Porous VN nanosheet arrays on MXene carbon fibers for flexible supercapacitors.

VN usually has poor rate performance and cycle stability. In this work, porous VN nanosheet arrays were prepared on carbon nanofibers embedded with Ti3C2Tx nanosheets by electrospinning and chemical vapor deposition. The 3D network accelerates the transfer of electrons and electrolyte ions, prevents the aggregation of VN and the self-stacking of MXene, and enhances cycle stability. The solid-state flexible device comprising Co3O4, MXCF@VN, and KOH/PVA exhibits exceptional energy densities of 83.95 W h kg-1 and robust cycling stability (82.8% retention after 20 000 cycles).

Ti3C2Tx MXene-embedded MnO2-based hydrophilic electrospun carbon nanofibers as a freestanding electrode for supercapacitors.

Herein, MnO2 nanoflowers are electrodeposited on a self-supported and electroconductive electrode in which 2D Ti3C2Tx nanosheets are encased in carbon nanofibers (MnO2@Ti3C2Tx/CNFs). This improves the conductivity and hydrophilicity of the MnO2 composite electrode. The asymmetric supercapacitor shows a high energy density of 46.4 W h kg-1 and a power density of 4 kW kg-1.

Identifying the influencing factors and constructing incentive pattern of residents' waste classification behavior using PCA-logistic regression.

With the acceleration of urbanization, domestic waste has become one of the most inevitable factors threatening the environment and human health. Waste classification is of great significance and value for improving urban environmental quality and promoting human well-being. Based on the theory of planned behavior, we added external and socio-economic factors to systematically examine how they affect residents' waste classification behavior (WCB). We collected 661 valid data through a questionnaire survey conducted in Jinan, a pilot city for waste classification in China. Key driving factors were identified by combining binary logistic regression and the principal component analysis. The results showed that the elderly, women, and people with higher education are more likely to participate in waste classification. Attitude, collaborative governance, and institutional pressure positively affect WCB, while subjective norm and infrastructure have a negative effect. Knowledge mastery and degree of publicity are positively and significantly related to WCB, but other perceived behavioral control sub-variables negatively affect WCB. Based on the results and status of waste classification in Jinan, we propose the multi-agent linkage governance pattern from various dimensions to explore a powerful guiding incentive that can enhance WCB and provide a reference for waste management policymakers.

Cobalt-Nickel Layered Double Hydroxides on Electrospun MXene for Superior Asymmetric Supercapacitor Electrodes.

Flexible electrodes for energy storage and conversion require a micro-nanomorphology and stable structure. Herein, MXene fibers (MX-CNF) are fabricated by electrospinning, and Co-MOF nanoarrays are prepared on the fibers to form Co-MOF@MX-CNF. Hydrolysis and etching of Co-MOF@MX-CNF in the Ni2+ solution produce cobalt-nickel layered double hydroxide (CoNi-LDH). The CoNi-LDH nanoarrays on the MX-CNF substrate have a large specific surface area and abundant electrochemical active sites, thus ensuring effective exposure of the CoNi-LDH active materials to the electrolyte and efficient pseudocapacitive energy storage and fast reversible redox kinetics for enhanced charging-discharging characteristics. The CoNi-LDH@MX-CNF electrode exhibits a discharge capacity of 996 F g-1 at a current density of 1 A g-1 as well as 78.62% capacitance retention after 3,000 cycles at 10 A g-1. The asymmetric supercapacitor (ASC) comprising the CoNi-LDH@MX-CNF positive electrode and negative activated carbon electrode shows an energy density of 48.4 Wh kg-1 at a power density of 499 W kg-1 and a capacity retention of 78.9% after 3,000 cycles at a current density of 10 A g-1. Density-functional theory calculations reveal the charge density difference and partial density of states of CoNi-LDH@MX-CNF confirming the large potential of the CoNi-LDH@MX-CNF electrode in energy storage applications.

MXene nanofibers confining MnOx nanoparticles: a flexible anode for high-speed lithium ion storage networks.

The electron and ion conductivities of anode materials such as MnOx affect critically the properties of anodes in Li-ion batteries. Herein, a three-dimensional (3D) nanofiber network (MnOx-MXene/CNFs) for high-speed electron and ion transport with a MnOx surface anchored and embedded inside is designed via electrospinning manganese ion-modified MXene nanosheets and subsequent carbonization. Ion transport analysis reveals improved Li+ transport on the MnOx-MXene/CNF electrode and first-principles density functional theory (DFT) calculation elucidates the Li+ adsorption and storage mechanism. The surface-anchored MnOx nanoparticles form extremely strong bonds with the nanofibers, and the internally embedded MnOx nanoparticles, due to the fiber confinement effect, ensure the structural stability during charging and discharging, achieving the so-called dual stabilization strategies for cyclic fluctuation. By electrospinning, self-restacking of MXene flakes can be prevented, thereby giving rise to a larger surface area and more accessible active sites on the flexible anode. Benefiting from the 3D network with excellent conductivity and stability, at high current densities, the MnOx-MXene/CNF anode exhibits outstanding electrochemical characteristics. Even after 2000 cycles, a reversible capacity of 1098 mA h g-1 can be obtained at 2 A g-1 with only 0.007208% decay rate. The MnOx-MXene/CNF anode also shows a significant rate performance such as 1268 mA h g-1 at 2 A g-1 and 1137 mA h g-1 at 5 A g-1 corresponding to an area specific capacity of 2.536 mA h cm-2 at 4 mA cm-2 and 2.274 mA h cm-2 at 10 mA cm-2, respectively. The results indicate that the MnOx-MXene/CNF anode has excellent Li-ion storage properties and great commercial potential.

MXene-encapsulated hollow Fe3O4 nanochains embedded in N-doped carbon nanofibers with dual electronic pathways as flexible anodes for high-performance Li-ion batteries.

Fe3O4 is one of the promising anode materials in Li-ion batteries and a potential alternative to graphite due to the high specific capacity, natural abundance, environmental benignity, non-flammability, and better safety. Nevertheless, the sluggish intrinsic reaction kinetics and huge volume variation severely limit the reversible capacity and cycling life. In order to overcome these hurdles and enhance the cycling life of Fe3O4, a one-dimensional (1D) nanochain structure composed of 2D Ti3C2-encapsulated hollow Fe3O4 nanospheres homogeneously embedded in N-doped carbon nanofibers (Fe3O4@MXene/CNFs) is designed and demonstrated as a high-performance anode in Li-ion batteries. The distinctive 1D nanochain structure not only inherits the high electrochemical activity of Fe3O4, but also exhibits excellent electron and ion conductivity. The Ti3C2 layer on the Fe3O4 hollow nanospheres forms the primary electron transport pathway and the N-doped carbon nanofiber network provides the secondary transport pathway. At the same time, Ti3C2 flakes partially accommodate the large volume change of Fe3O4 during Li+ insertion/extraction. Density functional theory (DFT) calculations demonstrate that the Fe3O4@MXene/CNFs electrode can efficiently enhance the adsorption of Li+ to promote Li+ storage. As a result of the electrospinning process, self-restacking of Ti3C2 flakes and aggregation of Fe3O4 nanospheres can be prevented resulting in a larger surface area and more accessible active sites on the flexible anode. The Fe3O4@MXene/CNFs anode has remarkable electrochemical properties at high current densities. For example, a reversible capacity of 806 mA h g-1 can be achieved at 2 A g-1 even after 500 cycles, corresponding to an area specific capacity of 1.612 mA h cm-2 at 4 mA cm-2 and a capacity as high as 613 mA h g-1 is retained at 5 A g-1, corresponding to an area capacity of 1.226 mA h cm-2 at 10 mA cm-2. The results indicate that the Fe3O4@MXene/CNFs anode has excellent properties for Li-ion storage.

Inter-overlapped MoS2/C composites with large-interlayer-spacing for high-performance sodium-ion batteries.

As a two-dimensional layered material with a structure analogous to that of graphene, molybdenum disulfide (MoS2) holds great promise in sodium-ion batteries (SIBs). However, recent research findings have revealed some disadvantages in two-dimensional (2D) materials such as poor interlayer conductivity and structural instability, resulting in poor rate performance and short cycle life for SIBs. Herein, we designed MoS2 nanoflowers with an ultra-wide spacing interlayer (W-MoS2/C) anchored on special double carbon tubes to construct three-dimensional (3D) nanostructures. When tested as an anode material in a SIB, the as-prepared CNT@NCT@W-MoS2/C sample achieves high capacities (530 and 230 mA h g-1 at current densities of 0.1 and 2 A g-1, respectively). Density functional theory (DFT) calculations demonstrate that the ultra-wide spacing MoS2/C structure is beneficial for the chemical adsorption of sodium ions and facilitates redox reactions. The wide interlayer spacing and the presence of an intermediate carbon layer provide a rapid diffusion channel for ions and offer a free space for volume expansion of the electrode material.

Ultra-thin NiS nanosheets as advanced electrode for high energy density supercapacitors.

Low energy density of supercapacitors is one of the major downsides for their practical applications. Here, a simple hydrothermal method was developed to synthesize NiS nanosheets on Ni foam. NiS nanosheets with a rough surface promise large electroactive surface area for energy storage, and show an ultra-high capacitance of 2587 F g-1 at a scan rate of 0.2 A g-1 (corresponding to the discharge time of 5563 s). The NiS nanosheets also present an outstanding cycling stability of 95.8% after 4000 cycles. As a positive electrode material for hybrid supercapacitors (HSC), NiS nanostructures provide a broad voltage window of 1.7 V. Our device also shows a high energy density of 38 W h kg-1 at a power density of 1.5 kW kg-1.

Self-limiting electrode with double-carbon layers as walls for efficient sodium storage performance.

As a promising energy storage device, sodium ion batteries (SIBs) have attracted more and more attention. Nevertheless, the radius of a sodium ion is much larger than that of a lithium ion, and it is still a significant challenge to solve the problem of volume expansion. In order to solve the problem of volume expansion, a rational nanostructure consisting of CNTs as a carbon matrix, and were sequentially coated with mesoporous SnO2 and N-doped porous carbon tube (NCT). Mesoporous SnO2 can alleviate the volume expansion caused by charge and discharge, and the N-doped porous carbon layer can further inhibit the volume expansion of SnO2. When used as an anode material in sodium ion batteries, the CNT@SnO2@NCT heterostructure achieves efficient capabilities (350 and 150 mA h g-1 at current densities of 0.1 and 2 A g-1, respectively).

Adaptation mechanism and tolerance of Rhodopseudomonas palustris PSB-S under pyrazosulfuron-ethyl stress.

BACKGROUND: Pyrazosulfuron-ethyl is a long lasting herbicide in the agro-ecosystem and its residue is toxic to crops and other non-target organisms. A better understanding of molecular basis in pyrazosulfuron-ethyl tolerant organisms will shed light on the adaptive mechanisms to this herbicide. RESULTS: Pyrazosulfuron-ethyl inhibited biomass production in Rhodopseudomonas palustris PSB-S, altered cell morphology, suppressed flagella formation, and reduced pigment biosynthesis through significant suppression of carotenoids biosynthesis. A total of 1127 protein spots were detected in the two-dimensional gel electrophoresis. Among them, 72 spots representing 56 different proteins were found to be differently expressed using MALDI-TOF/TOF-MS, including 26 up- and 30 down-regulated proteins in the pyrazosulfuron-ethyl-treated PSB-S cells. The up-regulated proteins were involved predominantly in oxidative stress or energy generation pathways, while most of the down-regulated proteins were involved in the biomass biosynthesis pathway. The protein expression profiles suggested that the elongation factor G, cell division protein FtsZ, and proteins associated with the ABC transporters were crucial for R. palustris PSB-S tolerance against pyrazosulfuron-ethyl. CONCLUSION: Up-regulated proteins, including elongation factor G, cell division FtsZ, ATP synthase, and superoxide dismutase, and down-regulated proteins, including ALS III and ABC transporters, as well as some unknown proteins might play roles in R. palustris PSB-S adaptation to pyrazosulfuron-ethyl induced stresses. Functional validations of these candidate proteins should help to develope transgenic crops resistant to pyrazosulfuron-ethyl.

Amorphous red phosphorus nanosheets anchored on graphene layers as high performance anodes for lithium ion batteries.

A facile solution-based method was developed to combine the advantage of amorphous nanoscale red P sheets and highly conductive graphene, forming a high-performance P/graphene composite anode for advanced lithium ion batteries. Graphene can be easily expanded into a 3D framework in solution with rich interior porosity and abundant adsorption points, which enables a large percentage of red P to be loaded and form a uniform P/graphene hybrid structure. The nanoscale and amorphous features of red P effectively reduce the volume expansion and mechanical stress within individual P sheets, thereby alleviating P pulverization during cycling. The well dispersed graphene serves as a buffer layer to accommodate the volume expansion and adsorb the stress during electrochemical reactions, thereby maintaining a robust electrode structure. Besides, the highly conductive graphene greatly enhances the ionic/electronic conductivity of the electrode, which favors efficient redox reactions and high P utilization. Based on the superior composite structure, the potentials of both components can be fully exerted, resulting in excellent electrochemical performance. The P/graphene electrode delivered a high reversible capacity of 1286 mA h g-1 based on the weight of the composite after 100 cycles at 200 mA g-1. Even at a high current density of 1000 mA g-1, the composite electrode exhibits a high capacity of 1125 mA h g-1, revealing its potential as a high-performance P-carbon composite anode for advanced lithium ion batteries.

Dinuclear zinc complex catalyzed asymmetric methylation and alkynylation of aromatic aldehydes.

A general AzePhenol dinuclear zinc catalytic system has been successfully developed and introduced into the asymmetric addition of dimethylzinc and alkynylzinc to aromatic aldehydes. In this system, an azetidine derived chiral ligand has proven to be an effective enantioselective promoter. Under the optimal reaction conditions, a series of chiral 1-hydroxyethyl (up to 99% ee) and secondary propargylic alcohols (up to 96% ee) were generated with good yields and enantioselectivities. Additionally, this novel catalytic system showed good functional group compatibility. Remarkably, the substituent's electronic nature alone is not sufficient to allow for exclusive enantioselectivity, an additional substituent's location also had an effect. We proposed that the formation of a stable and structural rigid transition state by the chelation of ortho substituted benzaldehydes to the zinc atom was responsible for the observed higher enantioselectivity. The possible catalytic cycles of both transformations accounting for the stereoselectivity were described accordingly.

Urchin-like NiCo2O4 nanoneedles grown on mesocarbon microbeads with synergistic electrochemical properties as electrodes for symmetric supercapacitors.

Here, we report a facile method to fabricate NiCo2O4 nanoneedles on mesocarbon microbeads (MCMB) and form a unique urchin-like core-shell structure. In this composite, the MCMB not only provided high conductivity to benefit effective electron transfer, but also offered abundant adsorption points to load the NiCo2O4 nanoneedles. The aggregation of the NiCo2O4 nanoneedles was therefore alleviated and each NiCo2O4 grain was unfolded to gain easy access to the electrolyte for efficient ion transfer. When the NiCo2O4@MCMB composite was evaluated as an electrode material for supercapacitors, a synergistic effect was exerted with high specific capacitance (458 F g-1 at 1 A g-1) and large reversibility (116% capacitance retention after 3000 cycles), both of which were of great advantage over individual MCMB and NiCo2O4 nanoneedles. The NiCo2O4@MCMB was also used to construct a symmetric supercapacitor, which showed enlarged voltage profiles and could light the LED device for a few minutes, further confirming its excellent electrochemical performance.

Desilylation-Activated Propargylic Transformation: Enantioselective Copper-Catalyzed [3+2] Cycloaddition of Propargylic Esters with ß-Naphthol or Phenol Derivatives.

A copper-catalyzed asymmetric [3+2] cycloaddition of 3-trimethylsilylpropargylic esters with either ß-naphthols or electron-rich phenols has been realized and proceeds by a desilylation-activated process. Under the catalysis of Cu(OAc)2⋅H2O in combination with a structurally optimized ketimine P,N,N-ligand, a wide range of optically active 1,2-dihydronaphtho[2,1-b]furans or 2,3-dihydrobenzofurans were obtained in good yields and with high enantioselectivities (up to 96 % ee). This represents the first desilylation-activated catalytic asymmetric propargylic transformation.

Highly diastereo- and enantioselective copper-catalyzed propargylic alkylation of acyclic ketone enamines for the construction of two vicinal stereocenters.

The first highly diastereo- and enantioselective propargylic alkylation of acyclic ketone enamines to form vicinal tertiary stereocenters has been reported by employing copper catalysis in combination with a bulky and structurally rigid tridentate ketimine P,N,N-ligand.

Solution growth of NiO nanosheets supported on Ni foam as high-performance electrodes for supercapacitors.

Well-aligned nickel oxide (NiO) nanosheets with the thickness of a few nanometers supported on a flexible substrate (Ni foam) have been fabricated by a hydrothermal approach together with a post-annealing treatment. The three-dimensional NiO nanosheets were further used as electrode materials to fabricate supercapacitors, with high specific capacitance of 943.5, 791.2, 613.5, 480, and 457.5 F g(-1) at current densities of 5, 10, 15, 20, and 25 A g(-1), respectively. The NiO nanosheets combined well with the substrate. When the electrode material was bended, it can still retain 91.1% of the initial capacitance after 1,200 charging/discharging cycles. Compared with Co3O4 and NiO nanostructures, the specific capacitance of NiO nanosheets is much better. These characteristics suggest that NiO nanosheet electrodes are promising for energy storage application with high power demands.

NiCo2O4 nanostructure materials: morphology control and electrochemical energy storage.

Three types of NiCo2O4 nanostructure, homogeneous NiCo2O4 nanoneedle arrays, heterogeneous NiCo2O4 nanoflake arrays and NiCo2O4 nanoneedle-assembled sisal-like microspheres are synthesized via facile solution methods in combination with thermal treatment. The NiCo2O4 nanoneedle arrays are evaluated as supercapacitor electrodes and demonstrate excellent electrochemical performances with a high specific capacitance (923 F g(-1) at 2 A g(-1)), good rate capability, and superior cycling stability. The superior capacitive performances are mainly due to the unique one dimensional porous nanoneedle architecture, which provides a faster ion/electron transfer rate, improved reactivity, and enhanced structural stability. The fabrication method presented here is facile, cost-effective and scalable, which may open a new pathway for real device applications.

Enantioselective synthesis of highly functionalized dihydrofurans through copper-catalyzed asymmetric formal [3+2] cycloaddition of ß-ketoesters with propargylic esters.

An enantioselective synthesis of highly functionalized dihydrofurans through a copper-catalyzed asymmetric [3+2] cycloaddition of ß-ketoesters with propargylic esters has been developed. With a combination of Cu(OTf)2 and a chiral tridentate P,N,N ligand as the catalyst, a variety of 2,3-dihydrofurans bearing an exocyclic double bond at the 2 position were obtained in good chemical yields and with good to high enantioselectivities. The exocyclic double bond can be hydrogenated in a highly diastereoselective fashion to give unusual cis-2,3-dihydrofuran derivatives, thus further enhancing the scope of this transformation.

Hierarchical mesoporous nickel cobaltite nanoneedle/carbon cloth arrays as superior flexible electrodes for supercapacitors.

Hierarchical mesoporous NiCo2O4 nanoneedle arrays on carbon cloth have been fabricated by a simple hydrothermal approach combined with a post-annealing treatment. Such unique array nanoarchitectures exhibit remarkable electrochemical performance with high capacitance and desirable cycle life at high rates. When evaluated as an electrode material for supercapacitors, the NiCo2O4 nanoneedle arrays supported on carbon cloth was able to deliver high specific capacitance of 660 F g-1 at current densities of 2 A g-1 in 2 M KOH aqueous solution. In addition, the composite electrode shows excellent mechanical behavior and long-term cyclic stability (91.8% capacitance retention after 3,000 cycles). The fabrication method presented here is facile, cost-effective, and scalable, which may open a new pathway for real device applications.

Enantioselective copper-catalyzed decarboxylative propargylic alkylation of propargyl ß-ketoesters with a chiral ketimine P,N,N-ligand.

The first enantioselective copper-catalyzed decarboxylative propargylic alkylation has been developed. Treatment of propargyl ß-ketoesters with a catalyst, prepared in situ from [Cu(CH3 CN)4 BF4 ] and a newly developed chiral tridentate ketimine P,N,N-ligand under mild reaction conditions, generates ß-ethynyl ketones in good yields and with high enantioselectivities without requiring the pregeneration of ketone enolates. This new process provides facile access to a range of chiral ß-ethynyl ketones in a highly enantioenriched form.