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A modified hydrothermal method was developed to synthesize tin oxide doped with highly dispersed silicon oxide. The microstructure, morphology and electrochemical performance of the mixtures were analyzed by X-ray diffraction (XRD), infra-red (IR), scanning electron microscopy (SEM) and electrochemical methods. The average size of the particles is about 30 nm. Silicon oxide as matrix should be able to support the anode changes accompanied by the formation of lithium–tin alloys, thus an improvement of the cycleability of the Li-ion battery would be expected. The electrochemical results showed that addition of silicon oxide reduces the irreversible capacity during the first discharge/charge cycle. The material delivers a charge capacity of more than 750 mAh g−1. The capacity loss per-cycle is about 0.9% after cycling 20 times. The electrochemical performance indicates that silicon oxide is an appropriate matrix and these composites are good anode candidates for application in lithium-ion batteries.

TiO 2 /short MWNTs nanocomposites were prepared by the sol–gel method using butyl titanate and short MWNTs as starting materials in the solvent of isopropyl alcohol. Their photocatalytic activity in the degradation of X-3B was studied. The effects of mass ratio of short MWNTs to butyl titanate, and heat-treatment temperature on the photoactivity of TiO 2 /short MWNTs nanocomposites were discussed. For comparison purpose, other photocatalysts were also employed in the photodegradation experiment. Thermogravimetric–differential thermal analysis (TG–DTA), scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV–Vis absorption spectra were utilized to characterize the prepared photocatalysts. The results showed that the TiO 2 /short MWNTs nanocomposites synthesized with 1% mass ratio of short MWNTs to butyl titanate had the best photoactivity.

Carbon nanotubes (CNTs) incorporated porous 3-dimensional (3D) CuS microspheres have been successfully synthesized via a simple refluxing method assisted by PVP. The composites are composed of flower-shaped CuS secondary microspheres, which in turn are assembled with primary nanosheets of 15–30 nm in thickness and fully integrated with CNT. The composites possess a large specific surface area of 189.6 m2 g−1 and a high conductivity of 0.471 S cm−1. As electrode materials for supercapacitors, the nanocomposites show excellent cyclability and rate capability and deliver an average reversible capacitance as high as 1960 F g−1 at a current density of 10 mA cm−2 over 10000 cycles. The high electrochemical performance can be attributed to the synergistic effect of CNTs and the unique microstructure of CuS. The CNTs serve as not only a conductive agent to accelerate the transfer of electrons in the composites, but also as a buffer matrix to restrain the volume change and stabilize the electrode structure during the charge/discharge process. The porous structure of CuS also helps to stabilize the electrode structure and facilitates the transport for electrons.

We report the synthesis of three dimensional (3D) NiCo2O4@NiCo2O4 nanocactus arrays grown directly on a Ni current collector using a facile solution method followed by electrodeposition. They possess a unique 3D hierarchical core-shell structure with large surface area and dual-functionalities that can serve as electrodes for both supercapacitors (SCs) and lithium-ion batteries (LIBs). As the SC electrode, they deliver a remarkable specific capacitance of 1264 F g−1 at a current density of 2 A g−1 and ~93.4% of capacitance retention after 5000 cycles at 2 A g−1. When used as the anode for LIBs, a high reversible capacity of 925 mA h g−1 is achieved at a rate of 120 mA g−1 with excellent cyclic stability and rate capability. The ameliorating features of the NiCo2O4 core/shell structure grown directly on highly conductive Ni foam, such as hierarchical mesopores, numerous hairy needles and a large surface area, are responsible for the fast electron/ion transfer and large active sites which commonly contribute to the excellent electrochemical performance of both the SC and LIB electrodes.

ZnCo2O4 nanoflakes, as electrodes for supercapacitors, are grown on a cellular nickel foam using a cost-effective hydrothermal procedure. The mesoporous ZnCo2O4 nanoflakes have large electroactive surface areas with strong adhesion to the Ni foam, allowing fast ion and electron transport. The nanoarchitecture electrodes deliver an excellent specific capacitance of 1220 F g(-1) at a current density of 2 A g(-1) in a 2 M KOH aqueous solution and a long-term cyclic stability of 94.2% capacitance retention after 5000 cycles. The fabrication strategy is facile, cost-effective, and can offer great promise for large-scale supercapacitor applications.

Novel flowerlike nanostructures consisting of Cu2O nanopetals were successfully synthesized by a facile wet chemical method for the first time. The synthesized products were systematically studied by X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. The results showed that the nucleation and growth of the nanoflowers were governed by a nucleation−dissolution−recrystallization growth mechanism. It is noteworthy that the initially formed Cu2O nanoparticles without addition of NaOH were crucial to the growth of the final nanoarchitectures. A UV−vis spectrum was used to estimate the band gap energies of the nanoflowers. Further control experiments were also carried out to investigate the factors that impact the morphology and size of the products. It was demonstrated that the concentrations of NaOH and cetyltrimethylammonium bromide (CTAB) play key roles in the formation of the as-synthesized nanoflowers. By adjusting the concentration of NaOH and CTAB, temperature,...

A method for synthesizing multiwalled carbon nanotubes (MWNTs) beaded with Cu2O nanospheres has been developed. In this work Cu(CH3COO)2?H2O served as the precursor and NaBH4 as the reducing agent, and the produced Cu2O nanoparticles were deposited on the MWNTs with the help of poly(vinyl pyrrolidone) (PVP). After increasing the ageing time, grapelike Cu2O nanospheres adhering to the MWNTs gradually came into being. The synthesized products were systematically studied by x-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. UV?vis absorption spectra were used to estimate the band gap energies of the hybrid system. The synthesis process was facile, efficient and not time-consuming. This method may shed light on integrating MWNTs with other oxide nanospheres and/or nanoparticles using a PVP medium, and lead to an exploration of the potential properties of nanocomposite hybrid materials.

Graphene nanomeshes (GNMs), new graphene nanostructures with tunable bandgaps, are potential building blocks for future electronic or photonic devices, and energy storage and conversion materials. In previous works, GNMs have been successfully prepared on Cu foils by the H2 etching effect. In this paper, we investigated the effect of Ar on the preparation of GNMs, and how the mean density and shape of them vary with growth time. In addition, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (TEM) revealed the typical hexagonal structure of GNM. Atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS) indicated that large copper oxide nanoparticles produced by oxidization in purified Ar can play an essential catalytic role in preparing GNMs. Then, we exhibited the key reaction details for each growth process and proposed a growth mechanism of GNMs in purified Ar.

As one of the most important research areas in lithium-ion batteries (LIBs), well-designed nanostructures have been regarded as key for solving problems such as lithium ion diffusion, the collection and transport of electrons, and the large volume changes during cycling processes. Here, hierarchical graphene-wrapped TiO2@Co3O4 coaxial nanobelt arrays (G-TiO2@Co3O4 NBs) have been fabricated and further investigated as the electrode materials for LIBs. The results show that the yielded G-TiO2@Co3O4 NBs possess a high reversible capacity, an outstanding cycling performance, and superior rate capability compared to TiO2 and TiO2@Co3O4 nanobelt array (TiO2@Co3O4 NBs) electrodes. The core–shell TiO2@Co3O4 NBs may contain many cavities and provide more extra spaces for lithium ion storage. The introduction of graphene into nanocomposite electrodes is favorable for increasing their electrical conductivity and flexibility. The integration of hierarchical core–shell nanobelt arrays and conducting graphene may induce a positive synergistic effect and contribute to the enhanced electrochemical performances of the electrode. The fabrication strategy presented here is facile, cost-effective, and can offer a new pathway for large-scale energy storage device applications.

(Li1−x Fe x OH)FeSe single crystals have been successfully synthesized by a hydrothermal ion-exchange technique. We have carried out systematic research on the influence of the concentration of selenourea (c m) on the superconducting properties of (Li1−x Fe x OH)FeSe single crystals. The optimized specimens possess an onset superconducting transition temperature T c of up to 42 K obtained at c m = 0.8 mol l−1, and the corresponding residual resistivity ratio (RRR = ρ (300 K)/ρ (T c)) is estimated to be 11. The vortex liquid-to-glass phase transition has been discussed based on the collective pinning model. The large distance between the H g and H c2 lines, as well as the much narrower region of the pinned vortex-liquid phase, indicate a weak vortex-pinning ability in (Li1−x Fe x OH)FeSe single crystals. The big out-plane anisotropy behavior versus temperature has been explored according to the anisotropic Ginzburg–Landau theory, and the anisotropy factor Γ displays linear behavior towards temperature similar to that of SmFeAsO1−x F x superconductors.

The indirect bandgap of single-crystalline silicon has so far precluded the full integration of silicon microelectronics with photonics-which is expected to allow the realization of low-cost, high-speed optical information processing and communication in the future. Here we report the growth of europium (Eu)-doped Si-SiO2 core-shell nanowires by an oxide-assisted chemical vapor deposition method. The Eu concentration in these nanowires is effectively improved by intentionally increasing the thickness of SiO2 shells. As a result, a strong Si-compatible red emission from Eu(3+) ions was observed under laser illumination. The effect of Eu(3+) concentration on the emission efficiency was comprehensively studied, with the highest efficiency at Eu content about 0.8 at%. The relaxation mechanism of this concentration dependent luminescence was further explored through lifetime measurements. In light of the strong characteristic red emission and nanoscale footprint, these nanowires are promising Si-compatible light emission materials for future integrated nanophotonics.

Large size single crystals of (Li1−x Fe x )OHFeSe have been synthesized via a hydrothermal ion-exchange technique using K0.8Fe2Se2 single crystals as the main raw material. The onset superconducting transition temperature is up to 40.3 K. The critical current density is as large as 1.9 × 105 A cm−2 at 5 K and self field. The upper critical fields have been determined by analyzing the relationship between resistivity and temperature under different applied fields along c-axis and ab-plane, respectively. An anisotropic factor about 11 is obtained, which is further confirmed by fitting the data obtained from the angle-dependent resistivity according to the anisotropic Ginzburg–Landau theory. The flux pinning potential (U 0/k B) is as large as 6429 and 3115 K at 0.1 T in H//ab and H//c orientation, respectively. However, the flux pinning potentials are very sensitive to the applied magnetic field and will fast decrease with increase of the magnetic field in both directions, which are obviously different from the Ba1−x K x Fe2As2 superconductor indicating a different flux pinning mechanism in the two kinds of superconductors.

Bismuth tungstate has attracted great attention as a new photocatalyst working under visible irradiation. In this paper, we demonstrate a facile hydrothermal route for controllable synthesis of novel Bi(2)WO(6) hierarchical hollow spheres with an ultrahigh specific surface area in the presence of poly(vinyl pyrrolidone) at a proper C(2)H(5)OH/CH(3)COOH/H(2)O volume ratio. The obtained products are systematically studied by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller (BET) and UV-vis absorption spectroscopy. It is shown that the Bi(2)WO(6) hollow spheres are constructed of numerous nanoplates while the nanoplates consist of a great deal of nanoparticles. UV-vis spectrum is used to estimate the band gap energy (about 2.90 eV) of the Bi(2)WO(6) hollow spheres. The ultrahigh BET specific surface area of ca. 45.0 m(2) g(-1) is displayed for the Bi(2)WO(6) hierarchical hollow spheres, which is much higher than that for all the previously reported Bi(2)WO(6) products. The Bi(2)WO(6) hierarchical hollow spheres are displayed to possess superior photocatalytic activity in the photodegradation of rhodamine B (RhB) under visible light irradiation over other morphological products.

A novel hierarchical Co3O4@α-Fe2O3 core–shell nanoneedle array (Co3O4@α-Fe2O3 NAs) on nickel foam substrate is synthesized successfully by a stepwise, seed-assisted, hydrothermal approach. This composite nanostructure serving as an anode material for lithium-ion batteries (LIBs) is advantageous in providing large interfacial area for lithium insertion/extraction and short diffusion pathways for electronic and ionic transport. The results show that a high initial discharge capacity of 1963 mA h g−1 at 120 mA g−1 was obtained by using these hierarchical Co3O4@α-Fe2O3 NAs heterostructures as an anode, and is retained at 1045 mA h g−1 after 100 cycles, better than that of pure Co3O4 nanoneedle arrays (Co3O4 NAs) and α-Fe2O3 film grown under similar conditions, indicating a positive synergistic effect of the material and structural hybridization on the enhancement of the electrochemical properties. The fabrication strategy presented here is facile, cost-effective, and scalable, which opens new avenues for the design of optimal composite electrode materials with improved performance.

Self-assembled hierarchical graphene@polyaniline (PANI) nanoworm composites have been fabricated using graphene oxide (GO) and aniline as the starting materials. The worm-like PANI nanostructures were successfully obtained via a simple polymerization route. The graphene-wrapped hierarchical PANI nanoworm structures could be prepared using a three-step process by dispersing the PANI nanoworms sequentially into the relevant solution. The morphologies and microstructures of the samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Electrochemical properties were also characterized by cyclic voltammetry (CV) and galvanostatic charge–discharge. The results indicated that the integration of graphene and the worm-like PANI nanocomposites possessed excellent electrochemical properties. These hierarchical worm-like graphene@PANI nanostructures could afford an interconnected network with a lot of well-defined nanopores, and further provided more active sites and excellent electron transfer path for improving the electric conductivity as well as good mechanical properties. Supercapacitor devices based on these self-assembled nanocomposites showed high electrochemical capacitance (488.2 F g−1) at a discharge rate of 0.5 A g−1, which also could effectively improve electrochemical stability and rate performances.

Self-assembled well-ordered whisker-like manganese dioxide (MnO2) arrays on carbon fiber paper (MOWAs) were synthesized via a simple in situ redox replacement reaction between potassium permanganate (KMnO4) and carbon fiber paper (CFP) without any other oxidant or reductant addition. The CFP serves as not only a sacrificial reductant and converts aqueous permanganate (MnO4−) to insoluble MnO2 in this reaction, but also a substrate material and guarantees MnO2 deposition on the surface. The electrochemical properties were examined by cyclic voltammograms (CV), galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS) in a three-electrode cell. According to the CV results, the ordered MOWAs yield high-capacitance performance with specific capacitance up to 274.1 F g−1 and excellent long cycle-life property with 95% of its specific capacitance kept after 5000 cycles at the current density of 0.1 A g−1. The high-performance hybrid composites result from a synergistic effect of large surface area and high degree of ordering of the ultrathin layer of MnO2 nanowhisker arrays, combined with the flexible CFP substrate and can offer great promise in large-scale energy storage device applications.

Successful synthesis of monodisperse nickel particles with narrow particle size distributions is reported for the first time via a simple solvothermal method with ultrasonic treatment using no surfactants. The Ni products are characterized by X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. The as-synthesized monodisperse Ni particles show a spherical morphology with the mean particle size of 46.2, 60.1 and 113.7 nm for the reaction time of 0.5, 1 and 3 h, respectively at a low temperature of 100 degrees C. The catalytic effect is investigated for the Ni particles on the thermal decomposition of ammonium perchlorate (AP) using differential thermal analysis and thermogravimetry. For the purpose of comparison, as-prepared and commercial non-monodisperse Ni particles are used for examining the catalytic effect. The monodisperse Ni particles show a superior catalytic effect over the non-monodisperse Ni counterparts with a similar mean particle size. The surface areas of Ni particles are measured by Brunauer-Emmett-Teller (BET) technique. A theoretical consideration is also presented for analysis of the surface areas of monodisperse and non-monodisperse particles. Both the BET and theoretical results show that the surface area of monodisperse particles is higher than that of non-monodisperse counterparts. Consequently, the catalytic effect of Ni particles on thermal decomposition of AP is explained in terms of the surface areas.

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.

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.