• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.445.1-445.1
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• 2014

Dye-sensitized solar cells (DSSCs) have been widely investigated as a next-generation solar cell because of their simple structure and low manufacturing cost. The $TiO_2$ film with thickness of $8{\sim}10{\mu}m$, which consists of nanoparticles, acts as both a scaffold with a high surface-to-volume ratio for the dye loading and a pathway to remove the electrons. However, charge carriers have to move across many particle boundaries by a hopping mechanism. So, one dimensional nanostructures such as nanotubes, nanorods and nanowires should improve charge carrier transportation by providing a facile direct electron pathway and lowering the diffusion resistance. However, the efficiencies of DSSCs using one dimensional nanostructures are less than the $TiO_2$ nanoparticle-based DSSCs. In this work, the patterned $TiO_2$ film with thickness of $3{\mu}m$ was deposited using photolithography process to decrease of electron pathway and increase of surface area and transmittance of $TiO_2$ films. Properties of the patterned $TiO_2$ films were investigated by various analysis method such as X-ray diffraction, field emission scanning electron microscopy (FESEM) and UV-visible spectrophotometer.

• Korean Journal of Materials Research
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• v.32 no.1
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• pp.14-22
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• 2022

To improve light absorption ability in the visible light region and the efficiency of the charge transfer reaction, Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst were synthesized. The reduced TiO₂ nanotube photocatalyst was fabricated by anodic oxidation of Ti plate, followed by an electrochemical reduction process using applied cathodic potential. For TiO₂ photocatalyst electrochemically reduced using an applied voltage of -1.3 V for 10 min, 38% of Ti⁴⁺ ions on TiO₂ surface were converted to Ti³⁺ ion. The formation of Ti³⁺ species leads to the decrease in the band gap energy, resulting in an increase in the light absorption ability in the visible range. To obtain better photocatalytic efficiency, Pd nanoparticles were decorated through photoreduction process on the surface of reduced TiO₂ nanotube photocatalyst (r10-TNT). The Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst exhibited enhanced photocurrent response, and high efficiency and rate constant for aniline blue degradation; these were ascribed to the synergistic effect of the new electronic state of the TiO₂ band gap energy induced by formation of Ti³⁺ species on TiO₂, and by improvement of the charge transfer reaction.

• Textile Coloration and Finishing
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• v.30 no.4
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• pp.245-255
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• 2018

In this study, cotton fabrics were coated with $TiO_2$ nanoparticles using 3-mercaptopropyltrimethoxysilane(3-MPTMS), which is highly reactive to cotton fabrics, as a medium, and the characteristics, antimicrobial properties, and photodegradation properties of the fibers were measured. The manufacturing process is as follows. (1) 3-MPTMS was added to isopropanol, and $TiO_2$ colloid was added to the mixture to prepare a solution. (2) Cellulose fibers were immersed in the prepared $3-MPTMS/TiO_2$ solution, stirred for 90 minutes at $45^{\circ}C$ in a constant temperature water bath, and dried thereafter. In order to identify the morphology of the cellulose fibers coated with $TiO_2$ nanoparticles, the surface was observed with a scanning electron microscope(SEM), and SEM-EDS was measured to identify the adhesion of $TiO_2$ nanoparticles. The SEM images showed $TiO_2$ nanoparticle and 3-MPTMS coated layers on the fibers and it was identified that $TiO_2$ nanoparticles were attached to the cellulose fibers. The antimicrobial activity of $3-MPTMS/TiO_2$-treated cotton fabrics was measured using a bacterial reduction method. $3-MPTMS/TiO_2$ cellulose fibers which was irradiated by ultra violet light, showed antimicrobial activity against Escherichia coli(ATCC 43895) and Staphylococcus aureus(ATCCBAA-1707) unlike unirradiated fibers. The cellulose fibers were stained with methylene blue and the photodegradation performance of the stained fabrics was analyzed. The stained fabrics showed high degradation performance with photolytic reactions of $TiO_2$ nanoparticles.

• Korean Journal of Materials Research
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• v.22 no.5
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• pp.249-252
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• 2012

Fe doped $TiO_2$ nanoparticles were prepared under high temperature and pressure conditions by mixture of metal nitrate solution and $TiO_2$ sol. Fe doped $TiO_2$ particles were reacted in the temperature range of 170 to $200^{\circ}C$ for 6 h. The microstructure and phase of the synthesized Fe doped $TiO_2$ nanoparticles were studied by SEM (FE-SEM), TEM, and XRD. Thermal properties of the synthesized Fe doped $TiO_2$ nanoparticles were studied by TG-DTA analysis. TEM and X-ray diffraction pattern shows that the synthesized Fe doped $TiO_2$ nanoparticles were crystalline. The average size and distribution of the synthesized Fe doped $TiO_2$ nanoparticles were about 10 nm and narrow, respectively. The average size of the synthesized Fe doped $TiO_2$ nanoparticles increased as the reaction temperature increased. The overall reduction in weight of Fe doped $TiO_2$ nanoparticles was about 16% up to ${\sim}700^{\circ}C$; water of crystallization was dehydrated at $271^{\circ}C$. The transition of Fe doped $TiO_2$ nanoparticle phase from anatase to rutile occurred at almost $561^{\circ}C$. The amount of rutile phase of the synthesized Fe doped $TiO_2$ nanoparticles increased with decreasing Fe concentration. The effects of synthesis parameters, such as the concentration of the starting solution and the reaction temperature, are discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.11
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• pp.949-956
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• 2007

Pool boiling critical heat flux (CHF) of nanofluids with oxide nanoparticles of $TiO_2$ or $Al_2O_3$ was experimentally investigated under atmospheric pressure. The results showed that a dispersion of oxide nanoparticles significantly enhances the CHF over that of pure water. Moreover it was found that nanoparticles were seriously deposited on the heater surface during pool boiling of nanofluids. CHF of pure water on a nanoparticle-deposited surface, which is produced during the boiling of nanofluids, was not less than that of nanofluids. The result reveals that the CHF enhancement of nanofluids is absolutely attributed to modification of the heater surface by the nanoparticle deposition. Then, the nanoparticle-deposited surface was characterized with parameters closely related to pool boiling CHF, such as surface roughness, contact angle, and capillary wicking. Finally, reason of the CHF enhancement of nanofluids is discussed based on the changes of the parameters.

• Particle and aerosol research
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• v.7 no.4
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• pp.113-121
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• 2011

The aerosol nanoparticles are suspected to be exposed to workers in nanomaterial manufacturing facilities. However, the exposure assessment method has not been established. One of important issues is to characterize background level of nanoparticles in workplaces. In this study, intensive aerosol measurements were made at a $TiO_2$ manufacturing laboratory for five consecutive days in May of 2010. The $TiO_2$ nanoparticles were manufactured by the thermal-condensation process in a heated tube furnace. The particle number size distribution was measured using a scanning mobility particle sizer every 5 min, in order to detect particles ranging from 14.5 to 664 nm in diameter. Total particle number concentration shows a severe diurnal variation irrespective of manufacturing process, which was governed by nanoparticles smaller than 50 nm in diameter. During the background monitoring periods, significant peak concentrations were observed between 2 p.m. and 3 p.m. due to the infiltration of secondary aerosol particles formed by photochemical smog. Although significant increase in nanoparticle concentration was also observed during the manufacturing process twice among three times, these particle peak concentrations were lower than those observed during the background measurement. It is suggested that the investigation of background particle contamination is needed prior to conducting main exposure assessment in nanomaterial manufacturing workplaces or laboratories.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.483.2-483.2
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• 2014

In this study, we describe a simple selective etching method that produces noncurling, freestanding, large-area, aligned $TiO_2$ nanotube (NT) with doubly ends opened. The novel selective etching process only removed the thin 2nd bottom layer from the physically and chemically stable thick amorphous 1st top layer under thermal treatment at $250^{\circ}C$, yielding ordered doubly open-ended NT (DNT) that could be easily transferred to an FTO substrate for the fabrication of front-illuminated dye sensitized solar cells (DSCs). The DNT-DSCs yielded a higher PCE (8.6%) than was observed from $TiO_2$ nanoparticle (TNP)-based DSCs (7.3%), for comparable film thicknesses of $16{\mu}m$, despite of 20% decreased amount of dye. Intensity-modulated photocurrent and photovoltage spectroscopy (IMPS and IMVS, respectively) revealed that the DNT-DSCs exhibited electron lifetimes that were 10 times longer than those of TNP-DSCs, which contributed to high device performances.

• Rapid Communication in Photoscience
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• v.2 no.3
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• pp.82-84
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• 2013

We fabricated dye-sensitized solar cells (DSSCs) with $TiO_2$ nanowire (NW)/nanoparticle (NP) composite and solidified nanogel as the photoelectrode and electrolyte, respectively. $TiO_2$ NWs were generated via pore-infiltration of titanium (IV) isopropoxide (TTIP) into a track-etched polycarbonate membrane with a pore diameter of 100 nm, followed by calcination at $500^{\circ}C$. Energy conversion efficiency of $TiO_2$ NW/NP-based DSSCs was always higher than that of NP-based cells. We attributed this to improved light scattering and electron transport by $TiO_2$ NWs, as verified by intensity modulation photocurrent spectroscopy (IMPS) and intensity modulation photovoltage spectroscopy (IMVS) analyses. Quasi-solid-state DSSCs with NW/NP composites exhibited 5.0% efficiency at 100 $mW/cm^2$, which was much greater than that of NP-based cells (3.2%).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.991-994
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• 2003

Electronic Paper용 무기소재로 $TiO_2$ 나노입자를 적용하기 위해서는 분산시 침전문제, 입자의 전기영동 속도향상을 위한 충분한 $\xi-potential$확보, 분산제 첨가시 안정적 결합을 위한 acidic site의 확보등의 문제가 해결되어야 한다. 이를 위해 저온균일침전법으로 $TiO_2$ 나노입자를 제조하였고, 폴리머 체인을 통하여 encapsulation하여 최적의 분산과 전기영동조건 확보를 위한 공정조건에 대해 연구하였다. 실험결과 다양한 분산매에 계면활성제를 1.0wt% 첨가시 유전율상수가 2.5인 분산매에서 가장 좋은 $\xi-potential$을 얻을 수 있었으며 이를 바탕으로 acidic site에 따른 폴리머 체인의 흡착실험 결과 pH $1{\sim}2$의 조건에서 제조된 $TiO_2$ 나노입자의 경우가 체인과의 흡착정도가 가장 좋아 분산특성을 향상시킬 수 있었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.6
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• pp.280-284
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• 2015

Au doped $TiO_2$ nanoparticles have been synthesized using a reverse micelle technique combined with metal alkoxide hydrolysis and condensation. Au doped $TiO_2$ was coated with glass substrate. The size of the particles and thickness of the coating can be controlled by manipulating the relative rates of the hydrolysis and condensation reaction of TTIP within the micro-emulsion. The average size of synthesized Au doped $TiO_2$ nanoparticle was about in the size range of 15 to 25 nm and the Au particles formed mainly the range of 2 to 10 nm in diameter. The effect of synthesis parameters, such as the molar ratio of water to TTIP and the molar ratio of water to surfactant, are discussed. The synthesized nanopaticles were coated on glass substrate by a spin coating process. The thickness of thin film was about 80 nm. The degradation of MB on a $TiO_2$ thin film was enhanced over 20 % efficiency by the incorporation of Au.