Department of Physics

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Gas sensing mechanism of H2S, NH3, NO2 and NO toxic gases on transition metal dichalcogenides based Janus MoSSe monolayers is investigated using the density functional theory. Three types of defects (i) molybdenum vacancy, (ii) selenium vacancy, and (iii) sulfur/selenium vacancy are considered and their formation energy is computed to predict the stability. We noticed that selenium vacancy is the most stable among other defects. The maximum adsorption energy for H2S, NH3, NO2 and NO molecules on pristine Janus MoSSe monolayer are ~ −0.156 eV, −0.203 eV, −0.252 eV, and −0.117 eV, respectively. NO2 gas molecule dissociates and forms oxygen doped NO adsorption in selenium and sulfur/selenium defect included MoSSe Janus monolayer. The adsorption energy values are ~ −3.360 eV and −3.404 eV for Se and S/Se defects included MoSSe layer, respectively. Further, the adsorption of NO2 molecule induced about 1μB magnetic moment. In contrast, NO molecule showed chemisorption, whereas H2S and NH3 molecules showed physisorption with their adsorption energies in the range of −0.146 to −0.238 eV and − 0.140 to −0.281 eV, respectively. The adsorption of H2S, NH3, NO2 and NO molecule on the pristine and defected monolayers suggest that selenium and sulfur/selenium vacancy defects are more prominent for NO2 and NO gas molecule adsorption. © 2019

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Applied Surface Science

Defect engineered MoSSe Janus monolayer as a promising two dimensional material for NO2 and NO gas sensing

The measurements of the ratios RK(∗) along with RD(∗) hint towards lepton flavor non universality which is in disagreement with the standard model. In this work, we reanalyze the four new physics models, which are widely studied in the literature as a candidates for the simultaneous explanations of these measurements. These are, standard model like vector boson (VB), SU(2) L-singlet vector leptoquark (U1), SU(2) L-triplet scalar leptoquark (S3) and SU(2) L triplet vector leptoquark (U3) models. We assume a coupling only to the third generation in the weak basis, so that the b→ sμ+μ- transition is generated only via mixing effects. Preforming a global fit to all relevant data, we show that the vector boson model violates the current upper bound on Br(τ→ 3 μ) and hence is inconsistent with the present data. Further, we show that within this framework, the U1 leptoquark model cannot simultaneously accommodate RK(∗) and RD(∗) measurements. We emphasize that this conclusion is independent of the additional constraints coming from renormaliztion group running effects and high-pT searches. In addition, we show that the S3 and U3 models are highly disfavored by the constraints coming from b→ sνν¯ data. Finally, we find a that hypothesis of two LQ particles is also challenged by b→ sν¯ ν data. © 2019, The Author(s).

European Physical Journal C

Lepton flavor non-universality in the B-sector: a global analyses of various new physics models

Quantum phase properties of photon added and subtracted displaced Fock states (and their limiting cases) are investigated from a number of perspectives, and it is shown that the quantum phase properties are dependent on the quantum state engineering operations performed. Specifically, the analytic expressions for quantum phase distributions and angular Q distribution as well as measures of quantum phase fluctuation and phase dispersion are obtained. The uniform phase distribution of the initial Fock states is observed to be transformed by the unitary operation (i.e., displacement operator) into non-Gaussian shape, except for the initial vacuum state. It is observed that the phase distribution is symmetric with respect to the phase of the displacement parameter and becomes progressively narrower as its amplitude increases. The non-unitary (photon addition/subtraction) operations make it even narrower in contrast to the Fock parameter, which leads to broadness. The photon subtraction is observed to be a more powerful quantum state engineering tool in comparison to the photon addition. Further, one of the quantum phase fluctuation parameters is found to reveal the existence of antibunching in both the engineered quantum states under consideration. Finally, the relevance of the engineered quantum states in the quantum phase estimation is also discussed. © 2019 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim

Annalen der Physik

Quantum Phase Properties of Photon Added and Subtracted Displaced Fock States

Controlling the arrangement and interface of nanoparticles is essential to achieve good transfer of charge, heat, or mechanical load. This is particularly challenging in systems requiring hybrid nanoparticle mixtures such as combinations of organic and inorganic materials. This work presents a process to coat vertically aligned carbon nanotube (CNT) forests with metal oxide nanoparticles using microwave-assisted hydrothermal synthesis. Hydrothermal processes normally damage delicate CNT forests, which is addressed here by a combination of lithographic patterning, transfer printing, and reduction of the synthesis time. This process is applied for the fabrication of structured Li-ion battery (LIB) electrodes where the aligned CNTs provide a straight electron transport path through the electrode and the hydrothermal coating process is used to coat the CNTs with conversion anode materials for LIBs. These nanoparticles are anchored on the surface of the CNTs and batteries fabricated following this process show a fourfold longer cyclability. Finally, this process is used to create thick electrodes (350 µm) with a gravimetric capacity of over 900 mAh g−1. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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Hydrothermal Coating of Patterned Carbon Nanotube Forest for Structured Lithium-Ion Battery Electrodes

The recovery and recrystallisation behaviours of cold rolled IF steel have been investigated by destructive (optical microscopy and hardness) and non-destructive electromagnetic sensor, (which allows direct measurement of strip samples with no surface preparation) techniques. The onset and completion of recrystallisation are clearly monitored through destructive techniques of optical microscopy and hardness measurements. The nucleation of new recrystallised grains is observed in the sample annealed at 600 °C/15 min, while completion of recrystallisation takes place at 700 °C/15 min. The destructive techniques are not very accurate in monitoring recovery, for example, changes in hardness of <20% are seen. In contrast, the magnetic properties of annealed steel show the onsets of both recovery and recrystallisation, with recovery accounting for ≈60% change in the coercivity value. Therefore, the measurement of magnetic softening through an electromagnetic sensor acts a crucial role for understanding recovery and recrystallisation behaviours of steels during industrial processing. The present investigation is aimed not only for controlling product quality but also saving characterisation time through off line monitoring during steel processing at industry. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

Philosophical Magazine

Assessment of recovery and recrystallisation behaviours of cold rolled IF steel through non-destructive electromagnetic characterisation

We report a one-dimensional planar optical waveguide with a transverse distribution of the inhomogeneous loss profile, which exhibits an exceptional point (EP). The waveguide hosts two leaky resonant modes, where the interaction between them in the vicinity of the EP is controlled by proper adjustment of the inhomogeneity in the attenuation profile only. We study the adiabatic dynamics of propagation constants of the coupled modes by quasistatic encirclement of control parameters around the EP. Realizing such an encirclement with the inhomogeneous loss distribution along the direction of light propagation, we report the breakdown of adiabatic evolution of two coupled modes through the waveguide in the presence of an EP. During conversion the output mode is irrespective of the choice of the input excited mode but depends on the direction of light transportation. This topologically controlled, robust scheme of asymmetric mode conversion in the platform of the proposed all-lossy waveguide structure may provide a means for implementation of state-transfer applications in chirality-driven waveguide-based devices. © 2018 American Physical Society.

Physical Review Applied

Nonadiabatic Modal Dynamics Around Exceptional Points in an All-Lossy Dual-Mode Optical Waveguide: Toward Chirality-Driven Asymmetric Mode Conversion

In our research we studied the influence of bending on the total magnetic losses, the coercivity of minor hysteresis loops and the virgin magnetization curves of amorphous ribbons and microwires prepared from Finemet-type alloy wound on a mandrel of different diameters. The impact of various factors contributing on static and dynamic magnetic properties through bending stress are discussed. The factors pertain to contribution of the magnetoelastic anisotropy, the onset of the strain-induced magnetization, the changes of domain structure and the mobility of domain walls. The major contribution of hysteresis losses as-compared to the eddy-current losses have been observed on changing the mandrel diameter in wound ribbons and wires. The total specific losses of the Finemet-type ribbons are lower than that of microwires at the frequencies ranging from 50 to 400 Hz. Observed difference in the magnetic properties is attributed to different magnetization processes of amorphous microwires and ribbons. A different geometry and magnetoelastic anisotropy of studied materials are most likely to influence the formation of different domain structures. © 2018 Elsevier B.V.

Journal of Alloys and Compounds

The impact of bending stress on magnetic properties of Finemet type microwires and ribbons

We have shown an exponential increase in the ratio of conductance in the on and off states of switching devices by controlling the surface morphology of the thin films for the device by depositing at different rotational speeds. The pinholes which are preferred topography on the surface at higher rotational speed give rise to higher on–off ratio of current from the devices fabricated at the speed. The lower rotational speed contributes to higher thickness of the film and hence no switching. For thicker films, the domain is formed due to phase segregation between the two components in the film, which also indicates that the film is far from thermal equilibrium. At higher speed, there is very little scope of segregation when the film is drying up. Hence, there are only few pinholes on the surface of the film which are shallow. So, the filamentary mechanism of switching in memory devices can be firmly established by varying the speed of thin film deposition which leads to phase segregation of the materials. Thus, the formation of filament can be regulated by controlling the thickness and the surface morphology. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.

Applied Physics A: Materials Science and Processing

Exponential increase in the on–off ratio of conductance in organic memory devices by controlling the surface morphology of the devices

In the present work, the unique negative differential resistance (NDR) and memory effect of an organic-metallic hybrid polymer based on the self-assembly of Fe(ii)-ions preceded by the synthesis of a newly designed multidentate Schiff's base ligand has been reported. The polymerization process was closely monitored in an absorbance study using a UV-vis spectrophotomer. The presence of sharp isosbestic points and saturation of absorbance at 1 : 1 ligand to metal concentration confirmed the stepwise growth of the polymer. A model monomer Fe-complex was also developed based on the model ligand, with the aim of understanding the properties of the polymer in a better way by comparative study but surprisingly both ligand and model ligand coordinate in a different fashion with the same Fe(ii)-metal ions under similar reaction conditions, though both of them have identical binding sites. It has been found that the monomer model complex is paramagnetic while the metallopolymer is diamagnetic in nature. FESEM images of thin films of the polymer revealed the presence of homogeneously distributed interparticulate mesopores which was further confirmed by surface area analysis. A long single strand of the polymer was found on the HOPG surface by AFM study. The cyclic voltammetry study indicated that both conjugated ligand and metallopolymers are electrochemically active. The bistable memory behaviour of the device fabricated on ITO has shown a negative differential resistance effect along with good RAM and ROM behaviour, showing the potential of this novel polymer as memristor. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

New Journal of Chemistry

Design, synthesis, and characterization of an Fe(ii)-polymer of a redox non-innocent, heteroatomic, polydentate Schiff's base ligand: negative differential resistance and memory behaviour

An approach for nanoscale covalent functionalization of graphite surfaces employing self-assembled molecular monolayers of n-alkanes as templating masks is presented. Linearly aligned aryl groups with a lateral periodicity of 5 or 7 nm are demonstrated utilizing molecular templates of different lengths. The key feature of this approach is the use of a phase separated solution double layer consisting of a thin organic layer containing template molecules topped by an aqueous layer containing aryldiazonium molecules capable of electrochemical reduction to generate aryl radicals which bring about surface grafting. Upon sweeping of the potential, lateral displacement dynamics at the n-alkane terminal edges acts in conjunction with electrochemical diffusion to result in templated covalent bond formation in a linear fashion. This protocol was demonstrated to be applicable to linear grafting of graphene. The present processing described herein is useful for the realization of rationally designed nanoscale materials. © 2018 American Chemical Society.