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On the basis of the intrinsic characteristics of the layered materials, here we report a universal principle for the production of intact monolayers via layer-by-layer exfoliation from their bulk via positive charge doping. At experimental accessible densities (

Hybrid organic-inorganic lead halide perovskites (HOIPs) possess significant photoelectric characteristics for solar energy conversion, but the presence of lead causes issues for eco-friendly applications. Halide double perovskites represent a green option for application in the optoelectronic field, especially X-ray detection systems. Despite the great efforts, the exploration of large-size lead-free iodide-based hybrid double perovskite single crystals for X-ray detection has been unsuccessful. Herein, we demonstrate that a large single crystal of the 2D (two-dimensional) semiconducting perovskite (C

Mullite fiberboards have been extensively used in heat-insulating refractory materials. To further improve the thermal insulation properties and reduce the density, we fabricated mullite fiberboards by vacuum filtration using hollow mullite fibers based on a ceiba fiber template. The effects of sintering temperature and type and content of high-temperature adhesives on the density, compressive strength, thermal conductivity, microstructure, and volume stability of mullite fiberboards were investigated. The results showed that the obtained mullite fiberboards have ultralow density of 0.1–0.2 g/cm3, low thermal conductivity of 0.0988–0.1230 W/(m·K) (at 500 °C), and compressive strength of 0.08–0.12 MPa, and they exhibit good volume stability at 1300 °C.

White-light emission (WLE) materials based on organic-inorganic hybrid lead halides have drawn considerable attention because of their applications in light-emission equipment. Despite considerable efforts, there is still a lack of two-dimensional (2D) lead-chlorine white-light emitting halides with high photoluminescence quantum efficiency (PLQE). Herein, we report the preparation of a new 2D layered hybrid halide, [DTHPE]Pb

The combination of sulfate radical-mediated advanced oxidation process (SA-AOP) and photocatalysis is researched as a highly efficient strategy for pollutant degradation in recent decades. To systematically study the synergistic effect between photocatalysis and peroxymonosulfate (PMS) induced SA-AOP, graphene oxide (GO) coupled graphitic carbon nitride (CN) composites were synthesized as catalyst. About 98% of bisphenol A was decomposed in CNGO/PMS/light system, which was significantly higher than that in CNGO/PMS or CNGO/light system, demonstrating the strong synergistic effect between photocatalysis and SA-AOP. CNGO was deactivated in catalyst/PMS system, but not in catalyst/PMS/light system, showing that the deactivation of CNGO in the presence of sulfate radicals was inhibited by the photocatalysis. The photogenerated electrons may directly reduce the oxidized GO, or react with the oxidative species which may oxidize GO, and thus maintain the activity of CNGO. In addition, the system temperature was elevated due to the light-to-heat conversion on GO. The increased reaction temperature accelerated the degradation reaction due to the improved the charge separation and molecular collision. This work explains the synergy effect between photocatalysis and SA-AOP from different perspectives, and provides a new idea to improve the reusability of carbonaceous catalyst.

The deep understanding of atomic-scale rolling friction and the charge transfer mechanism behind it is essential for developing submicrometre-scale electromechanical devices, especially for rolling...

With the advent of the era of big data, the model architecture of disease prediction has been transformed from cloud computing architecture to edge computing architecture to alleviate problems, such as single point of failure, huge burden of computing and long communication delays.However, due to the lack of trust among edge computing participants (herein referred to as medical institutions with data resources or data storage nodes), the patients’ personal privacy and security issues are still challenging, and there is an urgent need to propose new solutions with higher security. In this paper, we proposed a new disease prediction model with the edge computing framework based on blockchain and federated learning technology to realise full mining of data value, as well as protecting local data sharing security and privacy. In the process of federated learning with blockchain as the underlying platform working environment, we propose the concept of model accuracy as the selection indicator of data nodes in federated learning, which improves the accuracy of the federated learning model and optimizes the training delay.

Acquiring how the performance depends on structure is the most pivotal step of material design, preparation, and application. In particular, it is extremely significant to figure out the correlatio...

As a typical atomically-thin solid lubricant, graphene is widely utilized and investigated. However, the existence of defects in engineering graphene seriously damages its lubricating property. In this work, we theoretically report a novel approach to repair defects hence improve frictional property enabled by doping-induced modification. Graphene nanosheet has been doped with nitrogen and boron. Adjustments of atomic-scale friction due to nitrogen and boron doping in graphene nanosheet have been explored by density functional theory (DFT). Compared to boron-doped graphene, nitrogen-doped graphene exhibits low friction and its tribological properties improve with the doping concentration of nitrogen, which are attributed to the low interlayer interaction induced by the repulsive electrostatic forces between interlayers. We also elucidate that van der Waals and electrostatic interactions exhibit peculiar distributional proportion on the frictional properties for different doping species. Furthermore, through observing the charge transfer of different doping systems, the intrinsic characterization of charge introduction is thoroughly explored, which is the primary cause that affect the atomic-scale friction. The investigation provides a general strategy for modifying the lubricating property of graphene.

Amorphous carbon films with low friction and wear become a hotspot of research and engineering application for meeting the requirements of energy savings and environmental benefits. However, the co...

Ceiba fibers have excellent thermal insulating properties because of their hollow structures. Mullite fibers are widely used in heat-insulating refractory materials because of their low thermal conductivity and excellent thermal shock stability. However, unlike ceiba fibers, conventional mullite fibers have solid structures, which limits further development of the thermal insulating properties of mullite fibers. Inspired by their hollow structure, we used ceiba fibers as a template for preparing hollow mullite fibers. We immersed ceiba fibers in a precursor solution of Al(NO3)3 and ethyl orthosilicate (TEOS). The impregnated ceiba fibers were then dried and sintered at a high temperature to obtain hollow mullite fibers. The synthesis process, microstructures, phases, pore size distributions, and thermal conductivities of the resulting fibers were analyzed. The results showed that mullite fibers inherited the hollow structure of the ceiba fibers, and the resulting thermal conductivity was markedly reduced compared to solid mullite fibers.

The recently discovered and prepared honeycomb borophene is one of the many forms of borophene. For the first time, we studied the tribological properties of honeycomb borophene based on first principles and found that it has excellent tribological performance. As a two-dimensional material, honeycomb borophene has potential applications in the field of tribology. Correspondingly, we studied interlaminar charge transfer in several common heterojunctions and then explored its internal friction mechanism. The present work indicts that honeycomb borophene, a new type of two-dimensional material, may help broaden the research field of two-dimensional materials in tribology.

Strain, as an economic yet controllable approach for structural modulation, frequently plays a vital role in the preparation and performance optimization of two-dimensional nanomaterials (TNMs). Here, utilizing first-principles simulations, the analysis of energetics shows that the biaxial stretching and compressing could facilitate the vertical separation and horizontal sliding in graphene (Gr/Gr), hexagonal boron nitride (

Atomic-scale friction theory, and even superlubricity, is inseparable from charge redistribution, but lacks a bridge to establish the potential link between them. Here, we first report a quantized charge density fluctuation surface (CDFS) by assembling silicene/graphene and germanene/graphene heterostructures and their corresponding homogeneous bilayers for DFT calculations. By observing the PES morphology, we see that it exhibits a decrease in friction by more than two orders of magnitude. A crucial physical quantity controlling the friction was found to be the charge density fluctuation during the friction process via analyzing the CDFSs. Such CDFS holds a universal applicability in van der Waals materials, and is recommended to explore the friction cooperating with PES. This will be a new idea for exploring whether friction is related to electrical properties by defining the conversion factor K for a wide series of interactions, including metallic, covalent, and van der Waals bonding. In particular, the same conversion factor K exists for van der Waals bonding, and a mutual identification between the CDFS and PES can be achieved.

This bibliometric-based review analyses the trends in 1010 published articles (1990 to mid-2018) on the high-value application of Chlorella, and illustrates the evolution and latest tendencies at a global level by the number of publications and their distribution, issuing institutions and countries or regions, the sources and research direction, as well as the core-author and keywords. The results demonstrated that there is a burst in terms of the number of articles, and China, USA, Mexico, and Japan are the dominant countries in this area. The most relevant journals with this subject are Bioresource Technology and Hydrobiology, and the research mainly focuses on marine and freshwater biology, biotechnology and applied microbiology, energy and fuels, food science and technology, and environmental sciences. Overall, bibliometric analysis has shown that Chlorella application research is a very active field, and the future research will be conducted into construction of genetic engineering algae, high-density and low-cost culture systems, efficient harvesting and separation techniques, effective energy conversion, integrated photo-bioreactors, and molecular biology technology. Wastewater treatment, CO2 bio-fixation, biomass production, and biosynthesis of useful substances by cultivating microalgae are promising research fields.

This bibliometric-based review analyses the trends in 1010 published articles (1990 to mid-2018) on the high-value application of Chlorella, and illustrates the evolution and latest tendencies at a global level by the number of publications and their distribution, issuing institutions and countries or regions, the sources and research direction, as well as the core-author and keywords. The results demonstrated that there is a burst in terms of the number of articles, and China, USA, Mexico, and Japan are the dominant countries in this area. The most relevant journals with this subject are Bioresource Technology and Hydrobiology, and the research mainly focuses on marine and freshwater biology, biotechnology and applied microbiology, energy and fuels, food science and technology, and environmental sciences. Overall, bibliometric analysis has shown that Chlorella application research is a very active field, and the future research will be conducted into construction of genetic engineering algae, high-density and low-cost culture systems, efficient harvesting and separation techniques, effective energy conversion, integrated photo-bioreactors, and molecular biology technology. Wastewater treatment, CO(2) bio-fixation, biomass production, and biosynthesis of useful substances by cultivating microalgae are promising research fields.

Sulfate radical-based advanced oxidation process is a promising technology to degrade organic pollutants for water remediation. Photo-activation of peroxymonosulfate (PMS) has received increasing attention. From the aspect of solar energy, the utilization of near-infrared (NIR) light which accounts for about 50% of the solar energy in PMS activation is still challenging. Herein, we designed and synthesized few-layered graphite modified graphitic carbon nitride (GrCN) for whole-spectrum photo-activation of PMS. During the reaction, NIR light was converted to heat on few-layered graphite through photothermal effect to accelerate the chemical reactions via raising the system temperature. In addition to the photothermal effect, few-layered graphite also acted as cocatalyst to alter the band structure and promote the charge separation. Therefore, GrCN exhibited excellent activity in the degradation of bisphenol A with the addition of PMS under illumination. In addition, GrCN presented high reusability in the presence of sulfate radicals under illumination.

Polymorphism and stacking faults can seriously affect the physical properties of two-dimensional materials. What’s important, the biaxial strain has a significant impact on the structural transformation of two-dimensional materials and changes the related path, which ultimately leads to a phase structure different from zero strain. Also, external pressure or biaxial strain can change the crystal lattice without introducing impurities, making it a clean and controllable method for adjusting physical properties. In this paper, the AA2 and AB1 stack structures with relatively small energy are simulated by first-principles calculation to explain the isomorphic phase transition of h-BN under biaxial strain. Energy analysis shows that the AB1 stack is relatively stable without strain, and when the strain increases to 4.295 %, the AB1 stacking will spontaneously rotate into the AA2 stacking, which makes AA2 stable. By analyzing the density of states (DOS) and the electron density difference, the isomorphic phase transition is attributed to the weakening of the B–N bond by electron transfer between layers under strain conditions. The sliding behavior caused by biaxial strain at the atomic scale may be of fundamental importance for understanding the macroscopic friction behavior. In addition, the explanation of the isomorphic phase transition plays a very important role in the h-BN double layer as a future electronic and optoelectronic device material.

Revealing the microscopic origins of macroscopic properties and the correlations among them are of value to performance improvement and reasonable structure design of materials. Recently, the interlayer interactions and bandgap adjustment of two-dimensional materials have been attributed to electron redistribution (mainly charge transfer). However, it remains unclear how the distribution of electrons determines the change in interlayer interaction and bandgap simultaneously. Here, based on the first-principles calculations, we present an interesting physical phenomenon: there is a surprising negative correlation between relative potential energy (i.e., sliding energy barrier) and bandgap in hexagonal boron nitride (h-BN) bilayers. More notably, relative potential energy and bandgap will reverse at the same sliding position and normal pressure. The analysis of electronic structure indicate that the reversion of the potential energy fluctuation is induced by the reversal of the distribution of interlayer charge density, yet the change in bandgap is caused by the reversal of the contribution of B atomic electrons (p orbital) to the intralayer B–N bond. And ultimately, we concluded that the negative relationship between the potential energy and bandgap is the reflection of competitive relationship of electrons distribution between interlayer and intralayer.

The utilization of long-wave light (1000–2500 nm) in the solar spectrum is a difficulty in photocatalysis. Based on the Arrhenius equation, the activated carbon (AC)/graphitic carbon nitride (CN) composites were designed for photothermal-assisted photocatalytic water treatment. The short-wave solar energy can be converted to chemical energy on CN, and the long-wave solar energy to thermal energy by AC. The energetics and the interfacial charge transfer of activated carbon (AC)/graphitic carbon nitride (CN) composites (ACCN) were improved owing to the π bond between AC and CN. The excellent light absorption capacity (over 80%) led to higher photocatalytic reaction temperature due to the photothermal effect. The higher temperature accelerated the photocatalytic reaction and facilitates the charge transfer on ACCN. Hence, the optimal ACCN sample with good balance between photothermal and photocatalytic property could degrade 98% of sulfamerazine under simulated solar irradiation in 60 min. This work not only developed efficient and low-cost (~$1/kg) carbon-based photocatalysts with ultrahigh solar utilization, but also discussed the mechanism of photothermal effect on photocatalytic reaction.

Essentially, the interlayer interaction of the two-dimensional (2D) layered material is the overlap of electron clouds outside the nucleus atomically. When the layered material slides between layers, the contribution of electrons to the interlayer interaction is dominant, so it is expected to modify the electronic configuration of the system to change the interlayer interaction for the purpose of reducing interlayer sliding friction. In this paper, using density functional theory (DFT) calculation, we report an effective method to reduce the sliding friction between the two-layer hexagonal boron nitride layers for changing the hexagonal boron nitride electronic structure via introducing carbon. Research results indicate that the increase of the potential energy fluctuation along the sliding path increases with the increase of the load, which is caused by the difference of the degree of interlayer interaction on the sliding path with the increase of the load; at the same time, we found that the appearance of C at the B or N position can promote the interlayer charge transfer to different extents (B position is better than N position) in the BN/BN bilayer, and then produce the effect of reducing the energy barrier on the sliding path between the layers.