Self-supported bimetallic array superstructures for high-performance coupling electrosynthesis of formate and adipate.

The coupling electrosynthesis involving CO2 upgrade conversion is of great significance for the sustainable development of the environment and energy but is challenging. Herein, we exquisitely constructed the self-supported bimetallic array superstructures from the Cu(OH)2 array architecture precursor, which can enable high-performance coupling electrosynthesis of formate and adipate at the anode and the cathode, respectively. Concretely, the faradaic efficiencies (FEs) of CO2-to-formate and cyclohexanone-to-adipate conversion simultaneously exceed 90% at both electrodes with excellent stabilities. Such high-performance coupling electrosynthesis is highly correlated with the porous nanosheet array superstructure of CuBi alloy as the cathode and the nanosheet-on-nanowire array superstructure of CuNi hydroxide as the anode. Moreover, compared to the conventional electrolysis process, the cell voltage is substantially reduced while maintaining the electrocatalytic performance for coupling electrosynthesis in the two-electrode electrolyzer with the maximal FEformate and FEadipate up to 94.2% and 93.1%, respectively. The experimental results further demonstrate that the bimetal composition modulates the local electronic structures, promoting the reactions toward the target products. Prospectively, our work proposes an instructive strategy for constructing adaptive self-supported superstructures to achieve efficient coupling electrosynthesis.

Nickel-Catalyzed Cross-Coupling Reaction of Aryl Methyl Sulfides with Aryl Bromides.

A nickel-catalyzed cross-coupling reaction of aryl methyl sulfides with aryl bromides has been developed to access biaryls in yields of up to 86%. The reactions proceeded well using Ni(COD)2 as catalyst with the ligand BINAP (2,2'-bis(diphenylphosphanyl)-1,1'-binaphthalene) in the presence of magnesium. The method has a broad scope of substrates and is scalable. The wide availability of commercially available aryl bromides and the absence of preparation and preparation of organometallic reagents make the reaction of high application value.

Dearomatization Silylation of Benzofurans and Furopyridines via Silyl Radical Addition and Endocyclic C-O Bond Scission.

Direct introduction of silyl radicals to forge C-Si bonds is of central importance in organic synthesis, owing to the formidable potential of silyl groups as coupling partners for further derivatization reactions to achieve more valuable compounds. Cleavage of heteroaromatic endocyclic carbon-heteroatom bonds to assemble C-Si bonds is scarce. Here, we demonstrate a dearomatization silylation of benzofurans and furopyridines via silyl radical addition and C(2)-O bond scission under metal-catalyst-free and mild conditions. Preliminary mechanistic experiments suggest that these transformations involve radical/single-electron transfer and [1,5]-Brook rearrangement processes. This protocol for the total synthesis of Doxepin and oxyresveratrol derivatives is carried out. The silylated products in several transformation reactions have proven to be useful as synthetic intermediates.

Palladium-Catalyzed Cyanation of Aryl Sulfonium Salts.

A palladium-catalyzed cyanation of aryl dimethylsulfonium salts using cheap, nontoxic, and bench-stable K4[Fe(CN)6]·3H2O as the cyanating reagent has been developed. The reactions proceeded well under base-free conditions with various sulfonium salts and provided aryl nitrile with yields of up to 92%. Aryl sulfides can be transformed to aryl nitriles directly via a one-pot process, and the protocol is scalable. Density functional theory calculations were performed to investigate the reaction mechanism that involved a catalytic cycle involving oxidative addition, ligand exchange, reductive elimination, and regeneration to yield the product.

Si Doping-Induced Electronic Structure Regulation of Single-Atom Fe Sites for Boosted CO2 Electroreduction at Low Overpotentials.

Transition metal-based single-atom catalysts (TM-SACs) are promising alternatives to Au- and Ag-based electrocatalysts for CO production through CO2 reduction reaction. However, developing TM-SACs with high activity and selectivity at low overpotentials is challenging. Herein, a novel Fe-based SAC with Si doping (Fe-N-C-Si) was prepared, which shows a record-high electrocatalytic performance toward the CO2-to-CO conversion with exceptional current density (>350.0 mA cm-2) and ~100% Faradaic efficiency (FE) at the overpotential of <400 mV, far superior to the reported Fe-based SACs. Further assembling Fe-N-C-Si as the cathode in a rechargeable Zn-CO2 battery delivers an outstanding performance with a maximal power density of 2.44 mW cm-2 at an output voltage of 0.30 V, as well as high cycling stability and FE (>90%) for CO production. Experimental combined with theoretical analysis unraveled that the nearby Si dopants in the form of Si-C/N bonds modulate the electronic structure of the atomic Fe sites in Fe-N-C-Si to markedly accelerate the key pathway involving *CO intermediate desorption, inhibiting the poisoning of the Fe sites under high CO coverage and thus boosting the CO2RR performance. This work provides an efficient strategy to tune the adsorption/desorption behaviors of intermediates on single-atom sites to improve their electrocatalytic performance.

Rotating Bending Fatigue Behaviors of C17200 Beryllium Copper Alloy at High Temperatures.

The purpose of this paper is to investigate the fatigue properties of C17200 alloy under the condition of quenching aging heat treatment at high temperatures, and to provide a design reference for its application in a certain temperature range. For this purpose, the tensile and rotary bending fatigue (RBF) tests were carried out at different temperatures (25 °C, 150 °C, 350 °C, and 450 °C). The tensile strength was obtained, and relationships between the applied bending stress levels and the number of fatigue fracture cycles were fitted to the stress-life (S-N) curves, and the related equations were determined. The fractured surfaces were observed and analyzed by a scanning electron microscopy (SEM). The results show that the RBF fatigue performance of C17200 alloy specimens is decreased with the increase in test temperature. When the temperature is below 350 °C, the performance degradation amplitudes of mechanical properties and RBF fatigue resistance are at a low level. However, compared to the RBF fatigue strength of 1 × 107 cycles at 25 °C, it is decreased by 38.4% when the temperature reaches 450 °C. It is found that the fatigue failure type of C17200 alloy belongs to surface defect initiation. Below 350 °C, the surface roughness of the fatigue fracture is higher, which is similar to the brittle fracture, so the boundary of the fracture regions is not obvious. At 450 °C, due to the further increase in temperature, oxidation occurs on the fracture surface, and the boundary of typical fatigue zone is obvious.

Stepwise assembly and reversible structural transformation of ligated titanium coated bismuth-oxo cores: shell morphology engineering for enhanced chemical fixation of CO2.

Herein, we report the stepwise assembly and reversible transformation of atomically precise ligated titanium coated bismuth-oxide core nanostructures. The soluble and stable Bi38O45@Ti6-oxo clusters with weakly coordinated surface salicylate ligands were first prepared as precursors. Owing to the high surface reactivity of the Bi38O45 inner core, its shell composition and morphology could be systemically modified by assembly with various Ti ions and auxiliary ligands (L), especially those with different flexibility, bridging ability and steric hindrance. As a result, a series of new core-shell Bi38O44/45@Ti x L-oxo (x = 14, 16, 18 or 20) clusters containing gradually increasing shell Ti atoms were successfully synthesized. Among them, the Bi38Ti20-oxo cluster is the largest one in the family of heterometallic Bi/Ti-oxo clusters to date. In addition, the sensitized titanium outer shell can effectively improve the photocurrent response under visible light irradiation. More remarkably, the obtained core-shell Bi38O44/45@Ti x L-oxo clusters can serve as stable and efficient catalysts for CO2 cycloaddition with epoxides under ambient conditions, whose activity was significantly influenced by the outer ligated titanium shell structure. This work provides a new insight into the construction of atomically precise heterometallic core-shell nanostructures and also an interesting shell engineering strategy for tuning their physicochemical properties.

Divergent Paths, Same Goal: A Pair-Electrosynthesis Tactic for Cost-Efficient and Exclusive Formate Production by Metal-Organic-Framework-Derived 2D Electrocatalysts.

Electrosynthesis of formic acid/formate is a promising alternative protocol to industrial processes. Herein, a pioneering pair-electrosynthesis tactic is reported for exclusively producing formate via coupling selectively electrocatalytic methanol oxidation reaction (MOR) and CO2 reduction reaction (CO2 RR), in which the electrode derived from Ni-based metal-organic framework (Ni-MOF) nanosheet arrays (Ni-NF-Af), as well as the Bi-MOF-derived ultrathin bismuthenes (Bi-enes), both obtained through an in situ electrochemical conversion process, are used as efficient anodic and cathodic electrocatalysts, respectively, achieving concurrent yielding of the same high-value product at both electrodes with greatly reduced energy input. The as-prepared Ni-NF-Af only needs quite low potentials to reach large current densities (e.g., 100 mA cm-2 @1.345 V) with ≈100% selectivity for anodic methanol-to-formate conversion. Meanwhile, for CO2 RR in the cathode, the as-prepared Bi-enes can simultaneously exhibit near-unity selectivity, large current densities, and good stability in a wide potential window toward formate production. Consequently, the coupled MOR//CO2 RR system based on the distinctive MOF-derived catalysts displays excellent performance for pair-electrosynthesis of formate, delivering high current densities and nearly 100% selectivity for formate production in both the anode and the cathode. This work provides a novel way to design advanced MOF-derived electrocatalysts and innovative electrolytic systems for electrochemical production of value-added feedstocks.

Hydrangea-like Superstructured Micro/Nanoreactor of Topotactically Converted Ultrathin Bismuth Nanosheets for Highly Active CO2 Electroreduction to Formate.

An electrocatalytic carbon dioxide reduction reaction (CO2RR) is an appealing route to obtain the value-added feedstocks and alleviate the energy crisis. However, how to achieve high-performance electrocatalysts for CO2 reduction to formate is challenging owing to the poor intrinsic activity, insufficient conductivity, and low surface density of active sites. Herein, we fabricated an extremely active and selective hydrangea-like superstructured micro/nanoreactor of ultrathin bismuth nanosheets through an in situ electrochemical topotactic transformation of hierarchical bismuth oxide formate (BiOCOOH). The resulted bismuth nanosheet superstructure is in the form of three-dimensional intercrossed networks of ultrathin nanosheets, forming an ordered open porous structure through self-assembly, which can be used as a micro/nanoreactor to enable a large electrochemically active surface area as well as high atomic utilization. Such a distinctive nanostructure endows the material with high electrocatalytic performances for CO2 reduction to formate with near-unity Faradaic selectivity (>95%) in a wide potential window from -0.78 to -1.18 V. Furthermore, this micro/nanoreactor can give the high current densities over 300 mA cm-2 at low applied potentials without compromising selectivity in a flow cell reactor. Density functional theory (DFT) and in situ attenuated total reflection-infrared spectroscopy (in situ ATR-IR) were further conducted to interpret the CO2RR mechanisms.

Metal-Organic Layers Leading to Atomically Thin Bismuthene for Efficient Carbon Dioxide Electroreduction to Liquid Fuel.

Electrochemical reduction of CO2 to valuable fuels is appealing for CO2 fixation and energy storage. However, the development of electrocatalysts with high activity and selectivity in a wide potential window is challenging. Herein, atomically thin bismuthene (Bi-ene) is pioneeringly obtained by an in situ electrochemical transformation from ultrathin bismuth-based metal-organic layers. The few-layer Bi-ene, which possesses a great mass of exposed active sites with high intrinsic activity, has a high selectivity (ca. 100 %), large partial current density, and quite good stability in a potential window exceeding 0.35 V toward formate production. It even deliver current densities that exceed 300.0 mA cm-2 without compromising selectivity in a flow-cell reactor. Using in situ ATR-IR spectra and DFT analysis, a reaction mechanism involving HCO3 - for formate generation was unveiled, which brings new fundamental understanding of CO2 reduction.

Ligand-assisted capping growth of self-supporting ultrathin FeNi-LDH nanosheet arrays with atomically dispersed chromium atoms for efficient electrocatalytic water oxidation.

Self-supporting ultrathin FeNi-layered double hydroxide nanosheet arrays with atomically dispersed Cr atoms were firstly fabricated from stainless steel mesh by a facile ligand-assisted capping growth approach. Their unique nanostructure and a strong synergetic effect between the atomically dispersed Cr dopants and the active sites afford an exceptional OER activity.

Inlaying Ultrathin Bimetallic MOF Nanosheets into 3D Ordered Macroporous Hydroxide for Superior Electrocatalytic Oxygen Evolution.

Controllable synthesis of ultrathin metal-organic framework (MOF) nanosheets and rational design of their nano/microstructures in favor of electrochemical catalysis is critical for their renewable energy applications. Herein, an in situ growth method is proposed to prepare the ultrathin NiFe MOF nanosheets with a thickness of 1.5 nm, which are vertically inlaid into a 3D ordered macroporous structure of NiFe hydroxide. The well-designed composite delivers an efficient electrocatalytic performance with a low overpotential of 270 mV at a current density of 10 mA cm-2 and stable electrolysis as long as 10 h toward the electrochemical oxygen evolution reaction, much superior to the state-of-the-art RuO2 electrocatalyst. A comprehensive analysis demonstrates that the excellent performance originates from the desirable combination of the highly exposed active centers in the ultrathin bimetallic MOF nanosheets, effective electron conduction between MOF nanosheets and ordered macroporous hydroxide, and efficient mass transfer across the hierarchically porous hybridization. This study sheds light on the exploration of powerful protocols to gain diverse high-performance MOF nanosheets and may open a perspective to achieve their efficient electrocatalytic performance.

Self-assembled ruthenium (II) metallacycles and metallacages with imidazole-based ligands and their in vitro anticancer activity.

Six tetranuclear rectangular metallacycles were synthesized via the [2+2] coordination-driven self-assembly of imidazole-based ditopic donor 1,4-bis(imidazole-1-yl)benzene and 1,3-bis(imidazol-1-yl)benzene, with dinuclear half-sandwich p-cymene ruthenium(II) acceptors [Ru2(µ-η4-oxalato)(η6-p-cymene)2](SO3CF3)2, [Ru2(µ-η4-2,5-dioxido-1,4-benzoquinonato)(η6-p-cymene)2](SO3CF3)2 and [Ru2(µ-η4-5,8-dioxido-1,4-naphtoquinonato)(η6-p-cymene)2](SO3CF3)2, respectively. Likewise, three hexanuclear trigonal prismatic metallacages were prepared via the [2+3] self-assembly of tritopic donor of 1,3,5-tri(1H-imidazol-1-yl)benzene with these ruthenium(II) acceptors respectively. Self-selection of the single symmetrical and stable metallacycle and cage was observed although there is the possibility of forming different conformational isomeric products due to different binding modes of these imidazole-based donors. The self-assembled macrocycles and cage containing the 5,8-dioxido-1,4-naphtoquinonato (donq) spacer exhibited good anticancer activity on all tested cancer cell lines (HCT-116, MDA-MB-231, MCF-7, HeLa, A549, and HepG-2), and showed decreased cytotoxicities in HBE and THLE-2 normal cells. The effect of Ru and imidazole moiety of these assemblies on the anticancer activity was discussed. The study of binding ability of these donq-based Ru assemblies with ctDNA indicated that the complex 9 with 180° linear 1 ligand has the highest bonding constant Kb to ctDNA.

Deposition Process and Properties of Electroless Ni-P-Al2O3 Composite Coatings on Magnesium Alloy.

To improve the corrosion resistance and wear resistance of electroless nickel-phosphorus (Ni-P) coating on magnesium (Mg) alloy. Ni-P-Al2O3 coatings were produced on Mg alloy from a composite plating bath. The optimum Al2O3 concentration was determined by the properties of plating bath and coatings. Morphology growth evolution of Ni-P-Al2O3 composite coatings at different times was observed by using a scanning electronic microscope (SEM). The results show that nano-Al2O3 particles may slow down the replacement reaction of Mg and Ni2+ in the early stage of the deposition process, but it has almost no effect on the rate of Ni-P auto-catalytic reduction process. The anti-corrosion and micro-hardness tests of coatings reveal that the Ni-P-Al2O3 composite coatings exhibit better performance compared with Ni-P coating owing to more appropriate crystal plane spacing and grain size of Ni-P-Al2O3 coatings. Thermal shock test indicates that the Al2O3 particles have no effect on the adhesion of coatings. In addition, the service life of composite plating bath is 4.2 metal turnover, suggesting it has potential application in the field of magnesium alloy.

Multi-objective optimization for sensor placement against suddenly released contaminant in air duct system.

When a chemical or biological agent is suddenly released into a ventilation system, its dispersion needs to be promptly and accurately detected. In this work, an optimization method for sensors layout in air ductwork was presented. Three optimal objectives were defined, i.e. the minimum detection time, minimum contaminant exposure, and minimum probability of undetected pollution events. Genetic algorithm (GA) method was used to obtain the non-dominated solutions of multiobjectives optimization problem and the global optimal solution was selected among all of the non-dominated solutions by ordering solutions method. Since the biochemical attack occurred in a ventilation system was a random process, two releasing scenarios were proposed, i.e. the uniform and the air volume-based probability distribution. It was found that such a probability distribution affected the results of optimal sensors layout and also resulted in different detect time and different probability of undetected events. It was discussed how the objective functions are being compatible and competitive with each other, and how sensor quantity affect the optimal results and computational load. The impact of changes on other parameters was given, i.e. the deposition coefficient, the air volume distribution and the manual releasing. This work presents an angle of air ductwork design for indoor environment protection and expects to help in realizing the optimized sensor system design for sudden contaminant releasing within ventilation systems.

Engineering graphene with red phosphorus quantum dots for superior hybrid anodes of sodium-ion batteries.

Red phosphorus (P) has been considered to be one of the most promising anode materials for sodium-ion batteries (SIBs) because of its highest theoretical capacity (∼2600 mA h g-1). For the first time, we report a reliable hydrothermal method for the preparation of red phosphorus quantum dots (RPQDs) with commercial red P as a source. Moreover, an effective strategy was designed to fabricate RPQDs/rGO nanohybrids for addressing the intrinsic issues of red P as anode materials for SIBs. Benefiting from the nanostructuring of red P and the coupling of RPQDs with rGO, the obtained nanohybrids not only promote electron and ion transfer, but also effectively enhance the electronic conductivity, restrain the aggregation of RPQDs and buffer the large volume changes of red phosphorus during the charge-discharge process. The nanohybrids deliver an initial specific capacity of 1161 mA h g-1 and a low capacity deterioration rate of less than 0.12% per cycle even after 250 cycles at a current density of 200 mA g-1. The feasibility of large-scale production of the RPQDs/rGO nanohybrid, associated with its outstanding Na-ion storage properties and low cost, demonstrates that the RPQDs/rGO hybrid is a very promising anode material for SIBs.

[Design of ECG Signal Acquisition Terminal Based on ADS1298R].

The home health monitoring of the ECG signal acquisition and display terminal is designed with MSP430F6659 and ADS1298R chip of TI company. The basic principles of ECG col ection is introduced in the beginning, and then the overal scheme of the system is described by MSP430F6659 and ADS1298R chip as the core, and the modules peripheral interface, real-time display in LCD, data storage and USB are introduced. The ECG signal acquisition terminal designed in this paper has the characteristics of smal size, low power consumption and so on.

Synthesis of fluorinated carbazoles via C-H arylation catalyzed by Pd/Cu bimetal system and their antibacterial activities.

An effective intramolecular C-H arylation reaction catalyzed by a bimetallic catalytic system Pd(OAc)2/CuI for the synthesis of fluorine-substituted carbazoles from corresponding N-phenyl-2-haloaniline derivatives under ligand free conditions is demonstrated. The established method is effective for both N-phenyl-2-bromoaniline and N-phenyl-2-chloroaniline, and requires the low loading of Pd(OAc)2 (0.5 mol%). A series of new fluorinated carbazoles were synthesized in excellent yields using the protocol (>83%, 19 examples) and were fully characterized by (1)H, (13)C and (19)F NMR spectral data, HRMS and elemental analysis. All compounds were evaluated for their antibacterial activities against four bacteria (Bacillus subtilis, Staphylococcus aureus, Escherichia coli and methicillin-resistant S. aureus with resistance to gentamicin) by serial dilution technique. All tested compounds showed antibacterial activity against three test strains (S. aureus, B. subtilis and MRSA), and most of these compounds displayed pronounced antimicrobial activities against these three strains with low MIC values ranging from 0.39 to 6.25 µg/mL. Among them, compounds 7 and 14 exhibited potent inhibitory activity better than reference drugs meropenem and streptomycin. Three compounds (2, 4 and 5) showed antibacterial activity against E. coli. with MIC values from 12.5 to 25 µg/mL.

Synthesis and photophysical studies of self-assembled multicomponent supramolecular coordination prisms bearing porphyrin faces.

Multicomponent self-assembly, wherein two unique donor precursors are combined with a single metal acceptor instead of the more common two-component assembly, can be achieved by selecting Lewis-basic sites and metal nodes that select for heteroligated coordination spheres. Platinum(II) ions show a thermodynamic preference for mixed pyridyl/carboxylate coordination environments and are thus suitable for such designs. The use of three or more unique building blocks increases the structural complexity of supramolecules. Herein, we describe the synthesis and characterization of rectangular prismatic supramolecular coordination complexes (SCCs) with two faces occupied by porphyrin molecules, motivated by the search for new multichromophore complexes with promising light-harvesting properties. These prisms are obtained from the self-assembly of a 90° Pt(II) acceptor with a meso-substituted tetrapyridylporphyrin (TPyP) and dicarboxylate ligands. The generality of this self-assembly reaction is demonstrated using five dicarboxylate ligands, two based on a rigid central phenyl ring and three alkyl-spaced variants, to form a total of five free-base and five Zn-metallated porphyrin prisms. All 10 SCCs are characterized by (31)P and (1)H multinuclear NMR spectroscopy and electrospray ionization mass spectrometry, confirming the structure of each self-assembly and the stoichiometry of formation. The photophysical properties of the resulting SCCs were investigated revealing that the absorption and emission properties of the free-base and metallated porphyrin prisms preserve the spectral features associated with free TPyP.

Synthesis and characterization of novel chiral NHC-palladium complexes and their application in copper-free Sonogashira reactions.

A new series of chiral N-heterocyclic carbene (NHC) palladium complexes were synthesized from a relatively inexpensive amino acid, l-phenylalanine. All these compounds were fully characterized by (1)H-NMR, (13)C-NMR and elemental analysis. The X-ray molecular structures of two of the complexes were reported. The catalytic activity of the four palladium complexes was successfully tested in the Sonogashira reaction under copper free conditions in air. The palladium complex 3a provided good activity in the Sonogashira coupling reaction.