Search

Hypereutectic Al-Si-Cu coatings were prepared by supersonic atmospheric plasma spraying to enhance the surface performance of lightweight alloys. To find out optimum process conditions and achieve desirable coatings, this work focuses on the influence of three important parameters (in-flight particle temperature, impact velocity, and substrate temperature) on the collected splats morphology, coatings microstructure and microhardness. Results show that appropriate combinations of temperature and velocity of in-flight particles cannot only completely melt hypereutectic Al-Si-Cu particles, especially the primary Si phase, but also provide the particles with sufficient kinetic energy. Thus, the optimized coating consists of 98.6 % of fully-melted region with nanosized coupled eutectic and 0.9 % of porosity. Increasing the substrate deposition temperature promotes the transition from inhomogeneous banded microstructure to homogeneous equiaxed microstructure with a lower porosity level. The observations are further interpreted by a newly developed phase-change heat transfer model on quantitatively revealing the solidification and remelting behaviors of several splats deposited on substrate. Besides, phase evolutions including the formation of supersaturated α-Al matrix solid solution, growth of Si and Al2Cu phases at different process conditions are elaborated. An ideal microstructure (low fractions of unmelted/partially-melted regions and defects) together with solid solution, grain refinement, and second phase strengthening effects contributes to the enhanced microhardness of coating. This integrated study not only provides a framework for optimizing Al-Si based coatings via thermal spraying but also gives valuable insights into the formation mechanisms of this class of coating materials.

In order to improve mechanical properties of 6082 aluminum alloy, the SiCp/Al 6082 composites were prepared by the addition of the micron-sized SiC particles combined with the squeeze casting. The effects of the SiCp content and squeeze casting on the microstructure and mechanical properties of the 6082 aluminum alloy were investigated by SEM, EDS, TEM, tensile testing and hardness testing analysis methods. Research results exhibited that the SiCp content and squeeze casting had a significant impact on the microstructure and mechanical properties of the 6082 aluminum alloy. The addition of the SiCp refined the grain size of the 6082 aluminum alloy while caused the increase of the porosity with increasing the SiCp content, especially in the permanent mold casting condition. Compared to the permanent mold casting, the squeeze casting obviously reduced pore defects, refined grain size and made the SiCp distribute evenly as well as bond tightly with the Al matrix. The tensile strength, yield strength, elongation, elastic modulus and hardness of the 6082 aluminum alloy obtained with the SiCp and squeeze casting were remarkably improved, and the optimal mechanical properties were obtained with a 2 wt.% SiCp, and they increased 10.73 %, 72.7 %, 193.9 %, 23.5 % and 25.2 %, respectively, compared to those of the 6082 aluminum alloy obtained without SiCp and squeeze casting. The fracture surface of the SiCp/Al 6082 composites obtained with the squeeze casting was dense and exhibited a ductile fracture mode.

Donor-acceptor co-doped rutile TiO2 ceramics with colossal permittivity (CP) have been extensively investigated in recent years due to their potential applications in modern microelectronics. In addition to CP and low dielectric loss, voltage stability is an essential property for CP materials utilized in high-power and high-energy density storage devices. Unfortunately, the voltage stability of CP materials based on co-doped TiO2 does not catch enough attention. Here, we propose a strategy to enhance the voltage stability of co-doped TiO2, where different ionic defect clusters are formed by two acceptor ions with different radii to localize free carriers and result in high performance CP materials. The (Ta + Al + La) co-doped TiO2 ceramic with suitable La/Al ratio exhibits colossal permittivity with excellent temperature stability as well as outstanding dc bias stability. The density functional theory analysis suggests that L a 3 + A l 3 + V O • • T i 3 + defect clusters and Ta5+-Al3+ pairs are responsible for the excellent dielectric properties in (Ta + Al + La) co-doped TiO2. The results and mechanisms presented in this work open up a feasible route to design high performance CP materials via defect engineering.

Catalysts of Ni supported on home-made mesoporous alumina (Ni/M-Al2O3) were prepared via facile incipient impregnation method and calcined under different temperature (500–800 °C). Compared with catalysts of Ni supported on commercial alumina, they showed much higher conversion and lower carbon deposition in methane dry reforming (DRM). Among the catalysts, Ni/M-Al2O3-700 exhibited the highest DRM activity, with 77.6% CH4 conversion and 85.4% CO2 conversion at 700 °C. TPR revealed that almost all the Ni was in the form of NiAl2O4 spinel after calcination at 700 °C. Due to the strong metal-support interaction of NiAl2O4 structure, the Ni crystal size of Ni/M-Al2O3-700 after reduction was around 5 nm. TGA and TEM results showed its carbon deposition after 20 h DRM test was only 3.8% and mainly in the form of amorphous carbon. This work indicates that the formation of NiAl2O4 spinel is beneficial to activity and stability towards DRM reaction and controlling calcination temperature is crucial.

Catalysts/co-catalysts for cathodic oxygen reduction and anodic methanol oxidation reactions (ORR/MOR) play the major roles in promoting the commercialization of direct methanol fuel cells. Herein, bimetallic zeolite-imidazolate-frameworks (CoZn-ZIFs) is used as precursor to synthesize Co3O4@NPC/CuO composites as catalysts for ORR and Pt supports/co-catalysts for MOR. The ORR activity (E1/2 = 0.83 V) and long-term stability (activity retention of 85.5% after 30,000 s) of Co3O4@NPC/CuO-400 (400 °C) dodecahedron are better than those of commercial Pt/C (10 wt%) in alkaline electrolytes. The surface CuO with variable valence states (Cu0 and Cu2+) can be used as both the active component for ORR and the protective layer for Co3O4 to enhance catalytic stability. Partial removal of CoOx from carbon framework promotes the exposure of highly active sites (Co2+) on the Co3O4. For MOR, the mass activity of Pt-Co3O4@NPC/CuO-400 (5 wt%) (1947 mA mgPt−1) is much higher than that of Pt/C (751 mA mgPt−1), mainly attributing to that the Pt active sites are uniformly dispersed on Co3O4@NPC/CuO support. The strong interaction between Pt and CuO can reduce the bond strength of Pt-CO to enhance CO resistance. Co3O4 can activate H2O molecules to provide sufficient OH− species to promote MOR. This study provides a new idea for preparation of active ORR catalysts and MOR co-catalyst from bimetallic ZIFs.

We report the synthesis and characterization of a new water-soluble cavitand 1. The container features 2-aminobenzimidazole panels at the "rim" and pyridiniums at the "feet". In the solid state, a single-crystal X-ray structure of the organic-soluble precursor 2 showed a stable vase form. The structure is stabilized by hydrogen-bonded bridges between adjacent panels through solvents and ions. In aqueous solution, binding of hydrophobic and amphiphilic guest molecules to 1 was investigated using 1H NMR. Alkanes, alcohols, acids, diols, and diacids formed 1:1 host-guest complexes, and the guest conformations were deduced from characteristic chemical shift changes. In the presence of [Pd(ethylenediamine)(H2O)2·2NO3], cavitand 1 formed a complex incorporating two metals. The metal-coordinated cavitand also bound hydrophobic linear alkanes and difluorobenzene isomers in aqueous medium. The metallo-cavitand showed shape and size selectivity and was used to separate o-difluorobenzene from its isomers as observed by 19F NMR spectroscopy. The primary amino function of the cavitands offers possibilities for further elaboration to covalent clusters of these container compounds.

Anion redox chemistry plays a crucial role in Na-deficient or Na-rich oxide cathodes for sodium-ion batteries (SIBs). But the oxygen redox chemistry has been rarely reported in O3-type (Na-full) layered oxides for SIBs. Herein, we reveal the anion redox chemistry in O3-type NaMn1/3Fe1/3Ni1/3O2 (MFN) cathode material, and propose an integrated strategy combining ZrO2 coating and Zr4+ doping to tune the anionic redox chemistry and crystal structures which improves the activity, reversibility, and stability of O2−. Oxygen redox reactions with high reversibility and cyclic stability mainly occur between 4.0 V and 4.3 V. The structure of Na-O-TM is regulated by Zr4+ doping, and the electronic state of O-2p occupies a higher energy level by the regulation of Na-O-TM structure. The electrons can migrate from O2- more easily and O2−/O− contribute more capacity. Zr4+ doping optimizes the lattice structure, enlarges the Na layer, and decreases TMO2 layer, which reduces the diffusion resistance of Na+ and increases the structural stability. ZrO2 layer effectively mitigates the corrosion of the electrolyte and ensures the integrity of the structure, which inhibits the formation of Na2CO3 on the surface and decreases CO2 release. This study not only reveals the anion redox chemistry in O3-type layered oxide cathode material but also is available for insights into regulating the redox activity, reversibility, and stability of oxygen.

Carbon-molybdenum disulfide (C-MoS2) ultrathin nanosheets were prepared by a hydrothermal process, and then AgI/C-MoS2 were synthesized via an in-situ deposition method. This ternary heterojunction composite exhibited better photocatalytic activity compared with those of one-component (pristine MoS2) and bicomponent (AgI/MoS2 and C-MoS2) materials for the degradation of organic dyes under the visible-light irradiation. In particular, by comparing with AgI/MoS2, the significant role of conductive amorphous carbon in AgI/C-MoS2 in enhancing the charge transfer during the photocatalytic degradation of dyes was first confirmed by photocurrent response and electrochemical impedance spectroscopy (EIS). A possible photocatalytic mechanism was proposed based on the capture experiment results. Furthermore, a straightforward and interesting way had been applied to test the recycled/newly-prepared AgI/C-MoS2 composite for revealing its distinctive self-cleaning performance and recyclability characteristic besides its good photocatalytic activity. This work could provide a reference for the design of other new ternary heterojunction composite materials with special structures and properties.

Bone mineral consists of calcium hydroxy-carbonate apatite (HCA) that incorporates other minor cation substituents, primarily Na+ (0.5–0.8 wt %). We examine the carbonate species in various HCA spe...

Oxygen release and irreversible cation migration are the main causes of voltage fade in Li-rich transition metal oxide cathode. But their correlation is not very clear and voltage decay is still a bottleneck. Herein, we modulate the oxygen anionic redox chemistry by constructing Li2ZrO3 slabs into Li2MnO3 domain in Li1.21Ni0.28Mn0.51O2, which induces the lattice strain, tunes the chemical environment for redox-active oxygen and enlarges the gap between metallic and anionic bands. This modulation expands the region in which lattice oxygen contributes capacity by oxidation to oxygen holes and relieves the charge transfer from anionic band to antibonding metal–oxygen band under a deep delithiation. This restrains cation reduction, metal–oxygen bond fracture, and the formation of localized O2 molecule, which fundamentally inhibits lattice oxygen escape and cation migration. The modulated cathode demonstrates a low voltage decay rate (0.45 millivolt per cycle) and a long cyclic stability., Voltage fade is a critical issue for Li-rich transition metal oxide cathode. Here, the authors modulate the oxygen anionic redox chemistry and enlarges the gap between metallic and anionic states by constructing Li2ZrO3 slabs into Li2MnO3 domain in Li1.21Ni0.28Mn0.51O2 which fundamentally suppresses the voltage decay.

P2-type Na0.67Mn0.75Fe0.25O2 cathode materials with low cost and high specific capacity have aroused much interest for sodium-ion batteries. Nevertheless, the cyclic and structural stabilities need...

The argon power cycle is one of the most promising technologies for high efficiency and low emission hydrogen-fueled internal combustion engines. The application of coaxial injection technology in the hydrogen-fueled argon engine can improve the mixing process and the combustion performance of the H2/O2 mixture. In this study, an innovative H2–O2 coaxial injection combustion system was designed to investigate the jet flame characteristics of oxygen coaxially wrapped by hydrogen in a controllable argon thermal atmosphere. The findings of this study could provide a new perspective for designing hydrogen-fueled argon engines in the future. The influences of co-flow temperature, jet injection pressure, and excess oxygen coefficient were all determined. Observations of the flame showed a bright blue flame with a reddish glow in the far-burner region. Experimental results show that the flame length, cross-sectional area, and area/perimeter ratio first decrease with increasing jet injection pressure and subsequently increase, reaching maximum values at 0.4–0.6 MPa. When increasing the co-flow temperature from 1023 K to 1223 K, the cross-sectional area of the flame increases significantly by 61.1% at an excess oxygen coefficient of 0.4. Furthermore, the liftoff flame height shrinks when the co-flow temperature and the excess oxygen coefficient increase, while it rises along with an increasing jet injection pressure.

The bionic porous zirconia fiber was prepared by the microemulsion electrospinning method. The phase, morphology and pore structure of the fibers were tested by X-ray diffraction, FTIR, RAMAN, SEM, TEM, and BET. The results show that the fiber was t-ZrO2 phase and its average fiber diameter was about 120 nm. There was obvious multi-cavity hollow structure like the polar bear hair in the zirconia fiber. The BET specific surface area and BJH average pore diameter of the fiber was 23.8 m2/g, and 11 nm, respectively. As a result, the bionic porous zirconia fiber had low thermal conductivity of 0.075 W/m k and low infrared emissivity of 0.598 at 3–5 μm. Therefore, the bionic porous zirconia fiber could be used as infrared stealth material.

By increasing the charging voltage, a cell specific energy of >400 W h kg−1 is achievable with LiNi0.8Mn0.1Co0.1O2 in Li metal batteries. However, stable cycling of high-nickel cathodes at ultra-high voltages is extremely challenging. Here we report that a rationally designed sulfonamide-based electrolyte enables stable cycling of commercial LiNi0.8Co0.1Mn0.1O2 with a cut-off voltage up to 4.7 V in Li metal batteries. In contrast to commercial carbonate electrolytes, the electrolyte not only suppresses side reactions, stress-corrosion cracking, transition-metal dissolution and impedance growth on the cathode side, but also enables highly reversible Li metal stripping and plating leading to a compact morphology and low pulverization. Our lithium-metal battery delivers a specific capacity >230 mA h g−1 and an average Coulombic efficiency >99.65% over 100 cycles. Even under harsh testing conditions, the 4.7 V lithium-metal battery can retain >88% capacity for 90 cycles, advancing practical lithium-metal batteries. Charging at high voltages in principle makes batteries energy dense, but this is often achieved at the cost of the cycling stability. Here the authors design a sulfonamide-based electrolyte to enable a Li metal battery with a state-of-the-art cathode at an ultra-high voltage of 4.7 V while maintaining cyclability.

Metalorganic hydrides are a new class of hydrogen storage materials. Replacing the H of N–H or O–H functional groups using metal hydrides have been recently reported, which substantially improved the dehydrogenation properties of heteroaromatic organic hydrides by lowering their enthalpies of dehydrogenation (ΔHd), enabling dehydrogenation at much lower temperatures. Among the reported metalorganic hydrides, lithium carbazolide and sodium carbazolide appear to be the most attractive hydrogen storage/delivery material owing to its high hydrogen capacity (>6.0 wt%) and ideal ΔHd. Nevertheless, the interaction of carbazole and corresponding metal hydride to form metallo-carbazolide is a multistep process involving intensive ball milling and high temperature treatment, where the interaction was not investigated in detail. In this paper, both alkali metal hydrides and amides were employed to react with carbazole to synthesize corresponding carbazolides, aiming to broaden and optimize the synthetic method and understand the reaction mechanism. Our experimental results showed that around one equivalent of H2 or NH3 could be released from the reactions of carbazole and corresponding hydrides or amides, respectively. Instrumental spectroscopic analyses proved that metallo-carbazolides were successfully synthesized from all precursors. It is found that the alkali metal amides (i.e., LiNH2 and NaNH2) with stronger Lewis basicities as metal precursors could synthesize the metallo-carbazolides under milder conditions. Furthermore, quasi in situ nuclear magnetic resonance results revealed that alkali metal could replace H (H–N) gradually, donating more electrons to carbazole ring. Additionally, the solubilized alkali cation may unselectively interact with π-electron of aromatic systems of both carbazole molecules and carbazolide anions via electrostatic cation-π interactions.

To investigate the mutual effect of hydrogen, microstructures and stress concentration on the fatigue failure, fatigue behaviors of X65 steel welded joints in both air and saturated H2S solution were investigated at high cycle regime. The experimental result demonstrates that due to lower dislocation density observed by electron backscattered diffraction (EBSD), the fine grain heat affected zone (FGHAZ) is prone to induce cyclic strain localization and further lead to fatigue crack propagating along the FGHAZ in air. Furthermore, the quasi-cleavage with brittle-like fatigue striations and secondary crack on the fracture surface in saturated H2S solution is attributed to hydrogen embrittlement. Moreover, compared with base metal (BM) and FGHAZ, the weld metal (WM) and coarse grain heat affected zone (CGHAZ) are composed of bainite and martensite/austenite (M/A) phase, and more sensitive to hydrogen. Therefore, the fatigue crack is prone to grow along the interface between WM and CGHAZ under the normal applied stress.

Lithium-metal batteries (LMBs) are promising electrochemical energy storage devices with high energy densities. However, the extreme reactivity of metallic lithium, the large volumetric change of the electrode during cycling, and the notorious dendrite formation issues lead to low cyclic stability and safety concerns, hindering the practical application of LMBs. In particular, the intrinsic tendency of uneven lithium deposition and the large internal electrode stress lead to the piecing of solid electrolyte interphases (SEIs), thereby resulting in fast decay of the anode. We develop a facile laser processing technique to fabricate laser-structured copper foils (LSCFs) that are able to regulate the lithium deposition kinetics and increase the cycle life of LMBs. By simply scribing commercial foils using a 355 nm laser, microstructural features with fish-scale patterns are obtained. The lithium deposition follows a drastically different mode on the LSCF compared with commercial planar copper foils which relieves the internal stress of lithium and prohibits the piecing of SEI. A high Coulombic efficiency of >96% of the lithium metal anode is maintained for over 100 cycles on the LSCF at a current density of 1 mA cm-2 and an areal capacity of 1 mAh cm-2 while the benchmark decayed to below 80% after 50 cycles. Full cells based on LiFePO4 cathodes display a reasonable specific capacity of 125 mAh g-1 over 300 cycles at a rate of 1 C. This work provides a fast yet effective laser-based approach to construct highly stable lithium metal anodes.

The effects of solid carbon on NO electrocatalytic reduction in the presence of O2 content, as low as can be found in a gasoline engine, were investigated. Tubular solid-state fuel cells filled with Fe-loaded carbon materials (Fe-loaded activated carbon, Fe-AC, and Fe-loaded carbon black, Fe-BC) were fabricated for electrochemical reduction in the configuration of LSM as the cathode, NiO-YSZ mixed powder as the anode, and YSZ as the electrolyte. A moderate NO removal efficiency of 60% and maximum peak power density of 0.035 W cm−2 were achieved for Fe-AC in the presence of 1% O2, whereas no such performances were detected in the case of AC. Following TGA-MS and in-situ analyses of exit gases from the anodes, it can be concluded that Fe-loaded carbon materials promote CO formation in Boudouard reactions by utilizing excess oxygen transported from the cathode, which is capable of alleviating the impact of oxygen on NO removal while also enhancing electrical performance. The formation of CO contributes to the reduction of both concentration polarization loss and activation polarization loss at both electrodes.

Magnetic liquid metal is regarded as a promising material due to its integration of fluidic, metallic, and magnetic properties simultaneously. Previously, few methods of fabricating magnetic liquid metal have been proposed. However, either the alloying reaction inside the matrix or the poor performance in electrical and thermal conduction is troublesome in practical applications. Here, inspired by the mussel in nature, polydopamine is introduced to in situ reduce and immobilize silver shells on the surface of iron particles, and then the modified particles mix with liquid metal to prepare liquid metal-based magnetic suspensions (LMMSs). The silver shells can prevent iron particles from alloying with liquid metal and enhance the electrical and thermal conductivities of the LMMS concurrently. Besides, the LMMS thus obtained can keep its magnetism intact for a long period, at least during the 60 days of the test. Compared to directly mixing bare iron particles with liquid metal, the maximum electrical conductivities increase by at least 13.69% and the thermal conductivities increase by almost 4 times in the LMMS. The LMMS also exhibits potential applications in patterning and magnetic manipulation. This work puts forward a new strategy for preparing a LMMS with appealing properties and its broad applications are expected in the future.

Reduction of alkyl dihalide guests (2-5 and 7) with trialkylsilanes (R3 SiH) was performed in water-soluble host 1 to investigate the effects of confinement on fast radical reactions (k≥103 m-1 s-1 ). High selectivity (>95 %) for mono-reduced products was observed for primary and secondary dihalide guests under mild conditions. The results highlight the importance of host-guest complexation rates to modulate the product selectivity in radical reactions.

Surface enhanced Raman spectroscopy (SERS) is a promising sensing technique that can provide unique chemical and structural fingerprint information, but gaining reliable SERS quantitative data with high sensitivity and stability still remains a challenge. Although using a molecule as an internal standard (IS) can improve the SERS quantitative capability, the reliability and SERS measuring conditions for signal fluctuations during calibration based on IS are yet to be explored when the embedded IS molecules and target objects are located in different environments. Herein, a 3D hotspot matrix SERS platform based on Au@4-MPy@AgNPs was constructed in water with the assistance of glycerol and the dynamic signal changes from the IS, i.e. 4-Mpy, and target molecules were monitored during the process of evaporation with high sensitivity and stability. In contrast to the traditional water-dispersed drying film system, the variation trends of IS and target molecules were consistent in the glycerol-assisted liquid film protection system. Therefore, it is reasonable to calibrate the signal fluctuation by utilizing the embedded IS based on the construction strategy of a glycerol-assisted 3D hotspot platform. This work demonstrates a rational, reliable and precise SERS quantitative technique for testing analyte concentrations in practical systems and has great application prospects in the field of analytical chemistry.

Establishing a fast and effective extraction method for herbs is beneficial for the determination of their main compounds and estimating their quality. In this study, deep eutectic solvents (DESs) were optimized to simultaneously extract three main types of phenolic acids, i.e., regaloside B, regaloside C, and regaloside E, and polysaccharides from the bulbs of Lilium lancifolium Thunb. Based on the optimized extraction conditions, i.e., an extraction temperature of 50 °C, an extraction time of 40 min, a solid–liquid ratio of 1 : 25, and a ratio of water in the DES of 20%, the extracted amounts of regaloside B, regaloside C, and regaloside E reached 0.31 ± 0.06 mg g−1, 0.29 ± 0.03 mg g−1, and 3.04 ± 0.38 mg g−1, respectively. The extraction efficiencies were higher than those obtained using conventional organic solvents. Next, the polysaccharide levels were measured and compared with those obtained using a conventional hot water extraction method, and equivalent extraction efficiencies were obtained with the conventional hot water extraction method. This study provides a new application of deep eutectic solvents (DESs) for simultaneously extracting phenolic acids and polysaccharides from the bulbs of L. lancifolium Thunb. Considering the biodegradability and pharmaceutical acceptability, DESs as a class of green solvents could have wide applications in the extraction of natural products.

P2-type Na2/3Ni1/3Mn2/3O2 is one of the most promising cathode candidates for sodium-ion batteries due to its high specific capacity and high working voltage. However, a detrimental P2–O2 phase transition usually occurs at a high voltage (>4.2 V) leading to poor cycle stability. Herein, we propose to mitigate this critical issue through a controlled F−/Ca2+ dual-doping strategy with CaF2 as a dopant. The divalent Ca2+ ion doped in the Na layer stabilizes the layered structure at a high voltage when excessive Na+ is extracted. The more electronegative F− ion forms a stronger transition metal (TM)–F bond and reduces the electrostatic repulsion between the oxygen layers impeding the gliding of TMO2 layers. The Ca2+/F− co-doping successfully suppresses the unfavorable P2–O2 phase transition, and significantly improves the structural stability and cycling performance (27.1% vs. 87.2% after 500 cycles at 1C). Furthermore, density functional theory calculations combined with experimental tests reveal that the incorporation of Ca2+ and F− in Na sites and O sites facilitates the electronic and ionic conductivity owing to Na+/vacancy disordering, which enhances the high-rate capability. This study provides some insights into the design of long-life and high-rate cathode materials for sodium-ion batteries.

Reusable electronics have received widespread attention and are urgently needed. Here, nanocellulose-based liquid metal (NC-LM) printed circuit has been fabricated by the evaporation-induced transfer printing technology. In this way, the liquid metal pattern is embedded into the nanocellulose membrane, which is beneficial for the stability of the circuit during use. Besides, the NC-LM circuit is ultrathin with just tens of microns. In particular, the finished product is environmentally friendly because it can be completely dissolved by water, and both the liquid metal ink and the nanocellulose membrane can be easily recollected and reused, thereby reducing waste and pollution to the environment. Several examples of flexible circuits have been designed to evaluate their performance. The mechanism of evaporation-induced transfer printing technology involves the deposition, aggregation, and coverage tightly of the nanosized cellulose fibrils as the water evaporated. This study provides an economical and environmentally friendly way for the fabrication of renewable flexible electronics.

Fluorophores with photo-modulatory fluorescence properties are valuable for cutting-edge localization microscopy. The existing probes are either photo-activatable, or photo-switchable, but not both. We report a probe (DH-SiR), a leuco-dye obtained by reduction of Si-rhodamine, with both photo-activatable and photo-switchable fluorescence. The potential for super-resolution microscopy was showcased.

The water–gas shift (WGS) reaction is a key chemical process for CO removal and hydrogen generation in which CO and H2O are converted to CO2 and H2. The activation of H2O at the oxygen vacancy sites of a reducible oxide-supported catalyst is widely viewed as the critical step for this reaction. However, the strategy of rational fabrication of oxygen vacancies in reducible oxides to boost catalytic activity is rarely reported. Here, we report a facile method to fabricate oxygen vacancies through assembling an amorphous titanate overlayer on the surface of TiO2 support via alkali doping, aiming to improve its activity in WGS reaction. TEM, EPR, H2-TPR and XPS results verified that the titanate overlayer is in situ formed via alkali doping, where oxygen vacancies can be rationally regulated during reduction through tuning the amount of alkali. The ease of oxygen vacancy formation induced by alkali doping could be attributed to the lower Ti–O bond energy in titanate. It is shown that sodium-doped Ni/TiO2 with titanate overlayer on the support exhibited superior activity in WGS reaction compared with undoped catalyst, i.e., around threefold greater activity compared with undoped catalyst was achieved at 300 °C. Furthermore, the formation of CH4, a common side reaction in WGS on Ni-based catalysts, is suppressed on the sodium-doped Ni/TiO2. More importantly, the titanate overlayer strategy is successfully extended to other reducible oxide-supported catalysts, which provides a universal method to fabricate oxygen vacancies in reducible oxide-supported catalysts.

We disclose a transition-metal-free decarbonylative alkylation reaction for the synthesis of N-aryl α-hydroxy amides via precise cleavages and reorganizations of three C–C σ bonds. For the first time, a medium-sized cycloalkyl was used as a leaving group to initiate the decarbonylative alkylation process. We also demonstrate the concept of “one-pot” inert C–C bond activation/deuteration. This strategy allows the formation of α,β-deuterated hydroxyamides by using DMSO-d6 as a solvent.

Red pericarp associates with seed dormancy or preharvest sprouting (PHS) tolerance in crops. To identify this association's molecular mechanism, a PHS mutant Osviviparous1 (Osvp1) was characterized in rice and crossed with Kasalath, a red pericarp cultivar with Rc (red coleoptiles) genotype. Among the dehulled seeds of F2 progenies, RcRcvp1vp1 seeds performed a lower PHS rate than rcrcvp1vp1 seeds and showed shallower pigmentation than RcRcVP1VP1 seeds. Kasalath and SL9 (an RcRcVP1VP1 substitution line with Nipponbare background) showed more ABA sensitivity than the Nipponbare (rcrcVP1VP1) by the germination assay, and the transcriptional abundance of ABA signal genes OsABI2, OsSnRK2, OsVP1, ABI5, and especially OsVP1 increased in the red pericarp line SL9. Moreover, OsVP1 can directly bind Rc (bHLH) promoter by yeast one-hybrid, which activates Rc and OsLAR expression in red pericarp rice. Furthermore, a luciferase complementation imaging assay showed that OsVP1 interacts with transcriptions factors Rc and OsC1. These results indicate that OsVP1 promotes proanthocyanidin accumulation through the interaction among OsVP1, Rc, and OsC1 and then increases the plant's ABA sensitivity and PHS resistance.

In this paper, a fast and effective method based on multiple image features and a weighted K-means clustering algorithm is proposed to achieve the automatic grading of apples. The method provides a novel way of using four images (top, bottom and two sides) and average gray values for each apple to distinguish between the apple defects, stem and calyx. Furthermore, weighted features (MCSAD (maximum cross-sectional average diameter), circularity, PRA (proportion of red area) and defect regions) were carefully selected according to the requirements of the national apple grading standard, which improves the practicality of the proposed method. Finally, qualitative and quantitative evaluation results demonstrate that the total accuracy of the proposed multi-feature grading method is greater than 96%, which provides encouragement for the additional research and implementation of multi-feature automatic grading for the fruit industry.

Klebsiella pneumoniae causes pneumonia and liver abscesses in humans worldwide and contains virulence factor capsular polysaccharides and lipopolysaccharides linked to the cell wall. Although capsular polysaccharides are good antigens for vaccine production and capsular oligosaccharides conjugate vaccines are proven effective against infections caused by encapsulated pathogens, there is still no Klebsiella pneumoniae vaccine available. One obstacle is that the capsular polysaccharide of a dominated Klebsiella pneumoniae serotype K2 is difficult to synthesize chemically due to the three 1,2-cis linkages in its structure. In this study, we successfully synthesized K2 capsular polysaccharides from tetra- to octasaccharides in highly a stereoselective manner. Subsequently, three synthesized glycans were conjugated to DT protein to provide glycoconjugate vaccine candidates (DT-Hexa, DT-Hepta, and DT-Octa) that were used in in vivo immunization experiments in mice. The results of immunized studies showed all three glycoconjugates elicited antibodies that recognized all of the synthetic glycans at 1:200-fold dilution. Particularly, the DT-Hepta conjugate elicited a higher level of antibodies that can recognize longer glycan (octasaccharide) even at 1:12800-fold dilution and exhibited good bactericidal activity. Our results concluded that heptasaccharide is the minimal epitope and a potential candidate for the vaccine against the K2 sero group of Klebsiella pneumoniae.

A new and simple strategy towards electric-field-driven multiple chirality switching device has been designed and fabricated by combining a newly synthesized base-responsive chiroptical polymer switch (R-FLMA) and p-benzoquinone (p-BQ) via proton-coupled electron transfer (PCET) mechanism. Clear and stable triple chirality states (silence, positive, negative) of this device in visible band can be regulated reversibly (>1000 cycles) by adjusting voltage programs. Furthermore, such chiral switching phenomena are also accompanied by apparent changes of color and fluorescence. More importantly, the potential application of this device for a spatial light modulator has also been demonstrated.

Copper phyllosilicate supported over silica was prepared with ammonia evaporation method. Compared with the catalyst synthesized with conventional impregnation method, this novel catalyst showed a much higher activity and stability towards low-temperature water-gas shift reaction. Various characterization methods indicated the Cu nanoparticle in the catalyst had a superb small diameter around 3 nm, co-existent with abundant Cu+ sites. Based on the analysis via CO-adsorption, DRIFTS and in-situ mass spectrum, it was proved that CO could be adsorbed on Cu+ strongly and Cu+ acted as the active sites for CO activation. The reaction mechanism with dual active sites prevented the competitive adsorption of H2O and CO onto Cu0 sites, thereby improving the catalytic activity and stability.

Here, we report a β-galactosidase (β-Gal)-responsive photochromic fluorescent probe, NpG, that was designed to prebind to human serum albumin (HSA) to form the probe/protein hybrid, NpG@HSA. The formation of NpG@HSA led to an increase in fluorescence emission (520 nm) corresponding to the binding of the fluorescent naphthalimide unit with HSA. In addition, this enabled visualization of the spiropyran fluorescence emission in aqueous media. Our probe/protein hybrid approach afforded a unique imaging platform with enhanced cell permeability and solubility that was capable of visualizing the cellular uptake of NpG@HSA before its activation by β-Gal. The β-Gal-mediated cleavage of the galactose unit within the NpG@HSA hybrid resulted in the formation of NpM@HSA and an increase in red fluorescence emission (620 nm). The resultant merocyanine unit was then able to undergo photoisomerization (merocyanine ↔ spiropyran) to facilitate STORM (i.e., stochastic optical reconstruction microscopy) imaging with minimal phototoxicity and excellent photostability/reversibility. Using STORM, NpG@HSA was able to determine the subcellular distribution of β-Gal activity between cell lines with nanoscale precision. We believe that this system represents a versatile imaging platform for the design of photochromic fluorescent probes suitable for illuminating the precise location of disease-specific biomarkers in various cellular processes.

From a multitude of homonuclear and heteronuclear correlation magic-angle-spinning (MAS) NMR experiments, we present thorough structural and phase-quantification analyses of calcium phosphate cemen...

N-glycans on the cell surface provide distinct signatures that are recognized by different glycan-binding proteins (GBPs) and pathogens. Most glycans in humans are asymmetric and isomeric, yet their biological functions are not well understood due to their lack of availability for studies. In this work, we have developed an improved strategy for asymmetric N-glycan assembly and diversification using designed common core substrates prepared chemically for selective enzymatic fucosylation and sialylation. The resulting 26 well-defined glycans that carry the sialic acid residue on different antennae were used in a microarray as a representative application to profile the binding specificity of hemagglutinin (HA) from the avian influenza virus (H5N2). We found distinct binding affinity for the Neu5Ac-Gal epitope linked to the N-acetylglucosamine (GlcNAc) of different branches and only a minor effect in binding for the terminal galactose on different branches. Overall, the microarray analysis showed branch-biased and context-based recognition patterns.

Here, we demonstrate a novel donor-intermediate-receptor energy transfer model through a Ce3+ → Tb3+ → Eu3+ scheme in a CaTbAl3O7:Ce3+,Eu3+ nanocrystalline phosphor. A new type of CaTbAl3O7 and CaT...

Discovery of novel liver injury indicators and development of practical assays to detect target indicator(s) would strongly facilitate the diagnosis of liver disorders. Herein, an alternative biomarker discovery strategy was applied to find suitable endoplasmic reticulum-resident protein(s) as serologic indicator(s) for hepatocyte injury via analysis of the human proteome database among plasma and various organs. Both database searching and preliminary experiments suggested that human carboxylesterase 1A (CES1A), one of the most abundant and hepatic-restricted proteins, could serve as a good serologic indicator for hepatocyte injury. Then, a highly selective and practical bioluminescent sensor was developed for real-time sensing of CES1A in various biological systems including plasma. With the help of this bioluminescent sensor, the release of hepatic CES1A into the extracellular medium or the circulation system could be directly monitored. Further investigations demonstrated that serum activity levels of CES1A were elevated dramatically in mice with liver injury or patients with liver diseases. Collectively, this study provided solid evidence to support that CES1A was a novel serological indicator for hepatocyte injury. Furthermore, the strategy used in this study paved a new way for the rational discovery of practical indicators to monitor the dynamic progression of injury in a given tissue or organ.

Summary Template effects are at the origin of supramolecular chemistry, but the behavior of folded molecules is a relatively new undertaking. Water-soluble cavitand hosts bind hydrocarbons through hydrophobic effects and force long-chain guests into folded conformations. This brings their ends closer together, and sites that were remote in solution become neighbors in the confined space and affect each other’s reactivity. Amphiphilic guests fold in the cavitand to bury hydrophobic surfaces and expose the hydrophilic surfaces to the bulk solution. This arrangement leads to product distributions in monofunctionalization reactions that are significantly altered from the statistically determined outcomes in solution. The cavitand also acts as a template for macrocyclic processes involving direct reaction of the guests’ ends. We propose applying the effects of folding in cavitands to truly remote functionalization reactions and provide access to molecules that cannot be made by conventional means.

Ceria has been used for catalyst support for long time due to its unique structural properties resulting from oxygen vacancies and reversible valence change (Ce4+ and Ce3+). In this report, ceria nanorods (NR) and nanocubs (NC) were prepared with hydrothermal method and 5 wt% nickel was loaded on it. The effect of morphology of ceria supports for CO2 methanation reaction was studied. Characterization including TPR, TEM, XRD and XPS shows that Ni/CeO2-NR had a higher number of Ce3+ proportion compared with Ni/CeO2-NC. Both catalysts showed high conversion and selectivity for methane at low temperature range at200–250 °C and interestingly Ni/CeO2-NR exhibited a higher activity than Ni/CeO2–NC. A kinetic study and DRIFTs investigation were carried out to formulate the mechanism. It turned out that CO2 methanation on Ni/CeO2 goes through a formate route instead of CO2 dissociation and the oxygen vacant sites are supposed to be the active sites for the formate formation in this mechanism.

Storing hydrogen efficiently in condensed materials is a key technical challenge. Tremendous efforts have been given to inorganic hydrides containing B–H, Al–H and/or N–H bonds, while organic compounds with a great variety and rich chemistry in manipulating C–H and unsaturated bonds, however, are undervalued mainly because of their unfavourable thermodynamics and selectivity in dehydrogenation. Here, we developed a new family of hydrogen storage material spanning across the domain of inorganic and organic hydrogenous compounds, namely metallo-N-heterocycles, utilizing the electron donating nature of alkali or alkaline earth metals to tune the electron densities of N-heterocyclic molecules to be suitable for hydrogen storage in terms of thermodynamic properties. Theoretical calculations reveal that the enthalpies of dehydrogenation (ΔHd) of these metallo-N-heterocycles are dependent on the electronegativity of the metals. In line with our calculation results, sodium and lithium analogues of pyrrolides, imidazolides and carbazolides of distinct structures were synthesized and characterized for the first time, where the cation-π interaction was identified. More importantly, a reversible hydrogen absorption and desorption can be achieved over lithium carbazolide which has a hydrogen capacity as high as 6.5 ​wt% and a suitable enthalpy of dehydrogenation of 34.2 ​kJ ​mol−1-H2 for on-board hydrogen storage.

This paper investigated the combustion instability of spanwise positions in a hydrogen fueled scramjet combustor with a cavity flame holder. High-speed OH-PLIF technique was performed on a direct-connect supersonic combustion facility, and dynamic mode decomposition (DMD) as postprocessing. Combustion instability was investigated by characterizing the dominant frequencies and growth factors. By changing the equivalence ratio of hydrogen, the peak frequencies of scramjet mode and ramjet mode were obtained. Scramjet mode tended to have small oscillation at 150–200 Hz reflected by negative growth factors due to the stable flame structure. At ram-to-scram transition, oscillations at 80–120 Hz were remarkably enhanced due to the positive growth factors. In ramjet mode, the large differences of frequency characteristics in spanwise positions were observed. The dominant DMD modes near the cavity wall appeared to have negative growth factors leading to a stable flame with small oscillations. Besides, the characteristics of frequency-shift were affected by the positions of injector.

Objective To study the antipyretic and anti-inflammatory constituents from the active fraction of Reduning (RDN) Injection. Methods In this study, the active fraction of RDN Injection was screened by the LPS-induced mouse endotoxin shock model. The chemical constituents were isolated by chromatography on HP-20 macroporous adsorptive resins, silica gel, ODS columns and reverse phase MPLC and HPLC repeatedly, and their structures were elucidated based on spectroscopic analysis (HR-ESI-MS, NMR, ECD) and chemical methods. Meanwhile, we evaluated the anti-inflammatory activities of the isolates by measuring their inhibitory effects on TNF-α production in LPS stimulated RAW 264.7 macrophages. Results The 95% ethanol eluate of RDN Injection by the macroporous adsorption resin column was proved to be the antipyretic and anti-inflammatory active fraction of this injection. A novel iridoid, named jasminoide A (1), and a new guaiane sesquiterpenoid, named (1R,7R,8S,10R)-7,8,11-trihydroxy-4-guaien-3-one (2), were isolated from Reduning injection, and compound 2 can inhibit TNF-α production with IC50 values of 72.24 µmol/L. Conclusion In this study, two new terpenoids were isolated from Reduning Injection, and compound 2 showed inhibitory activity against LPS-activated TNF-α production in RAW 264.7 cells in vitro.

A new nitrogen-containing iridoid glycoside, named (7 R,3���R)-lonijapospiroside A (1), together with thirteen known iridoid glycosides, were isolated from the flower buds of Lonicera macranthoides. The structures of these compounds were established on the basis of spectroscopic analyses. Among them, compounds 1-4 are four diastereoisomers, and their absolute configurations were accurately established by the NOE spectra as well as comparison of their experimental and calculated ECD spectra. The anti-inflammatory activities of all isolates were evaluated by measuring their inhibitory effects on NO, IL-6, and TNF-�� production in LPS stimulated RAW 264.7 macrophages. Compound 14 exhibited anti-inflammatory activities by inhibiting IL-6 with an IC50 value of 54.70 ��M, comparable to that of the positive control (hydrocortisone, IC50: 62.6 �� 1.7 ��M).

Supramolecular capsules are desirable containers for the study of molecular behavior in small spaces and offer applications in transport, catalysis, and material science. We report here the use of chalcogen bonding to form container assemblies that are stable in water. Cavitands

In the present work, the geometry, electronic structure, and infrared spectra (IR) of meso-tetra-substituted porphyrin have been investigated theoretically. The optimization of geometries and electronic structure calculations of meso-tetraphenylporphyrin (TPP) and meso-tetra(3-pyridyl)porphyrin (T3PyP) are performed on the basis of density functional theory. The substitution of pyridyl for phenyl in meso-tetra-substituted porphyrins can result into the reduction of molecular size, including the molecular diameter, as well as the size of the central ring of porphin. It has also been found that the molecular orbital energies of T3PyP are smaller than the counterparts of TPP whereas there is almost no change in the HOMO–LOMO gap. Additionally, the infrared spectrum of TPP and T3PyP has been compared in order to determine whether there is a red shift or a blue shift.

The oxygen reduction reaction (ORR) plays an irreplaceable role in many energy-conversion processes. Low-cost catalysts with high activity and stability are eagerly needed to improve the sluggish O...

For the development of advanced flexible and wearable electronic devices, functional electrolytes with excellent conductivity, temperature tolerance, and desirable mechanical properties need to be engineered. Herein, an alkaline double-network hydrogel with high conductivity and superior mechanical and antifreezing properties is designed and promisingly utilized as the flexible electrolyte in all-solid-state zinc-air batteries. The conductive hydrogel is comprised of covalently cross-linked polyelectrolyte poly(2-acrylamido-2-methylpropanesulfonic acid potassium salt) (PAMPS-K) and interpenetrating methyl cellulose (MC) in the presence of concentrated alkaline solutions. The covalently cross-linked PAMPS-K skeleton and interpenetrating MC chains endow the hydrogel with good mechanical strength, toughness, an extremely rapid self-recovery capability, and an outstanding antifatigue property. Gratifyingly, the entrapment of a concentrated alkaline solution in the hydrogel matrix yields an extremely high ionic conductivity (105 mS cm-1 at 25 °C) and an excellent antifreezing capacity. The hydrogel retains comparable conductivity and eligible strength to withstand various mechanical deformations at -20 °C. The all-solid-state zinc-air batteries using PAMPS-K/MC hydrogels as flexible alkaline electrolytes exhibit comparable values of specific capacity (764.7 mAh g-1), energy capacity (850.2 mWh g-1), cycling stability, and mechanical flexibility. The batteries still possess competitive electrochemical performances even when the operating temperature drops to -20 °C.

This study represents a systematic chemical and biological study of the rufomycin (RUF) class of cyclic heptapeptides, which our anti-TB drug discovery efforts have identified as potentially promising anti-TB agents that newly target the caseinolytic protein C1, ClpC1. Eight new RUF analogues, rufomycins NBZ1-NBZ8 (1-8), as well as five known peptides (9-13) were isolated and characterized from the Streptomyces atratus strain MJM3502. Advanced Marfey's and X-ray crystallographic analysis led to the assignment of the absolute configuration of the RUFs. Several isolates exhibited potent activity against both pathogens M. tuberculosis H37Rv and M. abscessus, paired with favorable selectivity (selectivity index >60), which collectively underscores the promise of the rufomycins as potential anti-TB drug leads.

The thermal conductivity (TC) of gutta-percha, zinc oxide, and carbon nanotubes nanocomposites (GP/ZnO@CNTs) is improved greatly by the oriented CNTs, which is induced by shear field of the capillary rheometer. Furthermore, the effects of shear rate and temperature on the orientation of CNTs and the TC of the nanocomposites are investigated. The results of Raman show that the degree of orientation of CNTs increases with the increment of shear rate and/or temperature, which greatly improves the thermal conductance of the nanocomposites when the orientation degree is equal to 10.8. Compared with the GP/ZnO@CNTs nanocomposites with random CNTs, the highest TC of GP/ZnO@CNTs nanocomposites with oriented CNTs is increased by 81.2%, which is up to 2.50 W m−1K−1.

Understanding and controlling parasitic reactions at the electrode–electrolyte interface (EEI) in Li-ion batteries is essential to enhance and predict the battery cycle life. Recent work has shown ...