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1.
Inorg Chem ; 60(19): 14563-14581, 2021 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-34546034

RESUMO

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.

2.
J Phys Chem Lett ; 11(7): 2630-2636, 2020 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-32178515

RESUMO

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.

3.
Dalton Trans ; 48(43): 16279-16288, 2019 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-31621722

RESUMO

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.

4.
ACS Appl Mater Interfaces ; 11(24): 21741-21748, 2019 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-31091872

RESUMO

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.

5.
J Phys Chem Lett ; 10(4): 813-818, 2019 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-30621392

RESUMO

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.

6.
Phys Chem Chem Phys ; 20(23): 16167-16175, 2018 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-29855651

RESUMO

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%.

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