Level, distribution and sources of Np, Pu and Am isotopes in Peter the Great Bay of Japan sea.

Transuranium elements such as Np, Pu and Am, are considered to be the most important radioactive elements in view of their biological toxicity and environmental impact. Concentrations of 237Np, Pu isotopes and 241Am in two sediment cores collected from Peter the Great Bay of Japan Sea were determined using radiochemical separation combined with inductively coupled plasma mass spectrometry (ICP-MS) measurement. The 239,240Pu and 241Am concentrations in all sediment samples range from 0.01 Bq/kg to 2.02 Bq/kg and from 0.01 Bq/kg to 1.11 Bq/kg, respectively, which are comparable to reported values in the investigated area. The average atomic ratios of 240Pu/239Pu (0.20 ± 0.02 and 0.21 ± 0.01) and 241Am/239+240Pu activity ratios (3.32 ± 2.76 and 0.45 ± 0.17) in the two sediment cores indicated that the sources of Pu and Am in this area are global fallout and the Pacific Proving Grounds through the movement of prevailing ocean currents, and no measurable release of Np, Pu and Am from the local K-431 nuclear submarine incident was observed. The extremely low 237Np/239Pu atomic ratios ((2.0-2.5) × 10-4) in this area are mainly attributed to the discrepancy of their different chemical behaviors in the ocean due to the relatively higher solubility of 237Np compared to particle active plutonium isotopes. It was estimated using two end members model that 23% ± 6% of transuranium radionuclides originated from the Pacific Proving Grounds tests, and the rest (ca. 77%) from global fallout.

Kinetic features of solvent extraction by N,O-donor ligands of f-elements: a comparative study of diamides based on 1,10-phenanthroline and 2,2'-bipyridine.

A variant of microfluidic setup design for the study of extraction kinetics has been proposed. Mass transfer constants for Am(III) and Eu(III) and observed rate constants were obtained for N-,O-donor ligands featuring phenanthroline and bipyridyl cores. The possibility of determining rate constants for cations independently of each other makes it possible to observe the kinetic effect of separation. The extraction rate was found to be lower for the bipyridyl ligand, compared to phenanthroline. The values of the rotation barriers for the ligands were calculated using the DFT method. The values correlate with the obtained low extraction rate for the bipyridyl ligand. Also, crystallographic data showing anti-conformation for the bipyridyl ligand align with the kinetic data. Surface tension was also determined for the systems with the studied ligands. It is shown that at equal ligand concentrations, the value of surface tension agrees with the extraction rate. Furthermore, it is shown that for the bipyridyl ligand, prior contact of the organic phase with nitric acid significantly affects the surface tension.

4-Oxo-7-fluoro-1,10-phenanthroline-2,9-diamides: Synthesis, Structural Features, Lanthanide Complexes, and Am(III)/Ln(III) Solvent Extraction.

A highly efficient synthetic approach was developed for the synthesis of unsymmetrical 1,10-phenanthroline-2,9-diamides with two different substituents in the fourth and seventh positions of the phenanthroline core. The structures of these ligands were confirmed using various spectral methods including 2D-NMR and X-ray analysis. Quantum chemical calculations supported the presence of tautomeric forms of these ligands. Furthermore, it was discovered that these compounds exhibit polydentate ligand behavior toward lanthanide nitrates. The structural characteristics of the complexes formed between these ligands and lanthanide nitrates were investigated both in the solid state and in solution. To further understand the binding properties of these novel unsymmetrical ligands, the binding constants for potential complexes were quantitatively measured by using UV-vis spectrophotometric titration. This allowed for a comprehensive analysis of the binding affinity and stability of these complexes. Extraction experiments of f-elements were performed for symmetrical and unsymmetrical diamides. Overall, this study presents significant advancement in the synthesis and characterization of unsymmetrical 1,10-phenanthroline-2,9-diamides and provides valuable insights into their potential applications as polydentate ligands for lanthanide nitrates.

Sensing and extraction of hazardous metals by di-phosphonates of heterocycles: a combined experimental and theoretical study.

In this study, pyridine and phenanthroline diphosphonate ligands were investigated for the first time from the context of solvent extraction and potentiometric sensing of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II) cations. The extraction efficiency under the same conditions for phenanthroline-diphosphonates is considerably higher than that for pyridine ligands. At the same time, the pyridine-diphosphonates show pronounced selectivity towards lead in this metal series. The extraction systems with phenanthroline diphosphonates provided the most efficient extraction of Cd(II) and Pb(II) cations (D > 90). The newly developed pyridine and phenanthroline diphosphonate ligands have proven to be highly effective components in plasticized polymeric membranes. These ligands can be utilized to construct potentiometric ion sensors that exhibit a notable response specifically towards Pb(II) cations. Among the previously reported tetradentate ligands, the phenanthroline diphosphonate ligand, when incorporated into plasticized polymeric membranes, demonstrated the highest sensitivity towards d-metals and Pb(II). The structure of the single crystal complex of Pb(II) and Cd(II) with pyridine-diphosphonates was studied by X-ray diffraction analysis (XRD). The geometry of Cu(II), Zn(II), Cd(II) and Pb(II) complexes and the energy effect of the complex formation, including pseudo-oligomerization reactions, were determined by DFT calculations. The high sensing and extraction efficiency of diphosphonates with respect to Pb(II) is consistent with the minimum values of complex formation energies. The variation in sensory and extraction properties observed among the studied diphosphonate ligands is influenced by the ability to form polynuclear complexes with Pb(II) cations, whereas such properties are absent in the case of Cd(II) cations.

First 24-Membered Macrocyclic 1,10-Phenanthroline-2,9-Diamides-An Efficient Switch from Acidic to Alkaline Extraction of f-Elements.

A reaction of acyl chlorides derived from 1,10-phenanthroline-2,9-dicarboxylic acids with piperazine allows the preparation of the corresponding 24-membered macrocycles in good yield. The structural and spectral properties of these new macrocyclic ligands were thoroughly investigated, revealing promising coordination properties towards f-elements (Am, Eu). It was shown that the prepared ligands can be used for selective extraction of Am(III) from alkaline-carbonate media in presence of Eu(III) with an SFAm/Eu up to 40. Their extraction efficiency is higher than calixarene-type extraction of the Am(III) and Eu(III) pair. Composition of macrocycle-metal complex with Eu(III) was investigated by luminescence and UV-vis spectroscopy. The possibility of such ligands to form complexes of L:Eu = 1:2 stoichiometry is revealed.

Pyrrolidine-Derived Phenanthroline Diamides: An Influence of Fluorine Atoms on the Coordination of Lu(III) and Some Other f-Elements and Their Solvent Extraction.

Three pyrrolidine-derived phenanthroline diamides were studied as ligands for lutetium trinitrate. The structural features of the complexes have been studied using various spectral methods and X-ray. The presence of halogen atoms in the structure of phenanthroline ligands has a significant impact on both the coordination number of lutetium and the number of solvate water molecules in the internal coordination sphere. The stability constants of complexes with La(NO3)3, Nd(NO3)3, Eu(NO3)3, and Lu(NO3)3 were measured to demonstrate higher efficiency of fluorinated ligands. NMR titration was performed for this ligand, and it was found that complexation with lutetium leads to an approximately 13 ppm shift of the corresponding signal in the 19F NMR spectrum. The possibility of formation of a polymeric oxo-complex of this ligand with lutetium nitrate was demonstrated. Experiments on the liquid-liquid extraction of Am(III) and Ln(III) nitrates were carried out to demonstrate advantageous features of chlorinated and fluorinated pyrrolidine diamides.

Solvation-Anionic Exchange Mechanism of Solvent Extraction: Enhanced U(VI) Uptake by Tetradentate Phenanthroline Ligands.

Phenanthroline diamides (L) demonstrated a unique ability to extract uranium from nitric acid solutions into a polar organic solvent forming complexes of 1:2 stoichiometry as tight ion pairs {[UO2LNO3]+[UO2(NO3)3]-} by a novel extraction mechanism, which is a combination of two already well-known mechanisms: solvation and ion-pair anion exchange. A UV-vis study was used to confirm the formation of such complexes directly in the organic phase. Moreover, chemical synthesis and single crystal growth were performed to confirm unambiguously the structure of the complexes in the solid state.

Competing Routes in the Extraction of Lanthanide Nitrates by 1,10-Phenanthroline-2,9-diamides: An Impact of Structure of Complexes on the Extraction.

The fact of the fracture of the extraction curve of lanthanides by 1,10-phenanthroline-2,9-diamides is explained in terms of the structure of complexes, solvent extraction data and quantum chemical calculations. The solvent extraction proceeds in two competing directions: in the form of neutral complexes LLn(NO3)3 and in the form of tight ion pairs {[LLn(NO3)2 H2O]+ (NO3-).

Pyridine-di-phosphonates as chelators for trivalent f-elements: kinetics, thermodynamic and interfacial study of Am(III)/Eu(III) solvent extraction.

The fractionation of high-level radioactive waste from nuclear power plants simplifies the handling of its components, and facilitates the reduction of radiotoxic effects on the environment. The search and study of new ligands for solvent extraction, as one of the methods in fractionation, remains a complex and important research task. In this work, four pyridine diphosphonate ligands were synthesized. These ligands are part of the class of the N,O-donor extractants, which are selective towards Am(III). The separation factor SF(Am/Eu) for the best extractant reached values up to 10. The influence of the substituents on the efficiency of extraction and complexation of trivalent f-elements, the kinetics of extraction, and the behavior of the ligand at the interface were described. The effect of nitric acid concentration on the extraction was shown. The stoichiometry of the complexes was determined by slope analysis in solvent extraction experiment and verified by spectrophotometric titration in acetonitrile. Liquid tension experiments with a pendant drop method revealed the interfacial properties of the ligands in "F-3 solvent/H2O" and "F-3 solvent/HNO3" systems. The relationship between the surface activity and the ligand structure was shown. Studies of the extraction kinetics were performed in a modified Lewis cell. The effect of the ligand structure on the extraction rate was shown. The DFT calculation with the B3LYP density functional was used to explain the extraction properties of the ligands, including selectivity. The calculation of the pre-organization energy of the ligands explained the kinetics and extraction patterns for the studied series.

First Trifluoromethylated Phenanthrolinediamides: Synthesis, Structure, Stereodynamics and Complexation with Ln(III).

The first examples of 1,10-phenanthroline-2,9-diamides bearing CF3-groups on the side amide substituents were synthesized. Due to stereoisomerism and amide rotation, such complexes have complicated behavior in solutions. Using advanced NMR techniques and X-ray analysis, their structures were completely elucidated. The possibility of the formation of complex compounds with lanthanoids nitrates was shown, and the constants of their stability are quantified. The results obtained are explained in terms of quantum-chemical calculations.

Way to Enforce Selectivity via Steric Hindrance: Improvement of Am(III)/Eu(III) Solvent Extraction by Loaded Diphosphonic Acid Esters.

Hybrid donor extractants are a promising class of compounds for the separation of trivalent actinides and lanthanides. Here, we investigated a series of sterically loaded diphosphonate ligands based on bipyridine (BiPy-PO-iPr and BiPy-PO-cHex) and phenanthroline (Phen-PO-iPr and Phen-PO-cHex). We studied their complex formation with nitrates of trivalent f-elements in solvent extraction systems (Am and Eu) and homogeneous acetonitrile solutions (Nd, Eu, and Lu). Phenanthroline extractants demonstrated the highest efficiency and selectivity [SF(Am/Eu) up to 14] toward Am(III) extraction from nitric acid solutions among all of the studied diphosphonates of N-heterocycles. The binding constants established by UV-vis titration also indicated stronger binding of sterically impaired diphosphonates compared to the primary substituted diphosphonates. NMR titration and slope analysis during solvent extraction showed the formation of 2:1 complexes at high concentrations (>10-3 mol/L) for phenanthroline-based ligands. According to UV-vis titrations at low concentrations (10-5-10-6 mol/L), the phenanthroline-based ligands formed 1:1 complexes. Bipyridine-based ligands formed 1:1 complexes regardless of the ligand concentration. Luminescence titrations revealed that the quantum yields of the complexes with Eu(III) were 81 ± 8% (BiPy-PO-iPr) and 93 ± 9% (Phen-PO-iPr). Single crystals of the structures [Lu(µ2,κ4-(iPrO)2P(O)Phen(O)2(OiPr))(NO3)2]2 and Eu(Phen-PO-iPr)(NO3)3 were obtained by chemical synthesis with the Phen-PO-iPr ligand. X-ray diffraction studies revealed a closer contact of the f-element with the aromatic N atoms in the case of sterically loaded P═O ligands compared with sterically deficient ligands. Density functional theory calculations allowed us to rationalize the observed selectivity trends in terms of the bond length, Mayer bond order, and preorganization energy.

Unravelling the Material Composition Effects on the Gamma Ray Stability of Lead Halide Perovskite Solar Cells: MAPbI3 Breaks the Records.

In this work, we report a comparative study of the gamma ray stability of perovskite solar cells based on a series of perovskite absorbers including MAPbI3 (MA = methylammonium), MAPbBr3, Cs0.15FA0.85PbI3 (FA = formamidinim), Cs0.1MA0.15FA0.75PbI3, CsPbI3, and CsPbBr3. We reveal that the composition of the perovskite material strongly affects the radiation stability of the solar cells. In particular, solar cells based on the MAPbI3 were found to be the most resistant to gamma rays since this perovskite undergoes rapid self-healing due to the special gas-phase chemistry analyzed with ab initio calculations. The fact that the solar cells based on MAPbI3 can withstand a 1000 kRad gamma ray dose without any noticeable degradation of the photovoltaic properties is particularly exciting and shifts the paradigm of research in this field toward designing more dynamic rather than intrinsically robust (e.g., inorganic) materials.

The impact of alicyclic substituents on the extraction ability of new family of 1,10-phenanthroline-2,9-diamides.

Development of efficient extractants for the separation of actinides and lanthanides in the technologies of nuclear fuel cycle is one of the most urgent and complex tasks in modern nuclear energetics. New family of 4,7-dichloro-1,10-phenanthroline-2,9-dicarboxylic acid diamides based on cyclic amines was synthesized and shown to exhibit high selectivity in the La/Am pair separation (SF (Am/La ≈ 10)) and in the Am/Eu pair separation (SF (Am/Eu ≈ 12)). It was shown that pyrrolidine derived diamide is more efficient extractant for americium, curium and lanthanides from highly acidic HNO3 solution than its non-cyclic N,N,N',N'-tetraalkyl analogues. The structures of synthesized compounds were studied in details by IR, NMR spectroscopy, and single crystal X-ray diffraction. According to spectroscopy data, incorporation of aromatic rings to the amide fragment of ligand leads to complex dynamic behavior in solutions what is believed to strongly affect the extraction ability of synthesized ligands.

Unfolding the complexation and extraction of Am3+ and Eu3+ using N-heterocyclic aromatic diphosphonic acids: a combined experimental and DFT study.

Phosphonate based ligands are well known for the extraction of 'f' block elements. Three N,O-donor N-heterocyclic aromatic diphosphonate ligands were evaluated in the present work for the extraction/separation studies of Am3+ and Eu3+. Complexation studies in aqueous medium using luminescence titration indicated the formation of anionic complexes in the case of Eu3+. Two phase liquid-liquid extraction studies were, therefore, carried out by employing Aliquat-336 as the liquid anion exchanger. The results indicated the formation of a species with a metal-ligand stoichiometry of 1 : 3 in the case of pyridine-2,6-diphosphonic acid (PyPOH). In the case of 2,2'-bipyridine-6,6'-diphosphonic acid (BipyPOH), however, a 1 : 2 complex was extracted and 1,10-phenanthroline-2,9-diphosphonic acid (PhenPOH) extracts the Am3+ and Eu3+ ions by forming both 1 : 2 and 1 : 3 complexes. Formation of these kinds of anionic complexes was further confirmed using electrospray ionization mass spectrometry (ESI-MS). DFT calculations predicted the structure of the anionic complexes. The non-selectivity of these kinds of ligands between Am3+ and Eu3+ was attributed to the presence of unfavorable covalent interactions in the metal-ligand bonds.

Impressive Radiation Stability of Organic Solar Cells Based on Fullerene Derivatives and Carbazole-Containing Conjugated Polymers.

We explored the radiation stability of carbazole-based electron-donor conjugated polymers, acceptor fullerene derivative [60]PCBM, and their blends as active layer components of organic solar cells. An exposure to Î³ rays induced evident degradation effects in bulk samples of the pristine fullerene acceptor ([60]PCBM) and two investigated electron-donor conjugated polymers: PCDTBT and PCDTTBTBTT. The most severe radiation damage occurred in [60]PCBM as can be concluded from the significant losses in open circuit voltage, fill factor, and efficiency of photovoltaic (PV) devices comprising the exposed fullerene acceptor. Conjugated polymers PCDTBT and PCDTTBTBTT showed substantially different radiation stabilities: the samples of PCDTTBTBTT exposed to 200 Gy lost ∼25% of their nominal photovoltaic efficiency due to a substantial decay of all device parameters, while PCDTBT alone showed just a minor aging under the same conditions. The fullerene-polymer composites were much more resistant with respect to the radiation damage than the bulk samples of pristine materials. In particular, the PCDTBT/[60]PCBM composite films demonstrated an outstanding radiation stability while maintaining more than 80% of the initial photovoltaic efficiency after exposure to γ rays with a maximum absorbed dose of 6500 Gy. Considering an average annual radiation dose of 160 Gy according to the NASA estimations for satellites at geocentric Earth orbits, organic solar cells based on PCDTBT/[60]PCBM blends hold a promise to deliver lifetimes well above 10 years. The revealed impressive radiation stability of PCDTBT/[60]PCBM blends in combination with other advantages of organic solar cells, for example, their mechanical flexibility and lightweight, points to a bright future of this PV technology in space industry applications.

γ-Ray-Induced Degradation in the Triple-Cation Perovskite Solar Cells.

We report on the impact of γ radiation (0-500 Gy) on triple-cation Cs0.15MA0.10FA0.75Pb(Br0.17I0.83)3 perovskite solar cells. A set of experiments was designed to reveal the individual contributions of the hole-collecting bottom electrode, perovskite absorber, and electron transport layer (ETL) to the overall solar cell degradation under radiation exposure. We show that the glass/ITO/PEDOT:PSS hole-collecting electrode withstands a 500 Gy dose without any losses in the solar cell performance. In contrast, the perovskite absorber films and PC61BM ETL are very sensitive to γ rays, as can be concluded from the radiation-induced decay of the solar cell efficiency by ∼32-41%. Red shift of the perovskite emission bands and strong enhancement of the photoluminescence suggest that γ rays induce phase segregation of iodine-rich and bromine-rich domains, which represents the first reported example of the radiation-induced halide phase separation in perovskite films. The degradation pathway revealed here emphasizes the need for developing a new generation of metal halide absorbers and ETL materials with improved radiation stability to enable potential space applications of perovskite photovoltaics.

The electronic structure and the nature of the chemical bond in CeO2.

The X-ray photoelectron spectral structure of CeO2 valence electrons in the binding energy range of 0 to ∼50 eV was analyzed. The core-electron spectral structure parameters and the results of relativistic discrete-variational calculations of CeO8 and Ce63O216 clusters were taken into account. Comparison of the valence and the core-electron spectral structures showed that the formation of the inner (IVMO) and the outer (OVMO) valence molecular orbitals contributes to the spectral structure more than the many-body processes. The Ce 4f electrons were established to participate directly in chemical bond formation in CeO2 losing partially their f character. They were found to be localized mostly within the outer valence band. The Ce 5p atomic orbitals were shown to participate in the formation of both the inner and the outer valence molecular orbitals (MOs). A large part in the IVMO formation is taken by the filled Ce 5p1/2, 5p3/2 and O 2s atomic shells, while the Ce 5s electrons participate weakly in the chemical bond formation. The composition and the sequent order of the molecular orbitals in the binding energy range of 0 to ∼50 eV were established. A quantitative scheme for the molecular orbitals of CeO2 was built. This scheme is fundamental for understanding the nature of chemical bonding and also for the interpretation of other X-ray spectra of CeO2. Evaluations revealed that the IVMO electrons weaken the chemical bond formed by the OVMO electrons by 37%.