• 한국전자통신학회논문지
• /
• 제12권6호
• /
• pp.1219-1226
• /
• 2017

본 논문에서는 다용도로 사용 가능한 UV LED 바의 최적설계를 하였다. UV LED는 자외선을 방출하기 때문에 사용목적상 일정하게 자외선을 방출하는 것이 중요하다. 일정한 자외선이 방출되기 위해서는 동작 가능 입력 전압 범위 내에서 정전류원으로 구동되어야 하고 자외선 활용 특성 상 자외선 방출 유지 시간이 길기 때문에 방열이 특히 중요하다. 따라서 소비전력이 최소화 되도록 설계해야 한다. 또한 인체 보호가 필수적이기 때문에 거리 감지 센서와 블루투스를 이용해 인체 감지 여부에 따라 동작할 수 있게 알고리즘을 구성하였다. 자외선 UVA를 방출하기 위해 365nm UV LED 3개가 직렬로 사용되었으며 입력 전압 12V와 정전류 500mA에서 동작하며 효율은 87.5%, 소비전력은 6.006W이다. 그리고 자외선 조사량은 루트론 계측기로 측정하였을 경우 10cm 거리에서 $5.35mW/cm^2$으로 측정 되었다.

• Bulletin of the Korean Chemical Society
• /
• 제26권11호
• /
• pp.1776-1782
• /
• 2005

ZnSe/ZnS, UV-blue luminescent core shell quantum dots, were synthesized via a thermal decomposition reaction of organometallic zinc and solvent coordinated Selenium (TOPSe) in a hot solvent mixture. The synthetic conditions of the core (ZnSe) and the shell (ZnS) were independently studied at various reaction temperature conditions. The obtained colloidal nanocrystals at corresponding temperatures were characterized for their optical properties by UV-vis, room temperature solution photoluminescence (PL) spectroscopy, and further obtained powders were characterized by XRD, TEM, and EDXS analyses. The synthetic temperature condition to obtain the best PL emission intensity for the ZnSe core was 300 ${^{\circ}C}$, and for the optimum shell capping, the temperature was 135 ${^{\circ}C}$. At this temperature, solution PL spectrum showed a narrow emission peak at 427 nm with a PL efficiency of 15%. In addition, the measured particle sizes for the ZnSe/ZnS nanocomposite via TEM were in the range of 5 to 12 nm. Furthermore, we have synthesized water-soluble ZnSe/ZnS nanoparticles by capping the ZnSe/ZnS hydrophobic surface with mercaptoacetate (MAA) molecules. For the obtained aqueous colloidal solution, the UV-vis spectrum showed an absorption peak at 250 nm, and the solution PL emission spectrum showed a peak at 425 nm, which is similar to that for hydrophobic quantum dot ZnSe/ZnS. However, the calculated PL efficiency was relatively low (0.1%) due to the luminescence quenching by water and MAA molecules. The capping ligand was also characterized by FT-IR spectroscopy, with the carbonyl stretching peak in the mercaptoacetate molecule appearing at 1575 $cm ^{-1}$. Finally, the particle sizes of the MAA capped ZnSe/ZnS were measured by TEM, showing a range of 12 to 17 nm.

• Applied Biological Chemistry
• /
• 제51권4호
• /
• pp.276-280
• /
• 2008

식품 allergen 저감화 수단으로 자외선 조사의 타당성을 검토하고 자외선조사가 식품 단백질의 분자적 성질에 미치는 영향을 조사하고자 ovalbumin 용액에 자외선을 조사한 후 단백질의 분자량 분포와 2차구조 및 3차구조의 변화를 조사하였다. SDS-PAGE와 Gel permeation chromatography 결과 ovalbumin은 자외선 조사에 의하여 단백질이 분해되고 조사시간이 증가할수록 펩티드가 중합하는 형태를 나타냈다. Circular dichroism 연구는 자외선 조사에 의하여 ${\alpha}$-helix 구조가 감소하고 조사시간이 증가할 경우 compact denatured ovalbumin의 구조를 나타내는 2차구조의 변화를 나타냈다. 자외선 조사된 ovalbumin의 형광스펙트럼은 조사시간이 증가할수록 단백질의 maximum emission intensity가 감소하는 3차구조의 변화를 나타냈다. 결과적으로 자외선 조사는 ovalbumin의 분자적 성질을 변화시키며 allergen의 항원성을 변화시키는 수단으로 이용가능성을 시사한다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
• /
• pp.888-890
• /
• 1999

ZnO thin films on (001) sapphire substrates have been deposited by pulsed laser deposition using a Nd:YAG laser with the wavelength of 355 nm at an oxygen pressure of 350 mTorr. In order to investigate the effect of the substrate temperature on the properties of ZnO thin films, the experiment has been performed at various substrate temperatures in the range of $200^{\circ}C$ to $700^{\circ}C$. According to XRD, (002) textured ZnO films of high crystalline quality have been obtained by pulsed laser deposition technique. However, the intensity of UV emission is mostly depending on the stoichiometry of ZnO films.

• 대한화학회지
• /
• 제37권4호
• /
• pp.371-377
• /
• 1993

불안정한 분자의 방출분광학에 상요이 가능하도록 Fourier Transform 분광기를 변형시켰다. 불안정한 분자 라디칼 $CH_3S$는 고전압 직류 방전에 의한 supersonic expansion 속에서 jet 형태의 흐름으로 생성되었다. Supersonic expansion에 의하여 냉각된 라디칼의 형광 스펙트럼은 Fourier Transform UV/VIS 분광기에 의해서 얻어졌다. 스펙트럼의 signal/noise 비율은 증가하였으며, 분자 라디칼 $CH_3S$의 회전구조도 명확하게 볼 수 있었다.

• 한국재료학회지
• /
• 제18권11호
• /
• pp.623-627
• /
• 2008

For possible applications as luminescent materials for white-light emission using UV-LEDs, $Ba_2Mg(PO_4)_2:Eu^{2+}$ phosphors were prepared by a solid state reaction. The photoluminescence properties of the phosphor were investigated under ultraviolet ray (UV) excitation. The prepared phosphor powders were characterized to from a single phase of a monoclinic crystalline structure by a powder X-ray diffraction analysis. In the photoluminescence spectra, the $Ba_2Mg(PO_4)_2:Eu^{2+}$ phosphor showed an intense emission band centered at the 584 nm wavelength due to the f-d transition of the $Eu^{2+}$ activator. The optimum concentration of $Eu^{2+}$ activator in the $Ba_2Mg(PO_4)_2$ host, indicating the maximum emission intensity under the excitation of a 395 nm wavelength, was 5 at%. In addition, it was confirmed that the $Eu^{2+}$ ions are substituted at both $Ba^{2+}$ sites in the $Ba_2Mg(PO_4)_2$ crystal. On the other hand, the critical distance of energy transfer between $Eu^{2+}$ ions in the $Ba_2Mg(PO_4)_2$ host was evaluated to be approximately 19.3 A. With increasing temperature, the emission intensity of the $Ba_2Mg(PO_4)_2$:Eu phosphor was considerably decreased and the central wavelength of the emission peak was shifted toward a short wavelength.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
• /
• pp.35-36
• /
• 2000

The luminescence behaviors of Yttrium niobate and Bi doped Yttrium niobate were investigated under UV and low voltage electron excitations and interpreted with the first-principle calculations. In the UV excitation and emission spectra of $YNbO_4$ and $YNbO_4:Bi$, we were able to separate host contribution and Bi contribution and found that the shift in emission peak to longer wavelength is mainly due to Bi contribution. Using density functional theory, the cluster calculations were carried out for both $YNbO_4$ and $YNbO_4:Bi$. From the calculated density of states, we were also able to explain the charge transfer gap in the host and the effect of Bi in the excitation and emission spectra theoretically.

• Bulletin of the Korean Chemical Society
• /
• 제35권1호
• /
• pp.135-140
• /
• 2014

A bent-shape triazolyl derivative was synthesized via click chemistry, and its photophysical property was investigated in various solvents. In contrast to the invisible ultraviolet emission of other solutions, the chloroform solution exhibited a blue light emission at 460 nm. Furthermore, the blue fluorescence intensified as the UV exposure time at 365 nm increased. On the basis of $^1H$-NMR, pH paper, and acid-addition studies, we confirmed that chloroform was decomposed into HCl with the aid of the triazolyl derivative. The density functional theory calculations suggested that the eye-detectable blue fluorescence was attributed to an intramolecular charge transfer process of the protonated triazolyl derivative in the chloroform solution.

• 한국환경과학회지
• /
• 제31권8호
• /
• pp.677-689
• /
• 2022

In order to photocatalytically treat organic matter (COD_Cr) and chromaticity effectively, chemical coagulation and sedimentation processes were employed as a pretreatment of the leachate produced from landfill in Jeju Island. This was performed using FeCl₃·6H₂O as a coagulant. For the treated leachate, UV/TiO₂ and UV/TiO₂/H₂O₂ systems were investigated, using 4 types of UV lamps, including an ozone lamp (24 W), TiO₂ as a photocatalyst, and/or H₂O₂ as an initiator or inhibitor for photocatalytic degradation. In the chemical coagulation and sedimentation process using FeCl₃·6H₂O, optimum removal was achieved with an initial pH of 6, and a coagulant dosage of 2.0 g/L, culminating in the removal of 40% COD_Cr and 81% chromaticity. For the UV/TiO₂ system utilizing an ozone lamp and 3 g/L of TiO₂, the optimum condition was obtained at pH 5. However, the treated COD_Cr and chromaticity did not meet the emission standards (COD_Cr: 400 mg/L, chromaticity: 200 degrees) in a clean area. However, for a UV/TiO₂/H₂O₂ system using 1.54 g/L of H₂O₂ in addition to the above optimum UV/TiO₂ system, the results were 395 mg/L and 160 degrees, respectively, which were within the emission standard limits. The effect of the UV lamp on the removal of COD_Cr, and chromaticity of the leachate decreased in the order of ozone (24 W) lamp > 254 nm (24 W) lamp > ozone (14 W) lamp > 254 nm (14 W) lamp. Only COD_Cr and chromaticity treated with the ozone (24 W) lamp met the emission standards.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
• /
• pp.32-35
• /
• 2006

For the white UV-LED applications, $Eu^{2+}$-activated calcium aluminium silicate phosphors were synthesized for the first time and the structures and luminescence characteristics of these phosphors were investigated. The phosphors in this study emitted blue. green or blue-green light depending on the starting materials for synthesis. In addition, the structure was also changed when the different starting materials were used. When CaO and $CaCO_3$ was used as a starting material. tetragonal $Ca_2Al_2SiO_7$ was formed and blue-green and pure green light was emitted. respectively. However. in the case of $CaSiO_3$, triclinic $CaAl_2Si2O_8$ was formed and only pure blue emission was detected. The maximum emission intensity was obtained from $CaAl_2Si_2O_8:Eu^{2+}$ phosphors, which intensity was about 1.4 times higher than that of YAG:$Ce^{3+}$ phosphor used for blue LED.