Natural gas (NG), whose main component is methane, is an attractive fuel for vehicular applications. Realization of safe, cheap and convenient means and materials for high-capacity methane storage ...can significantly facilitate the implementation of natural gas fuelled vehicles. The physisorption based process involving porous materials offers an efficient storage methodology and the emerging porous metal-organic frameworks have been explored as potential candidates because of their extraordinarily high porosities, tunable pore/cage sizes and easily immobilized functional sites. In this view, we provide an overview of the current status of metal-organic frameworks for methane storage.
Porous metal-organic frameworks have been emerging as very promising materials for methane (natural gas) storage.
Purely organic room-temperature phosphorescence has attracted attention for bioimaging but can be quenched in aqueous systems. Here we report a water-soluble ultralong organic room-temperature ...phosphorescent supramolecular polymer by combining cucurbitnuril (CB7, CB8) and hyaluronic acid (HA) as a tumor-targeting ligand conjugated to a 4-(4-bromophenyl)pyridin-1-ium bromide (BrBP) phosphor. The result shows that CB7 mediated pseudorotaxane polymer CB7/HA-BrBP changes from small spherical aggregates to a linear array, whereas complexation with CB8 results in biaxial pseudorotaxane polymer CB8/HA-BrBP which transforms to relatively large aggregates. Owing to the more stable 1:2 inclusion complex between CB8 and BrBP and the multiple hydrogen bonds, this supramolecular polymer has ultralong purely organic RTP lifetime in water up to 4.33 ms with a quantum yield of 7.58%. Benefiting from the targeting property of HA, this supramolecular polymer is successfully applied for cancer cell targeted phosphorescence imaging of mitochondria.
Zinc‐ion batteries (ZIBs) have been extensively investigated and discussed as promising energy storage devices in recent years owing to their low cost, high energy density, inherent safety, and low ...environmental impact. Nevertheless, several challenges remain that need to be prioritized before realizing the widespread application of ZIBs. In particular, the development of zinc anodes has been hindered by many challenges, such as inevitable zinc dendrites, corrosion passivation, and the hydrogen evolution reaction (HER), which have severely limited the practical application of high‐performance ZIBs. This review starts with a systematic discussion of the origins of zinc dendrites, corrosion passivation, and the HER, as well as their effects on battery performance. Subsequently, we discuss solutions to the above problems to protect the zinc anode, including the improvement of zinc anode materials, modification of the anode–electrolyte interface, and optimization of the electrolyte. In particular, this review emphasizes design strategies to protect zinc anodes from an integrated perspective with broad interest rather than a view with limited focus. In the final section, comments and perspectives are provided for the future design of high‐performance zinc anodes.
A systematic and detailed summary of the research progress on zinc ion battery anodes is presented, including the causes of zinc dendrites, corrosion passivation and hydrogen evolution reaction on zinc anodes along with the existing strategies. Perspectives are provided for the future design of high‐performance zinc anodes.
The resistance of breast cancer cells to drugs is a major obstacle to effective cancer chemotherapy. Here, we study the function mechanisms of long non‐coding RNA XIST in chemoresistance of breast ...cancer to doxorubicin. We examined the 50% inhibitive concentration of doxorubicin to MDA‐MB‐231 and MDA‐MB‐231/ADM cells, showing that the doxorubicin resistance of MDA‐MB‐231/ADM cells was much higher than MDA‐MB‐231 cells. The gene or protein expression of XIST and ANLN were also higher in MDA‐MB‐231/ADM cells than that in MDA‐MB‐231 cells. Moreover, XIST overexpression promoted cell proliferation and inhibited apoptosis of doxorubicin‐treated MDA‐MB‐231 cells by promoting ANLN expression. XIST silencing inhibited cell proliferation and promoted apoptosis of doxorubicin‐treated MDA‐MB‐231/ADM cells by inhibiting ANLN expression. Luciferase reporter assay showed that XIST functioned as a competing endogenous RNA to repress miR‐200c‐3p, which controlled its downstream target ANLN. In conclusion, these data reveal that XIST promotes chemoresistance of breast cancer cells to doxorubicin by sponging miR‐200c‐3p to upregulate ANLN. This work explores the relationship between lncRNA XIST and doxorubicin resistance in breast cancer cells and highlights a novel therapeutic target for the treatment of breast cancer.
Electrochemical water splitting is a critical energy conversion process for producing clean and sustainable hydrogen; this process relies on low‐cost, highly active, and durable oxygen evolution ...reaction/hydrogen evolution reaction electrocatalysts. Metal cations (including transition metal and noble metal cations), particularly high‐valence metal cations that show high catalytic activity and can serve as the main active sites in electrochemical processes, have received special attention for developing advanced electrocatalysts. In this review, heterogenous electrocatalyst design strategies based on high‐valence metal sites are presented, and associated materials designed for water splitting are summarized. In the discussion, emphasis is given to high‐valence metal sites combined with the modulation of the phase/electronic/defect structure and strategies of performance improvement. Specifically, the importance of using advanced in situ and operando techniques to track the real high‐valence metal‐based active sites during the electrochemical process is highlighted. Remaining challenges and future research directions are also proposed. It is expected that this comprehensive discussion of electrocatalysts containing high‐valence metal sites can be instructive to further explore advanced electrocatalysts for water splitting and other energy‐related reactions.
High‐valence metal cations, including transition metal and noble metal cations, exhibit high catalytic activity and serve as the main active sites in electrochemical processes. This review discusses the design strategies, advances, challenges, and future directions of heterogenous electrocatalysts based on high‐valence metal sites for the application of electrochemical water splitting.
Photocatalytic hydrogen production using semiconductors is identified as one of the most promising routes for sustainable energy; however, it is challenging to harvest the full solar spectrum in a ...particulate photocatalyst for high activity. Herein, a hierarchical hollow black TiO2/MoS2/CdS tandem heterojunction photocatalyst, which allows broad‐spectrum absorption, thus delivering enhanced hydrogen evolution performance is designed and synthesized. The MoS2 nanosheets not only function as a cost‐effective cocatalyst but also act as a bridge to connect two light‐harvesting semiconductors into a tandem heterojunction where the CdS nanoparticles and black TiO2 spheres absorb UV and visible light on both sides efficiently, coupling with the MoS2 cocatalyst into a particulate photocatalyst system. Consequently, the photocatalytic hydrogen rate of the black TiO2/MoS2/CdS tandem heterojunction is as high as 179 µmol h−1 per 20 mg photocatalyst under visible‐light irradiation, which is almost 3 times higher than that of black TiO2/MoS2 heterojunctions (57.2 µmol h−1). Most importantly, the stability of CdS nanoparticles in the black TiO2/MoS2/CdS tandem heterojunction is greatly improved compared to MoS2/CdS because of the formation of tandem heterojunctions and the strong UV‐absorbing effect of black TiO2. Such a tandem architectural design provides new ways for synthesizing particulate photocatalysts with high efficiencies.
A particulate hierarchical hollow black TiO2/MoS2/CdS tandem heterojunction photocatalyst is fabricated by using MoS2 nanosheets as a cost‐effective cocatalyst and most importantly as a bridge, which shows broad‐spectrum response, long‐term stability, and excellent photocatalytic hydrogen evolution performance.
Oxygen electrocatalysis, i.e., oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), plays an extremely important role in oxygen‐based renewable‐energy technologies such as ...rechargeable metal‐air batteries, regenerative fuel cells and water splitting. Perovskite oxides have recently attracted increasing interest and hold great promise as efficient ORR and OER catalysts to replace noble‐metal‐based catalysts, owing to their high intrinsic catalytic activity, abundant variety, low cost, and rich resources. The introduction of perovskite‐carbon interfaces by forming perovskite/carbon composites may bring a synergistic effect between the two phases, thus benefiting the oxygen electrocatalysis. This review provides a comprehensive overview of recent advances in perovskite/carbon composites for oxygen electrocatalysis in alkaline media, aiming to provide insights into the key parameters that influence the ORR/OER performance of the composites, including the physical/chemical properties and morphologies of the perovskites, the multiple roles of carbon, the synthetic method and the synergistic effect. A special emphasis is placed on the origin of the synergistic effect associated with the interfacial interaction between the perovskite and the carbon phases for enhanced ORR/OER performance. Finally, the existing challenges and the future directions for the synthesis and development of more efficient oxygen catalysts based on perovskite/carbon composites are proposed.
A comprehensive review of recent developments of perovskite/carbon composites for oxygen electrocatalysis in alkaline media is provided, aiming to offer insights into key parameters that influence the ORR/OER performance and the origin of synergistic effect associated with the interfacial interaction in the composites. The existing challenges and future perspectives are also presented.
The development of clean and renewable energy materials as alternatives to fossil fuels is foreseen as a potential solution to the crucial problems of environmental pollution and energy shortages. ...Hydrogen is an ideal energy material for the future, and water splitting using solar/electrical energy is one way to generate hydrogen. Metal‐organic frameworks (MOFs) are a class of porous materials with unique properties that have received rapidly growing attention in recent years for applications in water splitting due to their remarkable design flexibility, ultra‐large surface‐to‐volume ratios and tunable pore channels. This review focuses on recent progress in the application of MOFs in electrocatalytic and photocatalytic water splitting for hydrogen generation, including both oxygen and hydrogen evolution. It starts with the fundamentals of electrocatalytic and photocatalytic water splitting and the related factors to determine the catalytic activity. The recent progress in the exploitation of MOFs for water splitting is then summarized, and strategies for designing MOF‐based catalysts for electrocatalytic and photocatalytic water splitting are presented. Finally, major challenges in the field of water splitting are highlighted, and some perspectives of MOF‐based catalysts for water splitting are proposed.
Metal‐organic frameworks (MOFs) as a class of porous materials have received growing attention these years for their applications in catalyzing the electrocatalytic and photocatalytic water splitting reactions. Recent progress in the exploitation of MOFs toward water splitting reactions is reviewed with highlights in the rational design of highly efficient MOF‐based catalysts. The perspectives for future research are also outlined.
A series of macrocyclic compounds, including crown ether, cyclodextrin, cucurbituril and pillararene, bound to various specific organic/inorganic/biological guest molecules and ions through various ...non-covalent interactions, can not only make a single system multifunctional but also endow the system with intelligence, especially for luminescent materials. Due to their excellent luminescence properties, such as long-lived excited states, sharp linear emission bands and large Stokes shift, lanthanides have shown great advantages in luminescence, and have been more and more applied in the design of advanced functional luminescent materials. Based on reported research, we summarize the progress of lanthanide luminescent materials based on different macrocyclic compounds from ion or molecule recognition to functional nano-supramolecular assembly of the lanthanide-macrocycle supramolecular system including photo-reaction mediated switch of lanthanide luminescent molecules, multicolor luminescence, ion detection and cell imaging of rare-earth up-conversion of macrocyclic supramolecular assembly. Finally, we put forward the prospects of future development of lanthanide luminescent macrocyclic supramolecular materials.
Macrocyclic compounds, including crown ether, cyclodextrin, cucurbituril and pillararene, bound to various specific guest molecules through various non-covalent interactions, can make the system multifunctional and endow system with intelligence.
Tail dependence networks of global stock markets Wen, Fenghua; Yang, Xin; Zhou, Wei‐Xing
International journal of finance and economics,
January 2019, 2019-01-00, 20190101, Volume:
24, Issue:
1
Journal Article
Peer reviewed
Open access
The Pearson correlation coefficient is used by many researchers to construct complex financial networks. However, it is difficult to capture the structural characteristics of financial markets that ...have extreme fluctuations. To solve this problem, we resort to tail dependence networks. We first build the edge information of the stock network by adopting Pearson's correlation coefficient and the symmetrized Joe–Clayton copula model, respectively. By using the planar maximally filtered graph method, we filter the edge information, obtain Pearson's correlation coefficient and tail dependence network, and compare their efficiencies. The community structure of the constructed networks is investigated. We find that the global efficiency of tail‐dependent networks is higher than that of the Pearson correlation networks. Further analysis of the nodes in the upper‐ and lower‐tail dependence networks reveals that the European markets are more influential than Asian and African markets during a booming market and a recession market. In addition, different cliques are found in the two tail dependence networks. The finding indicates that financial risks will impact geographically adjacent markets.
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