Abstract
The discovery of moiré superlattices (MSLs) opened an era in the research of ‘twistronics’. Engineering MSLs and realizing unique emergent properties are key challenges. Herein, we ...demonstrate an effective synthetic strategy to fabricate MSLs based on mechanical flexibility of WS
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nanobelts by a facile one-step hydrothermal method. Unlike previous MSLs typically created through stacking monolayers together with complicated method, WS
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MSLs reported here could be obtained directly during synthesis of nanobelts driven by the mechanical instability. Emergent properties are found including superior conductivity, special superaerophobicity and superhydrophilicity, and strongly enhanced electro-catalytic activity when we apply ‘twistronics’ to the field of catalytic hydrogen production. Theoretical calculations show that such excellent catalytic performance could be attributed to a closer to thermoneutral hydrogen adsorption free energy value of twisted bilayers active sites. Our findings provide an exciting opportunity to design advanced WS
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catalysts through moiré superlattice engineering based on mechanical flexibility.
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•A broad overview of ultrathin two-dimensional metal-organic frameworks materials for functional electronic devices.•An exhaustive summary of the preparative techniques for ...fabrication of ultrathin two-dimensional metal-organic frameworks.•A demonstration of the device performance enhanced by the active ultrathin two-dimensional metal-organic frameworks.
Ultrathin two-dimensional (2D) metal-organic framework (MOF) nanosheets with dimension-related chemical and physical properties, including large surface areas, high intrinsic porosities and abundant accessible active sites have attracted extensive interest in various functional electronic devices. In this review, we first introduce the special advantages of the ultrathin 2D MOF nanosheets. Then, we discuss the classifications of typical synthetic methods, such as top-down method and bottom-up method. Subsequently, we summarize the research advances on the applications of ultrathin 2D MOFs for functional electronic devices, including battery, supercapacitor, chemiresistive sensor, capacitive sensor, amperometric sensor, luminescent sensor, field effect transistor and white light-emitting diode, etc. Finally, we provide the challenges and perspectives on future synthesis and extensive applications of ultrathin 2D MOF nanosheets.
Haar wavelet operational matrix has been widely applied in system analysis, system identification, optimal control and numerical solution of integral and differential equations. In the present paper ...we derive the Haar wavelet operational matrix of the fractional order integration, and use it to solve the fractional order differential equations including the Bagley–Torvik, Ricatti and composite fractional oscillation equations. The results obtained are in good agreement with the existing ones in open literatures and it is shown that the technique introduced here is robust and easy to apply.
Edible plant oil (EPO) is an indispensable nutritional resource for human health. Various cultivars of oil-bearing plants are grown worldwide, and the chemical compositions of different plant oils ...are diverse. The extremely complex components in oils lead to diverse standards for evaluating the quality and safety of different EPOs. The environment poses great challenges to the EPO safety and quality during the entire industrial chain, including plant cultivation, harvesting, oil processing, and storage. Environmental risk factors include heavy metal or pesticide residue pollution, insect or harmful microbial infestation, and rancidity. Here, the diverse components in oil and various oil-producing processes are discussed, including plant species, oil yield, and composition complexity, environmental factors that degrade oil quality. Additionally, we propose a whole-industrial-chain monitoring system instead of current single-link-monitoring approach by monitoring and tracking the quality and safety of EPOs during the entire process of plant cultivation, raw materials harvest, oil process, and EPOs storage. This will provide guidance for monitoring the quality and safety of EPOs, which were challenged by the deteriorating environment.
Research on underwater image processing has increased significantly in the past decade due to the precious resources that exist underwater. However, it is still a challenging problem to restore ...degraded underwater images. Existing prior-based methods show limited performance in many cases due to their reliance on hand-crafted features. Therefore, in this paper, we propose an effective unsupervised generative adversarial network(GAN) for underwater image restoration. Specifically, we embed the idea of contrastive learning into the model. The method encourages two elements (corresponding patches) to map the similar points in the learned feature space relative to other elements (other patches) in the data set, and maximizes the mutual information between input and output through PatchNCE loss. We design a query attention (Que-Attn) module, which compares feature distances in the source domain, and gives an attention matrix and probability distribution for each row. We then select queries based on their importance measure calculated from the distribution. We also verify its generalization performance on several benchmark datasets. Experiments and comparison with the state-of-the-art methods show that our model outperforms others.
The electrical performance of two-dimensional transition metal dichalcogenides （TMDs） is strongly affected by the number of structural defects. In this work, we provide an optical spectroscopic ...characterization approach to correlate the number of structural defects and the electrical performance of WSe2 devices. Low-temperature photoluminescence （PL） spectra of electron-beam-lithography- processed WSe2 exhibit a clear defect-induced PL emission due to excitons bound to defects, which would strongly degrade the electrical performance. By adopting an electron-beam-free transfer-electrode technique, we successfully prepared a backgated WSe2 device containing a limited amount of defects. A maximum hole mobility of approximately 200 cm2.V -1.s-1 was achieved because of the reduced scattering sources, which is the highest reported value for this type of device. This work provides not only a versatile and nondestructive method to monitor the defects in TMDs but also a new route to approach the room-temperature phonon-limited mobility in high-performance TMD devices.
Fabrication of mechanically robust and catalyst-free vitrimers is of great importance, but often challenging. Herein, a facile strategy to achieve this goal by incorporation of intramolecular ...hydrogen bonds into the dynamic covalent network is demonstrated. Specifically, glycidyl methacrylate (GMA) is reacted with bio-renewable malic acid (MA) to generate a UV-curable resin containing ester linkages. On account of the proximity between the α-carbonyl and β-hydroxyl groups in MA, six-membered-ring intramolecular hydrogen bonds (O-H⋯O=C) are formed in the cross-linked network. This formation of intramolecular hydrogen bonds endows the network with enhanced and outstanding mechanical properties, showing tensile strength and Young's modulus of 117.7 MPa and 3.66 GPa, respectively. Meanwhile, the network is able to efficiently alter its topology without external catalyst through transesterifications reactions at high temperatures. We attributed this phenomenon to the presence of intramolecular hydrogen bonds which make the α-carbonyl carbon more positive and be more reactive towards nucleophilic attack, and thus facilitate the transesterification reaction. This work suggests a promising route to achieve catalyst-free thermosets with superior mechanical performances, good self-healing ability and reprocessability.
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•Fabricating mechanically robust and catalyst-free vitrimer by incorporating intramolecular H-bonds.•The vitrimer shows tensile strength of 117.7 MPa and Young’s modulus of 3.6 GPa.•Intramolecular H-bonds showed an accelerated effect on transesterification.•A UV-curable monomer is synthesized to achieve the vitrimer material.
Osteoarthritis (OA) is the most common degenerative joint disease and a major cause of pain and disability in adult individuals. The etiology of OA includes joint injury, obesity, aging, and ...heredity. However, the detailed molecular mechanisms of OA initiation and progression remain poorly understood and, currently, there are no interventions available to restore degraded cartilage or decelerate disease progression. The diathrodial joint is a complicated organ and its function is to bear weight, perform physical activity and exhibit a joint-specific range of motion during movement. During OA development, the entire joint organ is affected, including articular cartilage, subchondral bone, synovial tissue and meniscus. A full understanding of the pathological mechanism of OA development relies on the discovery of the interplaying mechanisms among different OA symptoms, including articular cartilage degradation, osteophyte formation, subchondral sclerosis and synovial hyperplasia, and the signaling pathway(s) controlling these pathological processes.
Defects in transition metal dichalcogenides (TMDs) play an important role in tailoring electrical and optical properties. Here we employ Ar+ plasma to controllably generate active defects in WSe2 ...monolayers to tune their optical properties. Two defect-activated PL emission peaks are emerging in the low temperature PL spectra of WSe2 monolayer treated with Ar+ plasma. These emissions are attributed to the recombination of excitons bound to different types of structural defects. The shallow level emission originates from the recombination of excitons at chalcogen vacancies, while the deep level emission might arise from other types of defects, such as transition metal vacancies, cluster of vacancies, rotational defects, or antisite defects. Our results demonstrate that Ar+ plasma treatment is an effective approach to induce desirable defects in TMDs monolayers and PL spectroscopy is an efficient method to investigate these defects.
The development of metallacycles with high stability and intense near-infrared (NIR) absorption is important for biomedical applications. However, very few molecular design strategies have been ...developed on such metallacycles. Herein, we report a new series of stable and well-defined NIR-absorbing metallacycles (M1–M3) through the Pt–acetylide coordination with highly efficient photoconversion performance for cancer phototherapy. The metallacycles showed high stability and strong NIR absorption, and the absorption peaks were red shifted approximately 30 nm in comparison with their corresponding precursors. The introduction of Pt into metallacycles promotes significant photoconversions, including the singlet-to-triplet and nonradiative transitions. Moreover, the fabricated M3 nanoparticles (M3-NPs) showed favorable photoconversions into both thermal effect and singlet oxygen generation upon NIR irradiation, achieving tumor ablation. This novel design of Pt-acetylide metallacycles possesses not only complex topological architectures but also a valuable paradigm for precise cancer phototherapy, which is important for grafting stimuli-responsive functional groups into metallacycles for the development of high-performance biomedical supramolecular materials.
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