Ammonia Molecules Research Articles

One-dimensionally confined ammonia molecules: A theoretical study

We examine a single-file chain of ammonia molecules in a carbon nanotube. To this end, we use i) molecular dynamics simulations (combined with the charges for ammonia nitrogen and hydrogen obtained from quantum chemistry) and ii) lattice-model calculations by M. Druchok et al. (2023) [7]. Our findings demonstrate the occurrence of the orientational quasiorder of the ammonia dipoles, which become parallel to the tube axis, at intermediate temperatures below 100 K.

Portable and reversible smart labels for non-destructive detection of seafood freshness via amine-response fluorescent ionic liquids

Herein, a functionalized ionic liquid (IL) 7-HDCP (7-hydroxycoumarin-quaternary phosphorus) was developed as NH3 trapping agents and fluorescent indicators to achieve in-time and on-site detection of seafood freshness. Interestingly, the IL displayed remarkable blue fluorescence “turn-on” enhancement to gaseous amine due to excellent amine solubility. By FTIR and 1H NMR spectrogram, this fluorescence “turn-on” phenomenon originated from the weak hydrogen bonding between the ester group of the coumarin functional group and the ammonia molecule. Moreover, the IL exhibited a rapid response (<11 s), prominent sensitivity (0.12 ppm), excellent selectivity (10 interfering substances) and outstanding reversibility (>22 cycles). Benefiting from ion characters, 7-HDCP obtained advantages of easy-to-fabricate and easy-to-use, which was fabricated by one-step simple immersion without aggregation-caused quenching phenomenon. This portable and sensitive smart label made of ion probes facilitates the timely and on-site NH3 detection in the early deterioration stages of aquatic products, enabling “early detection, early warning, and early treatment”.

Experimental and BEf-scaled cross sections for electron-impact excitation of ammonia molecules from near threshold to high-intermediate energy

Experimental and BEf-scaled cross sections for electron-impact excitation of ammonia molecules from near threshold to high-intermediate energy

Extended Ensemble Molecular Dynamics Study of Ammonia-Cellulose I Complex Crystal Models: Free-Energy Landscape and Atomistic Pictures of Ammonia Diffusion in the Crystalline Phase.

Here, we report extended ensemble molecular dynamics simulations of ammonia-cellulose I complex crystal models to evaluate the diffusion behavior of the guest ammonia molecules and the potential of mean force (PMF), namely, the free energy change along the chosen reaction coordinate, for migration of an ammonia molecule in the crystal models. Accelerated molecular dynamics simulations confirmed that ammonia molecules almost exclusively diffused through the hydrophilic channel even when the crystal framework was retained. Adaptive steered molecular dynamics simulations detected distinct PMF peaks with heights of approximately 7 kcal/mol as the ammonia molecule passed through the cellulose-chain layers. Introducing hybrid quantum mechanical and molecular mechanics theory to the adaptive steered molecular dynamics simulation effectively lowered the heights of the PMF peaks to approximately 5 kcal/mol, accompanied by a slight decrease in the baseline. Removal of the ammonia molecules in the neighboring channels resulted in a continuous increase in the baseline for the migration of an ammonia molecule in the hydrophilic channel. When the halves of the crystal model were separated to widen the hydrophilic channel to 0.2 nm, the PMF profiles exhibited an unexpected increase. This resulted from water structuring in the expanded hydrophilic channel, which disappeared with further expansion of the hydrophilic channel to 0.3 nm.

Linear scaling of charge transfer versus work function of Ammonia chemisorption on X-metal (X = Ag, Au, Pd, and Pt) surface

Although the d-band center theory can efficiently describe the interaction between gas molecules and transition metal surfaces, the specific reaction process and detailed adsorption criteria remain unclear. Therefore, we systemically investigated the adsorption process and mechanism of Ammonia (NH3) molecules on transition metal (i.e., Ag, Au, Pd and Pt) surfaces using first-principles calculations. Results indicate that the NH3 molecule undergoes chemisorption on the Pt (111) surface with considerable charge transfer and adsorption energy, indicating that Pt metal is a promising NH3-sensitive material. Furthermore, the chemisorption primarily entails the highest-occupied molecular orbital (HOMO) of NH3, and the metal atoms conform perfectly to the principles of energy-level matching, wave function matching, and maximal orbital wave function overlap. Notably, a linear relationship exists between the charge transfer of NH3 and the work function of X-metal substrates. Our findings provide a feasible way to efficiently design NH3-sensitive materials for experiments.

Liver support systems and liver transplantation in acute liver failure.

Acute liver failure (ALF) results in a multitude of complications that result in multi-organ failure. This review focuses on the pathophysiological processes and how to manage with these with artificial liver support and liver transplantation (LT). The pathophysiological sequence of events behind clinical deterioration in ALF comes down to two profound consequences of the failing liver. The first is the development of hyperammonemia, as the liver can no longer synthesize urea. The result is that the splanchnic system instead of removing ammonia becomes an ammonia-producing organ system that causes hepatic encephalopathy (HE) and cerebral oedema. The second complication is caused by the necrotic liver cells that release large molecules that originate from degrading proteins, that is damage associated molecular patterns (DAMPs) which causes inflammatory activation of intrahepatic macrophages and an overflow of DAMPs molecules into the systemic circulation resulting in a clinical picture that resembles septic shock. In this context the combined use of continuous renal replacement therapy (CRRT) and plasma exchange are rational and simple ways to remove ammonia and DAMPS molecules. This combination improve survival for ALF patients deemed not appropriate for LT, despite poor prognostic criteria, but also ensure a better stability of vital organs while awaiting LT. The combination of CRRT with albumin dialysis tends to have a similar effect. Currently, the selection criteria for LT for non-paracetamol cases appear robust while the criteria for paracetamol-intoxicated patients have become more unreliable and now consist of more dynamic prognostic systems. For patients that need LT for survival, a tremendous improvement in the post-LT results has been achieved during the last decade with a survival that now reach merely 90% which is mirroring the results seen after LT for chronic liver disease.

Anti-biofouling potential of extremely water-repellent carbon soot coatings immersed in a highly-contaminated seawater swamp

The undesired translocation of marine microorganisms during sailing and the excessive expenditures for ship hull repairment due to biofouling could be circumvented using superhydrophobic coatings. Unfortunately, the combined effect of underwater currents and colonizing activity of multitudinous foulants on the anti-microbial performance of existing non-wettable materials is still at infant stage. The paramount objective here is to evaluate for the first time the potential of two mechanically durable water-repellent soot coatings towards the inhibition of bacterial proliferation in “real-life” outdoor conditions. We demonstrate that upon one-week immersion in a seawater swamp, both specimens lose non-wettability due to dissolution of the trapped gas layer into the water basin, but yet manage to retard the biofilm development, compared to uncoated iron surfaces, and halt the settlement of some Gram-negative and Gram-positive bacterial strains. The noticed selectiveness in the anti-fouling behavior of tested samples is presumably attributed to differences in the cell envelopes, the extent of elicit oxidative stress and soot-mediated formation of toxic ammonia molecules via hydrogen bonding. These unknown so far anti-bacterial mechanisms of the soot expand the horizons of practical applicability beyond the conventional framework and emphasize on its possible future use as a therapeutic agent.

Synthesis and spectroscopic study of complex compounds of some 3D metals with the condensation product of 1-ferrocenylbutanedione-1,3 and succinic acid dihydrozide

We obtained by Claisen condensation β-diketone-1-ferrocenylbutanedione-1,3. The dicarboxylic acid dihydrazone of 1-ferrocenylbutanedione-1,3 (H4L) was synthesized by reacting succinic acid dihydrazide with ferrocenylacetone in a ratio of 2:1. Based on them, homobinuclear complex compounds with copper(II), zinc(II)and nickel(II) ions were obtained. The IR-, UV- and NMR spectra of the synthesized organic compounds were studied. The results of the studies showed that the H4L ligand in solution exists as a tautomeric mixture: diketone (A), keto-enol (B) and in dienol(C) forms. According to the results of spectroscopic studies, the complexes were assigned a square planar structure, where the four times deprotonated ligand residue is coordinated by each metal atom through two oxygen atoms and a nitrogen atom of the hydrazone fragment. The fourth position in the planar square of the trans-N2O2 coordination site is occupied by the ammonia molecule. Planar five- and six-membered metal cycles of synthesizers are practically coplanar with each other.

Elastomer-coated graphene biosensor and its response to enzymatic reactions

Graphene biosensors have the potential to be excellent applications of two-dimensional materials, because graphene has high mobility and specific surface area. However, it is difficult to stably obtain consistent responses from graphene biosensors owing to external disturbances and the lack of understanding their sensing mechanism. We propose a graphene biosensor coated with a gas-permeable silicone elastomer, poly(dimethylsiloxane). The elastomer coating allows only the gas molecules to reach the graphene surface, suppressing the disturbances from other factors, and thereby eliciting stable responses to target ammonia molecules in solution. It allowed us to clarify the relationship between ammonia production via urease reactions and conductivity changes of the graphene biosensor. The biosensor responses were modeled using the combination of the dissociation equilibrium of ammonia, Langmuir’s adsorption isotherm, and Michaelis–Menten equation. Findings of this study lay the foundation for practical applications of stable graphene biosensors based on our reasonable response model.

Complexities in the structural evolution with pressure of water-ammonia mixtures.

The structural evolution with pressure of icy mixtures of simple molecules is a poorly explored field despite the fundamental role they play in setting the properties of the crustal icy layer of the outer planets and of their satellites. Water and ammonia are the two major components of these mixtures, and the crystal properties of the two pure systems and of their compounds have been studied at high pressures in a certain detail. On the contrary, the study of their heterogeneous crystalline mixtures whose properties, due to the strong N-H⋯O and O-H⋯N hydrogen bonds, can be substantially altered with respect to the individual species has so far been overlooked. In this work, we performed a comparative Raman study with a high spatial resolution of the lattice phonon spectrum of both pure ammonia and water-ammonia mixtures in a pressure range of great interest for modeling the properties of icy planets' interiors. Lattice phonon spectra represent the spectroscopic signature of the molecular crystals' structure. The activation of a phonon mode in plastic NH3-III attests to a progressive reduction in the orientational disorder, which corresponds to a site symmetry reduction. This spectroscopic hallmark allowed us to solve the pressure evolution of H2O-NH3-AHH (ammonia hemihydrate) solid mixtures, which present a remarkably different behavior from the pure crystals likely to be ascribed to the role of the strong H-bonds between water and ammonia molecules characterizing the crystallites' surface.

A Facile and Surfactant-Free Electrochemical Synthesis of PtIr Nanocubes towards Ammonia Electro-Oxidation

Noble metal Pt catalyst has been identified as excellent electrocatalysts for the ammonia oxidation reaction (AOR). However, Pt’s scarcity, expensiveness, and toxicity hinder its large-scale commercial application. Herein, we report a facile and surfactant-free electrochemical synthesis method for the production of PtIr nanocubes. The PtIr nanocubes were in situ synthesized on carbon paper, and no organic additives were used at any stage in the synthesis of the catalyst. The formation of PtIr nanocubes was attributed to the synergy of the electro-adsorption/desorption of O-containing species and the preferential adsorption of hydrogen adatoms on PtIr(100) with a lower surface free energy. The obtained PtIr nanocubes exhibit an outstanding specific activity (SA) value of 1.34 mA cm−2, which is 1.5 and 3.8 times higher than Pt nanocubes (0.90 mA cm−2) and PtIr nanospheres (0.35 mA cm−2), respectively. The enhanced SA of the PtIr nanocubes can be ascribed to the synergic effects of multiple factors, including the (100) sites of the PtIr nanocubes, the dehydrogenation ability of Ir with respect to ammonia molecules, the electronic effects, and the clean surface of the catalyst due to the use of a “green” synthesis method. This work provides an effective strategy for the “green” synthesis of high-efficiency Pt-based metal catalysts with controllable shapes.

Selective Catalytic Epoxidation-Hydration of α-Pinene with Hydrogen Peroxide to Sobrerol by Durable Ammonium Phosphotungstate Immobilized on Imidazolized Activated Carbon.

It is presented that the activated carbon was carboxylated with hydrogen peroxide and then acylated with 2-methylimidazole to prepare the porous carbon support with a surface imidazolated modification. Through the adsorption of phosphotungstic acid on the fundamental site of an imidazolyl group and then adjusting the acid strength with the ammonia molecule, a catalytic carbon material immobilized with ammonium phosphotungstate (AC-COIMO-NH4PW) was obtained, which was used to catalyze a one-pot reaction of convenient α-pinene and hydrogen peroxide to sobrerol. The bifunctional active site originated from the dual property of ammonium phosphotungstate, as the oxidant and acid presenting a cooperatively catalytic performance, which effectively catalyzes the tandem epoxidation-isomerization-hydration of α-pinene to sobrerol, in which the solvent effect of catalysis simultaneously exists. The sobrerol selectivity was significantly improved after the acid strength weakening by ammonia. Monomolecular chemical bonding and anchoring of ammonium phosphotungstate at the basic site prevented the loss of the active catalytic species, and the recovered catalyst showed excellent catalytic stability in reuse. Using acetonitrile as the solvent at 40 °C for 4 h, the conversion of α-pinene could reach 90.6%, and the selectivity of sobrerol was 40.5%. The results of five cycles show that the catalyst presents excellent stability due to the tight immobilization of ammonium phosphotungstate bonding on the imidazolized activated carbon, based on which a catalytic-cycle mechanism is proposed for the tandem reaction.

ON THE SZEGED INDEX AND ITS NON-COMMUTING GRAPH

In chemistry, the molecular structure can be represented as a graph. Based on the information from the graph, its characterization can be determined by computing the topological index. Topological index is a numerical value that can be computed by using some algorithms and properties of the graph. Meanwhile, the non-commuting graph is a graph, in which two distinct vertices are adjacent if and only if they do not commute, where it is made up of the non-central elements in a group as a vertex set. In this paper, the Szeged index of the non-commuting graph of some finite groups are computed. This paper focuses on three finite groups which are the quasidihedral groups, the dihedral groups, and the generalized quaternion groups. The construction of the graph is done by using Maple software. In finding the Szeged index, some of the previous results and properties of the graph for the quasidihedral groups, the dihedral groups, and the generalized quaternion groups are used. The generalisation of the Szeged index of the non-commuting graph is then established for the aforementioned groups. The results are then applied to find the Szeged index of the non-commuting graph of ammonia molecule.

First-principles prediction of two-dimensional MXene (V2C, Ti2C, and Mo2C) as the catalyst for ammonia decomposition

The geometric structure, electronic structure and dehydrogenation mechanism of NH3 adsorbed on three MXene (V2C, Ti2C, and Mo2C) surfaces were studied by combining density functional theory with periodic plate model. The calculation results of adsorption energy showed that the order of adsorption energy of NHx(x = 0–3) was Mo2C < V2C < Ti2C. The results of the transition states showed that the desorption of nitrogen atoms was the rate-limiting step of the whole reaction. The surface of V2C was more conducive to the decomposition of ammonia gas for hydrogen production, while the surface of Ti2C and Mo2C was susceptible to the adsorption poisoning of N atoms. The results of electron structure study showed that the strong interaction between d orbitals of transition metal atoms near Fermi level and molecular orbitals of ammonia made ammonia molecules activated in different degrees, showing high adsorption performance and catalytic activity.

Physical Environments of the Luminosity Outburst Source NGC 6334I Traced by Thermal and Maser Lines of Multiple Molecules

We have conducted a systematic line survey, primarily focused on transitions of the methanol and ammonia molecules, and monitoring observations of masers toward the high-mass star-forming region NGC 6334I. These observations were undertaken between 2019 and 2022 in the C, K, Ka, and Q bands with the Tianma Radio Telescope. In total, 63 CH3OH (including 11 class I and nine class II maser or maser candidate), 18 13CH3OH, and 34 NH3 (including seven maser or maser candidate) transitions were detected. The emission is likely associated with the luminosity outburst source MM1. Rotation diagram analysis of multiple ammonia transitions shows that the gas temperature in the molecular core was a factor of 2 higher than that measured in previous observations in the pre-burst stage. This suggests that the molecular core has likely been heated by radiation originating from the luminosity outburst. Maser variability in the methanol and excited-state OH masers shows a general trend that the maser components associated with the luminosity outburst have decreased in their intensity since 2020. The decay in the maser luminosity indicates that the outburst is possibly declining, and as a result, the duration of the MM1 luminosity outburst may be shorter than the predicted 40 yr duration. Compared to the masers detected toward another luminosity outburst source, G358.93-0.03, abundant class I methanol masers and strong water maser flares were also detected toward NGC 633I, but masers from rare class II methanol transitions and new molecules were absent toward NGC 6334I. The large number of detections of maser transitions toward the two burst sources provided a database for further maser modeling to explore the physical environments associated with accretion burst events.

Multi-Criteria Analysis to Determine the Most Appropriate Fuel Composition in an Ammonia/Diesel Oil Dual Fuel Engine

The possibility to employ alternative fuels is gaining special interest in the marine sector. There are several suitable candidates for traditional fossil fuels substitution. Among them, ammonia is a promising solution that allows progress on decarbonization since the ammonia molecule does not contain carbon. Hence, the present work analyzes the use of ammonia as a potential fuel for a marine engine. Particularly, a dual fuel mode ammonia/diesel oil operation is proposed. As expected, the carbon dioxide emissions are reduced as the proportion of ammonia is increased. Nevertheless, other non-desirable substances are generated such as non-reacted ammonia, NOx and N2O. Due to these opposing effects, a multi-criteria analysis is proposed to characterize the most appropriate proportion of ammonia in the fuel. The environmental damage of the different pollutants was considered. Due to the important environmental adverse effects of NOx and N2O, only a maximum 20% ammonia percentage on the fuel was obtained as the most appropriate option. A higher ammonia content leads to excessive concentrations of NOx and N2O being emitted to the environment.

Potential energy surfaces of the [formula omitted] clusters in solvent phase: A DFT study

The solvation effects is important in understanding the process to form a solution. Although several processes take place in solution, these effects on the structures of molecular clusters have received less attention. In this work, we have investigated for the first time, the effects of solvent (ammonia) on the structures, energetics, dative bond and hydrogen bond networks of the Cu2+(NH3)n=1−10 clusters. We have explored thoroughly the potential energy surfaces (PESs) at the M06-2X/6-31++G(d,p) level of theory in the solvent phase (represented by a dielectric continuum medium) and compare them with the structures of the computed Cu2+(NH3)n=1−10 clusters in the gas phase. For the description of the dielectric continuum medium, we used the integral equation formalism of the polarized continuum model (IEF-PCM). Besides, we have reported the binding and clustering energies per ammonia molecule. It emerges from this study that the hexa- and penta-coordinated structures are located on the global minimum of the energies of PESs of the Cu2+(NH3)n=1−10 clusters. The stability rules of the Cu2+ ion are better respected in the solvent phase than in the gas phase. Both the distances of the dative bonds are shorter and hydrogen bonds are longer in the solvent phase than those in the gas phase. All the mentioned differences between the results in the solvent phase and those in the gas phase must thank to the polarization of the medium. For the prediction of binding and clustering electronic energy, a function is fitted and used to predict these energies at saturation in the solvent phase and those in the gas phase. In the solvent phase the value of binding energy is -2465kJmol−1 and -17 931kJmol−1 in the gas phase. Similarly, the values of clustering energies are -25kJmol−1 and -379kJmol−1 in solvent phase and in gas phase respectively. This large difference in the predicted energies in the solvent phase with respect to those in the gas phase is due to the fact the metal-ligand interaction is the influence by the implicit solvent in the solvent phase. In fact, the solvent phase may be better predicted considering the clusters in the dielectric continuum medium than those in the gas phase because of the polarization of the medium. NBO analysis confirms energetics analysis. We therefore recommend this fitted function for the study of such clusters.

Quantum state-resolved molecular dipolar collisions over four decades of energy.

Collisions between cold polar molecules represent a fascinating research frontier but have proven hard to probe experimentally. We report measurements of inelastic cross sections for collisions between nitric oxide (NO) and deuterated ammonia (ND3) molecules at energies between 0.1 and 580 centimeter-1, with full quantum state resolution. At energies below the ~100-centimeter-1 well depth of the interaction potential, we observed backward glories originating from peculiar U-turn trajectories. At energies below 0.2 centimeter-1, we observed a breakdown of the Langevin capture model, which we interpreted in terms of a suppressed mutual polarization during the collision, effectively switching off the molecular dipole moments. Scattering calculations based on an ab initio NO-ND3 potential energy surface revealed the crucial role of near-degenerate rotational levels with opposite parity in low-energy dipolar collisions.

Computational Screening of Ti3C2TX MXene by Controlling the Functionalized Catalyst for NH3 Gas Sensor

First‐principles calculations are used to research the adsorption behavior of ammonia on Ti3C2O2, Ti3C2F2, Ti3C2H2, Ti3C2S2, and Ti3C2Cl2. Herein, a total of four special adsorption sites α, β, γ, and δ are considered. The adsorption energy, charge transfer, and electronic properties of the gas‐adsorption system are calculated, and the better adsorption sites and adsorption functional groups of ammonia on Ti3C2T X with different functional groups are studied. The results show that the best adsorption positions of ammonia on Ti3C2O2, Ti3C2F2, Ti3C2H2, Ti3C2S2, and Ti3C2Cl2 are all α position. According to the analysis of differential charge density, adsorption energy, and charge transfer of ammonia molecules, the adsorption strength of ammonia molecules on Ti3C2 surfaces modified with different functional groups is Ti3C2H2 &gt; Ti3C2O2 &gt; Ti3C2F2 &gt; Ti3C2S2 &gt; Ti3C2Cl2. The ammonia molecule adsorbs on the surface of Ti3C2H2 exhibits the strongest adsorption energy (−0.787 eV), but the −H group is more likely to break and form other groups. Therefore, the Ti3C2 surface modified by −O group is more suitable for ammonia detection.

Study of gate induced sensitivity amplification in carbon nanotube thin film transistor based ammonia sensor

Gas sensors based on carbon nanotube thin film transistors (CNT TFT) have been widely investigated in the past. However, studies on the active sensing properties i.e. effects of gate induced variations in sensing of such devices are deficient. In this work the effects of gate voltage on the ammonia sensing properties of a single wall CNT TFT are investigated. It is observed that under the influence of a gate field, the device sensitivity and detection limit (LOD) can be improved by more than 11 and 6 times respectively. The amplification of sensor response is found to occur for both the gate polarities and this is attributed to a combination of two phenomena. Firstly, ab-initio Molecular dynamics (MD) based adsorption studies of ammonia molecules to a CNT device indicate that the introduction of a gate field leads to an increase in the adsorption energy of ammonia to the device especially for a positive gate which is directly relatable to the observed amplification in sensing. Additionally, in the negative gate regime, a reversible increase of the contact resistance induced by ammonia exposure is thought to be the primary contributing factor in increasing the responsivity of the sensor. This is also thought to contribute to improving the sensor selectivity at negative gate.