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D. Ehrt - One of the best experts on this subject based on the ideXlab platform.
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formation and UV Absorption of cerium europium and terbium ions in different valencies in glasses
Optical Materials, 2000Co-Authors: Heike Ebendorffheidepriem, D. EhrtAbstract:Cerium, europium and terbium ions can exist in diAerent valencies in glasses. The formation and ultraviolet (UV) Absorption features of the ions were studied in a fluoride phosphate (FP) and two phosphate glasses. Various melting conditions and X-ray irradiation were applied to change the redox states of the ions. Band separation of the UV Absorption spectra was carried out to reveal the components and to determine their spectroscopic properties. The UV Absorption spectra of the lower valent Eu 2a ,T b 3a and Ce 3a ions are due to 4f‐5d transitions, which are split in several bands by the local field around the rare-earth (RE) ions. The crystal field splitting of the trivalent ions diAers from the one of the divalent ion. The UV Absorption spectra of the higher valent Eu 3a ,T b 4a and Ce 4a ions are caused by charge transfer (CT) transitions from oxygen and fluorine to the RE ions. The positions and oscillator strengths of the 4f‐5d and CT transitions are studied in dependence on the RE and glass type. Furthermore, the ligand field strength of Eu 2a ions is investigated. Redox tendency, site symmetry and charge of the RE ions are important factors considering the influence of the RE type. DiAerent polarizability and electron donor power of the ligands as well as diAerent RE site symmetry in the glasses cause the compositional dependence of the transition properties. ” 2000 Elsevier Science B.V. All rights reserved.
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formation and UV Absorption of cerium europium and terbium ions in different valencies in glasses
Optical Materials, 2000Co-Authors: Heike Ebendorffheidepriem, D. EhrtAbstract:Abstract Cerium, europium and terbium ions can exist in different valencies in glasses. The formation and ultraviolet (UV) Absorption features of the ions were studied in a fluoride phosphate (FP) and two phosphate glasses. Various melting conditions and X-ray irradiation were applied to change the redox states of the ions. Band separation of the UV Absorption spectra was carried out to reveal the components and to determine their spectroscopic properties. The UV Absorption spectra of the lower valent Eu2+, Tb3+ and Ce3+ ions are due to 4f–5d transitions, which are split in several bands by the local field around the rare-earth (RE) ions. The crystal field splitting of the trivalent ions differs from the one of the divalent ion. The UV Absorption spectra of the higher valent Eu3+, Tb4+ and Ce4+ ions are caused by charge transfer (CT) transitions from oxygen and fluorine to the RE ions. The positions and oscillator strengths of the 4f–5d and CT transitions are studied in dependence on the RE and glass type. Furthermore, the ligand field strength of Eu2+ ions is investigated. Redox tendency, site symmetry and charge of the RE ions are important factors considering the influence of the RE type. Different polarizability and electron donor power of the ligands as well as different RE site symmetry in the glasses cause the compositional dependence of the transition properties.
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Estimation of deep-UV and UV Absorption coefficients of selected trace impurities in glasses
Glass science and technology, 1997Co-Authors: W. Seeber, D. EhrtAbstract:Glasses of the fluoride phosphate type were selected as suitable host materials for studying the UV Absorption behavior of several transition metal ions in different valence states (Fe 2+/3+ , Cu +/2+ , Pb 2+ , Ni 2+ , Cr 3+ ). Based on a large glass sample collection with series of transition metal-ion-doped fluoride phosphate glasses together with a carefully analytically determined real impurity content, the specific UV Absorption spectra of the mentioned ions could be estimated using nonlinear deconvolution of bands.
Terry A Egerton - One of the best experts on this subject based on the ideXlab platform.
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UV Absorption the primary process in photocatalysis and some practical consequences
Molecules, 2014Co-Authors: Terry A EgertonAbstract:TiO2 photochemistry studies generally address reactions of photogenerated charge-carriers at the oxide surface or the recombination reactions which control the proportion of charge carriers that reach the surface. By contrast, this review focuses on UV Absorption, the first photochemical step in semiconductor photocatalysis. The influence of particle size on Absorption and scattering of light by small TiO2 particles is summarized and the importance of considering, the particle size in the application, not the BET or X-ray line broadening size, is emphasized. Three different consequences of UV Absorption are then considered. First, two commercially important systems, pigmented polymer films and paints, are used to show that TiO2 can protect from direct photochemical degradation. Then the effect of UV Absorption on the measured photocatalytic degradation of aqueous solutions of organics is considered for two separate cases. Firstly, the consequences of UV Absorption by TiO2 on the generation of hydroxyl radicals from H2O2 are considered in the context of the claimed synergy between H2O2 and TiO2. Secondly, the effect of altered UV Absorption, caused by changed effective particle size of the catalyst, is demonstrated for photocatalysis of propan-2-ol oxidation and salicylic acid degradation.
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UV-Absorption—The Primary Process in Photocatalysis and Some Practical Consequences
Molecules, 2014Co-Authors: Terry A EgertonAbstract:TiO2 photochemistry studies generally address reactions of photogenerated charge-carriers at the oxide surface or the recombination reactions which control the proportion of charge carriers that reach the surface. By contrast, this review focuses on UV Absorption, the first photochemical step in semiconductor photocatalysis. The influence of particle size on Absorption and scattering of light by small TiO2 particles is summarized and the importance of considering, the particle size in the application, not the BET or X-ray line broadening size, is emphasized. Three different consequences of UV Absorption are then considered. First, two commercially important systems, pigmented polymer films and paints, are used to show that TiO2 can protect from direct photochemical degradation. Then the effect of UV Absorption on the measured photocatalytic degradation of aqueous solutions of organics is considered for two separate cases. Firstly, the consequences of UV Absorption by TiO2 on the generation of hydroxyl radicals from H2O2 are considered in the context of the claimed synergy between H2O2 and TiO2. Secondly, the effect of altered UV Absorption, caused by changed effective particle size of the catalyst, is demonstrated for photocatalysis of propan-2-ol oxidation and salicylic acid degradation.
James B. Burkholder - One of the best experts on this subject based on the ideXlab platform.
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UV Absorption spectrum of the clo dimer cl2o2 between 200 and 420 nm
Journal of Physical Chemistry A, 2009Co-Authors: Dimitrios K Papanastasiou, Vassileios C Papadimitriou, D W Fahey, James B. BurkholderAbstract:The UV photolysis of Cl2O2 (dichlorine peroxide) is a key step in the catalytic destruction of polar stratospheric ozone. In this study, the gas-phase UV Absorption spectrum of Cl2O2 was measured using diode array spectroscopy and absolute cross sections, σ, are reported for the wavelength range 200−420 nm. Pulsed laser photolysis of Cl2O at 248 nm or Cl2/Cl2O mixtures at 351 nm at low temperature (200−228 K) and high pressure (∼700 Torr, He) was used to produce ClO radicals and subsequently Cl2O2 via the termolecular ClO self-reaction. The Cl2O2 spectrum was obtained from spectra recorded following the completion of the gas-phase ClO radical chemistry. The spectral analysis used observed isosbestic points at 271, 312.9, and 408.5 nm combined with reaction stoichiometry and chlorine mass balance to determine the Cl2O2 spectrum. The Cl2O2 UV Absorption spectrum peaks at 244.5 nm with a cross section of 7.6−0.5+0.8 × 10−18 cm2 molecule−1 where the quoted error limits are 2σ and include estimated systematic ...
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UV Absorption spectrum of BrOCl
Journal of Photochemistry and Photobiology A-chemistry, 2000Co-Authors: James B. Burkholder, Gary Knight, John J. OrlandoAbstract:Abstract The UV Absorption cross sections for BrOCl in the gas phase have been measured over the wavelength range 230–390 nm. Absorption measurements were made at 298 K using a 100 cm long Absorption cell and a diode array spectrometer. BrOCl was generated in the gas phase by exposing a BrCl/Cl2/Br2 gas mixture to solid HgO. The BrOCl Absorption spectrum showed peaks at 272 (2.00×10−18 cm2 per molecule) and 320 nm (0.574×10−18 cm2 per molecule). Absorption cross sections were determined by mass balance following the decomposition of the gas mixture.
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UV Absorption cross-sections of cis-BrONO
Chemical Physics Letters, 2000Co-Authors: James B. Burkholder, John J. OrlandoAbstract:Abstract UV Absorption cross-sections for cis -BrONO in the gas phase have been measured over the wavelength range 200–365 nm. Absorption measurements were made following cw photolysis of Br 2 in Br 2 /NO 2 /N 2 mixtures in a 100 cm long temperature-regulated Absorption cell. The cis -BrONO Absorption spectrum shows two maxima in this wavelength range: at 228 nm (2.7×10 −18 cm 2 molecule −1 ) and 316 (0.41×10 −18 cm 2 molecule −1 ). cis -BrONO Absorption cross-sections were determined relative to BrNO 2 .
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Atmospheric fate of several hydrofluoroethanes and hydrochloroethanes: 2. UV Absorption cross sections and atmospheric lifetimes
Journal of Geophysical Research, 1991Co-Authors: John J. Orlando, James B. Burkholder, Stuart A. Mckeen, A. R. RavishankaraAbstract:The temperature dependent UV Absorption cross-sections of the hydrochlorofluoroethanes CF3CHFCl, CH3CF2Cl, and CF3CHCl2 are reported. The UV Absorption cross-sections were measured over the temperature range 203 to 295 K and the wavelength range 190 to 230 nm. The hydrofluorocarbons CH3CF2H and CF3CH2F were also studied at 295 K and upper limits for their UV Absorption cross-sections over the wavelength range 190 to 230 nm were obtained. The atmospheric lifetimes of these species were calculated using a one-dimensional atmospheric model, using the kinetic data obtained in the previous paper (Gierczak et al. 1991) and the Absorption cross-section data obtained in the present study.
Heike Ebendorffheidepriem - One of the best experts on this subject based on the ideXlab platform.
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formation and UV Absorption of cerium europium and terbium ions in different valencies in glasses
Optical Materials, 2000Co-Authors: Heike Ebendorffheidepriem, D. EhrtAbstract:Abstract Cerium, europium and terbium ions can exist in different valencies in glasses. The formation and ultraviolet (UV) Absorption features of the ions were studied in a fluoride phosphate (FP) and two phosphate glasses. Various melting conditions and X-ray irradiation were applied to change the redox states of the ions. Band separation of the UV Absorption spectra was carried out to reveal the components and to determine their spectroscopic properties. The UV Absorption spectra of the lower valent Eu2+, Tb3+ and Ce3+ ions are due to 4f–5d transitions, which are split in several bands by the local field around the rare-earth (RE) ions. The crystal field splitting of the trivalent ions differs from the one of the divalent ion. The UV Absorption spectra of the higher valent Eu3+, Tb4+ and Ce4+ ions are caused by charge transfer (CT) transitions from oxygen and fluorine to the RE ions. The positions and oscillator strengths of the 4f–5d and CT transitions are studied in dependence on the RE and glass type. Furthermore, the ligand field strength of Eu2+ ions is investigated. Redox tendency, site symmetry and charge of the RE ions are important factors considering the influence of the RE type. Different polarizability and electron donor power of the ligands as well as different RE site symmetry in the glasses cause the compositional dependence of the transition properties.
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formation and UV Absorption of cerium europium and terbium ions in different valencies in glasses
Optical Materials, 2000Co-Authors: Heike Ebendorffheidepriem, D. EhrtAbstract:Cerium, europium and terbium ions can exist in diAerent valencies in glasses. The formation and ultraviolet (UV) Absorption features of the ions were studied in a fluoride phosphate (FP) and two phosphate glasses. Various melting conditions and X-ray irradiation were applied to change the redox states of the ions. Band separation of the UV Absorption spectra was carried out to reveal the components and to determine their spectroscopic properties. The UV Absorption spectra of the lower valent Eu 2a ,T b 3a and Ce 3a ions are due to 4f‐5d transitions, which are split in several bands by the local field around the rare-earth (RE) ions. The crystal field splitting of the trivalent ions diAers from the one of the divalent ion. The UV Absorption spectra of the higher valent Eu 3a ,T b 4a and Ce 4a ions are caused by charge transfer (CT) transitions from oxygen and fluorine to the RE ions. The positions and oscillator strengths of the 4f‐5d and CT transitions are studied in dependence on the RE and glass type. Furthermore, the ligand field strength of Eu 2a ions is investigated. Redox tendency, site symmetry and charge of the RE ions are important factors considering the influence of the RE type. DiAerent polarizability and electron donor power of the ligands as well as diAerent RE site symmetry in the glasses cause the compositional dependence of the transition properties. ” 2000 Elsevier Science B.V. All rights reserved.
Seokwoo Jeon - One of the best experts on this subject based on the ideXlab platform.
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Extraordinary Enhancement of UV Absorption in TiO2 Nanoparticles Enabled by Low-Oxidized Graphene Nanodots
Journal of Physical Chemistry C, 2018Co-Authors: Hyewon Yoon, Byungha Shin, Yeonwoong Jung, Werayut Srituravanich, Minsu Park, Seokwoo JeonAbstract:Titanium oxide (TiO2) exhibits intrinsically strong Absorption of ultraviolet (UV) light, which has been utilized in a variety of applications, such as environmental purification/sterilization, health care, and energies. Accordingly, it is greatly demanded to precisely tune and further improve the UV Absorption of TiO2 to significantly broaden its versatility. Herein, we report an extraordinary enhancement of UV Absorption in TiO2 nanoparticles (NPs) incorporated with graphene nanodots (GNDs) of low oxygen concentration. Chemically bonded TiO2 NP/GND composites exhibit highly tunable UV Absorption, achieving over 243% enhancement of molar extinction coefficient at 336 nm. We found that the drastic improvement is a result of the direct charge transfer from the lowest unoccupied molecular orbitals of GNDs to the conduction bands of TiO2, enabled by wide/direct band gaps in GNDs with a small amount of oxygen. Also, the significantly improved power conversion efficiency (PCE ∼ 16.74%) and UV stability of the ...
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Extraordinary Enhancement of UV Absorption in TiO2 Nanoparticles Enabled by Low-Oxidized Graphene Nanodots
Journal of Physical Chemistry C, 2018Co-Authors: Hyewon Yoon, Byungha Shin, Jin Kim, Jungmo Kim, Daehan Kim, Yeonwoong Jung, Werayut Srituravanich, Minsu Park, Seokwoo JeonAbstract:© 2018 American Chemical Society. Titanium oxide (TiO2) exhibits intrinsically strong Absorption of ultraviolet (UV) light, which has been utilized in a variety of applications, such as environmental purification/sterilization, health care, and energies. Accordingly, it is greatly demanded to precisely tune and further improve the UV Absorption of TiO2to significantly broaden its versatility. Herein, we report an extraordinary enhancement of UV Absorption in TiO2nanoparticles (NPs) incorporated with graphene nanodots (GNDs) of low oxygen concentration. Chemically bonded TiO2NP/GND composites exhibit highly tunable UV Absorption, achieving over 243% enhancement of molar extinction coefficient at 336 nm. We found that the drastic improvement is a result of the direct charge transfer from the lowest unoccupied molecular orbitals of GNDs to the conduction bands of TiO2, enabled by wide/direct band gaps in GNDs with a small amount of oxygen. Also, the significantly improved power conversion efficiency (PCE ∼ 16.74%) and UV stability of the TiO2NP/GND composites reveal their high promise for applications benefiting from TiO2NP/GND composites, such as solar cells and photolysis.