Department Of Physics
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Item Electrochemical performance of a self-assembled two-dimensional heterostructure of rGO/MoS2/h-BN(Royal Society of Chemistry, 2020) Alegaonkar, A.P; Alegaonkar, P.S; Pardeshi, S.K.We report the preparation and electrochemical performance evaluation of a two-dimensional (2D) self-assembled heterostructure of graphene oxide (rGO), molybdenum disulphide (MoS2), and hexagonal boron nitride (h-BN). In the present study, the rGO-MoS2-h-BN (GMH) multi-layered GMH heterostructure is fabricated via an in situ chemical route. Based on material analysis, the composite consists of bond conformations of C-B-C, Mo-S, C-N, B-N, and Mo-C, indicating the layered stacks of rGO/h-BN/MoS2. In electrochemical analysis, the composite showed superior performance in the aqueous medium of cobalt sulphate (CoSO4) over other samples. CV measurements, performed over the range 10 to 100 mV s-1, showed a change in specific capacitance (Csp) from 800 to 100 F g-1. GMH showed almost no degradation up to 20?000 cycles @ 100 mV s-1. The calculated Csp, energy density (ED), and power density (PD) are discussed in light of Nyquist, Bode, and Ragone analysis. An equivalent circuit is simulated for the cell and its discrete electronic components are discussed. Due to its larger effective electron diffusion length > 1000 ?m, broadly, the composite showed battery-like characteristics, as supported by radical paramagnetic resonance and transport response studies. The symmetric electrodes prepared in one step are facile to fabricate, easy to integrate and involve no pre or post-treatment. They possess superior flat cell character, are cost effective, and are favourable towards practicality at an industrial scale, as demonstrated on the laboratory bench. The details are presented. The Royal Society of Chemistry.Item A glimpse on all-solid-state Li-ion battery (ASSLIB) performance based on novel solid polymer electrolytes: a topical review(Springer, 2020) Arya, A; Sharma, A.L.All-solid-state batteries are swiftly gaining the attention of the research community owing to their widespread applications in electric vehicles, digital electronics, portable appliances, etc. A battery comprises three components: cathode, anode and electrolyte. An electrolyte is the heart of the battery and plays a crucial role in the overall performance of the battery. In order to make the review more focused, all-solid-state Li-ion batteries (ASSLIBs) have been considered. This review covers the architecture of ASSLIBs, advantages, and characteristics of the solid polymer electrolytes. The important preparation methods are summarized, followed by the characterizations for testing the suitability of electrolytes for solid-state batteries. The discussion is focused on the "state of the art" in the field of solid-state batteries, device fabrication, and comparison in terms of capacity, energy density, and cyclic stability. In the last section, the ion conduction mechanism in different solid polymer electrolytes is discussed. Finally, it is tried to give a possible outlook for developing future hybrid and multifunctional electrolytes which can act as a bridge for developing solid-state batteries covering a broad range of applications. - 2020, Springer Science+Business Media, LLC, part of Springer Nature.Item Strain tunable Schottky barriers and tunneling characteristics of borophene/MX2 van der Waals heterostructures(Elsevier, 2020) Katoch, N; Kumar, A; Sharma, R; Ahluwalia, P.K; Kumar, J.Based on first-principle calculations, we report the strain induced changes in electronic properties and their influence on current-voltage (I?V) characteristics of the borophene (?12)/MX2 (M = Mo, W and X = S, Se) vdW heterostructures. The results reveal that the intrinsic electronic nature of borophene and MX2 is retained because of weak van der Waals interactions. However, p-type Schottky contacts are formed at the interface of the heterostructures. Application of the in-plane tensile and compression strains is effective in tuning the Schottky contacts and controlling the SBHs. Also, at the vertical pressure values of 5.46 and 5.25 GPa for ?12/MoS2 and ?12/WS2 respectively, Schottky contact changes from p-type to n-type. The I?V characteristics exhibit an ohmic behavior at low bias ±0.1 v and noticeable NDR on changing positive (negative) biases. Such strain tunable Schottky barriers may be influential in ?12/MX2 based high-performance nano- and optoelectronic devices. - 2020 Elsevier B.V.Item Optical absorbance in multilayer two-dimensional materials: Graphene and antimonene(American Institute of Physics Inc., 2020) Kumar A; Sachdeva G; Pandey R; Karna S.P.Antimonene, one of the group V elemental monolayers, has attracted intense interest due to its intriguing electronic properties. Here, we present the optical absorption properties of atomically flat antimonene for which the directional bonds between Sb atoms appear to be analogous to C-C bonds in graphene. The results, based on first-principles density functional theory calculations, predict the absorbance in multilayer antimonene to be comparable or higher than that calculated for multilayer graphene. Specifically, the IR absorption in antimonene is significantly higher with a prominent band at about 4 ?m associated with the dipole-allowed interband transitions. Furthermore, a strong dependence of absorbance on topology is predicted for both antimonene and graphene which results from the subtle variations in their stacking-dependent band structures. Our results suggest multilayer antimonene to be a good candidate material for optical power limiting applications in the IR region. - 2020 Author(s).Item Ion transport, dielectric, and electrochemical properties of sodium ion-conducting polymer nanocomposite: application in EDLC(Springer, 2020) Kumar, A; Madaan, M; Arya, A; Tanwar, S; Sharma, A.L.The present paper reports the investigation of structural, electrical, dielectric, and transport properties of the polyethylene oxide (PEO)-based polymer nanocomposite (PNC), with sodium hexafluorophosphate (NaPF6) salt and barium titanate (BaTiO3) as nanofillers. The PNC has been prepared via standard solution casting technique. The structural investigation has been investigated by X-ray diffraction and evidence the enhancement in amorphous content. The morphology has been examined by Field emission scanning electron microscopy technique and confirms the composite formation. The presence of polymer-ion and ion-ion interaction has been confirmed by the Fourier transform infrared spectra (FTIR) and evidences the PNC formation. The impedance spectroscopy has been performed to evaluate the ionic conductivity in the temperature range 40–100 °C.The increase of conductivity is obtained with the addition of nanofiller and temperature-dependent conductivity follows Arrhenius behavior. The PNC film having the highest conductivity exhibits low activation energy and indicates the fast ion migration. The ion transference number is close to unity and the voltage stability window is within the desirable limit. The complex permittivity and complex conductivity have been obtained and the plot has been fitted in the whole frequency window. The fitted plot is in perfect agreement with experimental data. The PNC having the highest conductivity has high dielectric strength and low relaxation time. It confirms the nanofiller role in enhancing ion migration. The ion transport parameters (n, ?, D) are also in correlation with impedance and dielectric analysis. The optimized PNC films have been used to prepare the Electric double-layer capacitors (EDLC) and it demonstrates the improved performance which may be attributed to the effective role played by nanofiller in boosting ion dynamics. - 2020, Springer Science+Business Media, LLC, part of Springer Nature.Item Novel phosphorus-based 2D allotropes with ultra-high mobility(Institute of Physics Publishing, 2020) Kaur, S; Kumar, A; Srivastava, S; Tankeshwar, K; Pandey, R.Electronic structure calculations based on density functional theory were performed to investigate structural, mechanical, and electronic properties of phosphorene-based large honeycomb dumbbell (LHD) hybrid structures and a new phosphorene allotrope, referred to as ??-P. The LHD hybrids (i.e., X6P4; X being C or Si or Ge or Sn) and ??-P have significantly higher bandgaps than the corresponding pristine LHD structures, except the case of C6P4, which is metallic. ??-P is found to be a highly flexible p-type material which shows strain-engineered photocatalytic activity in a highly alkaline medium. The carrier mobility of the considered systems is as high as 105 cm2 V-1 s-1 (specifically the electron mobility of LHD structures). The calculated STM images display the surface morphologies of the LHD hybrids and ??-P. The predicted phosphorus-based 2D structures with novel electronic properties may be candidate materials for nanoscale devices. - 2020 IOP Publishing Ltd.Item Electronic structure and carrier mobilities of twisted graphene helix(Elsevier, 2020) Thakur, R; Ahluwalia, P.K; Kumar, A; Mohan, B; Sharma, R.Density functional theory based calculations have been carried out to investigate the effect of twisting on electronic band structures and carrier mobilities of three prototypes of armchair graphene nanoribbons (AGNRs) within the fixed boundary conditions. It is found that twisting causes a modification in the bandgap values and the overall shape of band structures. The values of longitudinal acoustic deformation potential (DP) are found to be higher than the torsional acoustic DP values. The torsional strain is also found to have a profound effect on effective mass and mobilities of given AGNRs. The hole mobility of hydrogen passivated N = 8 AGNRs is found to be comparable with the carrier mobility of intrinsic graphene. The electron mobility of N = 8 AGNRs can be further increased with fluorine passivation. The width, passivation, and extent of twisting together determine n-type or p-type behavior of AGNRs. Fluorine passivated AGNRs are predicted to be potential candidates for mechanical and high-frequency switching. Our results suggest that twisting of AGNRs can be an effective mean for tuning their band structure and carrier mobility for applications in high-speed switching devices. 2020 Elsevier B.V.Item Nano-bio interface study between Fe content TiO2 nanoparticles and adenosine triphosphate biomolecules(Wiley, 2019) Barkhade, T; Phatangare, A; Dahiwale, S; Mahapatra, S.K; Banerjee, I.The advent of nano-biotechnology has inspired the interface interaction study between engineered nanoparticles (NPs) and biomolecules. The interaction between Fe content titanium dioxide (TiO2) NPs and adenosine triphosphate (ATP) biomolecules has been envisioned. The effect of Fe content in TiO2 matrix was studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The increase in Fe content caused a decrease in particle size with change in morphology from spherical to one-dimensional rod structure. The Fe incorporation in the TiO2 matrix reduced the transition temperature from anatase to rutile (A-R) phase along with formation of haematite phase of iron oxide at 400°C. The interaction of Fe content TiO2 NPs with ATP molecule has been studied using spectroscopic method of Raman scattering and infrared vibration spectrum along with TEM. Fe content in TiO2 has enhanced the interaction efficiency of the NPs with ATP biomolecules. Raman spectroscopy confirms that the NPs interact strongly with nitrogen (N7) site in the adenine ring of ATP biomolecule. Engineering of Fe content TiO2 NP could successfully tune the coordination between metal oxide NPs with biomolecules, which could help in designing devices for biomedical applications. © 2019 John Wiley & Sons, Ltd.Item Investigation on enhancement of electrical, dielectric and ion transport properties of nanoclay-based blend polymer nanocomposites(Springer, 2019) Arya, A; Sharma, A.L.An intercalated blend polymer nanocomposite (PNC) films based on blend (PEO–PVC), LiPF6 as salt and modified montmorillonite (MMMT) as nanoclay are prepared via solution cast method. The impact of the nanoclay on the morphology, structure, polymer–polymer, polymer–ion interactions, ionic conductivity, voltage stability window, glass transition temperature, dielectric permittivity, and ac conductivity has been explored. The structural analysis evidenced the formation of blended and intercalated polymer nanocomposites. The FTIR analysis confirmed the interaction between polymer–ion-nanoclay, and polymer intercalation is evidenced by the out-of-the-plane mode [Si–O mode] of MMMT. An increase in the fraction of free anions with clay addition is confirmed. The highest ionic conductivity of about ~ 8.2 × 10−5 S cm−1 (at RT) and 1.01 × 10−3 S cm−1 (at 100 °C) is exhibited by 5 wt% MMMT based PNC. A strong correlation is observed between the glass transition temperature, crystallinity, melting temperature (Tm), ionic conductivity, relaxation time, and dielectric strength. The dielectric data have been fitted and enhanced dielectric strength and lowering of the relaxation time (τε′andτm) with clay addition evidences the faster segmental motion of polymer chain. The intercalated PNC shows thermal stability up to ~ 300 °C, high ion transference number (~ 1), and broad voltage stability window of ~ 5 V. An absolute agreement between ion mobility (μ), diffusion coefficient (D), and ionic conductivity is observed. An ion transport mechanism has been proposed on the basis of experimental results. Therefore, the proposed PNC can be adopted as electrolyte cum separator for energy storage devices. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.Item Investigation of non linear dynamics of an excitable magnetron sputtering plasma(Elsevier, 2019) Sabavath, G; Shaw, P.K; Iyengar, A.N.S; Banerjee, I; Mahapatra, S.K.In this paper nonlinear dynamical behaviour of an excitable DC magnetron sputtering plasma has been investigated. Initially, plasma exhibited fixed point dynamics whereas with the increase in the discharge voltage, spikes were observed in the floating potential fluctuations. Furthermore, the increasing of discharge voltage resulted the increase in spikes. Power spectrum plot, normalized variance, recurrence plot and Hurst exponent are employed to extract the underlying feature of the floating potential fluctuations. A dip in the plot of normalized variance with variation in the control parameter has been seen, which is strongly indicative of coherence resonance like behaviour in the system. Power spectrum plot and Hurst exponent estimation are confirming the presence of coherence resonance behaviour. Apart from quantitative confirmation, visual verification of coherence resonance behavior has been carried out using recurrence plot analysis. It is noticed that the noise component increases with the increase in the discharge voltage and a suitable intrinsic noise strength plays an important role in generating the coherence resonance. © 2019