• Title, Summary, Keyword: uv-spectra

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Properties of Photoisomerization of Organic-Ultrathin Films (아조벤젠기를 갖는 장쇄지방산LB막의 광이성화 특성)

  • Kim, Moo-Goon;Park, Tae-Gone;Park, Keun-Ho
    • Proceedings of the KIEE Conference
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    • pp.1184-1186
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    • 1995
  • The absorption spectra of synthesis of azobenzene containing long chain fatty acids were investigated by UV spectrophotometer in chloroform solution. Also, the pressure-area isotherms of the molecules on the water-air interface were obtained and the LB films were fabricated onto a quartz slides and quartz crystals by the conventional Langmuir-Blodggett(LB) method. The UV absorption spectra of Langmuir-Blodggett(LB) films on quartz slides have been measured. From these measurements, following conclusions were obtained. Azobenzene containing long chain fatty acids show a photoisomerization by irradiation of UV light and visible light alternatively. At the pressure-area isotherms, the value of surface pressure increment were decreased when the number of $C_n$ increased. Also the LB films show a photoisomerization characteristics. So the LB film of azobenzene containing long chain fatty acid has possibility to being applied to functional molecular device such as photomemory and light switching.

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Emission Spectroscopy of Unstable Molecules using a Fourier Transform Spectrometer (Fourier Transform 분광기를 이용한 불안정한 분자의 방출분광학)

  • Sang Kuk Lee;Un Sik Kim
    • Journal of the Korean Chemical Society
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    • v.37 no.4
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    • pp.371-377
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    • 1993
  • Fourier Transform UV/VIS spectrometer has been modified for emission spectroscopy with the technique of supersonic expansion, in which the unstable molecular radical $CH_3S$ has been generated in a jet by a high voltage DC discharge. The fluorescence spectra of the supersonically cooled radical have been recorded on a Fourier Transform UV/VIS spectrometer. The ratio of signal to noise of the spectra has been improved substantially. Also the rotational structure has been clearly resolved for $CH_3S$ molecular radical.

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mPW1PW91 Calculated and Experimental UV/IR Spectra of Unsymmetrical trans-Stilbenes

  • Choe, Jong-In;Park, Seong-Jun;Cho, Chul-Hee;Kim, Chul-Bae;Park, Kwang-Yong
    • Bulletin of the Korean Chemical Society
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    • v.31 no.8
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    • pp.2175-2179
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    • 2010
  • Quantum mechanical properties of unsymmetrical and unfunctionalized trans-stilbene derivatives 1-3, which had been prepared by solid-phase parallel syntheses, were characterized using mPW1PW91/6-311G(d,p) (hybrid HF-DF) calculations. The total electronic energies, normal vibrational modes, Gibbs free energies, and HOMOs and LUMOs of sixteen different structures from three different groups were analyzed. The energy differences between the HOMOs and LUMOs of the various unsymmetrical trans-stilbenes are in accord with the maximum absorption peaks of the experimental UV spectra of 1-3. The calculated normal vibrational modes of 21 were comparable with its experimental IR spectrum. The $\pi$-conjugation in the para-connected biphenyl group of 2 is better than the one in the metaconnected biphenyl group on the shorter side of 3.

Preparation of Polyynes by the Laser Ablation of Graphite in Water and Organic Solvents

  • Shin, Seung-Keun;Park, Seung-Min
    • Bulletin of the Korean Chemical Society
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    • v.33 no.2
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    • pp.597-600
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    • 2012
  • Polyynes were formed by laser ablation of a graphite target in deionized water ($H_2O$ and $D_2O$) and various organic solvents such as acetonitrile, n-hexane, and c-hexane and were identified by analyzing ultraviolet (UV) absorption and Raman spectra. We assigned the major UV absorption peaks that coincided with the electronic transitions corresponding to linear polyyne chains. The UV absorption peak intensities of a polyyne solution decreased as the holding temperature of the solution increased. Also, the absorption spectra of polyynes obtained by laser ablation of a graphite target at different volume fractions of $H_2O$ and $D_2O$ were examined.

A study on the crystallization processing of photosensitive glass by FT-IR and FT-Raman spectroscopy (FT-IR과 FT-Raman 분광계를 이용한 광민감유리의 결정화 과정에 관한 연구)

  • 이명원;강원호
    • Electrical & Electronic Materials
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    • v.10 no.3
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    • pp.284-288
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    • 1997
  • FT-IR and FT-Raman spectra were measured for 15Li$_{2}$O.3Al$_{2}$O$_{3}$.78SiO$_{2}$. 4K$_{2}$O glass system after UV irradiations. Optimum UV irradiation time of Li$_{2}$O.SiO$_{2}$ crystalline phase was 60 seconds and crystalline phase of Li$_{2}$O.SiO$_{2}$ was leached out on 5% HF. 977 cm$^{1}$ band of FT-Raman spectra can be attributed to two-non bridging oxygen in unit cell for 1 hour and optimum crystallization was confirmed for 3 hrs, 630.deg. C.

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A Study on the Properties of Langmuir-Blodgett Films of Polyamic Acid containing p-Methoxyazobenzene (p-Methoxyazobenzene을 함유한 Polyamic acid의 Langmuir-Blodgett막 물성에 관한 연구)

  • Park, Keun-Ho;Lee, Seong-Rak
    • Journal of the Korean Applied Science and Technology
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    • v.15 no.1
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    • pp.55-62
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    • 1998
  • The absorption spectra of polyamic acid containing p-methoxyazobenzene in a mixture of N, N-dimethylacetamide(DMAC) and benzene(1:1 by volume) solution was induced photoisomerization by UV and visible light irradiation. This solution is influenced on temperature according to measure by UV-Vis Spectrophotometer. Ultra thin film of polyamic acid containing p-methoxyazobenzene was prepared on the hydrophilic quartz plate by Langmuir-Blodgett(LB) method. The precursor LB film was heated in a vacuum dry oven at $120^{\circ}C$ in order to convert it into the LB film of polyimide. The absorption spectra of LB films were also induced photoisomerization by UV and visible light irradiation.

Measuring gas metallicity of local AGNs using UV spectra

  • Shin, Jae-Jin;Woo, Jong-Hak
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.1
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    • pp.50.1-50.1
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    • 2012
  • As a tracer of star formation history, metallicity provides crucial information for understanding galaxy evolution. In the case AGN, gas metallicity is often derived from the flux ratio of UV emission lines, i.e., NV1240 and CIV1549. To investigate the dependence of metallicity on AGN luminosity, black hole mass, and accretion rate, we measure NV1240 and CIV1549 line fluxes and derive gas metallicity of a sample of 73 local Seyfert 1 galaxies and QSOs, using archival UV spectra obtained with the HST and IUE. In this work, we will present the metallicity of local AGN and its relation with AGN properties.

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A Study on UV Degradation of SBR and NR Containing Polymeric UV Stabilizer (고분자형 자외선 안정제를 함유한 SBR과 NR의 UV 노화 거동에 관한 연구)

  • Kaang, Shin-Young;Nam, Kyoung-Tae;Hong, Chang-Kook;Chae, Kyu-Ho
    • Elastomers and Composites
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    • v.41 no.3
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    • pp.182-193
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    • 2006
  • The retardation effects of a new polymeric UV stabilizer, DGEBA-HALS, on the UV degradation of SBR and NR were investigated in this study. The UV degradation behaviors of three different rubber compounds, without any photostabilizer and with commercial Cyabsorb UV-3529 and DGEBA-HALS, were compared. Also, the physical characteristics such as Young's modulus, tensile strength, blow-off deformation and crosslink density were examined. The Young's modulus was increased by UV irradiation for all samples, and the tensile strength, after UV irradiation, of the compound with UV stabilizer was better than that of the compound without stabilizer. Especially, the tensile strength of UV irradiated NR was improved by adding DGEBA-HALS. The results of blow-off deformation were in accord with those of Young's modulus. The degree of transmission of SBR compounds obtained from UV-vis transmission spectra was improved about 4% by adding the UV stabilizer. Commercial Cyabsorb UJV-3529 and DGEBA-HALS showed similar trends of transmission. The SEM photographs of SBR surface showed that the size of cracks created by UV irradiation became smaller by adding UV stabilizer. In particular, it is observed that the stabilization effect of DGEBA-HALS was better than that of commercial Cyabsorb UV-3529.

Color Enhancement of Natural Sapphires by High Pressure High Temperature Process

  • Song, Jeongho;Noh, Yunyoung;Song, Ohsung
    • Journal of the Korean Ceramic Society
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    • v.52 no.2
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    • pp.165-170
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    • 2015
  • We employed the high-pressure high temperature (HPHT) process to enhance the colors of natural sapphires to obtain a vivid blue. First, we analyze the content of the coloring agent $Fe_2O_3$ using the wavelength dispersive X-ray fluorescence (WD-XRF) method. The HPHT procedure operates under 1 GPa at various temperatures of 1700, 1750, and $1800^{\circ}C$ for 5 minutes using a cubic press. We determine the color changes using the optical microscopic images, UV-VIS near-infrared (NIR) spectra, micro-Raman spectra, and Fourier transform-infrared (FT-IR) spectra for all sapphire samples before and after the treatment. The optical microscopic results indicate that the HPHT process can enhance the sapphire color to a vivid blue at temperatures above $1750^{\circ}C$. The UV-VIS-NIR spectra identify the color changes explicitly and quantitatively through providing the Lab color scales and color differences. Both results demonstrate that the colors of natural sapphires can be enhanced to a vivid blue using the HPHT process above $1750^{\circ}C$ under 1 GPa for 5 minutes.

Effect of Film Thickness on Structural, Electrical, and Optical Properties of Sol-Gel Deposited Layer-by-layer ZnO Nanoparticles

  • Shariffudin, S.S.;Salina, M.;Herman, S.H.;Rusop, M.
    • Transactions on Electrical and Electronic Materials
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    • v.13 no.2
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    • pp.102-105
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    • 2012
  • The structural, electrical, and optical properties of layer-by-layer ZnO nanoparticles deposited using sol-gel spin coating technique were studied and now presented. Thicknesses of the thin films were varied by increasing the number of deposited layers. As part of our characterization process, XRD and FE-SEM were used to characterize the structural properties, current-voltage measurements for the electrical properties, and UV-Vis spectra and photoluminescence spectra for the optical properties of the ZnO thin films. ZnO thin films with thicknesses ranging from 14.2 nm to 62.7 nm were used in this work. Film with thickness of 42.7 nm gave the lowest resistivity among all, $1.39{\times}10^{-2}{\Omega}{\cdot}cm$. Photoluminescence spectra showed two peaks which were in the UV emission centered at 380 nm, and visible emission centered at 590 nm. Optical transmittance spectra of the samples indicated that all films were transparent (>88%) in the visible-NIR range. The optical band gap energy was estimated to be 3.21~3.26 eV, with band gap increased with the thin film thickness.