Nitrogen Atmosphere Research Articles

Interfacial nanoarchitectonics for enhanced photo-assisted thermo-catalytic conversion of glucose to 5-hydroxymethylfurfural

Photo-assisted thermo-catalytic conversion of glucose to 5-hydroxymethylfurfural (HMF) is one of the most promising ways for channeling solar energy. Photo-assisted thermo-catalytic conversion of glucose and HMF yield were improved with SnO2/Cr-MOFs/Cr(OH)3 catalysts under visible light irradiation at 135 ℃-165 ℃ nitrogen atmosphere. SnO2/Cr-MOFs/Cr(OH)3 afforded relatively high Lewis acidity and Brønsted acidity, which was beneficial for thermo-catalytic conversion of glucose. The light and the interface between SnO2 and Cr-MOFs/Cr(OH)3 assistantly promoted the HMF formation. The photo-generated holes (h+) under light irradiation was the driving force for the formation of “free” protons from water and carboxylic acid in Cr-MOFs, which acted as Brønsted acid sites to promote HMF formation. With 576 mg glucose as the substrate and DMSO as the solvent, 92 % glucose conversion with 43.2 % HMF yield was achieved at 150 ℃ for 2 h under nitrogen atmosphere and 500 W Xe lamp irradiation. The results demonstrate the promise of photo-assisted thermo-catalytic conversion of glucose in the future.

Enhancing efficiency and stability of perovskite solar cells via evaporated NdF3 surface passivation

Realizing efficient and stable perovskite photovoltaic devices remains a key challenge for further development in this field. Surface defects, especially those caused by unbound Pb, are often linked to the performance of these devices. This study demonstrates that NdF3 deposited on the surface of perovskite films effectively passivates unbound lead, thereby improving film quality. The resulting device achieved an power conversion efficiency (PCE) of 22.88% and exhibited good stability. Even after being stored in air for 1400 h, the device maintained its initial PCE of 87.5%. Additionally, after aging at 120 °C for 400 h in a nitrogen atmosphere, the device still retained 90% of its initial PCE. Furthermore, the device maintains 52% of its initial PCE after 1000 h of continuous light soaking.

Nitrogen-doped bean-like SiC-based nanofibers for thermal insulation and electromagnetic wave absorption

SiC nanofibers that can be used to absorb electromagnetic wave (EMW) radiation and as thermal insulators simultaneously are highly desirable. In this work, nitrogen-doped bean-like SiC-based nanofibers were prepared by a simple electrospinning and high-temperature pyrolysis in a nitrogen atmosphere, focusing on studying the effects of nitrogen atom doping on the microstructure, EMW absorption, and thermal insulation properties of the fibers. The results showed that nitrogen doping promoted the formation of the SiOxCyNz phase in the fibers, which improved their interfacial thermal resistance and endowed the fibers with extremely low thermal conductivities (∼0.024 W·m−1·K−1 at 25 ℃, 0.092 W·m−1·K−1 at 1000 ℃). Furthermore, the density of carbon defects in the fibers was improved by nitrogen doping, which created numerous new polarization centers and effectively improved the dielectric loss. With a 4 mm thickness, a minimum reflection loss of −51.8 dB was exhibited at 6.3 GHz, indicating that these fibers are highly promising as an absorption material in harsh environments.

Closing the sustainability loop: CuO-infused antibacterial cellulose-dominant matrices for multi-tasking wastewater clean-up and energy storage

In tandem with the water contamination brought about by emerging pollutants (EPs), bacterial contamination assumes a pivotal role in water pollution dynamics. Developing efficient yet uncomplicated adsorbents is crucial to meet these demands, even though it remains a challenging endeavor. Addressing this, a cost-effective and straightforward strategy has been proposed for creating a copper oxide (CuO) infused cellulose-dominant matrix (referred to as CuO@SBF) derived from Saccharum officinarum bagasse, aimed at effective ciprofloxacin (Cpf), and methylene blue (MB) dye adsorption, alongside exhibiting antibacterial activity. The CuO-infused SB filter exhibited remarkable effectiveness in capturing methylene blue (MB), surpassing the originally anticipated performance with an adsorption capacity of 361 mg/g, alongside exhibiting notable antibacterial efficacy, particularly with an 11 mm zone of inhibition against Bacillus cereus. In contrast, filters without CuO showed no inhibition zones, underscoring the significance of CuO for antibacterial properties. Beyond their primary function, the used CuO@SBF underwent high-temperature carbonization under nitrogen atmosphere, at 800 °C for 3 h for point-of-use energy storage devices. Remarkably, this subsequent application produced noteworthy outcomes, with the devices attaining a significant capacitance of 161 F/g at a current density of 0.3 A/g. This multifaceted application not only strengthens the adsorbents' sustainability and economic feasibility, but also opens up promising avenues for repurposing waste materials within the domain of energy storage. Hence, the dual-functional CuO@SB filter, boasting impressive antibacterial prowess, is poised to emerge as a prospective contender for effective emerging pollutant adsorption. Moreover, its multifaceted attributes suggest promising applications across diverse domains in the times ahead.

БИОТЕХНОЛОГИЧЕСКИЙ ПОТЕНЦИАЛ НОВЫХ ШТАММОВ УГЛЕВОДОРОДОКИСЛЯЮЩИХ БАКТЕРИЙ

The ingress of oil has a depressing effect on the soil biocenosis, which is enhanced in the presence of other pollutants (heavy metals, chlorides, herbicides), which ultimately leads to the withdrawal of significant land areas (including agricultural ones) from the target turnover. For the bioremediation of such areas, oil-degrading microorganisms are needed that are resistant to additional pollutants, as well as a set of useful properties that increase the efficiency of cleaning and restoring disturbed soils. In this work, three isolates were isolated that actively grew in a liquid medium containing oil. As a result of sequencing the nucleotide sequence of the 16S rRNA gene, it was reliably established that all strains belong to the species Acinetobacter calcoaceticus . The bacteria showed a high oil-oxidizing ability (89.7-97.0%), which was assessed by the degree of destruction of the aliphatic fraction, including in the presence of herbicides based on 2,4-dichlorophenoxyacetic acid (Octapon extra), imazethapyr (Tapir) and tribenuron-methyl ( Special forces) (degree of biodestruction 40.4-54.1%). Microorganisms used aromatic hydrocarbons (including polycyclic ones) as a carbon source. They demonstrated high cell surface hydrophobicity (78-85%) with respect to hexadecane and exhibited emulsifying activity of more than 50%. The bacteria were tolerant to the herbicides Tapir and Spetsnaz in amounts up to 1% volume (mass). The herbicide Octapon extra was more toxic to bacteria - the growth of all strains occurred at its concentration in the medium not higher than 0.5% volume. Microorganisms showed resistance to sodium chloride in an amount of 3.0-5.0% and lead ions (1.00-1.25 g/l). They produced the enzyme lipase and were capable of fixing atmospheric nitrogen and dissolving inorganic phosphate (including in the presence of oil or herbicides). The studied Acinetobacter spp. stimulated the growth of barley (aboveground and underground parts), especially the A. calcoaceticus strain P32 (elongation of shoots and roots by 15.3 and 49.5%, respectively). The data obtained indicate that all three strains have certain prospects for use in the purification of complexly contaminated soils.

Study on the curing characteristics and properties of phthalonitrile resin cured with organic guanidine

Bisphenol A-based phthalonitrile resin was synthesized by nucleophilic substitution reaction from bisphenol A and 4-nitrophthalonitrile, and then the obtained resin was cured with sulfaguanidine as a novel curing agent. The curing characteristics, kinetics, thermal stability and dynamic mechanical property were studied by standard thermal analysis techniques including DSC, TGA, and DMA. The peak temperature of exothermic peak ( Tp) and apparent activation energy ( Ea) of sulfaguanidine cured phthalonitrile resin were 263.20°C and 76.6 kJ·mol−1 respectively, much lower than those of traditional aromatic diamine cured resin. Moreover, the resin cured by sulfaguanidine showed excellent thermomechanical properties and thermal stability. The glass transition temperature ( Tg) was 284.8°C, the initial thermal decomposition temperature ( Td,5%) was 439.6°C, and the char yield at 800°C was 62.1% in nitrogen atmosphere. To sum up, organic guanidine cured phthalonitrile resin exhibits excellent curing characteristics (low Tp and Ea) and high thermal properties, which provides a promising approach to preparing phthalonitrile resin with high comprehensive performance.

Thermal degradation assessment, impact strength, and hardness of combination epoxy and polystyrene powder composite

The present study investigates the reactions of polystyrene and epoxy/polystyrene powder composites, exploring different weight percentages (8%, 12%, and 16%) of polystyrene during decomposition under highly elevated temperatures within a nitrogen atmosphere. The findings reveal that polystyrene content significantly influences the thermal behavior of pure epoxy, with a higher polystyrene content correlating with the increased thermal stability of the composites. This study observed a three-stage mass loss process by examining the reaction kinetics of thermal decomposition using the Coats-Redfern approach. Initially, weight reduction occurs due to moisture and volatile elimination, followed by a smooth mass loss phase attributed to weaker polymer chain linkages and, ultimately, char formation. Chemical kinetic parameters, such as activation energy and frequency factor, were successfully determined using the Coats-Redfern approach, with a first-order reaction observed across all data points, demonstrating a high R-square mean value of 99.8%. Differential scanning calorimetry (DSC) and thermal gravitational analysis (TGA) analyses revealed an increase in glass temperature from 86.95 to 92.85 °C and an elevation in activation energy from 75.38 to 92.85 kJ/mol with increasing polystyrene content (0–16 wt%). Furthermore, the study investigated the influence of thermodynamic parameters. In terms of mechanical properties, increasing polystyrene content reduced impact strength (from 8.5 to 4.23 Kj/m2). In contrast, hardness increased from 77.5 for pure epoxy to 80.4 at 12 wt% polystyrene content in the composite. These findings underscore the importance of thermal stability results in developing a comprehensive understanding of thermal decomposition processes, informing future research endeavors and industrial applications.

Single-cell transcriptome atlases of soybean root and mature nodule reveal new regulatory programs that control the nodulation process

The soybean root system is complex. In addition to being composed of various cell types, the soybean root system includes the primary root, the lateral roots, and the nodule, an organ in which mutualistic symbiosis with N-fixing rhizobia occurs. A mature soybean root nodule is characterized by a central infection zone where atmospheric nitrogen is fixed and assimilated by the symbiont, resulting from the close cooperation between the plant cell and the bacteria. To date, the transcriptome of individual cells isolated from developing soybean nodules has been established, but the transcriptomic signatures of cells from the mature soybean nodule have not yet been characterized. Using single-nucleus RNA-seq and Molecular Cartography technologies, we precisely characterized the transcriptomic signature of soybean root and mature nodule cell types and revealed the co-existence of different sub-populations of B. diazoefficiens–infected cells in the mature soybean nodule, including those actively involved in nitrogen fixation and those engaged in senescence. Mining of the single-cell-resolution nodule transcriptome atlas and the associated gene co-expression network confirmed the role of known nodulation-related genes and identified new genes that control the nodulation process. For instance, we functionally characterized the role of GmFWL3, a plasma membrane microdomain-associated protein that controls rhizobial infection. Our study reveals the unique cellular complexity of the mature soybean nodule and helps redefine the concept of cell types when considering the infection zone of the soybean nodule.

Submillimeter‐Scale Superlubric Triboelectric Nanogenerator

AbstractTriboelectric nanogenerator (TENG) for mechanical energy harvesting has been regarded as one of the most prospective energy technologies for the new era. However, inevitable material wear during triboelectrification results in output reduction and even failure of the TENG. In this work, a submillimeter‐scale superlubric TENG (SS‐TENG) is reported that enables ultra‐low friction coefficient (µ) and stable power generation. By using the micro/nano‐processing technology, the interdigital electrodes are embedded into the dielectric layer as a flat surface, on which the highly‐hydrogenated diamond‐like carbon (PLC) is deposited as the triboelectric layer to effectively reduce the friction coefficient. The frictional properties are systematically investigated at different parameters, in which a submillimeter‐scale (130 µm) superlubricity state (µ = 0.0084) is achieved at 4 N, 2 Hz and nitrogen atmosphere. Meanwhile, the SS‐TENG has a maximum power density of 3 mW m−2, which can remain stable at the superlubric condition. This work has first realized the freestanding‐mode superlubric TENG in submillimeter scale and provided a viable strategy for the development of long‐lifetime TENG, which may have great applications in frictional energy recovery from mechanical components, human joint motion, and the natural environment.

Defects in Nitrogen-Doped ZnO Nanoparticles and Their Effect on Light-Emitting Diodes.

In this study, the effect of defects on the acceptor properties of nitrogen-doped ZnO nanoparticles (NPs) was investigated through the fabrication of light-emitting diodes (LEDs). Nitrogen-doped ZnO NPs were synthesized by an arc discharge in-gas evaporation method and post-annealed at 800 °C in an oxygen and nitrogen atmosphere. The annealed ZnO NPs were characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and photoluminescence spectroscopy. It was found that the annealing of nitrogen-doped ZnO NPs in a nitrogen environment increased the number of zinc vacancies, while annealing in an oxygen environment increased the number of oxygen vacancies due to nitrogen desorption. The output characteristics of LEDs fabricated with oxygen-annealed NPs were degraded, while those with nitrogen-annealed NPs were significantly improved. From these results, the contribution of zinc vacancies to acceptor formation in ZnO NPs was confirmed for the first time in actual pn junction devices.

Effect of rapid thermal annealing on DC performance of Mg0.30Zn0.70O/Cd0.15Zn0.85O MOSHFET

This study focuses on a cost-effective method for fabrication of a metal oxide semiconductor-heterostructure field effect transistor (MOSHFET) based on MgZnO/CdZnO (MCO) using dual ion beam sputtering (DIBS), in contrast to the more expensive epitaxial growth system. The MOSHFETs developed in this research exhibit notable characteristics, such as a substantial two-dimensional electron gas (2DEG) transconductance (∼2.6 mS), a high ION/IOFF response ratio in the order of 108, and minimal gate leakage current. Furthermore, we explore the impact of rapid thermal annealing (RTA) on the drain current at various temperatures (600 °C and 800 °C). The results indicate a fourfold improvement in drain current compared to unannealed conditions, primarily attributed to reduced contact resistance and no degradation in term of MgZnO/CdZnO structure. Additionally, an analysis of post-RTA treatment under a nitrogen (N2) atmosphere on gate leakage current is presented. The investigation spans temperatures ranging from 400 °C to 800 °C, revealing that above 600 °C (gate leakage at 400 °C–600 °C is around ∼10−9 A), gate leakage in HFET is augmented by one order of magnitude (∼10−8 A) due to a phase change in the dielectric. These findings underscore the feasibility of DIBS-grown MCO MOSHFETs as an economical solution for the mass production of switching devices and sensors.

Crystalline as-deposited TiO 2 anatase thin films grown from TDMAT and water using thermal atomic layer deposition with in situ layer-by-layer air annealing

We report a new thermal atomic layer deposition (thermal-ALD) process including an air exposure as a third precursor to deposit crystalline TiO2 anatase thin films from tetrakis(dimethylamido)titanium(IV) (TDMAT) and water at deposition temperatures as low as 180 °C and film thicknesses as low as 10 nm. This ALD process enables TiO2-antase crystal growth during the deposition at low temperatures (< 220 °C). This additional oxidant pulse is used to fully oxidize the Ti to a 4+ state in the amorphous film, lowering the barrier to crystalline anatase formation. This new approach is informed by preliminary studies of post-deposition annealing (PDA) of thermal ALD films in both nitrogen and air atmospheres, which demonstrate the importance of having an oxidizing atmosphere to achieve the nucleation of the crystalline anatase phase. This oxidizing atmosphere is subsequently introduced into the ALD cycle as a third precursor and is shown to be more effective and efficient in promoting the crystalline transformation than even by post-deposition annealing. The crystalline anatase phase is verified by Raman spectroscopy and grazing incidence X-ray diffraction (GIXRD). The mechanism for crystallization during the TDMAT/H2O/air ALD cycle is probed by chemical state analysis via X-ray photoelectron spectroscopy (XPS). We propose that sub-oxidation in TiO2 thin films deposited by the thermal-ALD process inhibits crystallization during ALD from TDMAT/H2O chemistry. Scanning electron microscopy (SEM) is used to investigate the microstructure of these TiO2 thin films as a function of thickness (5 nm to 50 nm) and deposition temperature (180 °C to 220 °C). The reported layer-by-layer air anneal process is found to crystallize entire films in shorter total process times than thermal-ALD with ex situ post deposition annealing at identical temperatures, presumably due to the improved surface diffusion kinetics accessed during the deposition process.

Nitrogen addition has divergent effects on phosphorus fractions in four types of soils

BackgroundGlobally increasing atmospheric nitrogen (N) deposition has altered soil phosphorus (P) transformations and availability, and thereby influenced structure and function of terrestrial ecosystems. Edaphic characteristics and chemical form of deposited N could be important factors determining impacts of N deposition on soil P transformations, yet the underlying mechanisms remain largely unknown. Objectives of this study were to examine how mineral-N and amino N differently affect P fractions, and identify key soil properties determining N addition impacts on soil P transformations. Considering that amino N is an important component of deposited N and forest soils vary greatly in different regions, the results of present study can guide the management of forests across different soils under ongoing N deposition scenarios.MethodsWe conducted a 60-day laboratory experiment to investigate the effects of N addition (NH4NO3 and glycine) on soil P fractions and related biochemical properties in four representative forest soils (brown, yellow brown, aeolian sandy, and red soils) in China. Glycine and NH4NO3 were separately added at three rates (5, 10 and 20 g N m–2 yr–1).ResultsFirstly, the percent changes in organic P fractions with N addition were significantly greater than changes in inorganic P fractions across all soils. Secondly, the percent changes in P fractions with glycine and NH4NO3 additions were significantly correlated across all soils and treatments. However, glycine addition had significantly greater impacts on organic P fractions than NH4NO3 addition in the aeolian sandy and red soils with low organic carbon content. Thirdly, P fractions responded differently to N addition among the four soils. N-induced changes in microbial biomass and phosphatase activities, pH, exchangeable Ca2+ and Mg2+ contributed differently to the changes in P fractions with N addition in the four soils.ConclusionsThe different responses of P fractions to N addition in the four soils were mainly generated by the differences in extent of microbial N limitation, acid buffering capacity, and cation exchange capacity among the soils. The different impacts of mineral and amino N on soil P fractions can be ascribed to their divergent effects on soil pH, microbial biomass and activities.

Liquid phase epitaxy of GaN films on sapphire substrates under an atmospheric pressure nitrogen ambience

GaN films were grown on sapphire substrates using liquid phase epitaxy under an atmospheric pressure nitrogen ambience, employing molten Ga and Fe3N as a source mixture. Single-crystal GaN (0001) films were successfully grown on sapphire (0001) substrates within a growth temperature (T g) range of 750 °C–900 °C. When varying the Fe3N concentration in the range of 0.05–3 mol%, lower iron nitride resulted in high crystallinity of GaN (0001) films. The incorporation of iron atoms in GaN can negatively impact crystal quality. Parameterizing T g at a concentration of 0.1 mol% Fe3N showed that higher T g led to a reduction in the peak width of GaN (0002) X-ray rocking curves. However, at 3 mol%, elevating T g resulted in the degradation of the crystallinity of GaN. This degradation may be attributed to the increased solubility of iron atoms in GaN with increasing T g.

Dinitrogen-bridged ruthenium(II) complexes featuring dithiocarbamate ligands

In quest of low molecular weight metal-thiolate complexes as model complexes for nitrogenase, four binuclear ruthenium(II) dinitrogen-bridged complexes featuring dithiocarbamate ligands, [{(Me3tacn)Ru(κ2-S2CNR2)}2(µ-N2)][PF6]2 (Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane; 1, R = Me; 2, R = Et; 3, R = nPr; 4, R = iPr), were synthesized by reduction of [(Me3tacn)RuIII(κ2-S2CNR2)Cl]PF6 with zinc powder in a nitrogen atmosphere. A 16-electron mononuclear ruthenium(II) species [(Me3tacn)Ru(κ2-S2CNnPr2)]PF6 (3′) was isolated during preparation of 3, which may help elucidate the formation of complexes 1-4. Molecular structures of complexes 1, 2, 4 and 3′ were established by single crystal X-ray diffraction analysis. Moreover, complexes 1-4 were characterized by infrared, 1H NMR, UV–vis, fluorescence, Raman (solid state and solution state) spectroscopies and mass spectrometry, and their electrochemical properties were also investigated. Density functional theory (DFT) calculation was performed on complex 2 to study its Lewis structure and explain the UV–vis absorption spectra. Structural and DFT analyses demonstrate that N2 activation is accompanied by electron redistribution of the dithiocarbamate ligands.

Organic Molecule and Inorganic Salt Synergistic‐Modified SnO2 for Efficient Perovskite Solar Cells

Element doping and interface modification strategy are effective methods to regulate the electrical properties of SnO2 electron transport material, SnO2/perovskite (PVK) interface, and PVK crystal growth. Herein, rubidium fluoride (RbF) is introduced into SnO2 colloidal dispersion, and then an ultra‐thin layer of 4‐carboxy‐3‐fluorobenzoboric acid (FBCA) is applied to the SnO2 layer surface. This synergistic modification strategy can improve the electrical conductivity of the electron transport layer, increase the chemical connection of the buried interface, improve the crystallization and grain growth of PVK, and thus promote the performance and stability of devices. The results show that the PVK solar cells (PSCs) with the synergistic‐modified SnO2 electron transport material (M‐SnO2) obtain an optimum power conversion efficiency of 21.92% and the unencapsulated PSCs sustain 91% and 87% of the original value, which stored in a nitrogen atmosphere and ambient atmosphere (25 ± 5 °C, 30–50% relative humidity) more than 1000 h, respectively.

Preparation of magnetic composite sorbent based on exfoliated graphite with metallic iron, cobalt and nickel using melamine as a reducing agent

Known preparation methods of the magnetic sorbents based on exfoliated graphite (EG) with metallic phase take several hours and requires the use of a large amount of reducing gas at a high temperature, which is not technologically advanced. The aim of the work is to obtain EG modified with iron, cobalt, and nickel using new simple method. This method includes the thermal treatment in nitrogen atmosphere of the mixture of expandable graphite, Mn+ nitrates (Mn+ = Fe3+, Co2+, Ni2+) and melamine. The thermal decomposition of melamine leads to formation of ammonia, which reduces the products of the Mn+ nitrates decomposition (α-Fe2O3, Co3O4/CoO, NiO) to metallic iron, cobalt and nickel. The use of different amount of melamine as reducing agent leads to the formation of mixtures with different compositions containing iron oxides Fe3O4, FeO, metallic iron α-Fe, Fe-C alloy γ-(Fe,C) and iron carbide Fe3C, which were confirmed by Mossbauer spectroscopy. Metallic Co and Ni on the EG surface is formed in nitrogen atmosphere by reduction with carbon even without melamine. Obtained EG/Fe has the highest saturation magnetization of 54.7 emu/g. EG/Co and EG/Ni have lower saturation magnetization of 40.1 and 12.0 emu/g, which is due to lower saturation magnetization of the individual metals.

Deuterated chloroform replaces ultra-dry chloroform to achieve high-efficient organic solar cells

Chloroform is a common and excellent solvent for preparing high-efficient organic solar cells (OSCs), however, it is toxic and poisonable chemical. In comparisons, deuterated chloroform (DC) is less toxic and costly, and particularly, it is non-poisonable chemical. In this paper, we use DC to replace ultra-dry chloroform (UC) as the processing solvent for preparation of active layers of organic solar cells. First, we selected PM6:BTP-eC9 as the basic binary and counted 100 solar cells’ data, from which comparable device performance were obtained with use of DC and UC. Interestingly, DC showed better reproducibility, superior storage under a nitrogen atmosphere and a little better performance than UC. Both DC and UC gave rise of comparable hole and electron mobilities and similar charge recombination losses. Second, we based PM6:Y6 and D18-Cl:Y6 as the binaries and similar effects were obtained from both UC and DC when counting 30 devices for each binary. Third, the universality of the use of DC for preparing high-efficient OSCs were again checked with several binary and ternary systems. In all, this study demonstrate that DC can replace UC for use in the field of OSCs.

Two-step synthesis of tungsten disulfide and its evaluation as electrocatalyst for hydrogen evolution reaction (HER)

The development of affordable alternative energies has gained great interest in recent years. Among them, hydrogen evolution reaction (HER) from water splitting has become of great interest as a source of clean energy. This work aims to develop WS2 synthesized from WO3 prepared by a hydrothermal method assisted by ionic liquid (IL) 1-ethyl-3-methylimidazolium ethyl sulfate [EMIM][EtSO4]), and followed by a heat treatment under nitrogen (N2) atmosphere. Different proportions of IL were used to assess the effect in the WS2 morphology to improve the performance towards the HER in an acidic medium. The resulting compounds were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) with energy dispersive spectroscopy, and electrochemical techniques such as cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and chronoamperometric measurements. WS2 synthesized from WO3 employing IL depicted superior electrocatalytic performance for the HER compared to WS2 prepared without IL. The WS2 sample that involved 2 mL of IL (WS2-2) presented the smaller particle size and the largest crystallite size, two key parameters to perform adequate redox processes: in addition, this sample showed the lowest overpotential value (120 mV), a Tafel slope of 85 mV/dec, and the lowest charge transfer resistance value. These results showed that using the appropriate proportion of ionic liquid as an additive helps to generate smaller WS2 particles, thus generating higher current density, and reducing the overpotential value enhancing the electrocatalytic performance to carry out the HER.

Bioprospecting of endophytic diazotrophic microbes in sustainable agriculture: Review and prospects

Endophytic diazotrophic bacteria play an important role in developing sustainable modern agriculture. Endophytic bacteria can increase plant growth and yield by exhibiting antibiosis against phytopathogens. Biological mechanisms of atmospheric nitrogen fixation, phosphate solubilization, production of phytohormones and inhibition of plant pathogens and pests promote plant growth avoiding the need for chemical fertilizers and control agents. This review evaluates the groups of different endophytic bacteria, their prospects and challenges for sustainable agriculture. Several new bacterial strains were protected as bioinoculants or biopesticides. Formulations containing endophytic bacteria mainly were intended for seed coating or spraying and acted directly in the control of pests and diseases, as well as in increasing resistance to environmental stress. In many cases, they performed well in promoting the growth of plants by producing hormones that regulate or increase nutrient uptake. Bioprospecting in the case of this review is a systematic overview of the rational approach in harnessing beneficial plant-associated microbes to ensure food security in the future.