Madhupriya Samanta

Co3O4 Nanowires on Flexible Carbon Fabric as a Binder-Free Electrode for All Solid-State Symmetric Supercapacitor

Developing portable, lightweight, and flexible energy storage systems has become a necessity with the advent of wearable electronic devices in our modern society. This work focuses on the fabrication of Co3O4 nanowires on a flexible carbon fabric (CoNW/CF) substrate by a simple cost-effective hydrothermal route. The merits of the high surface area of the prepared Co3O4 nanostructures result in an exceptionally high specific capacitance of 3290 F/g at a scan rate of 5 mV/s, which is close to their theoretical specific capacitance. Furthermore, a solid-state symmetric supercapacitor (SSC) based on CoNW/CF (CoNW/CF//CoNW/CF) was fabricated successfully. The device attains high energy and power densities of 6.7 Wh/kg and 5000 W/kg. It also demonstrates excellent rate capability and retains 95.3% of its initial capacitance after 5000 cycles. Further, the SSC holds its excellent performance at severe bending conditions. When a series assembly of four such devices is charged, it can store sufficient energy to power a series combination of five light-emitting diodes. Thus, this SSC device based on a three-dimensional coaxial architecture opens up new strategies for the design of next-generation flexible supercapacitors.

Facile synthesis of ZnPc nanoflakes for cold cathode emission

The challenge of developing two dimensional metal phthalocyanine nanostructures by controlling the reaction protocols is successfully addressed in the present work by synthesizing zinc phthalocyanine (ZnPc) novel nanoflakes using a simple low temperature hydrothermal route. The as synthesized samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultra-violet visible spectrometer (UV-Vis), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscope (FESEM). The field emission or cold cathode emission characteristics of these phthalocyanine nanostructures have been reported for the first time here and it is shown that as prepared nanoflakes can act as electron field emitter having a turn-on field 4.7 V μm−1 at a current density of 1 μA cm−2 for an inter electrode distance of 130 μm. The local electric field distributions around nanoflakes were also further studied theoretically using a finite element method. The obtained results indicate that ZnPc nanoflakes are the potential candidate for electron emission based applications such as vacuum nanoelectronic devices and field emission display devices.

Novel Quaternary Chalcogenide/Reduced Graphene Oxide-Based Asymmetric Supercapacitor with High Energy Density

In this work we have synthesized quaternary chalcogenide Cu2NiSnS4 (QC) nanoparticles grown in situ on 2D reduced graphene oxide (rGO) for application as anode material of solid-state asymmetric supercapacitors (ASCs). Thorough characterization of the synthesized composite validates the proper phase, stoichiometry, and morphology. Detailed electrochemical study of the electrode materials and ASCs has been performed. The as-fabricated device delivers an exceptionally high areal capacitance (655.1 mF cm-2), which is much superior to that of commercial micro-supercapacitors. Furthermore, a remarkable volumetric capacitance of 16.38 F cm-3 is obtained at a current density of 5 mA cm-2 combined with a very high energy density of 5.68 mW h cm-3, which is comparable to that of commercially available lithium thin film batteries. The device retains 89.2% of the initial capacitance after running for 2000 cycles, suggesting its long-term capability. Consequently, the enhanced areal and volumetric capacitances combined with decent cycle stability and impressive energy density endow the uniquely decorated QC/rGO composite material as a promising candidate in the arena of energy storage devices. Moreover, Cu2NiSnS4 being a narrow band gap photovoltaic material, this work offers a novel protocol for the development of self-charging supercapacitors in the days to come.

Flower-like Cu2NiSnS4 microspheres for application as electrodes of asymmetric supercapacitors endowed with high energy density

Design of electrode materials for supercapacitors using earth-abundant and less-toxic metals is both cost effective and environmentally benign. The present study deals with the synthesis of flower-like Cu2NiSnS4 microspheres (FCMs) and utilizing the same as positive electrodes of solid-state asymmetric supercapacitors. Citric acid was used for the synthesis of Cu2NiSnS4 as the structure directing agent; a possible growth mechanism of the formation of flower-like microspheres is proposed. The as-prepared FCMs on nickel foam demonstrated a high specific capacitance of 1639 F g−1 at a scan rate of 5 mV s−1. The as-fabricated solid-state asymmetric device achieved high values of volumetric (8.81 F cm−3) and gravimetric (105.7 F g−1) capacitances. The device attained the maximum energy density of 2.57 mW h cm−3/30.88 W h kg−1 and high power density of 201.4 mW cm−3/2.42 kW kg−1. Superior capacitance retention of the device was confirmed as it maintained 95.7% of the initial capacitance after 2000 cycles. Thus, by effective integration on a large-scale basis, these supercapacitors have great potential for the development of sustainable energy storage systems using low-cost earth-abundant materials.

Solution processed, organic/inorganic nanostructure based bilayer device for diode application

Zinc oxide (ZnO) nanocapsules have been synthesized by simple hydrothermal method using ZnCl2 and KOH as precursor solution. Different tools, viz, FESEM, XRD, UV-Vis and FTIR spectroscopy have been used tocharacterizethe as synthesized nanoparticles. The average size of ZnOnanocapsules, as measured from the X ray diffraction measurements, were ∼ 21 nm. An organic-inorganic nanocomposite based bilayer device has been fabricated by depositing thin film of ZnO nanocapsules and copper phthalocyanine (CuPc) usingsolution cast method. The bilayer deviceexhibited excellent diode characteristics both in dark and under illumination with rectification ratio ca. 23 in dark when operated at 2 V. The nature of the current-voltage characteristics inverted when the order of film deposition was reversed, indicating a truly molecular phenomena of the rectification behavior. The device, under visible illumination, retained the rectification characteristics with higher value of rectification ratio, suggesting that the current nanocomposite based bilayer device might be a potential candidate for future applications in flexible and cost-effective photodiode, photosensor and photodetectors.

Sonocatalytic activity of solution processed zinc oxide nanowires: Efficient remediation of organic pollutants

This paper demonstrated the formation of Zinc Oxide (ZnO) nanowires by room temperature solution process and its catalytic activity towards the degradation of organic pollutants e.g. eosin B in aqueous medium when irradiated with ultrasonic vibrations without any external light illuminations. Our as prepared pure ZnO nanostructure exhibit sonocatalytic efficiency upto 75.13% within 100 minutes whereas by the sonolysis process, eosin B was degraded only upto 25.70% within same time. The effect of variation of sonocatalyst dosage on decolorization efficiency was also evaluated. The energy conversion mechanism was also discussed in details. Therefore, pure ZnO nanowires can be used as potential candidate for sonocatalytic degradation of organic contaminations for remediation of waste water.