Gas sensing properties of buckled bismuthene predicted by first-principles calculations

Bismuthene as a novel anode material of magnesium/zinc ion batteries with high capacity and stability: a DFT calculation

In our research, we utilize density functional theory (DFT) to explore the properties of magnesium and zinc atoms adsorbed on bismuthene. Our findings indicate that the hollow site is the most favorable adsorption site for Mg and Zn atoms on bismuthene. The results indicate that Mg and Zn adsorption on the bismuthene surface results in significantly high conductivity, with notable adsorption energies of -3.38 eV for Mg and -3.91 eV for Zn. The bismuthene structure can adsorb 9 Mg and 18 Zn atoms with negative average adsorption energy. These findings suggest excellent stability of bismuthene during the adsorption of magnesium and zinc. Notably, we propose theoretical storage capacities of 2308 mA h g-1 for magnesium-ion batteries (MgIBs) and 4616 mA h g-1 for zinc-ion batteries (ZnIBs), while maintaining structural stability during the adsorption of these metal ions. The observed average open-circuit voltages for bismuthene are 0.01 V for Mg and 0.03 V for Zn, with the material retaining its metallic properties throughout the adsorption process. Furthermore, the calculated diffusion barriers for Mg and Zn are 0.1 eV and 0.21 eV, respectively. Our findings like storage capacity, diffusion energies, and low OCV surpass those of most studied two-dimensional materials, positioning bismuthene as a promising anode material for metal-ion rechargeable batteries.

Designing High-Performance Nanoscale Spin-MOSFET Devices by Using Two-Dimensional Half-Metallic Cr2Se3

Constructing nanoscale spin devices has been a crucial pursuit in the field of nano spintronics. Here, by using the density functional theory (DFT) and nonequilibrium Green's function (NEGF) method, high-performance nanoscale spin-MOSFET devices using half-metallic 2D Cr2Se3 as electrodes are theoretically designed. Specifically, seven typical two-dimensional (2D) semiconductors, Sb, Bi, BP, BAs, MoTe2, WTe2, and WSeTe (with two different contacting surfaces), are considered here as the channel materials. The properties of contact interfaces between these 2D semiconductors and half-metallic 2D Cr2Se3 are first investigated. It is found that except BP and BAs (having Schottky contacts with Cr2Se3), the other 2D semiconductors have vertical Ohmic contacts with Cr2Se3 among which Cr2Se3/Sb, Cr2Se3/MoTe2, Cr2Se3/WTe2, Cr2Se3/WSeTe-Se, and Cr2Se3/WSeTe-Te retain the half-metallic characteristic. Then, these 2D semiconductors with Ohmic vertical contacts are further used to construct spin-MOSFET devices. The results show that devices constructed by half-metallic vertical contacting systems have nearly 100% SIE and therefore giant MR (>107%) when the gate voltage varies. Furthermore, four designed spin-MOSFET devices, namely, Cr2Se3/MoTe2, Cr2Se3/WTe2, Cr2Se3/WSeTe-Se, and Cr2Se3/WSeTe-Te spin-MOSFET have high efficient gate modulations on the magnitude of completely spin-polarized source-drain current with Cr2Se3/WTe2 having the smallest SS value of 134.1 mV/dec. The calculations suggest that Cr2Se3 is a good candidate for constructing spin-MOSFET devices. Our study sheds light on the design of high-performance nanoscale spin-MOSFET devices by using two-dimensional half-metallic electrodes.

Ag Modified SnS2 Monolayer as a Potential Sensing Material for C4F7N Decompositions: A Density Functional Theory Study

As the field of 2D materials rapidly evolves, substances such as graphene, metal dichalcogenides, MXenes, and MBenes have garnered extensive attention from scholars in the gas sensing domain due to their unique and superior properties. Based on first-principles calculations, this work explored the adsorption characteristics of both intrinsic and silver (Ag) doped tin disulfide (SnS2) toward the decomposition components of the insulating medium C4F7N (namely, CF4, C3F6, and COF2), encompassing the adsorption energy, charge transfer, density of state (DOS), band structure, and adsorption stability. The results indicated that Ag-doped SnS2 exhibited an effective and stable adsorption for C3F6 and COF2, whereas its adsorption for CF4 was comparatively weaker. Additionally, the potential for Ag-SnS2 in detecting C3F6 was highlighted, inferred from the contributions of the band gap variations. This research provides theoretical guidance for the application of Ag-SnS2 as a sensing material in assessing the operational status of gas-insulated equipment.

Proposals for gas-detection improvement of the FeMPc monolayer towards ethylene and formaldehyde by using bimetallic synergy

Development and fabrication of a novel gas sensor with superb performance are crucial for enabling real-time monitoring of ethylene (C2H4) and formaldehyde (H2CO) emissions from industrial manufacture. Herein, first-principles calculations and AIMD simulations were carried out to investigate the effect of the Fe-M dimer on the adsorption of C2H4 and H2CO on metal dimer phthalocyanine (FeMPc, M = Ti-Zn) monolayers, and the electronic structures and sensing properties of the above adsorption systems were systematically discussed. The results show that the FeMPc (M = Ti, V, Cr, Mn) monolayers interact with C2H4 and H2CO by chemisorption except for the FeMnPc/H2CO system, while the other adsorption systems are all characterized by physisorption. Interestingly, the adsorption strength of C2H4 and H2CO can be effectively regulated by the bimetallic synergy of the Fe-M dimer. Moreover, the FeCrPc and FeMnPc monolayers exhibit excellent sensitivity towards C2H4 and H2CO, and have short recovery time (4.69 ms-2.31 s) for these gases at room temperature due to the effective surface diffusion at 300 K. Consequently, the FeCrPc and FeMnPc materials can be utilized as high-performance, reusable gas sensors for detecting C2H4 and H2CO, and have promising applications in monitoring the release of ethylene and formaldehyde from industrial processes.

Toxic gas sensing performance of arsenene functionalized by single atoms (Ag, Au): a DFT study

The detection and removal of toxic gases from the air are imminent tasks owing to their hazards to the environment and human health. Based on DFT calculations with VdW correction, adsorption configurations, adsorption energies, and electronic properties were compared for the adsorption of toxic gas molecules (CO, NO, NO2, SO2, NH3 and H2S) on pure arsenene (p-arsenene) and Ag/Au-doped arsenene (Ag/Au-arsenene). Our calculations show that all molecules considered to chemisorb on Ag/Au-arsenene and the substitution of noble metal, particularly Ag, could remarkably enhance the interactions and charge transfer between the gas molecules and Ag/Au-arsenene. Thus, Ag/Au-arsenene is expected to show higher sensitivity in detecting CO, NO, NO2, SO2, NH3 and H2S molecules than p-arsenene. Furthermore, the changes in the vibrational frequencies of gas molecules and the work functions of Ag/Au-arsenene substrates upon adsorption are shown to be closely related to the adsorption energies and charge transfer between the molecules and Ag/Au-arsenene, which is dependent on the molecules. Therefore, Ag/Au-arsenene-based gas sensors are expected to show good selectivity of molecules. The analysis of theoretical recovery time suggested that Ag-arsenene shows high reusability while detecting H2S, CO, and NO, whereas Au-arsenene has high selectivity to sensing NO at room temperature. With the increase in work temperature and decrease in recovery times, Ag/Au-arsenene could be used to detect NH3 and NO2 from factory emission and automobile exhaust with quite good reusability. The above results indicated that Ag/Au-arsenene shows good performance in toxic gas sensing with high sensitivity, selectivity, and reusability at different temperatures.

Dimensionality reduction induced synergetic optimization of the thermoelectric properties in Bi2Si2X6 (X = Se, Te) monolayers

Different from three-dimensional bulk compounds, two-dimensional monolayer compounds exhibit much better thermoelectric performance on account of the quantum confinement and interface effect. Here, we present a systematic study on the electronic and thermal transport properties of bulk and monolayer Bi2Si2X6 (X = Se, Te) through theoretical calculations using density functional theory based on first-principles and Boltzmann transport theory. Monolayer Bi2Si2X6 are chemically, mechanically and thermodynamically stable semiconductors with suitable band gaps, and they have lower lattice thermal conductivity (κL) in the a/b direction than their bulk counterparts. The calculated κL of monolayer Bi2Si2Se6 (Bi2Si2Te6) is as low as 0.72 (0.95) W m-1 K-1 at 700 K. Moreover, monolayer Bi2Si2X6 exhibit a higher Seebeck coefficient compared with bulk Bi2Si2X6 owing to the sharper peaks in the electronic density of states (DOS). This results in a significant increase in power factor by dimensionality reduction. Combined with the synergetically suppressed thermal conductivity, the maximum ZT values for monolayer Bi2Si2Se6 and Bi2Si2Te6 are significantly enhanced up to 5.03 and 2.87 with p-type doping at 700 K, which are more than 2 times that of the corresponding bulk compounds. These results demonstrate the superb thermoelectric performance of monolayer Bi2Si2X6 for promising thermoelectric conversion applications.

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.

Adsorption of gas molecules on buckled GaAs monolayer: a first-principles study

The design of sensitive and selective gas sensors can be significantly simplified if materials that are intrinsically selective to target gas molecules can be identified. In recent years, monolayers consisting of group III-V elements have been identified as promising gas sensing materials. In this article, we investigate gas adsorption properties of buckled GaAs monolayer using first-principles calculations within the framework of density functional theory. We examine the adsorption energy, adsorption distance, charge transfer, and electron density difference to study the strength and nature of adsorption. We calculate the change in band structure, work function, conductivity, density of states, and optical reflectivity for analyzing its prospect as work function-based, chemiresistive, optical, and magnetic gas sensor applications. In this regard, we considered the adsorption of ten gas molecules, namely NH3, NO2, NO, CH4, H2, CO, SO2, HCN, H2S, and CO2, and noticed that GaAs monolayer is responsive to NO, NO2, NH3, and SO2 only. Specifically, NH3, SO2 and NO2 chemisorb on the GaAs monolayer and change the work function by more than 5%. While both NO and NO2 are found to be responsive in the far-infrared (FIR) range, NO shows better spin-splitting property and a significant change in conductivity. Moreover, the recovery time at room temperature for NO is observed to be in the sub-millisecond range suggesting selective and sensitive NO response in GaAs monolayer.

The elemental 2D materials beyond graphene potentially used as hazardous gas sensors for environmental protection

The intrinsic and electronic properties of elemental two-dimensional (2D) materials beyond graphene are first introduced in this review. Then the studies concerning the application of gas sensing using these 2D materials are comprehensively reviewed. On the whole, the carbon-, nitrogen-, and sulfur-based gases could be effectively detected by using most of them. For the sensing of organic vapors, the borophene, phosphorene, and arsenene may perform it well. Moreover, the G-series nerve agents might be efficiently monitored by the bismuthene. So far, there is still challenge on the material preparation due to the instability of these 2D materials under atmosphere. The synthesis or growth of materials integrated with the technique of surface protection should be associated with the device fabrication to establish a complete process for particular application. This review provides a complete and methodical guideline for scientists to further research and develop the hazardous gas sensors of these 2D materials in order to achieve the purpose of environmental protection.

First-principles prediction of strain-induced gas-sensing tuning in tin sulfide

A challenge in the application of two-dimensional (2D) SnS in gas-sensing field is that the SnS monolayer is highly sensitive to oxidizing gases, whereas it is naturally deactivated towards reducing gases. The non-sensitivity of SnS to reducing gases is a problem that needs to be solved urgently in an economic and effective manner. Hence, in this work, we propose a strategy of applying strain modulation on the SnS monolayer to optimize its sensitivity and selectivity for reducing gases fundamentally. Generally, the strain modulation applied on a semiconductor gives rise to a change in its band gap (BG). Based on the first-principles calculations, the strain on SnS was found to induce strong degeneracy and energy-level splitting. Unusually, the tensile strain (≥3%) applied could transform the SnS monolayer from indirect-gap semiconductors to direct-gap semiconductors, manifesting a promising optical application prospect but not appropriate for the gas-sensing filed. Comparatively, the compressive strain (≥3%) on SnS could generate new electronic states at the edge of the conduction band of the SnS monolayer, which increases the conductivity and the weak interaction. Thus, the adsorption of reducing gases on the SnS monolayer is enhanced from physisorption to chemisorption, resulting in a considerable increase in the sensitivity performance to the three reducing gas molecules (NH₃, H₂S, and CO). The induced symmetry breaking of the SnS monolayer under compressive strain leads to much higher surface activation towards reducing gases, which improves its adsorption capability and the ability of screening oxidizing gas molecules. The present work provides key information for novel designs of strain-sensitive dual-function sensors based on SnS.

Adsorption, Gas-Sensing, and Optical Properties of Molecules on a Diazine Monolayer: A First-Principles Study

Using first-principles calculations, the structural, electronic, and optical properties of CO2, CO, N2O, CH4, H2, N2, O2, NH3, acetone, and ethanol molecules adsorbed on a diazine monolayer were studied to develop the application potential of the diazine monolayer as a room-temperature gas sensor for detecting acetone, ethanol, and NH3. We found that these molecules are all physically adsorbed on the diazine monolayer with weak adsorption strength and charge transfer between the molecules and the monolayer, but the physisorption of only NH3, acetone, and ethanol remarkably modified the electronic properties of the diazine monolayer, especially for the obvious change in electric conductivity, showing that the diazine monolayer is highly sensitive to acetone, NH3, and ethanol. Further, the adsorption of NH3, acetone, and ethanol molecules remarkably modifies, in varying degrees, the optical properties of the diazine monolayer, such as work function, absorption coefficient, and the reflectivity, whereas adsorption of other molecules has infinitesimal influence. The different adsorption behaviors and influences of the electronic and optical properties of molecules on the monolayer show that the diazine monolayer has high selectivity to NH3, acetone, and ethanol. The recovery time of NH3, acetone, and ethanol molecules is, respectively, 1.2 μs, 7.7 μs, and 0.11 ms at 300 K. Thus, the diazine monolayer has a high application potential as a room-temperature acetone, ethanol, and NH3 sensor with high performance (high selectivity and sensitivity, and rapid recovery time).

2D Sb2C3 monolayer: A promising material for the recyclable gas sensor for environmentally toxic nitrogen-containing gases (NCGs)

Based on density functional theory investigation, we exposed the potential application of hexagonal Sb₂C₃ nanosheet as highly sensitive material for nitrogen-containing gases (NCGs) NH₃, NO₂ and NO molecules. Our rigorous simulations show that NH₃, NO₂ and NO molecules shows physisorption on the Sb₂C₃ nanosheet via vdW DFT-D3 interactions. The calculations were carried out by considering that the monolayer Sb₂C₃ as the sensor material modulated with its electrical conductivity when its surface adsorbs the gas molecules for their various orientations and positions. It is also found that the magnetic properties are induced in non-magnetic Sb₂C₃ nanosheet by adsorption of NO molecule. The interaction of the Sb₂C₃ nanosheet with the gas molecules is further analysed by the charge density difference (CDD), electrostatic potential (ESP) and Bader charge analysis. Our analysis indicates a strong possibility for the detection of NO₂ and NO gas molecules by the Sb₂C₃ based sensor, due to the associated significant changes in the conductivity and reasonable adsorption energy. Also, in the visible region at T = 300 K, very low recovery times have been found as 431 μs, 785.01 s and 53.8 μs for NH₃, NO₂ and NO, respectively, which strongly suggest the Sb₂C₃ nanosheets as a better reversible multi-time gas sensor material towards the NCGs adsorption. We also explored the humidity effect on the NCGs based 2D Sb₂C₃ sensor material. The current-voltage (I-V) characteristics also confirmed the suitability of 2D Sb₂C₃ in real-time applications. Overall, present work reveals that the 2D Sb₂C₃ nanosheets as a promising material for semiconductor-based nano sensors for environmentally hazard pollutants like NCG molecules.

Gas Adsorption Investigation on SiGe Monolayer: A First-Principle Calculation

The gas adsorption behaviors of CO, CO₂, SO₂, NO₂, NO, NH₃, H₂, H₂O, and O₂ on SiGe monolayer are studied using the first-principles calculation method. Three special adsorption sites and different gas molecule orientations are considered. Based on adsorption energy, band gap, charge transfer, and the electron localization function, the appropriate physical adsorptions of SO₂, NO, NH₃, and O₂ are confirmed. These gases possess excellent adsorption properties that demonstrate the obvious sensitiveness of SiGe monolayer to these gases. Moreover, SiGe may be used as a sensing material for some of them. NO₂ adsorption in different adsorption sites can be identified as chemical adsorption. Besides, the external electric field can effectively modify the adsorption strength. The range of 0 ~ - 2 V/nm can create a desorption effect when NH₃ adsorbs at the Ge site. The NH₃ adsorption models on Ge site are chosen to investigate the properties of the I-V curve. Our theoretical results indicate that SiGe monolayer is a promising candidate for gas sensing applications.