Optically Stimulated Artificial Synapse Based on Layered Black Phosphorus

The translation of biological synapses onto a hardware platform is an important step toward the realization of brain‐inspired electronics. However, to mimic biological synapses, devices till?date continue to rely on the need for simultaneously altering the polarity of an applied electric field or the output of these devices is photonic instead of an electrical synapse. As the next big step toward practical realization of optogenetics inspired circuits that exhibit fidelity and flexibility of biological synapses, optically?stimulated synaptic devices without a need to apply polarity?altering electric field are needed. Utilizing a unique photoresponse in black phosphorus (BP), here reported is an all?optical pathway to emulate excitatory and inhibitory action potentials by exploiting oxidation?related defects. These optical synapses are capable of imitating key neural functions such as psychological learning and forgetting, spatiotemporally correlated dynamic logic and Hebbian spike?time dependent plasticity. These functionalities are also demonstrated on a flexible platform suitable for wearable electronics. Such low‐power consuming devices are highly attractive for deployment in neuromorphic architectures. The manifestation of cognition and spatiotemporal processing solely through optical stimuli provides an incredibly simple and powerful platform to emulate sophisticated neural functionalities such as associative sensory data processing and decision making.     

Ambient Protection of Few‐Layer Black Phosphorus via Sequestration of Reactive Oxygen Species

Few‐layer black phosphorous (BP) has emerged as a promising candidate for next‐generation nanophotonic and nanoelectronic devices. However, rapid ambient degradation of mechanically exfoliated BP poses challenges in its practical deployment in scalable devices. To date, the strategies employed to protect BP have relied upon preventing its exposure to atmospheric conditions. Here, an approach that allows this sensitive material to remain stable without requiring its isolation from the ambient environment is reported. The method draws inspiration from the unique ability of biological systems to avoid photo‐oxidative damage caused by reactive oxygen species. Since BP undergoes similar photo‐oxidative degradation, imidazolium‐based ionic liquids are employed as quenchers of these damaging species on the BP surface. This chemical sequestration strategy allows BP to remain stable for over 13 weeks, while retaining its key electronic characteristics. This study opens opportunities to practically implement BP and other environmentally sensitive 2D materials for electronic applications.     

Is Photoprotection of PSII One of the Key Mechanisms for Drought Tolerance in Maize?

Drought is one of the most important abiotic stress factors limiting maize production worldwide. The objective of this study was to investigate whether photoprotection of PSII was associated with the degree of drought tolerance and yield in three maize hybrids (30Y87, 31R88, P3939). To do this, three maize hybrids were subjected to three cycles of drought, and we measured the activities of photosystem II (PSII) and photosystem I (PSI). In a second field experiment, three maize hybrids were subjected to drought by withholding irrigation, and plant water status, yield and yield attributes were measured. Drought stress decreased leaf water potential (Ψ_L) in three maize hybrids, and this reduction was more pronounced in hybrid P3939 (−40%) compared to that of 30Y87 (−30%). Yield and yield attributes of three maize hybrids were adversely affected by drought. The number of kernels and 100-kernel weight was the highest in maize hybrid 30Y87 (−56%, −6%), whereas these were lowest in hybrid P3939 (−88%, −23%). Drought stress reduced the quantum yield of PSII [Y(II)], photochemical quenching (qP), electron transport rate through PSII [ETR(II)] and NPQ, except in P3939. Among the components of NPQ, drought increased the Y(NPQ) with concomitant decrease in Y(NO) only in P3939, whereas Y(NO) increased in drought-stressed plants of hybrid 30Y87 and 31R88. However, an increase in cyclic electron flow (CEF) around PSI and Y(NPQ) in P3939 might have protected the photosynthetic machinery but it did not translate in yield. However, drought-stressed plants of 30Y87 might have sufficiently downregulated PSII to match the energy consumption in downstream biochemical processes. Thus, changes in PSII and PSI activity and development of NPQ through CEF are physiological mechanisms to protect the photosynthetic apparatus, but an appropriate balance between these physiological processes is required, without which plant productivity may decline.     

Photoluminescence Characteristics of Sol–Gel Materials Prepared from Bimetallic Erbium Alkoxides Coordinated by Al or Ti

Er³⁺-doped Al₂O₃–SiO₂ and TiO₂–SiO₂ powders were prepared by the sol–gel process using bimetallic erbium isopropoxides coordinated with Al or Ti. The local environment surrounding Er³⁺ ions was controlled orderly at the precursor stage. The phase development of two different systems as a function of temperature was characterized by XRD, and the amount of OH groups remaining within the samples was investigated by a Fourier-transformed infrared spectrometer with increasing annealing temperatures. The photoluminescence spectra and lifetimes of two systems annealed at different temperatures were measured and discussed. The strong emission and long lifetime were observed in Er³⁺-doped Al₂O₃–SiO₂ system, ascribed to the homogeneous distribution of Er³⁺ ion.     

Attenuation of iron-nitrilotriacetate (Fe-NTA)-mediated renal oxidative stress, toxicity and hyperproliferative response by the prophylactic treatment of rats with garlic oil

Iron nitrilotriacetate (Fe-NTA) is a potent nephrotoxic agent. In this communication we show that Fe-NTA-mediated nephrotoxicity is diminished by 1 wk of oral daily pretreatment of male albino Wistar rats with garlic oil given by gavage at 50 or 100 mg/kg body weight/ml corn oil. Intraperitoneal Fe-NTA treatment at a dose level of 9 mg Fe/kg body weight/10 ml enhances renal microsomal lipid peroxidation and hydrogen peroxide generation which are accompanied by a decrease in the activities of renal antioxidant enzymes (e.g. catalase, glutathione peroxidase, glutathione reductase and glutathione S-transferase), and a depletion in the level of renal glutathione. Parallel to these changes, a sharp increase in blood urea nitrogen and serum creatinine has been observed. In addition, Fe-NTA treatment also enhances renal ornithine decarboxylase (ODC) activity and increases [3H]thymidine incorporation into renal DNA. Prophylactic treatment of animals with garlic oil before the administration of Fe-NTA resulted in the diminution of Fe-NTA mediated injury. The enhancement of renal lipid peroxidation and hydrogen peroxide generation was decreased. In addition, there was recovery of glutathione depletion and inhibition of the activities of antioxidant enzymes. Similarly, in animals given the higher dose of garlic oil (100 mg/kg body weight) the enhanced blood urea nitrogen and serum creatinine levels, which are indicative of renal injury, showed a reduction of about 30% and 40%, respectively, in comparison with the group treated with Fe-NTA alone. Pretreatment with garlic oil also ameliorated the Fe-NTA-mediated induction of ODC activity and enhancement of [3H]thymidine incorporation into DNA in a dose-dependent manner. Our data suggest that garlic oil is a potent chemopreventive agent and may suppress Fe-NTA-induced nephrotoxicity.     

Functionalization of UiO-66-NH2 by In-Situ Incorporation of Nanomaterials to Enhance Photocatalytic Efficiency Towards Oxygen Evolution Reaction

The catalysts for oxygen evolution reaction (OER) are required to generate clean energy. Herein, one-step solvothermal synthesis and modification of amino functionalized Zr-based metal organic framework, UiO-66-NH₂, is reported. The catalytic efficiency of UiO-66-NH₂ towards OER is improved by incorporating the cerium-based nanocomposite such as Ce₂O₃, TiO₂/Ce₂O₃ and CoO/Ce₂O₃. The synthesized samples are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray, diffraction, and ultraviolet–visible spectroscopy. The synthesized materials are coated on nickel foam for investigating the catalytic activity towards OER by cyclic voltammetry and linear sweep voltammetry. Amongst, CoO/Ce₂O₃@UiO-66-NH₂/NF exhibits excellent OER-catalytic activity and delivers 10 mA cm^?2 current density at just 228 mV overpotential which is superior to many previously reported OER catalysts and its comparative products. To understand kinetics, Tafel slope is derived from LSV curve and is just 92 mV dec^?1.

Graphical Abstract

     

Nanocomposites of transition metals tungstate for potential applications in magnetic and microwave devices

Ni_2-xCo_x(WO₄)₂ and Ni_2-xMn_x(WO₄)₂ (x?=?0.0, 0.50, 1.0, 1.50 and 2.0) nanocomposites have been synthesized by facile hydrothermal method. The synthesized samples have been characterized by powder XRD and Scanning Electron Microscopy to analyze the structure and morphology. Structural analysis has revealed the single phase formation with wolframite monoclinic system for NiWO₄ samples. The calculated crystallite size ranges from 6 to 40 nm for the nanocomposites. Magnetic and dielectric parameters have also been studied. Magnetic susceptibility measurements of each sample have been carried out at room temperature (312 K) by using Sherwood magnetometer. A decrease in susceptibility values has been observed by increase in the concentration of manganese or cobalt in nickel tungstate leading to antiferromagnetic behavior. Dielectric measurements in the frequency range of 6 kHz to 1 MHz have been calculated. The analysis showed that dielectric parameters decrease with increase in frequency.     

Improvement in mechanical properties of sponge-gourd fibers through different chemical treatment as demonstrated by utilization of the Weibull distribution model

ABSTRACT

Sponge-gourd natural fibers obtained from Luffa cylindrica plant were chemically treated separately using 5?15 wt% NaOH, acetic anhydride and benzoyl chloride solutions. Surface morphological, mechanical and thermal characteristics of untreated and chemically treated fibers were studied. Untreated and modified surfaces of the fibers were characterized by field emission scanning electron microscopy. Tensile tests were carried out by equal length of single fibers to obtain their mechanical properties. The two-parameter Weibull distribution model was applied to find the variation in mechanical properties. Tensile strength, elastic modulus and thermal stability of the fibers were found to significantly increase after chemical treatment.