Department of Physics

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IIT Jodhpur

An electromagnetic sensing device, MagStar, has been developed by authors, measure both magnetic hysteresis loop and magnetic Barkhausen emission. The device explains its credibility for characterizing different types steels, SA213T22 and IF steel with varying microstructural phases treated at different heat treatment conditions. MagStar is also very versatile to be applicable for both industries and educational research due to its portability and low cost. © Springer Nature Singapore Pte Ltd 2018.

World University root node

Lecture Notes in Networks and Systems

Utilization of electromagnetic sensor for structural characterization of steels during processing and in-service components

The present investigation is focused on the structural transformation, microstructure and magnetocaloric effect (MCE) of Ni53Mn24Ga23 alloy in the form of melt spun ribbons prepared by rapid solidification technique. The properties have been compared with bulk alloy prepared by conventional melting-casting route. The rapidly solidified alloys revealed higher magnetic entropy change (−8.5 J.Kg−1K−1) compared to that of bulk (−7.7 J.Kg−1K−1). The high magnetic entropy change and low thermal hysteresis are correlated to different magnetostructural behaviour. © 2018

Materials Today Communications

Influence of rapid solidification on mangnetostructural and magnetocaloric effect in Ni53Mn24Ga23 alloy

We explore exceptional points (EP) in a dual-mode symmetric planar optical waveguide with transverse variation of inhomogeneous loss profile; where modal evolution alongside an EP is reported in the context of selective optical mode conversion. © 2018 The Author(s).

Optics InfoBase Conference Papers

All-lossy quasi-guided dual-mode optical waveguide exhibiting exceptional singularities

Investigations on inorganic luminescent nanomaterials have always gained enormous attention of the science community for their possible applications in the fields of bioimaging and biomedicine. In this succession, various 0D structures including CdSe, CdTe, ZnS, graphene quantum dots (GQDs), carbon nanodots (CNDs) etc. have been explored for their possible applications in the field of biology. Recently, molybdenum disulfide quantum dots (MoS2-QDs) have been explored as an alternative of graphene quantum dots (GQDs) for their possible applications in relevant fields. Herein we report a facile, eco-friendly and single step hydrothermal synthesis of in-situ functionalized molybdenum disulfide quantum dots (f-MoS2-QDs). During the synthesis, variation in the pH of the starting solution provided the controlling over particle size. These as synthesized f-MoS2-QDs have shown excitation dependent broad emission spectra, which could be fitted for a parabolic function. The broadening in the emission spectra might be attributed to the polydispersity of f-MoS2-QDs in colloidal suspension, which was further confirmed with time resolved photoluminescence (TRPL) measurement. Due to surface capping provided by various functional groups present in the colloidal suspension, f-MoS2-QDs have shown excellent stability in aqueous medium and only a 3% of decrement in PL intensity was recorded even after six months. These synthesized f-MoS2-QDs possessed a quantum yield (QY) of 2.3% in aqueous media. Due to their high photostability and biocompatibility, these f-MoS2-QDs have been revealed as a potential entrant for in vivo bioimaging in Drosophila. © 2018 Elsevier B.V.

Journal of Luminescence

Highly stable and bio-compatible luminescent molybdenum disulfide quantum dots for imaging of alimentary canal in Drosophila

Study of D{*} Polarization to Discriminate New Physics in (B)over-bar -&gt; D{*}tau(nu)over-bar

We carried out a detailed balance calculation of quantum dot sensitized solar cell based on widely used TiO2 as electron transport material and polysulfide electrolyte as hole transport material, considering the finite electrochemical potential level for these layers. The findings suggest that detailed balance efficiency decreases much faster for higher band gap quantum dots absorber as compared to that of ideal electron and hole transport layers. The detailed balance efficiency values are close to 20% without carrier multiplication for Eg near exciplex quantum dots, closer to experimental observation with finite Ediff limitation and without considering carrier multiplication, much smaller than the ideal case, which is close to 30% for ideal open circuit voltage. Thus, the present study shows the impact of limited/finite electron and hole transport material energy levels in designing QDSSCs, towards more realistic photovoltaic efficiency values. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.

Applied Physics A: Materials Science and Processing

Limiting efficiency factors and their consequences on quantum dot sensitized solar cells: a detailed balance study

Flexible electronics are being pursued as replacements for rigid consumer electronic products such as smartphones and tablets, as well as for wearable electronics, implantable medical devices, and RFIDs. Such devices require flexible batteries with electrodes that maintain their electro-chemical performance during multiple bending cycles. These electrodes typically consist of an active battery material blend with a conductive additive and a binder. Whilst the choice of active battery material is typically dictated by the desired battery power and energy requirements, there is more freedom in changing the conductive additives to cope with strain induced during the bending of flexible batteries. Here we compare the mechanical and electrical properties of free standing cathodes using lithium cobalt oxide (LiCoO2) as the active material and 10–20 wt% of amorphous carbon powder (CP) or carbon nanotubes (CNTs) as conductive additives. We found that the CNT based electrodes showed less crack formation during bending and have a Young's modulus up to 30 times higher than CP electrodes (10 wt% loading). Further, the electrical resistance of pristine CNT electrodes is 10 times lower than CP electrodes (20 wt% loading). This difference further increases to a 28 times lower resistance for CNT films after 2000 bending cycles. These superior properties of CNT films are reflected in the electrochemical tests, which show that after bending, only the electrodes with 20 wt% of CNTs remain operational. This study therefore highlights the importance of the conductive additives for developing reliable flexible batteries. © 2018 Elsevier B.V.

Fulltext

Materials Science and Engineering A

Carbon nanotube conductive additives for improved electrical and mechanical properties of flexible battery electrodes

The conformational stability of synthesized diphenyloxalohydrazide and dibenzoyloxalohydrazide fluoro derivatives has been investigated by extensive NMR studies that are ascertained by various levels of theoretical calculations. Two-dimensional 1H-19F HOESY NMR experiments revealed the close spatial proximity between two NMR-active nuclei, confirming the hydrogen bond (HB)-mediated interaction between them, further aiding in establishing the probable stable conformations of these molecules. The relaxed potential energy scan disclosed the energy-minimized most stable structure among the several possible multiple conformations, which is in concurrence with NMR interpretations. Atomistic molecular dynamics simulations have been employed to unequivocally establish the conformational stability and the nature of HB formation at varied temperatures. With the possibility of occurrence of a number of probable conformations, the percentage of occurrences of different types of HBs in them was determined by MD simulations. Their population analysis was carried out using a Boltzmann distribution, in addition to deriving their Gibbs free energies. The molecular interactions governing the stable conformations have not only been ascertained by experimental NMR interpretations but also corroborated by other theoretical computations, viz., quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI). © 2018 American Chemical Society.

Journal of Physical Chemistry A

Intramolecular Hydrogen Bonding Appetency for Conformational Penchants in Oxalohydrazide Fluoro Derivatives: NMR, MD, QTAIM, and NCI Studies

Hexagonal borocarbonitrides (BCN) are a class of 2D materials, which display excellent catalytic activity for water splitting. Here, we report the analysis of thermal stability, phonons and thermal conductivity of BCN monolayers over a wide range of temperatures using classical molecular dynamics simulations. Our results show that in contrast to the case of graphene and boron nitride monolayers, the out-of-plane phonons in BCN monolayers induce an asymmetry in the phonon density of states at all temperatures. Despite possessing lower thermal conducting properties compared to graphene and BN monolayers, the BCN nanosheets do not lose thermal conductivity as much as graphene and BN in the studied temperature range of 200-1000 K, and thus, BCN nanosheets are suitable for thermal interface device applications over a wide range of temperatures. Besides their promising role in water splitting, the above-mentioned results highlight the possibility of expanding the use of BCN 2D materials in thermal management applications and thermoelectrics. © 2018 The Royal Society of Chemistry.

Nanoscale

Phonons and thermal conducting properties of borocarbonitride (BCN) nanosheets

Solar cells and optoelectronics based on lead halide perovskites are generating considerable interest but face challenges with the use of toxic lead. In this study, we fabricate and characterize lead-free perovskites based on germanium and tin solid solutions, CH3NH3Sn(1-x)GexI3 (0 ≤ x ≤ 1). We show that these perovskite compounds possess band gaps from 1.3 to 2.0 eV, which are suitable for a range of optoelectronic applications, from single junction devices and top cells for tandems to light-emitting layers. Their thermodynamic stability and electronic properties are calculated for all compositions and agree well with our experimental measurements. Our findings demonstrate an attractive family of lead-free perovskite semiconductors with a favorable band-gap range for efficient single-junction solar cells. © 2018 American Chemical Society.