Presence Of NH Research Articles

Ar ions and oxygen plasma interactions of amine terminated organosilicate glass: A combined experimental and ab initio simulations study

Ar+ ion bombardment (900 eV) of organosilicate glass (OSG) in the presence of NH3 (1 × 10−6 Torr) yields an overlayer containing Si-NHx bonds. The NHx layer decreases the rate of carbon loss from the remaining film upon subsequent oxygen plasma exposure, due to preferential removal of N from the surface region. Ab initio density functional theory calculations have been performed to investigate the stability of the bonds present in low-k dielectrics utilizing a trimethyltrisiloxane model system. Calculated bond energies are 6.30 eV (Si-NH2), 6.27 eV (Si-OH), 5.69 eV (Si-CH3), and 5.54 eV (Si-H). The slightly higher calculated Si-NH2 bond energy is consistent with experiment and indicates that the nitrided OSG surface layer inhibits carbon loss in part by inhibition of O2 diffusion into the bulk.

Synthesis of highly dispersed MnOx–CeO2 nanospheres by surfactant-assisted supercritical anti-solvent (SAS) technique: The important role of the surfactant

In this work, highly dispersed mesoporous MnOx–CeO2 hollow nanospheres have been prepared using a surfactant-assisted supercritical anti-solvent (SAS) technique. The phase equilibria of methanol–CO2, precursor-methanol–CO2 and surfactant, precursor-methanol–CO2 systems were measured to preliminarily screen suitable surfactants. The MnOx–CeO2 particles were characterized using N2 adsorption/desorption, transmission electron microscopy (TEM) and X-ray diffraction (XRD). Polyvinylpyrrolidone (PVP) and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123) both efficiently reduced the interconnectivity and agglomeration of MnOx–CeO2 particles and led to the formation of highly dispersed particles with higher specific surface areas, more uniform pores and larger pore volumes. The effects of the SAS process parameters including the surfactant to precursor mass ratio, the temperature and the pressure, on the morphology, particle size, particle size distribution, specific surface area and pore volume of the particles were also investigated. In addition, the catalytic activities of the synthesized hollow nanospheres for the low temperature denitrification (deNOx) in the presence of NH3 were evaluated. Over the entire experimental temperature range (100–220°C), NO conversions of the MnOx–CeO2 particles prepared by introducing PVP or P123 during SAS were much higher than those for MnOx–CeO2 particles prepared without surfactants.

Three transition metal complexes with uncoordinated carboxyl groups: synthesis, structures, and luminescence properties

A new ligand 1-carboxymethyl-5-methyl-1H-pyrazole-4-carboxylic acid (H2L1) and its isomer 1-carboxymethyl-3-methyl-1H-pyrazole-4-carboxylic acid (H2L2) have been synthesized and characterized by IR and 1H NMR. Three complexes of these ligands, [M(HL1)2(H2O)2] (1: M = Zn; 2: M = Cu) and [Cd(HL2)2(H2O)2] (3) were synthesized by the reactions of H2L1 or H2L2 with the corresponding M(NO3)2·6H2O. The complexes were characterized by physico-chemical and spectroscopic methods, single-crystal X-ray diffraction, and thermogravimetric analysis. Complexes 1 and 2 are isostructural, while complex 3 crystallizes in the triclinic system. The M(II) atom in each of the complexes has a distorted octahedral geometry involving two oxygen and two nitrogen atoms from two anionic (HL1)− or (HL2)− ligands and two oxygen atoms from water ligands. Adjacent monomeric components are connected by hydrogen bonds to form a 3D supramolecular network. The free ligands and complexes 1 and 3 show dual-emissive luminescence in the solid state at room temperature. The luminescence intensity of solid complex 1 is weakened in the presence of NH3. Two new isomers, H2L1 and H2L2, and three complexes, [Zn(HL1)2(H2O)2], [Cu(HL1)2(H2O)2], and [Cd(HL2)2(H2O)2] have been synthesized, which display dual-emissive luminescence in the solid state.

Ammonia-mediated, large-scale synthesis of ammonia borane.

A simple, large-scale synthesis of ammonia borane from NaBH4 and (NH4)2SO4 at 0 °C-rt in THF containing 5% NH3 is described. The presence of ammonia is critical for the reaction to proceed and allows the reaction at high concentrations and ambient temperature without the need for anhydrous solvent or inert atmosphere.

Preparation of SiON film by plasma enhanced chemical vapor deposition and passivation on Si

The influences of technological condition on thickness and refractive index of the SiON films preprared by plasma enhanced chemical vapor deposition and the influence of SiON/SiNx stacked film on passivation performance on P-type silicon wafer are investigatied. The results show that the refractive index of SiON film varies from 1.48 to 2.1 and thickness varies from 30-60 nm by changing the gas flow of NH3 and the gas flow ratio of N2O/SiH4. The pressure and RF power mainly affect the thickness of the film. The greater the pressure, the higher the RF power, the faster the deposition rate is and the thicker the film is. The influences of temperature on the film thickness and refractive index can be ignored. The passivation shows that the passivation performance of P-type silicon film after annealing SiON/SiNx stacked films with a gas flow ratio of N2O/SiH4 20 and 30 in the absence and the presence of NH3, is best, which the implied voltages and the lifetimes of minority carriers are 652 mV, 56.7 μs and 649 mV, 50.8 μs, respectively. The passivation effect of SiON/SiNx stacked film is superior to that of the reference SiNx film.

Interaction of ammonia with intrazeolitic silver ions: Development of an ammonia sensor

This paper examines the interaction of ammonia with Ag+-exchanged zeolite Y (Ag-Y) over a range of temperatures (250–450°C). Impedance spectroscopy over the range of 0.5–107Hz indicates that the Ag+ motion within the zeolite is facilitated in the presence of ammonia. Infrared spectroscopy and X-ray photoelectron spectroscopy indicate that Ag+NH3 bonds are being formed. Temperature programmed desorption coupled with impedance spectroscopy show that the NH3 bonding to Ag+ is disrupted around 300°C. However, in the presence of excess NH3, a fraction of the Ag+NH3 bond survives up to 450°C. Control experiments show that there is no measurable autoreduction of Ag+, and therefore, proton-mediated change of impedance in the presence of NH3 is not considered relevant. The change in mobility of the Ag+ in the presence of NH3 has been exploited to design an impedance-based NH3 sensor at a fixed frequency of 1000Hz in the temperature range of 275–350°C, with the optimal sensor response at 300°C. No cross-sensitivity was observed for O2, CO, CO2 and propane. Nitric oxide showed minor interference. Water, however, did show an interference with a decrease in baseline impedance with increasing water. Thus, for practical applications of this sensor, the water content in the gas stream will need to be controlled to a constant value.

TiO2 Modified ZnO Thick Film Resistors As Ammonia Gas Sensors

Zinc oxide nanostructures were synthesized by chemical route method. The XRD spectrum indicates that the sample is wurtezite (hexagonal) structured ZnO with lattice constants of a = 3.249A 0 , c = 5.206 A 0 . Thick films of synthesized ZnO were prepared by screen printing technique. The TiO2 modified ZnO were obtained by dipping them into an aqueous solution of titanium tetrachloride for different interval of time. Gas sensing properties of pure and modified ZnO thick films were investigated. The TiO2 modified ZnO thick film dipped for 5 min were observed to be more sensitive as compared to other modified thick films at 125 0 C. The effect of surface microstructure and TiO2 concentrations on the sensitivity, selectivity, response and recovery of the sensor in the presence of NH3 and other gases ware studied and discussed. Copyright © 2013 VBRI press.

A Highly Distributed CuxAuy-Deposited Nanotube Carbon for Selective Reduction of NO in the Presence of NH3at Very Low Temperature

CuxAuy Deposited on carbon nanotubes prepared by solution plasma sputtering was used for first time as a catalyst for selective reduction of NO, in the presence of NH3, at low temperature. N2 and H2O are desirable during the NO reduction process; however, N2O is totally absent from the obtained products.

The influence of hydrogen on the stability of nitrates during H2-assisted SCR over Ag/Al2O3 catalysts – A DRIFT study

Silver/alumina is a promising catalyst for the selective catalytic reduction of NOx by hydrocarbons (HC-SCR) in excess of oxygen, especially when adding small amounts of hydrogen. The same material shows excellent low-temperature activity for NH3-SCR in the presence of hydrogen. Since NH3 has been proposed to be an intermediate in HC-SCR, it is possible that the role of hydrogen is the same for both systems. Here, we study the effect of H2 in the presence of excess O2 on the differently adsorbed nitrates and nitrites on the Al2O3 support and on nitrates on silver by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and show that nitrites are an intermediate in the formation of monodentate nitrate. Moreover, hydrogen promotes the conversion of nitrites and some bidentate nitrates to mainly monodentate and some bridge-bound nitrates. Although monodentate nitrates are stable, they do not poison the catalyst surface, since the NOx reduction remained constant during 10h of experiment at 250°C. Contrary to the effect on nitrates bound to Al2O3, no effect of hydrogen on nitrates formed on AgO was observed. These nitrates were stable in gas mixtures containing hydrogen but decompose easily in the presence of NH3 at 100°C. This indicates that the silver particles of an Ag/Al2O3 catalyst will not be poisoned by nitrates in H2-assisted NH3-SCR. Moreover, nitrates on silver migrate to the Al2O3 support already at 100°C.

Formation of Nitrous Acid during Ammonia Photooxidation on TiO2 under Atmospherically Relevant Conditions

Ammonia (NH3) from natural and anthropogenic sources is a globally distributed air pollutant, with emission rates expected to double over the next several decades. Selective catalytic oxidation (SCO) on TiO2 photocatalysts represents a potential strategy for NH3 pollution abatement. We show here that irradiation of TiO2 in the presence of NH3 under atmospheric conditions releases gas-phase nitrous acid (HONO), a potentially harmful precursor to atmospheric ozone, before it can be further reduced to N2. Chemical ionization mass spectrometry and diffuse reflection infrared spectroscopy measurements indicate that HONO is derived from the reduction of NO2 and NO3–, which are products of the water-catalyzed photooxidation of NH3. This represents the first experimental evidence of HONO formation from NH3 photooxidation and has important implications for understanding SCO processes and devising air pollution control strategies to remove NH3 from ambient air.

Near-edge x-ray absorption fine structure spectroscopy study of nitrogen incorporation in chemically reduced graphene oxide

The chemical reduction of exfoliated graphene oxide (GO) has gained widespread acceptance as a scalable route for the preparation of chemically derived graphene albeit with remnant topological defects and residual functional groups that preclude realization of the conductance of single-layered graphene. Reduction of GO with hydrazine is substantially effective in restoring the π-conjugated framework of graphene and leads to about a five-to-six orders of magnitude decrease of sheet resistance, but has also been found to result in incidental nitrogen incorporation. Here, the authors use a combination of x-ray photoelectron spectroscopy (XPS) and C, O, and N K-edge near-edge x-ray absorption fine structure (NEXAFS) spectroscopy to examine the local geometric and electronic structure of the incorporated nitrogen species. Both NEXAFS and XPS data suggest substantial recovery of the sp2-hybridized graphene framework upon chemical reduction and removal of epoxide, ketone, hydroxyl, and carboxylic acid species. Two distinct types of nitrogen atoms with pyridinic and pyrrolic character are identified in reduced graphene oxide. The N K-edge NEXAFS spectra suggest that the nitrogen atoms are stabilized within aromatic heterocycles such as pyrazole rings, which has been further corroborated by comparison to standards. The pyrazole fragments are thought to be stabilized by reaction of diketo groups on the edges of graphene sheets with hydrazine. The incorporation of nitrogen within reduced graphene oxide thus leads to local bonding configurations very distinct from substitutional doping observed for graphene grown by chemical vapor deposition in the presence of NH3.

A novel porous material constructed from linear helical cadmium(II) coordination polymer based on in-situ ligand reaction

A novel helical cadmium(II) coordination polymer cis , cis , trans -{[Cd(HIDC)(H 2 O) 2 ]·1/3H 2 O} n ( 1 ) has been obtained by the solvothermal reaction of hydrated CdCl 2 with 2 H -imidazole-4,5-dicarbonitrile (HIMDN) in the presence of NH 3 ·H 2 O. The packing of the six neighboring polymeric helical chains of the complex leads to a 1-D channel, which is occupied by lattice water molecules. The solid-state luminescence properties of 1 have been investigated at room temperature. A novel helical cadmium(II) coordination polymer cis , cis , trans -{[Cd(HIDC)(H 2 O) 2 ]·1/3H 2 O} n ( 1 ) has been obtained by the hydrothermal reaction of hydrated CdCl 2 with 2 H -imidazole-4,5-dicarbonitrile. The packing of the six neighboring polymeric helical chains of the complex leads to a 1-D channel. The solid-state luminescence properties of 1 have been investigated at room temperature. • A novel helical cadmium(II) coordination polymer was obtained. • The packing of helical chains of the complex leads to a 1-D channel. • In-situ reaction is a promising strategy for new multi-functional materials. • The luminescence properties of 1 have been measured.

Simultaneous removal of NO and SO2 from combustion fuel gases using supported copper oxide catalysts

Nitrogen oxide (NOx) and sulphur dioxide (SO2) emissions produced by the combustion of fuel in stationary sources, such as power stations, industrial heaters or cogeneration plants, cause significant environmental problems. Selective catalytic reduction (SCR) is a well established process for the control of NOx emissions mainly due to its efficiency, selectivity and economics. High removal efficiencies for both NOx and SO2 can be achieved with the use of copper oxide catalysts, as they act as sorbents for the latter - forming copper sulfate - and catalyze the reduction of the former - to N2, in the presence of NH3. An added advantage is that these catalysts are relatively easy to be regenerated under reducing conditions. This study examines the deactivation and regeneration procedures of copper oxide catalysts/sorbents that are supported on Al2O3, SiO2, CeO2-Al2O3, in the presence of SO2 and identifies the appropriate conditions for the simultaneous removal of NO and SO2. The results obtained indicate that copper oxide supported on alumina, ceria-alumina and silica carriers, can be used as effective catalysts for the simultaneous removal of NO and SO2. Furthermore, they can be easily regenerated with a gas mixture of 1 % NH3/Ar at an optimum temperature of 673 K and they retain their initial activity. Thus, the use of regenerative fixed bed catalytic reactor appears as one of the most promising technologies however, further research focusing in new catalytic materials performance is necessary.

A Computational Study of Detoxification of Lewisite Warfare Agents by British Anti-lewisite: Catalytic Effects of Water and Ammonia on Reaction Mechanism and Kinetics

trans-2-Chlorovinyldichloroarsine (lewisite, L agent, Lew-I) acts as a blistering agents. British anti-lewisite (BAL, 2,3-dimercaptopropanol) has long been used as an L-agent antidote. The main reaction channels for the detoxification proceed via breaking of As-Cl bonds and formation of As-S bonds, producing stable, nontoxic ring product [(2-methyl-1,3,2-dithiarsolan-4-yl)methanol]. M06-2X/GENECP calculations have been carried out to establish the enhanced rate of detoxification mechanism in the presence of NH3 and H2O catalysts in both gas and solvent phases, which has been modeled by use of the polarized continuum model (PCM). In addition, natural bond orbital (NBO) and atoms in molecules (AIM) analysis have been performed to characterize the intermolecular hydrogen bonding in the transition states. Transition-state theory (TST) calculation establishes that the rates of NH3-catalyzed (2.88 × 10(-11) s(-1)) and H2O-catalyzed (2.42 × 10(-11) s(-1)) reactions are reasonably faster than the uncatalyzed detoxification (5.44 × 10(-13) s(-1)). The results obtained by these techniques give new insight into the mechanism of the detoxification process, identification and thermodynamic characterization of the relevant stationary species, the proposal of alternative paths on modeled potential energy surfaces for uncatalyzed reaction, and the rationalization of the mechanistic role played by catalysts and solvents.

HUVEC biocompatibility and platelet activation of segmented polyurethanes prepared with either glutathione or its amino acids as chain extenders

Novel biodegradable segmented polyurethanes (SPUs) were synthesized with polycaprolactone diol, 4,4′-methylen bis (cyclohexyl isocyanate) (HMDI), and either L-glutathione or its constituent amino acids (L-glutamic acid, L-cysteine and glycine) as chain extenders. Fourier transform infrared spectroscopy analysis revealed the feasibility of obtaining polyurethanes through the presence of NH (Amide II), C–N, C–O, and C=O bands and the absence of NCO band. Differential scanning calorimetry and X-ray diffraction revealed that a semicrystalline polymer (T m = 42–52 °C; 2θ = 21.3° and 23°) was obtained in all cases, while dynamic mechanical analysis (DMA) revealed an amorphous phase (T g = −30 to −36 oC). These properties, in addition to their high molecular weight, led to high moduli and higher extensibilities when glycine and glutamic acid were used as chain extenders. Clotting times (Lee–White test) and activated partial thromboplastin time determined on these polyurethanes were longer than with glass. In addition, all synthesized SPU exhibited platelet activation indexes below the collagen type I positive control. Human umbilical vein endothelial cells viability was higher in SPUs containing either glycine or cysteine. The obtained results indicate that SPUs that use cysteine as chain extender are promising candidates for cardiovascular applications.

TiO2 nanotube-supported V2O5 catalysts for selective NO reduction by NH3

TiO2 nanotubes (TNT) were prepared by hydrothermal method at 140 °C for 23 h. The V2O5/TNT (VTNT) catalysts were obtained by impregnation in NH4VO3 solution. The VTNTs exhibited much higher denitration efficiency than those supported on the raw TiO2, and satisfactory resistance to water and sulfur. Results from BET, TEM, XRD, NH3-TPD and EPR verified that V2O5 was dispersed well on TNT, thus favoring NH3 adsorption, promoting the transformation from V5+ to V4+, conducing to the formation of oxygen vacancies and superoxide radicals in the presence of NH3 and O2, and then resulting in the high catalytic activity of VTNTs.

Computational and spectroscopic studies of a new Schiff base 3-hydroxy-4-methoxybenzylidene(2-hydroxyphenyl)amine and molecular structure of its corresponding zwitterionic form

Computational and spectroscopic properties of a novel Schiff base compound, 3-hydroxy-4-methoxybenzylidene(2-hydroxyphenyl)amine were studied. The crystal structures of the title compound and its corresponding zwitterionic form were analyzed by X-ray diffraction. The presence of NH, CO and CN stretching vibrations in IR spectrum strongly suggest that the title compound has zwitterionic form in the solid state. Molecular geometry of the title compound in the ground state has been calculated using the density functional method (DFT) at B3LYP 6-31++G(d,p) basis set and was compared with the experimental data. The calculated results of the title compound show that the optimized geometry can well reproduce the crystal structure. The molecule shows absorption bands at 345 and 363nm in EtOH. The shoulder-shaped bands at 415nm can be assigned to n→π* transitions. The absorption band is observed at 285nm in EtOH corresponds to the π→π* transitions.

Sorption Behavior of Nickel and Palladium in the Presence of NH3(aq)/NH4+

ABSTRACTIt is necessary to assess the impact of nitrate salts and their reduction products (e.g. NH3(aq)/NH4+) contained in low-level radioactive waste generated from nuclear reprocessing process for the safety assessment of geological disposal of the waste. In the present study, sorption behavior of Ni and Pd on pumice tuff was investigated in the presence of NH3(aq)/NH4+. Under various NH3(aq)/NH4+ concentration, pH and ionic strength conditions, distribution coefficient (Kd) of Ni and Pd on pumice tuff was determined by a batch experiment. For Ni system, the Kd values showed no significant dependence on initial NH4+ concentration ([NH4+]ini < 1 M) in neutral pH region, which agreed with the prediction from thermodynamic data. For Pd system, the Kd values decreased with an increase of [NH4+]ini, suggesting the formation of stable ammine complexes (Pd(NH3)m2+ (m: 1 – 4)). The obtained Kd values for Ni and Pd were analyzed using a surface complexation model. By taking complexes predicted by thermodynamic data into account, sorption behavior of Ni and Pd in the presence of NH3(aq)/NH4+ were well explained.

Three-dimensional B,N-doped graphene foam as a metal-free catalyst for oxygen reduction reaction

Using a modified chemical vapor deposition (CVD) method, we have prepared a class of new graphene foams (GFs) doped with nitrogen, boron or both. Nitrogen-doped graphene foams (N-GFs) with a nitrogen doping level of 3.1 atom% were prepared by CVD of CH4 in the presence of NH3 while boron-doped graphene foams (B-GFs) with a boron doping level of 2.1 atom% were produced by using toluene and triethyl borate as a carbon and a boron source. On the other hand, graphene foams co-doped with nitrogen (4.5 atom%) and boron (3 atom%) (BN-GFs) were prepared by CVD using melamine diborate as the precursor. In all cases, scanning electron microscope (SEM) images revealed well-defined foam-like microstructures, while electrochemical measurements showed much higher electrocatalytic activities toward oxygen reduction reaction for the doped graphene foams than their undoped counterparts.

Mechanism investigation of the reaction between triphenylphosphine, dialkyl acetylenedicarboxylates and 2-hydroxybenzimidazole: Experimental and theoretical study

In the recent work, NMR study and the stability of the Z- and the E- isomers were undertaken for the two rotational isomers of phosphorus ylides involving 2-hydroxybenzimidazole [namely dimethyl-2-(2-hydroxybenzimidazole-n-yl)-3-(triphenylphosp hanylidene) succinate] by natural population analysis (NPA) and atoms in molecules (AIM) methods. Quantum mechanical calculation was clarified how the ylides exist in solution as a mixture of the two geometrical isomers (Z- and E-) as a minor or major form. In addition, Kinetic studies were performed for the reaction between triphenylphosphine and dialkyl acetylenedicarboxilate in the presence of NH– heterocyclic compound, such as 2-hydroxybenzimidazole. To determine the kinetic parameters of the reaction, it was monitored by UV spectrophotometry. Useful information was obtained from studies of the effect of solvent and concentration of reactants on the rate of reaction. Proposed mechanism was confirmed according to the obtained results and steady state approximation and first step (k2) and third step of reaction were recognized as a rate determining step and fast step, respectively on the basis of experimental data.