High-performance VO2/CNT@PANI with core-shell construction enable printable in-planar symmetric supercapacitors.

As a progressive electronic energy storage device, the flexible supercapacitor holds tremendous promise for powering wearable/portable electronic products. Of various pseudocapacitor materials, vanadium dioxide (VO2) has garnered extensive attention due to its impressive theoretical capacitance. However, the challenges of inferior cycling life and lower energy density to be addressed. Herein, we prepare VO2 nanorods with winding carbon nanotubes (CNT) via a facile solvothermal route, followed by in situ polymerization of polyaniline (PANI) shell. Taking full advantage of the synergistic effect, the VO2/CNT@PANI composite delivers a high specific capacitance of 354.2F/g at 0.5 A/g and a long cycling life of âˆ¼ 88.2 % over 5000 cycles resulting from the enhanced conductivity of CNT and stabilization of PANI shell. By screen printing the formulated inks with outstanding rheological behaviours, we manufacture an in-planar VO2/CNT@PANI symmetric supercapacitor (VO2/CNT@PANI SSC) device featuring an orderly arrangement structure. This device yields a remarkable areal energy density of 99.57 µWh/cm2 at a power density of 387.5 µW/cm2 while retaining approximately âˆ¼ 87.6 % of its initial capacitance after prolonged use. Furthermore, we successfully powered a portable game machine for more than 2 min using two SSCs connected in series with ease. Therefore, this work presents a universal strategy that utilises combination and coating to boost electrochemical performance for flexible high-performance supercapacitors.

PANI-Coated VOx Nanobelts with Core-Shell Architecture for Flexible All-Solid-State Supercapacitor.

As a typical pseudocapacitor material, VOx possesses mixed valence states, making it an ideal electrode material for symmetric screen-printed supercapacitors. However, its high internal resistance and low energy density are the main hurdles to its widespread application. In this study, a two-dimensional PANI@VOx nanobelt with a core-shell architecture was constructed via a two-step route. This strategy involves the preparation of VOx using a solvothermal method, and a subsequent in situ polymerization process of the PANI. By virtue of the synergistic effect between the VOx core and the PANI shell, the optimal VOx@PANI has an enhanced conductivity of 0.7 ± 0.04 S/Ω, which can deliver a high specific capacitance of 347.5 F/g at 0.5 A/g, a decent cycling life of ~72.0%, and an outstanding Coulomb efficiency of ~100% after 5000 cycles at 5 A/g. Moreover, a flexible all-solid-state symmetric supercapacitor (VOx@PANI SSC) with an in-planar interdigitated structure was screen-printed and assembled on a nickel current collector; it yielded a remarkable areal energy density of 115.17 µWh/cm2 at an areal power density of 0.39 mW/cm2, and possessed outstanding flexibility and mechanical performance. Notably, a "Xiaomi" hygrothermograph (3.0 V) was powered easily by tandem SSCs with an operating voltage of 3.1 V. Therefore, this advanced pseudocapacitor material with core-shell architecture opens novel ideas for flexible symmetric supercapacitors in powering portable/wearable products.

Flexible High-Performance and Screen-Printed Symmetric Supercapacitor Using Hierarchical Rodlike V3O7 Inks.

The emergence of the Internet of things stimulates the pursuit of flexible and miniaturized supercapacitors. As an advanced technology, screen printing displays vigor and tremendous potential in fabricating supercapacitors, but the adoption of high-performance ink is a great challenge. Here, hierarchical V3O7 with rodlike texture was prepared via a facile template-solvothermal route; and the morphology, component, and valence bond information are characterized meticulously. Then, the screen-printed inks composed of V3O7, acetylene black, and PVDF are formulated, and the rheological behaviors are studied detailedly. Benefitting from the orderly aligned ink, the optimal screen-printed electrode can exhibit an excellent specific capacitance of 274.5 F/g at 0.3 A/g and capacitance retention of 81.9% after 5000 cycles. In addition, a flexible V3O7 symmetrical supercapacitor (SSC) is screen-printed and assembled on the Ag current collector, exhibiting a decent areal specific capacitance of 322.5 mF/cm2 at 0.5 mA/cm2, outstanding cycling stability of 90.8% even after 5000 cycles, satisfactory maximum energy density of 129.45 µWh/cm2 at a power density of 0.42 mW/cm2, and remarkable flexibility and durability. Furthermore, a single SSC enables the showing of an actual voltage of 1.70 V after charging, and no obvious self-discharge phenomenon is found, revealing the great applied value in supply power. Therefore, this work provides a facile and low-cost reference of screen-printed ink for large-scale fabrication of flexible supercapacitors.

Template-Free Preparation of α-Ni(OH)2 Nanosphere as High-Performance Electrode Material for Advanced Supercapacitor.

Although it is one of the promising candidates for pseudocapacitance materials, Ni(OH)2 is confronted with poor specific capacitance and inferior cycling stability. The design and construction of three-dimensional (3D) nanosphere structures turns out to be a valid strategy to combat these disadvantages and has attracted tremendous attention. In this paper, a 3D α-Ni(OH)2 nanosphere is prepared via a facile and template-free dynamic refluxing approach. Significantly, the α-Ni(OH)2 nanosphere possesses a high specific surface area (119.4 m2/g) and an abundant porous structure. In addition, the as-obtained α-Ni(OH)2 electrodes are investigated by electrochemical measurements, which exhibit a high specific capacitance of 1243 F/g at 1 A/g in 6 M KOH electrolyte and an acceptable capacitive retention of 40.0% after 1500 charge/discharge cycles at 10 A/g, which can be attributed to the sphere's unique nanostructure. Furthermore, the as-assembled Ni(OH)2-36//AC asymmetric supercapacitor (ASC) yields a remarkable energy density of 26.50 Wh/kg, with a power density of 0.82 kW/kg. Notably, two ASCs in series can light a 2.5 V red lamp sustainably for more than 60 min, as well as power an LED band with a rated power of 25 W. Hence, this 3D α-Ni(OH)2 nanosphere may raise great potential applications for next-generation energy storage devices.

Meta-Learning for Few-Shot Plant Disease Detection.

Plant diseases can harm crop growth, and the crop production has a deep impact on food. Although the existing works adopt Convolutional Neural Networks (CNNs) to detect plant diseases such as Apple Scab and Squash Powdery mildew, those methods have limitations as they rely on a large amount of manually labeled data. Collecting enough labeled data is not often the case in practice because: plant pathogens are variable and farm environments make collecting data difficulty. Methods based on deep learning suffer from low accuracy and confidence when facing few-shot samples. In this paper, we propose local feature matching conditional neural adaptive processes (LFM-CNAPS) based on meta-learning that aims at detecting plant diseases of unseen categories with only a few annotated examples, and visualize input regions that are 'important' for predictions. To train our network, we contribute Miniplantdisease-Dataset that contains 26 plant species and 60 plant diseases. Comprehensive experiments demonstrate that our proposed LFM-CNAPS method outperforms the existing methods.

Application of Response Surface Methodology for Improving the Yield of 1,5-bis(ptoluenesulfonyl)- 3,7-Dihydroxyoctahydro-1,5-Diazocine.

BACKGROUND: 3,3,7,7-tetrakis (difluoramino) octahydro-1,5-dinitro-1,5-diazocine (HNFX), as an important oxidizer in propellants, has received much attention due to its high density and energy. However, there are many difficulties that need to be solved, such as complex synthetic processes, low product yield, high cost of raw materials and complicated purification. In the synthesis of HNFX, the intermediate named 1,5-bis (p-toluenesulfonyl)-3,7-dihydroxyoctahydro-1, 5-diazocine (gem-diol), is difficult to synthesize. METHODS: A simple method was used to synthesize the gem-diol. This prepared gem-diol was characterized by FT-IR, 1H NMR, melting point and mass spectrometry. In order to increase the yield of gem-diol, response surface methodology (RSM) was introduced to optimize experimental conditions. RESULTS: After the establishment of the model, the optimal conditions of synthesis were found to be 9.33h for reaction time, 6.13wt. % for the concentration of NaOH and 1.38:1 for ratio of ECH (p-toluenesulfonamide): TCA (epichlorohydrin). Under the optimal conditions, the experimental value and the predicted value of yield were 22.18% and 22.92%, respectively. CONCLUSION: 1,5-bis (p-toluenesulfonyl)-3,7-dihydroxyoctahydro-1,5-diazocine (gem-diol) can be synthesized using the low cost of chemical materials, including p-toluenesulfonamide, epichlorohydrin, sodium hydroxide and ethanol. Response surface methodology (RSM) is an effective method to optimize the synthesis process, thereby improving the yield of gem-diol.

VO2(B)/Graphene Composite-Based Symmetrical Supercapacitor Electrode via Screen Printing for Intelligent Packaging.

More multipurpose and convenient demand driven by Radio Frequency Identification (RFID) and intelligent packaging require flexible power sources. A VO2(B)/graphene (VO2(B)/GN) core-shell composite was successfully synthesized by the hydrothermal treatment with V2O5 and graphite. The as-obtained sample was characterized by XRD, FT-IR, SEM, TEM, and XPS measurements. In addition, the electrochemical properties of VO2(B)/GN were tested. Due to its great electrochemical performance and mechanical properties, graphene could increase the electrochemical performance and strengthen the structural stability of the material at the same time. With increasing loading amount of GN, the specific capacitance of VO2(B)/GN increased correspondingly. With 20% GN loading, the initial discharge specific capacity could reach 197 F g-1 at 0.5 A g-1, and 160 F g-1 at 1 A g-1 in 0.5 M Na2SO4 electrolyte, which is better than that of pure rod-like VO2(B). The capacitance of the VO2(B)/GN (20%) composite electrode retains 95.49% after 1000 cycles, which is higher than that of a pure VO2(B) electrode (85.43%), indicating that the VO2(B)/GN composite possesses better cycling stability. Moreover, a symmetrical solid-state supercapacitor (SCs) using VO2(B)/GN(20%) as the anode was assembled. Four printed SCs were connected in series to light up a 1.5 V red LED. This demonstrates its potential application in intelligent packaging to trace food safety.

A facile synthesis of 1,3,6,8-pyrenesulfonic acid tetrasodium salt as a hydrosoluble fluorescent ink for anti-counterfeiting applications.

In this work, 1,3,6,8-pyrenesulfonic acid sodium salt (PTSA) was successfully synthesized via a one-step sulfonating reaction. This method is more convenient, effective and eco-friendly than the traditional one. The as-prepared PTSA exhibits pure blue fluorescence under UV light. Due to its excellent fluorescent properties and water solubility, PTSA was used to prepare water-soluble invisible inks based on hydroxyethyl cellulose (HEC) aqueous solution. Notably, the resulting inks possessed acceptable stability after being stored for 30 days. Besides, the red/green/blue fluorescent inks were obtained by adding extra pigments, all of which exhibited excellent rheology and thixotropy properties. Subsequently, various patterns, including a QR code, the logo of Wuhan University, Chinese characters and so on, were printed on non-background paper through ink-jet and screen printing, and the as-prepared materials exhibited good water solubility and outstanding fluorescence performances, indicating that the fluorescent PTSA material is a promising candidate for anti-counterfeiting applications.

Preparation of MgAl-EDTA-LDH based electrospun nanofiber membrane and its adsorption properties of copper(II) from wastewater.

Adsorption is recognized as one of the most promising technologies applied to remove heavy metals from contaminated water. However, the adsorption efficiency often decreases because of the aggregation and loss of adsorbents. Herein, a novel adsorbent was synthesized by intercalation ethylenediaminetetraacetic acid (EDTA) into layered double hydroxides (LDH) and subsequent encapsulated into PAN polymer matrix using electrospinning. The synthesized electrospun nanofiber membrane (MgAl-EDTA-LDH@PAN) was found to combine the advantages of LDH@PAN nanofiber membrane (high surface area, easy to separate, free from aggregation and loss) and EDTA (powerful chelating agent). The adsorption performance of the MgAl-EDTA-LDH@PAN was evaluated using Cu(II) as target metals by varying experimental conditions such as pH, contact time, initial adsorbent dosage, and temperature. The maximum adsorption capacity of MgAl-EDTA-LDH@PAN was 120.77mg/g with the initial Cu(II) concentrations ranging from 0.6 to 40mg/L. MgAl-EDTA-LDH@PAN was also used in real industrial contaminated water treatment, and the final effluent was approximate to class-I criteria of the National Wastewater Discharge Standard of China. (GB 8978-1996). In addition, Cu K-edge XAS and XPS analyses were applied for unraveling the adsorptive performance of MgAl-EDTA-LDH@PAN by revealing the molecular-level mechanism of Cu(II) uptake.