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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TLDR
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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Oxidation states of copper in preservative treated wood as studied by X-ray absorption near edge spectroscopy (XANES)
TL;DR: In this paper , the authors used X-ray absorption near edge spectroscopy (XANES) to examine the copper oxidation states in wood treated with several different wood preservatives as a function of time after treatment.
Journal ArticleDOI
Transition metal chromophores in glass beads of the classical and Hellenistic period: Bonding environment and colouring role
Fani Pinakidou,Maria Katsikini,E. C. Paloura,János Osán,Mateusz Czyzycki,Mateusz Czyzycki,Mateusz Czyzycki,Alessandro Migliori,E. Palamara,Nikolaos Zacharias,Andreas G. Karydas +10 more
TL;DR: In this article, the structural and colouring/decolouring role of transition metal (TM) ions in blue and green-blue soda-lime beads from Thebes, central Greece dated back to the Classical and Hellenistic period using non-destructive X-Ray Absorption Fine Structure (XAFS) spectroscopies.
Journal ArticleDOI
Origin of Hole‐Trapping States in Solution‐Processed Copper(I) Thiocyanate and Defect‐Healing by I2 Doping
Pimpisut Worakajit,Pinit Kidkhunthod,Thanasee Thanasarnsurapong,Saran Waiprasoet,Hideki Nakajima,Taweesak Sudyoadsuk,Vinich Promarak,Adisak Boonchun,Pichaya Pattanasattayavong +8 more
TL;DR: In this paper , a defect passivation strategy is introduced by adding solid I2 to the processing solution, which can substitute for the missing SCN− ligand, effectively healing the defective sites and restoring the coordination around Cu.
Journal ArticleDOI
Identification of catalytic activity descriptors for selective 5-Hydroxymethyl furfural electrooxidation to 2,5-Furandicarboxylic acid
William Hadinata Lie,Yuwei Yang,Jodie A. Yuwono,Constantine Tsounis,Muhammad Zubair,Joshua Wright,Lars Thomsen,Priyanka Kumari,Nicholas M. Bedford +8 more
TL;DR: Several transition metal oxides and hydroxides have been reported as active electrocatalysts towards the oxidation of 5-Hydroxymethyl furfural (HMF), an important biomass-derived compound for downstream sustainable chemical and transport fuel as mentioned in this paper .
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