• Journal of the Korean Ceramic Society
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• 제40권9호
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• pp.902-908
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• 2003

Au/TiO$_2$ core-shell structure nanoparticles were synthesised by sol-gel process, and the morphology and crystallinity of TiO$_2$ shell were investigated by TEM and UV-Vis. absorption spectrometer. Au/TiO$_2$ core-shell structure nanoparticles could be prepared by the hydrolysis of TOAA (Titanium Oxide Acethylacetonate) in Au colloid ethanol solution with $H_2O$. The thickness of TiO$_2$ shell on the surface of Au particles was about 1 nm. To investigate the crystallinity of TiO$_2$ shell, UV light with 254 nm and radioactive lay of $^{60}$ CO were irradiated on the TiO$_2$ coated Au colloid ethanol solution. The surface plasmon phenomenon of Au nanoparticles appeared only when the radioactive lay was irradiated on the TiO$_2$ coated Au colloid ethanol solution. From these results, it was found that the TiO$_2$ shell was amorphous and the MUA (Mercaptoundecanoic Acid) layer on the Au particle for its dispersion didn't act as an obstacle to disturb the movement of electron onto the surface of Au particle.

• Journal of the Korean Chemical Society
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• 제65권4호
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• pp.254-259
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• 2021

The purpose of this work is the development of a method for an effective, less expensive, rapid, and simultaneous determination of three phenolic compounds (caffeic acid, gallic acid, and quercetin) widely present in food resources and known for their antioxidant powers. The method relies on partial least squares (PLS) calibration of UV-visible spectroscopic data. This model was applied to simultaneously determine, the concentrations of caffeic acid (CA), gallic acid (GA), and quercetin (Q) in six herb infusion extracts: basil, chive, laurel, mint, parsley, and thyme. A wavelength range (250-400) nm, and an experimental calibration matrix with 21 samples of ternary mixtures composed of CA (6.0-21.0 mg/L), GA (10.0-35.2 mg/L), and Q (6.4-17.5 mg/L) were chosen. Spectroscopic data were mean-centered before calibration. Two latent variables were determined using the contiguous block cross-validation procedure after calculating the root mean square error cross-validation RMSECV. Other statistic parameters: RMSEP, R², and Recovery (%) were used to determine the predictive ability of the model. The results obtained demonstrated that UV-visible spectrometry and PLS regression were successfully applied to simultaneously quantify the three phenolic compounds in synthetic ternary mixtures. Moreover, the concentrations of CA, GA and Q in herb infusion extracts were easily predicted and found to be 3.918-18.055, 9.014-23.825, and 9.040-13.350 mg/g of dry sample, respectively.

• Applied Chemistry for Engineering
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• 제23권5호
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• pp.462-466
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• 2012

$\beta$-cyclodextrin ($\beta$-CD) polymers were prepared in a strong alkali condition solution (NaOH solution 30% (w/v)) using epichlorohydrin (EPI) as a cross-linker, and the molar ratio of EPI to $\beta$-CD was 10 : 1. The $\beta$-CD content in $\beta$-CD polymers is about 52%. In order to get the photo-responsible and pH-responsible, cinnamic acid was added to be inserted into the cavities of $\beta$-CD due to the hydrophobic interaction. The complex formation was confirmed using transmission electron microscope. The dimerization degree of complexes increased under UV irradiation at $\lambda$ = 365 nm but decreased under the UV irradiation at $\lambda$ = 254 nm. Dynamic light scattering analysis of particle sizes showed that the sizes of complexes did not change with different UV wavelength. Moreover, the complexes were pH-responsible because of the carboxyl group of cinnamic acid, but the size and zeta potential of the complex did not change in strong acid and alkali conditions.

• Bulletin of the Korean Chemical Society
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• 제33권5호
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• pp.1753-1758
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• 2012

A novel, efficient and controlled protocol for the synthesis and enhanced photocatalytic activity of $Au@TiO_2$ nanocomposite is developed. $TiO_2$ (P25) was pretreated by employing UV light (${\lambda}$ = 254 nm) and the pretreated $TiO_2$ was uniformly decorated by gold nanoparticles (AuNPs) in presence of sodium citrate and UV light. UV pretreatment makes the $TiO_2$ activated, as electrons were accumulated within the $TiO_2$ in the conduction band. These accumulated electrons facilitate the formation of AuNPs which were of very small size (2-5 nm), similar morphology and uniformly deposited at $TiO_2$ surface. It leads to formation of stable and crystalline $Au@TiO_2$ nanocomposites. The rapidity (13 hours), monodispersity, smaller nanocomposites and easy separation make this protocol highly significant in the area of nanocomposites syntheses. As-synthesized nanocomposites were characterized by TEM, HRTEM, TEM-EDX, SAED, XRD, UV-visible spectrophotometer and zeta potential. Dye degradation experiments of methyl orange show that type I ($Au@TiO_2$ nanocomposites in which $TiO_2$ was pretreated with UV light) has enhanced photocatalytic activity in comparison to type II ($Au@TiO_2$ nanocomposites in which $TiO_2$ was not pretreated with UV light) and $TiO_2$ (P25). This shows that pretreatment of $TiO_2$ provides type I a better catalytic activity.

• Elastomers and Composites
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• 제51권1호
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• pp.1-9
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• 2016

Characterization of the UV oxidation for raw natural rubber (NR) was investigated in controlled conditions through image and FT-IR analysis. The UV oxidation was performed on a thin film of natural rubber coated on a KBr window at 254 nm and room temperature to exclude the thermal oxidation. Before or after exposure to UV light, image of the NR thin film was observed at a right or tilted angle. FT-IR absorption spectra were measured in transmission mode with the UV irradiation time. The UV oxidation of NR was examined by the changes of absorption peaks at 3425, 1717, 1084, 1477, 1377, and $833cm^{-1}$ which were assigned to hydroxyl group (-OH), carbonyl group (-C=O), carbon-oxygen bond (-C-O), methylene group $(-CH_2-)$, methyl group $(-CH_3)$, and cis-methine group $(cis-CCH_3=CH-)$, respectively. During the initial exposure period, the results indicated that the appearance of carbonyl group was directly related to the reduction of cis-methine group containing carbon-carbon double bond (-C=C-). Most of aldehydes or ketones from carbon-carbon double bonds were formed very fast by chain scission. A lot of long wide cracks with one orientation at regular intervals which resulted in consecutive chain scission were observed by image analysis. During all exposure periods, on the other hand, it was considered that the continuous increment of hydroxyl and carbonyl group was closely related to the decrement of methylene and methyl group in the allylic position. Therefore, two possible mechanisms for the UV oxidation of NR were suggested.

• YAKHAK HOEJI
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• 제30권6호
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• pp.311-316
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• 1986

A new UV labeling reagent was developed and used in HPLC for the determination of prostaglandin $E_2$ which have weak UV light-absorbing property. This reagent, 2-bromoacetyltriphenylene, was synthesized by the bromination of 2-acetyltriphenylene which was obtained from triphenylene by Friedel-Crafts reaction. The wave length maximum (${\lambda}_{max}^{CH_3CN}$ of this reagent was 268nm. Prostaglandin E$_2$ was extracted from prostaglandin E$_2$-$\beta$-cyclodextrin using a Sep-pak $C_{18}$ cartridge. The prostaglandin E$_2$ was labeled with 2-bromoacetyl-triphenylene in aectonitrite using 18-crown-6-ether as catalyst. Derivatized prostaglandins were separated on a reversed-phase column (Radial-pak) $\mu$-Bondapak $C_{18}$ using acetonitrile: water=60:40 as mobile phase. The effluent was monitored by UV detector at 254nm filter kit. Linearity of calibration curve was obtained between 30ng and 140ng, and the lower limit of detection was 5ng.

• Journal of Industrial Technology
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• 제32권A호
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• pp.95-102
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• 2012

To advance luminance efficiency of Titania at visible range, N-doped $TiO_2$ was prepared by using ammonium hydroxide as a source of nitrogen. The photoactivities of the synthesized $TiO_2$ were evaluated on the basis of degradation of humic acid in aqueous solutions with different light sources, UV-C, UV-A and fluorescent lamp. As a result, at UV-C is high efficiency $UV_{254}$ decrease and TOC removal. In this study, the best synthetic conditions of N-doped $TiO_2$ were 5.0 M of ammonium hydroxide concentration and calcination temperature of $550^{\circ}C$. The degradation rate of humic acid as an evaluation of photoactivities of the catalysts were conducted with pH variation, decrease rate of molecular absorption, removal rate of total organic carbon and fluorescece evolution for humic acid solution. XRD and SEM were applied for analysis of surface analysis of the catalysts.

• Journal of Korean Society for Atmospheric Environment
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• 제16권E호
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• pp.39-46
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• 2000

Volatile Organic Compounds (VOCs) are considered as the precursors of atmospheric ozone and photochemical smog formation. In particular, chemical plants have produced a lot of VOCs and thus they have been forced to reduce or remove air emissions from the on-site chemical facilities. For the effective removal of VOCs produced in the chemical plants, the authors employed a titanium oxide(TiO$_2$) mediated photo-catalytic oxidation method. The initiation methods employed in this study to produce oxygen radicals for th photo-catalytic oxidation of the VOCs were Ultra-Violet(UV), Non-Thermal Plasma(NTS), and a combination of Uv and NTP. This study focused on a comparison of the removal efficiencies of VOCs as a function of the initiation method such as NTP and/or UV techniques. Removal efficiency change of VOCs as was investigated as a function of the wavelength of the UV lamp(254, 302, and 365 nm) and the degree of TiO$_2$ coating (10 and 30%). In this study, it was identified that removal efficiencies if the VOCs under the normal air environment were much better than those under the nitrogen gas environment containing small amount of oxygen. Removal efficiency by NTP technique was much better than the UV or the combination of UV and NTP techniques. In a comparison if UV wavelengths employed, it was found that shorter wavelength showed better removal efficiency, compared with longer ones. When the removal efficiencies of VOCs were compared in terms of the degree of TiO$_2$ coating, the higher TiO$_2$coating showed better removal efficiency that the lower TiO$_2$ coating

• Environmental Engineering Research
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• 제23권2호
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• pp.181-188
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• 2018

Photocatalytic oxidation in the presence of Fe-doped, Zn-doped or Fe-Zn co-doped $TiO_2$ was used to effectively decompose humic acids (HAs) in water. The highest HAs removal efficiency (65.7%) was achieved in the presence of $500^{\circ}C$ calcined 0.0010% Fe-Zn co-doped $TiO_2$ with the Fe:Zn ratio of 3:2. The initial solution pH value, inorganic cations and anions also affected the catalyst photocatalytic ability. The HAs removal for the initial pH of 2 was the highest, and for the pH of 6 was the lowest. The photocatalytic oxidation of HAs was enhanced with the increase of the $Ca^{2+}$ or $Mg^{2+}$ concentration, and reduced when concentrations of some anions increased. The inhibition order of the anions on $TiO_2$ photocatalytic activities was $CO{_3}^{2-}$ > $HCO_3{^-}$ > $Cl^-$, but a slightly promotion was achieved when $SO{_4}^{2-}$ was added. Total organic carbon (TOC) removal was used to evaluate the actual HAs mineralization degree caused by the $500^{\circ}C$ calcined 0.0010% Fe-Zn (3:2) co-doped $TiO_2$. For tap water added with HAs, the $UV_{254}$ and TOC removal rates were 57.2% and 49.9%, respectively. The $UV_{254}$ removal efficiency was higher than that of TOC because of the generation of intermediates that could significantly reduce the $UV_{254}$, but not the TOC.

• Analytical Science and Technology
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• 제14권1호
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• pp.80-87
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• 2001

This research was studied the action of the coupling ozone-hydrogen peroxide on aqueous humic acid. PEROXONE process is enhanced the generation of hydroxyl radicals which is effective for degradation of organic matters. Therefore the changes of $UV_{254}$ and TOC were investigated through the change of concentrations, injection time of $H_2O_2$, initial pH of aqueous humic acid and concentrations of radical savenger as $HCO_3{^-}$ in the PEROXONE processes. And the GC/ECD was used to detect the formaldehyde formed by ozonation of humic acid. From the experimental results, concentrations and injection time of $H_2O_2$ and initial pH in solution in the PEROXONE processes were very important for enhancing the efficiency of degradation in humic acid. The results indicated that removal efficiency of TOC was the highest when concentration of $H_2O_2$ was 5mg/L, injection time of $H_2O_2$ was 5 minutes and initial pH in solution was 10.5. And presence of alkalinity in solution was reduced the efficiency of treatment. The formaldehyde were formed less PEROXONE processes than only ozone. When initial pH in solution were changed from 3.5 to 10.5, the formaldehyde were formed highest concentration at pH 5.