Physics

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The β phase of tungsten has attracted great interest for spintronic applications due to its higher spin Hall angle compared to other elemental solids and large spin-orbit torque, but the stability of this phase is yet to be well understood as many different results are there in the literature mainly based on the film thickness, temperature, and overall growth conditions. The growth of films by sputter deposition has emerged as a promising technique to achieve β-W owing to its compatibility with current spintronic technology. We demonstrate here the efficient ability of dc magnetron sputtering to grow stable β-W films up to a thickness of ∼180 nm at room temperature by varying a set of deposition parameters like pressure, power, and deposition time and discuss the various underlying mechanisms. From these results, the optimized set of deposition parameters for growing β-W films is given. A clear understanding of the influence of oxygen in the atomic structure of β-W is obtained by varying the thickness of the films. This is confirmed from the ab initio molecular dynamics (MD) simulations, where the atomic structure is influenced by the oxygen doping concentration. A stable polycrystalline β phase can be achieved by controlled doping of oxygen. Additionally, a phase transformation from α to β with the doping of oxygen is also evident by MD simulations. © 2022 Author(s).

World University root node

(SoNS) School of Natural Sciences

Journal of Applied Physics

Growth-dependent structural ordering and stability in β-tungsten films for spintronic applications

Hirschsprung's disease (HD) is widely characterized by the absence of ganglion cells in the colon of infants and children resulting in a spectrum of diseases starting from constipation to intestinal obstruction. The disease can have a serious manifestation of Hirschsprung-associated enterocolitis which can lead to significant morbidity and even mortality. Presently the treatment includes surgical excision of the pathological segment of the colon. Identification of the segment requires histopathology and immunohistochemistry which is time-consuming and requires significant expertise of a pathologist. There is a gap in the management of the disease in the form of absence of suitable, sensitive, and efficient technologies to detect the pathological segment of the intestine, which could significantly reduce surgery duration in the operation theatre, as well as associated risks to patients. It, therefore, becomes a matter of extreme importance to develop a point-of-care platform for early and efficient identification of the occurrence of HD in neonates and older children during surgery. The present work reports on the development of an electrochemical enzymatic biosensor using anodized laser-induced graphene (aLIG) conjugated with acetylcholinesterase enzyme (AchE), for detection of HD as a function of acetylcholine – the key biomarker. The developed sensor was initially characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), while the sensor's analytical performance was assessed using CV. The sensor exhibited a limit of detection of 0.26 μM with a shelf life of 1 month, while remaining unperturbed in the presence of common interferants. The performance of the developed sensor was also examined in spiked serum samples and was observed to yield a high degree of linearity. © 2022 Elsevier B.V.

Diamond and Related Materials

Design and development of an electroanalytical enzymatic sensor using anodized laser induced graphene for the management of Hirschsprung Disease

Recently, the ternary active-layer-based organic solar cells have shown remarkable increment in the power conversion efficiency (PCE) by utilizing the synergistic effect of complementary absorption, band alignment, and nano-scale morphology enhancement. Non-fullerene acceptors (NFAs) are an important class of functional materials for the improved performance of ternary organic solar cells due to their role in improvising the light absorption and the morphology of the active layer. Here, the non-fullerene (NF) molecule, NAI-FN-NAI (BO), is used as the third component in the bulk heterojunction of PTB7-Th: PC71BM to fabricate the ternary organic solar cell. The magical number of the composition, i.e., 20% by weight of the NF in the ternary active layer resulted in the PCE of 8.1% devices, which is almost 35% higher efficiency than PTB7-Th: PC71BM binary devices having the PCE of 6%. The enhanced efficiency is observed even though the lessened effect of complementary absorption and band alignment factors of the NF. Such an improved efficiency is attributed in ternary devices to the nano-scale morphology enhancement. It could pave the way to realize the best possible bulk heterojunction blend to attain high PCE close to inorganic counterparts. © 2022 Wiley-VCH GmbH.

Physica Status Solidi (A) Applications and Materials Science

Non-Fullerene Acceptor-Based Nanomorphology Enhancement for Efficient Ternary Organic Solar Cells

Inverters are an indispensable component of any digital circuit. We report, for the first time, an organic unipolar inverter with the driver and the load transistors gated by ionic liquids (ILs). We have devised a new design strategy that exploits the considerably low saturation regime channel resistance of the IL-gated organic field-effect transistors. This simple and scalable fabrication methodology eliminates the need for different channel dimensions of the driver and the load transistors, thereby enabling the size reduction of circuits. We have achieved a gain exceeding 10 V V−1, attributable to high transistor transconductance (&gt;5 mS), at operating voltage &lt;1 V for the unipolar organic inverters, fabricated and characterized in the ambient environment. The switching threshold of the inverter has been tuned by up to 40% while maintaining a high gain by exploiting the strong influence of the gate electrode and the IL anion on the transistor behavior. The inverters exhibit an excellent noise margin of up to 60%, the highest noise margin reported for a low-voltage operating unipolar organic inverter. Solution-processable organic semiconductor-based high-performance, ambient-stable, and flexible-compatible inverters and subsequent integration of such devices into complex circuits will facilitate all-organic low-cost, and conformable electronic devices. © 2023 The Royal Society of Chemistry.

Journal of Materials Chemistry C

Ionic liquid gated unipolar inverters with tunable switching voltage and excellent noise margin

Examples of the β-Jacobi ensemble in random matrix theory specify the joint distribution of the transmission eigenvalues in scattering problems. For this application, the trace is of relevance as determining the conductance. Earlier, in the case β=1, the trace statistic was isolated in studies of covariance matrices in multivariate statistics. There, Davis showed that for β=1 the trace statistic could be characterised by (N+1)×(N+1) matrix differential equations, now understood for general β>0 as part of the theory of Selberg correlation integrals. However the characterisation provided was incomplete, as the connection problem of determining the linear combination of Frobenius type solutions that correspond to the statistic was not solved. We solve this connection problem for Jacobi parameters b and Dyson index β non-negative integers. The distribution then has the functional form of a series of piecewise power functions times a polynomial, and our characterisation gives a recurrence for the computation of the polynomials. For all β>0 we express the Fourier–Laplace transform of the trace statistic in terms of a generalised hypergeometric function based on Jack polynomials. © 2022 Elsevier B.V.

Physica D: Nonlinear Phenomena

Differential recurrences for the distribution of the trace of the β-Jacobi ensemble

Inspired by many biological systems such as lotus leaves, insect wings and rose petals, great attention has been devoted to the study and fabrication of artificial superhydrophobic surfaces with multiple functionalities. In the present study, a simple and ecological synthesis route has been employed for large scale fabrication of self-assembled, sustainable nanostructures on unprocessed and micro imprinted aluminum surfaces named ‘Nano’ and ‘Hierarchy’. The processed samples show extreme wettability ranging from superhydrophilicity to superhydrophobicity depending on post-processing conditions. The densely packed ellipsoidal nanostructures exhibited superhydrophobicity with excellent water, bacterial and dust repellency when modified by low surface energy material 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FOTES), characterized by a static contact angle of 163 ± 1° and contact angle hysteresis (CAH) ~3°. These coated surfaces show significant corrosion resistance with current density of 6 nA/cm2 which is 40 times lower than unprocessed counterpart and retain chemical stability after prolonged immersion in corrosive media. These surfaces show excellent self-cleaning ability with significantly low water consumption (&lt; 0.1 µl/mm2-mg) and prevent biofouling which ensures its applicability in biological environment and marine components. The nanostructured superhydrophilic aluminum shows maximum antibacterial activity due to disruption of cell membrane. This work can offer a simple strategy to large scale fabrication of multifunctional biomimetic metallic surfaces. © 2021

Mechanical Engineering

(SoE) School of Engineering

Colloids and Surfaces B: Biointerfaces

Bioinspired micro/nano structured aluminum with multifaceted applications

We re-examine Hawking radiation for a nonrotating (2 + 1)-dimensional Bañados–Teitelboim–Zanelli (BTZ) black hole and evaluate the transmission probability of tunneling through the barrier of the event horizon employing the standard method of WKB approximation. Our results are presented for both uncharged and charged cases. We also explore the associated thermodynamics in terms of Hawking temperature and provide estimates of black hole parameters like the surface gravity and entropy. © 2022 World Scientific Publishing Company

International Journal of Modern Physics A

Tunneling of hawking radiation for BTZ black hole revisited

For phase change materials (PCMs) to become a viable universal memory candidate and obsolete von-Neumann architecture, materials with very high crystallization speed are needed. Moreover, introducing prestructural ordering inside the material is also being touted as one of the promising techniques to reach the speed of SRAM or further down. In this aspect, GaSb alloys are showing much promise for not only having very low crystallization times by themselves, but also showing an enormous drop in the programming time while crystallizing the reamorphized material. Here, we demonstrate how the threshold switching behavior changes for the fully amorphous film in contrast with the disordered film with nucleation sites using conductive-atomic force microscopy. It is found that the required power and programming current for memory switching with nominally stoichiometric GaSb (44:56) are 23 nW and 6.2 nA, respectively. As expected for a nucleation-oriented PCM, the deposited thin film has two voltage thresholds during the local programming process, one for conduction and another for memory switching. However, when the nucleation sites are introduced inside the disordered film, the conduction and memory switching become simultaneous. This is also found to reduce the threshold power and SET current by 93% (1.5 nW) and 91% (550 pA), respectively. Furthermore, we also reveal the origin behind this behavioral change observed between these two thin films by using high-resolution transmission electron microscopy and synchrotron radiation photoelectron spectroscopy. © 2022 American Chemical Society.

Fulltext

Journal of Physical Chemistry C

Revealing the Impact of Prestructural Ordering in GaSb Thin Films

Antimicrobial coatings on metallic surfaces are rapidly emerging to combat bacterial pathogens. The excess use of conventional antibiotics increases the number of resistant strains at an alarming rate, which in turn leads to detrimental implications in the healthcare sector. Hence, it is of great importance in developing a new class of material with inherent bactericidal activity and good biocompatibility. In the present study, we have modified the aluminium surfaces by a coating of graphene oxide (GO) due to its excellent physicochemical properties, water dispersity and low cytotoxicity. Coatings were developed through facile and enviornment-friendly transfer method. The antimicrobial properties of GO coated aluminium are investigated against Gram-negative strain E. coli through agar plate counting and ‘Live/Dead’ fluorescence staining. Further, to shed light into the mechanism of antibacterial activity of GO at the molecular level, we have performed X-ray reflectivity (XRR) study considering a phospholipid multilayer as a model system to mimic bacteria cell membrane. Results show a significant bactericidal activity of the GO coatings compared to uncoated aluminium with lower concentration showing slightly better antibacterial property due to higher roughness. The obtained results may pave the way for engineering graphene-based antimicrobial coatings on a material surface using an easy, environment-friendly, cost-effective and straight forward processing route. © 2022 The Author(s)

Environmental Technology and Innovation

Graphene oxide coated aluminium as an efficient antibacterial surface

We examine the possibility of artificial Hawking radiation by proposing a non-PT-symmetric weakly pseudo-Hermitian two-band model containing a tilting parameter by pursuing Weyl semimetal blackhole analogy. We determine the tunneling probability using such a Hamiltonian through the event horizon that acts as a classically forbidden barrier. © 2022 Author(s).