Search

In the recent times sodium ion batteries (SIBs) have come to the forefront as an economic and resourceful alternative to lithium-ion batteries (LIBs) for powering portable electronic devices and large-scale grid storage. As the specific capacity, energy density and long cycle life of batteries depend upon the performance of anode materials; their quest is the ultimate need of the hour. Among the anode materials, the semimetallic pnictogens (As, Sb, Bi) and their compounds offer high gravimetric/volumetric capacities, but suffer from undesired volume expansion and inferior electrical conductivity. Herein, this paper reviews the recent progress in semimetallic pnictogens as alloying anodes and their compounds mainly as conversion-alloying anodes. Various debatable sodiation mechanisms (intercalation or alloying) have been presented with emphasis on in situ/ex situ advanced characterization methods well supported by theoretical modeling and calculations. The reviewed electrochemical reaction mechanisms, coherent structural designs and engineering provide a vital understanding of the electrochemical processes of Na+ ion storage. The existing challenges and perspectives are also presented, and several research directions are proposed from the aspects of special morphological design, employing conductive substrates, electrolyte additives and reducing particle size for technical and commercial success of SIBs.

In this work, ultrasound assisted catalytic removal of Rhodamine B (RhB) dye has been carried out in the presence of reduced Graphene Oxide enveloped Copper Phthalocyanine nanotube (RGO-CuPc) for the first time. This RGO-CuPc nanocomposite has been synthesized by in situ chemical reduction of Graphene Oxide (GO) with CuPc tube. Then our as prepared composite and pristine CuPc tubes are well characterized by various spectroscopic techniques such as X-Ray Diffraction, UV–vis and microscopic techniques like FESEM, HRTEM etc. Electrochemical EIS measurement has also been carried out to investigate charge transfer mechanism. These results confirm the purity of the as prepared samples. Efficient sonocatalytic RhB dye removal upto ∼92.22% is achieved by RGO-CuPc composite within 100 min as compared to pristine CuPc tube (∼70%). A plausible reaction pathway towards dye removal is discussed in detail. Also degradation performance in the presence of enhancer and scavenger has been investigated.

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.

Chemically derived topological insulator Bi2Se3 nanoflake/Si nanowire (SiNWs) heterojunctions were fabricated employing all eco-friendly cost-effective chemical route for the first time. X-ray diffraction studies confirmed proper phase formation of Bi2Se3 nanoflakes. The morphological features of the individual components and time-evolved hybrid structures were studied using field emission scanning electron microscope. High resolution transmission electron microscopic studies were performed to investigate the actual nature of junction whereas elemental distributions at junction, along with overall stoichiometry of the samples were analyzed using energy dispersive X-ray studies. Temperature dependent current–voltage characteristics and variation of barrier height and ideality factor was studied between 50 and 300 K. An increase in barrier height and decrease in the ideality factor were observed with increasing temperature for the sample. The rectification ratio (I+/I–) for SiNWs substrate over pristine Si ...

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 combin...

Synthesis of layered sheet like graphitic carbon nitride by pyrolysis of urea at different temperatures has been reported. The proper phase formation has been confirmed by X-ray diffraction study whereas field emission scanning and transmission electron microscope characterized the morphology of the material. Fourier transform infrared and Raman spectroscopy revealed the presence of different bonds in the sample. Thermal gravimetric analysis has been used to study the thermal stability of the material. Energy dispersive X-ray analysis further revealed the elemental composition of carbon and nitrogen in a proper stoichiometric ratio. Excitation dependent photoluminescence spectra of the as prepared samples have been studied in detail. It has been shown that synthesis condition can tailor the amount of defects present in the synthesized samples that in turn can change the photoluminescence properties of the material. The fluorescence spectra of the as prepared samples have been used to detect copper ions present in the sample. It has also been shown that the presence of defects which is mainly N-H functional groups can change the decay characteristics of the carrier in these samples which in turn changes the PL spectra.

Coalescence of unique properties of semiconductor and carbon nanotubes (CNTs) produces new advanced materials with exciting properties, which unwraps several new fields. Here, finite element modeling is employed to optimize the diameter of semiconducting zinc cadmium sulfide (Zn0.8Cd0.2S) microspheres on the wall of metallic CNTs to get the improved field emission property. Then, Zn0.8Cd0.2S microspheres are attached on COOH functionalized multiwalled CNTs (MWCNTs) by a simple one step solvothermal method for experimental corroboration. Field emission experiment shows a considerable enhancement of current density with respect to bare microspheres and functionalized CNTs. The turn-on field is found to be as low as 3V/μm at a current density of 10 μΑ/cm2 for the hybrid system. Density functional theory (DFT) calculation is carried out for the model structures of Zn0.8Cd0.2S and CNT-Zn0.8Cd0.2S to calculate the work functions. This improvement in field emission property of the hybrid system is demonstrated in terms of band bending, geometry, high field enhancement factor, low work function and electron affinity. Thus, non-field emitting microspheres with less toxicity have been transformed into a decent field emitter by the contribution of few carbon nanotubes.

This work highlights the synthesis of zinc blende ZnxCd1−xS ternary solid solutions with a tunable bandgap. Composition dependent band gaps are realized due to the effective band edge tuning of the solid solutions which in turn show decent photocatalytic behaviour. The bandgap of ZnxCd1−xS increases as Zn composition increases. It is interesting to note that the highest catalytic activity is observed for Zn0.8Cd0.2S (Eg = 2.83 eV) in the visible spectra due to the presence of defect states in the bandgap around 2.35 eV which has been explicated according to the results of photoluminescence spectra. Density of states (DOS) analysis provides further theoretical insight into the more negative conduction band edge for x = 0.8 than other samples. It also determines generation of intermediate states due to sulfur vacancy which is responsible for more electron–hole generation and the highest rate of Methyl Orange (MO) degradation under natural sunlight irradiation.

Bi2Se3 nanoflowers (NFs) and reduced graphene oxide (rGO) nanocomposite (BG) have been synthesized by a cost-effective, ecofriendly and easy hydrothermal route for the first time. Thorough characterizations confirm the phase, chemical composition and morphology of the samples. Room temperature transport measurement showed that the composite samples exhibit enhanced electrical conductivity compared to the pure Bi2Se3 nanoflowers (NFs). The possibility of using this composite in applications such as low macroscopic field emitters for cold cathode application has been investigated. For this, theoretical simulations are performed for pure and composite samples with graphene wrapping of different degrees and to evaluate the relation between the degree of rGO wrapping and the enhancement of FE properties, and the same was verified experimentally. It is observed that the enhancement factor for cold cathode emission of Bi2Se3–rGO (BG) composite is almost 5 times higher than that of pristine GO, 2.6 times that of rGO and nearly 1.5 times higher than that of pure Bi2Se3 NFs. The enhancement of the cold emission properties is attributed to suitable wrapping of rGO sheets over Bi2Se3 NFs. This produces more curvature at the nanoflakes edges and the electron affinities between the materials are favorable for the enhancement of cold cathode emission. The sample exhibiting the best FE properties also showed photoresponse properties under visible light excitation.

We present a general formulation of the ground state binding energy of a shallow hydrogenic impurity in spherical quantum dot with parabolic confinement, considering the effects of polarization and self energy. The variational approach within the effective mass approximation is employed here. The binding energy of an on-center impurity is computed for a $\mathrm{GaAs}$/ $\mathrm{{Al}_{x}{Ga}_{1-x}As}$ quantum dot as a function of the dot size with the dot barrier as parameter. The influence of polarization and self energy are also treated separately. Results indicate that the binding energy increases due to the presence of polarization charge, while decreases due to the self energy of the carrier. An overall enhancement in impurity binding energy, especially for small dots is noted., Comment: 9 pages, 2 figures

Supercapacitors or ultracapacitors are considered as one of the potential candidates in the domain of energy storage devices for the forthcoming generations. These devices have earned their significance in numerous applications, viz., to power hybrid electric/electric vehicles and other power and electronic systems which require electrical energy for their operation. Supercapacitors are the most versatile devices which are most widely used for delivery of electrical energy in short time and in arenas which demand long shelf life. Therefore, the development of supercapacitors has huge market requirements, and long-term progress is needed for their successful advancement and commercialization. Meanwhile, supercapacitors are also facing challenges such as technical problems, establishing electrical parameter models, consistency testing, and establishing industrial standards. In this paper, the above challenges and the future development opportunities of supercapacitors are introduced in detail. This perspective will provide corresponding guidance and new directions for the development of supercapacitors.

The present article intends to capture the impact of fly ash generated from Bakreswar Thermal Power Plant (BKTPP) on Chandrabhaga River of proximate location. Impacts have been captured giving emphasis on the morphological aspects of the channel and water quality standard. Chandrabhaga River (length: 26 km) of Birbhum district covers a mostly Rarh tract composed of coarse grain laterite soil. Field measurement of morphological parameters, water and soil samples collection from nine river sites and testing in laboratory reveal the following results: (1) In very proximate location of the fly ash pond, the river bed has raised up to 10–75 cm and the rate of aggradations declined downstream; (2) textural characteristics of bed materials have altered and become finer after huge influxing of fly ash; (3) leaching of finer fly ash particles in the pore space of the sand bed and consequent clogging has started which withstand the interaction between surface and subsurface flow; (4) suspended and dissolved load has increased by 62 % in comparison with the load before over spilling of fly ash from fly ash pond; (5) due to overloaded condition, more than 12,000 m3/year of fly ash is deposited over the river bed and it can defer the graded time of that river; (6) an analysis of physico-chemical properties of the collected water samples states that some of the parameters, e.g., turbidity, TDS, BOD, COD and DO, are not only beyond drinking standard but also beyond the standard of irrigation and aquatic life, specifically fishes; (7) fly ash contamination highly reduced carp fishes on which a troop of fishermen spend their livelihood and they are now in anxiety for the viability of their livelihood.

Two-dimensional topological insulator bismuth selenide (Bi2Se3) nanosheets (NSs) embedded in poly-methyl methacrylate (PMMA) are employed for the first time for the resistive switching (RS) application. Hexagonal 2D Bi2Se3 NSs are synthesized by a simple solvothermal method and combine with PMMA at different weight percentages of 2D Bi2Se3. Field emission scanning electron microscopy and transmission electron microscopy along with other characterizations such as X-ray photoelectron spectroscopy and Raman spectroscopy were performed for the characterization of Bi2Se3@PMMA hybrid system. The composite was deposited on a transparent, flexible polyethylene terephthalate substrate to form Ag/Bi2Se3@PMMA/indium doped tin oxide memory cell. I-V characteristics of the device revealed a stable and non-volatile memory effect. The device shows a significantly high resistance (RHRS/RLRS) ratio, more than 103, high retention time (more than 9000 s) with high reproducibility over a large number of (105) ac cycles. From the experimental data, RS performances are explained by using a charge trapping–detrapping mechanism. Owing to the increasing interest in flexible electronics, bending tests are carried out at various bending diameters (10–30 mm) to show the mechanical robustness of the proposed device.

Laser refractive surgery for myopia increases the eye's higher-order wavefront aberrations (HOA's). However, little is known about the impact of such optical degradation on post-operative image quality (IQ) of these eyes. This study determined the relation between HOA's and IQ parameters (peak IQ, dioptric focus that maximized IQ and depth of focus) derived from psychophysical (logMAR acuity) and computational (logVSOTF) through-focus curves in 45 subjects (18 to 31 yrs) before and 1-month after refractive surgery and in 40 age-matched emmetropic controls. Computationally derived peak IQ and its best focus were negatively correlated with the RMS deviation of all HOA's (HORMS) (r≥-0.5; p0.16 for all). Increase in HOA's after refractive surgery is therefore associated with a decline in peak IQ and a persistence of this sub-standard IQ over a larger dioptric range, vis-à-vis, before surgery and in age-matched controls. This optical deterioration however does not appear to significantly alter psychophysical IQ, suggesting minimal impact of refractive surgery on the subject's ability to resolve spatial details and their tolerance to blur.