Ammonia Molecules Research Articles

Mechanistic insights into Criegee intermediates with benzoic acid at gas-phase and air-water interface and nucleation of product

Since the detection of Criegee intermediates (CIs) in the gas phase, there has been a growing recognition of the important role of CIs in atmospheric oxidation. Further mechanistic investigations are required to fully elucidate the bimolecular reactions of CIs with atmospheric species, such as OH, RO2/HO2, and carbonyl compounds. This article primarily focused on the reactions of benzoic acid (BA) with syn- and anti- CH3CHOO (C2 CI) in both gas-phase and gas-liquid interface using density functional theory (DFT) and Born-Oppenheimer molecular dynamics (BOMD). The results reveal that the reactions of BA and anti-CH3CHOO represent the principal pathway in the gaseous phase, whereas the water-involved reactions exhibit higher energy barriers, rendering them less favorable for occurrence. At the air-water interface, the reactions of BA and C2 CI as well as the BA-catalyzed hydration take place on the picosecond scale, conforming to the stepwise mechanism. The direct reaction between BA and anti- CH3CHOO remains the main sink for C2 CI at the gas-liquid interface. Molecular dynamics (MD) simulations were employed to investigate the nucleation capabilities of the reaction products and to examine the influence of temperature and water molecules on the nucleation process. The product molecules of BA and C2 CI can form stable clusters with sulfuric acid, ammonia molecules, and water molecules within 30 ns? The nucleation ability tends to decrease with the elevation of temperature, and the presence of water molecules promotes the new particles formation (NPF). Therefore, BA and its products with CIs affect the budget of secondary organic aerosols (SOAs).

Differential entropy and thermokinetics of ammonia molecule adsorption on CaA zeolite (M-22)

Differential entropy and thermokinetics of ammonia molecule adsorption on CaA zeolite (M-22)

Transition Metal Nitrides for the Electrocatalysis of the Electrochemical Ammonia Synthesis

The direct electrochemical ammonia synthesis (EAS) from water and nitrogen using renewable energy shows great potential for future decentralized production of indispensable green ammonia and may, at least partially, supersede the fossil fuel-based Haber-Bosch process in the future [1]. Material innovation for the conversion of nitrogen to ammonia via the nitrogen reduction reaction (NRR) is one cornerstone for the successful development of the EAS technology. To date, only Lithium-mediated NRR has been demonstrated to show sufficient production rate and faradaic efficiency for a prospective application [2], while the reaction in aqueous electrolyte, independent of the studied material class, suffers from false-positive results due to low productions rates, low Faradaic efficiencies and complex contamination issues [3].Several catalyst systems are currently investigated for NRR in aqueous electrolytes. Transition metal nitrides (TMN) may offer an energetic advantage as electrocatalyst, because the NRR is expected to be catalyzed via the Mars-van-Krevelen mechanism (MvK) on TMNs. Here the protonation of a lattice nitrogen atom forms the first ammonia molecule. The resulting N-vacancy is filled by molecular nitrogen where one N adatom is subsequently protonated to form the second ammonia molecule. Thus, the N2 activation step occurs at the N-vacancy site and avoids the surface adsorption and dissociation of N2. Specific facets of Zr, Cr, V and Nb were described as stable, active and selective TMN catalysts for the NRR based on theoretical catalyst screening [4]. However, current literature studies state contradictory results and require the differentiation of genuine activity and non-catalytic decomposition of TMN catalysts [5], which is currently lacking.In our work, we address the synthesis of Zr-based TMNs, the electrochemical evaluation in a gas diffusion electrode setup and the trace analysis of ammonia by ion chromatography [6]. Only consideration of all three interconnected steps can give an indication of genuine NRR activity, where structural characterization after NRR experiments elucidates the stability of the material. Special interest is given to the role of surface oxynitrides and their ratio to the nitride phase for electrocatalytic NRR. Comparison of nanoparticulate catalysts to surface engineered thin film catalyst as well as insights from first principles simulation delivers a comprehensive characterization of the electrosynthesis of ammonia by TMNs.

Sulphated TiO2 Reduced by Ammonia and Hydrogen as an Excellent Photocatalyst for Bacteria Inactivation.

This study presents a relatively low-cost method for modifying TiO2-based materials for photocatalytic bacterial inactivation. The photocatalytic inactivation of Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus epidermidis) bacteria using modified sulphated TiO2 was studied. The modification focused on the reduction of TiO2 by ammonia agents and hydrogen at 400-450 °C. The results showed a high impact of sulphate species on the inactivation of E. coli. The presence of these species generated acid sites on TiO2, which shifted the pH of the reacted titania slurry solution to lower values, around 4.6. At such a low pH, TiO2 was positively charged. The ammonia solution caused the removal of sulphate species from TiO2. On the other hand, hydrogen and ammonia molecules accelerated the removal of sulphur species from TiO2, as did heating it to 450 °C. Total inactivation of E. coli was obtained within 30 min of simulated solar light irradiation on TiO2 heat-treated at 400 °C in an atmosphere of Ar or NH3. The S. epidermidis strain was more resistant to photocatalytic oxidation. The contact of these bacteria with the active titania surface is important, but a higher oxidation force is necessary to destroy their cell membrane walls because of their thicker cell wall than E. coli. Therefore, the ability of a photocatalyst to produce ROS (reactive oxidative species) will determine its ability to inactivate S. epidermidis. An additional advantage of the studies presented is the inactivation of bacteria after a relatively short irradiation time (30 min), which does not often happen with photocatalysts not modified with noble metals. The modification methods presented represent a robust and inexpensive alternative to photocatalytic inactivation of bacteria.

Quasi-atomic orbital analysis of halogen bonding interactions.

A quasi-atomic orbital analysis of the halogen bonded NH3⋯XF complexes (X = F, Cl, Br, and I) is performed to gain insight into the electronic properties associated with these σ-hole interactions. It is shown that significant sharing of electrons between the nitrogen lone pair of the ammonia molecule and the XF molecule occurs, resulting in a weakening of the X-F bond. In addition, the N-X bond shows increasing covalent character as the size of the halogen atom X increases. While the Mulliken outer complex NH3⋯XF appears to be overall the main species, the strength of the covalent interaction of the N-X bond becomes increasingly similar to that of the N-X bond in the [NH3X]+ cation as the size of X increases.

Theoretical study of the Cu2+-glycine interaction in ammonia and temperature effects

In this study, we have investigated the potential energy of surfaces of the various glycine tautomers, also the interaction between Cu2+ cation with these glycine tautomers in both the gas and solvent phases and for the first time, the glycine-Cu2+(NH3)n=3−6 clusters in the gas-phase. For the studied clusters, we reported their temperature-dependent conformer distributions, along with the binding energies per ammonia molecule and clustering energies. After comparing the binding energies obtained computationally by using the DLPNO-CCSD(T)/CBS level of theory to those obtained from ten DFT functionals (M06, M06HF, M06-2X, M08HX, MN15, MN12SX, ωB97XD, PW6B95D3, TPSSH, APFD), as well as from the ab initio MP2 method, we selected the DFT functional, M08HX, in conjunction with the aug-cc-pVDZ basis set, as our method of choice. Evidence emerged from our study that the solvation medium and the presence of the Cu2+ cation influence the stability of glycine tautomers. The relative stability of Gly-Cu2+(NH3)n clusters in the gas phase is influenced by the coordination of the Cu2+ cation. The study of the relative population in the gas phase of the Gly-Cu2+(NH3)n=3−6 clusters, predicts that for cluster size n=4, the structure of the more compact penta-coordinated Cu2+ ion dominates at low temperatures. Conversely, the conformers for the less compact tetra-coordinated Cu2+ cation are prevalent at high temperatures. For cluster size n=6 with more ammonia molecules per cluster, the conformers containing the compacted is penta-coordinated Cu2+ cation, are predominant at all temperatures. Binding energies computed for ionic interactions of the Gly-Cu2+ complexes, resulted in the following values at room temperature: the binding electronic energy (ΔEn), binding enthalpy (ΔHn) and binding free energy (ΔGn) of ionic interaction are respectively -218.3, -218.4, -211.6 kcal/mol in the gas phase and -93.8, -94.9, -85.2 kcal/mol in the solvent phase. In order to extrapolate this also to the Gly-Cu2+ ammonia clusters, a suitable function of best fit was applied. The computational prediction of binding electronic energy, binding enthalpy and binding free energy, per ammonia molecule in the gas phase, at saturation, produced the values -25.9, -26.1 and -17.0 kcal/mol, respectively. We therefore recommend this function fit for further study of such systems.

Energy Efficient Transshipment of Ammonia: A Numerical Study of Various Terminal Concepts

For the global transport and trade of hydrogen, ship transport is of central importance. Ammonia is a promising option for this task. In the ammonia molecule, hydrogen is stored through chemical bonding to nitrogen. In comparison to liquid hydrogen, liquid ammonia shows a higher volumetric energy density and shows advantages in terms of handling. To establish ammonia as a global climate‐neutral energy carrier, the production of green ammonia as well as an efficient supply chain plays important factors. Terminals are an essential part of the process chain as they enable the transshipment from ship to land and vice versa. In this study, the efficiency of various ammonia terminal concepts dealing with both pressure‐liquefied and cold‐liquefied green ammonia is targeted. Multiple terminal concepts are analyzed by thermodynamic investigation as well as numerical simulation. The concepts are compared by system behavior as well as electricity and heat demand under typical bunkering scenarios. The analysis of the concepts produces general design criteria for an efficient terminal design. It is shown that an export terminal is most efficient with a multistage expansion. Furthermore, the integration of the pressure tank as a condenser proves to be particularly suitable for an import terminal.

Electroconductive silver nanoparticle composite films for sensing ammonia in the presence of water vapor

Nanocomposite films (NCF) containing silver nanoparticles (AgNPs) separated by thin silica/poly-4-vinylpyridine/polyvinylpyrrolidone polymer layers were fabricated on several substrates by spin coating, dip coating, and drop casting methods. The films exhibit electrical conductivity that changes upon the exposure to moist ammonia and water vapors. Hydrogen bonding of ammonia and water molecules to the silica/polymer layers as well as the direct adsorption of ammonia molecules onto the silver surface accounted for the conductivity changes. Drop casting on nylon filter membranes resulted in the most reproducible films. Optical microscopy, atomic force microscopy, UV-Vis spectroscopy, SEM, and XRD were used for the characterization of the NCF. NCF fabricated with polyvinylpyrrolidone polymer layers exhibited 0.4 ppm limit of detection for ammonia in the presence of interfering water vapor. It is proposed that the films could be further developed as ammonia sensors for environmental and biomedical applications.

Photosynthesis of Benzonitriles on BiOBr Nanosheets Promoted by Vacancy Associates

AbstractPhotocatalytic organic functionalization reactions represent a green, cost‐effective, and sustainable synthesis route for value‐added chemicals. However, heterogeneous photocatalysis is inefficient in directly activating ammonia molecules for the production of high‐value‐added nitrogenous organic products when compared with oxygen activation in the formation of related oxygenated compounds. In this study, we report the heterogeneous photosynthesis of benzonitriles by the ammoxidation of benzyl alcohols (99 % conversion, 93 % selectivity) promoted using BiOBr nanosheets with surface vacancy associates. In contrast, the main reaction of catalysts with other types of vacancy sites is the oxidation of benzyl alcohol to benzaldehyde or benzoic acid. Experimental measurements and theoretical calculations have demonstrated a specificity of vacancy type with respect to product selectivity, which arises from the adsorption and activation of NH3 and O2 that is required to promote subsequent C−N coupling and oxidation to nitrile. This study provides a better understanding of the role of vacancies as catalytic sites in heterogeneous photocatalysis.

Photosynthesis of Benzonitriles on BiOBr Nanosheets Promoted by Vacancy Associates.

Photocatalytic organic functionalization reactions represent a green, cost-effective, and sustainable synthesis route for value-added chemicals. However, heterogeneous photocatalysis is inefficient in directly activating ammonia molecules for the production of high-value-added nitrogenous organic products when compared with oxygen activation in the formation of related oxygenated compounds. In this study, we report the heterogeneous photosynthesis of benzonitriles by the ammoxidation of benzyl alcohols (99 % conversion, 93 % selectivity) promoted using BiOBr nanosheets with surface vacancy associates. In contrast, the main reaction of catalysts with other types of vacancy sites is the oxidation of benzyl alcohol to benzaldehyde or benzoic acid. Experimental measurements and theoretical calculations have demonstrated a specificity of vacancy type with respect to product selectivity, which arises from the adsorption and activation of NH3 and O2 that is required to promote subsequent C-N coupling and oxidation to nitrile. This study provides a better understanding of the role of vacancies as catalytic sites in heterogeneous photocatalysis.

Mechanism of the Hydrazine Monohydrate Decomposition by Means of IR Spectroscopy <i>In Situ</i>

Pd-containing catalysts (1%Pd/Al2O3 and 5%Pd/Al2O3) deposited on aluminum oxide were studied in the decomposition reaction of hydrazine monohydrate. According to in situ IR spectroscopy, it was found that hydrazine monohydrate is adsorbed on the coordination unsaturated centers of the catalyst surface in a linear form. When the temperature rises, the adsorbed hydrazine monohydrate loses a water molecule, which is accompanied by a change in the geometry of the molecular complex. Adsorption of hydrazine on a support and its diffusion onto palladium clusters is a more advantageous process than direct adsorption on active centers. This circumstance shows that the hydrazine adsorbed on the support can be an intermediate of its decomposition process. The studied catalysts have a maximum activity in the temperature range of 100–120°C, while the ratio of hydrogen and nitrogen concentrations in the reaction products was equal to 2, which corresponds to 100% selectivity for hydrogen. As the reaction temperature increases, the selectivity decreases significantly. The explanation of the high selectivity for hydrogen at low temperatures is due to the fact that the adsorption of N2H4 is carried out through the formation of hydrogen–metal bonds. The hydrogen–metal bond strength in such a complex is higher than the nitrogen–metal bond strength, hence the barrier for breaking the N–H bond is lower than the barrier for breaking N–N bond, which leads to breaking N–H bond and preserving the N–N bond. At elevated temperatures, some of the hydrogen atoms formed recombine, the other reacts with the surface complexes of hydrazine to form the intermediate NH3–NH3, the breaking of the bond in which leads to the formation of ammonia molecules in the gas phase.

MIL-100(Fe) /ZnO nanocomposite sensors: An enhanced ammonia selectivity and low operating temperature

This study aims to enhance the response and selectivity of zinc oxide (ZnO) gas sensors by its incorporating in MIL-100(Fe) as a support material. ZnO nanocomposites were synthesized by impregnating MIL-100 with varying weight percentages of zinc oxide (10% to 20%). The fabricated sensors underwent characterization through XRD, FTIR, DRS (UV-Vis), SEM/EDS, and NH3-TPD techniques to assess their material composition and sensor performance. DRS (UV-Vis) techniques revealed a significant decrease in the band gap, from Tauc analysis, accompanied by a 20% decrease in the Schottky barrier of the nanocomposite, compare to ZnO. Furthermore, the optimal operating temperature for the MIL-100/ZnO nanocomposites was identified as 240 °C, contrasting with pure ZnO sensors that exhibited an increasing response with temperature. Notably, the MIL-100/ZnO nanocomposites exhibited substantially improved selectivity for ammonia, displaying 3–6 times higher selectivity compared to pure ZnO sensors. Additionally, the response to ammonia increased threefold in the MIL-100/ZnO nanocomposites. This enhancement in selectivity and response can be attributed to the synergistic interaction between ammonia molecules and the Lewis acid sites present in the MIL-100 framework, facilitated by coordination bonds. The findings underscore the immense potential of MIL-100/ZnO nanocomposites as a promising solution for augmenting the selectivity of ZnO gas sensors. This work contributes valuable insights towards the advancement of gas sensing technology and paves the way for the development of highly selective gas sensors with extensive applications across various fields.

Kinetic and structural details of urease inactivation by thiuram disulphides

This paper reports on the molecular details of the reactivity of urease, a nickel-dependent enzyme that catalyses the last step of organic nitrogen mineralization, with thiuram disulphides, a class of molecules known to inactivate the enzyme with high efficacy but for which the mechanism of action had not been yet established. IC50 values of tetramethylthiuram disulphide (TMTD or Thiram) and tetraethylthiuram disulphide (TETD or Disulfiram) in the low micromolar range were determined for plant and bacterial ureases. The X-ray crystal structure of Sporosarcina pasteurii urease inactivated by Thiram, determined at 1.68 Å resolution, revealed the presence of a covalent modification of the catalytically essential cysteine residue. This is located on the flexible flap that modulates the size of the active site channel and cavity. Formation of a Cys-S-S-C(S)-N(CH3)2 functionality responsible for enzyme inactivation was observed. Quantum-mechanical calculations carried out to rationalise the large reactivity of the active site cysteine support the view that a conserved histidine residue, adjacent to the cysteine in the active site flap, modulates the charge and electron density along the thiol SH bond by shifting electrons towards the sulphur atom and rendering the thiol proton more reactive. We speculate that this proton could be transferred to the nickel-coordinated urea amide group to yield a molecule of ammonia from the generated Curea-NH3+ functionality during catalysis.

Can a single ammonia and water molecule enhance the formation of methanimine under tropospheric conditions?: kinetics of •CH2NH2 + O2 (+NH3/H2O).

The aminomethyl (•CH2NH2) radical is generated from the photo-oxidation of methylamine in the troposphere and is an important precursor for new particle formation. The effect of ammonia and water on the gas-phase formation of methanimine (CH2NH) from the •CH2NH2 + O2 reaction is not known. Therefore, in this study, the potential energy surfaces for •CH2NH2 + O2 (+NH3/H2O) were constructed using ab initio//DFT, i.e., coupled-cluster theory (CCSD(T))//hybrid-density functional theory, i.e., M06-2X with the 6-311++G (3df, 3pd) basis set. The Rice-Ramsperger-Kassel-Marcus (RRKM)/master equation (ME) simulation with Eckart's asymmetric tunneling was used to calculate the rate coefficients and branching fractions relevant to the troposphere. The results show 40% formation of CH2NH at the low-pressure (<1 bar) and 100% formation of CH2NH2OO• at the high-pressure limit (HPL) condition. When an ammonia molecule is introduced into the reaction, there is a slight increase in the formation of CH2NH; however, when a water molecule is introduced into the reaction, the increase in the formation of CH2NH was from 40% to ∼80%. The calculated rate coefficient for •CH2NH2 + O2 (+NH3) [1.9 × 10-23cm3 molecule-1 s-1] and for CH2NH2 + O2 (+H2O) [3.3 × 10-17cm3 molecule-1 s-1] is at least twelve and six order magnitudes smaller than those for free •CH2NH2 + O2 (2 × 10-11cm3 molecule-1 s-1 at 298K) reactions, respectively. Our result is consistent with that of previous experimental and theoretical analysis and in good agreement with its isoelectronic analogous reaction. The work also provides a clear understanding of the formation of tropospheric carcinogenic compounds, i.e., hydrogen cyanide (HCN).

Incorporation of indium into GaN layers in the context of MOVPE thermodynamics and growth – Ab initio studies

Indium incorporation on the GaN surface (0001) has been analyzed in the context of InGaN growth by Metal Organic Vapor Phase Epitaxy (MOVPE). To understand phenomena at the atomic level, calculations based on Density Functional Theory (DFT) and thermodynamic analysis of the surface processes have been performed. The considerations are limited to the terrace on GaN (0001) surface, covered fully by NH3/NH2 species. The ab initio results indicate that the adsorption energy strongly depends on the electronic properties of the surface. The adsorption energy varies from EadsDFT=-10.0eV for fully NH2 covered to EadsDFT=-3.0eV for mixed 0.69 NH2 + 0.31 NH3 covered surface. This change is related to Fermi level position moved from within valence band, across the bandgap, up to within conduction band. The shift in Fermi energy impacts the energy gained during adsorption due to electron occupation of surface states. Furthermore, a comprehensive thermodynamic analysis was conducted, revealing an additional, albeit smaller, contribution from the vibrational degrees of freedom to free energy. The combined effect of these factors leads to an increase in the equilibrium pressures of indium related to the increase in hydrogen pressure, which correlates with high coverage by ammonia molecules. The results demonstrate that the significant reduction in indium incorporation into InGaN layers during MOVPE growth under conditions of low hydrogen concentration in the vapor can be attributed to the influence of hydrogen on In adsorption processes.

Highly Efficient Intramolecular Proton Transfer in p-Aminobenzoic Acid by a Single Ammonia Molecule as a Vehicle.

Proton transfer is classified into two mechanisms: the Grotthuss (proton-relay) and vehicle mechanisms. It has been well studied on gas-phase proton transfer by a proton relay involving multiple molecules. However, a vehicle mechanism in which a single molecule transports a proton has rarely been reported. Here, we have obtained clear evidence that the proton transfers efficiently between the two protonation sites in protonated p-aminobenzoic acid (PABA·H+) by a single ammonia molecule as a vehicle. The gaseous PABA·H+ ions were reacted with NH3 or ND3 under single-collision conditions in a cold ion trap, and the proton-transferred ions were identified by cryogenic ion mobility-mass spectrometry. A reaction intermediate PABA·H+·NH3 was also detected for the first time. The reaction pathway search calculations and ab initio molecular dynamics simulations supported the present experimental finding that intramolecular proton transfer occurs very efficiently by the vehicle mechanism.

Mechanism of Nitrogen Reduction to Ammonia in a Diiron Model of Nitrogenase.

Nitrogenase is a fascinating enzyme in biology that reduces dinitrogen from air to ammonia through stepwise reduction and protonation. Despite it being studied in detail by experimental and computational groups, there are still many unknown factors in the catalytic cycle of nitrogenase, especially related to the addition of protons and electrons and their order. A recent biomimetic study characterized a potential dinitrogen-bridged diiron cluster as a synthetic model of nitrogenase. Using strong acid and reductants, the dinitrogen was converted into ammonia molecules, but details of the mechanism remains unknown. In particular, it was unclear from the experimental studies whether the proton and electron transfer steps are sequential or alternating. Moreover, the work failed to establish what the function of the diiron core is and whether it split into mononuclear iron fragments during the reaction. To understand the structure and reactivity of the biomimetic dinitrogen-bridged diiron complex [(P2P'PhFeH)2(μ-N2)] with triphenylphosphine ligands, we performed a density functional theory study. Our computational methods were validated against experimental crystal structure coordinates, Mössbauer parameters, and vibrational frequencies and show excellent agreement. Subsequently, we investigated the alternating and consecutive addition of electrons and protons to the system. The calculations identify a number of possible reaction channels, namely, same-site protonation, alternating protonation, and complex dissociation into mononuclear iron centers. The calculations show that the overall mechanism is not a pure sequential set of electron and proton transfers but a mixture of alternating and consecutive steps. In particular, the first reaction steps will start with double proton transfer followed by an electron transfer, while thereafter, there is another proton transfer and a second electron transfer to give a complex whereby ammonia can split off with a low energetic barrier. The second channel starts with alternating protonation of the two nitrogen atoms, whereafter the initial double proton transfer, electrons and protons are added sequentially to form a hydrazine-bound complex. The latter split off ammonia spontaneously after further protonation. The various reaction channels are analyzed with valence bond and orbital diagrams. We anticipate the nitrogenase enzyme to operate with mixed alternating and consecutive protonation and electron transfer steps.

Adsorption and Desorption Behaviors of Ammonia on Zeolites at 473 K by the Pressure-Swing Method.

Adsorption and desorption behaviors of ammonia on the zeolites were investigated using the pressure-swing method to utilize the ammonia adsorbent at 473 K. For various (Y, A, L, and mordenite) types of zeolites, the effects of their pore sizes, countercation species, and number of adsorption sites on the ammonia adsorption behavior were evaluated. The adsorption capacity increased with increasing the pore size. The differences in the countercation species and the number of adsorption sites contributed to the ammonia adsorption process on the zeolites. Sodium cations strongly adsorb ammonia molecules. The adsorption/desorption of ammonia expanded and shrunk the zeolite crystal, suggesting that the pores in the zeolite were enlarged by the adsorption of ammonia molecules. Despite repetitive lattice expansion and shrinkage, the morphologies of the zeolite particles were not degraded. These results confirm that the zeolite showed high durability for the adsorption and desorption of ammonia at 473 K.

Surface Enhancement Effects of Tiny SnO2 Nanoparticle Modification on α-Fe2O3 for Room-Temperature NH3 Sensing.

The development of a gas sensor capable of detecting ammonia with high selectivity and rapid response at room temperature has consistently posed a formidable challenge. To address this issue, the present study utilized a one-step solvothermal method to co-assemble α-Fe2O3 and SnO2 by evenly covering SnO2 nanoparticles on the surface of α-Fe2O3. By controlling the morphology and Fe/Sn mole ratio of the composite, the as-prepared sample exhibits high-performance detection of NH3. At room temperature conditions, a gas sensor composed of α-Fe2O3@3%SnO2 demonstrates a rapid response time of 14 s and a notable sensitivity of 83.9% when detecting 100 ppm ammonia. Experiments and density functional theory (DFT) calculations suggest that the adsorption capacity of α-Fe2O3 to ammonia is enhanced by the surface effect provided by SnO2. Meanwhile, the existence of SnO2 tailors the pore structure and effective surface area of α-Fe2O3, creating multiple channels for the diffusion and adsorption of ammonia molecules. Additionally, an N-N heterostructure is formed between α-Fe2O3 and SnO2, which enhances the potential energy barrier and improves the ammonia sensing performance. Demonstration experiments have proved that the sensor shows significant advantages over commercial sensors in the process of ammonia detection in agricultural facilities. This work provides new insights into the perspectives on ammonia detection at room temperature.

A Review on Electrospun Nanofiber Composites for an Efficient Electrochemical Sensor Applications.

The present review article discusses the elementary concepts of the sensor mechanism and various types of materials used for sensor applications. The electrospinning method is the most comfortable method to prepare the device-like structure by means of forming from the fiber structure. Though there are various materials available for sensors, the important factor is to incorporate the functional group on the surface of the materials. The post-modification sanction enhances the efficiency of the sensor materials. This article also describes the various types of materials applied to chemical and biosensor applications. The chemical sensor parts include acetone, ethanol, ammonia, and CO2, H2O2, and NO2 molecules; meanwhile, the biosensor takes on glucose, uric acid, and cholesterol molecules. The above materials have to be sensed for a healthier lifestyle for humans and other living organisms. The prescribed review articles give a detailed report on the Electrospun materials for sensor applications.