Journal ArticleDOI
X-ray absorption edge determination of the oxidation state and coordination number of copper: application to the type 3 site in Rhus vernicifera laccase and its reaction with oxygen
Lung Shan Kau,Darlene J. Spira-Solomon,James E. Penner-Hahn,Keith O. Hodgson,Edward I. Solomon +4 more
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In this paper, a normalized difference edge analysis is used to quantitatively determine the oxidation states of the copper sites in type 2 copper-depleted (T2D) and native forms of the multicopper oxidase, Rhus vernicifera laccase.Abstract:
Cu X-ray absorption edge features of 19 Cu(I) and 40 Cu(II) model complexes have been systematically studied and correlated with oxidation state and geometry. Studies of Cu(I) model complexes with different coordination number reveal that an 8983-8984-eV peak (assigned as the Cu 1s ..-->.. 4p transition) can be correlated in energy, shape, and intensity with ligation and site geometry of the cuprous ion. These Cu(I) edge features have been qualitatively interpreted with ligand field concepts. Alternatively, no Cu(II) complex exhibits a peak below 8985.0 eV. The limited intensity observed in the 8983-8985-eV region for some Cu(II) complexes is associated with the tail of an absorption peak at approx. 8986 eV which is affected by the covalency of the equatorial ligands. These models studies allow accurate calibration of a normalized difference edge procedure which is used for the quantitative determination of Cu(I) content in copper complexes of mixed oxidation state composition. This normalized difference edge analysis is then used to quantitatively determine the oxidation states of the copper sites in type 2 copper-depleted (T2D) and native forms of the multicopper oxidase, Rhus vernicifera laccase. The type 3 site of the T2D laccase is found to be fully reduced and stable tomore » oxidation by O/sub 2/ or by 25-fold protein equivalents of ferricyanide, but it can be oxidized by reaction with peroxide. The increase in intensity of the 330-nm absorption feature which results from peroxide titration of T2D laccase is found to correlate linearly with the percent of oxidation of the binuclear copper site.« lessread more
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Preparation and characterization of colloidal copper xanthate nanoparticles
Yuri Mikhlin,Sergey Vorobyev,Sergey Vorobyev,S. V. Saikova,Yevgeny Tomashevich,Olga Yu. Fetisova,Svetlana G. Kozlova,Sergey M. Zharkov,Sergey M. Zharkov +8 more
TL;DR: In this paper, the formation of colloidal copper xanthate particles during the reactions of aqueous solutions of cupric sulfate and various potassium xanthates, which occur in flotation and water treatment slurries, was examined.
Journal ArticleDOI
Efficient synthesis of the Cu-SAPO-44 zeolite with excellent activity for selective catalytic reduction of NOx by NH3
Ying Xin,Ying Xin,Nana Zhang,Xiao Wang,Qian Li,Xicheng Ma,Yong-Xin Qi,Lirong Zheng,James A. Anderson,Zhaoliang Zhang,Zhaoliang Zhang +10 more
TL;DR: A small-pore Cu-chabazite zeolite, Cu-SAPO-44 was synthesized using a one-pot approach by combination of cyclohexylamine template and copper-amine complex.
Journal ArticleDOI
Chemical and structural characterization of copper adsorbed on mosses (Bryophyta)
Aridane G. González,Félix Jiménez-Villacorta,Anna K. Beike,Ralf Reski,Paola Adamo,Oleg S. Pokrovsky +5 more
TL;DR: The adsorption of copper on passive biomonitors (devitalized mosses Hypnum sp., Sphagnum denticulatum, Pseudoscleropodium purum and Brachythecium rutabulum) was studied under different experimental conditions such as a function of pH and Cu concentration in solution.
Journal ArticleDOI
Excited state molecular structure determination in disordered media using laser pump/X-ray probe time-domain X-ray absorption spectroscopy
TL;DR: It is proposed that the absorptive and emissive states of a metal-to-ligand-charge-transfer excited state have distinct geometries and is represented X-ray characterization of a molecular excited state in fluid solution on a nanosecond time scale.
Journal ArticleDOI
Characterizing the Structure and Defect Concentration of ZnO Nanoparticles in a Colloidal Solution
Thomas Rossi,Thomas J. Penfold,M. H. Rittmann-Frank,Marco Reinhard,J. Rittmann,Camelia N. Borca,Daniel Grolimund,Christopher J. Milne,Majed Chergui +8 more
TL;DR: In this article, the structure and defect concentration of colloidal solutions of ZnO nanoparticles, synthesized by a sol gel procedure (SG-NP), as well as commercially available ZnOs nanoparticles (SA-NP) are investigated by UV-vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray absorption spectra (XAS) and x-ray diffraction (XRD), in order to reveal the presence of both zinc and oxygen vacancies.
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