• Korean Journal of Materials Research
• /
• v.18 no.12
• /
• pp.640-644
• /
• 2008

ZnO/ZnS core/shell nanocrystals (${\sim}5-7\;nm$ in diameter) with a size close to the quantum confinement regime were successfully synthesized using polyol and thermolysis. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) analyses reveal that they exist in a highly crystalline wurtzite structure. The ZnO/ZnS nanocrystals show significantly enhanced UV-light emission (${\sim}384\;nm$) due to effective surface passivation of the ZnO core, whereas the emission of green light (${\sim}550\;nm$) was almost negligible. They also showed slight photoluminescence (PL) red-shift, which is possibly due to further growth of the ZnO core and/or the extension of the electron wave function to the shell. The ZnO/ZnS core/shell nanocrystals demonstrate strong potential for use as low-cost UV-light emitting devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.04b
• /
• pp.65-68
• /
• 2002

The effect of low-temperature ZnO buffer layer has been investigated for the optical properties of ZnO thin films. ZnO buffers and thin films have been deposited using the pulsed laser deposition technique. ZnO buffer layers were grown at $200^{\circ}C$ with various thickness of 0 to 60 nm, followed by raising the substrate temperature to $400^{\circ}C$ to grow $2{\mu}m$ ZnO thin films. The buffer layers could relax stresses induced by the lattice mismatch and different thermal expansion coefficients between ZnO thin films and sapphire substrate. In order to identify the optical properties of ZnO thin films, PL measurement was used. From the results of PL measurement, all the fabricated ZnO thin films with buffer layers have shown intensive UV emission with a narrow linewidth. ZnO thin films with buffer layer of 20 nm have shown the strongest UV emission. It was found that the use of ZnO buffer layer plays an important role to improve the intensive UV emission of the ZnO thin films.

• Microbiology and Biotechnology Letters
• /
• v.11 no.3
• /
• pp.155-161
• /
• 1983

The effects of ultraviolet light on bacteriophage f2 were investigated to determine the inactivation kinetics and its mechanism. The 260nm light showed a little higher inactivation rate than the one of 300 nm. In this work, our main concern was whether structural and/or conformational changes in the protein capsid could occur by UV irradiation. The inactivation for the first 20 minutes irradiation was rapid with a loss of about 4 logs and followed by a slower rate during the next 40 minutes with no survival noted in the samples irradiated for 90 minutes or longer. The structural change of the protein capsid was examined by optical spectroscopic techniques and electron microscopy. The absorption spectra of the UV irradiated phages showed no detectable differences in terms of the spectral shape and intensity from the control phage. However, the fluorescence emission spectroscopic data, i.e. 1) fluorescence quenching of tryptophan residues upon irradiation of 300 nm light, 2) enhancement of fluorescence emission of ANS (8-aniline-1-naphthalene sulfonate) bound to the intact phages compared to the one in the UV-treated phages, and 3) decrease of energy transfer efficiency from tryptophan to ANS in the UV-treated samples, presented remarkable differences between the intact and UV-treated phages. Such a structural alteration was also observed by electron microscopy The UV-treated phages appeared to be broken and empty capsids. Therefore, the inactivation of the bacteriophage f2 by UV irradiation is thought to be attributed to the structural change in the protein capsid as well as damage in the viral RNA by UV irradiation.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2000.01a
• /
• pp.29-30
• /
• 2000

CaS:Pb thin film used as phosphor layer in electroluminescent devices were deposited by an atomic layer deposition (ALD). The photoluminescence emission and excitation spectra were measured at 5 and 300K for the $CaS:Pb^{2+}$ phosphors with different Pb concentration from 0.001 at.% to 0.648 at.%. The emission spectra of these samples were characterized as UV emission and blue emission with the center of peak around 360 and 425nm, respectively. The UV emission was dominant at the low $Pb^{2+}$ concentration of 0.001 at%, whereas with increase of Pb concentration, the blue emission became a major component and to longer wavelength.

• Fibers and Polymers
• /
• v.6 no.2
• /
• pp.127-130
• /
• 2005

Intrinsic UV reflection and fluorescence behaviors of polycarbonate, polyurethane and poly(ethylene terephthalate) films were investigated in order to characterize the interaction of water in these films. During water sorption process, UV reflection spectra of polycarbonate and polyurethane films showed little peak position changes. Fluorescence emission spectra of polycarbonate films showed red spectral shifts from 332 nm with water immersion time. This red-shifted peak could be due to phenyl-2-phenoxybenzoate, which is one of the major thermal degradation products in polycarbonate. Fluorescence peaks of polyurethane films appeared at two different positions and the ratio of these peak intensities increased with increasing immersion time. In the case of PET films, the UV reflection spectrum showed the peak intensity around 340 nm to change in response to water sorption. The fluorescence near 388 nm probably due to ground state dimer exhibited sensitivity with water sorption, when excited at 340 nm.

• The Bulletin of The Korean Astronomical Society
• /
• v.43 no.2
• /
• pp.52.3-53
• /
• 2018

We compare vertical profiles of the extraplanar $H{\alpha}$ emission to those of the UV emission for 38 nearby edge-on late-type galaxies. It is found that detection of the "diffuse" extraplanar dust (eDust), traced by the vertically extended, scattered UV starlight, always coincides with the presence of the extraplanar $H{\alpha}$ emission. A strong correlation between the scale heights of the extraplanar $H{\alpha}$ and UV emissions is also found; the scale height at $H{\alpha}$ is found to be ~0.74 of the scale height at FUV. Our results may indicate the multiphase nature of the diffuse ionized gas and dust in the galactic halos. The existence of eDust in galaxies where the extraplanar $H{\alpha}$ emission is detected suggests that a larger portion of the extraplanar $H{\alpha}$ emission than that predicted in previous studies may be caused by $H{\alpha}$ photons that originate from H II regions in the galactic plane and are subsequently scattered by the eDust. This possibility raise an advantage in studying the extraplanar diffuse ionized gas. We also find that the scale heights of the extraplanar emissions normalized to the galaxy size correlate well with the star formation rate surface density of the galaxies. The properties of eDust in our galaxies is on a continuation line of that found through previous observations of the extraplanar polycyclic aromatic hydrocarbons emission in more active galaxies known to have galactic winds.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.355-357
• /
• 2001

ZnO thin films were deposited on (001) sapphire substrate at various ambient gas pressure by pulsed laser deposition(PLD). Oxygen was used as ambient gas, and oxygen gas pressure was varied from 1.0${\times}$10$\^$-6/ Torr to 500 mTorr during the film deposition. As oxygen gas pressure increase in the region below critical pressure photoluminescence(PL) intensity in UV and green region increase. As oxygen gas pressure increase in the region above critical pressure photoluminescence(PL) intensity in UV and green region decrease. Each of critical ambient gas Pressures was 350 mTorr for UV emission and 200 mTorr for green emission.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2006.08a
• /
• pp.1355-1359
• /
• 2006

Due to its efficient red emission, $Eu^{3+}$ ion has been doped in various host materials. $GdCa_4B_3O_{10}:Eu^{3+}$ phosphor for red emission has been prepared by solid state reaction. Photoluminescence properties for the phosphor under UV and VUV excitation were investigated. The $GdCa_4B_3O_{10}:Eu^{3+}$ phosphor under both excitation conditions shows typical red emission spectrum centered at 611 nm with several weak peaks due to energy transfer from $^5D_O\;to\;^7F_J(J=1,2,3,4)$ of $Eu^{3+}$ ion. On the other hand, the activator content exhibiting the concentration quenching under UV and VUV irradiation is 10 mole% and 2.5 mole%, respectively.

• Asian Journal of Atmospheric Environment
• /
• v.7 no.4
• /
• pp.199-208
• /
• 2013

Mercury exchange fluxes between atmosphere and soil surface were measured in two different types of soils; lawn soil (LS) and forest soil (FS). Average Hg emission from LS was higher than from FS although the soil Hg content was more than 2 times higher in forest soil. In LS, Hg emissions were much greater in warm season than in cold season; however, deposition was dominant in FS during warm season because of leafy trees blocking the solar radiation reaching on the soil surface. In both LS and FS, Hg fluxes showed significantly positive correlations with UV radiation and soil surface temperature during cold season. In addition, it was observed that emission showed positive correlation with UV radiation and soil temperature while there was negative relationship between deposition and UV radiation.

• Journal of Sensor Science and Technology
• /
• v.18 no.4
• /
• pp.316-321
• /
• 2009

Er-doped ZnO(ZnO:Er) films were deposited onto MgO wafers by ultrasonic spray pyrolysis at 550 $^{\circ}C$ varying the concentration of Er in the deposition source from 0.5 wt% to 3.0 wt%. Annealing of the films in a vacuum was carried out to increase the intensity of ultraviolet(UV) emission from the films. The annealing temperature was between 600$^{\circ}C$ and 800$^{\circ}C$. The crystallographic properties and surface morphology of the films were investigated by X-ray diffraction(XRD)and scanning electron microscope(SEM), respectively. The properties of photoluminescence(PL) for the films were investigated by the dependence of PL spectra on the annealing temperature. X-ray photoelectron spectroscopy(XPS) was conducted to find the composition change in the films by the annealing.