Stimulus of Work Function on Electron Transfer Process of Intermetallic Nickel-Antimonide Toward Bifunctional Electrocatalyst for Overall Water Splitting.

Engineering the intermetallic nanostructures as an effective bifunctional electrocatalyst for hydrogen and oxygen evolution reactions (HER and OER) is of great interest in green hydrogen production. However, a few non-noble metals act as bifunctional electrocatalysts, exhibiting terrific HER and OER processes reported to date. Herein the intermetallic nickel-antimonide (Ni─Sb) dendritic nanostructure via cost-effective electro-co-deposition method is designed and their bifunctional electrocatalytic property toward HER and OER is unrevealed. The designed Ni─Sb delivers a superior bifunctional activity in 1 m KOH electrolyte, with a shallow overpotential of ≈119 mV at -10 mA for HER and ≈200 mV at 50 mA for OER. The mechanism behind the excellent bifunctional property of Ni─Sb is discussed via "interfacial descriptor" with the aid of Kelvin probe force microscopy (KPFM). This study reveals the rate of electrocatalytic reaction depends on the energy required for electron and proton transfer from the catalyst's surface. It is noteworthy that the assembled Ni─Sb-90 electrolyzer requires only a minuscule cell voltage of ≈1.46 V for water splitting, which is far superior to the art of commercial catalysts.

Electrospun Polymer-Derived Carbyne Supercapacitor for Alternating Current Line Filtering.

The filtering device is a vital component of electronic goods that rectifies ripples which occur upon converting alternating current (AC) to direct current (DC) and attenuates high-frequency noise during switching or voltage declines. Classical filtering devices suffer from low performance metrics and are bulky, limiting their use in modern electronic devices. The fabrication process of electrode materials for high-frequency symmetric supercapacitor (HFSSC) is complicated, hindering commercialization. Herein, for the first time, the design of a high-performance stand-alone carbyne film comprised of sp/sp2 -hybridized carbon as an electrode for AC filtering under a wide frequency range is reported. The carbyne film as HFSSC shows the ideal capacitive behavior at ultrahigh scan rate of 10 000 V s-1 with excellent linearity which is top among the reported AC line filter capacitor. The carbyne HFSSC exhibits a high energy density of 703.25 µF V2  cm-2 at 120 Hz, which is superior to that of current commercial electrolytic filters and many reported AC line supercapacitors. As a proof of concept, a carbyne device is implemented in a real time AC to DC adaptor that demonstrates excellent filtering performance at high frequencies.

Nanostructured molybdenum oxide-based antibacterial paint: effective growth inhibition of various pathogenic bacteria.

The prevention of bacterial infections in the health care environment is paramount to providing better treatment. Covering a susceptible environment with an antimicrobial coating is a successful way to avoid bacterial growth. Research on the preparation of durable antimicrobial coatings is promising for both fundamental surface care and clinical care applications. Herein, we report a facile, efficient, and scalable preparation of MoO3 paint using a cost-effective ball-milling approach. The MoO3 nanoplates (synthesized by thermal decomposition of ammonium heptamolybdate) are used as a pigment and antibacterial activity moiety in alkyd resin binders and other suitable eco-friendly additives in the preparation of paint. Surface morphology, chemical states, bonding nature, and intermolecular interaction between the MoO3 and the alkyd resin were studied using Raman and x-ray photoelectron spectroscopic analysis. The antibacterial properties of a prepared MoO3 nanoplate against various bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Klebsiella pneumoniae) was determined using the microdilution method. Bacterial strains exposed to an MoO3 paint coated surface exhibit a significant loss of viability in a time-dependent manner. Fundamental modes of antibacterial activities ascribed from a biocompatible and durable MoO3 nanostructure incorporated into an alkyd resin complex are discussed. The obtained experimental findings suggest the potential utility of prepared MoO3-based paint coating for the prevention of health care associated infections.

Unravelling the Bi-Functional Electrocatalytic Properties of {Mo72Fe30} Polyoxometalate Nanostructures for Overall Water Splitting Using Scanning Electrochemical Microscope and Electrochemical Gating Methods.

This study reports the use of Keplerate-type {Mo72Fe30} polyoxometalate (POMs) nanostructures as a bi-functional-electrocatalyst for HER and OER in an alkaline medium with a lower overpotential (135 mV for HER and 264 mV for OER), and excellent electrochemical stability. The bi-functional catalytic properties of {Mo72Fe30} POM are studied using a scanning electrochemical microscope (SECM) via current mapping using substrate generation and tip collection mode. Furthermore, the bipolar nature of the {Mo72Fe30} POM nano-electrocatalysts is studied using the electrochemical gating via simultaneous monitoring of the electrochemical (cell) and electrical ({Mo72Fe30} POM) signals. Next, a prototype water electrolyzer fabricated using {Mo72Fe30} POM electrocatalysts showed they can drive 10 mA cm-2 with a low cell voltage of 1.62 V in lab-scale test conditions. Notably, the {Mo72Fe30} POM electrolyzers' performance assessment based on recommended conditions for industrial aspects shows that they require a very low overpotential of 1.89 V to drive 500 mA cm-2, highlighting their promising candidature toward clean-hydrogen production.

Surface activation of graphene oxide nanosheets by ultraviolet irradiation for highly efficient anti-bacterials.

A comprehensive investigation of anti-bacterial properties of graphene oxide (GO) and ultraviolet (UV) irradiated GO nanosheets was carried out. Microscopic characterization revealed that the GO nanosheet-like structures had wavy features and wrinkles or thin grooves. Fundamental surface chemical states of GO nanosheets (before and after UV irradiation) were investigated using x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Minimum inhibitory concentration (MIC) results revealed that UV irradiated GO nanosheets have more pronounced anti-bacterial behavior than GO nanosheets and standard antibiotic, kanamycin. The MIC of UV irradiated GO nanosheets was 0.125 µg ml⁻¹ for Escherichia coli and Salmonella typhimurium, 0.25 µg ml⁻¹ for Bacillus subtilis and 0.5 µg ml⁻¹ for Enterococcus faecalis, ensuring its potential as an anti-infective agent for controlling the growth of pathogenic bacteria. The minimum bactericidal concentration of normal GO nanosheets was determined to be two-fold higher than its corresponding MIC value, indicating promising bactericidal activity. The mechanism of anti-bacterial action was evaluated by measuring the enzymatic activity of ß-D-galactosidase for the hydrolysis of o-nitrophenol-ß-D-galactopyranoside.

Investigation of transfer characteristics of high performance graphene flakes.

In this article, we attempted a study on field effect transport characteristics of graphene flakes. These graphene flakes were exfoliated by mechanical peeling-off technique and the electrical contacts were patterned by photo-lithographic method. Graphene devices have shown better transfer characteristics which was obtained even in low-voltage (< 5 V). Back-gated graphene transistors were patterned on oxidized silicon wafers. A clear n-type to p-type transition at Dirac point and higher electron drain-current modulation in positive back-gate field with current minimum (the Dirac point) were observed at V(GS) = -1.7 V. The carrier mobility was determined from the measured transconductance. The transconductance of the graphene transistors was observed as high as 18.6 microS with a channel length of 68 microm. A maximum electron mobility of 1870 +/- 143 cm2/V x s and hole mobility of 1050 +/- 35 cm2/V x s were achieved at a drain bias 2.1 V which are comparatively higher values among reported for mechanically exfoliated graphene using lithographic method. The fabricated devices also sustained with high-current density for 40 hr in continuous operation without any change in device resistance, which could be applied for robust wiring applications.

ZnO piezoelectric fine wire gated graphene oxide field effect transistor.

Here we report the fabrication and characteristics of graphene oxide (GO) field effect transistor gated with piezopotential of ZnO fine wires on a flexible substrate. The FET device consists of GO thin film on the bottom and ZnO piezoelectric fine wire (PFW) on the top. In the FET device the GO serves as a carrier transport channel and ZnO PFW acts as a gate. When the substrate is bent, a piezopotential is generated in the ZnO PFW. The piezopotential created by the strain in the ZnO PFW was used to control the carrier transport in the GO channel. This device demonstrates the application of piezoelectric ZnO PFW for creating the gating effect on the semiconducting performance of GO film.

Topochemically prepared tungsten disulfide nanostructures as a novel pseudocapacitive electrode for high performance supercapacitor.

The topochemical preparation of nanostructured materials (NMs) has received significant attention in recent years due to the exceptional electrochemical properties exhibited by the resulting NMs. This work focuses on the preparation of two-dimensional tungsten di-sulfide (WS2) nanostructures through the topochemical conversion of tungsten trioxide (WO3) nanostructures and also evaluates their potential applications as electrode materials for supercapacitors (SCs). The X-ray diffraction and photoelectron studies conducted in this research reveal the conversion of hexagonal WO3 into hexagonal WS2 nanosheets, accompanied by changes in oxidation states. The FE-SEM and HR-TEM studies confirm the formation of WS2 in the sheet-like morphologies with lateral dimensions of 100 × 100 nm. The electrochemical investigation, using techniques such as CV, galvanostatic CD, and EIS, confirmed the presence of intercalation pseudocapacitance in the WS2 electrode, with a higher electrode-specific-capacitance (260 F g-1) than that of WO3 electrode. The WS2 symmetric SC delivered high device capacitance (59.17 F g-1), energy density (8.21 Wh kg-1) and power density (3,750 W kg-1) with better cyclic stability over 5000 cycles. These experimental findings show that the topochemically synthesized WS2as novel supercapacitor electrodes might be useful for the advancement of future-generation energy storage devices.

Effective regeneration of mixed composition of spent lithium-ion batteries electrodes towards building supercapacitor.

Recycling of different manufacturers of spent lithium-ion batteries cathode and anode via a simple regeneration process has an opportunity to fabricate new energy devices. In this study, the different manufacturers of spent LIB cathode pieces were subjected to lixiviation process and found the best-optimized conditions such as tartaric acid concentration (2.5 M), H2O2 concentration (7.5 vol%), solid-liquid ratio (80 g/L), temperature (80 °C), and lixiviation time (80 min) for maximum ~ 99% extraction efficiency of metals. Further, 3D-MnCo2O4 (MCO) spheres were regenerated from the cathode lixivium containing metal ions via hydrothermal technique. Besides, anode graphite and Al foils after cathode lixiviation were exploited to prepare reduced graphene oxide (RGO) at room temperature in a simple method. The electrochemical performance of both regenerated electrodes from spent LIBs was explored in the half-cell configuration using the 1 M Na2SO4 electrolyte. Additionally, the constructed MCO//RGO asymmetric supercapacitor device offers an operational voltage of 1.8 V and displays a high energy density of ~ 23.9 Wh kg-1 at 450 W kg-1 with 8000 cycles. This alternative recycling method proposes the possibility to construct high-energy storage devices from different compositions of spent LIBs.

Two Faces Under a Hood: Unravelling the Energy Harnessing and Storage Properties of 1T-MoS2 Quantum Sheets for Next-Generation Stand-Alone Energy Systems.

The two-dimensional 1T-MoS2 quantum sheets (QSs) continuously seek attention due to their extraordinary energy harnessing and storage properties towards designing an all-in-one self-charging power system (SCPS). Herein, we have utilized the superior dual-functional nature of exfoliated MoS2 QSs for SCPS via fabricating all-solid-state microsupercapacitors (MSC) as an energy storage device and triboelectric nanogenerator (TENG) with MoS2 QSs based charge-trapping interfacial layer as the energy harvester. The electrochemical analysis of MoS2 QSs MSC indicated their superior capacitive properties with a high areal capacitance (4.3 mF cm-2), energy density (0.38 µWh cm-2), and long cycle life. Furthermore, we emphasize the fabrication of MSC with shape diversity and performance uniformity via construction in several designable shapes, which exhibit superior electrochemical performances. The MoS2 QSs based charge-trapping layer enhances the output performance of TENG dramatically with a peak power density as large as 10 µW cm-2, which is 13-fold greater than that of the pristine TENG. As proof of the concept, we fabricated an all MoS2 based SCPS which showed their ability to self-charge up to a maximum of 1050 mV, outperforming many SCPS reported previously. Overall, this work creates a way to utilize the bifunctional properties of MoS2 QSs for the development of next-generation SCPS.

Decoupling Contact and Rotary Triboelectrification vs Materials Property: Toward Understanding the Origin of Direct-Current Generation in TENG.

Direct-current (DC) triboelectric nanogenerators (TENGs) are increasingly recognized as next-generation power sources for widespread applications. Research has recently focused on developing novel materials as active layers for DC TENGs and device configurations to elucidate the working mechanisms. In this work, we report the use of a carbyne (dehydrohalogenated poly(vinylidene fluoride) (PVDF)) film as a positive-type friction layer for DC TENGs for efficient harvesting of rotary energy. The fabricated carbyne-based rotary TENG generates an output voltage (120 V) with excellent mechanical stability and peak power density (500 µW m-2). The mechanism of DC output generation from the carbyne-based rotary TENG is explained based on halogen removal from PVDF and the electrostatic breakdown effect. Additionally, the humidity effects on the fabricated carbyne-based rotary TENG toward a self-powered humidity sensor are studied in detail with the aid of in situ Raman analysis, Fourier transform infrared spectroscopy, and open-circuit potential measurements. Together, our experimental results demonstrate that using carbyne as an active triboelectric layer for DC TENGs would greatly benefit the next generation of power devices.

Ferroelectric-semiconductor BaTiO3-Ag2O nanohybrid as an efficient piezo-photocatalytic material.

Piezo-photocatalysis is a new concept of utilizing nanohybrids comprising piezoelectric and photocatalytic materials for enhancement in advanced oxidation process under the presence of light and mechanical energy. In this study, we explored the effectiveness of piezo-photocatalysis via examining their catalytic activity towards the degradation of azo dye (Rhodamine-B) and standard pollutant (Phenol) catalyzed by ferroelectric-semiconductor (BaTiO3-Ag2O) nanohybrids. Further, the enhancement in piezo-photocatalysis has been achieved via persulfate activation and the role of free radicals was examined by quenchers. A plausible mechanism for the improved piezo-photocatalysis of BaTiO3-Ag2O nanohybrid using persulfate activation has been discussed in detail. The removal mechanism of Rhodamine-B has been investigated using analytical techniques such as HPLC and EPR. Our experimental study demonstrated that the combination of piezo-photocatalysis with persulfate activation will provide higher reaction rate which will be beneficial towards the degradation of complex molecular pollutants derived from industrial sectors.

Topochemically synthesized MoS2 nanosheets: A high performance electrode for wide-temperature tolerant aqueous supercapacitors.

This work describes the formation of two-dimensional molybdenum di-sulfide (MoS2) nanosheets via topochemical sulfurization of MoO3 microplates and its applications towards wide-temperature tolerant supercapacitors. Physico-chemical characterizations such as XRD, FE-SEM, HR-TEM, XPS and elemental mapping analysis revealed the formation of MoS2 nanosheets with lateral size in the range of 200 nm. The electrochemical properties of the MoS2 electrode using three-electrode configuration tests revealed the presence of pseudocapacitive mechanism of charge-storage with a high capacitance (119.38 F g-1) from cyclic voltammetry profiles and superior cyclic stability of 95.1% over 2000 cycles. The symmetric supercapacitor (SSC) fabricated using MoS2 electrodes delivered a high-energy density (6.56 Wh kg-1) and high-power density (2500 W kg-1) with long cycle life. The electrochemical performance of the MoS2 SSC exhibited ~121% improvement at 80 °C compared to that achieved at 20 °C and the mechanism of improved properties were examined with the use of electrochemical impedance spectroscopy. These experimental results indicate usefulness of topochemically synthesized MoS2 for construction of wide-temperature tolerant supercapacitors that can be useful in a variety of industrial sectors.

Probing the energy conversion process in piezoelectric-driven electrochemical self-charging supercapacitor power cell using piezoelectrochemical spectroscopy.

The design and development of self-charging supercapacitor power cells are rapidly gaining interest due to their ability to convert and store energy in an integrated device. Here, we have demonstrated the fabrication of a self-charging supercapacitor using siloxene sheets as electrodes and siloxene-based polymeric piezofiber separator immobilized with an ionogel electrolyte. The self-charging properties of the fabricated device subjected to various levels of compressive forces showed their ability to self-charge up to a maximum of 207 mV. The mechanism of self-charging process in the fabricated device is discussed via "piezoelectrochemical effect" with the aid of piezoelectrochemical spectroscopy measurements. These studies revealed the direct evidence of the piezoelectrochemical phenomenon involved in the energy conversion and storage process in the fabricated device. This study can provide insight towards understanding the energy conversion process in self-charging supercapacitors, which is of significance considering the state of the art of piezoelectric driven self-charging supercapacitors.

Blue TiO2 nanosheets as a high-performance electrode material for supercapacitors.

We are reporting the use of blue titanium oxide (b-TiO2) nanostructures as advanced electrode material for high performance supercapacitor for the first time. A one-pot hydrothermal route was employed for the oxidation of layered titanium diboride (TiB2) into b-TiO2 nanosheets. The b-TiO2 nanosheets are prepared via hydrothermal oxidation of TiB2. Physico-chemical characterizations such as X-ray diffraction, UV-visible, photoluminescence spectroscopy, electron spin resonance spectroscopy, laser Raman spectrum, X-ray photoelectron spectroscopy, and morphological studies revealed the formation of sheet-like b-TiO2 nanostructures. The energy storage properties of the b-TiO2 electrode were examined using aqueous and organic electrolytes. The cyclic voltammetry and charge-discharge analysis of b-TiO2 electrode using 1 M Na2SO4 revealed their pseudocapacitive nature with a high specific capacitance (∼19 mF cm-2). The b-TiO2 based symmetric supercapacitor (SSC) device using organic liquid (1 M TEABF4) works over a wide operating potential window (3 V) and delivered a high specific capacitance (6.67 F g-1 or 3.58 mF cm-2), possess high energy density and power density with excellent cyclic stability over 10,000 cycles. Collectively, these studies demonstrated the usefulness of b-TiO2 as a novel electrode material for high performance supercapacitor.

Carbyne-enriched carbon anchored on nickel foam: A novel binder-free electrode for supercapacitor application.

Carbon- and carbon derivatives are widely employed as efficient electrode materials for supercapacitor applications. Herein, we demonstrate a cost-effective dip-coating process followed by dehydrohalogenation of PVDF-Ni for the preparation of carbyne enriched carbon anchored on nickel (CEC-Ni) as high-performance electrode material. The removal of halogens in the prepared CEC-Ni were widely characterized using XRD, XPS, Laser Raman, and FT-IR analysis. The occurrence of carbon-carbon vibration in the prepared CEC-Ni foam was confirmed using FT-IR spectroscopy. Laser Raman analysis confirms that the CEC-Ni foam contains both sp and sp2 hybridized carbon. The electrochemical properties of prepared carbyne enriched carbon anchored on nickel foam electrode (CEC-NiE) showed an ideal capacitive properties and delivered a maximum specific capacitance of about 106.12 F g-1 with excellent cyclic retention. Furthermore, the mechanism of charge-storage in the CEC-NiE was analyzed using Dunn's method. In additon, the asymmetric supercapacitor device was fabricated using CEC-NiE as positive and rGO as negative electrode achieved a remarkable energy density of 33.57 Wh Kg-1 with a maximal power density of 14825.71 W Kg-1. These results suggested that the facile preparation of CEC-NiE could be a promising and effective electrode material for future energy storage application.

Understanding the Thermal Treatment Effect of Two-Dimensional Siloxene Sheets and the Origin of Superior Electrochemical Energy Storage Performances.

Two-dimensional siloxene sheets are an emerging class of materials with an eclectic range of potential applications including electrochemical energy conversion and storage sectors. Here, we demonstrated the dehydrogenation/dehydroxylation of siloxene sheets by thermal annealing at high temperature (HT) and investigated their supercapacitive performances using ionic liquid electrolyte. The X-ray diffraction analysis, spectroscopic (Fourier transform infrared, laser Raman, and X-ray photoelectron spectroscopy) studies, and morphological analysis of HT-siloxene revealed the removal of functional groups at the edges/basal planes of siloxene, and preservation of oxygen-interconnected Si6 rings with sheet-like structures. The HT-siloxene symmetric supercapacitor (SSC) operates over a wide potential window (0-3.0 V), delivers a high specific capacitance (3.45 mF cm-2), high energy density of about 15.53 mJ cm-2 (almost 2-fold higher than that of the as-prepared siloxene SSC), and low equivalent series resistance (compared to reported silicon-based SSCs) with excellent rate capability and long cycle life over 10 000 cycles.

Copper molybdenum sulfide anchored nickel foam: a high performance, binder-free, negative electrode for supercapacitors.

Herein, we are demonstrating the use of a binder-free electrode based on copper-molybdenum-sulfide nanostructures grown on nickel foam (CMS/Ni) as a novel negative electrode for supercapacitors. The cyclic voltammetry and charge-discharge analyses reveal the pseudocapacitive nature of the CMS/Ni electrode with a high specific capacity of 633 mAh g-1 (∼20-fold higher than the binder-based CMS electrode) which is mainly due to their superior electronic conductivity and short ion transport pathways. Furthermore, the fabricated symmetric supercapacitor using the CMS/Ni electrode delivered a high device capacitance (265.62 F g-1), high energy density (23.61 Wh kg-1) and long cycle-life. The results ensure that the CMS/Ni binder-free electrode will be a promising negative electrode for high-performance supercapacitors.

Cardioprotective effect of the Hibiscus rosa sinensis flowers in an oxidative stress model of myocardial ischemic reperfusion injury in rat.

BACKGROUND: The present study investigates the cardioprotective effects of Hibiscus rosa sinensis in myocardial ischemic reperfusion injury, particularly in terms of its antioxidant effects. METHODS: The medicinal values of the flowers of Hibiscus rosa sinensis (Chinese rose) have been mentioned in ancient literature as useful in disorders of the heart. Dried pulverized flower of Hibiscus rosa sinensis was administered orally to Wistar albino rats (150-200 gms) in three different doses [125, 250 and 500 mg/kg in 2% carboxy methyl cellulose (CMC)], 6 days per week for 4 weeks. Thereafter, rats were sacrificed; either for the determination of baseline changes in cardiac endogenous antioxidants [superoxide dismutase, reduced glutathione and catalase] or the hearts were subjected to isoproterenol induced myocardial necrosis. RESULTS: There was significant increase in the baseline contents of thiobarbituric acid reactive substances (TBARS) [a measure of lipid per oxidation] with both doses of Hibiscus Rosa sinensis. In the 250 mg/kg treated group, there was significant increase in superoxide dismutase, reduced glutathione, and catalase levels but not in the 125 and 500 mg/kg treated groups. Significant rise in myocardial thiobarbituric acid reactive substances and loss of superoxide dismutase, catalase and reduced glutathione (suggestive of increased oxidative stress) occurred in the vehicle treated hearts subjected to in vivo myocardial ischemic reperfusion injury. CONCLUSION: It may be concluded that flower of Hibiscus rosa sinensis (250 mg/kg) augments endogenous antioxidant compounds of rat heart and also prevents the myocardium from isoproterenol induced myocardial injury.

Inhibitory Effect of Zinc Sulfide Nanoparticles Towards Breast Cancer Stem Cell Migration and Invasion.

Cancer stem cells are demonstrated to be a highly malignant cancer with an extremely high migratory ability and conventional therapies have little effect on preventing cancer migration and invasion. In this study, we investigated the inhibitory effect of zinc sulfide (ZnS) nanoparticles towards the migration and invasion of breast cancer stem cells MCF-7-SC. The cytotoxicity studies and the Hoechst staining experiments suggested that there is no obvious toxicity of ZnS has been observed upto a concentration of 400 µg/mL. ZnS nanoparticles significantly inhibited the wound healing in the MCF-7-SC cells. The cell invasion assay and western blot analysis results suggested that ZnS nanoparticles inhibited the metastasis of MCF-7-SCs in dose-dependent manner by suppressing epithelial-mesenchymal transition process. Overall, our experimental analysis suggested that nano ZnS has the ability to inhibit cancer stem cell migration and invasion, which can open up new insights in the cancer therapy.