Hierarchical Ni-Co-Mn hydroxide hollow architectures as high-performance electrodes for electrochemical energy storage.

In this study, hierarchical Ni-Co-Mn hydroxide hollow architectures were successfully achieved via an etching process. We first performed the synthesis of NiCoMn-glycerate solid spheres via a solvothermal route, and then NiCoMn-glycerate as the template was etched to convert into hierarchical Ni-Co-Mn hydroxide hollow architectures in the mixed solvents of water and 1-methyl-2-pyrrolidone. Hollow architectures and high surface area enabled Ni-Co-Mn hydroxide to manifest a specific capacitance of 1626 F g-1 at 3.0 A g-1, and it remained as large as 1380 F g-1 even at 3.0 A g-1. The Ni-Co-Mn hydroxide electrodes also displayed notable cycle performance with a decline of 1.6% over 5000 cycles at 12 A g-1. Moreover, an asymmetric supercapacitor assembled with this electrode exhibited an energy density of 44.4 W h kg-1 at 1650 W kg-1 and 28.5 W h kg-1 at 12 374 W kg-1. These attractive results demonstrate that hierarchical Ni-Co-Mn hydroxide hollow architectures have broad application prospects in supercapacitors.

Effects of Preparation Parameters of NiAl Oxide-Supported Au Catalysts on Nitro Compounds Chemoselective Hydrogenation.

Effects of preparation parameters of NiAl oxide-supported Au nanocatalysts on their performance in the chemoselective hydrogenation of nitro compounds were investigated. The deposition-precipitation method, low Au loading, and low Ni/Al molar ratio of the support contributed to the generation of small-sized Au nanoparticles. High catalytic properties were related to the small sizes of Au particles and appropriate basicity of supports. Accordingly, the 0.43% Au/NiAlO-2-500 (the Ni/Al molar ratio of the support = 2) showed high activity and excellent selectivity for nitro hydrogenation. It also showed good versatility for other nitro compounds and good recyclability. Interestingly, for the first time, this Au catalyst switched its selectivity to vinyl hydrogenation by mere regulation of the composition of the support (the Ni/Al molar ratio of the support = 4). The observed shift in selectivity was ascribed to the different adsorption behaviors of the nitro and vinyl group on Au nanocatalysts. It provides a novel and facile strategy to construct Au nanocatalysts with high activity and switchable selectivity for hydrogenation of nitro compounds by the fine tuning of preparation parameters.

Self-Template Synthesis of Hybrid Porous Co3 O4 -CeO2 Hollow Polyhedrons for High-Performance Supercapacitors.

In this work, hybrid porous Co3 O4 -CeO2 hollow polyhedrons have been successfully obtained via a simple cation-exchange route followed by heat treatment. In the synthesis process, ZIF-67 polyhedron frameworks are firstly prepared, which not only serve as a host for the exchanged Ce3+ ions but also act as the template for the synthesis of hybrid porous Co3 O4 -CeO2 hollow polyhedrons. When utilized as electrode materials for supercapacitors, the hybrid porous Co3 O4 -CeO2 hollow polyhedrons delivered a large specific capacitance of 1288.3 F g-1 at 2.5 A g-1 and a remarkable long lifespan cycling stability (<3.3 % loss after 6000 cycles). Furthermore, an asymmetric supercapacitor (ASC) device based on hybrid porous Co3 O4 -CeO2 hollow polyhedrons was assembled. The ASC device possesses an energy density of 54.9 W h kg-1 , which can be retained to 44.2 W h kg-1 even at a power density of 5100 W kg-1 , indicating its promising application in electrochemical energy storage. More importantly, we believe that the present route is a simple and versatile strategy for the preparation of other hybrid metal oxides with desired structures, chemical compositions and applications.

Self-template synthesis of hollow ellipsoid Ni-Mn sulfides for supercapacitors, electrocatalytic oxidation of glucose and water treatment.

In this work, we have successfully developed a simple self-template route for preparation of hollow ellipsoid Ni-Mn sulfides. This route involves the synthesis of solid Ni-Mn ellipsoids via a chemical precipitation method. Then, using thioacetamide (TAA) as the sulfur source, the solid Ni-Mn ellipsoids can be easily converted to hollow ellipsoid Ni-Mn sulfides in ethanol via sulfidation reaction. The as-synthesized hollow ellipsoid Ni-Mn sulfides possess large specific surface areas and porous structures. Benefiting from these structural and compositional advantages, the electrochemical performance of the hollow ellipsoid Ni-Mn sulfides is studied. As expected, the hollow ellipsoid Ni-Mn sulfides show a high specific capacitance of 1636.8 F g-1 at 2.0 A g-1 and good cycling stability (only 4.9% loss after 4000 cycles) as electrode materials for supercapacitors. Furthermore, electrocatalytic oxidation of glucose based on the synthesized hollow ellipsoid Ni-Mn sulfides is also performed. The hollow ellipsoid Ni-Mn sulfides present high sensitivity and selectivity, good stability and a low detection limit (0.02 µM). In addition, the as-synthesized hollow ellipsoid Ni-Mn sulfides exhibit good ability to remove the Congo red dyes from water, which gives them potential application in water treatment. The current work makes a major contribution to the design and preparation of hollow metal sulfide structures, as well as their potential applications in supercapacitors, electrocatalytic oxidation of glucose and water treatment.

Mesoporous hybrid NiOx-MnOx nanoprisms for flexible solid-state asymmetric supercapacitors.

Mesoporous hybrid NiOx-MnOx nanoprisms have been successfully prepared in this work. The synthesis process involves a facile solvothermal method for preparation of Ni-Mn precursor particles and a subsequent annealing treatment. These mesoporous hybrid NiOx-MnOx nanoprisms have a high surface area of 101.6 m(2) g(-1). When evaluated as electrode materials in supercapacitors, the as-prepared mesoporous hybrid NiOx-MnOx nanoprisms deliver a specific capacitance of 1218 F g(-1) at a current density of 2.0 A g(-1). More importantly, the mesoporous hybrid NiOx-MnOx nanoprisms were successfully used to construct flexible solid-state asymmetric supercapacitors. The device shows a specific capacitance of 149.1 mF cm(-2) at 2.0 mA cm(-2), a good cycling stability with only 2.9% loss of capacitance after 5000 charge-discharge cycles, and good mechanical flexibility under different bending angles. These results support the promising application of mesoporous hybrid NiOx-MnOx nanoprisms as advanced supercapacitor materials.

Comparison of NiS2 and α-NiS hollow spheres for supercapacitors, non-enzymatic glucose sensors and water treatment.

NiS2 hollow spheres are successfully prepared by a one-step template free method. Meanwhile, α-NiS hollow spheres can also be synthesized via the calcination of the pre-obtained NiS2 hollow spheres at 400 °C for 1 h in air. The electrochemical performances of the as-prepared NiS2 and α-NiS hollow sphere products are evaluated. When used for supercapacitors, compared with NiS2 hollow spheres, the α-NiS hollow sphere electrode shows a large specific capacitance of 717.3 F g(-1) at 0.6 A g(-1) and a good cycle life. Furthermore, NiS2 and α-NiS hollow spheres are successfully applied to fabricate non-enzymatic glucose sensors. In particular, the α-NiS hollow spheres exhibit good catalytic activity for the oxidation of glucose, a fast amperometric response time of less than 5 s, and the detection limit is estimated to be 0.08 µM. More importantly, compared with other normally co-existing interfering species, such as ascorbic acid, uric acid and dopamine, the electrode modified with α-NiS hollow spheres shows good selectivity. Moreover, the α-NiS hollow spheres also present good capacity to remove Congo red organic pollutants from wastewater by their surface adsorption ability.

Bottom-up-then-up-down Route for Multi-level Construction of Hierarchical Bi2S3 Superstructures with Magnetism Alteration.

A bottom-up-then-up-down route was proposed to construct multi-level Bi2S3 hierarchical architectures assembled by two-dimensional (2D) Bi2S3 sheet-like networks. BiOCOOH hollow spheres and flower-like structures, which are both assembled by 2D BiOCOOH nanosheets, were prepared first by a "bottom-up" route through a "quasi-emulsion" mechanism. Then the BiOCOOH hierarchical structures were transferred to hierarchical Bi2S3 architectures through an "up-down" route by an ion exchange method. The obtained Bi2S3 nanostructures remain hollow-spherical and flower-like structures of the precursors but the constructing blocks are changed to 2D sheet-like networks interweaving by Bi2S3 nanowires. The close matching of crystal lattices between Bi2S3 and BiOCOOH was believed to be the key reason for the topotactic transformation from BiOCOOH nanosheets to 2D Bi2S3 sheet-like nanowire networks. Magnetism studies reveal that unlike diamagnetism of comparative Bi2S3 nanostructures, the obtained multi-level Bi2S3 structures display S-type hysteresis and ferromagnetism at low field which might result from ordered structure of 2D networks.

Sodium-Doped Mesoporous Ni2P2O7 Hexagonal Tablets for High-Performance Flexible All-Solid-State Hybrid Supercapacitors.

A simple hydrothermal method has been developed to prepare hexagonal tablet precursors, which are then transformed into porous sodium-doped Ni2P2O7 hexagonal tablets by a simple calcination method. The obtained samples were evaluated as electrode materials for supercapacitors. Electrochemical measurements show that the electrode based on the porous sodium-doped Ni2P2O7 hexagonal tablets exhibits a specific capacitance of 557.7 F g(-1) at a current density of 1.2 A g(-1) . Furthermore, the porous sodium-doped Ni2P2O7 hexagonal tablets were successfully used to construct flexible solid-state hybrid supercapacitors. The device is highly flexible and achieves a maximum energy density of 23.4 Wh kg(-1) and a good cycling stability after 5000 cycles, which confirms that the porous sodium-doped Ni2P2 O7 hexagonal tablets are promising active materials for flexible supercapacitors.

Mesoporous ZnS-NiS Nanocomposites for Nonenzymatic Electrochemical Glucose Sensors.

Mesoporous ZnS-NiS composites are prepared via ion- exchange reactions using ZnS as the precursor. The prepared mesoporous ZnS-NiS composite materials have large surface areas (137.9 m(2) g(-1)) compared with the ZnS precursor. More importantly, the application of these mesoporous ZnS-NiS composites as nonenzymatic glucose sensors was successfully explored. Electrochemical sensors based on mesoporous ZnS-NiS composites exhibit a high selectivity and a low detection limit (0.125 µm) toward the oxidation of glucose, which can mainly be attributed to the morphological characteristics of the mesoporous structure with high specific surface area and a rational composition of the two constituents. In addition, the mesoporous ZnS-NiS composites coated on the surface of electrodes can be used to modify the mass transport regime, and this alteration can, in favorable circumstances, facilitate the amperometric discrimination between species. These results suggest that such mesoporous ZnS-NiS composites are promising materials for nonenzymatic glucose sensors.

Three-dimensional honeycomb-like networks of birnessite manganese oxide assembled by ultrathin two-dimensional nanosheets with enhanced Li-ion battery performances.

Three-dimensional (3D) honeycomb-like birnessite networks composed of ultrathin two-dimensional (2D) nanosheets were firstly synthesized through a facile and low-cost synthetic route. By using carbon microspheres as a template instead of graphene, hierarchical birnessite structures assembled by ultrathin nanosheets including york-shell and hollow structures were obtained besides the ultrathin birnessite nanosheets with a thickness of about 0.7 nm. By assembling carbon spheres into an ordered 3D array, novel 3D honeycomb-like birnessite structures assembled by ultrathin nanosheets were firstly prepared. When evaluated as an anode material for Li-ion batteries, the 3D honeycomb-like networks show enhanced electrochemical performances with high capacities, excellent cycling stability and good rate capability, which can be ascribed to the novel 3D honeycomb-like macroporous structure with a 3D inverse opal structure, well-ordered macropores, interconnected walls and a regular periodicity.

NiS hollow spheres for high-performance supercapacitors and non-enzymatic glucose sensors.

α-NiS and ß-NiS hollow spheres were successfully synthesized via the Kirkendall effect under different hydrothermal conditions. The obtained α-NiS and ß-NiS hollow spheres were evaluated as electrode materials for supercapacitors. Importantly, the α-NiS hollow sphere electrode has a large specific capacitance (562.3 F g(-1) at 0.60 A g(-1)) and good cycling property (maintaining about 97.5% at 2.4 A g(-1) after 1000 cycles). Furthermore, the as-prepared α-NiS and ß-NiS hollow spheres were successfully applied to construct electrochemical glucose sensors. Especially, the α-NiS hollow spheres exhibit a good sensitivity (155 µA mM(-1) cm(-2)), low detection limit (0.125 µM), and a wide linear range.

Assembling CdS mesoporous nanosheets into 3D hierarchitectures for effective photocatalytic performance.

3D hierarchical CdS mesoporous nanosheets are prepared via a facile hydrothermal method in the presence of soulcarboxymthyi chitosan. By investigation of various reaction parameters, it is demonstrated that the reaction temperature and the amounts of ammonia, thiourea and Cd(NO3)2 play important roles in the formation of 3D hierarchical CdS. The optical properties of 3D hierarchical CdS are investigated using ultraviolet-visible (UV-vis) spectroscopy. A photocatalytic activity experiment reveals that the as-synthesized 3D hierarchical CdS exhibits an excellent photocatalytic performance for the degradation of aqueous solutions of methyl orange (MO) under visible light illumination, suggesting that the 3D hierarchical CdS nanomaterial might be a promising candidate for treatment of organic pollutants in waste water.

Microwave-assisted synthesis of NiS2 nanostructures for supercapacitors and cocatalytic enhancing photocatalytic H2 production.

Uniform NiS2 nanocubes are successfully synthesized with a microwave-assisted method. Interestingly, NiS2 nanocubes, nanospheres and nanoparticles are obtained by controlling microwave reaction time. NiS2 nanomaterials are primarily applied to supercapacitors and cocatalytic enhancing photocatalytic H2 production. Different morphologies of NiS2 nanostructures show different electrochemical and cocatalytic enhancing H2 production activities. Benefited novel nanostructures, NiS2 nanocube electrodes show a large specific capacitance (695 F g(-1) at 1.25 A g(-1)) and excellent cycling performance (the retention 93.4% of initial specific capacitance after 3000 cycles). More importantly, NiS2 nanospheres show highly cocatalytic enhancing photocatalytic for H2 evolution, in which the photocatalytic H2 production is up to 3400 µmol during 12 hours under irradiation of visible light (λ>420 nm) with an average H2 production rate of 283 µmol h(-1).

Single-crystalline hyperbranched nanostructure of iron hydroxyl phosphate Fe5(PO4)4(OH)3·2H2O for highly selective capture of phosphopeptides.

Single-crystalline hyperbranched nanostructures of iron hydroxyl phosphate Fe5(PO4)4(OH)3·2H2O (giniite) with orthorhombic phase were synthesized through a simple route. They have a well-defined dendrite fractal structure with a pronounced trunk and highly ordered branches. The toxicity test shows that the hyperbranched nanostructures have good biocompatibility and low toxicity level, which makes them have application potentials in life science. The study herein demonstrated that the obtained hyperbranched giniite nanostructures show highly selective capture of phosphopeptides and could be used as a kind of promising nanomaterial for the specific capture of phosphopeptides from complex tryptic digests with the detection of MALDI-TOF mass spectrometry.

Water amount dependence on morphologies and properties of ZnO nanostructures in double-solvent system.

ZnO materials with a range of different morphologies have been successfully synthesized via a simple double-solvothermal method in the presence of glycine. The morphologies of the products can be controlled from superstructures to microrods by adjusting the amount of water in the EtOH/H2O system. Photoluminescence (PL) studies reveal that the more amount of water was used, the stronger PL relative intensity of the green emission is, but the weaker ultraviolet emission. This might be attributed to the more defects of the products when the more water was used. The catalytic studies show that all the samples have good abilities to decrease decomposition temperature around 300°C and the decomposition temperature lowers with the increase of the relative intensity of ZnO green emission.

Evolution of nickel sulfide hollow spheres through topotactic transformation.

In this study, a topotactic transformation route was proposed to synthesize single-crystalline ß-NiS hollow spheres with uniform phase and morphology evolving from polycrystalline α-NiS hollow spheres. Uniform polycrystalline α-NiS hollow spheres were firstly prepared with thiourea and glutathione as sulfur sources under hydrothermal conditions through the Kirkendall effect. By increasing the reaction temperature the polycrystalline α-NiS hollow spheres were transformed to uniform ß-NiS hollow spheres. The ß-NiS crystals obtained through the topotactic transformation route not only have unchanged morphology of hollow spheres but are also single-crystalline in nature. The as-prepared NiS hollow spheres display a good ability to remove the organic pollutant Congo red from water, which makes them have application potential in water treatment.

Bi-directional-bi-dimensionality alignment of self-supporting Mn3O4 nanorod and nanotube arrays with different bacteriostasis and magnetism.

Self-supported Mn3O4 patterns of aligned nanorods and nanotubes were synthesized through a bi-directional-bi-dimensionality growth model by using sodium gluconate and urea as additives under mild hydrothermal conditions without the use of any substrates. In one direction, Mn3O4 grows to form one-dimensional nanorods or nanotubes, while in the other direction Mn3O4 grows into two-dimensional nanoplates to support the nanorods or nanotubes to align into arrays. These two kinds of new nanostructures, a nanotube pattern and a nanorod pattern, show similar and good bacteriostasis for Gram positive bacteria, but for Gram negative bacteria the nanotube pattern shows much better bacterial restraint than the nanorod pattern. Magnetic studies show that the nanorod arrays display similar magnetic properties to the commercial Mn3O4, while the nanotube arrays show different ferromagnetic behaviors with enhanced remnant magnetization and saturation magnetization (Ms) at low temperature.

Two-dimensional ß-MnO2 nanowire network with enhanced electrochemical capacitance.

Conventional crystalline ß-MnO2 usually exhibits poor electrochemical activities due to the narrow tunnels in its rutile-type structure. In this study, we synthesized a novel 2D ß-MnO2 network with long-range order assembled by ß-MnO2 nanowires and demonstrated that the novel 2D ß-MnO2 network exhibits enhanced electrochemical performances. The 2D network is interwoven by crossed uniform ß-MnO2 nanowires and the angle between the adjacent nanowires is about 60°. Such a novel structure makes efficient contact of ß-MnO2 with electrolyte during the electrochemical process, decreases the polarization of the electrode and thus increases the discharge capacity and high-rate capability. The specific capacitance of the obtained 2D ß-MnO2 network is 453.0 F/g at a current density of 0.5 A/g.

Biomolecule-assisted construction of cadmium sulfide hollow spheres with structure-dependent photocatalytic activity.

In this study, we report the synthesis of monodispersive solid and hollow CdS spheres with structure-dependent photocatalytic abilities for dye photodegradation. The monodispersive CdS nanospheres were constructed with the assistance of the soulcarboxymthyi chitosan biopolymer under hydrothermal conditions. The solid CdS spheres were corroded by ammonia to form hollow CdS nanospheres through a dissolution-reprecipitation mechanism. Their visible-light photocatalytic activities were investigated, and the results show that both the solid and the hollow CdS spheres have visible-light photocatalytic abilities for the photodegradation of dyes. The photocatalytic properties of the CdS spheres were demonstrated to be structure dependent. Although the nanoparticles comprising the hollow spheres have larger sizes than those comprising the solid spheres, the hollow CdS spheres have better photocatalytic performances than the solid CdS spheres, which can be attributed to the special hollow structure.

Controlled growth and applications of complex metal oxide ZnSn(OH)6 polyhedra.

We successfully controlled the crystallographic surface of ZnSn(OH)(6) crystals and systematically obtained ZnSn(OH)(6) crystals in different shapes including cubes, truncated cubes, cuboctahedrons, truncated octahedrons, and octahedrons using a simple solvothermal method in a methylcellulose (MC) ethanol/water solution. By simply adjusting the amount of the NaOH solution added to the reaction system, we observed the shape evolution of ZnSn(OH)(6) particles from cube to octahedron, with the sizes gradually increasing from about 200 nm to 1-2 µm. These results not only provide ZnSn(OH)(6) polyhedra bound by different lattice planes, but also make it possible to investigate the morphology-property relationship of ZnSn(OH)(6) particles with different morphologies obtained under similar conditions. The antibacterial activities of the as-prepared ZnSn(OH)(6) polyhedral particles were studied. It was found that the antibacterial activities of ZnSn(OH)(6) particles against Escherichia coli depend on the shape of the ZnSn(OH)(6) particles, demonstrating that the surface structure of nanocrystals affects the antibacterial activity. Additionally, the obtained ZnSn(OH)(6) polyhedra can be applied as precursors for Zn(2)SnO(4)/SnO(2) composites with different morphologies by calcining at 600 °C.