• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.253-254
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• 2008

The $TiO_2$ Pastes was prepared with the starting materials of $TiO_2$ (P-25), ethyl cellulose, a-terpineol and bis(2-ethylhexyl) phthalate, and this $TiO_2$ paste application for dye-sensitized solar cells (DSSCs) were investigated. In order to improved transparency of $TiO_2$ photoanode films, $TiO_2$ paste was changed ethyl cellulose and a-terpineol contents. The morphology of prepared $TiO_2$ films were investigated by field emission scanning electron microscopy (FE-SEM). The electrochemical properties of the thin films and the performance of DSSCs were measured by photovoltaic-current density and AC impedance. Energy conversion efficiency was obtained about 5.7% at ethyl cellulose and a-terpineol on best mixed ratio under illumination with AM 1.5 ($100mWcm^{-2}$)simulated sunlight.

• Environmental Engineering Research
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• v.13 no.3
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• pp.136-140
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• 2008

$TiO_2$ photocatalyst has been known to exhibit a notable disinfecting activity against a broad spectrum of microorganisms. A lot of commercial $TiO_2$ photocatalyst products have been developed for antimicrobial purposes. However, a standard method has not yet been proposed for use in testing antimicrobial activity. In this study, we developed a $TiO_2$ photocatalytic adhesion test method with film as the standard testing method for the evaluation of antimicrobial activity. This method was devised by modifying the previous antimicrobial products test method, which has been widely used, and considering the characteristics of $TiO_2$ photocatalytic reaction. The apparatus for testing the antimicrobial activity was composed of a Black Light Blue (BLB) lamp as UV-A light source, a Petri dish as the cover material, and a polypropylene film as the adhesion film. The standard $TiO_2$ photocatalyst sample, Degussa P25 $TiO_2$ - coated glass, could only be used once. The optimal initial concentration of the microorganism, proper light intensity, and light irradiation time were determined to be $10^6$ CFU/mL, 1.0 mW/$cm^2$, and 3 hr, respectively, for testing and evaluating antimicrobial activity on the $TiO_2$ surface.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.3
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• pp.284-294
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• 2006

Statement of problem. Proliferation of Candida albicans is primarily within the plaque on the fitting surface of the denture rather than on the inflamed mucosa. Consequently, the treatment of the denture is equally important as treatment of the tissue. Cleansing and disinfection should be efficiently carried-out as the organisms can penetrate into the voids of the acrylic resin and grow in them, from which they can continue to infect and reinfect bearing tissues. Purpose. The purpose of this study was to evaluate the applicability of photocatalytic reaction to eliminate Candida albicans from acrylic resin denture base, and to investigate the anti-fungal effect with various UVA illumination time. Materials and Methods. The specimens were cured by the conventional method following the manufacturer's instruction using thermal polymerized denture base resin (Vertex RS: Dentimex, Netherlands). $TiO_2$ photocatalyst sol(LT), which is able to be coated at normal temperature, was made from the Ti-alkoxide progenitor. The XRD patterns, TEM images and nitrogen absorption ability of the $TiO_2$ photocatalyst sol(LT) were compared with the commercial $TiO_2$ photocatalyst P-25. The experimental specimens were coated with the mixture of the $TiO_2$ photocatalyst sol(LT) and binder material (silane) using dip-coater, and uncoated resin plates were used as the control group. Crystallinity of $TiO_2$ of the specimen was tested by the XRD. Size, shape and chemical compositions were also analyzed using the FE-SEM/ EDS. The angle and methylene blue degradation efsciency were measured for evaluating the photocatalytic activity of the $TiO_2$ film. Finally, the antifungal activity of the specimen was tested. Candida albicans KCTC 7629(1 ml, initial concentration $10^5$ cells/ ml) were applied to the experiment and control group specimens and subsequently two UVA light source with 10W, 353 nm peak emission were illuminated to the specimens from 15cm above. The extracted $2{\mu}l$ of sample was plated on nutrient agar plate ($Bacto^{TM}$ Brain Heart Infusion; BD, USA) with 10 minute intervals for 120 minute, respectively. It was incubated for 24 hours at $37^{\circ}C$ and the colony forming units (CFUs) were then counted. Results. Compared the characteristics of LT photocatalyst with commercial P-25 photocatalyst, LT were shown higher activity than P-25. The LT coated experimental specimen surface had anatase crystal form, less than 20 nm of particle size and wide specific surface area. To evaluate the photocatalytic activity of specimens, methylene blue degradation reaction were used and about 5% of degradation rate were measured after 2 hours. The average contact angle was less than $20^{\circ}$ indicating that the LT photocatalyst had hydrophilicity. In the antifungal activity test for Candida albicans, 0% survival rate were measured within 30 minute after irradiation of UVA light. Conclusion. From the results reported above, it is concluded that the UVA-LT photocatalytic reaction have an antifungal effect on the denture surface Candida albicans, and so that could be applicable to the clinical use as a cleaning method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.4032-4038
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• 2014

Vegetable fatty acid solid soap requires a drying process for moisture evaporation and hardness after being manufactured through saponification. Although the soap is manufactured by mixing additives mainly from natural ingredients, existing studies have focused primarily on the usability of vegetable solid soap. Consequently, research into the physical properties of vegetable fatty acid solid soap mixed with natural ingredients has been unsatisfactory. Therefore, this study attempted to compare and observe the changes in the physical properties (pH, surface tension, critical micelle concentration, and cleansing power) of solid soap in accordance with the drying period and additives (tea tree E.O and $TiO_2$) using pH paper, the Du Nouy measurement method, sedimentation method, and ultrasound washer. Regardless of the mixture with additives, vegetable fatty acid solid soap showed the same pH, and there was no change in the pH while maintaining pH 8 beginning from the $2^{nd}$ weeks to $12^{th}$ weeks of drying. In addition, as a result of measuring the surface tension and CMC, regardless of the drying period, only the soap added with $TiO_2$ showed an even value of 62.5mg/L, whereas the other soap specimens showed a decline in CMC to 25mg/L on the fourth week of drying. As a result of measuring the detergency, the removal efficiency of vegetable fatty acid solid soap mixed with tea tree E.O and $TiO_2$ and dried for four weeks was 4.50~4.65%, which was higher than that of the vegetable fatty acid solid soap without additives (3.62~3.92%).

• Korean Journal of Environmental Agriculture
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• v.22 no.4
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• pp.284-289
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• 2003

Titanium mesoporous materials have received increasing attention as a new photocatalyst in the field for photocatalytic degradation of organic compounds. The photocatalytic degradation of chlorothalonil by mesoporous titanium oxo-phoswhate (Ti-MCM) was investigated in aqueous suspension for comparison with $TiO_2$, (Degussa, P25) using as an effective photocatalyst of organic pollutants. Mesoporous form of titanium Phosphate has been prepared by reaction of sulfuric acid and titanium isopropoxide in the presence or n-hexadecyltrimethylammonium bromide. The XRD patterns of Ti-MCM are hexagonal phases with d-spacings of 4.1 nm. Its adsorption isotherm for chlorothalonil reached at reaction equilibrium within 60 min under dark condition with 28% degradation efficiency. The degradation ratio of chlorothalonil after 9 hours under the UV radiation condition (254 nm) exhibited 100% by Ti-MCM and 88% by $TiO_2$. However, these degradation kinetics in static state showed a slow tendency compared to that of stirred state because of a low contact between titanium matrices and chlorothalonil. Also, degradation efficiency of chlorothalonil was increased with decreasing initial concentration and with increasing pH of solution. As results of this study, it was clear that mesoporous titanium oxo-phosphate with high surface area and crystallinity could be used to photo- catalytic degradation of various organic pollutants.

• Bulletin of the Korean Chemical Society
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• v.29 no.6
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• pp.1217-1223
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• 2008

A series of Zr,S co-doped $TiO_2$ were synthesized by a modified sol-gel method and characterized by various spectroscopic and analytical techniques. The presence of sulfur caused a red-shift in the absorption band of $TiO_2$. Co-doping of sulfur and zirconium (Zr-$TiO_2$-S) improves the surface properties such as surface area, pore volume, and pore diameter and also enhances the thermal stability of the anatase phase. The Zr-$TiO_2$-S systems are very effective visible-light active catalysts for the degradation of toluene. All reactions follow pseudo firstorder kinetics with the decomposition rate reaching as high as 77% within 4 h. The catalytic activity decreases in the following order: Zr-$TiO_2$-S >$TiO_2$-S >Zr-$TiO_2$>$TiO_2$$\approx$ P-25, demonstrating the synergic effect of codoping with zirconium and sulfur. When the comparison is made within the series of Zr-$TiO_2$-S, the catalytic performance is found to be a function of Zr-contents as follows: 3 wt % Zr-TiO2-S >0.5 wt % Zr-$TiO_2$-S> 5 wt % Zr-$TiO_2$-S >1 wt % Zr-$TiO_2$-S. Higher calcination temperature decreases the reactivity of Zr-$TiO_2$-S.

• Journal of the Korean Ceramic Society
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• v.39 no.6
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• pp.550-557
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• 2002

TiO$_2$ particles coated on fly ash composites for use in photocatalyst were synthesized by the precipitation dropping method and heated at $700^{\circ}C$ for 2 h. The pH of reaction solution, the addition rate of NH$_4$HCO$_3$, the stirring speed, the reaction temperature and the concentration of TiC1$_4$ had a pronounced effect on the nature of precipitated TiO$_2$ particles on the surface off fly ash and the crystal structure of precipitated TiO$_2$ particles. At an addition rate of NH$_4$HCO$_3$; 1.0 ml/min, the pH of the reaction solution; 6, the stirring speed; 1,000 rpm and the reaction temperature; 8$0^{\circ}C$, about 10 nm of TiO$_2$ particle size and homogeneous precipitated layer on the surface of a fly ash was achieved. On the contrary, at an addition rate of NH$_4$HCO$_3$; 0.3,0.5 ml/min, the pH of the reaction solution; 2 and 11, the stirring speed; 300~500 rpm and the reaction temperature; lower than 5$0^{\circ}C$:, Inhomogeneous precipitated layer was developed on a fly ash. TiO$_2$ particles with anatase phase was formed as-dried precipitation at the low concentration of Tic14, the high addition rate of NH$_4$HCO$_3$ and the high reaction temperature, the crystalline fraction of anatase increased with raising heat-treatment temperature and rutile phase began to formation at 80$0^{\circ}C$. The crystal size of TiO$_2$ particles increased with raising the heat-treatment temperature, the crystal size was showed about 21 m at $700^{\circ}C$. Anatase type of TiO$_2$ coated on the fly ash heated at $700^{\circ}C$ for 2 h showed 1.25 g/cm$^3$of particle density, 82.8% of strength and 69.5 Lab of whiteness and can be used as a photocatalyst.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.2 s.31
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• pp.17-22
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• 2004

In this study, BNT($BaO-Nd_{2}O_3-TiO_2$) and $70P_{2}O_5-5B_{2}O_3-(25-x)BaO-xNa_{2}O$ glass-ceramic composites were fabricated and investigated in order to apply for low temperature cofired ceramic. The prepared BNT based glass-ceramic composites were sintered at $800{\sim}950^{\circ}C$ with the glass fit contents ranging from 10 to $15\;wt\%$. The properties such as sintering and dielectric property were investigated in the ceramic compositions according to the phosphate glass frit. The dielectric constant was varied between 10 to 40 and shrinkage rate was increased according to increasing glass frit.

• Journal of the Korean Ceramic Society
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• v.45 no.11
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• pp.688-693
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• 2008

This paper presents a study on the photocatalytic reaction about the composite particles of $TiO_2$-coated phosphors under visible light irradiation. Nanocrystalline titanium dioxide layers were directly coated on the alkaline earth aluminate phosphor, $CaAl_2O_4:Eu^{2+},\;Nd^{3+}$ particles by an sol-gel processing method. The photocatalytic reaction was analyzed with the degradation of methylene blue (MB) aqueous solution under UV and visible light irradiations. $TiO_2$-coated phosphor powders showed different photocatalytic mechanism, compared with pure $TiO_2$ (P-25, Degussa). Under UV-irradiation, $TiO_2$-coated phosphor powders showed slow photocatalytic reactivity in the early stage and fast in the latter, compared with that of pure $TiO_2$. However, $TiO_2$-coated phosphor powders showed much faster photocatalytic reactivity than that of pure $TiO_2$ under visible irradiation. In addition, the characterizations of the $TiO_2$-coated phosphor powders were conducted by a X-ray diffractometer (XRD), transmission electron microscope (TEM), and energy dispersive spectroscopy (EDS).

• Membrane and Water Treatment
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• v.9 no.6
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• pp.393-403
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• 2018

In this research commercial polyethersulfone (PES) membrane was modified using $TiO_2$ nanoparticles (P-25 Degussa) and further irradiated using UV light to overcome the hydrophobicity and fouling nature of the membrane. Further the membranes were characterized using SEM and FTIR. Contact angle measurements study confirmed the hydrophilic tendency of the modified membrane by decreasing the contact angle from $73^{\circ}$ to $20.28^{\circ}$. The modified membranes showed higher flux and better anti-fouling properties as compared to the unmodified counterparts. The optimum conditions were found to be 0.5 wt% $TiO_2$ loading with 60 min membrane immersion and 10 min UV light illumination. The effect of different pH conditions of feed was analysed. Real wastewater filtration experiments also indicated better performance of modified membranes as opposed to neat PES membranes.