NO Molecules Research Articles

Hemoglobin’s β-subunit is primed to synergize oxygen delivery with nitric oxide-mediated increased blood flow

Hemoglobin (Hb) undergoes a well-documented R[Formula: see text]T quaternary transition from a high [Formula: see text] affinity R state to a low [Formula: see text] affinity T state to optimize [Formula: see text] delivery to tissues. Also, red blood cells (RBCs) release a nitrovasodilator that increases blood flow to boost [Formula: see text] delivery. Hb’s R[Formula: see text]T transition coordinates its [Formula: see text] desaturation and RBC nitrovasodilator release by much-debated mechanisms. Here we investigate the allosterically controlled [Formula: see text]-nitrosation of Hb at its conserved βCys93 (i.e., SNO-Hb formation) for nitrovasodilator release. First, we examined NO[Formula: see text]/deoxyHb (HbFeII) incubations following aeration to mimic RBC NO production by the nitrite reductase activity of HbFeII and trapping of the nascent NO by βCys93 to give SNO-Hb on HbFeII conversion to oxyHb (HbFeO2). We confirmed SNO-Hb formation in the incubations with yields modulated by RBC antioxidant enzymes and [Formula: see text] but not CO. Since FeO2 hemes scavenge free NO, we hypothesized NO channeling within Hb and found by molecular dynamics simulations that most unligated NO molecules placed in the β-distal heme pocket (βDP) rapidly diffuse into a wide β-tunnel connecting the βDP to Hb’s central cavity and βCys93. Contraction of the central cavity brings NO closer to βCys93 in R-state plus βPhe71 and βTyr145 adopt conformations favorable to thiol access and SNO-Hb formation. In T-state, the SNO group is surface-exposed and destabilized to extrude NO. Thus, its structure, dynamics and conserved reactive thiol (βCys93) suggest that the β-subunit evolved to synergize [Formula: see text] and nitrovasoactivity delivery to tissues as a function of Hb [Formula: see text] saturation.

High-entropy oxide (FeCoNiCrMn)3O4 for room-temperature NO2 sensors

High-entropy oxides (HEOs) with a multi-cation structure have attracted significant attention in the fields of electrochemistry owing to their high entropy stability and cocktail effect. However, there has been very limited research on the use of HEO in the field of sensing. In this work, we utilized FeCoNiCrMn high-entropy alloys as the precursor to synthesize (FeCoNiCrMn)3O4 HEO and investigated their crystal structure, microscopic morphology, elemental valence state information, and gas sensing performance. The sensor exhibited decent response to NO2 at room temperature (RT) without any modification or sensitization methods. To verify the gas sensing mechanism, we simulated the interaction between five metal elements in HEO and the NO2 molecules by density functional theory, which reveals a crucial synergistic effect from the multiple cations to enhance the adsorption and charge transfer of NO2 molecules. This work explores the application potential of (FeCoNiCrMn)3O4 in low-power gas sensors and enriches the material selection for RT sensors.

Effect of exchange reactions and NO vibrational excitation on shock-heated air component flows

Shock-heated flows of air components are studied using the state-to-state approach taking into account coupled vibrational energy transitions and state-specific chemical reactions. Effects of exchange reactions and vibrational excitation of NO molecules on the fluid-dynamic variables and vibrational distributions are evaluated; the results are compared to experimental data and direct simulations Monte Carlo; satisfactory agreement is obtained. It is shown that the effects are opposite in mixtures with and without initial admixture of NO. Whereas in NO/N2/Ar mixture the effect of NO vibrational excitation is important, in air it is negligible. Exchange reactions in air are more important than in NO/N2/Ar mixture.

Mechanisms for deNOx and deN2O Processes on FAU Zeolite with a Bimetallic Cu-Fe Dimer in the Presence of a Hydroxyl Group-DFT Theoretical Calculations.

In this paper, a detailed mechanism is discussed for two processes: deNOx and deN2O. An FAU catalyst was used for the reaction with Cu-Fe bimetallic adsorbates represented by a dimer with bridged oxygen. Partial hydration of the metal centres in the dimer was considered. Ab initio calculations based on the density functional theory were used. The electron parameters of the structures obtained were also analysed. Visualisation of the orbitals of selected structures and their interpretations are presented. The presented research allowed a closer look at the mechanisms of processes that are very common in the automotive and chemical industries. Based on theoretical modelling, it was possible to propose the most efficient catalyst that could find potential application in industry-this is the FAU catalyst with a Cu-O-Fe bimetallic dimer with a hydrated copper centre. The essential result of our research is the improvement in the energetics of the reaction mechanism by the presence of an OH group, which will influence the way NO and NH3 molecules react with each other in the deNOx process depending on the industrial conditions of the process. Our theoretical results suggest also how to proceed with the dosage of NO and N2O during the industrial process to increase the desired reaction effect.

Termolecular Eley–Rideal pathway for catalytic oxidation of nitric oxide on [Pt2]0,± dimers using O2

AbstractA comprehensive density functional theory (DFT) investigation of the catalytic oxidation of NO to NO2 on neutral and charged [Pt2]0,± dimers has been considered employing M06L/def2TZVP level of theory. Single as well as co‐adsorption energies of NO and O2 molecules suggest that the traditional Langmuir Hinshelwood (LH) mechanism and less explored termolecular Eley–Rideal (TER) and termolecular Langmuir Hinshelwood (TLH) mechanisms, are suitable for a full catalytic reaction pathway in which two NO molecules are converted to two NO2 molecules, initiated by an activated O2 molecule. Activation barrier reveals that the TER mechanism is found to be more reliable in converting two NO molecules into two NO2 molecules on [Pt2]¯ dimer. In addition to shedding light on the intrinsic characteristics of Pt2 dimers, the study will serve as a benchmark for investigating the oxidation process of NO to NO2 utilizing models of termolecular chemical processes.

The development of sensitive graphene-based surface acoustic wave sensors for NO2 detection at room temperature

Bilayer graphene (Bl-Gr) and sulphur-doped graphene (S-Gr) have been integrated with LiTaO3 surface acustic wave (SAW) sensors to enhance the performance of NO2 detection at room temperature. The sensitivity of the Bl-Gr SAW sensors toward NO2, measured at room temperature, was 0.29º/ppm, with a limit of detection of 0.068 ppm. The S-Gr SAW sensors showed 0.19º/ppm sensitivity and a limit of detection of 0.140 ppm. The origin of these high sensitivities was attributed to the mass loading and elastic effects of the graphene-based sensing materials, with surface changes caused by the absorption of the NO2 molecules on the sensing films. Although there are no significant differences regarding the sensitivity and detection limit of the two types of sensors, the measurements in the presence of interferent gases and various humidity conditions outlined much better selectivity and sensing performances towards NO2 gas for the Bl-Gr SAW sensors.Graphical

Mechanism of adsorption and gas-sensing of hazardous gases by MoS2 monolayer decorated by Pdn (n=1–4) clusters

The adsorption behaviors of hazardous gases (NO2 and SO2) on MoS2 monolayer decorated by Pdn (n=1–4) clusters (Pdn-MoS2) are investigated by first-principles calculations, and the performance of Pdn-MoS2 gas sensors has also been studied in this work. Our results show that Pdn nanocluster can enhance the electrical conductivity of MoS2 monolayer with band gaps of Pdn-MoS2 (n=1–4) sharply decreased, and the adsorption performance of NO2 and SO2 with higher adsorption energy and larger charge transfer. Thus, Pdn-MoS2 show higher sensitive to NO2 and SO2 molecules compared with pristine MoS2. The band gaps of Pdn-MoS2 can be further decreased upon the adsorption of NO2 and SO2 (except for SO2/Pd4-MoS2), indicating Pdn-MoS2 (n=1–3) gas sensor shows improved gas-sensitive response to both NO2 and SO2, and Pd4-MoS2 shows improved gas-sensitive response only to NO2. The recovery time analysis indicates that Pdn-MoS2 (n=1–4) is applicable to be utilized as NO2 and SO2 scavenger at ambient temperature, and the recovery process can be realized simply by heating. Our results indicate that Pdn-MoS2 (n=1–4) monolayer is a favorable candidate as adsorbent for detection and removal of NO2 and SO2, and also provides guidance for further study of the MoS2 monolayer decorated by transition metal clusters.

In situ growth of TiO2 on Ti3C2Tx MXene for improved gas-sensing performances

In this study, in situ prepared multiple semiconducting TiO2 in a metallic Ti3C2Tx channel were investigated, which were derived from the Ti3AlC2 MAX phase by oxidation treatments. Several tiny TiO2 particles were in situ formed on the Ti3C2Tx MXene surface when it was heated to 150 °C at ambient conditions. The phase transformation of pristine Ti3C2Tx MXene to oxidized TiO2 was accelerated when the gas-sensing channel was heated to higher temperatures up to 200 °C, yielding a TiO2/Ti3C2Tx composite. The experimental results revealed that the heat-treatment temperature played an important role in the gradual development of the morphology and gas-sensing activity of the TiO2/Ti3C2Tx sensing channel. In particular, the optimal heating temperature of the composite resulted in a good response and recovery time for NO2 molecules. Furthermore, first-principles calculations indicated the good sensing ability of the TiO2/Ti3C2Tx composite for NO2 than for other gases. These results suggest a new strategy for developing gas-sensing ability by forming a Schottky barrier through a simple process.

Room temperature gas sensor based on rGO/Bi2S3 heterostructures for ultrasensitive and rapid NO2 detection

Bismuth sulfide (Bi2S3) is a promising material for detecting NO2 molecules at room temperature thanks to its narrow and tunable bandgap. However, pure Bi2S3 suffers from some sensing blemish because of its low electroconductivity and poor charge transfer efficiency. Herein, we synthesized the high sensing response room temperature NO2 detection materials composed of Bi2S3 nanoflowers and reduced graphene oxide (rGO). The formed conductive network and heterojunctions between Bi2S3 nanoflowers and rGO nanosheets dramatically improve the conductivity and electron transfer efficiency. The excellent rGO/Bi2S3 sensor shows a high sensing response of 9.8 (approximately two times higher than that of the pure Bi2S3) and rapid response speed of 22 s (almost half of the pure Bi2S3) upon exposure to 1 ppm NO2 at room temperature. Meanwhile, the rGO/Bi2S3 sensor displays superb humidity-independent, selectivity, and stability. These improved NO2 sensing behaviors can be attributed to the heterointerfaces and the hybrid effects, which accelerate charge transfer efficiency between NO2 molecules and the surface of rGO/Bi2S3 heterostructure. To enable on-line detection of ambient hazardous gas, we designed a portable wireless NO2 detector based on rGO/Bi2S3 heterostructure. This study offer an insightful guidance for improving the NO2 sensing behaviors of metal chalcogenides.

First-principles exploration of N- and Pd-doped graphene as CO and NO2 gas sensor for operation status evaluation in AIS

To evaluate the operation status of air insulated switchgears (AIS), this work purposes N- and Pd- embedded graphene (N- and Pd-graphene) as potential gas sensors upon two typical faults gases (CO and NO2) from the first-principles simulations. It is found that the N and Pd atoms can be stably trapped on the C-vacancy of the C-defected graphene with the formation energy of −12.17 and −5.12 eV, respectively. N-graphene behaves physisorption towards CO and NO2 molecules while Pd-graphene behaves chemisorption instead. The resistance-type and work function (WF)-based sensing mechanisms of N- and Pd-graphene upon such two gas species are illustrated and uncovered by analyzing their deformations of electronic property and WF in the gas adsorption systems, which reveals the potential of Pd-graphene as a resistive CO and NO2 sensor, N-graphene as a resistive NO2 sensor, as well as the N- and Pd-graphene as WF-based gas sensor for NO2 detection. This work highlights the comparison of adsorption and sensing performances between N- and Pd-graphene upon two typical gas sensors in AIS, which would be meaningful to explore novel graphene-based sensing materials facilitating their investigations and applications in the power system.

The Effect of Ligand Field on Enhanced Electrocatalytic Performance of NO Reduction Under Applied Potential

We employed density functional theory to investigate Co-N4/Gra single-atom catalysts, focusing on the modification of axial ligand (X=-F, -CN and -C3H4N2) and examined the influence of ligand field and electric potential on eNORR. Our results demonstrate that Co-N4[X]/Gra exhibit favorable thermodynamic adsorption (ΔG *NO < 0) and remarkable activation activity toward NO molecules. Co-N4/Gra demonstrates a limiting potential of −0.13 V with the potential-determining step (PDS) of *NH3 → * + NH3(g). Notably, under the introduction of ligands, Co-N4[F]/Gra achieves the most favorable overpotential of −0.07 V, superior to most of NORR electrocatalysts, and meanwhile shows an exceptional selectivity of 99.99% for eNORR compared to competitive hydrogen evolution reaction. Under the solvent environment, Co-N4/Gra features the triggering potentials of −0.33 V for a pH of 1, −0.71 V for a pH of 7, and −1.10 V vs RHE for a pH of 13, respectively. Additionally, the potential reduces the desorption energy and adsorption energy of NH3, facilitating the accessibility of the NH3 desorption step (PDS) and promoting NO reduction. Thus, under realistic conditions, the Co ion’s active site displays variable valence electrons and forms a dynamic interplay with the ligand field effect, rendering a crucial effect on the adsorption of reaction species during the eNORR.

NO Dissociation on Platinum and Platinum-Rhodium Alloy: A Theoretical Investigation

In this computational study, the preferential adsorption and co-adsorption sites of various chemical species (N, O, and NO) on the Pt (111) and Rh3Pt (111) surfaces were identified. The preferential adsorption site for NO and co-adsorption sites for N and O on the Pt (111) surface are the hollow (fcc) sites; and these on the Rh3Pt (111) surface are the hollow (fcc1) site and hollow N(hcp2)-O(fcc1) sites, respectively. The activation energies of the NO dissociation reaction on the Pt (111) and Rh3Pt (111) catalytic surfaces are 2.35 and 2.02 eV, respectively. The lower activation energy of the NO decomposition on the Rh3Pt (111) surface is explained by the stronger back-donation from the 4d orbital of the Rh atoms to the 2π* anti-bonding orbital of the NO molecule. The activation energies of the N and O recombination reaction on the Pt (111) and Rh3Pt (111) catalytic surfaces are 1.51 and 2.30 eV, respectively. The study indicates that the Rh3Pt (111) surface not only facilitates the NO decomposition but also better prevents N and O from recombination. Copyright © 2024 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Theoretical insights into the structural, electronic and gas-sensing properties of Sc-decorated black phosphorus via strain engineering

Structural and electronic properties of Sc-decorated black phosphorus (SP) and its gas sensing for NO molecule were investigated using density functional theory with the emphasis on the response to applied strain. It found that SP transformed into indirect bandgap semiconductor, and converted into a metal characteristic under strain. SP showed strong interaction with the NO with a high adsorption energy of −2.92 eV since the orbital hybridization and extensive charge transfer, and exhibited 3.3-fold sensitivity compared to black phosphorus, suggesting that SP was a potential NO sensor. Furthermore, strain engineering provided an effective route to facilitate the desorption of NO.

High switching characteristics and sensing-performance improvement of two-dimensional MN4 (M = Be, Mg, Ga) monolayer based nanodevices

Beryllium tetrazolium nitride (BeN4) has recently been synthesized under high pressure by laserheated diamond anvil electrodes as a new class of two-dimensional layered materials. Inspired by this, we perform first-principles calculations to investigate the electronic transport properties of MN4 (M = Be, Mg and Ga) monolayers and their gas sensing properties towards nitride-gases (NH3, NO2, NO). The obtained results show that BeN4 exhibits semi-metallic properties, MgN4 is a semiconductor with a bandgap of 0.13 eV, and the GaN4 monolayer presents strong metallic properties. Interestingly, the BeN4 and MgN4 monolayers are found to have anisotropic Dirac cones. The MN4-based 2D devices all exhibit excellent conductance as well as strong anisotropic transport, with maximum switching ratios of 107 and 104 for MgN4 and BeN4, respectively. The adsorption properties indicate that the adsorption of NH3, NO2, and NO molecules on MN4 monolayers are all chemisorptions, with the system owning much larger adsorption energies and bader charge transfers of the NO2 and NO molecules than those for the NH3 molecules, suggesting the MN4 monolayer has strong selective adsorption and responsiveness to NO2 and NO molecules. The designed gas sensor based on MgN4 show good response characteristics for NO molecules, as evidenced by the maximum current changes before and after adsorption of 30.31 µA, respectively. In summary, MN4 (M = Be, Mg and Ga) monolayers can be important candidates for high switching ratio devices and for the detection and trapping of toxic gas molecules NO.

Study on the Transport Properties of SO2 and NO at the Interface of H2O2 Solutions Using Molecular Dynamics.

Gas-liquid interfaces have a unique structure different from the bulk phase due to the complex intermolecular interactions within them and are regarded as barriers that prevent gases from entering solution or as channels that affect gas reactions. In this study, the adsorption and mass-transfer mechanisms of sulfur dioxide and nitric oxide at the gas-liquid interface of a H2O2 solution were comprehensively analyzed using molecular dynamics (MD) simulations. The analysis on molecule angle showed that H2O molecules tended to align parallel to the solution surface on the surface of the H2O2 solution. Regardless of whether the gas was adsorbed on the surface of the solution or not, H2O2 molecules were always perpendicular to the interface of the solution. The analysis on molecule angle and radial distribution function revealed that the H atoms of H2O molecules had a corresponding turn, and SO2 molecules were greatly affected by the attraction of H2O2 molecules during the adsorption of gas molecules on the interface. Steered MD was utilized to investigate the mass-transfer process of SO2 and NO molecules across the gas-liquid interface. The S atoms of SO2 molecules were significantly influenced by H2O2 molecules, while the O atoms of NO molecules gradually transitioned from the gas phase to the liquid phase. The results provided information on how gas molecules interacted with the surface of the solution and the specific details of the molecular orientation at the solution surface.

Enhanced response characteristics of NO2 gas sensor based on ultrathin SnS2 nanoplates: Experimental and DFT study

Layered-metal dichalcogenides with extraordinary characteristics of vast surface area, tunable bandgap and superior adsorption capability enable the potential for application in gas sensors. However, the synthesis of effective material for enhanced response performance remains a challenge. Herein, we exploited a fascinating sensitivity and selectivity towards NO2 gas detection using SnS2 nanoflakes prepared via the hydrothermal method. SnS2 nanoflakes with a thickness of 25 nm and an average diameter of approximately 500 nm show the potential for the detection of NO2 gas at low concentrations of ppb levels. The sensing properties of the SnS2 sensors were investigated for different concentrations of NO2 at various operating temperatures. The sensor exhibits the highest gas-sensing response of 161 at 250 οC upon exposure to 5 ppm of NO2 gas with fast response and recovery times. In addition, the sensor shows excellent selectivity with a low detection limit of ppb level. The electronic structure and gas-sensing mechanism are elucidated via finding density of states, charge density, and band structure based on DFT study which is calculated by the Vienna ab-initio simulation package (VASP). The considerable small adsorption energy reveals a physisorption of the NO2 molecules on the SnS2 surface (-0.174 eV), indicating the SnS2 nanoflakes are intriguing candidates for the speedy detection of NO2 gas.

Selective reduction of NO by CO using copper-aluminum oxides from hydrotalcite-type precursors: Study of chemical species and thermal stability

The objective of this work was to analyze the influence of Al on copper catalysts, regarding thermal stability and performance during NO reduction by CO. Two copper-based catalysts were prepared by precipitation and subsequent calcination at 600 °C, with and without aluminum in their composition (CuAl-HT-c and Cu-p). The precursor CuAl-HT was synthesized to obtain a hydrotalcite structure. The catalysts obtained after calcination of the precursors were characterized by N2 physisorption, TPR, N2O titration, in situ XRD and in situ XANES. They showed good catalytic performance, however with Cu-p being the most active but with larger formation of N2O (important greenhouse gas). In this catalyst, the interaction between the adsorbed NO molecules is facilitated, probably due to the higher concentration of Cu+.Regarding the aged catalysts, Cu-p was deactivated due to sintering, which is attributed to the lack of aluminum. CuAl-HT-c-900 had its performance improved during aging, either because the reduction of NO by CO is a structure-sensitive reaction for this catalyst (and the increase in particle size after aging is related to larger activity), or because of the presence of copper aluminate, which can also improve activity and selectivity.

Towards rational design in electrochemical denitrification by analyzing pH dependence.

A small fraction of NOx (<1%) always exists in CO2 feedstock (e.g. exhausted gas), which can significantly reduce the efficiency of CO2 electroreduction by ∼30%. Hence, electrochemical denitrification is the precondition of CO2 electroreduction. The pH effect is a key factor, and can be used to tune the selectivity between N2 and N2O production in electrochemical denitrification. However, there has been much controversy for many years about the origin of pH dependence in electrocatalysis. To this end, we present a new scheme to accurately model the pH dependence of the electrochemical mechanism. An extremely small pH variation from pH 12.7 to pH 14 can be accurately reproduced for N2O production. More importantly, the obviously different pH dependence of N2 production, compared to N2O, can be attributed to a cascade path. In other words, the N2 was produced from the secondary conversion of the as-produced N2O molecule (the major product), instead of the original reactant NO. This is further supported by more than 35 experiments over varying catalysts (Fe, Ni, Pd, Cu, Co, Pt and Ag), partial pressures (20%, 50% and 100%) and potentials (from-0.2 to 0.2V vs. reversible hydrogen electrode). All in all, the insights herein overturn long-lasting views in the field of NO electroreduction and suggest that rational design should steer away from catalyst engineering toward reactor optimization.

Biaxila strain modulated high anisotropic gas-sensing performance of C5N-based two-dimensional devices: A first-principles study

Two-dimensional carbon nitride materials have been widely used in many applications such as device fabrication, gas adsorption and separation due to their abundant element resources, high physicochemical stability and excellent electronic properties. In this paper, density functional theory and non-equilibrium Green's function method are used to study the electronic structure, transport characteristics and gas sensitivity of C5N-based structures. The results show that the electron transport exhibits obvious anisotropy, in which the electron transport in the armchair direction is more conductive than that in the zigzag direction. It is worth noting that the negative differential resistance effect exists in both directions. Furthermore, the transport and sensing characteristics of inorganic molecules (NO, CO, NO2, SO2, and NH3) adsorbed on the C5N monolayer are studied. The results show that CO, SO2 and NH3 exist on the surface of C5N in the form of physical adsorption, while NO and NO2 adhere to the surface of C5N in the form of chemical adsorption. The designed C5N gas sensor exhibits high sensitivity to NO and NO2 molecules, reaching 81 % sensitivity to NO2 at a 0.1 V bias voltage. Finally, the effect of strain on the adsorption properties of gas sensing devices is studied. Studies have shown that the application of -4 % strain in the armchair direction significantly increases the current of NO and NO2, significantly improving the performance of the gas sensor. Whether strain is applied to the device or gas adsorption, C5N materials always maintain significant anisotropy. This study shows that C5N is a highly anisotropic and sensitive two-dimensional material, which has broad application potential in the field of electronic properties and gas sensing.

SnS2 with different exposed crystal planes for NO2 gas sensing

Tin disulfide (SnS2), is an emerging two-dimensional metal sulfide material with high electronegativity and suitable bandgap, making it a promising candidate for NO2 sensors. In this study, SnS2 thin sections with different exposed crystal planes were prepared from two different sulfur sources, and the effects of crystal sections on the growth of SnS2 and its NO2 sensing performance were studied. SnS2 micro sheets with (101) exposed crystal plane (SnS2-M) showed a smaller specific surface area than SnS2 nano sheets with (100) exposed crystal plane (SnS2-N). However, the crystal structure grown along the (101) plane direction provides a more favorable pathway for NO2 molecules, enhancing gas molecule adsorption and desorption, and exhibiting excellent performance in terms of sensitivity, repeatability, and response time. The gas sensing performance is not only influenced by the specific surface area but also significantly differs due to the exposure of different crystal planes. This result provides a certain reference value for the preparation of SnS2 with different crystal plane orientations for enhanced NO2 sensing.