N2 Gas Research Articles

Enhancing CO2/N2 and CO2/CH4 Separation Properties of PES/SAPO-34 Membranes Using Choline Chloride-Based Deep Eutectic Solvents as Additives

CO2 separation is an important environmental method mainly used in reducing CO2 emissions to mitigate anthropogenic climate change. The use of mixed-matrix membranes (MMMs) arrives as a possible answer, combining the high selectivity of inorganic membranes with high permeability of organic membranes. However, the combination of these materials is challenging due to their opposing nature, leading to poor interactions between polymeric matrix and inorganic fillers. Many additives have been tested to reduce interfacial voids, some of which showed potential in dealing with compatibility problems, but most of them lack further studies and optimization. Deep eutectic solvents (DESs) have emerged as IL substitutes since they are cheaper and environmentally friendly. Choline chloride-based deep eutectic solvents were studied as additives in polyethersulfone (PES)/SAPO-34 membranes to improve CO2 permeability and CO2/N2 and CO2/CH4 selectivity. SAPO-34 crystals of 150 nm with a high surface area and microporosity were synthesized using dry-gel methodology. The PES/SAPO-34 membranes were optimized following previous work and used in a defined composition, using 5 or 10 w/w% of DES during membrane preparation. All MMMs were characterized by their ideal gas permeability using N2 and CO2 pure gasses. Selected membranes were also tested using CH4 pure gas. The results presented that 5 w/w%, in polymer mass, of ChCl–glycerol presented the best result over the synthesized membranes. An increase of 200% in CO2 permeability maintains the CO2/N2 selectivity for the non-modified PES/SAPO-34 membrane. A CO2/CH4 selectivity of 89.7 was obtained in PES/SAPO-34/ChCl-glycerol membranes containing 5 w/w% of this DES, which is an outstanding ideal separation performance for MMMs when compared to other results in the literature. FTIR analysis reiterates the presence of glycerol in the membranes prepared. Dynamic Mechanical Thermal Analysis (DMTA) shows that the addition of 5 w/w% of DES does not impact the membrane flexibility or polymer structure. However, in concentrations higher than 10 w/w%, the inclusion of DES could lead to high membrane rigidification without impacting the overall thermal resistance. SEM analysis of DES-enhanced membranes presented asymmetric final membranes and reaffirmed the results obtained in DMTA about rigidified structures and lower zeolite–polymer interaction with higher concentrations of DES.

Microbes in Agriculture: Prospects and Constraints to Their Wider Adoption and Utilization in Nutrient-Poor Environments

Microbes such as bacteria and fungi play important roles in nutrient cycling in soils, often leading to the bioavailability of metabolically important mineral elements such as nitrogen (N), phosphorus (P), iron (Fe), and zinc (Zn). Examples of microbes with beneficial traits for plant growth promotion include mycorrhizal fungi, associative diazotrophs, and the N2-fixing rhizobia belonging to the α, β and γ class of Proteobacteria. Mycorrhizal fungi generally contribute to increasing the surface area of soil-root interface for optimum nutrient uptake by plants. However, when transformed into bacteroids inside root nodules, rhizobia also convert N2 gas in air into ammonia for use by the bacteria and their host plant. Thus, nodulated legumes can meet a high proportion of their N requirements from N2 fixation. The percentage of legume N derived from atmospheric N2 fixation varies with crop species and genotype, with reported values ranging from 50–97%, 24–67%, 66–86% 27–92%, 50–92%, and 40–75% for soybean (Gycine max), groundnut (Arachis hypogea), mung bean (Vigna radiata), pigeon pea (Cajanus cajan), cowpea (Vigna unguiculata), and Kersting’s groundnut (Macrotyloma geocarpum), respectively. This suggests that N2-fixing legumes require little or no N fertilizer for growth and grain yield when grown under field conditions. Even cereals and other species obtain a substantial proportion of their N nutrition from associative and endophytic N2-fixing bacteria. For example, about 12–33% of maize N requirement can be obtained from their association with Pseudomonas, Hebaspirillum, Azospirillum, and Brevundioronas, while cucumber can obtain 12.9–20.9% from its interaction with Paenebacillus beijingensis BJ-18. Exploiting the plant growth-promoting traits of soil microbes for increased crop productivity without any negative impact on the environment is the basis of green agriculture which is done through the use of biofertilizers. Either alone or in combination with other synergistic rhizobacteria, rhizobia and arbuscular mycorrhizal (AM) fungi have been widely used in agriculture, often increasing crop yields but with occasional failures due to the use of poor-quality inoculants, and wrong application techniques. This review explores the literature regarding the plant growth-promoting traits of soil microbes, and also highlights the bottle-necks in tapping this potential for sustainable agriculture.

Hydrophobic hyper-cross-linked polymer shells encapsulating dispersed nanoscale CuS boosting mercury immobilization

Metal sulfides (MSs) hold significant promise for environmental remediation but are hindered by their low accommodation capacity and poor water resistance. Herein, this work reports a hybrid strategy to address these limitations by assembling highly dispersed CuS nanoparticles within the hyper-cross-linked polymer (HCP). Benefiting from the super-hydrophobicity and well-developed porosity of HCP, alongside the high dispersion and multiple active sites of CuS nanoparticles, the resultant CuS@HCP exhibits exceptional water resistance, enhanced surface area, high mass transfer ability, and substantial Hg0 adsorption capacity. The Hg0 adsorption capacity (Q90) of CuS@HCP3 reaches 1.25 and 1.391 mg/g under N2 and simulated flue gas, respectively. Notably, the normalized Q90 of coated CuS surpasses that of pristine CuS by 25-fold under N2 + 15 % H2O and its durability outstrips most previously reported mineral sulfides even in complex simulated flue gas. Universal research confirms MSs@HCP (M = Zn, Sn, and Fe) equally demonstrate over 15-fold increment in Hg0 retention under high humidity conditions compared to the pristine MSs. Such HCP hybrid strategy universally and effectively optimizes the accommodation capacity and water resistance of MSs, endowing MSs@HCP broad application prospects.

Combining nonthermal N2 plasma with a denitrifying biofilm reactor for PFAS-contaminated wastewater remediation

Perfluoroalkyl and polyfluoroalkyl substances (PFAS), commonly known as ’forever chemicals,’ pose significant environmental threats to water bodies due to their persistence and toxicity. Traditional remediation methods are often ineffective or costly. In response, this study presents a novel two-step solution combining nonthermal nitrogen (N2) plasma degradation with a denitrifying biofilm reactor to treat PFAS-contaminated wastewater efficiently. Treatment by N2 plasma resulted into PFOA and PFDA degradation efficiencies up to 45% and 60%, respectively. The low cost of N2 gas makes N2 plasma more favorable (compared to e.g. Ar plasma) for practical applications. The biofilm reactor, inoculated with activated sludge and packed by expanded clay aggregates (ECA), could efficiently remove the inorganic nitrogen produced by N2 plasma. CH3COONa was utilized as a carbon source to supply energy for denitrifying bacteria. The total nitrogen (TN) removal efficiency was up to 90% at a C/N ratio of 4.0. Also, UV254 (40–50%), turbidity (80–90%) and COD (80–90%) were removed in the biofilm reactor. Due to the non-biodegradability of PFAS, their removal (initially up to 60–90%) in the biofilm reactor was attributed to ad- or absorption on sludge and ECA. The bioreactor offers a cost-effective solution to the issue of secondary inorganic nitrogen pollution caused by N2-containing plasma. This is beneficial for broadening the practical use of both N2 plasma and air plasma. The two-step process is not only applicable for treating PFAS-contaminated wastewater but can also be applied to various fields suitable for N2 and air plasma applications.

Silica/klucel nanocomposite as promising durable adsorbent for lead removal from industrial effluents

The removal of heavy metals, such as lead, from industrial wastewater is imperative due to their detrimental effects on both human health and the environment. This study delves into investigating the feasibility of employing a novel adsorbent, specifically a silica/klucel nanocomposite, for effectively extract lead from industrial effluents. The synthesis of this nanocomposite involved a simple and cost-effective method, combining silica nanoparticles with klucel. XRD, FTIR, E-SEM, Raman, and N2 gas adsorption at − 196 °C tools were employed to prospect the formation of silica/klucel nanocomposite. Outstandingly, treating 50 ml of 50 mg/l of lead with 10 mg of adsorbent exhibited rapid removal, which reached a maximum (95%) at 60 min contact time. The resulting composite demonstrated remarkable adsorption capabilities, primarily attributed to two factors: the expansive surface area of silica nanoparticles 139.1 m2/g and the porous structure provided by klucel. Through batch adsorption experiments, the nanocomposite’s proficiency in removing lead ions from aqueous solutions became evident. The kinetics of the adsorption process were found to adhere closely to a pseudo-second-order model, hinting at chemical adsorption as the rate-determining step. Langmuir isotherm model revealed that lead ions tend to form a monolayer on the surface of the nanocomposite and the maximum adsorption capacity (qm) was 63.938 mg/g. Additionally, the nanocomposite, exhibited notable stability and could be reused multiple times, where 65% removal efficiency was announced until the 7th cycle without significant degradation in performance. In summary, the silica/klucel nanocomposite emerges as a promising and eco-friendly adsorbent for removing lead from industrial effluents. Its efficient performance and sustainability offer a compelling solution to combat heavy metal contamination, thereby contributing to environmental preservation and human well-being.

Co‐Pyrolytic Recycling of Bakelite and Polymethyl Methacrylate: Kinetic, Synergistic, and Thermodynamic Analysis

AbstractBakelite, a thermosetting plastic, has limited feasibility for thermal recycling processes such as pyrolysis, unlike thermoplastics, due to its inherent tendency to get charred upon heating and difficulty in being converted into valuable fuel and chemical compounds. In this study, the co‐pyrolysis of bakelite and poly methyl methacrylate is explored to improve the thermal degradation and thus recycling feasibility of bakelite by pyrolysis. The kinetics and thermodynamics of the co‐pyrolysis of blended samples are analyzed using different kinetics models. The thermal degradation experiments of the sample are conducted from ambient to 1000 °C at five various heating rates of 5, 10, 20, 30, and 50 °C/min in an inert N2 gas environment. The results showed that adding poly methyl methacrylate to bakelite changes the pyrolytic degradation temperature and weight loss trend. The kinetic analysis reveals that the thermal degradation at 220–345 °C follows an F2.5 order‐based model with an average activation energy of 181 kJ/mol, while the degradation at 345–475 °C follows an F2 order‐based model with an average activation energy of 318 kJ/mol. The enthalpy changes and free energy change associated with thermal degradation exhibit a positive trend while that of entropy change shows a negative trend. With blending the free energy change and entropy change decreased while enthalpy change increased. During batch pyrolysis at 450 °C, the PMMA‐Bakelite blend generates oil (49.17 %), wax (12.36 %), residue (15.36 %), and gas (23.11 %). According to FTIR and GC‐MS analyses, the pyrolytic oil produced by the co‐pyrolysis of the blended sample at 450 °C comprises 32.23 % saturated hydrocarbons (C9–40), 20.97 % unsaturated hydrocarbons (C6–24), and 46.80 % oxygenated material (C5–19). These findings can assist in the optimization of pyrolysis reactor design for the recycling of thermosetting plastics.

A Facile Two-Step Utilization of Sorghum Waste Derived Activated Carbon

Sorghum (Sorghum bicolor (L.) Moench) is an agricultural commodity that produces waste, including stems, during its cultivation. Sorghum stems can be used as an alternative precursor for forming activated carbon (AC) with a high surface area by utilizing ZnCl2 as an activator and followed by a pyrolysis process at 750 °C under N2 gas. In this study, AC from sorghum stems was sequentially used as an adsorbent for heavy metals in wastewater, as well as applied as an anode material for lithium-ion batteries. From the characterization analysis, the synthesized AC has an amorphous structure, a high carbon content of > 90%, and a surface area of 1189 m2/g. AC was applied to adsorb 10, 50, and 100 ppm of metal cobalt (Co) at 30 °C. The adsorption isotherm and kinetics of metal Co showed an adsorption capacity of around 28.2 mg/g. The Langmuir isotherm model also describes Co adsorption and follows the pseudo-first-order equation. As for the Li-ion anode material, the ACs material is fabricated on a cylindrical battery with LiNi0.8Co0.1Mn0.1O2 as the counter cathode material. The specific discharge capacity results are 104 mAh/g at the voltage window of 2.7-4.3 V. The sequential utilization of sorghum stem-derived activated carbon can improve the product’s sustainability, and such an approach is promising to be applied in other biomass-based waste treatments.Keywords: Activated carbon, adsorption, battery, biomass, sorghum

Enhancement of removing OH bonds from low-temperature deposited silicon oxide films by adding water vapor into NH3 gas annealing at 130 oC

Abstract It was found that annealing with water-vapor-added NH3 gas (water-added NH3) is more effective than with dry NH3 at removing residual OH bonds in silicon oxide (SiOx) films deposited by atmospheric chemical vapor deposition with an organic silicon source. Fourier transform infrared spectra showed that reduction amount of OH bonds using the water-added NH3 was ~4 or ~1.3 times larger than using the conventional dry N2 or dry NH3 mixed with N2 gas without water, respectively. This result is something strange because water can be a potential candidate of OH sources. The effect of water vapor on OH-bond removal can be explained by considering following three factors. One is that low-temperature SiOx films are constrained somewhat, the second is that strained Si-O-Si bonds are in higher or more unstable energy state than strain-free ones, and the third is that highly strained bonds are easily hydroxylated to form Si-OH bonds.

Machine Learnable Language for the Chemical Space of Nanopores Enables Structure-Property Relationships in Nanoporous 2D Materials.

The synthesis of nanoporous two-dimensional (2D) materials has revolutionized fields such as membrane separations, DNA sequencing, and osmotic power harvesting. Nanopores in 2D materials significantly modulate their optoelectronic, magnetic, and barrier properties. However, the large number of possible nanopore isomers makes their study onerous, while the lack of machine-learnable representations stymies progress toward structure-property relationships. Here, we develop a language for nanopores in 2D materials, called STring Representation Of Nanopore Geometry (STRONG), that opens the field of 2D nanopore informatics. We show that STRONGs are naturally suited for machine learning via recurrent neural networks, predicting formation energies/times of arbitrary nanopores and transport barriers for CO2, N2, and O2 gas molecules, enabling structure-property relationships. The machine learning models enable the discovery of specific nanopore topologies to separate CO2/N2, O2/CO2, and O2/N2 gas mixtures with high selectivity ratios. We also enable the rapid enumeration of unique configurations of stable, functionalized nanopores in 2D materials via STRONGs, allowing systematic searching of the vast chemical space of nanopores. Using the STRONGs approach, we find that a mix of hydrogen and quinone functionalization results in the most stable functionalized nanopore configuration in graphene, a discovery made feasible by expedited chemical space exploration. Additionally, we also unravel the STRONGs approach as ∼1000 times faster than graph theory algorithms to distinguish nanopore shapes. These advances in the language-based representation of 2D nanopores will accelerate the tailored design of nanoporous materials.

Marine N2-fixer Crocosphaera waterburyi.

Marine N2-fixing cyanobacteria, including the unicellular genus Crocosphaera, are considered keystone species in marine food webs. Crocosphaera are globally distributed and provide new sources of nitrogen and carbon, which fuel oligotrophic microbial communities and upper trophic levels. Despite their ecosystem importance, only one pelagic, oligotrophic, phycoerythrin-rich species, Crocosphaera watsonii, has ever been identified and characterized as widespread. Herein, we present a new species, named Crocosphaera waterburyi, enriched from the North Pacific Ocean. C. waterburyi was found to be phenotypically and genotypically distinct from C. watsonii, active in situ, distributed globally, and preferred warmer temperatures in culture and the ocean. Additionally, C. waterburyi was detectable in 150- and 4000-meter sediment export traps, had a relatively larger biovolume than C. watsonii, and appeared to aggregate in the environment and laboratory culture. Therefore, it represents an additional, previously unknown link between atmospheric CO2 and N2 gas and deep ocean carbon and nitrogen export and sequestration.

Bioremediation of nitrate in agricultural drainage ditches: Impacts of low-grade weirs on microbiomes and nitrogen cycle gene abundance

Artificial drainage is essential for the success of modern agriculture, but it can also accelerate the movement of nutrients, especially nitrate, from soil to surrounding and downstream water bodies. Removal of nitrate from agricultural drainage by using controlled drainage systems, such as ditches installed with low-grade weirs, has been shown to help reduce nutrient loading into watersheds. However, the effect of low-grade weirs varies greatly, likely due to the differences in climate, system designs (e.g., hydraulic characteristics), and the resulting variation in microbial structures and functions in the ditch. In this study, we analyzed the temporal and spatial dynamics of microbiomes in a paired ditch system with weir-installed and uninstalled (control) channels over two years by using the 16S rRNA gene amplicon sequencing and the high-throughput quantitative PCR targeting various N cycle-associated genes [the Nitrogen Cycle Evaluation (NiCE) chip]. The installation of the low-grade weir had a significant impact on the microbiome structure and the distribution of denitrifiers. Microbiome structures also differed significantly between the ditch inlets and the outlets. Denitrification functional genes were more abundant in the inlets than in the other locations and in the channel installed with a low-grade weir. Additionally, oxygenic denitrifiers that utilize nitric oxide dismutase (nod) to produce N2 and O2 gases from nitric oxide were detected in the ditch channels, suggesting the occurrence of nitrate removal process that bypasses the production of nitrous oxide (N2O). The ditch microbiomes sampled during high-flow seasons (i.e., spring and fall) exhibited greater similarity to each other than microbiomes sampled during low-flow seasons (i.e., summer). Taken together, this study indicates that the low-grade weirs have the potential to foster a more favorable environment for denitrifiers, resulting in an increase in the abundance of denitrification functional genes. These findings could offer valuable insights into system management and optimization strategies.

Adsorption and evolution of N2 molecules over ZnO monolayer: a combined DFT and kinetic Monte-Carlo insight

AbstractA large surface area, wide band gap, and unique bonding property between Zn and O atoms make the hexagonal ZnO monolayer attractive as a gas sensor. In the present work, the adsorption and evolution of nitrogen (N2) molecules over a ZnO monolayer have been studied using two different theoretical methods: van der Waals density functional theory (vdW-DFT) and kinetic Monte-Carlo (kMC) simulation. The adsorption and diffusion (hopping over the surface) energy of a N2 gas molecule has been calculated considering the different sites over the ZnO substrate using the revPBE-vdW functional. Bader charge, electron localization function analysis, density of states and band structure plotting have been used to understand the adsorption mechanism. Lateral repulsive interaction between two N2 molecules limits the maximum packing number of gas molecules within one hexagonal ring. The output of the vdW-DFT calculation has been fed to the kMC code to predict the rate of adsorption, desorption, and diffusion, along with the overall surface coverage at different temperatures and pressures. Finally, the change in the N2 adsorption energy has been predicted with the increase of the ZnO layer number.

Advances in Selective Detection of Cadaverine by Electronic, Optical, and Work Function Sensors Based on Cu-Modified B12N12 and Al12N12 Nanocages: A Density Functional Theory (DFT) Study.

This work explores Cu-modified B12N12 and Al12N12 nanocages for cadaverine diamine (Cad) detection using advanced density functional theory (DFT) calculations. The study found that Cu modification altered the geometry of the nanocages, increased the dipole moment, reduced the energy gap, and enhanced the reactivity. While pristine B12N12 and Al12N12 were not sensitive to Cad, the modified Cu(b64)B12N12 and Cu(b66)Al12N12 nanocages showed significantly higher electronic sensitivity (Δgap = 39.8% and 35.6%, respectively), surpassing the literature data. However, molecular dynamics (MD) revealed that the Cu(b66)Al12N12 nanocage is not stable in the long term, since the nanocage changes configuration to Cu(b64)Al12N12, which is less sensitive and has an even longer recovery time for Cad sensing. Adsorption energy analysis (Eads) showed a strong interaction of Cad/nanocages, while charge analysis suggested that the nanocages act as Lewis acids, accepting electrons from Cad. UV-vis spectra confirmed that Cu(b64)B12N12 responds optically to the presence of Cad. Furthermore, Cu(b64)B12N12 showed greater sensitivity to Cad compared to NO, H2, H2S, CO, COCl2, N2O, N2 gases, or H2O, showing high selectivity to diamine against interfering gases or water, standing out as a promising material for environmental applications in electronic, optical or work function sensors for cadaverine detection, even in humid environments.

Spectroscopic, structural characterization, along with DFT calculation, of a new cadmium(II) acetato meso-arylporphyrin: Theoretical study on NO2, CO2, N2, NO2, and SO2 gas-sensing and analysis of electrical conductance and dielectric properties

The paper presents a combined experimental and computational investigation of the cadmium(II) (acetato)‑meso-tetra(para-methoxyphenyl)porphyrin ion complex [Cd(TMPP)(OAc)]- (complex 1), which was prepared by the reaction of [Cd(TMPP)] with an excess of NaOAc and crysptand-222 in chloroform. This new Cd(II) meso‑arylporphyrin was characterized by elementary analysis and UV–Vis, IR, and 1H NMR spectroscopic techniques along with single crystal X-ray diffraction. This later study shows that the Cd2+center ion adopts a distorted square pyramidal geometry and is coordinated by the four nitrogens of the TMPP porphyrinate and the oxygen atom of the acetato axial ligand. The intermolecular interactions in the crystal lattice of [Cd(TMPP)(OAc)]-, determined using the PLATON program and Hirshfeld surfaces analysis, are of types O__H…O, C__H…H, C__H…Cl, C__H…Cg and C__Cl…Cg (Cg is the centroid of a phenyl or a pyrrole ring) involving the [Cd(TMPP)(OAc)]- ion complex, the [Na(crypt-222)]+ counterion, and the chloroform and water molecules found in the crystal lattice of complex 1. Using DFT calculations at the DFT/B3LYP-D3/lanL2DZ level of theory HOMO–LUMO orbitals of 1 and several global reactive parameters of this compound were calculated. The 3D-MEP plots of [Cd(TMPP)(OAc)]- were also determined. This theoretical study includes the sensing properties of complex 1 and the NO2, CO2, N2, and SO2 gas molecules. Furthermore, experimental tests have been carried out concerning the impedance and dielectric spectroscopy of the InGa/[Cd(TMPP)(OAc)]/InGa device.

Tunnel silicon oxynitride phase transformation for n-type polysilicon passivating contacts in crystalline silicon solar cells

The study investigates the fabrication and characterization of tunnel oxynitride (TON) layers produced using Plasma-Enhanced Chemical Vapor Deposition (PECVD) at different pressure and power variations. The aim is to explore TON layers as potential substitutes for conventional SiO2 in Tunnel Oxide Passivated Contact (TOPCon) solar cells. Foe this purpose, an effective oxide thickness (EOT) of 1.1–1.2 nm and 1.5–1.6 nm has been achieved by treating the TON samples with NH3 and N2 gas plasma, respectively. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed critical variations in the chemical bonding within TON layers, which exhibit different properties based on the deposition conditions. The presence of nitrogen-nitrogen and nitrogen–hydrogen bonds is prominently influenced by changes in the PECVD parameters, directly affecting the layer’s optical and electronic properties. Notably, the presence of hydroxyl (O–H) and amino (NH2) groups within the TON structure suggests an improvement in surface passivation, essential for optimizing solar cell performance and durability. A lifetime of 737 and 823 μs has been recorded for N2 and NH3 samples, compared to the NAOS 710 μs reference sample. NH3 plasma-treated samples show an improved iVoc of 736 mV, indicating better phase transformation and passivation quality than N2 plasma treatment and the NAOS reference sample.

Comparison of Mercury Intrusion and Nitrogen Adsorption Measurements for the Characterization of Certain Natural Raw Materials Deposits

The porosity of materials is important in many applications, products and processes, such as electrochemical devices (electrodes, separator, active components in batteries), porous thin film, ceramics, soils, construction materials, ..etc. This can be characterized in many different methods, and the most important methods for industrial purposes are the N2 gas adsorption and mercury porosimetry. In the present paper, both of these techniques have been used to characterize some of Iraqi natural raw materials deposits. These are Glass Sand, Standard Sand, Flint Clay and Bentonite. Data from both analyses on the different types of natural raw materials deposits are critically examined and discussed. The results of specific surface areas showed considerable difference between the two sets of data on the same material. This indicates that the material have an external surface which can not be measure by mercury porosimeter. Also pore size distribution data obtained from N2 adsorption measurements shows a wide range of the smallest pore size. This result suggests that materials have micropores using IUPAC definitions of pore size.

Elliptically polarized high-order harmonic generation from N[formula omitted]-CO mixed gases

We theoretically study the elliptically polarized high-order harmonic generation from N2-CO mixed gases. Our simulations show that the polarization of HHG is highly sensitive to both the mixing ratio and molecular alignment angle. In particular, even a small addition of CO gas results in a significant enhancement of harmonic ellipticity compared to pure N2 gas. Under a proper mixing ratio and molecular alignment angle, a large ellipticity of HHG is observed, which is larger than that in reported N2-Ar mixture. Furthermore, when considering the molecular alignment effect, the dependence of ellipticity of HHG on mixing ratio exhibits slight variations. These findings pave the way for generating elliptically polarized extreme ultraviolet pulses.

Apparent effective ionization coefficient in N2 and O2 gas mixtures determined with two separate methods

N2:O2 gas mixtures are important for applications of atmospheric pressure plasmas such as ozone production, air purification from VOCs and NOx and surface treatments. Fundamental parameters such as the effective ionization coefficient are inputs for theoretical plasma models for applications and must thus be accurately known. This work determined the apparent effective ionization coefficient in N2:O2 mixtures in a broad reduced electric field strength E/N range of 150–1200 Td with two separate methods and compared with BOLSIG+ calculations of reduced effective ionization coefficient. Additionally, the equilibrium distance required to establish a steady-state electron energy distribution was estimated from spatial profiles of optical emission.

Cu-trimesate and mesoporous silica composite as adsorbent showing enhanced CO2/CH4 and CO2/N2 selectivity for biogas and flue gas separation

Due to their diverse structure, high porosity, and tunable functionality, Metal-Organic Frameworks (MOFs) hold great potential as materials for diverse applications, including gas separation. Material science researchers are focusing on creating flexible materials that have special properties. Most of the latest research mainly concentrates on fabricating composite materials of MOFs and other functional materials. These MOF-based composites can mitigate the limitations of pure MOFs and may even perform better than the individual components. Here, we present a systematic study on the effect of solvent in synthesising a composite (Cu-BTC@SBA-15) of Cu-trimesate MOF (aka CuBTC) and ordered mesoporous silica SBA-15, showing considerable improvement in selectivity for CO2 adsorption from the flue gas and biogas. The pristine Cu-BTC, SBA-15 and the composites with different content of Cu-BTC were characterized by PXRD, BET, FT-IR, SEM, TEM and TGA techniques. The pure gas adsorption isotherms were measured for CO2, CH4, and N2 gases. Ideal Adsorbed Solution Theory (IAST) is used for the binary selectivity calculations for gas systems such as CO2/CH4 and CO2/N2 in the context of biogas and flue gas separation. The composite exhibited an increase in CO2/CH4 selectivity by 39 % compared to pure Cu-BTC and 85 % compared to pure SBA-15. For the CO2/N2 system, the composite showed 38 % higher selectivity than Cu-BTC. The work has significance in the design of effective MOF-based composites for CO2 separation. Our work might open up a new route to design multifunctional materials for worldwide applications through an adsorptive and or mixed matrix membrane route.

Unveiling gas transport mechanisms in tunable MXene nanochannels: Insights from molecular dynamics simulations

MXene-based membranes have shown tremendous potential in gas separation applications. Here, molecular dynamics (MD) simulations are used to investigate the effects of varying the structural parameters of Ti₃C₂O₂ nanochannels on the permeation and separation performance of H₂, CO₂, N₂, and CH₄ gases. The results demonstrate that the interlayer spacing significantly influences gas permeability, with wider channels generally exhibiting higher permeance. Channel length, however, has a relatively minor impact on permeability, varying by gas species. Potential of mean force (PMF) analysis reveals that CO₂ molecules face a notable energy barrier at the channel entrance and have the strongest interactions with the MXene interface within the channel, potentially leading to blockage. Spatial density analysis further confirms this CO₂ blockage phenomenon, which diminishes as the interlayer spacing increases. In terms of gas separation selectivity, H₂/CH₄ and H₂/CO₂ mixtures exhibit high selectivity, with maximum values of 41.08 and 27.06, respectively. Notably, the H₂/CO₂ system exhibits a positive correlation between permeability and selectivity, breaking the traditional permeability-selectivity trade-off. This anomalous behavior can be attributed to the CO₂ blockage effect. This study provides theoretical guidance for the design and optimization of MXene-based membrane materials in practical applications.