• Title/Summary/Keyword: Transmittance spectra

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The Effect of SiO2 Shell on the Suppression of Photocatalytic Activity of TiO2 and ZnO Nanoparticles

  • Lee, Min Hee;Patil, Umakant Mahadev;Kochuveedu, Saji Thomas;Lee, Choon Soo;Kim, Dong Ha
    • Bulletin of the Korean Chemical Society
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    • v.33 no.11
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    • pp.3767-3771
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    • 2012
  • In this study, we investigate the potential use of $TiO_2@SiO_2$ and $ZnO@SiO_2$ core/shell nanoparticles (NPs) as effective UV shielding agent. In the typical synthesis, $SiO_2$ was coated over different types of $TiO_2$ (anatase and rutile) and ZnO by sol-gel method. The synthesized $TiO_2@SiO_2$ and $ZnO@SiO_2$ NPs were characterized by UV-Vis, XRD, SEM and TEM. The UV-vis absorbance and transmittance spectra of core@shell NPs showed an efficient blocking effect in the UV region and more than 90% transmittance in the visible region. XRD and SAED studies confirmed the formation of amorphous $SiO_2$ coated over the $TiO_2$ and ZnO NPs. The FESEM and TEM images shows that coating of $SiO_2$ over the surface of anatase, rutile $TiO_2$ and ZnO NPs resulted in the increase in particle size by ~30 nm. In order to study the UV light shielding capability of the samples, photocatalytic degradation of methylene blue dye on $TiO_2@SiO_2$ and $ZnO@SiO_2$ NPs was performed. Photocatalytic activity for both types of $TiO_2$ NPs was partially suppressed. In comparison, the photocatalytic activity of ZnO almost vanished after the $SiO_2$ coating.

Effect of CuO on the Optical and Structural Properties of Phosphate Glass for Near-Infrard Filter (근적외선 필터용 인산계 유리의 광학적 특성 및 구조적 특성에 미치는 CuO 의 영향)

  • Kim, Seong-Il;Hwang, Jong-Hee;Lim, Tae-Young;Kim, Jin-Ho;Kim, Young-Ho;Lee, Jong-Hwa;Choi, Deuk-Kyun
    • Korean Journal of Materials Research
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    • v.19 no.12
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    • pp.657-660
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    • 2009
  • Optical characteristics and structural changes depending on CuO content in phosphate glasses that are used in near-infrared (near-IR) filters were investigated. With phosphate glasses that contain 1-9 mol% CuO, changes in optical transmittance, optical absorption, and color coordinate were measured with a UV-VIS spectrophotometer. An XPS (X-ray photoelectron spectroscopy) analysis was performed to determine valence of copper ion that influences optical characteristics in near-IR filter glasses. Structural changes in glasses depending on CuO content were also analyzed by FT-IR (Fourier transform infrared) and Raman spectrophotometers. From the UV-VIS spectrophotometer results, strong absorption peaks at 220 & 900 nm were found and transmittance was decreased. The color coordinates of the glasses were shifted to the green color direction with CuO addition for increasing absorption of long wavelength range spectra, in spite of the amount of $Cu^{2+}$, which gives a blue color to glasses, and which was increased in XPS results. Also, structural de-polymerization of glasses with CuO addition were found by FT-IR and Raman results.

Applications of Discrete Wavelet Analysis for Predicting Internal Quality of Cherry Tomatoes using VIS/NIR Spectroscopy

  • Kim, Ghiseok;Kim, Dae-Yong;Kim, Geon Hee;Cho, Byoung-Kwan
    • Journal of Biosystems Engineering
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    • v.38 no.1
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    • pp.48-54
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    • 2013
  • Purpose: This study evaluated the feasibility of using a discrete wavelet transform (DWT) method as a preprocessing tool for visible/near-infrared spectroscopy (VIS/NIRS) with a spectroscopic transmittance dataset for predicting the internal quality of cherry tomatoes. Methods: VIS/NIRS was used to acquire transmittance spectrum data, to which a DWT was applied to generate new variables in the wavelet domain, which replaced the original spectral signal for subsequent partial least squares (PLS) regression analysis and prediction modeling. The DWT concept and its importance are described with emphasis on the properties that make the DWT a suitable transform for analyzing spectroscopic data. Results: The $R^2$ values and root mean squared errors (RMSEs) of calibration and prediction models for the firmness, sugar content, and titratable acidity of cherry tomatoes obtained by applying the DWT to a PLS regression with a set of spectra showed more enhanced results than those of each model obtained from raw data and mean normalization preprocessing through PLS regression. Conclusions: The developed DWT-incorporated PLS models using the db5 wavelet base and selected approximation coefficients indicate their feasibility as good preprocessing tools by improving the prediction of firmness and titratable acidity for cherry tomatoes with respect to $R^2$ values and RMSEs.

Effects of an a-C:H Anti-Reflective Coating on the Cell Efficiency of Dye-Sensitized Solar Cells (DSSCs) (수소화된 비정질 탄소 반사방지 코팅층이 염료감응형 태양전지의 효율에 미치는 영향)

  • Song, Jae-Sil;Kim, Nam-Hoon;Park, Yong Seob
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.32 no.4
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    • pp.281-286
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    • 2019
  • Raman spectra of a-C:H thin films deposited with an unbalanced magnetron sputtering system showed that the G peak shifted to a higher wavenumber as the target power density increased and $I_D/I_G$ ratio increased from 0.902 to 1.012. Moreover, the transmittance of a-C:H films fabricated at 60 nm tended to decrease with increasing target power density; at 550 nm in the visible light region, the transmittance decreased from 69% to 58%. The rms surface roughness values of the a-C:H thin films decreased with increasing target power density, and varied from 1.11 nm to 0.71 nm. In order to achieve efficient light trapping, the light scattering at the rough interface must be enhanced. Consequently, the surface roughness of the thin film will decrease with the target power density. Further, the refractive index and reflectivity of the a-C:H thin films increased with increasing target power density; however, the Brewster angle decreased with the target power density. Hence, dye-sensitized solar cells using an a-C:H antireflective coating increased the CE, $V_{OC}$, and $J_{SC}$ by approximately 8.6%, 5.5%, and 4.5%, respectively.

Effect of Deposition Temperature on the Optical Properties of La2MoO6:Dy3+,Eu3+ Phosphor Thin Films (증착 온도에 따른 La2MoO6:Dy3+,Eu3+ 형광체 박막의 광학 특성)

  • Cho, Shinho
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.32 no.5
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    • pp.387-392
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    • 2019
  • $Dy^{3+}$ and $Eu^{3+}$-co-doped $La_2MoO_6$ phosphor thin films were deposited on sapphire substrates by radio-frequency magnetron sputtering at various growth temperatures. The phosphor thin films were characterized using X-ray diffraction (XRD), scanning electron microscopy, ultraviolet-visible spectroscopy, and fluorescence spectrometry. The optical transmittance, absorbance, bandgap, and photoluminescence intensity of the $La_2MoO_6$ phosphor thin films were found to depend on the growth temperature. The XRD patterns demonstrated that all the phosphor thin films, irrespective of growth temperatures, had a tetragonal structure. The phosphor thin film deposited at a growth temperature of $100^{\circ}C$ indicated an average transmittance of 85.3% in the 400~1,100 nm wavelength range and a bandgap energy of 4.31 eV. As the growth temperature increased, the bandgap energy gradually decreased. The emission spectra under ultraviolet excitation at 268 nm exhibited an intense red emission line at 616 nm and a weak emission line at 699 nm due to the $^5D_0{\rightarrow}^7F_2$ and $^5D_0{\rightarrow}^7F_4$ transitions of the $Eu^{3+}$ ions, respectively, and also featured a yellow emission band at 573 nm, resulting from the $^4F_{9/2}{\rightarrow}^6H_{13/2}$ transition of the $Dy^{3+}$ ions. The results suggest that $La_2MoO_6$ phosphor thin films can be used as light-emitting layers for inorganic thin film electroluminescent devices.

Structural, optical, and morphological properties of BaWO4:Sm3+ phosphor thin films grown at different deposition temperature (서로 다른 증착 온도에서 성장된 BaWO4:Sm3+ 형광체 박막의 구조, 광학, 표면 형상의 특성)

  • Cho, Shinho
    • Journal of the Korean institute of surface engineering
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    • v.55 no.2
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    • pp.96-101
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    • 2022
  • The effects of the growth temperature on the structural, optical, and morphological properties of BaWO4:Sm3+ phosphor thin films were investigated. The BaWO4:Sm3+ thin films were grown on quartz substrates at several growth temperatures by radio-frequency magnetron sputtering. All the thin films crystallized in a tetragonal structure with a main BaWO4 (112) diffraction peak. The 830 nm-thick BaWO4:Sm3+ thin films grown at 300 ℃ exhibited numerous polygon-shaped particles. The excitation spectra of BaWO4:Sm3+ thin films consisted of a broad excitation band in the 200-270 nm with a maximum at 236 nm due to the O2--Sm3+ charge transfer and two small bands peaked at 402 and 463 nm, respectively. Under 236 nm excitation, the BaWO4:Sm3+ thin films showed an intense red emission peak at 641 nm due to the 4G5/26H9/2 transition of Sm3+, indicating that the Sm3+ ions occupied sites of non-inversion symmetry in the BaWO4 host lattice. The highest emission intensity was observed for the thin film grown at 300 ℃, with a 51.8% transmittance and 5.09 eV bandgap. The average optical transmittance in the wavelength range of 500-1100 nm was increased from 53.2% at 200 ℃ to 60.8% after growing at 400 ℃. These results suggest that 300 ℃ is the optimum temperature for growing redemitting BaWO4:Sm3+ thin films.

Effects of deposition temperature on the properties of SnO2:Eu3+ thin films grown by radio-frequency magnetron sputtering (증착 온도가 라디오파 마그네트론 스퍼터링으로 성장한 SnO2:Eu3+ 박막의 특성에 미치는 영향)

  • Shinho Cho
    • Journal of the Korean institute of surface engineering
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    • v.56 no.3
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    • pp.201-207
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    • 2023
  • Eu3+-doped SnO2 (SnO2:Eu3+) phosphor thin films were grown on quartz substrates by radio-frequency magnetron sputtering. The deposition temperature was varied from 100 to 400 ℃. The X-ray diffraction patterns showed that all the thin films had two mixed phases of SnO2 and Eu2Sn2O7. The 880 nmthick SnO2:Eu3+ thin film grown at 100 ℃ exhibited numerous pebble-shaped particles. The excitation spectra of SnO2:Eu3+ thin films consisted of a strong and broad peak at 312 nm in the vicinity from 250 to 350 nm owing to the O2--Eu3+ charge transfer band, irrespective of deposition temperature. Upon 312 nm excitation, the SnO2:Eu3+ thin films showed a main emission peak at 592 nm arising from the 5D07F1 transition and a weak 615 nm red band originating from the 5D07F2 transition of Eu3+. As the deposition temperature increased, the emission intensities of two bands increased rapidly, approached a maximum at 100 ℃, and then decreased slowly at 400 ℃. The thin film deposited at 200 ℃ exhibited a band gap energy of 3.81 eV and an average transmittance of 73.7% in the wavelength range of 500-1100 nm. These results indicate that the luminescent intensity of SnO2:Eu3+ thin films can be controlled by changing the deposition temperature.

The Effect of Substrate Temperature on the Electrical, Electronic, Optical Properties and the Local Structure of Transparent Nickel Oxide Thin Films

  • Lee, Kangil;Kim, Beomsik;Kim, Juhwan;Park, Soojeong;Lee, Sunyoung;Denny, Yus Rama;Kang, Hee Jae;Yang, Dong-Seok
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.397-397
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    • 2013
  • The electrical, electronic, optical properties and the local structure of Nickel Oxide (NiO) thin film have been investigated by X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), UV-spectrometer,Hall Effect measurement and X-ray absorption spectroscopy (XAS). The XPS results show that the Ni 2p spectra for all films consist of $Ni2p_{3/2}$ at around 854.5 eV which indicate the presence of Ni-O bond from NiO phase and for the annealed film at temperature above $200^{\circ}C$ shows the coexist Ni oxide and Ni metal phase. The REELS spectra showed that the band gaps of the NiO thin films were abruptly decreased with increasing temperature. The values of the band gaps are consistent with the optical band gaps estimated by UV-Spectrometer. The optical transmittance spectra shows that the transparency of NiO thin films in the visible light region was deteriorated with higher temperature due to existence of $Ni^0$. Hall Effect measurement suggest that the NiO thin films prepared at relatively low temperatures (RT and $100^{\circ}C$) are suitable for fabricating p-type semiconductor which showed that the best properties was achieved at $100^{\circ}C$, such as a low resistivity of $7.49{\Omega}.cm$. It can be concluded that the annealing process plays a crucial role in converting from p type to n type semiconductor which leads to reducing electrical resistivity of NiO thin films. Furthermore, the extended X-ray absorption fine structure (EXAFS) spectrum at the Ni K-edge was used to address the local structure of NiO thin films. It was found that the thermal treatments increase the order in the vicinity of Ni atom and lead the NiO thin films to bunsenite crystal structure. Moreover, EXAFS spectra show in increasing of coordination number for the first Ni-O shell and the bond distance of Ni-O with the increase of substrate temperature.

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Determination of Optical Constants of Organic Light-Emitting-Material Alq3 Using Jellison-Modine Dispersion Relation (Jellison Modine 분산식을 이용안 유기발광물질 Alq3의 광학상수 결정)

  • Park, Myung-Hee;Lee, Soon-Il;Koh, Ken-Ha
    • Journal of Korean Ophthalmic Optics Society
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    • v.10 no.4
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    • pp.267-272
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    • 2005
  • We deposited thin films of organic light-emitting-material $Alq_3$(alumina quinoline) on silicon and slide-glass substrates using thermal evaporation method, and measured spectra of ellipsometry angles ${\Delta}$ and ${\Psi}$ in the photon-energy range of 1.5~5.0 eV using a variable angle spectroscopic ellipsometer. The optical constants, refractive index and extinction coefficient, of $Alq_3$ were determined via the dispersion parameters extracted from the curve-fitting process based on Jellison-Modine dispersion function. The reliability of determined optical constants were verified through the comparison of measured and simulated transmittance curves and the good agreement between simulated absorption-coefficient curves and absorbance spectra measured using a spectrophotometer.

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Angular dependence of emision pattern in top-emission organic light-emitting diodes (전면 유기 발광 다이오드의 각도에 따른 발광 패턴 연구)

  • Joo, Hyun-Woo;Mok, Rang-Gyun;Kim, Tae-Wan;Jang, Kyung-Wook;Song, Min-Jong;Lee, Ho-Shik;An, Hui-Chul;Na, Su-Hwan
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.277-278
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    • 2009
  • We have studied an angular dependence of emission pattern of top-emssion organic light-emitting diodes (TEOLED). Device structure is Al(100nm)/TPD(40nm)/$Alq_3$(60nm)/LiF(0.5nm)/Al(2nm)/Ag(30nm). N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine (TPD) and tris-(8-hydroxyquinoline) aluminium ($Alq_3$)were used as a hole transport layer and emission layer, respectively. Organic layers and cathode were thermally evaporated at $2\times10^{-5}$torr. The evaporation rate of the organic material was maintained to be $1.5\sim2.0{\AA}/s$, and that of metal layer to be $0.5\sim5{\AA}/s$. A transmittance of a cathode electrode(Al/Ag) in visible region is about 25~30%. In order to measure view-angle dependent intensity, electroluminenscence spectra of the device at each angle were integrated. Angle dependent emission spectra of the device do not show blue shift. Emission intensity of the device that the going straight characteristic is stronger the bottom-emission organic light-emitting diodes is shown.

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