A new flatland buddy as toxic gas scavenger: A first principles study

Pd-Adsorbed SiN3 Monolayer as a Promising Gas Scavenger for SF6 Partial Discharge Decomposition Components: Insights from the First-Principles Study

Gas-insulated switchgear (GIS) equipment must be protected by detecting and eliminating the toxic SF6 partial discharge decomposition components. This study employs first-principles calculations to thoroughly investigate the interaction between a Pd-adsorbed SiN3 monolayer (Pd-SiN3) and four typical SF6 decomposition gases (H2S, SO2, SOF2, and SO2F2). The study also investigates the associated geometric, electrical, and optical characteristics along with the sensing sensitivity and desorption efficiency. The ab initio molecular dynamics (AIMD) simulations demonstrated the favorable stability of the Pd-SiN3 monolayer. Furthermore, the Pd-SiN3 monolayer exhibited strong chemisorption behavior toward H2S, SO2, SOF2, and SO2F2 gases because of the higher adsorption energies of -2.717, -2.917, -2.457, and -2.025 eV, respectively. Furthermore, significant changes occur in the electronic and optical characteristics of the Pd-SiN3 monolayer following the adsorption of these gases, resulting in remarkable sensitivity of the Pd-SiN3 monolayer in relation to electrical conductivity and optical absorption. Meanwhile, all of these gas adsorption systems exhibited extremely long recovery times. The aforementioned theoretical findings suggest that the Pd-SiN3 monolayer has the potential to be an effective gas scavenger for the storage or removal of the SF6 decomposition components. Additionally, it might function as a reliable one-time sensor for detecting these gases. The results potentially provide valuable theoretical guidance for maintaining the normal operation of the SF6 insulation devices.

CO and HCHO Sensing by Single Au Atom-Decorated WS2 Monolayer for Diagnosis of Thermal Aging Faults in the Dry-Type Reactor: A First-Principles Study

CO and HCHO are the main pyrolysis gases in long-term running dry-type reactors, and thus the diagnosis of thermal insulation faults inside such devices can be realized by sensing these gases. In this paper, a single Au atom-decorated WS2 (Au-WS2) monolayer is proposed as an original sensing material for CO or HCHO detection to evaluate the operation status of dry-type reactors. It was found that the Au atom prefers to be adsorbed at the top of the S atom of the pristine WS2 monolayer, wherein the binding force is calculated as -3.12 eV. The Au-WS2 monolayer behaves by chemisorption upon the introduction of CO and HCHO molecules, with the adsorption energies of -0.82 and -1.01 eV, respectively. The charge density difference was used to analyze the charge-transfer and bonding behaviors in the gas adsorptions, and the analysis of density of state as well as band structure indicate gas-sensing mechanisms. As calculated, the sensing responses of the Au-WS2 monolayer upon CO and HCHO molecule introduction were 58.7% and -74.4%, with recovery times of 0.01 s and 11.86 s, respectively. These findings reveal the favorable potential of the Au-WS2 monolayer to be a reusable and room-temperature sensing candidate for CO and HCHO detections. Moreover, the work function of the Au-WS2 monolayer was decreased by 13.0% after the adsorption of CO molecules, while it increased by 1.2% after the adsorption of HCHO molecules, which implies its possibility to be a work-function-based gas sensor for CO detection. This theoretical report paves the way for further investigations into WS2-based gas sensors in some other fields, and it is our hope that our findings can stimulate more reports on novel gas-sensing materials for application in evaluating the operation conditions of dry-type reactors.

Adsorption Mechanisms of TM3 (TM = Mo, Ru, Au)-Decorated Tin Sulfide Monolayers for the Decomposition of Gas Components under Fault Conditions in Oil-Immersed Transformers

Oil-immersed transformers play a pivotal role owing to their environmentally friendly characteristics, compact footprint, and cost-effectiveness. Ensuring the online monitoring of oil-immersed transformers is a fundamental measure to ensure the secure and stable operation of modern power systems. In this paper, metal particle cluster-doped SnS is firstly used in the adsorption and sensing of decomposition components (CO, C2H2) under fault conditions in oil-immersed transformers. The study comprehensively analyzed band structure, differential charge density, density of states, and molecular orbital theory to unveil the adsorption and sensing mechanisms of target gases. The findings suggest that the modification of metal particle clusters can enhance the surface electronic properties of single-layer SnS. In the regions of metal particle clusters and the gas-surface reaction area, electronic activity is significantly heightened, primarily attributed to the contribution of d-orbital electrons of the metal cluster structures. The modified SnS exhibits adsorption capacity in the following order: Ru3-SnS > Mo3-SnS > Au3-SnS. Additionally, the modified material demonstrates increased competitiveness for C2H2, with adsorption types falling under physical chemistry adsorption. Different metal elements exert diverse effects on the electronic distribution of the entire system, providing a theoretical foundation for the preparation of corresponding sensors. The findings in this work offer numerical insights for the further preparation and development of SnS nanosensors, concurrently shedding light on the online monitoring of faults in oil-immersed transformers.

Exploring the sensing potential of Fe-decorated h-BN toward harmful gases: a DFT study

Gas sensing technology has a broad impact on society, ranging from environmental and industrial safety to healthcare and everyday applications, contributing to a safer, healthier, and more sustainable world. We studied pure and Fe-decorated hexagonal boron nitride (h-BN) gas sensor for monitoring of carbon-based gases using density functional theory (DFT). The calculations utilized the Generalized Gradient Approximation with the Perdew-Burke-Ernzerhof (GGA-PBE) exchange-correlation functional. The novelty of our study lies in the investigation of the adsorption of harmful gases such as carbonyl sulfide, carbinol, carbimide, and carbonyl fluoride on both pure and Fe-decorated h-BN. The deviation in structural, electronic, and adsorption properties of h-BN due to Fe decoration has been studied along with the sensing ability to design said material towards carbon monoxide (CO), carbon dioxide (CO2), carbonyl sulfide (COS), carbinol, (CH4O), carbimide (CH2N2), and carbonyl fluoride (CF2O) gases. Gases such as CO, COS, CH2N2, and CF2O exhibited chemisorption, while CO2, and CH4O exhibited physisorption behavior. The introduction of Fe altered the semiconductor properties of h-BN and rendered it metallic. Enhanced electronic properties were observed due to a robust hybridization occurring between the d-orbitals of Fe-decorated BN and the gas molecules. The extended recovery periods observed for gases, aside from CO2, indicate their adhesive interactions with Fe-decorated h-BN. The reduction in desorption duration as temperature rises allows Fe-decorated h-BN to function as a reversible gas sensor. This research opens up a novel pathway for the synthesis and advancement of cost-effective, environmentally friendly double-atom catalysts with high sensitivity for capturing and detecting molecules such as CO, COS, CH2N2, CO2, CH4O, and CF2O.

Adsorption of NO2, NO, NH3, and CO on Noble Metal (Rh, Pd, Ag, Ir, Pt, Au)-Modified Hexagonal Boron Nitride Monolayers: A First-Principles Study

To investigate the application of modified hexagonal boron nitride (h-BN) in the detection and monitoring of harmful gases (NO2, NO, NH3, and CO), first-principles calculations are applied to study the geometric structure and electronic behavior of the adsorption system. In this paper, the four adsorption sites, namely, B, N, bridge, and hollow sites, are considered to explore the stable adsorption structure of metals (M = Rh, Pd, Ag, Ir, Pt, and Au) on the BN surface. The calculation results demonstrate that the geometric structures of metal at the N-site are relatively stable. Subsequently, the different adsorption structures of NO2, NO, NH3, and CO on M-BN are researched. The electron transfer, charge difference density, and work function of the stable adsorption structure are calculated. The results show that NO2, NO, and CO have the strongest adsorption capacity in the Ir-BN system, with adsorption energies of -2.705, -5.064, and -3.757 eV, respectively. The Pt-BN system has an excellent adsorption performance (-2.251 eV) for NH3. Compared with the M-BN system, the work function of the adsorption system increases after adsorbing NO2, while it decreases after adsorbing NH3. This work shows that h-BN with metal modification is a potential material for online monitoring of harmful gases.

Adsorption of NO2, SO2, H2S, and NH3 on Os-Doped WSe2 Monolayers: A First-Principles Study

In this study, DFT calculations are used to analyze the adsorption of industrial waste gases (NO2, SO2, H2S, and NH3) on WSe2 monolayers. The adsorption energy, energy band, density of states, charge transfer, and recovery time of the adsorption structures between the target gas molecules and the Os-doped WSe2 are studied. Compared with pure WSe2 monolayer, Os surface bonding doping WSe2 (Os-modified WSe2) and Os doping with Se vacancy of WSe2 (Os-embedded WSe2) exhibit improved gas molecule adsorption ability. Among them, the adsorption energy of the Os-modified WSe2 monolayer on NO2, SO2, H2S, and NH3 is greater than that of the WSe2 monolayer. At the same time, it is proved that the Os-embedded WSe2 can be used as a gas sensor for H2S and NH3 gas molecules at a high temperature.

Adsorption of industry affiliated gases on buckled aluminene for gas sensing applications

INTRODUCTION

First-principles calculations were used to study the adsorption behavior of environmentally significant gases CO, CO₂, NO, NO₂, SO, and SO₂ on pure buckled aluminene (b-Al) for gas sensing applications. Therefore, structural, electronic, and adsorption properties including adsorption energy values and recovery time have been calculated and discussed.

METHODS

All the structures were optimized using Amsterdam Density Functional (ADF) code BAND. In addition, triple zeta polarization basis with slater-type orbitals were utilized.

RESULTS

For every gas analyzed, we observed favorable adsorption energy values and charge transfer occurring between the gas molecule and b-Al. In the valance band, there was a strong hybridization between the p orbitals of gas and b-Al, this led to enhanced conductivity in the density of states (DOS). The recovery time suggested that the adsorption of NO, NO₂, SO, and SO₂ gases on b-Al is good for the application of reversible gas sensors. The recovery time indicated that the b-Al material is very sensitive to NO, NO₂, SO, and SO₂ gas molecules.

CONCLUSION

The conclusion in light of all these results is that b-Al based materials can appear as a probable candidate for high gas sensing performance.

Identification and sensing of hydrogen fluoride (HF) on aluminum phosphide (Al24P24) nanocage in both gas and water phases: electronic study via density-functional theory computations

CONTEXT

Hydrogen fluoride (HF) is extensively present in environmental and industrial pollutants. It may harm the health of humans and animals. This work evaluated the adsorption of an (HF)n linear chain (n = 1, 2, 3, and 4) onto an AlP nanocage through ab initio calculations for the evaluation of its performance in sensing and monitoring (HF)n within aqueous and gaseous media.

METHODS

The present work adopted density functional theory (DFT) at the 6-311 G (d, p) basis set to analyze (HF)n linear chain adsorption onto AlP nanocages with the B3LYP functional. This paper examined the adsorption energy, configuration optimization, work function, and charge transfer. In addition, the contributions of the HF linear chain size to electronic properties and adsorption energy were measured. The dimer form of HF on the surface of AlP nanocages was found to have the highest stability based on the adsorption energy values. Once (HF)n was adsorbed onto the nanocage, the HOMO-LUMO energy gap experienced a large reduction from 3.87 to 3.03 eV, enhancing electrical conductivity. In addition, AlP nanocages may serve in the sensing of (HF)n under multiple environmental pollutants.

On using non-Kekulé triangular graphene quantum dots for scavenging hazardous sulfur hexafluoride components

The goal of present study is to explore how the size and functionalization of graphene quantum dots (GQDs) affect their sensing capabilities. Specifically, we investigated the adsorption of SO₂, SOF₂, SO₂F₂, and SF₆ on GQDs that were functionalized with -CH₃, -COCH₃, and -NH₂. We used density functional theory to analyse the electronic properties of these functionalized GQDs and found that the functionalization significantly altered their electronic properties. For example, the B3LYP H-L gap of pristine triangulene was 3.9eV, while the H-L gap of functionalized triangulene ranged from 2.8 eV to 3.6 eV (using the B3LYP functional). Our results indicate that -NH₂ functionalized phenalenyl and triangulene provide strong interaction with SO₂, with adsorption energies of -0.429 eV and -0.427 eV, respectively. These adsorption properties exhibit physisorption, leading to high gas sensitivity and superior recovery time. The findings of this study provide new insights into the potential use of GQDs for detecting the decomposed constituents of sulfur hexafluoride, which can be beneficial for assessing the operation status of SF₆ insulated devices. Overall, our calculations suggest that functionalized GQDs can be employed in gas insulated systems for partial discharge detection.

Different Doping of VSe2 Monolayers as Adsorbent and Gas Sensing Material for Scavenging and Detecting SF6 Decomposed Species

The application of intrinsic and transition metals (TM)-doped VSe₂ monolayers for the detection of faulty gases in SF₆ electrical insulated equipment is investigated based on first-principles calculations. The electron density difference, density of state, and adsorption energy are analyzed to further clarify the reaction mechanism. The results show that the intrinsic VSe₂ monolayer has weak adsorption performance for SO₂ and SOF₂ molecules, but the adsorption properties of the system are significantly improved after doping TM atoms. Among them, the TM-doped VSe₂ monolayer has better sensing performance for SO₂ than for SOF₂ molecules. Furthermore, the modulating effect of biaxial strain on the gas-sensitive properties of TM-doped VSe₂ system is also analyzed. Finally, the recovery time of the gas molecules on the solid adsorbent is evaluated. The results confirm that the TM-doped VSe₂ monolayer can be used as a novel sensing material or scavenger to ensure the normal operation of SF₆ electrical insulated equipment. This will provide a prospective insight for experimenters to implement VSe₂-based sensing materials or scavengers.

Adsorption Properties of NF3 and N2O on Al- and Ga-Doped Graphene Surface: A Density Functional Theory Study

SF6/N2 gas mixture decomposition components can reflect the operation status inside GIS, and be used for fault diagnosis and monitoring inside GIS. NF3 and N2O are the characteristic decomposition components of SF6/N2 mixed gas. In order to find a potential gas sensitivity material for the detection of NF3 and N2O. This paper investigated the adsorption properties of NF3 and N2O on Al- and Ga- doped graphene monolayers based on density functional theory. Through the analysis of adsorption distance, charge transfer, adsorption energy, energy band structure, etc., the results indicated that the adsorption effect of Al- and Ga-doped graphene to NF3 and N2O are probably good, and these nanomaterials are potential to apply for the monitoring of GIS internal faults.

Ni-Decorated ZnO Monolayer for Sensing CO and HCHO in Dry-Type Transformers: A First-Principles Theory

This work implements first-principles simulations in order to investigate the Ni-decorating property on the ZnO monolayer and the sensing property of the Ni-decorated ZnO (Ni–ZnO) monolayer upon CO and HCHO molecules formed in the dry-type transformers. The results reveal that the Ni dopant is stably anchored on the TO site of the ZnO surface forming the Ni–Zn and Ni–O bonds with the binding energy (Eb) of −1.75 eV. Based on the adsorption energy (Ead) of −1.49 and −2.22 eV for CO and HCHO on the Ni–ZnO monolayer, we determined the chemisorption for two such systems. The band structure (BS) and atomic density of state (DOS) of the gas adsorbed systems are analyzed to comprehend the electronic property of the Ni–ZnO monolayer in the gas adsorptions. Besides, the change of bandgap and work function uncover the sensing potential of Ni–ZnO monolayer upon CO and HCHO detections, with admirable electrical response (15,394.9% and −84.6%). The findings in this work manifest the potential of Ni–ZnO monolayer for CO and HCHO sensing to evaluate the operation condition of the dry-type transformers.

Suitability of chlorobenzene-based single-electron transistor as HCN, AsH3, and COCl2 sensor

A density functional theory (DFT)-based first principle approach has been employed to investigate the suitability of chlorobenzene-based single-electron transistor (SET) for the detection of few toxic gases such as hydrogen cyanide, arsine, and phosgene. The adsorption aspect of toxic gas molecules on the chlorobenzene with different orientations has been analyzed. The attributes such as charge density, molecular energy spectrum, density of states, and Mulliken population have been computed to scrutinize the effect of gas molecules on the surface of chlorobenzene. The sensing mechanism of adsorbate (toxic gases) with the adsorbent (chlorobenzene) has been authenticated in a single-electron transistor (SET) environment through total energy vs. gate voltage plot and charge stability diagram. The recovery time of the chlorobenzene-based SET gas sensor on the adsorption of HCN, AsH₃, and COCl₂ has been computed as 1.93 ns, 0.45 ns, and 36.31 ns, respectively. Based on these findings, it is interesting to see that the COCl₂ gas molecule shows strong physical adsorption with the most significant adsorption distance (3.629 Å) with chlorobenzene, while AsH₃-adsorbed chlorobenzene SET displays a low recovery time in comparison with other considered gases. The present analysis confirms a significantly better range of detection and improved recovery time using chlorobenzene-based single-electron transistor.

Metal-Decorated Phthalocyanine Monolayer as a Potential Gas Sensing Material for Phosgene: A First-Principles Study

Research into a gas sensing material with excellent performance to detect or remove toxic phosgene (COCl2) is of great significance to environmental and biological protection. In the present work, the adsorption performance of COCl2 on pristine phthalocyanine (Pc) and metal-decorated Pc (MePc, Me = Cu, Ga, and Ru) monolayers was studied by first-principles calculations. The results show that the absorption process of COCl2 on pristine Pc and CuPc both belong to physisorption, indicating that they are not suitable gas sensing materials for COCl2. When Pc sheets are decorated by Ga and Ru atoms, the adsorption of COCl2 is changed into chemisorption, and the corresponding adsorption energies are -0.57 and -0.50 eV for GaPc and RuPc, respectively. The microcosmic mechanism between COCl2 and adsorbents (GaPc, RuPc) was clarified by the analysis of the density of states, the charge density difference, and the Hirshfeld charge. In addition, the COCl2 adsorption results in a significant conductivity variation of the RuPc monolayer, demonstrating it exhibits a high sensitivity to the COCl2 molecule. Meanwhile, quick desorption processes were noticed at various temperatures for the COCl2/RuPc system. Consequently, the RuPc monolayer can be considered as a potential candidate for phosgene sensors because of the moderate adsorption strength, high sensitivity, and fast desorption speed.

Borophene as an emerging 2D flatland for biomedical applications: current challenges and future prospects

Recently, two-dimensional (2D)-borophene has emerged as a remarkable translational nanomaterial substituting its predecessors in the field of biomedical sensors, diagnostic tools, high-performance healthcare devices, super-capacitors, and energy storage devices. Borophene justifies its demand due to high-performance and controlled optical, electrical, mechanical, thermal, and magnetic properties as compared with other 2D-nanomaterials. However, continuous efforts are being made to translate theoretical and experimental knowledge into pragmatic platforms. To cover the associated knowledge gap, this review explores the computational and experimental chemistry needed to optimize borophene with desired properties. High electrical conductivity due to destabilization of the highest occupied molecular orbital (HOMO), nano-engineering at the monolayer level, chemistry-oriented biocompatibility, and photo-induced features project borophene for biosensing, bioimaging, cancer treatment, and theragnostic applications. Besides, the polymorphs of borophene have been useful to develop specific bonding for DNA sequencing and high-performance medical equipment. In this review, an overall critical and careful discussion of systematic advancements in borophene-based futuristic biomedical applications including artificial intelligence (AI), Internet-of-Things (IoT), and Internet-of-Medical Things (IoMT) assisted smart devices in healthcare to develop high-performance biomedical systems along with challenges and prospects is extensively addressed. Consequently, this review will serve as a key supportive platform as it explores borophene for next-generation biomedical applications. Finally, we have proposed the potential use of borophene in healthcare management strategies.

From Fundamental to CO2 and COCl2 Gas Sensing Properties of Pristine and Defective Si2BN Monolayer

The capability of Si2BN monolayer (Si2BN-ML) in sensing CO2 and COCl2 molecules is investigated by analyzing the structural, electronic, mechanical and gas sensing properties of defect-free and defective Si2BN-ML. Electronic...

C-doping anisotropy effects on borophene electronic transport

The electronic transport anisotropy for different C-doped borophene polymorphs (β₁₂andχ₃) was investigated theoretically combining density functional theory and non-equilibrium Green's function. The energetic stability analysis reveals that B atoms replaced by C is more energetically favorable forχ₃phase. We also verify a directional character of the electronic band structure on C-doped borophene for both phases. Simulated scanning tunneling microscopy and also total density of charge confirm the directional character of the bonds. The zero bias transmission forβ₁₂phase atE-E_F= 0 shows that C-doping induces a local current confinement along the lines of doped sites. TheI-Vcurves show that C-doping leads to an anisotropy amplification in theβ₁₂than in theχ₃. The possibility of confining the electronic current at an specific region of the C-doped systems, along with the different adsorption features of the doped sites, poses them as promising candidates to highly sensitive and selective gas sensors.

InP3 Monolayer as a Promising 2D Sensing Material in SF6 Insulation Devices

In this letter, we perform a first-principles study on the adsorption performance of the InP3 monolayer upon three SF6 decomposed species, including SO2, SOF2, and SO2F2, to investigate its potential as a resistance-type, optical or field-effect transistor gas sensor. Results indicate that the InP3 monolayer exhibits strong chemisorption upon SO2 but weak physisorption upon SO2F2. The most admirable adsorption behavior is upon SOF2, which provides a favorable sensing response (-19.4%) and recovery property (10.4 s) at room temperature as a resistance-type gas sensor. A high response of 180.7% upon SO2 and a poor one of -1.9% upon SO2F2 are also identified, which reveals the feasibility of the InP3 monolayer as a resistance-type sensor for SO2 detection with recycle use via a heating technique to clean the surface. Moreover, the InP3 monolayer is a promising optical sensor for SO2 detection due to the obvious changes in adsorption peaks within the range of ultraviolet and is a desirable field-effect transistor sensor for selective and sensitive detection of SO2 and SOF2 given the evident changes of Q T and E g under the applied electric field.

Adsorption of SF6 Decomposition Products by the S Vacancy Structure and Edge Structure of SnS2: A Density Functional Theory Study

Detecting the composition and concentration of SF6 decomposition products is an effective method to evaluate the state of gas-insulated switchgear. Based on density functional theory, in this work we investigated the adsorption properties of four typical SF6 decomposition products (H2S, SO2, SOF2, SO2F2) on an SnS2 S vacancy structure (SnS2-Sv) and SnS2 edge structure (SnS2-edge). By calculating the adsorption energy, charge transfer, and comparing the density of states (DOS) of each system before and after the adsorption of gas molecules, the physical and chemical interactions between SnS2 with different structures and gas molecules were investigated. The results show that SnS2-Sv has the largest adsorption energy for SO2 and has obvious chemical interactions. The S vacancy can effectively capture an O atom in SO2, causing SO2 to firmly adsorb in the S vacancy. In addition, the adsorption of the four gases on the SnS2-edge is physical adsorption, in which the 50% S edge structure has the largest adsorption energy for H2S, reaching -0.52 eV, and there is also a large charge transfer between the 50% S edge structure and H2S. Although the adsorption energy of SnS2-edge to the four gases is smaller than SnS2-Sv, it is still greater than the pristine SnS2. This paper explores the adsorption properties of SnS2-Sv and SnS2-edge for SF6 decomposition products, providing insights for the development of SnS2-based gas sensors.

Imparting α-Borophene with High Work Function by Fluorine Adsorption: A First-Principles Investigation

Increasing the work function of borophene over a large range is crucial for the development of borophene-based anode materials for highly efficient electronic devices. In this study, the effect of fluorine adsorption on the structures and stabilities, particularly on the work function, of α-borophene (BBP), was systematically investigated via first-principles density functional theory. The calculations indicated that BBP was well-stabilized by fluorine adsorption and the work functions of metallic fluorine-adsorbed BBPs (F_n-BBPs) sharply increased with increasing fluorine content. Moreover, the work function of F-BBP was close to that of the frequently used anode material Au and even, for other F_n-BBPs, higher than that of Pt. Furthermore, we have comprehensively discussed the factors, including substrate deformation, charge transfer, induced dipole moment, and Fermi and vacuum energy levels, affecting the improvement of work function. Particularly, we have demonstrated that the charge redistribution of the substrate induced by the bonding interaction between fluorine and the matrix predominantly contributes to the observed increase in the work function. Additionally, the effect of fluorine adsorption on the increase in the work function of BBP was significantly stronger than that of silicene or graphene. Our results concretely support the fact that F_n-BBPs can be extremely attractive anode materials for electronic device applications.

First-principles study of pristine and Li-doped borophene as a candidate to detect and scavenge SO2gas

In this research, the potential application of borophene as gas sensor device is explored. The first-principles theory is employed to investigate the sensing performance of pristine and Li-doped borophene for SO₂and five main atmospheric gases (including CH₄, CO₂, N₂, CO and H₂). All gases are found to be adsorbed weakly on pristine borophene, which shows weak physical interaction between the pristine borophene and gases. The gas adsorption performance of borophene is improved by the doping of Li atom. The results of adsorption energy suggest that Li-borophene exhibits high selectivity to SO₂molecule. Moreover, analyses of the charge transfer, density of states and work function also confirm the introduction of Li adatom on borophene significantly enhances the selectivity and sensitivity to SO₂. In addition, desorption time of gas from pristine and Li doped borophene indicates the Li-borophene has good desorption characteristics for SO₂molecule at high temperatures. This research would be helpful for understanding the influence of Li doping on borophene and presents the potential application of Li-borophene as a SO₂gas sensor or scavenger.

SF6 decomposed gas sensing performance of van der Waals layered cobalt oxyhydroxide: insights from a computational study

The detection of SF₆ decomposition products plays a significant part in identifying and assessing the electric discharge faults in SF₆ insulation equipment. We performed dispersion corrected density functional theory calculations to study the adsorption performance of CoOOH upon SO₂, SF₄, SOF₂, CF₄, and SO₂F₂ toxic gases, to investigate their potential application as a gas sensor. The results clearly show a weak force between the CoOOH sheet, and the molecular gas with moderate adsorption strength enhances the desorption processes. According to Löwdin charge population analysis, electrons transfer from the molecular gas to the CoOOH surface, where the molecular gas behaves like an electron donor. The lower bandgap energy of the adsorption systems compared with pristine CoOOH significantly increases its electrical conductivity and gas sensing performance. The higher charge transfer and adsorption energy of the SOF₂ adsorption system compared with the other four molecular gas is due to orbital hybridization around the Fermi energy. The theoretical computed adsorption energy with ultrahigh sensitivity and fast recovery time suggests that SF₆ decomposed gases reusability is achieved with CoOOH as a resistance-type gas sensor.

Recent Development of Gas Sensing Platforms Based on 2D Atomic Crystals

Sensors, capable of detecting trace amounts of gas molecules or volatile organic compounds (VOCs), are in great demand for environmental monitoring, food safety, health diagnostics, and national defense. In the era of the Internet of Things (IoT) and big data, the requirements on gas sensors, in addition to sensitivity and selectivity, have been increasingly placed on sensor simplicity, room temperature operation, ease for integration, and flexibility. The key to meet these requirements is the development of high-performance gas sensing materials. Two-dimensional (2D) atomic crystals, emerged after graphene, have demonstrated a number of attractive properties that are beneficial to gas sensing, such as the versatile and tunable electronic/optoelectronic properties of metal chalcogenides (MCs), the rich surface chemistry and good conductivity of MXenes, and the anisotropic structural and electronic properties of black phosphorus (BP). While most gas sensors based on 2D atomic crystals have been incorporated in the setup of a chemiresistor, field-effect transistor (FET), quartz crystal microbalance (QCM), or optical fiber, their working principles that involve gas adsorption, charge transfer, surface reaction, mass loading, and/or change of the refractive index vary from material to material. Understanding the gas-solid interaction and the subsequent signal transduction pathways is essential not only for improving the performance of existing sensing materials but also for searching new and advanced ones. In this review, we aim to provide an overview of the recent development of gas sensors based on various 2D atomic crystals from both the experimental and theoretical investigations. We will particularly focus on the sensing mechanisms and working principles of the related sensors, as well as approaches to enhance their sensing performances. Finally, we summarize the whole article and provide future perspectives for the development of gas sensors with 2D materials.

Adsorption of atmospheric gas molecules (NH3, H2S, CO, H2, CH4, NO, NO2, C6H6 and C3H6O) on two-dimensional polyimide with hydrogen bonding: a first-principles study

In this study, we investigated the effects of hydrogen bond acceptors on the surface of two-dimensional polyimide towards NH₃, H₂S, CO, H₂, CH₄, NO, NO₂, C₆H₆ and C₃H₆O gas molecules through first-principles study based on density functional theory.

Ultrahigh sensitivity with excellent recovery time for NH3 and NO2 in pristine and defect mediated Janus WSSe monolayers

We demonstrated ultrahigh sensitivity with excellent recovery time for H2S, NH3, NO2, and NO molecules on the sulfur and selenium surfaces of Janus WSSe monolayers using density functional theory. The selenium surface of the WSSe monolayer showed strong adsorption in comparison to the sulfur surface. The respective adsorption energies for H2S, NH3, NO2 and NO molecules are -0.193 eV, -0.220 eV, -0.276 eV, and -0.189 eV. These values are higher than the experimentally reported values for ultrahigh sensitivity gas sensors based on MoS2, MoSe2, WS2, and WSe2 monolayers. The computed adsorption energy and recovery time suggest that the desorption of gas molecules can be achieved easily in the WSSe monolayer. Further, the probable vacancy defects SV, SeV, and (S/Se)V and antisite defects SSe, and SeS are considered to understand their impact on the adsorption properties with respect to the pristine WSSe monolayer. We observed that the defect-including WSSe monolayers showed enhanced adsorption energy with fast recovery, which makes the Janus WSSe monolayer an excellent material for nanoscale gas sensors with ultrahigh sensitivity and excellent recovery time.

Undulated silicene and germanene freestanding layers: why not?

Silicene and germanene freestanding layers are usually described as a honeycomb lattice formed by two hexagonal sub-lattices presenting a height difference, namely the layer buckling. In this work, first-principles calculations show that silicene and germanene can be rippled at 0 K with various wavelengths, without any compressive strain of the layer. For germanene, the height difference between two Ge atoms from the same sub-lattice can be as high as 4.7 [Formula: see text] for an undulation length of 81 [Formula: see text]. The deformations are related to slight (lower than 1.7°) bond angle modifications, and the energy cost is remarkably low, lying between 0.1 and 0.8 meV per atom. These undulations modify the electronic structure, opening a gap of 15 meV.

Using Pd-Doped γ-Graphyne to Detect Dissolved Gases in Transformer Oil: A Density Functional Theory Investigation

To realize a high response and high selectivity gas sensor for the detection dissolved gases in transformer oil, in this study, the adsorption of four kinds of gases (H₂, CO, C₂H₂, and CH₄) on Pd-graphyne was investigated, and the gas sensing properties were evaluated. The energetically-favorable structure of Pd-Doped γ-graphyne was first studied, including through a comparison of different adsorption sites and a discussion of the electronic properties. Then, the adsorption of these four molecules on Pd-graphyne was explored. The adsorption structure, adsorption energy, electron transfer, electron density distribution, band structure, and density of states were calculated and analyzed. The results show that Pd prefers to be adsorbed on the middle of three C≡C bonds, and that the band gap of γ-graphyne becomes smaller after adsorption. The CO adsorption exhibits the largest adsorption energy and electron transfer, and effects an obvious change to the structure and electronic properties to Pd-graphyne. Because of the conductance decrease after adsorption of CO and the acceptable recovery time at high temperatures, Pd-graphyne is a promising gas sensing material with which to detect CO with high selectivity. This work offers theoretical support for the design of a nanomaterial-based gas sensor using a novel structure for industrial applications.

CrI3-WTe2: A Novel Two-Dimensional Heterostructure as Multisensor for BrF3 and COCL2 Toxic Gases

A new multisensor (i.e. resistive and magnetic) CrI₃-WTe₂ heterostructure (HS) to detect the toxic gases BrF₃ and COCl₂ (Phosgene) has been theoretically studied in our present investigation. The HS has demonstrated sensitivity towards both the gases by varying its electronic and magnetic properties when gas molecule interacts with the HS. Fast recovery time (<0.14 fs) under UV radiation has been observed. We have considered two configurations of BrF₃ adsorbed HS; (1) when F ion interacts with HS (C1) and (2) when Br ion interacts with HS (C2). In C1 case the adsorption energy E_ad is observed to be −0.66 eV while in C2 it is −0.95 eV. On the other hand in case of COCl₂E_ad is found to be −0.42 eV. Magnetic moments of atoms are also found to vary upon gas adsorption indicates the suitability of the HS as a magnetic gas sensor. Our observations suggest the suitability of CrI₃-WTe₂ HS to respond detection of the toxic gases like BrF₃ and COCl₂.

An ab initio study of sensing applications of MoB2 monolayer: a potential gas sensor

Using first principles density functional theory, we have studied the interaction mechanism of NO2 and SO2 gas molecules on an MoB2 monolayer, for gas sensing applications. The selectivity for a particular gas by the sensor has been analyzed through electronic structure calculations and adsorption studies. The calculations have been performed by considering the fact that the MoB2 monolayer as a sensing material encounters a change in its electrical properties, when gas molecules with different orientations get adsorbed on the surface. From the density of states study, we find better selectivity for NO2 as compared to SO2, as the latter leaves the electronic structure of the sensing material unaffected. Further, the adsorption curves support the above fact as the larger value of adsorption energy (Ead ∼ -1 eV) for NO2 indicates stronger adsorption. The chemisorptive nature for NO2, in contrast with the relatively weaker physisorption for SO2, additionally supports the fact that NO2 gas has a better perspective for MoB2 sensor application. Charge density plots for each case are in good agreement with the above conclusions. The faster recovery time attributes the MoB2 monolayer better as a sensor material for NO2 interaction.

Pristine and Cu decorated hexagonal InN monolayer, a promising candidate to detect and scavenge SF6 decompositions based on first-principle study

We carried out the first-principle study of four types of SF₆ decompositions adsorbed on pristine and Cu atom decorated hexagonal InN monolayer. The adsorption structures, adsorption energy, electron transfer, band structure, density of states and desorption properties were discussed to evaluate the possible application of InN monolayer in field of adsorbent and gas sensor. The results revealed that the pristine InN monolayer has the largest adsorption energy to SO₂ with evident chemical interactions. The introduction of Cu adatom on InN monolayer significantly enhanced the chemical interactions between the InN monolayer and the SO₂, SOF₂, SO₂F₂ gas molecule but declined the adsorption energy of HF. We also investigated the electronic properties of all adsorption configurations and estimated the desorption time of every gas molecule from pristine and Cu decorated InN monolayer to evaluate the potential application in noxious gas detecting and scavenging in gas insulated switch-gear (GIS).

"Haeckelite", a new low dimensional cousin of boron nitride for biosensing with ultra-fast recovery time: a first principles investigation

We performed state-of-the-art first principles calculations under the framework of dispersion corrected density functional theory to investigate the electronic and vibrational properties of a recently found allotrope of BN, with octagonal and square ring forming planar haeckelite structures (haeck-BN). We further investigated the adsorption mechanism of five nucleobases adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U) over haeck-BN to explore its applicability in biosensing. The dispersion correction (DFT-D2) is included to appropriately consider van der Waals interactions. The order of adsorption energy of nucleobases over haeck-BN has the following order: G > T > A ≈ C > U. Significant variation in electronic properties, density of states and work function confirm the adsorption of nucleobases. To check the reusability of haeck-BN as a biosensor toward nucleobases, we calculated the recovery time. Ultrafast recovery times (in millisecond) of 292 ms, 130 ms, 120 ms, 160 ms and 0.6 ms were predicted for G, A, C, T and U, respectively. Our finding suggests that haeck-BN can be utilized as a biosensor for the detection of nucleobases due to its superiority to graphene, h-BN and boron nitride nanotubes, and can be further explored for photocatalysis.