The long-lived fission product 126Sn (105 years) (Weast (1972)) is of substantial interest in the context of nuclear waste disposal in deep underground repositories. However, the prevalent redox state, the aqueous speciation as well as the reactions at the mineral-water interface under the expected anoxic conditions are a matter of debate. Therefore, in this PhD thesis I present work on the reactions of SnII with three Fe-bearing minerals as a function of pH, time, and SnII loading under anoxic condition with O2 level < 2 ppmv. The first mineral, goethite, contains only trivalent Fe (FeIIIOOH), the second, magnetite, contains both FeII and FeIII (FeIIFeIII2O4), and the third, mackinawite (FeIIS), contains only divalent Fe. The uptake behavior of the three mineral surfaces was investigated by batch sorption studies. Tin redox state was investigated by Sn-K X-ray absorption near-edge structure (XANES) spectroscopy, and the local, molecular structure of the expected Sn surface complexes and precipitates was studied by extended X-ray absorption fine-structure (EXAFS) spectroscopy. Selected samples were also investigated by transmission electron microscopy (TEM) to elucidate the existence and nature of secondary, Fe- and /or Sn containing solids, and by Mössbauer spectroscopy to study FeII and FeIII in the minerals. Based on the such-obtained molecular-level information, surface complexation models (SCM) were fitted to the batch sorption data to derive surface complexation constants. In the presence of the FeIII-bearing minerals magnetite and goethite, I observed a rapid uptake and oxidation of SnII to SnIV. The local structure determined by EXAFS showed two Sn-Fe distances of about 3.15 and 3.60 Å in line with edge and corner sharing arrangements between octahedrally coordinated SnIV and the Fe(O,OH)6 octahedra at the magnetite and goethite surfaces. While the respective coordination numbers suggested formation of tetradentate inner-sphere complexes between pH 3 and 9 for magnetite, bidentate inner-sphere complexes (single edge-sharing (1E) and corner-sharing (2C)) prevail at the goethite surface at pH > 3, with the relative amount of 2C increasing with Sn loading. The interfacial electron transfer between sorbed SnII and structural FeIII potentially leads to dissolution of FeII and transformation to secondary FeII/FeIII oxide minerals. There is no clear evidence to confirm the reductive dissolution in the Sn/ magnetite system, Rietveld refinement of XRD patterns, however, indicates an increase of FeII/FeIII ratio in the magnetite structure. For the Sn/goethite system, dissolved FeII increased with SnII loading at the lowest pH investigated, indicative of reductive dissolution. At pH >5, spherical and cubic particles of magnetite were observed by TEM, and their number increased with SnII loading. Based on previous finding, this secondary mineral transformation of goethite should proceed via dissolution and recrystallization. The molecular structure and oxidation state of sorbed Sn were then used to fit the batch sorption data of magnetite and goethite with SCM. The sorption data on magnetite were fit with the diffuse double layer model (DLM) employing two different complexes, the first ( = -14.97±0.35) prevailing from pH 2 to 9, and the second ( = -17.72±0.50), which forms at pH > 9 by co-adsorption of FeII, thereby increasing sorption at this high pH. The sorption data on goethite were fitted with the charge distribution–multisite complexation model (CD-MUSIC). Based on the EXAFS-derived presence of two different bidentate inner-sphere complexes ((≡FeOH)(≡Fe3O)Sn(OH)3 (1E) and (≡FeOH)2Sn(OH)3) (2C)), sorption affinity constants of 15.5 ±1.4 for the 1E complex and of 19.2 ±0.6 for the 2C complex were obtained. The model is not only able to predict sorption across the observed pH range, but also the transition from a roughly 50/50 distribution of the two complexes at 12.5 µmol/g Sn loading, to the prevalence of the 2C complex at higher loading, in line with the EXAFS data. The retention mechanism of SnII by mackinawite is significantly dependent on the solution pH, reflecting the transient changes of the mackinawite surface in the sorption process. At pH <7, SnII is retained in its original oxidation state. It forms a surface complex, which is characterized by two short (2.38 Å) Sn-S bonds, which can be interpreted as the bonds towards the S-terminated surface of mackinawite, and two longer Sn-S bonds (2.59 Å), which point most likely towards the solution phase, completing the tetragonal SnS4 innersphere sorption complex. Precipitation of SnS or formation of a solid solution with mackinawite could be excluded. At pH > 9, SnII is completely oxidized by an FeII/FeIII (hydr)oxide, most likely green rust, forming on the surface of mackinawite. Six O atoms at 2.04 Å and 6 Fe atoms at 3.29 Å demonstrate a structural incorporation by green rust, where SnIV substitutes for Fe in the crystal structure. The transition between SnII and SnIV and between sulfur and oxygen coordination takes place between pH 7 and 8, in accordance with the transition from the mackinawite stability field to more oxidized Fe-bearing minerals. The uptake processes of SnII by mackinawite are largely in line with the uptake processes of divalent cations of other soft Lewis-acid metals like Cd, Hg and Pb. Very different Sn retention mechanisms were hence active, including oxidation to SnIV and formation of tetradentate and bidentate surface complexes of the SnIV hydroxo moieties on goethite and magnetite, and in the case of mackinawite a SnII sulfide species forming a bidentate surface complex at low pH, and structural incorporation of SnIV by an oxidation product, green rust, at high pH. In all three mineral systems and largely independent on the retention mechanisms, inorganic SnII was strongly retained, with Rd values always exceeding 5, across the relatively wide pH range relevant for the near and far-field of nuclear waste respositories. For the goethite and magnetite systems, the retention could be well modeled with surface complexation models based on the molecular structural data. This is an important contribution to the safety case for future nuclear waste repositories, since such SCMs provide reliable means for predicting the radioactive dose released by 126Sn from nuclear waste into the biosphere across a wide range of physicochemical conditions typical for the engineered as well as natural barriers.

Objective of this project was the study of interaction processes between humic substances, U(VI), Np(V) and kaolinite KGa-1b. It contributed to the attainment of a better process understanding, the improvement of the knowledge on the interaction of humic substances and metal ions and the enhancement of the thermodynamic database. With a synthetic humic acid (HA), N-containing functional groups of HA were characterized by 15N-NMR spectroscopy. Based on these results, model studies of the influence of amino groups on the complexation behavior of HA were performed. Spectroscopic studies with amino acids show that the amino group do not contribute to the U(VI) complexation at pH 4. The impact of kaolinite on the formation of HA and humic substance-kaolinite-sorbates was studied in model syntheses. The results exhibit that the presence of kaolinite during the syntheses mainly influences the yields on HA and their elemental compositions. Synthetic humic substance-kaolinite-sorbates were isolated. Under exclusion of CO2, the U(VI) complexation by HA was investigated at pH 7 by means of the conventional time-resolved laser-induced fluorescence spectroscopy (TRLFS) and TRLFS with ultrafast pulses. Complexation parameters for the ternary complex UO2(OH)HA(I) were determined. Studies of the Np(V) reduction in presence of HA with different functionalities under anaerobic conditions have shown that Np(V) is reduced to Np(IV) by HA. The redox capacity depends on the HA functionality. Applying a modified HA it was verified that phenolic/acidic OH groups play a dominating role in the Np(V) reduction. The influence of HA on the U(VI) and Np(V) sorption onto kaolinite was investigated in batch experiments. In dependence on the experimental conditions, HA effects the sorption and consequently the mobility of U(VI) and Np(V). From studies of the U(VI) sorption onto synthetic humic substance-kaolinite-sorbates it was concluded that the structure and functionality of sorbed/associated humic substances considerably influence the sorption behavior of U(VI). The structure of U(VI)-kaolinite-surface complexes in presence of HA was studied by means of X-ray absorption spectroscopy and TRLFS and compared to those of U(VI)-kaolinite-complexes. Investigations of the migration of HA and U(VI) in the laboratory system kaolinite-water were carried out in diffusion experiments. The migration of HA in compacted clay is governed by diffusion and influenced by its colloidal properties. Humic substances exert an immobilizing effect on the U(VI) transport in compacted kaolinite.

The interaction behavior of humic acids with uranium(VI) and the influence of humic substances on the migration behavior of uranium was investigated. A main focus of this work was the synthesis of four different humic acid model substances and their characterization and comparison to the natural humic acid from Aldrich. A radiometric method for the determination of humic acid functional groups was applied in addition to conventional methods for the determination of the functionality of humic acids. The humic acid model substances show functional and structural properties comparable to natural humic acids. Modified humic acids with blocked phenolic OH were synthesized to determine the influence of phenolic OH groups on the complexation behavior of humic acids. A synthesis method for 14C-labeled humic acids with high specific activity was developed. The complexation behavior of synthetic and natural humic acids with uranium(VI) was investigated by X-ray absorption spectroscopy, laser-induced fluorescence spectroscopy and FTIR spectroscopy. The synthetic model substances show an interaction behavior with uranium(VI) that is comparable to natural humic acids. This points to the fact that the synthetic humic acids simulate the functionality of their natural analogues very well. For the first time the influence of phenolic OH groups on the complexation behavior of humic acids was investigated by applying a modified humic acid with blocked phenolic OH groups. The formation of a uranyl hydroxy humate complex was identified by laserspectroscopic investigations of the complexation of Aldrich humic acid with uranium(VI)at pH 7. The migration behavior of uranium in a sandy aquifer system rich in humic substances was investigated in column experiments. A part of uranium migrates non-retarded through the sediment, bound to humic colloids. The uranium migration behavior is strongly influenced by the kinetically controlled interaction processes of uranium with the humic colloids. The influence of humic acids on the sorption of uranium(VI) onto phyllite was investigated in batch experiments using two different humic acids. The uranium(VI) sorption onto the rock phyllite is influenced by the pH-dependent sorption behavior of the humic acids.

Radionuklide werden in vielen Bereichen der Forschung, der Medizin, des Militärs und der Industrie eingesetzt. Aufgrund ihrer vielseitigen Anwendungen können Radionuklide durch anthropogene Einflüsse in die Umwelt gelangen. Durch Migration der radioaktiven Stoffe von oberflächennahen Bereichen durch tiefere Erdschichten bis hin zum Grundwasser können Radionuklide durch ihre chemotoxischen und radiotoxischen Eigenschaften ein Sicherheitsrisiko für das Ökosystem darstellen. Die im Boden allgegenwärtig vorkommenden, myzelbildenden Pilze können aufgrund ihrer schnellen und großflächigen Durchdringung des Erdreichs sowie ihrer hohen Lebenserwartung von mehreren hundert Jahren das Migrationsverhalten von Radionukliden im Erdboden beeinflussen. In Pilzen wird aus diesem Grund ein hohes Potential für Strahlenschutzvorsorgemaßnahmen und biologischen Sanierungsmethoden gesehen. Daher wurden in dieser Arbeit die molekularen Wechselwirkungen von verschiedenen Pilzspezies der Abteilung der Basidiomyzeten mit U(VI) und Eu(III) untersucht. Die aus der Promotionsarbeit resultierenden Erkenntnisse tragen zu einem besseren Verständnis der Wechselwirkungen der ausgewählten Pilze Schizophyllum commune, Pleurotus ostreatus, Lentinus tigrinus und Leucoagaricus naucinus mit Uran und Europium bei. Es konnte festgestellt werden, dass die grundlegende chemische Komplexierung von U(VI) bei dem Bioassoziationsprozess in allen Pilzbiomassen bezüglich der direkten chemischen Umgebung gleich ist. Es werden in allen vier Pilzen vier Komplexe gebildet. Identifizierte Gruppen möglicher Liganden sind zum einen phosphorylierte Zellwandpolysaccharide oder -proteine sowie phosphorylierte Aminosäuren. Jedoch unterscheidet sich die zelluläre Lokalisation der bioassoziierten Metallen bei den Pilzen. Im Fall der Bioassoziation von Eu(III) werden ebenfalls Spezies mit ähnlicher chemischer Zusammensetzung gebildet, wobei es auch hier zu unterschiedlichen Lokalisationen in der Zelle kommt. Die Untersuchungen zeigen, dass trotz der ähnlichen chemischen Komplexierung der zugrundeliegende Bioassoziationsmechanismus von Pilz zu Pilz variiert. Experimente unter naturnahen Bedingungen zeigten, dass dieselben oder zumindestens ähnliche Bioassoziationsmechanismen stattfinden wie unter Laborbedingungen, so dass davon ausgegangen werden kann, dass auch in der Natur ähnliche Bioassoziationsmechanismen stattfinden und die Laborergebnisse damit übertragbar sind. In Experimenten mit Mikrokosmen konnte außerdem der Transport von bioakkumulierten Metallen innerhalb der Hyphe erstmalig demonstriert werden. Dadurch konnte gezeigt werden, dass die in die Zelle aufgenommenen Metalle prinzipiell über den gesamten Organismus verteilt werden kann. Die vorliegende Promotionsarbeit zeigt somit, dass Pilze im Allgemeinen ein großes Potential für biologische Sanierungs- und vor allem für Strahlenschutzvorsorgemaßnahmen besitzen auf Grund der großen Mengen an assoziiertem U(VI) und teilweise Eu(III), der Bildung stabiler Komplexe mit phosphatischen Bioliganden und durch Bioakkumulation in das Zellinnere. Die unterschiedlichen biochemischen Wechselwirkungen der untersuchten Pilzarten, die mit der Radionuklidexposition verbunden sind, haben jedoch gezeigt, dass die untersuchten Pilzspezies unterschiedliche Bioassoziationsprozesse verwenden und dadurch unterschiedliche Effektivität bei der Immobilisierung besitzen.

The growing development of nanotechnology has resulted in an increased use of nanoparticles (NPs) in various applications ranging from medicine, military, to daily consumer products. There is a concern that NPs can be dispersed into the environment in various ways, for example to air and water during manufacture, use, incineration or recycling of products and thus pose a risk to health and the environment. Risk assessments of NPs are hence necessary. One property of NPs, which may make them very useful and at the same time potentially harmful, is their small size (in nanometer range) and hence high surface area per NP mass.This study forms part of the National Mistra Environmental Nanosafety Research Program. The program provides an interdisciplinary platform for researchers from e.g. nanoscience, medicine, chemistry, material science, life cycle analysis, and social science. Specific aspects of this program involve characterization of NPs in different environmental settings, toxicity studies of aquatic organisms, integrated risk assessment of NPs, and societal dimensions of nanosafety. The contribution of this thesis within the program includes studies of stability and mobility of metal NPs and their extent of transformation/dissolution upon environmental interaction. Environmental risk assessments of NPs require a detailed understanding of how they change in terms of physical and chemical properties (charge, size, and surface oxide composition), important aspects for their stability, mobility, and reactivity in the environment. Generated data is highly relevant for the other activities of the Mistra Environmental Nanosafety program, e.g. to gain an improved understanding and design of particle dispersions and ecotoxicity studies, as any environmental interaction will result in the transformation/dissolution of the NPs and change the surface chemistry (e.g. adsorption of natural organic matter, changes in surface oxide properties), aspects that largely influence their speciation and potential toxicity.Common sonication protocols exist to prepare particle dispersions for different in vitro studies. The influence of key parameters stipulated by these protocols on the particle size, transformation/dissolution, and extent of sedimentation was investigated for bare metal NPs. Improved knowledge on these aspects is crucial for design and interpretation of results of NP-related investigations. Reactive metal NPs such as Cu and Mn NPs started to dissolve and release metals already during the probe sonication step of the stock solution, and that the presence of bovine serum albumin (often added as a stabilizing agent) enhanced this process. Even though prolonged sonication time i.e. increased delivered acoustic energy, reduced the size of formed agglomerates, sedimentation was still significant. As a consequence, administered doses from pipetted stock solutions were significantly lower (30-70%) than the nominal doses. The main reason behind the significant extent of agglomeration, with concomitant sedimentation, is related to the strong van der Waals forces prevailing between metal NPs. It is hence essential to determine the administrated dose of metallic NPs in e. g. nanotoxicological testing.Interactions between metallic NPs and natural organic matter (NOM) were studied in terms of stability, mobility and metal dissolution in order to mimic a potential exposure scenario. NOM was represented by humic acid (HA), a main component of organic matter in the environment, and by dihydroxybenzoic acid (DHBA), a small degradation product of NOM. Sedimentation of the Cu, and the Al NPs were slower in the presence of NOM in freshwater compared with freshwater only, whereas the effect of NOM was small for the Mn NPs. Stabilization was related to surface adsorption of NOM, which increased the steric repulsion between the particles, and in the case of HA also increased the magnitude of the zeta potential (resulting in increased electrostatic repulsion). Slight initial increase in particle stability wasobserved in freshwater containing DHBA, but after 24 h, sedimentation of the NPs was comparable to the conditions in freshwater only. The presence of HA (at a concentration of 20 mg/L) was found to stabilize the NPs in freshwater for more than 24 h. However, both the lower and higher HA concentration (2 and 40 mg/L) resulted in agglomeration of the Cu and Al NPs already within a few hours. Mn NPs were more stable in terms of sedimentation in freshwater at all three humic acid concentrations. This concludes that the concentration and type of NOM largely influence the stability of the studied metal NPs in solution. In contrast, SiO2 NPs were not influenced by the presence of NOM in terms of stability, most probably predominantly related to smaller attractive van der Waals forces and larger electrostatic repulsion (due to higher surface charge) compared with the metal NPs.Metal release from the Cu and Al NPs was enhanced in the presence of NOM, whereas no significant influence was observed for the Mn NPs. All metal NPs were dissolved relatively fast; 10% or more of the particle mass was dissolved within 24 h. Speciation predictions revealed rapid complexation between released Cu and Al in solution and NOM, reducing the bioavailability, whereas less complexation was evident for released Mn (as ions). In all, rapid agglomeration and sedimentation imply that any risks associated with the environmental dispersion of these metal NPs will be limited to the vicinity of their source. Mn NPs, having lower sedimentation rates than the Cu and Al NPs, and lack of solution complexation of released ions will likely have a relatively higher probability to be mobile and transported to other aquatic settings.

In dieser Arbeit wurde die Wechselwirkung von U(VI) und Eu(III) mit den Pflanzenzelllinien Brassica napus und Daucus carota sowie mit B. napus-Pflanzen mit verschiedenen biochemischen, systembiologischen, spektroskopischen und mikroskopischen Methoden untersucht. Die Untersuchungen der Wechselwirkung von Uran und Europium mit den Pflanzenzelllinien (B. napus und D. carota) gaben einen umfassenden Einblick in Mobilisierungs- und Immobilisierungsprozesse auf zellulärer und molekularer Ebene. Für beide Pflanzenzelllinien konnten dabei vergleichbare Ergebnisse hinsichtlich der Immobilisierungskinetik erhalten werden. Für U(VI) und Eu(III) konnte eine Immobilisierung durch die Wechselwirkung mit den Pflanzenzellen in zeit- und konzentrationsabhängigen Bioassoziationsstudien nachgewiesen werden, welche im direkten Zusammenhang mit der Aufnahme in die Pflanze und einem potentiellen Eintrag in die Nahrungskette steht. Die dabei beobachteten Veränderungen die Zellvitalität betreffend zeigen, dass sowohl Uran als auch Europium Stressreaktionen in den Zellen auslösen. Für U(VI) wurde für die Wechselwirkung mit beiden Pflanzenzelllinien bei einer Ausgangskonzentration von 20 µM U(VI) ein einstufiger Bioassoziationsprozess nachgewiesen. Eine Immobilisierung konnte auch für die – unter Umweltbedingungen hohe – Konzentration von 200 µM U(VI) beobachtet werden, wobei die Lokalisation von Uran in den Pflanzenzellen belegte, dass dieses aktiv in die Zellen aufgenommen wurde und sich dort in großen Mengen ablagerte. Außerdem wurde basierend auf dem Nachweis einer Kolokalisation von Uran und Phosphor auf eine Anbindung von Uran an (organische) Phosphate geschlossen, was durch XAS-Untersuchungen bestätigt werden konnte. Innerhalb der Zelle konnte die Präzipitation und erstmalig die intrazelluläre Sorption von Uran an Biomembranen nachgewiesen werden. Die Kinetik der Immobilisierung zeigte jedoch für diese hohe U(VI)-Konzentration im Vergleich zu 20 µM U(VI) einen anderen Verlauf, welcher neben der Immobilisierung auch Phasen der (Re-)Mobilisierung von Uran aufwies. Für D. carota äußerte sich diese verringerte Immobilisierung in einer verlangsamten Bioassoziation zu Beginn der Exposition. Für B. napus konnte für längere Expositionszeiten eine Re-Mobilisierung von Uran beobachtet werden, was einen mehrstufigen Bioassoziationsprozess zur Folge hatte, bei welchem bis zu 51% des zuvor immobilisierten Urans wieder in Lösung freigesetzt wurde. Diese Phasen der erhöhten Mobilität von Uran standen dabei in zeitlicher Übereinstimmung mit dem Auftreten einer neuen U(VI)-Spezies in den Nährmedien. Insgesamt wurden in beiden Systemen chemisch identische oder sehr ähnliche U(VI)-Spezies identifiziert. Mittels HPLC, NMR und TRLFS gelang die Identifizierung der U(VI)-Metabolitspezies als Uranyl(VI)-Malat-2:2-Komplex. Es wurde der Beleg erbracht, dass Malat, welches von den Zellen gebildet wird, in das Nährmedium freigesetzt wird und U(VI) komplexiert, was eine geringere Immobilisierung von Uran zur Folge hat. Weiterhin konnte belegt werden, dass das Phänomen der Mobilisierung von Uran für beide Pflanzenzelllinien auftritt und mit der Entstehung eines U(VI)-Malat-Komplexes in den Nährmedien in Verbindung steht. Mittels Proteomics als Methode der Systembiologie konnten Hinweise auf eine Anreicherung von Malat innerhalb des Citratzyklus in Folge der U(VI)-Exposition erhalten werden, die diese Hypothese zusätzlich untermauern. Aufbauend auf den Untersuchungen dieser Arbeit kann geschlussfolgert werden, dass die Immobilisierung von Uran durch die Komplexierung mit freigesetzten Pflanzenzellmetaboliten verringert werden kann. Diese (Re-)Mobilisierungsprozesse müssen für eine zuverlässige Modellierung des Radionuklidtransports in der Umwelt berücksichtigt werden, da mit einer erhöhten Bioverfügbarkeit von Radionukliden ein größeres Umweltrisiko einhergehen kann. Die Bioassoziation von Eu(III) mit beiden Pflanzenzelllinien zeigte sowohl für die niedrigere (30 µM) als auch für die höhere (200 µM) Ausgangskonzentration einen einstufigen Prozess, der zur Immobilisierung von Europium innerhalb von 24 bis 48 h führte. Mittels TRLFS war keine Bildung einer (die Mobilität erhöhenden) Eu(III)-Metabolitspezies nachweisbar, wie es für U(VI) der Fall war. Die Lokalisation von Europium in den Zellen belegte auch hier die Akkumulation, wobei sich jedoch ein anderes Bild der Immobilisierung verglichen mit Uran bot. Für Europium konnte keine vermehrte Anbindung an Biomembranen beobachtet werden und Präzipitate traten nur in geringem Maße auf. Dafür zeigten sich lokale Ablagerungen von europium- und phosphorhaltigen Agglomeraten in Zellwand und Cytoplasma, wobei für Letzteres eine Anbindung an Proteinstrukturen (Komplexierung von Europium) wahrscheinlich ist. Damit ist für Europium, ebenso wie für Uran, eine Anbindung an (organische) Phosphate in der Zelle anzunehmen. Es konnten für die Wechselwirkung von U(VI) und Eu(III) mit beiden Pflanzenzelllinien die Teilprozesse der Biosorption, Bioakkumulation, Biokomplexierung und Biopräzipitation nachgewiesen werden, welche simultan und innerhalb von 24 h Exposition in den Zellen ablaufen. Für Uran gibt es zudem spektroskopische Hinweise auf eine Bioreduktion über einen Ein-Elektronen-Transfer. Untersuchungen zur Aufnahme von Uran und Europium in D. carota-Zellen lieferten zudem Hinweise, dass Calcium-Ionenkanäle einen möglichen Weg für die Aufnahme von Uran in die Zellen darstellen. Proteomics-Analysen von U(VI)-exponierten B. napus-Zellen zeigten außerdem eine deutliche Überexpression von Calcium-transportierenden ATPasen, die ebenfalls auf einen Zusammenhang zwischen Uranaufnahme und Calcium-Homöostase hindeuten. Die Untersuchung der Wechselwirkung von Uran und Europium mit B. napus-Pflanzen zeigte ebenso wie die Studien mit Suspensionszellkulturen eine Immobilisierung beider Metalle, wobei die Aufnahme und Translokation von Uran und Europium in den Pflanzen einen potentiellen Eintrittspfad dieser in die Nahrungskette darstellen. Mithilfe der chemischen Mikroskopie konnten in B. napus-Wurzeln nach 72 h Exposition mit 200 µM Eu(III) drei Eu(III)-Spezies ortsaufgelöst bestimmt werden, die eine Aufnahme und Komplexierung von Eu(III) in die Pflanze belegen. Insgesamt konnte durch die Anwendung verschiedener hochmoderner Methoden in dieser Arbeit ein umfassender Einblick in die Wechselwirkungen von U(VI) und Eu(III) als Analogon für Am(III) und Cm(III) mit Pflanzen auf zellulärer und molekularer Ebene gegeben werden, der zu einem tieferen Prozessverständnis beiträgt. Neben spektroskopischen, mikroskopischen und biochemischen Methoden lieferten auch systembiologische Untersuchungen mittels Proteomics Einblicke in Veränderungen der Proteinexpression der Zellen. Abschließend lässt sich sagen, dass Uran und Europium durch die Interaktion mit Pflanzen(zellen) immobilisiert werden, jedoch dabei die Art und Weise der Wechselwirkung stark von dem jeweiligen Metall abhängt. Die Untersuchungen dieser Arbeit zeigen, dass Pflanzen im Falle einer Freisetzung von Radionukliden aus einem Endlager und eines Eintritts in die Biosphäre über das Grundwasser eine entscheidende Rolle für deren Migrationsverhalten in der Umwelt spielen können. Gleichzeitig geht mit einer Immobilisierung der Radionuklide ein Eintrag in die Nahrungskette und damit ein potentielles Gesundheitsrisiko einher. Das generierte Prozessverständnis liefert erheblich tiefere Einblicke in die Wechselwirkungen zwischen Radionukliden und Pflanzen, als es die bisher für die Risikoabschätzung eines Endlagers herangezogenen Transferfaktoren ermöglichen. Es dient der Weiterentwicklung biogeochemischer und radioökologischer Modelle, die wiederum zuverlässigere Dosisabschätzungen erlauben. Um die Interaktion mit anderen sechswertigen Actiniden wie PuO22+ und NpO22+ einschätzen zu können und damit zuverlässige Sicherheitsbeurteilungen zu ermöglichen, sind zukünftig vergleichbare Untersuchungen auch mit diesen, für die Radiotoxizität in Endlagern relevanten, Vertretern durchzuführen.

Analysis of the molecular speciation of organic compounds in solution is essential for the understanding of ionic complexation. The Raman spectroscopic technique was chosen for this purpose because it allows the identification of compounds in different states and it can give information about the molecular geometry from the analysis of the vibrational spectra. In this research the ionisation steps of relevant pharmaceutical material have been studied by means of potentiometry coupled with Raman spectroscopy; the protonation and deprotonation behaviour of the molecules were studied in different pH regions. The abundance of the different species in the Raman spectra of aqueous salicylic acid, paracetamol, citric acid and salicylaldoxime have been identified, characterised and confirmed by numerical treatment of the observed spectral data using a multiwavelength curve-fitting program. The non-destructive nature of the Raman spectroscopic technique and the success of the application of the multiwavelength curve-fitting program demonstrated in this work have offered a new dimension for the rapid identification and characterisation of pharmaceuticals in solution and have indicated the direction of further research. The work also covers the formation of novel cocrystal systems with pharmaceutically relevant materials. The existence of new cocrystals of salicylic acid-nicotinic acid, DLphenylalanine , 6-hydroxynicotinic acid, and 3,4-dihydroxybenzoic acid with oxalic acid have been identified from stoichiometric mixtures using combined techniques of Raman spectroscopy (dispersive and transmission TRS), X-ray powder diffraction and thermal analysis. Raman spectroscopy has been used to demonstrate a number of important aspects regarding the nature of the molecular interactions in the cocrystal. Cocrystals of II salicylic acid ¿ benzamide, citric acid-paracetamol and citric acid -benzamide have been identified with similar analytical approaches and structurally characterised in detail with single crystal X-ray diffraction. From these studies the high selectivity and direct micro sampling of Raman spectroscopy make it possible to identify spectral contributions from each chemical constituent by a peak wavenumber comparison of single-component spectra (API and guest individually) and the two- component sample material (API/guest), thus allowing a direct assessment of cocrystal formation to be made. Correlation of information from Raman spectra have been made to the X-ray diffraction and thermal analysis results. Transmission Raman Spectroscopy has been applied to the study cocrystals for the first time. Identification of new phases of analysis of the low wavenumber Raman bands is demonstrated to be a key advantage of the TRS technique. / Libyan government and Misurata University

No description available.

The research presented in this thesis focused on pseudorotaxanes and supramolecular polymers based on a new recognition motif, the dibenzo-24-crown-8/paraquat recognition motif. Main kinds of pseudorotaxanes and rotaxanes and various protocols used for the study of them were discussed first. By preparation and characterization of a series of pesudorotaxanes based on DB24C8 and paraquat derivatives, it was found that these complexes were stabilized by N+...O interactions, C-H...O hydrogen bonding, and face-to-face p-stacking interactions. Because methyl protons of paraquat are involved in hydrogen bonding to the host, the substitution of any methyl hydrogen on paraquat causes apparent association constant of the pseudorotaxane to decrease. The concentration dependence of apparent association constants, Ka,exp, of fast exchange host-guest systems was studied for the first time by using complexes based on viologens and crown ethers as examples. While the bis(hexafluorophosphate) salts of paraquat derivatives are predominantly ion paired in acetone (and other low dielectric constant solvents presumably) the complex based on dibenzo-24-crown-8 and paraquat is not ion paired in solution, resulting in concentration dependence of Ka,exp. However, four complexes of two different bis(m-phenylene)-32-crown-10 (BMP32C10) derivatives and bis(p-phenylene)-34-crown-10 (BPP3C10) with viologens are ion paired in solution, as shown by the fact that Ka,exp is not concentration dependent for these systems involving hosts with freer access to bound guests. X-ray crystal structures support these soluton-based assessments in that there is clearly ion pairing of the cationic guest and its PF6- counterions in the solid states of the latter four examples, but not in the former. The complexes based on the new dibenzo-24-crown-8/paraquat recognition motif are thus different from the complexes based on two old recognition motifs: the BPP34C10/BMP32C10-paraquat and DB24C8-ammonium motives. In order to compare these recognition motives further, the selectivity between two hosts, DB24C8 and BPP34C10, and two guests, dimethyl paraquat and dibenzyl ammnonium salt, was discussed. By individual and competitive complexation studies, it was demonstrated that DB24C8 is a better host than BPP34C10 for paraquat, and that paraquat is a better guest than dibenzyl ammonium salt for DB24C8. Finally the DB24C8-paraquat recognition motif was successfully applied in the preparation the first star-shaped supramolecular polymer based on a tetraparaquat guest and a DB24C8 functionalized polystyrene oligomer. A model system based on this guest and DB24C8 was also studied for comparison. It was found that the complexation in these two systems is cooperative, as are most biological complexations of multitopic species. Due to the ready availability of DB24C8 and paraquat derivatives, the new recognition motif should prove to be very valuable for self-assembly of other more sophisticated supramolecular systems. / Master of Science

The present PhD thesis entitled “Design, Synthesis and Evaluation of Chromofluorogenic Probes for Contaminating Species” is focused on the development of new chromo-fluorogenic sensors based on the principles of molecular recognition. The first part of this thesis is focused on the design and synthesis of suitable organic compounds as sensors for metal cations. The selected sensing paradigm was the binding site-signalling subunit approach. The synthetized receptors employs a chromophore (fluorescein or BODIPY) skeleton as signalling subunit and it is functionalized with aminoethoxy moieties as binging site; the metal coordination reduces the electron-donating ability of the nitrogen atom conjugated to the chromophore resulting in optical changes noticeable to the naked-eye. The sensing behavior is highly selective to trivalent cations (Fe3+, Al3+ and Cr3+) with remarkable limits of detection. The receptors based on BODIPYdyes retain the sensing abilities in mixed aqueous solutions. The remaining chapters of the thesis are centered in the detection and removal of nerve agents surrogates. The design, synthesis, characterization and application of new BODIPY chemosensors were studied. These chemosensors were designed containing different reactive sites in order to avoid interferences produced by acids or hydrolysis products, and also be able to distinguish between the different G-nerve agent mimics (DCNP and DFP). The BODIPY-probes allows screening of nerve agent surrogates with remarkable limits of detection and optical changes noticeable to the naked-eye. The sensing abilities are retained in solid support, allowing practical application in real-time monitoring by simple colorimetric tests. The displacement assay approach has been used to develop a selective sensor for V-nerve agent surrogates versus G-type. For this purpose, two Eu3+ and Au3+ BODIPY-complexes were prepared. In this case, V-surrogate is capable of coordinate the metallic center, releasing the BODIPY ligand. This causes a change in the optical properties visible to the naked-eye. Finally, the use of supramolecular-based organocatalyst for destruction of OP nerve agent surrogates was studied. Hydrolysis studies were performed in presence of 1,3-diindolylureas and thioureas, amines, aminoalcohol and glycols. Addition of catalyst enhances the electrophilic character of the P atom, and the final nucleophilic attack of water that results in the formation of the corresponding less toxic organophosphate derivatives, thus higher hydrolysis rates are obtained. / Barba Bon, A. (2014). Design, Synthesis and Evaluation of Chromo-fluorogenic Probes for Contaminating Species [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48521