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In situ DRIFT spectroscopy was developed to observe the preferential adsorption of D2 over H2 at active CuI sites to show the chemical affinity quantum sieving effect for hydrogen isotope separation in microporous adsorbents.

Cancer-associated fibroblasts (CAFs) reconstitute cancer stemness. This study aims to investigate whether the loss of CAF-derived exosomal miR-34c-5p contributes to the maintenance of stem-like properties of laryngeal squamous cell carcinoma (LSCC).Exosomes from primarily cultured CAFs and paired normal fibroblasts (NFs) were collected and identified. The differential expression of exosomal miR-34c-5p between CAFs and NFs was detected by next-generation sequencing. In vitro and in vivo assays were performed to examine the effects of miR-34c-5p on the maintenance of stem-like properties.MiR-34c-5p expression is significantly reduced in CAF-derived exosomes. In vitro and in vivo assays revealed that exosomal miR-34c-5p can regulate the stem-like properties of LSCC cells, such as proliferation, invasion, sphere and plate colony formation, chemoresistance, tumorigenicity in nude mice, as well as the expression of cancer stem cell genes.Loss of miR-34c-5p in CAF-derived exosomes contributes to the maintenance of stem-like phenotypes of LSCC.

The primary purpose of this work is to develop a novel model for comprehensively investigating the hydrogen storage performance under the framework of diffusion of hydrogen atoms through hydride layer. The proposed model is constructed upon perfectly mathematical-physical equations, by taking into account complicated multi-scale and multi-physics coupling actions. Importantly, three-dimensional numerical simulations are performed to explore the coupling effects of micro diffusion, mesoscopic permeation, and macroscopic fluid flow. An analytical approach accounting for the characteristics of reaction bed, particle, and crystal grain is presented as well. In addition, a parametric analysis is conducted to reveal that the hydride particle dimension, particle porosity, grain size, and diffusion coefficient of reacted layer have a significant effect on overall hydrogen storage performance, highlighting that grain size and hydrogen diffusion coefficient are vital factors that need to be considered for material preparation and design.

Cycling stability of ZrCo–H system is extremely important for the long-term operation of the storage and delivery system (SDS) in ITER. Herein, the optimal cycling operation parameters were systematically investigated. It indicates that various parameters, such as hydrogen pressure, temperature, composition, and stoichiometric ratio of H atoms, will all affect the cycling performance of the ZrCo–H system significantly. The decline rate of the hydrogen capacity of the ZrCo–H system is positively correlated with the hydrogen pressure. The experimental result shows that 54% of hydrogen capacity decreases under 28.1 kPa hydrogen pressure, while 30% of attenuation is obtained when the pressure is decreased to 8.1 kPa after 14 cycles. In terms of temperature, the lowest cycling attenuation can be maintained at about 25% after 14 cycles when the dehydrogenation temperature at 550 °C. The effects of doping elements, Hf and Ti, on the cycling stability of ZrCo–H system are also compared. The Zr0.8Ti0.2Co sample exhibits higher cycling capacity than ZrCo and Zr0.8Hf0.2Co samples. The extremely excellent behavior can be achieved when all ZrCo alloys are continuously evacuated during the hydrogen release process, and the attenuation of only 1.1% is observed for Zr0.8Ti0.2Co after 15 cycles. Besides, the cycling attenuation is related to residual stoichiometric ratio of H atoms in ZrCo alloy during the cycling test. When the residual H atoms proportion exceeds 1 in ZrCo during dehydrogenation, hydrogen cycling capacity hardly fades. The XRD results reveal that the disproportionation of ZrCo is directly associated with the cycling degradation, yielding the more stable products of ZrCo2 and ZrH2, However, the disproportionation can be avoided during the cycling process by controlling the stoichiometric ratio of H atoms remained in ZrCo above 1. This study demonstrates that the cycling performance of ZrCo can be substantially improved when the operation parameters are properly adjusted, which provides a significant important reference for durable running of SDS in ITER.

To further explore the application feasibility of Zr2Co alloy in tritium-related fields, hydrogenation/dehydrogenation properties of this material of crystalline or amorphous structure, prepared by arc melting or melt spinning, were studied by pressure-composition temperature measurement, X-ray diffraction, differential scanning calorimeter, thermal desorption spectroscopy. It was found that the two kinds of Zr2Co alloys can absorb hydrogen in a close full concentration of ~9 mmol/g, and may have similar equilibrium hydrogen pressure in the order of 10−6 Pa at room temperature. In their hydrogenated samples various hydrides were observed to form, including ZrH2, Zr2CoH5, ZrCoH3 and an amorphous one with gradually decreasing general thermostability. The amorphous alloy exhibited easier hydrogen induced disproportionation caused by highly stable ZrH2 and much slower hydrogen absorption kinetics. This disproportionation behavior of the crystalline alloy was found to be entirely suppressed by changing heating process. The results firmly indicate that crystalline Zr2Co alloy could be more favorable for tritium treatment due to very low equilibrium pressure and the feasibility of eliminating the disproportionation.

First-principles calculations were performed to investigate the effects of alloying substitutions (i.e. Ti, Hf, Sc, Cu and Fe) on the anti-disproportionation ability of ZrCo alloy. For the first time, we revealed the disproportionation mechanism from the energy point of view and provided a new theoretical method to predict whether the substitution element has the ability to enhance the anti-disproportionation performance of ZrCo alloy. Based on the hydrogen atom occupancy behavior in ZrCoH3 and the results of our calculation of binding energy, the hydrogen atom migration model during hydrogenation and theoretical computational model were established. Through structural optimization, a series of stable 2 × 1 × 2 ZrCoH3 supercells were obtained, which contain four hydrogen atoms occupying 8e site and various substitution atoms with different amounts except for pure system. The binding energy of hydrogen atom in the 8e site and activation energy of diffusing from 8e site to 4c2 site of these ZrCoH3 supercells were calculated. The results showed that the substitution of Ti and Hf increased the binding energy of hydrogen atom in the 8e site, while the substitution of Fe, Cu and Sc decreased the binding energy of hydrogen atom in the 8e site. Meanwhile, both of Ti and Hf substitution reduced the activation energy of diffusing from 8e site to 4c2 site, while all of Fe, Cu and Sc substitution increased the activation energy of diffusing from 8e site to 4c2 site. These results indicated that hydrogen-induced disproportionation was the inherent property of ZrCo alloy, and element substitution can restrain or accelerate disproportionation by affecting both the binding energy and activation energy. With simultaneous consideration of the binding energy and activation energy, the effect of these alloying substitutions on the anti-disproportionation ability could be ascertained and the results were in good agreement with the previous theoretical and experimental results.

Tritium target is of crucial importance in relation to the development of neutron generator apparatus. However, the prevalent Ti target is now suffering from the intricate procedures for activation, limited tritium content at room temperature (RT) and poor ability to fix the helium. Herein, a succession of new type ZrCo(Ti) alloy targets were designed and fabricated by magnetron sputtering. Firstly, the influence of technological parameters (types of substrate, sputtering temperatures, sputtering time and annealing temperatures) on the assemblage and also the hydrogen storage properties of the ZrCo films were systemically studied. The results show that high sputtering temperature is benefit to acquiring high crystallinity of ZrCo films, but the substrates seem to have no significant effect on that. The thickness and grain size of ZrCo film are both positively related to the sputtering time. However, the hydrogen uptake capacities (0.14 wt%~0.79 wt%) for all the prepared ZrCo films are relatively low. After that, the composition and microstructure of the ZrCo films were further regulated and optimized. On the one hand, Zr1-xTixCo films were constructed by introduction of Ti element, achieving a higher hydrogen absorption capacity (~0.7 wt%), but with weak thermal stability in the subsequent hydrogen desorption process (~80% of hydrogen escaped at 500 °C). On the other hand, the surface of the ZrCo film was modified by a thin layer of Ti, forming a serious of double-layer ZrCo/Ti films. The ZrCo/Ti composite films not only achieve extremely high hydrogen storage capacity (1.85 wt%), but also maintain strong thermal stability (only 15.7% of hydrogen escaped at 500 °C). These findings related to the ZrCo(Ti) films in this paper provide crucial reference for the development of tritiated ZrCo film targets, and spark inspiration even for the design of other new-type tritiated film target.

In this study, ZrCo1-xMox (x = 0, 0.05, 0.1, 0.15, 0.2) alloys were prepared via vacuum arc-melting method. The effects of substituting Co with Mo on the structure, initial activation behaviors, and thermodynamic properties of the afore-mentioned alloys were systematically investigated. The results showed that ZrCo1-xMox (x = 0, 0.05, 0.1, 0.15) alloys exhibited a single ZrCo phase and their corresponding hydrides, a ZrCoH3 phase. Furthermore, ZrCo0.8Mo0.2 alloy consisted of ZrCo phase and a trace of ZrMo2 phase, and the hydride contained ZrCoH3 and ZrH phases. As the Mo content was increased, the initial activation period decreased significantly from 19277 s for ZrCo to 576 s for ZrCo0.8Mo0.2, which was closely related to the catalytic effect of ZrMo2. The plateau width of pressure composition temperature curves were shortened, and the equilibrium pressures of hydrogen desorption decreased slightly as Mo content increased. Additionally, the experiments showed that the anti-disproportionation performance was greatly improved by Mo substitution. The extent of disproportionation decreased from 64.28% for ZrCo to 24.11% for ZrCo0.8Mo0.2. The positive effect of Mo substitution on improving the anti-disproportionation property of ZrCo alloy was attributed to the reduction of hydrogen atom in 8f2 and 8e sites, which decreased the driving force of the disproportionation reaction.

Habitat fragmentation is considered a major threat to biodiversity worldwide. Two endangered species, the blood pheasant (Ithaginis cruentus) and the blue eared pheasant (Crossoptilon auritum), co-exist in a fragmented forest in the Qilian Mountains. However, how their habitats react to the fragmenting landscape remains unclear. Therefore, we carried out a field survey in the core habitat of the two species in Qilian Mountains National Park and used the MaxEnt Model to predict their potential distribution and to assess the protection efficiency. Then, we utilized a modified within-patch fragmentation categorizing model to identify how their functional fragmentations differentiated. The results showed that the habitat utilization of the two pheasant species was significantly different, with a potential distribution area of 18,281 km2 for the blood pheasant and 43,223 km2 for the blue eared pheasant. The habitat of the blue eared pheasant is highly fragmented with 27.7% categorized as ‘Interior’ and 49.3% as ‘Edge’, while the habitat of the blood pheasant is more severe with 2.1% categorized as ‘Interior’ and 50.4% as ‘Edge’. Analysis shows that large areas of habitat for the two pheasants remain unprotected by the Qilian Mountains National Park. The intense grazing and human infrastructure may have a large effect on the currently highly fragmented landscape. Future measurements are needed to alleviate this conflict.

Both theoretical and experimental studies indicate that the kinetic properties of H2 storage in ZrCo can be significantly improved by element substitution. Here, both molecular and atomic hydrogen adsorption on the Hf-decorated ZrCo (110) surface have been systematically studied by employing density functional theory calculations. Through our investigation, we find that both the number of stable adsorption sites and the adsorption energy of the H atom increase when a Zr atom is substituted by a Hf atom. Conversely, the H atom diffusion barrier decreases. The increases in both the stable adsorption sites and the energy change that is caused by the decoration of Hf shows that more hydrogen might be adsorbed on the Hf-decorated ZrCo (110) surface, thereby improving the hydrogen storage capacity of the ZrCo-based alloy. In addition, the H2 dissociation barrier is lowered on the Hf-decorated surface. The adsorption mechanism of hydrogen on the decorated surface has been analyzed on the basis of several chemical bonding analysis methods. PDOS analysis shows that H s and Co s-, and d orbital hybridization energy decreases, which indicates that the adsorption strength of H atoms on the doped surface is weakened, thereby decreasing the hydrogen diffusion energy barrier. The present results are in line with prior experimental results and provide fundamental information regarding the adsorption process, which may be beneficial for understanding and estimating the hydrogen storage capacity of Hf-decorated ZrCo materials.

The interactions of dopants with point defects such as that between vacancies and helium can affect helium evolution and ultimately the macroscopic properties of materials. Herein, the microscopic vacancy trapping mechanism for He defects and the formation of small HemVacn (consisting of m He atoms and n vacancies) clusters in pure and Ti-doped ZrCo systems are investigated by carrying out an extensive set of first-principles calculations based on density functional theory. Our results uncover the following: the helium atom can segregate from the adjacent interstitial (tetrahedral and octahedral) sites towards the vacancy center spontaneously, and therefore, a single He atom is energetically favorable to occupy a vacancy whether in the pure or in the doped system. The dopant Ti can act as a trapping center for He impurities similar to a vacancy. Moreover, it can improve the trapping ability and increase the trapping radius of the vacancies for helium. As for the effect of the Ti atom on the trapping of multiple helium atoms by the vacancy, the higher barrier in the doped systems than in the pure one implies that doping inhibits the formation of large HemVac clusters. Furthermore, in order to evaluate the effect of dopant Ti on the stability of He atoms in multiple vacancies, the binding energies of a helium atom, a vacancy (Vac), and a self-interstitial atom (SIA) to a helium–vacancy cluster (HemVacn) were obtained and compared with that of the pure system. The results suggest that the cluster growth can be inhibited by the dopant Ti, and therefore, the formation of large helium bubbles is also hindered. All the binding energies do not depend much on the cluster size but primarily on the helium-to-vacancy ratio (m/n) of the clusters. The stability of the clusters is decided by the competitive processes among the emission of He atoms, vacancies, and SIAs, and also depends on the helium-to-vacancy ratio. The present results provide an in-depth explanation for the effect of the dopant on helium behavior and could aid future tritium storage material design.

The structural, electronic, dynamic and thermodynamic properties of Zr1-xHfxH2 (where x is the concentration of constituent element Hf, which changes in the range from 0 to 1 with step size Δx = 0.1) are investigated using first-principle calculations. These are done using the density-functional theory (DFT) and density functional perturbation theory (DFPT) within Generalized Gradient Approximation (GGA) and employing virtual-crystal approximation (VCA) method. The lattice constant gradually decreases from 3.527 A to 3.474 A with Hf substitute ratio increasing and the variation is quite small. The electronic density of states (DOS) of Zr1-xHfxH2 gradually expands when x value varies from 0 to 1 and all of these compounds show metallic nature and the metallicity increases. The analyses of charge density and the charge density differences indicate that the Zr1-xHfx-H interactions in the hydride are primarily metallic with a small ionic component, and the metallic nature enhances as x increases. Moreover, with Hf substitute ratio increasing, the optical branch and the acoustical branch of the phonon spectrum have a larger separation, which grows from 23.24 THz (ZrH2) to 25.48 THz (HfH2), and the phonon density of states gets wider. The calculated thermodynamic properties indicate stronger thermodynamic stability of ZrH2 than HfH2.

Background: Accurate detection of cerebral oxygen saturation (rSO2) may be useful for neonatal brain injury prevention, and the normal range of rSO2 of neonates at high altitude remained unclear. Objective: To compare cerebral rSO2 and cerebral fractional tissue oxygen extraction (cFTOE) at high-altitude and low-altitude areas in healthy neonates and neonates with underlying diseases. Methods: 515 neonates from low-altitude areas and 151 from Tibet were enrolled. These neonates were assigned into the normal group, hypoxic-ischemic encephalopathy (HIE) group, and other diseases group. Near-infrared spectroscopy was used to measure rSO2 in neonates within 24 h after admission. The differences of rSO2, pulse oxygen saturation (SpO2), and cFTOE levels were compared between neonates from low- and high-altitude areas. Results: (1) The mean rSO2 and cFTOE levels in normal neonates from Tibet were 55.0 ± 6.4% and 32.6 ± 8.5%, significantly lower than those from low-altitude areas (p < 0.05). (2) At high altitude, neonates with HIE, pneumonia (p < 0.05), anemia, and congenital heart disease (p < 0.05) have higher cFTOE than healthy neonates. (3) Compared with HIE neonates from plain areas, neonates with HIE at higher altitude had lower cFTOE (p < 0.05), while neonates with heart disease in plateau areas had higher cFTOE than those in plain areas (p < 0.05). Conclusions: The rSO2 and cFTOE levels in normal neonates from high-altitude areas are lower than neonates from the low-altitude areas. Lower cFTOE is possibly because of an increase in blood flow to the brain, and this may be adversely affected by disease states which may increase the risk of brain injury.

The thermodynamically and kinetically stable regions of the temperature–H2 pressure phase boundaries for the ZrCo H system were established using the Temperature-Concentration-Isobar (TCI) method. Based on this, the enthalpy change and entropy change values of dehydrogenation and disproportionation reactions were successfully obtained. The average enthalpy change (ΔH) and entropy change (ΔS) estimated from the phase boundaries for dehydrogenation of ZrCoH3 to ZrCo are respectively 103.07 kJ mol−1H2 and 148.85 J mol−1 H2 K−1, which are well agreement with the data reported in literature. The average ΔH and ΔS were estimated to be −120.91 kJ mol−1H2 and -149.32 J mol−1 H2 K−1 for the disproportionation of ZrCoH3, whereas the ΔH and ΔS were calculated to be −84.6 kJ mol−1H2 and -92.29 J mol−1 H2 K−1 for disproportionation of ZrCo. In addition, it was found from the established phase boundaries that the anti-disproportionation property of ZrCo alloy can be enhanced if the phase boundaries of hydrogenation/dehydrogenation are far away from the phase boundaries of disproportionation by adjusting the thermodynamics. Meanwhile, it is possible to keep ZrCo away from disproportionation even at high temperature of 650 °C under hydrogen atmosphere, if the temperature-H2 pressure trajectory is carefully controlled without crossing the phase boundaries of disproportionation. Therefore, the established phase boundaries can be used as a guide to the eye avoiding disproportionation and improving the anti-disproportionation property of ZrCo alloy.

Thermodynamics, kinetics and selectivity of H2 and D2 on zeolite 5A have been investigated by isotherm adsorption/desorption and thermal desorption spectroscopy (TDS) at temperatures below 77 K. The experimental adsorption isotherms show an increasing amount of gas adsorbed with decreasing temperature from 77 K to 30 K, and D2/H2 adsorption ratio is slightly larger than 1. In addition, the enthalpy of D2 (ΔH) adsorption obtained from adsorption isotherms is for different uptakes always larger than for H2 indicating a stronger D2 adsorption. The kinetics of H2 adsorption/desorption is faster than of D2 at different temperatures (30–50 K), pressures (10-400 mbar) and gas composition due to the faster H2 self-diffusion in zeolite 5A at low temperature. Furthermore, D2/H2 selectivity increases gradually and reaches a constant value with increasing loading time and pressure, and it is 8.83, 6.42, 4.98, 3.96 and 4.04 at 30, 35, 40, 50 and 60 K at 50 mbar, respectively. The D2/H2 separation in zeolite 5A is controlled by the thermodynamic equilibrium of adsorption under the experimental conditions applied here. To the best of our knowledge, this is the first report on the hydrogen isotope selectivity of zeolite 5A at temperatures below 77 K.

The title compound,, [Fe4Ni(C3H6S2)2(C7H14S4)(CO)10]·2CH2Cl2, is reported as a biomimic model for the active site of [FeFe]-hydrogenases. Bis(2-mercaptoethyl)-1,3-propanedithio ether nickel(II) was firstly introduced into [Fe2(C3H6S2)(CO)5] as an S-containing ligand. It coordinates with two [Fe2(C3H6S2)(CO)5] groups, and a five-metal core complex is formed. The Fe2S2core is in a butterfly conformation. The Fe—Fe distances in the [Fe2(C3H6S2)(CO)5] groups are 2.5126 (6) and 2.5086 (7) Å. The distances between the adjacent Fe and Ni atoms are 3.5322 (1) and 3.5143 (1) Å. There are intramolecular C—H...O and C—H...S contacts present in the complex. In the crystal, the five metal cores are linkedviaC—H...O hydrogen bonds, forming columns lying parallel to (110). The dichloromethane solvent molecules are each partially disordered over two positions and only one is linked to the five-metal core complex by a C—H...O hydrogen bond.

Uranium alloys containing a low concentration of titanium have received wide attention due to their greatly enhanced corrosion resistance and outstanding mechanical performances. Herein, we investigated the effect of macroscopic defects on the corrosion behavior of U-0.79 wt%Ti (denoted as U-Ti) alloy in 0.01 M NaCl solution using traditional electrochemical testing technologies and a novel scanning electrochemical composite probe (SECP). The results demonstrate that pitting corrosion occurs rapidly on the alloy surface due to macroscopic defects. Moreover, macroscopic defects led to a decrease in corrosion potential and polarization resistance, and an increase in corrosion current density. Furthermore, the potential and pH value distributions were detected in the same region using the composite probe. The results show that the region around the macroscopic defects become corrosion-active positions and the potential difference (vs. the average potential of the alloy surface) in this area is significantly higher than that at positions without macroscopic defects, while the opposite was observed for the pH value distribution. In addition, the distribution of the vertical direction (Z) potential at the active point was clearly different from that at the inactive point. A possible reason for this could lie in the difference in the electric field distribution and electrode reaction type between the active point and inactive point on the alloy surface.

In this work, the unusual reproportionation phenomenon, which occurs under hydrogen atmosphere, has been studied for the first time by combing temperature-programmed dehydrogenation and XRD characterization. The phase transition from ZrCo2–ZrH2 to ZrCo for reproportionation was clearly observed without vacuum pumping. It was shown that the reproportionation could take place even under hydrogen pressure of 0.65 bar at 640 °C. In addition, the reproportionation behaviors under different initial hydrogen pressures were investigated and the onset boundary for reproportionation was successfully established. The original insight into the unusual reproportionation phenomenon reveals that there is a stable region for ZrCo under hydrogen atmosphere at high temperature. On the basis of this work, it is hopeful that the application of ZrCo at high temperature will be substantially broadened.

Helium can cause segregation of solute atoms in the material, and in turn, the segregated solute atoms will have a great influence on the behavior of helium. Studying the behavior of helium in tritium storage materials is very important for the design of materials with strong helium retention capacity. In this paper, the first-principles method based on density functional theory is used to study the segregation of doped atoms Ti caused by defects (He atoms) in ZrCo system, and the effect of segregated Ti atoms on He behavior. The effect of segregated Ti atoms on the stability of He atoms was explored. The CI-NEB method was used to simulate the variance of the trapping for He atoms by vacancy in the pure and doped systems. Finally, it was found that the number of He atoms trapped by the vacancy is reduced due to the Ti cage. In addition, the Ti cage has a certain pinning effect on He atoms. In short, the segregated Ti inhibits the migration of He and hinders the flow of He to the grain boundaries, thereby suppressing the helium embrittlement effect.

The structure and electrochemical properties of a nickel tri­pyridine–di­amine complex are reported. The complex has two redox couples at −1.50 and −1.80 V (versus F c +/0) based on nickel., The mononuclear nickel title complex (acetonitrile-κN){N-benzyl-N,N′,N′-tris­[(6-methyl­pyridin-2-yl)meth­yl]ethane-1,2-di­amine}­nickel(II) bis­(tetra­fluor­ido­borate), [Ni(C30H35N5)(CH3CN)](BF4)2, was prepared from the reaction of Ni(BF4)2·6H2O with N-benzyl-N,N′,N′-tris­[(6-methyl­pyridin-2-yl)meth­yl]ethane-1,2-di­amine (bztmpen) in aceto­nitrile at room temperature. With an open site occupied by the aceto­nitrile mol­ecule, the nickel(II) atom is chelated by five N-atom sites from the ligand and one N atom from the ligand, showing an overall octa­hedral coordination environment. Compared with analogues where the 6–methyl substituent is absent, the bond length around the Ni2+ cation are evidently longer. Upon reductive dissociation of the acetro­nitrile mol­ecule, the title complex has an open site for a catalytic reaction. The title complex has two redox couples at −1.50 and −1.80 V (versus F c +/0) based on nickel. The F atoms of the two BF4 − counter-anions are split into two groups and the occupancy ratios refined to 0.611 (18):0.389 (18) and 0.71 (2):0.29 (2).

The evolution of the compositions in two typical regions on U-0.79wt%Ti alloy surface exposed in a salt fog environment was investigated by x-ray photoelectron spectroscopy (XPS) during vacuum annealing. The results show that pitting corrosion tends to occur around titanium inclusions on the alloy surface in the environment containing chloride ions. The compositions in the two regions were transformed with experimental temperature increasing. The complex oxide compound, α-U3O8, was detected by both XPS and Raman spectrum in the blackened region, while UO2+x/UO2 were the main oxide compounds in the other region where pitting corrosion did not occur. The different compositions in the two typical regions were slightly changed as temperature ramps up from room condition to 200°C. The α-U3O8 in the blackened region started to be reduced to UO2 while UO2+x in the other region to be converted into UO2 at 300°C. An oxycarbide (UOxCy) compound was observed due to the reaction between UO2 and carbon at 400°C. Betwe...

The mononuclear copper title complex {N,N,N′,N′-tetrakis[(6-methylpyridin-2-yl)methyl]ethane-1,2-diamine-κ6N}copper(II) bis(tetrafluoridoborate), [Cu(C30H36N6)](BF4)2, is conveniently prepared from the reaction of Cu(BF4)2·6H2O withN,N,N′,N′-tetrakis[(6-methylpyridin-2-yl)methyl]ethane-1,2-diamine (tmpen) in acetonitrile at room temperature in air. The complex shows a distorted octahedral environment around the CuIIcation (site symmetry 2) and adopts the centrosymmetric space groupC2/c. The presence of the 6-methyl substituent hinders the approach of the pyridine group to the CuIIcore. The bond lengths about the CuIIatom are significantly longer than those of analogues without the 6-methyl substituents.

The catalytic mechanism of Ti doped NaAlH 4 for hydrogen storage remains unconfirmed. Here, we investigated the evolution of active species in Ti doped NaAlH 4 system by XRD, XPS and TEM. The results reveal that the evolution of the Ti addition in doped NaAlH 4 is Ti 3+ → amorphous Ti 0 → Al Ti species → Al 3 Ti intermetallic. TEM results show that the average particle size of the Al Ti species and Al 3 Ti intermetallic is about 30 nm, and Ti element is uniformly distributed in Al matrix. In further, we discussed the catalytic mechanism and role of active species in Ti doped NaAlH 4 system according to experimental and theoretical calculation. The rehydrogenation process of Ti doped NaAlH 4 system can be divided into three steps: (1) H 2 dissociation, (2) H atom spillover and alanes (Al x H y ) formation and (3) complex hydrides formation. The addition of Ti can catalyze the process of H 2 dissociation, H atom spillover and formation of alanes. More importantly, the current work may provide a general approach to investigate the catalytic mechanism of other doped complex hydrides for hydrogen storage system.

Samples NaAlH x D 4−x (0 ≤ x ≥ 4) have been synthesized through a direct hydrogen isotope absorption/desorption cycles using Ti-doped NaAlH 4 as source material, and then the interaction between hydrogen/deuterium and obtained NaAlH x D 4−x and its hydrogen isotope effect were investigated. The results show that hydrogen isotope desorption/absorption kinetics of NaAlH x D 4−x is enhanced with increasing the hydrogen concentration. In addition, NaAlH x D 4−x exhibits kinetics isotope effect during both hydrogen isotope desorption and absorption processes, and the isotope effect keeps stable during cycling. Our study may enable NaAlH 4 to be used as hydrogen isotope separation material in future based on its kinetics isotope effect.

We have performed state-of-the-art ab initio calculations based on density functional theory to study the effect of Ti on helium dissolution and migration in a dilute Ti-doped ZrCo system. The formation energy of He-related defects predicts that it is preferable to occupy the VZr (Zr vacancy) at first. As for the Heint (interstitial site He), the results corroborate that Hetet (tetrahedral site He) is more stable than Heoct (octahedral site He) by 0.25 eV. The Heoct in the vicinity of Ti atoms becomes unstable, being relaxed into a nearby tetrahedral site, unlike in the pure ZrCo. We also reveal that ZrCo is susceptible to dopant Ti in terms of helium diffusion. The energy barrier for a Hetet to diffuse into a neighboring tetrahedral site is found to be about three times as large as the migration barrier between two adjacent octahedral interstitial sites (0.35 vs. 0.12 eV). In addition, the He atom can migrate from one octahedral site to another without going through a tetrahedral one in pure ZrCo. Furthermore, Hetet needs to overcome higher energy barriers of 0.27 eV and 0.58 eV in Ti-doped ZrCo than in the pure one (0.22 eV and 0.35 eV) along the 1nn (the first nearest neighbor) → 1nn → 2nn (the second nearest neighbor) pathway with the He atom escaping away from the Ti region. In addition, the dissociative energy barrier of the HeZr (Zr position substituted by the He atom) or HeCo (Co position substituted by the He atom) is somewhat higher in the presence of Ti than the pure one. All these conclusions elucidate that Ti acts as a trapping center for He impurities and blocks interstitial He mobility in ZrCo alloys.

Compared with pristine ZrCo(110), the adsorption, dissociation, and successive diffusion of hydrogen on the Ti-decorated ZrCo(110) have been investigated based on first-principles calculation. For the purpose of having fast absorption kinetics, both activation processes need to overcome small energy barriers. The adsorption energies of molecular as well as atomic hydrogen on the Ti-decorated ZrCo(110) surface were calculated using first-principles calculations with the periodic density functional theory (DFT). The H2 molecule on ZrCo(110) and Ti-doped ZrCo(110) surfaces could be spontaneously partially dissociated due to the interaction with the substrate surfaces, producing H atoms strongly chemisorbed to the hollow sites. The H2 dissociation energy barrier and the H diffusion barrier were also determined. Our results show that the activation energy for H2 dissociation on the decorated surface (0.052 eV) is much smaller than that of the pure surface (0.524 eV), elucidating that the activation condition of H2 on the pure ZrCo(110) is more severe than that on the Ti-doped surface. Particularly, Ti-decoration facilitates the H2 dissociation. Moreover, the re-desorption performance of the two dissociated H atoms is improved by lowering the energetic barrier from 1.798 eV (on the pure surface) to 1.315 eV (on the decorated surface). The calculations also reveal that decorating the surface with Ti eliminates the barrier for the into-bulk penetration of a hydrogen atom. Based on the local density of states, the Bader charge and differential charge density, as well as the influence of the Ti atom on topological properties were analyzed. Theoretical results presented in this study are generally in well accordance with the available theoretical and experimental data.

Zeolites have been considered to be viable candidates for hydrogen isotopes separation in a technological scale due to the well-defined channel, low cost and good thermal and radiation stability. Here, we report a strategy to separate hydrogen isotopes using Ag(I) exchanged ZSM-5(Ag(I)-ZSM-5) zeolite based on strong chemical affinity quantum sieving (CAQS) effect. The thermal desorption spectra (TDS) results reveal that the hydrogen isotope separation on Ag(I)-ZSM-5 zeolite can be achieved at and above liquid nitrogen temperature with a D2/H2 selectivity of 8.7 at 77 K. In addition, 95.1% of deuterium can be enriched through three adsorption/desorption cycles from a mixture with a deuterium concentration of 2.5%. Structural characterization and density functional theory calculations reveal that the high hydrogen isotope selectivity of Ag(I)-ZSM-5 zeolite can be attributed to the strong chemical affinity on Ag(I) site with a large hydrogen isotope effect. Moreover, the hydrogen isotope selectivities (including S (D2/DH), S (T2/D2), S (T2/TD) and S (T2/TH)) on Ag(I)-ZSM-5 are predicted under difference temperatures. Control of the chemical affinity quantum sieving effect of active sites in pore interiors of easily scalable zeolites has unlocked their potential in challenging hydrogen isotopes separation.

Twin interactions associated with {11 $$ \overline{2} $$ 1} (E2) twins in titanium deformed by high strain rate (~2600 s−1) compression were studied using electron backscatter diffraction technique. Three types of twins, {10 $$ \overline{1} $$ 2} (E1), {11 $$ \overline{2} $$ 2} (C1), and {11 $$ \overline{2} $$ 4} (C3), were observed to interact with the preformed E2 twins in four parent grains. The E1 variants nucleated at twin boundaries of some E2 variants. And the C3 twins were originated from the intersection of C1 and E2. The selection of twin variant was investigated by the Schmid factors (SFs) and the twinning shear displacement gradient tensors (DGTs) calculations. The results show that twin variants that did not follow the Schmid law were more frequently observed under high strain rate deformation than quasi-static deformation. Among these low-SF active variants, 73 pct (8 out of 11) can be interpreted by DGT. Besides, 26 variants that have SF values close to or higher than their active counterparts were absent. Factors that may affect the twin variant selections were discussed.

Deformation twins in cast uranium strained to 4.2% and 6.2% by quasi static compression were investigated using electron backscattered diffraction and transmission electron microscopy. Twin types of {130}, ‘{172}’, {112} and ‘{176}’ were observed in present experiment. All the operative twin variants in each twin type have the highest Schmid factor among the equivalent variants. Some {130} twins in cast uranium were inclined to disappear during subsequent loading through the re-twinning processes with Schmid factor values greater than 0.4. The ‘(−176)’ variant was identified by indexing the electron diffraction pattern combining with the stereographic projection analysis. Twin pairs of ‘(−176)’–‘(−17−2)’ occurred in the adjacent grains were well matched with the geometric compatibility factor value of 0.933.

Fast and efficient activation of ZrCo is beneficial to promote its application to hydrogen isotopes storage in the fusion energy field. To obtain the optimum activation procedures, the influences of temperature and hydrogen pressure on the activation behavior of ZrCo were systematically investigated. Experimental results showed that fast and efficient activation of ZrCo could be achieved by optimizing the temperature and hydrogen pressure conditions of the activation procedures including initial evacuation, hydrogenation and dehydrogenation. It was found that initial evacuation at temperature higher than 300 °C was clearly beneficial to the subsequent hydrogenation process. Hydrogen absorption rate of ZrCo during the activation process could be enhanced by increasing the hydrogenation temperature, whereas hydrogen pressures had an indiscernible impact on the hydrogenation process. Compared with other temperatures and hydrogen pressures, 100 °C and 0.8 bar H2 was a preferred condition for hydrogenation of ZrCo. In addition, it was demonstrated that dehydrogenation at high temperature over 500 °C was favorable to enable activated ZrCo to own high hydrogen capacity. As a result, optimum procedures composed of initial evacuation at 500 °C, hydrogenation at 100 °C under 0.8 bar H2 and dehydrogenation at 500 °C under vacuum were highly recommended for fast and efficient activation of ZrCo.

In the present work, the efficient and fast synthesis method of LiBH 4 using LiH + MgB 2 as starting material was experimentally verified. It was found that the conversion of LiH + MgB 2 into LiBH 4 + MgH 2 was rapidly completed in ∼15 min under 7 MPa H 2 at 673 K. Meanwhile, LiBH 4 was successfully separated from MgH 2 using MTBE (methyl tert-butyl ether) as solvent. Kinetics analysis results not only suggested that the rate limiting step during formation process of LiBH 4 from LiH + MgB 2 is nucleation/growth controlled but also indicated that the formation process of LiBH 4 is probably controlled by heterogeneous nucleation and one-direction growth. Our kinetics analysis result provides a plausible explanation for the significantly kinetic enhancement of transition metal halides or oxides in the Li-Mg-B-H hydrogen storage system.

The authors describe a highly sensitive platform for the determination of uranyl ion (UO2 2+) that is based on the integration of an UO2 2+-specific DNAzyme and a target-catalyzed hairpin assembly. Each DNAzyme consists of an enzyme strand (E-DNA) and a substrate strand (S-DNA). The S-DNA is selectively cleaved in the presence of UO2 2+. The released fragment of S-DNA hybridizes with hairpin probe 1 (H1) immobilized on a gold electrode. This is accompanied by unfolding of H1 which induces the hybridization with hairpin 2 (H2). The DNA fragment spontaneously dissociates from the surface and then initiates the next hybridization cycle. After multiple cycling, the electrochemical probe Methylene Blue (MB) is added to intercalate into the minor grooves of the dsDNA. The combination of signal amplification and the use of a highly specific DNAzyme results in a highly sensitive sensor for UO2 2+. At a typical working voltage of −0.22 V (vs Ag/AgCl), a linear response is found range for the 10 pM to 1 nM concentration range, and the detection limit is as low as 2 pM. This strategy provides a powerful and generally applicable tool that may be extended to other metal ions for which specific DNAzymes and signal probes are available.

A novel strategy for ultrasensitive detection of UO22+ was proposed by using a UO22+-specific DNAzyme and two free labeled DNA hairpins. The principle and detection processes of this electrochemical biosensor for amplification detection of UO22+ were described. The detection conditions of the biosensor, such as the concentration of hairpins, pH, and the incubation time of HCR, were optimized. Under optimal conditions, this biosensor demonstrated a high sensitivity of UO22+ detection with the dynamic concentration range spanning from 0.05 to 4 nM and a detection limit of 20 pM at the 3Sblank level, providing a promising strategy for on site and real-time monitoring of uranium.