Physics

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The possibilities of the precise control of wetting properties of a series of laser-induced graphene (LIG) films consisting of microscale air pockets on top of nano-scale surface roughness using electrowetting are demonstrated. By application of a marginal DC bias (∼2 V), water can efficiently wet as well as can be pumped through the superhydrophobic LIG substrates. Interestingly, the electrowetting phenomenon is strongly dependent on the applied voltage polarity and it causes an abrupt wetting transition from superhydrophobic (contact angle ∼152°) Cassie state to superhydrophilic (contact angle ∼7°) Wenzel state on the LIG films. By analyzing the voltage polarity dependent electrowetting results with an equivalent electrical circuit model at the solid-liquid interface, and considering the hierarchical dual surface roughness (micro-nano scale), the transition between the “slippy” Cassie state and the “sticky” Wenzel states is explained. Furthermore, we demonstrate that the unique structural characteristics of the custom-designed micropatterned LIGs, with precisely tailored surface energy by simple post-annealing treatment, enable easy preparation of superhydrophobic LIG films. The approach to prepare stable superhydrophobic LIG with voltage polarity dependent wetting mode transition is used here to controllably transport of water through 3D porous LIG surfaces. © 2021 Elsevier Ltd

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(SoNS) School of Natural Sciences

Fulltext

Carbon

Polarity dependent electrowetting for directional transport of water through patterned superhydrophobic laser induced graphene fibers

Advancement of the memristor-based artificial synapse (AS) is urgently needed for rapid progress in neuromorphic devices. The precise structural and chemical engineering of metal oxide layers by metal dopants (Ni) is presented as an innovative way to set off a decent performance of the AS. An ON/OFF ratio of 103as well as data retention and endurance capabilities of 104s and 103cycles, respectively, are achieved. With these properties, the symmetric alteration in conductance states, short-term plasticity (STP) and long-term plasticity (LTP) are realized within the same device, and compared with the reported values to establish its excellent cognitive behavioural ability. Our combined experimental and the DFT-based first-principles calculation results reveal that the rational designing of AS using metal-cations (Ni) can promote an ultra-low-power of ∼2.55 fJ per pulse (lower than human brain ∼10 fJ per pulse) for STP, promising for next-generation smart memory devices. Here, Ni endorses strong electronic localization, which in turn familiarizes trap states within the forbidden energy gap and improves short-term memory loss. Further, it modifies the local electrostatic barriers to stimulate modulatory action (as commonly observed in the mammalian brain) for LTP. Overall, this work provides a novel pathway to overcome the technological bottleneck. © The Royal Society of Chemistry 2021.

Journal of Materials Chemistry C

Metal-induced progressive alteration of conducting states in memristors for implementing an efficient analog memory: a DFT-supported experimental approach

An annealing temperature-driven appearance of a sharp dual-band edge in the ultraviolet-visible absorption spectrum of electrochemically anodized TiO2 nanotubes (TNTs) and the corresponding impact on the photodegradation of organic dyes is reported based on the evolution of an anatase (A)/rutile (R) phase junction. Systematic X-ray diffraction followed by a micro-Raman analysis illustrates the impact of annealing between 500 and 900 °C in promoting the anatase-to-rutile phase transformation with a higher degree of crystallinity through an evolution of an intermediate mixed phase. X-ray photoelectron spectroscopy (XPS) further reveals a clear transition from the sub-stoichiometric to stoichiometric TNTs with increasing annealing temperature. Moreover, the valence band (VB) XPS along with the ultraviolet photoelectron spectroscopy (UPS) analysis suggests the possible band alignment at the A/R interface, whereas the X-ray absorption spectroscopy (XAS) at the Ti L- and O K-edges confirms a systematic change from an anatase to a rutile phase owing to the modification in local symmetry. To validate our experimental results, especially the formation of a dual-band edge at the A/R phase junction in TNTs, theoretical calculations using density functional theory (DFT) were also performed. Here, a one-to-one analysis of our theoretical and experimental results not only shows a good agreement to each other but also illustrates the microscopic origin behind the formation of a dual-band edge in mixed phase TNTs as well as the observed variation in Raman and XPS spectra with annealing temperature. Finally, an improved photocatalytic degradation of methylene blue aqueous solution is demonstrated in the presence of a mixed phase and explained in the framework of an efficient transfer of photogenerated electrons from the conduction band (CB) of R to the CB of A and holes from the VB of A to the VB of R across the phase junction in tube walls. © 2021 American Chemical Society.

Journal of Physical Chemistry C

Unveiling Temperature-Mediated Dual-Band Edge in TiO2Nanotubes with Enhanced Photocatalytic Effect

Crystalline Si films incorporated with Al are important for applications in microelectronics and solar cells. In this paper, we report on the morphology of crystalline Si surfaces in Al/amorphous-Si bilayer thin films under ion beam irradiation at 100 °C. Micro-Raman and transmission electron microscopy studies show that best crystallization is achieved at a fluence of 1 × 1012 ions cm-2. The contact angle of Si surfaces (after chemically etched unreacted Al), referred to as absorber surfaces, decreases with increasing ion fluence. These surfaces are hydrophobic in nature and the hydrophobicity decreases with increasing ion fluence. Fractal and multifractal analysis of atomic force microscopy images, along with system energy/unit cell and Laplace pressure calculations, supports our observations. Moreover, the calculated multiple scattering cross sections of light, along with reflectivity measurements, indicate that absorber surfaces of best crystalline films have the lowest reflectivity. The present results suggest that such surfaces having low optical reflectance and a hydrophobic nature can be used as photon absorber layers for advanced solar cell devices. © 2021 Author(s).

Journal of Applied Physics

Influence of fractal and multifractal morphology on the wettability and reflectivity of crystalline-Si thin film surfaces as photon absorber layers for solar cell

The Royal Society of Chemistry, with the agreement of the authors, hereby wholly retracts this RSC Advances review article due to a significant amount of unattributed overlap of content in the Introduction, Section 6 and Conclusions with a npj 2D Materials and Applications article by Thomas Mueller et al., which was not cited in this article.1 In addition, there are portions of text overlap with papers cited in the main article, in particular ref. 64 in Section 2, ref. 92 in Section 3, ref. 104 in Section 4 and ref. 138 in Section 5. The authors also regret their oversight in omitting to attribute Fig. 5 to its original source (ref. 92 in the original article). Signed: Bhaskar Kaviraj and Dhirendra Sahoo Date: 22nd March 2021 Retraction endorsed by Laura Fisher, Executive Editor, RSC Advances © The Royal Society of Chemistry 2021.

RSC Advances

Retraction: Physics of excitons and their transport in two dimensional transition metal dichalcogenide semiconductors (RSC Adv. (2019) 9 (25439–25461) DOI: 10.1039/c9ra03769a)

Anodized aluminum oxide (AAO) in amorphous form is shown to be a prospective phosphor for optically stimulated luminescence (OSL) by implanting 50 keV carbon ions at a fluence of 1 × 1016 ions/cm2 at room temperature. An almost 20-fold enhancement in continuous wave OSL (CW-OSL) sensitivity is obtained in carbon-doped AAO (C:AAO) by exposing to beta radiation, while an almost linear increase in CW-OSL intensity is recorded with increasing dose from 0.3 to 5 Gy. However, cathodoluminescence (CL) suggests an upsurge of oxygen vacancies, especially F+ and F22+ centers, at the cost of F center-related defects in C:AAO. Detailed X-ray photoelectron spectroscopy (XPS) analysis further reveals that the implanted carbon atoms can act as cationic impurities in AAO and stabilize the nearby F+ centers via substitution of Al3+ by C2+. The combined CL and XPS results are also shown to be capable of illustrating the CW-OSL response. This study would, therefore, be a benchmark for understanding the role of carbon in the substitutional sites of AAO for generating OSL active electron traps. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.

Journal of Materials Science: Materials in Electronics

Carbon doping-induced defect centers in anodized alumina with enhanced optically stimulated luminescence

A cellular membrane, primarily a lipid bilayer, surrounds the internal components of a biological cell from the external components. This self-assembled bilayer is known to be perturbed by ionic liquids (ILs) causing malfunctioning of a cellular organism. In the present study, surface-sensitive X-ray scattering techniques have been employed to understand this structural perturbation in a lipid multilayer system formed by a zwitterionic phospholipid, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine. The ammonium and phosphonium-based ILs with methanesulfonate anions are observed to induce phase-separated domains in the plane of a bilayer. The lamellar X-ray diffraction peaks suggest these domains to correlate across the bilayers in a smectic liquid crystalline phase. This induced IL-rich lamellar phase has a very low lamellar repeat distance, suggesting the formation of an interdigitated bilayer. The IL-poor phase closely related to the pristine lipid phase shows a decrement in the in-plane chain lattice parameters with a reduced tilt angle. The ammonium and phosphonium-based ILs with a relatively bulky anion, p-toluenemethanesulfonate, have shown a similar effect. © 2021 American Chemical Society. All rights reserved.

ACS Omega

Ionic liquid-induced phase-separated domains in lipid multilayers probed by x-ray scattering studies

<p>Atmospheric degradation of the metallic components initiated by the accumulation of contaminants and humidity significantly limits the performance and sustainability of many engineering systems. Aluminium and its alloys are widely used in different industries such as food processing, marine, aerospace, automobiles and household appliances. The leaching of aluminium can cause significant environmental and health-related issues. In the present study, a facile and environment-friendly (hot water treatment) processing route was utilized to fabricate sustainable Al surfaces without the use of any chemical reagents and toxic solvents. The developed nanostructured Al surface showed immense mechanical, chemical and thermal durability restricting corrosion and leaching of aluminium. The processed Al composed of self-assembled 2D nanostructures showed extreme wettability ranging from superhydrophilic (θ &lt; 5°) to superhydrophobicity (SHS) (θ &gt; 160°), depending upon post-processing conditions. The developed SHS has showed high water (droplet impacts) and dust repellence under static and dynamic conditions. This is related with effective entrapment of air, prompted by the presence of nanostructured morphology, leading to stable Cassie state. Results showed that SHS possess better self-cleaning ability compared to the superhydrophilic counterpart. The SHS showed better sustainability in terms of high thermal stability in a temperature range of −80 °C to 350 °C and corrosion resistance under prolonged immersion for 48 h in salt media. Compared to unprocessed counterpart, SHS showed 40 times reduction in the corrosion rate, which is significantly high when compared with several other processing routes. The present study showed an eco-friendly and straightforward approach which can be effectively used for fabricating multifunctional metallic surfaces with widespread applications. © 2020 Elsevier Ltd</p>

Mechanical Engineering

(SoE) School of Engineering

Journal of Cleaner Production

Green manufacturing of nanostructured Al-Based sustainable self-cleaning metallic surfaces

SrTiO3 is a wide bandgap cubic perovskite oxide and displays many exotic properties, i.e., transparent conductivity, photocatalysis, metallicity, ferroelectricity, superconductivity, colossal magnetoresistance, two-dimensional electron gas, etc., due to the manipulations of defect chemistry and constituent elements via impurity doping. This paper reports on the intricacy of the structural and optoelectronic properties of the epitaxially stabilized 5 at. % Ta-doped SrTiO3 (001) thin films on LaAlO3 (001) substrates by systematically varying the growth temperature and oxygen partial pressure during the pulsed laser deposition process. The influences of Ta dopant and growth parameters on the epitaxial quality of these layers are understood by determining the dopant location and its concentration in the SrTiO3 lattice. The complex relationships of optical and electronic properties on growth parameters, dopant concentration, and single crystal quality of the films are demonstrated. The observed low resistivity (∼5 × 10-3 ω cm) and high optical transparency (∼85%-90%) of optimized Ta-doped SrTiO3 films offer it as an exciting material for next generation transparent optoelectronics. © 2021 Author(s).

Ta-doped SrTiO3epitaxial thin film: A promising perovskite for optoelectronics

Rechargeable magnesium-sulfur (Mg/S) batteries are considered a promising energy storage devices for grid-scale applications due to their high theoretical energy density, safety, and low cathode cost. However, the Mg/S batteries suffer from the low practical energy density mainly arising from the rapid dissolution of polysulfides and slow reaction kinetics between Mg and solid-phase sulfur. In this regard, we have introduced here the magnesium polysulfide (MgSx) catholyte as a liquid-phase active material to conquer the sluggish redox kinetics of Mg/S batteries. A polyaniline-coated carbon cloth (CC@PANI) has been incorporated as a current collector and a reservoir for magnesium-polysulfide(MgSx) catholyte. The MgSx containing CC@PANI cathode (i.e., CC@PANI@MgSx cathode) exhibits an initial reversible specific capacity of 514 mA h g−1 and retains 428 mA h g−1 after 25 cycles. The effect of MgSx catholyte on the electrochemical performance of the Mg/S batteries have been closely investigated through post-cycling characterization of Mg anode and computational studies. Besides, the phase transition of sulfur during magnesiation a complete reaction has been studied in the current report. © 2020