• The Korean Journal of Ceramics
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• 제1권3호
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• pp.152-154
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• 1995

A non-hydrolytic sol-gel process was developed to fabricate low-hydroxyl hard gels. The reaction of tert-butyl alcohol with silicon halides provided transparent low-hydroxyl hard gels. Some properties such as transparency, density, and refractive index was successfully doped into the hard gel matrices. The absorption spectrum of an erbium-doped methylsilsesquioxane was investigated to decide the pumping wavelength of an argon laser. The luminescence of the erbium-doped gel at 664 nm seems to be due to $4^F{9/2}\to 4^I_{15/2}$ transition.

• The Korean Journal of Ceramics
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• 제4권1호
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• pp.28-32
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• 1998

This paper reports on photoluminescence (PL), luminescence decay curves, and compositional analysis of porous silicon(PS) which is aged under air ambient by Fourier transform infrared vibrational spectroscopy (FTIR) and by Auger electron spectroscopy (AES). Porous silicos which has been aged under air ambient yields two PL band structures, i.e. blue/violet PL and red PL. The evolution of a blue/violet band is pronounced, especially for thin PS film which is prepared in dilute HF solution. The blue/violet PL band has been observed initially to increrase rapidly with aging, then saturated with further atmospheric aging. The ambient air aged PS exhibits a fast decay time of sub-nanosecond at room temperature and shows appreciably faster decay time than that at 20K. Atmospheric aging of this thin blue/violet luminescing PS yield non-stoichiometric oxide judging from the vibrational spectra of Si-O and AES analysis.

• 한국전기전자재료학회논문지
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• 제20권11호
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• pp.932-938
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• 2007

The structural, optical, and electrical properties of ZnO thin films grown on glass by radio-frequency (rf) magnetron sputtering were investigated. The mixture flow ratio of $O_2$ to Ar, which was operated with sputtering gas, was chosen as a parameter for growing high-qualify ZnO thin films. The structural properties and surface morphologies of the thin films were characterized by the X-ray diffraction and the atomic force microscope, respectively. As for the optical properties of the films, the optical absorbance was measured in the wavelength range of 300-1100 nm by using UV-VIS spectrophotometer. The optical transmittance, absorption coefficient, and optical bandgap energy of ZnO thin films were calculated from the measured data. The crystallinity of the films was improved and the bandgap energy was increased from 3.08 eV to 3.23 eV as the oxygen flow ratio was increased from 0 % to 50 %. Furthermore, The ultraviolet and violet luminescences were observed by using photoluminescence spectroscopy. The hall mobility was decreased with the increase of oxygen flow ratio.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 추계학술발표대회 및 bio-venture fair
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• pp.187-190
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• 2000

본 연구는 5가지의 발광성 미생물을 이용하여 유해 방사선으로 알려져 있는 ${\gamma}-rays$가 여러가지 cellular stresses 중, 특히 유전자 손상과 생물막 손상을 유발하였는데, 이들의 손상 정도가 총 방사선량과 상관관계가 있음을 발생하는 bioluminescence 로써 확인하였다. 뿐만 아니라, 선량률의 변화를 통하여 방사선으로 인한 유전자 손상 및 일반적인 독성 효과가 큰 영향을 받는 것을 확인하였는데, 선량률 증가에 따라 이들 손상정도가 증가하는 것으로 보아 선량률이 genetic 및 radioprotecion에 심각한 영향을 미치는 것을 확인하였다.

• 한국재료학회지
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• 제19권5호
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• pp.281-287
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• 2009

ZnO thin film was grown on a sapphire single crystal substrate by plasma assisted molecular beam epitaxy. In addition to near band edge (NBE) emissions, both blue and green luminescences are also observed together. The PL intensity of the blue luminescence (BL) range from 2.7 to 2.9 eV increased as the amount of activated oxygen increased, but green luminescence (GL) was weakly observed at about 2.4 eV without much change in intensity. This result is quite unlike previous studies in which BL and GL were regarded as the transition between shallow donor levels such as oxygen vacancy and interstitial zinc. Based on the transition level and formation energy of the ZnO intrinsic defects predicted through the first principle calculation, which employs density functional approximation (DFA) revised by local density approximation (LDA) and the LDA+U approach, the green and blue luminescence are nearly coincident with the transition from the conduction band to zinc vacancies of $V^{2-}_{Zn}$ and $V^-_{Zn}$, respectively.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2754-2758
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• 2009

Three novel phosphorescent 2-phenylpyridine-based iridium(III) complexes, $[(ppy)_2Ir(P\^{}N)]PF6\;(1),\;[(dfppy)_2Ir(P\^{}N)]PF_6$ (2), and $[(dfmppy)_2 Ir(P\^{}N)]PF6$ (3), where $P\^{}N$ = 2-[(diphenylphosphino)methyl]pyridine (dppmp), were synthesized and characterized. The absorption, photoluminescence, cyclic voltammetry and thermal stability of the complexes were investigated. The complexes showed bright blue luminescences at wavelengths of 448 $\sim$ 500 nm at room temperature in $CHCl_3$ and revealed that the $\pi$-acceptor ability of the phosphorous atom in the ancillary dppmp ligand plays an important role in tuning emission color resulting in a blue-shift emission. The single crystal structure of $[(dfmppy))_2Ir(P\^N)]PF_6$ was determined using X-ray crystallography. The iridium metal center adopts a distorted octahedral structure coordinated to two dfmppy and one dppmp ligand, showing cis C-C and trans N-N chelate dispositions. There is a $\pi-\pi$ overlap between π electrons delocalized in the difluorophenyl rings.