Structural electrochemical study of hemoglobin by in situ circular dichroism thin layer spectroelectrochemistry

Secondary and tertiary or quaternary structural changes in hemoglobin (HB) during an electroreduction process were studied by in situ circular dichroism (CD) spectroelectrochemistry with a long optical path thin-layer cell. By means of singular value decomposition least-squares analysis, CD spectra in the far-UV region give two similar a components with different CD intensity, indicating slight denaturation in the secondary structures due to the electric field effect. CD spectra in the Soret band show a R --> T transition of two quaternary structural components induced by electroreduction of the heme, which changes the redox states of the center ion from Fe3+ to Fe2+ and the coordination number from 6 to 5. The double logarithmic analysis shows that electroreduction of hemoglobin follows a chemical reaction with R --> T transition. Some parameters in the electrochemical process were obtained: formal potential, E-0t = -0.167 V; electrochemical kinetic overpotential, DeltaE(0) = -0.32 V; standard electrochemical reaction rate constant, k(0) = 1.79 x 10(-5) cm s(-1); product of electron transfer coefficient and electron number, alphan=0.14; and the equilibrium constant of R --> T transition, K-c = 9.0.

Effect of network modifiers on spectroscopic properties of erbium-doped phosphate glasses

The integrated absorption cross section Sigma(abs), I peak emission cross section sigma(cmi), Judd-Ofeld intensity parameters Omega(iota) ( t = 2,4,6), and spontaneous emission probability A(R) of Er3+ ions were determined for Erbium doped alkali and alkaline earth phosphate glasses. It is found the compositional dependence of sigma(emi) 5 almost similar to that of Sigma(abs), which is determined by the sum, of Omega(1) (3 Omega(2) + 10 Omega(4) + 21 Omega(6)). In addition, the compositional dependence of Omega(1) was studied in these glass systems. As a result, compared with. Omega(4) and Omega(6) the Omega(2) has a stronger compositional dependence on the ionic radius and content of modifers. The covalency of Er-O bonds in phosphate glass is weaker than that in silicate glass, germanate glass, aluminate glass, and tellurate glass, since Omega(6) of phosphate glass is relatively large. A(R) is affected by the covalency of the Er3+ ion sites and corresponds to the Omega(6) value.

Effect of alkaline-earth metal composition on spectroscopic properties of Er3+ in fluorophosphate glasses

Optical spectroscopic properties of Er3+-doped alkaline-earth metal modified fluoropho sphate glasses have been investigated experimentally for developing broadband fiber and planar amplifiers. The results show a strong correlation between the alkaline-earth metal content and the spectroscopic parameters such as absorption and emission cross sections, full widths at half-maximum and Judd-Ofelt intensity parameters. It is found that strontium ions could have more influences on the Judd-Ofelt intensity parameters and the absorption and emission cross sections than other alkaline-earth metal ions such as Mg2+, Ca2+, Ba2+. The sample containing 23 mol% strontium fluoride exhibits the maximum emission cross section of 7.58 x 10(-21) cm(2), the broadest full width at half-maximum of 65 nm and the longer lifetime of 8.6 ms among the alkaline-earth metal modified fluorophosphates glasses studied. The Judd-Ofelt intensity parameter Omega(6)s, the emission cross sections and the full widths at half-maximum in the Er3+-doped fluorophosphate glasses studied are larger than in the silicate and phosphate glasses.

Effect of lithium-potassium mixed alkali on spectroscopic properties of Er3+-doped aluminophosphate glasses

Er3+-doped lithium-potassium mixed alkali aluminophosphate glasses belonging to the oxide system xK(2)O-(15x)Li2O-4B(2)O(3)-11Al(2)O(3)-5BaO-65P(2)O(5) are obtained in a semi-continuous melting quenching process. Spectroscopic properties of Er3+-doped glass matrix have been analysed by fitting the experimental data with the standard Judd-Ofelt theory. It is observed that Judd-Ofelt intensity parameters-Omega(t)(t=2, 4 and 6) of Er3+ change when the second alkali is introduced into glass matrix. The variation of line strength S-ed[I-4(13/2),I-4(15/2)] follows the same trend as that of the Omega(6) parameter. The effect of mixed alkali on the spectroscopic properties of the aluminophosphate glasses, such as absorption cross-section, stimulated emission cross-section, spontaneous emission probability, branching ratio and the radiative lifetime, has also been investigated in this paper.

Spectroscopic properties of neodymium doped high silica glass and aluminum codoping effects on the enhancement of fluorescence emission

Nd3+ -codoped and Al3+-Nd3+-codoped high silica glasses have been prepared by sintering nanoporous glasses impregnated with Nd3+ stop and Al3+ ions. The Judd-Ofelt intensity parameters Omega(2,4,6) of Nd3+-doped high silica glasses were obtained and used to analyze aluminum codoping effects. Fluorescence properties of Nd3+-doped high silica glasses strongly depend on the Al3+ concentration. While Nd3+ ion absorption and emission intensities of obviously increase when aluminum is added to Nd3+-doped high silica glasses, fluorescence lifetimes decrease and aluminum codoping has almost no influence on the radiative quantum efficiencies. This indicates that aluminum codoping is responsible for an anti-quenching effect through a local modification of rare-earth environments rather than through physical cluster dispersion.

钕离子掺杂和钕铝共掺高硅氧玻璃的光谱性质研究

Nd-doped and Nd-Al-codoped high silica glasses were obtained by sintering porous glass impregnated with Nd3+ and Al3+ ions. The absorption, fluorescence spectra and fluorescence lifetime of Nd-doped and Nd-Al-codoped high silica glasses were measured. The intensity parameters Omega(1), ( t = 2, 4, 6), fluorescence lifetime, radiative quantum efficiency and stimulated emission cross section were calculated by Judd-Ofelt theory. The effect of aluminum codoping on the fluorescence and structural properties of Nd-doped silica glass has been discussed. By comparing the spectroscopic properties with other Nd-doped oxide glasses and commercial silicate glasses, this Nd-doped high silica glass is likely to be a promising laser material for use in high power and high repetition rate lasers.

Efficient frequency upconversion emission in Er3+-doped novel strontium lead bismuth glass

Er3+ -doped strontium lead bismuth glass for developing upconversion lasers has been fabricated and characterized. The Judd-Ofelt intensity parameters Omega(1) (t = 2,4,6), calculated based on the experimental absorption spectrum and Judd-Ofelt theory, were found to be Omega(2) = 2.95 x 10(-20), Omega(4) = 0-91 X 10(-20), and Omega(6) = 0.36 x 10(-20) cm(2). Under 975 nm excitation, intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions H-2(11/2) --> I-4(15/2), S-4(3/2) I-4(15/2), and F-4(9/2) --> I-4(15/2) respectively were observed. The upconversion mechanisms are discussed based oil the energy matching and quadratic dependence on excitation power, and the dominant mechanisms are excited state absorption and energy transfer upconversion for the green and red emissions. The long-lived I-4(11/2) level is supposed to serve as the intermediate state responsible for the upconversion processes. (C) 2004 Published by Elsevier B.V.

Effect of PbCl2 addition on structure, OH- content, and upconversion luminescence in Yb3+/Er3+-codoped germanate glasses

Yb3+/ Er3+-codoped oxychloride germanate glasses have been synthesized by a conventional melting and quenching method. Structural properties were obtained based on Raman-spectra investigation, indicating that PbCl2 plays an important role in the formation of the glass network and has an important influence on the phonon density and the maximum phonon energy. The Judd - Ofelt intensity parameters and quantum efficiencies were calculated based on the Judd - Ofelt theory and lifetime measurements. The enhanced upconversion luminescence intensity of Er3+ with increasing PbCl2 content could not be explained only by the maximum phonon-energy change of the host glasses. For the first time, the effect of PbCl2 addition on phonon density, OH- content, and upconversion luminescence in oxychloride glasses has been discussed and evaluated. The results show that the effect of phonon density and OH- content on upconversion luminescence in oxychloride glasses is much stronger than that of the decrease of the maximum phonon energy. The possible upconversion luminescence mechanisms have also been estimated and are discussed.

Effect of chloride ions' introduction on structural, thermal stability, and spectroscopic properties in Yb3+Er3+-codoped germanate-bismuth-lead glasses

Yb3+Er3+-codoped chloride-modified germanate-bismuth-lead glasses have been synthesized by the conventional melting and quenching method. Structural and thermal stability properties have been obtained on the basis of the Raman spectra and differential thermal analysis, which indicate that the PbCl2 addition has an important influence on the phonon density of states, maximum phonon energy, and thermal stability of host glasses. The Judd-Ofelt intensity parameters and quantum efficiencies were calculated on the basis of the Judd-Ofelt theory and lifetime measurements. For the 1.53 mu m emission band, the full widths at the half-maximum increase and peak wavelengths are blueshifted with increasing PbCl2 content. Moreover, the effect of the PbCl2 addition on the phonon density of states, OH- content, and upconversion luminescence has been discussed and evaluated. Our results reveal that, with increasing PbCl2 content, the decrease of phonon density and OH- content contributes more to the enhanced upconversion emissions than that of maximum phonon energy. (c) 2005 Optical Society of America

Host dependent frequency upconversion of Er3+-doped oxyfluoride germanate glass

Er3+-doped oxyfluoride germanate glasses have been synthesized by the conventional melting and quenching method. The Judd-Ofelt intensity parameters were calculated based on the Judd-Ofelt theory and absorption spectra measurements. With the substitution of PbF2 for PbO, the Omega(2) parameter decreases, while the Omega(6) parameter increases. These change trends indicate that fluoride anions come to coordinate erbium cations and the covalency of the Er-O bond decreases. Structural and thermal stability properties were obtained by Raman spectra and differential thermal analysis, indicating that PbF2 plays an important role in the formation of glass network and has an important influence on the maximum phonon energy and thermal stability of host glasses. Intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions H-2(11/2) -> I-4(15/2), S-4(3/2) -> I-4(15/2), and F-4(9/2) -> I-4(15/2), respectively, were simultaneously observed at room temperature. With increasing PbF2 content, the intensity of red (657nm) emissions increases significantly, while that of the green (525 and 546nm) emission increases slightly. The results indicate that PbF, has more influence on the red (657nm) emission than the green (525 and 546nm) emissions in oxyfluoride germanate glasses. The possible upconversion luminescence mechanisms have also been estimated and discussed. (c) 2005 Elsevier B.V. All rights reserved.

Infrared-to-visible upconversion fluorescence of Er3+-doped novel lithium-barium-lead-bismuth glass

Er3+-doped lithium-barium-lead-bismuth glass for developing upconversion lasers has been fabricated and characterized. The Judd-Ofelt intensity parameters Omega(t) (t = 2, 4, 6), calculated based on the experimental absorption spectrum and Judd-Ofelt theory, were found to be Omega(2) = 3.05 x 10(-20) cm(2), Omega(4) = 0.95 x 10(-20) cm(2), and Omega(6) = 0.39 x 10(-20) cm(2). Under 975 nm excitation, intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions H-2(11/2) -> I-4(15/2), S-4(3/2) -> I-4(15/2), and F-4(9/2) -> I-4(15/2), respectively, were observed at room temperature. The upconversion mechanisms are discussed based on the energy matching and quadratic dependence on excitation power, and the dominant mechanisms are excited state absorption and energy transfer upconversion for the green and red emissions. The long-lived I-4(11/2) level is supposed to serve as the intermediate state responsible for the intense upconversion processes. The intense upconversion luminescence of Er3+-doped lithium-barium-lead-bismuth glass may be a potentially useful material for developing upconversion optical devices. (c) 2004 Elsevier B.V. All rights reserved.

Characterization of Er3+-doped Na2O-WO3-TeO2 glass for ion-exchanged waveguide amplifiers and lasers

Er^(3+)-doped Na2O-WO3-TeO2 glass consistent with standard ion-exchange technology has been fabricated and characterized. The measured absorption and emission spectra of the glass were analyzed by the Judd-Ofelt and McCumber theories. The intensity parameters are Ω2 = 7.01

碱金属和碱土金属氟化物对掺Er^3＋氟磷酸盐玻璃光谱性质的影响

研究了碱金属和碱土金属离子修饰的掺Er^3＋氟磷酸盐玻璃的光谱性质，讨论了碱金属和碱土金属对铒氟磷玻璃的吸收和发射截面、荧光半高宽，Judd-Ofelt强度参数和上转换发光强度等光谱性质的影响，并与一些传统氧化物玻璃系统进行了比较．研究表明碱金属K^＋和碱土金属Sr^2＋掺杂高的玻璃更适宜用作光放大器基质．含12mol％K^＋的氟磷玻璃展现出7．83×10^-21cm^2的高发射截面和最小的荧光上转换强度；含23mol％Sr^2＋的氟磷玻璃则有7．58×10^-21cm^2的高发射截面、65nm的荧光半高

Growth and its spectroscopic properties of Sm : YAP crystal

Sm3+-doped yttrium aluminum perovskite (YAP) single crystal was grown by Czochralski (CZ) method. The absorption and fluorescence spectra along the crystallographic axis b were measured at room temperature. Judd-Ofelt theory was used to calculate the intensity parameters (Omega(t)), the spontaneous emission probability, the branching ratio and the radiative lifetime of the state (4)G(5/2). The peak emission cross-sections were also estimated at 567, 607, and 648 nm wavelengths. (c) 2006 Elsevier B.V. All rights reserved.

Spectroscopic properties of Nd3+-doped high silica glass prepared by sintering porous glass

A new kind of Nd3+, -doped high silica glass (SiO2 > 96% (mass fraction)) was obtained by sintering porous glass impregnated with Nd3+, ions. The absorption and luminescence properties of high silica glass doped with different Nd3+, concentrations were studied. The intensity parameters Omega(t) (t = 2, 4, 6), spontaneous emission probability, fluorescence lifetime, radiative quantum efficiency, fluorescence branching ratio, and stimulated emission cross section were calculated using the Judd-Ofelt theory. The optimal Nd3+ concentration in high silica glass was 0.27% (mole fraction) because of its high quantum efficiency and emission intensity. By comparing the spectroscopic parameters with other Nd3+ doped oxide glasses and commercial silicate glasses, the Nd3+-doped high silica glasses are likely to be a promising material used for high power and high repetition rate lasers.