• Title/Summary/Keyword: UV-emission

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Characteristics of Halophosphate Phosphor for Long-wavelength UV Prepared by Spray Pyrolysis (분무열분해법에 의해 합성된 장파장 자외선용 할로포스페이트계 형광체의 특성)

  • Sohn, Jong-Rak;Kang, Yun-Chan;Park, Hee-Dong;Yoon, Soon-Gil
    • Korean Journal of Materials Research
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    • v.12 no.7
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    • pp.555-559
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    • 2002
  • Blue-emitting $Sr_{10}$($PO$)$_{6}$ $Cl_2$:$Eu^{2+}$ and $_{(Sr,Mg) }$ 10/($PO_4$)$_{6}$ $Cl_2$:$Eu^{2+}$ phosphor particles for application of long-wavelength UV LED were prepared by ultrasonic spray pyrolysis. The luminescence characteristics under long- wave-length ultraviolet of the $Sr_{10}$ ($PO_4$)$_{6}$ $Cl_2$:$Eu^{2+}$ and (Sr,Mg)$_{10}$ ($PO_4$)$_{6}$ $Cl_2$:$^Eu{2+}$ phosphor particles prepared by the spray pyrolysis were compared with that of the commercial product. The PL intensity of the $Sr_{10}$ ($PO_4$)$_{6}$ $Cl_2$:$Eu^{2+}$ particles prepared by the spray pyrolysis was lower than that of the commercial $Sr_{10}$ ($PO_4$)$_{6}$ $Cl_2$:$Eu^{2+}$ particles because prepared $Sr_{10}$ ($PO_4$)$_{6}$ $Cl_2$:$Eu^{2+}$ phosphor particles had porous structure and hollow morphology. However, the PL intensity of the (Sr,Mg)$_{10}$($PO_4$)$_{6}$ $Cl_2$:$Eu^{2+}$ phosphor particles prepared by the spray pyrolysis was 8% higher than that of the commercial one. The high brightness of $(Sr,Mg)_{10}$ ($PO_4$)$_{6}$ $Cl_2$:Eu$^{2+}$ phosphor particles prepared by spray pyrolysis is due to the dense structure and high crystallinity of particles. The TEX>$(Sr,Mg)<_{10}$ ($PO_4$)$_{6}$ /$Cl_2$:$Eu^{ 2+}$ phosphor particles had main emission peak t 448 nm under long- wavelength ultraviolet.

Preparation and Application of Rehmannia Glutinosa Extract Incorporated Functional Chitosan Based Biomaterials (지황 추출물 첨가 chitosan 기반 기능성 바이오 소재 제조 및 응용)

  • Lee, Si-Yeon;Kim, Kyeong-Jung;Kim, Youn-Sop;Yoon, Soon-Do
    • Applied Chemistry for Engineering
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    • v.33 no.2
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    • pp.195-201
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    • 2022
  • The main objective of this work is to prepare Rehmannia glutinosa extract (RE) incorporated functional chitosan (CH) based biomaterials and evaluate their physical properties, RE release properties, inhibitory effect of melanogenesis, and antioxidant and elastase inhibitory activities. RE incorporated CH based biomaterials were synthesized by a casting method and UV curing process. The surface and cross sections of prepared biomaterials were characterized by a field emission scanning electron microscope (FE-SEM). The physical properties such as tensile strength and elongation at break were also investigated. To apply the transdermal drug delivery system, RE release properties were examined with pH 4.5, 5.5, and 6.5 buffer solutions and artificial skin test at 36.5 ℃. Results indicated that RE release of RE incorporated biomaterials with/without the addition of plasticizers [glycerol (GL) and citric acid (CA)] at pH 6.5 was about 1.10 times higher than that of at pH 4.5. In addition, results of the artificial skin test verified that RE was released constantly for 6 h. To verify the applicability of the prepared biomaterials, tyrosinase, 2,2-diphenyl-1-picrylhydrazyl (DPPH), and elastase assays were investigated. Results indicated that RE incorporated biomaterials added CA exhibited tyrosinase activation, DPPH radical scavenging activity rate, and elastase activation of 45.12, 89.40, and 59.94%, respectively.

Removal Characteristics of Organic Matters in Pretreatment and Reverse Osmosis Membrane Processes for Seawater Desalination (해수담수화 전처리 및 역삼투막여과 공정의 유기물 제거특성)

  • Kim, Dong-Kwan;Choi, June-Seok;Lee, Chang-Kyu;Kim, Jinho;Choi, Jeong-Hak;Lee, Wontae
    • Journal of Korean Society of Environmental Engineers
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    • v.36 no.7
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    • pp.492-497
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    • 2014
  • This study investigated removal characteristics of organic matters in pretreatment and reverse osmosis (RO) membrane processes for seawater desalination. Also, the influence of the changes in characteristics of organic matters on the membrane fouling was assessed. The pretreatment processes included dual media filtration (DMF), pressurized membrane filtration (MF), and submerged membrane filtration (SMF). Turbidity, UV absorption at 254 nm, dissolved organic carbon, size exclusion chromatography (SEC), fluorescence excitation emission matrix (FEEM), and transparent exopolymer particles (TEP) in raw and processed waters were analyzed. Ions and minerals were not removed by any pretreatment process tested, but were removed over 99% through the RO membrane process. Hydrophobic organics, which can play major role in organic membrane fouling, were relatively readily removed compared with hydrophilic ones. Membrane based pretreatment such as MF and SMF exhibited better removals of organics than conventional DMF. As the levels of organics in pretreated water decreased, the silt density index (SDI) decreased. MF treated water exhibited the lowest SDI value; this is possibly due to the lowest TEP ($0.1-0.4{\mu}m$) concentrations.

Luminescence characteristics of bismuth and europium co-doped yttrium oxide red phosphor for white light emitting diodes (Bi와 Eu이 도핑된 yttrium oxide의 white LED용 적색 형광체 발광 특성)

  • Park, W.J.;Jung, M.K.;Yoon, S.G.;Yoon, D.H.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.16 no.3
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    • pp.112-115
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    • 2006
  • The red emission properties of $Bi^{3+}$ co-doped $Y_2O_3:Eu^{3+}$ prepared by the solid-state reaction was investigated, in order to verify its potential to act as the red emitting phosphor of white LEDs. The emission spectrum consisted of a weak band at 581, 587, 5931 and 599 nm, with maximum sharp peaks occurring at about 611 nm due to the $^5D_0{\rightarrow}^7F_2$ transition of $Eu^{3+}$, while the excitation spectrum exhibited a broad band between 290 and 430 mm with peaks occurring in the range of $310{\sim}390nm$. Also, SEM image of the sample containing 0.43 mol% $H_3BO_3$ and 2.08 mol% $BaCl_2{\cdot}2H_2O$ phosphor particles grew to achieve diameters of $700{\sim}800nm$.

Dye-Sensitized Solar Cell Based on TiO2-Graphene Composite Electrodes (TiO2와 Graphene 혼합물을 전극으로 사용한 염료감응형 태양전지특성 연구)

  • Battumur, T.;Yang, Wooseung;Ambade, S.B.;Lee, Soo-Hyoung
    • Korean Chemical Engineering Research
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    • v.50 no.1
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    • pp.177-181
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    • 2012
  • Dye-sensitized solar cells(DSSCs) based on $TiO_2$ film photo anode incorporated with different amount of grapheme nanosheet(GNS) are fabricated and their photovoltaic performance are investigated. The $TiO_2$-GNS composite electrode has been prepared by a direct mixing method. The DSSC performance of this composite electrode was measured using N3 dye as a sensitizer. The performance of DSSCs using the $TiO_2$-GNS composite electrodes is dependent on the GNS loading in the electrodes. The results show that the DSSCs incorporating 0.01 wt% GNS in $TiO_2$photo anode demonstrates a maximum power conversion efficiency of 5.73%, 26% higher than that without GNS. The performance improvement is ascribed to increased N3 dye adsorption, the reduction of electron recombination and back transport reaction as well as enhancement of electron transport with the introduction of GNS. The presence of both $TiO_2$(anatase) and GNS has been confirmed by FieldEmission Scanning Electron Microscopy(FE-SEM). The decrease in recombination due to GNS in DSSCs has been investigated by the Electrochemical Impedance Spectroscopy.

Synthesis and Anaiysis of Photohnninescence Properties of $^5D_1$$^7F_1$ Transition in $LaGaO_3$:$Eu^{3+}$ Red Phosphor ($LaGaO_3$:$Eu^{3+}$형광체의 합성 및 발광 특성)

  • Kim, Kyoung Hwa;Choi, Yoon Young;Sohn, Kee Sun;Kim, Chang Hae;Park, Hee Dong;Choe, Se Young
    • Journal of the Korean Chemical Society
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    • v.44 no.5
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    • pp.453-459
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    • 2000
  • FED has deserved an intensive attentioD as a new flat panel display. The present investigationaims at undemtanding the photoluminescence and cathodoluminescent properties of hGaO$_3$: $Eu^{3+}$ phosphor bytaking into account the possibility that this phosphor could be applied for FED. In onler to investigate on.sucha detailed behavior; 8everM experimental skil18 Je conducted to the LaGaO$_3$:$Eu^{3+}$ phosphoL The excimtion srectrum artd emission spectmn were rnezsured in the UV range and then decay curve of $^5D_0$+$^7F_j$transitions\vas examined. The decay behavior of $^5D_0$ emission was anMyzed by a newly Iuoposed cross-relaxation mech-ani8In in asswiation with inteFwnter di1ffision (or migration). The cross-mlaxation from $^5D_0$ to CTB (Cha'geTransfer Band) wuld be a quite retsonable by considering the excitation spectrum. It could be also found thatthe quenching type was changed from ditfrsion controlled process to the direct quenching process -s inJeasing $Eu^{3+}$ oncntration.

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Properties of ZnO nanostructures by metal deposited on Si substrates (Metal 증착한 Si 기판 상의 ZnO 나노 구조 특성)

  • Jang, Hyeon-Gyeong;Jung, Mi-Na;Park, Seung-Hwan;Shin, Dae-Hyeon;Yang, Min;Yao, Takafumi;Chang, Ji-Ho
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • v.9 no.1
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    • pp.1034-1037
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    • 2005
  • The variation of shapes and related properties of ZnO nanostructures grown on the metal pattern and Si substrate have been investigated. Ni, Cr metal patterns were formed on Si (111) substrates by e-beam evaporation, and ZnO nanostructures were fabricated on it by using thermal evaporation of Zn powder in air. Growth temperature was controlled from 500 $^{\circ}$C to 700 $^{\circ}$C. When the growth temperature was relatively low, no considerable effect was found. However, UV emission intensity decreased, and Green-emission intensity, which is regarded as originated from the defect state in the ZnO nanostructure, increased as growth temperature increase. Also, the variation of nanostructure shape at high temperature (700 $^{\circ}$C) is understood in terms of the enhanced incorporation of metal vapor during the nanostructure formation.

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Syntheses and Characterizations of Serine and Threonine Capped Water-Dispersible ZnS:Mn Nanocrystals and Comparison Study of Toxicity Effects on the growth of E. coli by the Methionine, Serine, Threonine, and Valine Capped ZnS:Mn Nanocrystals

  • Lim, Eun-Ju;Park, Sang-Hyun;Byun, Jong-Hoe;Hwang, Cheong-Soo
    • Bulletin of the Korean Chemical Society
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    • v.33 no.5
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    • pp.1741-1747
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    • 2012
  • Water-dispersible ZnS:Mn nanocrystals were synthesized by capping the surface of the nanocrystals with conventional aminoacids ligands: serine and threonine. The aminoacids capped ZnS:Mn nanocrystal powders were characterized by XRD, HR-TEM, EDXS, ICP-AES and FT-IR spectroscopy. The optical properties were also measured by UV/Vis and solution photoluminescence (PL) spectroscopies in aqueous solvents. The solution PL spectra showed broad emission peaks around 600 nm with PL efficiencies of 9.7% (ZnS:Mn-Ser) and 15.4% (ZnS:Mn-Thr) respectively. The measured particle sizes for the aminoacid capped ZnS:Mn nanocrystals by HR-TEM images were about 3.0-4.0 nm, which were also supported by Debye-Scherrer calculations. In addition, cytotoxic effects of four aminoacids capped ZnS:Mn nanocrsystals over the growth of wild type E. coli were investigated. Although toxicity in the form of growth inhibition was observed with all the aminoacids capped ZnS:Mn nanocrystals at higher dose (1 mg/mL), ZnS:Mn-Met and ZnS:Mn-Thr appeared non-toxic at doses less than 100 ${\mu}g$/mL. Low biological toxicities were seen at doses less than 10 ${\mu}g$/ mL for all nanocrystals.

Optimization of aircraft fuel consumption and reduction of pollutant emissions: Environmental impact assessment

  • Khardi, Salah
    • Advances in aircraft and spacecraft science
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    • v.1 no.3
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    • pp.311-330
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    • 2014
  • Environmental impact of aircraft emissions can be addressed in two ways. Air quality impact occurs during landings and takeoffs while in-flight impact during climbs and cruises influences climate change, ozone and UV-radiation. The aim of this paper is to investigate airports related local emissions and fuel consumption (FC). It gives flight path optimization model linked to a dispersion model as well as numerical methods. Operational factors are considered and the cost function integrates objectives taking into account FC and induced pollutant concentrations. We have compared pollutants emitted and their reduction during LTO cycles, optimized flight path and with analysis by Dopelheuer. Pollutants appearing from incomplete and complete combustion processes have been discussed. Because of calculation difficulties, no assessment has been made for the soot, $H_2O$ and $PM_{2.5}$. In addition, because of the low reliability of models quantifying pollutant emissions of the APU, an empirical evaluation has been done. This is based on Benson's fuel flow method. A new model, giving FC and predicting the in-flight emissions, has been developed. It fits with the Boeing FC model. We confirm that FC can be reduced by 3% for takeoffs and 27% for landings. This contributes to analyze the intelligent fuel gauge computing the in-flight fuel flow. Further research is needed to define the role of $NO_x$ which is emitted during the combustion process derived from the ambient air, not the fuel. Models are needed for analyzing the effects of fleet composition and engine combinations on emission factors and fuel flow assessment.

Multi-Core Fiber Based Fiber Bragg Gratings for Ground Based Instruments

  • Min, Seong-Sik;Lindley, Emma;Leon-Saval, Sergio;Lawrence, Jon;Bland-Hawthorn, Joss
    • The Bulletin of The Korean Astronomical Society
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    • v.40 no.1
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    • pp.53.2-53.2
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    • 2015
  • Fiber Bragg gratings (FBGs) are the most compact and reliable method of suppressing atmospheric emission lines in the infrared for ground-based telescopes. It has been proved that real FBGs based filters were able to eliminate 63 bright sky lines with minimal interline losses in 2011 (GNOSIS). Inscribing FBGs on multi-core fibers offers advantages. Compared to arrays of individual SMFs, the multi-core fiber Bragg grating (MCFBG) is greatly reduced in size, resistant to damage, simple to fabricate, and easy to taper into a photonics lantern (PRAXIS). Multi-mode fibers should be used and the number of modes has to be large enough to capture a sufficient amount of light from the telescope. However, the fiber Bragg gratings can only be inscribed in the single-mode fiber. A photonic lantern bi-directionally converts multi-mode to single-mode. The number of cores in MCFBGs corresponds to the mode. For a writing system consisting of a single ultra-violet (UV) laser and phase mask, the standard writing method is insufficient to produce uniform MCFBGs due to the spatial variations of the field at each core within the fiber. Most significant technical challenges are consequences of the side-on illumination of the fiber. Firstly, the fiber cladding acts as a cylindrical lens, narrowing the incident beam as it passes through the air-cladding interface. Consequently, cores receive reduced or zero illumination, while the focusing induces variations in the power at those that are exposed. The second effect is the shadowing of the furthest cores by the cores nearest to the light source. Due to a higher refractive index of cores than the cladding, diffraction occurs at each core-cladding interface as well as cores absorb the light. As a result, any core that is located directly behind another in the beam path is underexposed or exposed to a distorted interference pattern from what phase mask originally generates. Technologies are discussed to overcome the problems and recent experimental results are presented as well as simulation results.

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