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UV-visible Absorption Spectra (uv-visible + absorption_spectrum)
Selected AbstractsEffect of reduction/oxidation treatment on blue photorefraction in In:Fe:Cu:LiNbO3 crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2010Suhua Luo Abstract In:Fe:Cu:LiNbO3 crystals with reduced/oxidized treatments were prepared by the Czochralski method. The defect structure was analyzed by the UV-Visible absorption spectra. The blue photorefractive properties, such as the refractive index change, response time, recording sensitivity, dynamic range as well as two-wave coupling gain coefficient, were also investigated at 488 nm wavelength using the two-wave coupling experiment. Comparing the as-grown and oxidized In:Fe:Cu:LiNbO3 crystals, the reduced sample has the highest recording sensitivity and largest dynamic range. Meanwhile, the high diffraction efficiency is still maintained. Experimental results definitely show that reduction treatment is an effective method to improve the blue photorefractive performance of In:Fe:Cu:LiNbO3 crystals. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Morphologies-Controlled Synthesis and Optical Properties of Bismuth Tungstate Nanocrystals by a Low-Temperature Molten Salt MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2006Lijin Xie Well-crystallized bismuth tungstate (Bi2WO6) powders with different morphologies were successfully synthesized via a low-temperature molten salt method. The powders were characterized by X-ray diffraction, transmission electron microscopy, and UV-Vis, respectively. It was found that the variation of morphology of the obtained Bi2WO6 powder mainly depends on the different reaction temperatures and the weight ratio of LiNO3,NaNO3 salt to precursor. In addition, the UV-Visible absorption spectra showed that the synthesized powders had strong light absorption properties not only in the ultraviolet light but also in the visible light region. [source] Electrocatalytic Oxidation of Glucose by the Glucose Oxidase Immobilized in Graphene-Au-Nafion BiocompositeELECTROANALYSIS, Issue 3 2010Kangfu Zhou Abstract Graphene was successfully prepared and well separated to individual sheets by introducing SO3,. XRD and TEM were employed to characterize the graphene. UV-visible absorption spectra indicated that glucose oxidase (GOx) could keep bioactivity well in the graphene-Au biocomposite. To construct a novel glucose biosensor, graphene, Au and GOx were co-immobilized in Nafion to further modify a glassy carbon electrode (GCE). Electrochemical measurements were carried out to investigate the catalytic performance of the proposed biosensor. Cyclic voltammograms (CV) showed the biosensor had a typical catalytic oxidation response to glucose. At the applied potential +0.4,V, the biosensor responded rapidly upon the addition of glucose and reached the steady state current in 5,s, with the present of hydroquinone. The linear range is from 15,,M to 5.8,mM, with a detection limit 5,,M (based on the S/N=3). The Michaelis-Menten constant was calculated to be 4.4,mM according to Lineweaver,Burk equation. In addition, the biosensor exhibits good reproducibility and long-term stability. Such impressive properties could be ascribed to the synergistic effect of graphene-Au integration and good biocompatibility of the hybrid material. [source] Structural, electronic, bonding, magnetic, and optical properties of bimetallic [RunAum]0/+ (n + m , 3) clustersJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 16 2010Dimitrios N. Garbounis Abstract The structural, electronic, bonding, magnetic, and optical properties of bimetallic [RunAum]0/+ (n + m , 3; n, m = 0,3) clusters were computed in the framework of the density functional theory (DFT) and time-dependent DFT (TD-DFT) using the full-range PBE0 non local hybrid GGA functional combined with the Def2-QZVPP basis sets. Several low-lying states have been investigated and the stability of the ground state spinomers was estimated with respect to all possible fragmentation schemes. Molecular orbital and population analysis schemes along with computed electronic parameters illustrated the details of the bonding mechanisms in the [RunAum]0/+ clusters. The TD-DFT computed UV-visible absorption spectra of the bimetallic clusters have been fully analyzed and compared to those of pure gold and ruthenium clusters. Assignments of all principal electronic transitions are given and interpreted in terms of contribution from specific molecular orbital excitations. © 2010 Wiley Periodicals, Inc. J Comput Chem 2010 [source] [5-(p -alkoxy)phenyl-10, 15, 20-tri-phenyl] porphyrin and their rare earth complex liquid crystallineJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 4 2007Miao Yu Abstract Three series of porphyrin liquid crystalline compounds, [5-(p -alkoxy)phenyl-10, 15, 20-tri-phenyl] porphyrin and their rare earth complexes (Tb (III), Dy (III), Er (III), Yb (III)), with a hexagonal columnar discotic columnar(Colh) phase have been synthesized. These compounds were characterized by elemental analysis, molar conductances, UV-visible spectra, infrared spectra, luminescence spectra, and cyclic voltammetry. These compounds exhibit more than one mesophases, which transition points of temperature change from ,33.6 to 16.0,°C, and transition points of temperature for isotropic liquid also increase from 4.9 to 38.2,°C, with increasing chain length. Their surface photovoltage (SPV) response have also been investigated by the means of surface photovoltage spectroscopy (SPS) and field-induced surface photovoltage spectroscopy (EFISPS). It was found that their SPV bands are analogous with the UV-visible absorption spectra and derived from the same transition. Copyright © 2007 John Wiley & Sons, Ltd. [source] Single-Line EPR Spectra from Radicals Encapsulated in Aggregates of Amphiphilic Block Copolymers with Hydrophobic Dendritic Pendants in WaterMACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2006Kana Tamano Abstract Summary: A water-insoluble organic 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical is solubilized in aqueous solutions of aggregates of amphiphilic block copolymers with hydrophobic dendritic pendants. The number (100,200) of DPPH molecules solubilized in an aggregate, which is evaluated from UV-visible absorption spectra, is in agreement with that of the DPPH radicals determined from electron paramagnetic resonance (EPR) spectroscopy. The DPPH radicals are stably solubilized without decomposition in the polymer aggregates. The radicals exhibit a single-line EPR absorption, which is narrowed by the interspin interaction, and indicates the assembly formation of DPPH radicals in polymer aggregates. These results suggest the effective utilization of the DPPH radical as a spin-probe indicator in aqueous solutions. When DPPH is solubilized in aqueous solutions of NaAMPS- b -G2(n3), the polymer solutions become purple colored, which is characteristic of the DPPH radical. [source] Characterization of copper binding to the peptide amyloid-,(1,16) associated with Alzheimer's diseaseBIOPOLYMERS, Issue 1 2006Qing-Feng Ma Abstract Amyloid-, peptide (A,) is the principal constituent of plaques associated with Alzheimer's disease (AD) and is thought to be responsible for the neurotoxicity associated with the disease. Copper binding to A, has been hypothesized to play an important role in the neruotoxicity of A, and free radical damage, and Cu2+ chelators represent a possible therapy for AD. However, many properties of copper binding to A, have not been elucidated clearly, and the location of copper binding sites on A, is also in controversy. Here we have used a range of spectroscopic techniques to characterize the coordination of Cu2+ to A,(1,16) in solution. Electrospray ionization mass spectrometry shows that copper binds to A,(1,16) at pH 6.0 and 7.0. The mode of copper binding is highly pH dependent. Circular dichroism results indicate that copper chelation causes a structural transition of A,(1,16). UV-visible absorption spectra suggest that three nitrogen donor ligands and one oxygen donor ligand (3N1O) in A,(1,16) may form a type II square-planar coordination geometry with Cu2+. By means of fluorescence spectroscopy, competition studies with glycine and L -histidine show that copper binds to A,(1,16) with an affinity of Ka , 107M,1 at pH 7.8. Besides His6, His13, and His14, Tyr10 is also involved in the coordination of A,(1,16) with Cu2+, which is supported by 1H NMR and UV-visible absorption spectra. Evidence for the link between Cu2+ and AD is growing, and this work has made a significant contribution to understanding the mode of copper binding to A,(1,16) in solution. © 2006 Wiley Periodicals, Inc. Biopolymers 83: 20,31, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] | |||||||||||||