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Structural and compositional inhomogeneity is common in zeolites and considerably affects their properties. Thickness-limited lateral resolution, lack of depth resolution, and electron dose-constrained focusing limit local structural studies of zeolites in conventional transmission electron microscopy (TEM). We demonstrate that a multislice ptychography method based on four-dimensional scanning TEM (4D-STEM) data can overcome these limitations. Images obtained from a ~40-nanometer-thick MFI zeolite exhibited a lateral resolution of ~0.85 angstrom that enabled the identification of individual framework oxygen (O) atoms and the precise determination of the orientations of adsorbed molecules. Furthermore, a depth resolution of ~6.6 nanometers allowed probing of the three-dimensional distribution of O vacancies, as well as the phase boundaries in intergrown MFI and MEL zeolites. The 4D-STEM ptychography can be generally applied to other materials with similar high electron-beam sensitivity.

Although isomerism is a typical and significant phenomenon in organic chemistry, it is rarely found in covalent organic framework (COF) materials. Herein, for the first time, we report a controllable synthesis of topological isomers in three-dimensional COFs via a distinctive tetrahedral building unit under different solvents. Based on this strategy, both isomers with dia or qtz net (termed JUC-620 and JUC-621) have been obtained, and their structures are deter-mined by combining powder X-ray diffraction and transmission electron microscopy. Remarkably, these architectures show a dis-tinct difference in their porous features, e.g., JUC-621 with qtz net exhibits permanent mesopores (up to ~ 2.3 nm) and high surface area (~ 2060 m2 g-1), which far surpasses those of JUC-620 with dia net (pore size of ~1.2 nm and surface area of 980 m2 g-1). Further-more, mesoporous JUC-621 can remove dye molecules efficiently and achieves excellent iodine adsorption (up to 6.7 g g-1), which is 2.3 times that of microporous JUC-620 (~2.9 g g-1). This work thus provides a new way for constructing COF isomers and promotes structural diversity and promising applications of COF mate-rials.

Polyimide covalent organic framework (PI-COF) materials that can realize intrinsic redox reactions by changing the charge state of their electroactive sites are considered as emerging electrode materials for rechargeable devices. However, the highly crystalline PI-COFs with hierarchical porosity are less reported due to the rapid reaction between monomers and the poor reversibility of the polyimidization reaction. Here, we developed a water-assistant synthetic strategy to adjust the reaction rate of polyimidization, and PI-COF (COFTPDA-PMDA) with kgm topology consisting of dual active centers of N,N,N',N'-tetrakis(4-aminophenyl)-1,4-benzenediamine (TPDA) and pyromellitic dianhydride (PMDA) ligands was successfully synthesized with high crystallinity and porosity. The COFTPDA-PMDA possesses hierarchical micro-/mesoporous channels with the largest surface area (2669 m2/g) in PI-COFs, which can promote the Li+ ions and bulky bis(trifluoromethanesulfonyl)imide (TFSI-) ions in organic electrolyte to sufficiently interact with the dual active sites on COF skeleton to increase the specific capacity of cathode materials. As a cathode material for lithium-ion batteries, COFTPDA-PMDA@50%CNT which integrated high surface area and dual active center of COFTPDA-PMDA with carbon nanotubes via π-π interactions gave a high initial charge capacity of 233 mAh/g (0.5 A/g) and maintains at 80 mAh/g even at a high current density of 5.0 A/g after 1800 cycles. This work was supported by the Jilin Province Science and Technology Development Plan (20210101112JC and 20220101048JC), the National Natural Science Foundation of China (21871104, 21621001, 22288101, and 22133005), the Natural Science foundation of Shanghai (20ZR1427600), and the Opening Project of State Key Laboratory of High Performance Ceramics and Superfine Microstructure (SKL202105SIC).

This research is supported by the AMPM CCF fund (FCC/1/1972-43-01) to Y.H. from King Abdullah University of Science and Technology and the research grant to F.L. from the National Natural Science Foundation of China (No. 61971201).

The capture of radioactive I

The periodic bulk structures of metal–organic frameworks (MOFs) can be solved by diffraction-based techniques; however, their non-periodic local structures—such as crystal surfaces, grain boundaries, defects, and guest molecules—have long been elusive due to a lack of suitable characterization tools. Recent advances in (scanning) transmission electron microscopy ((S)TEM) has made it possible to probe the local structures of MOFs at atomic resolution. In this article, we discuss why high-resolution (S)TEM of MOFs is challenging and how the new low-dose techniques overcome this challenge, and we review various MOF structural features observed by (S)TEM and important insights gained from these observations. Our discussions focus on real-space imaging, excluding other TEM-related characterization techniques (e.g. electron diffraction and spectroscopy). While the bulk structures of metal–organic frameworks can be solved by diffraction-based techniques, characterization of their local structures has been lacking. Here the authors review recent advances in (scanning) transmission electron microscopy that have made it possible to probe the local structures of MOFs at atomic resolution.

Oxide-/hydroxide-derived copper electrodes exhibit excellent selectivity toward C2+ products during the electrocatalytic CO2 reduction reaction (CO2RR). However, the origin of such enhanced selectivity remains controversial. Here, we prepared two Cu-based electrodes with mixed oxidation states, namely, HQ-Cu (containing Cu, Cu2O, CuO) and AN-Cu (containing Cu, Cu(OH)2). We extracted an ultrathin specimen from the electrodes using a focused ion beam to investigate the distribution and evolution of various Cu species by electron microscopy and electron energy loss spectroscopy. We found that at the steady stage of the CO2RR, the electrodes have all been reduced to Cu0, regardless of the initial states, suggesting that the high C2+ selectivities are not associated with specific oxidation states of Cu. We verified this conclusion by control experiments in which HQ-Cu and AN-Cu were pretreated to fully reduce oxides/hydroxides to Cu0, and the pretreated electrodes showed even higher C2+ selectivity compared with their unpretreated counterparts. We observed that the oxide/hydroxide crystals in HQ-Cu and AN-Cu were fragmented into nanosized irregular Cu grains under the applied negative potentials. Such a fragmentation process, which is the consequence of an oxidation-reduction cycle and does not occur in electropolished Cu, not only built an intricate network of grain boundaries but also exposed a variety of high-index facets. These two features greatly facilitated the C-C coupling, thus accounting for the enhanced C2+ selectivity. Our work demonstrates that the use of advanced characterization techniques enables investigating the structural and chemical states of electrodes in unprecedented detail to gain new insights into a widely studied system.

Metal–organic frameworks (MOFs) with a high density of metal nodes have great potential in the application of heterogeneous catalysis. However, identifying the real active site in MOF structures and tuning its amount to further improve its catalytic performance are still a great challenge. In this paper, defective UiO-66 modulated with trifluoroacetic acid (TFA) was synthesized and used for the conversion of cyclohexanone to cyclohexanol via hydrogen transfer. We found that not all structural defects were responsible for catalytic reaction, and only structural defects where open metal sites are created by a modulator were effective for cyclohexanone conversion. Then we successfully tuned the number of each type of effective structural defect (that is, missing-cluster defects or missing-linker defects) in modulated UiO-66 via precise control of the synthetic/treatment conditions. Our experimental results showed that the creation of both types of structural defects can increase the amount of effective open metal sites and then enhance their catalytic performances under the same conditions. Furthermore, the mechanism study confirmed that this reaction indeed proceeded on effective open metal sites. Our findings have further deepened the understanding of the roles of structural defects in MOF heterogeneous catalysis.

With the development of ultralow-dose (scanning) transmission electron microscopy ((S)TEM) techniques, atomic-resolution imaging of highly sensitive nanomaterials has recently become possible. However, applying these techniques to the study of sensitive bulk materials remains challenging due to the lack of suitable specimen preparation methods. We report that cryogenic focused ion beam (cryo-FIB) can provide a solution to this challenge. We successfully extracted thin specimens from metal-organic framework (MOF) crystals and a hybrid halide perovskite single-crystal film solar cell using cryo-FIB without damaging the inherent structures. The high quality of the specimens enabled the subsequent (S)TEM and electron diffraction studies to reveal complex unknown local structures at an atomic resolution. The obtained structural information allowed us to resolve planar defects in MOF HKUST-1, three-dimensionally reconstruct a concomitant phase in MOF UiO-66, and discover a new CH

Thermoelectric materials are typically highly degenerate semiconductors, which require high carrier concentration. However, the efficiency of conventional doping by replacing host atoms with alien ones is restricted by solubility limit, and, more unfavorably, such a doping method is likely to cause strong charge-carrier scattering at ambient temperature, leading to deteriorated electrical performance. Here, an unconventional doping strategy is proposed, where a small trace of alien atoms is used to stabilize cation vacancies in Cu

Traditional electrolysis of water produces hydrogen with a purity of ∼98%. Using ion transport membranes to prevent the migration of oxygen (O2) from the anode to the cathode, the purity of H2 can be increased to ∼99.8%, but it still cannot fulfill the requirement for use in fuel cells (>99.97%). Here, we report that modifying a commercial ionic membrane (Nafion) with carbon dots (CDs) can further inhibit O2 permeation across the membrane, while effectively improving its ion transportability. The key to achieve these effects is the rational design and proper loading of the CDs, which narrows the pore size of the membrane from ∼4 nm to

Integrated differential phase-contrast scanning transmission electron microscopy (iDPC-STEM) is capable of directly probing guest molecules in zeolites, owing to its sufficient and interpretable image contrast for both heavy and light elements under low-dose conditions. This unique ability is demonstrated by imaging volatile organic compounds adsorbed in zeolite Silicalite-1; iDPC-STEM was then used to investigate molybdenum supported on various zeolites including Silicalite-1, ZSM-5, and mordenite. Isolated single-Mo clusters were observed in the micropores of ZSM-5, demonstrating the crucial role of framework Al in driving Mo atomically dispersed into the micropores. Importantly, the specific one-to-one Mo-Al interaction makes it possible to locate Al atoms, that is, catalytic active sites, in the ZSM-5 framework from the images, according to the positions of Mo atoms in the micropores.

Aromatic alcohols are essential components of many solvents, coatings, plasticizers, fine chemicals, and pharmaceuticals. Traditional manufacturing processes involving the oxidation of petroleum-de...

Summary Defect sites are often proposed as key active sites in the design of catalysts. A promising strategy for improving activity is to achieve a high density of homogeneously dispersed atomic defects; however, this is seldom accomplished in metals. We hypothesize that vacancy-rich catalysts could be obtained through the synthesis of quantum dots (QDs) and their electrochemical reduction during the CO2 reduction reaction (CO2RR). Here, we report that QD-derived catalysts (QDDCs) with up to 20 vol % vacancies achieve record current densities of 16, 19, and 25 mAcm−2 with high faradic efficiencies in the electrosynthesis of formate, carbon monoxide, and ethylene at low potentials of –0.2, –0.3, and –0.9 V versus reversible hydrogen electrode (RHE), respectively. The materials are stable after 80 hr of CO2RR. These CO2RR performances in aqueous solution surpass those of previously reported catalysts by 2×. Together, X-ray absorption spectroscopy and computational studies reveal that the vacancies produce a local atomic and electronic structure that enhances CO2RR.

Defect engineering of metal-organic frameworks (MOFs) offers promising opportunities for tailoring their properties to specific functions and applications. However, determining the structures of defects in MOFs-either point defects or extended ones-has proved challenging owing to the difficulty of directly probing local structures in these typically fragile crystals. Here we report the real-space observation, with sub-unit-cell resolution, of structural defects in the catalytic MOF UiO-66 using a combination of low-dose transmission electron microscopy and electron crystallography. Ordered 'missing linker' and 'missing cluster' defects were found to coexist. The missing-linker defects, reconstructed three-dimensionally with high precision, were attributed to terminating formate groups. The crystallization of the MOF was found to undergo an Ostwald ripening process, during which the defects also evolve: on prolonged crystallization, only the missing-linker defects remained. These observations were rationalized through density functional theory calculations. Finally, the missing-cluster defects were shown to be more catalytically active than their missing-linker counterparts for the isomerization of glucose to fructose.

Background. Patient Perceived Value (PPV) provides a valuable perspective to explain why the government reforms on health system in terms of functional medical treatment performance improvement did not decrease the crowded waiting line or increased patient satisfaction in China. Methods. Questionnaires comprising seven constructs were sent to patients from seven highly recognized hospitals in Zhejiang Province of China. It was collected via face-by-face in a twelve-month period (2019), and 2586 valid data were collected for SPSS statistic accordingly. Results. Besides the significance of the functional medical treatment values (such as the treatment effectiveness, accurate price, standardization, and normalization), the emotional values (reasonable waiting time, convenient accessibility, communication with doctors/nurses) were significant in patients’ consciousness. Patient medical treatment seeking preferences were affected by patients’ background characteristics and perceived value, which consequently produced differentiated patients’ satisfaction. Patients’ characteristics, which related to the age, gender, illness conditions, educational, and income level, would have different demanding in medical treatment seeking. These young female patients in outpatient or in mild illness conditions with higher educational and income levels tend to be relatively high in timing and convenience demanding. Conclusion. This result would change the policy maker and hospitals to considerate the patients’ emotional value as well as functional value in providing medical treatment. Classified patients’ time arrangement tactics consistent with distinguished characteristics, equipped up with convenient accessibility and interconnected medical treatment environment design, can create valuable patients’ satisfaction in China.

Objective Magnetic resonance imaging (MRI) is gradually replacing computed tomography (CT) in the examination of bones and joints. The accurate and automatic segmentation of the bone structure in the MRI of the shoulder joint is essential for the measurement and diagnosis of bone injuries and diseases. The existing bone segmentation algorithms cannot achieve automatic segmentation without any prior knowledge, and their versatility and accuracy are relatively low. For this reason, an automatic segmentation algorithm based on the combination of image blocks and convolutional neural networks is proposed. Methods First, we establish 4 segmentation models, including 3 U-Net-based bone segmentation models (humeral segmentation model, joint bone segmentation model, humeral head and articular bone segmentation model as a whole) and a block-based Alex Net segmentation model; Then we use 4 segmentation models to obtain the candidate bone area, and accurately detect the location area of the humerus and joint bone by voting. Finally, the Alex Net segmentation model is further used in the detected bone area to segment the bone edge with the accuracy of the pixel level. Results The experimental data is obtained from 8 groups of patients in the orthopedics department of our hospital. Each group of scan sequence includes about 100 images, which have been segmented and labeled. Five groups of patients were used for training and five-fold cross-validation, and three groups of patients were used to test the actual segmentation effect. The average accuracy of Dice Coefficient, Positive Predicted Value (PPV) and Sensitivity reached 0.91 ± 0.02, respectively. 0.95 ± 0.03 and 0.95 ± 0.02. Conclusions The method in this paper is for a small sample of patient data sets, and only through deep learning on 2D medical images, very accurate shoulder joint segmentation results can be obtained, provide clinical diagnostic guidance to orthopedics. At the same time, the proposed algorithm framework has a certain versatility and is suitable for the precise segmentation of specific organs and tissues in MRI based on a small sample data.

Background: Enlarged financial and managerial resources spending on medical improvement had rarely to decrease the crowed waiting line or increase the patient satisfaction. Investigating patients’ perceived value (PPV) gain an insight of patients’ satisfaction. PPV is a valuable perspective for hospitals to strategically improve medical care quality and performance from functional and emotional sides. - Methods: According to the theory of perceived value, an empirical study had been carried out by field survey and data collection in 7 well-known hospitals in Zhejiang Province China. 2586 questionnaires with valid data were analyzed according to PPV.- Results: Beside of the importance of functional values (effectiveness of treatment effect, reasonable and accurate prices, standardization and normalization, convenience and accessibility), the emotional values (communication with doctors/nurses, comfortable environment and facilitates) were highlighted. The preferences of patients’ perceived value were influenced by patients’ background features, and then the differentiation of patients’ satisfaction was proceeded. These patients, who are young, female, outpatient, light ill condition, high educational level and high income, tend to be relatively high demanding on medical care services but in high dissatisfaction level. Additionally, the findings show an advantage to pass the reasonability of waiting time to patients’ thought.- Conclusion: Classified convenience receiving approaches according to differentiated PPV and background features of patients, equipped up with e-enabled health care environment, can bring worthwhile patients’ satisfaction in Chinese hospitals .

Exposing catalytically active metal sites in metal-organic frameworks with maintained porosity could accelerate electron transfer, leading to improved performances in electrochemical energy storage and conversion. Here, we report a series of quasi-ZIF-67 obtained from low temperature calcination of ZIF-67 for electrocatalytic oxygen evolution reaction (OER) and reveal the nanostructural structure via the spherical aberration-corrected transmission electron microscopy. The quasi-ZIF-67-350 not only possesses a large Brunauer-Emmett-Teller surface area of 2038.2 m

Oxide-/hydroxide-derived copper electrodes exhibit excellent selectivity toward C

We gratefully acknowledge the financial support from King Abdullah University of Science and Technology; Competitive Research Grant (URF/1/1378) and Baseline Funding, and from Chinese NSFC (51672309) and the Fundamental Research Funds for the Central Universities (18CX07009A).

Interfaces and their misfit defects determine the material properties of a wide range of applications, such as electronic devices, photocatalysts, and structural materials. However, current atomic-level understanding of interfacial structures is limited. Here we reveal that a special interfacial structure, a mismatched but oriented interface formed by two differently structured facets, gives rise to Ag3PO4 polypods at room temperature in aqueous solution. Transmission and scanning electron microscopy results suggest that interfaces of {1 0 0} and {1 1 0}({1 0 0}/(1 1 0}), {1 0 0}/{1 1 1}, {1 1 0}/{1 1 1}, and {1 0 0}/{1 0 0} have certain orientation relationships, corresponding to the structural energy minima and coincident site lattices of interfacial atoms, as demonstrated by molecular dynamics simulations. Density functional theory calculations indicate that the formation of pyrophosphates and/or phosphates rotation across the interface, as well as deformation of Ag-O bonds, compensate for the lattice mismatch at the interfaces. Our work opens a new avenue for a much wider range of interfacial structures, allow for a higher diversity of structures, and shines light on tailoring crystal structures, morphologies, and their resulting properties.

Charging and discharging lithium ion batteries (LIBs) in a matter of seconds to tens of seconds rather than hours can potentially lead to technological breakthroughs and bring about lifestyle changes. This work aims to enable ultrafast Li-ions charge/discharge ability for LIBs by significantly accelerating the diffusion kinetics of Li + ions and enhancing the electric conductivity in LiFePO 4 cathode material. An innovative method was developed to synthesize LiFePO 4 /C nanocomposite with secondary particles structure containing uniform (20–50 nm) and highly crystalline LiFePO 4 single nanoparticles which are free from any anti-site defects ( e.g. Fe · Li ) and uniformly coated by a highly graphitized carbon-shell network with good electronic conduction. The LiFePO 4 /C material was formed from a FePO 4 · x H 2 O/poly(furfuryl alcohol) nanocomposite, which was prepared through a self-regulated in situ polymerization restriction method, followed by a rapid wet-chemistry lithiation (H + /Li + ion exchange) and subsequent calcination. Benefiting from the ultra-small size of the LiFePO 4 nanoparticles, absence of Fe · Li defects, and a continuous 3D carbon network, the LiFePO 4 /C nanocomposite demonstrated ultrafast lithium-storage rates when used as a cathode material in lithium half-cells, which required only 21.6 s to reach a complete discharge at a rate of 150 C while still maintaining a high specific capacity of 95.4 mAh g −1 .

The Co@N-C nanocatalysts derived by direct carbonization of Co-containing metal organic framework (MOF) structure under N2 flow have been prepared for their application as catalyst in reducing 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) assisted by NaBH4. Under inert gas treatment, we obtained Co0 phase-based nanocatalyst which inherited their former MOF precursor morphology. The resultant nanocatalysts were denoted as Co@N-C 600, 700, 800 corresponding to the respective carbonization temperatures and each was characterized using powder X-Ray diffraction (PXRD), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), surface area-porosity and transmission electron microscopy (TEM). We found that Co@N-C 700 presented the desired properties with largest surface area (262.800 m2/g), high crystallinity with better Co nanoparticle dispersed on the C-N matrix and sufficient amount of Co per gram of nanocatalyst without obvious particle aggregation. All of the nanocatalysts could catalyze 1.25 mM 4-NP to 4-AP per mg catalyst per second which is comparatively remarkable performance compared to previous reposts. Most importantly, as predicted Co@N-C 700 possessed the highest catalytic activity with 6 times consecutive catalytic reactions in successfully reducing 100% 4-NP to 4-AP. The catalytic activity was speculated due to the Co nanoparticle as catalytic active site worked synergistically with C-N matrix as conductive layer which could provide and transport electrons for catalytic reduction reaction.

We have systematically changed the number of atomic layers stacked in 2D SnO nanosheet anodes and studied their sodium ion battery (SIB) performance. The results indicate that as the number of atomic SnO layers in a sheet decreases, both the capacity and cycling stability of the Na ion battery improve. The thinnest SnO nanosheet anodes (two to six SnO monolayers) exhibited the best performance. Specifically, an initial discharge and charge capacity of 1072 and 848 mAh g–1 were observed, respectively, at 0.1 A g–1. In addition, an impressive reversible capacity of 665 mAh g–1 after 100 cycles at 0.1 A g–1 and 452 mAh g–1 after 1000 cycles at a high current density of 1.0 A g–1 was observed, with excellent rate performance. As the average number of atomic layers in the anode sheets increased, the battery performance degraded significantly. For example, for the anode sheets with 10–20 atomic layers, only a reversible capacity of 389 mAh g–1 could be obtained after 100 cycles at 0.1 A g–1. Density functional ...

The recent study of a wide range of layered transition metal dichalcogenides (TMDCs) has created a new era for device design and applications. In particular, the concept of van der Waals epitaxy (vdWE) utilizing layered TMDCs has the potential to broaden the family of epitaxial growth techniques beyond the conventional methods. We report herein, for the first time, the monolithic high-power, droop-free, and wavelength tunable InGaN/GaN nanowire light-emitting diodes (NW-LEDs) on large-area MoS2 layers formed by sulfurizing entire Mo substrates. MoS2 serves as both a buffer layer for high-quality GaN nanowires growth and a sacrificial layer for epitaxy lift-off. The LEDs obtained on nitridated MoS2 via quasi vdWE show a low turn-on voltage of ∼2 V and light output power up to 1.5 mW emitting beyond the “green gap”, without an efficiency droop up to the current injection of 1 A (400 A cm−2), by virtue of high thermal and electrical conductivities of the metal substrates. The discovery of the nitride/layered TMDCs/metal heterostructure platform also ushers in the unparalleled opportunities of simultaneous high-quality nitrides growth for high-performance devices, ultralow-profile optoelectronics, energy harvesting, as well as substrate reusability for practical applications.

Metal–organic frameworks (MOFs) as a class of crystalline porous solids have attracted considerable attention due to their promising potential performance. MOFs have been recently proved to be ideal sacrificial templates for fabricating their respective derivatives by changing the thermal conditions. However, uncertainties still remain, and the direct observation of transition from MOF to metal nanoparticles (NPs) dispersed in carbon matrix is an important and crucial task for the development of MOF-derived materials. Here, transmission electron microscopy (TEM) combined with in situ hot stage technique was applied to directly observe the transition from MOF to metal NPs. Through in situ TEM experiment, the nanocrystals of Ni–ntca precursor (ntca = 1,4,5,8-naphthalenetetra carboxylic acid) are pyrolyzed under the temperature of 400, 500, or 600 °C to synthesize abundant Ni-NPs embedded in hierarchically porous carbon composites. Furthermore, the as-prepared samples show high catalytic activity and stability for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with NaBH4 in aqueous conditions. More importantly, Ni@C-600, which has nickel contents of 72.8%, shorten the reduction time to 3.5 min with high conversion of nearly 100%. When the catalyst is applied to recycle after being separated from the reaction by an extern magnet, it still keeps high conversion of 92% after 8 cycles, addressing the high stability of the composites. It is believed that these results will further facilitate the exploration of the technique of the TEM combined with in situ hot stage as a powerful tool in the carbonization of MOFs to obtain MOF-derived materials with different applications.