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To address the most significant environmental challenges, the quest for high-performance gas sensing materials is crucial. Among numerous two-dimensional materials, this study investigates the gas-sensitive capabilities of monolayer As, Sb, and Bi materials. To compare the gas detection abilities of these three materials, we employ first-principles calculations to comprehensively study the adsorption behavior of NO and NO2 gas molecules on the material surfaces. The results indicate that monolayer Bi material exhibits reasonable adsorption distances, substantial adsorption energies, and significant charge transfer for both NO and NO2 gases. Therefore, among the materials studied, it demonstrates the best gas detection capability. Furthermore, monolayer As and Sb materials exhibit remarkably high capacities for adsorbing NO and NO2 gas molecules, firmly interacting with the gas molecules. Gas adsorption induces changes in the material's work function, suggesting the potential application of these two materials as catalysts. [ABSTRACT FROM AUTHOR]

Predicting and designing highly gas‐sensitive semiconductors is crucial for solving growing environmental problems. Herein, four lateral heterostructures (LHSs), As6/Sb6 AC‐/ZZ‐LHSs and Sb6/Bi6 AC‐/ZZ‐LHSs, are constructed. The adsorption of NO molecule on these LHSs is investigated using first‐principle calculations. The results indicate that the adsorption of NO molecule on As6/Sb6 LHS with armchair (AC) interface is physisorption, whereas NO molecule is chemically adsorbed on As6/Sb6 LHS with zigzag (ZZ) interface and Sb6/Bi6 AC‐/ZZ‐LHSs, with strong adsorption energy and large charge transfer. All LHSs act as charge donors for the NO molecule. Meanwhile, the adsorption of NO molecule causes a significant change in the electronic properties of As6/Sb6 ZZ‐LHS and Sb6/Bi6 AC‐/ZZ‐LHSs, which shows that these LHSs have great potential for application in NO gas sensors. [ABSTRACT FROM AUTHOR]

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 SO2 and 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 SO2 molecule. 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 SO2 molecule 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 SO2 gas sensor or scavenger. [ABSTRACT FROM AUTHOR]

The adsorption of CO, CO2, CH4, H2, N2 and N2O on armchair (5,5) boron nitride nanotube (BNNT) with and without the doping of transition metals (TM), i.e. Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu or Zn, was investigated using the density functional theory calculation. The results indicate all the considered gases are physically adsorbed by weak interaction on the pure BNNT, revealing that pure BNNT has poor sensing performance for these gases. TM are then doped in the B or N vacancy of BNNT to improve the sensitivity and selectivity. As a result, it was found that the gas adsorption performance of BNNT is obviously enhanced due to the introduction of TM dopant atom. In particularly, according to the results of adsorption energy, Cu doped BNNT (Cu-BNNT) system shows a high selectivity toward CO molecule compared with other metal doped systems. This is further confirmed by the density of state, energy gap and charge transfer analyses. Furthermore, based on the sensor performance analysis, it was found that Cu-BNNT also has favorable desorption characteristics for CO. Therefore, this study concluded that Cu-BNNT can be used as a superior sensor material with high sensitivity, selectivity and favorable recycle time for CO gas. [ABSTRACT FROM AUTHOR]

In this paper, we adopted the first-principles calculations to investigate the sensing properties of the GeP monolayer to four SF6 decomposition gas molecules (H2S, SO2, SO2F2 and SOF2). By discussing the calculated adsorption energy, charge transfer, work function variation combined with charge density difference and electron localization function analysis, we find that GeP monolayer exhibits favorable adsorption strength to SO2 molecule with the most intense charge interaction. And SO2 adsorption can remarkably change the density of states (DOS) of GeP monolayer. Furthermore, we also study the adsorption performance of SO2 molecule on GeP monolayer under applied biaxial strain and external electric field. And the results demonstrate that applying negative electric field can significantly enhance the sensitivity of GeP monolayer to SO2. Therefore, GeP monolayer is a potential candidate for highly sensitive and selective tunable SF6 decomposition gas sensor for on-line diagnostics of power equipment. [ABSTRACT FROM AUTHOR]

[Display omitted] • WO 3 shows X-Ray induced photochromic properties by W6+ to W5+. The transformation of tungsten oxide from yellow (without X-ray) to blue green (60 min) under X-ray radiation of varying duration, and it is a continuous process. Under X-ray irradiation treatment, some of the W-O bonds break, causing the oxygen molecules to leave the surface lattice and creating oxygen vacancies. One oxygen vacancy in WO 3 generally causes two electrons, which reduces W6+ ions into W5+. The product is H x WO 3 , resulting in a reduction in the crystalline volume and band gap of the sample. Simultaneously thermally annealed pre- and post-X-ray irradiation samples, both of which are the same color after cooling. This new finding extends the photochromic energy range of tungsten oxide and has important implications for the design and fabrication of other X-ray-induced photochromic materials for charge transfer, which will certainly benefit the development of next-generation X-ray detection materials. [ABSTRACT FROM AUTHOR]

AlGaAs materials are used in a variety of cutting-edge devices and the band gap states after the surface oxidization is found with Fermi level pinning. With first-principle calculations, we explore the formation of gap states during the initial stage of native-oxide growth on Al 0.5 Ga 0.5 As (001) surface. The results indicate that oxygen adsorption at the bridge sites of Al (Ga)-As satisfies the bond saturation and doesn't lead to any effect on the surface gap states. The breaking of As-As dimer results in the defect states in band gap with Fermi level pining due to the replacement of oxygen. In the oxidization process, it is found that the As-As dimer is very easy to be broken. In addition, the defect states in band gap maybe disappear after the full oxidization of surface with the elimination of unsaturated As on surface. With these gap states, some absorption peaks are found to appear in the range of 0–1 eV in the absorption spectra. [ABSTRACT FROM AUTHOR]

• High selectivity and sensitivity of GeP monolayer to nitrogen oxides. • The variation of work function change can be used to distinguish NO 2 and NO. • Compressive strain improve sensitivity of GeP to NO 2 without raising recovery time. • Applied negative electric field can greatly enhance response of GeP monolayer to NO 2. The sensing properties of GeP monolayer to small gas molecule (CO, CO 2 , O 2 , H 2 O, NH 3 , NO and NO 2) have been investigated by performing first-principle calculations. Based on calculated adsorption distance, adsorption energy and charge transfer, we find that GeP monolayer is the most sensitive to NO 2 and NO molecules, and all gas molecules act as acceptors to gain electrons from GeP monolayer. The adsorption energy of NO 2 is smaller than that of NO molecule, which implies that NO 2 is more easily desorbed from GeP. And different work function changes also indicate the possibility to identify NO 2 and NO in an oxygen-free environment. Moreover, we apply uniaxial and biaxial strains to GeP monolayer and find that a small biaxial compressive strain can effectively enhance the sensitivity of work function type sensor based GeP to NO 2 molecule without increasing recovery time. We also discuss the effect of external vertical electric field on the adsorption performance of NO 2 molecule. The negative electric field can significantly increase the adsorption strength, charge transfer and work function change of NO 2 -GeP system. Our results indicate that GeP monolayer is a potential candidate for NO 2 gas sensor. [ABSTRACT FROM AUTHOR]

• Adsorption properties of SF6 decomposition components on ceria surface were compared based on DFT calculations. • Adsorption of H 2 S, SO 2 and SOF 2 cause conspicuous charge redistribution on CeO 2 (110) surface. • CeO 2 (110) shows higher sensitivity to H 2 S, SO 2 and SOF 2 in comparison with SF 6. The detection of sulfur hexafluoride (SF 6) decomposition components is significant for monitoring the conditions of SF 6 -gas-insulated equipment. In present study, the adsorption of SF 6 and its decomposition components (H 2 S, SO 2 , SOF 2 , and SO 2 F 2) on ceria (110) was investigated by performing calculations based on density functional theory (DFT). Adsorption energy, adsorption configuration, charge transfer, density of states, potential energy and work function for molecular adsorption were adopted to evaluate the performance of ceria (110) on sensing SF 6 decomposition components. Among all the gas molecules, H 2 S, SO 2 and SOF 2 were chemically adsorbed on ceria surface with the adsorption energy following the order: SOF 2 > SO 2 > H 2 S, while SO 2 F 2 and SF 6 were physically adsorbed on the substrate. Besides, the amount of charge transfer and work function modification of H 2 S, SO 2 and SOF 2 molecule's adsorption were larger than those of SO 2 F 2 and SF 6. These calculation results demonstrated ceria (110) showed prominent sensitivity to H 2 S, SO 2 and SOF 2 while less activity to SF 6 , which means sensor based on ceria is promising for detecting H 2 S, SO 2 and SOF 2 in SF 6 gas background, and thus has the potential to online monitor the working condition of SF 6 -gas-insulated equipment. [ABSTRACT FROM AUTHOR]