Physics

<p>Shiv Nadar University is a comprehensive, multidisciplinary, research-focused, and student-centric University offering a full range of academic programs at the undergraduate, postgraduate and doctoral level. With state-of-the-art infrastructure, the University comprises of academic wings, sophisticated labs, international standard sports facilities, amphitheaters, auditorium, conference rooms and smart classrooms. The University&rsquo;s goal is to become internationally recognized for the quality of its research and creative endeavors and their applicability to improving quality of life, generating new insights and expanding the boundaries of human knowledge creativity. Committed to excellence in teaching, research and service, the University aims to serve the higher education needs of India and the world beyond.</p>

Shiv Nadar University

Ionic liquids (ILs) are the attractions of researchers today due to their vast area of potential applications. For biomedical uses, it becomes essential to understand their interactions with cellular membrane. Here, the membrane is mimicked with lipid bilayer and monolayer composed of liver lipids extract. Three archetypal imidazolium based ILs, 1-decyl-3-methylimidazolium tetrafluoroborate ([DMIM][BF4] or [C10MIM][BF4]), 1-octyl-3-methylimidazolium tetrafluoroborate, ([OMIM][BF4] or [C8MIM][BF4]) and 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4] or [C2MIM][BF4]) having different alkyl chain lengths are used in the present study. The isothermal titration calorimetry (ITC) measurements showed that [DMIM][BF4] interacts strongest with the liver lipid membrane compared to other two ILs which have relatively shorter alkyl chain length. The low values of stoichiometry ratio of ILs indicates that ILs penetrate within the core of the lipid bilayer. The interaction of ILs with the liver lipid membrane is found to be mainly driven by entropy which could be due to the change in the structure of the lipid membrane at local or global scales. Dynamic light scattering (DLS) measurements indicate that there are no changes in the size of vesicles due to addition of [DMIM][BF4] indicating stability of the vesicles. On the other hand, x-ray reflectivity (XRR) measurements showed a concentration dependent change in the monolayer structure. At low concentration of the IL, the monolayer thickness decreases, exhibiting an increase in the electron density of the layer. However, at higher concentrations, the monolayer thickness increases proving a concentration dependent effects of the IL on the arrangement of the molecules. © 2021

World University root node

(SoNS) School of Natural Sciences

Biochimica et Biophysica Acta - Biomembranes

Thermodynamics and structure of model bio-membrane of liver lipids in presence of imidazolium-based ionic liquids

Multiple input multiple output (MIMO) approach in fiber optical communication has emerged as an effective proposition to address the ever increasing demand for information exchange. In the ergodic case, the multiple channels, associated with multiple modes or cores or both in the optical fiber, is modeled by the Jacobi ensemble of random matrices. A key quantity for assessing the performance of MIMO systems is the mutual information (MI). We focus here on the case of an arbitrary transmission covariance matrix and derive exact determinant based results for the moment generating function (MGF) of mutual information (MI), and thereby address the scenario of unequal power per excited mode. The MGF is used to obtain Gaussian- and Weibull-distribution based approximations for the probability density function (PDF), cumulative distribution function (CDF) or, equivalently, the outage probability, and also the survival function (SF) or reliability function. Moreover, a numerical Fourier inversion approach is implemented to obtain the PDF, CDF, and SF directly from the MGF. The MGF is further used to investigate the ergodic capacity, which is the first moment (mean) of the mutual information. The analytical results are found to be in excellent agreement with Monte Carlo simulations. Our study goes beyond the earlier investigations where covariance matrix proportional to identity matrix has been considered which corresponds to equal power allocation per excited mode. © 2021 Elsevier GmbH

Optik

Optical MIMO communication with unequal power allocation to channels

The graphene family, especially graphene oxide (GO), has captured increasing prospects in the biomedical field due to its excellent physicochemical properties. Understanding the health and environmental impact of GO is of great importance for guiding future applications. Although their interactions with living organisms are omnipresent, the exact molecular mechanism is yet to be established. The cellular membrane is the first barrier for a foreign molecule to interact before entering into the cell. In the present study, a model system consisting of a lipid monolayer at the air-water interface represents one of the leaflets of this membrane. Surface pressure-area isotherms and advanced synchrotron X-ray scattering techniques have been employed to comprehend the interaction by varying the electrostatics of the membrane. The results depict a strong GO interaction with positively charged phospholipids, weak interaction with zwitterionic lipids, and interestingly negligible interaction with negatively charged lipids. GO flakes induce significant changes in the out-of-plane organization of a positively charged lipid monolayer with a minor influence on in-plane assembly of lipid chains. This interaction is packing-specific, and the influence of GO is much stronger at lower surface pressure. Even though for zwitterionic phospholipids, the GO flakes may partly insert into the lipid chains, the X-ray scattering results indicate that the flakes preferentially lie horizontally underneath the positively charged lipid monolayer. This in-depth structural description may pave new perspectives for the scientific community for the development of GO-based biosensors and biomedical materials. © 2021 American Chemical Society.

ACS Applied Materials and Interfaces

Self-Assembly of Graphene Oxide Nanoflakes in a Lipid Monolayer at the Air-Water Interface

There are great efforts of synthesizing imidazolium-based ionic liquids (ILs) for developing new antibiotics as these molecules have shown strong antibacterial activities. Compared to a single-hydrocarbon-chained IL, the lipid analogues (LAs) with two chains are more effective. In the present study, the LA molecule MeIm(COOH)Me(Oleylamine)Iodide has been synthesized and its surface activities along with the effectiveness in restructuring of a model cellular membrane have been quantified. The molecule is found to be highly surface active as estimated from the area-pressure isotherm of a monolayer of the molecules formed at the air-water interface. The X-ray reflectivity (XRR) studies of a monolayer dip-coated on a hydrophilic substrate have shown the structural properties of the layer which resembles to those of unsaturated phospholipids. The LA molecules are observed to fluidize a phospholipid bilayer formed by the saturated lipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). At a lower surface pressure, the lipid monolayer of DPPC has exhibited a thickening effect at a low concentration of added LA and a thinning effect at higher concentration. However, at a high surface pressure of the monolayer, the thickness is found to decrease monotonically. The in-plane pressure-dependent interaction of LA molecules with model cellular membrane and the corresponding perturbation in the structure and physical properties of the membrane may be linked to the strong lysing effect of these types of molecules. © 2019 American Chemical Society.

Langmuir

Surface Activities of a Lipid Analogue Room-Temperature Ionic Liquid and Its Effects on Phospholipid Membrane

Hilbert-Schmidt distance is one of the prominent distance measures in quantum information theory which finds applications in diverse problems, such as construction of entanglement witnesses, quantum algorithms in machine learning, and quantum-state tomography. In this work, we calculate exact and compact results for the mean-square Hilbert-Schmidt distance between a random density matrix and a fixed density matrix, and also between two random density matrices. In the course of derivation, we also obtain corresponding exact results for the distance between a Wishart matrix and a fixed Hermitian matrix, and two Wishart matrices. We verify all our analytical results using Monte Carlo simulations. Finally, we apply our results to investigate the Hilbert-Schmidt distance between reduced density matrices generated using coupled kicked tops. © 2020 American Physical Society.

Fulltext

Physical Review A

Wishart and random density matrices: Analytical results for the mean-square Hilbert-Schmidt distance

Li7 nuclear magnetic resonance and terahertz (THz) spectroscopies are used to probe magnetic excitations and their field dependence in the hyperhoneycomb Kitaev magnet $\beta$-Li2IrO3. Spin-lattice relaxation rate (1/T1) measured down to 100 mK indicates the gapless nature of the excitations at low fields (below Hc≃2.8 T), in contrast to the gapped magnon excitations found in the honeycomb Kitaev magnet $\alpha$-RuCl3 at zero applied magnetic field. At higher temperatures in $\beta$-Li2IrO3, 1/T1 passes through a broad maximum without any clear anomaly at the Ne{\'{e}}l temperature TN≃38 K, suggesting the abundance of low-energy excitations that are indeed observed as two peaks in the THz spectra; both correspond to zone-center magnon excitations. At higher fields (above Hc), an excitation gap opens and a redistribution of the THz spectral weight is observed without any indication of an excitation continuum, in contrast to $\alpha$-RuCl3 where an excitation continuum was reported.

Physical Review B

Field evolution of low-energy excitations in the hyperhoneycomb magnet $\beta$-Li2IrO3

Microwave synthesis was optimized for preparing novel monoclinic Tin-doped barium niobate ceramics (Ba1-xSnxNb2O6; x = 0.0, 0.01, 0.05, 0.1, 0.2, 0.3) BSN. The intensity of monoclinic phase formation was observed to decrease on increasing tin as dopant indicating decreased crystallinity. Strained crystalline phase was observed in undoped sample that became severe on doping tin. Monoclinic metal alloy Sn2O3 formation was confirmed on increasing tin doping beyond 5\%. Electronic configuration of tin (II) oxide supports the local site-wise monoclinic disorder in crystal structure due to sterically active lone pair. Such a disorder arranges increased number of degenerate energy states and reduce effective energy gap between conduction band minimum and valence band maximum. All BSN compositions were investigated for monoclinic phase stabilization, ultra-violet absorption, dielectric response, raman modes and type of carrier concentration along with hall resistivity. All measurements possessed inflexion corresponding to 5\% tin doping indicating successful site substitution and estimated Sn2O3 metal formation beyond this. The values of reducing optical energy band gap, transparency to visible spectrum, hall resistivity and dc conductivity indicated utility of these materials as a target for growing transparent conducting oxide (TCO) films for substituting well-known indium tin oxide (ITO). © 2019

Journal of Alloys and Compounds

Microwave derived monoclinic Ba1-xSnxNb2O6 materials as an alternative of ITO

Hume-Rothery rules along with Vegard's law form the basis of systematic doping variation resulting into similar changes in unit cell parameters and volume. Many recent reports have highlighted positive–negative departure from Vegard's law in binary semiconducting systems and a few oxide alloys as well. The current work targets investigations on the missing response of bismuth molybdate on low tungsten doping onto molybdenum sites (Bi2Mo1−xWxO6). Bismuth molybdate and bismuth tungstate have been widely reported for lattice oxygen migration-driven photocatalytic response and pressure-sensitive Raman scattering. Octahedral tilting in low-tungsten-doped Bi2Mo0.94W0.06O6 carries an interesting lattice oxygen folding toward a–c plane. As a result, unit cell polarity increases drastically and becomes a source for intense Raman scattering phase that is normally observable at pressures around 8.3 GPa. An interesting departure from Vegard's law behavior at around 5–6\% tungsten doping confirms nearly identical unit cell structure rather than mix unit cell-based alloy formation. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Physica Status Solidi (B) Basic Research

Deviations from Vegard's Law and Intense Raman Scattering in Low-Doped Bi2Mo1−xWxO6 (x = 0–10%) Ceramics

An environmentally compatible organic solar cell (OSC) has potential to build a global clean energy infrastructure for the world. However, much less attention has been focused on the structures sourced from greener origins to enhance the sustainability aspect of these devices. Herein, we report a rational design, synthesis, and characterization of donor (D)-acceptor (A)-based green organic small molecules, consisting of difluoro-2,1,3-benzothiadiazole (BTF2) as the acceptor, with thiophene (T) and renewable resource materials, cardanol (C) and guaiacol (G) as the donor materials. The reference molecule, abbreviated as T4BTF2, is fully petro-sourced, while C2T2BTF2 and G2T2BTF2 are partly renewable origin molecules. Broad and strong absorption characteristics ranging from 300 to 600 nm along with high thermal stability are supportive for utility of the green origin small molecules in solar cells. Density functional theory (DFT) calculations revealed that G2T2BTF2 is more highly planar than C2T2BTF2 due to the difference in the positioning of the alkyl/alkoxy chain. With bulk heterojunction OSCs with PC71BM as the acceptor, G2T2BTF2 exhibited a high Voc of 0.83 V among all the analyzed small molecules. When compared with the reference molecule T4BTF2, G2T2BTF2 showed a high PCE of 5.56\% with a high Jsc of 10.98 mA/cm2 and FF of 0.61, whereas the PCEs of T4BTF2 and C2T2BTF2 are 3.98\% and 3.23\%, respectively. Our work demonstrates a rational approach to synthesize and develop green organic semiconductors using the biofeedstock derived starting materials for realizing efficient and environment compatible OSCs. Copyright © 2020 American Chemical Society.

Chemistry

ACS Sustainable Chemistry and Engineering

Cardanol- And Guaiacol-Sourced Solution-Processable Green Small Molecule-Based Organic Solar Cells

This review is intended for readers who want to have a quick understanding on the theoretical underpinnings of coherent states and squeezed states which are conventionally generated from the prototype harmonic oscillator but not always restricting to it. Noting that the treatments of building up such states have a long history, we collected the important ingredients and reproduced them from a fresh perspective but refrained from delving into detailed derivation of each topic. By no means we claim a comprehensive presentation of the subject but have only tried to recapture some of the essential results and pointed out their interconnectivity. © 2020 World Scientific Publishing Company.