128-132
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• 2020

Total organic carbon (TOC) analysis equipment, which was previously used to prevent eutrophication in advance, is heavy, bulky, and expensive; therefore, so it is difficult to be carried and has been used as an experimental unit. In this study, a through-carbon analysis chip that integrates pretreatment through photocatalytic oxidation and carbon dioxide measurement using a pH indicator was investigated. Both the total carbon - inorganic carbon method and the nonpurgeable organic carbon (NPOC) measurement method require an acidification part for injecting an acid solution for inorganic carbon measurement and removal, an oxidation part for total carbon or NPOC oxidation and a measurement part for Carbon dioxide (CO₂) measurement. Among them, the measurement of oxidation and CO₂ requires physical technology. The proposed TOC analysis chip decomposed into CO₂ as a result of the oxidizing of organic carbon using a photocatalyst, and the pH indicator that was changed by the generated CO₂ was optically measured. Although the area of the sample of the oxidation part and the pH indicator of the measurement part were distinguished in an enclosed space, CO₂ was quantified by producing an oxidation part and a measurement part that shared the same air in one chip. The proposed TOC analysis chip is less expensive and smaller, cost and size are disadvantages of existing organic carbon analysis equipment, because it does not require a separate carrier gas to transport the CO₂ gas in the oxidation part to the measurement part.

• Korean Journal of Materials Research
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• v.29 no.12
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• pp.790-797
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• 2019

To improve photocatalytic performance, CdS nanoparticle deposited TiO₂ nanotubular photocatalysts are synthesized. The TiO₂ nanotube is fabricated by electrochemical anodization at a constant voltage of 60 V, and annealed at 500 for crystallization. The CdS nanoparticles on TiO₂ nanotubes are synthesized by successive ionic layer adsorption and reaction method. The surface characteristics and photocurrent responses of TNT/CdS photocatalysts are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Vis spectrometer and LED light source installed potentiostat. The bandgaps of the CdS deposited TiO₂ photocatalysts are gradually narrowed with increasing of amounts of deposited CdS nanoparticles, which enhances visible light absorption ability of composite photocatalysts. Enhanced photoelectrochemical performance is observed in the nanocomposite TiO₂ photocatalyst. However, the maximum photocurrent response and dye degradation efficiency are observed for TNT/CdS30 photocatalyst. The excellent photocatalytic performance of TNT/CdS30 catalyst can be ascribed to the synergistic effects of its better absorption ability of visible light region and efficient charge transport process.

• Journal of the Korean Ceramic Society
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• v.39 no.6
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• pp.535-539
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• 2002

In this study photoadsorption propreties of Ag ion in AgNO$_3$ solution by TiO$_2$nanopowder synthesized by homogeneous precipitation process at low temperature were investigated. It was found that the photocatalytic redliction in AgNO$_3$solution was occurred by TiO$_2$nanopowder even under th sun light irradiation, although the reduction of Ag ions was slow with th small adsorption of 9.32 ppm. Notably the Ag adsorption was promoted in th dark condition probably owing to the chestnut bur shape of TiO$_2$ nanopowder itself. In the application of UV the Ag ions were completely adsorbed within 120 min, showing more significant photocatalytic reaction. The measured adsorption reaction rate and adsorption equilibrium rate constants were 0.0004 g/min and 1494.20(120 $m^2$/g), respectively.

• Bulletin of the Korean Chemical Society
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• v.35 no.7
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• pp.2004-2008
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• 2014

This paper reports the facile synthesis methods of zinc oxide (ZnO) nanoparticles, Z1-Z10, using diethylene glycol (DEG) and polyethylene glycol (PEG400). The particle size and morphology were correlated with the PEG concentration and reaction time. With 0.75 mL of PEG400 in 150 mL of DEG and a 20 h reaction time, the ZnO nanoparticles began to disperse from a collective spherical grain shape. The ZnO nanoparticles were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and a $N_2$ adsorption-desorption studies. The Brunauer-Emmett-Teller (BET) surface areas of Z4, Z5 and Z10 were 157.083, 141.559 and 233.249 $m^2/g$, respectively. The observed pore diameters of Z4, Z5 and Z10 were 63.4, 42.0 and 134.0 ${\AA}$, respectively. The pore volumes of Z4, Z5 and Z10 were 0.249, 0.148 and 0.781 $cm^3/g$, respectively. The photocatalytic activity of the synthesized ZnO nanoparticles was evaluated by methylene blue (MB) degradation, and the activity showed a good correlation with the $N_2$ adsorption-desorption data.

• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.308-312
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• 2012

Nitrogen doped $TiO_2$ photocatalysts were prepared by ammonia for exploring the visible light photocatalytic activity. To explore the visible light photocatalytic activity of the nitrogen doped $TiO_2$ photocatalyst, the removal of methylene blue dye was investigated under the sunlight. SEM images showed that the flocculated particle sizes of N-doped $TiO_2$ decreased due to the reaction with ammonia. XRD patterns demonstrated that the samples calcined at temperatures up to $600^{\circ}C$ and doped with nitrogen using ammonia clearly showed rutile as well as anatase peaks. The XPS results showed that the nitrogen composition onto $TiO_2$ increased according to the reaction time with ammonia. Photocatalytic activity of the nitrogen doped $TiO_2$ was better than that of undoped $TiO_2$. Nitrogen doping onto the $TiO_2$ also affected the crystal type of $TiO_2$ photocatalyst.