Crystalline and porous covalent organic frameworks (COFs) and metal‐organic frameworks (MOFs) materials have attracted enormous attention in the field of photocatalytic H2 evolution due to their ...long‐range order structures, large surface areas, outstanding visible light absorbance, and tunable band gaps. In this work, we successfully integrated two‐dimensional (2D) COF with stable MOF. By covalently anchoring NH2‐UiO‐66 onto the surface of TpPa‐1‐COF, a new type of MOF/COF hybrid materials with high surface area, porous framework, and high crystallinity was synthesized. The resulting hierarchical porous hybrid materials show efficient photocatalytic H2 evolution under visible light irradiation. Especially, NH2‐UiO‐66/TpPa‐1‐COF (4:6) exhibits the maximum photocatalytic H2 evolution rate of 23.41 mmol g−1 h−1 (with the TOF of 402.36 h−1), which is approximately 20 times higher than that of the parent TpPa‐1‐COF and the best performance photocatalyst for H2 evolution among various MOF‐ and COF‐based photocatalysts.
Effective separation: A novel MOF/COF hybrid material assembled by covalent connecting two components, exhibits effective visible‐light‐driven photocatalytic H2 evolution due to the ideal band matching and effectively promoting the separation of the photogenerated charges and holes.
Nanomoulding with amorphous metals Tang, Hong X; Schroers, Jan; Kumar, Golden
Nature (London),
02/2009, Letnik:
457, Številka:
7231
Journal Article
Recenzirano
Nanoimprinting promises low-cost fabrication of micro- and nano-devices by embossing features from a hard mould onto thermoplastic materials, typically polymers with low glass transition temperature. ...The success and proliferation of such methods critically rely on the manufacturing of robust and durable master moulds. Silicon-based moulds are brittle and have limited longevity. Metal moulds are stronger than semiconductors, but patterning of metals on the nanometre scale is limited by their finite grain size. Amorphous metals (metallic glasses) exhibit superior mechanical properties and are intrinsically free from grain size limitations. Here we demonstrate direct nanopatterning of metallic glasses by hot embossing, generating feature sizes as small as 13 nm. After subsequently crystallizing the as-formed metallic glass mould, we show that another amorphous sample of the same alloy can be formed on the crystallized mould. In addition, metallic glass replicas can also be used as moulds for polymers or other metallic glasses with lower softening temperatures. Using this 'spawning' process, we can massively replicate patterned surfaces through direct moulding without using conventional lithography. We anticipate that our findings will catalyse the development of micro- and nanoscale metallic glass applications that capitalize on the outstanding mechanical properties, microstructural homogeneity and isotropy, and ease of thermoplastic forming exhibited by these materials.
Magnon dark modes and gradient memory Zhang, Xufeng; Zou, Chang-Ling; Zhu, Na ...
Nature communications,
11/2015, Letnik:
6, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Extensive efforts have been expended in developing hybrid quantum systems to overcome the short coherence time of superconducting circuits by introducing the naturally long-lived spin degree of ...freedom. Among all the possible materials, single-crystal yttrium iron garnet has shown up recently as a promising candidate for hybrid systems, and various highly coherent interactions, including strong and even ultrastrong coupling, have been demonstrated. One distinct advantage in these systems is that spins form well-defined magnon modes, which allows flexible and precise tuning. Here we demonstrate that by dissipation engineering, a non-Markovian interaction dynamics between the magnon and the microwave cavity photon can be achieved. Such a process enables us to build a magnon gradient memory to store information in the magnon dark modes, which decouple from the microwave cavity and thus preserve a long lifetime. Our findings provide a promising approach for developing long-lifetime, multimode quantum memories.
Influenza A virus （IAV） infects the respiratory tract in humans and causes significant morbidity and mortality worldwide each year. Aggressive inflammation, known as a cytokine storm, is thought to ...cause most of the damage in the lungs during IAV infection. Dysfunctional coagulation is a common complication in pathogenic influenza, manifested by lung endothelial activation, vascular leak, disseminated intravascular coagulation and pulmonary microembolism. Importantly, emerging evidence shows that an uncontrolled coagulation system, including both the cellular （endothelial cells and platelets） and protein （coagulation factors, anticoagulants and fibrinolysis proteases） components, contributes to the pathogenesis of influenza by augmenting viral replication and immune pathogenesis. In this review, we focus on the underlying mechanisms of the dysfunctional coagulatory response in the Dathogenesis of IAV.
Command-and-control environmental regulation is a traditional environmental policy that is still widely used in developing countries. This study examined a rarely discussed but significant issue for ...environmental sustainability and economic development—the impact of command-and-control environmental regulation on enterprise total factor productivity growth—based on a large enterprise-level sample. Employing China’s “Two Control Zone” policy as a quasi-natural experiment, we used a Chinese industrial enterprise panel dataset from 1998 to 2007 to estimate the effects of command-and-control environmental regulation in a difference-in-difference framework. It is found that command-and-control environmental regulation hassignificantly hindered the growth of enterprise total factor productivity, and this negative effect was lagging and continuous. In addition, we leaned that this negative effect mainly came from the increase in costs of enterprises and the negative impact on the enterprise resource allocation efficiency. When considering enterprise heterogeneity in terms of pollution intensity, size, and ownership, the study further found that the negative effects are exacerbated for enterprises in more heavily polluting industries, those of smaller size, and those owned by foreign companies, respectively. Our research is a reexamination of the Porter hypothesis in China, and fills the gap in the literature on the micro effects of command-and-control policy on enterprise total factor productivity for developing countries. Based on a rigorous empirical analysis, we conclude that it is difficult to achieve a win–win scenario with sustainable environmental development and enterprise total factor productivity growth under command-and-control environmental regulation. Environmental regulations should have clear objectives and take a flexible approach, and it is necessary to adopt diversified environmental regulation policies based on market instruments.
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•Command-and-control environmental regulation hindered the enterprise TFP growth.•Increasing cost and lower resource allocation efficiency are main influence channels.•TFP of heavily polluted enterprise is more hindered than lightly polluted enterprise.•TFP of small enterprise is more inhibited by TCZ policy than large enterprise.•TFP of foreign enterprises is more hindered by TCZ policy than domestic enterprise.
Covalent‐organic frameworks (COFs) have been recognized as a new type of promising photocatalysts for hydrogen evolution. To investigate how different functional groups attached in the backbone of ...COFs affect the overall photocatalytic H2 evolution, for the first time, we selected and synthesized a series of ketoenamine‐based COFs with the same host framework as model system. It includes TpPa−COF−X (X=−H, −(CH3)2, and −NO2) with three different groups attached in the backbone of TpPa−COF. We systematically investigated the differences in morphology, light‐absorption intensity and band gap of these 2D COFs. The results of photocatalytic H2 evolution measurements indicate that the TpPa−COF−(CH3)2 shows the best activity, while the activity of TpPa−COF−NO2 is relatively low compared to that of other two COFs in the system. Moreover, the separation ability of photogenerated charge was also followed the order of TpPa−COF−(CH3)2>TpPa−COF>TpPa−COF−NO2. The best photocatalytic H2 production performance of TpPa−COF−(CH3)2 in these systems should be mainly attributed to the better electron‐donating ability of −CH3 groups compared to −H or −NO2 group, which result in more efficient charge transferring in the inner of the material. This work demonstrates that reasonably adding electron‐donating group in TpPa−COFs can lead to a better photocatalytic H2 evolution activity, and which is meaningful for further design of efficient COF‐based photocatalysts for H2 evolution.
Photocatalysis: A series ketoenamine‐based COFs of TpPa−COF−X (X=−H, −(CH3)2, and −NO2) exhibit significant difference on the visible light absorbance and efficiency of photocatalytic H2 evolution, which can be attributed to strengthen charge carrier mobilities both in‐plane and in the stacking direction because of the electron‐donating groups.
A novel niobium oxyiodate sulfate, Nb2O3(IO3)2 (SO4), was fabricated by a rational multi‐component design under moderate hydrothermal conditions. This multi‐component design is inspired by an ...interesting niobium oxysulfate reaction, which opens a new door for synthetic method to effectively introduce refractory metals such as Nb into crystal structures by hydrothermal synthesis. Nb2O3(IO3)2(SO4) features a cube‐like topological structure with a large phase‐matching second harmonic generation (SHG) response (6×KDP), a wide transparency window (0.38–8 μm), and a high laser damage threshold (LDT) (20×AgGaS2). It has the highest thermostability (stable up to 580 °C under air) among reported non‐centrosymmetric (NCS) iodates and sulfates and is stable in water and even concentrated H2SO4. Furthermore, Nb2O3(IO3)2(SO4) is a unique nonlinear optical (NLO) material among iodates and sulfates, because its SHG effect is mainly caused by the MO6 units rather than the IO3 or SO4 units, which is demonstrated by density functional theory (DFT) calculations.
Oh my‐obium! The synthesis of crystalline Nb2O3(IO3)2(SO4) under moderate hydrothermal conditions is reported. The highly thermostable crystal features a strong second‐harmonic‐generation response, a wide transparency window, and a high laser damage threshold.
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