NO Molecules Research Articles

Transition metals (Fe, Ni and Zn) doped GaN nanosheets and their adsorption performance towards SO2 and NO2 toxic gases: A DFT-D approach

The emissions of SO2 and NO2 gases in the atmosphere through different sources can cause environmental problems such as air pollution and acid rain. The electronic properties of gallium nitride nanosheets (GaNNSs) as a semiconductor material can be tuned by transition metals doping. In this work, the adsorption performance of M (M = Fe, Ni and Zn) doped gallium nitride nanosheets (GaNNSs) towards SO2 and NO2 toxic gases were scrutinized by dispersion corrected density functional theory (DFT-D) calculations at PBE-D/DNP level of theory. Specific attention is paid to obtaining insights into the adsorption and sensing features of pristine and M-doped GaNNSs (MGa,N-GaNNS) towards SO2 and NO2 molecules. The energies of adsorption were calculated to be −27.2 kcal mol−1 for SO2-GaNNS and −11.8 kcal mol−1 for NO2-GaNNS complexes. The range of adsorption energies on the M-doped GaNNSs was −8.9 (NO2-ZnGa-GaNNS) to −72.1 (NO2–FeN-GaNNS) and −19.7 (SO2-FeGa-GaNNS) to −51.0 (SO2–FeN-GaNNS) kcal mol−1, indicating that FeN-GaNNS is energetically more favorable than other M-doped GaNNSs for NO2 and SO2 adsorption. The changes in the energy gaps of adsorption complexes revealed that the ZnN-GaNNS and ZnGa-GaNNS could be suitable better for sensing NO2 and SO2 gases, respectively. The present results are helpful not only to understand the adsorption nature of the NO2 and SO2 gases on M-doped GaNNS but also can provide helpful guidance for developing GaN-based sensors.

In silico study of adsorption of oxide gases by MN4 (M = Be, Mg) monolayers

In response to the continuously increasing pollution and hazards due to gas leakage, density functional theory based simulation of MN4 (M = Be, Mg) monolayer (ML) was performed. The computed cohesive energy of −2.28 eV/atom for BeN4 ML as well as −2.03 eV/atom for MgN4 ML, and absence of imaginary frequencies in the phonon dispersion curves suggest dynamical stability of both the MLs. The stable structures of MN4 MLs attain monoclinic configuration. The electronic band structure and electron density of states show, the semi-metallic behaviour of both the MLs. With the adsorption energy of −1.64 eV and −2.68 eV, for BeN4 and MgN4 ML, respectively, NO2 is superiorly sensed by MN4 MLs. The charge transfer of −0.452e (BeN4 ML) and −0.646e (MgN4 ML), from gas molecule to the ML, provide assurance for strong adsorption. Also, both the MLs are good at sensing SO2, as the adsorption energies are −0.87 eV (BeN4 ML) and −1.64 eV (MgN4 ML). Both NO2 and SO2 gas molecules contribute at the Fermi level in the projected density of states (PDOS), referring to the transition of MN4 ML, from semi-metallic to metallic, after the adsorption. Besides, in the current–voltage (I-V) characteristics, the extremely sensitive behaviour of MN4 ML towards NO2 gas molecule can be observed, as the current for NO2 adsorbed MN4 ML shoots really high at voltage as low as 0.6 V, which makes MN4 MLs excellent pick as sensing arrays in NO2 gas sensors.

Stable Isotope Analysis of Greenhouse Gases Requires Analyte Preconcentration

Nitrous oxide (N2O) is an important trace gas contributing to global warming and depletion of ozone in the stratosphere. Its increasing abundance is caused mainly by anthropogenic sources, such as application of fertilizers in agriculture or emissions from industry. To understand the N2O global budget, its sources and sinks need to be well-described and quantified. In this project, a new method for N2O source appointment was developed that can help with this task. The method is based on analysis of the eight most abundant isotopic molecules of N2O, using quantum cascade laser absorption spectroscopy (QCLAS). The applicability of the method towards the N2O biogeochemical cycle was demonstrated on a prominent N2O source (bacterial denitrification) and the most important N2O sink (UV photolysis) on samples prepared in laboratory experiments. An extension of the QCLAS method to natural samples can be achieved by hyphenation with a preconcentration technique that increases concentration of the analyte and standardizes the sample matrix. This article provides an overview of currently applied preconcentration techniques in the field of greenhouse-gas analysis and a description of the preconcentration device TREX that will be employed in future projects with the developed QCLAS method.

Dissociative multi-ionization of N2O molecules in strong femtosecond laser field.

Multi-ionization and subsequent Coulomb explosion (CE) of the N2O molecule irradiated by a linearly polarized 800nm laser field is investigated by a reaction microscope, where a number of CE channels of N2Oq+ with q ≤ 5 for two-body fragmentation and q ≤ 8 for three-body fragmentation were observed. For two-body CE, by analyzing the internuclear separations extracted from kinetic energy releases (KERs), dissociation branching fractions, and laser intensity dependence, interestingly, we found that fragmentation N2O5+ → N3+ + NO2+ is produced directly from dissociating N2O3+ via non-sequential stairstep ionization, whereas most of the others result from the sequential stairstep ionization. For three-body CE, 25 fragmentation channels of N2Oq+ (q = 3-8) are distinguished in the present charge-encoded multi-photoion coincidence plot, and the concerted fragmentation mechanism is nominated in a typical Dalitz plot. With the help of the numerical computation with the measured KERs and momentum correlation angles, the geometric structures of molecular ions prior to fragmentation are reconstructed, which display the bending motion and simultaneous two-bond stretching before the CE. Increasing of the bond length for high charged N2Oq+ indicates the dominating stairstep ionization in the three-body fragmentation.

Detection of hot electron-driven photochemical reaction of steady- state NO2 gas molecules by surface–enhanced Raman spectroscopy

In this work, a steady-state detection method of 50 ppm of nitrogen dioxide NO2 gas in a polyethylene (PET) bag using surface-enhanced Raman spectroscopy (SERS) is reported for the first time. SERS was performed on different shapes of gold nanostructures, gold nanostars (GNS) and nanoporous gold film (NPG). In both, the vibrational modes assigned to the adsorbents of NO2 molecules such as NO2, NO, NO−3, N2O3, and N2O5 were detected. The generation of adsorbents is due to the photo-chemical reaction driven by the hot electrons generated at the surface of gold nanostructures. Our finding is supported by a finite element simulation excluding the plasmon-induced photo-thermal process due to the long duration of excitation compared to the duration of SERS measurement. The mechanism of NO2 photochemical reactions is explained, confirming the adsorption of NO2 molecules on the gold surface towards their oxygen atoms.

Interactions of nitric oxide molecules with pure and oxidized silver clusters Agn ±/AgnO± (n=11-13): A computational study.

In this work, we have studied, within density functional theory, the interaction of NO with pure and oxidized silver clusters, both anionic and cationic, composed from 11 to 13 Ag atoms. In that size interval, shell closing effects are not expected, and structural and electronic odd-even effects will determine the strength of interaction. First, we obtained that species Agn ± and AgnO± with odd number of electrons (n = 12) adsorb NO with higher energy than their neighbors (n = 11 and 13). This result is in agreement with the facts observed in recent mass spectroscopy measurements, which were performed, however, at finite temperature. The adsorption energy is about twice for oxidized clusters compared to pure ones and higher for anions than for cations. Second, the adsorption of another NO molecule on AgnNO± forms Agn(NO)2 ±, with the dimer (NO)2 in cis configuration, and binding the two N atoms with two neighbor Ag atoms. The n = 12 species show the higher adsorption energy again. Third, in the absence of reaction barriers, all complexes Agn(NO)2 ± dissociate spontaneously into AgnO± and N2O, except the n = 12 anion. The maximum high barrier along the dissociation path of Ag13(NO)2 - is about 0.7eV. Further analysis of projected density of states for Ag11-13(NO)x ± (x = 0, 1, 2) molecules shows that bonding between NO and Ag clusters mainly occurs in the energy range between -3.0 and 3.0eV. The overlap between 4d of Ag and 2p of N and O is larger for Ag12(NO)2 ± than for neighbor sizes. For n = 12, the d bands are close to the (NO)22π orbital, leading to extra back-donation charge from the 4d of Ag to the closer 2π orbital of (NO)2.

A new 2D metallic K3Cl2 nanosheet as a promising candidate of NO2 gas sensor and capturer

Based on first-principles computations and global search method, we identify a new two-dimensional K3Cl2 nanosheet with unique structural and electrical properties. Formation energy and phonon spectrum calculations and ab initio molecular dynamics (AIMD) simulations confirm the stability of this predicted structure. The metallic character of the K3Cl2 can be maintained under tensile uniaxial and biaxial strains. The calculation demonstrates that K3Cl2 nanosheet can effectively detect NO2 molecules from the mixture of H2, H2O, NH3, CO, NO, NO2 and CO2. Thereason of the conversion from metal to semiconductor of K3Cl2 adsorbing different number of NO2 molecules mightlie in the change of bonding/antibonding state of K-N, K-O and NO bonds. Our calculated results show that K3Cl2 nanosheet is a promising NO2 gas sensor and capturer with high selectivity and sensitivity.

Constructing n-type doped perovskite from Ti-bearing solid waste to boost the NO-to-NO2 oxidation

The structure-activity relationships of perovskites for SCR deNOx remain unclear. Also, their applications are extremely limited by the high fabrication cost. Here A feasible molten salt method is proposed to directly fabricate modified CaTiO3 from Ti-bearing solid waste. Following this method, multiple perovskite-based structures are constructed by doping CaTiO3 with lanthanides and transition elements. Pristine CaTiO3 is incapable of removing NO in the temperature range from 100 °C to 300 °C. Encouragingly, CaTiO3 doped with Ce and Mn displays astonishing low-temperature activity, acquiring 99% NO removal at 145 °C with light illumination (GHSV = 36,000 h−1). For the perovskite with the ABO3 formula, the adsorption property of NO could be tuned by the electron occupancy of the eg-parentage orbitals in the BO6 octahedron. The doping elements of Mn and Ce provide new sites to activate gaseous NO molecules. More importantly, the n-type doping by substituting Ca with Ce introduces excess valency electrons, facilitating the formation of monodentate nitrate and NO2 desorption, thereby promoting the fast SCR process. This work not only provides new insights into the perovskite-based SCR catalysts spanning low-cost fabrication and structure construction but offers a novel strategy for the utilization of Ti-bearing blast furnace slag.

Oxidation of methane and ethylene over Al incorporated N-doped graphene: A comparative mechanistic DFT study

It is generally recognized that developing effective methods for selective oxidation of hydrocarbons to generate more useful chemicals is a major challenge for the chemical industry. In the present study, density functional theory calculations are conducted to examine the catalytic partial oxidation of methane (CH4) and ethylene (C2H4) by nitrous oxide (N2O) over Al-incorporated porphyrin-like N-doped graphene (AlN4-Gr). Adsorption energies for the most stable configurations of CH4, C2H4, and N2O molecules over the AlN4-Gr catalyst are determined to be −0.25, −0.64, and −0.40 eV, respectively. According to our findings, N2O can be efficiently split into N2 and Oads species with a negligible activation energy on the AlN4-Gr surface. Meanwhile, CH4 and C2H4 molecules compete for reaction with the activated oxygen atom (Oads) that stays on the surface. The energy barriers for partial methane oxidation through the CH4 + Oads → CH3° + HOads and CH3° + HOads → CH3OH reaction steps are 0.16 eV and 0.27 eV, respectively. Furthermore, the produced CH3OH may be overoxidized by Oads to give formaldehyde and water molecules by overcoming a relatively low activation barrier. The activation barriers for C2H4 epoxidation are small and comparable to those for CH4 oxidation, implying that AlN4-Gr is highly active for both reactions. The high energy barrier for the 1,2-hydrogen shift in the OCH2CH2 intermediate, on the other hand, makes the production of acetaldehyde impossible under normal conditions. According to the population analysis, the AlN4-Gr serves as a strong electron donor to aid in the charge transfer between the Al atom and the Oads moiety, which is necessary for the activation of CH4 and C2H4. The findings of the present study may pave the way for a better understanding of the catalytic oxidation the CH4 and C2H4, as well as for the development of highly efficient noble-metal free catalysts for these reactions.

DFT Insight to Ag2O Modified InN as SF6-N2 Mixture Decomposition Components Detector

In gas-insulated switchgear (GIS), partial discharge (PD) can be monitored by detecting sulfur hexafluoride-nitrogen (SF6-N2) decomposition components. In this paper, silver oxide (Ag2O) modification was introduced to improve the gas-sensing properties of graphene-like indium nitride (InN). The adsorption process of NO2, SO2F2, SOF2 and SOF4 on Ag2O-InN was simulated based on the first principles calculation and density functional theory (DFT). The gas sensing mechanism was revealed by density of states theory and molecular orbital theory. It is found that Ag2O doping greatly improves the adsorption properties of InN to NO2 and SOF2 molecules. The adsorption capacity of Ag2O-InN to the four gas molecules is: NO2 > SOF2 > SOF4 > SO2F2. All adsorptions can proceed spontaneously, and the gas molecules are electron donors and Ag2O-InN is an electron acceptor. Through the analysis of recovery time, it is found that NO2 is difficult to desorb from the substrate due to the significant adsorption energy of −2.201 eV, while SOF4, SOF2 and SO2F2 have a moderate adsorption energy of −0.185 eV, −0.754 eV and 0.173 eV and extremely short desorption time. The conductivity of the whole system changed after these four gases were adsorbed on the Ag2O-InN monolayer. In summary, Ag2O-InN can be used as NO2 adsorbent and gas sensors to detect SOF4, SOF2 and SO2F2. This paper provides a method for on-line monitoring of partial discharge in GIS.

Oxygen Molecule Formation and the Puzzle of Nitrogen Dioxide and Nitrogen Oxide during Lightning Flash.

Unlike the compounds of the natural air atmosphere, the lightning systems are primarily focused on NO(X2Π), NO2(12A'), and O(3P) concentrations that occurred newly and highly in the ground electronic structure. While the NO/NO2 concentrations ratio is about 2000 during the lightning flash, this ratio becomes about 0.8 right after the lightning flash. The reason for this decrease in the ratio is the disappearance of the high temperature that prevents the formation of NO2 (with the combination of NO and O) and of the photon energy that causes its dissociation (NO2 + hv → NO + O) right after the lightning flash. However, this study will focus on the reactions that contribute to the NO concentration, except for the combination of N and O atoms during lightning flash. To do this, it was focused on the reactive scattering states (especially the NO-exchange) of the NO + O collision and the photo-dissociation of NO2, which provide the formation of the NO molecule in the ground electronic state. This case raises important questions. To what extent do the NO-exchange reaction and the photo-dissociation of NO2 contribute to the atmospherically observed NO molecules? or how can the vibrational quantum states of the NO molecules formed by the photo-dissociation be effected on the NO + O1 collision to produce a NO1 molecule? These conditions may contribute to the concentrations of NO high during lightning flashes. Under low collision energy (between 0.1 and 0.3 eV), the NO (v = 0) population dissociated by a photon can act as reactants in the NO-exchange reactive scattering on the doublet electronic state. Since it is assumed that all of the NO2 molecules are due to NO in the lightning flash system, this is one of the reasons that makes the NO population so high during lightning flash. Therefore, in the light of considering that the lightning system supports the formation of highly vibrating molecular groups, it might also support the formation of O2 molecules. In particular, it was shown that the v = 4 quantum state of the NO molecule over the doublet state between collision energies of 0.9-1.5 eV and the v = 5 quantum state of the NO molecule over the quartet state between collision energies of 1.0-1.5 eV contribute to O2 formation.

First-principles study of the monolayer MoSeTe for gas sensing applications

The monolayer MoSeTe is a two-dimensional material similar to graphene. Herein, the adsorption characteristic of NO 2 , CH 4 , CO and NO molecules on the monolayer MoSeTe has been studied by first-principles calculations. All of the above gas molecules are tending to adsorb on the Te-layer surface rather than the Se-layer surface, and the values of their adsorption energies on the monolayer MoSeTe surface are all negative. Among them, the adsorption energy of NO 2 gas molecule on the monolayer MoSeTe is obviously stronger than that of other gas molecules, indicating the strong interaction between them. Because the charge transfer between the N -based molecules and monolayer MoSeTe are more than that of the C-based molecules, the monolayer MoSeTe can be used as the gas sensor material for detecting the N -based gases. These theoretical outcomes may provide useful guidance for the monolayer MoSeTe as an ideal material for detecting the N -based gases.

Penta-BeP2 Monolayer: A Superior Sensor for Detecting Toxic Gases in the Air with Excellent Sensitivity, Selectivity, and Reversibility.

Directly and quickly detecting toxic gases in the air is urgently needed in industrial production and our daily life. However, the poor gas selectivity and low sensitivity under ambient conditions limit the development of gas sensors. In this work, we demonstrate that the penta-BeP2 monolayer is an excellent toxic gas sensor by using first-principles calculations. The calculated results show that the semiconducting penta-BeP2 monolayer can chemisorb toxic gas molecules (including CO, NH3, NO, and NO2) with distinct charge transfer (-0.182 to 1.129 e) but negligibly interact with ambient gas molecules (including H2, N2, H2O, O2, and CO2), indicating high gas selectivity for primary environmental gases. The calculated I-V curves show that the penta-BeP2 monolayer exhibits a fast response with toxic gas molecules. Upon interaction with CO, NH3, NO, and NO2 molecules at a bias voltage of 0.7 V, the currents are 10.23, 14.48, 32.10, and 129.90 times that of the pristine penta-BeP2 monolayer, respectively, which induces high sensitivity values of 9.23, 13.48, 31.10, and 128.90, respectively. Moreover, the moderate adsorption energies of all toxic gas molecules guarantee that the penta-BeP2 monolayer possesses good reversibility at room temperature with a short recovery time. Herein, all of our results indicate that the penta-BeP2 monolayer could be a superior candidate for sensing toxic gases with high selectivity, sensitivity, and reversibility.

What Determines the Drastic Reactivity of Nbn+ Clusters with Nitric Oxide under Thermalized Conditions?

We report an in-depth study of the adsorption and reaction of NO with cationic Nbn+ (n = 1-20) clusters under thermalized conditions in a laminar flow tube reactor in tandem with a customized triple quadrupole mass spectrometer (FT-TQMS). It is found that the small-sized Nbn+ clusters (2 ≤ n ≤ 7) readily react with NO giving rise to dominant fragmentation products pertaining to the loss of a stable diatomic molecule NbO or NbN. In contrast, the reaction products of larger-sized clusters (n ≥ 10) proceed through diverse channels, including NO adsorption, N2/N2O release, and even NO2 formation. These experimental observations provided the incentive for us to dig deep into the reaction mechanism with the help of DFT calculations. In contrast to the NO-donation coordination in transition metal complexes, here the cationic Nbn+ clusters exhibit dominant electronic donation in initiating the reactions with NO molecules. We fully demonstrated the reaction rate constants, compared the reaction energy diagram of typical Nbn+ clusters, and unveiled the distinct interaction mechanism of niobium clusters available for NO activation and conversion.

Vibrational Relaxation of Highly Vibrationally Excited Molecules Scattered from Au(111): Role of the Dissociation Barrier

Energy transfer during molecular collisions at a metal surface represents a sensitive probe of the molecule–surface interaction potential. Here, via molecular dynamics calculations on several first-principles neural network potentials, we find that the vibrational energy transfer dynamics of highly vibrationally excited NO and CO molecules scattered from Au(111) are strongly correlated with their respective potential energy landscapes in the vicinity of the dissociation barrier. Our results not only reproduce the observed significantly less vibrational relaxation of CO (vi = 17) than NO (vi = 16) scattered from Au(111) and attribute it to the different dissociation barriers in the two systems, but also show a dramatic change of dynamics due to a minor adjustment of the energy landscape near the barrier in the CO case. We find that the BEEF-vdW density functional based potential largely overestimates the vibrational relaxation of CO (vi = 17) even in the absence of any nonadiabatic energy loss, despite its good description for CO adsorption on Au(111). We also discuss the possibility of integrating the validated adiabatic potential with first-principles determined diabatic states towards a more complete description of the non-adiabatic energy transfer in these benchmark systems.

Calcium poisoning mechanism on the selective catalytic reduction of NOx by ammonia over the γ-Fe2O3 (001) surface.

γ-Fe2O3 has an excellent low-temperature selective catalytic reduction (SCR) deNOx performance, but its resistance to alkaline earth metal calcium (Ca) is poor. In particular, the detailed mechanism of Ca poisoning on the γ-Fe2O3 catalyst at the atomic level is not clear. Hence, the density functional theory method was used in this research to investigate the influence mechanism of Ca poisoning on the NH3-SCR over the γ-Fe2O3 catalyst surface. The findings reveal that NH3, NO, and O2 molecules can bind to the γ-Fe2O3 (001) surface to generate coordinated ammonia, monodentate nitroso, and adsorption oxygen species, respectively. The main active site is Fe1-top. For the γ-Fe2O3 with Ca poisoning, the Ca atom has a high adsorption energy on the surface of γ-Fe2O3 (001), which covers the catalyst surface and reduces the active sites. The presence of Ca atom decreases the adsorption performance of NH3, while slightly improving the NO and O2 adsorption. In particular, the Ca atom restrains the NH3 activation and NH2 formation, which is detrimental to the NH3-SCR process.

Poly(3-aminophenylboronic acid) as a sensitive electrical and optical sensor material for detection of some air pollutants: A computational study

This paper has addressed the adsorption of CO, CO2, NO, NO2, SO2 and SO3 molecules on poly(3-aminophenylboronic acid) (PAPBA) chain at M06-2X/6-311G++(d,p) level of theory to explore the potential gas sensing application of PAPBA. The conduction of PAPBA is significantly improved upon CO, NO, NO2, SO2 and SO3 adsorption with different %ΔEg values (−79.74%, −850.85%, −26.70%, −972.91%, and −1101.49%, respectively) for each molecule demonstrating there is a considerable change in the electrical conductivity of PAPBA chain fits to any type of molecule. Furthermore, the absorption spectra of PAPBA chain was sensitive to adsorption of NO, NO2, SO2 and SO3 molecules (with ΔEλmax values, −0.64, −0.67, −0.11, and −0.59, respectively) which indicates that this chain can be applied as an optical sensor material for detection of mentioned gas molecules. The calculated recovery times for all studied gas molecules were between 3.826 e-10 to 1.624 e-4 s which implies on the conformance of the PAPBA chain as a sensor. The natural bond orbital (NBO) charge distribution and analysis, the density of states (DOS), reduced density gradient (RDG), non-covalent interactions (NCI) index, and UV–visible analysis were performed for the pure PAPBA chain as well as different gas/PAPBA complexes in order to further understand the electronic characteristics of the studied systems. Such investigations open new opportunities for the rational design of novel and qualified electrical and optical sensors for the detection air pollutant molecules.

Estimating monthly global ground-level NO2 concentrations using geographically weighted panel regression

Predicting long-term ground-level nitrogen dioxide (NO2) is important globally to support environmental and public health research and to provide information to governments and society for air pollution control policies. The ozone monitoring instrument (OMI), onboard Aura Satellite, detects monthly global tropospheric column amounts (TrCA) of NO2 molecules. However, the relationship between the ground-level NO2 concentration and TrCA of NO2 molecules remains elusive because NO2 molecules in the air are not evenly distributed vertically. We use geographically weighted panel regression (GWPR) to examine the relationship between satellite-derived data, measured ground-level NO2 concentrations, and several controlling meteorological variables from January 2015 to October 2021. The GWPR can analyze unbalanced panel data and capture the spatial variability of the relationship. Based on the GWPR estimation, 82 monthly global ground-level NO2 concentrations are predicted from January 2015 to October 2021. The GWPR is reliable, as indicated by the 10-fold cross-validation. The accuracy of the raster prediction of global ground-level NO2 from January 2015 to October 2021 is 69.61%. The coefficient of correlation, root mean square error and mean absolute error between globally predicted and measured ground-level NO2 are 0.838, 7.84 μg/m3 and 4.07 μg/m3, respectively, while the mean of globally measured ground-level NO2 is 19.47 μg/m3. Overall, this research provides critical basic data to environmental and public health science and valuable information for governments and societies to make more reasonable policies.

A first-principles study of gas molecule adsorption on two-dimensional borophene

The effect of two-dimensional borophene on the adsorption properties of gas molecules was studied by first-principles method. The adsorption energies of gas molecule on the four adsorbed site were first computed. Through compare these adsorption energies of different adsorbed site, the most stable of adsorption configuration were determined. In order to confirm the interaction mechanism of gas molecule and borophene, the charge population of borophene-gas molecule were computed. The calculated shows that the CO, NO and NO2 molecule are adsorbed on the borophene nanosheet with chemical adsorption. The further charge population analysis of the borophene-CO and the borophene-NO adsorption system shows that the electrons transfer from borophene nanosheet to CO and NO molecule. It is can be seen that the borophene acts as electron donor and gas molecule acts as electron acceptor. Based on the above the calculation and analysis, we concluded that the borophene materials is an excellent candidates to detect gas molecules.

Enhanced NO2-sensing performances of CeO2 nanoparticles on MoS2 at room temperature

The composites of CeO2 nanoparticles and MoS2 nanosheets are prepared by hydrothermal method. It is found that the CeO2/MoS2 composites exhibit the better NO2-sensing response at room temperature (RT), with the sensitivity towards 5 ppm NO2 higher than that of pure MoS2 by 69.1%, and 85% of the resistance can be returned within 900 s. The sensor also possesses the characteristics of a fast response, a reliable long-term stability and an excellent selectivity. Based on the first-principle calculations, the adsorption energy of CeO2/MoS2 composites to NO2 is much higher than that of MoS2, enhancing the adsorption ability of NO2. Moreover, the CeO2/MoS2 composites could suppress the aggregation of nanosheets and nanoparticles, and thus provide plenty of active sites for adsorption of NO2 molecules. As a result, the room-temperature NO2-sensing response is enhanced substantially.