Layered double hydroxides (LDHs) are a class of functional anionic clays, which consist of positively charged host layers (brucite‐like M(OH)6 octahedra) and interlayer anions. By virtue of their ...unique combination of structural features (including the tunability of both host layers and interlayer guest anion, exfoliation property, structure topological transformation, confinement effect), LDHs have many potential applications in heterogeneous catalysis—as catalysts themselves, catalyst supports, or catalyst precursors. In addition, the properties of LDH‐based catalysts can be tailored for specific purposes by facile modulation of their surface/interface defect structure (e.g., oxygen vacancy defects or metal defects), controlling the concentration/strength of surface acid/base sites, tuning the geometric/electronic structure of active sites, or by taking advantage of the confinement effect intrinsic to 2D materials. In addition, by utilizing the topological structural transformation of LDH precursors, supported metal catalysts can be obtained (as single metals, bimetallic alloys or heterostructures, and intermetallic compounds) with tunable particle size/morphology and intriguing electronic properties. The main focus of this review is on recent advances in structure design, preparation, and catalytic applications of LDH‐based heterogeneous catalysts. In addition, future challenges and development strategies are discussed from the viewpoints of modulation of intrinsic active sites and establishment of scalable fabrication processes.
By virtue of the unique structural merits of layered double hydroxides (LDHs) (e.g., tunability of both host layers and interlayer guest anion, exfoliation property, structure topological transformation, confinement effect), LDHs show extensive applications as catalysts, supports, or catalyst precursors (e.g., single‐metal, bimetallic alloy or heterostructure, and intermetallic compounds) in heterogeneous catalysis.
Anthurium andraeanum, an important ornamental flower, has to go through a growth-delaying period after transfer from tissue culture to soil, which requires time and extra costs. Furthermore, during ...this period, the plantlets are highly susceptible to bacterial infections, which results in impaired development and severe losses. Here, we aimed to address whether application of the endophytic fungus, Piriformospora indica protects the A. andraeanum root system during the critical propagation period, and whether P. indica reduce the mortality rate by stimulating the host's resistance against diseases.
We demonstrate that P. indica shortens the recovery period of Anthurium, promotes growth and confers disease resistance. The beneficial effect of P. indica results in faster elongation of Anthurium roots early in the interaction. P. indica-colonized plants absorb more phosphorus and exhibit higher photosynthesis rates than uncolonized control plants. Moreover, higher activities of stress-related enzymes, of jasmonic acid levels and mRNA levels of jasmonic acid-responsive genes suggest that the fungus prepares the plant to respond more efficiently to potentially upcoming threats, including bacterial wilt.
These results suggest that P. indica is a helpful symbiont for promoting Anthurium rooting and development. All our evidences are sufficient to support the disease resistance conferred by P. indica through the plant-fungal symbiosis. Furthermore, it implicates that P. indica has strong potential as bio-fertilizer for utilization in ornamental plant cultivation.
Tens of thousands of metal–organic frameworks (MOFs) have been developed in the past two decades, and only ≈100 of them have been demonstrated as porous and hydrophobic. These hydrophobic MOFs ...feature not only a rich structural variety, highly crystalline frameworks, and uniform micropores, but also a low affinity toward water and superior hydrolytic stability, which make them promising adsorbents for diverse applications, including humid CO2 capture, alcohol/water separation, pollutant removal from air or water, substrate‐selective catalysis, energy storage, anticorrosion, and self‐cleaning. Herein, the recent research advancements in hydrophobic MOFs are presented. The existing techniques for qualitatively or quantitatively assessing the hydrophobicity of MOFs are first introduced. The reported experimental methods for the preparation of hydrophobic MOFs are then categorized. The concept that hydrophobic MOFs normally synthesized from predesigned organic ligands can also be prepared by the postsynthetic modification of the internal pore surface and/or external crystal surface of hydrophilic or less hydrophobic MOFs is highlighted. Finally, an overview of the recent studies on hydrophobic MOFs for various applications is provided and suggests the high versatility of this unique class of materials for practical use as either adsorbents or nanomaterials.
The structural design, preparation strategies, characterization methods, and potential applications of hydrophobic metal–organic frameworks (MOFs), a class of unique materials with both microporosity and hydrophobicity, are overviewed herein. It is highlighted that hydrophobic MOFs can be prepared by some facile procedures, and this type of materials can act as either advanced adsorbents or nanomaterials.
•General guiding principles for exchange reactions of metal ions or ligands in MOFs have been proposed.•Significant advance has been made to enhance the stability of MOFs by metal-ion exchange ...reactions.•New ligand exchange reactions have been developed in recent works to fine tune the pore characteristics of MOFs.
There has been considerable interest and importance in using the “exchange reaction” to synthesize, modify, or functionalize metal-organic frameworks (MOFs), since the “exchange” can achieve desired changes in their structures and performances for various applications. In 2014, we published a critical review on this topic, in which the exchange of metal ions, ligands, and guests was discussed in detail. In the past five years, much progress has been made and some new and important results were published, which significantly promoted the development of MOF chemistry. In this review, the exchange reactions of the two main components of MOFs, namely metal center ions and ligands, are summarized based on the new results since 2014. The influence factors and processes of the exchange reactions are firstly discussed for guiding the design of functional MOFs. The lately reported works on exchange reactions of MOFs classified into two groups with seven subgroups are then introduced. Finally, a perspective is given, expecting that the exchange reactions will play a more and more important role in exploring novel or functional MOFs for applications in the future.
In arid and semi-arid ecosystems, the biocrust serves as an important biological interface in the topsoil. Although the biocrust and vascular plant and soil are closely related, microbial diversity ...and functional characteristics in biocrusts of different vegetation communities and soil habitats, especially in watershed conditions, is poorly understood. In this study, biocrust samples were collected from two different soil substrate habitats, the loess and the aeolian sandy soil, as well as three plant communities consisting of Stipa bungeana, Artemisia ordosica, and Populus simonii, with the farmland soil acting as the control at the small watershed scale in the interlaced water and wind eroded area of Northern Shaanxi, China. To characterise the microbial diversity and functionality within biocrusts, a total of 4705 and 219 16S and 18S rDNA OTUs, respectively, were classified using high-throughput sequencing. Proteobacteria, Actinobacteria, and Bacteroidetes were dominant in prokaryotic community, whereas Ascomycota and Basidiomycota were dominant in fungal community in biocrusts. Principal coordinate analysis and hierarchical clustering demonstrated significant differences in prokaryotic and fungal communities between farmland soil and biocrusts, and soil parent materials could be a major factor in shaping the difference in the microbial communities of biocrusts relative to the vegetation types. Soil pH and carbon were dominant environmental factors that affected the prokaryotic and fungal communities in biocrusts. Hence, we demonstrated that the biocrust can significantly improve the topsoil properties in the study region, while their prokaryotic and fungal communities are largely determined by soil properties and environmental parameters.
•Biocrust microbiomes can influence dryland ecosystem biodiversity and functions.•Plant community and soil substrate can affect biocrust development and microbial community.•Soil parent materials largely shaped biocrust microbial communities under watershed condition on the Loess Plateau of China.
•Natural and anthropogenic uranium contaminations cause latent risks to public health.•We reviewed the major health risks upon natural uranium exposure.•Chemotoxicity of natural uranium is ...predominant for chronic exposure at the environmental low doses.•Recent advances in toxicological mechanisms involved in the chemotoxicity of uranium are comprehensively presented.
Uranium contamination is a global health concern. Regarding natural or anthropogenic uranium contamination, the major sources of concern are groundwater, mining, phosphate fertilizers, nuclear facilities, and military activities. Many epidemiological and laboratory studies have demonstrated that environmental and occupational uranium exposure can induce multifarious health problems. Uranium exposure may cause health risks because of its chemotoxicity and radiotoxicity in natural or anthropogenic scenarios: the former is generally thought to play a more significant role with regard to the natural uranium exposure, and the latter is more relevant to enriched uranium exposure. The understanding of the health risks and underlying toxicological mechanisms of uranium remains at a preliminary stage, and many controversial findings require further research. In order to present state-of-the-art status in this field, this review will primarily focus on the chemotoxicity of uranium, rather than its radiotoxicity, as well as the involved toxicological mechanisms. First, the natural or anthropogenic uranium contamination scenarios will be briefly summarized. Second, the health risks upon natural uranium exposure, for example, nephrotoxicity, bone toxicity, reproductive toxicity, hepatotoxicity, neurotoxicity, and pulmonary toxicity, will be discussed based on the reported epidemiological cases and laboratory studies. Third, the recent advances regarding the toxicological mechanisms of uranium-induced chemotoxicity will be highlighted, including oxidative stress, genetic damage, protein impairment, inflammation, and metabolic disorder. Finally, the gaps and challenges in the knowledge of uranium-induced chemotoxicity and underlying mechanisms will be discussed.
Being conductive and flexible, 2D transition metal nitrides and carbides (MXenes) can serve in Li–S batteries as sulfur hosts to increase the conductivity and alleviate the volume expansion. However, ...the surface functional groups, such as OH and F, weaken the ability of bare MXenes in the chemisorption of polysulfides. Besides, they create numerous hydrogen bonds which make MXenes liable to restack, resulting in substantial loss of active area and, thus, inaccessibility of ions and electrolyte. Herein, a facile, one‐step strategy is developed for the growth of TiO2 quantum dots (QDs) on ultrathin MXene (Ti3C2Tx) nanosheets by cetyltrimethylammonium bromide‐assisted solvothermal synthesis. These QDs act as spacers to isolate the MXene nanosheets from restacking, and preserve their 2D geometry which guarantees larger electrode–electrolyte contact area and higher sulfur loading. The stronger adsorption energy of polysulfides with TiO2 (than with Ti3C2Tx), as proven by density functional theory calculations, is essential for better on‐site polysulfide retention. The ultrathin nature and protected conductivity ensure rapid ion and electron diffusion, and the excellent flexibility maintains high mechanical integrity. In result, the TiO2 QDs@MXene/S cathode exhibits significantly improved long‐term cyclability and rate capability, disclosing a new opportunity toward fast and stable Li–S batteries.
TiO2 quantum dots (QDs) are grown on ultrathin MXene nanosheets by a facile, one‐step strategy through cetyltrimethylammonium bromide‐assisted solvothermal synthesis, resulting in TiO2 QDs@MXene nanohybrids that serve as a high‐performance sulfur host toward fast and stable Li–S batteries.
Hepatocytes, the major parenchymal cells in the liver, play pivotal roles in metabolism, detoxification, and protein synthesis. Hepatocytes also activate innate immunity against invading ...microorganisms by secreting innate immunity proteins. These proteins include bactericidal proteins that directly kill bacteria, opsonins that assist in the phagocytosis of foreign bacteria, iron-sequestering proteins that block iron uptake by bacteria, several soluble factors that regulate lipopolysaccharide signaling, and the coagulation factor fibrinogen that activates innate immunity. In this review, we summarize the wide variety of innate immunity proteins produced by hepatocytes and discuss liver-enriched transcription factors （e.g. hepatocyte nuclear factors and CCAAT/enhancer-binding proteins）, pro-inflammatory mediators （e.g. interleukin （IL）-6, IL-22, IL-lp and tumor necrosis factor-a）, and downstream signaling pathways （e.g. signal transducer and activator of transcription factor 3 and nuclear factor-KB） that regulate the expression of these innate immunity proteins. We also briefly discuss the dysregulation of these innate immunity proteins in chronic liver disease, which may contribute to an increased susceDtibilitv to bacterial infection in oatients with cirrhosis.
How parental histone (H3-H4)
tetramers, the primary carriers of epigenetic modifications, are transferred onto leading and lagging strands of DNA replication forks for epigenetic inheritance remains ...elusive. Here we show that parental (H3-H4)
tetramers are assembled into nucleosomes onto both leading and lagging strands, with a slight preference for lagging strands. The lagging-strand preference increases markedly in budding yeast cells lacking Dpb3 and Dpb4, two subunits of the leading strand DNA polymerase, Pol ε, owing to the impairment of parental (H3-H4)
transfer to leading strands. Dpb3-Dpb4 binds H3-H4 in vitro and participates in the inheritance of heterochromatin. These results indicate that different proteins facilitate the transfer of parental (H3-H4)
onto leading versus lagging strands and that Dbp3-Dpb4 plays an important role in this poorly understood process.
Carrier mobility is one of the key issues for applications of organic semiconductors in electronic and optoelectronic devices. Organic single crystals possess much higher carrier mobility compared to ...amorphous films. However, unipolar properties with unbalanced hole and electron transporting ability have been a bottleneck for the high performance of organic single crystal‐based devices. Here, well‐balanced ambipolar organic single crystals are developed by mixing of n‐ and p‐type molecules with maintained single‐crystalline structures. Carrier mobility of the ambipolar single crystals is manipulated by tuning the mixing ratio, and nearly equal hole and electron mobility can be achieved. Highly efficient single crystal‐based organic light‐emitting devices (OLEDs) are demonstrated by employing the ambipolar crystals as the mixed host for a red emitter pentacene to realize efficient exciton confinement and energy transfer within the emissive layer. As a result, maximum luminance of 5467 cd m−2 and current efficiency of 2.82 cd A−1 are achieved, which represents, to the best of the authors’ knowledge, the record performance for the organic single crystal‐based OLEDs to date. The strategy to manipulate the charge‐transport properties of the organic single crystals in this work represents a significant step toward practical applications of the organic single crystals in optoelectronics.
Well‐balanced ambipolar organic single crystals are developed by mixing n‐type BTPB and p‐type BSB‐Me molecules, and the hole and electron mobilities are manipulated to be nearly equal. Organic light‐emitting devices based on these ambipolar crystals exhibit a record luminance, current efficiency, and external quantum efficiency. The strategy to manipulate the charge‐transport properties of the organic single crystals in this work represents a significant step toward practical applications of the organic single crystals in optoelectronics.
PDF
