Search

An available strategy is rationally designed to modify the electrode surfaces with specific electric property based on the controllable surface modifications. In this way, the substitution of oxygen with sulfur can be realized on the surfaces of nickel-cobalt-based molybdate with low temperature chemical vapor deposition method, in which the structures are well-retained. The obtained electrode materials after sulfuration at low temperature are transformed to be nickel-cobalt-based molybdate which is covered with a thin layer of sulfides. Compared with NixCoyMoO4 precursor, the formation of nanocrystalline particles (5–10 nm in size) on the surfaces of the nanosheets after sulfuration will supply much more electrochemical active centers, facilitating the improvement the electrochemical performance of the electrode materials. The oxides-sulfides electrode (NixCoyMoO4@MoS2/CoS/NiS) exhibits a good specific capacity of 1689 F g−1, satisfactory cycle performance with an outstanding retention (90.6%) after 5000 cycles. Besides, an excellent retention of the capacitances (85.3%) can be maintained as the current density is high to be 30 A g−1. Furthermore, the corresponding flexible all-solid-state battery hybrid supercapacitor is developed with the energy density high to be 60.4 W h kg−1 at 800.6 W kg−1 and remarkable stability (94.4% retention) after 5000 cycles.

Nanorod vanadium sulfide anchored on reduced graphene oxide nanosheets composite is prepared by a simple solvothermal method. As an electrode material for lithium-ion batteries, the composite with 13 wt% reduced graphene oxide delivers 1886.3 and 1322.3 mAh g−1 specific capacities for the initial discharge and charge, respectively, resulting in 70.1% of Coulombic efficiency, and has a good capacity retention with 1181.9 mAh g−1 after 50 cycles, much higher than that of pure vanadium sulfide submicrospheres. It exhibits a good cycling stability and an enhanced high-rate capability. Lithium storage mechanism is investigated by cyclic voltammetry, electrochemical impedance spectrum and discharge-charge measurements. The results show that the vanadium sulfide with reduced graphene oxide composite can convert to sulfur + vanadium with reduced graphene oxide composite after the first cycle, and the reduced graphene oxide can effectively inhibit the dissolution of polysulfide while metal vanadium increases electrode electronic conductivity, leading to an enhanced electrochemical performance. The composite is proved to be a promising functional material associated with lithium-sulfur batteries.

The electrode materials as the key component of supercapacitors have attracted considerable research interests, especially for nickel/cobalt based materials by virtue of their superior electrochemical performance with multiple oxidation states for richer redox reactions, abundant natural resources, lower prices and toxicity. There are many advanced electrodes based on the nickel/cobalt materials exploited for the application of supercapacitors, however, some controversial statements have induced some confusion. Herein, we refine the mechanism of energy storage for the nickel/cobalt based materials for supercapacitors and reclassify them into battery-type materials with the corresponding devices named as hybrid supercapacitors.

An efficient and convenient reversed-phase high-performance liquid chromatography method has been developed and validated for the quantitative determination of cholic acid bulk drugs and their related impurities. Chromatographic separation was performed on a YMC-Pack ODS-AQ column (250 mm × 4.6 mm, S-5 μm, 12 nm), and the mobile phase consisted of acetonitrile, methanol, and diluted formic acid solution (pH 2.5) at a flow rate of 1.0 mL/min. The analytes were monitored using a refractive index detector at 30 °C, and the column temperature was 30 °C. Under the above chromatographic conditions, the method has good specificity and specified impurities can be effectively separated. The proposed method is found to have linearity in the 2.0–80.0 μg/mL concentration range with correlation coefficients of not less than 0.9999. The compounds analyzed in the solutions are stable for at least 7 days, and spike recoveries for all specified impurities range from 91.3% to 109.3% with relative standard deviations (RSDs)...

High-security deformable energy-storage devices that are mechanically robust, with considerable energy and power densities are becoming desirable for smart wearable electronics. Here, a highly flexible hydrogel-based all-solid-state hybrid supercapacitor was rationally designed and assembled, with unique NiCo2O4@NixCoyMoO4 (x : y = 3 : 1) nanostructures as the electrode, which was bio-inspired by the curling up and relaxation of hedgehogs. The hybrid supercapacitor shows no obvious decay in capacitance during bending to different states, indicating its outstanding flexibility and mechanical stability. The capacitance was still maintained at 92.0% of the initial value, even after continuous bending for 3000 cycles. The highly monodisperse NiCo2O4@NixCoyMoO4 nanostructures releasing stress during bending is responsible for the favorable stability and flexibility. Furthermore, the hybrid supercapacitor displayed outstanding electrochemical performance, with a high specific capacitance of 207 F g-1 at 1 A g-1, a high energy density of 64.7 W h kg-1 at 749.6 W kg-1, and favorable cycling stability (nearly 100% after 10 000 cycles). The flexible hybrid supercapacitor could be charged with a solar cell and served as the power source to light up LEDs. This simple and reliable hybrid supercapacitor, with extraordinary mechanical stability and electrochemical performance, is a promising power source for smart wearable electronics.

3D network-like, ultrathin, and controllable NixCo1–xMoO4 (0 ≤ x ≤ 1) nanosheets on carbon cloth have been successfully designed and synthesized by a one-step hydrothermal process. All these NixCo1–xMoO4 (0 ≤ x ≤ 1) nanosheets possess similar morphologies and structures with thin nanosheets. The electrochemical performance can be optimized when x = 0.75, owing to the synergistic effect of nickel and cobalt ions. The Ni0.75Co0.25MoO4 nanosheets exhibit high specific capacity of 726.6 C g–1 at 1 A g–1, excellent rate capability maintaining about 73% at 20 A g–1, and favorable cycling stability with about 97.2% retention of the initial after 3000 cycles. The corresponding hybrid supercapacitor exhibits high specific capacity of 99 F g–1 at 1 A g–1 and high energy density of 35.2 Wh kg–1 at the power density of 800 W kg–1. The high specific capacity, excellent rate capability, and favorable cycling performance elucidate that these NixCo1–xMoO4 (0 ≤ x ≤ 1) nanosheets possess tremendously promising applications...

Ni0.5Co0.5(OH)2 nanosheets coated CuCo2O4 nanoneedles arrays were successfully designed and synthesized on carbon fabric. The core/shell nanoarchitectures directly served as the binder-free electrode with a superior capacity of 295.6 mAh g−1 at 1 A g−1, which still maintained 220 mAh g−1 even at the high current density of 40 A g−1, manifesting their enormous potential in hybrid supercapacitor devices. The as-assembled CuCo2O4@Ni0.5Co0.5(OH)2//AC hybrid supercapacitor device exhibited favorable properties with the specific capacitance as high as 90 F g−1 at 1 A g−1 and the high energy density of 32 Wh kg−1 at the power density of 800 W kg−1. Furthermore, the as-assembled device also delivered excellent cycling performance (retaining 91.9% of the initial capacitance after 12,000 cycles at 8 A g−1) and robust mechanical stability and flexibility, implying the huge potential of present hierarchical electrodes in energy storage devices.

CdS decorated CuS structures have been controllably synthesized through a one-pot hydrothermal method. The morphologies and compositions of the as-prepared samples could be concurrently well controlled by simply tuning the amount of CdCl2 and thiourea. Using this strategy, the morphology of the products experienced from messy to flower-like morphologies with multiple porous densities, together with the phase evolution from pure CuS to the CdS/CuS composites. Serving as a photocatalyst, the samples synthesized with the addition of 1 mmol cadmium chloride and 3 mmol thiourea during synthetic process, showed the best photocatalytic activity, which could reach a maximum photocatalytic efficiency of 93% for methyl orange (MO) photodegradation after 150 min. The possible mechanism for the high photocatalytic efficiency of the sample was proposed by investigating the composition, surface area, structure, and morphology before and after photocatalytic reaction.

Hierarchically porous polypyrrole nanowires/manganese oxides nanoflakes (MnO 2 NFs@PPy NWs) core/shell nanostructures were successfully constructed through a simple, convenient and environmentally friendly method by using PPy nanowires as the core buffer and K-Birnessite type MnO 2 as the shell. The core/shell nanostructures effectively increase active surface areas and decrease the ion transmission distance, which is conducive to the efficient transfer of ions. The MnO 2 NFs@PPy NWs core/shell nanostructures exhibited not only high specific capacitance (276 F g −1 at 2 A g −1 ) but also excellent capacitance retained ratio of 72.5% under extreme charge/discharge conditions (200 F g −1 at 20 A g −1 ) due to the synergistic effect by combining the merits of MnO 2 and PPy. Using such hierarchical nanostructure as the positive electrode, we further demonstrate that ultra-flexible asymmetrical supercapacitors (AFSCs) (MnO 2 @PPy//AC) possess excellent cycling stability (90.3% after 6000 cycles at 3 A g −1 ), mechanical flexibility, large voltage operation window (1.8–2.0 V vs. SCE) and high energy densities at all charge/discharge conditions (25.8 W h kg −1 at the power density of 901.7 W kg −1 , and 17.1 W h kg −1 at the power density of 9000 W kg −1 , respectively).

Different Bi 2 S 3 nanoarchitectures (nanorods and nanobelts) were successfully synthesized with a facile solvothermal method at different temperature. The nanobelts transformed into nanorods when the temperature was 200 °C increased from 150 °C. The nanorod-morphology was kept even the temperature was further increased. The galvanostatic charge/discharge performance showed that the prepared Bi 2 S 3 nanorods had good performance of discharge efficiency at current density from 1 A g −1 to 4 A g −1 . The specific capacitance was 270 F g −1 at a current density of 1 A g −1 . Furthermore, the nanorods were also used as the efficient UV-light photocatalysts for the degradation of Rhodamine B (RhB), which showed almost complete degradation (∼87%) of RhB dye at 100 min.

Millions of smart home speakers, such as Amazon Echo and Google Home, have been purchased by U.S. consumers. However, the security and privacy of smart home speakers have not been rigorously examined, which raise critical security and privacy concerns. In this paper, we investigate untold and severe privacy leakage of smart home speakers. Specifically, we examine a new passive attack, referred to as voice command fingerprinting attack, on smart home speakers. We demonstrate that a passive attacker, who can only eavesdrop encrypted traffic between a smart home speaker and a cloud server, can infer users' voice commands and compromise the privacy of millions of U.S. consumers. We formulate the attacks by harnessing machine learning algorithms. In addition to leveraging accuracy, we propose a new privacy metric, named semantic distance, to assess the privacy leakage with natural language processing. Our experiment results on a real-world dataset suggest that voice command fingerprinting attacks can correctly infer 33.8% of voice commands by eavesdropping encrypted traffic. Our results also show that existing padding methods can diminish an attacker's accuracy to 14.7%, but would cause high communication overhead (548%) and long time delay (330%).

Molybdenum dioxide (MoO 2 ) nanoparticles were synthesized on carbon fibers by a facile hydrothermal method. The XRD results reveal that the obtained nanoparticles have a monoclinic phase with diameter in the range of tens of nanometers, which could be directly functionalized for application in the lithium-ion batteries (LIBs). The annealed MoO 2 nanoparticles exhibit high specific capacity and excellent cycling stability. A high discharge capacity of 1117 mA h g −1 can maintain after 50 cycles at the rate of 0.5 C. In view of the excellent lithium storage properties and the ease in large-scale preparation, the as-synthesized MoO 2 nanoparticles might be used as promising anode materials for high-performance LIBs.

CuxO (CuO, CuO/Cu2O, and Cu2O) nanostructures have been controllably synthesized through a facile low-temperature solution method. The morphologies and compositions of CuxO nanostructures were well controlled by tuning the reductant amount of hydroxylamine hydrochloride, which experienced the transformation of nanosheets to octahedrons as well as the phase change of CuO to Cu2O. The as-grown samples showed photodegradation selectivity to MO (maximum photocatalytic efficiency of 52% for methyl orange (MO) and 16% for rhodamine B (RhB) after 180 min photodegradation) and different photocatalytic activities in the absence or presence of H2O2 (62% without H2O2 and 82% with H2O2). The morphological transformations of as-grown samples were observed after the photocatalytic measurement in the presence of H2O2. The structural and morphological features after photodegradation were studied by XPS, SEM, and TEM investigations, revealing the possible mechanism of the as-prepared samples whereby the photodegradation of organic dyes occurred on the surface with respect to the adsorption ability, structure, and morphology of CuxO. In addition, H2O2 played an important role in the photodegradation of organic dyes.

Hierarchical nickel oxide/graphene oxide (NiO/GO) and nickel oxide/graphene oxide/silver (NiO/GO/Ag) heterostructures were sucessfully fabricated as high-performance supercapacitors electrode materials by using a hydrothermal process and a photoreduction process. The experimental results showed that the NiO/GO/Ag heterostructure electrodes showed better electrochemical performance than those of NiO/GO and bare NiO nanosheets. The NiO/GO/Ag electrode exhibited a higher specific capacitance of 229 F g−1 at a current density of 1 A g−1, higher than that of 161 F g−1 for NiO/GO composites. Furthermore, NiO/GO/Ag electrode also showed good rate capability (still 200 F g−1 at 6 A g−1) and cycling stability (24% loss after 2000 repetitive cycles at a scan rate of 20 mV s−1). The enhanced capacitive performance of the NiO/GO/Ag composites was mainly attributed to the introduction of Ag nanoparticles, which increased the electrical conductivities of the composites, and promoted the electron transfer between the active components. This study suggested that NiO/GO/Ag composites were a promising class of electrode materials for high performance energy storage applications.

Norfloxacin complexes Co(nor)2·8H2O (nor=norfloxacin) and [Co(nor)(phen)]NO3·2H2O (phen=1,10-phenanthroline) were synthesized and their biological activity on Tetrahymena and Escherichia coli (E.coli) was assayed by means of microcalorimetry. Massive experimental parameters such as the growth constant k, inhibitory ratio I, half inhibition concentration IC50 and generation time TG were obtained. Data showed that with the increase of exposing complex concentration, both complexes exhibited strong inhibition during the growth of organisms. While toxic degrees were quite different on Tetrahymena and E. coli, due to various toxic mechanisms. And complex molecular volume and the ability of the complex penetrating into cells may be the keys.

Molybdenum dioxide (MoO 2 ) nanoparticles with the size of 200 nm in diameter were synthesized by a facile hydrothermal method. The nanoparticles were directly functionalized as supercapacitors (SCs) electrodes and photocatalysts. The electrochemical studies showed that the SCs demonstrated high capacitance of 621 F g −1 , which was 3 times larger than previous reports. Furthermore, they exhibited good cyclic performance with 90% capacity retention after 1000 cycles at a current density of 1 A g −1 . The photocatalytic activities were evaluated by the degradation of methylene blue (MB) and rhodamine B (RhB), respectively, and the nanoparticles demonstrated preferred selectivity on the degradation of RhB (70%) than that of MB (30%).

Energy storage devices with high security, stability and flexibility are desirable for newly smart wearable electronics. Herein, the moss-like nickel cobalt bimetallic phosphides (Ni-Co-P) nanosheet arrays on carbon fabrics are rationally designed and synthesized, which are directly treated as the electrodes to assemble highly flexible all-solid-state hybrid supercapacitors. The synthesized Ni-Co-P nanosheet arrays exhibit outstanding electrochemical performance and excellent stability owing to architectural advantages and compositional synergistic effect, which are further theoretically supported by calculations with density functional theory (DFT). The as-assembled hybrid supercapacitors deliver a high energy density of 48.4 Wh kg−1 at 811.2 W kg−1 accompanying a satisfactory cyclic stability (about 88.8 % retention after 8000 cycles). What's more, there is no obvious decline for the capacitance after bending 1,000 times under different bending states, implying excellent flexibility and mechanical stability of these bio-inspired nanosheet arrays. The outstanding mechanical stability and electrochemical performance demonstrate the promising potential of the hybrid supercapacitor as energy storage devices.

Zinc metal as anodes has been widely used for electrochemical energy storage devices using aqueous electrolytes, due to its cost effective, eco-friendliness, as well as low redox potential in aqueous solutions. However, Zn prefers to grow into plate-like structures that vertically stand on current collectors. They protrude toward separators or break during cycles, thereby provoking internal short circuit and/or poor cycling stability. Here, polypyrrole is exploited to manipulate the nucleation/growth of zinc via the interaction between –NH and Zn2+. The resultant Zn microplates grow nearly parallel to the current collector, effectively avoiding the negative effects. The performances of PPy-coated Zn as the anode are greatly improved, as demonstrated in symmetric PPy-coated Zn//PPy-coated Zn, PPy-coated Zn//active carbon and PPy-coated Zn//δ-MnO2. Especially for PPy-coated Zn//active carbon, it can stably run at 5 A g−1 for 12,000 cycles with a capacity retention of 96%. The results indicate the promising potential of conductive polymers in advanced zinc anodes.

ZnO@NiO core–shell heterostructures with high photocatalytic efficiency and reusability were prepared via electrochemical deposition on carbon fiber cloth substrates. Their photocatalytic properties were investigated by measuring the degradation of rhodamine B and methyl orange (MO) under ultraviolet light irradiation. The photodegradation efficiency of the ZnO@NiO heterostructures toward both dyes was better than those of the pure ZnO nanorods and NiO nanosheets. The higher performance could be attributed to the formation of p–n heterojunction between ZnO and NiO. Especially, the ZnO@NiO heterostructure formed upon deposition of NiO for 10 min degraded 95% of MO under ultraviolet light irradiation for 180 min. The high photodegradation efficiency of the ZnO@NiO heterostructures was also attributed to the high separation efficiency of photogenerated carriers, as confirmed by the higher photocurrent of the ZnO@NiO heterostructures (eightfold) when compared with that of the pure ZnO nanorods. Moreover, the high photodegradation efficiency of the ZnO@NiO heterostructures was maintained over three successive degradation experiments and decreased to 90% after the third cycle. Electronic supplementary material The online version of this article (10.1186/s11671-018-2676-1) contains supplementary material, which is available to authorized users.

The reaction of tricarboxytriphenyl amine (H3TCA) with CdII and auxiliary ligand 4,4′-bis(1-imidazolyl)biphenyl (bimb) afforded [Cd3(TCA)2(bimb)·(DMA)6]n (1) containing a two-fold interpenetrating three-dimensional microporous framework. Compound 1 showed remarkable adsorption enthalpies for CO2 and H2 and good H2/N2 selectivity at low temperature. Moreover, activated 1 showed a highly selective adsorption towards CO2 over N2 and CH4 under ambient conditions. Interestingly, compound 1 selectively removed methyl orange (MO) over methylene blue (MB) from contaminated water with good recyclability, and possessed the second highest adsorption capacity for MO among the MOFs reported to date. Remarkably, complex 1 showed strong guest-dependent luminescence behavior.

The ubiquity of sensor enabled by Wireless Sensor Network (WSN) technologies cover many areas of modern daily lives. This offers the possibility to measure, simulate and control environments, from natural resources to urban environments. It is usually use Internet of Things (IoT) for centralized management or control of machines, equipment and personnel. This paper use WSN to get temperature and transmit to computer. The key enabling technologies and application domains that are likely to widely use in the near future.

Manganese dioxide (MnO2) nanoarchitectures including microspheres assembled by nanosheets and hollow urchins assembled by nanorods have been successfully synthesized using a facile and efficient hydrothermal method at 150 °C. The effects of concentrations of the reactants and reaction time on the structures and morphologies of MnO2 were systematically investigated. The experimental results showed that the morphologies of MnO2 transformed into nanosheet-assembled microspheres (10 min) from nanorod-assembled hollow urchins (5 min) by tuning the suitable reaction time. The nanorod-assembled hollow urchins experienced the morphology transformation cycle from urchin to a disordered structure to urchin with the extension of the reaction time. Furthermore, the nanorods with different diameters and lengths were formed with different concentrations of reactants at the same reaction time (8 h). The MnO2 nanorods fabricated with 0.59 g KMnO4 showed a maximum specific capacitance (198 F g(-1)) with a good rate capability and excellent cycling stability (maintained 94% after 2000 cycles). Furthermore, the nanosheet-assembled microspheres exhibited the higher specific capacitance of 131 F g(-1) at 1 A g(-1) with a long-term cycling stability for the samples at different reaction times. These results indicated their promising applications as high-performance supercapacitor electrodes and provided a generic guideline in developing different nanostructured electrode materials for electrochemical energy storage.

Ag/Cu2O microstructures with diverse morphologies have been successfully synthesized with different initial reagents of silver nitrate (AgNO3) by a facile one-step solvothermal method. Their structural and morphological characteristics were carefully investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and the experimental results showed that the morphologies transformed from microcubes for pure Cu2O to microspheres with rough surfaces for Ag/Cu2O. The photocatalytic activities were evaluated by measuring the degradation of methyl orange (MO) aqueous solution under visible light irradiation. The photocatalytic efficiencies of MO firstly increased to a maximum and then decreased with the increased amount of AgNO3. The experimental results revealed that the photocatalytic activities were significantly influenced by the amount of AgNO3 during the preparation process. The possible reasons for the enhanced photocatalytic activities of the as-prepared Ag/Cu2O composites were discussed.

In recent years, the research on supercapacitors has ushered in an explosive growth, which mainly focuses on seeking nano-/micro-materials with high energy and power densities. Herein, this review will be arranged from three aspects. We will summarize the controllable architectures of spinel NiCo2O4 fabricated by various approaches. Then, we introduce their performances as supercapacitors due to their excellent electrochemical performance, including superior electronic conductivity and electrochemical activity, together with the low cost and environmental friendliness. Finally, the review will be concluded with the perspectives on the future development of spinel NiCo2O4 utilized as the supercapacitor electrodes.

ZnO nanorods and ZnO@CdS heterostructures have been fabricated on carbon fiber cloth substrates via hydrothermal and electrochemical deposition. Their photocatalytic properties were investigated by measuring the degradation of methylene blue under ultraviolet light irradiation. The result illustrated that the photodegradation efficiency of ZnO@CdS heterostructures was better than that of pure ZnO nanorods, in which the rate constants were about 0.04629 and 0.02617 min(-1). Furthermore, the photocurrent of ZnO@CdS heterostructures achieved 10(2) times enhancement than pure ZnO nanorods, indicating that more free carriers could be generated and transferred in ZnO@CdS heterostructures, which could be responsible for the increased photocatalytic performance.