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Developing an atomistic understanding of ionizing radiation induced changes to organic materials is necessary for intentional design of greener and more sustainable materials for radiation shielding and detection. Cocrystals are promising for these purposes, but a detailed understanding of how the specific intermolecular interactions within the lattice upon exposure to radiation affect the structural stability of the organic crystalline material is unknown. This study evaluates atomistic‐level effects of γ radiation on both single‐ and multicomponent organic crystalline materials and how specific noncovalent interactions and packing within the crystalline lattice enhance structural stability. Dose studies were performed on all crystalline systems and evaluated via experimental and computational methods. Changes in crystallinity were evaluated by p‐XRD and free radical formation was analyzed via EPR spectroscopy. Type of intermolecular interactions and packing within the crystal lattice was delineated and related to the specific free radical species formed and the structural integrity of each material. Periodic DFT and HOMO‐LUMO surface mapping calculations provided atomistic‐level identifications of the most probable sites for the radicals formed upon exposure to γ radiation and relate intermolecular interactions and molecular packing within the crystalline lattice to experimental results.

 

Through a combination of many analytical approaches, we show that a metal organic nanotube (UMON) displays selectivity for H 2 O over all types of heavy water (D 2 O, HDO, HTO). Water adsorption experiments combined with vibrational and radiochemical analyses reveal significant differences in uptake and suggest that surface adsorption processes may be a key driver in water uptake for this material. 

Uranium (U) contamination of drinking water often affects communities with limited resources, presenting unique technology challenges for U 6+ treatment. Here, we develop a suite of chemically functionalized polymer (polyacrylonitrile; PAN) nanofibers for low pressure reactive filtration applications for U 6+ removal. Binding agents with either nitrogen-containing or phosphorous-based ( e.g. , phosphonic acid) functionalities were blended (at 1–3 wt%) into PAN sol gels used for electrospinning, yielding functionalized nanofiber mats. For comparison, we also functionalized PAN nanofibers with amidoxime (AO) moieties, a group well-recognized for its specificity in U 6+ uptake. For optimal N-based (Aliquat® 336 or Aq) and P-containing [hexadecylphosphonic acid (HPDA) and bis(2-ethylhexyl)phosphate (HDEHP)] binding agents, we then explored their use for U 6+ removal across a range of pH values (pH 2–7), U 6+ concentrations (up to 10 μM), and in flow through systems simulating point of use (POU) water treatment. As expected from the use of quaternary ammonium groups in ion exchange, Aq-containing materials appear to sequester U 6+ by electrostatic interactions; while uptake by these materials is limited, it is greatest at circumneutral pH where positively charged N groups bind negatively charged U 6+ complexes. In contrast, HDPA and HDEHP perform best at acidic pH representative of mine drainage, where surface complexation of the uranyl cation likely drives uptake. Complexation by AO exhibited the best performance across all pH values, although U 6+ uptake via surface precipitation may also occur near circumneutral pH values and at high (10 μM) dissolved U 6+ concentrations. In simulated POU treatment studies using a dead-end filtration system, we observed U removal in AO-PAN systems that is insensitive to common co-solutes in groundwater ( e.g. , hardness and alkalinity). While more research is needed, our results suggest that only 80 g (about 0.2 lbs.) of AO-PAN filter material would be needed to treat an individual's water supply (contaminated at ten-times the U.S. EPA maximum contaminant level for U) for one year. 

Current synthetic pathways for uranyl peroxide materials introduce high initial concentrations of aqueous H₂O₂that decline over time. Alternatively, in situ generation of organic peroxide would maintain constant concentrations of peroxide over prolonged periods of time and open new pathways to novel uranyl peroxide compounds. Herein, we demonstrate this concept through the synthesis of a nanotube‐like uranyl peroxide phosphate (NUPP), Na₁₂[(UO₂)(μ‐O₂)(HPO₄)]₆(H₂O)₄₀, making use of the inhibited autoxidation of benzaldehyde in benzyl alcohol solutions in the presence of phosphonate ligands. The unique feature ofNUPPis the bent dihedral angle U‐(μ‐O₂)‐U (123.9°±0.4° to 124.6°±0.5°), which allows hexameric uranyl peroxide macrocycles to adopt the nanotubular topology and prevents the formation of nanocapsules. Raman spectroscopy of the solution phase confirms our mechanistic understanding of the reaction pathway and confirms that consistent levels of peroxide are generated in situ over an extended period of time.

 

Current synthetic pathways for uranyl peroxide materials introduce high initial concentrations of aqueous H₂O₂that decline over time. Alternatively, in situ generation of organic peroxide would maintain constant concentrations of peroxide over prolonged periods of time and open new pathways to novel uranyl peroxide compounds. Herein, we demonstrate this concept through the synthesis of a nanotube‐like uranyl peroxide phosphate (NUPP), Na₁₂[(UO₂)(μ‐O₂)(HPO₄)]₆(H₂O)₄₀, making use of the inhibited autoxidation of benzaldehyde in benzyl alcohol solutions in the presence of phosphonate ligands. The unique feature ofNUPPis the bent dihedral angle U‐(μ‐O₂)‐U (123.9°±0.4° to 124.6°±0.5°), which allows hexameric uranyl peroxide macrocycles to adopt the nanotubular topology and prevents the formation of nanocapsules. Raman spectroscopy of the solution phase confirms our mechanistic understanding of the reaction pathway and confirms that consistent levels of peroxide are generated in situ over an extended period of time.