Gert Bernhard - Academia.edu (original) (raw)
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Papers by Gert Bernhard
Journal of Alloys and Compounds, Jun 1, 1998
Applied Spectroscopy, Jul 1, 2008
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Journal of Radioanalytical and Nuclear Chemistry, 2010
ABSTRACT Cryogenic techniques are currently used in scanning tunnelling microscopy (STM) and sing... more ABSTRACT Cryogenic techniques are currently used in scanning tunnelling microscopy (STM) and single molecule spectroscopy. Recently such cryogenic devices have also been adapted to time resolved laser-induced fluorescence spectroscopy (TRLFS) systems applied to uranium(VI). In our study, we interpret TRLFS results obtained for the uranyl(VI) glucose system at room temperature (RT) and under cryogenic conditions of 153K (cryo-TRLFS). A uranyl(VI) glucose complex was only identified by cryo-TRLFS measurements at pH 5 and not by RT measurements. The uranyl(VI) glucose complex was characterized by five emission bands at 499.0, 512.1, 525.2, 541.7, and 559.3nm and a fluorescence lifetime of 20.9±2.9μs. The uranyl(VI) glucose complex formation constant was calculated for the first time to be logßI=0.1M=15.25±0.96. Cryo-TRLFS investigation opens up new possibilities for the determination of complex formation constants since interfering quenching effects often encounter at RT are suppressed by measurements at cryogenic conditions. KeywordsUranyl-Glucose-Laser fluorescence spectroscopy-TRLFS-Cryogenic conditions-Cryo-TRLFS
Wissenschaftliche Berichte Fzka, 2008
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2009
To date only a small number of studies have investigated the chemical speciation of complexes and... more To date only a small number of studies have investigated the chemical speciation of complexes and the fluorescence properties of metal ions whose emitted fluorescence lifetime is in the range of only few nanoseconds. This is due to a lack of advanced methods which allow the conduction of these measurements. In the current study we set up a new time-resolved laser fluorescence spectroscopy system with which the fluorescence properties of metal ions with very short fluorescence lifetimes such as uranium(IV) and its compounds can be investigated. By studying the fluorescence properties of uranium(IV) in perchloric acid, we showed uranium(IV) to have a detection limit of 5 x 10(-7)M and a fluorescence decay time of 2.74+/-0.36 ns. We further investigated the fluorescence properties of uranium(IV) during the reaction with fluoride and applied our novel laser system to study the complexation of uranium(IV) with fluoride. Our data revealed the formation of a 1:1 complex of uranium(IV) and ...
Uranium, Mining and Hydrogeology, 2008
The complexation of uranium(IV) with the organic model ligands citric acid, succinic acid and man... more The complexation of uranium(IV) with the organic model ligands citric acid, succinic acid and mandelic acid has been investigated in dependence on acidity (0.1 M to 1.0 M) and ionic strength (0.11 M to 1.0 M) by UV-Vis spectroscopy. In the citrate media, the formation of 1:1 and 1:2 complexes was detected. The stability constants for 1:1 and 1:2 uranium(IV) citrate complexes of the type MpHqLr were determined with log β101 = 13.5 ± 0.2 and log β102 = 25.1 ± 0.2. The stability constants determined for the complexation of uranium(IV) with succinic acid and mandelic acid are lower.
Sulfate-reducing bacteria (SRB) frequently occur in the deep granitic rock aquifers at the Äspö H... more Sulfate-reducing bacteria (SRB) frequently occur in the deep granitic rock aquifers at the Äspö Hard Rock Laboratory (Äspö HRL), Sweden. The new SRB strain Desulfovibrio äspöensis could be iso-lated. The objective of this project was to explore the basic interaction mechanisms of uranium, curium, neptunium and plutonium with cells of D. äspöensis DSM 10631T. The cells of D. äspöensis were successfully cultivated under anaerobic conditions as well in an optimized bicarbonate-buffered mineral medium as on solid medium at 22 °C. To study the interaction of D. äspöensis with the actinides, the cells were grown to the mid-exponential phase (four days). The collected biomass was usually 1.0±0.2 gdry weight/L. The purity of the used bacterial cultures was verified using microscopic techniques and by applying the Amplified Ribosomal DNA Restriction Enzyme Analysis (ARDREA). The interaction experiments with the actinides showed that the cells are able to remove all four actinides from the su...
Radiochimica Acta, 2001
ABSTRACT
Radiochimica Acta, 2000
ABSTRACT
Talanta, Jan 3, 2002
Carbon-13 cross-polarization magic-angle spinning nuclear magnetic resonance spectroscopy ((13)C-... more Carbon-13 cross-polarization magic-angle spinning nuclear magnetic resonance spectroscopy ((13)C-CP/MAS-NMR) was applied to study the chemical modification process of humic acids (HA) with diazomethane and the subsequent alkaline hydrolysis of the methylated HA. This modification process results in HA with selectively blocked phenolic OH groups, which can be used for metal ion binding studies with humic substances. Different chemically modified and unmodified natural and synthetic HA with carbon-13 of natural abundance were investigated. In addition, carbon-13 labeled modified synthetic HA, that were synthesized with [(13)C]diazomethane as methylation reagent, were studied to confirm the assumed modification process and to determine the type of functional groups that have the highest affinity for methylation with diazomethane. The results of the NMR studies with carbon-13 labeled modified HA show that predominantly carboxyl and phenolic OH groups are methylated with diazomethane res...
Journal of Alloys and Compounds, Jun 1, 1998
Applied Spectroscopy, Jul 1, 2008
Journal of Radioanalytical and Nuclear Chemistry, 2010
ABSTRACT Cryogenic techniques are currently used in scanning tunnelling microscopy (STM) and sing... more ABSTRACT Cryogenic techniques are currently used in scanning tunnelling microscopy (STM) and single molecule spectroscopy. Recently such cryogenic devices have also been adapted to time resolved laser-induced fluorescence spectroscopy (TRLFS) systems applied to uranium(VI). In our study, we interpret TRLFS results obtained for the uranyl(VI) glucose system at room temperature (RT) and under cryogenic conditions of 153K (cryo-TRLFS). A uranyl(VI) glucose complex was only identified by cryo-TRLFS measurements at pH 5 and not by RT measurements. The uranyl(VI) glucose complex was characterized by five emission bands at 499.0, 512.1, 525.2, 541.7, and 559.3nm and a fluorescence lifetime of 20.9±2.9μs. The uranyl(VI) glucose complex formation constant was calculated for the first time to be logßI=0.1M=15.25±0.96. Cryo-TRLFS investigation opens up new possibilities for the determination of complex formation constants since interfering quenching effects often encounter at RT are suppressed by measurements at cryogenic conditions. KeywordsUranyl-Glucose-Laser fluorescence spectroscopy-TRLFS-Cryogenic conditions-Cryo-TRLFS
Wissenschaftliche Berichte Fzka, 2008
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2009
To date only a small number of studies have investigated the chemical speciation of complexes and... more To date only a small number of studies have investigated the chemical speciation of complexes and the fluorescence properties of metal ions whose emitted fluorescence lifetime is in the range of only few nanoseconds. This is due to a lack of advanced methods which allow the conduction of these measurements. In the current study we set up a new time-resolved laser fluorescence spectroscopy system with which the fluorescence properties of metal ions with very short fluorescence lifetimes such as uranium(IV) and its compounds can be investigated. By studying the fluorescence properties of uranium(IV) in perchloric acid, we showed uranium(IV) to have a detection limit of 5 x 10(-7)M and a fluorescence decay time of 2.74+/-0.36 ns. We further investigated the fluorescence properties of uranium(IV) during the reaction with fluoride and applied our novel laser system to study the complexation of uranium(IV) with fluoride. Our data revealed the formation of a 1:1 complex of uranium(IV) and ...
Uranium, Mining and Hydrogeology, 2008
The complexation of uranium(IV) with the organic model ligands citric acid, succinic acid and man... more The complexation of uranium(IV) with the organic model ligands citric acid, succinic acid and mandelic acid has been investigated in dependence on acidity (0.1 M to 1.0 M) and ionic strength (0.11 M to 1.0 M) by UV-Vis spectroscopy. In the citrate media, the formation of 1:1 and 1:2 complexes was detected. The stability constants for 1:1 and 1:2 uranium(IV) citrate complexes of the type MpHqLr were determined with log β101 = 13.5 ± 0.2 and log β102 = 25.1 ± 0.2. The stability constants determined for the complexation of uranium(IV) with succinic acid and mandelic acid are lower.
Sulfate-reducing bacteria (SRB) frequently occur in the deep granitic rock aquifers at the Äspö H... more Sulfate-reducing bacteria (SRB) frequently occur in the deep granitic rock aquifers at the Äspö Hard Rock Laboratory (Äspö HRL), Sweden. The new SRB strain Desulfovibrio äspöensis could be iso-lated. The objective of this project was to explore the basic interaction mechanisms of uranium, curium, neptunium and plutonium with cells of D. äspöensis DSM 10631T. The cells of D. äspöensis were successfully cultivated under anaerobic conditions as well in an optimized bicarbonate-buffered mineral medium as on solid medium at 22 °C. To study the interaction of D. äspöensis with the actinides, the cells were grown to the mid-exponential phase (four days). The collected biomass was usually 1.0±0.2 gdry weight/L. The purity of the used bacterial cultures was verified using microscopic techniques and by applying the Amplified Ribosomal DNA Restriction Enzyme Analysis (ARDREA). The interaction experiments with the actinides showed that the cells are able to remove all four actinides from the su...
Radiochimica Acta, 2001
ABSTRACT
Radiochimica Acta, 2000
ABSTRACT
Talanta, Jan 3, 2002
Carbon-13 cross-polarization magic-angle spinning nuclear magnetic resonance spectroscopy ((13)C-... more Carbon-13 cross-polarization magic-angle spinning nuclear magnetic resonance spectroscopy ((13)C-CP/MAS-NMR) was applied to study the chemical modification process of humic acids (HA) with diazomethane and the subsequent alkaline hydrolysis of the methylated HA. This modification process results in HA with selectively blocked phenolic OH groups, which can be used for metal ion binding studies with humic substances. Different chemically modified and unmodified natural and synthetic HA with carbon-13 of natural abundance were investigated. In addition, carbon-13 labeled modified synthetic HA, that were synthesized with [(13)C]diazomethane as methylation reagent, were studied to confirm the assumed modification process and to determine the type of functional groups that have the highest affinity for methylation with diazomethane. The results of the NMR studies with carbon-13 labeled modified HA show that predominantly carboxyl and phenolic OH groups are methylated with diazomethane res...