• Title, Summary, Keyword: titania

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Method to Increase the Surface Area of Titania Films and Its Effects on the Performance of Dye-Sensitized Solar Cells

  • Ko, Young-Seon;Kim, Min-Hye;Kwon, Young-Uk
    • Bulletin of the Korean Chemical Society
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    • v.29 no.2
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    • pp.463-466
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    • 2008
  • We report a method to increase the surface area of the titania films used as the anodes of dye-sensitized solar cells (DSSCs) by applying additional titania-coating. The modification was achieved by spin-coating a coating solution that contained a surfactant with a titania source onto the titania electrodes, followed by calcination. Previous similar attempts without a surfactant all reported decreased surface areas. We fabricated DSSCs by using the modified titania films as the anode and measured their performances. The increased surface area increased the amount of adsorbed dyes, which resulted in increased current densities. At the same time, the titania-coating increased both the open-circuit voltage and the current density by reducing the charge-recombination rates of the injected electrons, similar to the results of literatures. Therefore, our method shows an additional mechanism to increase the current density of DSSCs in addition to the other mechanisms of surface modifications with titania-coatings.

Superhydrophilicity of Titania Hybrid Coating Film Imposed by UV Irradiation without Heat-treatment (저온 경화형 초친수성 티타니아 하이브리드 졸의 제조와 친수성 특성 평가에 관한 연구)

  • Kim, Won-Soo;Park, Won-Kyu
    • Journal of Technologic Dentistry
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    • v.29 no.1
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    • pp.121-131
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    • 2007
  • A preparation process's conditions of aqueous sol which contains anatase-type nano titania particles with photocatalyic properties was established by using Yoldas process, so called, DCS(Destabilization of Colloidal Solution) process in this study. And crystal size change and phase transformation of titania particles in aqueous titania sol depending on reaction conditions was investigated by a light scattering method and XRD analysis of frozen dried powders, respectively. This sol with photo catalytic nano titania particles was used to the following hydrophilic hybrid coating film's fabrication and its properties was evaluated. Subsequently, for coating film using the above mentioned aqueous titania sol, non-aqueous titania sol was prepared without any chemical additives and its time stability according to aging time was investigate. By using the above mentioned aqueous titania sol and non-aqueous sol, a complex oxide coating sol for metal and ceramic substrate and a organic-inorganic hybrid coating sol for polymer substrate was prepared and it's hydrophilicity depending on UV irradiation conditions was evaluated. As a conclusions, the following results were obtained. (1)Aqueous titania sol The average particle size of titania in formed aqueous titania sol was distributed between 20$\sim$90nm range depending on reaction conditions. And the crystal phase of titania powders obtained by frozen drying method was changed from amorphous state to anatase and subsequently transformed to rutile crystal phase and it is attributed to concentration gradient in aqueous sol. (2)Non-aqueous titania sol Non-aqueous titania sol was prepared using methanol as a solvent and a little distilled water for hydrolysis and nitric acid as a catalyst were used. The obtained non-aqueous titania sol was stable at room temperature for 20 days. Additionally, non-aqueous titania sol with addition of chealating reagent such as acethylaceton and ethylene glycol prolonged the stability of sol by six months. (3)Complex sol and hybrid sol with super hydrophilicity The above mentioned aqueous titania sol as a main photocataylic component and non-aqueous titania sol as a binder for coating process was used to prepare a complex sol used for metal, ceramic and wood material substrate and also to prepare the organic-inorganic hybrid sol for polymer substrate such as polycarbonate and polyethylene, in which process APMS(3-Aminopropyltrimethoxysilane), GPTS(3-Glycidoxypropyl-trimethoxysilane) as a hydrophilic silane compound and HEMA(2-Hydroxyethyl methacrylate) as a forming network in hybrid coating film were used. The hybrid coating film such as prepared through this process showed a superhydrophilicity below 1$10^{\circ}$ depending on processing conditions and a pencil's hardness over 6 H.

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Electrochemical Determination of Dopamine Based on Carbon Nanotube-Sol-Gel Titania-Nafion Composite Film Modified Electrode

  • Park, Ji-Ae;Kim, Byung-Kun;Choi, Han-Nim;Lee, Won-Yong
    • Bulletin of the Korean Chemical Society
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    • v.31 no.11
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    • pp.3123-3127
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    • 2010
  • A highly sensitive electrochemical detection method for dopamine (DA) has been developed by relying on a multiwalled carbon nanotube (CNT)-sol-gel titania-Nafion composite film modified glassy carbon (GC) electrode. The CNT-titania-Nafion/GC electrode exhibited excellent electrocatalytic activity towards DA. Therefore, the CNT-titania-Nafion/GC electrode showed improved voltammetric and amperometric responses for DA compared to those obtained with both titania-Nafion/GC and Nafion/GC electrodes. The CNT-titania-Nafion/GC electrode gave a linear response ($R^2$ = 0.999) for DA from $0.5\;{\mu}M$ to 0.5 mM with a detection limit (S/N = 3) of $0.1\;{\mu}M$ and a good sensitivity of 150 mA/M while other electrodes such as CNT-Nafion/GC, titania-Nafion/GC, and a bare GC gave a sensitivity of 89, 39, and 36 mA/M, respectively. Besides, the CNT-titania-Nafion/GC electrode displayed very fast response time within 2 s. The modified electrode showed good selectivity against ascorbic acid. The modified electrode showed good stability and reproducibility. The CNT-titania-Nafion/GC electrode was applied to the determination of DA in urine and serum samples.

FT-IR Spectroscopic Characterization of Oxidized and Reduced Titania

  • Kim, Kwan
    • Bulletin of the Korean Chemical Society
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    • v.11 no.5
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    • pp.396-399
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    • 1990
  • Fourier transform infrared spectroscopy has been applied to the characterization of titania surface. The bands due to surface OH groups were observed to be more intense in the reduced titania than in the oxidized titania. The IR spectra of CO adsorbed on titania exhibited two C-O stretching bands, namely at 2187 and 2209 cm$^{-1}$. The intensities were stronger in the oxidized titania.The 2187 cm$^{-1}$-peak was attributed to CO coordinated to $Ti^{4+}_{5c}$ (subscriptindicates the coordination number of the coordinatively unsaturated cation by oxygen ions), while the 2209 cm-1-peak due to the $Ti^{4+}_{4c}{\cdots}$CO complex.

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Room Temperature Chemical Vapor Deposition for Fabrication of Titania Inverse Opals: Fabrication, Morphology Analysis and Optical Characterization

  • Moon, Jun-Hyuk;Cho, Young-Sang;Yang, Seung-Man
    • Bulletin of the Korean Chemical Society
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    • v.30 no.10
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    • pp.2245-2248
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    • 2009
  • This paper demonstrates room temperature chemical vapor deposition (RTCVD) for fabricating titania inverse opals. The colloidal crystals of monodisperse polymer latex spheres were used as a sacrificial template. Titania was deposited into the interstices between the colloidal spheres by altermate exposures to water and titanium tetrachloride (Ti$Cl_4$) vapors. The deposition was achieved under atmospheric pressure and at room temperature. Titania inverse opals were obtained by burning out the colloidal template at high temperatures. The filling fraction of titania was controlled by the number of deposition of Ti$Cl_4$ vapor. The morphology of inverse opals of titania were investigated. The optical reflection spectra revealed a photonic band gap and was used to estimate the refractive index of titania.

Preparation of Nanophase Titania Film by Plasma Spraying

  • Zhu, Yingchun;Huang, Minhui
    • Journal of the Korean Vacuum Society
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    • v.6 no.S1
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    • pp.23-26
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    • 1997
  • Nanophase titania film was obtained by plasma spraying. The structure of titania film was investigated with transmission electron microscopy (TEM). It was found taht the film was composed of grains with mean particle size of 15nm. The crystal structure of nanophase titania film was found to be anatase phase by electron diffraction.

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Surface Properties of Silane-Treated Titania Nanoparticles and Their Rheological Behavior in Silicone Oil

  • Hwang, Joon-Sik;Lee, Jeong-Woo;Chang, Yoon-Ho
    • Macromolecular Research
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    • v.13 no.5
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    • pp.409-417
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    • 2005
  • The surface of rutile titania nanoparticles was chemically modified by reacting with alkoxy silane. The surface and rheological properties in silicone oil having a wide range of viscosity were investigated. Total surface free energy($\gamma_S$) of the titania particles decreased from 53.12 to 26.94 mJ/$m^2$ as the silane used for surface treatment was increased from 0 to 5.0 wt$\%$. The surface free energy of neat silane was 25.5 mJ/$m^2$, which is quite close to that oftitania particles treated with 5.0 wt$\%$ silane. Due to the hydrophobic nature oftreated-titania, the contact angle was accordingly higher for polar solvent in the order of water>ethylene glycol> formamide>$\alpha$-bromonaphthalene. In sum of rheological behavior, as the applied shear stress or viscosity of the silicone oil increased, the titania particles tend to form layers and agglomerated clusters, showing shear-thinning and shear-thickening behaviors, sequentially. A good dispersion of discrete titania particles obeying a Newtonian flow behavior was achieved at a surface energy or low concentration of silane-treated titania particles in hydrophobic silicone oil.

Biodistribution of Inhaled Titania ($TiO_2$) Nanoparticles in Rats (백서에서 흡인된 티타니아 나노입자의 생체 내 분포에 관한 연구)

  • Choi, Se-Hoon;Park, Kay-Hyun;Jheon, San-Hhoon;Kim, Joo-Hyun;Chung, Jin-Haeng;Cho, So-Hye;Park, Jong-Ku;Kim, Tae-Heon
    • Korean Journal of Bronchoesophagology
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    • v.16 no.1
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    • pp.33-38
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    • 2010
  • Titania nanomaterials are widely used as cosmetics and dyes, however the impacts on human health are uncertain, We investigated the biodistribution of inhaled titania nanoparticles in rats, Methods Eight weeks-old SD rats were intubated and inhaled with 3 mg titania nanoparticles, twice a week, for 2 weeks, After inhalation, the rats were sacrificed and tissues or heart, lung. intestine, brain, and liver were obtained, We investigated the tissues with optical microscope (OM), transmission electron microscope (EM), scanning EM, And to analyze titania concentration of each tissue, we lysed the tissues with radioimmunoprecipitation assay (RlPA) lysis buffer or acid. Results Granulation tissues in lung were confirmed on the optical microscope, however the other organs had no abnormalities in OM images, In EM images, the rats which inhaled titania nanoparticles showed calcium deposition at heart, brain, and intestine, Titania concentration in lung was increased on the inhaled rat sacrificed I month after last exposure. Conclusion Inhaled titania nanoparticles is thought to be deposited and make inflammatory reaction in lung, and the deposition was not efficiently cleared over a month. However inhaled titania nanoparticles may rarely pass through the alveolus-blood barrier and distribute to other organs of the bod.

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Fluorescence Spectroscopic and Atomic Force Microscopic Studies on the Microstructure of Polyimide/Silica-Titania Ternary Hybrid Composites

  • Park, Hae-Dong;Ahn, Ki-Youl;Mohammad A. Wahab;Jo, Nam-Ju;Kim, Il;Kim, Gyuhyun;Lee, Won-Ki;Ha, Chang-Sik
    • Macromolecular Research
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    • v.11 no.3
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    • pp.172-177
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    • 2003
  • Biphenyltetracarboximide-phenylene diamine polyimide/silica-titania ternary hybrid composites were Prepared by thermal imidization and sol-gel reaction. Fluorescence spectroscopic, scanning electron microscopy, and atomic force microscopy studies revealed that the addition of small amount of titania showed profound effects on the microstructure and photophysical behaviors of polyimide/silica hybrid composites, when the content of silica-titania mixture was small or when the ratio of silica to titania in the mixture was high.

Visible Light Photoelectrocatalytic Properties of Novel Yttrium Treated Carbon Nanotube/Titania Composite Electrodes

  • Zhang, Feng-Jun;Chen, Ming-Liang;Zhang, Kan;Oh, Won-Chun
    • Bulletin of the Korean Chemical Society
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    • v.31 no.1
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    • pp.133-139
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    • 2010
  • Photoelectrocatalytic decolorization of methlene blue (MB) in the presence of two types of carbon nanotube/titania and yttrium-treated carbon nanotube/titania electrodes in aqueous solutions were studied under visible light. The prepared composite electrodes were characterized by X-ray diffraction, transmission and scanning electron microscopy, energy dispersive X-ray analysis, and photoelectrocatalytic activity. The photoelectrocatalytic performances of the supported catalysts were evaluated for the decolorization of MB solution under visible light irradiation. The results showed that yttrium incorporation enhanced the decolorization rate of MB. It was found that the photoelectrocatalytic degradation of a MB solution could be attributed to the combined effects caused by the photo-degradation of titania, the electron assistance of carbon nanotube network, the enhancement of yttrium and a function of the applied potential. The repeatability of photocatalytic activity was also tested. The presence of yttrium enhanced the hydrophillicity of yttrium-carbon nanotubes/titania electrode because more OH groups can be adsorbed on the surface.