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Gert Bernhard - One of the best experts on this subject based on the ideXlab platform.
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Curium(III) Speciation Studies with Cells of a Groundwater Strain of Pseudomonas fluorescens
Geomicrobiology Journal, 2013Co-Authors: Henry Moll, Laura Lütke, Astrid Barkleit, Gert BernhardAbstract:Ubiquitous Pseudomonads have great potential to influence the speciation and mobility of actinides in the environment. This study explores the unknown interaction between Curium(III) and cell-suspensions of Pseudomonas fluorescens (CCUG 32456) isolated from the Aspo site, Sweden. The interaction between Curium(III) and P. fluorescens cells was studied at trace Curium(III) concentrations (0.3 μM) using time-resolved laser-induced fluorescence spectroscopy. Extraction studies have shown that the biosorption of Curium(III) is a reversible process. Two Cm3+−P. fluorescens (CCUG 32456) species were identified, R−O−PO3H−Cm2+ and R−COO−Cm2+, having emission maxima at 599.6 and 601.9 nm, respectively. The corresponding surface complexation constants were determined to be log β111 = 12.7 ± 0.6 and log β110 = 6.1 ± 0.5, respectively.
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complexation study of europium iii and Curium iii with urea in aqueous solution investigated by time resolved laser induced fluorescence spectroscopy
Inorganica Chimica Acta, 2009Co-Authors: Anne Heller, Astrid Barkleit, Gert Bernhard, Jorguwe AckermannAbstract:Abstract The complex formation of europium(III) and Curium(III) with urea in aqueous solution has been studied at I = 0.1 M (NaClO 4 ), room temperature and trace metal concentrations in the pH-range of 1–8 at various ligand concentrations using time-resolved laser-fluorescence spectroscopy. While for Curium(III) the luminescence maximum is red shifted upon complexation, in case of europium(III) emission wavelengths remain unaltered but a significant change in peak splitting occurs. Both heavy metals form weak complexes of the formulae ML 3+ and MLOH 2+ with urea. Stability constants were determined to be log β 110 = −0.12 ± 0.05 and log β 11-1 = −6.86 ± 0.15 for europium(III) and log β 110 = −0.28 ± 0.12 and log β 11-1 = −7.01 ± 0.15 for Curium(III).
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Curium(III) Complexation with Desferrioxamine B (DFO) Investigated Using Fluorescence Spectroscopy
Bulletin of the Chemical Society of Japan, 2008Co-Authors: Henry Moll, Maja Glorius, Gert BernhardAbstract:Hydroxamate-type siderophores like desferrioxamine B (DFO) are the most common siderophores ubiquitously found in the environment. These naturally occurring chelating substances have the potential to enhance the solubility and mobility of actinides by forming soluble complexes. The unknown interaction between Curium(III) and aqueous DFO species is the subject of this paper. The reactions between soluble species of Curium(III) and DFO were studied at trace Curium(III) concentrations (3 × 10 -7 M) in 0.1M NaClO 4 using time-resolved laser-induced fluorescence spectroscopy (TRLFS). Three Cm 3+ -DFO species, M p H q L r , could be identified from the luminescence spectra, CmH 2 DFO 2+ , CmHDFO + , and CmDFO, having emission maxima at 599, 611, and 614 nm, respectively. The large formation constants, log β 121 = 31.62 ± 0.23, log β 111 = 25.70 ± 0.17, and log β 101 = 16.80 ± 0.40, compared to those of other chelating agents illustrate the unique complexation properties of hydroxamate-type siderophores. An indirect excitation mechanism for the Curium(III) luminescence was observed in the presence of the DFO molecules.
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Curium(III) complexation with pyoverdins secreted by a groundwater strain of Pseudomonas fluorescens.
Biometals : an international journal on the role of metal ions in biology biochemistry and medicine, 2007Co-Authors: Henry Moll, Anna Johnsson, Mathias Schäfer, Karsten Pedersen, Herbert Budzikiewicz, Gert BernhardAbstract:Pyoverdins, bacterial siderophores produced by ubiquitous fluorescent Pseudomonas species, have great potential to bind and thus transport actinides in the environment. Therefore, the influence of pyoverdins secreted by microbes on the migration processes of actinides must be taken into account in strategies for the risk assessment of potential nuclear waste disposal sites. The unknown interaction between Curium(III) and the pyoverdins released by Pseudomonas fluorescens (CCUG 32456) isolated from the granitic rock aquifers at the Aspo Hard Rock Laboratory (Aspo HRL), Sweden, is the subject of this paper. The interaction between soluble species of Curium(III) and pyoverdins was studied at trace Curium(III) concentrations (3 × 10−7 M) using time-resolved laser-induced fluorescence spectroscopy (TRLFS). Three Cm3+—P. fluorescens (CCUG 32456) pyoverdin species, MpHqLr, could be identified from the fluorescence emission spectra, CmH2L+, CmHL, and CmL−, having peak maxima at 601, 607, and 611 nm, respectively. The large formation constants, log β121 = 32.50 ± 0.06, log β111 = 27.40 ± 0.11, and log β101 = 19.30 ± 0.17, compared to those of other chelating agents illustrate the unique complexation properties of pyoverdin-type siderophores. An indirect excitation mechanism for the Curium(III) fluorescence was observed in the presence of the pyoverdin molecules.
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Complex formation of Curium(III) with amino acids of different functionalities: L-threonine and O -phospho-L-threonine
Journal of Coordination Chemistry, 2007Co-Authors: Henry Moll, Gert BernhardAbstract:The speciation of Curium(III) with L-threonine and O-phospho-L-threonine was determined by time-resolved laser-induced fluorescence spectroscopy (TRLFS) at trace Cm(III) concentrations (3 × 10−7 M). Curium species of the type MpHqLr were identified in the L-threonine- and O-phospho-L-threonine system. These complexes are characterized by their individual luminescence spectra and luminescence lifetimes. The following formation constants were determined (a) for L-threonine: log β101 = 6.72 ± 0.07, log β102 = 10.22 ± 0.09, and log β1–22 =−(7.22 ± 0.19) at ionic strength I = 0.5 M and (b) for O-phospho-L-threonine: log β121 = 18.03 ± 0.13 and log β111 = 14.17 ± 0.09 at ionic strength I = 0.154 M. Possible structures of the identified Curium species are discussed on the basis of the luminescence lifetime measurements and the magnitude of the formation constants.
Ralf Sudowe - One of the best experts on this subject based on the ideXlab platform.
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separation of americium in high oxidation states from Curium utilizing sodium bismuthate
Analytical Chemistry, 2016Co-Authors: Jason M. Richards, Ralf SudoweAbstract:A simple separation of americium from Curium would support closure of the nuclear fuel cycle, assist in nuclear forensic analysis, and allow for more accurate measurement of neutron capture properties of 241Am. Methods for the separation of americium from Curium are however complicated and time-consuming due to the similar chemical properties of these elements. In this work a novel method for the separation of americium from Curium in nitric acid media was developed using sodium bismuthate to perform both the oxidation and separation. Sodium bismuthate is shown to be a promising material for performing a simple and rapid separation. Curium is more strongly retained than americium on the undissolved sodium bismuthate at nitric acid concentrations below 1.0 M. A separation factor of ∼90 was obtained in 0.1 M nitric acid. This separation factor is achieved within the first minute of contact and is maintained for at least 2 h of contact. Separations using sodium bismuthate were performed using solid–liquid ex...
Jason M. Richards - One of the best experts on this subject based on the ideXlab platform.
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separation of americium in high oxidation states from Curium utilizing sodium bismuthate
Analytical Chemistry, 2016Co-Authors: Jason M. Richards, Ralf SudoweAbstract:A simple separation of americium from Curium would support closure of the nuclear fuel cycle, assist in nuclear forensic analysis, and allow for more accurate measurement of neutron capture properties of 241Am. Methods for the separation of americium from Curium are however complicated and time-consuming due to the similar chemical properties of these elements. In this work a novel method for the separation of americium from Curium in nitric acid media was developed using sodium bismuthate to perform both the oxidation and separation. Sodium bismuthate is shown to be a promising material for performing a simple and rapid separation. Curium is more strongly retained than americium on the undissolved sodium bismuthate at nitric acid concentrations below 1.0 M. A separation factor of ∼90 was obtained in 0.1 M nitric acid. This separation factor is achieved within the first minute of contact and is maintained for at least 2 h of contact. Separations using sodium bismuthate were performed using solid–liquid ex...
S. Heathman - One of the best experts on this subject based on the ideXlab platform.
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Structural investigation of californium under pressure
Physical Review B: Condensed Matter and Materials Physics, 2013Co-Authors: S. Heathman, T. Le Bihan, S. Yagoubi, B. Johansson, R. AhujaAbstract:The high-pressure structural behavior of californium has been studied experimentally and theoretically up to 100 GPa. A valence change from divalent to trivalent forms was observed under modest pressure revealing californium to be the only actinide to exhibit more than one metallic valence at near to ambient conditions as is the case for cerium in the lanthanide series. Three metallic valencies and four different crystallographic phases were observed in californium as a function of pressure. High-pressure techniques, synchrotron radiation, and ab initio electronic structure calculations of total energies were used to investigate the material and to determine the role which californium's 5f electrons play in influencing these transitions. The crystallographic structures observed are similar to those found in the preceding actinide elements, Curium and americium, with the initially localized 5f states becoming completely delocalized under the influence of high pressure
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The unique high-pressure behavior of Curium probed further using alloys
Journal of Alloys and Compounds, 2007Co-Authors: S. Heathman, T. Le Bihan, Richard G. Haire, Rajeev Ahuja, Wei Luo, Börje JohanssonAbstract:The changing role of the 5f electrons across the actinide series has been of prime interest for many years. The remarkable behavior of americium's 5f electrons under pressure was determined experimentally a few years ago and it precipitated a strong interest in the heavy element community. Theoretical treatments of americium's behavior under pressure followed and continue today. Experimental and theoretical findings regarding Curium's behavior under pressure have shown that the pressure behavior of Curium was not a mirror image of that for americium. Rather, one of the five crystallographic phases observed with Curium (versus four for americium) was a unique monoclinic structure whose existence is due to a spin stabilization effect by Curium's 5f(7) electronic configuration and its half-filled 5f-shell. We review briefly the behavior of pure Curium under pressure but focus on the pressure behaviors of three Curium alloys with the intent of comparing them with pure Curium. An important experimental finding confirmed by theoretical computations, is that dilution of Curium with its near neighbors is sufficient to prevent the formation of the unique C2/c phase that appears in pure Cm metal under pressure. As this unique C2/c phase is very sensitive to having a 5f7 configuration to maximize the magnetic spin polarization, dilution of this state with adjacent actinide neighbors reduces its stability.
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A High-Pressure Structure in Curium Linked to Magnetism
Science (New York N.Y.), 2005Co-Authors: S. Heathman, T. Le Bihan, Richard G. Haire, A. Lindbaum, M. Idiri, Peter S. Normile, Rajeev Ahuja, Börje Johansson, G. H. LanderAbstract:Curium lies at the center of the actinide series and has a half-filled shell with seven 5f electrons spatially residing inside its radon core. As a function of pressure, Curium exhibits five different crystallographic phases up to 100 gigapascals, of which all but one are also found in the preceding element, americium. We describe here a structure in Curium, Cm III, with monoclinic symmetry, space group C2/c, found at intermediate pressures (between 37 and 56 gigapascals). Ab initio electronic structure calculations agree with the observed sequence of structures and establish that it is the spin polarization of Curium's 5f electrons that stabilizes Cm III. The results reveal that Curium is one of a few elements that has a lattice structure stabilized by magnetism.
Henry Moll - One of the best experts on this subject based on the ideXlab platform.
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Curium(III) Speciation Studies with Cells of a Groundwater Strain of Pseudomonas fluorescens
Geomicrobiology Journal, 2013Co-Authors: Henry Moll, Laura Lütke, Astrid Barkleit, Gert BernhardAbstract:Ubiquitous Pseudomonads have great potential to influence the speciation and mobility of actinides in the environment. This study explores the unknown interaction between Curium(III) and cell-suspensions of Pseudomonas fluorescens (CCUG 32456) isolated from the Aspo site, Sweden. The interaction between Curium(III) and P. fluorescens cells was studied at trace Curium(III) concentrations (0.3 μM) using time-resolved laser-induced fluorescence spectroscopy. Extraction studies have shown that the biosorption of Curium(III) is a reversible process. Two Cm3+−P. fluorescens (CCUG 32456) species were identified, R−O−PO3H−Cm2+ and R−COO−Cm2+, having emission maxima at 599.6 and 601.9 nm, respectively. The corresponding surface complexation constants were determined to be log β111 = 12.7 ± 0.6 and log β110 = 6.1 ± 0.5, respectively.
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Curium(III) Complexation with Desferrioxamine B (DFO) Investigated Using Fluorescence Spectroscopy
Bulletin of the Chemical Society of Japan, 2008Co-Authors: Henry Moll, Maja Glorius, Gert BernhardAbstract:Hydroxamate-type siderophores like desferrioxamine B (DFO) are the most common siderophores ubiquitously found in the environment. These naturally occurring chelating substances have the potential to enhance the solubility and mobility of actinides by forming soluble complexes. The unknown interaction between Curium(III) and aqueous DFO species is the subject of this paper. The reactions between soluble species of Curium(III) and DFO were studied at trace Curium(III) concentrations (3 × 10 -7 M) in 0.1M NaClO 4 using time-resolved laser-induced fluorescence spectroscopy (TRLFS). Three Cm 3+ -DFO species, M p H q L r , could be identified from the luminescence spectra, CmH 2 DFO 2+ , CmHDFO + , and CmDFO, having emission maxima at 599, 611, and 614 nm, respectively. The large formation constants, log β 121 = 31.62 ± 0.23, log β 111 = 25.70 ± 0.17, and log β 101 = 16.80 ± 0.40, compared to those of other chelating agents illustrate the unique complexation properties of hydroxamate-type siderophores. An indirect excitation mechanism for the Curium(III) luminescence was observed in the presence of the DFO molecules.
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Curium(III) complexation with pyoverdins secreted by a groundwater strain of Pseudomonas fluorescens.
Biometals : an international journal on the role of metal ions in biology biochemistry and medicine, 2007Co-Authors: Henry Moll, Anna Johnsson, Mathias Schäfer, Karsten Pedersen, Herbert Budzikiewicz, Gert BernhardAbstract:Pyoverdins, bacterial siderophores produced by ubiquitous fluorescent Pseudomonas species, have great potential to bind and thus transport actinides in the environment. Therefore, the influence of pyoverdins secreted by microbes on the migration processes of actinides must be taken into account in strategies for the risk assessment of potential nuclear waste disposal sites. The unknown interaction between Curium(III) and the pyoverdins released by Pseudomonas fluorescens (CCUG 32456) isolated from the granitic rock aquifers at the Aspo Hard Rock Laboratory (Aspo HRL), Sweden, is the subject of this paper. The interaction between soluble species of Curium(III) and pyoverdins was studied at trace Curium(III) concentrations (3 × 10−7 M) using time-resolved laser-induced fluorescence spectroscopy (TRLFS). Three Cm3+—P. fluorescens (CCUG 32456) pyoverdin species, MpHqLr, could be identified from the fluorescence emission spectra, CmH2L+, CmHL, and CmL−, having peak maxima at 601, 607, and 611 nm, respectively. The large formation constants, log β121 = 32.50 ± 0.06, log β111 = 27.40 ± 0.11, and log β101 = 19.30 ± 0.17, compared to those of other chelating agents illustrate the unique complexation properties of pyoverdin-type siderophores. An indirect excitation mechanism for the Curium(III) fluorescence was observed in the presence of the pyoverdin molecules.
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Complex formation of Curium(III) with amino acids of different functionalities: L-threonine and O -phospho-L-threonine
Journal of Coordination Chemistry, 2007Co-Authors: Henry Moll, Gert BernhardAbstract:The speciation of Curium(III) with L-threonine and O-phospho-L-threonine was determined by time-resolved laser-induced fluorescence spectroscopy (TRLFS) at trace Cm(III) concentrations (3 × 10−7 M). Curium species of the type MpHqLr were identified in the L-threonine- and O-phospho-L-threonine system. These complexes are characterized by their individual luminescence spectra and luminescence lifetimes. The following formation constants were determined (a) for L-threonine: log β101 = 6.72 ± 0.07, log β102 = 10.22 ± 0.09, and log β1–22 =−(7.22 ± 0.19) at ionic strength I = 0.5 M and (b) for O-phospho-L-threonine: log β121 = 18.03 ± 0.13 and log β111 = 14.17 ± 0.09 at ionic strength I = 0.154 M. Possible structures of the identified Curium species are discussed on the basis of the luminescence lifetime measurements and the magnitude of the formation constants.
