Morphology Control of Mixed Metallic Organic Framework for High-Performance Hybrid Supercapacitors.

The study presents the binder-free synthesis of mixed metallic organic frameworks (MMOFs) supported on a ternary metal oxide (TMO) core as an innovative three-dimensional (3D) approach to enhance electron transport and mass transfer during the electrochemical charge-discharge process, resulting in high-performance hybrid supercapacitors. The research demonstrates that the choice of organic linkers can be used to tailor the morphology of these MMOFs, thus optimizing their electrochemical efficiency. Specifically, a NiCo-MOF@NiCoO2@Ni electrode, based on terephthalic linkers, exhibits highly ordered porosity and a vast internal surface area, achieving a maximum specific capacity of 2320 mC cm-2, while maintaining excellent rate capability and cycle stability. With these performances, the hybrid supercapacitor (HSC) achieves a maximum specific capacitance of 424.6 mF cm-2 (specific capacity 653.8 mC cm-2) and 30.7 F cm-3 with energy density values of 10.1 mWh cm-3 at 167.4 mW cm-3 (139.8 µWh cm-2 at 2310 µW cm-2), which are higher than those of previously reported MMOFs based electrodes. This research introduces a novel approach for metal organic framework based HSC electrodes, diverging from the traditional emphasis on metal ions, in order to achieve the desired electrochemical performance.

Quaternary Cu2FeSnS4/PVP/rGO Composite for Supercapacitor Applications.

Electrochemical energy storage is a current research area to address energy challenges of the modern world. The Cu2FeSnS4/PVP/rGO-decorated nanocomposite using PVP as the surface ligand was explored in a simple one-step solvothermal route, for studying their electrochemical behavior by designing asymmetric hybrid supercapacitor devices. The full cell three-electrode arrangements delivered 748 C/g (62.36 mA h/g) at 5 mV/s employing CV and 328 F/g (45.55 mA h/g) at 0.5 A/g employing GCD for the Cu2FeSnS4/PVP/rGO electrode. The half-cell two-electrode device can endow with 73 W h/kg and 749 W/kg at 1 A/g energy and power density. Furthermore, two Cu2FeSnS4/PVP/rGO//AC asymmetric devices connected in series for illuminating a commercial red LED more than 1 min were explored. This work focuses the potential use of transition-metal chalcogenide composite and introduces a new material for designing high-performance supercapacitor applications.

NiMoO4 nanorods photocatalytic activity comparison under UV and visible light.

Waste water remediation is the ongoing hot research topic that can reduce the water scarcity all over the world. By reducing the pollutants in the waste water drawn from industries and other sources will be more useful for domestic purposes. To reduce the rate of pollutants in water may also help in improving the aquatic environment and decreases other side effects. Efficient and cost effective catalysts were in search for both dye degradation and water remediation treatment applications. NiMoO4 nanorods were prepared by employing co-precipitation method with different stirrer time (2 h, 4 h and 6 h). The formation of NiMoO4 was substantiated employing X-ray diffractometer analysis (XRD). Vibrational and rotational property of the samples was analyzed by FT-IR spectra and Raman spectra. The optical property was further confirmed by UV-vis spectral studies. Morphological analysis studies revealed growth of nanorods with 6 h stirrer time. The photocatalytic behavior of the obtained product was carried out under both UV light (364 nm) and visible light irradiation. The samples subjected to visible light environment showed better efficiency on degrading the methylene blue (MB) dye. The efficiency obtained under UV irradiation were 20%, 31%, 33%, 41% and efficiency obtained in visible light irradiation were 27%, 42%, 46%, 55% with respect to bare methylene blue (MB), MB with NiMoO4 (2 h), MB with NiMoO4 (4 h), MB with NiMoO4 (6 h) catalyst added. NiMoO4 sample with 6 h stirrer time and fine nanorods growth will be the good candidate for future use.

Three-dimensional Bi2O3/Ti microspheres as an advanced negative electrode for hybrid supercapacitors.

Herein, we report a novel, low-temperature solvothermal method to grow 3D-Bi2O3 flower-like microspheres on Ti substrates as a binder-free negative electrode for supercapacitor applications. The Bi2O3/Ti electrode showed an areal capacitance of 1.65 F cm-2 at 4 mA cm-2. Moreover, the 3D-NiCo2O4||3D-Bi2O3 hybrid device delivered high energy and power densities of 31.17 µW h cm-2 and 7500 µW cm-2, respectively. The more optimal energy storage performance based on the strong adhesion of the current collector and self-assembled three-dimensional nanostructures permits efficient electron and ion transportation.

CoNiSe2 Nanostructures for Clean Energy Production.

Comparative investigation of the electrochemical oxygen evolution reaction (OER) activity for clean energy production was performed by fabricating three different electrodes, namely, NiSe2, CoSe2, and CoNiSe2, synthesized by hydrothermal treatment. Cubic, orthorhombic, and hexagonal structures of NiSe2, CoSe2, and CoNiSe2 were confirmed by X-ray diffraction (XRD) and also by other characterization studies. Perfect nanospheres, combination of distorted nanospheres and tiny nanoparticles, and sharp-edge nanostructures of NiSe2, CoSe2, and CoNiSe2 were explored by surface morphological images. Higher OER activity of the binary CoNiSe2 electrode was achieved as 188 mA/g current density with a comparatively low overpotential of 234 mV along with higher conductivity and low charge transfer resistance when compared to its unary NiSe2 and CoSe2 electrodes. A low Tafel slope value of 82 mV/dec was also achieved for the same binary CoNiSe2 electrode in a half-cell configuration. The overall 100% retention achieved for all of the fabricated electrodes in a stability test of OER activity suggested that the excellent optimum condition was obtained during the synthesis. This could definitely be a revelation in the synthesis of novel binary combinations of affordable metal selenides for clean energy production.

3D-Flower-Like Copper Sulfide Nanoflake-Decorated Carbon Nanofragments-Modified Glassy Carbon Electrodes for Simultaneous Electrocatalytic Sensing of Co-existing Hydroquinone and Catechol.

A copper sulfide nanoflakes-decorated carbon nanofragments-modified glassy carbon electrode (CuS-CNF/GCE) was fabricated for the electrocatalytic differentiation and determination of hydroquinone (HQ) and catechol (CC). The physicochemical properties of the CuS-CNF were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. The electrocatalytic determination of HQ and CC over the CuS-CNF/GCE was evaluated by cyclic voltammetry and differential pulse voltammetry. An excellent detection limit and sensitivity of the CuS-CNF/GCE are obtained (0.293 µM and 0.259 µM) with a sensitivity of 184 nA µM-1 cm-2 and 208 nA µM-1 cm-2 (S/N=3) for HQ and CC, respectively. In addition, the CuS-CNF/GCE shows a selective identification of HQ and CC over potential interfering metal ions (Zn2+, Na+, K+, NO3-, SO42-, Cl-) and organic compounds (ascorbic acid, glucose), and a satisfactory recovery is also obtained in the spiked water samples. These results suggest that the CuS-CNF/GCE can be used as an efficient electrochemical sensor for the simultaneous determination of co-existing environmental pollutants such as HQ and CC in water environments with high selectivity and acceptable reproducibility.

NiCo2S4 nanosheet-decorated 3D, porous Ni film@Ni wire electrode materials for all solid-state asymmetric supercapacitor applications.

Wire type supercapacitors with high energy and power densities have generated considerable interest in wearable applications. Herein, we report a novel NiCo2S4-decorated 3D, porous Ni film@Ni wire electrode for high performance supercapacitor application. In this work, a facile method is introduced to fabricate a 3D, porous Ni film deposited on a Ni wire as a flexible electrode, followed by decoration with NiCo2S4 as an electroactive material. The fabricated NiCo2S4-decorated 3D, porous Ni film@Ni wire electrode displays a superior performance with an areal and volumetric capacitance of 1.228 F cm-2 and 199.74 F cm-3, respectively, at a current density of 0.2 mA cm-1 with a maximum volumetric energy and power density (EV: 6.935 mW h cm-3; PV: 1.019 W cm-3). Finally, the solid state asymmetric wire type supercapacitor is fabricated using the fabricated NiCo2S4-decorated 3D, porous Ni film@Ni wire as a positive electrode and N-doped reduced graphene oxide (N-rGO) as a negative electrode and this exhibits good areal and volumetric capacitances of CA: 0.12 F cm-2 and CV: 19.57 F cm-2 with a higher rate capability (92%). This asymmetric wire type supercapacitor demonstrates a low leakage current and self-discharge with a maximum volumetric energy (EV: 5.33 mW h cm-3) and power (PV: 855.69 mW cm-3) density.

Human Interactive Triboelectric Nanogenerator as a Self-Powered Smart Seat.

A lightweight, flexible, cost-effective, and robust, single-electrode-based Smart Seat-Triboelectric Nanogenerator (SS-TENG) is introduced as a promising eco-friendly approach for harvesting energy from the living environment, for use in integrated self-powered systems. An effective method for harvesting biomechanical energy from human motion such as walking, running, and sitting, utilizing widely adaptable everyday contact materials (newspaper, denim, polyethylene covers, and bus cards) is demonstrated. The working mechanism of the SS-TENG is based on the generation and transfer of triboelectric charge carriers between the active layer and user-friendly contact materials. The performance of SS-TENG (52 V and 5.2 µA for a multiunit SS-TENG) is systematically studied and demonstrated in a range of applications including a self-powered passenger seat number indicator and a STOP-indicator using LEDs, using a simple logical circuit. Harvested energy is used as a direct power source to drive 60 blue and green commercially available LEDs and a monochrome LCD. This feasibility study confirms that triboelectric nanogenerators are a suitable technology for energy harvesting from human motion during transportation, which could be used to operate a variety of wireless devices, GPS systems, electronic devices, and other sensors during travel.

Multifunctional Nanocarpets for Cancer Theranostics: Remotely Controlled Graphene Nanoheaters for Thermo-Chemosensitisation and Magnetic Resonance Imaging.

A new paradigm in cancer theranostics is enabled by safe multifunctional nanoplatform that can be applied for therapeutic functions together with imaging capabilities. Herein, we develop a multifunctional nanocomposite consisting of Graphene Oxide-Iron Oxide -Doxorubicin (GO-IO-DOX) as a theranostic cancer platform. The smart magnetic nanoplatform acts both as a hyperthermic agent that delivers heat when an alternating magnetic field is applied and a chemotherapeutic agent in a cancer environment by providing a pH-dependent drug release to administer a synergistic anticancer treatment with an enhanced T2 contrast for MRI. The novel GO-IO-DOX nanocomposites were tested in vitro and were observed to exhibit an enhanced tumoricidal effect through both hyperthermia and cancer cell-specific DOX release along with an excellent MRI performance, enabling a versatile theranostic platform for cancer. Moreover the localized antitumor effects of GO-IO-DOX increased substantially as a result of the drug sensitization through repeated application of hyperthermia.

Flexible, Hybrid Piezoelectric Film (BaTi(1-x)Zr(x)O3)/PVDF Nanogenerator as a Self-Powered Fluid Velocity Sensor.

We demonstrate a flexible piezoelectric nanogenerator (PNG) constructed using a hybrid (or composite) film composed of highly crystalline BaTi(1-x)Zr(x)O3 (x = 0, 0.05, 0.1, 0.15, and 0.2) nanocubes (abbreviated as BTZO) synthesized using a molten-salt process embedded into a poly(vinylidene fluoride) (PVDF) matrix solution via ultrasonication. The potential of a BTZO/PVDF hybrid film is realized in fabricating eco-friendly devices, active sensors, and flexible nanogenerators to interpret its functionality. Our strategy is based on the incorporation of various Zr(4+) doping ratios into the Ti(4+) site of BaTiO3 nanocubes to enhance the performance of the PNG. The flexible nanogenerator (BTZO/PVDF) exhibits a high electrical output up to ∼11.9 V and ∼1.35 µA compared to the nanogenerator (BTO/PVDF) output of 7.99 V and 1.01 µA upon the application of cyclic pushing-releasing frequencies with a constant load (11 N). We also demonstrate another exciting application of the PNG as a self-powered sensor to measure different water velocities at an outlet pipe. The average maximum peak power of the PNG varies from 0.2 to 15.8 nW for water velocities ranging from 31.43 to 125.7 m/s during the water ON condition. This study shows the compositional dependence approach, fabrication of nanostructures for energy harvesting, and self-powered devices in the field of monitoring for remote area applications.

Piezoelectric-driven self-charging supercapacitor power cell.

In this work, we have fabricated a piezoelectric-driven self-charging supercapacitor power cell (SCSPC) using MnO2 nanowires as positive and negative electrodes and a polyvinylidene difluoride (PVDF)-ZnO film as a separator (as well as a piezoelectric), which directly converts mechanical energy into electrochemical energy. Such a SCSPC consists of a nanogenerator, a supercapacitor, and a power-management system, which can be directly used as a power source. The self-charging capability of SCSPC was demonstrated by mechanical deformation under human palm impact. The SCSPC can be charged to 110 mV (aluminum foil) in 300 s under palm impact. In addition, the green light-emitting diode glowed using serially connected SCSPC as the power source. This finding opens up the possibility of making self-powered flexible hybrid electronic devices.

Gate-tunable photoresponse of defective graphene: from ultraviolet to visible.

We report the gate-tunable photoresponse of a defective graphene over the ultraviolet (UV) and the visible light illumination, where the defect was generated by plasma irradiation. Plasma induced Dirac point shift indicates the p-doping effect. Interestingly the defective-graphene field effect transistor (defective-GFET) showed a negative shift upon UV illumination, whereas the device showed a positive shift under visible light illumination, along with the change in the photocurrent. The defective-GFET device showed a high photoresponsivity of 37 mA W(-1) under visible light, that is ∼3 times higher than that of the pristine graphene device. Photoinduced molecular desorption causes the UV light responsivity to 18 mA W(-1). This study shows that the tunable photodetector with high responsivity is feasible by introducing an artificial defect on graphene surface.

Self-powered pH sensor based on a flexible organic-inorganic hybrid composite nanogenerator.

In this study, we developed an innovative, flexible, organic-inorganic hybrid composite nanogenerator, which was used to drive a self-powered microwire-based pH sensor. The hybrid composite nanogenerator was fabricated using ZnO nanowire and piezoelectric polymer poly(vinylidene fluoride), through a simple, inexpensive solution-casting technique. The fabricated hybrid composite nanogenerator delivered a maximum open-circuit voltage of 6.9 V and a short-circuit current of 0.96 µA, with an output power of 6.624 µW under uniaxial compression. This high-performance, electric poling free composite nanogenerator opens up the possibility of industrial-scale fabrication. The hybrid nanogenerator demonstrated its ability to drive five green LEDs simultaneously, without using an energy-storage device. Additionally, we constructed a self-powered pH sensor, using a ZnO microwire powered with our hybrid nanogenerator. The output voltage varied according to changes in the pH level. This study demonstrates the feasibility of using a hybrid nanogenerator as a self-powered device that can be extended for use as a biosensor for environmental monitoring and/or as a smart, wearable, vibration sensor in future applications.

Self-induced gate dielectric for graphene field-effect transistor.

We report the electronic characteristics of an avant-garde graphene-field-effect transistor (G-FETs) based on ZnO microwire as top-gate electrode with self-induced dielectric layer. Surface-adsorbed oxygen is wrapped up the ZnO microwire to provide high electrostatic gate-channel capacitance. This nonconventional device structure yields an on-current of 175 µA, on/off current ratio of 55, and a device mobility exceeding 1630 cm(2)/(V s) for holes and 1240 cm(2)/(V s) for electrons at room temperature. Self-induced gate dielectric process prevents G-FETs from impurity doping and defect formation in graphene lattice and facilitates the lithographic process. Performance degradation of G-FETs can be overcome by this avant-garde device structure.