• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.771-776
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• 2017

The cover glass of mobile displays and photovoltaic cells needs a functional coating, such as an anti-reflection and self-cleaning coating. Numerous studies have been conducted on the engineering application of biomimetic functional surfaces, such as moth eye and lotus leaf Anti-reflection coantings of silica nanoparticles could enhance the light transmittance. $TiO_2$ photocatalyst coatings have been applied to self-cleaning functional films. In this study, transparent hydrophobic anti-reflective coatings consisting of thin layers of $SiO_2/TiO_2$ nanoparticles were fabricated on a slide glass substrate by the sol-gel process and dip-coating process. The dependence of the surface morphology of the functional coatings was investigated by the atomic force microscopy (AFM), contact angle measurement, and UV-visible spectroscopy. It was found that the coating of $TiO_2$ nanoparticles exhibited a high average transmittance comparable to that of the bare slide glass substrate in the visible light range. The bi-layered functional coating of 7 nm $SiO_2$/7nm $TiO_2$ nanoparticles exhibits a transparent hydrophobic surface with a contact angle of $110^{\circ}$ and an improvement of the average transmittance of 2.3% compared to the bare slide glass substrate in the visible light range.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.550-555
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• 2001

A diamond-like carbon(DLC) films were deposited on the borosilicate glass substrate by radio frequency plasma enhanced chemical deposition(rf-PECVD). The $methane(CH_4)-hydrogen(H_2)$ gas mixture was used as precursor gas. The morphologies, the structure and the optical properties of the DLC films were investigated by SEM, Raman and UV spectrometer. The deposition rate was slightly increased with the hydrogen concentration in the gas mixture and it maintained constant at over 25 sccm of the gas flow rate. The optical band gap calculated by UV spectra decreased with increase of deposition time and DC self bias, but that were not effected by hydrogen content. Most effective parameter on the transmittance of film was bias voltage, especially in the range of ultra violet and visible light.

• Textile Coloration and Finishing
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• v.26 no.2
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• pp.88-98
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• 2014

This study is to assess the photocatalytic degradation of PET and Nylon 6 films containing nano-sized $TiO_2$ powders of anatase and rutile types. The PET and Nylon 6 films containing six kinds of the nanoparticles were prepared by melt casting method using a heating press machine. Reflectance in visible region and water contact angles of the irradiated PET and Nylon 6 composite films decreased with increasing UV/$O_3$ irradiation. Also the enhanced hydrophilicity has a close relationship with the increase in the Lewis base parameter, which indicates more oxidized polymer surfaces. The photocatalytic degradation of the nanocomposite films increased with increasing $TiO_2$ content and UV energy, which is more significant with the anatase types rather than the rutile types. The amide linkages in the Nylon 6 seemed to be more susceptible to the UV light compared to the ester groups in the PET, particularly in the presence of the $TiO_2$ photocatalysts. The photoscission and photodegradation of the polymers in the composites produced more degraded structure assisted by the photocatalytic activity of the $TiO_2$ nanoparticles. Also the composite films can bleach the methylene blue dyes more easily under the UV/$O_3$ irradiation, suggesting the photobleaching activity of the $TiO_2$ nanoparticles.

• Polymer(Korea)
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• v.31 no.5
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• pp.393-398
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• 2007

We studied the mechanism of liquid crystal alignment on polyvinylfluorocinnamate (PVCN-F) films which were irradiated by UV using polarized fourier transform infrared (FT-IR) spectroscopy and ultraviolet/visible (UV/Vis) spectroscopy. UV irradiation of PVCN-F films caused decrease of vinylene -C=C- stretching peak area at $1638cm^{-1}$ and shift of conjugated C:0 stretching vibration at $1712cm^{-1}\;to\;1734cm^{-1}$ which is caused by nonconjugated C=O stretching nitration. To study the orientation direction of 5CB liquid crystal (LC) molecules in the liquid crystal cell with PUV irradiation, rubbing treatment or without any treatment on the PVCN-F alignment layer, we used polarized FT-IR dichroism technique. We successfully measured 5CB LC alignment directions, which are perpendicular to the irradiated PUV polarization direction and parallel to the rubbing direction in the liquid crystal cell without using dichroic dyes.

• Bulletin of the Korean Space Science Society
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• 2004.10b
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• pp.372-375
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• 2004

The UV radiometer payload was launched successfully from the west coastal area of Korea Peninsula aboard KSR-III on 28, Nov 2002. KSR-III was the Korean third generation sounding rocket and was developed as intermediate step to larger space launch vehicle with liquid propulsion engine system. UV radiometer onboard KSR-III consists of UV and visible band optical phototubes to measure the direct solar attenuation during rocket ascending phase. For UV detection, 4 channel of sensors were installed in electronics payload section and each channel has 255, 290, 310nm center wavelengths, respectively. 450nm channel was used as reference for correction of the rocket attitude during the flight. Transmission characteristics of all channels were calibrated precisely prior to the flight test at the Optical Lab. in KARI (Korea Aerospace Research Institute). During a total of 231s flight time, the onboard data telemetered to the ground station in real time. The ozone column density was calculated by this telemetry raw data. From the calculated column density, the vertical ozone profile over Korea Peninsula was obtained with sensor calibration data. Our results had reasonable agreements compared with various observations such as ground Umkhr measurement at Yonsei site, ozonesonde at Pohang site, and satellite measurements of HALOE and POAM. The sensitivity analysis of retrieval algorithm for parameters was performed and it was provided that significant error sources of the retrieval algorithm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.3
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• pp.266-274
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• 2023

Recently, sterilization technology has received increasing interest due to the COVID-19 pandemic and required safety precautions. Particularly, sterilization devices using near ultraviolet (UV) with a 405 nm wavelength are also drawing attention. It has a UV-C wavelength and other sterilization effects. Its blue-colored light on the boundary between UV and visible light is used as a light-emitting diode (LED) lamp for 405 nm sterilization, owing to its longer wavelengths than UV rays. However, the 405 nm wavelength contains blue light that can damage the eyes and skin during prolonged exposures and affect the emotional and biological parts of the body. Currently, 405 nm sterilization LED light registers are circulating in the market. However, they have not undergone safety tests for blue-light hazards. Thus, with the active distribution of sterilization LED lights, solid safety standards and management systems are essential to protect users from blue-light hazards. Accordingly, in this study, we conducted spectral radiance and spectral radiative luminance tests on 405 nm sterilization LED registers available in the market by the measurement criteria of IEC 62471. Safety standards must be established to secure users' safety against blue light hazards at a time when 405nm sterilization LED lights are actively distributed due to COVID-19.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.5
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• pp.712-720
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• 2022

In this study, we evaluated the production and photoreactivity of CDOM of two polar phytoplanktons - Phaeocystis antarctica and Phaeocystis pouchetii, in order to find out UV effects on phytoplanktons. In visible region, CDOM in media of both phytoplanktons under UV-R decreased during 48hrs incubation period. However, in UV region CDOM decreased 30 % in the media of P. antarctica, but increased 10% in media of P. pouchetii, compared to CDOM concentrations of control after 48 hr incubation. This result indicates that biota in polar environment would not well protected from UV-R harmful effect when P. antarctica is dominant because of loss of CDOM, but when P. pouchetii is dominant species, production of UV absorbing organic matter could play more efficiently for UV screening for marine biota. Also we confirmed that FDOM of humic substance (C-peak) produced by these phtoplanktons under UV-R stress were well matched with fluorescence characteristics of the UV-protecting compound, MAAs. This finding shows that Phaeocystis pouchetti with low photoreactivity would contribute to DOM pool of polar marine environment under stratification by global warming.

• Journal of Powder Materials
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• v.16 no.3
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• pp.196-202
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• 2009

A visible-light photoactive $TiO_{2-x}N_x$ photocatalyst was synthesized successfully by means of cogrinding of anatase-$TiO_2(a-TiO_2)$ in $NH_3$ ambient, followed by heat-treatment at $200^{\circ}C$ in air environment. In general, it is well known that the grinding-operation induces phase transformation of a-$TiO_2$ to rutile $TiO_2$. This study investigates the influence of the amount of $NH_3$ gas on the phase transformation rate of a-$TiO_2$ and enhancement of visible-light photocatalytic activity, and also examines the relation between the photocatalytic activity and the period of grinding time. The phase transformation rate of a-$TiO_2$ to rutile is retarded with the amount of NH3 injected. And the visible-light photocatalytic activity of samples, was more closely related to the period of grinding time than $NH_3$ amount injected, which means that the doping amount of nitrogen into $TiO_2$ more effective to mechanical energy than $NH_3$ amount injected. XRD, XPS, FT-IR, UV-vis, Specific surface area (SSA), NOx decomposition techniques are employed to verify above results more clearly.

• Journal of the Korean Ceramic Society
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• v.56 no.3
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• pp.284-290
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• 2019

Ternary MoS₂/graphene (G)-TiO₂ photocatalysts were prepared by a simple hydrothermal method. The morphology, phase structure, band gap, and catalytic properties of the prepared samples were investigated by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, UV-vis spectrophotometry, and Brunauer-Emmett-Teller surface area measurement. The H₂ production efficiency of the prepared catalysts was tested in methanol-water mixture under visible light. MoS₂/G-TiO₂ exhibited the highest activity for photocatalytic H₂ production. For 5 wt.% and 1 wt.% MoS₂ and graphene (5MT-1G), the production rate of H₂ was as high as 1989 µmol^-1h^-1. The catalyst 5MT-1G showed H₂ production activity that was ~ 11.3, 5.6, and 4.1 times higher than those of pure TiO₂, 1GT, and 5MT, respectively. The unique structure and morphology of the MoS₂/G-TiO₂ photocatalyst contributed to its improved hydrogen production efficiency under visible light.

• Journal of Environmental Science International
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• v.28 no.11
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• pp.971-981
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• 2019

This study evaluated the photocatalytic oxidation efficiency of volatile organic compounds by $Cu_2O-TiO_2$ under visible-light irradiation. $Cu_2O-TiO_2$ was synthesized by an ultrasonic-assisted method. The XRD result indicated successful p-n type photocatalysts. However, no diffraction peaks belonging to $TiO_2$ were observed for the $Cu_2O-TiO_2$. The Uv-vis spectra result revealed that the synthesized $Cu_2O-TiO_2$ can be activated under visible-light irradiation. The FE-TEM/EDS result showed the formation of synthesized nanocomposites in the commercial P25 $TiO_2$, the undoped $TiO_2$, and $Cu_2O-TiO_2$ and componential analysis in the undoped $TiO_2$ and $Cu_2O-TiO_2$. The photocatalytic oxidation efficiencies of benzene, toluene, ethylbenzene, and o-xylene with $Cu_2O-TiO_2$ were higher than those of P25 $TiO_2$ and undoped $TiO_2$. These results indicate that the prepared $Cu_2O-TiO_2$ photocatalyst can be applied effectively to control gaseous BTEX.