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Increased reactivity of radiation-damaged quartz in the alkaline pore water of concrete and its role in radionuclide transport is a subject that is becoming increasingly important as nuclear power plants (NPPs) around the world reach end-of-life. Quartz contributes more than half the weight of most concretes and up to 40 % of the total radioactive waste volume associated with the dismantling of an NPP. The gamma-emitting radionuclides are the major contributors to the radiation dose rate in the concrete biological shield in the intermediate term after NPP shut-down. The appreciable activity and associated half-lives of these radionuclides pose a problem not only during the safe dismantling of NPPs, but also in terms of processing the concrete to reduce the active waste volume for final disposal in a repository. While thermal neutrons are captured by atomic nuclei according to their thermal neutron cross-sections, fast neutrons undergo collision cascades, which cause defects in the structure of materials. The concentration of defects accumulates as a function of neutron energy and fluence. The high covalency and the density of Si-O bonds in tectosilicates, primarily quartz, followed by feldspars, makes these minerals very susceptible to radiation damage. In this study, two inactive concrete powder samples were placed inside an instrumentation channel passing through the first biological shielding of an operating German NPP, respectively for a half- and a full fuel cycle. Using a plant-specific 3D-reactor model in conjunction with Monte Carlo neutron transport calculations, neutron fluences at the sample positions and the resulting gamma activities are calculated. We compare the measured and calculated activities of the gamma-emitting radionuclides Synchrotron X-ray powder diffractometry was used to examine structural changes on sub-nanoscale. The local structure of the silicate aggregate minerals was investigated by solid-state magic angle spinning nuclear magnetic resonance (NMR) Spectroscopy using 27Al and 29Si as probes. With this work we wish to gain insights into the potential for alkali-silica reaction (ASR) in radiation-damaged concrete and the role this plays in the transport or sorption of radionuclides either present in situ via neutron activation or ex situ due to transport of leaked reactor cooling water.

Cyano‐substituted polyphenylene vinylenes (PPVs) have been in the focus of research for several decades due to their interesting optoelectronic properties and potential applications in organic electronics. With the advent of organic two‐dimensional (2D) crystals, the question arose how the chemical and optoelectronic advantages of PPVs evolve in 2D compared to their linear counterparts. In this work, we present the efficent synthesis of two novel 2D fully sp²‐carbon‐linked crystalline PPVs and investigate the essentiality of inorganic bases for their catalytic formation. Notably, among all bases screened, cesium carbonate (Cs₂CO₃) plays a crucial role and enables reversibility in the first step with subsequent structure locking by formation of a C=C double bond to maintain crystallinity, which is supported by density functional theory (DFT) calculation. We propose a quantifiable energy diagram of a “quasi‐reversible reaction” which allows to identify further suitable C‐C bond formation reactions for 2D polymerizations. Moreover, we delineate the narrowing of the HOMO‐LUMO gap by expanding conjugation into two dimensions. To enable environmentally benign processing, we further perform the post‐modification of 2D PPVs, which renders stable dispersions in the aqueous phase.

Since signal separation by lanthanide shift reagents [1,2] has been replaced by elaborate pulse sequences and high-field spectrometers, lanthanides have advanced from auxiliaries to real objects of interest, also as inactive analogues for trivalent actinides in consequence of their similar chemistry. Here we want to report on interactions and structures of the Ln(III) (La3+, Eu3+ and, where applicable, Y3+) with selected systems, i.e., L-lactate [3], inorganic (poly)borates [4] and organoborates [5]. Small organic molecules such as lactate are important as model molecules and potential complexing agents found throughout the biosphere. Borates are ubiquitous in nature. In the context of nuclear waste disposal they occur in remarkable amounts in salt formations being potential host rocks for nuclear waste repositories, but also in boron containing cooling water or borosilicate glass coquilles for spent nuclear fuel. Organoborates are considered due to possible reaction of the former compounds and, additionally, suggested as analogues to model the interaction between Ln/An and borates in general. Among several possible structures, infrared (IR) and NMR measurements, supported by density functional theory (DFT) calculation, revealed that lactate forms Ln(III) (and Am3+) complexes with both the carboxyl and hydroxyl group involved. Polyborates, i.e., triborate and pentaborate form soluble weak aqueous Ln(III) complexes prior to precipitation as amorphous white solids, whereas condensation to higher polyborates can be excluded. Two signals in both the 89Y and the 11B NMR spectra probably arise from two coordination sites, which may reflect the polyborate species found in the supernatant solution. The organoborates formed by the reaction of boric acid and, e.g., lactate or salicylate also possess a tetra-coordinated boron atom [BO4], considered as the responsible site for Ln(III) interaction in inorganic (poly)borates. Since the (poly)borate/boric acid equilibrium is strongly concentration and pH dependent, their replacement by organic analogues allows investigations at both lower total boron concentrations and pH values. [1] Hinckley, C. C. J. Am. Chem. Soc. 1969, 91, 5160–5162. [2] Gansow, O. A.; Willcott, M. R.; Lenkinski, R. E. J. Am. Chem. Soc. 1971, 93, 4295–4297. [3] Barkleit, A.; Kretzschmar, J.; Tsushima, S.; Acker, M. Dalton Trans. 2014, 43, 11221–11232. [4] Schott, J.; Kretzschmar, J.; Acker, M.; Eidner, S.; Kumke, M. U.; Drobot, B.; Barkleit, A.; Taut, S.; Brendler, V.; Stumpf, T. Dalton Trans. 2014, 43, 11516–11528. [5] Schott, J; Kretzschmar, J; Acker, M.; Tsushima, S.; Barkleit, A.; Taut, S.; Brendler, V.; Stumpf, T., Dalton Trans., in preparation.

Chitin is known to adsorb various metals. Therefore, chitin containing materials are taken into consideration as filter materials for contaminated waters. Marine sponges of the order Verongida form three-dimensional networks of fibrous chitin, which can easily be extracted. In the hydrated state, these networks are flexible, mechanically stable and can be cut or pressed into any desired form. Here, we show for the first time that chitin-based networks of sponge origin are useful for effective uranium adsorption. They adsorb U(VI) from solution with a higher sorption capacity than many other chitinous sorbents from fungal biomass. Solid-state NMR, infrared and Raman spectroscopy indicated that the U(VI) is bound to the chitin by weak interactions such as hydrogen bonds. 90 % of the U(VI) could be desorbed using diluted hydrochloric acid. Uranium adsorption and desorption did not result in any destruction of the chitin material.

Transport pores were introduced into a crystalline silicoalumophosphate (SAPO-34) using carbon materials as hard templates. Carbon nanoparticles and carbon nanotubes were added as secondary templates during the hydrothermal synthesis. By using a mixed template (morpholine and TEAOH) in the SAPO-34 synthesis it was possible to maintain the crystallinity, the surface area and decrease the formation of amorphous phase. The obtained materials were characterized with XRD, SEM, NMR, NH 3-TPD, EDX and N 2-physisorption measurements. n-Butane uptake experiments as well as catalytic test revealed that the type of carbon material is important for the accessibility of the hierarchical pore system. The mesopores created by carbon nanoparticles are located inside the particle but do not form a three-di mensional mesopore network. A significant improvement in the kinetic uptake of n-butane and in the conversion of methanol could be observed for the carbon nanotube-templated materials, containing mesopores accessible from the outside of the particle. Reactivation experiments revealed transport pores to be stable even after several regeneration cycles.

Lanthanides have become a useful tool in NMR spectroscopy within the last 40 years. Due to their paramagnetic properties they can be utilized as probes to determine the binding sites of biologically or environmentally relevant organic molecules as they cause significant line broadenings and / or paramagnetic induced shifts. In our former and actual research we investigate the interactions, thermodynamic and kinetic behaviour of actinides and biomolecules. Lanthanides can easily be used as inactive analogues for trivalent actinides in consequence of their similar chemistry. As one major result, determined by solution and solid state NMR spectroscopy, we have found out that lanthanide ions are able to act as linkers to build up polymeric structures of bifunctional organic acids such as pyromellitic acid [1] or phosphorylated amino acids. For instance, in the case of O-phospho-L-serine the lanthanide ions can serve as a bridge between the carboxylate and the phosphate group of two amino acid molecules to form repetitive macromolecules. The influence of pH and temperature has also been studied. The results were confirmed by dynamic light scattering and FT-IR spectroscopy as well as by isothermal titration calorimetry and laser-induced fluorescence spectroscopy. Future investigations will focus on actinides, in particular the trivalent americium ion, possibly showing similar chemical reactions. [1] A. Barkleit, S. Tsushima, O. Savchuk, J. Philipp, K. Heim, M. Acker, S. Taut, K. Fahmy, Inorg. Chem. 50 (2011), 5451-5459.

Lanthanides have become a useful tool in NMR spectroscopy within the last 40 years. Due to their paramagnetic properties they can be utilized as probes to determine the binding sites of biologically or environmentally relevant organic molecules as they cause significant line broadenings and / or paramagnetic induced shifts. In our former and actual research we investigate the interactions between actinides and biomolecules, revealing the structure as well as thermodynamic and kinetic behaviour. Lanthanides can easily be used as inactive analogues for trivalent actinides in consequence of their similar chemistry. We found out that lanthanide ions are able to act as linkers to build up polymeric structures of bifunctional organic acids such as phosphorylated amino acids. For instance, in the case of O-phospho-L-serine the lanthanide ions can serve as a bridge between the carboxylate and the phosphate group of two amino acid molecules to form macromolecules with repetitive units. Solid state NMR spectroscopy was the most feasible tool for structure elucidation, proving that both the phosphate and the carboxylic group are involved in the complexation. By means of 1D and 2D methods it was confirmed that both functional groups lose their protons and, thus, must be the binding sites for the lanthanides, whereas the protons of the amino group are unaffected. The interactions between the lanthanides (Eu3+, La3+) and the phosphorylated acids can be monitored by solution 31P-NMR spectroscopy and confirmed by dynamic light scattering. After mixing the reactants, colloids are formed immediately. After some minutes up to hours the formed aggregates precipitate. Different temperature, pH and ionic strength conditions may be object of further investigations.