• 한국분말재료학회지
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• 제25권3호
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• pp.257-262
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• 2018

The coupling of two semiconducting materials is an efficient method to improve photocatalytic activity via the suppression of recombination of electron-hole pairs. In particular, the coupling between two different phases of $TiO_2$, i.e., anatase and rutile, is particularly attractive for photocatalytic activity improvement of rutile $TiO_2$ because these coupled $TiO_2$ powders can retain the benefits of $TiO_2$, one of the best photocatalysts. In this study, anatase $TiO_2$ nanoparticles are synthesized and coupled on the surface of rutile $TiO_2$ powders using a microemulsion method and heat treatment. Triton X-100, as a surfactant, is used to suppress the aggregation of anatase $TiO_2$ nanoparticles and disperse anatase $TiO_2$ nanoparticles uniformly on the surface of rutile $TiO_2$ powders. Rutile $TiO_2$ powders coupled with anatase $TiO_2$ nanoparticles are successfully prepared. Additionally, we compare the photocatalytic activity of these rutile-anatase coupled $TiO_2$ powders under ultraviolet (UV) light and demonstrate that the reason for the improvement of photocatalytic activity is microstructural.

• 한국재료학회지
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• 제16권8호
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• pp.524-528
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• 2006

On the synthesis of Au/$TiO_2$ core-shell structure nanoparticle, the effect of concentration of $Ti^{4+}$ and reaction temperature on the morphology and optical property of Au/$TiO_2$ core-shell nanoparticles is examined. A gold colloid was prepared by $HAuCl_4{\cdot}4H_2O\;and\;C_6H_5Na_3{\cdot}2H_2O$. Titanium stock solution was prepared by mixing solution of titanium(IV) isopropoxide (TTIP) and triethanolamine (TEOA). The concentrations of $Ti^{4+}$ stock solution were adjusted to $10.01{\sim}0.3$ mM, and then the gold colloid is added to the $Ti^{4+}$ stock solution. Au/$TiO_2$ core-shell structure nanoparticles could be prepared by the hydrolysis of the $Ti^{4+}$ stock solution at $80^{\circ}C$. The size of synthesized Au nanoparticles was 15 nm. The thickness of $TiO_2$ shell on the surface of gold particles was about 10 nm. The absorption peak of synthesized Au/$TiO_2$ core-shell nanoparticles shifted towards the red end of the spectrum by about 3 nm because of the formation of $TiO_2$ shell on the surface of gold particles. The good $TiO_2$ shell is produced when $Ti^{4+}$ concentration is varied between 0.01 and 0.05 mM, and reaction temperature is maintained at $80^{\circ}C$. The crystal structure of $TiO_2$ shell was amorphous.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.99-102
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• 2009

$TiO_2$ nanotube arraysdecorated with ${\alpha}-Fe_2O_3$ were prepared by forming a nanotube-like $TiO_2$ film on a Ti sheet using an anodization process, followed by electrochemical deposition treatment to decorate hematite (${\alpha}-Fe_2O_3$) nanoparticles on the $TiO_2$ nanotube arrays. The SEM and XRD results revealed that the ${\alpha}-Fe_2O_3$ nanoparticles were homogeneously embedded on the surface of the $TiO_2$ nanotube arrays. The activity of hydrogen production by photocatalytic water decomposition for the ${\alpha}-Fe_2O_3/TiO_2$ nanotube array composite was examined under visible light irradiation.

• 멤브레인
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• 제20권2호
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• pp.120-126
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• 2010

본 연구에서는 $TiO_2$ 나노입자로 표면침적된 polyethersulfone (PES) 정밀여과 분리막이 자연유기물로 인한 분리막 막힘현상(파울링)에 미치는 영향을 관찰하였다. $TiO_2$ 나노입자로 표면침적된 PES 정밀여과 분리막의 자연유기물 파울링 거동에 $TiO_2$ 나노입자의 결정구조와 용액의 pH 그리고 $Ca^{+2}$이 미치는 영향을 관찰하였다. 연구결과, $TiO_2$ 나노입자로 표면 개질된 정밀여과 분리막은 자연유기물에 의한 파울링 현상을 현저하게 감소시킬 수 있음을 확인 할 수 있었다. 그러나 이와같은 현상은 $TiO_2$ 나노입자의 결정구조와 용액의 성상에 매우 의존하는 것으로 나타났다. 자연유기물 파울링의 감소는 결정구조가 상대적으로 불안정한 anatase $TiO_2$ 나노입자를 분리막에 표면침적 시, 용액 중 $Ca^{+2}$이 존재하지 않을 때 상대적으로 높은 pH에서 효과적인 것으로 관찰되었다. 그러나 $Ca^{+2}$의 첨가 시 이와 같은 효과는 높은 pH에서 더욱 증가할 수 있음을 확인할 수 있었다. 반면, 결정구조가 상대적으로 안정한 rutile $TiO_2$ 나노입자의 경우 자연유기물의 파울링 감소는 용액의 조성에 큰 영향을 받지 않는 것으로 나타났다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.937-939
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• 2007

Carbon nanotubes (CNTs) have used as an electron field emitter of the field emission display (FED) due to their characteristics of high-electron emission, rapid response and low power consumption. However, to commercialize the FED with CNT emitter, some fundamental problems regarding life time and emission efficiency have to be solved. In this study, we investigated the $TiO_2$ coated CNT as a field emitter. $TiO_2$ nanoparticles can coated on CNT surface by chemical solution method. $TiO_2$ nanoparticles had uniform size with the average size of about 2.4 nm to 3.1 nm. Field emission performance of CNT coated with $TiO_2$ nanoparticles was evaluated and discussed.

• 한국세라믹학회지
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• 제40권9호
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• pp.902-908
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• 2003

Au/TiO$_2$ core-shell 구조 나노 미립자가 졸-겔법에 의해서 제조되었고, TiO$_2$ shell의 형상과 결정성이 TEM과 UV-Vis. absorption spectrometer에 의해서 조사되었다. Au/TiO$_2$ core-shell 나노 미립자는 Au 콜로이드 에탄올 수용액 중에서 TOAA(Titanium Oxide Acethylacetonate)의 가수분해에 의해 합성될 수 있었다. Au 나노 미립자의 표면에 형성된 TiO$_2$ shell의 두께는 약 1 nm이었다. TiO$_2$ shell의 결정성을 조사하기 위하여. TiO$_2$가 피복된 Au 콜로이드 에탄올 용액에 254 nm의 자외선과 $^{60}$Co의 방사선을 조사하였다. Au 나노 미립자의 surface plasmon 현상은 방사선이 조사되었을 때만 나타났고, 이 결과로부터 TiO$_2$ shell은 비정질 상태임을 알 수 있었으며, Au의 분산성 향상을 위해 표면에 처리된 MUA(Mercaptoundecanoic Acid)층은 전자의 이동을 방해하는 장애물로 작용하지 않음을 확인할 수 있었다.

• 한국세라믹학회지
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• 제55권3호
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• pp.239-243
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• 2018

Up to now, microstructure changes of photocatalysts have been studied to improve photocatalytic activity. Especially, to improve the adsorption of reactants and reactive sites, porous and fine crystal structures have received much attention because of their large specific surface area. In this study, $TiO_2$ nanotubes were synthesized by hydrothermal method using $TiO_2$ nanoparticles; nanotubes were evaluated by oxidized methylene blue reduction test. Using synthesized $TiO_2$ nanotubes, results of TEM showed that the $TiO_2$ nanoparticles were changed into folding sheets and nanotubes. XRD results showed that the peaks of the nanoparticles almost disappeared and only the rutile (110) and anatase (200) peaks were observed. Comparison of photocatalytic properties of nanoparticles and nanotube structures was performed by measuring the UV-vis absorbance with reducing oxidized methylene blue. As a result, the reduction rate of nanotubes was found to be $0.24{\mu}mol/s$, which was 2.6 times higher than the rate of reduction of nanoparticles.

• 한국환경과학회지
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• 제19권5호
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• pp.577-584
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• 2010

The generation of $TiO_2$ nanoparticles by a thermal decomposition of titanium tetraisopropoxide (TTIP) was carried out experimentally using a tubular electric furnace at various synthesis temperatures (700, 900, 1100 and $1300^{\circ}C$) and precursor heating temperatures (80, 95 and $110^{\circ}C$). Effects of degree of crystallinity, surface area and anatase mass fraction of those $TiO_2$ nanoparticles on photocatalytic properties such as decomposition of methylene blue was investigated. Results show that the primary particle diameter obtained from thermal decomposition of TTIP was considerably smaller than the commercial photocatalyst (Degussa, P25). Also, those specific surface areas were more than 134.4 $m^2$/g. Resultant $TiO_2$ nanoparticles showed improved photocatalytic activity compared with Deggusa P25. This is contributed to the higher degree of crystallinity, surface area and anatase mass fraction of $TiO_2$ nanoparticles compared with P25.

• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3362-3366
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• 2013

A simple and quick separation technique for selenite in natural water was developed using $TiO_2$@$SiO_2/Fe_3O_4$ nanoparticles. For the synthesis of nanoparticles, a polymer-assisted sol-gel method using hydroxypropyl cellulose (HPC) was developed to control particle dispersion in the synthetic procedure. In addition, titanium butoxide (TBT) precursor, instead of the typical titanium tetra isopropoxide, was used for the formation of the $TiO_2$ shell. The synthesized nanoparticles were used to separate selenite ($Se^{4+}$) in the presence of $Se^{6+}$ or selenium anions for the photocatalytic reduction to $Se^0$ atom on the $TiO_2$ shell, followed by magnetic separation using $Fe_3O_4$ nanoparticles. The reduction efficiency of the photocatalytic reaction was 81.4% at a UV power of 6W for 3 h with a dark adsorption of 17.5% to the nanoparticles, as determined by inductively coupled plasma-mass spectrometry (ICP-MS). The developed separation method can be used for the speciation and preconcentration of selenium cations in environmental and biological analysis.

• Environmental Analysis Health and Toxicology
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• 제23권1호
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• pp.63-65
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• 2008

The tissue distribution of $TiO_2$, nanopaprticles was investigated in mice after oral administration, and skin treatment. Male mice were treated with the dose of 5 g/kg of $TiO_2$ for three consecutive days and sacrificed at 24 hours after the last administration. As results, the orally administered $TiO_2$ nanoparticels were shown to be distributed in the testis, lung, and brain at 24 hours after the last treatment. Kidney does not seem to be the main target of $TiO_2$ nanoparticle distribution. It means that $TiO_2$ nanoparticles (17 nm) are easily absorbed through entero-gastric system and may cause toxicity in brain, lung, and reproductive organs. The distribution of skin treatment showed the same pattern like oral administration.