NO2 Gas Molecules Research Articles

Interaction study of CO and NO pollutant gases with pristine, defected and doped α-CX (X=N, P) monolayers using density functional theory

CO and NO are two of the most pollutant gases that exist in the environment, which makes their tracing highly crucial. In this problem, we have investigated the adsorption performances of highly toxic CO and NO gases over pristine, defect-tuned, and Aluminium (Al)-doped α-CX (X=N, P) monolayers. In addition to the adsorption properties, we have calculated electronic properties such as band structure, projected density of states (PDOS) and charge transfer, sensing properties such as work function and recovery time for pristine, defect-tuned, and Al-doped α-CX before and after the gas adsorption process. Given the poor adsorption energies and large adsorption distances, pristine α-CX monolayers are not suitable candidates for the toxic gas sensors. In case of functionalized α-CX, the adsorption energy is highest in case of C-defected α-CN for CO gas adsorption. For interaction of NO gas molecule with functionalized α-CX, Al-doped α-CN is deemed to be best candidate for adsorption. The computed recovery times are extremely long (exceeding several hours) in the best-case scenarios, this implies that C-defected α-CN and Al-doped α-CN are most suitable for CO and NO gas removal applications.

A 2D-0D-2D Sandwich Heterostructure toward High-Performance Room-Temperature Gas Sensing.

The construction of two-dimensional (2D) van der Waals (vdW) heterostructures over black phosphorus (BP) has been attracting significant attention to better utilize its inherent properties. The sandwich of zero-dimensional (0D) noble metals within BP-based vdW heterostructures can provide efficient catalytic channels, modulating their surface redox potentials and therefore inducing versatile functionalities. Herein, we realize a 2D WS2-Au-BP heterostructure, in which Au nanoparticles are connected between BP and WS2 via ionic bonds. The ultralow conduction band minimum position, the reduced adsorption energies of O2, and the increased dissociation barrier energy of O2- into 2O contribute greatly to improving the long-term stability of BP in the air. The formation of heterostructures can reduce the potential barrier energy in target gas molecules, thus enhancing the absorption energy and charge transfer. Taking the paramagnetic NO2 gas molecules as a representative, a stable response magnitude of 2.11 to 100 ppb NO2 is achieved for 80 days, which is far larger than the initial responses of most BP-based materials. A practical gas sensing system is also developed to demonstrate its real-world implementation. This work provides a promising demonstration of 0D noble metal within 2D BP-based vdW heterostructure for simultaneously improving the long-term stability and room-temperature reversible gas sensing.

Atomic insights into the interaction of N2, CO2, NH3, NO, and NO2 gas molecules with Zn2(V, Nb, Ta)N3 ternary nitride monolayers.

The search for promising carrier blocking layer materials with high stability, including resistance to surface inhibition by environmental molecules that cause a drop in carrier mobility, is critical for the production of tandem solar cells. Based on density functional theory calculations, the reaction of atmospheric gases, including N2, CO2, NH3, NO, and NO2, with three promising Zn2(V, Nb, Ta)N3 monolayers is discovered. The results suggest the chemical adsorption of NH3 and physical adsorption of NO and NO2. In addition, the Zn2(V, Nb, Ta)N3 monolayers are characterized by a weak bonding with N2 and CO2. Charge redistribution is found at the interface between the monolayers and NH3, NO and NO2 molecules, leading to the formation of a local surface dipole that affects the functionality of the Zn2(V, Nb, Ta)N3 monolayers. The Zn2VN3 monolayer is less reactive with atmospheric gases and thus is the most promising for application in tandem solar cells. Notably, the revealed nontrivial behavior of the Zn2(V, Nb, Ta)N3 monolayers towards N-containing gases makes them promising for application in gas sensing. Specifically, the Zn2TaN3 monolayer is the most promising for application in molecular sensing due to its high reversibility and distinguished interaction with NH3, NO, and NO2 gases.

Adsorption and sensing performance of air pollutants on a β-TeO2 monolayer: a first-principles study.

Two-dimensional (2D) β-TeO2 is a novel semiconductor with potential applications in electronic circuits due to its air-stability and ultra-high carrier mobility. In this study, we explore the possibility of using a 2D β-TeO2 monolayer for the detection of gaseous pollutants including SO2, NO2, H2S, CO2, CO, and NH3 gas molecules based on first-principles calculations. The adsorption properties including the adsorption energy, adsorption distance and charge transfer indicate that the interaction between 2D β-TeO2 and the six gases is via a physisorption mechanism. Among the six gas adsorption systems, the SO2 adsorption system has the most negative adsorption energy and the largest charge transfer. In addition, the adsorption of SO2 obviously changes the electrical conductivity of the β-TeO2 monolayer because the band gap decreases from 2.727 eV to 1.897 eV after adsorbing SO2. Our results suggest that the 2D β-TeO2 should be an eminently promising SO2 sensing material.

Two-dimensional Janus X2STe (X = B, Al) monolayers: the effect of surface selectivity and adsorption of small gas molecules on electronic and optical properties.

This investigation delves into the adsorption characteristics of CO, NO, NO2, NH3, and O2 on two-dimensional (2D) Janus group-III materials, specifically Al2XY and B2XY. The examination covers adsorption energies and heights, diverse adsorption sites, and molecular orientations. Employing first-principles analysis, a comprehensive assessment of structural, electronic, and optical properties is conducted. The findings highlight NO2 as a prominent adsorbate, emphasizing the Te surface of 2D Al2STe and B2STe materials as particularly adept for NO2 detection, based on considerations of adsorption energy, height, and charge transfer. Additionally, the study underscores the heightened sensitivity of work function changes in the B2STe material. The adsorption properties of all gas molecules, except for NO2, on both materials were determined to be physical. Upon adsorption of the NO2 gas molecule onto the B2STe Janus material, it was observed that the material exhibited weak chemical adsorption behavior, which was confirmed by the adsorption energy, larger band gap change, electron localization function, work function changes and charge transfer from the material. This research provides valuable insights into the gas-sensing potential of 2D Janus materials.

Cu- and Al-Decorated Monolayer TiSe2 for Enhanced Gas Detection Sensitivity: A DFT Study.

The rapid industrial development has contributed to worsening global pollution, necessitating the urgent development of highly sensitive, cost-effective, and portable gas sensors. In this work, the adsorption of CO, CO2, H2S, NH3, NO, NO2, O2, and SO2 gas molecules on pristine and Cu- and Al-decorated monolayer TiSe2 has been investigated based on first-principles calculations. First, the results of the phonon spectrum and ab initio molecular dynamics simulations demonstrated that TiSe2 is dynamically stable. In addition, compared to pristine TiSe2 (-0.029 to -0.154 eV), the adsorption energy of gas molecules (excluding CO2) significantly decreased after decorated with Cu or Al (-0.212 to -0.977 eV in Cu-decorated TiSe2, -0.438 to -2.896 eV in Al-decorated TiSe2). Among them, NH3 and NO2 have the lowest adsorption energies in Cu and Al-decorated TiSe2, respectively. Further research has shown that the decrease in adsorption energy of gas molecules is mainly due to orbital hybridization and charge transfer between decorated Cu and Al atoms and gas molecules. These findings suggest that TiSe2 decorated with Cu and Al can effectively improve its sensitivity to NH3 and NO2, respectively, making it promising in gas sensing applications.

Ultrasensitive and reversible NO2 gas sensor based on SnS2/TiO2 heterostructures for room temperature applications

Nitrogen dioxide (NO2) is one of the toxic gases produced by chemical industries, power plants, and vehicles. In this work, we demonstrate an inexpensive sensing platform for NO2 detection at room temperature (RT-32 °C) based on a charge transfer mechanism. Three-dimensional hierarchical SnS2 and SnS2/mesoporous TiO2 nanocomposites were synthesized via the solvothermal method. SnS2/20 wt% mesoporous TiO2 nanocomposites sample showed 245.4% enhanced response compared to pristine SnS2. The fabricated device exhibits excellent selectivity among all other interfering gases with one-month stability. The rapid response and enhanced response achieved were obtained for the minimum concentration of 2 ppm NO2. The formation of heterojunction between SnS2 and mesoporous TiO2 has a synergetic effect, providing more active sites and porous structures for the detection of NO2 gas molecules.

Theoretical evaluation of gas sensing and capturing characteristics on the point defective diboron dinitride monolayer

Defects can significantly alter the properties of 2D material surfaces, thereby affecting the application results. In this work, the adsorption behaviors of H2S, SO2, NH3, and NO2 gas molecules on rationally defective diboron dinitride (n-BN) monolayers in the presence and absence of an external electric field and moisture condition are studied by the first-principles calculation approach. The results demonstrate that the boron and nitrogen defects are more likely to be generated and both defective monolayers have strong absorption effects on SO2 and NO2 gas molecules with absolute values of adsorption energy above 2.5 eV. And the conductivity change after adsorption of NO2 molecule is particularly pronounced in nitrogen defect monolayer, thus greatly increasing the sensitivity to the gas molecule. Based on the high sensitivity, the defective monolayer could be an ideal one-time scavenger for SO2 and NO2 gas molecules. While the H2S and NH3 molecules could obtain the appropriate adsorption energy and the adjustable recovery time on the defective monolayer under the dry or existent external electric field environment. These results make it possible to design a useable gas device with good gas sensing and capturing characteristics on the defective n-BN monolayer.

Insights into different toxic molecular gases on the Fe-dimer anchored at C2N monolayer as potential sorbents and gas sensors: A theoretical approach

The fundamental aspects, including geometric structure, adsorption energy, thermodynamic properties, charge transfer, and magnetic properties of carbon nitride C2N and double-atom catalyst (Fe2@C2N) monolayers with the adsorption of CO, NO, HCN, CS2, and SO2 molecules, were investigated using DFT and DFT-D3 correction dispersion methods. Compared to pristine C2N, the Fe2@C2N monolayer is more energetically efficient with high adsorption energies and has apparent charge transfer with these toxic gases. Our results revealed that NO preferred to be adsorbed on the Fe2@C2N with a superior Eads of −7.006 eV. The electric conductivity, sensitivity, and selectivity of C2N are significantly influenced by CO, NO, HCN, CS2, and SO2 molecules. Moreover, the opening of band gaps induced by the adsorption of NO gas molecules at Fe2@C2N can be used as an electronic signal to detect NO gas. Intriguingly, the partial density of states (PDOS) indicated that the NO adsorption of pristine C2N and Fe2@C2N monolayers exhibited half-metallicity behavior and magnetic properties. Non-covalent interactions (NCI) and the quantum theory of atoms in molecules (QTAIM) descriptors were examined to analyze the interaction process. This study can provide a new avenue for synthesizing and developing highly sensitive candidates and inexpensive green double-atom catalysts to capture and detect CO, NO, HCN, CS2, and SO2 molecules from the atmosphere at ambient temperature.

Adsorption performance of CO, NO and NH3 hazardous gas molecules over B9N9 and Al9N9 nanorings: Acumen from density functional theory

The hazardous gases CO, NO and NH3 can cause significant damage to the environment and human health which makes a necessity to develop a suitable sensing material to prevent the environment and human health damage. Here, by using density functional theory, we studied the interaction of toxic gas molecules with X9N9 (X = B, Al) nanorings for assessment of sensing application. We observed the strong interaction of NH3 gas molecule with both X9N9 nanorings and CO and NO gas molecules only with Al9N9 nanoring. There is a charge transfer between nanorings and gas molecules which results into the induction of dipole moment. Due to change in LUMO and HOMO energies of the nanorings after interaction, significant modification in the electrical conductivity and work function are observed. The X9N9 nanorings for NH3 gas molecules and Al9N9 nanoring for NO gas molecule can be utilized as an electronic sensor as well as work function-based sensors. However, longer recovery time of NH3 gas molecules with X9N9 nanorings and CO and NO gas molecule with Al9N9 nanoring reveals its application as storage of these hazardous gases and/or removal of gas molecules from a targeted environment.

Titanium-doped graphite-type silicon carbide biosensor for detecting and eliminating gaseous pollution: A green chemistry approach by molecular simulation study

Regarding thermal strength, chemical stability and surface reactivity of silicon carbide (SiC), it is possible to allocate it as a suitable gas detector for commercial application. Therefore, this research was focused on the investigation of the chemo-resistivity properties of SiC nanosheet through doping with the transition metal. Thermochemical, electric and magnetic properties of titanium (Ti)-doped graphene-like monolayer silicon carbide (SiC) sheet have been studied by the first-principles methods based on the density functional theory (DFT) for scavenging of gas molecules of CO, CO2, NO, NO2. The results recommend that the adsorption of these gas molecules on Ti-embedded monolayer SiC sheet is more energetically desired than that on the pristine ones. Gas molecules of CO, CO2, NO, NO2 have been adsorbed on the Ti site of doped monolayer SiC through the formation of covalent bonds. The assumption of chemical adsorptions has been approved by the projected density of states (PDOS) and charge density difference plots. Charge density difference calculations also indicate that the electronic densities were mainly accumulated on the adsorbate of CO, CO2, NO, NO2 gas molecules. The results in this investigation can indicate the competence of transition metal doped silicon carbide nanosheet in sensor devices.

Confined oxidation of 2D WS2 nanosheets forming WO3/WS2 nanocomposites for room temperature NO2 gas sensing application

In this article, we synthesized WO3/WS2 nanocomposites by facile hydrothermal synthesis followed by thermal annealing treatment and analysed its gas sensing properties. The thermal annealing process was carried out in different temperatures from 400 ℃ to 600 ℃ to form WO3/WS2 nanocomposite. During the thermal annealing process, the hydrothermally synthesized pure WS2 nanosheets undergo partial oxidation constructing WO3 on the surface developing active heterojunctions leading to increment in the sensing performance. The fabricated WO3/WS2 samples showed superior sensitivity and selectivity towards NO2 gas molecules. The pristine WS2 nanosheets showed a response of 26% towards 10 ppm of NO2 gas with a response and recovery time of 13 s /18 s, whereas WO3/WS2 nanocomposite prepared by annealing at 600 ℃ showed a maximum response of around 123% with a short response time of 11 s and recovery time of 163 s. The DFT calculations were performed to understand the gas sensing performance and interfacial charge transfer between the WO3/WS2 nanocomposite and gas molecules. Therefore, this study demonstrates that the indigenous heterojunctions contribute extensively to improving the gas detection capabilities of WO3/WS2 nanocomposites at room temperature.

Analytic modelling of quantum capacitance and carrier concentration for [formula omitted]-borophene FET based gas sensor

In this work, we investigate the physical and electronic properties of β12 - borophene FET-based gas sensor using a theoretical quantum capacitance model based on tight-binding approach. We study the impact of adsorbed NH3, NO, NO2 and CO gas molecule on its density of states, carrier concentration, quantum capacitance and I–V characteristics. We found a remarkable variation in the energy band structure and the density of states (DOS) of the β12 - borophene in the presence of the adsorbed gas molecule. The appearance of non-identical Van-Hove singularities in the DOS in the presence of adsorbed gas molecules strongly indicates the high sensitivity of β12 - borophene. We found a significant increase in the carrier concentration for NH3 gas while it decreases for all other gases. Moreover, a drastic change in quantum capacitance and current–voltage relation is also observed in adsorbed gases. The different properties of the given gas molecules are compared with the pristine borophene and found to exhibit distinct wrinkles in each case, thereby indicating the strong selectivity of our proposed gas sensor. Though β12 - borophene is found to be highly sensitive for all studied gases, the NO gas is found to be most sensitive compared to the others.

UV light activated g-C3N4 nanoribbons coated surface acoustic wave sensor for high performance sub-ppb level NO2 detection at room temperature

The demand for efficient gas sensors in detecting low ppb-level NO2 gas is increasing rapidly for the human life and environmental protection. In this regard, surface acoustic wave (SAW) based gas sensor with selectively coated one dimensional (1D) graphitic carbon nitride (g-C3N4/GCN) nanostructure interface layer is a viable strategy for the sub-ppb level NO2 gas detection at room temperature (RT∼30 °C). Here, we explore SAW gas sensor employed with 1D GCN nanoribbons (NRs) for NO2 detection under UV-irradiation at RT. Intriguingly, the GCN NRs SAW sensor achieves an ultrahigh frequency response (Δf∼28.13 kHz), short response/recovery times (131 s/116 s), excellent selectivity to NO2 (10 ppm) gas and also records a lowest detection limit (∼42 ppb) under UV activation at RT. The enhanced sensing performances were attributed to the high mass loading effect induced by the enhanced charge transfer between the 1D GCN NRs surface and NO2 gas molecules, boosted by the photoexcited charge carriers, numerous surface sites, and improved specific surface area of 1D GCN NRs. The proposed GCN NRs SAW sensor demonstrates exceptional repeatability, good long-term stability with a minimal loss in its Δf, and exhibited robust sensitivity towards NO2 (10 ppm) under diverse relative humidity conditions (0–80%) at RT. The peculiar sensing results of GCN NRs SAW sensor was elucidates using energy band theory sensing mechanism assisted with resistive type gas sensor. Overall, this study offers significant insights into the development of cost-effective real-time RT based NO2 sensor, paving the way for practical air quality monitoring.

Polymeric interfacial engineering approach to perovskite-functionalized organic transistor-type gas sensors

Organic semiconductors (OSCs) are promising sensing materials for printed organic gas sensors. Although OSCs show promise since they are mechanically flexible, cost-effective, and lightweight, they still face challenges related to low sensitivity and poor stability under ambient conditions; their development therefore lags that of inorganic-based gas sensors. Functional nanomaterials can be incorporated into organic semiconductors to complement the gas sensitivity and stability. Herein, we describe the fabrication of novel organic–inorganic hybrid gas sensors via the blending of perovskite nanocrystals and conductive polymer. We introduced a perovskite-structured material, CsPbBr3, into a conductive polymer matrix, which substantially improved its gas-sensing performance while maintaining its high responsivity and response rates. To further improve the adsorption of target gas molecules, we modified the surface of the perovskite using a zwitterionic polymer subjected to a hydration treatment. The results demonstrate that the amide group of the encapsulation polymer exhibits high affinity toward NO2 gas molecules and that this affinity becomes more pronounced upon hydration of the polymer. We also demonstrate the perovskite materials in the semiconducting polymer layer can protect the polymer thin film against oxidation during prolonged storage under ambient conditions because of the perovskite crystals’ ability to adsorb oxidizing molecules.

Discovering a catholyte free design for gas phase electrocatalytic NO gas reduction to NH3 at room temperature

Nitric oxide (NOx) is one of the most contributors to the health risks associated with breathing in flue gases and it is crucial to eliminate this pollutant from the air when solid waste is burned. Electrochemical gas phase reduction of NO to NH3 is the promising method to mitigating the accumulation of NO gas pollutants and producing a valuable NH3 as a product at room temperature. In this investigation, for the first time, we designed a catholyte-free cell for gas phase electrochemical NO to NH3 conversion using K2[Ni(CN)4] coated carbon felt (CF) electrode as a electrocatalyst at room temperature. Herein, K2[Ni(CN)4] heterogeneous mediator transfers the electron between the NO gas molecule and electrode. The NO removal efficiency and NH3 formation were simultaneously monitored by using online gas phase FTIR spectroscopy. In the catholyte-free gas phase NORR process, the K2[Ni(CN)4]/CF electrode exhibits excellent NORR performance, with a high NH3 yield rate of 1128.9 µmol h−1 cm−2, an excellent 89.5 % NH3 faradaic efficiency at − 1 V vs quasi reference Ag and enhanced long term NORR durability. It is noteworthy that, this is the highest yield rate and faradaic efficiency of NH3 during gas phase NORR at room temperature. In addition, K2[Ni(CN)4]/CF electrocatalyst exhibits 99 % of NO removal efficiency with the formation of value-added product (NH3). Moreover, the proposed electrocatalyst shows excellent chemical, and morphological stability after long durability NORR operations. Furthermore, the detailed electrode-electrolyte free cell, NORR reduction mechanism was proposed. Present discovery provides great insights for sustainable NORR operations in real-site applications.

Adsorption Properties of Ptn (n = 1-3) Cluster-Doped SnS2 and MoTe2 toward Vehicle Emissions: CO, CO2, and NO.

The interaction mechanism between CO, CO2, and NO gas molecules and Ptn-SnS2 (n = 1-3) and Ptn-MoTe2 (n = 1-3) is analyzed based on density functional theory calculations. For Pt2-SnS2, the structure of Pt2-SnS2 is deformed during CO2 adsorption. For Pt3-SnS2, its structure is also significantly deformed when the gas is adsorbed. Pt2-SnS2 is not suitable for the detection and adsorption of CO2 gas, while Pt3-SnS2 is not suitable for the detection and adsorption of these three gases. According to the density of states and molecular orbital analysis, the conductivity of the adsorption system of Pt-SnS2 remains almost unchanged after the adsorption of CO, so Pt-SnS2 is not suitable for the detection of CO gases. The adsorption of gases on intrinsic MoTe2 is a weakly interacting physical adsorption. Doping with one to three Pt atoms all resulted in different degrees of enhancement of the adsorption capacity of the substrates for these three target gases. However, for Pt2-MoTe2 and Pt3-MoTe2, the structure of these two materials undergoes significant deformation upon NO adsorption. In addition, the interaction between Pt3-MoTe2 and CO2 is weak, and the conductivity of this system is almost unaffected by CO2 adsorption. In addition, all other constructions are suitable for the detection of the corresponding gases. This paper provides a theoretical basis for the development of gas sensors for the detection of automotive and industrial emission gases.

Simple chemical synthesis of CeO2 nanoparticles for toxic NO2 gas detection

CeO2 nanoparticles (NPs) were synthesized using a cost-effective simple chemical method without any surfactant or additives at low temperature and short reaction time. The various techniques employed to investigate effect of annealing temperatures on structural, morphological and chemiresistive properties of the prepared CeO2 NPs, which were decorated on the glass substrates by drop casting technique. The CeO2 NPs exhibited cubic crystal structure and porous morphology, with specific surface area 52.92 m2/g for the C3 sample. This specific surface area is significant for achieving superb gas sensing performance. The optimized operating temperature was 150 °C, illustrated outstanding response of 57% towards 100 ppm, 12% response to 1 ppm of toxic NO2 gas was observed than other test gases with good reproducibility, excellent response (tres), recovery (trec) time, and notable stability (85%). The interaction between NO2 gas molecules and CeO2 NPs surface is analysed by impedance spectroscopy.

Magnetic ε-Phosphorene for Sensing Greenhouse Gas Molecules.

It is critical for gas sensors that sense greenhouse gas molecules to have both good sensitivity and selectivity for water molecules in the ambient environment. Here, we study the charge transfer, IV curves, and electric field tuning of vanadium-doped monolayer ϵ-phosphorene as a sensor for NO, NO2, and H2O gas molecules via first-principle and transport calculations. We find that the paramagnetic toxic molecules of NO and NO2 have a high adsorption energy on V-ϵ-phosphorene, which originates from a large amount of charge transfer driven by the hybridisation of the localised spin states of the host with the molecular frontier orbital. Using the non-equilibrium Green's function, we investigate the IV responses with respect to the adsorption of different molecules to study the performance of gas molecule sensors. Our IV curves show a larger amount of changes in resistance of the paramagnetic NO and NO2 than nonmagnetic H2O gas molecules, suggesting both sensitivity and selectivity. Moreover, our calculations show that an applied external electric field (gate voltage) can effectively tune the amount of charge transfer. More charge transfer makes the sensor more sensitive to the molecule, while less charge transfer can reduce the adsorption energy and remove the adsorbed molecules, allowing for the repeated use of the sensor.

Edge enriched MoS2 micro flowered structure for high performance NO2 sensor

In this work, we showed that the chemisorption of nitrogen oxide (NO2) gas molecule is significantly enhanced in the case of a vertically oriented (VO) MoS2-based device, at low operating temperature. We fabricated a VO-MoS2-micro flower layer using the hydrothermal process followed by the sonication technique. To determine the surface morphology and crystallinity of the MoS2 nanosheets, we have done microscopy and spectroscopy analysis, while to confirm the vertical orientation of MoS2 we performed Raman spectroscopy. We observed that the MoS2 orientation has a significant impact on the gas sensing performance. The presence of unsaturated and dangling bonds on the sensing surface encourages the strong chemisorption process of analyte gas molecules. We have examined the gas sensing performance for the fabricated device at different concentration levels of NO2 gas molecules. Moreover, we also evaluated the stability, response, and recovery time of the device toward 50 ppm of NO2 gas molecule. The fabricated device exhibited a response and recovery time of ∼13 and ∼110 s, respectively, upon exposure to 50 ppm of NO2. Further, the proposed device was exposed to various other gas molecules to examine the selectivity and it shows excellent sensing response towards NO2 gas molecules.