Physics

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Shiv Nadar University

The potential biomedical applications of ionic liquids (ILs) need an understanding of the effects of the molecules in living organisms. Researchers are still exploring the molecular level description of this interaction. Any foreign molecule affecting a living organism has to interact first with the outer layer of a cell, which is mainly composed of a phospholipid bilayer. Here, to understand the membrane-IL interaction, a zwitterionic lipid has been chosen to prepare multilamellar vesicles (MLVs) which are the model cellular membranes. Small angle x-ray diffraction study has revealed the change in inter-bilayer spacing in the presence of imidazolium based ILs in the ripple phase of the bilayer. The investigation was extended further to understand the role of a negatively charged lipid in the MLVs. This study indicates that the cations of an IL screen electrostatic repulsion between the negatively charged lipids and induce the formation of a vesicle. © 2020 American Institute of Physics Inc.. All rights reserved.

(SoNS) School of Natural Sciences

AIP Conference Proceedings

Effect of ionic liquids on the structures of ripple phases of model cellular membranes

We investigate the spectral fluctuations and electronic transport properties of chaotic mesoscopic cavities using Kwant, an open source Python programming language based package. Discretized chaotic billiard systems are used to model these mesoscopic cavities. For the spectral fluctuations, we study the ratio of consecutive eigenvalue spacings, and for the transport properties, we focus on Landauer conductance and shot noise power. We generate an ensemble of scattering matrices in Kwant, with desired number of open channels in the leads attached to the cavity. The results obtained from Kwant simulations, performed without or with magnetic field, are compared with the corresponding random matrix theory predictions for orthogonally and unitarily invariant ensembles. These two cases apply to the scenarios of preserved and broken time-reversal symmetry, respectively. In addition, we explore the orthogonal to unitary crossover statistics by varying the magnetic field and examine its relationship with the random matrix transition parameter. © 2020 Author(s).

Chaos

Electronic transport in chaotic mesoscopic cavities: A Kwant and random matrix theory based exploration

Superhydrophobic surfaces with high adhesion have attracted huge attention in recent research works due to their versatile applications including transportation of microdroplet without any loss. Modification of metallic surfaces to achieve such properties is important to extend their applications. Especially, the superhydrophobic surfaces with very low bacterial adhesion have attracted intense attention in medical, food, and pharmaceutical industries. Here, we have fabricated different micropatterns on aluminium surfaces using a simple and cost-effective micro-imprinting technique. The surface chemistry was modified through a coating of low surface energy material 1H, 1H, 2H, 2H-perfluorooctyl-trichlorosilane (FOTS) using vapor deposition technique. Surface morphology of the samples was investigated using scanning electron microscopy (SEM) and contact profilometer. Results show a significant influence of the surface morphology on the wetting, adhesion and anti-bacterial properties. Surfaces composed of discrete micropillars showed higher de-wetting compared to surface containing continuous zig-zag micro lines even despite lower roughness factor. However, the opposite trend was observed in case of adhesion. These results are explained based on wetting state and difference in liquid-air interface pinning. Further, the developed samples showed higher water-retaining ability compared to rose-petal along with superhydrophobicity. The surface with micropillar structures with higher roughness factor exhibited improved non-fouling behavior which has been quantified by spot assay and atomic force microscopy (AFM). This study opens up the possibility of fabricating multifunctional metal surfaces on a large scale by a cost-effective, environment friendly and easily scalable processing route. © 2020 IOP Publishing Ltd.

Mechanical Engineering

(SoE) School of Engineering

Surface Topography: Metrology and Properties

Effect of topography and chemical treatment on the hydrophobicity and antibacterial activities of micropatterned aluminium surfaces

Direct synthesis of a nano-structured carbon hybrid consisting of vertically aligned carbon nanograsses on top of boron-doped nanocrystalline diamond is demonstrated and the carbon hybrid is further applied as an electrode material for the fabrication of supercapacitors. The hybrid film combines the dual advantages of sp2 (carbon nanograss) and sp3 (nanocrystalline diamond) bonded carbon, possessing not only the excellent electrical characteristics of sp2 carbon but also the exceptional electrochemical stability of sp3 carbon. As a result, the specific capacitance of the as-prepared hybrid material reaches up to 0.4 F cm-2, one of the highest reported in diamond-based supercapacitors. The entire electrochemical results exhibit enhanced electron transfer efficiency with remarkable stability of 95\% of capacitance retention even after 10 000 cycles.

World University root node

Fulltext

Nanoscale

Single-step grown boron doped nanocrystalline diamond-carbon nanograss hybrid as an efficient supercapacitor electrode

Pulp and paper industry generates large wastewater volumes containing recalcitrant and toxic compounds in various forms. These compounds are highly toxic and standard primary/secondary treatments are unable to filter heavy metal contaminants besides organic species. An emerging demand of advance level treatment is the motivation of current work that explores possibility of using thick sand of deep aquifers as an adsorbent to remove inorganic and organic contaminants simultaneously from wastewater besides desalination. Popular ultrasonic cavitation is used to accelerate degradation of toxic organic effluent into less toxic open ring structures besides curing heavy metals to form new bonds during adsorption. Because of extreme local environment due to cavitation, heavy metals coagulate in silicon-aluminum atomic meshes and carbon nano tubes for less toxic new crystalline structure. Significant changes in physico-chemical investigations like pH, chemical oxygen demand and colour towards drinkable water standards indicate effective adsorption resulting into wastewater purification. © 2019

Chemical Engineering

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Ultrasonic cavitation tailored wastewater purification and desalination using thick sand of highly permeable deep aquifer

The aluminum industrial waste red mud was successfully utilized as a novel adsorbent for the removal of arsenic (As) ions from water. The arsenate (As (V)) adsorption efficacy of red mud nanoparticles was also investigated. Red mud nanoparticles were prepared by ball milling raw red mud for 10 h, yielding particles’ size of 20 nm on average. The As (V) adsorption on these nanoparticles strongly depended on the size of the nanoparticles. As (V) removal increased from 58 to 83\% by reducing the size of red mud particles from 200 to 20 nm. Detail kinetics and transport study confirmed the pseudo-second-order kinetic process which was governed by external mass transport. The Freundlich (and Langmuir) isotherms confirm that the arsenate adsorption capacity changes from 2.28 mg/g (1.84 mg/g) to 2.54 mg/g (1.96 mg/g) for reduction of particles from size 200 nm to 20 nm. Water filter columns made with red mud nanoparticles prepared by ball milling for 10 h showed better filtration performance than the filter packed with raw red mud. Both the hydraulic conductivity and the As (V) removal (8 mm/h and 61\% respectively) of influent 1 mg/L As (V) by red mud nanoparticles were greater than the raw red mud (3.2 mm/h and 54\%). The modified red mud column filters also exhibited a higher efficiency than the raw red mud filters to remove Escherichia coli and Staphylococcus aureus from the water. Overall, this research shows that nanomaterials derived from aluminum processing waste can be a promising material for water filtration. © 2020, Springer Nature Switzerland AG.

Life Sciences

SN Applied Sciences

Potential use of smartly engineered red mud nanoparticles for removal of arsenate and pathogens from drinking water

This work demonstrates the applicability of red-mud-reduced graphene oxide (RM-rGO) nanocomposites (NCs) for the reliable and selective electrochemical (EC) detection of arsenic. The new NC material shows excellent anti-interference activity toward arsenic (As3+) ions with the cooccurrence of other common cations (Cd2+, Cr2+, Zn2+, Pb2+, and Hg2+). Especially, the NC is exceptionally selective for As3+ ions in the presence of Cu2+ ions, which is stated to be the main interfering agent in the EC detection of As3+. Under optimal experimental conditions, the new NC displays a high sensitivity (2.49 μA ppb-1) as well as a very low detection limit (0.07 ppb) toward As3+ detection. This excellent EC performance of the composite is accounted for by the high adsorption proficiency of hematite (Fe2O3)-phase-rich red mud nanoparticles and enhanced electron-transfer kinetics due to the presence of rGO. © 2020 American Chemical Society.

ACS Applied Nano Materials

Red Mud-Reduced Graphene Oxide Nanocomposites for the Electrochemical Sensing of Arsenic

We compute an s-channel 2 → 2 scalar scattering φφ → Φ → φφ in the Gaussian wave-packet formalism at the tree level. We find that wave-packet effects, including shifts of the pole and the width of the propagator of Φ, persist even when we do not take into account the time boundary effect for 2 → 2 proposed earlier. An interpretation of the result is that a heavy scalar 1 → 2 decay Φ → φφ, taking into account the production of Φ, does not exhibit the in-state time boundary effect unless we further take into account in-boundary effects for the 2 → 2 scattering. We also show various plane-wave limits. © The Author(s) 2020. Published by Oxford University Press on behalf of the Physical Society of Japan.

Progress of Theoretical and Experimental Physics

Scalar scattering amplitude in the Gaussian wave-packet formalism

Halide perovskite (HP) materials are actively researched for resistive switching (RS) memory devices due to their current-voltage hysteresis along with low-temperature processability, superior charge mobility, and simple fabrication. In this study, all-inorganic RbPbI3 perovskite has been doped with Cl in the halide site and incorporated as a switching media in the Ag/RbPbI3-xClx/ITO structure, since pure RbPbI3 is nonswitchable. Five compositions of the RbPbI3-xClx (x = 0, 0.3, 0.6, 0.9, and 1.2) films are fabricated, and the conductivity was found to be increasing upon increase in Cl concentration, as revealed by dielectric and I-V measurements. The device with a 20\% chloride-substituted film exhibits a higher on/off ratio, extended endurance, long retention, and high-density storage ability. Finally, a plausible explanation of the switching mechanism from iodine vacancy-mediated growth of conducting filaments (CFs) is provided using conductive atomic force microscopy (c-AFM). The c-AFM measurements reveal that pure RbPbI3 is insulating in nature, whereas Cl-doped films demonstrate resistive switching behavior. Copyright © 2020 American Chemical Society.

ACS Applied Materials and Interfaces

Induced Vacancy-Assisted Filamentary Resistive Switching Device Based on RbPbI3- xClxPerovskite for RRAM Application

Ionic liquids (ILs) have recently become very popular molecules because of their fascinating properties, which can be exploited in industrial and biomedical applications. There are several recent reports which suggest strong interaction of these molecules with bio-membrane. This interaction, which leads to complete disruption of the cell membrane leading to cell death, can be very useful in designing anti-microbial agents. Here, we have studied the effect of an ionic liquid tetrabutylammonium methanesulfonate (TAM) on a model cellular membrane composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipids. While differential scanning calorimetry study indicates a fluidity effect, the x-ray reflectivity measurements exhibit the formation of a new phase in the membrane. © 2020 American Institute of Physics Inc.. All rights reserved.