SF6 Molecules Research Articles

Doping engineering modulated adsorption and sensing performance of β-tellurene towards greenhouse gas molecules

Abstract CO2, CH4, CF4, CCl3F, CCl2F2, HCF2Cl, N2O and SF6 are well-known greenhouse gases that cause serious threat to the earth's ecological environment. To expand the application and development of two-dimensional (2D) materials in the field of greenhouse gas sensing, adsorption of the greenhouse gases on the pristine β-tellurene monolayer was investigated by first-principles calculations to estimate the potential application of β-tellurene as a monitor for greenhouse gas. The results indicate that β-tellurene exhibits favorable adsorption capabilities for greenhouse gases, especially demonstrating selective sensing potential for SF6 molecules due to the changes in electronic structures after gas exposure. The effects of noble metal atoms doping on structural, electronic and SF6 sensing properties were systematic estimated. The calculation results revealed that doping with different transition metal (TM) atom could bring diverse electronic properties to β-tellurene. Among them, doping with Os, Pd, Pt, Rh, and Ru could effectively enhance the electronic delocalization, improving the detection sensitivity for β-tellurene. In addition, TM doping could also improve the recovery time of β-tellurene by two orders of magnitude, and provided the possibility for β-tellurene as a work function type sensing material. By delving into the gas sensing properties of β-tellurene with TM doping, we provided a valuable guidance for the design of innovative tellurene- based sensing 2D materials for devices and technologies.

Thermodynamic phase equilibria of binary SF6–N2O hydrates and their structural analysis for the hydrate-based greenhouse gas capture

The increasing greenhouse gas (GHG) emissions from industrial activities have driven the development of efficient and environmentally safe GHG capture technologies. Clathrate hydrates, primarily composed of water, have attracted significant attention for their potential in GHG capture due to their ability to manage large emissions and their environmental advantages over materials like amine-based sorbents and metal-organic frameworks. This study investigates the hydrate-based capture of SF6 and N2O, two potent GHGs, to develop an effective GHG capture process. Phase equilibrium measurements demonstrate that binary SF6-N2O hydrates can form under moderate thermodynamic conditions, even with a small proportion of SF6, highlighting the feasibility of using hydrate-based methods to capture GHG mixtures. Furthermore, the formation of binary SF6-N2O hydrates enhances GHG volumetric storage capacity compared to pure SF6 hydrates. The guest compositions calculated for each binary SF6-N2O hydrate phase, along with spectroscopic analyses (Powder X-Ray Diffraction and Raman spectroscopy), confirm that the high GHG uptake in binary hydrates results from N2O molecules occupying the small cages of structure II hydrates, which are inaccessible to the larger SF6 molecules. These findings suggest that both the small and large cages of sII hydrates can be practically utilized for efficient capture of GHG mixture (SF6 and N2O) under mild conditions, thereby increasing the storage density of GHGs within the hydrate structure.

Nanoarchitectonics of Methyl and Aldehyde Group-Decorated SOD-Type Metal-Azolate Framework for SF6 Capture and Recovery.

Sulfur hexafluoride (SF6) is widely used as an insulating gas, being an etchant and contrast agent in the electrical, semiconductor, and medical industries. However, due to its long lifetime and high global warming potential in the atmosphere, SF6 must be carefully handled to prevent leakage during production and usage. Herein, we report a sod-net metal-azolate framework (MAF) named MAF-stu-111, which decorates methyl and aldehyde groups in the porous windows, showing high adsorption affinity for SF6 at low pressure. Stability tests, gas adsorption, and breakthrough experiments demonstrated that MAF-stu-111 possesses excellent water and chemical stability, fully reversible SF6 uptake, high SF6/N2 separation selectivity (10:90, 285.2), good reusability, and high SF6 recovery purity (99.03%). Theoretical calculations revealed that hydrogen atoms of methyl and aldehyde groups can form multiple hydrogen bonds with SF6 molecules, which ensure that SF6 molecules are firmly held within the MAF-stu-111 framework, playing a key role in the selective separation of SF6/N2.

Experimental Study of the Drift Motion of SF6 Molecules under the Action of CO2-Laser Radiation

Experimental Study of the Drift Motion of SF6 Molecules under the Action of CO2-Laser Radiation

Dual-network DNA-silk fibroin hydrogels with controllable surface rigidity for regulating chondrogenic differentiation.

Osteoarthritis (OA) is a common joint disease known for cartilage degeneration, leading to a substantial burden on individuals and society due to its high disability rate. However, current clinical treatments for cartilage defects remain unsatisfactory due to the unclear mechanisms underlying cartilage regeneration. Tissue engineering hydrogels have emerged as an attractive approach in cartilage repair. Recent research studies have indicated that stem cells can sense the mechanical strength of hydrogels, thereby regulating their differentiation fate. In this study, we present the groundbreaking construction of dual-network DNA-silk fibroin (SF) hydrogels with controllable surface rigidity. The supramolecular networks, formed through DNA base-pairing, induce the development of β-sheet structures by constraining and aggregating SF molecules. Subsequently, SF was cross-linked via horseradish peroxidase (HRP)-mediated enzyme reactions to form the second network. Experimental results demonstrated a positive correlation between the surface rigidity of dual-network DNA-SF hydrogels and the DNA content. Interestingly, it was observed that dual-network DNA-SF hydrogels with moderate surface rigidity exhibited the highest effectiveness in facilitating the migration of bone marrow mesenchymal stem cells (BMSCs) and their chondrogenic differentiation. Transcriptome sequencing further confirmed that dual-network DNA-SF hydrogels primarily enhanced chondrogenic differentiation of BMSCs by upregulating the Wnt and TGF-β signaling pathways while accelerating collagen II synthesis. Furthermore, in vivo studies revealed that dual-network DNA-SF hydrogels with moderate surface rigidity significantly accelerated cartilage regeneration. In summary, the dual-network DNA-SF hydrogels represent a promising and novel therapeutic strategy for cartilage regeneration.

Reactive molecular dynamics simulations on the pyrolysis of SF6

There are occasionally partial over-thermal faults in gas-insulated equipment inducing SF6 insulating medium to dissociate. It remains unclear at the atomic scale how this chemically stable gas pyrolyzes at high temperatures. To date, there is a lack of micro-level investigations on the molecular behavior of SF6 at high temperatures. In particular, it requires an effective force field to characterize the evolution of the reactions involving SF6 and low-fluorine sulfides. The paper aims to fill the gap in this field by performing reactive molecular dynamics (MD) simulations. In this work, MD simulations were carried out on a system consisting of more than 100 SF6 molecules using a new developed reactive force field The dissociation of SF6 and the subsequent reactions involving low-fluorine sulfides at high temperatures were simulated. The variation of all species in the system were recorded to investigate the effects of the temperature and pressure on the pyrolysis process. The obtained data was then used to establish the relationship between the reaction rate and temperature, thereby formulating Arrhenius law. Furthermore, the trajectories of SF6 and other species were observed at the atomic level. Snapshots of key frames during the reaction helped us to explore the interaction mechanism of free F atoms with SF6 molecules and SF5 fragments. It was found that the early dissociation of SF6 mainly comes from the thermal vibrations of the molecule itself, while the later decomposition of SF6, SF5 and others is related to high-speed collisions by F atoms. This work contributes to the understanding of the mechanism of SF6 pyrolysis and lays a foundation for more MD investigations.

Adsorption study of SF6 molecules on Pt-doped two-dimensional material Ti3C2Tx Mxene

In this paper, the effects of transition metal atom Pt doping on the structural parameters and electronic properties of the two-dimensional material Ti3C2Tx MXene (T = OH, O or F) as well as the adsorption interaction between the doped material and SF6 are investigated based on density functional theory calculations. To investigate the SF6 adsorption mechanism, the adsorption structure, adsorption energy, charge transfer, and density of states of Pt atom-doped Ti3C2Tx after the adsorption of SF6 molecules were analyzed. The results showed that the electronic properties and chemical activity of the doped Ti3C2Tx changed significantly compared to those before doping. In addition, Pt-doped Ti3C2(OH)2 has good adsorption ability on SF6 molecules, and its adsorption type is chemisorption; in the relevant sites, SF6 undergoes chemical bond breaking, and the doping of Pt improves the catalytic effect of Ti3C2(OH)2. The adsorption capacity of Pt-doped Ti3C2O2 and Ti3C2F2 for SF6 molecules is much weaker than that of Pt-doped Ti3C2(OH)2, physical adsorption occurred, and there was almost no degradation of SF6; the doping of Pt did not improve the catalytic effect of Ti3C2O2 and Ti3C2F2.

Pore engineering in cost-effective and stable Al-MOFs for efficient capture of the greenhouse gas SF6

The capture and separation of the greenhouse gas sulfur hexafluoride (SF6) from nitrogen (N2) holds significant potential for mitigating the greenhouse effect and yielding economic advantages for the semiconductor industry. In this study, a pair of isoreticular cost-effective and stable metal–organic frameworks (MOFs) with slightly different pore environments (CAU-10-H and CAU-10-Py) were prepared at >10 g scale for SF6/N2 separation. CAU-10-Py exhibited a remarkable improvement in SF6 uptake capacity at both low pressure (1.13 mmol/g at 0.1 bar and 298 K, compared to 0.68 mmol/g) and elevated pressure (2.11 mmol/g at 1 bar and 278 K, compared to 1.07 mmol/g). The ideal adsorbed solution theory (IAST) selectivity of SF6/N2 (10/90) was found to be 204 for CAU-10-Py and 123 for CAU-10-H. These enhanced capacities and selectivity endow CAU-10-Py a highly promising candidate for SF6 capture. Single crystal structural analysis, 77 K N2 adsorption data and theoretical calculations indicated that the substitution of benzene by pyridine slightly expand the pore diameter, facilitating more efficient accommodation of SF6 within the channel pores. The SF6 molecule is adsorbed around four benzene rings in CAU-10-H but trapped by two pyridine rings in CAU-10-py, resulting in one fold increase in adsorption capacity. Intriguingly, time-dependant adsorption experiments revealed that CAU-10-Py exhibited a higher SF6 adsorption rate and a lower N2 adsorption rate compared to CAU-10-H, further highlighting the benefit of CAU-10-Py for SF6/N2 separation. Dynamic breakthrough experiments conducted under simulated working conditions further confirmed the outstanding SF6/N2 separation performance of CAU-10-Py. Considering its excellent regeneration ability and cycling performance, this cost-effective and easily scalable MOF demonstrates great promise for SF6/N2 separation.

Sülfür Hekzaflorür Molekülünün Elektron Etkisi ile İyonlaşma İkili Diferansiyel Tesir Kesitlerinin Ölçümü

Sulfur hexafluoride (SF6) is a widely used insulator in the industry, but it also has a high global warming potential. Studying electron impact ionization of SF6, particularly measuring the energy and angular distributions of the collision products, can provide valuable information about the underlying physics of the collision process and the nature of SF6 molecule. In this study, double differential cross sections (DDCSs) for electron impact ionization of SF6 have measured using a crossed beam experimental setup. The incident electron beam, with an energy range of 50-350 eV, was directed towards a target gas composed of SF6, and scattered electrons were detected as a function of the energy and scattering angle. The findings of this study offer significant insights into the molecular structure of SF6 and will contribute to enhancing the understanding of charged particle interactions involving SF6.

Increase in the Efficiency of the Isotope-Selective Infrared Laser Multiphoton Dissociation of 11BCl3 Molecules in a Mixture with SF6 Serving As a Sensitizer and an Acceptor of Radicals

A strong increase in the efficiency of the isotope-selective infrared laser multiphoton dissociation of 11BCl3 molecules in the natural mixture with 10BCl3 by radiation of a pulsed CO2 laser in the case of admixture of SF6 molecules, which serve as a sensitizer and simultaneously acceptors of radicals, Cl atoms formed in the dissociation of BCl3 molecules, has been detected. The yield and selectivity of dissociation of 11BCl3 molecules increase by several times and the threshold energy density for the dissociation of molecules decreases significantly in the case of their irradiation in the mixture with SF6 compared to irradiation without SF6. This property allows the single-frequency isotope-selective dissociation of 11BCl3 molecules by unfocused laser radiation at a moderate energy density (≈3–5 J/cm2), which is important and relevant for the practical implementation of the laser separation of boron isotopes.

Increase in the Efficiency of the Isotope-Selective Infrared Laser Multiphoton Dissociation of 11BCl3 Molecules in a Mixture with SF6 Serving As a Sensitizer and an Acceptor of Radicals

A strong increase in the efficiency of the isotope-selective infrared laser multiphoton dissociation of 11BCl3 molecules in the natural mixture with 10BCl3 by radiation of a pulsed CO2 laser in the case of admixture of SF6 molecules, which serve as a sensitizer and simultaneously acceptors of radicals, Cl atoms formed in the dissociation of BCl3 molecules, has been detected. The yield and selectivity of dissociation of 11BCl3 molecules increase by several times and the threshold energy density for the dissociation of molecules decreases significantly in the case of their irradiation in the mixture with SF6 compared to irradiation without SF6. This property allows the single-frequency isotope-selective dissociation of 11BCl3 molecules by unfocused laser radiation at a moderate energy density (≈3–5 J/cm2), which is important and relevant for the practical implementation of the laser separation of boron isotopes.

The role of multi-photon dissociation of high pressure SF6 gas in TEA CO2 lasers pulse shaping

High pressure SF6 gas has been irradiated by intense TEA CO2 laser pulses with different wavelengths around 10.6μm and then, temporal variations of the transmitted laser pulses have been characterized at different energy fluences and gas pressures. It has been shown that for every fluence above the multi-photon dissociation threshold of SF6 molecules, there is a certain cut-off pressure at which the pulse spike is completely quenched. While, the pulse tail escapes with an appreciable fraction of its initial energy. FTIR spectra of the irradiated gases together with other experimental evidences have clearly revealed the occurrence of laser induced multi-photon dissociation of SF6 molecules, that should be considered as the main responsible for the observed pulse shaping effects.

Экспериментальное изучение дрейфового движения молекул SF-=SUB=-6-=/SUB=- под действием излучения CO-=SUB=-2-=/SUB=--лазера

Experiments were continued to study the physical nature of the drift motion of SF6 molecules under the action of radiation from a repetitively pulsed CO2-laser. To explain the physical nature of the effect, such phenomena as a change in the transport cross-section during laser excitation of molecules, the phenomenon of optical tweezers, thermal diffusion are considered. However, the most reasonable physical explanation of the nature of this effect is the fractionation of a gas mixture as a result of gas dynamic diffusion at the front of a cyclically expanding gas (a variant of barodiffusion).

Experimental study of the drift motion of SF-=SUB=-6-=/SUB=- molecules under the action of CO-=SUB=-2-=/SUB=--laser radiation

Experiments were continued to study the physical nature of the drift motion of SF6 molecules under the action of radiation from a repetitively pulsed CO2-laser. To explain the physical nature of the effect, such phenomena as a change in the transport cross-section during laser excitation of molecules, the phenomenon of optical tweezers, thermal diffusion are considered. However, the most reasonable physical explanation of the nature of this effect is the fractionation of a gas mixture as a result of gas dynamic diffusion at the front of a cyclically expanding gas (a variant of barodiffusion). Keywords: fractionation of gas mixture, thermal diffusion, optical tweezers, barodiffusion.

The adsorption and decomposition of SF6 over defective and hydroxylated MgO surfaces: A DFT study

Plasma degradation is one of the most effective methods for the abatement of greenhouse gas sulfur hexafluoride (SF6). To evaluate the potential of MgO as a catalyst in plasma degradation, we investigate the catalytic properties of MgO on SF6 adsorption and activation by density functional theory (DFT) where the O-defective and hydroxylated surfaces are considered as two typical plasma-generated surfaces. Our results show that perfect MgO (001) and (111) surfaces cannot interact with SF6 and only physical adsorption happens. In case of O-defective MgO surfaces, the O vacancy is the most stable adsorption site. SF6 undergoes a decomposition to SF5 and F over the O-defective MgO (001) surface and undergoes an elongation of the bottom S-F bond over the O-defective (111) surface. Besides, SF6 shows a physically adsorption at the stepsite of the MgO (001) surface, accompanied by small changes in its bond angle and length. Furthermore, SF6 is found to be physically and chemically adsorbed over 0.5 and 1.0 ML (monolayer) H-covered O-terminated MgO (111) surfaces, respectively. The SF6 molecule undergoes a self-decomposition on the 1.0 ML hydroxylated surface via a surface bonding process. This study shows that defective and hydroxylated MgO surfaces have the surface capacities for SF6 activation, which shows that MgO has potential as packing material in SF6 waste treatment in packed-bed plasmas.

Cu n Clusters (n = 13, 43, and 55) as Possible Degradant Agents of mSF6 Molecules (m = 1, 2): A DFT Study.

In order to obtain the structural and electronic properties of pristine copper clusters and Cu13–SF6, Cu43–SF6, Cu55–SF6, Cu13–2SF6, Cu43–2SF6, and Cu55–2SF6 systems, DFT calculations were carried out. For Cu13–mSF6, its surface suffers a drastic deformation, and Cu43–mSF6 at its outer surface reveals strong interaction for the first chemical molecule; when the second molecule is interacting, these outer surfaces are not severely affected. These two cases degraded fully the first SF6 molecule; however the second molecule is bonded to the latter systems and for Cu55–mSF6 (m = 1 and 2) a structural transformation from SF6 →SF4 appears as well as inner and outer shells that display slight deformations. The electronic gaps do not exhibit drastic changes after adsorption of mSF6 molecules, and the magnetic moment remains without alterations. The whole system shows thermal and vibrational stability. In addition, for Cu13–mSF6 the values of the optical gap and intensity of the optical exhibit changes with respect to the pristine case (Cu13), and the rest of the systems do not exhibit major oscillations. These icosahedral copper clusters emerge as a good option to degrade mSF6 molecules.

Rectified SiC-Fe2O3 heterostructures for high efficient activation and degradation of sulfur hexafluoride in air atmosphere

Sulfur hexafluoride (SF6) has a global warming potential of 23,900 CO2 equivalent during 100 years and is the strongest greenhouse gas. Therefore, it is essential to develop a degradation method for SF6. The space charge region in heterojunctions can form charged active sites, thus facilitating the absorption and decomposition of SF6 molecules. Herein, rectified SiC-Fe2O3 heterostructures were designed and in-situ generated from SiC-FeOOH composites during the thermal degradation of SF6. The heterostructures can completely decompose 2 vol% SF6 in air atmosphere at 700 °C, and have a higher initial degradation ratio of 93.6% and a degradation amount of 99.0 mL g−1. Detailed characterizations reveal that electron donor SiC can facilitate the absorption of SF6 molecules via electrostatic attraction, and the electron acceptor Fe2O3 can offer electrons to SF6 molecules to break S-F bonds. The concept of such heterostructures makes it possible to deal with large-scale leaks of low-concentration SF6.

On the Possibility of the Effective Isotope-Selective Infrared Dissociation of 235UF6 Molecules Vibrationally Excited by Bichromatic Laser Radiation

Using the spectroscopic data on the 235UF6 and 238UF6 molecules and on the lasing frequencies of CF4 and para-H2 lasers and recent results, a method has been proposed to increase the efficiency of the isotope-selective infrared laser dissociation of 235UF6 molecules under nonequilibrium thermodynamic shock conditions. The method involves two processes: (i) the resonant multiphoton excitation of 235UF6 molecules to the 3ν3 or 2ν3 vibrational states by the bichromatic infrared radiation of two CF4 or para-H2 lasers and (ii) the irradiation of 235UF6 molecules with SF6 molecules serving as sensitizers resonantly absorbing the radiation of these lasers. The essence of the method has been described. Schemes and parameters for isotope-selective dissociation of 235UF6 molecules using this method has been presented.

Theoretical study of the interaction of SF6 molecule on Ti3C2Tx surfaces

At present, searching for efficient methods to degrade sulfur hexafluoride (SF6) is a worldwide hotspot. Due to the abundant active groups on the surface, MXene is regarded as an ideal catalyst support. In this paper, the potential active sites of Ti3C2Tx (T = OH, F, O) for SF6 degradation were studied using density functional theory (DFT) method. The results show the adsorption of SF6 on Ti3C2(OH)2 is significantly stronger than that on Ti3C2F2 and Ti3C2O2. Among typical adsorption sites on Ti3C2(OH)2, SF6 exhibited the strongest interaction at OH-1 site. Complex electron orbital interactions occurred between SF6 and Ti3C2(OH)2. Adsorption energy reached −6.739 eV and about 1.414e transferred from Ti3C2(OH)2 to SF6. Structure of SF6 changed obviously and chemical adsorption occurred in this process. However, on Ti3C2F2 and Ti3C2O2, gas–solid interactions were weak and the structures had little change, which was mainly physical adsorption. Compared with common catalysts such as Ag, α‑Al2O3 and BaTiO3, Ti3C2(OH)2 showed better catalytic activity for SF6 degradation. By strong adsorption of the active site on the surface, the degradation products were separated from each other, which weakened SF6 recombination and promoted the further degradation. The results provide theoretical support for MXene acting as a catalyst to efficiently degrade SF6.

Neural network simulation for selective dissociation of SF6 molecules by single-mode and multi-mode carbon dioxide lasers

Selective dissociation of sulfur hexafluoride molecules was simulated using single-mode and multi-mode carbon dioxide lasers using a two-layer feedforward neural network with 4 and 2nodes in the first and second layers, respectively. Existing experimental results (Sajad et al., 2004 [1]) were used to train and verify neural networks. Simulation was performed using MATLAB software neural network toolbox. Using the trained neural network, the results of non-existent physical conditions in the previous experimental results were predicted and presented.