Gas Molecules Research Articles

Electrochemical C(sp3)−H Functionalization Using Acetic Acid as a Hydrogen Atom Transfer Reagent

AbstractIn this study, we developed a novel electrochemical protocol that enables the functionalization of inherently inert C(sp3)−H bonds. In this protocol, one‐electron oxidation of acetic acid was used to successfully generate methyl radical, which cleaves the benzylic C(sp3)−H bonds of the substrates via a hydrogen atom transfer (HAT) process, and further reaction with the formed species yields the targeted C(sp3)−H functionalized products. To the best of our knowledge, this is the first example of the use of acetic acid in a HAT process. Notably the reaction has environment‐friendly and fine atom economy nature: the reaction is driven by the electrochemical conditions in the absence of expensive or hazardous reagents, producing only gaseous small molecules, hydrogen, carbon dioxide, and methane, as side products.

Ionization Processes of Negative Corona Discharge Part 1. Review and Experiment

The purpose of the research is an experimental study of physical processes in the near-electrode zones of negative point electrodes in an electronegative gas (air) under the condition of a high-voltage field.Methods. Video image analysis, current-voltage characteristics measurements, and spectroscopy are used. The current-voltage characteristics of the corona discharge ignition voltage in the environment are measured, the problem of experimental identification of surface charges, the mechanism of negative corona discharge ignition, and the ionic structure of streamers is studied, degradation of electrodes during negative corona discharge, spectrum of corona discharge creation and electromagnetic sound.Results. It is shown that at small radii of curvature of needle electrodes, the development of a negative corona discharge is due to the cold emission of electrons, and on flat and slightly curved negative electrodes, due to the capture of surface electrons by electron-withdrawing molecules. The mechanism of ignition of a corona discharge in an electronegative gas with a negative needle, the structure of streamers from negative needles, the emission spectrum and ethonic degradation of electrodes have been studied.Conclusions. The ignition of a negative corona discharge at small radii of the tips of the pointed needles (ro less than tens of microns) is due to the cold emission of electrons followed by impact ionization of neutral molecules. With slightly curved electrodes, the appearance of a negative corona discharge is due to the capture of surface electrons by electronegative gas molecules with subsequent plasma-chemical reactions. The formation of surface electrons depends on many factors: the presence and structure of oxide films (roughness, defects, etc.), which determine the electron work function and form local fields at the tips of microtips. The appearance of a corona discharge leads to degradation of the corona electrodes, expressed in the spraying of the tips of the points and the melting of the needles. In the dark region of the negative corona discharge (U < U*), photons in the in the ultraviolet spectrum (UV spectrum) are emitted, and when U > U*, in addition to UV photons, photons in the visible region of the spectrum are emitted. Glow fluctuations are caused by the chaotic dynamics of the formation of injection centers (melted tubercles - ectons) on the surface of the corona electrode. The ignition of a corona discharge is accompanied by sound emission with a frequency of about 300 Hz.

Toward a Comprehensive Understanding of the Anomalously Small Contact Angle of Surface Nanobubbles.

Experimental studies have demonstrated that the gas phase contact angle (CA) of a surface nanobubble (SNB) is much smaller than that of a macroscopic gas bubble. This reduced CA plays a crucial role in prolonging the lifetime of SNBs by lowering the bubble pressure and preventing gas molecules from dissolving in the surrounding liquids. Despite extensive efforts to explain the anomalously small CA, a consensus about the underlying reasons is yet to be reached. In this study, we conducted experimental investigations to explore the influence of gas molecules adsorbed at the solid-liquid interface on the CA of SNBs created through the solvent exchange (SE) method and temperature difference (TD). Interestingly, no significant change is observed in the CA of SNBs on highly oriented pyrolytic graphite (HOPG) surfaces. Even for nanobubbles on micro/nano pancakes, the CA only exhibited a slight reduction compared to SNBs on bare HOPG surfaces. These findings suggest that gas adsorption at the immersed solid surface may not be the primary factor contributing to the small CA of the SNBs. Furthermore, the CA of SNBs formed on polystyrene (PS) and octadecyltrichlorosilane (OTS) substrates was also investigated, and a considerable increase in CA was observed. In addition, the effects of other factors including impurity, electric double layer (EDL) line tension, and pinning force upon the CA of SNBs were discussed, and a comprehensive model about multiple factors affecting the CA of SNBs was proposed, which is helpful for understanding the abnormally small CA and the stability of SNBs.

Graphene in gas separation membranes—State-of-the-art and potential spoors

Graphene and derivatives have been frequently used to form advanced nanocomposites. A very significant utilization of polymer/graphene nanocomposite was found in the membrane sector. The up-to-date overview essentially highpoints the design, features, and advanced functions of graphene nanocomposite membranes towards gas separations. In this concern, pristine thin layer graphene as well as graphene nanocomposites with poly(dimethyl siloxane), polysulfone, poly(methyl methacrylate), polyimide, and other matrices have been perceived as gas separation membranes. In these membranes, the graphene dispersion and interaction with polymers through applying the appropriate processing techniques have led to optimum porosity, pore sizes, and pore distribution, i.e., suitable for selective separation of gaseous molecules. Consequently, the graphene derived nanocomposites brought about numerous revolutions in high performance gas separation membranes. The structural diversity of polymer/graphene nanocomposites has facilitated the membrane selective separation, permeation, and barrier processes especially in the separation of desired gaseous molecules, ions, and contaminants. Future research on the innovative nanoporous graphene-based membrane can overcome design/performance related challenging factors for technical utilizations.

Molecular simulations of hydrogen diffusion in underground porous media: Implications for storage under varying pressure, confinement, and surface chemistry conditions

Assessing the feasibility of porous formations for hydrogen geo-storage demands a comprehensive understanding of hydrogen (H2) transport behavior in porous media at subsurface conditions. In this study, we employ molecular dynamics simulations to evaluate the effects of pressure (20–500 atm), pore size (2–20 nm), and surface composition on H2 diffusion and interactions within organic and inorganic slit pores. Our analysis of H2 density profiles and interaction energies reveals a distinct preference for H2 molecules to adsorb more readily onto graphene surfaces than kaolinite surfaces. However, self-diffusion results demonstrate that H2 molecules interact relatively weakly with both substrate types. Further insights are provided by velocity autocorrelation functions, emphasizing the occurrence of wall-mediated collisions as H2 molecules diffuse along the pore surfaces, particularly within kaolinite. This highlights the significance of surface roughness in mitigating H2 loss via diffusion in subsurface nanopores, given the small molecular size of H2 and its limited interactions with both organic and inorganic materials. Furthermore, the results demonstrate that self-diffusion coefficients in both pore types increase with pore size and decrease with pressure. Notably, surface composition plays a critical role in low-pressure environments, with self-diffusion coefficients beginning to converge beyond a pressure of 100 atm. Self-diffusion coefficients also become less sensitive to slit aperture beyond a pressure of 50 atm. In high-pressure environments, hydrogen transport is governed by thermal collisions between gas molecules, leading to negligible property variations between pore types. These findings hold significance in the investigation of efficient H2 storage within porous media and caprock formations.

Gas‐Induced Electrical and Magnetic Modulation of Two‐Dimensional Conductive Metal−Organic Framework

Controlled modulation of electronic and magnetic properties in stimuli‐responsive materials provides valuable insights for the design of magnetoelectric or multiferroic devices. This paper demonstrates the modulation of electrical and magnetic properties of a semiconductive, paramagnetic metal−organic framework Cu3(C6O6)2 with small gaseous molecules, NH3, H2S, and NO. This study merges chemiresistive and magnetic tests to reveal that the MOF undergoes simultaneous changes in electrical conductance and magnetization that are uniquely modulated by each gas. The features of response, including direction, magnitude, and kinetics, are modulated by the physicochemical properties of the gaseous molecules. This study advances the design of multifunctional materials capable of undergoing simultaneous changes in electrical and magnetic properties in response to chemical stimuli.

Gas-Induced Electrical and Magnetic Modulation of Two-Dimensional Conductive Metal-Organic Framework.

Controlled modulation of electronic and magnetic properties in stimuli-responsive materials provides valuable insights for the design of magnetoelectric or multiferroic devices. This paper demonstrates the modulation of electrical and magnetic properties of a semiconductive, paramagnetic metal-organic framework Cu3(C6O6)2 with small gaseous molecules, NH3, H2S, and NO. This study merges chemiresistive and magnetic tests to reveal that the MOF undergoes simultaneous changes in electrical conductance and magnetization that are uniquely modulated by each gas. The features of response, including direction, magnitude, and kinetics, are modulated by the physicochemical properties of the gaseous molecules. This study advances the design of multifunctional materials capable of undergoing simultaneous changes in electrical and magnetic properties in response to chemical stimuli.

DFT studies of the structural and electronic properties of PdGen (n= 1-11) clusters and adsorption capacity for some gas molecules

Abstract Density Functional Theory (DFT) calculations have been employed for the theoretical exploration of the geometric structures and electronic characteristics of PdGen (n = 1 - 11) clusters. An analysis of the second- order energy differences indicates that PdGe7 and PdGe10 clusters possess superior thermodynamic stability. PdGe10 showcases the highest chemical stability and the lowest chemical activity, attributed to its largest energy gap value (Eg). Vertical ionization potential (VIP) and vertical electron affinity (VEA) exhibit the decreasing and increasing trends, respectively, with the increase of the number n of Ge atoms. PdGe10 presents the highest electronegativity among these clusters. The study on the adsorption properties of PdGen (n=7,10) clusters with gases such as CO, NO, NO2, NH3, SO2 and H2S yields the adsorption structures, adsorption energies, Mulliken charge transfer, and changes in electronic properties. All the listed gas molecules chemically adsorb onto PdGe7. PdGe10 has a better adsorption performance for NO2, while its adsorption ability for CO is poorer. The potentiality of PdGen (n = 7, 10) clusters as gas sensors is also evaluated, which reveals that NO adsorption significantly affects the electronic properties, especially conductivity, of the systems. PdGe10 has an appropriate NO adsorption capacity and significant charge transfer, with the adsorption energy of -0.278 eV and the recovery time of about 10-9 seconds, indicating its fast response and hence good potentiality as the NO sensor. In contrast, PdGe7 has a higher adsorption capability towards NO with a lower adsorption energy of -1.16 eV, leading to difficulty in desorption and a longer recovery time of over 12 hours. Thus, PdGe10 would act as a potential gas sensing material.

Enantioselective Nickel‐Catalyzed Denitrogenative Transannulation En Route to N‐N Atropisomers

Nickel‐catalyzed transannulation reactions triggered by the extrusion of small gaseous molecules have emerged as a powerful strategy for the efficient construction of heterocyclic compounds. However, it’s asymmetric synthesis remains challenging because of the difficulty in controlling stereo‐ and regioselectivity. Herein, we report the first nickel‐catalyzed asymmetric synthesis of N–N atropisomers by the denitrogenative transannulation of benzotriazones with internal alkynes. A broad range of N–N atropisomers was obtained with excellent regio‐ and enantioselectivity under mild conditions. Moreover, density functional theory (DFT) calculations provided insights into the nickel‐catalyzed reaction mechanism and enantioselectivity control.

Enantioselective Nickel-Catalyzed Denitrogenative Transannulation En Route to N-N Atropisomers.

Nickel-catalyzed transannulation reactions triggered by the extrusion of small gaseous molecules have emerged as a powerful strategy for the efficient construction of heterocyclic compounds. However, it's asymmetric synthesis remains challenging because of the difficulty in controlling stereo- and regioselectivity. Herein, we report the first nickel-catalyzed asymmetric synthesis of N-N atropisomers by the denitrogenative transannulation of benzotriazones with internal alkynes. A broad range of N-N atropisomers was obtained with excellent regio- and enantioselectivity under mild conditions. Moreover, density functional theory (DFT) calculations provided insights into the nickel-catalyzed reaction mechanism and enantioselectivity control.

Low experimental thermal conductivity of zirconium metal-organic framework UiO-66

Using laser flash analysis, the low thermal conductivity of the pressed Zirconium metal-organic framework (UiO-66) powder pellet was obtained. As a result, the density ρ, thermal diffusivity α, specific heat capacity cP, and low thermal conductivity κexp of the pressed UiO-66 powder pellet at 300 K are observed to be 1.258 g/cm3, 0.001 59 cm2/s, 0.7765 J/g K, and 0.156 W/m K, respectively. Due to the presence of the 12-coordinated nodes with six transfer pathways, the thermal transport of the UiO-66 particles is preferred through linkers to metal sites. The low thermal conductivity follows the trend of vacuum < argon (Ar) < air < helium (He) since the entrapped gas molecules provide additional heat transfer channels inside the particles and between the particles. The low thermal conductivity along with a weak temperature-dependent thermal conductivity are elucidated in terms of boundary scattering.

Theoretical study on the capture of toxic gases by ionic liquids encapsulated in assembled belt[14[pyridine

In the current study, self-assembled belt[14]pyridine (BP) encapsulated IL (tetramethylammonium chloride (TMACl)) is theoretically explored to capture greenhouse gases (GHGs) at B3LYP-D3/6-311G(d,p) level of theory. The encapsulation of TMACl in assembled belt[14]pyridine is thermodynamically feasible as revealed through high interaction energy value of −50.7 kcal/mol. Moreover, the results of capturing of gas molecules (SO2, CO2, CO and CH4) show that attractive forces involved in capturing of gases are strong van der Waals forces i.e., London dispersion forces and electrostatic interactions. The synergic effect of self-assembled belts and ionic liquid results in significantly high interaction energy values ranging from −7.88 to −25.92 kcal/mol for capturing of gas molecules. Furthermore, the interaction between BP-TMACl and gas molecules is studied in detail through natural bond orbital (NBO) analysis. NBO results show the charge transfer between the fragments (BP-TMACl and gases) which is further validated through EDD analysis. The charge shifts towards all of the captured gas molecules but the most prominent change in NBO charges is shown by captured SO2. The successful charge transfer indicates better interaction in the designed systems. Additionally, the type and strength of interactions involved in the process of encapsulation is studied through quantum theory of atoms in molecules (QTAIM) and noncovalent interactions (NCI) analysis. NCI analysis clearly shows that gases are captured by BP-TMACl complex through strong van der Waals forces. However, in capturing of SO2, strong electrostatic attractive forces are also involved. The nature of attractive forces is confirmed through QTAIM analysis. Furthermore, the relation between recovery time and desorption energy of captured gas molecules has been studied. The strongest absorption for SO2 results in prolonged recovery time for it (as compared to the other gas molecules). AIMD analysis is performed to find the dynamical stability of assembled-belts before and after loading ionic liquids along with gases to be captured. These results reveal that assembled-belts are suitable for encapsulation of ionic liquids along with capturing of gases. Overall, the best results are shown for SO2 capture. The study intends to deliver valuable information on the important progress in the environmental-remediation field and we hope our work is going to inspire more investigators to provide novel research on such challenging tasks.

Influence of Be vacancy on 2D BeN4 single-layer for enhanced H2S sensing: prediction from first-principles simulations

Abstract A notable surge in research interest directed towards the exploration and development of two-dimensional (2D) materials, specifically in the realm of advancing nano-devices, with a special focus on applications in gas detection, has been observed. Among these materials, the spotlight has fallen on a newly synthesized single-layered Dirac Semimetal, known as BeN4, which holds great promise as a potential candidate for an efficient gas sensor. The current investigation uses first-principles calculations to examine the H2S detection capability of pristine and point-defect-tempted BeN4 single-layers. The H2S molecule has been observed to be weakly adsorbed on pure BeN4 through weak Van der Waals (vdW) interaction exhibiting very low adsorption energy of -0.0726 eV and insignificant charge transport. The impact of the Be vacancy point defect in BeN4 was the surge in H2S adsorption energy to -0.582 eV, manifested by enhanced charge transmission (0.02e) from the H2S molecule to the BeN4 with Be defects. The reasonable physical steadiness and modest recovery time (6 ms) at ambient conditions indicate the possibility of Be point-defected BeN4 being a contender as a sensor material for designing and developing a robust H2S gas sensor. In addition, the sensor exhibited a selective response towards the H2S gas molecules. Our findings will provide a reference line for the fabrication of innovative H2S detectors, showcasing the practical implications of the observed enhancements in H2S adsorption energy and charge transmission in Be point-defected BeN4 structures.

Round-the-Clock and Continuous Generation of Hydrogen and Oxygen

The main methods of industrial hydrogen production are: steam restructuring of methane and natural gas; coal gasification; biotechnology; water electrolysis. The most efficient method for producing pure hydrogen and oxygen is to produce pure hydrogen and oxygen in a photoelectrochemical cell. A photoelectrochemical cell produces hydrogen and oxygen directly from solar energy. In a photoelectrochemical cell, a combined anode, made from silicon semiconductor and metal mesh with large cells, submerged in water electrolyte solution, agitated by four photons of light, forms an oxygen molecule, which in the form of a gas bubble lifts from the surface of anode to the free surface of the water electrolyte solution. Two hydrogen cations, formed because of the dissociation of water, reaching the cathode, form a gaseous hydrogen molecule, which, turn into an electrolysis bubble, lifts from surface of cathode to the free surface of the water electrolyte solution. The article presents a new method for round-the-clock and continuous generation of hydrogen and oxygen, using a developed photoelectrolyzer-generator, taking a horizontally located combine anode, made from silicon semiconductor and metal mesh with large cells and burnt graphite cathode (electrolysis base) at the bottom of the photoelectrolyzer-generator; a membrane from fire hose material, located between electrodes; device, regulating the gap between the electrodes. Round-the-clock and continuous production of hydrogen and oxygen in the photoelectrolyzer-generator is ensured by using lamp, including LED with a daylight battery charger as a useful electrical load, which brightens the combined anode, made from silicon semiconductor and metal mesh with large cells at night until the morning and by continuously filling the photoelectrolyzer-generator with water.

Niobium doped MoS2 with double S vacancy defects as gas sensing materials for sulfur-containing gas molecules: A first-principle investigation

Electronic and adsorption properties of MoS2 with single S vacancy (MoS2 (VS)) and double S vacancy defects (MoS2 (V2S)) toward three gas molecules (SO2, H2S and SO3) are studied based on the density functional theory (DFT). The adsorption energy, energy band, density of states (DOS), charge density difference (CDD), highest occupied molecule orbital/lowest unoccupied molecule orbital (HOMO/LUMO) and work function are calculated. The results indicate that pristine MoS2 is not suitable for high-sensitivity sensing detection for SO2, H2S and SO3, which exhibits weak adsorption forces. At the same time, MoS2 (VS) and MoS2 (V2S) are still physical adsorption for three gas molecules. Therefore, the synergistic effect of double S vacancies and Nb doping on the adsorption characteristics of MoS2 is studied. The results show that the adsorption type of both MoS2 (V2S)/2Nb and MoS2 (V2S)/3Nb for H2S is changed from physical adsorption to chemical adsorption. The corresponding physical mechanism is discussed.

Computational investigation on adsorption and activation of atmospheric pollutants CO, NO and SO on small cobalt clusters

The adsorption of CO, NO and SO on cobalt clusters (Co2-7) were investigated using density functional theory. The adsorption energy supports efficient chemisorption of greenhouse gases on the cobalt clusters, with CO and NO forming one to three CoC and CoN bonds, respectively, the first being the most stable. The SO formed bidentate complexes with CoS and CoO bonds in ConSO structures, displaying notably high adsorption energy. The interactions between Con clusters and gas molecules (G) result in weakened bonds of CO, NO, and SO, evident through increased bond lengths, red-shifted frequencies, and lowered local vibrational force constants in ConG complexes. The results with Bond weakening and charge transfer from metal to gas molecules suggest strong catalytic potential for small cobalt clusters in activating gas molecules. The current research findings hold significance in the quest for efficient catalytic processes to capture and recycle gaseous pollutants, contributing to a sustainable future.

Hydrogen-rich water irrigation promotes fruit ripening and nutritional composition in tomato

Hydrogen gas (H2), as a gaseous molecule, plays vital roles in plant growth and development. However, whether H2 plays a role in fruit ripening of tomato is still unknown. Here, we explore the effect of hydrogen-rich water (HRW) irrigation on fruit ripening and nutritional composition in tomato. HRW irrigation enhanced lightness (L* value) and redness (a* value), and declined yellowness (b* value), accelerated fruit color transition. HRW reduced chlorophyll a, chlorophyll b, and total chlorophyll content and enhanced carotenoid, lycopene, and lutein accumulation. Moreover, HRW promoted chlorophyll degradation-related and carotenoid-synthesis related gene expression. In addition, HRW modulated the cell wall component content, enhanced fruit softening-related enzyme activity, and upregulated fruit softening-related and ripening-related gene expression, but decreased fruit firmness. Also, HRW irrigation promoted the accumulation of sucrose, starch, soluble protein, and soluble sugar, as well as increasing the sugar-acid ratio and partial aroma composition. Therefore, H2 may be a promising eco-friendly way to improve tomato cultivation and other agricultural practices.

Selective adsorption and sensing mechanism of ZnFe2O4 (111) surface towards toxic gases:A first-principles study

ZnFe2O4 possesses an excellent gas-sensing performance, but its sensing mechanism towards different toxic gas molecules requires further exploration. In this study, the competitive adsorption and sensing properties of several toxic gases (NO2, NO, SO2, CO, H2S, and NH3) on the ZnFe2O4 (111) surface were investigated using density functional theory (DFT) calculations. The adsorption energy, charge transfer (QT), occupation function, adsorption free energy, charge density difference (CDD), and density of states (DOS) were compared. The results reveal that the ZnFe2O4 (111) surface exhibits obvious adsorption for NH3, H2S, NO2, and H2O, besides the selectivity of NH3 molecule is highest. Strong chemical interactions exist between these harmful gas molecules and the ZnFe2O4 (111) surface. This study offers valuable theoretical insights into the selective adsorption and sensing mechanism, contributing to the development of high-performance gas sensors to detect toxic gases.

Modeling of gas sensor based on zinc oxide thin films by feedback loop using operational amplifier

Nanostructured Zincoxide thin-film is widely used as a sensing material because of its tunable surface microstructure and wide optical bandgap but synthesizing a film with desired value of resistance and reproducibility of film is challenging, particularly by chemical method. In this work, we showed how a ZnO film of arbitrary resistance can be used as a sensor without application of heat using operational amplifier. Zinc oxide thin film was synthesized by using the Sol-gel method (Spin coating) and was characterized by XRD and SEM which revealed wurtzite polycrystalline nature of Zinc oxide film with average grain size 17–25 nm. In this report, we designed a noble electronic circuit capable of detecting analyte gas molecule even if very small change in film resistance occurs due to the influence of gas molecule. In recently available sensors, the quality of the film degrades over time due to repeated heating and cooling, resulting in a reduced lifetime for the sensor. To address this issue and achieve higher sensitivity, as well as to fabricate an affordable, portable, precise, energy-efficient and durable device, this electronic model offers advantages over classical temperature-dependent sensors.

An orally active carbon monoxide-releasing molecule enhances beneficial gut microbial species to combat obesity in mice

Carbon monoxide (CO), a gaseous signaling molecule, has shown promise in preventing body weight gain and metabolic dysfunction induced by high fat diet (HFD), but the mechanisms underlying these effects are largely unknown. An essential component in response to HFD is the gut microbiome, which is significantly altered during obesity and represents a target for developing new therapeutic interventions to fight metabolic diseases. Here, we show that CO delivered to the gut by oral administration with a CO-releasing molecule (CORM-401) accumulates in faeces and enriches a variety of microbial species that were perturbed by a HFD regimen. Notably, Akkermansia muciniphila, which exerts salutary metabolic effects in mice and humans, was strongly depleted by HFD but was the most abundant gut species detected after CORM-401 treatment. Analysis of bacterial transcripts revealed a restoration of microbial functional activity, with partial or full recovery of the Krebs cycle, β-oxidation, respiratory chain and glycolysis. Mice treated with CORM-401 exhibited normalization of several plasma and fecal metabolites that were disrupted by HFD and are dependent on Akkermansia muciniphila's metabolic activity, including indoles and tryptophan derivatives. Finally, CORM-401 treatment led to an improvement in gut morphology as well as reduction in inflammatory and metabolic profiles. Our findings provide therapeutic insights on the efficacy of CO as a potential prebiotic to combat obesity, identifying the gut microbiota as a crucial target for CO-mediated pharmacological activities against metabolic disorders.