Department Of Physics
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Item STRUCTURAL AND ELECTROCHEMICAL PROPERTIES OF INTERCALATED AND DISPERSED TYPE POLYMER NANOCOMPOSITE FILMS(Central University of Punjab, 2019) Arya, Anil; Sharma, A. L.The renewable and green source of energy now becomes the burning topic for worldwide research among the scientists. The demand for such energy resources is increasing day by day and it becomes the lifeblood of modern society. Global warming, finite fossil-fuel supplies, and city pollution conspire to make the use of environmentfriendly energy sources. Due to the enlarged dependency of a modern human being on energy resources in every sector and a limited supply of fossil fuels, leads to two main problematic consequences: (1) vulnerability of nation-states to fossil-fuel imports and (2) CO2 emissions that are acidifying our oceans and creating global warming. The controlled environment/climate has drawn the attention of the scientific community towards development and replacement of fossil fuels by an alternative/efficient energy resources. The prospective renewable energy resources are solar, tidal, hydro, wind energy etc. Next challenge comes to store it and could be supplied as per the demand. The said challenge could be overcome through the electrochemical storage/conversion devices (ESCDs) like supercapacitor, Lithium-ion batteries (LIB) and fuel cells. Especially, LIB having the ability to the portability of stored energy and to deliver it as and when required without gaseous exhaust, unlike fossil fuels. A secondary battery converts chemical energy into electrical energy and vice versa. Its structure is composed of a positive electrode as a cathode, a negative electrode as an anode, and electrolyte. Simultaneous movement of ions and electrons occurs in the battery system; ions flow through the electrolyte while electrons are generated at the anode and flow towards the cathode via an external circuit. The heart of the battery is the electrolyte as it is sandwiched between both electrodes and participate in charging/discharging. Although all the three components affect the overall cell performance, the electrolyte is dominating in nature and deciding the specific capacity, energy density, working voltage and the lifespan of the battery. Various types of electrolytes are liquid electrolytes, semi-gel and gel electrolytes. However, safety issues with lithium-metal anodes, the reaction of volatile/flammable organic solvents and the leakage of electrolytes have hindered the commercialization of any lithium-ion battery based on such electrolyte. The drawbacks associated with the battery comprising of above-mentioned electrolyte pushes us to develop new generation solid state polymer nanocomposite films (PNC films) which could possess inherent safety and good compatibility with electrodes as compared with liquid, semi-gel and gel electrolytes. v PNC films have numerous advantages like they are light in weight, flexible, have interfacial compatibility, no leakage issue and are very processable. Most importantly, they are very safe. SPEs are prepared by dissolving lithium salts in a high-molecularweight polymer matrix. The polymer acts as the host for the transmission of lithium ions through the motion of polymer segments. Solid polymer based electrolytes appear to be attractive as they can compensate for the volume changes of electrodes by elastic and plastic deformation. A PEO-based SPE is the most preferred polymer host in the research system due to its flexible backbone and ability to solvate lithium ions, with the coordination number dependent upon the salt concentration and identity of the anion. The main advantage of a PEO is its high solvation power. Hence it can form a complex easily with many alkali salts and provides a direct path for cation migration due to the presence of the ether group in the polymer backbone. But the low conductivity value (10–10 S cm−1 ) and poor mechanical properties of PEOs at ambient temperatures limit their use in devices. Many approaches have been explored to improve the ionic conductivity in order to suppress the concentration polarization and desirable electrochemical properties such as polymer blending, cross-linking, the addition of nano-sized fillers etc. Out of these approaches at host polymer level blending seems more appropriate and justified. Further to scale the relevant properties parameters by minimizing the concentration polarization, two novel approach i.e. (i) nanofiller dispersed polymer nanocomposites, and (ii) intercalated polymer nanocomposites have been adopted. The idea behind using nanofiller was the expectation to get percolation pathways composed of inorganic fillers grains through a flexible polymeric matrix. Such a phenomenon could lead to an increase in ionic conductivity followed, possibly, by an enhancement of the cation transport number while preserving mechanical properties and flexibility of the composite electrolyte prepared in the thin film configuration. The second one is also a thought-provoking approach and plays key role in (i) suppressing the concentration polarization by avoiding anion mobility, (ii) enhancement of the ion migration by allowing the cation coordinated polymer chain confinement in clay galleries, and (iii) negative surface charge on clay acts as Lewis acid and competes with Li+ cation to form complex with polymer which reduces ion coupling. An attempt has been made to understand the role of nanofiller and nanoclay in dispersed and intercalated blend polymer nanocomposites prepared by solution cast technique. A strong correlation exists between crystallinity, conductivity, free ion area, the number density of charge carriers, ion mobility, diffusion coefficient, activation energy, and glass transition temperature. Polymer-intercalated polymer nanocomposites display remarkable higher ionic conductivity, broad voltage stability window, high specific capacity and open-circuit voltage than the dispersed based polymer nanocomposites. Here we provide a cumulative account of an efficient polymer nanocomposite materials to identify their importance in the energy storage/conversion devices.Item Spectroscopic analysis of Muga silk nanoparticles synthesized by microwave method(Wiley-Blackwell Publishing Ltd, 2020) Asapur, P; Banerjee, I; Sahare, P.D; Mahapatra, S.Muga silk nanoparticles (MSNP) were synthesized using a microwave-assisted radiolysis method. The effect of microwave on the Muga protein secondary structures was analyzed. The evolution of the secondary structure from random coils to the ?-sheets was determined by using FTIR, circular dichroism and X-ray diffraction techniques. The results showed that Muga silk fibroin protein contained the primary structure in silk-I state. When the protein was irradiated with microwave, nanoparticle synthesis was possible having silk-II state imparting crystallinity. The silk nanoparticles were characterized by a particle size analyzer and found to be of ~240�nm in size. The optical properties of these nanoparticles were studied by UV�vis. spectroscopy and photoluminescence. For studying thermal properties, differential scanning calorimetry was performed that revealed early glass transition, which could be attributed to the presence of water and proteins. It also revealed that nanoparticles are thermally stable. Such studies are important for understanding more about the MSNP and would be beneficial for their further wide applications. � 2020 International Union of Biochemistry and Molecular Biology, Inc.Item Natural Basil as Photosensitizer with ZnO Thin Films for Solar Cell Applications(Taylor and Francis Ltd, 2020) Shiyani, T; Mahapatra, S.K; Banerjee, I.The hybrid solar cell has been fabricated using natural dye extracted from basil or ocimum leaves and ZnO thin film. The extracted natural dye was deposited on ZnO thin films and dried at room temperature. The semiconductor layer of ZnO was fabricated on FTO-coated glass substrate using magnetron sputtering with a thickness of 500 nm. A photocathode was prepared from the Au�Pd mixture using sputtering for a top electrode. ZnO has been confirmed using X-ray diffraction and UV�visible absorption spectroscopy measurements. The photovoltaic characteristics of the prepared DSSCs were studied by measuring the I�V characteristics under the illumination of halogen light. Photocurrent and photovoltage both are increased in the cell. The value of short-circuit current (Isc), open-circuit voltage (Voc), and photon energy conversion efficiency (?) were calculated for a dye-sensitized solar cell (DSSC). DSSCs provide the promising light to electrical energy conversion efficiency due to their low-cost fabrication, environmentally friendly elements, and low maintenance. DSSC offers transparent solar cell modules with the capabilities of the use of hybrid composition such as organic and inorganic materials. The basil/ZnO-based hybrid devices can also be useful for photoelectrochemical cell and water splitting applications. � 2020, � 2020 IETE.Item Surface-engineered gadolinium oxide nanorods and nanocuboids for bioimaging(University of Science and Technology Beijing, 2020) Chawda, N.R; Mahapatra, S.K; Banerjee, I.Abstract: Folic acid and D-gluconic acid-capped gadolinium oxide nanorods and nanocuboids were synthesized via co-precipitation method. Comparative study of relaxivity factor on the role of capping and morphology for enhancing contrast ability for T1 and T2 magnetic resonance imaging (MRI) was investigated. The obtained r2/r1 ratio for folic acid and D-gluconic acid-capped gadolinium oxide nanorods and nanocuboids was 1.5 and 1.3, respectively. The nanocrystals were characterized and presented with properties such as good dispersity and stability required for standard contrast agent used in MRI. The characterization and the analysis of capping agent for nanocrystals suggest the preferable use of carbohydrate moieties with higher number of hydroxyl functional group reacted with urea and hydrogen peroxide for desired morphology and anisotropic growth. Thermogravimetric�differential thermal analysis (TG�DTA) illustrated the amount of capping, transition temperature from Gd(OH)3 to GdOOH and crystallization temperature from GdOOH to Gd2O3. These nanocrystals would be significant for other biomedical applications such as drug delivery when equipped with well-functionalized drug molecules. Graphic abstract: Synergistic effects and mechanism of urea, hydrogen peroxide and capping agent for growth and morphology. [Figure not available: see fulltext.] � 2020, The Nonferrous Metals Society of China and Springer-Verlag GmbH Germany, part of Springer Nature.Item Pressure and electric field tuning of Schottky contacts in PdSe2/ZT-MoSe2 van der Waals heterostructure(Institute of Physics Publishing, 2020) Jakhar, M; Singh, J; Kumar, A; Tankeshwar, K.A two-dimensional van der Waals (vdW) heterostructure (PdSe2/ZT-MoSe2) has been investigated through vdW corrected density functional theory. ZT-MoSe2 acts as a Dirac material with an anisotropic Dirac cone and variable Fermi velocity (0.52-1.91 105 ms-1). The intrinsic Schottky barrier height can be effectively tuned by applying external pressure and an electric field to the heterostructure. The p-type Schottky barrier transforms into a p-type ohmic contact at pressure P ? 16 GPa. A positive electric field induces p-type ohmic contact while a negative electric field results in the transition from p-type Schottky contact to n-type Schottky contact, and finally to n-type ohmic contact at the higher values of the field. Moreover, the external positive (negative) electric field induces n-type (p-type) doping of ZT-MoSe2 in the heterostructure and remarkably controls the charge carrier concentration. Our results demonstrate that controlling the external pressure and electric field in a PdSe2/ZT-MoSe2 heterostructure can result in an unprecedented opportunity for the design of high-performance nanodevices. � 2020 IOP Publishing Ltd.Item Stability, electronic and mechanical properties of chalcogen (Se and Te) monolayers(Royal Society of Chemistry, 2020) Singh, J; Jamdagni, P; Jakhar, M; Kumar, A.The successful experimental fabrication of 2D tellurium (Te) has resulted in growing interest in the monolayers of group VI elements. By employing density functional theory, we have explored the stability and electronic and mechanical properties of 1T-MoS2-like chalcogen (?-Se and ?-Te) monolayers. Phonon spectra are free from imaginary modes suggesting these monolayers to be dynamically stable. The stability of these monolayers is further confirmed by room temperature AIMD simulations. Both ?-Se and ?-Te are indirect gap semiconductors with a band gap (calculated using the hybrid HSE06 functional) of 1.16 eV and 1.11 eV, respectively, and these gaps are further tunable with mechanical strains. Both monolayers possess strong absorption spectra in the visible region. The ideal strengths of these monolayers are comparable with those of many existing 2D materials. Significantly, these monolayers possess ultrahigh carrier mobilities of the order of 103 cm2 V-1 s-1. Combining the semiconducting nature, visible light absorption and superior carrier mobilities, these monolayers can be promising candidates for the superior performance of next-generation nanoscale devices. This journal is � the Owner Societies.Item Selection of best composition of Na+ ion conducting PEO-PEI blend solid polymer electrolyte based on structural, electrical, and dielectric spectroscopic analysis(Springer, 2020) Pritam, Arya A; Sharma, A.L.In this paper, we report the investigation on structural, electrical, dielectric properties, and ion dynamics of novel blend polymer electrolyte matrix (PEO-PEI) complexed with sodium hexafluorophosphate salt. All the solid polymer electrolyte films have been synthesized via solution cast method. The SPE films were characterized by the X-ray diffraction, field emission scanning electron microscope, impedance-dielectric spectroscopy, and thermogravimetric analysis. The morphology of the SPE alters with salt addition and confirms the blend polymer complex formation. The FTIR analysis evidenced the complex formation, and increase in the fraction of free ions is achieved. The ionic conductivity exhibits a maximum at the stoichiometric ratio O/Na = 10 and follows the Arrhenius behavior. The fraction of free ions is maximum for the SPE film with the highest ionic conductivity. The optimum electrolyte possesses a voltage stability window of about 4�V, excellent thermal stability up to 380��C, and high ionic transference number (~ 1). The complex permittivity and conductivity have been simulated in whole frequency window to extract relaxation time and dielectric strength. The dielectric constant and relaxation time exhibited sequentially a maximum and minimum for the SPE film with the highest ionic conductivity. The loss tangent peak shifts toward high frequency with addition of salt, and it infers the faster ion dynamics in the polymer matrix. Then the ion transport parameters number density of charge carriers (n), ion mobility (?), and diffusion coefficient (D) have been obtained by three methods (FTIR, impedance spectroscopy, and loss tangent method) and are in absolute correlation with the impedance results. An ion transport mechanism has been proposed based on experimental findings. � 2019, Springer-Verlag GmbH Germany, part of Springer Nature.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.