MoS2 is an important member of the transition metal dichalcogenides that is emerging as a potential 2D atomically thin layered material for low power electronic and optoelectronic applications. ...However, for MoS2 a critical fundamental question of significant importance is how the surface energy and hence the wettability is altered at the nanoscale in particular, the role of crystallinity and orientation. This work reports on the synthesis of large area MoS2 thin films on insulating substrates (SiO2/Si and Al2O3) with different surface morphology via vapor phase deposition by varying the growth temperatures. The samples were examined using transmission electron microscopy and Raman spectroscopy. From contact angle measurements, it is possible to correlate the wettability with crystallinity at the nanoscale. The specific surface energy for few layers MoS2 is estimated to be about 46.5 mJ/m2. Moreover a layer thickness-dependent wettability study suggests that the lower the thickness is, the higher the contact angle will be. Our results shed light on the MoS2–water interaction that is important for the development of devices based on MoS2 coated surfaces for microfluidic applications.
Efficiency of hydrogen evolution via water electrolysis is mainly impeded by the kinetically sluggish oxygen evolution reaction (OER). Thus, it is of great significance to develop highly active and ...stable OER catalyst for alkaline water electrolysis or to substitute the more kinetically demanding acidic OER with a facile electron-donating reaction such that OER is no longer the bottleneck half-reaction for either acidic or alkaline water electrolysis. Herein, the hierarchical Fe–Ni phosphide shelled with ultrathin carbon networks on Ni foam (FeNiP@C) is reported and shows exceptional OER activity and enhanced chemical stability in 1 M KOH. This unique electrode provides large active sites, facile electron transport pathways, and rapid gas release, resulting in a remarkable OER activity that delivers a current density of 100 mA/cm2 at an overpotential of 182 mV with a Tafel slope of 56 mV/dec. Combining the hydrogen evolution reaction with organic pollutant (methylene blue) oxidation, a multifunctional electrolyzer for simultaneous cost-effective hydrogen generation and organic pollutant decomposition in acid wastewater is proposed. Our strategies in this work provide attractive opportunities in energy- and environment-related fields.
The present study explores the suitability of chemical reaction-based and diffusion-based kinetic models for defining the biosorption of Cu(II), Cd(II) and Pb(II) by
Phormidium sp.-dominated mat. The ...time-course data of metal sorption by the test mat significantly (
r
2
=
0.932–0.999) fitted to the chemical reaction-based models namely pseudo-first-order, -second-order, and the general rate law. However, these models fail to accurately describe the kinetics of metal biosorption due either to prefixed order or unjustifiable change in rate constant and reaction order with varying concentrations of metal and biomass in the solution. The diffusion-based models, namely, the intra-particle diffusion model and the external mass transfer model fitted well to the time-course metal sorption data, thus suggesting involvement of both external and intra-particle diffusion processes in sorption of test metals by mat biomass. However, the Boyd kinetic expression clearly showed that the external mass transfer is the dominant process.
Chickpea (Cicer arietinum L.) is an important pulse crop grown and consumed all over the world, especially in the Afro-Asian countries. It is a good source of carbohydrates and protein, and protein ...quality is considered to be better than other pulses. Chickpea has significant amounts of all the essential amino acids except sulphur-containing amino acids, which can be complemented by adding cereals to the daily diet. Starch is the major storage carbohydrate followed by dietary fibre, oligosaccharides and simple sugars such as glucose and sucrose. Although lipids are present in low amounts, chickpea is rich in nutritionally important unsaturated fatty acids such as linoleic and oleic acids. β-Sitosterol, campesterol and stigmasterol are important sterols present in chickpea oil. Ca, Mg, P and, especially, K are also present in chickpea seeds. Chickpea is a good source of important vitamins such as riboflavin, niacin, thiamin, folate and the vitamin A precursor β-carotene. As with other pulses, chickpea seeds also contain anti-nutritional factors which can be reduced or eliminated by different cooking techniques. Chickpea has several potential health benefits, and, in combination with other pulses and cereals, it could have beneficial effects on some of the important human diseases such as CVD, type 2 diabetes, digestive diseases and some cancers. Overall, chickpea is an important pulse crop with a diverse array of potential nutritional and health benefits.
There are very limited published data on the neurologic complications associated with coronavirus disease 2019 (COVID-19) in the pediatric population. Here we present the first 2 pediatric cases of ...presumed COVID-19 related cytotoxic lesions of the corpus callosum. Similar to reports in adults, these cases suggest that the COVID-19 infection in children may rarely mediate a hyperinflammatory response that can cause CNS pathology. As the pandemic continues further, the presentation of cytotoxic lesions of the corpus callosum should prompt radiologists to consider COVID-19, among other known causes.
The granules of
Spirogyra neglecta biomass, diameter 0.2–0.5
mm, were successfully prepared by boiling it in urea–formaldehyde mixture. Metal sorption performance of the column packed with
Spirogyra ...granules was assessed under variable operating conditions, such as, different influent metal concentrations, bed heights and flow rates. These conditions greatly influenced the breakthrough time and volume, saturation time and volume, and the ability of the column to attain saturation after reaching the breakthrough. The experimental breakthrough curves obtained under varying experimental conditions were modeled using Bohart–Adams, Wolborska, Thomas, Yoon–Nelson and modified dose–response models. The first two models were valid only in representing the initial part of the breakthrough curves; however, the other three models were good in representing the entire breakthrough curve. The granule-packed column could be successfully used up to 6 and 9 cycles of sorption and desorption for the removal of Cu(II) and Pb(II), respectively. The column could efficiently remove different metals from real industrial effluents, and hence the test biomass (
Spirogyra granules) is a good candidate for commercial application.
Experimental breakthrough curves for the sorption Pb(II) by the
Spirogyra granule-packed column at different bed heights.
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Spirogyra granule-packed column promisingly sorbed metals from aqueous systems. ► Operating conditions greatly influenced the service time of the column. ► Several empirical models successfully predicted experimental breakthrough curves. ► The column showed good reusability during multiple cycles of sorption–desorption. ► The column efficiently removed several metals from real industrial effluents.
The two-dimensional (2D) semiconductor molybdenum disulfide (MoS2) has attracted widespread attention for its extraordinary electrical-, optical-, spin-, and valley-related properties. Here, we ...report on spin-polarized tunneling through chemical vapor deposited multilayer MoS2 (∼7 nm) at room temperature in a vertically fabricated spin-valve device. A tunnel magnetoresistance (TMR) of 0.5–2% has been observed, corresponding to spin polarization of 5–10% in the measured temperature range of 300–75 K. First-principles calculations for ideal junctions result in a TMR up to 8% and a spin polarization of 26%. The detailed measurements at different temperature, bias voltages, and density functional theory calculations provide information about spin transport mechanisms in vertical multilayer MoS2 spin-valve devices. These findings form a platform for exploring spin functionalities in 2D semiconductors and understanding the basic phenomena that control their performance.
The pH-dependent metal sorption by Oscillatoria- and Phormidium-dominated mats was effectively expressed by the Hill function. The estimated Hill functions can fruitfully predict the amount of metal ...sorbed at a particular initial pH. Pretreatment of biomass with 0.1mmolL−1 HCl was more effective than pretreatment with CaCl2, HNO3, NaOH, and SDS in enhancing metal sorption ability of the biomass. Desorption of metal ions in the presence of 100mmolL−1 HCl from metal-loaded mat biomass was completed within 1h. After six cycles of metal sorption/desorption, sorption decreased by 6–15%. Only 6% and 11% of the biomass derived from the Oscillatoria sp.- and Phormidium sp.-dominated mats was lost during the cycling. The cyanobacterial mats seem to have better potential than several biomass types for use in metal sorption from wastewaters as they are ubiquitous, self-immobilized, and have good reusability.
Atomically thin layers of 2D WS2 offer a realization of novel valley-selective electronics and power-efficient optoelectronic device fabrication due to large spin splitting at the top of the valence ...band and high quantum efficiency. However, the synthesis of the large-area monolayer WS2 film through chemical vapor deposition (CVD) method is in a rudimentary stage. Here we report a modified CVD method to synthesize high-crystalline monolayer WS2 (1L) with uniform size distribution over a large area. The intensity of the second-order Raman modes in 1L WS2 is enhanced, particularly the overtone of the acoustic mode LA(M), when the excitation wavelength is in the vicinity of B exciton. The variation in the intensity profile of the first-order Raman modes for 1L and bulk WS2 in (laser-energy-dependent) resonant Raman scattering processes is discussed within the third-order perturbation theory.
ABSTRACT
Many algae have immense capability to sorb metals, and there is considerable potential for using them to treat wastewaters. Metal sorption involves binding on the cell surface and to ...intracellular ligands. The adsorbed metal is several times greater than intracellular metal. Carboxyl group is most important for metal binding. Concentration of metal and biomass in solution, pH, temperature, cations, anions and metabolic stage of the organism affect metal sorption. Algae can effectively remove metals from multi-metal solutions. Dead cells sorb more metal than live cells. Various pretreatments enhance metal sorption capacity of algae. CaCl2 pretreatment is the most suitable and economic method for activation of algal biomass. Algal periphyton has great potential for removing metals from wastewaters. An immobilized or granulated biomass-filled column can be used for several sorption/desorption cycles with unaltered or slightly decreased metal removal. Langmuir and Freundlich models, commonly used for fitting sorption data, cannot precisely describe metal sorption since they ignore the effect of pH, biomass concentration, etc. For commercial application of algal technology for metal removal from wastewaters, emphasis should be given to: (i) selection of strains with high metal sorption capacity, (ii) adequate understanding of sorption mechanisms, (iii) development of low-cost methods for cell immobilization, (iv) development of better models for predicting metal sorption, (v) genetic manipulation of algae for increased number of surface groups or over expression of metal binding proteins, and (vi) economic feasibility.
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