• Clean Technology
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• v.20 no.3
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• pp.306-313
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• 2014

Nanoporous $TiO_2$ films are commonly used as working electrodes in dye-sensitized solar cells (DSSCs). So far, there have been attempts to synthesize films with various $TiO_2$ nanostructures to increase the power-conversion efficiency. In this work, vertically aligned rutile $TiO_2$ nanorods were grown on fluorinated tin oxide (FTO) glass by hydrothermal synthesis, followed by deposition of an anatase $TiO_2$ film. This new method of anatase $TiO_2$ growth avoided the use of a seed layer that is usually required in hydrothermal synthesis of $TiO_2$ electrodes. The dense anatase $TiO_2$ layer was designed to behave as the electron-generating layer, while the less dense rutile nanorods acted as electron-transfer pathwaysto the FTO glass. In order to facilitate the electron transfer, the rutile phase nanorods were treated with a $TiCl_4$ solution so that the nanorods were coated with the anatase $TiO_2$ film after heat treatment. Compared to the electrode consisting of only rutile $TiO_2$, the power-conversion efficiency of the rutile-anatase hybrid $TiO_2$ electrode was found to be much higher. The total thickness of the rutile-anatase hybrid $TiO_2$ structures were around $4.5-5.0{\mu}m$, and the highest power efficiency of the cell assembled with the structured $TiO_2$ electrode was around 3.94%.

• Clean Technology
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• v.19 no.1
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• pp.22-29
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• 2013

A comparison of photo-efficiency on dye-sensitized solar cells (DSCs) assembled by using $TiO_2$ materials with different structures and crystallite sizes were investigated in this study. The size and structure of $TiO_2$ have been controlled by pHs and calcination temperatures using solvothermal and sol-gel methods, respectively. Six types of $TiO_2$ samples are obtained; 8.9, 12.8, and 20.2 nm sized $TiO_2$ particles, and the other types using sol-gel method were anatase-rutile mixtures on the structure. The highest photo-efficiency which is remarkable result reached to 8.6% over DSC assembled by anatase $TiO_2$ with 20.2 nm particle size.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.48-49
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• 2008

유도결합플라즈마를 적용한 화학기상증착법으로 $TiO_2$ 박막을 얻었다. 박막의 특성 조절을 위해 수소유량을 변화시켰다. 수소 유량을 증가시킴에 따라 박막의 표면 형상, 결정성, 결정 구조 및 광촉매 특성이 변하였다. 고밀도 플라즈마가 반응 기체의 분해를 촉진함으로써 외부 가열없이 아나타제 $TiO_2$가 만들어졌다. 적절한 양의 수소를 첨가했을 때, 루타일 상으로 상전이가 발생하였다. 화학기상증착법에서 루타일 $TiO_2$는 일반적으로 900 K 이상의 고온에서 형성되는 것으로 알려져 있다. 수소의 역할을 고찰하기 위해 랭뮤어 탐 침법과 발광 분광기를 이용한 플라즈마 진단을 수행하였다.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.197-203
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• 2002

The TiO$_2$ coating solutions were synthesized with different concentrations (T1-0.7N, T2-2.0N) of hydrochloric acid used as catalyst. and TiO$_2$ thin films were prepared by sol-gel dip coating. Their structural and optical properties were examined as a function of calcination temperature. XRD results showed that T1 thin films calcined at 400~80$0^{\circ}C$ had the anatase phase, while those calcined at 100$0^{\circ}C$ had the rutile phase. T2 thin films calcined at 40$0^{\circ}C$ and $600^{\circ}C$ had the anatase phase, with the rutile phase for calcination at 80$0^{\circ}C$. Crystallinity of T2 thin films was superior to that of T1 thin films. The crystallite size of TiO$_2$ thin films increased with increasing calcination temperature, and the crystallite size of anatase phase in T2 thin films was larger than that in T1 thin films, but the crystallite size of rutile phase in T2 thin films was smaller. The surface morphology of the films showed that the films were formed more densely in the rutile phase than in the anatase phase, this phenomenon appeared conspicuously in T2 thin films. The transmittance of the samples with thin films on quartz glass calcined at 100$0^{\circ}C$ was significantly reduced at wavelength range about 300-700 nm due to the increased absorption originating from the change of crystallite phase and composition of the films and the scattering effect originating from increasing crystallite size. The refractive index of TiO$_2$ thin films increased, and hence the film thickness as well as the porosity of TiO$_2$ thin films decreased with increasing calcination temperature. Furthermore, the refractive index of T2 thin films was higher than T1 thin films, and porosity of T2 films was lower.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.680-680
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• 2013

염료감응 태양전지를 구성하는 중요한 요소 중 하나인 나노입자 산화물 $TiO_2$는 태양전지 내부의 전자이동과 밀접한 관련이 있어 Cell의 개방전압(Voc) 및 단락전류밀도(Jsc) 특성을 결정짓는 주요 요소이다. 때문에 염료감응 태양전지의 문제점인 효율 증대를 위해서는 $TiO_2$의 각종 특성을 연구할 필요가 있다. 본 논문에서는 $TiO_2$의 두께 및 소성온도를 변화시킴에 따라 제반 되는 각종 전기적 특성들을 조사해 보았고 그 원인들을 고찰해 보았다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.846-849
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• 2013

Thin film of $TiO_2$ was obtained by the sol-gel dip method on the brosilicate glass substrate. It was found that the film was about $1.5{\mu}m$ thick as obtained by 4 successive coatings and annealed at varied temperatures ranged from $300^{\circ}C$ to $1100^{\circ}C$ for 2 hrs. The substrate used was having the surface area of $100mm^2$. Increasing the annealing temperature caused to change in mineralogical phase of titanium oxide i.e., amorphous, crystalline antase to rutile phases. The particle size of the titanium oxide film were ranged from $0.1{\sim}0.54{\mu}m$ estimated by the SEM analysis. The material showed an absorbance maximum at the wavelength 390nm obtained by UV-visible spectrophotometer. These results therefore, indicated that the $TiO_2$ film obtained relatively at low annealing temperature consisted predominantly with anatase phase; possessed higher photocatalytic behavior i.e., 2.4 times higher than that of only UV lamp irradiation.

• Korean Journal of Optics and Photonics
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• v.17 no.3
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• pp.296-302
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• 2006

ILow-temperature $TiO_2$ sol was synthesized with various catalyst contents by using a sol-gel method. $TiO_2$ thin films were produced by a dip-coating method and their optical, structural and photocatalytic properties were examined. Transmittance of $TiO_2$ thin films with 0.10 mol, 0.25 mol, 0.50 mol and 0.75 mol catalyst content showed high transmittance in the visible range. XRD results showed the anatase-to-rutile phase transition was accelerated with increasing catalyst content and the crystallinity size of the $TiO_2$ thin films increased with increasing catalyst content. SEM results indicated that the particle size of the $TiO_2$ thin films was the smallest with catalyst content of 0.25 mol. Photocatalytic results showed that methylene blue was completely decomposed in the presence of anatase film prepared with 0.10 mol, 0.25 mol and 0.50 mol catalyst content.

• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.156-161
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• 2018

$TiO_2$ photocatalyst powders were prepared by chlorination method and sol-gel method. Specific surface area and crystalline (i.e., anatase and rutile) of the catalyst varied depending on manufacture conditions and method. TTIP-sol photocatalyst had higher methylene blue (MB) decomposition characteristics than photocatalyst from chlorination method and TBOT-sol. MB removal efficiency from aqueous solution with TTIP-sol photocatalyst was over 90%. Experimental results showed that the $TiO_2$ photocatalyst with a single anatase phase and a large specific surface area had high decomposition characteristics of organic materials.

• 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.

• Journal of the Korean Electrochemical Society
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• v.12 no.1
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• pp.47-53
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• 2009

In this study, highly ordered AAO (Anodic Aluminum Oxide) with nanopores was prepared by commercial grade Al substrate containing 3.5 wt.% impurities through two step anodizing method. Nanopores of prepared AAO arrays were used as templates for preparing nanofiber. $TiO_2$ was deposited by using DP (deposition-precipitation) method into AAO pores to grow nanofiber. Au particles were loaded on this $TiO_2$ nanofiber which was grown vertically. Prepared 2 wt.% $Au/TiO_2$ nanofiber was characterized by XRD, SEM and Raman. The crystal structure was analyzed by the XRD. SEM was used to observe pore size and pore wall thickness. Photocatalytic activity of co-oxidation was compared with $TiO_2$ and $Au/TiO_2$ nanofiber on AAO arrays.