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[en] Thorium and its compounds have been widely investigated as important nuclear materials. Previous research focused on the potential use of thorium hydrides, such as ThH, ThH, and ThH, as nuclear fuels. Here, we report studies of the anion, ThH, by anion photoelectron spectroscopy and computations. The resulting experimental and theoretical vertical detachment energies (VDE) for ThH are 4.09 eV and 4.11 eV, respectively. These values and the agreement between theory and experiment facilitated the characterization of the structure of the ThH anion and showed its neutral counterpart, ThH to be a superhalogen. ThH, which exhibits a C structure with five Th-H single bonds, possesses the largest known H/M ratio among the actinide elements, M. The adaptive natural density partitioning (AdNDP) method was used to further analyze the chemical bonding of ThH and to confirm the existence of five Th-H single bonds in the ThH molecular anion. (© 2020 Wiley‐VCH GmbH)
[en] Effective capture of radioactive iodine is of paramount importance for the safe and long-term storage of fission products in the nuclear fuel cycle. Herein, a series of functionalized Th-UiO-66 MOFs was employed as a model to investigate the effects of substituents on iodine adsorption in both solution and vapor states. Sorption studies revealed that the electro-donating amino group exhibits the most positive role on increasing the removal rate of iodine from cyclohexane and the uptake capacity of iodine vapor. Particularly, the disubstituted Th-UiO-66-(NH) can effectively remove 91.9 % of iodine (300 mg L) from cyclohexane and capture 969 mg g iodine vapor, significantly higher than 59.6 % and 334 mg g of untagged Th-UiO-66, respectively. In addition, the substituent effect on the radiolytic stability of MOFs was for the first time investigated, leading to the unearthing of one of the most radioresistant MOFs Th-UiO-66-NH reported to date. (© 2020 Wiley‐VCH GmbH)
[en] Coordination compounds are well-known compounds that are being used as new materials for lithium storage because of their unique advantages, that is, designable structures, abundant active sites, and facile as well as mild synthetic routes. However, the electrode stability, low rate performance, and cycle life of coordination compounds are currently the main issues preventing their application as electrode materials, and the lithium-storage mechanism in coordination networks is not well understood. Herein, isostructural one-dimensional coordination compounds were synthesized to study their lithium-storage performance. Co-HIPA and Ni-HIPA showed superior electrolyte stability than other M-HIPAs, and Co-HIPA displayed a superior reversible capacity and cycle stability, excellent rate performance, and clear voltage platform. DFT calculations and kinetic analysis revealed the influence of the metal center with different electronic structures on the lithium-storage mechanism. (© 2020 Wiley‐VCH GmbH)
[en] Constructing Z-scheme heterojunction photocatalyst with strong redox ability to make for enhanced photocatalytic performance and efficient charge separation is extremely attractive but still underdeveloped. Herein, a Z-scheme heterojunction structured La(OH)@InS composite (labeled by "LIS") with photocatalytic for the methylene orange (MO) degradation under simulated light irradiation has been developed. The as-prepared LIS, together with commercial La(OH) and pure InS fabricated with the identical processing method and starting materials as those of LIS, was characterized by X-ray diffraction, UV–vis diffuse reflectance spectra, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectra and electrochemical impedance spectroscopy. The results show the heterojunction of La(OH)/InS has prolonged the lifetime of the photo-generated carriers. The photocatalytic activity test shows that over only a small amount (0.02 g in 100 ml MO) of LIS, the photodegradation rate of 95% toward MO can be obtained in 90 min, which is about 3.4 times higher than that over pure InS. The active species trapping experiments indicate that there were four active species playing roles in photodegradation as the following order: e = ∙OH < h< ∙O. A mechanism of Z-scheme heterojunction was proposed and well explained the enhanced photocatalytic performance. This work provides a new cost-effective photocatalyst with high photocatalytic properties.
[en] Tailoring the specific stacking sequence (polytypes) of layered materials represents a powerful strategy to identify and design novel physical properties. While nanostructures built upon transition-metal dichalcogenides (TMDs) with either the 2H or 3R crystalline phases have been routinely studied, knowledge of TMD nanomaterials based on mixed 2H/3R polytypes is far more limited. In this work, mixed 2H/3R free-standing WS nanostructures displaying a flower-like configuration are fingerprinted by means of state-of-the-art transmission electron microscopy. Their rich variety of shape-morphology configurations is correlated with relevant local electronic properties such as edge, surface, and bulk plasmons. Machine learning is deployed to establish that the 2H/3R polytype displays an indirect band gap of E = 1.6 eV. Further, high resolution electron energy-loss spectroscopy reveals energy-gain peaks exhibiting a gain-to-loss ratio greater than unity, a property that can be exploited for cooling strategies of atomically-thin TMD nanostructures and devices built upon them. The findings of this work represent a stepping stone towards an improved understanding of TMD nanomaterials based on mixed crystalline phases. (© 2021 The Authors. Annalen der Physik published by Wiley‐VCH GmbH)
[en] PtRu bimetallic nanoparticles embedded in MOF-derived porous carbons (PtRu-PCs) were synthesized by first loading PtRu bimetallic nanoparticles into a UiO66-NH host matrix and then going in situ carbonization at high temperatures. In the synthetic strategy, UiO66-NH was used not only as a precursor to limit the aggregation and migration of PtRu bimetallic nanoparticles, but also as a self-sacrificial template to improve the conductivity. The as-prepared PtRu-PCs were characterized by SEM, TEM, XRD, and XPS. The PtRu-PC-based sensor had excellent sensitivity with a detection limit of 0.024 μM (S/N = 3). The developed method was successfully applied to real water samples with a recovery rate of 92–107%.
[en] In this contribution, we demonstrate room temperature growth of highly oriented single-phase nanocrystalline films of VO(A) on glass substrates using pulsed laser deposition (PLD) technique under high oxygen pressure and small target–substrate separation. The structural, morphological, optical, electrical and compositional properties of the deposited thin films have been studied by means of X-ray diffraction, atomic force microscopy, spectrophotometry, 04-point probe method and X-ray photoelectron spectroscopy, respectively. The plasma under which VO(A) was grown has been analyzed by means of time- and space-resolved optical emission spectroscopy (OES) and Langmuir probe (LP) techniques. We evidenced a correlation between growth conditions and plasma characteristics. While OES showed that at the deposition distance corresponding to the length of the visible plasma, the plasma species are completely thermalized and characterized by a very low degree of excitation, the LP technique indicated a formation of charged clusters within the gas phase. By combining OES and LP data, a quadruple plasma structure has been shown. The growth of under-stoichiometric (comparing to the parent VO target) nanocrystalline VO(A) phase has been attributed to nanoparticle formation in the gas phase under a plasma environment rarefied in oxygen atoms due to the scattering and backscattering effects. This finding opens up the opportunity to grow VO polymorphs at very low temperature by PLD for novel promising new device functionalities.
[en] The uranyl cation, (U(VI)O), has previously demonstrated photocatalytic reactivity in organic solutions, which results in the formation of uranyl peroxide species. Past studies indicated that the phototransformation process typically ends with the formation of uranyl peroxide solid phases. In the current study, we explore the transformation of uranyl nitrate crown ether complexes, (18-crown-6)[UO(NO)(HO)] ⋅ 2 HO (1 a), (18-crown-6)[UO(NO)(HO)] (1 b), and (18-crown-6) [K(18-crown-6)] [(UO)(OH)(NO)(HO)] (2) in the presence of ethanol to create a uranyl peroxide intermediate phase, (18-crown-6)[(UO)(O)(NO)(HO)] (3), followed by a second alteration to a black solid (4). These compounds were structurally evaluated using both single-crystal and powder X-ray diffraction and then further characterized using Raman, NMR, and XPS spectroscopy. The initial transformation from the yellow uranyl nitrate phase (1 a, 1 b, and 2) to the uranyl peroxide (3) follow previously reported mechanisms. The second transformation to the black phase (4) is likely due to additional degradation of the 18-crown-6 molecule as a result of hydrogen abstraction and ring-opening. In addition, we discuss the nature of confinement effects to impact the hydrogen abstraction process and the possibility that nitrate anions in the system may synergistically enhance the degradation process and lead to the formation of 4. (© 2020 Wiley‐VCH GmbH)
[en] The advancement of p–n photodiode fabrication employing rare-earth materials has created cogent interest in the field of semiconductor device technology. We report on the formation of pure and Sn-doped CeO thin films assembled through spray pyrolysis technique to enhance the p-Si/n-Sn:CeO diode performance. A polycrystalline nature of cubical crystal structured Sn-CeO thin films was developed on glass slides with various doping levels of tin (0, 2, 4 and 6 wt%). The crystallite size was found to decline with increasing Sn wt%. A uniform surface with tiny spherical-like crystallite grains was observed through the FE-SEM microscope. The existence of Sn ions with the CeO system was confirmed by the EDX and XPS spectrum. The effect of Sn doping on the optical absorption and band gap of CeO was evaluated, in which the 2 wt% Sn exhibited lower Eg value with maximum absorption. The Sn ions enhanced the electrical conductivity suggesting the semiconducting nature of the films. The p-Si/n-Sn:CeO diode was fabricated, and its performance was analyzed under dark and light intensity of 100 mW/cm. The photosensitivity of the device varied from 17.11 to 671.65%. The ON–OFF photoresponse of 6 wt% Sn is relatively higher than that of pure CeO.
[en] Novel Ni-Pd and Cu-Pd bimetallic nano alloys was designed and heterogenized on the highly robust ABPBI [poly(2,5-benzimidazole)] polymer in high yields using NaBH4 as reducing agent. These were versatile ligand free catalysts for the Mizoroki–Heck reaction and Suzuki–Miyaura coupling. The bimetallic Ni-Pd-ABPBI catalyst for the Mizoroki–Heck reaction of 4-iodo anisole could be recycled 5 times with high yields. Aryl bromides could also be activated for the Mizoroki–Heck reaction using Cu-Pd-ABPBI NP catalysts, with moderate yields. (author)