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Sample records for nh3 temperature-programmed desorption

  1. A dynamic calibration technique for temperature programmed desorption spectroscopy.

    PubMed

    Hurst, K E; Heben, M J; Blackburn, J L; Gennett, T; Dillon, A C; Parilla, P A

    2013-02-01

    A novel, rapid and accurate calibration procedure as a means for quantitative gas desorption measurement by temperature programmed desorption (TPD) spectroscopy is presented. Quantitative measurement beyond the linear regime of the instrument is achieved by associating an instantaneous calibrated molar flow rate of gas to the detector response. This technique is based on fundamental methods, and is independently verified by comparison to the hydrogen desorption capacity of a known standard metal hydride with known stoichiometry. The TPD calibration procedure described here may be used for any pure gas, and the accuracy is demonstrated for the specific case of hydrogen. PMID:23464247

  2. Negative ion formation in electron-stimulated desorption of CF2Cl2 coadsorbed with polar NH3 on Ru(0001).

    PubMed

    Solovev, S; Kusmierek, D O; Madey, T E

    2004-01-01

    Photon-induced dissociation of CF2Cl2 (freon-12) in the stratosphere contributes substantially to atmospheric ozone depletion. We report recent results on dissociation and negative ion formation in electron-stimulated desorption (ESD) of CF2Cl2 on Ru(0001), when CF2Cl2 is coadsorbed with a polar molecule (NH3), for electron energies ranging from 50 to 300 eV. Two different time-of-flight methods are used in this investigation: (a) an ESD ion angular distribution detector with wide collection angle and (b) a quadrupole mass spectrometer with narrow collection angle and high mass resolution. Many negative ESD fragments are seen (F-, Cl-, FCl-, CF-, F2-, and Cl2-), whose intensities depend on the surface preparation. Using both detectors we observe a giant enhancement of Cl- and F- yields for ESD of CF2Cl2 coadsorbed with approximately 1 ML of NH3; this enhancement (>10(3) for Cl-) is specific to certain ions, and is attributed to an increased probability of dissociative electron attachment due to "trapped" low-energy secondary electrons, i.e., precursor states of the solvated electron in NH3. In further studies, the influence of polar NH3 spacer layers (1-10 ML) on ESD of top-layer CF2Cl2 is determined, and compared with thick films of condensed CF2Cl2. The magnitudes and energy dependences of the Cl- yields are different in these cases, due to several contributing factors. PMID:15267934

  3. Temperature programmed desorption studies of water interactions with Apollo lunar samples 12001 and 72501

    NASA Astrophysics Data System (ADS)

    Poston, Michael J.; Grieves, Gregory A.; Aleksandrov, Alexandr B.; Hibbitts, Charles A.; Dyar, M. Darby; Orlando, Thomas M.

    2015-07-01

    The desorption activation energies for water molecules chemisorbed on Apollo lunar samples 72501 (highlands soil) and 12001 (mare soil) were determined by temperature programmed desorption experiments in ultra-high vacuum. A significant difference in both the energies and abundance of chemisorption sites was observed, with 72501 retaining up to 40 times more water (by mass) and with much stronger adsorption interactions, possibly approaching 1.5 eV. The dramatic difference between the samples may be due to differences in mineralogy and surface exposure age. The distribution function of water desorption activation energies for sample 72501 was used as an initial condition to simulate water persistence through a temperature profile matching the lunar day.

  4. Design and construction of a semiautomatic temperature programmed desorption apparatus for ultrahigh vacuum

    NASA Astrophysics Data System (ADS)

    Kondratyuk, Petro; Yates, John T.

    2005-01-01

    A computer-controlled system that allows acquisition of large volumes of temperature programmed desorption data under ultrahigh vacuum conditions has been designed and tested. The vacuum part of the system consists of a sample mounted on a rotation-translation manipulator, a shielded quadrupole mass spectrometer for the desorption flux measurement, and a collimated molecular beam doser for adsorbate delivery. The experiment involves a series of tasks: (1) dosing of the adsorbate onto the surface; (2) calibration of the mass spectrometer gain; (3) translating the dosed sample to the mass spectrometer position; (4) linearly ramping the temperature of the sample to acquire the desorption spectrum; and (5) cooling the sample. In the system described here, these tasks are accomplished automatically. As a result, the time needed for the experiment and the potential for operator errors are substantially reduced. The performance of the system is demonstrated for CCl4 adsorbed on gold-supported single wall carbon nanotubes.

  5. Monte Carlo simulations of temperature-programmed and isothermal desorption from single-crystal surfaces

    SciTech Connect

    Lombardo, S.J. . Dept. of Chemical Engineering Lawrence Berkeley Lab., CA )

    1990-08-01

    The kinetics of temperature-programmed and isothermal desorption have been simulated with a Monte Carlo model. Included in the model are the elementary steps of adsorption, surface diffusion, and desorption. Interactions between adsorbates and the metal as well as interactions between the adsorbates are taken into account with the Bond-Order-Conservation-Morse-Potential method. The shape, number, and location of the TPD peaks predicted by the simulations is shown to be sensitive to the binding energy, coverage, and coordination of the adsorbates. In addition, the occurrence of lateral interactions between adsorbates is seen to strongly effect the distribution of adsorbates is seen to strongly effect the distribution of adsorbates on the surface. Temperature-programmed desorption spectra of a single type of adsorbate have been simulated for the following adsorbate-metal systems: CO on Pd(100); H{sub 2} on Mo(100); and H{sub 2} on Ni(111). The model predictions are in good agreement with experimental observation. TPD spectra have also been simulated for two species coadsorbed on a surface; the model predictions are in qualitative agreement with the experimental results for H{sub 2} coadsorbed with strongly bound atomic species on Mo(100) and Fe(100) surfaces as well as for CO and H{sub 2} coadsorbed on Ni(100) and Rh(100) surfaces. Finally, the desorption kinetics of CO from Pd(100) and Ni(100) in the presence of gas-phase CO have been examined. The effect of pressure is seen to lead to an increase in the rate of desorption relative to the rate observed in the absence of gas-phase CO. This increase arises as a consequence of higher coverages and therefore stronger lateral interactions between the adsorbed CO molecules.

  6. Simulation Analysis of the NH3-H2O Two-Stage Desorption Type Absorption Refrigerator Driven by Low Grade Waste Heat

    NASA Astrophysics Data System (ADS)

    Takei, Toshitaka; Kimijima, Shinji; Saito, Kiyoshi; Kawai, Sunao

    Recently, from a view point of the environmental protection, NH3-H2O absorption refrigerator attracts attention in the field of the refrigeration and the air conditioning. Since NH3-H2O absorption refrigerators can produce below zero degree products, this type of refrigerators have many usages in the refrigeration. This paper describes the two-stage desorption type absorption refrigerator driven by waste heat of co-generation system. There are two absorption cycles which are operated under the condition of the different pressure and the solution concentration in this absorption refrigerator. It becomes essential to clarify the characteristics of this absorption refrigerator since the operating conditions are changed through out the year in the co-generation system. Particularly, in this paper, we investigate the effects of evaporating temperature of ammonia and cooling water temperature for the performance of this absorption refrigerator by simulation analysis. Through out the research, it is shown that COP can be improved when evaporating temperature is higher or cooling water temperature is lower. In addition to this, it is obtained that the necessary temperature of hot water becomes lower in such condition. As a result, the effectiveness of using this absorption refrigerator under the operating condition of which hot watertemperatureis90∼100[°C] and evaporating temperature is -10∼- 20 [°C] is clarified

  7. TEMPERATURE-PROGRAMMED DESORPTION: PRINCIPLES, INSTRUMENT DESIGN, AND DEMONSTRATION WITH NAALH4

    SciTech Connect

    Stowe, A; Ragaiy Zidan, R

    2006-11-07

    This article is a brief introduction to temperature-programmed desorption (TPD), an analytical technique devised to analyze, in this case, materials for their potential as hydrogen storage materials. The principles and requirements of TPD are explained and the different components of a generic TPD apparatus are described. The construction of a modified TPD instrument from commercially available components is reported together with the control and acquisition technique used to create a TPD spectrum. The chemical and instrumental parameters to be considered in a typical TPD experiment and the analytical utility of the technique are demonstrated by the dehydrogenation of titanium-doped NaAlH{sub 4} by means of thermally programmed desorption.

  8. Temperature-programmed desorption studies of the interactions of OD and CO with Pt(111)

    NASA Astrophysics Data System (ADS)

    Weibel, Michael A.; Backstrand, Kyle M.; Curtiss, Thomas J.

    2000-01-01

    Temperature-programmed desorption (TPD) measurements were made to probe the interactions of hydroxyl radicals (OD) with Pt(111). A pure, intense molecular beam of OD was prepared by filtering the effluent from a supersonic corona discharge D2O/He source through an electrostatic hexapole. The hexapole selectively transmitted only OD radicals in the |JΩM>=|{3}/{2} {3}/{2} {3}/{2}> rotational state and eliminated any D2O, oxygen or hydrogen atoms, or other contaminants from the beam. Experiments were carried out by dosing the surface with OD at a surface temperature of TS=275 K. Oxide states formed were characterized by desorption temperatures of TS=700, 735, and 790 K. The 735 K feature is believed to correspond to a near-surface oxide (PtOx) as seen previously in O3/Pt(111) studies. CO titration experiments revealed three CO2 desorption features: dominant features at TS=340 K and TS=440 K, the latter being perhaps due to oxidation via the PtOx. Another set of experiments were carried out by dosing OD at a surface temperature of TS=150 K. Major D2O desorption features were observed at TS=210 K corresponding to the decomposition of an OD-intermediate layer and at TS=170 K corresponding to molecular water desorption. The O2 TPD spectra showed the same three features observed at the higher dosing temperature, however, in substantially different ratios. CO oxidation experiments also revealed new behavior. Five CO2 desorption features were detected: the dominant features near TS≈300 K and at TS≈440 K, a smaller feature at TS=650 K, and two minor features at TS≈185 and 230 K. Others have seen the latter two features previously in O2/CO Pt(111) studies.

  9. Qualitative and quantitative analysis of complex temperature-programmed desorption data by multivariate curve resolution

    NASA Astrophysics Data System (ADS)

    Rodríguez-Reyes, Juan Carlos F.; Teplyakov, Andrew V.; Brown, Steven D.

    2010-10-01

    The substantial amount of information carried in temperature-programmed desorption (TPD) experiments is often difficult to mine due to the occurrence of competing reaction pathways that produce compounds with similar mass spectrometric features. Multivariate curve resolution (MCR) is introduced as a tool capable of overcoming this problem by mathematically detecting spectral variations and correlations between several m/z traces, which is later translated into the extraction of the cracking pattern and the desorption profile for each desorbate. Different from the elegant (though complex) methods currently available to analyze TPD data, MCR analysis is applicable even when no information regarding the specific surface reaction/desorption process or the nature of the desorbing species is available. However, when available, any information can be used as constraints that guide the outcome, increasing the accuracy of the resolution. This approach is especially valuable when the compounds desorbing are different from what would be expected based on a chemical intuition, when the cracking pattern of the model test compound is difficult or impossible to obtain (because it could be unstable or very rare), and when knowing major components desorbing from the surface could in more traditional methods actually bias the quantification of minor components. The enhanced level of understanding of thermal processes achieved through MCR analysis is demonstrated by analyzing three phenomena: i) the cryogenic desorption of vinyltrimethylsilane from silicon, an introductory system where the known multilayer and monolayer components are resolved; ii) acrolein hydrogenation on a bimetallic Pt-Ni-Pt catalyst, where a rapid identification of hydrogenated products as well as other desorbing species is achieved, and iii) the thermal reaction of Ti[N(CH 3) 2] 4 on Si(100), where the products of surface decomposition are identified and an estimation of the surface composition after the thermal reaction is afforded. Since this work constitutes, to the best of our knowledge, the first effort to introduce multivariate analysis to TPD data, the procedures, algorithms and strategies employed are described in full detail.

  10. Temperature programmed desorption characterization of oxidized uranium surfaces: Relation to some gas-uranium reactions

    SciTech Connect

    Danon, A.; Koresh, J.E.; Mintz, M.H.

    1999-08-31

    The chemisorption characteristics and surface composition of oxidation overlayers developing on metals when exposed to oxidizing atmospheres are important in determining the protective ability of these layers against certain gas-phase reactions (e.g., corrosion and hydriding). In the present study, a special setup of supersonic molecular beam-temperature-programmed desorption was utilized to determine the different chemisorbed species present on oxidized uranium surfaces. The main identified species included water (in different binding forms) and hydrogen. The latter hydrogen originates from the water-uranium oxidation reaction, which produces uranium dioxide and two types of hydrogen: a near surface hydride and a surface-chemisorbed form that desorbs at a lower temperature than that of the hydride. Assignments of the different water desorption peaks to different binding sites were proposed. In general, four water desorption features were identified (labeled W{sub 0}, W{sub 1}, W{sub 2}, and W{sub 3}, respectively, in the order of increasing desorption temperatures). These features correspond to a reversibly chemisorbed molecular form (W{sub 0}), a more tightly bound water (chemisorbed on different type of oxide sites) or hydroxyl clusters (W{sub 1}), and strongly bounded (possibly isolated) hydroxyl groups (W{sub 2}). The highest temperature peak (W{sub 3}) is related to the formation of complex water-carbo-oxy compounds and is present only on oxidation overlayers, which contain proper chemisorbed carbo-oxy species. The relation of the water and hydrogen thermal release behavior to some problems addressed to certain effects observed in hydrogen-uranium and water-uranium reactions is discussed. For the latter, a microscopic mechanism is proposed.

  11. H(2)O Outgassing Properties of Fumed and Precipitated Silica Particles by Temperature-Programmed Desorption.

    PubMed

    Dinh; Balooch; LeMay

    2000-10-15

    Temperature-programmed desorption was performed at temperatures up to 850 K on as-received fumed and precipitated silica particles. Physisorbed water molecules on both types of silica had activation energies in the range of 38-61 kJ/mol. However, the activation energies of desorption for chemisorbed water varied from approximately 80 to >247 kJ/mol for fumed silica, Cab-O-Sil-M-7D, and approximately 96 to 155 kJ/mol for precipitated silica, Hi-Sil-233. Our results suggest that physisorbed water can be effectively pumped away at room temperature (or preferably at 320 K) in a matter of hours. Chemisorbed water with high activation energies of desorption (>126 kJ/mol) will not escape silica surfaces in 100 years even at 320 K, while a significant amount of the chemisorbed water with medium activation energies (80-109 kJ/mol) will leave the silica surfaces in that time span. Most of the chemisorbed water with activation energies <126 kJ/mol can be pumped away in a matter of days in a good vacuum environment at 500 K. We had previously measured about 0.1-0.4 wt% of water in silica-reinforced polysiloxane formulations containing approximately 21% Cab-O-Sil-M-7D and approximately 4% Hi-Sil-233. Comparing present results with these formulations, we conclude that the adsorbed H(2)O and the Si-OH bonds on the silica surfaces are the major contributors to water outgassing from these types of silica-filled polymers. Copyright 2000 Academic Press. PMID:11017751

  12. Adsorption and desorption of dibenzothiophene on Ag-titania studied by the complementary temperature-programmed XPS and ESR

    NASA Astrophysics Data System (ADS)

    Samokhvalov, Alexander; Duin, Evert C.; Nair, Sachin; Tatarchuk, Bruce J.

    2011-02-01

    Adsorption, desorption and structure of the surface chemical compounds formed upon interaction of dibenzothiophene (DBT) in solution of n-octane with the sulfur-selective Ag/Titania sorbent for the ultradeep desulfurization of liquid fuels was characterized by the temperature-programmed X-ray photoemission spectroscopy (XPS) and Electron Spin Resonance. Adsorption of DBT proceeds via chemisorption via the oxygen-containing surface groups. Desorption of DBT and thermal regeneration of the “spent” Ag/Titania were studied by the complementary temperature-programmed XPS and ESR from 25 °C to 525 °C, in the high vacuum vs. air. The XPS spectrum of the pure DBT is reported for the first time.

  13. Mechanistic understanding of CoO-catalyzed hydrogen desorption from a LiBH4·NH3-3LiH system.

    PubMed

    Zhang, Yi; Liu, Yongfeng; Zhang, Xin; Li, You; Gao, Mingxia; Pan, Hongge

    2015-08-28

    Addition of a minor quantity of CoO significantly reduces the dehydrogenation temperature, accelerates the dehydrogenation rate and increases the hydrogen purity of the LiBH4·NH3-3LiH system. The LiBH4·NH3-3LiH-0.1CoO sample exhibits optimal dehydrogenation properties because it releases 8.5 wt% of hydrogen below 250 °C, which is approximately 90 °C lower than that of the pristine sample. At 200 °C, approximately 8.0 wt% of hydrogen is released from the LiBH4·NH3-3LiH-0.1CoO sample within 100 min, whereas only 4.1 wt% is released from the pristine sample under identical conditions. The EXAFS analyses reveal that upon heating, CoO is first reduced to metallic Co at 130 °C and then partially combines with B to form a Co-B species. The in situ formed Co and Co-B are finely dispersed in the dehydrogenated intermediates, and they play critical roles as active catalysts in favour of breaking the B-H bonds of the Li-B-N-H species. This effectively decreases the thermodynamic and kinetic barriers of the dehydrogenation reaction of the LiBH4·NH3-3LiH system. PMID:26207564

  14. The dissociation kinetics of NO on Rh(111) as studied by temperature programmed static secondary ion mass spectrometry and desorption

    NASA Astrophysics Data System (ADS)

    Borg, H. J.; Reijerse, J. F. C.-J. M.; van Santen, R. A.; Niemantsverdriet, J. W.

    1994-12-01

    Temperature programmed static secondary ion mass spectrometry (TPSSIMS) and temperature programmed desorption (TPD) have been used to study the kinetics of adsorption, dissociation, and desorption of NO on Rh(111). At 100 K, NO adsorption is molecular and proceeds via mobile precursor state kinetics with a high initial sticking probability. SSIMS indicates the presence of two distinct NO adsorption states, indicative of threefold adsorption at low coverage, and occupation of bridge sites at higher coverages. Three characteristic coverage regimes appear with respect to NO dissociation. At low coverages θNO<0.25 ML, NO dissociates completely at temperatures between 275 and 340 K. If we neglect lateral interactions and assume pure first order dissociation kinetics, we find effective values for the activation barrier and preexponential factor of 40±6 kJ/mol and 106±1 s-1 for the dissociation of 0.15-0.20 ML NO. However, if we assume that a NO molecule needs an ensemble of three to four vacant sites in order to dissociate, the preexponential factor and activation energy are ˜1011 s-1 and 65 kJ/mol, in better agreement with transition state theory expectations. The Nads and Oads dissociation products desorb as N2 and O2, respectively, with desorption parameters Edes=118±10 kJ/mol and νdes=1010.1±1.0 s-1 for N2 in the zero coverage limit. At higher coverages, the desorption kinetics of N2 is strongly influenced by the presence of coadsorbed oxygen. In the medium coverage range 0.25<θNO<0.50 ML, part of the NO desorbs molecularly, with an estimated desorption barrier of 113±10 kJ/mol and a preexponential of 1013.5±1.0 s-1. Dissociation of NO becomes progressively inhibited due to site blocking, the onset shifting from 275 K at 0.25 ML to 400 K, coinciding with the NO desorption temperature, at a coverage of 0.50 ML. The accumulation of nitrogen and oxygen atoms on the highly covered surface causes a destabilization of the nitrogen atoms, which results in an additional low-temperature desorption state for N2. For high initial NO coverages above 0.50 ML, the dissociation is completely self-inhibited, indicating that all sites required for dissociation are blocked. The desorption of the more weakly bound—presumably bridged—NO does not generate the sites required for dissociation; these become only available after the desorption of—presumably triply coordinated—NO.

  15. New method for the temperature-programmed desorption (TPD) of ammonia experiment for characterization of zeolite acidity: a review.

    PubMed

    Niwa, Miki; Katada, Naonobu

    2013-10-01

    In this review, a method for the temperature-programmed desorption (TPD) of ammonia experiment for the characterization of zeolite acidity and its improvement by simultaneous IR measurement and DFT calculation are described. First, various methods of ammonia TPD are explained, since the measurements have been conducted under the concepts of kinetics, equilibrium, or diffusion control. It is however emphasized that the ubiquitous TPD experiment is governed by the equilibrium between ammonia molecules in the gas phase and on the surface. Therefore, a method to measure quantitatively the strength of the acid site (?H upon ammonia desorption) under equilibrium-controlled conditions is elucidated. Then, a quantitative relationship between ?H and H0 function is proposed, based on which the acid strength ?H can be converted into the H0 function. The identification of the desorption peaks and the quantitative measurement of the number of acid sites are then explained. In order to overcome a serious disadvantage of the method (i.e., no information is provided about the structure of acid sites), the simultaneous measurement of IR spectroscopy with ammonia TPD, named IRMS-TPD (infrared spectroscopy/mass spectrometry-temperature-programmed desorption), is proposed. Based on this improved measurement, Brnsted and Lewis acid sites were differentiated and the distribution of Brnsted OH was revealed. The acidity characterized by IRMS-TPD was further supported by the theoretical DFT calculation. Thus, the advanced study of zeolite acidity at the molecular level was made possible. Advantages and disadvantages of the ammonia TPD experiment are discussed, and understanding of the catalytic cracking activity based on the derived acidic profile is explained. PMID:23868494

  16. Study of temperature-programmed desorption of tert-butylamine to measure the surface acidity of solid catalysts

    SciTech Connect

    Aguayo, A.T.; Arandes, J.M.; Olazar, M.; Bilbao, J. )

    1991-08-01

    In this paper, the technique of temperature-programmed desorption of tert-butylamine is described to measure the surface acidity of solid catalysts. The use of this base has advantages over the use of ammonia, pyridine, and n-butylamine. The desorption measurement is carried out by two methods, gas chromatography and thermogravimetry, and the advised conditions are described for both methods. Catalysts of SiO{sub 2}/Al{sub 2}O{sub 3}, bifunctionals of Ni-SiO{sub 2}/Al{sub 2}O{sub 3}, and a commercial cracking zeolite have been studied. A comparison of the desorption results with those of the other acidity measurement techniques (such as titration with n-butylamine in the liquid phase and kinetic measurement of isomerization of n-butenes as the test reaction) allows the acidity measured with tert-butylamine desorption to be classified as strong, corresponding to the active sites in most of the reactions among the hydrocarbon compounds catalyzed by acids.

  17. Improving of understanding of beta-hexachlorocyclohexane (HCH) adsorption on activated carbons by temperature-programmed desorption studies.

    PubMed

    Passé-Coutrin, Nady; Maisonneuve, Laetitia; Durimel, Axelle; Dentzer, Joseph; Gadiou, Roger; Gaspard, Sarra

    2016-01-01

    In order to understand the interactions between beta-hexachlorocyclohexane (HCH) and chemical groups at activated carbon (AC) surface, the solid samples were hydrogenated aiming to decrease the amounts of oxygenated groups. Two AC samples designated by BagH2O and BagP1.5 were prepared by water vapor activation and phosphoric acid activation, respectively, of sugarcane bagasse used as an AC precursor. A more simple molecule 1,2,3-trichloropropane (TCP) is used as a model of chlorinated compound. The AC were characterized by infrared, X-ray photoelectron spectroscopy (XPS), Raman resonance spectroscopies, as well as temperature-programmed desorption coupled with mass spectrometry (TPD-MS). BagP1.5 and BagH2O AC surface contained oxygenated groups. Upon hydrogenation, a decrease of most of these group amxounts was observed for both samples, while hydroxyl groups increased. On the basis of temperature-programmed desorption data obtained for AC samples contaminated with TCP or HCH, it was possible to determine the type of hydrogen bond formed between each AC and HCH. PMID:26018287

  18. Temperature-programmed desorption study of NO reactions on rutile TiO2(110)-1×1

    DOE PAGESBeta

    Kim, Boseong; Dohnalek, Zdenek; Szanyi, Janos; Kay, Bruce D.; Kim, Yu Kwon

    2016-02-24

    In this study, systematic temperature-programmed desorption (TPD) studies of NO adsorption and reactions on rutile TiO2(110)-1 × 1 surface reveal several distinct reaction channels in a temperature range of 50–500 K. NO readily reacts on TiO2(110) to form N2O, which desorbs between 50 and 200 K (LT N2O channels), which leaves the TiO2 surface populated with adsorbed oxygen atoms (Oa) as a by-product of N2O formation. In addition, we observe simultaneous desorption peaks of NO and N2O at 270 K (HT1 N2O) and 400 K (HT2 N2O), respectively, both of which are attributed to reaction-limited processes. No N-derived reaction productmore » desorbs from TiO2(110) surface above 500 K or higher, while the surface may be populated with Oa's and oxidized products such as NO2 and NO3. The adsorbate-free TiO2 surface with oxygen vacancies can be regenerated by prolonged annealing at 850 K or higher. Detailed analysis of the three N2O desorption yields reveals that the surface species for the HT channels are likely to be various forms of NO dimers.« less

  19. Temperature Programmed Desorption of Quench-condensed Krypton and Acetone in Air; Selective Concentration of Ultra-trace Gas Components.

    PubMed

    Suzuki, Taku T; Sakaguchi, Isao

    2016-01-01

    Selective concentration of ultra-trace components in air-like gases has an important application in analyzing volatile organic compounds in the gas. In the present study, we examined quench-condensation of the sample gas on a ZnO substrate below 50 K followed by temperature programmed desorption (TPD) (low temperature TPD) as a selective gas concentration technique. We studied two specific gases in the normal air; krypton as an inert gas and acetone as a reactive gas. We evaluated the relationship between the operating condition of low temperature TPD and the lowest detection limit. In the case of krypton, we observed the selective concentration by exposing at 6 K followed by thermal desorption at about 60 K. On the other hand, no selectivity appeared for acetone although trace acetone was successfully concentrated. This is likely due to the solvent effect by a major component in the air, which is suggested to be water. We suggest that pre-condensation to remove the water component may improve the selectivity in the trace acetone analysis by low temperature TPD. PMID:27063719

  20. The effect of oxygen vacancies on the binding interactions of NH3 with rutile TiO2(110) -1×1

    SciTech Connect

    Kim, Boseong; Li, Zhenjun; Kay, Bruce D.; Dohnalek, Zdenek; Kim, Yu Kwon

    2012-11-21

    A series of NH3 temperature-programmed desorption (TPD) spectra was taken after the NH3 dose at 70 K on rutile TiO2(110)-1×1 surfaces with the oxygen vacancy (VO) concentrations of ~0% (p-TiO2) and 5% (r-TiO2), respectively, to study the effect of VO’s on the desorption energy of NH3 as a function of the coverage, θ. Our results show that at zero coverage limit, the desorption energy of NH3 on r-TiO2 is 115 kJ/mol, which is 10 kJ/mol less than that on p-TiO2. The desorption energy from the Ti4+ sites decreases with increasing θ due to the repulsive NH3 - NH3 interactions and approaches ~ 55 kJ/mol upon the saturation of Ti4+ sites (θ = 1 monolayer, ML) on both p- and r-TiO2. The absolute saturation coverage is determined to be about 10% smaller on r-TiO2 than that on p-TiO2. Further, the trailing edges of the NH3 TPD spectra on the hydroxylated TiO2(110) (h-TiO2) appear to be the same as that on r-TiO2 while those on oxidized TiO2(110) (o-TiO2) shift to higher temperatures. We present the detailed analysis of the results and reconcile the observed differences based on the repulsive adsorbate-adsorbate interactions between neighboring NH3 molecules and the surface charge associated with the presence of VO’s. Besides NH3, no other reaction products are observed in the TPD spectra.

  1. Dosimeter-Type NOx Sensing Properties of KMnO4 and Its Electrical Conductivity during Temperature Programmed Desorption

    PubMed Central

    Groβ, Andrea; Kremling, Michael; Marr, Isabella; Kubinski, David J.; Visser, Jacobus H.; Tuller, Harry L.; Moos, Ralf

    2013-01-01

    An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed. In addition to its application as a low level NOx dosimeter, KMnO4 shows potential as a precious metal free lean NOx trap material (LNT) for NOx storage catalysts (NSC) enabling electrical in-situ diagnostics. With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer. The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres. Further insight into the NOx sorption-dependent conductivity of the KMnO4-based material is obtained by the novel eTPD method that combines electrical characterization with classical temperature programmed desorption (TPD). The NOx loading amount increases proportionally to the NOx exposure time at sorption temperature. The cumulated NOx exposure, as well as the corresponding NOx loading state, can be detected linearly by electrical means in two modes: (1) time-continuously during the sorption interval including NOx concentration information from the signal derivative or (2) during the short-term thermal NOx release. PMID:23549366

  2. Dosimeter-type NOx sensing properties of KMnO4 and its electrical conductivity during temperature programmed desorption.

    PubMed

    Groß, Andrea; Kremling, Michael; Marr, Isabella; Kubinski, David J; Visser, Jacobus H; Tuller, Harry L; Moos, Ralf

    2013-01-01

    An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed. In addition to its application as a low level NOx dosimeter, KMnO4 shows potential as a precious metal free lean NOx trap material (LNT) for NOx storage catalysts (NSC) enabling electrical in-situ diagnostics. With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer. The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres. Further insight into the NOx sorption-dependent conductivity of the KMnO4-based material is obtained by the novel eTPD method that combines electrical characterization with classical temperature programmed desorption (TPD). The NOx loading amount increases proportionally to the NOx exposure time at sorption temperature. The cumulated NOx exposure, as well as the corresponding NOx loading state, can be detected linearly by electrical means in two modes: (1) time-continuously during the sorption interval including NOx concentration information from the signal derivative or (2) during the short-term thermal NOx release. PMID:23549366

  3. Temperature-programmed desorption study of the selective oxidation of alcohols on silica-supported vanadium oxide.

    PubMed

    Feng, T; Vohs, J M

    2005-02-17

    The partial oxidation of methanol and ethanol on silica-supported vanadium oxide catalysts was studied using temperature-programmed desorption (TPD), Raman spectroscopy, and diffuse reflectance infrared spectroscopy (DRIFTS). Methanol TPD results for V2O5/SiO2 samples as a function of vanadia loading in conjunction with X-ray diffraction data and Raman spectra indicated that dispersed vanadia on silica agglomerates into vanadia crystallites during a CH3OH TPD experiment. For ethanol-dosed samples, agglomeration of the dispersed vanadia was less severe, and it was possible to measure the activation energy for the dehydrogenation of adsorbed ethoxides to produce CH3CHO. Assuming a preexponential factor of 10(13) s(-1), the activation energy for this reaction was estimated to be 132 kJ/mol. The results of this study further demonstrate that there is a relatively weak interaction between vanadia and silica and suggest that adsorbed methoxide species help facilitate agglomeration of dispersed vanadia. PMID:16851203

  4. UV-Raman spectroscopy, X-ray photoelectron spectroscopy, and temperature programmed desorption studies of model and bulk heterogeneous catalysts

    SciTech Connect

    Tewell, Craig R.

    2002-08-19

    X-ray photoelectron spectroscopy (XPS) and Temperature Programmed Desorption (TPD) have been used to investigate the surface structure of model heterogeneous catalysts in ultra-high vacuum (UHV). UV-Raman spectroscopy has been used to probe the structure of bulk model catalysts in ambient and reaction conditions. The structural information obtained through UV-Raman spectroscopy has been correlated with both the UHV surface analysis and reaction results. The present day propylene and ethylene polymerization catalysts (Ziegler-Natta catalysts) are prepared by deposition of TiCl{sub 4} and a Al(Et){sub 3} co-catalyst on a microporous Mg-ethoxide support that is prepared from MgCl{sub 2} and ethanol. A model thin film catalyst is prepared by depositing metallic Mg on a Au foil in a UHV chamber in a background of TiCl{sub 4} in the gas phase. XPS results indicate that the Mg is completely oxidized to MgCl{sub 2} by TiCl{sub 4} resulting in a thin film of MgCl{sub 2}/TiCl{sub x}, where x = 2, 3, and 4. To prepare an active catalyst, the thin film of MgCl{sub 2}/TiCl{sub x} on Au foil is enclosed in a high pressure cell contained within the UHV chamber and exposed to {approx}1 Torr of Al(Et){sub 3}.

  5. Optimizing the crystallinity and acidity of H-SAPO-34 by fluoride for synthesizing Cu/SAPO-34 NH3-SCR catalyst.

    PubMed

    Ma, Jing; Si, Zhichun; Wu, Xiaodong; Weng, Duan; Ma, Yue

    2016-03-01

    A series of H-SAPO-34 zeolites were synthesized by a hydrothermal method in fluoride media. The as-synthesized H-SAPO-34 zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 physisorption, temperature-programmed desorption of NH3 (NH3-TPD) and nuclear magnetic resonance (NMR) measurements. The results showed that a certain concentration of F(-) anions promoted the nucleation and crystallization of H-SAPO-34. The H-SAPO-34 synthesized in the fluoride media showed high crystallinity, uniform particle size distribution, large specific surface area and pore volume, and enhanced acidity. Therefore, Cu/SAPO-34 based on the fluoride-assisted zeolite showed a broadened temperature window for the selective catalytic reduction of NO by NH3 (NH3-SCR) reaction due to the enhanced acidity of the zeolite and the improved dispersion of copper species. PMID:26969071

  6. Adsorption and decomposition of formic acid on MgO(001) surface as investigated by temperature programmed desorption and sum-frequency generation spectroscopy: Recurrence induced defect sites

    NASA Astrophysics Data System (ADS)

    Yamamoto, Hiroyoshi; Watanabe, Nobuyuki; Wada, Akihide; Domen, Kazunari; Hirose, Chiaki

    1997-03-01

    The change of the MgO(001) surface during the adsorption and thermal desorption of formic acid was investigated by temperature programmed desorption (TPD) and infrared-visible sum-frequency generation SFG spectroscopy. The TPD results revealed that the feature of desorption signals changed as the adsorption/thermal desorption process was repeated, despite no significant change of the low energy electron diffraction (LEED) pattern. The surface formate, produced by dissociative adsorption of formic acid, decomposed at 560 K and 700 K, giving H2O+CO and H2+CO2 as primary and minor products, respectively, but the broad desorption peak of H2O started to appear at 300 K. The 560 K peak appeared from an early stage, while the 700 K peak gained intensity as the experiment was repeated and the density of defects increased. The adsorption site for the 700 K peak was ascribed to the catalytic reaction of magnesia powder. The SFG spectra gave three resonance peaks of CH stretching bands at 2850 cm-1, 2870 cm-1, and 2920 cm-1 with a different dependence on the dose time, history of surface, and polarization of incident visible beam. The former two bands were assigned to the formates with bridged configuration, and the third band to the formate with unidentate configuration. The polarization dependence suggested that the CH bonds of bridged formates stood perpendicular to the surface, and that of the unidentate formate tilted approximately 30° from the surface normal. A vibration nonresonant background signal was present on the SFG signal, showing characteristic dependence on the polarization of incident light beams, as well as the coverage and history of the surface, and was interpreted as originating from the defect sites on the surface.

  7. Thermal transformation of bioactive caffeic acid on fumed silica seen by UV-Vis spectroscopy, thermogravimetric analysis, temperature programmed desorption mass spectrometry and quantum chemical methods.

    PubMed

    Kulik, Tetiana V; Lipkovska, Natalia O; Barvinchenko, Valentyna M; Palyanytsya, Borys B; Kazakova, Olga A; Dudik, Olesia O; Menyhárd, Alfréd; László, Krisztina

    2016-05-15

    Thermochemical studies of hydroxycinnamic acid derivatives and their surface complexes are important for the pharmaceutical industry, medicine and for the development of technologies of heterogeneous biomass pyrolysis. In this study, structural and thermal transformations of caffeic acid complexes on silica surfaces were studied by UV-Vis spectroscopy, thermogravimetric analysis, temperature programmed desorption mass spectrometry (TPD MS) and quantum chemical methods. Two types of caffeic acid surface complexes are found to form through phenolic or carboxyl groups. The kinetic parameters of the chemical reactions of caffeic acid on silica surface are calculated. The mechanisms of thermal transformations of the caffeic chemisorbed surface complexes are proposed. Thermal decomposition of caffeic acid complex chemisorbed through grafted ester group proceeds via three parallel reactions, producing ketene, vinyl and acetylene derivatives of 1,2-dihydroxybenzene. Immobilization of phenolic acids on the silica surface improves greatly their thermal stability. PMID:26939077

  8. Study of the adsorption reactions of thiophene on Cu(I)/HY-Al2O3 by Fourier transform infrared and temperature-programmed desorption: adsorption, desorption, and sorbent regeneration mechanisms.

    PubMed

    Tang, Xiao-Lin; Shi, Li

    2011-10-01

    This work mainly involved the investigation of the adsorption of thiophene on Cu(I)-supported HY-Al(2)O(3). It demonstrated a high sulfur capacity of 10 mg sulfur/g sorbent when the HY/Al(2)O(3) mass ratio was 3, loaded with 12% copper, calcined at 550 °C, and tested at ambient temperature. In situ Fourier transform infrared (FTIR) and temperature-programmed desorption (TPD) results indicated that the adsorption mechanisms on Cu(I)/HY-Al(2)O(3) primarily were π-complexation and sulfur-adsorbent (S-M; σ) bonds. Pyridine-FTIR showed the total weak Lewis acid contribution to the Cu(I)/HY-Al(2)O(3) adsorption desulfurization performance. PMID:21870798

  9. Regeneration of field-spent activated carbon catalysts for low-temperature selective catalytic reduction of NOx with NH3

    SciTech Connect

    Jeon, Jong Ki; Kim, Hyeonjoo; Park, Young-Kwon; Peden, Charles HF; Kim, Do Heui

    2011-10-15

    In the process of producing liquid crystal displays (LCD), the emitted NOx is removed over an activated carbon catalyst by using selective catalytic reduction (SCR) with NH3 at low temperature. However, the catalyst rapidly deactivates primarily due to the deposition of boron discharged from the process onto the catalyst. Therefore, this study is aimed at developing an optimal regeneration process to remove boron from field-spent carbon catalysts. The spent carbon catalysts were regenerated by washing with a surfactant followed by drying and calcination. The physicochemical properties before and after the regeneration were investigated by using elemental analysis, TG/DTG (thermogravimetric/differential thermogravimetric) analysis, N2 adsorption-desorption and NH3 TPD (temperature programmed desorption). Spent carbon catalysts demonstrated a drastic decrease in DeNOx activity mainly due to heavy deposition of boron. Boron was accumulated to depths of about 50 {mu}m inside the granule surface of the activated carbons, as evidenced by cross-sectional SEM-EDX analysis. However, catalyst activity and surface area were significantly recovered by removing boron in the regeneration process, and the highest NOx conversions were obtained after washing with a non-ionic surfactant in H2O at 70 C, followed by treatment with N2 at 550 C.

  10. Effects of Alkali and Alkaline Earth Cocations on the Activity and Hydrothermal Stability of Cu/SSZ-13 NH3-SCR Catalysts

    SciTech Connect

    Gao, Feng; Wang, Yilin; Washton, Nancy M.; Kollar, Marton; Szanyi, Janos; Peden, Charles HF

    2015-10-13

    Using a three-step aqueous solution ion-exchange method, cocation modified Cu/SSZ-13 SCR catalysts were synthesized. These catalysts, in both fresh and hydrothermally aged forms, were characterized with several methods including temperature-programmed reduction by H2 (H2-TPR), temperature-programmed desorption of NH3 (NH3-TPD), and 27Al solid-state nuclear magnetic resonance (NMR) and diffuse reflectance Infrared Fourier Transform (DRIFT) spectroscopies. Their catalytic performance was probed using steady-state standard NH3-SCR. Characterization results indicate that cocations weaken interactions between Cu-ions and the CHA framework making them more readily reducible. By removing a portion of Brønsted acid sites, cocations also help to mitigate hydrolysis of the zeolite catalysts during hydrothermal aging as evidenced from 27Al NMR. Reaction tests show that certain cocations, especially Li+ and Na+, promote low-temperature SCR rates while others show much less pronounced effects. In terms of applications, our results indicate that introducing cocations can be a viable strategy to improve both low- and high-temperature performance of Cu/SSZ-13 SCR catalysts.

  11. [Poisoning effect of Ca depositing over Mn-Ce/TiO2 catalyst for low-temperature selective catalytic reduction of NO by NH3].

    PubMed

    Zhou, Ai-Yi; Mao, Hua-Feng; Sheng, Zhong-Yi; Tan, Yue; Yang, Liu

    2014-12-01

    Calcium carbonate (CaCO3), calcium sulfate (CaSO4), and calcium chloride (CaCl2) were chosen as the precursors to prepare the Ca salts deposited Mn-Ce/TiO2 catalysts through an impregnation method. The influence of Ca on the performance of the Mn-Ce/TiO2 catalyst for low-temperature selective catalytic reduction of NO by NH3 was investigated. Experimental results showed that Ca salts had negative effects on the activity of Mn-Ce/TiO2 and the precursors of Ca salts also affected the catalytic activity. The precursor CaCl2 had a greater impact on the catalytic activity, while CaCO3 had minimal effect. The samples were characterized by Brunner-Emmet-Teller measurements (BET), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and NH3temperature programmed desorption (NH3 -TPD). The characterization results indicated that the significant changes in physical and chemical properties of Mn-Ce/TiO2 were observed after Ca was deposited on the catalysts. The significant decreases in surface areas and NH,3adsorption amounts were observed after Ca was deposited on the catalysts, which could be considered as the main reasons for the deactivation of Ca deposited Mn-Ce/TiO,2 PMID:25826949

  12. Temperature-programmed decomposition desorption of mercury species over activated carbon sorbents for mercury removal from coal-derived fuel gas

    SciTech Connect

    M. Azhar Uddin; Masaki Ozaki; Eiji Sasaoka; Shengji Wu

    2009-09-15

    The mercury (Hg{sup 0}) removal process for coal-derived fuel gas in the integrated gasification combined cycle (IGCC) process will be one of the important issues for the development of a clean and highly efficient coal power generation system. Recently, iron-based sorbents, such as iron oxide (Fe{sub 2}O{sub 3}), supported iron oxides on TiO{sub 2}, and iron sulfides, were proposed as active mercury sorbents. The H{sub 2}S is one of the main impurity compounds in coal-derived fuel gas; therefore, H{sub 2}S injection is not necessary in this system. HCl is also another impurity in coal-derived fuel gas. In this study, the contribution of HCl to the mercury removal from coal-derived fuel gas by a commercial activated carbon (AC) was studied using a temperature-programmed decomposition desorption (TPDD) technique. The TPDD technique was applied to understand the decomposition characteristics of the mercury species on the sorbents. The Hg{sup 0}-removal experiments were carried out in a laboratory-scale fixed-bed reactor at 80-300{sup o}C using simulated fuel gas and a commercial AC, and the TPDD experiments were carried out in a U-tube reactor in an inert carrier gas (He or N{sub 2}) after mercury removal. The following results were obtained from this study: (1) HCl contributed to the mercury removal from the coal-derived fuel gas by the AC. (2) The mercury species captured on the AC in the HCl{sup -} and H{sub 2}S-presence system was more stable than that of the H{sub 2}S-presence system. (3) The stability of the mercury surface species formed on the AC in the H{sub 2}S-absence and HCl-presence system was similar to that of mercury chloride (HgClx) species. 25 refs., 12 figs., 1 tab.

  13. Low Temperature Catalyst for NH3 Removal

    NASA Technical Reports Server (NTRS)

    Monje, Oscar; Melendez, Orlando

    2013-01-01

    Air revitalization technologies maintain a safe atmosphere inside spacecraft by the removal of C02, ammonia (NH3), and trace contaminants. NH3 onboard the International Space Station (ISS) is produced by crew metabolism, payloads, or during an accidental release of thermal control refrigerant. Currently, the ISS relies on removing NH3 via humidity condensate and the crew wears hooded respirators during emergencies. A different approach to cabin NH3 removal is to use selective catalytic oxidation (SCO), which builds on thermal catalytic oxidation concepts that could be incorporated into the existing TCCS process equipment architecture on ISS. A low temperature platinum-based catalyst (LTP-Catalyst) developed at KSC was used for converting NH3 to H20 and N2 gas by SCO. The challenge of implementing SCO is to reduce formation of undesirable byproducts like NOx (N20 and NO). Gas mixture analysis was conducted using FTIR spectrometry in the Regenerable VOC Control System (RVCS) Testbed. The RVCS was modified by adding a 66 L semi-sealed chamber, and a custom NH3 generator. The effect of temperature on NH3 removal using the LTP-Catalyst was examined. A suitable temperature was found where NH3 removal did not produce toxic NO, (NO, N02) and N20 formation was reduced.

  14. Bonding of NH3 to Cu

    NASA Technical Reports Server (NTRS)

    Bauschlicher, C. W., Jr.

    1985-01-01

    Bagus et al. (1984) have studied the chemisorption of NH3 at the on-top site of Cu(100), using a cluster model, Cu5(1,4)NH3. On the basis of the value of the NH3 chemisorption energy obtained, it was concluded that NH3 chemisorbs directly above a Cu atom. In order to consider also other sites, Al(111) was substituted for Cu(100). Chemisorption on Al can be quite different from a transition metal, however, and questions arise regarding the suitability of the choice of the Al model. Thus, in this note, NH3 into hollows is considered for Cu(111). Attention is given to the conduction of self-consistent field calculations, problems of site determination, and the consideration of electrostatic interaction.

  15. TES/Aura L3 Ammonia (NH3) Daily (TL3NH3D)

    Atmospheric Science Data Center

    2015-08-28

    TES/Aura L3 Ammonia (NH3) Daily (TL3NH3D) News:  TES News ... Level:  L3 Instrument:  TES/Aura L3 Ammonia Spatial Coverage:  5.3 x 8.5 km Spatial ... Data: TES Order Tool Parameters:  Ammonia Order Data:  Reverb:   Order Data ...

  16. TES/Aura L2 Ammonia (NH3) Nadir (TL2NH3N)

    Atmospheric Science Data Center

    2015-01-30

    TES/Aura L2 Ammonia (NH3) Nadir (TL2NH3N) News:  TES News ... Level:  L2 Instrument:  TES/Aura L2 Ammonia Spatial Coverage:  5.3 x 8.5 km nadir ... Data: TES Order Tool Parameters:  Ammonia Order Data:  Reverb:   Order Data ...

  17. TES/Aura L2 Ammonia (NH3) Nadir (TL2NH3NS)

    Atmospheric Science Data Center

    2015-01-30

    TES/Aura L2 Ammonia (NH3) Nadir (TL2NH3NS) News:  TES News ... Level:  L2 Platform:  TES/Aura L2 Ammonia Spatial Coverage:  5.3 x 8.5 km nadir ... Data: TES Order Tool Parameters:  Ammonia Order Data:  Reverb:   Order Data ...

  18. Diode laser saturation spectroscopy of NH3

    NASA Technical Reports Server (NTRS)

    Jennings, D. E.

    1978-01-01

    Saturation of molecular transitions using a tuneable diode laser was demonstrated for the first time using a standing-wave cavity configuration with an f/8 beam focussed at the sample. Observed saturation effects in NH3 transitions near 888/cm include sub-Doppler (Lamb-dip) resonances at line center.

  19. A study of the reactions of ethanol on CeO{sub 2} and Pd/CeO{sub 2} by steady state reactions, temperature programmed desorption, and in situ FT-IR

    SciTech Connect

    Yee, A.; Morrison, S.J.; Idriss, H.

    1999-09-10

    The reaction of ethanol on unreduced and H{sub 2}-reduced CeO{sub 2} and 1 wt% Pd/CeO{sub 2} has been investigated by steady state reactions, temperature programmed desorption (TPD), and in situ Fourier transform infrared (FT-IR) spectroscopy. Steady state reactions have shown a zero reaction order dependency for diatomic oxygen at and above 20%, while the addition of Pd to CeO{sub 2} decreases the apparent activation energy of the reaction from 75 kJ/mol on CeO{sub 2} alone to 40 kJ/mol (Pd/CeO{sub 2}). TPD experiments following ethanol adsorption on both CeO{sub 2} and Pd/CeO{sub 2} have shown desorption profiles corresponding to unreacted ethanol and various reaction and decomposition products (acetaldehyde, acetone, CO, CO{sub 2}, and methane). Ethanol conversion to reaction products was increased by the addition of Pd, from 15 to 30% on CeO{sub 2} and H{sub 2}-reduced CeO{sub 2}, to 71 and 63% on Pd/CeO{sub 2} and H{sub 2}-reduced Pd/CeO{sub 2}, respectively.

  20. TES/Aura L2 Ammonia (NH3) Lite Nadir (TL2NH3LN)

    Atmospheric Science Data Center

    2015-08-26

    TES/Aura L2 Ammonia (NH3) Lite Nadir (TL2NH3LN) News:  TES News ... Level:  L2 Instrument:  TES/Aura L2 Ammonia Spatial Coverage:  5.3 km nadir Spatial ... OPeNDAP Access:  OPeNDAP Parameters:  Ammonia Order Data:  Reverb:   Order Data ...

  1. The influence of the potassium promoter on the kinetics and thermodynamics of CO adsorption on a bulk iron catalyst applied in Fischer-Tropsch synthesis: a quantitative adsorption calorimetry, temperature-programmed desorption, and surface hydrogenation study.

    PubMed

    Graf, Barbara; Muhler, Martin

    2011-03-01

    The adsorption of carbon monoxide on an either unpromoted or potassium-promoted bulk iron catalyst was investigated at 303 K and 613 K by means of pulse chemisorption, adsorption calorimetry, temperature-programmed desorption and temperature-programmed surface reaction in hydrogen. CO was found to adsorb mainly molecularly in the absence of H(2) at 303 K, whereas the presence of H(2) induced CO dissociation at higher temperatures leading to the formation of CH(4) and H(2)O. The hydrogenation of atomic oxygen chemisorbed on metallic iron was found to occur faster than the hydrogenation of atomically adsorbed carbon. At 613 K CO adsorption occurred only dissociatively followed by recombinative CO(2) formation according to C(ads) + 2O(ads)→ CO(2(g)). The presence of the potassium promoter on the catalyst surface led to an increasing strength of the Fe-C bond both at 303 K and 613 K: the initial differential heat of molecular CO adsorption on the pure iron catalyst at 303 K amounted to 102 kJ mol(-1), whereas it increased to 110 kJ mol(-1) on the potassium-promoted sample, and the initial differential heat of dissociative CO adsorption on the unpromoted iron catalyst at 613 K amounted to 165 kJ mol(-1), which increased to 225 kJ mol(-1) in the presence of potassium. The calorimetric CO adsorption experiments also reveal a change of the energetic distribution of the CO adsorption sites present on the catalyst surface induced by the potassium promoter, which was found to block a fraction of the CO adsorption sites. PMID:21170422

  2. A SCR Model Calibration Approach with Spatially Resolved Measurements and NH3 Storage Distributions

    DOE PAGESBeta

    Song, Xiaobo; Parker, Gordon G.; Johnson, John H.; Naber, Jeffrey D.; Pihl, Josh A.

    2014-11-27

    The selective catalytic reduction (SCR) is a technology used for reducing NO x emissions in the heavy-duty diesel (HDD) engine exhaust. In this study, the spatially resolved capillary inlet infrared spectroscopy (Spaci-IR) technique was used to study the gas concentration and NH3 storage distributions in a SCR catalyst, and to provide data for developing a SCR model to analyze the axial gaseous concentration and axial distributions of NH3 storage. A two-site SCR model is described for simulating the reaction mechanisms. The model equations and a calculation method was developed using the Spaci-IR measurements to determine the NH3 storage capacity andmore » the relationships between certain kinetic parameters of the model. Moreover, a calibration approach was then applied for tuning the kinetic parameters using the spatial gaseous measurements and calculated NH3 storage as a function of axial position instead of inlet and outlet gaseous concentrations of NO, NO2, and NH3. The equations and the approach for determining the NH3 storage capacity of the catalyst and a method of dividing the NH3 storage capacity between the two storage sites are presented. It was determined that the kinetic parameters of the adsorption and desorption reactions have to follow certain relationships for the model to simulate the experimental data. Finally, the modeling results served as a basis for developing full model calibrations to SCR lab reactor and engine data and state estimator development as described in the references (Song et al. 2013a, b; Surenahalli et al. 2013).« less

  3. NH 3 soil and soil surface gas measurements in a triticale wheat field

    NASA Astrophysics Data System (ADS)

    Neftel, A.; Blatter, A.; Gut, A.; Högger, D.; Meixner, F.; Ammann, C.; Nathaus, F. J.

    We present a new approach for a continuous determination of NH 3 concentration in the open pore space of the soil and on the soil surface. In a semi-permeable membrane of 0.5 m length a flow of 0.5 s1pm maintained. In the tube the NH 3 concentration adjusts itself to the surrounding air concentration by diffusion through the membrane. Continuous measurements have been performed in a triticale wheat field over a period of several weeks in a field experiment at Bellheim (FRG) during June and July 1995 within the frame of the European program EXAMINE (Exchange of Atmospheric Ammonia with European Ecosystems). Soil concentrations are generally below the detection limit of 0.1 μg m -3. We conclude, that the investigated soil is generally a sink for NH 3. The NH 3 concentration on the soil surface shows a diurnal variation due to a combination of physico-chemical desorption and adsorption phenomena associated with changes in wetness of the surrounding surfaces and the NH 3 concentration in the canopy.

  4. Acidity and basicity of hydrotalcite derived mixed Mg-Al oxides studied by test reaction of MBOH conversion and temperature programmed desorption of NH{sub 3} and CO{sub 2}

    SciTech Connect

    Kustrowski, Piotr; Chmielarz, Lucjan; Bozek, Ewa; Sawalha, Murad; Roessner, Frank

    2004-02-02

    Mg-Al hydrotalcites intercalated with five different interlayer anions--CO{sub 3}{sup 2-}, SO{sub 4}{sup 2-}, Cl{sup -}, HPO{sub 4}{sup 2-} or terephthalate--were synthesized by either the coprecipitation or ion-exchange method. The structure of the as-synthesized samples and the presence of intended anions in the interlayer gallery of hydrotalcites were determined by X-ray diffraction and FTIR spectroscopy. On calcination at 600 deg. C the materials were transformed into mixed metal oxides. The kind of the counterbalancing anions present in the parent hydrotalcite influences strongly textural parameters of the obtained Mg-Al oxides. Both temperature-programmed desorption of NH{sub 3} and CO{sub 2}, and test reaction of 2-methyl-3-butyn-2-ol (MBOH) conversion were used to determine the acidity and basicity of the samples. The hydrotalcite derived mixed Mg-Al oxides showed the presence of Broensted and Lewis acid and base sites. However, the strong basic character of the solids caused that acetone and acetylene were observed as the major products of MBOH conversion.

  5. Condensation and vaporization studies of CH3OH and NH3 ices: major implications for astrochemistry.

    PubMed

    Sandford, S A; Allamandola, L J

    1993-11-10

    In an extension of previously reported work on ices containing H2O, CO, CO2, SO2, H2S, and H2, we present measurements of the physical and infrared spectral properties of ices containing CH3OH and NH3. The condensation and sublimation behavior of these ice systems is discussed and surface binding energies are presented for all of these molecules. The surface binding energies can be used to calculate the residence times of the molecules on grain surfaces as a function of temperature. It is demonstrated that many of the molecules used to generate radio maps of and probe conditions in dense clouds, for example CO and NH3, will be significantly depleted from the gas phase by condensation onto dust grains. Attempts to derive total column densities solely from radio maps that do not take condensation effects into account may vastly underestimate the true column densities of any given species. Simple CO condensation onto and vaporization off of grains appears to be capable of explaining the observed depletion of gas phase CO in cold, dense molecular cores. This is not the case for NH3, however, where thermal considerations alone predict that all of the NH3 should be condensed onto grains. The fact that some gas phase NH3 is observed indicates that additional desorption processes must be involved. The surface binding energies of CH3OH, in conjunction with this molecule's observed behavior during warm up in H2O-rich ices, is shown to provide an explanation of the large excess of CH3OH seen in many warm, dense molecular cores. The near-infrared spectrum and associated integrated band strengths of CH3OH-containing ice are given, as are middle infrared absorption band strengths for both CH3OH and NH3. PMID:11540092

  6. Condensation and vaporization studies of CH3OH and NH3 ices: Major implications for astrochemistry

    NASA Technical Reports Server (NTRS)

    Sandford, Scott A.; Allamandola, Louis J.

    1993-01-01

    In an extension of previously reported work on ices containing H2O, CO, CO2, SO2, H2S, and H2, we present measurements of the physical and infrared spectral properties of ices containing CH3OH and NH3. The condensation and sublimation behavior of these ice systems is discussed and surface binding energies are presented for all of these molecules. The surface binding energies can be used to calculate the residence times of the molecules on grain surfaces as a function of temperature. It is demonstrated that many of the molecules used to generate radio maps of and probe conditions in dense clouds, for example CO and NH3, will be significantly depleted from the gas phase by condensation onto dust grains. Attempts to derive total column densities solely from radio maps that do not take condensation effects into account may vastly underestimate the true column densities of any given species. Simple CO condensation onto and vaporization off of grains appears to be capable of explaining the observed depletion of gas phase CO in cold, dense molecular cores. This is not the case for NH3, however, where thermal considerations alone predict that all of the NH3 should be condensed onto grains. The fact that some gas phase NH3 is observed indicates that additional desorption processes must be involved. The surface binding energies of CH3OH, in conjunction with this molecule's observed behavior during warm up in H2O-rich ices, is shown to provide an explanation of the large excess of CH3OH seen in many warm, dense molecular cores. The near-infrared spectrum and associated integrated band strengths of CH3OH-containing ice are given, as are middle infrared absorption band strengths for both CH3OH and NH3.

  7. Condensation and Vaporization Studies of CH3OH and NH3 Ices: Major Implications for Astrochemistry

    NASA Technical Reports Server (NTRS)

    Sandford, Scott A.; Allamandola, Louis J.

    1993-01-01

    In an extension of previously reported work on ices containing H20, CO, CO2, SO2, H2S, and H2, We present measurements of the physical and infrared spectral properties of ices containing CH30H and NH3.The condensation and sublimation behavior of these ice systems is discussed and surface binding energies are presented for all of these molecules. The surface binding energies can be used to calculate the residence times of the molecules on grain surfaces as a function of temperature. It is demonstrated that many of the molecules used to generate radio maps of and probe conditions in dense clouds, for example CO and NH3, will be significantly depleted from the gas phase by condensation onto dust grains. Attempts to derive total column densities solely from radio maps that do not take condensation effects into account may vastly underestimate the true column densities of any given species. Simple CO condensation onto and vaporization off of grains appears to be capable of explaining the observed 87 of gas phase CO in cold, dense molecular cores. This is not the case for NH3, however, where thermal considerations alone predict that all of the NH3 should be condensed onto grains. The fact that some gas phase NH3 is observed indicates that additional desorption processes must be involved. The surface binding energies of CH3OH, in conjunction with this molecule's observed behavior during warm up in H2O-rich ices, is shown to provide an explanation of the large excess of CH3OH seen in many warm, dense molecular cores. The near-infrared spectrum and associated integrated band strengths of CH3OH-containing ice are given, as are middle infrared absorption band strengths for both CH3OH and NH3.

  8. Condensation and vaporization studies of CH3OH and NH3 ices: Major implications for astrochemistry

    NASA Astrophysics Data System (ADS)

    Sandford, Scott A.; Allamandola, Louis J.

    1993-11-01

    In an extension of previously reported work on ices containing H2O, CO, CO2, SO2, H2S, and H2, we present measurements of the physical and infrared spectral properties of ices containing CH3OH and NH3. The condensation and sublimation behavior of these ice systems is discussed and surface binding energies are presented for all of these molecules. The surface binding energies can be used to calculate the residence times of the molecules on grain surfaces as a function of temperature. It is demonstrated that many of the molecules used to generate radio maps of and probe conditions in dense clouds, for example CO and NH3, will be significantly depleted from the gas phase by condensation onto dust grains. Attempts to derive total column densities solely from radio maps that do not take condensation effects into account may vastly underestimate the true column densities of any given species. Simple CO condensation onto and vaporization off of grains appears to be capable of explaining the observed depletion of gas phase CO in cold, dense molecular cores. This is not the case for NH3, however, where thermal considerations alone predict that all of the NH3 should be condensed onto grains. The fact that some gas phase NH3 is observed indicates that additional desorption processes must be involved. The surface binding energies of CH3OH, in conjunction with this molecule's observed behavior during warm up in H2O-rich ices, is shown to provide an explanation of the large excess of CH3OH seen in many warm, dense molecular cores. The near-infrared spectrum and associated integrated band strengths of CH3OH-containing ice are given, as are middle infrared absorption band strengths for both CH3OH and NH3.

  9. Growth of an Ultrathin Zirconia Film on Pt3Zr Examined by High-Resolution X-ray Photoelectron Spectroscopy, Temperature-Programmed Desorption, Scanning Tunneling Microscopy, and Density Functional Theory

    PubMed Central

    2014-01-01

    Ultrathin (∼3 Å) zirconium oxide films were grown on a single-crystalline Pt3Zr(0001) substrate by oxidation in 1 × 10–7 mbar of O2 at 673 K, followed by annealing at temperatures up to 1023 K. The ZrO2 films are intended to serve as model supports for reforming catalysts and fuel cell anodes. The atomic and electronic structure and composition of the ZrO2 films were determined by synchrotron-based high-resolution X-ray photoelectron spectroscopy (HR-XPS) (including depth profiling), low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and density functional theory (DFT) calculations. Oxidation mainly leads to ultrathin trilayer (O–Zr–O) films on the alloy; only a small area fraction (10–15%) is covered by ZrO2 clusters (thickness ∼0.5–10 nm). The amount of clusters decreases with increasing annealing temperature. Temperature-programmed desorption (TPD) of CO was utilized to confirm complete coverage of the Pt3Zr substrate by ZrO2, that is, formation of a closed oxide overlayer. Experiments and DFT calculations show that the core level shifts of Zr in the trilayer ZrO2 films are between those of metallic Zr and thick (bulklike) ZrO2. Therefore, the assignment of such XPS core level shifts to substoichiometric ZrOx is not necessarily correct, because these XPS signals may equally well arise from ultrathin ZrO2 films or metal/ZrO2 interfaces. Furthermore, our results indicate that the common approach of calculating core level shifts by DFT including final-state effects should be taken with care for thicker insulating films, clusters, and bulk insulators. PMID:25688293

  10. Effects of Si/Al Ratio on Cu/SSZ-13 NH3-SCR Catalysts: Implications for the active Cu species and the Roles of Brønsted Acidity

    SciTech Connect

    Gao, Feng; Washton, Nancy M.; Wang, Yilin; Kollar, Marton; Szanyi, Janos; Peden, Charles HF

    2015-09-03

    Cu/SSZ-13 catalysts with three Si/Al ratios of 6, 12 and 35 were synthesized with Cu incorporation via solution ion exchange. The implications of varying Si/Al ratios on the nature of the multiple Cu species that can be present in the SSZ-13 zeolite are a major focus of this work, as highlighted by the results of a variety of catalyst characterization and reaction kinetics measurements. Specifically, catalysts were characterized with surface area/pore volume measurements, temperature programmed reduction by H2 (H2-TPR), NH3 temperature programmed desorption (NH3-TPD), and DRIFTS and solid-state nuclear magnetic resonance (NMR) spectroscopies. Catalytic properties were examined using NO oxidation, ammonia oxidation, and standard ammonia selective catalytic reduction (NH3-SCR) reactions on selected catalysts under differential conditions. Besides indicating possible variably active multiple Cu species for these reactions, the measurements are also used to untangle some of the complexities caused by the interplay between redox of Cu ion centers and Brønsted acidity. All three reactions appear to follow a redox reaction mechanism, yet the roles of Brønsted acidity are quite different. For NO oxidation, increasing Si/Al ratio lowers Cu redox barriers, thus enhancing reaction rates. Brønsted acidity appears to play essentially no role for this reaction. For standard NH3-SCR, residual Brønsted acidity plays a significant beneficial role at both low- and high-temperature regimes. For NH3 oxidation, no clear trend is observed suggesting both Cu ion center redox and Brønsted acidity play important and perhaps competing roles. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.

  11. Degradation mechanism of CH3NH3PbI3 perovskite materials upon exposure to humid air

    NASA Astrophysics Data System (ADS)

    Shirayama, Masaki; Kato, Masato; Miyadera, Tetsuhiko; Sugita, Takeshi; Fujiseki, Takemasa; Hara, Shota; Kadowaki, Hideyuki; Murata, Daisuke; Chikamatsu, Masayuki; Fujiwara, Hiroyuki

    2016-03-01

    Low stability of organic-inorganic perovskite (CH3NH3PbI3) solar cells in humid air environments is a serious drawback which could limit practical application of this material severely. In this study, from real-time spectroscopic ellipsometry characterization, the degradation mechanism of ultra-smooth CH3NH3PbI3 layers prepared by a laser evaporation technique is studied. We present evidence that the CH3NH3PbI3 degradation in humid air proceeds by two competing reactions of (i) the PbI2 formation by the desorption of CH3NH3I species and (ii) the generation of a CH3NH3PbI3 hydrate phase by H2O incorporation. In particular, rapid phase change occurs in the near-surface region and the CH3NH3PbI3 layer thickness reduces rapidly in the initial 1 h air exposure even at a low relative humidity of 40%. After the prolonged air exposure, the CH3NH3PbI3 layer is converted completely to hexagonal platelet PbI2/hydrate crystals that have a distinct atomic-scale multilayer structure with a period of 0.65 ± 0.05 nm. We find that conventional x-ray diffraction and optical characterization in the visible region, used commonly in earlier works, are quite insensitive to the surface phase change. Based on results obtained in this work, we discuss the degradation mechanism of CH3NH3PbI3 in humid air.

  12. A Comparative Study of N2O Formation during the Selective Catalytic Reduction of NOx with NH3 on Zeolite Supported Cu Catalysts

    SciTech Connect

    Chen, Hai-Ying; Wei, Zhehao; Kollar, Marton; Gao, Feng; Wang, Yilin; Szanyi, Janos; Peden, Charles HF

    2015-09-01

    A comparative study was carried out on a small-pore CHA.Cu and a large-pore BEA.Cu zeolite catalyst to understand the lower N2O formation on small-pore zeolite supported Cu catalysts in the selective catalytic reduction (SCR) of NOx with NH3. On both catalysts, the N2O yield increases with an increase in the NO2/NOx ratios of the feed gas, suggesting N2O formation via the decomposition of NH4NO3. Temperature-programmed desorption experiments reveal that NH4NO3 is more stable on CHA.Cu than on BEA.Cu. In situ FTIR spectra following stepwise (NO2 + O2) and (15NO + NH3 + O2) adsorption and reaction, and product distribution analysis using isotope-labelled reactants, unambiguously prove that surface nitrate groups are essential for the formation of NH4NO3. Furthermore, CHA.Cu is shown to be considerably less active than BEA.Cu in catalyzing NO oxidation and the subsequent formation of surface nitrate groups. Both factors, i.e., (1) the higher thermal stability of NH4NO3 on CHA.Cu, and (2) the lower activity for this catalyst to catalyze NO oxidation and the subsequent formation of surface nitrates, likely contribute to the higher SCR selectivity with less N2O formation on this catalyst as compared to BEA.Cu. The latter is determined as the primary reason since surface nitrates are the source that leads to the formation of NH4NO3 on the catalysts.

  13. NH3 column abundances over Lauder, New Zealand

    NASA Technical Reports Server (NTRS)

    Murcray, Frank J.; Goldman, Aaron; Matthews, Andrew; Johnston, Paul; Rinsland, Curtis

    1989-01-01

    Gaseous NH3 has been observed in the atmosphere over central New Zealand with infrared absorption spectra. The amount of NH3 shows marked variability, which is strongly correlated with time of day and season. The pattern is similar to data obtained in Denver, Colorado, but is much more variable than data from Hampton, Virginia. The rapid variability indicates a residence time of 8 hours in some cases.

  14. The NH3 spectrum in Saturn's 5 micron window

    NASA Technical Reports Server (NTRS)

    Bjoraker, G. L.; Fink, U.; Larson, H. P.; Johnson, J. R.

    1983-01-01

    Spectra of Saturn's 5-micron window were obtained at the Infrared Telescope Facility on Mauna Kea, Hawaii. The spectra have a resolution of 1.2/cm, and some exhibit extremely low amounts of approximately 300-micron ppt telluric H2O. The Saturn spectra show absorptions by the 2nu2 band of NH3. Long-path laboratory comparison spectra of NH3 were acquired and show considerable deviations in intensity from theoretical predictions. The calibration of Saturn's observed NH3 features with the laboratory data gives 2.0 + or - 0.5 m-amagat of NH3 using the 2nu2 Q-branch at 5.32 microns. The R(1) and R(2) lines yield an abundance about 3 times greater. Absorptions outside the range of the Q-branch can be accounted for by solid NH3 of 10-20 microns equivalent path length. The origin of Saturn's 5-micron flux is mostly thermal with some admixture of solar reflected radiation. A depletion of Saturn's NH3 abundance below the solar value is indicated, but confirmation of this conclusion will require a better understanding of the atmospheric penetration depth at 5 microns and more rigorous modeling of the spectral line formation.

  15. Bias in modeled bi-directional NH3 fluxes associated with temporal averaging of atmospheric NH3 concentrations

    EPA Science Inventory

    Direct flux measurements of NH3 are expensive, time consuming, and require detailed supporting measurements of soil, vegetation, and atmospheric chemistry for interpretation and model parameterization. It is therefore often necessary to infer fluxes by combining measurements of...

  16. Adsorption of NH3 onto activated carbon prepared from palm shells impregnated with H2SO4.

    PubMed

    Guo, Jia; Xu, Wang Sheng; Chen, Yan Lin; Lua, Aik Chong

    2005-01-15

    Adsorption of ammonia (NH3) onto activated carbons prepared from palm shells impregnated with sulfuric acid (H2SO4) was investigated. The effects of activation temperature and acid concentration on pore surface area development were studied. The relatively large micropore surface areas of the palm-shell activated carbons prepared by H2SO4 activation suggest their potential applications in gas adsorption. Adsorption experiments at a fixed temperature showed that the amounts of NH3 adsorbed onto the chemically activated carbons, unlike those prepared by CO2 thermal activation, were not solely dependent on the specific pore surface areas of the adsorbents. Further adsorption tests for a wide range of temperatures suggested combined physisorption and chemisorption of NH3. Desorption tests at the same temperature as adsorption and at an elevated temperature were carried out to confirm the occurrence of chemisorption due to the interaction between NH3 and some oxygen functional groups via hydrogen bonding. The surface functional groups on the adsorbent surface were detected by Fourier transform infrared spectroscopy. The amounts of NH3 adsorbed by chemisorption were correlated with the contents of elemental oxygen present in the adsorbents. Mechanisms for chemical activation and adsorption processes are proposed based on the observed phenomena. PMID:15571683

  17. Evidence of amino acid precursors: C-N bond coupling in simulated interstellar CO2/NH3 ices

    NASA Astrophysics Data System (ADS)

    Esmaili, Sasan

    2015-08-01

    Low energy secondary electrons are abundantly produced in astrophysical or planetary ices by the numerous ionizing radiation fields typically encountered in space environments and may thus play a role in the radiation processing of such ices [1]. One approach to determine their chemical effect is to irradiate nanometer thick molecular solids of simple molecular constituents, with energy selected electron beams and to monitor changes in film chemistry with the surface analytical techniques [2].Of particular interest is the formation of HCN, which is a signature of dense gases in interstellar clouds, and is ubiquitous in the ISM. Moreover, the chemistry of HCN radiolysis products such as CN- may be essential to understand of the formation of amino acids [3] and purine DNA bases. Here we present new results on the irradiation of multilayer films of CO2 and NH3 with 70 eV electrons, leading to CN bond formations. The electron stimulated desorption (ESD) yields of cations and anions are recorded as a function of electron fluence. The prompt desorption of cationic reaction/scattering products [4], is observed at low fluence (~4x1013 electrons/cm2). Detected ions include C2+, C2O2+, C2O+, CO3+, C2O3+ or CO4+ from pure CO2, and N+, NH+, NH2+, NH3+, NH4+, N2+, N2H+ from pure NH3, and NO+, NOH+ from CO2/NH3 mixtures. Most saliently, increasing signals of negative ion products desorbing during prolonged irradiation of CO2/NH3 films included C2-, C2H-, C2H2-, as well as CN-, HCN- and H2CN-. The identification of particular product ions was accomplished by using 13CO2 and 15NH3 isotopes. The chemistry induced by electrons in pure films of CO2 and NH3 and mixtures with composition ratios (3:1), (1:1), and (1:3), was also studied by X-ray photoelectron spectroscopy (XPS). Irradiation of CO2/NH3 mixed films at 22 K produces species containing the following bonds/functional groups identified by XPS: C=O, O-H, C-C, C-O, C=N and N=O. (This work has been funded by NSERC).

  18. Photodissociation of NH3 at 106-200 nm

    NASA Technical Reports Server (NTRS)

    Suto, M.; Lee, L. C.

    1983-01-01

    The absorption and fluorescence cross sections for NH3 are measured in the 106-200 nm region using synchrotron radiation as the light source. The threshold wavelengths for the production of the NH (b to X) and NH (c to a) emissions from NH3 dissociation are measured and compared with previous measurements. The heat of formation of NH determined from these thresholds agrees well with the value determined from thermochemical data. The process of dissociation of NH3 into NH2(2AL) and H2(S) has a significant quantum yield whose maximum at 134 nm is about twice the NH(c) production yield. All the vibronic levels of the B and C states produce the NH2(2A1) emission, contrary to previous theoretical interpretations.

  19. Gaseous NH3 Confers Porous Pt Nanodendrites Assisted by Halides.

    PubMed

    Lu, Shuanglong; Eid, Kamel; Li, Weifeng; Cao, Xueqin; Pan, Yue; Guo, Jun; Wang, Liang; Wang, Hongjing; Gu, Hongwei

    2016-01-01

    Tailoring the morphology of Pt nanocrystals (NCs) is of great concern for their enhancement in catalytic activity and durability. In this article, a novel synthetic strategy is developed to selectively prepare porous dendritic Pt NCs with different structures for oxygen reduction reaction (ORR) assisted by NH3 gas and halides (F(-), Cl(-), Br(-)). The NH3 gas plays critical roles on tuning the morphology. Previously, H2 and CO gas are reported to assist the shape control of metallic nanocrystals. This is the first demonstration that NH3 gas assists the Pt anisotropic growth. The halides also play important role in the synthetic strategy to regulate the formation of Pt NCs. As-made porous dendritic Pt NCs, especially when NH4F is used as a regulating reagent, show superior catalytic activity for ORR compared with commercial Pt/C catalyst and other previously reported Pt-based NCs. PMID:27184228

  20. Urban NH3 levels and sources in a Mediterranean environment

    NASA Astrophysics Data System (ADS)

    Reche, Cristina; Viana, Mar; Pandolfi, Marco; Alastuey, Andrés; Moreno, Teresa; Amato, Fulvio; Ripoll, Anna; Querol, Xavier

    2012-09-01

    Urban NH3 concentrations were mapped in Barcelona (Spain) by means of passive samplers (dosimeters). Average NH3 levels were 9.5 μg m-3 in summer and 4.4 μg m-3 in winter, higher than those reported in other urban background sites in Europe, this being especially notable in summer. During this season, values were significantly higher at urban background than at traffic sites, probably indicating the impact of emissions from biological sources, such as humans, sewage systems and garbage containers. Thus, the volatilization of NH3 from the aerosol phase seems to be significant enough during summer to dominate over traffic emissions. Conversely, in winter levels were higher at traffic sites, suggesting a contribution from vehicle emissions. Indeed, NH3 levels decreased by 55% with increasing distance (50 m) to the direct emissions from traffic. A significant correlation between NH3 concentrations averaged for the different districts of the city and the number of waste containers per hm2 was also obtained, highlighting the necessity for controlling and reducing the emissions from garbage collection systems. The urban topography of the Barcelona historical city centre, characterised by narrow streets with a high population density, seemed to exert a strong influence on NH3 levels, with levels reaching up to 30 μg m-3 as a consequence of limited dispersion and ventilation conditions. The impact of the sewage system emissions was also detected with an increase of levels when measuring immediately above the source, even though further studies are required to evaluate the relevance of these emissions.

  1. A Sensitive Survey of Ammonia (NH3) in Comets

    NASA Astrophysics Data System (ADS)

    Magee-Sauer, Karen P.; Villanueva, G. L.; Bonev, B. P.; Paganini, L.; DiSanti, M. A.; Mumma, M. J.

    2012-10-01

    Being the fully reduced form of nitrogen, ammonia (NH3) is a key molecule for understanding the nitrogen chemistry in comets and to properly characterize the primordial conditions under which these icy bodies formed. Yet, its abundance has not been well characterized, even though NH3 is a major reservoir of volatile nitrogen in comets. To date the abundance has been directly measured in only 10 comets, all at radio and infrared wavelengths. This small sample is largely due to the difficulty in measuring emission from NH3 since its emission is normally weak, can be affected by terrestrial extinction, and (without sufficient spectral resolution) is not resolved from other volatile cometary emissions. In this paper, we present a search for NH3 in seven comets using archival data acquired by our Team using the NIRSPEC instrument at the Keck-2 telescope and the CSHELL instrument at the NASA Infrared Telescope Facility, both atop Mauna Kea, HI. Using an updated fluorescence model that is based on millions of ammonia spectral lines (Villanueva et al., in prep.), we present relative abundances of NH3 with respect to H2O. We find the relative abundance of NH3/H2O varies from 0.3% to 1.6% in these seven comets, and we compare this indicator with other properties measured for these comets (isotopic fractionation and mixing ratios of selected primary volatiles). We gratefully acknowledge support from NASA’s Postdoctoral Program (LP), the NASA Astrobiology Institute (PI MJM), NASA’s Planetary Astronomy (PI GLV; PI MJM; PI DiSanti) and Planetary Atmospheres (PI DiSanti, PI Villanueva) programs, and from NSF Planetary Astronomy program (PI BPB).

  2. Enhanced NH3 emission from swine liquid waste

    NASA Astrophysics Data System (ADS)

    Lee, S.; Robarge, W. P.; Walker, J. T.

    2010-12-01

    Swine animal feeding operations are sources of emissions for various gases [ammonia (NH3), hydrogen sulfide (H2S), carbon dioxide (CO2), volatile organic carbons (VOCs)], and fine particulate matter. Gaseous emissions from simple aqueous systems are typically controlled by temperature, pH, wind speed, total dissolved concentration of the chemical species of interest (e.g. NH3+NH4+ = TAN), and the Henry’s law constant. Ammonia emissions from three different sources [ammonium sulfate (AS), swine anaerobic lagoon liquid (SLL), and pit liquid (SPL) from swine housing units] were evaluated using a small flow-through teflon-lined chamber (SFTC; 0.3m × 0.2m × 0.15m) under controlled laboratory conditions. The SFTC was designed for 100% collection efficiency of NH3 gas emitted from the liquids. The internal volume of the chamber, 9 L, was exchanged 1.1 times per minute. All three liquid formulations exhibit the expected response in emissions with changes in temperature and pH. However, NH3 emissions from the SPL and SLL are ~5 times those from pure solutions of AS. Furthermore, the enhancement in NH3 emissions was a function of TAN concentration, decreasing in intensity at higher TAN and approaching rates comparable to the pure solutions of AS. The difference in emissions with solutions of equivalent TAN suggests a synergistic mechanism that is enhancing NH3 emissions in SPL and SLL. Concurrent measurements as part of the National Air Emissions Monitoring Study at the swine operations originally sampled for SPL and SLL document the emissions of CO2, H2S and VOCs (primarily acetic, propionic and butyric acids) at levels that are comparable to observed NH3 emissions. To date, only additions of NaHCO3 to the SPL and SLL have been found to enhance NH3 emissions and exhibit the same response to increasing TAN as exhibited by the original SPL and SLL solutions. Possible reactions that could enhance emissions will be discussed.

  3. Energy transfer in NH3-He collisions. [in interstellar gas

    NASA Technical Reports Server (NTRS)

    Green, S.

    1980-01-01

    The paper presents a new electron gas intermolecular NH3-He potential determined by the Hartree-Fock results of Davis, Boggs, and Mehrotra (1979) with semiempirical long-range induction and dispersion terms. The resulting potential agrees with beam scattering and pressure broadening measurements; it was also found that the quadrupole induced dipole interaction is not as effective as the short range anisotropy. It was concluded that discrepancies remain in the quantitative description of energy transfer in the NH3-He system; discrepancies result from improper consideration of the dependence of cross-sections on degenerate magnetic quantum levels in the experimental investigation.

  4. Reaction pathway investigation on the selective catalytic reduction of NO with NH3 over Cu/SSZ-13 at low temperatures.

    PubMed

    Su, Wenkang; Chang, Huazhen; Peng, Yue; Zhang, Chaozhi; Li, Junhua

    2015-01-01

    The mechanism of the selective catalytic reduction of NO with NH3 was studied using Cu/SSZ-13. The adspecies of NO and NH3 as well as the active intermediates were investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy and temperature-programmed surface reaction. The results revealed that three reactions were possible between adsorbed NH3 and NOx. NO2(-) could be generated by direct formation or NO3(-) reduction via NO. In a standard selective catalytic reduction (SCR) reaction, NO3(-) was hard to form, because NO2(-) was consumed by ammonia before it could be further oxidized to nitrates. Additionally, adsorbed NH3 on the Lewis acid site was more active than NH4(+). Thus, SCR mainly followed the reaction between Lewis acid site-adsorbed NH3 and directly formed NO2(-). Higher Cu loading could favor the formation of active Cu-NH3, Cu-NO2(-), and Cu-NO3(-), improving the SCR activity at low temperature. PMID:25485842

  5. Rotationally inelastic scattering and potential calculation for NH3+He

    NASA Astrophysics Data System (ADS)

    Meyer, H.; Buck, U.; Schinke, R.; Diercksen, G. H. F.

    1986-05-01

    In a crossed molecular beam experiment, time-of-flight distributions of NH3 molecules scattered from He have been measured as a function of the deflection angle at E=97.7 meV. The spectra, which cover a center-of-mass angular range from 97° to 168° show appreciable rotational energy transfer in the backward direction. These data, which are sensitive to the repulsive anisotropy of the interaction potential, are used together with the diffraction oscillations of total differential cross section to determine a new rigid rotor potential surface for NH3-He. The potential is constructed by combining large basis set self-consistent-field (SCF) calculations with damped long range dispersion coefficients. The two free parameters of the damping function are determined by fitting the measured data to calculations using the quantal coupled states approximation. The potential is in reasonable agreement with calculations where correlation effects are included and reproduces the measured second virial coefficients.

  6. NH3 in IRC plus 10216. [infrared astronomy

    NASA Technical Reports Server (NTRS)

    Betz, A. L.; Mclaren, R. A.; Spears, D. L.

    1978-01-01

    Ammonia was detected in the circumstellar envelope of IRC +10216 by means of three infrared absorption lines in the nu sup 2 band around 950/cm. The lines are fully resolved at a resolution of 0.22 km/sec and indicate that most of the circumstellar gas is accelerated to expansion velocities around 14 km/sec within a few stellar radii. The NH3 profiles indicate a rotational temperature between 400 and 700 K, and H2 density between 10 to the 8th power/cu cm and 10 to the 10th power/cu cm, and NH3 column density of 10 to the 17th power/sq cm. The H2 density indicates that the mass of the circumstellar envelope within a 1 arcsec radius is approximately 0.1 solar masses.

  7. Studies of elastic e-NH3 collisions

    NASA Technical Reports Server (NTRS)

    Pritchard, H. P.; Lima, M. A. P.; Mckoy, V.

    1989-01-01

    Differential and momentum-transfer cross sections for the elastic scattering of electrons by NH3 have been obtained for collision energies of between 2.5 and 20 eV using the fixed-nuclei static-exchange approximation of the Schwinger variational principle. At intermediate and large scattering angles, good agreement is found between calculated and relative experimental cross sections. The differential cross sections reveal evidence of a weak d-wave enhancement around 8 eV.

  8. Communication: overtone (2NH) spectroscopy of NH3-Ar.

    PubMed

    Didriche, K; Fldes, T; Vanfleteren, T; Herman, M

    2013-05-14

    The ? (1(1)) ? ? (0(0)) 2NH (?1+?3) band of the NH3-Ar van der Waals complex formed in a supersonic jet expansion, with origin at 6628 cm(-1) was recorded at high-resolution using cavity ring down spectroscopy. The analysis leads to upper state rotational constants and J-dependent predissociation lifetimes estimated from linewidth analysis, with a mean value about 0.6 ns. PMID:23676017

  9. Advanced ammonia (NH3) monitoring system for industrial applications

    NASA Astrophysics Data System (ADS)

    Spector, Oded; Jacobson, Esther

    1999-12-01

    The present paper describes an Electro-Optical Monitoring System developed for the real time in-situ monitoring of Ammonia (NH3) emissions, at very low concentrations in air, well below the hazardous levels. Ammonia is the starting chemical for almost all industrially produced nitrogen compounds and is therefore one of the most important inorganic raw materials. Due to its unique chemical and physical characteristics, the Ammonia (NH3) anhydrous gas is used in various industrial applications such as: Air Conditioning, Refrigeration (including space shuttles), Agriculture and Chemical Processing. NH3 gas, being a highly irritant toxic and flammable gas with a pungent odor detectable by human perception at 53 ppm, has a TLV-TWA of 25 ppm (TLV-STEL of 35 ppm) and a lower explosive limit (LEL) of 15% in air. Being extremely corrosive and irritating to the skin, eyes, nose and respiratory tract, (irritation begins at 130 - 200 ppm), exposures to high concentrations (above 2500 ppm) are life threatening, thus early detection of Ammonia at concentrations up to 50 ppm is essential to prevent its toxic influence. Existing detection methods for NH3 rely mainly on chemical sensors and analytical methods that require the gas to be sampled and introduced into the detection system via a probe, compared to various standards (for determining the concentration) and the result is not always reflecting the actual gas concentration. The emerging optical open path remote sensing technology that analyzes the specific 'finger print' absorption characteristics of NH3 in various narrow spectral bands, specifically in the UV solar blind band, is discussed including the rationale of the detection algorithm and system design. The system offers warning and alarm signals set at the above low concentration detection sensitivity, (10 - 50 ppm(DOT)m) thus providing reliable Ammonia detection over an air path from 3 (including air-duct applications) to 400 ft (1 - 120 m). Typical installations of Ammonia Monitoring Systems, field and laboratory test data are discussed, including spectral cross sensitivity analysis with interfering chemicals and changing environmental conditions (heat, humidity).

  10. NH3-SCR denitration catalyst performance over vanadium-titanium with the addition of Ce and Sb.

    PubMed

    Xu, Chi; Liu, Jian; Zhao, Zhen; Yu, Fei; Cheng, Kai; Wei, Yuechang; Duan, Aijun; Jiang, Guiyuan

    2015-05-01

    Selective catalytic reduction technology using NH3 as a reducing agent (NH3-SCR) is an effective control method to remove nitrogen oxides. TiO2-supported vanadium oxide catalysts with different levels of Ce and Sb modification were prepared by an impregnation method and were characterized by X-ray diffractometer (XRD), Brunauer-Emmett-Teller (BET), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), Raman and Hydrogen temperature-programmed reduction (H2-TPR). The catalytic activities of V5CexSby/TiO2 catalysts for denitration were investigated in a fixed bed flow microreactor. The results showed that cerium, vanadium and antimony oxide as the active components were well dispersed on TiO2, and the catalysts exhibited a large number of d-d electronic transitions, which were helpful to strengthen SCR reactivity. The V5CexSby/TiO2 catalysts exhibited a good low temperature NH3-SCR catalytic activity. In the temperature range of 210 to 400°C, the V5CexSby/TiO2 catalysts gave NO conversion rates above 90%. For the best V5Ce35Sb2/TiO2 catalyst, at a reaction temperature of 210°C, the NO conversion rate had already reached 90%. The catalysts had different catalytic activity with different Ce loadings. With the increase of Ce loading, the NO conversion rate also increased. PMID:25968261

  11. Adsorption, diffusion, dewetting, and entrapment of acetone on Ni(111), surface-modified silicon, and amorphous solid water studied by time-of-flight secondary ion mass spectrometry and temperature programmed desorption

    NASA Astrophysics Data System (ADS)

    Souda, Ryutaro

    2011-10-01

    Interactions of acetone with the silicon surfaces terminated with hydrogen, hydroxyl, and perfluorocarbon are investigated; results are compared to those on amorphous solid water (ASW) to gain insights into the roles of hydrogen bonds in surface diffusion and hydration of acetone adspecies. The surface mobility of acetone occurs at 60 K irrespective of the surface functional groups. Cooperative diffusion of adspecies results in a 2D liquid phase on the H- and perfluorocarbon-terminated surfaces, whereas cooperativity tends to be quenched via hydrogen bonding on the OH-terminated surface, thereby forming residues that diffuse slowly on the surface after evaporation of the physisorbed species (i.e., 2D liquid). The interaction of acetone adspecies on the non-porous ASW surface resembles that on the OH-terminated Si surface, but the acetone molecules tend to be hydrated on the porous ASW film, as evidenced by their desorption during the glass-liquid transition and crystallization of water. The roles of micropores in hydration of acetone molecules are discussed from comparison with the results using mesoporous Si substrates.

  12. The ground state far infrared spectrum of NH3

    NASA Technical Reports Server (NTRS)

    Poynter, R. L.; Margolis, J. S.

    1983-01-01

    The NH3 far infrared spectrum is particularly useful for the study of planetary composition and atmospheric dynamics. Studies of this spectrum were conducted by Dowling (1969), Helminger et al. (1971), and Urban et al. (1981). Sattler et al. (1981) have reported measurements of a few nu2 lines with tunable diode lasers. By using simple sum rules, these lines and accurate ground state inversion lines considered by Poynter and Kakar (1975) have been employed in the present investigation to deduce a few of the far infrared ground state transitions. An extensive set of high signal/noise, high resolution (0.0048 per cm) scans of the nu2 bands of NH3 from about 600 per cm through about 1300 per cm ait a series of low pressures have been made in order to accurately determine both the line positions and strengths. The obtained data provide line positions with an absolute accuracy of about 0.0001 per cm in the more favorable cases.

  13. Sensing Mechanisms for Carbon Nanotube Based NH3 Gas Detection

    SciTech Connect

    Peng, Ning; Zhang, Qing; Chow, Chee L.; Tan, Ooi K.; Marzari, Nicola N.

    2009-03-31

    There has been an argument on carbon nanotube (CNT) based gas detectors with a field-effect transistor (FET) geometry: do the response signals result from charge transfer between adsorbed gas molecules and the CNT channel and/or from the gas species induced Schottky barrier modulation at the CNT/metal contacts? To differentiate the sensing mechanisms, we employed three CNTFET structures, i.e., (1) the entire CNT channel and CNT/electrode contacts are accessible to NH3 gas; (2) the CNT/electrode contacts are passivated with a Si3N4 thin film, leaving the CNT channel open to the gas and, in contrast, (3) the CNT channel is covered with the film, while the contacts are open to the gas. We suggest that the Schottky barrier modulation at the contacts is the dominant mechanism from room temperature to 150°C. At higher temperatures, the charge transfer process contributes to the response signals. There is a clear evidence that the adsorption of NH3 on the CNT channel is facilitated by environmental oxygen.

  14. NH3 in IRC +10216. [carbon star undergoing mass loss

    NASA Technical Reports Server (NTRS)

    Betz, A. L.; Mclaren, R. A.; Spears, D. L.

    1979-01-01

    Ammonia has been detected in the circumstellar envelope of IRC +10216 by means of three infrared absorption lines in the nu-2 band around 950 kaysers. The profiles are well resolved at a resolution of 0.22 km/s and show that most of the circumstellar gas is accelerated to expansion velocities around 14 km/s within a few stellar radii. The observed ammonia requires a rotational temperature between 400 and 700 K, an H2 density between 100 million and 10 billion per cu cm, and an NH3 column density of 10 to the 17th per sq cm. The H2 density indicates that the mass of the circumstellar envelope within a 1 arcsec radius is about 0.1 solar mass.

  15. A variationally computed line list for hot NH3

    NASA Astrophysics Data System (ADS)

    Yurchenko, S. N.; Barber, R. J.; Tennyson, J.

    2011-05-01

    We present 'BYTe', a comprehensive 'hot' line list for the ro-vibrational transitions of ammonia, 14NH3, in its ground electronic state. This line list has been computed variationally using the program suite TROVE, a new spectroscopically determined potential energy surface and an ab initio dipole moment surface. BYTe, is designed to be used at all temperatures up to 1500 K. It comprises 1138 323 351 transitions in the frequency range from 0 to 12 000 cm-1, constructed from 1373 897 energy levels below 18 000 cm-1 having J values ≤36. Comparisons with laboratory data confirm the accuracy of the line list which is suitable for modelling a variety of astrophysical problems including the atmospheres of extrasolar planets and brown dwarfs.

  16. Parallel operation of NH3 screw compressors - the optimum way

    NASA Astrophysics Data System (ADS)

    Pijnenburg, B.; Ritmann, J.

    2015-08-01

    The use of more smaller industrial NH3 screw compressors operating in parallel seems to offer the optimum way when it comes to fulfilling maximum part load efficiency, increased redundancy and other highly requested features in the industrial refrigeration industry today. Parallel operation in an optimum way can be selected to secure continuous operation and can in most applications be configured to ensure lower overall operating economy. New compressors are developed to meet requirements for flexibility in operation and are controlled in an intelligent way. The intelligent control system keeps focus on all external demands, but yet striving to offer always the lowest possible absorbed power, including in future scenarios with connection to smart grid.

  17. MetNH3: Metrology for ammonia in ambient air

    NASA Astrophysics Data System (ADS)

    Braban, Christine; Twigg, Marsailidh; Tang, Sim; Leuenberger, Daiana; Ferracci, Valerio; Martin, Nick; Pascale, Celine; Hieta, Tuomas; Pogany, Andrea; Persijn, Stefan; van Wijk, Janneke; Gerwig, Holger; Wirtze, Klaus; Tiebe, Carlo; Balslev-Harder, David; Niederhausen, Bernhardt

    2015-04-01

    Measuring ammonia in ambient air is a sensitive and priority issue due to its harmful effects on human health and ecosystems. The European Directive 2001/81/EC on 'National Emission Ceilings for Certain Atmospheric Pollutants (NEC)' regulates ammonia emissions in the member states. However, there is a lack of regulation to ensure reliable ammonia measurements namely in applicable analytical technology, maximum allowed uncertainty, quality assurance and quality control (QC/QA) procedures as well as in the infrastructure to attain metrological traceability. Validated ammonia measurement data of high quality from air monitoring networks are vitally important for identifying changes due to implementations of environment policies, for understanding where the uncertainties in current emission inventories are derived from and for providing independent verification of atmospheric model predictions. The new EURAMET project MetNH3 aims to develop improved reference gas mixtures by static and dynamic gravimetric generation methods, develop and characterise laser based optical spectrometric standards and establish the transfer from high-accuracy standards to field applicable methods. MetNH3started in June 2014 and in this presentation the first results from the metrological characterisation of a commercially available cavity ring-down spectrometer (CRDS) will be discussed. Also first tests and results from a new design, Controlled Atmosphere Test Facility (CATFAC), which is to be characterised and used to validate the performance of diffusive samplers, denuders and on-line instruments, will be reported. CAFTEC can be used to control test parameters such as ammonia concentration, relative humidity and wind speed. Outline plans for international laboratory and field intercomparisons in 2016 will be presented.

  18. Optical Constants of NH3 and NH3:N2 Amorphous Ices in the Near-infrared and Mid-infrared Regions

    NASA Astrophysics Data System (ADS)

    Zanchet, Alexandre; Rodríguez-Lazcano, Yamilet; Gálvez, Óscar; Herrero, Víctor J.; Escribano, Rafael; Maté, Belén

    2013-11-01

    Ammonia ice has been detected on different astrophysical media ranging from interstellar medium (ISM) particles to the surface of various icy bodies of our solar system, where nitrogen is also present. We have carried out a detailed study of amorphous NH3 ice and NH3:N2 ice mixtures, based on infrared (IR) spectra in the mid-IR (MIR) and near-IR (NIR) regions, supported by theoretical quantum chemical calculations. Spectra of varying ice thicknesses were obtained and optical constants were calculated for amorphous NH3 at 15 K and 30 K and for a NH3:N2 mixture at 15 K over a 500-7000 cm-1 spectral range. These spectra have improved accuracy over previous data, where available. Moreover, we also obtained absolute values for the band strengths of the more prominent IR features in both spectral regions. Our results indicate that the estimated NH3 concentration in ISM ices should be scaled upward by ~30%.

  19. Theoretical investigation of HNgNH3(+) ions (Ng = He, Ne, Ar, Kr, and Xe).

    PubMed

    Gao, Kunqi; Sheng, Li

    2015-04-14

    The equilibrium geometries, harmonic frequencies, and dissociation energies of HNgNH3(+) ions (Ng = He, Ne, Ar, Kr, and Xe) were investigated using the following method: Becke-3-parameter-Lee-Yang-Parr (B3LYP), Boese-Matrin for Kinetics (BMK), second-order Møller-Plesset perturbation theory (MP2), and coupled-cluster with single and double excitations as well as perturbative inclusion of triples (CCSD(T)). The results indicate that HHeNH3(+), HArNH3(+), HKrNH3(+), and HXeNH3(+) ions are metastable species that are protected from decomposition by high energy barriers, whereas the HNeNH3(+) ion is unstable because of its relatively small energy barrier for decomposition. The bonding nature of noble-gas atoms in HNgNH3(+) was also analyzed using the atoms in molecules approach, natural energy decomposition analysis, and natural bond orbital analysis. PMID:25877572

  20. Theoretical investigation of HNgNH3+ ions (Ng = He, Ne, Ar, Kr, and Xe)

    NASA Astrophysics Data System (ADS)

    Gao, Kunqi; Sheng, Li

    2015-04-01

    The equilibrium geometries, harmonic frequencies, and dissociation energies of HNgNH3+ ions (Ng = He, Ne, Ar, Kr, and Xe) were investigated using the following method: Becke-3-parameter-Lee-Yang-Parr (B3LYP), Boese-Matrin for Kinetics (BMK), second-order Møller-Plesset perturbation theory (MP2), and coupled-cluster with single and double excitations as well as perturbative inclusion of triples (CCSD(T)). The results indicate that HHeNH3+, HArNH3+, HKrNH3+, and HXeNH3+ ions are metastable species that are protected from decomposition by high energy barriers, whereas the HNeNH3+ ion is unstable because of its relatively small energy barrier for decomposition. The bonding nature of noble-gas atoms in HNgNH3+ was also analyzed using the atoms in molecules approach, natural energy decomposition analysis, and natural bond orbital analysis.

  1. Observational constraints on solar nebula nitrogen chemistry - N2/NH3

    NASA Technical Reports Server (NTRS)

    Womack, Maria; Wyckoff, Susan; Ziurys, L. M.

    1992-01-01

    Observations of N2(+) and NH2 in Comet Halley and N2H(+) and NH3 in nine Galactic star-forming regions are used to determine the average N2/NH3 abundance ratio in these objects. For Comet Halley, N2/NH3 of about 0.1 is found, and for the quiescent gas in a sample of star-forming regions, N2/NH3 of about 170 +/- 100. The cometary N2/NH3 ratio corrected for gas-phase elemental nitrogen depletion in Comet Halley indicates that the gas component in the comet-forming region of the solar nebula was N2/NH3 of about 4. It is concluded that more realistic models which include condensation fractionation effects are required before the N2 and NH3 abundances in comet volatiles can be related to star-forming regions.

  2. Elevated CO2 decreases the Photorespiratory NH3 production but does not decrease the NH3 compensation point in rice leaves.

    PubMed

    Miyazawa, Shin-Ichi; Hayashi, Kentaro; Nakamura, Hirofumi; Hasegawa, Toshihiro; Miyao, Mitsue

    2014-09-01

    The exchange of gaseous NH3 between the atmosphere and plants plays a pivotal role in controlling the global NH3 cycle. Photorespiration generates NH3 through oxygenation instead of carboxylation by the CO2-fixing enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). The future increase in the atmospheric CO2 concentration, [CO2], is expected to reduce plant NH3 production by suppressing RuBisCO oxygenation (Vo). We measured the net leaf NH3 uptake rate (FNH3) across NH3 concentrations in the air (na) ranging from 0.2 to 1.6 nmol mol(-1) at three [CO2] values (190, 360 and 750 µmol mol(-1)) using rice plants. We analyzed leaf NH3 gas exchange using a custom-made whole-leaf chamber system, and determined the NH3 compensation point (γ), a measure of potential NH3 emission, as the x-intercept of the linear relationship of FNH3 as a function of na. Our γ values were lower than those reported for other plant species. γ did not decrease under elevated [CO2], although leaf NH4 (+) content decreased with decreasing Vo at higher [CO2]. This was also the case for γ estimated from the pH and NH4 (+) concentration of the leaf apoplast solution (γ'). γ' of rice plants, grown at elevated [CO2] for months in a free-air CO2 enrichment facility, was also not decreased by elevated [CO2]. These results suggest that suppression of RuBisCO oxygenation by elevated [CO2] does not decrease potential leaf NH3 emission in rice plants. PMID:24951312

  3. A model of nitrogen isotope fractionation during leaf-atmosphere NH3(g) exchange

    NASA Astrophysics Data System (ADS)

    Johnson, J. E.; Field, C. B.; Berry, J. A.

    2012-12-01

    To date, the isotopic composition of NH3(g) in the atmosphere has been ascribed to two processes: volatilization from soils that generates isotopically depleted ammonia and precipitation events that scavenge isotopically enriched ammonium and deposit it to the land surface, leaving residual, isotopically depleted ammonia aloft. Here, we present a mathematical model describing nitrogen isotope fractionation during exchange between NH3(aq) in leaves and NH3(g) in the atmosphere. Two approaches are used to derive the model. The first is a classical, substitution-based method that yields only the equilibrium solution. The second is a matrix-based method that also yields the complete solution. With both approaches, the model predicts that efflux of NH3(g) from leaves isotopically depletes atmospheric NH3(g), whereas uptake isotopically enriches residual atmospheric NH3(g). When there is bidirectional exchange of NH3(g) (i.e., when atmospheric NH3(g) is close to the foliar NH3(g) compensation point), the model predicts that atmospheric NH3(g) can become either isotopically enriched or depleted. These results suggest that exchange between NH3(aq) in leaves and NH3(g) in the atmosphere contributes to variation in the nitrogen isotopic composition of NH3(g) in the atmosphere as well as organic nitrogen in plants, and should be considered in analyses of the distribution of nitrogen isotopes at natural abundance and tracer levels. Thus, the model may be useful for distinguishing between multiple sources and sinks for ammonia in the atmosphere, studying processes within the atmospheric reactive nitrogen cycle, and interpreting records of the isotopic composition of nitrogen-containing atmospheric gases (e.g., N2O) and particles (e.g., NH4+ and NO3- aerosols). In addition, the matrix-based modeling approach that is introduced may be useful for quantifying isotope dynamics in other complex systems in which the classical approach for determining equilibrium solutions becomes unwieldy, or dynamics are of particular interest.

  4. Structure-Activity Relationships in NH3-SCR over Cu-SSZ-13 as Probed by Reaction Kinetics and EPR Studies

    SciTech Connect

    Gao, Feng; Walter, Eric D.; Karp, Eric M.; Luo, Jin-Yong; Tonkyn, Russell G.; Kwak, Ja Hun; Szanyi, Janos; Peden, Charles HF

    2013-04-01

    Cu-SSZ-13 catalysts with various Cu loadings were prepared via solution ion exchange. The hydrated samples were studied with Electron Paramagnetic Resonance (EPR). Cu2+ ion coordination numbers were obtained by analyzing the hyperfine structures while Cu-Cu distances were estimated from line broadening of the EPR features. By coupling EPR and temperature-programmed reduction (TPR) results, two Cu2+ ion locations were suggested. Standard and fast NH3-SCR, as well as non-selective NH3 oxidation reactions were carried out over these catalysts at high space velocities. For the SCR reaction, intra-particle diffusion limitation was found throughout the reaction temperatures investigated. Although clear structure-activity relationships cannot be derived, the reaction results allow for reactant diffusivities and Cu2+ ion locations to be estimated. The slower NH3 oxidation reaction, on the other hand, is kinetically limited at low temperatures, and, therefore, allows for a correlation between Cu2+ ion location and reaction kinetics to be made. Furthermore, the dynamic Cu2+ ion motion as a function of temperature could also be derived from the NH3 oxidation kinetics.

  5. Experimental binding energies for the metal complexes [Mg(NH3)n]2+, [Ca(NH3)n]2+, and [Sr(NH3)n]2+ for n = 4-20 determined from kinetic energy release measurements.

    PubMed

    Bruzzi, E; Raggi, G; Parajuli, R; Stace, A J

    2014-09-18

    A supersonic source of clusters has been used to prepare neutral complexes of ammonia in association with a metal atom. From these complexes the following metal-containing dications have been generated: [Mg(NH3)n](2+), [Ca(NH3)n](2+), and [Sr(NH3)n](2+), and for n in the range 4-20, kinetic energy release measurements following the evaporation of a single molecule have been undertaken using a high resolution mass spectrometer. Using finite heat bath theory, these data have been transformed into binding energies for individual ammonia molecules attached to each of the three cluster systems. In the larger complexes (n > 6) the results exhibit a consistent trend, whereby the experimental binding energy data for all three metal ions are very similar, suggesting that the magnitude of the charge rather than charge density influences the strength of the interaction. From a comparison with data recorded previously for (NH3)nH(+) it is found that the 2+ charge on a metal ion has an effect on the binding energy of molecules in complexes containing up to 20 solvent molecules. Although subject to comparatively large experimental errors, the results recorded for Ca(2+) and Sr(2+) when n ≤ 6 show evidence for the formation of an inner solvation shell containing up to 6 molecules. However, Mg(2+) exhibits relatively low binding energies when n = 5 and 6, which suggests that a second shell starts to form before there are 6 ammonia molecules bound to the metal ion. This conclusion is supported by DFT calculations and it is proposed that these complexes could take the form [Mg(NH3)4(NH3)](2+) when n = 5 and either [Mg(NH3)4(NH3)2](2+) or [Mg(NH3)5(NH3)](2+) when n = 6. In each case, additional molecules are hydrogen bonded to one or more molecules in the inner solvation shell. PMID:24964399

  6. Analyte separation utilizing temperature programmed desorption of a preconcentrator mesh

    DOEpatents

    Linker, Kevin L.; Bouchier, Frank A.; Theisen, Lisa; Arakaki, Lester H.

    2007-11-27

    A method and system for controllably releasing contaminants from a contaminated porous metallic mesh by thermally desorbing and releasing a selected subset of contaminants from a contaminated mesh by rapidly raising the mesh to a pre-determined temperature step or plateau that has been chosen beforehand to preferentially desorb a particular chemical specie of interest, but not others. By providing a sufficiently long delay or dwell period in-between heating pulses, and by selecting the optimum plateau temperatures, then different contaminant species can be controllably released in well-defined batches at different times to a chemical detector in gaseous communication with the mesh. For some detectors, such as an Ion Mobility Spectrometer (IMS), separating different species in time before they enter the IMS allows the detector to have an enhanced selectivity.

  7. Rotational study of the NH3-CO complex: Millimeter-wave measurements and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Surin, L. A.; Potapov, A.; Dolgov, A. A.; Tarabukin, I. V.; Panfilov, V. A.; Schlemmer, S.; Kalugina, Y. N.; Faure, A.; van der Avoird, A.

    2015-03-01

    The rotational spectrum of the van der Waals complex NH3-CO has been measured with the intracavity OROTRON jet spectrometer in the frequency range of 112-139 GHz. Newly observed and assigned transitions belong to the K = 0-0, K = 1-1, K = 1-0, and K = 2-1 subbands correlating with the rotationless (jk)NH3 = 00 ground state of free ortho-NH3 and the K = 0-1 and K = 2-1 subbands correlating with the (jk)NH3 = 11 ground state of free para-NH3. The (approximate) quantum number K is the projection of the total angular momentum J on the intermolecular axis. Some of these transitions are continuations to higher J values of transition series observed previously [C. Xia et al., Mol. Phys. 99, 643 (2001)], the other transitions constitute newly detected subbands. The new data were analyzed together with the known millimeter-wave and microwave transitions in order to determine the molecular parameters of the ortho-NH3-CO and para-NH3-CO complexes. Accompanying ab initio calculations of the intermolecular potential energy surface (PES) of NH3-CO has been carried out at the explicitly correlated coupled cluster level of theory with single, double, and perturbative triple excitations and an augmented correlation-consistent triple zeta basis set. The global minimum of the five-dimensional PES corresponds to an approximately T-shaped structure with the N atom closest to the CO subunit and binding energy De = 359.21 cm-1. The bound rovibrational levels of the NH3-CO complex were calculated for total angular momentum J = 0-6 on this intermolecular potential surface and compared with the experimental results. The calculated dissociation energies D0 are 210.43 and 218.66 cm-1 for ortho-NH3-CO and para-NH3-CO, respectively.

  8. Rotational study of the NH3-CO complex: millimeter-wave measurements and ab initio calculations.

    PubMed

    Surin, L A; Potapov, A; Dolgov, A A; Tarabukin, I V; Panfilov, V A; Schlemmer, S; Kalugina, Y N; Faure, A; van der Avoird, A

    2015-03-21

    The rotational spectrum of the van der Waals complex NH3-CO has been measured with the intracavity OROTRON jet spectrometer in the frequency range of 112-139 GHz. Newly observed and assigned transitions belong to the K = 0-0, K = 1-1, K = 1-0, and K = 2-1 subbands correlating with the rotationless (jk)NH3 = 00 ground state of free ortho-NH3 and the K = 0-1 and K = 2-1 subbands correlating with the (jk)NH3 = 11 ground state of free para-NH3. The (approximate) quantum number K is the projection of the total angular momentum J on the intermolecular axis. Some of these transitions are continuations to higher J values of transition series observed previously [C. Xia et al., Mol. Phys. 99, 643 (2001)], the other transitions constitute newly detected subbands. The new data were analyzed together with the known millimeter-wave and microwave transitions in order to determine the molecular parameters of the ortho-NH3-CO and para-NH3-CO complexes. Accompanying ab initio calculations of the intermolecular potential energy surface (PES) of NH3-CO has been carried out at the explicitly correlated coupled cluster level of theory with single, double, and perturbative triple excitations and an augmented correlation-consistent triple zeta basis set. The global minimum of the five-dimensional PES corresponds to an approximately T-shaped structure with the N atom closest to the CO subunit and binding energy De = 359.21 cm(-1). The bound rovibrational levels of the NH3-CO complex were calculated for total angular momentum J = 0-6 on this intermolecular potential surface and compared with the experimental results. The calculated dissociation energies D0 are 210.43 and 218.66 cm(-1) for ortho-NH3-CO and para-NH3-CO, respectively. PMID:25796250

  9. The selective catalytic reduction of NO with NH3 over a novel Ce-Sn-Ti mixed oxides catalyst: Promotional effect of SnO2

    NASA Astrophysics Data System (ADS)

    Yu, Ming'e.; Li, Caiting; Zeng, Guangming; Zhou, Yang; Zhang, Xunan; Xie, Yin'e.

    2015-07-01

    A series of novel catalysts (CexSny) for the selective catalytic reduction of NO by NH3 were prepared by the inverse co-precipitation method. The aim of this novel design was to improve the NO removal efficiency of CeTi by the introduction of SnO2. It was found that the Ce-Sn-Ti catalyst was much more active than Ce-Ti and the best Ce:Sn molar ratio was 2:1. Ce2Sn1 possessed a satisfied NO removal efficiency at low temperature (160-280 °C), while over 90% NO removal efficiency maintained in the temperature range of 280-400 °C at the gas hourly space velocity (GHSV) of 50,000 h-1. Besides, Ce2Sn1 kept a stable NO removal efficiency within a wide range of GHSV and a long period of reacting time. Meanwhile, Ce2Sn1 exhibited remarkable resistance to both respectively and simultaneously H2O and SO2 poisoning due to the introduction of SnO2. The promotional effect of SnO2 was studied by N2 adsorption-desorption, X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS) and H2 temperature programmed reduction (H2-TPR) for detail information. The characterization results revealed that the excellent catalytic performance of Ce2Sn1 was associated with the higher specific surface area, larger pore volume and poorer crystallization. Besides, the introduction of SnO2 could result in not only greater conversion of Ce4+ to Ce3+ but also the increase amount of chemisorbed oxygen, which are beneficial to improve the SCR activity. More importantly, a novel peak appearing at lower temperatures through the new redox equilibrium of 2Ce4+ + Sn2+ ↔ 2Ce3+ + Sn4+ and higher total H2 consumption can be obtained by the addition of SnO2. Finally, the possible reaction mechanism of the selective catalytic reduction over Ce2Sn1 was also proposed.

  10. Measurements of NH3 absorption coefficients with a C-13/O-16/2 laser

    NASA Technical Reports Server (NTRS)

    Allario, F.; Seals, R. K., Jr.

    1975-01-01

    Measurements of NH3 absorption coefficients are presented for several transitions of a C-13(O-16)2 laser for small concentrations of NH3(p less than 1 torr) for absorption lines broadened to 1 atm with N2. NH3 absorption coefficients were determined for laser transitions R(8)(920.2194 wavelengths/cm) to R(28)(933.8808 wavelengths/cm) of the 00 1 - (10 0,02 0)I band. The strongest absorption coefficient K = 36.09 + or - 1.43 per (atm-cm) was measured for the R(18) transition for the NH3 line, aQ(6,6), and is larger than has been found in any previous measurements with a CO2 laser. The dependence of K on total pressure was also obtained for select transitions, and the frequency separation between the R(18) laser transition and the neighboring NH3 line aQ(6,6) was determined to be 550 + or - 50 MHz. These results are significant for long path absorption monitoring of NH3 with CO2 lasers since the path length can be reduced by approximately 40% and for heterodyne detection of NH3 since the relative position of the laser transition to the NH3 absorption line is well within the bandpass of Hg-Cd-Te photomixers.

  11. Conformational Transformations of (C12 H25 NH3 (+) )(Pyridinesulfonate) in the Solid State.

    PubMed

    Funada, Atsushi; Uchikawa, Shota; Hoshino, Norihisa; Takeda, Takashi; Akutagawa, Tomoyuki

    2016-03-18

    The phase-transition behaviors, crystal structures, and dielectric properties of four kinds of simple 1:1 organic salts of (C12 H25 NH3 (+) )(benzenesulfonate) and (C12 H25 NH3 (+) )(pyridine sulfonates) were examined from the viewpoint of intermolecular hydrogen-bonding interactions and dynamic conformational transformation in molecular assemblies. Crystals of (C12 H25 NH3 (+) )(benzenesulfonate) and (C12 H25 NH3 (+) )(3-pyridinesulfonate) were isostructural and solid-solid and solid-liquid-crystal smectic A (SmA) phase transitions were observed. These two crystals formed rodlike cation-anion assemblies. However, the two salts, (C12 H25 NH3 (+) )(2-pyridinesulfonate) and (C12 H25 NH3 (+) )(4-pyridinesulfonate), formed largely bent L-shaped cation-anion conformations. Interesting conformational transformations from rodlike to L-shaped assemblies were observed in (C12 H25 NH3 (+) )(2-pyridinesulfonate) and (C12 H25 NH3 (+) )(3-pyridinesulfonate). PMID:26781846

  12. Urban NH3 levels and sources in six major Spanish cities.

    PubMed

    Reche, Cristina; Viana, Mar; Karanasiou, Angeliki; Cusack, Michael; Alastuey, Andrés; Artiñano, Begoña; Revuelta, M Aranzazu; López-Mahía, Purificación; Blanco-Heras, Gustavo; Rodríguez, Sergio; Sánchez de la Campa, Ana M; Fernández-Camacho, Rocío; González-Castanedo, Yolanda; Mantilla, Enrique; Tang, Y Sim; Querol, Xavier

    2015-01-01

    A detailed spatial and temporal assessment of urban NH3 levels and potential emission sources was made with passive samplers in six major Spanish cities (Barcelona, Madrid, A Coruña, Huelva, Santa Cruz de Tenerife and Valencia). Measurements were conducted during two different periods (winter-autumn and spring-summer) in each city. Barcelona showed the clearest spatial pattern, with the highest concentrations in the old city centre, an area characterised by a high population density and a dense urban architecture. The variability in NH3 concentrations did not follow a common seasonal pattern across the different cities. The relationship of urban NH3 with SO2 and NOX allowed concluding on the causes responsible for the variations in NH3 levels between measurement periods observed in Barcelona, Huelva and Madrid. However, the factors governing the variations in A Coruña, Valencia and Santa Cruz de Tenerife are still not fully understood. This study identified a broad variability in NH3 concentrations at the city-scale, and it confirms that NH3 sources in Spanish urban environments are vehicular traffic, biological sources (e.g. garbage containers), wastewater treatment plants, solid waste treatment plants and industry. The importance of NH3 monitoring in urban environments relies on its role as a precursor of secondary inorganic species and therefore PMX. Further research should be addressed in order to establish criteria to develop and implement mitigation strategies for cities, and to include urban NH3 sources in the emission inventories. PMID:25194477

  13. Ultrafast and sensitive room temperature NH3 gas sensors based on chemically reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Hu, Nantao; Yang, Zhi; Wang, Yanyan; Zhang, Liling; Wang, Ying; Huang, Xiaolu; Wei, Hao; Wei, Liangmin; Zhang, Yafei

    2014-01-01

    Ultrafast and sensitive room temperature NH3 gas sensors based on chemically reduced graphene oxide (rGO) are demonstrated in this work. rGO, which was prepared via the reduction of graphene oxide by pyrrole, exhibited excellent responsive sensitivity and selectivity to ammonia (NH3) gas. The high sensing performance of these rGO sensors with resistance change as high as 2.4% and response time as fast as 1.4 s was realized when the concentration of NH3 gas was as low as 1 ppb. Furthermore, the rGO sensors could rapidly recover to their initial states with IR illumination. The devices also showed excellent repeatability and selectivity to NH3. These rGO sensors, with low cost, low power, and easy fabrication, as well as scalable properties, showed great potential for ultrasensitive detection of NH3 gas in a wide variety of fields.

  14. Ultrafast and sensitive room temperature NH3 gas sensors based on chemically reduced graphene oxide.

    PubMed

    Hu, Nantao; Yang, Zhi; Wang, Yanyan; Zhang, Liling; Wang, Ying; Huang, Xiaolu; Wei, Hao; Wei, Liangmin; Zhang, Yafei

    2014-01-17

    Ultrafast and sensitive room temperature NH3 gas sensors based on chemically reduced graphene oxide (rGO) are demonstrated in this work. rGO, which was prepared via the reduction of graphene oxide by pyrrole, exhibited excellent responsive sensitivity and selectivity to ammonia (NH3) gas. The high sensing performance of these rGO sensors with resistance change as high as 2.4% and response time as fast as 1.4 s was realized when the concentration of NH3 gas was as low as 1 ppb. Furthermore, the rGO sensors could rapidly recover to their initial states with IR illumination. The devices also showed excellent repeatability and selectivity to NH3. These rGO sensors, with low cost, low power, and easy fabrication, as well as scalable properties, showed great potential for ultrasensitive detection of NH3 gas in a wide variety of fields. PMID:24334417

  15. Phase transition, thermal dissociation and dynamics of NH3 ligands in [Cd(NH3)4](ReO4)2.

    PubMed

    Hetmańczyk, Łukasz; Hetmańczyk, Joanna

    2016-07-01

    High temperature phase transition in [Cd(NH3)4](ReO4)2 at Tc=368.5K (on heating) was reported for the first time. Thermal stability was investigated by thermal analysis methods. The titled compound decomposes in three main stages. The first two are connected with deamination process whereas in the last step Re2O7 evaporates. The activation energy for NH3 lost processes was estimated from TG measurements. The dynamics of NH3 ligands in the low temperature phase was probed by various complementary techniques. Temperature dependent band shape analysis of properly chosen infrared and Raman scattering vibrational bands was performed. It was found that activation energy for NH3 reorientational motion (below 300K) is rather small and is equal to ca. 4kJmol(-1). The quasielastic neutron scattering measurements revealed that NH3 groups perform fast stochastic reorientational motion even in the low temperatures. The neutron and X-ray powder diffraction data do not revealed any drastic changes in the crystal structure in the wide temperature range. PMID:27070528

  16. Seasonal NH 3 emissions for the continental united states: Inverse model estimation and evaluation

    NASA Astrophysics Data System (ADS)

    Gilliland, Alice B.; Wyat Appel, K.; Pinder, Robert W.; Dennis, Robin L.

    Significant uncertainty exists in the seasonal distribution of NH 3 emissions since the predominant sources are animal husbandry and fertilizer application. Previous studies that estimated bottom-up and top-down NH 3 emissions have provided the most comprehensive information available about the seasonality of NH 3 emissions. In this study, this bottom-up and top-down emission information is combined with the most recent 2001 USEPA National Emission Inventory (NEI) to construct a best prior estimate of seasonal NH 3 emissions. These emission estimates are then used in an annual 2001 USEPA Community Multiscale Air Quality (CMAQ) model simulation for the continental United States. A key objective of this study is to evaluate these prior NH 3 emission estimates and test the top-down inverse modeling method for a different year and a larger modeling domain than used previously. Based on the final posterior NH 3 emission estimates, the inverse modeling results suggest that the annual total NEI NH 3 emissions are reasonable and that a previous high bias in older USEPA emission inventories has been addressed in the updated inventory. Inverse modeling results suggest that the prior NH 3 emission estimates should be increased in the summer and decreased in the winter, while results for the spring and fall are questionable due to precipitation prediction biases. A final conclusion from this study is that total NH x (NH 3 and aerosol NH 4+) air concentration data are essential for quantitative top-down analyses of NH 3 emissions that can extend beyond what is possible using precipitation chemistry data.

  17. Photosynthesis of Quercus suber is affected by atmospheric NH3 generated by multifunctional agrosystems.

    PubMed

    Pintó-Marijuan, Marta; Da Silva, Anabela Bernardes; Flexas, Jaume; Dias, Teresa; Zarrouk, Olfa; Martins-Loução, Maria Amélia; Chaves, Maria Manuela; Cruz, Cristina

    2013-12-01

    Montados are evergreen oak woodlands dominated by Quercus species, which are considered to be key to biodiversity conservation and ecosystem services. This ecosystem is often used for cattle breeding in most regions of the Iberian Peninsula, which causes plants to receive extra nitrogen as ammonia (NH(3)) through the atmosphere. The effect of this atmospheric NH(3) (NH(3atm)) on ecosystems is still under discussion. This study aimed to evaluate the effects of an NH(3atm) concentration gradient downwind of a cattle barn in a Montado area. Leaves from the selected Quercus suber L. trees along the gradient showed a clear influence of the NH(3) on δ(13)C, as a consequence of a strong limitation on the photosynthetic machinery by a reduction of both stomatal and mesophyll conductance. A detailed study of the impact of NH(3atm) on the photosynthetic performance of Q. suber trees is presented, and new mechanisms by which NH(3) affects photosynthesis at the leaf level are suggested. PMID:24150034

  18. Towards validation of ammonia (NH3) measurements from the IASI satellite

    NASA Astrophysics Data System (ADS)

    Van Damme, M.; Clarisse, L.; Dammers, E.; Liu, X.; Nowak, J. B.; Clerbaux, C.; Flechard, C. R.; Galy-Lacaux, C.; Xu, W.; Neuman, J. A.; Tang, Y. S.; Sutton, M. A.; Erisman, J. W.; Coheur, P. F.

    2014-12-01

    Limited availability of ammonia (NH3) observations is currently a barrier for effective monitoring of the nitrogen cycle. It prevents a full understanding of the atmospheric processes in which this trace gas is involved and therefore impedes determining its related budgets. Since the end of 2007, the Infrared Atmospheric Sounding Interferometer (IASI) satellite has been observing NH3 from space at a high spatiotemporal resolution. This valuable data set, already used by models, still needs validation. We present here a first attempt to validate IASI-NH3 measurements using existing independent ground-based and airborne data sets. The yearly distributions reveal similar patterns between ground-based and space-borne observations and highlight the scarcity of local NH3 measurements as well as their spatial heterogeneity and lack of representativity. By comparison with monthly resolved data sets in Europe, China and Africa, we show that IASI-NH3 observations are in fair agreement but that they are characterized by a smaller variation in concentrations. The use of hourly and airborne data sets to compare with IASI individual observations allows to investigate the impact of averaging as well as the representativity of independent observations for the satellite footprint. The importance of considering the latter and the added value of densely located airborne measurements at various altitudes to validate IASI-NH3 columns are discussed. Perspectives and guidelines for future validation work on NH3 satellite observations are presented.

  19. Towards validation of ammonia (NH3) measurements from the IASI satellite

    NASA Astrophysics Data System (ADS)

    Van Damme, M.; Clarisse, L.; Dammers, E.; Liu, X.; Nowak, J. B.; Clerbaux, C.; Flechard, C. R.; Galy-Lacaux, C.; Xu, W.; Neuman, J. A.; Tang, Y. S.; Sutton, M. A.; Erisman, J. W.; Coheur, P. F.

    2015-03-01

    Limited availability of ammonia (NH3) observations is currently a barrier for effective monitoring of the nitrogen cycle. It prevents a full understanding of the atmospheric processes in which this trace gas is involved and therefore impedes determining its related budgets. Since the end of 2007, the Infrared Atmospheric Sounding Interferometer (IASI) satellite has been observing NH3 from space at a high spatio-temporal resolution. This valuable data set, already used by models, still needs validation. We present here a first attempt to validate IASI-NH3 measurements using existing independent ground-based and airborne data sets. The yearly distributions reveal similar patterns between ground-based and space-borne observations and highlight the scarcity of local NH3 measurements as well as their spatial heterogeneity and lack of representativity. By comparison with monthly resolved data sets in Europe, China and Africa, we show that IASI-NH3 observations are in fair agreement, but they are characterized by a smaller variation in concentrations. The use of hourly and airborne data sets to compare with IASI individual observations allows investigations of the impact of averaging as well as the representativity of independent observations for the satellite footprint. The importance of considering the latter and the added value of densely located airborne measurements at various altitudes to validate IASI-NH3 columns are discussed. Perspectives and guidelines for future validation work on NH3 satellite observations are presented.

  20. Rotational Dynamics of Organic Cations in CH3NH3PbI3 Perovskite

    NASA Astrophysics Data System (ADS)

    Chen, Tianran; Foley, Benjamin; Ipek, Bahar; Tyagi, Madhusudan; Copley, John; Brown, Craig; Choi, Joshua; Lee, Seung-Hun

    Methylammonium lead iodide (CH3NH3PbI3) based solar cells have shown impressive power conversion efficiencies of above 20%. However, the microscopic mechanism of the high photovoltaic performance is yet to be fully understood. Particularly, the dynamics of CH3NH3+ cations and their impact on relevant processes are still poorly understood. Using elastic and quasi-elastic neutron scattering techniques and group theoretical analysis, we studied rotational modes of the CH3NH3+ cation in CH3NH3PbI3. Our results show that, in the cubic and tetragonal phases, the CH3NH3+ ions exhibit four-fold rotational symmetry of the C-N axis (C4) along with three-fold rotation around the C-N axis (C3) , while in orthorhombic phase only C3 rotation is present. Around room temperature, the characteristic relaxation time for the C4 rotation is found to be 5ps while for the C3 rotation is 1ps. The T-dependent rotational relaxation times were fitted with Arrhenius equations to obtain activation energies. Our data show a close correlation between the C4 rotational mode and the temperature dependent dielectric permittivity. Our findings on the rotational dynamics of CH3NH3+ and the associated dipole have important implications on understanding the low exciton binding energy and slow charge recombination rate in CH3NH3PbI3 which are directly relevant for the high solar cell performance.

  1. NH3 Emission from Fertilizer Application: A Collaborative Study in the Midwestern U.S.

    NASA Astrophysics Data System (ADS)

    Myles, L.; Koloutsou-Vakakis, S.; Bernacchi, C.; Lehmann, C.; Saylor, R. D.; Heuer, M.; Sibble, D.; Caldwell, J. A.; Balasubramanian, S.; Nelson, A. J.; Rood, M. J.

    2014-12-01

    Atmospheric ammonia (NH3) is a precursor for secondary particulate matter and a contributor to soil acidification and eutrophication when deposited to land and surface waters. Fertilizer application is a major source of atmospheric NH3, particularly in intensive agricultural regions such as the Midwestern U.S. Quantification of NH3 emission from fertilized crops remains highly uncertain, which limits the representativeness of NH3 emissions that are used in air quality models. A collaborative study to improve understanding of NH3 emission from fertilizer application focused on [1] measurement of above-canopy NH3 fluxes from a fertilized corn field in Illinois using the relaxed eddy accumulation (REA) and flux gradient methods and in-canopy fluxes with the inverse Lagrangian dispersion analysis method, [2] estimation of NH3 emissions at the regional scale using a process-based approach with available archived independent variables, and the currently used top-down approach, in order to compare and determine differences in predicted spatial and temporal variability of NH3 emissions, and [3] performance of spatial analysis to determine spatial and temporal patterns of ammonia emissions and relate them to independent variables characteristic of land use, soil, meteorology, and agricultural management practices. NH3 flux was measured over and within a maize canopy from pre-cultivation through senescence (May-September 2014) at the University of Illinois at Urbana-Champaign (UIUC) Energy Biosciences Institute Energy Farm, and data from the field study was incorporated into models to facilitate connection of local emissions with the regional scale and to improve understanding of the processes that drive emission and deposition.

  2. Field measurements and recent advances in detection of NH3 and HNO3

    NASA Astrophysics Data System (ADS)

    Roscioli, J. R.; Herndon, S. C.; Nowak, J. B.; Zahniser, M. S.; Nelson, D. D.

    2014-12-01

    Ammonia and nitric acid play important roles in aerosol, cloud, and OH chemistry. Presented here are results from several field studies of HNO3 and NH3 sources in the mid- and southwestern United States. Particular focus is paid to NH3 emissions from farming and feedlot operations, and airborne HNO3 measurements over the Denver Metro area. Accurately measuring these species' concentrations on a fast timescale has historically been complicated due to their tendency to slowly and irreversibly interact with instrument surfaces. Recent efforts aimed at mitigating these effects using new inlet technologies will be presented, with demonstrations of time responses of ~1 second for both NH3 and HNO3.

  3. Shock-excited NH3 (3, 3) masers in the NGC 6334 star-forming region

    NASA Technical Reports Server (NTRS)

    Kraemer, Kathleen E.; Jackson, James M.

    1995-01-01

    We report the discovery of four NH3 (3, 3) masers in the NGC 6334 star formation region. The masers are found in two of the seven far-infrared continuum sources where high-mass star formation is taking place in this molecular cloud. These masers occur at the ends of high-velocity molecular outflows; no maser emission was found near regions without high-velocity outflows. The NH3 masers are not associated with any other type of maser. These results confirm that the NH3 (3, 3) masers are caused by shocks and probably mark the location where the molecular outflow jet impinges upon the ambient medium.

  4. Photolysis of CO-NH3 mixtures and the Martian atmosphere

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Williams, E. A.; Nicodem, D. E.; Hubbard, J. S.; Voecks, G. E.

    1974-01-01

    It has already been noted (Ferris and Nicodem, 1972) that although neither CO2 nor H2O affected the rate of NH3 photolysis, CO accelerated the photodecomposition of ammonia, with the formation of a solid product. The photolysis of NH3 in the presence of CO is investigated in greater detail not only because of the potential significance to atmospheric photochemistry on Mars, but also because of the possibility of photocatalytic reactions of NH3 and CO on the Martian surface and in the interstellar medium. These photoreactions may also have occurred on the primitive earth.

  5. Laser-Induced Reactivity of NH_3 on GaAs Surface

    NASA Astrophysics Data System (ADS)

    Vivet, L.; Dubreuil, B.; Gibert-Legrand, T.; Barthe, M. F.; Perrin, C.

    1997-01-01

    We have studied the reactivity of NH3 on GaAs (100) surface irradiated by 280 nm laser beam at low fluence (< 50 mJ cm^{-2} per pulse) in an experimental set-up which allows a very sensitive characterization of the surface state using mass spectrometry. Thanks to this analysis technique we could follow desorbed NHx (x = 2, 3) species during the laser treatment; this phase achieved, GaN^+ could be identified as an evidence of N fixation using laser desorption mass spectrometry of the treated surface. This characterization mode demonstrates the fluence and laser shot number dependencies on laser treatment efficiency. At 280 nm the N fixation is maximum for laser fluence of about 25 mJ cm^{-2} (per pulse). Still even in the best nitridation conditions, the process appears to be of little efficiency, since it leads to the formation of less than one monolayer of GaN. These results combined with a numerical model of GaAs laser heating give evidence for the laser-induced nitridation to be thermally assisted. Nous avons étudié la réactivité de NH3 sur la surface d'un échantillon de GaAs irradié par un faisceau laser UV (280 nm) de faible fluence (< 50 mJ cm^{-2}). Les expériences ont été menées dans un dispositif expérimental utilisant la spectrométrie de masse et permettant une caractérisation présise de l'état de la surface. Grâce à cette technique d'analyse nous avons pu suivre les espèces NHx^+ (x = 2, 3) désorbées pendant le traitement laser, cette étape terminée, nous avons détecté, par la spectrométrie de masse associée à la désorption laser, les ions GaN^+ émis depuis la surface traitée, ils indiquent que la nitruration de GaAs s'est bien produite pendant le traitement. Cette technique de caractérisation nous a permis d'étudier l'influence de la fluence et du nombre de tirs laser sur l'efficacité du traitement. À 280 nm l'efficacité de la nitruration assistée par laser du GaAs est maximum pour une fluence laser proche de 25 mJ cm^{-2} (par tir). Cependant même dans les conditions optimales de nitruration, le processus apparaît peu efficace puisqu'il conduit à la formation de moins d'une monocouche de GaN. Ces résultats expérimentaux couplés à un modèle numérique du chauffage laser de GaAs ont montré que le laser produit, pour les réactions de surface, des effets essentiellement thermiques proches de ceux obtenus par un chauffage conventionnel, lent, du substrat de GaAs.

  6. 3-D agricultural air quality modeling: Impacts of NH3/H2S gas-phase reactions and bi-directional exchange of NH3

    NASA Astrophysics Data System (ADS)

    Wang, Kai; Zhang, Yang

    2014-12-01

    Accurately simulating the transport and fate of reduced nitrogen (NHx = ammonia (NH3) + ammonium (NH4+))- and sulfur-containing compounds emitted from agricultural activities represents a major challenge in agricultural air quality modeling. In this study, the Community Multiscale Air Quality (CMAQ) modeling system is further developed and improved by implementing 22 ammonia (NH3)/hydrogen sulfide (H2S) related gas-phase reactions and adjusting a few key parameters (e.g., emission potential) for bi-directional exchange of NH3 fluxes. Several simulations are conducted over the eastern U.S. domain at a 12-km horizontal resolution for January and July 2002 to examine the impacts of those improved treatments on air quality. The 5th generation mesoscale model (MM5) and CMAQ predict an overall satisfactory and consistent performance with previous modeling studies, especially for 2-m temperature, 2-m relative humidity, ozone (O3), and fine particulate matter (PM2.5). High model biases exist for precipitation in July and also dry/wet depositions. The updated model treatments contribute to O3, NHx, and PM2.5 by up to 0.4 ppb, 1.0 μg m-3, and 1.0 μg m-3 in January, respectively, and reduce O3 by up to 0.8 ppb and contribute to NHx and PM2.5 by up to 1.2 and 1.1 μg m-3 in July, respectively. The spatial distributions of O3 in both months and sulfur dioxide (SO2) in January are mainly affected by inline dry deposition velocity calculation. The spatial distributions of SO2 and sulfate (SO42-) in July are affected by both inline dry deposition velocity and NH3/H2S reactions. The variation trends of NH3, NHx, ammonium nitrate (NH4NO3), PM2.5 and total nitrogen (TN) are predominated by bi-directional exchange of NH3 fluxes. Uncertainties of NH3 emission potentials and empirical constants used in the bi-directional exchange scheme may significantly affect the concentrations of NHx and PM2.5, indicating that a more accurate and explicit treatment for those parameters should be considered in the future work.

  7. Cross sections for direct and dissociative ionization of NH3 and CS2 by electron impact

    NASA Technical Reports Server (NTRS)

    Rao, M. V. V. S.; Srivastava, S. K.

    1991-01-01

    A crossed electron beam-molecular beam collision geometry is used to measure cross sections for the production of positive ions by electron impact on NH3 and CS2. Ionization cross-section data for NH3 and the values of various cross sections are presented, as well as ionization efficiency curves for CS2. Considerable differences are found between the various results on NH3. The present values are close to the data of Djuric et al. (1981). The semiempirical calculations of Hare and Meath (1987) differ considerably in the absolute values of cross sections. Discrepancies were observed in comparisons of cross sections of other fragment ions resulting from the ionization and dissociate ionization of NH3.

  8. Indirect measurement of N-14 quadrupolar coupling for NH3 intercalated in potassium graphite

    NASA Technical Reports Server (NTRS)

    Tsang, T.; Fronko, R. M.; Resing, H. A.

    1987-01-01

    A method for indirect measurement of the nuclear quadrupolar coupling was developed and applied to NH3 molecules in the graphite intercalation compound K(NH3)4.3C24, which has a layered structure with alternating carbon and intercalant layers. Three triplets were observed in the H-1 NMR spectra of the compound. The value of the N-14 quadrupolar coupling constant of NH3 (3.7 MHz), determined indirectly from the H-1 NMR spectra, was intermediate between the gas value of 4.1 MHz and the solid-state value of 3.2 MHz. The method was also used to deduce the (H-1)-(H-1) and (N-14)-(H-1) dipolar interactions, the H-1 chemical shifts, and the molecular orientations and motions of NH3.

  9. Trigonal-Bipyramidal Coordination in First Ammoniates of ZnF2: ZnF2(NH3)3 and ZnF2(NH3)2.

    PubMed

    Richter, Theresia M M; LeTonquesse, Sylvain; Alt, Nicolas S A; Schlücker, Eberhard; Niewa, Rainer

    2016-03-01

    Single crystals of ZnF2(NH3)3 and ZnF2(NH3)2 were obtained under ammonothermal conditions (250 °C, 196 MPa and 500 °C, 136 MPa). Upon thermal decomposition of both ZnF2(NH3)3 and ZnF2(NH3)2, a microcrystalline powder of ZnF2(NH3) was obtained. ZnF2(NH3)3 and ZnF2(NH3)2 represent probable intermediates in a conceivable ammonothermal synthesis of the semiconductor Zn3N2 and manifest a rare trigonal-bipyramidal coordination of F(-) and NH3 ligands around Zn(2+) according to single-crystal X-ray diffraction. Thermal analysis of all three compounds showed not only ZnF2(NH3) but also ZnF2(NH3)2 to be decomposition intermediates of ZnF2(NH3)3 prior to the formation of ZnF2. All three compounds demonstrate hydrogen bonds, as indicated by the intensities and half-widths of the bands in the vibrational spectra and by short N-H···F distances in the crystal structures of ZnF2(NH3)3 and ZnF2(NH3)2. With ZnF2(NH3)3, ZnF2(NH3)2, and ZnF2(NH3), we present the first ammoniates of ZnF2. PMID:26894942

  10. Global distributions, time series and error characterization of atmospheric ammonia (NH3) from IASI satellite observations

    NASA Astrophysics Data System (ADS)

    Van Damme, M.; Clarisse, L.; Heald, C. L.; Hurtmans, D.; Ngadi, Y.; Clerbaux, C.; Dolman, A. J.; Erisman, J. W.; Coheur, P. F.

    2014-03-01

    Ammonia (NH3) emissions in the atmosphere have increased substantially over the past decades, largely because of intensive livestock production and use of fertilizers. As a short-lived species, NH3 is highly variable in the atmosphere and its concentration is generally small, except near local sources. While ground-based measurements are possible, they are challenging and sparse. Advanced infrared sounders in orbit have recently demonstrated their capability to measure NH3, offering a new tool to refine global and regional budgets. In this paper we describe an improved retrieval scheme of NH3 total columns from the measurements of the Infrared Atmospheric Sounding Interferometer (IASI). It exploits the hyperspectral character of this instrument by using an extended spectral range (800-1200 cm-1) where NH3 is optically active. This scheme consists of the calculation of a dimensionless spectral index from the IASI level1C radiances, which is subsequently converted to a total NH3 column using look-up tables built from forward radiative transfer model simulations. We show how to retrieve the NH3 total columns from IASI quasi-globally and twice daily above both land and sea without large computational resources and with an improved detection limit. The retrieval also includes error characterization of the retrieved columns. Five years of IASI measurements (1 November 2007 to 31 October 2012) have been processed to acquire the first global and multiple-year data set of NH3 total columns, which are evaluated and compared to similar products from other retrieval methods. Spatial distributions from the five years data set are provided and analyzed at global and regional scales. In particular, we show the ability of this method to identify smaller emission sources than those previously reported, as well as transport patterns over the ocean. The five-year time series is further examined in terms of seasonality and interannual variability (in particular as a function of fire activity) separately for the Northern and Southern Hemispheres.

  11. Quantifying Uncertainty in Daily Temporal Variations of Atmospheric NH3 Emissions Following Application of Chemical Fertilizers

    NASA Astrophysics Data System (ADS)

    Balasubramanian, S.; Koloutsou-Vakakis, S.; Rood, M. J.

    2014-12-01

    Improving modeling predictions of atmospheric particulate matter and deposition of reactive nitrogen requires representative emission inventories of precursor species, such as ammonia (NH3). Anthropogenic NH3 is primarily emitted to the atmosphere from agricultural sources (80-90%) with dominant contributions (56%) from chemical fertilizer usage (CFU) in regions like Midwest USA. Local crop management practices vary spatially and temporally, which influence regional air quality. To model the impact of CFU, NH3 emission inputs to chemical transport models are obtained from the National Emission Inventory (NEI). NH3 emissions from CFU are typically estimated by combining annual fertilizer sales data with emission factors. The Sparse Matrix Operator Kernel Emissions (SMOKE) model is used to disaggregate annual emissions to hourly scale using temporal factors. These factors are estimated by apportioning emissions within each crop season in proportion to the nitrogen applied and time-averaged to the hourly scale. Such approach does not reflect influence of CFU for different crops and local weather and soil conditions. This study provides an alternate approach for estimating temporal factors for NH3 emissions. The DeNitrification DeComposition (DNDC) model was used to estimate daily variations in NH3 emissions from CFU at 14 Central Illinois locations for 2002-2011. Weather, crop and soil data were provided as inputs. A method was developed to estimate site level CFU by combining planting and harvesting dates, nitrogen management and fertilizer sales data. DNDC results indicated that annual NH3 emissions were within ±15% of SMOKE estimates. Daily modeled emissions across 10 years followed similar distributions but varied in magnitudes within ±20%. Individual emission peaks on days after CFU were 2.5-8 times greater as compared to existing estimates from SMOKE. By identifying the episodic nature of NH3 emissions from CFU, this study is expected to provide improvements in predicting atmospheric particulate matter concentrations and deposition of reactive nitrogen.

  12. Toxic effects of Zn2+, Cu2+, Cd2+ and NH3 on Chinese prawn

    NASA Astrophysics Data System (ADS)

    Zang, Weiling; Xu, Xuancheng; Dai, Xilin; Zhu, Zhengguo; Xu, Guirong; Xu, Renguo

    1993-09-01

    This study deals with the toxic effects of Zn2+, Cu2+, Cd2+ and NH3 on Chinese prawn ( Penaeus orientalis). The median lethal concentrations of the toxic matters on Chinese prawn were determined. Cd2+>Cu2+>Zn2+>NH3-Nm is the toxic order of these chemicals to Chinese prawn. The toxic order of concentrated Zn2+ and Cd2+ in tissues and organs of Chinese prawn is in the order. gill>shell+appendage>viscera>muscle.

  13. Kinetics of xanthan production when NH3-N limits biomass synthesis and glucose limits polysaccharide synthesis.

    PubMed

    Schweickart, R W; Quinlan, A V

    1989-05-01

    The bacterium Xanthomonas campestris, which synthesizes the commercially important polysaccharide xanthan, was grown aseptically in 1.2 L fermenters using semicontinuous cell culture technique (d' = 0.0035 h-1). The effects of carbon-substrate concentration on xanthan production were investigated at three initial glucose concentrations (Go = 15, 20, 25 g/L). Cell biomass synthesis was nitrogen-limited by use of a chemically defined medium that contained NH3-N as the sole nitrogen source at a concentration where it was exhausted before glucose. A linear relationship between biomass synthesis and NH3-N depletion was observed. This relationship remained valid only until NH3-N exhaustion, after which biomass concentration slowly rose another 20 percent before declining. Another linear relationship was found between xanthan synthesis and glucose uptake. This relationship was unaffected by the disappearance of NH3-N and held through glucose exhaustion. The quasi-stoichiometric yield coefficients obtained for each linear relationship were not affected by G0-. Biomass synthesis kinetics showed no variation with G0 before NH3-N exhaustion; afterwards, cell biomass decline was delayed by increasing G0. Xanthan synthesis kinetics displayed no detectable response to depletion of NH3-N and plateauing of biomass concentration; however, there was a marked slow down in the net rate of xanthan synthesis and a drop in xanthan yield after cell biomass decline became noticeable. PMID:2733412

  14. Improvement of thermal stability of nickel silicide film using NH3 plasma treatment

    NASA Astrophysics Data System (ADS)

    Park, Jingyu; Jeon, Heeyoung; Kim, Hyunjung; Jang, Woochool; Kim, Jinho; Kang, Chunho; Yuh, Junhan; Jeon, Hyeongtag

    2014-09-01

    In this study, the effects of NH3 plasma pre-treatment on the characteristics of NiSi films were investigated. Nickel film was deposited on a Si(100) substrate by meal-organic chemical vapor deposition (MOCVD) using Ni(iPr-DAD)2 as a Ni precursor and NH3 gas as a reactant. Before the Ni deposition, silicon substrate was treated by NH3 plasma with various flow rates to adjust the amount of inserted hydrogen and nitrogen atoms. The Ni films showed a considerable low sheet resistance around 12 Ω/□, irrespective of the NH3 plasma pre-treatment conditions. The sheet resistance of the all Ni films was decreased after annealing at 500 °C due to formation of a low resistive NiSi phase. NiSi films with a high flow rate of NH3 plasma pre-treatment exhibited a lower sheet resistance and smoother interface between NiSi and the Si substrate than the low flow rate of the NH3 plasma pre-treated NiSi films because lots of nitrogen atoms incorporated at grain boundary of NiSi which result in reduce total surface/interface energy of NiSi and enhancement interface characteristics.

  15. Atmospheric NO2 and NH3 deposition into a typical agro-ecosystem in Southeast China.

    PubMed

    Cui, Jian; Zhou, Jing; Yang, Hao; Peng, Ying; He, Yuanqiu; Chan, Andy

    2011-11-01

    The dry deposition of atmospheric nitrogen (including NO(2) and NH(3)) into a typical agro-ecosystem in Southeast China during 2006-2007 was estimated. Results indicated that the dry deposition velocities of NO(2) and NH(3) ranged from 0.04-0.24 cm s(-1) and 0.09-0.47 cm s(-1), respectively. The higher values appeared in the non-crop growing period. Concentrations of atmospheric NO(2) and NH(3) ranged from 24.64-104.10 ?gN m(-3) and 14.40-389.6 ?gN m(-3), respectively. Variation of the NH(3) mixing ratio showed a clear double-peak. NO(2) and NH(3) deposition fluxes were 74.68-80.75 kgN ha(-1), which was equivalent to 162.4 and 175.5 kg ha(-1) of urea applied in 2006-2007. The N deposition fluxes were 13.91-40.38 and 5.33-22.73 kgN ha(-1) in peanut and rice growing periods, accounting for 8.18%-40.38% and 2.13%-23.06% of N fertilizer usages, respectively. NO(2) and NH(3) deposition were significant for the red soil farmland. PMID:21987178

  16. On the Interaction of CO and NH3 with BH3 and BF3

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Ricca, Alessandra; Langhoff, Stephen R. (Technical Monitor)

    1994-01-01

    BH3CO, BF3CO, BH3NH3, and BF3NH3 have been studied using density functional theory (DFT). The computed geometries are in reasonable agreement with experiment. BF3CO is found to be weakly bound. The binding energies of BH3CO, BH3NH3 , and BF3NH3 have also been computed using the coupled cluster singles and doubles level of theory, including a perturbational estimate of the connected triples [CCSD(T)]. These CCSD(T) calculations are performed using correlation consistent polarized-valence triple-zeta basis sets. These are expected to be the most accurate binding energies to date. The DFT binding energies are in good agreement with those obtained at the CCSD(T) level. The bonding is analyzed using the constrained space orbital variation (CSOV) technique. In addition to analyzing the bonding in BH3CO, BH3NH3, and BF3NH3, the CSOV approach is used to study why the bonding in BF3CO is so weak.

  17. Unipolar self-doping behavior in perovskite CH3NH3PbBr3

    NASA Astrophysics Data System (ADS)

    Shi, Tingting; Yin, Wan-Jian; Hong, Feng; Zhu, Kai; Yan, Yanfa

    2015-03-01

    Recent theoretical and experimental reports have shown that the perovskite CH3NH3PbI3 exhibits unique ambipolar self-doping properties. Here, we show by density-functional theory calculation that its sister perovskite, CH3NH3PbBr3, exhibits a unipolar self-doping behavior—CH3NH3PbBr3 presents only good p-type conductivity under thermal equilibrium growth conditions. We further show that despite a large bandgap of 2.2 eV, all dominant defects in CH3NH3PbBr3 create shallow levels, which partially explains the ultra-high open-circuit voltages achieved by CH3NH3PbBr3-based thin-film solar cells. Our results suggest that the perovskite CH3NH3PbBr3 can be both an excellent solar cell absorber and a promising low-cost hole-transport material for lead halide perovskite solar cells.

  18. Dynamics and fragmentation of van der Waals and hydrogen bonded cluster cations: (NH3)n and (NH3BH3)n ionized at 10.51 eV.

    PubMed

    Yuan, Bing; Shin, Joong-Won; Bernstein, Elliot R

    2016-04-14

    A 118 nm laser is employed as a high energy, single photon (10.51 eV/photon) source for study of the dynamics and fragmentation of the ammonia borane (NH3BH3) cation and its cluster ions through time of flight mass spectrometry. The behavior of ammonia ion and its cluster ions is also investigated under identical conditions in order to explicate the ammonia borane results. Charge distributions, molecular orbitals, and spin densities for (NH3BH3)n and its cations are explored at both the second-order perturbation theory (MP2) and complete active space self-consistent field (CASSCF) theory levels. Initial dissociation mechanisms and potential energy surfaces for ionized NH3BH3, NH3, and their clusters are calculated at the MP2/6-311++G(d,p) level. Protonated clusters (NH3)xH(+) dominate ammonia cluster mass spectra: our calculations show that formation of (NH3)n-1H(+) and NH2 from the nascent (NH3)n (+) has the lowest energy barrier for the system. The only common features for the (NH3)n (+) and (NH3BH3)n (+) mass spectra under these conditions are found to be NHy (+) (y = 0,…,4) at m/z = 14-18. Molecular ions with both (11)B and (10)B isotopes are observed, and therefore, product ions observed for the (NH3BH3)n cluster system derive from (NH3BH3)n clusters themselves, not from the NH3 moiety of NH3BH3 alone. NH3BH2 (+) is the most abundant ionization product in the (NH3BH3)n (+) cluster spectra: calculations support that for NH3BH3 (+), an H atom is lost from the BH3 moiety with an energy barrier of 0.67 eV. For (NH3BH3)2 (+) and (NH3BH3)3 (+) clusters, a B(δ+)⋯H(δ-)⋯(δ-)H⋯(δ+)B bond can form in the respective cluster ions, generating a lower energy, more stable ion structure. The first step in the (NH3BH3)n (+) (n = 2, 3) dissociation is the breaking of the B(δ+)⋯H(δ-)⋯(δ-)H⋯(δ+)B moiety, leading to the subsequent release of H2 from the latter cluster ion. The overall reaction mechanisms calculated are best represented and understood employing a CASSCF natural bond orbital description of the valence electron distribution for the various clusters and monomers. Comparison of the present results with those found for solid NH3BH3 suggests that NH3BH3 can be a good hydrogen storage material. PMID:27083729

  19. Dynamics and fragmentation of van der Waals and hydrogen bonded cluster cations: (NH3)n and (NH3BH3)n ionized at 10.51 eV

    NASA Astrophysics Data System (ADS)

    Yuan, Bing; Shin, Joong-Won; Bernstein, Elliot R.

    2016-04-01

    A 118 nm laser is employed as a high energy, single photon (10.51 eV/photon) source for study of the dynamics and fragmentation of the ammonia borane (NH3BH3) cation and its cluster ions through time of flight mass spectrometry. The behavior of ammonia ion and its cluster ions is also investigated under identical conditions in order to explicate the ammonia borane results. Charge distributions, molecular orbitals, and spin densities for (NH3BH3)n and its cations are explored at both the second-order perturbation theory (MP2) and complete active space self-consistent field (CASSCF) theory levels. Initial dissociation mechanisms and potential energy surfaces for ionized NH3BH3, NH3, and their clusters are calculated at the MP2/6-311++G(d,p) level. Protonated clusters (NH3)xH+ dominate ammonia cluster mass spectra: our calculations show that formation of (NH3)n-1H+ and NH2 from the nascent (NH3)n+ has the lowest energy barrier for the system. The only common features for the (NH3)n+ and (NH3BH3)n+ mass spectra under these conditions are found to be NHy+ (y = 0,…,4) at m/z = 14-18. Molecular ions with both 11B and 10B isotopes are observed, and therefore, product ions observed for the (NH3BH3)n cluster system derive from (NH3BH3)n clusters themselves, not from the NH3 moiety of NH3BH3 alone. NH3BH2+ is the most abundant ionization product in the (NH3BH3)n+ cluster spectra: calculations support that for NH3BH3+, an H atom is lost from the BH3 moiety with an energy barrier of 0.67 eV. For (NH3BH3)2+ and (NH3BH3)3+ clusters, a Bδ+⋯Hδ-⋯δ-H⋯δ+B bond can form in the respective cluster ions, generating a lower energy, more stable ion structure. The first step in the (NH3BH3)n+ (n = 2, 3) dissociation is the breaking of the Bδ+⋯Hδ-⋯δ-H⋯δ+B moiety, leading to the subsequent release of H2 from the latter cluster ion. The overall reaction mechanisms calculated are best represented and understood employing a CASSCF natural bond orbital description of the valence electron distribution for the various clusters and monomers. Comparison of the present results with those found for solid NH3BH3 suggests that NH3BH3 can be a good hydrogen storage material.

  20. SEASONAL NH3 EMISSION ESTIMATES FOR THE EASTERN UNITED STATES BASED ON AMMONIUM WET CONCENTRATIONS AND AN INVERSE MODELING METHOD

    EPA Science Inventory

    Significant uncertainty exists in the magnitude and variability of ammonia (NH3) emissions. NH3 emissions are needed as input for air quality modeling of aerosols and deposition of nitrogen compounds. Approximately 85% of NH3 emissions are estimated to come from agricultural ...

  1. Study on adsorption and desorption of ammonia on graphene.

    PubMed

    Zhang, Zhengwei; Zhang, Xinfang; Luo, Wei; Yang, Hang; He, Yanlan; Liu, Yixing; Zhang, Xueao; Peng, Gang

    2015-12-01

    The gas sensor based on pristine graphene with conductance type was studied theoretically and experimentally. The time response of conductance measurements showed a quickly and largely increased conductivity when the sensor was exposed to ammonia gas produced by a bubble system of ammonia water. However, the desorption process in vacuum took more than 1 h which indicated that there was a larger number of transferred carriers and a strong adsorption force between ammonia and graphene. The desorption time could be greatly shortened down to about 2 min by adding the flow of water-vapor-enriched air at the beginning of the recovery stage which had been confirmed as a rapid and high-efficiency desorption process. Moreover, the optimum geometries, adsorption energies, and the charge transfer number of the composite systems were studied with first-principle calculations. However, the theoretical results showed that the adsorption energy between NH3 and graphene was too small to fit for the experimental phenomenon, and there were few charges transferred between graphene and NH3 molecules, which was completely different from the experiment measurement. The adsorption energy between NH4 and graphene increased stage by stage which showed NH4 was a strong donor. The calculation suggested that H2O molecule could help a quick desorption of NH4 from graphene by converting NH4 to NH3 or (NH3)n(H2O)m groups, which was consistent with the experimental results. This study demonstrates that the ammonia gas produced by a bubble system of ammonia water is mainly ammonium groups of NH3 and NH4, and the NH4 moleculars are ideal candidates for the molecular doping of graphene while the interaction between graphene and the NH3 moleculars is weak. PMID:26377212

  2. Study on adsorption and desorption of ammonia on graphene

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengwei; Zhang, Xinfang; Luo, Wei; Yang, Hang; He, Yanlan; Liu, Yixing; Zhang, Xueao; Peng, Gang

    2015-09-01

    The gas sensor based on pristine graphene with conductance type was studied theoretically and experimentally. The time response of conductance measurements showed a quickly and largely increased conductivity when the sensor was exposed to ammonia gas produced by a bubble system of ammonia water. However, the desorption process in vacuum took more than 1 h which indicated that there was a larger number of transferred carriers and a strong adsorption force between ammonia and graphene. The desorption time could be greatly shortened down to about 2 min by adding the flow of water-vapor-enriched air at the beginning of the recovery stage which had been confirmed as a rapid and high-efficiency desorption process. Moreover, the optimum geometries, adsorption energies, and the charge transfer number of the composite systems were studied with first-principle calculations. However, the theoretical results showed that the adsorption energy between NH3 and graphene was too small to fit for the experimental phenomenon, and there were few charges transferred between graphene and NH3 molecules, which was completely different from the experiment measurement. The adsorption energy between NH4 and graphene increased stage by stage which showed NH4 was a strong donor. The calculation suggested that H2O molecule could help a quick desorption of NH4 from graphene by converting NH4 to NH3 or (NH3)n(H2O)m groups, which was consistent with the experimental results. This study demonstrates that the ammonia gas produced by a bubble system of ammonia water is mainly ammonium groups of NH3 and NH4, and the NH4 moleculars are ideal candidates for the molecular doping of graphene while the interaction between graphene and the NH3 moleculars is weak.

  3. Rotational dynamics of organic cations in the CH3NH3PbI3 perovskite.

    PubMed

    Chen, Tianran; Foley, Benjamin J; Ipek, Bahar; Tyagi, Madhusudan; Copley, John R D; Brown, Craig M; Choi, Joshua J; Lee, Seung-Hun

    2015-12-14

    Methylammonium lead iodide (CH3NH3PbI3) based solar cells have shown impressive power conversion efficiencies of above 20%. However, the microscopic mechanism of the high photovoltaic performance is yet to be fully understood. Particularly, the dynamics of CH3NH3(+) cations and their impact on relevant processes such as charge recombination and exciton dissociation are still poorly understood. Here, using elastic and quasi-elastic neutron scattering techniques and group theoretical analysis, we studied rotational modes of the CH3NH3(+) cation in CH3NH3PbI3. Our results show that, in the cubic (T > 327 K) and tetragonal (165 K < T < 327 K) phases, the CH3NH3(+) ions exhibit four-fold rotational symmetry of the C-N axis (C4) along with three-fold rotation around the C-N axis (C3), while in the orthorhombic phase (T < 165 K) only C3 rotation is present. At around room temperature, the characteristic relaxation times for the C4 rotation are found to be τC4 ≈ 5 ps while for the C3 rotation τC3 ≈ 1 ps. The T-dependent rotational relaxation times were fitted with Arrhenius equations to obtain activation energies. Our data show a close correlation between the C4 rotational mode and the temperature dependent dielectric permittivity. Our findings on the rotational dynamics of CH3NH3(+) and the associated dipole have important implications for understanding the low exciton binding energy and a slow charge recombination rate in CH3NH3PbI3 which are directly relevant for the high solar cell performance. PMID:26549203

  4. Human SLC4A11 Is a Novel NH3/H+ Co-transporter.

    PubMed

    Zhang, Wenlin; Ogando, Diego G; Bonanno, Joseph A; Obukhov, Alexander G

    2015-07-01

    SLC4A11 has been proposed to be an electrogenic membrane transporter, permeable to Na(+), H(+) (OH(-)), bicarbonate, borate, and NH4 (+). Recent studies indicate, however, that neither bicarbonate or borate is a substrate. Here, we examined potential NH4 (+), Na(+), and H(+) contributions to electrogenic ion transport through SLC4A11 stably expressed in Na(+)/H(+) exchanger-deficient PS120 fibroblasts. Inward currents observed during exposure to NH4Cl were determined by the [NH3]o, not [NH4 (+)]o, and current amplitudes varied with the [H(+)] gradient. These currents were relatively unaffected by removal of Na(+), K(+), or Cl(-) from the bath but could be reduced by inclusion of NH4Cl in the pipette solution. Bath pH changes alone did not generate significant currents through SLC4A11, except immediately following exposure to NH4Cl. Reversal potential shifts in response to changing [NH3]o and pHo suggested an NH3/H(+)-coupled transport mode for SLC4A11. Proton flux through SLC4A11 in the absence of ammonia was relatively small, suggesting that ammonia transport is of more physiological relevance. Methylammonia produced currents similar to NH3 but with reduced amplitude. Estimated stoichiometry of SLC4A11 transport was 1:2 (NH3/H(+)). NH3-dependent currents were insensitive to 10 μM ethyl-isopropyl amiloride or 100 μM 4,4'- diisothiocyanatostilbene-2,2'-disulfonic acid. We propose that SLC4A11 is an NH3/2H(+) co-transporter exhibiting unique characteristics. PMID:26018076

  5. MARVEL analysis of the measured high-resolution spectra of 14NH3

    NASA Astrophysics Data System (ADS)

    Al Derzi, Afaf R.; Furtenbacher, Tibor; Tennyson, Jonathan; Yurchenko, Sergei N.; Császár, Attila G.

    2015-08-01

    Accurate, experimental rotational-vibrational energy levels and line positions, with associated labels and uncertainties, are reported for the ground electronic state of the symmetric-top 14NH3 molecule. All levels and lines are based on critically reviewed and validated high-resolution experimental spectra taken from 56 literature sources. The transition data are in the 0.7-17 000 cm-1 region, with a large gap between 7000 and 15 000 cm-1. The MARVEL (Measured Active Rotational-Vibrational Energy Levels) algorithm is used to determine the energy levels. Out of the 29 450 measured transitions 10 041 and 18 947 belong to ortho- and para-14NH3, respectively. A careful analysis of the related experimental spectroscopic network (SN) allows 28 530 of the measured transitions to be validated, 18 178 of these are unique, while 462 transitions belong to floating components. Despite the large number of spectroscopic measurements published over the last 80 years, the transitions determine only 30 vibrational band origins of 14NH3, 8 for ortho- and 22 for para-14NH3. The highest J value, where J stands for the rotational quantum number, for which an energy level is validated is 31. The number of experimental-quality ortho- and para-14NH3 rovibrational energy levels is 1724 and 3237, respectively. The MARVEL energy levels are checked against ones in the BYTe first-principles database, determined previously. The lists of validated lines and levels for 14NH3 are deposited in the Supporting Information to this paper. Combination of the MARVEL energy levels with first-principles absorption intensities yields a huge number of experimental-quality rovibrational lines, which should prove to be useful for the understanding of future complex high-resolution spectroscopy on 14NH3; these lines are also deposited in the Supporting Information to this paper.

  6. Effects of atmospheric ammonia (NH3) on terrestrial vegetation: a review.

    PubMed

    Krupa, S V

    2003-01-01

    At the global scale, among all N (nitrogen) species in the atmosphere and their deposition on to terrestrial vegetation and other receptors, NH3 (ammonia) is considered to be the foremost. The major sources for atmospheric NH3 are agricultural activities and animal feedlot operations, followed by biomass burning (including forest fires) and to a lesser extent fossil fuel combustion. Close to its sources, acute exposures to NH3 can result in visible foliar injury on vegetation. NH3 is deposited rapidly within the first 4-5 km from its source. However, NH3 is also converted in the atmosphere to fine particle NH4+ (ammonium) aerosols that are a regional scale problem. Much of our current knowledge of the effects of NH3 on higher plants is predominantly derived from studies conducted in Europe. Adverse effects on vegetation occur when the rate of foliar uptake of NH3 is greater than the rate and capacity for in vivo detoxification by the plants. Most to least sensitive plant species to NH3 are native vegetation > forests > agricultural crops. There are also a number of studies on N deposition and lichens, mosses and green algae. Direct cause and effect relationships in most of those cases (exceptions being those locations very close to point sources) are confounded by other environmental factors, particularly changes in the ambient SO2 (sulfur dioxide) concentrations. In addition to direct foliar injury, adverse effects of NH3 on higher plants include alterations in: growth and productivity, tissue content of nutrients and toxic elements, drought and frost tolerance, responses to insect pests and disease causing microorganisms (pathogens), development of beneficial root symbiotic or mycorrhizal associations and inter species competition or biodiversity. In all these cases, the joint effects of NH3 with other air pollutants such as all-pervasive O3 or increasing CO2 concentrations are poorly understood. While NH3 uptake in higher plants occurs through the shoots, NH4+ uptake occurs through the shoots, roots and through both pathways. However, NH4+ is immobile in the soil and is converted to NO3- (nitrate). In agricultural systems, additions of NO3- to the soil (initially as NH3 or NH4+) and the consequent increases in the emissions of N2O (nitrous oxide, a greenhouse gas) and leaching of NO3- into the ground and surface waters are of major environmental concern. At the ecosystem level NH3 deposition cannot be viewed alone, but in the context of total N deposition. There are a number of forest ecosystems in North America that have been subjected to N saturation and the consequent negative effects. There are also heathlands and other plant communities in Europe that have been subjected to N-induced alterations. Regulatory mitigative approaches to these problems include the use of N saturation data or the concept of critical loads. Current information suggests that a critical load of 5-10 kg ha(-1) year(-1) of total N deposition (both dry and wet deposition combined of all atmospheric N species) would protect the most vulnerable terrestrial ecosystems (heaths, bogs, cryptogams) and values of 10-20 kg ha(-1) year(-1) would protect forests, depending on soil conditions. However, to derive the best analysis, the critical load concept should be coupled to the results and consequences of N saturation. PMID:12713921

  7. Electric polarization of CH3NH3PbI3 and enhancement by Cl substitution

    NASA Astrophysics Data System (ADS)

    Yan, Wen-Li; Lu, Guang-Hong; Liu, Feng

    As a prototype of organic-inorganic hybrid perovskite, CH3NH3PbI3 has attracted extensive attention recently due to its applications in high power-conversion-efficiency solar cells. In comparison with its inorganic perovskite counterparts such as CsPbI3, the organic cation CH3NH3+ is expected to play multiple important roles in distorting crystal structures and thus band structures as well as creating local electrically polarized domains to help separate charge carriers. Using first-principles method and berry phase theory, the electric polarization vectors of CH3NH3PbI3 have been calculated. The off-center displacement of Pb within the PbI6 octahedral is shown to introduce major intrinsic polarization, with additional contributions from off-center displacement of CH3NH3+ within PbI3 cage and charge polarization within the organic cation. With chlorine substitution of iodine, the electronegativity difference between halogen and Pb becomes larger, and the lattice distortion and hence the electric polarization increases, which provides a possible mechanism to further assist charge carrier separation in solar cell devices. This is consistent with enhanced photovoltaics properties of CH3NH3PbI3-xClx found in recent experiments. This work is supported by China Scholarship Council (Grant No. 201306020117) and US DOE-BES (Grant No. DE-FG02-04ER46148).

  8. Thermal Durability of Cu-CHA NH3-SCR Catalysts for Diesel NOx Reduction

    SciTech Connect

    Schmieg, Steven J.; Oh, Se H.; Kim, Chang H.; Brown, David B.; Lee, Jong H.; Peden, Charles HF; Kim, Do Heui

    2012-04-30

    Multiple catalytic functions (NOx conversion, NO and NH3 oxidation, NH3 storage) of a commercial Cu-zeolite urea/NH3-SCR catalyst were assessed in a laboratory fixed-bed flow reactor system after differing degrees of hydrothermal aging. Catalysts were characterized by using x-ray diffraction (XRD), 27Al solid state nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM) / energy dispersive X-ray (EDX) spectroscopy to develop an understanding of the degradation mechanisms during catalyst aging. The catalytic reaction measurements of laboratory-aged catalysts were performed, which allows us to obtain a universal curve for predicting the degree of catalyst performance deterioration as a function of time at each aging temperature. Results show that as the aging temperature becomes higher, the zeolite structure collapses in a shorter period of time after an induction period. The decrease in SCR performance was explained by zeolite structure destruction and/or Cu agglomeration, as detected by XRD/27Al NMR and by TEM/EDX, respectively. Destruction of the zeolite structure and agglomeration of the active phase also results in a decrease in the NO/NH3 oxidation activity and the NH3 storage capacity of the catalyst. Selected laboratory aging conditions (16 h at 800oC) compare well with a 135,000 mile vehicle-aged catalyst for both performance and characterization criteria.

  9. Re-estimating NH3 Emissions from Chinese Cropland by a New Nonlinear Model.

    PubMed

    Zhou, Feng; Ciais, Philippe; Hayashi, Kentaro; Galloway, James; Kim, Dong-Gill; Yang, Changliang; Li, Shiyu; Liu, Bin; Shang, Ziyin; Gao, Shuoshuo

    2016-01-19

    Ammonia (NH3) released to the atmosphere leads to a cascade of impacts on the environment, yet estimation of NH3 volatilization from cropland soils (VNH3) in a broad spatial scale is still quite uncertain in China. This mainly stems from nonlinear relationships between VNH3 and relevant factors. On the basis of 495 site-years of measurements at 78 sites across Chinese croplands, we developed a nonlinear Bayesian tree regression model to determine how environmental factors modulate the local derivative of VNH3 to nitrogen application rates (Nrate) (VR, %). The VNH3-Nrate relationship was nonlinear. The VR of upland soils and paddy soils depended primarily on local water input and Nrate, respectively. Our model demonstrated good reproductions of VNH3 compared to previous models, i.e., more than 91% of the observed VR variance at sites in China and 79% of those at validation sites outside China. The observed spatial pattern of VNH3 in China agreed well with satellite-based estimates of NH3 column concentrations. The average VRs in China derived from our model were 14.8 ± 2.9% and 11.8 ± 2.0% for upland soils and paddy soils, respectively. The estimated annual NH3 emission in China (3.96 ± 0.76 TgNH3·yr(-1)) was 40% greater than that based on the IPCC Tier 1 guideline. PMID:26710302

  10. Theoretical study of adsorption and dissociation of NH3 on pentanuclear Fe(111) surface

    NASA Astrophysics Data System (ADS)

    Purwiandono, G.; Triyono; Wijaya, K.

    2016-02-01

    Theoretical study regarding the adsorption and dissociation of NH3 molecule on Fe(111) surface has been carried out. The method used was DFT-B3LYP, and the basis sets used were ECP and 6-311G**. This research aimed at giving the theoretical understanding of adsorption and dissociation of NH3 molecule on Fe(111) surface. The adsorption and dissociation were studied based on the energetic parameter, bond length, electron population, vibration and orbital interaction. The result of theoretical calculation revealed that the on top position is the interaction position with the minimum energy for the adsorption of NH3 molecule on Fe(111) surface. The analysis of electron population of the two composing molecular orbitals indicated that the transfer of electron has an important role in the mechanism of adsorption. The visualization of molecular orbital showed that the transfer of electron occurred in the electron pairs of the interacting orbital. Relating to the adsorption mechanism and the overlapping of interaction orbitals, NH3 molecule provides the Highest Occupied Molecular Orbital (HOMO) as the interaction pair for the Lowest Unoccupied Molecular Orbital (LUMO) on Fe surface. The insignificant difference between the oxidation state of N and H atoms as well as the higher hemolytic N-H bond dissociation energy (compared to heterolytic dissociation) cause the adsorption mechanism of NH3 on Fe(111) model to occur through homolytic-dissociative chemisorption.

  11. Laboratory Spectral Studies of NH3 Ice Mixtures Relevant to Astrophysical Environments

    NASA Astrophysics Data System (ADS)

    White, Douglas; Mastrapa, R. M. E.; Gerakines, P. A.; Sandford, S. A.

    2012-05-01

    Small quantities of NH3 have been detected in interstellar environments such as icy grain mantles and cometary environments via infrared (IR) absorption spectroscopy in the range λ = 0.9-25 μm (e.g., Hagen et al., 1980; Crovisier, 1997; Lacy et al., 1998). In our presentation, we will describe spectral studies of some H2O-dominated ice mixtures containing small amounts (≤10%) of NH3. We also present spectral data collected at the University of Alabama at Birmingham Astrophysics Laboratory of H2O-dominated ice mixtures containing NH3 (White 2010). Positions and profiles of absorption features of NH3 are noted according to temperature and mixture, along with the profiles of H2O. Mixtures with other species such as CO2 are also investigated. These results may then be used to identify IR spectral signatures from NH3 and other species from observational data from ground- and space-based observatories. Crovisier, J. 1997, Earth Moon and Planets, 79, 125 Hagen, W., Allamandola, L. J., & Greenberg, J. M. 1980, A&A, 86, L3 Lacy, J. H., Faraji, H., Sandford, S. A., & Allamandola, L. J. 1998, The Astrophysical Journal Letters, 501, L105 White, D. W. 2010, PhD thesis, University of Alabama at Birmingham

  12. Mechanism of NH4(+) Recruitment and NH3 Transport in Rh Proteins.

    PubMed

    Baday, Sefer; Orabi, Esam A; Wang, Shihao; Lamoureux, Guillaume; Bernèche, Simon

    2015-08-01

    In human cells, membrane proteins of the rhesus (Rh) family excrete ammonium and play a role in pH regulation. Based on high-resolution structures, Rh proteins are generally understood to act as NH3 channels. Given that cell membranes are permeable to gases like NH3, the role of such proteins remains a paradox. Using molecular and quantum mechanical calculations, we show that a crystallographically identified site in the RhCG pore actually recruits NH4(+), which is found in higher concentration and binds with higher affinity than NH3, increasing the efficiency of the transport mechanism. A proton is transferred from NH4(+) to a signature histidine (the only moiety thermodynamically likely to accept a proton) followed by the diffusion of NH3 down the pore. The excess proton is circulated back to the extracellular vestibule through a hydrogen bond network, which involves a highly conserved and functionally important aspartic acid, resulting in the net transport of NH3. PMID:26190573

  13. Detection of NH3 by quartz crystal microbalance coated with TiO2

    NASA Astrophysics Data System (ADS)

    Georgieva, V.; Donkov, N.; Spassov, L.; Petkov, P.; Gadjanova, V.

    2008-05-01

    A quartz resonator with a thin TiO2 film is investigated in view of possible applications as a sensor for detecting the presence of ammonia in the ambient. A study of the sorption properties of thin TiO2 films to NH3 vapors is also presented. The films are deposited using electron beam evaporation. In order to determine the sorption ability of TiO2 to NH3, a quartz crystal microbalance (QCM) with a thin TiO2 film is used, the latter serving as a receptor for the NH3 gas. The AT-cut 16-MHz quartz resonator allows conversion of the additional mass load that occurs as a result of sorption into a frequency shift. The experiments are carried out by measuring the QCM resonant frequency shift due to the absorption of vapors from an aqueous solution of NH3 with different concentration ranging from 100 to 1000 ppm. The experimental results obtained indicate that the variation of the resonant frequency is a function of the ammonia concentration. This demonstrates that a QCM covered with a thin TiO2 layer is sensitive to ammonia vapors at room temperature and is capable of detecting NH3 concentrations in the range investigated (100-1000 ppm).

  14. Density dependence of the 5 micron infrared spectrum of NH3

    NASA Technical Reports Server (NTRS)

    Chapados, Camille; Bjoraker, Gordon L.; Birnbaum, George

    1990-01-01

    Measurements of dilute mixtures of NH3 in H2 were made in the window region 1900-2100/cm of the NH3 spectrum to determine is behavior with increasing pressure of H2. The spectra of pure H2, pure NH3, and mixtures of the two, in the total pressure range from 2.38 to 8.17 atm at 309 K, were obtained with a 975-cm white-cell. Synthetic spectra were calculated using precise line strengths, line positions, and a Lorentz profile. The experimental and calculated spectra are in reasonably good agreement, except that the former is super-imposed on a rather flat background not given by the calculation. A possible mechanism for this background is suggested.

  15. NH2 fluorescence efficiencies and the NH3 abundance in Comet Halley

    NASA Technical Reports Server (NTRS)

    Tegler, Stephen; Wyckoff, Susan

    1989-01-01

    If NH3 is the dominant source of the NH2 observed in comet spectra, then the NH3 abundance can in principle be accurately determined. Fluorescence efficiencies for the (0, v-prime/2/, O) to (0, 0, 0) progression of NH2 bands are calculated for NH2 bands likely to be observed in the 4500-8200-A region of comets. The results differ from previous determinations of the NH2 band fluorescence efficiencies by factors in the range 1.4-5.9, leading t6o significant changes in previously reported NH2 production rates in comets. A recalculation of the NH3/H2O abundance ratio in Comet Halley gives about (0.5 + or - 0.2) percent in better agreement with the Giotto ion-mass-spectrometer results of Allen et al (1987).

  16. NH2 fluorescence efficiencies and the NH3 abundance in Comet Halley

    NASA Astrophysics Data System (ADS)

    Tegler, S.; Wyckoff, S.

    1989-08-01

    If NH3 is the dominant source of the NH2 observed in comet spectra, then the NH3 abundance can in principle be accurately determined. Fluorescence efficiencies for the (0, v-prime/2/, O) to (0, 0, 0) progression of NH2 bands are calculated for NH2 bands likely to be observed in the 4500-8200-A region of comets. The results differ from previous determinations of the NH2 band fluorescence efficiencies by factors in the range 1.4-5.9, leading t6o significant changes in previously reported NH2 production rates in comets. A recalculation of the NH3/H2O abundance ratio in Comet Halley gives about (0.5 + or - 0.2) percent in better agreement with the Giotto ion-mass-spectrometer results of Allen et al (1987).

  17. Facile route to freestanding CH3NH3PbI3 crystals using inverse solubility

    PubMed Central

    Kadro, Jeannette M.; Nonomura, Kazuteru; Gachet, David; Grätzel, Michael; Hagfeldt, Anders

    2015-01-01

    CH3NH3PbI3 was found to exhibit inverse solubility at high temperatures in γ-butyrolactone. Making use of this unusual, so far unreported phenomenon, we present a facile method for the growth of freestanding crystals of CH3NH3PbI3 from solution without addition of any capping agents or seed particles. Large, strongly faceted crystals could be grown within minutes. This finding may aid in understanding the crystallization process of CH3NH3PbI3 from solution that may lead to improved morphological control of film deposition for a range of device architectures. Our process offers a facile and rapid route to freestanding crystals for use in a broad range of characterization techniques. PMID:26123285

  18. Resonances in rotationally inelastic scattering of NH3 and ND3 with H2.

    PubMed

    Ma, Qianli; van der Avoird, Ad; Loreau, Jrme; Alexander, Millard H; van de Meerakker, Sebastiaan Y T; Dagdigian, Paul J

    2015-07-28

    We present theoretical studies on the scattering resonances in rotationally inelastic collisions of NH3 and ND3 molecules with H2 molecules. We use the quantum close-coupling method to compute state-to-state integral and differential cross sections for the NH3/ND3-H2 system for collision energies between 5 and 70 cm(-1), using a previously reported potential energy surface [Maret et al., Mon. Not. R. Astron. Soc. 399, 425 (2009)]. We identify the resonances as shape or Feshbach resonances. To analyze these, we use an adiabatic bender model, as well as examination at the scattering wave functions and lifetimes. The strength and width of the resonance peaks suggest that they could be observed in a crossed molecular beam experiment involving a Stark-decelerated NH3 beam. PMID:26233134

  19. LPG and NH3 sensing characteristics of DC electrochemically deposited Co3O4 films

    NASA Astrophysics Data System (ADS)

    Shelke, P. N.; Khollam, Y. B.; Gunjal, S. D.; Koinkar, P. M.; Jadkar, S. R.; Mohite, K. C.

    2015-03-01

    Present communication reports the LPG and NH3 sensing properties of Co3O4 films prepared on throughly cleaned stainless steel (SS) and copper (CU) substrates by using DC electrochemical deposition method followed by air annealing at 350°C/2 h. The resultant films are characterized by using X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). The LPG and NH3 gas sensing properties of these films are measured at room temperature (RT) by using static gas sensing system at different concentrations of test gas ranging from 25 ppm to 350 ppm. The XRD and Raman spectroscopy studies clearly indicated the formation of pure cubic spinel Co3O4 in all films. The LPG and NH3 gas sensing properties of films showed (i) the increase in sensitivity factor (S.F.) with gas concentrations and (ii) more sensibility to LPG as compared to NH3 gas. In case of NH3 gas (conc. 150 ppm) and LPG gas (conc. 60 ppm) sensing, the maximum S.F. = 270 and 258 are found for the films deposited on CU substrates, respectively. For all films, the response time (3-5 min.) is found to be much higher than the recovery time (30-50 sec). For all films, the response and recovery time are found to be higher for LPG as compared to NH3 gas. Further, repeatability-reproducibility in gas sensing properties is clearly noted by analysis of data for number of cycles recorded for all films from different set of depositions.

  20. Mixing of Dust and NH3 Observed Globally over Anthropogenic Dust Sources

    NASA Technical Reports Server (NTRS)

    Ginoux, P.; Clarisse, L.; Clerbaux, C.; Coheur, P.-F.; Dubovik, O.; Hsu, N. C.; Van Damme, M.

    2012-01-01

    The global distribution of dust column burden derived from MODIS Deep Blue aerosol products is compared to NH3 column burden retrieved from IASI infrared spectra. We found similarities in their spatial distributions, in particular their hot spots are often collocated over croplands and to a lesser extent pastures. Globally, we found 22% of dust burden collocated with NH3, with only 1% difference between land-use databases. This confirms the importance of anthropogenic dust from agriculture. Regionally, the Indian subcontinent has the highest amount of dust mixed with NH3 (26 %), mostly over cropland and during the pre-monsoon season. North Africa represents 50% of total dust burden but accounts for only 4% of mixed dust, which is found over croplands and pastures in Sahel and the coastal region of the Mediterranean. In order to evaluate the radiative effect of this mixing on dust optical properties, we derive the mass extinction efficiency for various mixtures of dust and NH3, using AERONET sunphotometers data. We found that for dusty days the coarse mode mass extinction efficiency decreases from 0.62 to 0.48 square meters per gram as NH3 burden increases from 0 to 40 milligrams per square meter. The fine mode extinction efficiency, ranging from 4 to 16 square mters per gram, does not appear to depend on NH3 concentration or relative humidity but rather on mineralogical composition and mixing with other aerosols. Our results imply that a significant amount of dust is already mixed with ammonium salt before its long range transport. This in turn will affect dust lifetime, and its interactions with radiation and cloud properties

  1. Partial phase diagram for the system NH3-H2O - The water-rich region

    NASA Technical Reports Server (NTRS)

    Johnson, M. L.; Schwake, A.; Nicol, M.

    1984-01-01

    Phase boundaries of the H2O-NH3 system for (NH3)/x/(H2O)/1-x/ have been determined with diamond-anvil cells for mixtures in two composition ranges: (1) for x in the range from 0 to 0.3, at pressures up to 4 GPa at 21 C, and (2) for x in the range from 0.46 to 0.50, at pressures up to 5 GPa from 150 to 400 K. Phases were identified visually with a microscope and polarized optics. The NH3.2(H2O) phase is strongly anisotropic with a much smaller refractive index than that of ice VII and cracks in two nonperpendicular networks. NH3.H2O has a refractive index closer to that of Ice VII and does not appear to form cracks. Both phases are colorless. Phase boundaries were determined on both increasing and decreasing pressures, and compositions of the ammonia ices were determined by estimating relative amounts of water and ammonia ices at known overall compositions. For low-ammonia compositions (x equal to or less than 0.15), the following assemblages succedd one another as pressure increases: liquid; liquid and Ice VI (at 1.0 + GPa); liquid and Ice VII (at 2.1 GPa); Ice VII and NH3.H2O (at 3.5 GPa). For x in the range from 0.15 to 0.30, the water ice and liquid fields are replaced by the NH3.2(H2O) and liquid field at pressures down to 1.0 GPa and lower.

  2. Scattering of NH3 and ND3 with rare gas atoms at low collision energy

    NASA Astrophysics Data System (ADS)

    Loreau, J.; van der Avoird, A.

    2015-11-01

    We present a theoretical study of elastic and rotationally inelastic collisions of NH3 and ND3 with rare gas atoms (He, Ne, Ar, Kr, Xe) at low energy. Quantum close-coupling calculations have been performed for energies between 0.001 and 300 cm-1. We focus on collisions in which NH3 is initially in the upper state of the inversion doublet with j = 1, k = 1, which is the most relevant in an experimental context as it can be trapped electrostatically and Stark-decelerated. We discuss the presence of resonances in the elastic and inelastic cross sections, as well as the trends in the inelastic cross sections along the rare gas series and the differences between NH3 and ND3 as a colliding partner. We also demonstrate the importance of explicitly taking into account the umbrella (inversion) motion of NH3 in order to obtain accurate scattering cross sections at low collision energy. Finally, we investigate the possibility of sympathetic cooling of ammonia using cold or ultracold rare gas atoms. We show that some systems exhibit a large ratio of elastic to inelastic cross sections in the cold regime, which is promising for sympathetic cooling experiments. The close-coupling calculations are based on previously reported ab initio potential energy surfaces for NH3-He and NH3-Ar, as well as on new, four-dimensional, potential energy surfaces for the interaction of ammonia with Ne, Kr, and Xe, which were computed using the coupled-cluster method and large basis sets. We compare the properties of the potential energy surfaces corresponding to the interaction of ammonia with the various rare gas atoms.

  3. Correlation of superconductivity with crystal structure in (NH3)yC sxFeSe

    NASA Astrophysics Data System (ADS)

    Zheng, Lu; Miao, Xiao; Sakai, Yusuke; Goto, Hidenori; Uesugi, Eri; Eguchi, Ritsuko; Nishiyama, Saki; Sugimoto, Kunihisa; Fujiwara, Akihiko; Kubozono, Yoshihiro

    2016-03-01

    The superconducting transition temperature Tc of ammoniated metal-doped FeSe (NH3)yMxFeSe (M : metal atom) has been scaled with the FeSe plane spacing, and it has been suggested that the FeSe plane spacing depends on the location of metal atoms in (NH3)yMxFeSe crystals. Although the crystal structure of (NH3)yL ixFeSe exhibiting a high Tc (˜44 K) was determined from neutron diffraction, the structure of (NH3)yMxFeSe exhibiting a low Tc (˜32 K) has not been determined thus far. Here, we determined the crystal structure of (NH3)yC s0.4FeSe (Tc=33 K ) through the Rietveld refinement of the x-ray diffraction (XRD) pattern measured with synchrotron radiation at 30 K. The XRD pattern was analyzed based on two different models, on-center and off-center, under a space group of I 4 /m m m . In the on-center structure, the Cs occupies the 2 a site and the N of N H3 may occupy either the 4 c or 2 b site, or both. In the off-center structure, the Cs may occupy either the 4 c or 2 b site, or both, while the N occupies the 2 a site. Only an on-center structure model in which the Cs occupies the 2 a and the N of N H3 occupies the 4 c site provided reasonable results in the Rietveld analysis. Consequently, we concluded that (NH3)yC s0.4FeSe can be assigned to the on-center structure, which produces a smaller FeSe plane spacing leading to the lower Tc.

  4. Scattering of NH3 and ND3 with rare gas atoms at low collision energy.

    PubMed

    Loreau, J; van der Avoird, A

    2015-11-14

    We present a theoretical study of elastic and rotationally inelastic collisions of NH3 and ND3 with rare gas atoms (He, Ne, Ar, Kr, Xe) at low energy. Quantum close-coupling calculations have been performed for energies between 0.001 and 300 cm(-1). We focus on collisions in which NH3 is initially in the upper state of the inversion doublet with j = 1, k = 1, which is the most relevant in an experimental context as it can be trapped electrostatically and Stark-decelerated. We discuss the presence of resonances in the elastic and inelastic cross sections, as well as the trends in the inelastic cross sections along the rare gas series and the differences between NH3 and ND3 as a colliding partner. We also demonstrate the importance of explicitly taking into account the umbrella (inversion) motion of NH3 in order to obtain accurate scattering cross sections at low collision energy. Finally, we investigate the possibility of sympathetic cooling of ammonia using cold or ultracold rare gas atoms. We show that some systems exhibit a large ratio of elastic to inelastic cross sections in the cold regime, which is promising for sympathetic cooling experiments. The close-coupling calculations are based on previously reported ab initio potential energy surfaces for NH3-He and NH3-Ar, as well as on new, four-dimensional, potential energy surfaces for the interaction of ammonia with Ne, Kr, and Xe, which were computed using the coupled-cluster method and large basis sets. We compare the properties of the potential energy surfaces corresponding to the interaction of ammonia with the various rare gas atoms. PMID:26567658

  5. Ultraviolet-gas phase and -photocatalytic synthesis from CO and NH3. [photolysis products

    NASA Technical Reports Server (NTRS)

    Hubbard, J. S.; Voecks, G. E.; Hobby, G. L.; Ferris, J. P.; Williams, E. A.; Nicodem, D. E.

    1975-01-01

    Ammonium cyanate is identified as the major product of the photolysis of gaseous NH3-CO mixtures at 206.2 or 184.9 nm. Lesser amounts of urea, biurea, biuret semicarbazide, formamide and cyanide are observed. A series of 18 reactions underlying the formation of photolysis products is presented and discussed. Photocatalytic syntheses of C-14-urea, -formamide, and -formaldehyde are carried out through irradiation of (C-14)O and NH3 in the presence of Vycor, silica gel, or volcanic ash shale surfaces. The possible contributions of the relevant reactions to the abiotic synthesis of organic nitrogen compounds on Mars, the primitive earth, and in interstellar space are examined.

  6. Modeling of Jupiter's millimeter wave emission utilizing laboratory measurements of ammonia (NH3) opacity

    NASA Technical Reports Server (NTRS)

    Joiner, Joanna; Steffes, Paul G.

    1991-01-01

    The techniques used to make laboratory measurements of the millimeter wave opacity from gaseous ammonia under simulated Jovian conditions are described. The results are applied to a radiative transfer model, which is used to compute Jupiter's millimeter wavelength emission. The absorptivity of gaseous NH3 is measured to reduce one of the largest uncertainties in modeling Jupiter's millimeter wave emission. Several other millimeter wave opacity sources are examined. New expressions are given for computing the absorptivity of NH3, H2O, cloud condensates, and pressure-induced absorption. Jupiter's reliable millimeter wavelength observations are compared with synthetic emission spectra which utilize these new absorption expressions.

  7. Influence of the guest molecule on the rotational potential for NH 3 groups in Hofmann clathrates

    NASA Astrophysics Data System (ADS)

    Vorderwisch, P.; Hautecler, S.; Kearley, G. J.; Kubanek, F.

    2000-11-01

    Inelastic neutron scattering has been used to investigate the influence of different guest molecules, G, on the rotational hindering potential for NH 3 in Hofmann clathrates Ni(NH 3) 2Ni(CN) 4 · mG. Non-polar guests (benzene and biphenyl) lead to quasi-free rotor environments. For polar guests (water, aniline, phenol, dioxane), dipolar interactions give rise to an increase of the rotational barrier; most often, complex spectra result from statistical orientational disorder of the guest molecules.

  8. "NH3 and PH3 Line Parameters: The 2000 HITRAN Update and New Results"

    SciTech Connect

    Kleiner, I; Tarrago, G.; Cottaz, C; Sagui, L; Brown, L.R.; Poynter, R. L.; Pickett, H M.; Chen, P; Pearson, J C.; Sams, Robert L.; Blake, G A.; Matsuura, S; Nemtchinov, V; Varanasi, Prasad; Fusina, L; Di Lonardo, G

    2003-11-01

    The line parameters of ammonia and phosphine have been revised using new results for line positions, intensities and line widths. The improvements for NH3 in the HITRAN 2000, containing some 29084 lines (corresponding to more than twice the number of lines present in the 1996 HITRAN database for this molecule) involved replacing pure-rotational and infrared transitions from 0 to 5294 cm-1 with new calculations. This update focuses on the 0-3700 cm-1 spectral range of the 14NH3 isotopomer. New PH3 parameters available from 770 to 2156 cm-1 for future updates are described and contrasted with the parameters in HITRAN 2000.

  9. Global distributions and trends of atmospheric ammonia (NH3) from IASI satellite observations

    NASA Astrophysics Data System (ADS)

    Van Damme, M.; Clarisse, L.; Heald, C. L.; Hurtmans, D.; Ngadi, Y.; Clerbaux, C.; Dolman, A. J.; Erisman, J. W.; Coheur, P. F.

    2013-09-01

    Ammonia (NH3) emissions in the atmosphere have strongly increased in the past decades, largely because of the intensive livestock production and use of fertilizers. As a short-lived species, NH3 is highly variable in the atmosphere and its concentration is generally small, except in and close to local source areas. While ground-based measurements are possible, they are challenging and sparse. Advanced infrared sounders in orbit have recently demonstrated their capability to measure NH3, offering a new tool to refine global and regional budgets. In this paper we describe an improved retrieval scheme of NH3 total columns from the measurements of the Infrared Atmospheric Sounding Interferometer (IASI). It exploits the hyperspectral character of this instrument by using an extended spectral range (800-1200 cm-1) where NH3 is optically active. This scheme consists of the calculation of a dimensionless spectral index from the IASI level1C radiances, which is subsequently converted to a total NH3 column using look-up-tables built from forward radiative transfer model simulations. We show how to retrieve the NH3 total columns from IASI quasi-globally and twice daily, above both land and sea, without large computational resources and with an improved detection limit. The retrieval also provides error characterization on the retrieved columns. Five years of IASI measurements (1 November 2007 to 31 October 2012) have been processed to acquire the first global and multiple-year dataset of NH3 total columns, which are evaluated and compared to similar products from other retrieval methods. Spatial distributions from the five years dataset are provided and analyzed at global and regional scales. We show in particular the ability of this method to identify smaller emission sources than those reported previously, as well as transport patterns above sea. The five year time series is further examined in terms of seasonality and inter-annual variability (in particular as a function of fire activity) separately for the Northern and Southern Hemispheres.

  10. Liquid Phase Deposition Of Thin Titanium Dioxide Films For NH3 Detection

    NASA Astrophysics Data System (ADS)

    Georgieva, V.; Stefchev, P.; Stefanov, P.; Spassov, L.; Raicheva, Z.; Ivanova, K.

    2007-04-01

    TiO2 thin films are prepared by a new method called Liquid Phase Deposition (LDP). The layers are obtained by the reaction between the metal fluorocomplex and boric acid in aqueous solution. The morphology of the films and the composition are investigated by scanning electron microscopy (SEM) and x-ray photoelectron spectrometry (XPS). The sorption properties of TiO2 film to NH3 are measured by the Quartz Crystal Microbalance (QCM) method. A correlation between NH3 concentration and the sorption ability of as-deposited and annealed samples is obtained.

  11. Determination of structure and phase transition of nanophase NH3BH3 embedded in MCM-41 mesoporous silica

    NASA Astrophysics Data System (ADS)

    Kim, Hyunjeong; Karkamkar, Abhi; Autrey, Thomas; Chupas, Peter; Proffen, Thomas

    2010-03-01

    Nanocomposition of ammonia borane (AB), NH3BH3, by loading AB in a mesoporous silica has shown great improvement in the hydrogen storage properties [1]; faster hydrogen desorption was observed at reduced temperature and the formation of borazine, by-products that affects hydrogen purity, was significantly suppressed. Even though an improvement was striking, its lack of long-range structural order and relatively light composed elements hinder conventional structural analyses. We have employed the atomic pair distribution function (PDF) analysis to investigate the nanophase AB residing in mesoporous channels of MCM-41 [2]. Temperature dependent x-ray PDF study shows that the AB confined in pores does not undergo the orthorhombic to tetragonal phase transition at 225 K that was observed in the bulk molecular crystal. Instead, it stays in the high temperature tetragonal phase over a temperature range of 110-240 K and becomes amorphous above 240 K. [1] A. Gutowska et al., Angew. Chem. Int. Ed., 44, 3578-3582 (2005). [2] H. J. Kim et al., J. Am. Chem. Soc., 131, 13749-13755 (2009).

  12. Effect of metal ions doping (M = Ti4+, Sn4+) on the catalytic performance of MnOx/CeO2 catalyst for low temperature selective catalytic reduction of NO with NH3

    NASA Astrophysics Data System (ADS)

    Xiong, Yan; Tang, Changjin; Dong, Lin

    2015-04-01

    Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China The abatement of nitrogen oxides (NOx) emission from exhaust gases of diesel and stationary sources is a significant challenge for economic and social development. Ceria-based solid solutions were synthesized and used as supports to prepare MnOx/Ce0.8Ti0.2O2 and MnOx/Ce0.8Sn0.2O2 catalysts (Mn/CeTi and Mn/CeSn) for low temperature selective catalytic reduction of NO by NH3 (NH3-SCR). The effects of Ti or Sn doping on the catalytic performance of MnOx/CeO2 catalyst were investigated. Experimental results show that doping of Ti or Sn increases the NO removal efficiency of MnOx/CeO2. The NO conversion of Mn/CeTi catalyst is more than 90 % at temperature window of 175 ~ 300 °C under a gas hour space velocity of 60,000 mL.g-1.h-1. Modified catalysts are also found to exhibit greatly improved resistance to sulfur-poisoning. NH3-TPD results suggest that NH3 desorption on the catalysts is observed over a wide temperature range, due to the variability of adsorbed NH3 species with different thermal stabilities. Doping of Ti and Sn into Mn/CeO2 greatly increased the NH3 adsorption ability of the composites which could promote the SCR reaction. Characterization results also indicate that doping of Ti or Sn brings about catalysts with higher BET surface area, enhanced oxygen storage capacity and increased surface acidity.

  13. Effect of Ti or Sn doping on the catalytic performance of MnOx/CeO2 catalyst for low temperature selective catalytic reduction of NO with NH3

    NASA Astrophysics Data System (ADS)

    Xiong, Yan; Tang, Changjin; Dong, Lin

    2015-04-01

    The abatement of nitrogen oxides (NOx) emission from exhaust gases of diesel and stationary sources is a significant challenge for economic and social development. Ceria-based solid solutions were synthesized and used as supports to prepare MnOx/Ce0.8Ti0.2O2 and MnOx/Ce0.8Sn0.2O2 catalysts (Mn/CeTi and Mn/CeSn) for low temperature selective catalytic reduction of NO by NH3 (NH3-SCR). The effects of Ti or Sn doping on the catalytic performance of MnOx/CeO2 catalyst were investigated. Experimental results show that doping of Ti or Sn increases the NO removal efficiency of MnOx/CeO2. The NO conversion of Mn/CeTi catalyst is more than 90 % at temperature window of 175 ~ 300 °C under a gas hour space velocity of 60,000 mL•g-1•h-1. Modified catalysts are also found to exhibit greatly improved resistance to sulfur-poisoning. NH3-TPD results suggest that NH3 desorption on the catalysts is observed over a wide temperature range, due to the variability of adsorbed NH3 species with different thermal stabilities. Doping of Ti and Sn into Mn/CeO2 greatly increased the NH3 adsorption ability of the composites which could promote the SCR reaction. Characterization results also indicate that doping of Ti or Sn brings about catalysts with higher BET surface area, enhanced oxygen storage capacity and increased surface acidity. X-ray photoelectron spectroscopy (XPS) analysis of spent catalysts following SCR reaction in the presence of SO2 verify that the loss of surface Mn species was inhibited by doping of Ti, which contributes to extend the catalyst durability.

  14. Conformation of NH 3 and C 2H 4 molecules approaching a metal surface

    NASA Astrophysics Data System (ADS)

    Flores, F.; Gabbay, I.; March, N. H.

    1981-10-01

    Using a semiempirical approach to the conformation of free space molecules, the HNH angle in NH 3 adsorbed on Ru(001) is estimated to increase by about 1°. For C 2H 4, both HCC and HCH angles are predicted to decrease.

  15. Parametrization of electron impact ionization cross sections for CO, CO2, NH3 and SO2

    NASA Technical Reports Server (NTRS)

    Srivastava, Santosh K.; Nguyen, Hung P.

    1987-01-01

    The electron impact ionization and dissociative ionization cross section data of CO, CO2, CH4, NH3, and SO2, measured in the laboratory, were parameterized utilizing an empirical formula based on the Born approximation. For this purpose an chi squared minimization technique was employed which provided an excellent fit to the experimental data.

  16. Saturated absorption in NH3 demonstrated using a tuneable diode laser

    NASA Technical Reports Server (NTRS)

    Jennings, D. E.

    1978-01-01

    Saturation of molecular transitions using a tunable diode laser has been demonstrated for the first time using a standing-wave-cavity configuration with the laser beam focused at the sample. Observed saturation effects in NH3 transitions near 888 kaysers include sub-Doppler (Lamb-dip) resonances at the line center.

  17. Kinetics of gas-liquid reaction between NO and Co(NH3)6(2+).

    PubMed

    Long, Xiang-li; Xiao, Wen-De; Yuan, Wei-kang

    2005-08-31

    Wet ammonia desulphurization process can be retrofitted for combined removal of SO2 and NO from the flue gas by adding soluble cobalt(II) salts into the aqueous ammonia solutions. The Co(NH3)6(2+) formed by ammonia binding with Co2+ is the active constituent of scrubbing NO from the flue gas streams. A stirred vessel with a plane gas-liquid interface was used to measure the chemical absorption rates of nitric oxide into the Co(NH3)6(2+) solution under anaerobic and aerobic conditions separately. The experiments manifest that the nitric oxide absorption reaction can be regarded as instantaneous when nitric oxide concentration levels are parts per million ranges. The gas-liquid reaction becomes gas film controlling as Co(NH3)6(2+) concentration exceeds 0.02 mol/l. The NO absorption rate is proportional to the nitric oxide inlet concentration. Oxygen in the gas phase is favorable to the absorption of nitric oxide. But it is of little significance to increase the oxygen concentration above 5.2%. The NO absorption rate decreases with temperature. The kinetic equation of NO absorption into the Co(NH3)6(2+) solution under aerobic condition can be written as. PMID:15869841

  18. Ground-based FTIR measurements of NH3 total columns and comparison with IASI data

    NASA Astrophysics Data System (ADS)

    Vigouroux, Corinne; De Mazière, Martine; Desmet, Filip; Hermans, Christian; Langerock, Bavo; Scolas, Francis; Van Damme, Martin; Clarisse, Lieven; Coheur, Pierre-François

    2013-04-01

    Atmospheric ammonia (NH3) dominates global emissions of total reactive nitrogen. It has an impact on human health, as a precursor of fine particulate matter, and on Earth's ecosystems, via deposition. The main source of global NH3 emissions is agriculture, the remaining ones being the oceans, natural vegetation, humans, wild animals and biomass burning. The global atmospheric budget of NH3 is still very uncertain in chemical models, highlighting the critical need for satellite and ground-based observations. We present, for the first time, time-series (2009 - 2011) of NH3 total columns obtained from ground-based FTIR measurements. These observations are performed at Reunion Island (21°S, 55°E), one of the two subtropical stations, in Southern Hemisphere, of the ground-based Network for the Detection of Atmospheric Composition Change (NDACC) equipped with FTIR instruments. The seasonal and inter-annual variabilities of ammonia observed at Reunion Island from the ground are compared to the ones derived from recent IASI data obtained with a new retrieval method based on the calculation of a Hyperspectral Range Index.

  19. Dry Cleaning Technology for Removal of Silicon Native Oxide Employing Hot NH3/NF3 Exposure

    NASA Astrophysics Data System (ADS)

    Ogawa, Hiroki; Arai, Tomoharu; Yanagisawa, Michihiko; Ichiki, Takanori; Horiike, Yasuhiro

    2002-08-01

    A new dry cleaning technology for removal of silicon (Si) native oxides from contact holes employing a hot ammonium (NH3)/nitrogen trifluoride (NF3) mixture has been studied. The NH3/NF3 mixture heated at a high temperature in a quartz tube enabled etching of the silicon dioxide (SiO2) film placed in the downstream region. The mechanism of the etching reaction which was investigated using in-situ infrared spectroscopy and X-ray photoelectron spectroscopy analysis was revealed as follows: NF3 alone in the NH3/NF3 mixture was decomposed above 600°C, probably producing NFx (x=1, 2) and fluorine atoms. These active species reacted with NH3, thereby generating ammonium hydrogen fluoride (NH4F \\cdot HF) and/or ammonium fluoride (NH4F) in the gas phase which are considered to be SiO2 etchants. The reaction of these molecules with SiO2 generated an ammonium hexafluorosilicate ((NH4)2SiF6) product on the Si surface which was liberated at a temperature above 70°C, leaving the hydrogen terminated surface. The application of this method to actual contact holes demonstrated successful removal of the Si native oxide grown on the Si surface at the hole bottom.

  20. The breath ammonia measurement of the hemodialysis with a QCM-NH3 sensor.

    PubMed

    Ishida, Hitoshi; Satou, Toshio; Tsuji, Kiichi; Kawashima, Norimichi; Takemura, Hideo; Kosaki, Yasuhiro; Shiratori, Seimei; Agishi, Tetuzou

    2008-01-01

    Recently, expired gases are analyzed non-invasively for monitoring the substances in the blood. Breath ammonia has been shown to correlate with BUN (blood urea nitrogen) and Cr (creatinine), both of which are indicators of solute removal in hemodialysis. In this study, breath ammonia concentration was continuously measured using a crystal oscillator QCM (quartz crystal microbalance) during the expiration of patients undergoing dialysis treatment. The results show that NH3 (ammonia) decreased gradually as the treatment proceeded. A strong correlation was observed between changes in the frequency of the QCM gas sensor and both the pre-dialysis BUN level (r=0.71, p<0.05) and the post-dialysis BUN level (r=0.90, p<0.05). NH3 was found to fall precipitously during dialysis. The differences were statistically significant. In addition, we found a statistically significant correlation between BUN and NH3 in expired gas. These results suggest that continuous measurement of NH3 is useful to assess the status of solute removal during hemodialysis. PMID:18408261

  1. Solid state transformation of the crystalline monohydrate (CH3NH3)PbI3(H2O) to the (CH3NH3)PbI3 perovskite.

    PubMed

    Imler, Gregory H; Li, Xia; Xu, Bolei; Dobereiner, Graham E; Dai, Hai-Lung; Rao, Yi; Wayland, Bradford B

    2015-06-30

    Colorless crystals of (CH3NH3·H2O)PbI3 spontaneously lose water at 298 K which triggers a transformation to the black (CH3NH3)PbI3 perovskite in the solid state as a porous microcrystalline solid with nanoscale substructure, but the dihydrate (CH3NH3)4PbI6·2H2O) requires much more forcing conditions to produce (CH3NH3)PbI3. PMID:26083000

  2. Towards a carbon independent and CO2-free electrochemical membrane process for NH3 synthesis.

    PubMed

    Kugler, K; Ohs, B; Scholz, M; Wessling, M

    2014-04-01

    Ammonia is exclusively synthesized by the Haber-Bosch process starting from precious carbon resources such as coal or CH4. With H2O, H2 is produced and with N2, NH3 can be synthesized at high pressures and temperatures. Regrettably, the carbon is not incorporated into NH3 but emitted as CO2. Valuable carbon sources are consumed which could be used otherwise when carbon sources become scarce. We suggest an alternative process concept using an electrochemical membrane reactor (ecMR). A complete synthesis process with N2 production and downstream product separation is presented and evaluated in a multi-scale model to quantify its energy consumption. A new micro-scale ecMR model integrates mass, species, heat and energy balances with electrochemical conversions allowing further integration into a macro-scale process flow sheet. For the anodic oxidation reaction H2O was chosen as a ubiquitous H2 source. Nitrogen was obtained by air separation which combines with protons from H2O to give NH3 using a hypothetical catalyst recently suggested from DFT calculations. The energy demand of the whole electrochemical process is up to 20% lower than the Haber-Bosch process using coal as a H2 source. In the case of natural gas, the ecMR process is not competitive under today's energy and resource conditions. In future however, the electrochemical NH3 synthesis might be the technology-of-choice when coal is easily accessible over natural gas or limited carbon sources have to be used otherwise but for the synthesis of the carbon free product NH3. PMID:24557153

  3. A Water Maser and NH3 Survey of GLIMPSE Extended Green Objects

    NASA Astrophysics Data System (ADS)

    Cyganowski, C. J.; Koda, J.; Rosolowsky, E.; Towers, S.; Donovan Meyer, J.; Egusa, F.; Momose, R.; Robitaille, T. P.

    2013-02-01

    We present the results of a Nobeyama 45 m H2O maser and NH3 survey of all 94 northern GLIMPSE extended green objects (EGOs), a sample of massive young stellar objects (MYSOs) identified based on their extended 4.5 μm emission. We observed the NH3(1,1), (2,2), and (3,3) inversion lines, and detected emission toward 97%, 63%, and 46% of our sample, respectively (median rms ~ 50 mK). The H2O maser detection rate is 68% (median rms ~ 0.11 Jy). The derived H2O maser and clump-scale gas properties are consistent with the identification of EGOs as young MYSOs. To explore the degree of variation among EGOs, we analyze subsamples defined based on mid-infrared (MIR) properties or maser associations. H2O masers and warm dense gas, as indicated by emission in the higher-excitation NH3 transitions, are most frequently detected toward EGOs also associated with both Class I and II CH3OH masers. Ninety-five percent (81%) of such EGOs are detected in H2O (NH3(3,3)), compared to only 33% (7%) of EGOs without either CH3OH maser type. As populations, EGOs associated with Class I and/or II CH3OH masers have significantly higher NH3 line widths, column densities, and kinetic temperatures than EGOs undetected in CH3OH maser surveys. However, we find no evidence for statistically significant differences in H2O maser properties (such as maser luminosity) among any EGO subsamples. Combining our data with the 1.1 mm continuum Bolocam Galactic Plane Survey, we find no correlation between isotropic H2O maser luminosity and clump number density. H2O maser luminosity is weakly correlated with clump (gas) temperature and clump mass.

  4. Nucleobases and Prebiotic Molecules in Organic Residues Produced from the Ultraviolet Photo-Irradiation of Pyrimidine in NH3 and H2O+NH3 Ices

    NASA Technical Reports Server (NTRS)

    Nuevo, Michel; Milam, Stefanie N.; Sandford, Scott

    2012-01-01

    Although not yet identified in the interstellar medium (ISM), N-heterocycles including nucleobases the information subunits of DNA and RNA are present in carbonaceous chondrites, which indicates that molecules of biological interest can be formed in non-terrestrial environments via abiotic pathways. Recent laboratory experiments and ab-initio calculations have already shown that the irradiation of pyrimidine in pure H2O ices leads to the formation of a suite of oxidized pyrimidine derivatives, including the nucleobase uracil. In the present work, NH3:pyrimidine and H2O:NH3:pyrimidine ice mixtures with different relative proportions were irradiated with UV photons under astrophysically relevant conditions. Liquid- and gas-chromatography analysis of the resulting organic residues has led to the detection of the nucleobases uracil and cytosine, as well as other species of prebiotic interest such as urea and small amino acids. The presence of these molecules in organic residues formed under abiotic conditions supports scenarios in which extraterrestrial organics that formed in space and were subsequently delivered to telluric planets via comets and meteorites could have contributed to the inventory of molecules that triggered the first biological reactions on their surfaces.

  5. C60-mediated hydrogen desorption in Li-N-H systems

    NASA Astrophysics Data System (ADS)

    Qian, Zhao; Li, Sa; Pathak, Biswarup; Moysés Araújo, C.; Ahuja, Rajeev; Jena, Puru

    2012-12-01

    Hydrogen desorption from a LiH + NH3 mixture is very difficult due to the formation of the stable LiNH4 compound. Using cluster models and first-principles theory, we demonstrate that the C60 molecule can in fact significantly improve the thermodynamics of ammonia-mediated hydrogen desorption from LiH due to the stabilization of the intermediate state, LiNH4. The hydrogen desorption following the path of LiNH4-C60 → LiNH3-{{C}}_{6 0}+\\frac{1}{2}{{H}}_{2} is exothermic. Molecular dynamic simulations show that this reaction can take place even at room temperature (300 K). In contrast, the stable LiNH4 compound cannot desorb hydrogen at room temperature in the absence of C60. The introduction of C60 also helps to restrain the NH3 gas which is poisonous in proton exchange membrane fuel cell applications.

  6. C60-mediated hydrogen desorption in Li-N-H systems.

    PubMed

    Qian, Zhao; Li, Sa; Pathak, Biswarup; Araújo, C Moysés; Ahuja, Rajeev; Jena, Puru

    2012-12-01

    Hydrogen desorption from a LiH + NH(3) mixture is very difficult due to the formation of the stable LiNH(4) compound. Using cluster models and first-principles theory, we demonstrate that the C(60) molecule can in fact significantly improve the thermodynamics of ammonia-mediated hydrogen desorption from LiH due to the stabilization of the intermediate state, LiNH(4). The hydrogen desorption following the path of LiNH(4)-C(60) → LiNH(3)-C(60) + 1/2H(2) is exothermic. Molecular dynamic simulations show that this reaction can take place even at room temperature (300 K). In contrast, the stable LiNH(4) compound cannot desorb hydrogen at room temperature in the absence of C(60). The introduction of C(60) also helps to restrain the NH(3) gas which is poisonous in proton exchange membrane fuel cell applications. PMID:23138595

  7. Chasing the Elusive Benzofuran Impurity of the THR Antagonist NH-3: Synthesis, Isotope Labeling, and Biological Activity.

    PubMed

    Singh, Latika; Pressly, Brandon; Mengeling, Brenda J; Fettinger, James C; Furlow, J David; Lein, Pamela J; Wulff, Heike; Singh, Vikrant

    2016-03-01

    We have synthesized and established the structure of a long-suspected, but hitherto unknown, benzofuran side product (EBI) formed during the synthesis of NH-3. Understanding the mechanism of its formation has enabled isotope (D) labeling. We further developed a highly efficient method for separating EBI from NH-3. Interestingly, EBI was found to be a very potent thyroid hormone receptor (THR) agonist, while NH-3 is an antagonist. In this process, we have also achieved a significantly improved synthesis of NH-3. PMID:26849160

  8. Synthesis and Evaluation of Cu/SAPO-34 Catalysts for NH3-SCR 2: Solid-state Ion Exchange and One-pot Synthesis

    SciTech Connect

    Gao, Feng; Walter, Eric D.; Washton, Nancy M.; Szanyi, Janos; Peden, Charles HF

    2015-01-01

    Cu-SAPO-34 catalysts are synthesized using two methods: solid-state ion exchange (SSIE) and one-pot synthesis. SSIE is conducted by calcining SAPO-34/CuO mixtures at elevated temperatures. For the one-pot synthesis method, Cu-containing chemicals (CuO and CuSO4) are added during gel preparation. A high-temperature calcination step is also needed for this method. Catalysts are characterized with surface area/pore volume measurements, temperature programmed reduction (TPR), electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopies, and scanning electron microscopy (SEM). Catalytic properties are examined using standard ammonia selective catalytic reduction (NH3-SCR) and ammonia oxidation reactions. In Cu-SAPO-34 samples formed using SSIE, Cu presents both as isolated Cu2+ ions and unreacted CuO. The former is highly active and selective in NH3-SCR, while the latter catalyzes a side reaction; notably, the non-selective oxidation of NH3 above 350 ºC. Using the one-pot method followed by a high-temperature aging treatment, it is possible to form Cu SAPO-34 samples with predominately isolated Cu2+ ions at low Cu loadings. However at much higher Cu loadings, isolated Cu2+ ions that bind weakly with the CHA framework and CuO clusters also form. These Cu moieties are very active in catalyzing non-selective NH3 oxidation above 350 ºC. Low-temperature reaction kinetics indicate that Cu-SAPO-34 samples formed using SSIE have core-shell structures where Cu is enriched in the shell layers; while Cu is more evenly distributed within the one-pot samples. Reaction kinetics also suggest that at low temperatures, the local environment next to Cu2+ ion centers plays little role on the overall catalytic properties. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle under contract number DE-AC05-76RL01830. The authors also thank Shari Li (PNNL) for surface area/pore volume measurements, and Bruce W. Arey (PNNL) for SEM measurements. Discussions with Drs. A. Yezerets, K. Kamasamudram, J.H. Li, N. Currier and J.Y. Luo from Cummins, Inc. and H.Y. Chen and H. Hess from Johnson-Matthey are greatly appreciated.

  9. Absorption of NH3 on pristine and defected boron nitride nanosheets: A first principle study

    NASA Astrophysics Data System (ADS)

    Li, Hui; Chen, Zheng; Fang, Xiaoliang; Tie, Deyou

    2015-12-01

    Versatile functional groups can be connected to Boron Nitride nanosheet (BNNS) through Lewis acid/base interaction for targeted applications. However, there have been few experimental reports about Lewis acid attack at the N atoms on BNNS, so far as we see. VdW-DFT is employed in this paper to investigate the interaction between NH3 representing Lewis base and pristine or defected BNNS. Comparing the binding energy, separation and charge distribution of NH3 and pristine or defected BNNS systems, the distinctive defect in BNNS is found to be the key role in the absorption progress. Thus, it is supposed that the missing of Lewis acid and BNNS complex can be attributed to the absence of N vacancies and B-edges in BNNS.

  10. Potential energy surface and bound states of the NH3-Ar and ND3-Ar complexes.

    PubMed

    Loreau, J; Liévin, J; Scribano, Y; van der Avoird, A

    2014-12-14

    A new, four-dimensional potential energy surface for the interaction of NH3 and ND3 with Ar is computed using the coupled-cluster method with single, double, and perturbative triple excitations and large basis sets. The umbrella motion of the ammonia molecule is explicitly taken into account. The bound states of both NH3-Ar and ND3-Ar are calculated on this potential for total angular momentum values from J = 0 to 10, with the inclusion of Coriolis interactions. The energies and splittings of the rovibrational levels are in excellent agreement with the extensive high-resolution spectroscopic data accumulated over the years in the infrared and microwave regions for both complexes, which demonstrates the quality of the potential energy surface. PMID:25494745

  11. Calculations on the rate of the ion-molecule reaction between NH3(+) and H2

    NASA Technical Reports Server (NTRS)

    Herbst, Eric; Defrees, D. J.; Talbi, D.; Pauzat, F.; Koch, W.

    1991-01-01

    The rate coefficient for the ion-molecule reaction NH3(+) + H2 yields NH4(+) + H has been calculated as a function of temperature with the use of the statistical phase space approach. The potential surface and reaction complex and transition state parameters used in the calculation have been taken from ab initio quantum chemical calculations. The calculated rate coefficient has been found to mimic the unusual temperature dependence measured in the laboratory, in which the rate coefficient decreases with decreasing temperature until 50-100 K and then increases at still lower temperatures. Quantitative agreement between experimental and theoretical rate coefficients is satisfactory given the uncertainties in the ab initio results and in the dynamics calculations. The rate coefficient for the unusual three-body process NH3(+) + H2 + He yields NH4(+) + H + He has also been calculated as a function of temperature and the result found to agree well with a previous laboratory determination.

  12. Comparison of the biological NH3 removal characteristics among four inorganic packing materials.

    PubMed

    Hirai, M; Kamamoto, M; Yani, M; Shoda, M

    2001-01-01

    Four inorganic packing materials were evaluated in terms of their availability as a packing material of a packed tower deodorization apparatus (biofilter) from the viewpoints of biological NH3 removal characteristics and some physical properties. Porous ceramics (A), calcinated cristobalite (B), calcinated and formed obsidian (C), granulated and calculated soil (D) were used. The superiority of these packing materials determined based on the values of non-biological removal per unit weight or unit volume of packing material, complete removal capacity of NH3 per unit weight of packing material per day or unit volume of packing material per day and pressure drop of the packed bed was in the order of A approximately = C > B > or = D. Packing materials A and C with high porosity, maximum water content, and suitable mean pore diameter showed excellent removal capacity. PMID:16233018

  13. Copper (II) oxide nanowires for p-type conductometric NH3 sensing

    NASA Astrophysics Data System (ADS)

    Shao, F.; Hernández-Ramírez, F.; Prades, J. D.; Fàbrega, C.; Andreu, T.; Morante, J. R.

    2014-08-01

    Copper (II) oxide (CuO) is a metal oxide suitable for developing solid state gas sensors. Nevertheless, a detailed insight into the chemical-to-electrical transduction mechanisms between gas molecules and this metal oxide is still limited. Here, individual CuO nanowires were evaluated as ammonia (NH3) and hydrogen sulphide (H2S) sensors, validating the p-type character of this semiconductor. The working principle behind their performance was qualitatively modeled and it was concluded that adsorbed oxygen at the surface plays a key role necessary to explain the experimental data. Compared to their counterparts of SnO2 nanowires, an appreciable sensitivity enhancement to NH3 for concentrations below 100 ppm was demonstrated.

  14. On the reaction CH2O + NH3 Yields CH2NH + H2O

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Bauschlicher, Charles W., Jr.; Ricca, Alessandra; Bakes, E. L. O.; Arnold, James (Technical Monitor)

    2000-01-01

    We study the energetics of CH2O + NH3-Yields CH2NH + H2O in the gas phase at the B3LYP and CCSD(T)levels. This reaction is shown to have a sizeable barrier. Ionization of NH3 reduces the barrier to about 5 kcal/mol. We also show that in water, a proton catalyzed mechanism yields no barriers in excess of the reaction endothermicity. Since this reaction has been proposed as one of the steps in interstellar synthesis of glycine, the simplest amino acid, this work suggests that the formation of amino acids is occurring in and/or on interstellar water ice grains, and not in the gas phase.

  15. Porous Anatase TiO2 Thin Films for NH3 Vapour Sensing

    NASA Astrophysics Data System (ADS)

    Ponnusamy, Dhivya; Madanagurusamy, Sridharan

    2015-12-01

    Anatase titanium dioxide (TiO2) thin films were deposited onto cleaned glass substrates by a direct current (DC) reactive magnetron sputtering technique for different deposition times from 10 min to 40 min, which resulted in films of different thicknesses. Characterization techniques, such as x-ray diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM) were used to characterize the structural and morphological properties of the TiO2 thin films. XRD patterns showed the formation of (101) crystal anatase facets. The grain size values of the film increased with increased deposition time, and the films deposited at 40 min exhibited a porous structure. Anatase TiO2 thin films exhibited excellent sensing response, fast response and recovery time, as well as good stability and selectivity towards ammonia (NH3). The enhanced NH3 sensing behavior of anatase TiO2 films is attributed to the porous morphology and oxygen vacancies.

  16. High-resolution absorption measurements of NH3 at high temperatures: 500-2100 cm-1

    NASA Astrophysics Data System (ADS)

    Barton, Emma J.; Yurchenko, Sergei N.; Tennyson, Jonathan; Clausen, Snnik; Fateev, Alexander

    2015-12-01

    High-resolution absorption spectra of NH3 in the region 500-2100 cm-1 at temperatures up to 1027 C and approximately atmospheric pressure (101320 mbar) are measured. NH3 concentrations of 1000 ppm, 0.5% and 1% in volume fraction were used in the measurements. Spectra are recorded in high temperature gas flow cells using a Fourier Transform Infrared (FTIR) spectrometer at a nominal resolution of 0.09 cm-1. Measurements at 22.7 C are compared to high-resolution cross sections available from the Pacific Northwest National Laboratory (PNNL). The higher temperature spectra are analysed by comparison to a variational line list, BYTe, and experimental energy levels determined using the MARVEL procedure. Approximately 2000 lines have been assigned, of which 851 are newly assigned to mainly hot bands involving vibrational states as high as v2=5.

  17. Low energy studies (e,2e) studies from Ammonia (NH3)

    NASA Astrophysics Data System (ADS)

    Chaluvadi, Hari; Madison, Don; Nixon, K. L.; Murray, Andrew J.; Ning, Chuangang; Colgan, James

    2012-10-01

    Experimental and theoretical Triply Differential Cross Sections (TDCS) will be presented for electron-impact ionization of Ammonia (NH3) for highest occupied molecular orbital (HOMO), next highest occupied molecular orbital (NHOMO) and next next highest occupied molecular orbital (N^2HOMO). M3DW (molecular 3-body distorted wave) results will be compared with experiment for coplanar geometry. The final state electron energies and observation angles are symmetric.

  18. NH3 quantum rotators in Hofmann clathrates: intensity and width of rotational transition lines

    NASA Astrophysics Data System (ADS)

    Vorderwisch, Peter; Sobolev, Oleg; Desmedt, Arnaud

    2004-07-01

    Inelastic structure factors for rotational transitions of uniaxial NH3 quantum rotators, measured in a Hofmann clathrate with biphenyl as guest molecule, agree with those calculated for free rotators. A finite intrinsic line width, found for rotational transitions involving the rotational level j=3 at low temperature, supports a recently suggested model based on resonant rotor-rotor coupling. Present address: LPCM, CNRS-Université de Bordeaux I, 351 Cours de Libération, Talence F-33405, France.

  19. Computational investigation of NH3 adsorption and dehydrogenation on a W-modified Fe(111) surface.

    PubMed

    Hsiao, Ming-Kai; Su, Chia-Hao; Liu, Ching-Yang; Chen, Hui-Lung

    2015-11-11

    Hydrogen gas will play an important role in the future since it could be a replacement for gasoline, heating oil, natural gas, and other fuels. In previous reports ammonia (NH3), which has a high hydrogen content, provides a promising mode for the transferring and storing of hydrogen for its on-site generation. Therefore, the dehydrogenation of NH3 on a metal surface has been studied widely in the last few decades. In our study, we employed monolayer tungsten metal to modify the Fe(111) surface, denoted as W@Fe(111), and calculated the adsorption and dehydrogenation behaviors of NH3 on W@Fe(111) surface via first-principles calculations based on density functional theory (DFT). The three adsorption sites of the surface, top (T), 3-fold-shallow (S), and 3-fold-deep (D) were considered. The most stable structure of the NHx (x = 0-3) species on the surface of W@Fe(111) have been predicted. The calculated activation energies for NHx (x = 1-3) dehydrogenations are 19.29 kcal mol(-1) (for H2N-H bond activation), 29.17 kcal mol(-1) (for HN-H bond activation) and 27.94 kcal mol(-1) (for N-H bond activation), and the entire process is exothermic by 33.05 kcal mol(-1). To gain detailed knowledge of the catalytic processes of the NH3 molecule on the W@Fe(111) surface, the physical insights between the adsorbate/substrate interaction and interface morphology were subjected to a detailed electronic analysis. PMID:26524324

  20. Relativity, gold, closed-shell interactions, and CsAu.NH3.

    PubMed

    Pyykkö, Pekka

    2002-10-01

    The chemical properties of gold are strongly influenced by relativistic effects. One example is the large electronegativity of Au, which qualitatively explains the stability of (solid or liquid) cesium auride, Cs(+)Au(-), and other systems with Au(-) ions. An especially impressive compound is CsAu.NH(3), the structure and bonding of which are discussed. Future possibilities for finding further aurides are outlined. PMID:12370896

  1. SIMPLE DESIGN FOR AUTOMATION OF TUNGSTEN(VI) OXIDE TECHNIQUE FOR MEASUREMENT OF NH3, AND HNO3

    EPA Science Inventory

    The tungstic acid technique for collection and analysis of NH3 and HNO3 concentrations in the ambient air has been automated in a simple and cost-effective design. The design allows complete separation of HNO3 and NH3 during detection. Unattended operation in field trials has bee...

  2. Hydrothermal synthesis and NH3 gas sensing property of WO3 nanorods at low temperature

    NASA Astrophysics Data System (ADS)

    Dien Nguyen, Dac; Vuong Dang, Duc; Chien Nguyen, Duc

    2015-09-01

    One-dimensional self-assembled single-crystalline hexagonal tungsten trioxide (WO3) nanostructures were synthesized by wet chemical-assisted hydrothermal processing at 120 °C for 24 h using sodium tungstate and hydrochloric acid. Urchin-like hierarchical nanorods (petal size: ∼16 nm diameter and 110 nm length) were obtained. The samples were characterized by field emission scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy and x-ray diffraction. Sensors based on WO3 nanorods were fabricated by coating them on SiO2/Si substrate attached with Pt interdigitated electrodes. NH3 gas-sensing properties of WO3 nanorods were measured at different temperatures ranging from 50 °C to 350 °C and the response was evaluated as a function of ammonia gas concentration. The gas-sensing results reveal that WO3 nanorods sensor exhibits high sensitivity and selectivity to NH3 at low operating temperature (50 °C). The maximum response reached at 50 °C was 192 for 250 ppm NH3, with response and recovery times of 10 min and 2 min, respectively.

  3. Development and evaluation of optical fiber NH3 sensors for application in air quality monitoring

    NASA Astrophysics Data System (ADS)

    Huang, Yu; Wieck, Lucas; Tao, Shiquan

    2013-02-01

    Ammonia is a major air pollutant emitted from agricultural practices. Sources of ammonia include manure from animal feeding operations and fertilizer from cropping systems. Sensor technologies with capability of continuous real time monitoring of ammonia concentration in air are needed to qualify ammonia emissions from agricultural activities and further evaluate human and animal health effects, study ammonia environmental chemistry, and provide baseline data for air quality standard. We have developed fiber optic ammonia sensors using different sensing reagents and different polymers for immobilizing sensing reagents. The reversible fiber optic sensors have detection limits down to low ppbv levels. The response time of these sensors ranges from seconds to tens minutes depending on transducer design. In this paper, we report our results in the development and evaluation of fiber optic sensor technologies for air quality monitoring. The effect of change of temperature, humidity and carbon dioxide concentration on fiber optic ammonia sensors has been investigated. Carbon dioxide in air was found not interfere the fiber optic sensors for monitoring NH3. However, the change of humidity can cause interferences to some fiber optic NH3 sensors depending on the sensor's transducer design. The sensitivity of fiber optic NH3 sensors was found depends on temperature. Methods and techniques for eliminating these interferences have been proposed.

  4. Observation of orbiting resonances in He(3S1) + NH3 Penning ionization

    NASA Astrophysics Data System (ADS)

    Jankunas, Justin; Jachymski, Krzysztof; Hapka, Michał; Osterwalder, Andreas

    2015-04-01

    Resonances are among the clearest quantum mechanical signatures of scattering processes. Previously, shape resonances and Feshbach resonances have been observed in inelastic and reactive collisions involving atoms or diatomic molecules. Structure in the integral cross section has been observed in a handful of elastic collisions involving polyatomic molecules. The present paper presents the observation of shape resonances in the reactive scattering of a polyatomic molecule, NH3. A merged-beam study of the gas phase He(3S1) + NH3 Penning ionization reaction dynamics is described in the collision energy range 3.3 μeV < Ecoll < 10 meV. In this energy range, the reaction rate is governed by long-range attraction. Peaks in the integral cross section are observed at collision energies of 1.8 meV and 7.3 meV and are assigned to ℓ = 15,16 and ℓ = 20,21 partial wave resonances, respectively. The experimental results are well reproduced by theoretical calculations with the short-range reaction probability Psr = 0.035. No clear signature of the orbiting resonances is visible in the branching ratio between NH3+ and NH2+ formation.

  5. Constraints on the NH3 and PH3 distributions in the Great Red Spot

    NASA Technical Reports Server (NTRS)

    Wagener, R.; Caldwell, J.; Owen, T.

    1986-01-01

    Medium resolution (10 A) UV spectra were obtained for the Great Red Spot (GRS) and South Tropical Zone (STZ) of Jupiter using the low dispersion mode of the IUE spectrometers at wavelengths from 1900-2200 A. The scans were carried out to determine the coloring agent for the GRS to improve the database for developing photochemical models of the feature. The wavelengths were selected to cover the absorption features of NH3 and PH3. The resulting data were interpreted using a vertically inhomogeneous Rayleigh scattering radiative transfer model. Various NH3 concentrations were explored in an effort to fit the data, taking into account changes which would occur at different atmospheric pressure levels and due to the projected temperature fields. A forbidden NH3/forbidden H2 mixing ratio that was calculated at the 80-125 mbar pressure level in the GRS was enhanced by 3-10 percent relative to the STZ. An upper limit was obtained for the mixing ratio of PH3 in the GRS that is significantly lower than previously predicted concentrations, implying that vertical transport in the GRS is not much greater than in adjacent regions.

  6. Constraints on the NH3 and PH3 distributions in the Great Red SPOT

    NASA Astrophysics Data System (ADS)

    Wagener, R.; Caldwell, J.; Owen, T.

    1986-04-01

    Medium resolution (10 A) UV spectra were obtained for the Great Red Spot (GRS) and South Tropical Zone (STZ) of Jupiter using the low dispersion mode of the IUE spectrometers at wavelengths from 1900-2200 A. The scans were carried out to determine the coloring agent for the GRS to improve the database for developing photochemical models of the feature. The wavelengths were selected to cover the absorption features of NH3 and PH3. The resulting data were interpreted using a vertically inhomogeneous Rayleigh scattering radiative transfer model. Various NH3 concentrations were explored in an effort to fit the data, taking into account changes which would occur at different atmospheric pressure levels and due to the projected temperature fields. A forbidden NH3/forbidden H2 mixing ratio that was calculated at the 80-125 mbar pressure level in the GRS was enhanced by 3-10 percent relative to the STZ. An upper limit was obtained for the mixing ratio of PH3 in the GRS that is significantly lower than previously predicted concentrations, implying that vertical transport in the GRS is not much greater than in adjacent regions.

  7. Dynamics of CH3NH3PbI3 from first principles simulations

    NASA Astrophysics Data System (ADS)

    Kachmar, Ali; Carignano, Marcelo

    2015-03-01

    We address the dynamical and optical properties of CH3NH3PbI3 using molecular dynamics simulations based on forces calculated with density functional theory. We have studied the three stable phases of CH3NH3PbI3 but most of the effort was dedicated to the intermediate tetragonal phase, which is stable at standard ambient conditions. In this case, two different system sizes have been considered, one with 8 unit cells (384 atoms) and a larger one with 27 unit cells (1296 atoms). The total simulated time reached 40 ps. Our findings reveal the interplay between the thermal energy of the system and the electronic degrees of freedom. For example, the organic molecule undergoes relatively fast rotations and the energy band gap, approximated by the LUMO-HOMO energy difference, fluctuates around the equilibrium value of ~1.5 eV with a width of 0.2 eV. The rotation of the CH3NH3 molecule is not isotropic, and more importantly, it is quite sensitive to the size of the simulation box. Our study also provides a quantitative measure for the finite size effects affecting the calculated properties and provides a contextual scenario on which to analyze the more typical density functional theory studies based on static calculations on optimal structures. The authors acknowledge the HPC resources of Texas A&M University at Qatar.

  8. VizieR Online Data Catalog: MSX high-contrast IRDCs with NH3 (Chira+,

    NASA Astrophysics Data System (ADS)

    Chira, R.-A.; Beuther, H.; Linz, H.; Walmsley, C. M.; Menten; K. M.; Bonfman, L.

    2013-02-01

    Based on MSX data, a catalogue of more than 10,000 candidate IRDCs was compiled. From this catalogue we selected a complete sample of northern hemisphere high-contrast IRDCs with Galactic longitudes >=19.27° (and nine exceptions with Galactic longitudes <19°). The sample was observed in ammonia (1,1) and (2,2) inversion transitions with the Effelsberg 100-m telescope. NH3 parameters are derived for 109 sample sources. For each source galactic coordinates, brightness temperatures, line width FWHMs and optical depths of (1,1) and (2,2) inversion lines and LSR velocity of (1,1) inversion line are given. Furthermore, we derived the rotation and kinetic temperatures, ammonia column densities, kinematic distances and virial masses using the NH3 data. In addition, notes about whether the sources being associated with Spitzer sources or not are given. Using ATLASGAL data, the 870 micron flux densities gas masses, virial parameters, H2 column densities and NH3 abundances are given. In addition, we listed the sample sources where no ammonia which did not fulfil our selection criteria. (4 data files).

  9. Kinetics and gas-surface dynamics of GaN homoepitaxial growth using NH 3-seeded supersonic molecular beams

    NASA Astrophysics Data System (ADS)

    McGinnis, A. J.; Thomson, D.; Davis, R. F.; Chen, E.; Michel, A.; Lamb, H. H.

    2001-11-01

    The kinetics of homoepitaxial growth of GaN thin films on metal-organic chemical vapor deposition (MOCVD)-grown GaN(0 0 0 1)/AlN/6H-SiC substrates was probed using NH 3-seeded supersonic molecular beams. NH 3 was seeded in H 2 and He and antiseeded in N 2 and Ar in order to obtain incident kinetic energies of 0.08-1.8 eV. Nozzle temperatures of 35-600 °C were used to adjust the NH 3 internal energy. Intense NH 3 beams (fluxes >2×10 15 cm-2 s-1 at the substrate) are produced for low seeding percentages (<5%) in the lighter carrier gases, because the heavier species (NH 3) is focused along the centerline of the beam. The NH 3 flux is proportional to the ratio of its molecular weight to the average molecular weight of the binary gas mixture. A steady-state Langmuir-Hinshelwood kinetics model was used to extract zero-coverage NH 3 sticking coefficient ( αNH 30) values from GaN growth kinetics data. An αNH 30 value of 0.14 at 750 °C was determined using seeded supersonic beams of NH 3 in He with incident kinetic energies of 0.4-0.5 eV. In comparison, GaN growth rates using low-energy NH 3 molecules (0.03 eV) from a leak valve indicate an αNH 30 of 0.29. Growth rate measurements using NH 3 beams with kinetic energies of 0.08-1.8 eV confirmed that αNH 30 generally decreases with increasing incident kinetic energy, leading us to conclude that NH 3 chemisorption on GaN(0 0 0 1) is unactivated and occurs via a precursor-mediated mechanism. Internal energy enhancement of NH 3 chemisorption via a precursor-mediated channel is proposed to explain the effects of nozzle temperature on GaN growth kinetics. The effects of NH 3 incident kinetic energy on film morphology are indirect. Rough, highly faceted films are observed under Ga-limited growth conditions. The surface morphology of films grown under NH 3-limited conditions changes from rough to smooth as the effective V/III ratio is decreased.

  10. Melting phase relations in the system H2O - NH3 at high pressure

    NASA Astrophysics Data System (ADS)

    Sugimura, E.; Hirose, K.; Komabayashi, T.; Ohishi, Y.; Hirao, N.; Dubrovinsky, L. S.

    2012-12-01

    The density models of Uranus and Neptune constrained by their gravitational moments from Voyager mission suggest that mantles of these planets may be predominantly comprised of water (H2O), methane (CH4), and ammonia (NH3). The impurities in pure water would greatly influence the phase relations in the water-rich system expected in the icy mantle, which must be known to construct a plausible planetary model. One of important effects of the impurity is on the liquidus temperature (Tliq), since it decides the actual presence of solid phase within the icy mantle. In order to determine Tliq in H2O-rich region of the H2O - CH4 - NH3 ternary system, the melting phase relations in the H2O - CH4 and H2O - NH3 systems must be accurately known. However, previous melting experiments on each binary system were limited to several gigapascals, thus need to be explored to higher P-T conditions for application in interiors of Uranus and Neptune. We have investigated high-pressure (P) and -temperature (T) melting phase relations in the H2O - NH3 system based on a combination of visual observation and angle-dispersive x-ray diffraction (XRD) measurements at BL10XU, SPring-8. High-P-T conditions were generated in an externally-resistive heated diamond anvil cell (DAC). Starting material was 20wt% NH3 aqueous solution whose composition was checked via Tliq of the solution measured in a DAC at near atmospheric pressure. The aqueous solution was loaded into a gold-lined hole in a preindented rhenium gasket in order to insulate the sample from rhenium. Pressure was determined from the unit-cell volume of gold liner. Melting and freezing of the sample were detected by monitoring disappearance/appearance of diffraction peaks of solid and diffuse scattering of liquids, as well as observing melting/crystallization of crystal grains under microscope. Up to 20 GPa at room temperature, in addition to ice VII, diffraction peaks of bcc-like phase, which is most likely to be the reported phase VI of ammonia monohydrate (AMH VI), were observed, although the diffraction peaks were either too broad or too few to specify its structure. When temperature was raised until diffuse scattering appeared, the diffraction peaks of AMH VI disappeared, indicating ice VII is the liquidus phase. Newly obtained Tliq were higher than all the exiting melting curves of pure H2O determined in externally-heated DAC by 50 K at 15 GPa at minimum. This contradicts the previous reports that the H2O - NH3 system is eutectic, i.e. Tliq of our sample should be lower than the melting temperature of the H2O end member. We will discuss possible sources for this discrepancy. We also propose a new phase diagram of the system H2O - NH3 and possible implications for the structure of the icy planets.

  11. Similar binding of the carcinostatic drugs cis-[Pt(NH3)2Cl2] and [Ru(NH3)5Cl] Cl2 to tRNAphe and a comparison with the binding of the inactive trans-[Pt(NH3)2Cl2] complex - reluctance in binding to Watson-Crick base pairs within double helix.

    PubMed Central

    Rubin, J R; Sabat, M; Sundaralingam, M

    1983-01-01

    A comparative study of the binding of square planar cis- and trans-[Pt(NH3)2Cl2] complexes and the octahedral [Ru(NH3)5(H2O)]3+ complex to tRNAphe from yeast was carried out by X-ray crystallography. Both of the carcinostatic compounds, cis-[Pt(NH3)2Cl2] and [Ru(NH3)5(H2O)]3+ show similarities in their mode of binding to tRNA. These complexes bind specifically to the N(7) positions of guanines G15 and G18 in the dihydrouridine loop. [Ru(NH3)5(H2O)]3+ has an additional binding site at N(7) of residue G1 after extensive soaking times (58 days). A noncovalent binding site for ruthenium is also observed in the deep groove of the acceptor stem helix with shorter (25 days) soaking time. The major binding site for the inactive trans-[Pt(NH3)Cl2] complex is at the N(1) position of residue A73, with minor trans-Pt binding sites at the N(7) positions of residues Gm34, G18 and G43. The similarities in the binding modes of cis-[Pt(NH3)2Cl2] and [Ru(NH3)5(H2O)]3+ are expected to be related to their carcinostatic properties. PMID:6353373

  12. Two-center three-electron bonding in ClNH3 revealed via helium droplet infrared laser Stark spectroscopy: Entrance channel complex along the Cl + NH3 → ClNH2 + H reaction

    NASA Astrophysics Data System (ADS)

    Moradi, Christopher P.; Xie, Changjian; Kaufmann, Matin; Guo, Hua; Douberly, Gary E.

    2016-04-01

    Pyrolytic dissociation of Cl2 is employed to dope helium droplets with single Cl atoms. Sequential addition of NH3 to Cl-doped droplets leads to the formation of a complex residing in the entry valley to the substitution reaction Cl + NH3 → ClNH2 + H. Infrared Stark spectroscopy in the NH stretching region reveals symmetric and antisymmetric vibrations of a C3v symmetric top. Frequency shifts from NH3 and dipole moment measurements are consistent with a ClNH3 complex containing a relatively strong two-center three-electron (2c-3e) bond. The nature of the 2c-3e bonding in ClNH3 is explored computationally and found to be consistent with the complexation-induced blue shifts observed experimentally. Computations of interconversion pathways reveal nearly barrierless routes to the formation of this complex, consistent with the absence in experimental spectra of two other complexes, NH3Cl and Cl-HNH2, which are predicted in the entry valley to the hydrogen abstraction reaction Cl + NH3 → HCl + NH2.

  13. Two-center three-electron bonding in ClNH3 revealed via helium droplet infrared laser Stark spectroscopy: Entrance channel complex along the Cl + NH3 → ClNH2 + H reaction.

    PubMed

    Moradi, Christopher P; Xie, Changjian; Kaufmann, Matin; Guo, Hua; Douberly, Gary E

    2016-04-28

    Pyrolytic dissociation of Cl2 is employed to dope helium droplets with single Cl atoms. Sequential addition of NH3 to Cl-doped droplets leads to the formation of a complex residing in the entry valley to the substitution reaction Cl + NH3 → ClNH2 + H. Infrared Stark spectroscopy in the NH stretching region reveals symmetric and antisymmetric vibrations of a C3v symmetric top. Frequency shifts from NH3 and dipole moment measurements are consistent with a ClNH3 complex containing a relatively strong two-center three-electron (2c-3e) bond. The nature of the 2c-3e bonding in ClNH3 is explored computationally and found to be consistent with the complexation-induced blue shifts observed experimentally. Computations of interconversion pathways reveal nearly barrierless routes to the formation of this complex, consistent with the absence in experimental spectra of two other complexes, NH3Cl and Cl-HNH2, which are predicted in the entry valley to the hydrogen abstraction reaction Cl + NH3 → HCl + NH2. PMID:27131544

  14. Rovibrational spectra of ammonia. II. Detailed analysis, comparison, and prediction of spectroscopic assignments for 14NH3, 15NH3, and 14ND3.

    PubMed

    Huang, Xinchuan; Schwenke, David W; Lee, Timothy J

    2011-01-28

    Several aspects of ammonia rovibrational spectra have been investigated using the new HSL-2 potential energy surface that includes an approximate correction for nonadiabatic effects. The unprecedented accuracy of rovibrational energy levels and transition energies computed using HSL-2 was demonstrated in Part I of this study. For (14)NH(3), new assignments for a few ν(3) + ν(4) band transitions and energy levels are suggested, and discrepancies between computed and HITRAN energy levels in the 2ν(4) band are analyzed (2ν(4) is the most difficult band below 5000 cm(-1)). New assignments are suggested for existing or missing 2ν(4) levels. Several new vibrational bands are identified from existing, unassigned HITRAN data, including 2ν(2) + ν(4), (ν(3) + ν(4)) -A(')∕A("), ν(1) + 2ν(2), and 2ν(2) + 2ν(4). The strong mixing between the 2ν(4) and 2ν(2) + ν(4) bands is carefully examined and found to be the source of the difficulties in the experimental modeling of 2ν(4). Discussion is presented for preliminary J = 10 results, where the overall root-mean-square error is estimated to be less than 0.039 cm(-1). The analysis of the 4ν(2) band demonstrates both the reliability and the accuracy of predictions from HSL-2. The full list of computed J = 0 band origins (with assignments) and the inversion splittings up to 7000-8000 cm(-1) above the zero-point energy are presented. J = 0-2 levels are reported for those bands below 5100 cm(-1) that are missing from the HITRAN database. For (15)NH(3), excellent agreement is found for the available ν(2) and ν(3) + ν(4)(E) transition energies, but significant deficiencies are shown for HITRAN levels and several corrections are suggested. The (15)N isotopic effects are presented for the J = 0-6 levels of 13 HITRAN bands. For (14)ND(3), we reproduce the pure rotational inversion spectra line frequencies with an accuracy similar to that for (14)NH(3). However, it is not possible to reproduce simultaneously all four pairs of inversion-split vibrational fundamentals to better than 0.05 cm(-1) uncertainty. It is suggested that a reanalysis of some suspicious (14)ND(3) fundamental bands is required. The analyses presented here and in Part I show that rovibrational energy levels and transition frequencies computed with HSL-2 (with nonadiabatic corrections) remain highly accurate well beyond the experimental data used in the refinement procedure. Calculations using HSL-2 are capable of revealing many deficiencies in experimental analyses of ammonia spectra and provide reliable predictions with similar accuracy. It is expected that the results of this study will be useful in the future interpretation of high-resolution spectra from laboratory experiments or from astronomical observations. The present work represents a very significant advance in the state of our knowledge of the spectroscopy of ammonia and its isotopologues. PMID:21280739

  15. Rovibrational spectra of ammonia. II. Detailed analysis, comparison, and prediction of spectroscopic assignments for 14NH3,15NH3, and 14ND3

    NASA Astrophysics Data System (ADS)

    Huang, Xinchuan; Schwenke, David W.; Lee, Timothy J.

    2011-01-01

    Several aspects of ammonia rovibrational spectra have been investigated using the new HSL-2 potential energy surface that includes an approximate correction for nonadiabatic effects. The unprecedented accuracy of rovibrational energy levels and transition energies computed using HSL-2 was demonstrated in Part I of this study. For 14NH3, new assignments for a few ν3 + ν4 band transitions and energy levels are suggested, and discrepancies between computed and HITRAN energy levels in the 2ν4 band are analyzed (2ν4 is the most difficult band below 5000 cm-1). New assignments are suggested for existing or missing 2ν4 levels. Several new vibrational bands are identified from existing, unassigned HITRAN data, including 2ν2 + ν4, (ν3 + ν4) -A'/A'', ν1 + 2ν2, and 2ν2 + 2ν4. The strong mixing between the 2ν4 and 2ν2 + ν4 bands is carefully examined and found to be the source of the difficulties in the experimental modeling of 2ν4. Discussion is presented for preliminary J = 10 results, where the overall root-mean-square error is estimated to be less than 0.039 cm-1. The analysis of the 4ν2 band demonstrates both the reliability and the accuracy of predictions from HSL-2. The full list of computed J = 0 band origins (with assignments) and the inversion splittings up to 7000-8000 cm-1 above the zero-point energy are presented. J = 0-2 levels are reported for those bands below 5100 cm-1 that are missing from the HITRAN database. For 15NH3, excellent agreement is found for the available ν2 and ν3 + ν4(E) transition energies, but significant deficiencies are shown for HITRAN levels and several corrections are suggested. The 15N isotopic effects are presented for the J = 0-6 levels of 13 HITRAN bands. For 14ND3, we reproduce the pure rotational inversion spectra line frequencies with an accuracy similar to that for 14NH3. However, it is not possible to reproduce simultaneously all four pairs of inversion-split vibrational fundamentals to better than 0.05 cm-1 uncertainty. It is suggested that a reanalysis of some suspicious 14ND3 fundamental bands is required. The analyses presented here and in Part I show that rovibrational energy levels and transition frequencies computed with HSL-2 (with nonadiabatic corrections) remain highly accurate well beyond the experimental data used in the refinement procedure. Calculations using HSL-2 are capable of revealing many deficiencies in experimental analyses of ammonia spectra and provide reliable predictions with similar accuracy. It is expected that the results of this study will be useful in the future interpretation of high-resolution spectra from laboratory experiments or from astronomical observations. The present work represents a very significant advance in the state of our knowledge of the spectroscopy of ammonia and its isotopologues.

  16. Investigation of the Hydrolysis of Perovskite Organometallic Halide CH3NH3PbI3 in Humidity Environment

    NASA Astrophysics Data System (ADS)

    Zhao, Jiangtao; Cai, Bing; Luo, Zhenlin; Dong, Yongqi; Zhang, Yi; Xu, Han; Hong, Bin; Yang, Yuanjun; Li, Liangbin; Zhang, Wenhua; Gao, Chen

    2016-02-01

    Instability of emerging perovskite organometallic halide in humidity environment is the biggest obstacle for its potential applications in solar energy harvest and electroluminescent display. Understanding the detailed decay mechanism of these materials in moisture is a critical step towards the final appropriate solutions. As a model study presented in this work, in situ synchrotron radiation x-ray diffraction was combined with microscopy and gravimetric analysis to study the degradation process of CH3NH3PbI3 in moisture, and the results reveal that: 1) intermediate monohydrated CH3NH3PbI3·H2O is detected in the degradation process of CH3NH3PbI3 and the final decomposition products are PbI2 and aqueous CH3NH3I; 2) the aqueous CH3NH3I could hardly further decompose into volatile CH3NH2, HI or I2; 3) the moisture disintegrate CH3NH3PbI3 and then alter the distribution of the decomposition products, which leads to an incompletely-reversible reaction of CH3NH3PbI3 hydrolysis and degrades the photoelectric properties. These findings further elucidate the picture of hydrolysis process of perovskite organometallic halide in humidity environment.

  17. Investigation of the Hydrolysis of Perovskite Organometallic Halide CH3NH3PbI3 in Humidity Environment

    PubMed Central

    Zhao, Jiangtao; Cai, Bing; Luo, Zhenlin; Dong, Yongqi; Zhang, Yi; Xu, Han; Hong, Bin; Yang, Yuanjun; Li, Liangbin; Zhang, Wenhua; Gao, Chen

    2016-01-01

    Instability of emerging perovskite organometallic halide in humidity environment is the biggest obstacle for its potential applications in solar energy harvest and electroluminescent display. Understanding the detailed decay mechanism of these materials in moisture is a critical step towards the final appropriate solutions. As a model study presented in this work, in situ synchrotron radiation x-ray diffraction was combined with microscopy and gravimetric analysis to study the degradation process of CH3NH3PbI3 in moisture, and the results reveal that: 1) intermediate monohydrated CH3NH3PbI3·H2O is detected in the degradation process of CH3NH3PbI3 and the final decomposition products are PbI2 and aqueous CH3NH3I; 2) the aqueous CH3NH3I could hardly further decompose into volatile CH3NH2, HI or I2; 3) the moisture disintegrate CH3NH3PbI3 and then alter the distribution of the decomposition products, which leads to an incompletely-reversible reaction of CH3NH3PbI3 hydrolysis and degrades the photoelectric properties. These findings further elucidate the picture of hydrolysis process of perovskite organometallic halide in humidity environment. PMID:26924112

  18. Investigation of the Hydrolysis of Perovskite Organometallic Halide CH3NH3PbI3 in Humidity Environment.

    PubMed

    Zhao, Jiangtao; Cai, Bing; Luo, Zhenlin; Dong, Yongqi; Zhang, Yi; Xu, Han; Hong, Bin; Yang, Yuanjun; Li, Liangbin; Zhang, Wenhua; Gao, Chen

    2016-01-01

    Instability of emerging perovskite organometallic halide in humidity environment is the biggest obstacle for its potential applications in solar energy harvest and electroluminescent display. Understanding the detailed decay mechanism of these materials in moisture is a critical step towards the final appropriate solutions. As a model study presented in this work, in situ synchrotron radiation x-ray diffraction was combined with microscopy and gravimetric analysis to study the degradation process of CH3NH3PbI3 in moisture, and the results reveal that: 1) intermediate monohydrated CH3NH3PbI3·H2O is detected in the degradation process of CH3NH3PbI3 and the final decomposition products are PbI2 and aqueous CH3NH3I; 2) the aqueous CH3NH3I could hardly further decompose into volatile CH3NH2, HI or I2; 3) the moisture disintegrate CH3NH3PbI3 and then alter the distribution of the decomposition products, which leads to an incompletely-reversible reaction of CH3NH3PbI3 hydrolysis and degrades the photoelectric properties. These findings further elucidate the picture of hydrolysis process of perovskite organometallic halide in humidity environment. PMID:26924112

  19. Validation of techniques for fast response measurement of HNO 3 and NH 3 and determination of the [NH 3] [HNO 3] concentration product

    NASA Astrophysics Data System (ADS)

    Harrison, Roy M.; Msibi, I. M.

    Semi-continuous analysers for ammonia and nitric acid have been constructed, using modifications to published designs. The ammonia analyser is based upon a diffusion scrubber, and that for nitric acid upon conversion of HNO 3 to NO 2 (via NO) and analysis by luminol chemiluminescence. Both have response times of around 5 min and detection limits of around 100 ppt. Comparison of the semi-continuous analysers with conventional filter pack and denuder procedures shows good agreement. The nitric acid analyser correlates extremely closely with the filter pack method, whilst the ammonia analyser is highly comparable with measurements made by annular denuder. Both instruments become less reliable at relative humidities above 90%. The instruments have been used to measure [NH 3] [HNO 3] concentration products at a site in suburban Birmingham. In general, these concentration products conform extremely well to values predicted from chemical thermodynamics for the equilibrium dissociation of pure ammonium nitrate. The exception is for measurements made at very high humidities, here it appears that kinetic constraints lead to a slow reaction and actual atmospheric concentration products appreaciably exceed equilibrium values.

  20. NH3 is involved in the NH4+ transport induced by the functional expression of the human Rh C glycoprotein.

    PubMed

    Bakouh, Naziha; Benjelloun, Fatine; Hulin, Philippe; Brouillard, Franck; Edelman, Aleksander; Chrif-Zahar, Baya; Planelles, Gabrielle

    2004-04-16

    Renal ammonium (NH3 + NH4+) transport is a key process for body acid-base balance. It is well known that several ionic transport systems allow NH4+ transmembrane translocation without high specificity NH4+, but it is still debated whether NH3, and more generally, gas, may be transported by transmembrane proteins. The human Rh glycoproteins have been proposed to mediate ammonium transport. Transport of NH4+ and/or NH3 by the epithelial Rh C glycoprotein (RhCG) may be of physiological importance in renal ammonium excretion because RhCG is mainly expressed in the distal nephron. However, RhCG function is not yet established. In the present study, we search for ammonium transport by RhCG. RhCG function was investigated by electrophysiological approaches in RhCG-expressing Xenopus laevis oocytes. In the submillimolar concentration range, NH4Cl exposure induced inward currents (IAM) in voltage-clamped RhCG-expressing cells, but not in control cells. At physiological extracellular pH (pHo) = 7.5, the amplitude of IAM increased with NH4Cl concentration and membrane hyperpolarization. The amplitude of IAM was independent of external Na+ or K+ concentrations but was enhanced by alkaline pHo and decreased by acid pHo. The apparent affinity of RhCG for NH4+ was affected by NH3 concentration and by changing pHo, whereas the apparent affinity for NH3 was unchanged by pHo, consistent with direct NH3 involvement in RhCG function. The enhancement of methylammonium-induced current by NH3 further supported this conclusion. Exposure to 500 microm NH4Cl induced a biphasic intracellular pH change in RhCG-expressing oocytes, consistent with both NH3 and NH4+ enhanced influx. Our results support the hypothesis of a specific role for RhCG in NH3 and NH4+ transport. PMID:14761968

  1. Photochemistry of NH3, CH4 and PH3 - Possible applications to the Jovian planets

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Morimoto, J. Y.; Benson, R.; Bossard, A.

    1982-01-01

    It is found that the photolysis of NH4 at 185 nm in the presence of a two-fold excess of CH4 results in the loss of about 0.25 mole of CH4 per mole of NH3 decomposed. The loss is shown to arise from the abstraction of hydrogen atoms from CH4 by photolytically generated hot hydrogen atoms. It is concluded that NH3 photolysis in the H2-abundant atmosphere of Jupiter is not responsible for the presence of the carbon compounds observed there, such as ethane, acetylene, and hydrogen cyanide, but may have had a role in the early atmosphere of Titan. Also, it is found that the photolysis of PH3 with a 206 nm light source gives P2H4, which in turn is converted to a red-brown solid. The course of the photolysis is not changed appreciably when the temperature is lowered to 157 K except that the concentration of P2H4 increases, while the presence of H2 has no effect on the P2H4 yield. Photolysis of 9:1 NH3:PH3 is found to give a rate of decomposition of PH3 that is comparable with that observed by the direct photolysis of PH3 and comparable amounts of the red-brown solid and P2H4 are observed. In addition, the implications of these results for the structures of the compounds responsible for the wide array of colors observed in the atmosphere of Jupiter are examined.

  2. H2O/Ni(100) and NH3/Ni(100) - A computational approach

    NASA Technical Reports Server (NTRS)

    Bauschlicher, C. W., Jr.

    1985-01-01

    The adsorption of NH3 and H2O on the Ni(100) is treated using a cluster model. The adsorption is found to have only a small effect on the HXH angle. Rotation about the principal ligand axis requires virtually no energy. Ligand tilts of 15 deg are found to require small amounts of energy, leading to the suggestion that the ESDIAD signal is a result of excited tilting modes, not a change in the HXH angle. For H2O additional bending modes are considered and all are found to be quite flat in energy.

  3. M dependence in the analysis of NH3-He microwave double resonance experiments

    NASA Technical Reports Server (NTRS)

    Davis, S. L.; Green, S.

    1983-01-01

    New close-coupled calculations of laboratory-frame, m-dependent cross sections for rotational excitation in NH3-He collisions are used to examined the validity of using degeneracy averaged values in the analysis of four-level double resonance experiments. It is found that the proper use of m-dependent cross sections and absorption probabilities produces only minor changes in the calculated Delta I/I (the fractional change in the signal absorption intensity when pumping radiation is applied) and does not, therefore, resolve the discrepancies between theoretical and experimental values that were noted in previous studies.

  4. Spectroscopic line parameters of NH3 and PH3 in the far infrared

    NASA Technical Reports Server (NTRS)

    Husson, N.; Goldman, A.; Orton, G.

    1982-01-01

    NH3 and PH3 rotation and rotation-inversion line parameters in the far to medium IR are calculated for remote sounding purposes of planetary atmospheres; 1607 lines of (N-14)H3, 362 lines of (N-15)H3 and 325 lines of PH3 are compiled. The absolute intensity formulation has been reviewed in the case of rotation and rotation-inversion lines of molecules with C(3v) symmetry. The justification for the general agreement between the authors, and comparisons with other published expressions are given.

  5. OT1_ccodella_1: Peering into the protostellar shocks: NH3 emission at high-velocities

    NASA Astrophysics Data System (ADS)

    Codella, C.

    2010-07-01

    Ammonia and water are key molecules for determining the physical and chemical structure of star forming regions because of their large abundance variations. In shocked regions where jets driven by low-mass protostars impact the surrounding medium, the NH3 and H2O abundances undergo a dramatic enhancement due to ice grain mantle sublimation. Thanks to the very recent HIFI (CHESS KPs) observations performed towards the prototype L1157 outflow, we compared the line profiles due to the NH3(1_0-0_0) and H2O(1_10-1_01) transitions in the HIFI-band 1b. The high-spectral resolution provided by HIFI allowed us to observe a striking difference in profile between water and ammonia, with H2O emitting at definitely higher velocities. In Codella et al. (2010) we propose that such difference reflects different formation mechanisms: while NH3 is believed to be a direct product of grain surface reactions, water is enhanced by the release of the icy mantles as well as by endothermic reactions occurring in the warm (> 220 K) shocked gas, which convert all gaseous atomic oxygen into water. We propose here the obvious next step, i.e. to observe the NH3(1_0-0_0) line at 572.5 GHz in a sample of 8 bright low-mass outflow spots already observed in the H2O(1_10-1_01) line within the WISH KP. The analysis of the profiles in such sample will allow us to: (i) determine whether the difference in profiles is unique to L1157 or a common characteristic of chemically rich outflows; (ii) provide clues to the physical characteristics of the shock and of the pre-existing material. Such analysis will be performed by using a suite of chemical, PDR, radiative transfer and shocks models which our team has developed. The present proposal can be considered as a WISH+CHESS KPs synergy and indeed it gathers components of the teams leading the investigations of protostellar outflows in both CHESS and WISH Herschel GT-KPs.

  6. Overtone, 2NH (ν1 + ν3) spectroscopy of 15NH3-Ar

    NASA Astrophysics Data System (ADS)

    Vanfleteren, T.; Földes, T.; Herman, M.; Di Lonardo, G.; Fusina, L.

    2015-12-01

    We report on the observation of the Π (11; 2NH) ← Σ (00; ground state) band in 15NH3-Ar, with origin at 6615.943 cm-1, using jet-cooled cw-cavity ring-down spectroscopy. The rotational temperature is estimated to be 7 K. Nineteen rotational lines were assigned. Perturbations were evidenced from anomalous line positions and line widths, but not unraveled. Upper state rotational constants were obtained from the analysis of the nine unperturbed R/P lines. The e-symmetry upper state predissociation lifetimes appear to decrease with J‧, from about 1.2 ns to 250 ps from J‧ = 1 to 9.

  7. A DFT study of reaction pathways of NH3 decomposition on InN (0001) surface

    NASA Astrophysics Data System (ADS)

    Walkosz, Weronika; Zapol, Peter; Stephenson, G. Brian

    2012-08-01

    Reaction pathways for complete decomposition of ammonia on the InN (0001) surface are investigated using first principles calculations. We show that while the initial NH3 decomposition on this surface can proceed by H dissociation, its further decomposition is most favorable by H transfer. The calculated low diffusion barriers for the decomposed species on the surface imply that the metal-organic chemical vapor deposition growth of InN is a reaction-limited process rather than diffusion-limited at low adsorbate coverage.

  8. Second-sphere coordination in anion binding: Synthesis and characterization of hexaamminecobalt(III) salts [Co(NH 3) 6](L) 3·3H 2O and [Co(NH 3) 6]Cl(L) 2, L=(CH 3) 3C 6H 2SO 3 and X-ray structure determination of [Co(NH 3) 6]Cl(L) 2

    NASA Astrophysics Data System (ADS)

    Sharma, Raj Pal; Bala, Ritu; Sharma, Rajni; Singh, Kamal Nain; Ferretti, Valeria

    2006-02-01

    The reaction of hexaamminecobalt(III) chloride with sodium salt of mesitylenesulphonic acid in aqueous medium (1:3 molar ratio) leads to formation of two products of hexaamminecobalt(III) salts [Co(NH 3) 6](L) 3·3H 2O and [Co(NH 3) 6]Cl(L) 2, L=(CH 3) 3C 6H 2SO 3. These cobalt(III) complexes have been characterized by elemental analyses and spectroscopic techniques (e.g. UV/Visible, IR and NMR). Single crystal X-ray structure determination of title complex salt revealed supramolecular hydrogen bonding network between ionic groups (i.e. oxygen atoms of C 9H 11SO 3- and Cl -) and NH groups of coordinated NH 3 molecules, i.e. N-H⋯O - and N-H⋯Cl - interactions resulting in bilayer formation, the bilayers being anchored by Cl - ions. The formation of definite salts of composition [Co(NH 3) 6](L) 3·3H 2O and [Co(NH 3) 6]Cl(L) 2 and measurement of solubility products suggests that [Co(NH 3) 6] 3+ present in [Co(NH 3) 6]Cl 3 is a promising purely inorganic anion binding agent for the weakly coordinating sulphonate anion.

  9. Flexible NH3 sensors fabricated by in situ self-assembly of polypyrrole.

    PubMed

    Su, Pi-Guey; Lee, Chi-Ting; Chou, Cheng-Yi

    2009-12-15

    Novel flexible NH(3) gas sensors were formed by the in situ self-assembly of polypyrrole (PPy) on plastic substrates. A negatively charged substrate was prepared by the formation of an organic monolayer (3-mercapto-1-propanesulfonic acid sodium salt-MPS) on a polyester (PET) substrate using a pair of comb-like Au electrodes. Two-cycle poly(4-styrenesulfonic acid) sodium salt/poly(allylamine hydrochloride) (PSS/PAH) bilayers (precursor layer) were then layer-by-layer (LBL) deposited on an MPS-modified substrate. Finally, a monolayer of PPy self-assembled in situ and PPy multilayer thin films self-assembled LBL in situ on a (PSS/PAH)(2)/MPS/Au/Cr/PET substrate. The thin films were analyzed by atomic force microscopy (AFM). The effects of the precursor layer (PSS), the deposition time of the monolayer of PPy and the number of PPy multilayers on the gas sensing properties (response) and the flexibility of the sensors were investigated to optimize the fabrication of the film. Additionally, other sensing properties such as sensing linearity, reproducibility, response and recovery times, as well as cross-sensitivity effects were studied. The flexible NH(3) gas sensor exhibited a strong response that was comparable to or even greater than that of sensors that were fabricated on rigid substrate at room temperature. PMID:19836549

  10. Rotationally elastic total cross sections for NH3 on electron impact over a wide energy range

    NASA Astrophysics Data System (ADS)

    Vinodkumar, Minaxi; Limbachiya, Chetan; Antony, Bobby

    2011-10-01

    Electron molecule collisions are important over incident energy from very low (0.01 eV) to intermediate and high energies (10 keV). We present rotationally elastic total cross sections for electron scattering for NH3 from 0.01 eV to 2 keV using two different theoretical formalisms. We use Quantemol-N formalism for calculating total cross sections up to threshold of the target and the Spherical Optical Complex Potential (SCOP) method for calculating total cross sections beyond threshold up to 2 keV. Electron molecule collisions are important over incident energy from very low (0.01 eV) to intermediate and high energies (10 keV). We present rotationally elastic total cross sections for electron scattering for NH3 from 0.01 eV to 2 keV using two different theoretical formalisms. We use Quantemol-N formalism for calculating total cross sections up to threshold of the target and the Spherical Optical Complex Potential (SCOP) method for calculating total cross sections beyond threshold up to 2 keV. MVK and BA thank DST, CGL thanks UGC new Delhi.

  11. Chemi-luminescence measurements of hyperthermal Xe+/Xe2+ + NH3 reactions.

    PubMed

    Prince, Benjamin D; Steiner, Colby P; Chiu, Yu-Hui

    2012-04-14

    Luminescence spectra are recorded for the reactions of Xe(+) + NH(3) and Xe(2+) + NH(3) at energies ranging from 11.5 to 206 eV in the center-of-mass (E(cm)) frame. Intense features of the luminescence spectra are attributed to the NH (A (3)Π(i)-X (3)Σ(-)), hydrogen Balmer series, and Xe I emission observable for both primary ions. Evidence for charge transfer products is only found through Xe I emission for both primary ions and NH(+) emission for Xe(2+) primary ions. For both primary ions, the absolute NH (A-X) cross section increases with collision energy before leveling off at a constant value, approximately 9 × 10(-18) cm(2), at about 50 eV while H-α emission increases linearly with collision energy. The nascent NH (A) populations derived from the spectral analysis are found to be independent of collision energy and have a constant rotational temperature of 4200 K. PMID:22502525

  12. NH3 and NH2 in the coma of Comet Brorsen-Metcalf

    NASA Technical Reports Server (NTRS)

    Tegler, Stephen C.; Burke, Luke F.; Wyckoff, Susan; Womack, Maria; Fink, Uwe; Disanti, Michael

    1992-01-01

    Evidence consistent with NH3 ice in the nucleus of Comet Brorsen-Metcalf as the source of the NH2 observed in the comet coma is presented. The distribution of NH2 is symmetric and shows no evidence for jet structure at the 3-sigma significance level above background emission. An azimuthal average of the NH2 image produces an NH2 surface brightness profile for Comet Brorsen-Metcalf which yields a factor of about-10 improvement in the signal-to-noise ratio over previous 1D long-slit NH2 observations, and provides a significant constraint on the NH2 photodissociation time scale in comets. A Monte Carlo simulation of the comet coma, assuming that NH2 is the primary source of NH2, is described and compared with the observations. For an observed production rate, Q(H2O) is approximately equal to 7 x 10 exp 28 molecules/s, collisional effects on the NH3 and NH2 outflow had at most an approximately 10-percent effect on the NH2 surface brightness profile. Because Comet Brorsen-Metcalf showed no significant dust or gas production rate variability, it is argued that steady state conditions best match the comet at the time of the observations.

  13. The production of NH(A 3Pi i) through photodissociative excitation of NH3

    NASA Technical Reports Server (NTRS)

    Wu, C. Y. Robert

    1987-01-01

    The NH(A-X) emission produced by photodissociation of NH3 is examined using a line emission source in the 600-1340 A region. It is observed that the production of the NH(A 3Pi i) photofragment involves a spin-forbidden transition. Fluorescence spectra of NH3 are derived and analyzed. The relationship between fluorescence cross sections and fluorescence count rates and gas pressure is studied. The fluorescence cross sections of NH(A-X) are calculated as 2.1 x 10 to the -22nd, 3.1 x 10 to the -22nd, 3.0 x 10 to the -21st, 1.5 x 10 to the -20th, and 3.4 x 10 to the -20th sq cm for the primary photon wavelength of 1239, 1184, 1065, 1037, and 976 A, respectively; and the corresponding fluorescence quantum yields are 0.00002, 0.00003, 0.0012, 0.0085, and 0.015.

  14. Enhanced NH3-Sensitivity of Reduced Graphene Oxide Modified by Tetra-α-Iso-Pentyloxymetallophthalocyanine Derivatives.

    PubMed

    Li, Xiaocheng; Wang, Bin; Wang, Xiaolin; Zhou, Xiaoqing; Chen, Zhimin; He, Chunying; Yu, Zheying; Wu, Yiqun

    2015-12-01

    Three kinds of novel hybrid materials were prepared by noncovalent functionalized reduced graphene oxide (rGO) with tetra-α-iso-pentyloxyphthalocyanine copper (CuPc), tetra-α-iso-pentyloxyphthalocyanine nickel (NiPc) and tetra-α-iso-pentyloxyphthalocyanine lead (PbPc) and characterized by Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-vis), Raman spectra, X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), and atomic force microscope (AFM). The as-synthesized MPc/rGO hybrids show excellent NH3 gas-sensing performance with high response value and fast recovery time compared with bare rGO. The enhancement of the sensing response is mainly attributed to the synergism of gas adsorption of MPc to NH3 gas and conducting network of rGO with greater electron transfer efficiency. Strategies for combining the good properties of rGO and MPc derivatives will open new opportunities for preparing and designing highly efficient rGO chemiresistive gas-sensing hybrid materials for potential applications in gas sensor field. PMID:26403926

  15. The ν1 and ν3 band system of 15NH3

    NASA Astrophysics Data System (ADS)

    Fusina, Luciano; Nivellini, Giandomenico; Spezzano, Silvia

    2011-09-01

    The infrared spectrum of 15NH3 has been investigated by high-resolution Fourier transform infrared spectroscopy in the region of the stretching fundamentals. A large number of ro-vibration transitions in the 3050-3650 cm-1 spectral range has been recorded and assigned to the fundamentals ν1 and ν3, and to the 2ν 4 overtone bands. In total, 1606 transitions involving the (s) and (a) inversion-rotation-vibration levels have been identified and assigned. They include 256 perturbation-allowed transitions with selection rules ΔK = ±2, Δl = -1 in ν3 and Δl = +2 in 2ν4^±2, and ΔK = ±3, Δl = 0 in ν1 and 2ν4^0. All assigned transitions were fitted simultaneously to a model Hamiltonian that includes all symmetry-allowed interactions between and within the excited state levels in order to obtain accurate sets of spectroscopic parameters for both inversion states. The standard deviation of the fit, 0.034 cm-1, is about 70 times larger than the estimated measurement precision. This result is similar to that reported for the same band system in 14NH3 by Kleiner et al. [J. Mol. Spectrosc. 193, 46 (1999)] and is a consequence of the neglect of vibration and ro-vibration interactions between the analysed states and vibrationally excited states with close energies.

  16. Nitrogen defects from NH3 in rare-earth sesquioxides and ZrO2.

    PubMed

    Polfus, Jonathan M; Norby, Truls; Haugsrud, Reidar

    2011-01-01

    Effects of nitrogen defects on the electrical properties of RE(2)O(3) (RE = Nd, Gd, Er, Y) and ZrO(2) have been investigated by equilibration in ammonia (NH(3)) atmospheres in the temperature range 1000-1200 °C. The electrical conductivity in ammonia corresponded to that in H(2)-Ar mixtures of similar pO(2). However, upon replacing ammonia with an inert gas, the conductivity increases abruptly, typically one order of magnitude, before gradually returning to its equilibrium value. A defect model based on dissolution and dissociation of effectively neutral imide defects substituting oxide ions, NH, is proposed to describe this behavior. Conductivity measurements are interpreted in terms of nitrogen acceptors which are passivated by protons in the presence of H(2)(g), and subsequently compensated by positive charge carriers in an inert atmosphere as out-diffusion of hydrogen leaves an effective acceptor, N. In the case of Y(2)O(3), a NH concentration of 0.7 mol% was estimated from quantification of the nitrogen and hydrogen contents of a sample quenched in NH(3). PMID:21069229

  17. Neutral tricoordinated beryllium(0) compounds--isostructural to BH(3) but isoelectronic to NH(3).

    PubMed

    De, Susmita; Parameswaran, Pattiyil

    2013-04-01

    The electronic structure and reactivity of neutral tricoordinated Be(0) compounds BeL(3), L = CO (1), NHC (2) and PMe(3) (3) are explored by quantum mechanical calculations. These BeL(3) complexes are found to be planar or nearly planar like electron deficient BH3 but isoelectronic with NH3 and possess three L→Be donor-acceptor bonds. The Be atom can be considered as sp(2)-hybridized with a lone pair in the highly diffused 2p(z)-orbital in contrast to the sp(3) hybridization in isoelectronic NH(3). Even though the lone pair on Be is stabilized through π-back donation or hyperconjugative interaction with the ligands, yet it is highly reactive towards Lewis acids such as H(+), BH(3) and W(CO)(5). The calculated gas phase protonation energies reveal that the NHC complex 2 and the trimethylphosphine complex 3 are 'super basic' in nature. Promising ligand property of BeL(3) has also been noted with BH(3) and transition metal fragment W(CO)(5). Besides, the reactivity of 2 and 3 is found to be more as compared to 1. PMID:23360926

  18. Enhanced NH3-Sensitivity of Reduced Graphene Oxide Modified by Tetra-α-Iso-Pentyloxymetallophthalocyanine Derivatives

    NASA Astrophysics Data System (ADS)

    Li, Xiaocheng; Wang, Bin; Wang, Xiaolin; Zhou, Xiaoqing; Chen, Zhimin; He, Chunying; Yu, Zheying; Wu, Yiqun

    2015-09-01

    Three kinds of novel hybrid materials were prepared by noncovalent functionalized reduced graphene oxide (rGO) with tetra-α-iso-pentyloxyphthalocyanine copper (CuPc), tetra-α-iso-pentyloxyphthalocyanine nickel (NiPc) and tetra-α-iso-pentyloxyphthalocyanine lead (PbPc) and characterized by Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-vis), Raman spectra, X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), and atomic force microscope (AFM). The as-synthesized MPc/rGO hybrids show excellent NH3 gas-sensing performance with high response value and fast recovery time compared with bare rGO. The enhancement of the sensing response is mainly attributed to the synergism of gas adsorption of MPc to NH3 gas and conducting network of rGO with greater electron transfer efficiency. Strategies for combining the good properties of rGO and MPc derivatives will open new opportunities for preparing and designing highly efficient rGO chemiresistive gas-sensing hybrid materials for potential applications in gas sensor field.

  19. Axicons et Pompage Optique du Laser NH(3) dans L'infrarouge Moyen

    NASA Astrophysics Data System (ADS)

    Couture, Marc

    Cette these propose une nouvelle application des axicons: le pompage optique axial. On presente d'abord une investigation theorique et experimentale des proprietes de focalisation d'un systeme forme de deux axicons reflecteurs, examinant en particulier les effets de divers defauts de positionnement. On presente ensuite les resultats obtenus avec une configuration de pompage optique (un laser NH _3 pompe a l'aide d'un laser CO _2-TEA) ou ce systeme sert a la fois a decoupler les deux cavites et focaliser la radiation de pompage. Les caracteristiques de l'emission laser dans l'infrarouge moyen sont explorees dans les conditions maximisant l'efficacite, qui se compare a celle obtenue avec d'autres configurations. Finalement, on expose les resultats du pompage d'un melange de NH _3 et de gaz-tampons a pression supra-atmospherique, qui indiquent que ce sont les melanges ternaires qui permettent d'obtenir un effet laser a la plus haute pression, soit 1,4 bar.

  20. HCN and NH3 formation during coal/char gasification in the presence of NO.

    PubMed

    Lin, Jian-Ying; Zhang, Shu; Zhang, Lian; Min, Zhenhua; Tay, Huiling; Li, Chun-Zhu

    2010-05-15

    Understanding the conversion of coal-N during gasification is an important part of the development of gasification-based power generation technologies to reduce NO(x) emissions from coal utilization. This study investigated the conversion of coal-N in the presence of NO during the gasification of three rank-ordered coals and their chars in steam and low-concentration O(2). Our results show that NO can be incorporated into the char structure during gasification. The inherent char-N and the N incorporated into the char from NO-char reactions behave very similarly during gasification. During the gasification in steam, significant amounts of HCN and NH(3) can be formed from the incorporated N structure in char, especially for the relatively "aged" chars, mainly due to the availability of abundant H radicals on the char surface during the gasification in steam. During the gasification in 2000 ppm O(2), the formation of HCN or NH(3) from the N structures in char, including those incorporated into the char from the NO-char reactions, was not a favored route of reaction mainly due to the lack of H on char surface in the presence of O(2). PMID:20415414

  1. Decomposition of NH3 and H2 on ZrB2 (0001) surface

    NASA Astrophysics Data System (ADS)

    Walkosz, Weronika; Manandhar, Kedar; Trenary, Michael; Zapol, Peter

    2012-02-01

    Group III nitride semiconductors (AlN, GaN, InN, and their alloys) are important materials for applications in solid-state lighting, optoelectronics, and photovoltaics. However, the lack of lattice--matched substrates for their growth results in less than optimal material quality. In the last decade, zirconium diboride (ZrB2) has been demonstrated as a promising substrate for GaN growth because of its similar lattice constant and thermal expansion properties when compared to the nitride. Moreover, the high electrical conductivity of ZrB2 makes it desirable for many GaN-based device applications. In this talk, we present results of density functional theory calculations for the reactivity of the ZrB2(0001) surface towards the N precursor, NH3, and the carrier gas, H2, commonly used in metal organic chemical vapor deposition and molecular beam epitaxy of nitrides. Two different terminations of ZrB2(0001) surface, the Zr and B terminations, are considered and assessed in terms of their catalytic properties toward NH3 and H2 decomposition. The theoretical results are analyzed in connection with our recent XPS and RAIRS measurements.

  2. Crystal structure of [Co(NH3)6][Co(CO)4]2

    PubMed Central

    Müller, Thomas G.; Kraus, Florian

    2015-01-01

    Hexaamminecobalt(II) bis­[tetra­carbonyl­cobaltate(-I)], [Co(NH3)6][Co(CO)4]2, was synthesized by reaction of liquid ammonia with Co2(CO)8. The CoII atom is coordinated by six ammine ligands. The resulting polyhedron, the hexa­amminecobalt(II) cation, exhibits point group symmetry -3. The Co-I atom is coordinated by four carbonyl ligands, leading to a tetra­carbonyl­cobaltate(−I) anion in the shape of a slightly distorted tetra­hedron, with point group symmetry 3. The crystal structure is related to that of high-pressure BaC2 (space group R-3m), with the [Co(NH3)6]2+ cations replacing the Ba sites and the [Co(CO)4]− anions replacing the C sites. N—H⋯O hydrogen bonds between cations and anions stabilize the structural set-up in the title compound. PMID:26594524

  3. Effects of NO2 and NH3 from road traffic on epiphytic lichens.

    PubMed

    Frati, L; Caprasecca, E; Santoni, S; Gaggi, C; Guttova, A; Gaudino, S; Pati, A; Rosamilia, S; Pirintsos, S A; Loppi, S

    2006-07-01

    The results of a survey aimed at investigating whether NO2 and NH3 emitted by road traffic can influence lichen diversity, lichen vitality and the accumulation of nitrogen in lichen thalli are reported. For this purpose, distance from a highway in a rural environment of central Italy was regarded as the main parameter to check this hypothesis. The results of the present survey indicated that road traffic is not a relevant source of NH3. On the other hand, NO2 concentrations, although rather low, were negatively correlated with distance from the highway according to a typical logarithmic function. No association between NO2 concentrations and the diversity of epiphytic lichens was found, probably because of the low NO2 values measured. Also bark properties were not influenced by distance from the highway. Accumulation of nitrogen, reduction in the content of chlorophyll a, chlorophyll b and total carotenoids were found in transplanted thalli of Evernia prunastri, but NO2 was not responsible for these changes, which were probably caused by applications of N-based fertilizers. PMID:16310300

  4. Correlations between NH3(1,1) and far-IR emission

    NASA Astrophysics Data System (ADS)

    Stenholm, L. G.; Baud, B.; Mauersberger, R.

    1986-06-01

    NH3 (1,1 and 2,2) observations obtained using a 1024-channel autocorrelator and K-band maser amplifier at the 100-m Effelsberg radio telescope (angular resolution 40 arcsec at 1.3 cm; velocity resolution 0.16 km/s; rms error 0.1 K) are reported for six Taurus-region IRAS sources for which the 100-micron flux is greater than the 60-micron flux. The data are presented in maps and tables and compared with the IRAS FIR data in graphs. A strong correlation between the NH3 line intensity and the 100-micron flux and an anticorrelation between peak main-beam brightness temperature and Delta-V (where V is the line velocity) are observed and found to be consistent with the hypothesis of Henriksen and Turner (1984), that the velocity field in molecular clouds is controlled by star/cloud turbulence, with a conversion of small-scale angular momentum to larger-scale turbulence.

  5. High resolution NH3 studies of nearby star-forming regions

    NASA Astrophysics Data System (ADS)

    Friesen, Rachel

    2014-07-01

    Stars form within dense molecular cores. These cores are often embedded within larger structures, such as clumps and filaments, particularly in clustered star-forming environments. Indeed, large-scale maps of the continuum emission from dust have revealed the ubiquity of filaments in star-forming regions. The condensation and fragmentation of cores within larger structures is therefore a critical step in the star formation process, but continuum data alone do not provide key information, such as the gas kinematics, needed to discern between evolutionary scenarios. I will present new results from large NH3 studies of nearby star-forming regions, including Taurus and Serpens South. While NH3 primarily traces high density gas, sensitive observations over Serpens South reveal extensive, low brightness emission between the prominent cores and filaments, and show directly the frequently (but not invariably) sharp transitions between turbulent and quiescent gas in the high density regions. I will discuss the hierarchical structure of the dense gas in Serpens South, with comparisons between two- and three-dimensional analysis, and analyze the importance of thermal fragmentation in the filaments and cores over a range of physical scales.

  6. Etude calorimtrique et structure cristalline du putrescinium monohydrognomonophosphate dihydrate NH 3(CH 2) 4NH 3HPO 42H 2O

    NASA Astrophysics Data System (ADS)

    Kamoun, Slaheddine; Jouini, Amor

    1990-11-01

    Chemical preparation, calorimetric studies, and crystal structure are given for a new monophosphate. The putrescinium monohydrogen monophosphate dihydrate salt is monoclinic with the unit cell dimensions a = 6.541(1) , b = 16.648(3) , c = 9.175(1) , ? = 95.74(1), V = 994.1(5) 3, Dm = 1.498 Mgm -3, Dx = 1.484 Mgm -3, ? = 2.732 mm -1, space group {P2 1}/{c} with Z = 4. The structure was solved by the Patterson method and refined to a final value of 0.046 for 1732 observed independent reflections. The structure shows a layer arrangement perpendicular to the overlinec axis: planes of the [HPO 4] 2- tetrahedra alternate with planes of the [(CH 2) 4(NH 3) 2] 2+ dication. The zeolitic water molecules are located between these planes separated by a distance of 2.294 . The monohydrogen phosphate group is roughly tetrahedral with the symmetry 3 m. The P?O distances in this group range from 1.495(2) to 1.592(2) . The amino groups of putrescine are protonated. The putrescinium dication has an extensive all- trans configuration with a noncrystallographic inversion center. The cohesion and the stability of the atomic arrangement result from three kinds of hydrogen bonds, N?HO, P?OHO(w), and O(W)?HO. The differential scanning calorimetric study shows that the dehydration of this salt occurs in two steps respectively at 105 and 121C with a loss of one water molecule per step. The anhydrous salt undergoes four phase transitions respectively at temperatures of 133, 143, 159, and 165C.

  7. Surface Decorating of CH3NH3PbBr3 Nanoparticles with the Chemically Adsorbed Perylenetetracarboxylic Diimide.

    PubMed

    Zhu, Ruimin; Gao, Chengguang; Sun, Tingting; Shen, Li; Sun, Dejun; Li, Xiyou

    2016-04-01

    An organic dye-modified organolead halide CH3NH3PbBr3 nanoparticle (cubic) is prepared successfully by using a perylenetetracarboxylic diimide (PDI) bearing an -NH3(+) headgroup as the capping ligand. The nanopartilces are homogeneous with high crystallinity. The photoluminescence of perovskite is quenched completely by the chemically adsorbed PDI molecules. This efficient fluorescence quenching has confirmed that the PDI molecules are anchored on the surface of CH3NH3PbBr3 nanoparticle. The resulting nanoparticles can be dispersed in organic solvents, and the resulting dispersion remains stable for days. This result provides a general guideline for surface engineering of organolead halide CH3NH3PbBr3 nanoparticles. PMID:26972739

  8. Growth study of chemical beam epitaxy of GaN xP 1 - x using NH 3 and tertiarybutylphosphine

    NASA Astrophysics Data System (ADS)

    Li, N. Y.; Wong, W. S.; Tomich, D. H.; Dong, H. K.; Solomon, J. S.; Grant, J. T.; Tu, C. W.

    1996-07-01

    A study in the growth of GaN xP 1 - x epilayers by chemical beam epitaxy using tertiarybutylphosphine (TBP), ammonia (NH 3), and elemental Ga or triethylgallium is reported. Monitoring reflection high-energy electron diffraction (RHEED) intensity oscillations, we observe that both group-III- and group-V-induced incorporation rates are increased when NH 3 is introduced into a single cracker with TBP. From the difference in the periods of group-V-induced RHEED intensity oscillations, a 16% N incorporation is expected, but X-ray rocking curve measurement shows only 0.08% N. Using separate TBP and NH 3 crackers results in no enhancement in incorporation rates. We conclude that the cracking efficiency of TBP is increased with NH 3 co-injection.

  9. Sources and Impacts of Atmospheric NH3: Current Understanding and Frontiers for Modeling, Measurements, and Remote Sensing in North America

    EPA Science Inventory

    Ammonia (NH3) contributes to widespread adverse health impacts, affects the climate forcing of ambient aerosols, and is a significant component of reactive nitrogen, deposition of which threatens many sensitive ecosystems. Historically, the scarcity of in situ measurements and th...

  10. Detection of a CO and NH3 gas mixture using carboxylic acid-functionalized single-walled carbon nanotubes.

    PubMed

    Dong, Ki-Young; Choi, Jinnil; Lee, Yang Doo; Kang, Byung Hyun; Yu, Youn-Yeol; Choi, Hyang Hee; Ju, Byeong-Kwon

    2013-01-01

    Carbon nanotubes (CNT) are extremely sensitive to environmental gases. However, detection of mixture gas is still a challenge. Here, we report that 10 ppm of carbon monoxide (CO) and ammonia (NH3) can be electrically detected using a carboxylic acid-functionalized single-walled carbon nanotubes (C-SWCNT). CO and NH3 gases were mixed carefully with the same concentrations of 10 ppm. Our sensor showed faster response to the CO gas than the NH3 gas. The sensing properties and effect of carboxylic acid group were demonstrated, and C-SWCNT sensors with good repeatability and fast responses over a range of concentrations may be used as a simple and effective detection method of CO and NH3 mixture gas. PMID:23286690

  11. The photolysis of NH3 in the presence of substituted acetylenes - A possible source of oligomers and HCN on Jupiter

    NASA Technical Reports Server (NTRS)

    Ferris, James P.; Jacobson, Richard R.; Guillemin, Jean C.

    1992-01-01

    An NMR spectral study is presently conducted of NH3 photolysis in the presence of substituted acetylenes with NMR spectra and gas chromatography. Quantum yields and percentage conversions to products are reported. It is shown that acetylenic hydrocarbons generated during methane photolysis in Jupiter's stratosphere can react with radicals formed by NH3 photolysis to yield nonvolatile, yellow-brown polymers, alkylnitriles, and in due course, HCN, as observed on Jupiter.

  12. Characterization of NH3 Seeded He Supersonic Free-Jet Beams for Growth of GaN Thin Films.

    NASA Astrophysics Data System (ADS)

    Torres, V. M.; Meloni, M. A.; Doak, R. B.; Lai, K.; Lamb, H. H.; Davis, R. F.

    1996-03-01

    The characterization of NH3 supersonic seeded He free-jet beams (SSFJ) is presented. The mean kinetic energy and energy spreads were determined as a function of the product of nozzle pressure times nozzle diameter, nozzle temperature and NH3 content. Preliminary results on the growth of GaN thin films using SSFJ in conjunction with a Triethylgallium doser is presented. The nozzle temperature had a noticeable effect on the surface morphology of the films.

  13. Synergistic formation of sulfate and ammonium resulting from reaction between SO2 and NH3 on typical mineral dust.

    PubMed

    Yang, Weiwei; He, Hong; Ma, Qingxin; Ma, Jinzhu; Liu, Yongchun; Liu, Pengfei; Mu, Yujing

    2016-01-14

    The heterogeneous reactions of SO2 and NH3 on typical mineral oxides were investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). A new sulfate formation pathway was proposed where NH3 accelerated the formation of sulfate species. The results revealed that surface hydroxyls and oxygen played principal roles in the conversion of SO2 to sulfate. It was proposed that NH3 adsorbed onto Lewis acid sites, and hydroxyls and water molecules adsorbed on the surfaces of mineral dust. The enhancement of surface Lewis basicity by NH3 induced more SO2 molecules to adsorb on the surface, which were further oxidized to sulfate by interacting with surface hydroxyls and oxygen atoms. The formation of sulfate, in turn, contributed to the adsorption of NH3, mainly as NH4(+) due to enhanced Brønsted acid sites. The IC results showed that the synergistic effect between SO2 and NH3 was more significant on acidic oxides like γ-Al2O3 and α-Fe2O3 compared to basic oxides like MgO. PMID:26650181

  14. NH3-treated WO3 as low-cost and efficient counter electrode for dye-sensitized solar cells.

    PubMed

    Song, Dandan; Chen, Zhao; Cui, Peng; Li, Meicheng; Zhao, Xing; Li, Yaoyao; Chu, Lihua

    2015-01-01

    A novel low-cost and efficient counter electrode (CE) was obtained by treating catalytic inert tungsten trioxide (WO3) nanomaterial in NH3 atmosphere at elevated temperatures. The formation of tungsten oxynitride from WO3 after NH3 treatment, as evidenced by X-ray photoelectron spectroscopy and X-ray diffraction, increases the catalytic activity of the CE. Correspondingly, the power conversion efficiency (PCE) of the DSC is significantly increased from 0.9% for pristine WO3 CE to 5.9% for NH3-treated WO3 CE. The photovoltaic performance of DSC using NH3-treated WO3 CE is comparable to that of DSC using standard Pt CE (with a PCE of 6.0%). In addition, it is also shown that NH3 treatment is more efficient than H2 or N2 treatment in enhancing the catalytic performance of WO3 CE. This work highlights the potential of NH3-treated WO3 for the application in DSCs and provides a facile method to get highly efficient and low-cost CEs from catalytic inert metal oxides. PMID:25852314

  15. Phase transitions in [Co(NH3)6](ClO4)3 investigated by neutron scattering methods

    NASA Astrophysics Data System (ADS)

    Hetmańczyk, Łukasz; Górska, Natalia; Hetmańczyk, Joanna; Mikuli, Edward; Natkaniec, Ireneusz

    2013-02-01

    [Co(NH3)6](ClO4)3 was investigated by neutron scattering methods in the temperature range of 20-290 K. Neutron powder diffraction revealed that the crystal structure does not change at the TC2 and TC3 phase transitions. High temperature phases are orientationally disordered. QENS study showed that NH3 ligands perform rapid reorientational motion around their 3-fold axes in a wide temperature range. However, below TC3 some excess of elastic scattering is observed, which can be explained by the assumption that only half of the NH3 groups reorient fast enough to contribute to the QENS broadening, whereas the remaining NH3 groups reorient more slowly. The activation energy for NH3 jumps, estimated from the temperature dependence of QENS broadening, is small but comparable with the results obtained for other hexaammine complexes. Quantum chemical calculation, carried out on the basis of DFT for isolated [Co(NH3)6]3+ cation and ClO4- anion, and experimental (IR, RS, IINS) spectra are in good agreement.

  16. NH3, H2S, and the Radio Brightness Temperature Spectra of the Giant Planets

    NASA Technical Reports Server (NTRS)

    Spilker, Thomas R.

    1995-01-01

    Recent radio interferometer observations of Neptune enable comparisons of the radio brightness temperature (T(sub B)) spectra of all four giant planets. This comparison reveals evidence for fundamental differences in the compositions of Uranus' and Neptune's upper tropospheres, particularly in their ammonia (NH3) and hydrogen sulfide (H2S) mixing ratios, despite those planets' outward similarities. The tropospheric abundances of these constituents yield information about their deep abundances, and ultimately about the formation of the planets from the presolar nebula (Atreya et al.). Figures 1, 2, 3, and 4 show the T(sub B) spectra of Jupiter, Saturn, Uranus, and Neptune, respectively, from 0.1 to tens of cm wavelength. The data shown are collected from many observers. Data for Jupiter, Saturn, and Uranus are those cataloged by de Pater and Massie (1985), plus the Saturn Very Large Array (VLA) data by Grossman et al. Figure 3, Uranus, shows only data acquired since 1973. Before 1973 Uranus' T(sub B) increased steadily as its pole moved into view, causing significant scatter in those data. Neptune data at greater than 1 cm, all taken at the VLA, are collected from de Pater and Richmond, de Pater et al., and Hofstadter. For a variety of reasons, such as susceptibility to source confusion, single-dish data at those wavelengths are much noisier than the more reliable VLA data and have been ignored. Single-dish data by Griffin and Orton shortward of 0.4 cm are shown, along with the Owens Valley Radio Observatory (interferometer) datum at 0.266 cm by Muhleman and Berge. Spectra of Jupiter, Saturn, and Neptune share certain gross characteristics. In each spectrum, T(sub B) at 1.3 cm is approximately 120-140 K, less than approximately 30 K different from that at 0.1 cm. All three spectra show a break in slope at or near 1.3 cm, with T(sub B) increasing fairly rapidly with wavelength longward of 1.3 cm. Visible and IR spectroscopy show that NH3, whose strong inversion spectrum peaks at appropximately 1.3 cm, is an important tropospheric species at Jupiter and Saturn. Its signature on the Jovian radio spectrum is obvious, causing the prominent "hole" at 1.3 cm. At Saturn it is more subdued but is the source of that spectrum's change in slope at 1.3 cm. Radiative transfer models of Jupiter and Saturn with near-solar deep NH3 abundances agree well with the data (e.g., de Pater).

  17. Trends of NO-, NO 2-, and NH 3-emissions from gasoline-fueled Euro-3- to Euro-4-passenger cars

    NASA Astrophysics Data System (ADS)

    Heeb, Norbert V.; Saxer, Christian J.; Forss, Anna-Maria; Brühlmann, Stefan

    Vehicular emissions of reactive nitrogen compounds (RNCs) such as nitric oxide (NO), nitrogen dioxide (NO 2), and ammonia (NH 3) have a substantial impact on urban air quality. NO and NO 2 support the photochemical formation of ozone, and NH 3 is involved in the atmospheric formation of secondary aerosols. Vehicular NO is mainly formed during combustion, whereas NO 2 and NH 3 are both secondary pollutants of the catalytic converter systems. Herein we report on tail-pipe RNC emissions of gasoline-fueled Euro-3- and Euro-4-passenger cars at transient driving from 0 to 150 km h -1. Two sets of 10 in-use vehicles with comparable engine size and mileage were studied with time-resolved chemical ionization-mass spectrometry (CI-MS). Each vehicle was tested in 7 different driving cycles including the legislative European (EDC) and the US FTP-75 driving cycles. Mean emission factors (EFs) for different traffic situations are reported and effects of cold start, velocity, acceleration, and deceleration are discussed. Furthermore, critical operating conditions supporting the de novo formation of NH 3 have been identified. In the EDC, mean NO- and NH 3-EFs of 57±26 and 16±12 mg km -1 were obtained for Euro-3-vehicles; those of the Euro-4-technology were lower by about 25% and 33% at the levels of 43±46 and 10±7 mg km -1, respectively. NO 2 emissions of the investigated three-way catalyst (TWC) vehicles accounted for <1% of the detected RNCs, whereas NH 3 was found to be the dominant RNC for most vehicle conditions. Molar NH 3 proportions varied from about 0.4-0.8, as soon as catalyst light-off occurred. NO was found in large excess only during the cold-start period. Catalyst light-off is indicated by a fast transition from NO- to NH 3-rich exhaust. Velocity and acceleration had pronounced effects on the RNC emission characteristics. Mean velocity-dependent EFs for NO and NH 3 varied by about one order of magnitude from 10 to 74 and 15 to 161 mg km -1 for Euro-3-vehicles and from 12 to 44 and 7 to 144 mg km -1 for the Euro-4 fleet. We conclude that the investigated Euro-3- and Euro-4-vehicles are mainly operated under slightly reducing conditions, where the NH 3 emissions dominate over those of the NO. Under these conditions, both vehicle fleets on an average fulfilled the valid Euro-3 and Euro-4 limits for nitrogen oxides (NO x) of 150 and 80 mg km -1, respectively (as NO 2 equivalents).

  18. Improving the Photoluminescence Properties of Perovskite CH3NH3PbBr3-xClx Films by Modulating Organic Cation and Chlorine Concentrations.

    PubMed

    Yan, Jun; Zhang, Bing; Chen, Yunlin; Zhang, Ao; Ke, Xiaohan

    2016-05-25

    The photoluminescence (PL) properties of inorganic-organic perovskites can be drastically changed by tuning the halogen composition, especially the Cl content. However, our research demonstrated that in addition to the influence of Cl concentration, the PL emission intensity of CH3NH3PbBr3 strongly depends on the content of CH3NH3Br in the coating solution. The effects of CH3NH3Br and Cl concentrations on the PL properties of CH3NH3PbBr3-xClx were investigated. We found that a strong PL emission intensity of CH3NH3PbBr3 can be obtained from solutions with a high CH3NH3Br concentration. The PL emission intensities of CH3NH3PbBr3-xClx films were enhanced by adjusting the molar ratio of PbBr to PbCl2 only in a highly concentrated CH3NH3Br environment. Moreover, it was found that an optimum CH3NH3Br/PbBr2/PbCl2 ratio in the precursor solutions can be used to obtain the strongest PL emission intensity of CH3NH3PbBr3-xClx films. Further studies revealed that both CH3NH3Br and Cl concentrations significantly influence the CH3NH3PbBr3-xClx films evolution, which affects their PL properties. PMID:27163386

  19. Atomic Structures of CH3NH3PbI3 (001) Surfaces.

    PubMed

    She, Limin; Liu, Meizhuang; Zhong, Dingyong

    2016-01-26

    We report on the atomic structures of methylammonium (MA) lead iodide (CH3NH3PbI3) perovskite surfaces, based on a combined scanning tunneling microscopy and density functional theory calculation study. A reconstructed surface phase with iodine dimers, coexisting with the pristine zigzag phase, was found at the MA-iodine-terminated (001) surfaces of the orthorhombic perovskite films grown on Au(111) surfaces. The reorientation of surface MA dipoles, which strengthens the interactions with surface iodine anions, resulting in a slight energy reduction of 34 meV per unit cell, is responsible for the surface iodine dimerization. According to our calculation, the surface MA dipoles weaken the surface polarity and are therefore considered to be stabilizing the surface structures. PMID:26643387

  20. The design and technology development for A 150 mlb resistojet for H2 or NH3

    NASA Technical Reports Server (NTRS)

    Page, R. J.; Stoner, W. A.

    1982-01-01

    A 150 mlb thrust level hybrid resistojet which may operate on either H2 or NH3 is described whose design technique allows temperature distribution forecasting by means of a microcomputer-implemented mathematical model. The longer computer run times that accompany the exclusive use of BASIC, relative to assembled languages, are offset by the flexibility offered and the reduction of reprogramming and debugging efforts. The integration of a compact first-stage coiled heater with a concentric tubular gas heater offers direct matching of the 28 V terminal of the spacecraft system, while keeping maximum heater wall temperatures to less than 60 K over that of the gas temperature at the throat. Among the novel materials employed are grain-stabilized rhenium for heating elements and high purity aluminas for insulators.

  1. Recombination of electrons with NH4/+/-/NH3/n-series ions

    NASA Technical Reports Server (NTRS)

    Huang, C.-M.; Biondi, M. A.; Johnsen, R.

    1976-01-01

    The paper examines the recombination of electrons with ammonium-series cluster ions, NH4(+)-(NH3)n, for two reasons: (1) NH4(+) may be a significant ion in the lower atmospheres of the earth and the outer planets, and (2) to investigate the weak temperature dependence of the cluster ion's recombination coefficient. A microwave afterglow mass spectrometer was used to determine the recombination coefficients for the first five members of the ammonium series, (18+) through (86+), at temperatures between 200 and 410 K. The electron temperature dependence of the recombination coefficient was determined for (35+) and (52+), the n = 1 and 2 cluster ions, over the temperature range 300-3000 K.

  2. Zwitterion formation in titan ice analogs: reaction between HC3N and NH3.

    PubMed

    Couturier-Tamburelli, Isabelle; Sessouma, Bintou; Chiavassa, Thierry; Piétri, Nathalie

    2012-11-01

    A zwitterion is formed in the laboratory at low temperatures in the solid phase from the thermal reaction of HC(3)N and NH(3). We report for the first time its infrared spectrum. We study its reaction using Fourier transform infrared spectroscopy. Its reaction rate is estimated to be k(T) = 2.9 × 10(5) exp(-2.3 ± 0.1 (kJ mol(-1))/RT). Calculations using density functional theory (B3LYP/6-31g**) are used to characterize all the species (complexes, zwitterions, and transition states) and are in good agreement with the infrared spectra. The structure of the zwitterion is determined planar and it is characterized by a N-C bond around 1.5 Å. PMID:23075265

  3. Intense Pulsed Light Sintering of CH3NH3PbI3 Solar Cells.

    PubMed

    Lavery, Brandon W; Kumari, Sudesh; Konermann, Hannah; Draper, Gabriel L; Spurgeon, Joshua; Druffel, Thad

    2016-04-01

    Perovskite solar cells utilizing a two-step deposited CH3NH3PbI3 thin film were rapidly sintered using an intense pulsed light source. For the first time, a heat treatment has shown the capability of sintering methylammonium lead iodide perovskite and creating large crystal sizes approaching 1 μm without sacrificing surface coverage. Solar cells with an average efficiency of 11.5% and a champion device of 12.3% are reported. The methylammonium lead iodide perovskite was subjected to 2000 J of energy in a 2 ms pulse of light generated by a xenon lamp, resulting in temperatures significantly exceeding the degradation temperature of 150 °C. The process opens up new opportunities in the manufacturability of perovskite solar cells by eliminating the rate-limiting annealing step, and makes it possible to envision a continuous roll-to-roll process similar to the printing press used in the newspaper industry. PMID:26943510

  4. Impacts of anthropogenic SOx, NOx and NH3 on acidification of coastal waters and shipping lanes

    NASA Astrophysics Data System (ADS)

    Hunter, Keith A.; Liss, Peter S.; Surapipith, Vanisa; Dentener, Frank; Duce, Robert; Kanakidou, Maria; Kubilay, Nilgun; Mahowald, Natalie; Okin, Greg; Sarin, Manmohan; Uematsu, Mitsuo; Zhu, Tong

    2011-07-01

    The acidification of the ocean by anthropogenic CO2 absorbed from the atmosphere is now well-recognized and is considered to have lowered surface ocean pH by 0.1 since the mid-18th century. Future acidification may lead to undersaturation of CaCO3 making growth of calcifying organisms difficult. However, other anthropogenic gases also have the potential to alter ocean pH and CO2 chemistry, specifically SOx and NOx and NH3. We demonstrate using a simple chemical model that in coastal water regions with high atmospheric inputs of these gases, their pH reduction is almost completely canceled out by buffering reactions involving seawater HCO3- and CO32- ions. However, a consequence of this buffering is a significant decrease in the uptake of anthropogenic CO2 by the atmosphere in these areas.

  5. Synthesis of sealed sponge ZnO nanospheres through a novel NH3-evaporation method

    NASA Astrophysics Data System (ADS)

    Cheng, Lihong; Zheng, Liaoying; Li, Guorong; Yin, Qingrui; Jiang, Kyle

    2008-02-01

    Sealed sponge ZnO nanospheres are prepared through a novel NH3-evaporation method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and N2 physisorption analysis show that the samples obtained are ZnO nanospheres with hexagonal wurtzite structure. The particle size is in the range 80-130 nm and the pores inside are estimated to be in the range 2-35 nm. During the preparation process, the carboxyls derived from the polyacrylamide hydrolyzation tend to attach to the particle surface and bring about the interaction between particles by hydrogen bonding. Results show that the polyacrylamide and alcohol are crucial to the formation of the sealed sponge ZnO, by forming a diffusion layer around the particle. The formation mechanism is considered to be controlled by the diffusion of Zn2+ through the diffusion layer, and the mass transmission between the initial particles.

  6. Structure and stability in TMC-1: Analysis of NH3 molecular line and Herschel continuum data

    NASA Astrophysics Data System (ADS)

    Fehér, O.; Tóth, L. V.; Ward-Thompson, D.; Kirk, J.; Kraus, A.; Pelkonen, V.-M.; Pintér, S.; Zahorecz, S.

    2016-05-01

    Aims: We examined the velocity, density, and temperature structure of Taurus molecular cloud-1 (TMC-1), a filamentary cloud in a nearby quiescent star forming area, to understand its morphology and evolution. Methods: We observed high signal-to-noise (S/N), high velocity resolution NH3(1,1), and (2, 2) emission on an extended map. By fitting multiple hyperfine-split line profiles to the NH3(1, 1) spectra, we derived the velocity distribution of the line components and calculated gas parameters on several positions. Herschel SPIRE far-infrared continuum observations were reduced and used to calculate the physical parameters of the Planck Galactic Cold Clumps (PGCCs) in the region, including the two in TMC-1. The morphology of TMC-1 was investigated with several types of clustering methods in the parameter space consisting of position, velocity, and column density. Results: Our Herschel-based column density map shows a main ridge with two local maxima and a separated peak to the south-west. The H2 column densities and dust colour temperatures are in the range of 0.5-3.3 × 1022 cm-2 and 10.5-12 K, respectively. The NH3 column densities and H2 volume densities are in the range of 2.8-14.2 × 1014 cm-2 and 0.4-2.8 × 104 cm-3. Kinetic temperatures are typically very low with a minimum of 9 K at the maximum NH3 and H2 column density region. The kinetic temperature maximum was found at the protostar IRAS 04381+2540 with a value of 13.7 K. The kinetic temperatures vary similarly to the colour temperatures in spite of the fact that densities are lower than the critical density for coupling between the gas and dust phase. The k-means clustering method separated four sub-filaments in TMC-1 with masses of 32.5, 19.6, 28.9, and 45.9 M⊙ and low turbulent velocity dispersion in the range of 0.13-0.2 km s-1. Conclusions: The main ridge of TMC-1 is composed of four sub-filaments that are close to gravitational equilibrium. We label these TMC-1F1 through F4. The sub-filaments TMC-1F1, TMC-1F2, and TMC-1F4 are very elongated, dense, and cold. TMC-1F3 is a little less elongated and somewhat warmer, and probably heated by the Class I protostar, IRAS 04381+2540, which is embedded in it. TMC-1F3 is approximately 0.1 pc behind TMC1-F1. Because of its structure, TMC-1 is a good target to test filament evolution scenarios.

  7. Desorption Kinetics of Methanol, Ethanol, and Water from Graphene

    SciTech Connect

    Smith, R. Scott; Matthiesen, Jesper; Kay, Bruce D.

    2014-09-18

    The desorption kinetics of methanol, ethanol, and water from graphene covered Pt(111) are investigated. The temperature programmed desorption (TPD) spectra for both methanol and ethanol have well-resolved first, second, third, and multilayer layer desorption peaks. The alignment of the leading edges is consistent with zero-order desorption kinetics from all layers. In contrast, for water the first and second layers are not resolved. At low water coverages (< 1 ML) the initial desorption leading edges are aligned but then fall out of alignment at higher temperatures. For thicker water layers (10 to 100 ML), the desorption leading edges are in alignment throughout the desorption of the film. The coverage dependence of the desorption behavoir suggests that at low water coverages the non-alignment of the desorption leading edges is due to water dewetting from the graphene substrate. Kinetic simulations reveal that the experimental results are consistent with zero-order desorption. The simulations also show that fractional order desorption kinetics would be readily apparent in the experimental TPD spectra.

  8. Investigation of the stability of Co-doped apatite ionic conductors in NH 3

    NASA Astrophysics Data System (ADS)

    Headspith, D. A.; Orera, A.; Slater, P. R.; Young, N. A.; Francesconi, M. G.

    2010-12-01

    Hydrogen powered solid oxide fuel cells (SOFCs) are of enormous interest as devices for the efficient and clean production of electrical energy. However, a number of problems linked to hydrogen production, storage and transportation are slowing down the larger scale use of SOFCs. Identifying alternative fuel sources to act as intermediate during the transition to the full use of hydrogen is, therefore, of importance. One excellent alternative is ammonia, which is produced on a large scale, is relatively cheap and has the infrastructure for storage and transportation already in place. However, considering that SOFCs operate at temperatures higher than 500 °C, a potential problem is the interaction of gaseous ammonia with the materials in the cathode, anode and solid electrolyte. In this paper, we extend earlier work on high temperature reactions of apatite electrolytes with NH 3 to the transition metal (Co) doped systems, La 9.67Si 5CoO 26 and La 10(Si/Ge) 5CoO 26.5. A combination of PXRD, TGA and XAFS spectroscopy data showed a better structural stability for the silicate systems. Apatite silicates and germanates not containing transition metals tend to substitute nitride anions for their interstitial oxide anions, when reacted with NH 3 at high temperature and, consequentially, lower the interstitial oxide content. In La 9.67Si 5CoO 26 and La 10(Si/Ge) 5CoO 26.5 reduction of Co occurs as a competing process, favouring lower levels of nitride-oxide substitution.

  9. Conductivity of p(AAc) Cryogel and Its Li+, Na+, and K+ Salts for NH3 Sensing

    NASA Astrophysics Data System (ADS)

    Sahiner, Nurettin; Demirci, Sahin; Sel, Kivanc

    2016-04-01

    Poly(acrylic acid) [p(AAc)] cryogel has been synthesized by a cryopolymerization technique under cryogenic conditions. The synthesized p(AAc) cryogel was treated with LiOH, NaOH, and KOH to generate corresponding salt forms of carboxylic acid groups within the p(AAc) cryogel network for activation as p(AAc)-Li+, p(AAc)-Na+, and p(AAc)-K+, respectively. The synthesized p(AAc)-based cryogels were characterized via Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis, and scanning electron microscopy. The room-temperature electrical conductivity of the p(AAc), p(AAc)-Li+, p(AAc)-Na+, and p(AAc)-K+ cryogels was measured as 10-11 S cm-1, 10-10 S cm-1, 10-9 S cm-1, and 10-8 S cm-1, respectively. Furthermore, the p(AAc) cryogel and its salt forms were tested as sensor materials for NH3 gas by exposing them to NH3 vapor for 60 min under ambient conditions. Upon exposure to NH3 vapor, it was found that the conductivity of the bare p(AAc) and p(AAc)-K+ cryogels increased by up to 105- and 102-fold, respectively, compared with their NH3 unexposed states. The increase in conductivity for the other salt forms of p(AAc) cryogel was about 60-fold compared with their bare form. The conductivity increase for the p(AAc) and p(AAc)-K+ cryogels was therefore further investigated by changing the NH3 vapor exposure time, revealing that these materials could be used as sensors for NH3. It was further found that a 5 min NH3 gas exposure time was sufficient for p(AAc)-K+ cryogel to generate a detectable response via a change in the conductivity of the matrix.

  10. Effects of acute NH3 air pollution on N-sensitive and N-tolerant lichen species.

    PubMed

    Paoli, Luca; Maslaňáková, Ivana; Grassi, Alice; Bačkor, Martin; Loppi, Stefano

    2015-12-01

    Lichens are sensitive to the presence of ammonia (NH3) in the environment. However, in order to use them as reliable indicators in biomonitoring studies, it is necessary to establish unequivocally the occurrence of certain symptoms following the exposure to NH3 in the environment. In this paper, we simulated an episode of acute air pollution due to the release of NH3. The biological effects of acute air pollution by atmospheric NH3 have been investigated using N-sensitive (Flavoparmelia caperata) and N-tolerant (Xanthoria parietina) species. Lichen samples were exposed to ecologically relevant NH3 concentrations for 8 weeks, simulating three areas of impact: a control area (2 μg/m(3)), an area of intermediate impact (2-35 μg/m(3)) and an area of high impact (10-315 μg/m(3)), with a peak of pollution reached between the fourth and fifth week. Ammonia affected both the photobiont and the mycobiont in F. caperata, while in X. parietina only the photosynthetic performance of the photobiont was altered after exposure to the highest concentration. In the photobiont of F. caperata we recorded chlorophyll degradation as indicated by OD435/415 ratio, decrease of the photosynthetic performance (as reflected by the maximum quantum yield of primary photochemistry FV/FM and the performance index PIABS); in the mycobiont, ergosterol reduction, membrane lipid peroxidation (as reflected by the increase of thiobarbituric acid reactive substances), alteration (decrease) of the secondary metabolite usnic acid. No effects were detected on caperatic acid and dehydrogenase activity. In X. parietina, the only signal determined by NH3 was the alteration of FV/FM and the performance index PIABS. The results suggest that physiological parameters in N-sensitive lichens well reflect the effects of NH3 exposure and can be applied as early indicators in monitoring studies. PMID:26342688

  11. Effect of ambient NH 3 levels on PM 2.5 composition in the Great Smoky Mountains National Park

    NASA Astrophysics Data System (ADS)

    Olszyna, Kenneth J.; Bairai, Solomon T.; Tanner, Roger L.

    Continuous measurements were made of gaseous NH 3, gaseous HNO 3, PM 2.5 sulfate, aerosol mass, air temperature, and relative humidity (RH), and 24-h filter samples of PM 2.5 aerosols were analyzed to determine the effects of ambient NH 3 levels on PM 2.5 aerosol composition. These measurements were conducted from 2 to 15 August 2002, at Look Rock, TN, at an air monitoring station located on a mountain ridge (elevation ˜800 m MSL) on the southwestern edge of the Great Smoky Mountains National Park. A strong diurnal pattern was observed for gaseous NH 3 levels at this site with higher daytime and much lower NH 3 during the night hours. The diurnal variability of both gaseous NH 3 concentrations and RH suggests that conditions controlling aerosol nitrate formation and acidic aerosol neutralization are complex. The observations during this 2-week long sampling period showed that measurable NH 4NO 3 aerosol was not present under the ambient conditions encountered. However, modest perturbations from observed ambient conditions could have enabled NH 4NO 3 aerosol production. The extent of neutralization of sulfate aerosol collected on filters indicates that there was insufficient regional NH 3 to neutralize the acidic sulfate aerosols to the degree predicted from local NH 3 and RH conditions. Incomplete neutralization of acidic sulfate could also result if neutralization proceeds more slowly under field conditions compared to laboratory conditions or model predictions. Continuous measurements of aerosol ammonium and/or acidity are needed to determine if ammonia availability or kinetic limitations (or both) restrict neutralization of acidic sulfate aerosols, a key factor for modeling and exposure studies.

  12. Relative CO2/NH3 selectivities of AQP1, AQP4, AQP5, AmtB, and RhAG

    PubMed Central

    Musa-Aziz, Raif; Chen, Li-Ming; Pelletier, Marc F.; Boron, Walter F.

    2009-01-01

    The water channel aquaporin 1 (AQP1) and certain Rh-family members are permeable to CO2 and NH3. Here, we use changes in surface pH (pHS) to assess relative CO2 vs. NH3 permeability of Xenopus oocytes expressing members of the AQP or Rh family. Exposed to CO2 or NH3, AQP1 oocytes exhibit a greater maximal magnitude of pHS change (ΔpHS) compared with day-matched controls injected with H2O or with RNA encoding SGLT1, NKCC2, or PepT1. With CO2, AQP1 oocytes also have faster time constants for pHS relaxation (τpHs). Thus, AQP1, but not the other proteins, conduct CO2 and NH3. Oocytes expressing rat AQP4, rat AQP5, human RhAG, or the bacterial Rh homolog AmtB also exhibit greater ΔpHS(CO2) and faster τpHs compared with controls. Oocytes expressing AmtB and RhAG, but not AQP4 or AQP5, exhibit greater ΔpHS(NH3) values. Only AQPs exhibited significant osmotic water permeability (Pf). We computed channel-dependent (*) ΔpHS or Pf by subtracting values for H2O oocytes from those of channel-expressing oocytes. For the ratio ΔpHS(CO2)*/Pf*, the sequence was AQP5 > AQP1 ≅ AQP4. For ΔpHS(CO2)*/ΔpHS(NH3)*, the sequence was AQP4 ≅ AQP5 > AQP1 > AmtB > RhAG. Thus, each channel exhibits a characteristic ratio for indices of CO2 vs. NH3 permeability, demonstrating that, like ion channels, gas channels can exhibit selectivity. PMID:19273840

  13. The tropospheric abundances of NH3 and PH3 in Jupiter's Great Red Spot, from Voyager IRIS observations.

    PubMed

    Griffith, C A; Bezard, B; Owen, T; Gautier, D

    1992-01-01

    To investigate the chemistry and dynamics of Jupiter's Great Red Spot (GRS), the tropospheric abundances of NH3 and PH3 in the GRS are determined and compared to those of the surrounding region, the South Tropical Zone (STZ). These gases well up from deep in the atmosphere, and, in the upper troposphere, are depleted by condensation (in the case of NH3), chemical reactions, and UV photolysis. At Jupiter's tropopause, the chemical lifetimes of NH3 and PH3 are comparable to the time constant for vertical transport over the atmospheric scale height. The distributions of these gases are therefore diagnostic of the rate of vertical transport in the upper troposphere and lower stratosphere. Three groups of Voyager IRIS spectra are analyzed, two of the STZ and one of the GRS. The two groups of STZ spectra are defined on the basis of their radiances at 602 and 226 cm-1, which reflect, respectively, the temperature near 150 mbar and the cloud opacity in the 300-600 mbar region. One selection of STZ spectra is chosen to have the same radiance as does the GRS at 226 cm-1. The other STZ selection has a significantly greater radiance, indicative of reduced cloudiness. Variations in the abundances of NH3 and PH3 are determined within the STZ, as a background for our studies of the GRS. Within the uncertainty of our measurements (-55% and +75%), the PH3 mixing ratio at 600 mbar is 3 x 10(-7), the same for all three selections. The NH3 mixing ratio profile in the pressure region between 300 and 600 mbar is the same within error (-25% and +50% at 300 mbar) for both STZ selections. In the GRS, however, NH3 is significantly depleted at 300 mbar, with an abundance of 25% that derived for the STZ selections. Since the GRS is believed to be a region of strong vertical transport, our finding of a depletion of NH3 below the tropopause within the GRS is particularly unexpected. One of the STZ selections has a temperature-pressure profile similar to that of the GRS below the 300-mbar level; therefore, condensation at this level does not easily explain the low NH3 abundance in the GRS. All samples are taken at essentially the same latitude; photolysis and/or charged particle precipitation is probably not directly responsible either. The observed NH3 depletion may have a dynamical origin or result from some unidentified chemical processes at work in the GRS. PMID:11540935

  14. Global analytical potential energy surface for the electronic ground state of NH3 from high level ab initio calculations.

    PubMed

    Marquardt, Roberto; Sagui, Kenneth; Zheng, Jingjing; Thiel, Walter; Luckhaus, David; Yurchenko, Sergey; Mariotti, Fabio; Quack, Martin

    2013-08-15

    The analytical, full-dimensional, and global representation of the potential energy surface of NH(3) in the lowest adiabatic electronic state developed previously (Marquardt, R.; et al. J. Phys. Chem. B 2005, 109, 84398451) is improved by adjustment of parameters to an enlarged set of electronic energies from ab initio calculations using the coupled cluster method with single and double substitutions and a perturbative treatment of connected triple excitations (CCSD(T)) and the method of multireference configuration interaction (MRCI). CCSD(T) data were obtained from an extrapolation of aug-cc-pVXZ results to the basis set limit (CBS), as described in a previous work (Yurchenko, S.N.; et al. J. Chem. Phys 2005, 123, 134308); they cover the region around the NH3 equilibrium structures up to 20,000 hc cm(1). MRCI energies were computed using the aug-cc-pVQZ basis to describe both low lying singlet dissociation channels. Adjustment was performed simultaneously to energies obtained from the different ab initio methods using a merging strategy that includes 10,000 geometries at the CCSD(T) level and 500 geometries at the MRCI level. Characteristic features of this improved representation are NH3 equilibrium geometry r(eq)(NH(3)) ? 101.28 pm, ?(eq)(NH(3)) ? 107.03, the inversion barrier at r(inv)(NH(3)) ? 99.88 pm and 1774 hc cm(1) above the NH(3) minimum, and dissociation channel energies 41,051 hc cm(1) (for NH(3) ? ((2)B(2))NH(2) + ((2)S(1/2))H) and 38,450 hc cm(1) (for NH(3) ? ((3)?())NH +((1)?(g)(+))H(2)); the average agreement between calculated and experimental vibrational line positions is 11 cm(1) for (14)N(1)H(3) in the spectral region up to 5000 cm(1). A survey of our current knowledge on the vibrational spectroscopy of ammonia and its isotopomers is also given. PMID:23688044

  15. Validation of flux measurements with artificial sources: simulating CH4 from cows and NH3 emissions from medium plot scales

    NASA Astrophysics Data System (ADS)

    Sintermann, Jörg; Felber, Raphael; Häni, Christoph; Ammann, Christof; Neftel, Albrecht

    2014-05-01

    Mitigation of ammonia (NH3) emissions with detrimental environmental effects as well as of greenhouse gas emissions (GHG: CO2, N2O, CH4) are key challenges faced by the agricultural production sector. While NH3 originates mainly from polluted surfaces, e.g. after slurry application, the main source for CH4 emissions are cows and other ruminating animals, representing point sources. There are two widespread state-of-the-art techniques to determine agricultural emissions: eddy covariance (EC) flux measurements and Lagrangian stochastic (LS) dispersion modelling, namely the WindTrax (WT) model. Whereas GHG emissions can be measured with both techniques, NH3 emissions are usually not feasible with EC measurements due to the stickiness of NH3 molecules on surfaces. In addition, point sources render difficulties for the interpretation of EC flux data. We tested the EC technique and the WT model using artificial sources with known gas release rates. i) The effect of a point source on EC fluxes was investigated by placing an artificial CH4 source with known release rate upwind of the EC tower at two different heights and during different wind conditions. ii) The WT model was checked with a NH3 release grid of 314 m2 of known source strength. Ambient NH3 concentrations were measured by open path DOAS systems and impinger sampling. The CH4 concentration timeseries influenced by the point source showed a similar pattern as in the presence of cows upwind of the EC system. CH4 release rates from the point source were reproduced by the EC flux measurement with stationary background conditions only. The experiments with the NH3 release showed that WT performs well for emission determination, even in complex terrain (asphalt surrounded by grassland) with associated micrometeorology, given a realistic description of the vertical profile of wind velocity. Calculated gas recoveries ranged between 73 to 105%. Such a result is encouraging considering the immanent uncertainties from a NH3 experiment (variable background concentration, relatively small downwind concentrations, NH3 interception on ground/tubing).

  16. Characterization of Biochar using Temperature Programmed Oxidation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biochar from the fast pyrolysis of biomass was characterized by Temperature Programmed Oxidation. This technique can be used to assess the oxidative reactivity of carbonaceous solids where higher temperature reactivity indicates greater structural order. The samples examined include soy and barley...

  17. Evaluation of a regional air-quality model with bidirectional NH3 exchange coupled to an agroecosystem model

    NASA Astrophysics Data System (ADS)

    Bash, J. O.; Cooter, E. J.; Dennis, R. L.; Walker, J. T.; Pleim, J. E.

    2013-03-01

    Atmospheric ammonia (NH3) is the primary atmospheric base and an important precursor for inorganic particulate matter and when deposited NH3 contributes to surface water eutrophication, soil acidification and decline in species biodiversity. Flux measurements indicate that the air-surface exchange of NH3 is bidirectional. However, the effects of bidirectional exchange, soil biogeochemistry and human activity are not parameterized in air quality models. The US Environmental Protection Agency's (EPA) Community Multiscale Air-Quality (CMAQ) model with bidirectional NH3 exchange has been coupled with the United States Department of Agriculture's (USDA) Environmental Policy Integrated Climate (EPIC) agroecosystem model. The coupled CMAQ-EPIC model relies on EPIC fertilization timing, rate and composition while CMAQ models the soil ammonium (NH4+) pool by conserving the ammonium mass due to fertilization, evasion, deposition, and nitrification processes. This mechanistically coupled modeling system reduced the biases and error in NHx (NH3 + NH4+) wet deposition and in ambient aerosol concentrations in an annual 2002 Continental US (CONUS) domain simulation when compared to a 2002 annual simulation of CMAQ without bidirectional exchange. Fertilizer emissions estimated in CMAQ 5.0 with bidirectional exchange exhibits markedly different seasonal dynamics than the US EPA's National Emissions Inventory (NEI), with lower emissions in the spring and fall and higher emissions in July.

  18. Fragmentation of doubly charged ammonia cations NH{3/++} studied by the photoion-photoion coincidence (PIPICO) method

    NASA Astrophysics Data System (ADS)

    Winkoun, D.; Dujardin, G.

    1986-03-01

    Doubly charged NH{3/++} cations were produced by double photoionization of neutral ammonia molecules by using the synchrotron radiation from ACO as a photon source of variable energy in the 35 49 eV energy range. The fragmentation of NH{3/++} was studied by the photoion-photoion coincidence (PIPICO) method. NH{3/++} cations were produced in thetilde X^1 A 1 andtilde B^1 electronic states of which the onset energies were measured at, respectively, 35.4±0.5 eV and 44.5±0.5 eV. It was shown that the NH{3/++} ions, initially produced in theirtilde X^1 A 1 state, rapidly dissociate (in less than 50 ns), into NH{2/+} + H+. Furthermore, the comparison with results obtained by other methods indicates that NH{3/++} ions can either be long-lived (τ>10 µs) or slowly dissociating (1 µs<τ<10 µs) or rapidly dissociating (τ<50 ns), depending on their geometry and/or internal energy in theirtilde X^1 E A 1 electronic state.

  19. Reversible flexible structural changes in multidimensional MOFs by guest molecules (I2, NH3) and thermal stimulation

    NASA Astrophysics Data System (ADS)

    Chen, Yang; Li, Libo; Yang, Jiangfeng; Wang, Shuang; Li, Jinping

    2015-03-01

    Three metal-organic frameworks (MOFs), [Cu(INA)2], [Cu(INA)2I2] and [Cu(INA)2(H2O)2(NH3)2], were synthesized with 3D, 2D, and 0D structures, respectively. Reversible flexible structural changes of these MOFs were reported. Through high temperature (60-100 °C) stimulation of I2 or ambient temperature stimulation of NH3, [Cu(INA)2] (3D) converted to [Cu(INA)2I2] (2D) and [Cu(INA)2(H2O)2(NH3)2] (0D); as the temperature increased to 150 °C, the MOFs changed back to their original form. In this way, this 3D MOF has potential application in the capture of I2 and NH3 from polluted water and air. XRD, TGA, SEM, NH3-TPD, and the measurement of gas adsorption were used to describe the changes in processes regarding the structure, morphology, and properties.

  20. Shock-heated NH3 in a Molecular Jet Associated with a High-Mass Young Star.

    PubMed

    Zhang; Hunter; Sridharan; Cesaroni

    1999-12-20

    We present the discovery of shock-excited NH3 in a well-collimated jet associated with the extremely young high-mass star IRAS 20126+4104. The NH3 (3, 3) and (4, 4) emission is dominated by three clumps along the SiO jet. At the end of the jet, there exists strong and broad (+/-10 km s-1) NH3 (3, 3) emission. With typical brightness temperatures greater than 500 K, the overall emission indicates a weakly inverted population and appears in an arc, consistent with the excitation by bow shocks. There are two bright spots in the NH3 (3, 3) emission with brightness temperatures of approximately 2000 K. The narrow line width (1.5 km s-1 FWHM), the small sizes (<0&farcs;3), and the unusually high brightness temperature of the features are indicative of maser emission. Our observations provide clear evidence that NH3 (3, 3) masers are excited in shock regions in molecular outflows. PMID:10577953

  1. Electronic Structure and Optical Properties of α-CH3NH3PbBr3 Perovskite Single Crystal.

    PubMed

    Park, Ji-Sang; Choi, Sukgeun; Yan, Yong; Yang, Ye; Luther, Joseph M; Wei, Su-Huai; Parilla, Philip; Zhu, Kai

    2015-11-01

    The electronic structure and related optical properties of an emerging thin-film photovoltaic material CH3NH3PbBr3 are studied. A block-shaped α-phase CH3NH3PbBr3 single crystal with the natural ⟨100⟩ surface is synthesized solvothermally. The room-temperature dielectric function ε = ε1 + iε2 spectrum of CH3NH3PbBr3 is determined by spectroscopic ellipsometry from 0.73 to 6.45 eV. Data are modeled with a series of Tauc-Lorentz oscillators, which show the absorption edge with a strong excitonic transition at ∼2.3 eV and several above-bandgap optical structures associated with the electronic interband transitions. The energy band structure and ε data of CH3NH3PbBr3 for the CH3NH3(+) molecules oriented in the ⟨111⟩ and ⟨100⟩ directions are obtained from first-principles calculations. The overall shape of ε data shows a qualitatively good agreement with experimental results. Electronic origins of major optical structures are discussed. PMID:26722966

  2. High Resolution Infrared and Microwave Spectra of NH3-HCCH and NH3-OCS Complexes: Studies of Weak C-H\\cdotsN Hydrogen Bond and Electric Multipole Interactions

    NASA Astrophysics Data System (ADS)

    Liu, Xunchen; Xu, Yunjie

    2011-06-01

    C-H\\cdotsN weak hydrogen bond is of much current interest. We report the first high resolution infrared spectroscopic study of a prototypical C-H\\cdotsN bonded system, i.e. NH3-HCCH, at the vicinity of the ν4 band of NH3. The spectrum has been recorded using an infrared spectrometer equipped with an astigmatic multipass cell aligned for 366 passes and a room temperature external cavity quantum cascade laser at the 6 μm region. The perpendicular band spectrum of symmetric top rotor observed is consistent with the previous microwave and infrared studies at 3 μm. We also extended the previous microwave measurement to higher J and K. For the related NH3-OCS complex, microwave spectrum of J up to 6 and infrared spectrum at the vicinity of the ν4 band of NH3 have been recorded and analyzed for the first time. Comparison has been made with the previously studied isoelectronic complexes such as NH3-N2O and NH3-CO2. The source of the difference will be discussed with the aid of ab initio calculations. G.T. Fraser, K.R. Leopold, and W. Klemperer, J. Chem. Phys. 80(4), 1423, (1984) G. Hilpert, G.T. Fraser, and A.S. Pine, J. Chem. Phys. 105(15), 6183, (1996) G.T. Fraser, D.D. Nelson, JR., G.J. Gerfen, and W. Klemperer, J. Chem. Phys. 83(11), 5442, (1985) G.T. Fraser, K.R. Leopold, and W. Klemperer, J. Chem. Phys. 81(6), 2577, (1984)

  3. Validation of model calculation of ammonia deposition in the neighbourhood of a poultry farm using measured NH 3 concentrations and N deposition

    NASA Astrophysics Data System (ADS)

    Sommer, S. G.; Østergård, H. S.; Løfstrøm, P.; Andersen, H. V.; Jensen, L. S.

    Substantial emission of ammonia (NH 3) from animal houses and the related high local deposition of NH 3-N are a threat to semi-natural nitrogen-deficient ecosystems situated near the NH 3 source. In Denmark, there are regulations limiting the level of NH 3 emission from livestock houses near N-deficient ecosystems that are likely to change due to nitrogen (N) enrichment caused by NH 3 deposition. The models used for assessing NH 3 emission from livestock production, therefore, need to be precise, as the regulation will affect both the nature of the ecosystem and the economy of the farmer. Therefore a study was carried out with the objective of validating the Danish model used to monitor NH 3 transport, dispersion and deposition from and in the neighbourhood of a chicken farm. In the study we measured NH 3 emission with standard flux measuring methods, NH 3 concentrations at increasing distances from the chicken houses using passive diffusion samplers and deposition using 15N-enriched biomonitors and field plot studies. The dispersion and deposition of NH 3 were modelled using the Danish OML-DEP model. It was also shown that model calculations clearly reflect the measured NH 3 concentration and N deposition. Deposition of N measured by biomonitors clearly reflected the variation in NH 3 concentrations and showed that deposition was not significantly different from zero ( P < 0.05) at distances greater than 150-200 m from these chicken houses. Calculations confirmed this, as calculated N deposition 320 m away from the chicken farm was only marginally affected by the NH 3 emission from the farm. There was agreement between calculated and measured deposition showing that the model gives true estimates of the deposition in the neighbourhood of a livestock house emitting NH 3.

  4. Controlled reaction for improved CH3NH3PbI3 transition in perovskite solar cells.

    PubMed

    Zhao, J J; Wang, P; Liu, Z H; Wei, L Y; Yang, Z; Chen, H R; Fang, X Q; Liu, X L; Mai, Y H

    2015-10-28

    Hybrid halide perovskites represent one of the most promising solutions toward the fabrication of all solid nanostructured solar cells, with improved efficiency and long-term stability. This article aims at investigating the properties of CH3NH3PbI3 with controlled loading time in CH3NH3I solution via a two-step sequential deposition and correlating them with their photovoltaic performances. It is found that the optimum PCE of the loading time in the CH3NH3I solution is possible only at a relatively short time (10 min). Prolonging the loading time will degrade the perovskite film, and deteriorate the device performance by introducing a large amount of excessive defects and recombination. However, even if the material band gap remains substantially unchanged, a suitable loading time can dramatically improve the charge transport within the perovskite layer, exhibiting the out-standing performances of meso-superstructured solar cells. PMID:26399298

  5. The tropospheric abundances of NH3 and PH3 in Jupiter's Great Red Spot, from Voyager IRIS observations

    NASA Technical Reports Server (NTRS)

    Griffith, Caitlin A.; Bezard, Bruno; Owen, Tobias; Gautier, Daniel

    1992-01-01

    The tropospheric abundances of NH3 and PH3 in Jupiter's Great Red Spot (GRS) are presently determined on the basis of a group of Voyager IRIS spectra, and compared with those of the surrounding South Tropical Zone (STZ) obtained from another two groups of IRIS spectra, in order to characterize the GRS's chemistry and dynamics. Although the GRS is believed to be a region of strong vertical transport, NH3 depletion is surprisingly found to occur below the tropopause within the GRS. Since one of the STZ's selections has a temperature-pressure profile similar to that of the GRS below the 300 mbar level, condensation cannot explain the low NH3 abundance in the GRS.

  6. Temperature dependent optical properties of CH3NH3PbI3 perovskite by spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Jiang, Yajie; Soufiani, Arman Mahboubi; Gentle, Angus; Huang, Fuzhi; Ho-Baillie, Anita; Green, Martin A.

    2016-02-01

    Mixed organic-inorganic halide perovskites have emerged as a promising new class of semiconductors for photovoltaics with excellent light harvesting properties. Thorough understanding of the optical properties of these materials is important for photovoltaic device optimization and the insight this provides for the knowledge of energy band structures. Here we present an investigation of the sub-room temperature dependent optical properties of polycrystalline thin films of CH3NH3PbI3 perovskites that are of increasing interest for photovoltaics. The complex dielectric function of CH3NH3PbI3 in the energy range of 0.5-4.1 eV is determined between 77 K and 297 K using spectroscopic ellipsometry. An increase in optical permittivity as the temperature decreases is illustrated for CH3NH3PbI3. Optical transitions and critical points were analyzed using the energy dependent second derivative of these dielectric functions as a function of temperature.

  7. Enhancement of NH3 sensing performance in flower-like ZnO nanostructures and their growth mechanism

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Liu, Tianmo; Hao, Jinghua; Lin, Liyang; Zeng, Wen; Peng, Xianghe; Wang, Zhongchang

    2015-12-01

    ZnO nanostructures hold substantial promise for gas-sensing applications owing to their outstanding ethanol sensing performance, yet their sensing performance toward NH3 has rarely been reported. Here, we report on a successful preparation of sunflower-like ZnO nanostructures and ZnO nanoparticle via a facile hydrothermal method, and demonstrate that the ZnO nanoflowers have high gas-sensing performances toward NH3 under a low concentration of 10-50 ppm. Further structural characterization reveals that the sunflower-like nanostructure comprises six triangles-like and one sphere-like nanostructures, and the triangle-like nanostructure is single crystalline with {0 0 1} crystal face. As a consequence of their unique morphology, the nanoflowers show much improved NH3 sensing performances than the nanoparticles with a high sensitivity of 49.5.

  8. Molecular motions in a novel ferroelectric crystal (CH 3NH 3) 5Bi 2Br 11 studied by NMR

    NASA Astrophysics Data System (ADS)

    Piekara-Sady, L.; Jakubas, R.; Piślewski, N.

    1989-11-01

    The temperature dependence of the 1H relaxation times T1, T1 ρ and T1 D were studied in the ferroelectric (CH 3NH 3) 5Bi 2Br 11. Three kinds of motions of the methylammonium cation, i.e. (1) rotations of the CH 3 and NH 3 groups about C 3 axis, (2) reorientation of the whole cation about C 3 axis forming an angle α = 13° with the C 3 axis of NH 3 and CH 3 groups, (3) 180° flip motion of the methylammonium cation, have been observed separately. The small activation energies of these motions imply that the cations experience a weak crystal field.

  9. Two-stage biofilter for effective NH3 removal from waste gases containing high concentrations of H2S.

    PubMed

    Chung, Ying-Chien; Ho, Kuo-Ling; Tseng, Ching-Ping

    2007-03-01

    A high H2S concentration inhibits nitrification when H2S and NH3 are simultaneously treated in a single biofilter. To improve NH3 removal from waste gases containing concentrated H2S, a two-stage biofilter was designed to solve the problem. In this study, the first biofilter, inoculated with Thiobacillus thioparus, was intended mainly to remove H2S and to reduce the effect of H2S concentration on nitrification in the second biofilter, and the second biofilter, inoculated with Nitrosomonas europaea, was to remove NH3. Extensive studies, which took into account the characteristics of gas removal, the engineering properties of the two biofilters, and biological parameters, were conducted in a 210-day operation. The results showed that an average 98% removal efficiency for H2S and a 100% removal efficiency for NH3 (empty bed retention time = 23-180 sec) were achieved after 70 days. The maximum degradation rate for NH3 was measured as 2.35 g N day(-1) kg of dry granular activated carbon(-1). Inhibition of nitrification was not found in the biofilter. This two-stage biofilter also exhibited good adaptability to shock loading and shutdown periods. Analysis of metabolic product and observation of the bacterial community revealed no obvious acidification or alkalinity phenomena. In addition, a lower moisture content (approximately 40%) for microbial survival and low pressure drop (average 24.39 mm H2O m(-1)) for system operation demonstrated that the two-stage biofilter was energy saving and economic. Thus, the two-stage biofilter is a feasible system to enhance NH3 removal in the concentrated coexistence of H2S. PMID:17385601

  10. Emission factor of ammonia (NH3) from on-road vehicles in China: tunnel tests in urban Guangzhou

    NASA Astrophysics Data System (ADS)

    Liu, Tengyu; Wang, Xinming; Wang, Boguang; Ding, Xiang; Deng, Wei; Lü, Sujun; Zhang, Yanli

    2014-05-01

    Ammonia (NH3) is the primary alkaline gas in the atmosphere that contributes to formation of secondary particles. Emission of NH3 from vehicles, particularly gasoline powered light duty vehicles equipped with three-way catalysts, is regarded as an important source apart from emissions from animal wastes and soils, yet measured emission factors for motor vehicles are still not available in China, where traffic-related emission has become an increasingly important source of air pollutants in urban areas. Here we present our tunnel tests for NH3 from motor vehicles under ‘real world conditions’ in an urban roadway tunnel in Guangzhou, a central city in the Pearl River Delta (PRD) region in south China. By attributing all NH3 emissions in the tunnel to light-duty gasoline vehicles, we obtained a fuel-based emission rate of 2.92 ± 0.18 g L-1 and a mileage-based emission factor of 229.5 ± 14.1 mg km-1. These emission factors were much higher than those measured in the United States while measured NO x emission factors (7.17 ± 0.60 g L-1 or 0.56 ± 0.05 g km-1) were contrastingly near or lower than those previously estimated by MOBILE/PART5 or COPERT IV models. Based on the NH3 emission factors from this study, on-road vehicles accounted for 8.1% of NH3 emissions in the PRD region in 2006 instead of 2.5% as estimated in a previous study using emission factors taken from the Emission Inventory Improvement Program (EIIP) in the United States.

  11. Open-path Atmospheric N2O, CO, and NH3 Measurements Using Quantum Cascade Laser Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sun, K.; Khan, A.; Miller, D. J.; Rafferty, K.; Schreiber, J.; Puzio, C.; Portenti, M.; Silver, J.; Zondlo, M. A.

    2010-12-01

    We develop a compact, mid-infrared quantum cascade (QC) laser based sensor to perform high precision measurements of N2O and CO simultaneously. Since CO is a good tracer of anthropogenic emissions, simultaneous measurements of CO and N2O allow us to correlate the sources of N2O emissions. The thermoelectrically (TE) cooled, and continuous wave QC laser enables room-temperature and unattended operation. The laser is scanned over the absorption features of N2O and CO near 4.54 μm by laser current modulation. A novel cylindrical multi-pass optical cell terminated at the (N/2)th spot is used to simplify the optical configuration by separating the laser and TE cooled detector. Our systems are open-path and non-cryogenic, which avoids vacuum pump and liquid nitrogen. This configuration enables a future design of a non-intrusive, compact (shoe box size), and low-power (10W) sensor. Wavelength modulation spectroscopy (WMS) is used to enhance measurement sensitivity. Higher-harmonic detection (4f and 6f) is performed to improve the resolution between the nearly overlapping N2O and CO lines. Relevant atmospheric N2O and CO concentration is measured, with a detection limit of 0.3 ppbv for N2O and 2 ppbv for CO for 1 s averaging in terms of noise. We also develop an open-path high sensitivity atmospheric ammonia (NH3) sensor using a very similar instrument design. A 9.06 μm QC laser is used to probe absorption features of NH3. Open-path detection of NH3 is even more beneficial due to the surface absorption effect of NH3 and its tendency to readily partition into condensed phases. The NH3 sensor was deployed at the CALNEX 2010 field campaign. The entire system was stable throughout the campaign and acquired data with 10 s time resolution under adverse ambient temperatures and dusty conditions. The measurements were in general agreement with other NH3 and trace gases sensors. Both the N2O/CO and NH3 sensors will be deployed in a local eddy-covariance station to examine long term stability and detection limit in the field. Future sensor applications include characterizing urban and agricultural N2O and NH3 emission sources and quantifying their respective fluxes.

  12. Depletion of the heaviest stable N isotope is associated with NH4+/NH3 toxicity in NH4+-fed plants

    PubMed Central

    2011-01-01

    Background In plants, nitrate (NO3-) nutrition gives rise to a natural N isotopic signature (δ15N), which correlates with the δ15N of the N source. However, little is known about the relationship between the δ15N of the N source and the 14N/15N fractionation in plants under ammonium (NH4+) nutrition. When NH4+ is the major N source, the two forms, NH4+ and NH3, are present in the nutrient solution. There is a 1.025 thermodynamic isotope effect between NH3 (g) and NH4+ (aq) which drives to a different δ15N. Nine plant species with different NH4+-sensitivities were cultured hydroponically with NO3- or NH4+ as the sole N sources, and plant growth and δ15N were determined. Short-term NH4+/NH3 uptake experiments at pH 6.0 and 9.0 (which favours NH3 form) were carried out in order to support and substantiate our hypothesis. N source fractionation throughout the whole plant was interpreted on the basis of the relative transport of NH4+ and NH3. Results Several NO3--fed plants were consistently enriched in 15N, whereas plants under NH4+ nutrition were depleted of 15N. It was shown that more sensitive plants to NH4+ toxicity were the most depleted in 15N. In parallel, N-deficient pea and spinach plants fed with 15NH4+ showed an increased level of NH3 uptake at alkaline pH that was related to the 15N depletion of the plant. Tolerant to NH4+ pea plants or sensitive spinach plants showed similar trend on 15N depletion while slight differences in the time kinetics were observed during the initial stages. The use of RbNO3 as control discarded that the differences observed arise from pH detrimental effects. Conclusions This article proposes that the negative values of δ15N in NH4+-fed plants are originated from NH3 uptake by plants. Moreover, this depletion of the heavier N isotope is proportional to the NH4+/NH3 toxicity in plants species. Therefore, we hypothesise that the low affinity transport system for NH4+ may have two components: one that transports N in the molecular form and is associated with fractionation and another that transports N in the ionic form and is not associated with fractionation. PMID:21575190

  13. Separation of H2S and NH3 gases from tofu waste water-based biogas using activated carbon adsorption

    NASA Astrophysics Data System (ADS)

    Harihastuti, Nani; Purwanto, P.; Istadi, I.

    2015-12-01

    Research on the separation of H2S and NH3 gases from tofu waste water-based biogas has been conducted to improve the content of CH4 of biogas in order to increase calorific value. Biogas from tofu waste water contained many kinds of gases such as: CH4 of 53-64%, CO2 of 36-45%, H2S of 3,724-5,880 mg/Nm3, NH3 of 0.19-70.36 mg/Nm3, and H2O of 33,800-19,770,000 mg/Nm3. In fact, CO2, H2S, NH3, and moisture are impurities that have disturbance to human and environment, so that they are necessary to be separated from biogas. Particularly, H2S and NH3 have high toxicity to people, particularly the workers in the tofu industry. Therefore, separation of H2S and NH3 from biogas to increase calorific value is the focus of this research. The method used in this research is by adsorption of H2S and NH3 gases using activated carbon as adsorbent. It also used condensation as pretreatment to remove moisture content in biogas. Biogas was flowed to adsorption column (70 cm height and 9 cm diameter containing activated carbon as much as 500 g) so that the H2S and NH3 gases were adsorbed. This research was conducted by varying flow rate and flow time of biogas. From this experiment, it was found that the optimum adsorption conditions were flow rate of 3.5 l/min and 4 hours flow time. This condition could reach 99.95% adsorption efficiency of H2S from 5,879.50 mg/Nm3 to 0.67 mg/Nm3, and 74.96% adsorption efficiency of NH3 from 2.93 mg/Nm3 to 0.73 mg/Nm3. The concentration of CH4 increased from 63.88% to 76.24% in the biogas.

  14. The Bonding of NO2, NH3, and CH2NY to Models of a (10,0) Carbon Nanotube

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    2004-01-01

    We have studied the bonding of NO2, NH3, and CH2NH to a (10,O) carbon nanotube using the MP2 and ONIOM methods with extended basis sets. We find bond strengths of 3.5, 3.6. and 6.3 kcal/mol for NO2, NH3, and CH2NH, respectively, using the ONIOM method with the high accuracy part treated at the MP2/aug-CC-pVTZ level and the remainder of the CNT approximated at the UFF level and including an estimate of basis set superposition error using the counterpoise method.

  15. The efficiency limit of CH3NH3PbI3 perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Sha, Wei E. I.; Ren, Xingang; Chen, Luzhou; Choy, Wallace C. H.

    2015-06-01

    With the consideration of photon recycling effect, the efficiency limit of methylammonium lead iodide (CH3NH3PbI3) perovskite solar cells is predicted by a detailed balance model. To obtain convincing predictions, both AM 1.5 spectrum of Sun and experimentally measured complex refractive index of perovskite material are employed in the detailed balance model. The roles of light trapping and angular restriction in improving the maximal output power of thin-film perovskite solar cells are also clarified. The efficiency limit of perovskite cells (without the angular restriction) is about 31%, which approaches to Shockley-Queisser limit (33%) achievable by gallium arsenide (GaAs) cells. Moreover, the Shockley-Queisser limit could be reached with a 200 nm-thick perovskite solar cell, through integrating a wavelength-dependent angular-restriction design with a textured light-trapping structure. Additionally, the influence of the trap-assisted nonradiative recombination on the device efficiency is investigated. The work is fundamentally important to high-performance perovskite photovoltaics.

  16. IR spectrum of the protonated neurotransmitter 2-phenylethylamine: dispersion and anharmonicity of the NH3(+)-? interaction.

    PubMed

    Bouchet, Aude; Schtz, Markus; Chiavarino, Barbara; Crestoni, Maria Elisa; Fornarini, Simonetta; Dopfer, Otto

    2015-10-21

    The structure and dynamics of the highly flexible side chain of (protonated) phenylethylamino neurotransmitters are essential for their function. The geometric, vibrational, and energetic properties of the protonated neutrotransmitter 2-phenylethylamine (H(+)PEA) are characterized in the N-H stretch range by infrared photodissociation (IRPD) spectroscopy of cold ions using rare gas tagging (Rg = Ne and Ar) and anharmonic calculations at the B3LYP-D3/(aug-)cc-pVTZ level including dispersion corrections. A single folded gauche conformer (G) protonated at the basic amino group and stabilized by an intramolecular NH(+)-? interaction is observed. The dispersion-corrected density functional theory calculations reveal the important effects of dispersion on the cation-? interaction and the large vibrational anharmonicity of the NH3(+) group involved in the NH(+)-? hydrogen bond. They allow for assigning overtone and combination bands and explain anomalous intensities observed in previous IR multiple-photon dissociation spectra. Comparison with neutral PEA reveals the large effects of protonation on the geometric and electronic structure. PMID:25757357

  17. Selective catalytic reduction operation with heavy fuel oil: NOx, NH3, and particle emissions.

    PubMed

    Lehtoranta, Kati; Vesala, Hannu; Koponen, Päivi; Korhonen, Satu

    2015-04-01

    To meet stringent NOx emission limits, selective catalytic reduction (SCR) is increasingly utilized in ships, likely also in combination with low-priced higher sulfur level fuels. In this study, the performance of SCR was studied by utilizing NOx, NH3, and particle measurements. Urea decomposition was studied with ammonia and isocyanic acid measurements and was found to be more effective with heavy fuel oil (HFO) than with light fuel oil. This is suggested to be explained by the metals found in HFO contributing to metal oxide particles catalyzing the hydrolysis reaction prior to SCR. At the exhaust temperature of 340 °C NOx reduction was 85-90%, while at lower temperatures the efficiency decreased. By increasing the catalyst loading, the low temperature behavior of the SCR was enhanced. The drawback of this, however, was the tendency of particle emissions (sulfate) to increase at higher temperatures with higher loaded catalysts. The particle size distribution results showed high amounts of nanoparticles (in 25-30 nm size), the formation of which SCR either increased or decreased. The findings of this work provide a better understanding of the usage of SCR in combination with a higher sulfur level fuel and also of ship particle emissions, which are a growing concern. PMID:25780953

  18. Quasielastic neutron scattering of -NH3 and -BH3 rotational dynamics in orthorhombic ammonia borane

    SciTech Connect

    Hess, Nancy J.; Hartman, Michael R.; Brown, Craig; Mamontov, Eugene; Karkamkar, Abhijeet J.; Heldebrant, David J.; Daemen, Luke L.; Autrey, Thomas

    2008-06-27

    Neutrons scattering techniques are ideally suited to directly probe H in materials due to the large incoherent scattering cross-section of hydrogen atom, and have been invaluable in providing direct insight into the local fluctuations and large amplitude motions in AB. Dihydrogen bonding may have a significant affect on materials to be used to store hydrogen for fuel-cell powered applications. We have noticed a trend of low temperature release of H2 in materials composed of hydridic and protonic hydrogen. This phenomenon has caught our attention and motivated our interest to gain more insight into dihydrogen bonding interactions in AB. We present results from a thorough Quasielastic Neutron Scattering (QENS) investigation of diffusive hydrogen motion in NH311BH3 and ND311BH3 to obtain (1) a direct measure of the rotational energy barriers the protonated species and (2) a confirmation of the 3-site jump model for rotational motion. The amplitude of the energy barrier of rotation of BH3 and NH3 determined by QENS are compared to those determined for BD3 and ND3 determined by 2H NMR studies.

  19. Spectral intensities in the nu(sub 1) band of NH3

    NASA Technical Reports Server (NTRS)

    Pine, A. S.; Dang-Nhu, M.

    1993-01-01

    Intensities have been measured for individual transitions in the Q and R branches of the nu(sub 1) band of NH3 using a difference-frequency laser spectrometer. The data yield an integrated band strength of S(sup 0 sub v) = 219.36 +/- 1.03/sq cm/MPa at 297 K, corresponding to a transition moment of absolute value of mu(sub v) = 8.535(20) x 10(exp -32) C x m, and a Herman-Wallis correction factor,(1 + alpha(sub J)m), where alpha(sub J) = 0.0209(20). The intensities of a few lines for K greater than or equal to 7 were noticeably perturbed by a perpendicular Coriolis interaction with 2nu(sub 4)(E, l = 2), so were excluded from the fit. A small sample of nu(sub 3) band lines occurring in the nu(sub 1) band scans also yields a rough estimate of the nu(sub 3) band intensity with evident irregular perturbations.

  20. Photochemical reactions in interstellar grains photolysis of CO, NH3, and H2O

    NASA Technical Reports Server (NTRS)

    Agarwal, V. K.; Ferris, J. P.; Schutte, W.; Greenberg, J. M.; Briggs, R.

    1985-01-01

    The interstellar grains are currently considered to be the basic building blocks of comets and, possibly, meteorites. To test this theory, a simulation of the organic layer accreted onto interstellar dust particles was prepared by slow deposition of a CO:NH3:H2O gas mixture on an Al block at 10 K, with concomitant irradiation with vacuum UV. The results of the HPLC and IR analyses of the nonvolatile residue formed by photolysis at 10 K are compared with those observed at 77 K and 298 K. Some of the compounds that may be present on the surfaces of interstellar dust particles have been identified, and some specific predictions concerning the types of molecular species present in comets could be drawn. The results also suggest that photochemical reactions may have been important for the formation of meteorite components. The implication of the findings to the questions of the source of organic matter on earth and the origin of life are discussed.

  1. Absorption coefficients of solid NH3 from 50 to 7000 per cm

    NASA Technical Reports Server (NTRS)

    Sill, G.; Fink, U.; Ferraro, J. R.

    1980-01-01

    Thin-film spectra of solid NH3 at a resolution of 1 per cm were used to determine its absorption coefficient over the range 50-7000 per cm. The thin films were formed inside a liquid N2 cooled dewar using a variety of substrates and dewar windows. The spectra were recorded with two Fourier spectrometers, one covering the range from 1 to 4 microns and the other from 2.6 to 200 microns. The thickness of the films was measured with a laser interference technique. The absorption coefficients were determined by application of Lambert's law and by a fitting procedure to the observed spectra using thin-film theory. Good agreement was found with the absorption coefficients recently determined by other investigators over a more restricted wavelength range. A metastable phase was observed near a temperature of 90 K and its absorption coefficient is reported. No other major spectral changes with temperature were noted for the range 88-120 K.

  2. Proton transfer in the [phenol-NH3]+ system: An experimental and ab initio study

    NASA Astrophysics Data System (ADS)

    Kim, Ho-Tae; Green, Richard J.; Qian, Jun; Anderson, Scott L.

    2000-04-01

    Mass-analyzed threshold ionization (MATI) has been used to prepare phenol cations in selected vibrational states, including the ground state. Reactions of ground state C6H5OH+ with ND3, studied in a guided ion-beam apparatus, are reported, along with related ab initio calculations. This paper focuses on the energetics and product branching in the proton transfer (PT) channel. Based on thermochemistry in the literature, combined with calculations of the intracomplex PT barrier, PT was expected to make up a large fraction of the total reactive scattering. Experimentally, it is found that PT has a small cross section with clear threshold behavior, and the conclusion is that the PT reaction is endoergic by 4.5±1 kcal/mole. Assuming that NH3 has a proton affinity of 204.0 kcal/mole, this results in a proton affinity for phenoxy radical of 208.7 kcal/mole, and a neutral PhO-H bond energy of 91.1 kcal/mole. The results are used to reinterpret previous dissociative photoionization studies of phenol-ammonia complexes.

  3. Efficient thermal conductance in organometallic perovskite CH3NH3PbI3 films

    NASA Astrophysics Data System (ADS)

    Chen, Qi; Zhang, Chunfeng; Zhu, Mengya; Liu, Shenghua; Siemens, Mark E.; Gu, Shuai; Zhu, Jia; Shen, Jiancang; Wu, Xinglong; Liao, Chen; Zhang, Jiayu; Wang, Xiaoyong; Xiao, Min

    2016-02-01

    Perovskite-based optoelectronic devices have shown great promise for solar conversion and other optoelectronic applications, but their long-term performance instability is regarded as a major obstacle to their widespread deployment. Previous works have shown that the ultralow thermal conductivity and inefficient heat spreading might put an intrinsic limit on the lifetime of perovskite devices. Here, we report the observation of a remarkably efficient thermal conductance, with a conductivity of 11.2 ± 0.8 W m-1 K-1 at room temperature, in densely packed perovskite CH3NH3PbI3 films, via noncontact time-domain thermal reflectance measurements. The temperature-dependent experiments suggest the important roles of organic cations and structural phase transitions, which are further confirmed by temperature-dependent Raman spectra. The thermal conductivity at room temperature observed here is over one order of magnitude larger than that in the early report, suggesting that perovskite device performance will not be limited by thermal conductance.

  4. DFT based study of transition metal nano-clusters for electrochemical NH3 production.

    PubMed

    Howalt, J G; Bligaard, T; Rossmeisl, J; Vegge, T

    2013-05-28

    Theoretical studies of the possibility of producing ammonia electrochemically at ambient temperature and pressure without direct N2 dissociation are presented. Density functional theory calculations were used in combination with the computational standard hydrogen electrode to calculate the free energy profile for the reduction of N2 admolecules and N adatoms on transition metal nanoclusters in contact with an acidic electrolyte. This work has established linear scaling relations for the dissociative reaction intermediates NH, NH2, and NH3. In addition, linear scaling relations for the associative reaction intermediates N2H, N2H2, and N2H3 have been determined. Furthermore, correlations between the adsorption energies of N, N2, and H have been established. These scaling relations and the free energy corrections are used to establish volcanoes describing the onset potential for electrochemical ammonia production and hence describe the potential determining steps for the electrochemical ammonia production. The competing hydrogen evolution reaction has also been analyzed for comparison. PMID:23598667

  5. Two-Dimensional CH3NH3PbI3 Perovskite: Synthesis and Optoelectronic Application.

    PubMed

    Liu, Jingying; Xue, Yunzhou; Wang, Ziyu; Xu, Zai-Quan; Zheng, Changxi; Weber, Bent; Song, Jingchao; Wang, Yusheng; Lu, Yuerui; Zhang, Yupeng; Bao, Qiaoliang

    2016-03-22

    Hybrid organic-inorganic perovskite materials have received substantial research attention due to their impressively high performance in photovoltaic devices. As one of the oldest functional materials, it is intriguing to explore the optoelectronic properties in perovskite after reducing it into a few atomic layers in which two-dimensional (2D) confinement may get involved. In this work, we report a combined solution process and vapor-phase conversion method to synthesize 2D hybrid organic-inorganic perovskite (i.e., CH3NH3PbI3) nanocrystals as thin as a single unit cell (∼1.3 nm). High-quality 2D perovskite crystals have triangle and hexagonal shapes, exhibiting tunable photoluminescence while the thickness or composition is changed. Due to the high quantum efficiency and excellent photoelectric properties in 2D perovskites, a high-performance photodetector was demonstrated, in which the current can be enhanced significantly by shining 405 and 532 nm lasers, showing photoresponsivities of 22 and 12 AW(-1) with a voltage bias of 1 V, respectively. The excellent optoelectronic properties make 2D perovskites building blocks to construct 2D heterostructures for wider optoelectronic applications. PMID:26910395

  6. Adsorption capacity of H2O, NH3, CO, and NO2 on the pristine graphene

    NASA Astrophysics Data System (ADS)

    Lin, Xianqing; Ni, Jun; Fang, Chao

    2013-01-01

    First-principles together with statistical mechanics calculations have been performed to study the adsorption behavior of H2O, NH3, CO, and NO2 on the pristine graphene. In the first-principles calculations, we find that the most recent van der Waals (vdW) density functional vdW-DF2 gives even larger binding energies (Eb) that those obtained with the local density approximation, indicating vdW-DF2 may be inappropriate for describing the interaction between these molecules and graphene. With the potential energy curves of the molecules on graphene calculated by the density functional theory, the adsorption capacity (n) of the molecules on the pristine graphene is calculated with the statistical mechanics method. NO2 has the largest n of the order of 108 cm-2 among the four molecules on graphene at room temperature and concentration of 1.0 ppm, but still smaller by almost two order than that on graphene devices estimated from the experimental results. This is probably due to the strong binding of NO2 to the graphene edges with terminating oxygen atoms with Eb as large as 1.0 eV. The calculations of the adsorption capacity of small polar molecules on the pristine graphene and comparison with the experimental values may contribute to the understanding of the mechanism and designing of graphene based gas sensors.

  7. Dependence of nitrogen doping on TiO 2 precursor annealed under NH 3 flow

    NASA Astrophysics Data System (ADS)

    Fang, Xiaoming; Zhang, Zhengguo; Chen, Qinglin; Ji, Hongbing; Gao, Xuenong

    2007-04-01

    N-doped TiO 2 photocatalysts were prepared by annealing two different precursors, P25 and a TiO 2 xerogel powder under NH 3/Ar flow at 500, 550, and 600 °C. The xerogel powder prepared by peptizing Ti(OH) 4 with HNO 3 was composed of nanoparticles and had large specific surface area. During the annealing process, the xerogel powder underwent increase in crystallinity, grain growth and phase transformation, whereas P25 did not show obvious changes. Compared with the N-doped TiO 2 photocatalysts from P25, the N-doped TiO 2 photocatalysts from the xerogel powder possessed higher concentrations of the substitutional nitrogen and exhibited more obvious absorption in the visible light region. The N-doped TiO 2 photocatalysts from the xerogel powder exhibited obvious visible-light activities for photodegrading methylene blue and the sample prepared at 500 °C achieved the best performance with a rate constant ( k) about 0.44 h -1, whereas those from P25 did not exhibit improved visible-light activities.

  8. Selective autocatalytic reduction of NO from sintering flue gas by the hot sintered ore in the presence of NH3.

    PubMed

    Chen, Wangsheng; Luo, Jing; Qin, Linbo; Han, Jun

    2015-12-01

    In this paper, the selective autocatalytic reduction of NO by NH3 combined with multi-metal oxides in the hot sintered ore was studied, and the catalytic activity of the hot sintered ore was investigated as a function of temperature, NH3/NO ratio, O2 content, H2O and SO2. The experimental results indicated that the hot sintered ore, when combined with NH3, had a maximum denitration efficiency of 37.67% at 450 °C, 3000 h(-1) gas hourly space velocity (GHSV) and a NH3/NO ratio of 0.4/1. Additionally, it was found that O2 played an important role in removing NOx. However, high O2 content had a negative effect on NO reduction. H2O was found to promote the denitration efficiency in the absence of SO2, while SO2 inhibited the catalytic activity of the sintered ore. In the presence of H2O and SO2, the catalytic activity of the sintered ore was dramatically suppressed. PMID:26363262

  9. Observations and analysis of the Jovian spectrum in the 10-micron nu-2 band of NH3

    NASA Technical Reports Server (NTRS)

    Lacy, J. H.; Larrabee, A. I.; Wollman, E. R.; Geballe, T. R.; Townes, C. H.; Bregman, J. D.; Rank, D. M.

    1975-01-01

    Observations of the nu-2 band of NH3 in the Jovian atmosphere have been made at resolutions varying from 4 per cm to 0.15 per cm. The observations have been interpreted by computation of synthetic atmospheric spectra. Derived atmospheric parameters include a pressure of 0.5 atm at 145 K and a minimum temperature of 118 K.

  10. From soft harmonic phonons to fast relaxational dynamics in CH3NH3PbBr3

    NASA Astrophysics Data System (ADS)

    Swainson, I. P.; Stock, C.; Parker, S. F.; Van Eijck, L.; Russina, M.; Taylor, J. W.

    2015-09-01

    The lead-halide perovskites, including CH3NH3PbBr3 , are components in cost effective, highly efficient photovoltaics, where the interactions of the molecular cations with the inorganic framework are suggested to influence the electronic and ferroelectric properties. CH3NH3PbBr3 undergoes a series of structural transitions associated with orientational order of the CH3NH3 (methylammonium) molecular cation and tilting of the PbBr3 host framework. We apply high-resolution neutron scattering to study the soft harmonic phonons associated with these transitions, and find a strong coupling between the PbBr3 framework and the quasistatic CH3NH3 dynamics at low energy transfers. At higher energy transfers, we observe a PbBr6 octahedra soft mode driving a transition at 150 K from bound molecular excitations at low temperatures to relatively fast relaxational excitations that extend up to ˜50 -100 meV. We suggest that these temporally overdamped dynamics enables possible indirect band gap processes in these materials that are related to the enhanced photovoltaic properties.

  11. Galvanic deposition of Rh and Ru on randomly structured Ti felts for the electrochemical NH3 synthesis.

    PubMed

    Kugler, Kurt; Luhn, Mareike; Schramm, Jean André; Rahimi, Khosrow; Wessling, Matthias

    2015-02-01

    Nowadays NH3 is exclusively synthesized by the Haber process. Unfortunately, the energy demand and the CO2 emissions due to H2 production are high. Hydrogen production utilizes precious carbon sources such as coal and natural gas. In the past we proposed an alternative process concept using a membrane electrode assembly in an electrochemical membrane reactor (ecMR). At the anode H2O is oxidized at an IrMMO catalyst to form protons. By applying an external potential to the ecMR N2 is reduced to NH3 at the cathode. Just recently Rh and Ru were identified as possible cathodic electrocatalysts by DFT calculations. We present an easy and highly efficient method for galvanic coatings of Rh and Ru on randomly structured Ti felts to be used in a membrane electrode assembly. Linear sweep voltammetry measurements give a slightly higher activity of Ru for the liquid phase electrochemical NH3 synthesis. The NH4(+) concentration reached is 8 times higher for Ru than for Rh. From an economical point of view, Ru is also more feasible for an electrochemical NH3 synthesis process. Such electrodes can now be evaluated in an ecMR in comparison to recently demonstrated Ti-based electrodes. PMID:25556769

  12. Chloride Incorporation Process in CH3NH3PbI3-xClx Perovskites via Nanoscale Bandgap Maps

    PubMed Central

    Chae, Jungseok; Dong, Qingfeng; Huang, Jinsong; Centrone, Andrea

    2016-01-01

    CH3NH3PbI3-xClx perovskites enable fabrication of highly efficient solar cells. Chloride ions benefit the morphology, carrier diffusion length and stability of perovskite films; however, whether those benefits stem from the presence of Cl− in the precursor solution or from their incorporation in annealed films is debated. In this work, the photothermal induced resonance (PTIR), an in situ technique with nanoscale resolution, is leveraged to measure the bandgap of CH3NH3PbI3-xClx films obtained by a multicycle coating process that produces high efficiency (≈ 16 %) solar cells. Because chloride ions modify the perovskite lattice, thereby widening the bandgap, measuring the bandgap locally yields the local chloride content. After a mild annealing (60 min, 60°C) the films consist of Cl-rich (x < 0.3) and Cl-poor phases that, upon further annealing (110 °C), evolve into a homogenous Cl-poorer (x < 0.06) phase, suggesting that methylammonium-chrloride is progressively expelled from the film. Despite the small chloride content, CH3NH3PbI3-xClx films show better thermal stability up to 140 °C with respect CH3NH3PbI3 films fabricated with the same methodology. PMID:26528710

  13. Role of hydrogen-bonding and its interplay with octahedral tilting in CH3NH3PbI3.

    PubMed

    Lee, Jung-Hoon; Bristowe, Nicholas C; Bristowe, Paul D; Cheetham, Anthony K

    2015-04-14

    First principles calculations on the hybrid perovskite CH3NH3PbI3 predict strong hydrogen-bonding which influences the structure and dynamics of the methylammonium cation and reveal its interaction with the tilting of the PbI6 octahedra. The calculated atomic coordinates are in excellent agreement with neutron diffraction results. PMID:25766075

  14. Formation of TiO2 Thin Films using NH3 as Catalyst by Metalorganic Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Jung, Sung-Hoon; Kang, Sang-Won

    2001-05-01

    We have studied metalorganic chemical vapor deposition of TiO2 thin films using titanium tetra-isopropoxide [TTIP, Ti(O--C3H7)4] and NH3 as a catalyst at deposition temperatures ranging from 250 to 365°C. At deposition temperatures above 330°C, pyrolytic self-decomposition of TTIP is dominant regardless of the use of NH3, and the activation energy for TiO2 film formation is 152 kJ/mol. At deposition temperatures below 330°C, the films can be formed with the help of the catalytic activity of NH3, and the activation energy is reduced to 55 kJ/mol. TiO2 films deposited through the pyrolytic self-decomposition of TTIP have an anatase structure before and after performing post-deposition annealing in oxygen ambient for 30 min at 750°C. On the other hand, the as-deposited films formed through the catalytic reaction of TTIP with NH3 incorporate nitrogen impurities and have microcrystallites of the rutile structure within the amorphous matrix. However, the post-deposition annealing, the nitrogen impurities are completely removed from the films, and the films are converted into polycrystalline TiO2 films with the rutile structure, which have a high dielectric constant of 82 and a low leakage current.

  15. Charge transport in bulk CH3NH3PbI3 perovskite

    NASA Astrophysics Data System (ADS)

    Slonopas, Andre; Foley, Benjamin J.; Choi, Joshua J.; Gupta, Mool C.

    2016-02-01

    The variation of leakage current and polarization hysteresis properties for bulk CH3NH3PbI3 perovskite was studied as a function of temperature to understand the reported hysteresis in photocurrent and the role of ferroelectricity. The leakage current decreased by two orders of magnitude when the temperature was lowered from 350 K to 100 K. The transitions in leakage current were observed at structural phase transition temperatures. The temperature dependence study allowed the identification of current conduction mechanism based on various models for ferroelectrics and insulating materials. Our results show that the leakage current is governed by the space charge limited conduction mechanism which should be considered in addition to ion conduction and ferroelectricity when analyzing current-voltage hysteresis for thin film and bulk materials. The Mott's variable range hopping model fits well to the experimental data indicating the charge conduction is through hopping mechanism from 300 K to 160 K and possibly tunneling below 160 K. The conclusions from polarization hysteresis study are: (1) the hysteresis loop shape is highly dependent upon frequency and show non-saturating behavior, an indicative of strong non-ferroelectric contributions such as resistive component. (2) No domain switching current was observed between the temperature range of 100 K-350 K. (3) An electric field off-set was observed in polarization-electric field curves and it was dependent upon the frequency and temperature. This offset could be caused by the accumulation of vacancies at one interface, which could give rise to hysteresis in forward and reverse bias photocurrent. (4) The time dependence study of instantaneous current as the voltage was increased linearly show strong resistive contribution to hysteresis loop at temperatures above 200 K and capacitive contribution at 100 K.

  16. ZnO Nanoparticles/Reduced Graphene Oxide Bilayer Thin Films for Improved NH3-Sensing Performances at Room Temperature

    NASA Astrophysics Data System (ADS)

    Tai, Huiling; Yuan, Zhen; Zheng, Weijian; Ye, Zongbiao; Liu, Chunhua; Du, Xiaosong

    2016-03-01

    ZnO nanoparticles and graphene oxide (GO) thin film were deposited on gold interdigital electrodes (IDEs) in sequence via simple spraying process, which was further restored to ZnO/reduced graphene oxide (rGO) bilayer thin film by the thermal reduction treatment and employed for ammonia (NH3) detection at room temperature. rGO was identified by UV-vis absorption spectra and X-ray photoelectron spectroscope (XPS) analyses, and the adhesion between ZnO nanoparticles and rGO nanosheets might also be formed. The NH3-sensing performances of pure rGO film and ZnO/rGO bilayer films with different sprayed GO amounts were compared. The results showed that ZnO/rGO film sensors exhibited enhanced response properties, and the optimal GO amount of 1.5 ml was achieved. Furthermore, the optimal ZnO/rGO film sensor showed an excellent reversibility and fast response/recovery rate within the detection range of 10-50 ppm. Meanwhile, the sensor also displayed good repeatability and selectivity to NH3. However, the interference of water molecules on the prepared sensor is non-ignorable; some techniques should be researched to eliminate the effect of moisture in the further work. The remarkably enhanced NH3-sensing characteristics were speculated to be attributed to both the supporting role of ZnO nanoparticles film and accumulation heterojunction at the interface between ZnO and rGO. Thus, the proposed ZnO/rGO bilayer thin film sensor might give a promise for high-performance NH3-sensing applications.

  17. Emergence of Multiple Superconducting Phases in (NH3)yMxFeSe (M: Na and Li)

    PubMed Central

    Zheng, Lu; Miao, Xiao; Sakai, Yusuke; Izumi, Masanari; Goto, Hidenori; Nishiyama, Saki; Uesugi, Eri; Kasahara, Yuichi; Iwasa, Yoshihiro; Kubozono, Yoshihiro

    2015-01-01

    We previously discovered multiple superconducting phases in the ammoniated Na-doped FeSe material, (NH3)yNaxFeSe. To clarify the origin of the multiple superconducting phases, the variation of Tc was fully investigated as a function of x in (NH3)yNaxFeSe. The 32 K superconducting phase is mainly produced in the low-x region below 0.4, while only a single phase is observed at x  =  1.1, with Tc =  45 K, showing that the Tc depends significantly on x, but it changes discontinuously with x. The crystal structure of (NH3)yNaxFeSe does not change as x increases up to 1.1, i.e., the space group of I4/mmm. The lattice constants, a and c, of the low-Tc phase (Tc = 32.5 K) are 3.9120(9) and 14.145(8) Å, respectively, while a = 3.8266(7) Å and c = 17.565(9) Å for the high-Tc phase (~46 K). The c increases in the high Tc phase, implying that the Tc is directly related to c. In (NH3)yLixFeSe material, the Tc varies continuously within the range of 39 to 44 K with changing x. Thus, the behavior of Tc is different from that of (NH3)yNaxFeSe. The difference may be due to the difference in the sites that the Na and Li occupy. PMID:26239256

  18. ZnO Nanoparticles/Reduced Graphene Oxide Bilayer Thin Films for Improved NH3-Sensing Performances at Room Temperature.

    PubMed

    Tai, Huiling; Yuan, Zhen; Zheng, Weijian; Ye, Zongbiao; Liu, Chunhua; Du, Xiaosong

    2016-12-01

    ZnO nanoparticles and graphene oxide (GO) thin film were deposited on gold interdigital electrodes (IDEs) in sequence via simple spraying process, which was further restored to ZnO/reduced graphene oxide (rGO) bilayer thin film by the thermal reduction treatment and employed for ammonia (NH3) detection at room temperature. rGO was identified by UV-vis absorption spectra and X-ray photoelectron spectroscope (XPS) analyses, and the adhesion between ZnO nanoparticles and rGO nanosheets might also be formed. The NH3-sensing performances of pure rGO film and ZnO/rGO bilayer films with different sprayed GO amounts were compared. The results showed that ZnO/rGO film sensors exhibited enhanced response properties, and the optimal GO amount of 1.5 ml was achieved. Furthermore, the optimal ZnO/rGO film sensor showed an excellent reversibility and fast response/recovery rate within the detection range of 10-50 ppm. Meanwhile, the sensor also displayed good repeatability and selectivity to NH3. However, the interference of water molecules on the prepared sensor is non-ignorable; some techniques should be researched to eliminate the effect of moisture in the further work. The remarkably enhanced NH3-sensing characteristics were speculated to be attributed to both the supporting role of ZnO nanoparticles film and accumulation heterojunction at the interface between ZnO and rGO. Thus, the proposed ZnO/rGO bilayer thin film sensor might give a promise for high-performance NH3-sensing applications. PMID:26956599

  19. Selective catalytic reduction of NOx with NH3 over a Cu-SSZ-13 catalyst prepared by a solid state ion exchange method

    SciTech Connect

    Wang, Di; Gao, Feng; Peden, Charles HF; Li, Junhui; Kamasamudram, Krishna; Epling, William S.

    2014-06-01

    A novel solid state method was developed to synthesize Cu-SSZ-13 catalysts with excellent NH3-SCR performance and durable hydrothermal stability. After the solid state ion exchange (SSIE) process, the SSZ framework structure and surface area was maintained. In-situ DRIFTS and NH3-TPD experiments provide evidence that isolated Cu ions were successfully exchanged into the pores, which are the active centers for the NH3-SCR reaction.

  20. NH3 formation and utilization in regenerationof Pt/Ba/Al2O3 NOx storage-reduction catalyst with H2

    SciTech Connect

    Partridge Jr, William P; Choi, Jae-Soon

    2009-01-01

    The nature of H2 regeneration of a model Pt/Ba/Al2O3 LNT catalyst was investigated with specific focus on intra-catalyst formation and utilization of NH3 and its role in catalyst regeneration. In-situ measurements of the transient intra-catalyst species (H2, NH3, N2, NOx) distributions at different temperatures were used to detail the reaction evolution along the catalyst axis. Comparison of the species transients identifies unique individual natures for the reductant (H2), inert product (N2) and intermediate-reductant product (NH3) which readily explain the conventional effluent species sequence as an integral effect. The data demonstrates that NH3 is created on similar timescales as the N2 product inside the catalyst, but consumed as aggressively as H2 reductant along the catalyst. This spatiotemporal NH3 behavior experimentally confirms that Intermediate-NH3 regeneration pathway is active. Analysis at 200 and 325 C indicates equivalent local NOx storage, H2 consumption and regeneration effectiveness, but differing NH3/N2 ratio, suggesting a temperature-dependence of partitioning between Direct-H2 and Intermediate-NH3 regeneration pathways. Further experimental and numerical work is needed to more clearly understand the partitioning between the possible regeneration pathways. Nevertheless, the experimental data show that intermediate NH3 plays a significant role in LNT catalyst regeneration.

  1. Rapid Ammonia Gas Transport Accounts for Futile Transmembrane Cycling under NH3/NH4+ Toxicity in Plant Roots1[C][W

    PubMed Central

    Coskun, Devrim; Britto, Dev T.; Li, Mingyuan; Becker, Alexander; Kronzucker, Herbert J.

    2013-01-01

    Futile transmembrane NH3/NH4+ cycling in plant root cells, characterized by extremely rapid fluxes and high efflux to influx ratios, has been successfully linked to NH3/NH4+ toxicity. Surprisingly, the fundamental question of which species of the conjugate pair (NH3 or NH4+) participates in such fluxes is unresolved. Using flux analyses with the short-lived radioisotope 13N and electrophysiological, respiratory, and histochemical measurements, we show that futile cycling in roots of barley (Hordeum vulgare) seedlings is predominately of the gaseous NH3 species, rather than the NH4+ ion. Influx of 13NH3/13NH4+, which exceeded 200 µmol g–1 h–1, was not commensurate with membrane depolarization or increases in root respiration, suggesting electroneutral NH3 transport. Influx followed Michaelis-Menten kinetics for NH3 (but not NH4+), as a function of external concentration (Km = 152 µm, Vmax = 205 µmol g–1 h–1). Efflux of 13NH3/13NH4+ responded with a nearly identical Km. Pharmacological characterization of influx and efflux suggests mediation by aquaporins. Our study fundamentally revises the futile-cycling model by demonstrating that NH3 is the major permeating species across both plasmalemma and tonoplast of root cells under toxicity conditions. PMID:24134887

  2. Characterization of Cu-SSZ-13 NH3 SCR Catalysts: an in situ FTIR Study

    SciTech Connect

    Szanyi, Janos; Kwak, Ja Hun; Zhu, Haiyang; Peden, Charles HF

    2013-01-23

    The adsorption of CO and NO over Cu-SSZ-13 zeolite catalysts, highly active in the selective catalytic reduction of NOx with NH3, was investigated by FTIR spectroscopy, and the results obtained were compared to those collected from other Cu-ion exchanged zeolites (Y,FAU and ZSM-5). At low CO pressures at room temperature (295 K) CO form monocarbonyls exclusively on the Cu+ ions, while in the presence of gas phase CO dicarbonyls on Cu+ and adsorbed CO on Cu2+ centers form, as well. At low (cryogenic) sample temperatures tricarbonyl formation on Cu+ sites was also observed. The adsorption of NO produces IR bands that can be assigned to nitrosyls bound to both Cu+ and Cu2+ centers, and NO+ species located in charge compensating cationic positions of the chabasite framework. On the reduced Cu-SSZ-13 samples the formation of N2O was also detected. The assignment of the adsorbed NOx species was aided by adsorption experiments with isotopically labeled 15NO. The movement of Cu ions from the sterically hindered six member ring position to the more accessible cavity positions as a result of their interaction with adsorbates (NO and H2O) was clearly evidenced. Comparisons of the spectroscopy data obtained in the static transmission IR system to those collected in the flow-through diffuse reflectance cell points out that care must be taken when conclusions are drawn about the adsorptive and reactive properties of metal cation centers based on a set of data collected under well defined, specific experimental conditions. Financial support was provided by the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program. This work was performed in the Environmental Molecular Sciences Laboratory (EMSL) at the Pacific Northwest National Laboratory (PNNL). The EMSL is a national scientific user facility supported by the US DOE, Office of Biological and Environmental Research. PNNL is a multi-program national laboratory operated for the US DOE by Battelle.

  3. Study of the structural phase transitions of (CH 3NH 3) 3Sb 2Cl 9 (MACA) and (CH 3NH 3) 3Bi 2Cl 9 (MACB) by infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Bator, G.; Jakubas, R.; Malarski, Z.

    1991-06-01

    Infrared spectra of polycrystalline (CH 3NH 3) 3Sb 2Cl 9 and (CH 3NH 3) 3Bi 2Cl 9 have been studied in the temperature range 90-300 K. A systematic temperature dependence study of the internal modes has been carried out. We discuss the effects of the dynamic state of methylammonium (MA) cations on their vibrational spectra. The results show that the dynamics of MA cations in both compounds is similar in higher (about 300 K) and lower temperature (in the vicinity of 100 K) regions. Substantial differences are revealed in the intermediate temperature interval. The results are in good agreement with earlier dielectric, calorimetric and 1H NMR studies.

  4. [NH3, N2O, CH4 and CO2 emissions from growing process of caged broilers].

    PubMed

    Zhou, Zhong-Kai; Zhu, Zhi-Ping; Dong, Hong-Min; Chen, Yong-Xing; Shang, Bin

    2013-06-01

    To obtain Ammonia and greenhouse gas (GHG) emission factors of caged broilers, ammonia (NH3), methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions of broilers aged 0 d to 42 days were monitored in caged broilers production systems located in Shandong province. Gas concentrations of incoming and exhaust air streams were measured by using INNOVA 1312 multi-gas monitor with multi-channel samplers. Building ventilation rates were determined by on site FANS (Fan Assessment Numeration System) measurement systems. The NH3 emission factors showed a trend of increase at the beginning and then decreased with the broiler ages. The NH3 emission rates were 8.5 to 342.1 mg x (d x bird)(-1) and the average daily emission rate was 137.9 mg x (d x bird)(-1) [48.6 g x (d x AU)(-1)] over the 42-d period. The GHGs emission rates were 19.5-351.9 mg x (d x bird)(-1) with an average of 154.5 mg x (d x bird)(-1) [54.4 g x (d x AU)(-1)] for CH4, and 2.2- 152.9 g x (d x bird)(-10 with an average of 65.9 g x (d x bird)(-1) [23.2 kg x (d x AU)(-1)] for CO2. No emission of N2O was observed. The CH4 and CO2 emission rates increased with the increase of broilers ages. The total NH3 emission over the 42 d growing period averaged (5.65 +/- 1.02) g x (bird x life cycle)(-1). The NH3 emission contribution in different growth phase to the total emission were 33.6% in growth phase 1 (0-17 day, GP1), 36.4% in GP2 (18-27 days), and 29.9% in GP3 (28-42 days), respectively. The NH3 emission in GP2 was significantly higher than emission in GP1 and GP3. CH4 and CO2 cumulative emission rates were (6.30 +/- 0.16) g x (bird(-1) x life cycle)(-1) and (2.68 +/- 0.18) kg x (bird x life cycle)(-1), respectively. The cumulative emission rates of CH4 and CO2 in GP3 were significantly higher than emission rates in GP2 and in GP1, accounting for 50% of total emissions. The results of this study could provide the data support for mitigation of gas emission from broilers production. PMID:23947019

  5. Novel nanoporous MnOx (x=∼1.75) sorbent for the removal of SO2 and NH3 made from MnC2O4·2H2O.

    PubMed

    Ma, Xiaowei; Campbell, Nicholas; Madec, Lénaïc; Rankin, Matthew A; Croll, Lisa M; Dahn, J R

    2016-03-01

    In this work, nanoporous manganese oxides (MnOx) were prepared by thermal decomposition of MnC2O4·2H2O at 225°C for 6h in air. The manganese oxalate dihydrate precipitate was made from manganese sulfate and ammonium oxalate during ultrasonication and stirring. The physical properties of the oxalate precursors and the resulting MnOx samples were characterized with SEM, TGA-DSC, FTIR and powder XRD. The specific surface areas and porosity of MnOx were studied by single-point BET and multi-point N2 adsorption-desorption measurements. The amorphous MnOx from oxalate prepared by sonication showed a specific surface area as large as 499.7m(2)/g. Dynamic SO2 and NH3 flow tests indicated that the adsorption capacity of MnOx, especially for SO2, can be increased by increased surface area. Compared to the best Mn3O4-impregnated activated carbon adsorbent, nanoporous MnOx could remove approximately three times as much SO2 and a comparable amount of NH3 per gram of adsorbent. This could lead to respirators of lower weight and smaller size which will be attractive to users. PMID:26692496

  6. Isomer-Selective Detection of Aromatic Molecules in Temperature-Programmed Desorption for Model Catalysis.

    PubMed

    Winbauer, Andreas; Kollmannsberger, Sebastian L; Walenta, Constantin A; Schreiber, Patrick; Kiermaier, Josef; Tschurl, Martin; Heiz, Ueli

    2016-05-17

    Based on three different molecules dosed on a Pt(111) single crystal the selectivity and sensitivity of REMPI-TPD in UHV is investigated for a potential application in heterogeneous catalysis. It is shown that the two structural isomers ethylbenzene and p-xylene can be discriminated by REMPI in a standard TPD experiment. The latter is not possible for the ionization with electrons in a Q-MS. It is further demonstrated by benzene TPD studies that the sensitivity of the REMPI-TOF-MS is comparable to commercial EI-Q-MS solutions and enables the detection of less than 0.6% molecules of a monolayer. PMID:27078611

  7. Phase transition and NH3 dynamics in [Ni(NH3)4](ReO4)2 studied by infrared absorption, X-ray powder diffraction and neutron scattering methods

    NASA Astrophysics Data System (ADS)

    Hetmańczyk, Łukasz; Hetmańczyk, Joanna

    2016-05-01

    The phase transition in [Ni(NH3)4](ReO4)2 detected previously by differential scanning calorimetry (DSC) at Tch = 188 K was now investigated by infrared absorption (FT-IR), incoherent inelastic and elastic neutron scattering (IINS, ND), and X-ray powder diffraction (XRPD) methods. The reorientational dynamics of NH3 groups was investigated by infrared band shape analysis (IRBS) and quasielastic neutron scattering (QENS) methods. The infrared data show that some of the bands split in the vicinity of the phase transition temperature, which suggests a change in the crystal structure. The systematic narrowing of particular bands at cooling is also observed, but reorientational dynamics of NH3 is not stopped at the phase transition temperature, which is fully confirmed by the QENS analysis. The broadening of the quasielastic neutron scattering peak is clearly visible below the phase transition temperature. Both NPD and XRPD measurements indicate that a small change of crystal structure is associated with the phase transition.

  8. Concentration-Dependent Effects on Intracellular and Surface pH of Exposing Xenopus oocytes to Solutions Containing NH3/NH4+

    PubMed Central

    Jiang, Lihong; Chen, Li-Ming; Behar, Kevin L.

    2010-01-01

    Others have shown that exposing oocytes to high levels of NH3/NH4+ (10–20 mM) causes a paradoxical fall in intracellular pH (pHi), whereas low levels (e.g., 0.5 mM) cause little pHi change. Here we monitored pHi and extra-cellular surface pH (pHS) while exposing oocytes to 5 or 0.5 mM NH3/NH4+. We confirm that 5 mM NH3/NH4+ causes a paradoxical pHi fall (−ΔpHi ≅ 0.2), but also observe an abrupt pHS fall (−ΔpHS ≅ 0.2)—indicative of NH3 influx—followed by a slow decay. Reducing [NH3/NH4+] to 0.5 mM minimizes pHi changes but maintains pHS changes at a reduced magnitude. Expressing AmtB (bacterial Rh homologue) exaggerates −ΔpHS at both NH3/NH4+ levels. During removal of 0.5 or 5 mM NH3/NH4+, failure of pHS to markedly overshoot bulk extracellular pH implies little NH3 efflux and, thus, little free cytosolic NH3/NH4+. A new analysis of the effects of NH3 vs. NH4+ fluxes on pHS and pHi indicates that (a) NH3 rather than NH4+ fluxes dominate pHi and pHS changes and (b) oocytes dispose of most incoming NH3. NMR studies of oocytes exposed to 15N-labeled NH3/NH4+ show no significant formation of glutamine but substantial NH3/NH4+ accumulation in what is likely an acid intracellular compartment. In conclusion, parallel measurements of pHi and pHS demonstrate that NH3 flows across the plasma membrane and provide new insights into how a protein molecule in the plasma membrane—AmtB—enhances the flux of a gas across a biological membrane. PMID:19242745

  9. A simple rule for determining the band offset at CH3NH3PbI3/organic semiconductor heterojunctions

    NASA Astrophysics Data System (ADS)

    Thibau, E. S.; Llanos, A.; Lu, Z. H.

    2016-01-01

    Organo-metal halide perovskites have recently emerged as a highly promising class of semiconductors for optoelectronic device applications. Integrating these hybrid materials within organic molecular thin film devices is key to fabricate functional devices. By evaporating ultra-thin films of organic semiconductor on thermally evaporated CH3NH3PbI3 and using in-situ ultraviolet photoemission spectroscopy, we directly measure the interfacial energy offset between CH3NH3PbI3 valence band maximum and the highest occupied molecular orbital for 5 different archetypal organic semiconductors. It is found that the energy offsets scale linearly as a function of the ionization energies of the organic semiconductors. The experimental data are in excellent agreement with a theoretical model for ideal semiconductor heterojunctions.

  10. Excellent activity and selectivity of Cu-SSZ-13 in the selective catalytic reduction of NOx with NH3

    SciTech Connect

    Kwak, Ja Hun; Tonkyn, Russell G.; Kim, Do Heui; Szanyi, Janos; Peden, Charles HF

    2010-10-21

    Superior activity and selectivity of a Cu ion-exchanged SSZ-13 zeolite in the selective catalytic reduction (SCR) of NOx with NH3 were observed, in comparison to Cu-beta and Cu-ZSM-5 zeolites. Cu-SSZ-13 was not only more active in the NOx SCR reaction over the entire temperature range studied (up to 550 °C), but also more selective toward nitrogen formation, resulting in significantly lower amounts of NOx by-products (i.e., NO2 and N2O) than the other two zeolites. In addition, Cu-SSZ-13 demonstrated the highest activity and N2 formation selectivity in the oxidation of NH3. The results of this study strongly suggest that Cu-SSZ-13 is a promising candidate as a catalyst for NOx SCR with great potential in after-treatment systems for either mobile or stationary sources.

  11. Deposition of silicon nitride from SiCl4 and NH3 in a low pressure RF plasma

    NASA Technical Reports Server (NTRS)

    Ron, Y.; Raveh, A.; Carmi, U.; Inspektor, A.; Avni, R.

    1983-01-01

    Silicon nitride coatings were deposited in a low-pressure (1-10 Torr) RF plasma from SiCl4 and NH3 in the presence of argon onto stainless martensitic steel grounded and floating substrates at 300 C and 440 C respectively. The heating of the substrates depends mainly on the position and the induced RF power. The coatings were identified as silicon nitride by X-ray investigation and were found to contain chlorine by energy-dispersive analysis of X-rays. The growth rate, the microhardness and the chlorine concentration of the coatings were determined as a function of the total gas pressure, the RF power input and the NH3-to-SiCl4 ratio. It was observed that the coatings on the floating substrates have higher deposition rates and are of superior quality.

  12. Removal of SO2 from O2-containing flue gas by activated carbon fiber (ACF) impregnated with NH3.

    PubMed

    Xu, Lüsi; Guo, Jia; Jin, Feng; Zeng, Hancai

    2006-02-01

    Adsorption of SO(2) from the O(2)-containing flue gas by granular activated carbons (GACs) and activated carbon fibers (ACFs) impregnated with NH(3) was studied in this technical note. Experimental results showed that the ACFs were high-quality adsorbents due to their unique textural properties. In the presence of moisture, the desulphurization efficiency for the ACFs was improved significantly due to the formation of sulfuric acid. After NH(3) impregnation of ACF samples, nitrogen-containing functional groups (pyridyl C(5)H(4)N- and pyrrolyl C(4)H(4)N-) were detected on the sample surface by using an X-ray photoelectron spectrometer. These functional groups accounted for the enhanced SO(2) adsorption via chemisorption and/or catalytic oxidization. PMID:15982716

  13. Sonochemical synthesis of CH3NH3PbI3 perovskite ultrafine nanocrystal sensitizers for solar energy applications.

    PubMed

    Bhooshan Kumar, Vijay; Gouda, Laxman; Porat, Ze'ev; Gedanken, Aharon

    2016-09-01

    The organic-inorganic hybrid perovskite CH3NH3PbI3 is becoming an interesting material in the field of energy harvesting. This material is one of the cleanest and cheapest components in solar cells which is available in ample amounts. However, most of the previous research work was done on thin film of this material. In the present work we describe the preparation of a powder containing nanoparticles of CH3NH3PbI3 using a sonochemical method. Characterization of the product was done by various methods, such as HRTEM, FTIR, PL, DLS and XRD. The particles were found to be highly crystalline (tetragonal crystal structure), polygonal in shape and having diameters of 10-40nm. PMID:27150745

  14. Exploring the PX3:NCH and PX3:NH3 potential surfaces, with X = F, Cl, and Br

    NASA Astrophysics Data System (ADS)

    Alkorta, Ibon; Elguero, José; Del Bene, Janet E.

    2015-11-01

    Ab initio MP2/aug‧-cc-pVTZ calculations have been carried out to explore the PX3:NCH and PX3:NH3 potential surfaces, with X = F, Cl and Br. Four unique minima exist on the PX3:NCH surfaces, and three on the PX3:NH3 surfaces. Complexes stabilized by pnicogen bonds, hydrogen bonds, halogen bonds, and electrostatic interactions have been found at these minima. The global minimum on each surface is a complex with a P···N pnicogen bond. Binding energies at corresponding minima are ordered with respect to the PX3 molecules as PF3 < PCl3 < PBr3. Charge-transfer stabilizes all complexes with intermolecular bonds.

  15. Thermodynamic study of the chemical vapor deposition in the SiCl3CH3-NH3-H2 system

    NASA Astrophysics Data System (ADS)

    Ren, Haitao; Zhang, Litong; Su, Kehe; Zeng, Qingfeng; Guan, Kang; Cheng, Laifei

    2015-03-01

    The gas-phase reaction thermodynamic of the chemical vapor deposition in the SiCl3CH3-NH3-H2 system was investigated with a relatively complete set of 443 species, in which the thermochemistry data include the heat capacities, entropies, enthalpies of formation, and Gibbs energies of formation were calculated. Five condensed phases, silicon carbide (α-SiC and β-SiC), silicon nitride (Si3N4), graphite (C) and silicon (Si) were taken into consideration. The distribution of the equilibrium concentration of the 443 species was obtained. The effects of temperature and reactant ratios of SiCl3CH3/(SiCl3CH3 + NH3) on the formation and yield of condensed phases were discussed.

  16. Effect of tube radius on the exohedral chemical functionalization of boron-nitride zigzag nanotubes with NH3

    NASA Astrophysics Data System (ADS)

    Zahedi, Ehsan

    2012-09-01

    The interaction between zigzag BNNTs with chirality index n=3-10 and ammonia has been studied at the level of B3LYP/6-31G*. Ammonia can be chemically adsorbed on (3,0) to (7,0) BNNTs and physically adsorbed on other studied BNNTs. From NBO analysis charge transfer occur from NH3 to BNNTs and change in the natural electron configuration of B atom of BNNTs at adsorption site for the (3,0) and (4,0) BNNTs cases is larger than others. The DOS result show that after functionalization of BNNTs with NH3 molecules electronic properties of tubes are largely preserved and can be viewed as some kind of harmless modification. Electronic analysis revealed that the interaction of zigzag BNNTs with ammonia is more electrostatic (ionic) in nature, rather than the sole covalent and electrostatic nature increased with increasing of tube diameter.

  17. Ultrasensitive room temperature NH3 sensor based on a graphene-polyaniline hybrid loaded on PET thin film.

    PubMed

    Bai, Shouli; Zhao, Yangbo; Sun, Jianhua; Tian, Ye; Luo, Ruixian; Li, Dianqing; Chen, Aifan

    2015-05-01

    This research was motivated by the need to develop a smart ammonia (NH3) sensor based on a flexible polyethylene terephthalate (PET) thin film loaded with a reduced graphene oxide-polyaniline (rGO-PANI hybrid) using in situ chemical oxidative polymerization. The sensor not only exhibited high sensitivity, good selectivity and a fast response at room temperature but was also flexible, cheap and had wearable characteristics. PMID:25845668

  18. Evaluating 4 years of atmospheric ammonia (NH3) over Europe using IASI satellite observations and LOTOS-EUROS model results

    NASA Astrophysics Data System (ADS)

    Van Damme, M.; Wichink Kruit, R. J.; Schaap, M.; Clarisse, L.; Clerbaux, C.; Coheur, P.-F.; Dammers, E.; Dolman, A. J.; Erisman, J. W.

    2014-08-01

    Monitoring ammonia (NH3) concentrations on a global to regional scale is a challenge. Due to the limited availability of reliable ground-based measurements, the determination of NH3 distributions generally relies on model calculations. Novel remotely sensed NH3burdens provide valuable insights to complement traditional assessments for clear-sky conditions. This paper presents a first quantitative comparison between Atmospheric Sounding Interferometer (IASI) satellite observations and LOTOS-EUROS model results over Europe and Western Russia. A methodology to account for the variable retrieval sensitivity of the measurements is described. Four years of data (2008-2011) highlight three main agricultural hot spot areas in Europe: the Po Valley, the continental part of Northwestern Europe, and the Ebro Valley. The spatial comparison reveals a good overall agreement of the NH3 distributions not only in these source regions but also over remote areas and over sea when transport is observed. On average, the measured columns exceed the modeled ones, except for a few cases. Large discrepancies over several industrial areas in Eastern Europe and Russia point to underestimated emissions in the underlying inventories. The temporal analysis over the three hot spot areas reveals that the seasonality is well captured by the model when the lower sensitivity of the satellite measurements in the colder months is taken into account. Comparison of the daily time series indicates possible misrepresentations of the timing and magnitude of the emissions. Finally, specific attention to biomass burning events shows that modeled plumes are less spread out than the observed ones. This is confirmed for the 2010 Russian fires with a comparison using in situ observations.

  19. The role of NH3 and hydrocarbon mixtures in GaN pseudo-halide CVD: a quantum chemical study.

    PubMed

    Gadzhiev, Oleg B; Sennikov, Peter G; Petrov, Alexander I; Kachel, Krzysztof; Golka, Sebastian; Gogova, Daniela; Siche, Dietmar

    2014-11-01

    The prospects of a control for a novel gallium nitride pseudo-halide vapor phase epitaxy (PHVPE) with HCN were thoroughly analyzed for hydrocarbons-NH3-Ga gas phase on the basis of quantum chemical investigation with DFT (B3LYP, B3LYP with D3 empirical correction on dispersion interaction) and ab-initio (CASSCF, coupled clusters, and multireference configuration interaction including MRCI+Q) methods. The computational screening of reactions for different hydrocarbons (CH4, C2H6, C3H8, C2H4, and C2H2) as readily available carbon precursors for HCN formation, potential chemical transport agents, and for controlled carbon doping of deposited GaN was carried out with the B3LYP method in conjunction with basis sets up to aug-cc-pVTZ. The gas phase intermediates for the reactions in the Ga-hydrocarbon systems were predicted at different theory levels. The located π-complexes Ga…C2H2 and Ga…C2H4 were studied to determine a probable catalytic activity in reactions with NH3. A limited influence of the carbon-containing atmosphere was exhibited for the carbon doping of GaN crystal in the conventional GaN chemical vapor deposition (CVD) process with hydrocarbons injected in the gas phase. Our results provide a basis for experimental studies of GaN crystal growth with C2H4 and C2H2 as auxiliary carbon reagents for the Ga-NH3 and Ga-C-NH3 CVD systems and prerequisites for reactor design to enhance and control the PHVPE process through the HCN synthesis. PMID:25316343

  20. Optical bleaching of perovskite (CH3NH3)PbI3 through room-temperature phase transformation induced by ammonia.

    PubMed

    Zhao, Yixin; Zhu, Kai

    2014-02-14

    Ammonia induces a phase transformation of perovskite (CH3NH3)PbI3, leading to a rapid (<1 s) change in its color from brown to colorless (400-800 nm). This color change is reversed within seconds upon removing the NH3 source. PMID:24390126

  1. Fiber-Amplifier-Enhanced QEPAS Sensor for Simultaneous Trace Gas Detection of NH3 and H2S

    PubMed Central

    Wu, Hongpeng; Dong, Lei; Liu, Xiaoli; Zheng, Huadan; Yin, Xukun; Ma, Weiguang; Zhang, Lei; Yin, Wangbao; Jia, Suotang

    2015-01-01

    A selective and sensitive quartz enhanced photoacoustic spectroscopy (QEPAS) sensor, employing an erbium-doped fiber amplifier (EDFA), and a distributed feedback (DFB) laser operating at 1582 nm was demonstrated for simultaneous detection of ammonia (NH3) and hydrogen sulfide (H2S). Two interference-free absorption lines located at 6322.45 cm−1 and 6328.88 cm−1 for NH3 and H2S detection, respectively, were identified. The sensor was optimized in terms of current modulation depth for both of the two target gases. An electrical modulation cancellation unit was equipped to suppress the background noise caused by the stray light. An Allan-Werle variance analysis was performed to investigate the long-term performance of the fiber-amplifier-enhanced QEPAS sensor. Benefitting from the high power boosted by the EDFA, a detection sensitivity (1σ) of 52 parts per billion by volume (ppbv) and 17 ppbv for NH3 and H2S, respectively, were achieved with a 132 s data acquisition time at atmospheric pressure and room temperature. PMID:26506351

  2. Irradiation of NH3-CH4 mixtures as a model of photochemical processes in the Jovian planets and Titan

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Morimoto, J. Y.

    1981-01-01

    The reactions occurring upon the ultraviolet irradiation of ammonia-methane mixtures are investigated in a simulation of the atmospheric chemistry of the Jovian planets and Titan. Gas mixtures were irradiated at 185 nm at temperatures from 156-298 K, and product and reactant concentrations were determined by means of gas chromatography. The ratio of the moles of CH4 lost per mole of NH3 decomposed is found to be 0.25, with the extent of CH4 decomposition independent of temperature. The absence of a temperature effect suggests that nonthermal atoms, probably hydrogen, initiate CH4 decomposition by the extraction of a hydrogen atom. A decrease in CH4 loss with increasing pressure or the addition of other gases to the photolysis mixture, and the lack of an increase in NH3 photolysis with CH4 pressure support this mechanism. Major reaction products obtained include C2H2, C3H8 or CH3NH2, and C4H10. Considerations of atmospheric concentrations of H2 and He indicate that NH3 photolysis does not contribute to CH4 decomposition on Jupiter, Saturn, Uranus, and Neptune, although it may have had a role in the formation of the Titan atmosphere.

  3. Effect of phosphogypsum and dicyandiamide as additives on NH3, N20 and CH4 emissions during composting.

    PubMed

    Luo, Yiming; Li, Guoxue; Luo, Wenhai; Schuchardt, Frank; Jiang, Tao; Xu, Degang

    2013-07-01

    A laboratory scale experiment of composting in a forced aeration system using pig manure with cornstalks was carried out to investigate the effects of both phosphogypsum and dicyandiamide (DCD, C2H4N4) as additives on gaseous emissions and compost quality. Besides a control, there were three amended treatments with different amounts of additives. The results indicated that the phosphogypsum addition at the rate of 10% of mixture dry weight decreased NH3 and CH4 emissions significantly during composting. The addition of DCD at the rate of 0.2% of mixture dry weight together with 10% of phosphogypsum further reduced the N2O emission by affecting the nitrification process. Reducing the phosphogypsum addition to 5% in the presence of 0.2% DCD moderately increased the NH3 emissions but not N2O emission. The additives increased the ammonium content and electrical conductivity significantly in the final compost. No adverse effect on organic matter degradation or the germination index of the compost was found in the amended treatments. It was recommended that phosphogypsum and DCD could be used in composting for the purpose of reducing NH3, CH4 and N2O emissions. Optimal conditions and dose of DCD additive during composting should be determined with different materials and composting systems in further study. PMID:24218845

  4. Free NH 3 quantum rotations in Hofmann clathrates: structure factors and line widths studied by inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Sobolev, O.; Vorderwisch, P.; Desmedt, A.

    2005-01-01

    Quantum rotations of NH 3 groups in Hofmann clathrates Ni-Ni-C 6H 6 and Ni-Ni-C 12H 10 have been studied using inelastic neutron scattering. Calculations of the dynamical structure factor for a free uniaxial quantum rotor reproduce the neutron scattering data with respect to their Q- and T-dependence as well as the relative intensities for the 0 → 1, 0 → 2 and 1 → 2 transitions. Though the effective NH 3 rotation constant is different from the gas phase value, the effective radius of rotation (i.e., the average distance of protons from the rotation axis) is equal or very close to the geometrical value r = 0.94 Å for a NH 3 group. Comparing the experimental data with the calculated dynamical structure factor for the 0 → 3 transition it could be shown, that the corresponding transition line, in contrast to transitions between j = 0,1,2 levels measured so far, has a finite width at T = 0 K.

  5. A novel [Ag(NH3)2]+ probe for chemiluminescent imaging detection of proteins after polyacrylamide gel electrophoresis.

    PubMed

    Xiong, Xin; Wang, Zhenzhen; Baeyens, Willy R G; Delanghe, Joris R; Huang, Zhi; Huang, Guangming; Ouyang, Jin

    2007-08-01

    The development of a novel [Ag(NH3)2]+ probe chemiluminescence (CL)-based imaging method for the detection of various proteins after PAGE is described. The detection is based upon the probe [Ag(NH3)2]+ catalyzing the CL reaction of the luminol-potassium persulfate system. The proposed method detects various proteins labeled by [Ag(NH3)2]+ and expands the application scope to SDS gels. It also detects proteins directly in polyacrylamide gels, without tedious transferring procedures. Furthermore, successful identification of proteins by peptide mass profiling using ionization MS was easily performed, and no pretreatments of gel prior to digestion are needed. Detection limits for standard marker proteins match CBB-R250 staining and the linear dynamic range is superior to CBB-R250 staining and silver staining. The CL imaging conditions, including luminescent reagents, silver ion concentration, the ammonia-controlled system and the washing reagents parameters have also been optimized. PMID:17610207

  6. Revealing the role of organic cations in hybrid halide perovskite CH3NH3PbI3

    PubMed Central

    Motta, Carlo; El-Mellouhi, Fedwa; Kais, Sabre; Tabet, Nouar; Alharbi, Fahhad; Sanvito, Stefano

    2015-01-01

    The hybrid halide perovskite CH3NH3PbI3 has enabled solar cells to reach an efficiency of about 20%, demonstrating a pace for improvements with no precedents in the solar energy arena. Despite such explosive progress, the microscopic origin behind the success of such material is still debated, with the role played by the organic cations in the light-harvesting process remaining unclear. Here van der Waals-corrected density functional theory calculations reveal that the orientation of the organic molecules plays a fundamental role in determining the material electronic properties. For instance, if CH3NH3 orients along a (011)-like direction, the PbI6 octahedral cage will distort and the bandgap will become indirect. Our results suggest that molecular rotations, with the consequent dynamical change of the band structure, might be at the origin of the slow carrier recombination and the superior conversion efficiency of CH3NH3PbI3. PMID:25912782

  7. Biological gas channels for NH3 and CO2: evidence that Rh (Rhesus) proteins are CO2 channels.

    PubMed

    Kustu, S; Inwood, W

    2006-01-01

    Physiological evidence from our laboratory indicates that Amt/Mep proteins are gas channels for NH3, the first biological gas channels to be described. This view has now been confirmed by structural evidence and is displacing the previous belief that Amt/Mep proteins were active transporters for the NH4+ ion. Still disputed is the physiological substrate for Rh proteins, the only known homologues of Amt/Mep proteins. Many think they are mammalian ammonium (NH4+ or NH3) transporters. Following Monod's famous dictum, "Anything found to be true of E. coli must also be true of elephants" [Perspect. Biol. Med. 47(1) (2004) 47], we explored the substrate for Rh proteins in the unicellular green alga Chlamydomonas reinhardtii. C. reinhardtii is one of the simplest organisms to have Rh proteins and it also has Amt proteins. Physiological studies in this microbe indicate that the substrate for Rh proteins is CO2 and confirm that the substrate for Amt proteins is NH3. Both are readily hydrated gases. Knowing that transport of CO2 is the ancestral function of Rh proteins supports the inference from hematological research that a newly evolving role of the human Rh30 proteins, RhCcEe and RhD, is to help maintain the flexible, flattened shape of the red cell. PMID:16563833

  8. Origin of High Electronic Quality in Solar Cell Absorber CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Yin, Wanjian; Shi, Tingting; Wei, Suhua; Yan, Yanfa

    Thin-film solar cells based on CH3NH3PbI3 halide perovskites have recently shown remarkable performance. First-principle calculations and molecular dynamic simulations show that the structure of pristine CH3NH3PbI3 is much more disordered than the inorganic archetypal thin-film semiconductor CdTe. However, the structural disorders from thermal fluctuation, point defects and grain boundaries introduce rare deep defect states within the bandgaps; therefore, the material has high electronic quality. We have further shown that this unusually high electronic quality is attributed to the unique electronic structures of halide perovskite: the strong coupling between cation lone-pair Pb s orbitals and anion p orbitals and the large atomic size of constitute cation atoms. We further found that although CH3NH3PbI3 GBs do not introduce a deep gap state, the defect level close to the VBM can still act as a shallow hole trap state. Cl and O can spontaneously segregate into GBs and passivate those defect levels and deactivate the trap state.

  9. Ultrasound-assistant preparation of Cu-SAPO-34 nanocatalyst for selective catalytic reduction of NO by NH3.

    PubMed

    Panahi, Parvaneh Nakhostin; Niaei, Ali; Salari, Darush; Mousavi, Seyed Mahdi; Delahay, Gérard

    2015-09-01

    The influence of the various preparation methods of Cu-SAPO-34 nanocatalysts on the selective catalytic reduction of NO with NH3 under excess oxygen was studied. Cu-SAPO-34 nanocatalysts were prepared by using four techniques: conventional impregnation (IM), ultrasound-enhanced impregnation (UIM), conventional deposition precipitation (DP) using NaOH and homogeneous deposition precipitation (HDP) using urea. These catalysts were characterized in detail by various techniques such as N2-sorption, XRD, TEM, H2-TPR, NH3-TPD and XPS to understand the catalyst structure, the nature and the dispersed state of the copper species, and the acid sites for NH3 adsorption. All of the nanocatalysts showed high activities for NO removal. However, the activities were different and followed the sequence of Cu-SAPO-34 (UIM)>Cu-SAPO-34 (HDP)>Cu-SAPO-34 (IM)>Cu-SAPO-34 (DP). Based on the obtained results, it was concluded that the NO conversion on Cu-SAPO-34 nanocatalysts was mainly related to the high reducibility of the isolated Cu(2+) ions and CuO species, the number of the acid sites and the dispersion of CuO species on SAPO-34. PMID:26354702

  10. Star-forming regions of the Aquila rift cloud complex. II. Turbulence in molecular cores probed by NH3 emission

    NASA Astrophysics Data System (ADS)

    Levshakov, S. A.; Henkel, C.; Reimers, D.; Wang, M.

    2014-07-01

    Aims: We intend to derive statistical properties of stochastic gas motion inside the dense, low-mass star-forming molecular cores that are traced by NH3(1, 1) and (2, 2) emission lines. Methods: We use the spatial two-point autocorrelation (ACF) and structure functions calculated from maps of the radial velocity fields. Results: The observed ammonia cores are characterized by complex intrinsic motions of stochastic nature. The measured kinetic temperature ranges between 8.8 K and 15.1 K. From NH3 excitation temperatures of 3.5-7.3 K, we determine H2 densities with typical values of nH2~ (1-6) × 104 cm-3. The ammonia abundance, X = [NH3]/[H2], varies from 2 × 10-8 to 1.5 × 10-7. We find oscillating ACFs, which eventually decay to zero with increasing lags on scales of 0.04 ≲ ℓ ≲ 0.5 pc. The current paradigm supposes that the star-formation process is controlled by the interplay between gravitation and turbulence with the latter preventing molecular cores from a rapid collapse due to their own gravity. Thus, oscillating ACFs may indicate a damping of the developed turbulent flows surrounding the dense but less turbulent core, a transition to dominating gravitational forces and, hence, to gravitational collapse. Appendix A is available in electronic form at http://www.aanda.org

  11. Surface Properties of CH3NH3PbI3 for Perovskite Solar Cells.

    PubMed

    Haruyama, Jun; Sodeyama, Keitaro; Han, Liyuan; Tateyama, Yoshitaka

    2016-03-15

    Perovskite solar cells (PSCs) have attracted considerable interest because of their high potential for solar energy conversion. Power conversion efficiencies of the PSCs have rapidly increased from 3.8 to over 20% only in the past few years. PSCs have several similarities to dye-sensitized solar cells in their device compositions; mesoporous TiO2 (mp-TiO2) is sensitized by light-absorbing components and placed into a medium containing hole transporting materials (HTMs). On the other hand, the perovskite materials for the light-harvesting, for example, CH3NH3PbI3 (MAPbI3), have a greater advantage for the photovoltaic applications; extremely long photocarrier diffusion lengths (over 1 μm) enable carrier transports without singnificant loss. In this respect, the surface states, that can be possible recombination centers, are also of great importance. Availability of solution processes is another important aspect in terms of low cost fabrication of PSCs. Two-step methods, where PbI2 is first introduced from solution onto a mp-TiO2 film and subsequently transformed into the MAPbI3 by the exposition of a solution containing MAI, suggest that use of such a high PbI2 concentration is crucial to obtain higher performance. The experiments also indicate that the PbI2-rich growth condition modifies TiO2/ or HTM/MAPbI3 interfaces in such a way that the photocarrier transport is improved. Thus, the characteristics of surfaces and interfaces play key roles in the high efficiencies of the PSCs. In this Account, we focus on the structural stability and electronic states of the representative (110), (001), (100), and (101) surfaces of tetragonal MAPbI3, which can be regarded as reasonable model HTM/MAPbI3 interfaces, by use of first-principles calculations. By examining various types of PbIx polyhedron terminations, we found that there are two major phases on all of the four surface facets. They can be classified as vacant- and flat-type terminations, and the former is more stable than the latter under thermodynamically equilibrium conditions. More interestingly, both terminations can coexist especially on the more probable (110) and (001) surfaces. Electronic states, that is, projected density of states, of the stable-vacant and PbI2-rich-flat terminations on the two surfaces are almost the same as that in bulk MAPbI3. These surfaces can contribute to the long carrier lifetime actually observed for the PSCs because they have no midgap surface states. Furthermore, the shallow surface states on the (110) and (001) flat terminations can be efficient intermediates for hole transport to HTMs. Consequently, the formation of the flat terminations under the PbI2-rich condition will be beneficial for the improvement of PSC performance. PMID:26901120

  12. Thermal decomposition pathway and desorption study of isopropanol and tert-butanol on Si(100)

    NASA Astrophysics Data System (ADS)

    Kim, Jaehyun; Kim, Kwansoo; Yong, Kijung

    2002-09-01

    Thermal decomposition pathway and desorption of isopropanol (IPA) and tert-butanol on Si(100) were studied using temperature programed desorption. Adsorbed alcohols studied were decomposed into atomic hydrogen and alkoxy on the surface. During heating the sample up to 1000 K, acetone, propylene, and hydrogen were desorbed as decomposition products of IPA on Si(100). Desorption pathways of IPA on Si(100) were largely consistent with those on metal surfaces: beta-hydride elimination reaction to acetone and C-O scission to propylene. For tert-butanol, which has no beta-hydrogen, isobutene and hydrogen were observed as main desorption products. copyright 2002 American Vacuum Society.

  13. N2 and CO Desorption Energies from Water Ice

    NASA Astrophysics Data System (ADS)

    Fayolle, Edith C.; Balfe, Jodi; Loomis, Ryan; Bergner, Jennifer; Graninger, Dawn; Rajappan, Mahesh; Öberg, Karin I.

    2016-01-01

    The relative desorption energies of CO and N2 are key to interpretations of observed interstellar CO and N2 abundance patterns, including the well-documented CO and N2H+ anti-correlations in disks, protostars, and molecular cloud cores. Based on laboratory experiments on pure CO and N2 ice desorption, the difference between CO and N2 desorption energies is small; the N2-to-CO desorption energy ratio is 0.93 ± 0.03. Interstellar ices are not pure, however, and in this study we explore the effect of water ice on the desorption energy ratio of the two molecules. We present temperature programmed desorption experiments of different coverages of 13CO and 15N2 on porous and compact amorphous water ices and, for reference, of pure ices. In all experiments, 15N2 desorption begins a few degrees before the onset of 13CO desorption. The 15N2 and 13CO energy barriers are 770 and 866 K for the pure ices, 1034-1143 K and 1155-1298 K for different submonolayer coverages on compact water ice, and 1435 and 1575 K for ˜1 ML of ice on top of porous water ice. For all equivalent experiments, the N2-to-CO desorption energy ratio is consistently 0.9. Whenever CO and N2 ice reside in similar ice environments (e.g., experience a similar degree of interaction with water ice) their desorption temperatures should thus be within a few degrees of one another. A smaller N2-to-CO desorption energy ratio may be present in interstellar and circumstellar environments if the average CO ice molecules interacts more with water ice compared to the average N2 molecules.

  14. Ft-Ir Measurements of NH_3 Line Intensities in the 60 - 550 CM-1 Using Soleil/ailes Beamline

    NASA Astrophysics Data System (ADS)

    Sung, Keeyoon; Yu, Shanshan; Pearson, John; Manceron, Laurent; Kwabia Tchana, F.; Pirali, Olivier

    2015-06-01

    Ammonia (NH_3) has been found ubiquitous, e.g., in the interstellar medium, low-mass stars, Jovian planets of our solar system, and possibly in the low temperature exoplanets. Their spectroscopic line parameters are essential in the accurate interpretation of the planetary and astrophysical spectra observed with Herschel, SOFIA, ALMA, and JWST. In our previous paper, the NH_3 line positions in the far-IR region were studied for the ground state and ν_2 in an unprecedented accuracy, which revealed significant deficiencies in the NH_3 intensities, for instance, some weak ΔK = 3 lines were predicted to be ~100 times stronger. Measurement of line intensity for these lines in a consistent manner is demanded because the ΔK = 3 forbidden lines are only way other than collisions and l-doubled states to excite NH_3 to K > 0 levels. Recalling that NH_3 transition lines in the high J and K up to 18 were detected toward the galactic center in the star forming region of Sgr B_2, their accurate intensity measurements are critical in explaining the observed high K excitation, which will provide insights into radiative-transfer vs.levels. The interaction between a large amplitude torsional motion and the hyperfine coupling may also lead to a less known hyperfine effect, the so-called magnetic spin-torsion coupling, which was first studied by Heuvel and Dymanus and which has not yet been conclusively evidenced. In this talk, the magnetic hyperfine structure of the non-rigid methanol molecule will be investigated experimentally and theoretically. 13 hyperfine patterns were recorded using two molecular beam microwave spectrometers. These patterns, along with previously recorded ones,^c were analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling. The theoretical approach setup to analyze the observed data accounts for the spin-torsion coupling, in addition to the familiar magnetic spin-rotation and spin-spin couplings, and relies on symmetry considerations to build a hyperfine coupling Hamiltonian and a spin-rotation-torsion wavefunction compatible with the Pauli exclusion principle. In the talk, the results of the analysis will be presented. The hyperfine coupling parameters retrieved will be discussed and we hope to be able to conclusively evidence the effects of the magnetic spin-torsion. S. Yu, et al. J. Chem. Phys. (2010) 174317/1-174317/14. Coudert and Lopez, J. Mol. Spectrosc.~239 (2006) 135; and Tudorie, Coudert, Huet, Jegouso, and Sedes, J. Chem. Phys.~134 (2011) 074314

  15. Fabrication and characterization of perovskite-based CH3NH3Pb1-xGexI3, CH3NH3Pb1-xTlxI3 and CH3NH3Pb1-xInxI3 photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Ohishi, Yuya; Oku, Takeo; Suzuki, Atsushi

    2016-02-01

    Perovskite-type CH3NH3PbI3-based photovoltaic devices were fabricated and characterized. Doping effects of thallium (Tl), indium (In), or germanium (Ge) element on the photovoltaic properties and surface structures of the perovskite phase were investigated. The open circuit voltage increased by Ge addition, and fill factors were improved by adding a small amount of Ge, Tl or In. In addition, the wavelength range of incident photon conversion efficiencies was expanded by the Tl addition.

  16. Estimating NH3 emissions from agricultural fertilizer application in China using the bi-directional CMAQ model coupled to an agro-ecosystem model

    NASA Astrophysics Data System (ADS)

    Fu, X.; Wang, S. X.; Ran, L. M.; Pleim, J. E.; Cooter, E.; Bash, J. O.; Benson, V.; Hao, J. M.

    2015-06-01

    Atmospheric ammonia (NH3) plays an important role in atmospheric aerosol chemistry. China is one of the largest NH3 emitting countries with the majority of NH3 emissions coming from agricultural practices, such as fertilizer application and livestock production. The current NH3 emission estimates in China are mainly based on pre-defined emission factors that lack temporal or spatial details, which are needed to accurately predict NH3 emissions. This study provides the first online estimate of NH3 emissions from agricultural fertilizer application in China, using an agricultural fertilizer modeling system which couples a regional air quality model (the Community Multi-scale Air Quality model, or CMAQ) and an agro-ecosystem model (the Environmental Policy Integrated Climate model, or EPIC). This method improves the spatial and temporal resolution of NH3 emissions from this sector. We combined the cropland area data of 14 crops from 2710 counties with the Moderate Resolution Imaging Spectroradiometer (MODIS) land use data to determine the crop distribution. The fertilizer application rates and methods for different crops were collected at provincial or agricultural region levels. The EPIC outputs of daily fertilizer application and soil characteristics were input into the CMAQ model and the hourly NH3 emissions were calculated online with CMAQ running. The estimated agricultural fertilizer NH3 emissions in this study were approximately 3 Tg in 2011. The regions with the highest modeled emission rates are located in the North China Plain. Seasonally, peak ammonia emissions occur from April to July. Compared with previous researches, this study considers an increased number of influencing factors, such as meteorological fields, soil and fertilizer application, and provides improved NH3 emissions with higher spatial and temporal resolution.

  17. Metal-Borohydride-Modified Zr(BH4 )4 ⋅8 NH3 : Low-Temperature Dehydrogenation Yielding Highly Pure Hydrogen.

    PubMed

    Huang, Jianmei; Ouyang, Liuzhang; Gu, Qinfen; Yu, Xuebin; Zhu, Min

    2015-10-12

    Due to its high hydrogen density (14.8 wt %) and low dehydrogenation peak temperature (130 °C), Zr(BH4 )4 ⋅8 NH3 is considered to be one of the most promising hydrogen-storage materials. To further decrease its dehydrogenation temperature and suppress its ammonia release, a strategy of introducing LiBH4 and Mg(BH4 )2 was applied to this system. Zr(BH4 )4 ⋅8 NH3 -4 LiBH4 and Zr(BH4 )4 ⋅8 NH3 -2 Mg(BH4 )2 composites showed main dehydrogenation peaks centered at 81 and 106 °C as well as high hydrogen purities of 99.3 and 99.8 mol % H2 , respectively. Isothermal measurements showed that 6.6 wt % (within 60 min) and 5.5 wt % (within 360 min) of hydrogen were released at 100 °C from Zr(BH4 )4 ⋅8 NH3 -4 LiBH4 and Zr(BH4 )4 ⋅8 NH3 -2 Mg(BH4 )2 , respectively. The lower dehydrogenation temperatures and improved hydrogen purities could be attributed to the formation of the diammoniate of diborane for Zr(BH4 )4 ⋅8 NH3 -4 LiBH4 , and the partial transfer of NH3 groups from Zr(BH4 )4 ⋅8 NH3 to Mg(BH4 )2 for Zr(BH4 )4 ⋅8 NH3 -2 Mg(BH4 )2 , which result in balanced numbers of BH4 and NH3 groups and a more active H(δ+) ⋅⋅⋅(-δ) H interaction. These advanced dehydrogenation properties make these two composites promising candidates as hydrogen-storage materials. PMID:26315468

  18. Estimating NH3 emissions from agricultural fertilizer application in China using the bi-directional CMAQ model coupled to an agro-ecosystem model

    NASA Astrophysics Data System (ADS)

    Fu, X.; Wang, S. X.; Ran, L. M.; Pleim, J. E.; Cooter, E.; Bash, J. O.; Benson, V.; Hao, J. M.

    2015-01-01

    Atmospheric ammonia (NH3) plays an important role in atmospheric chemistry. China is one of the largest NH3 emitting countries with the majority of NH3 emissions coming from the agricultural practices, such as fertilizer application and livestock. The current NH3 emission estimates in China are mainly based on pre-defined emission factors that lack the temporal or spatial details, which are needed to accurately predict NH3 emissions. In this study, we estimate, for the first time, the NH3 emission from the agricultural fertilizer application in China online using an agricultural fertilizer modeling system coupling a regional air quality model (the Community Multi-Scale Air Quality model, CMAQ) and an agro-ecosystem model (the Environmental Policy Integrated Climate model, EPIC), which improves the spatial and temporal resolution of NH3 emission from this sector. Cropland area data of 14 crops from 2710 counties and the Moderate Resolution Imaging Spectroradiometer (MODIS) land use data are combined to determine the crop distribution. The fertilizer application rate and method for different crop are collected at provincial or agriculture-regional level. The EPIC outputs of daily fertilizer application and soil characteristics are inputed into the CMAQ model and the hourly NH3 emission are calculated online with CMAQ running. The estimated agricultural fertilizer NH3 emission in this study is about 3 Tg in 2011. The regions with the highest modeled emission rates are located in the North China Plain. Seasonally, the peak ammonia emissions occur from April to July.Compared with previous researches, this method considers more influencing factors, such as meteorological fields, soil and the fertilizer application, and provides improved NH3 emission with higher spatial and temporal resolution.

  19. Analysis of desorption species from MOS structure surfaces induced by gate voltages

    NASA Astrophysics Data System (ADS)

    Hirota, Nozomu; Hattori, Ken; Daimon, Hiroshi

    2014-03-01

    Hot carriers, which have energies over the Fermi level, are able to activate surface reaction. A MOS structure is able to generate tunable hot carriers under gate bias-voltages, would be suitable for the hot-carrier injection to surface from the metal side, but not vacuum side. In this research, I desire to make a proposition of catalytic devices using MOS structures. Desorption is one of the important paths in catalytic reaction, and would be observed when the bais-voltage is applied. We found desorption on N2O exposed MOS (Fe/SiO2/ p-Si) structure, detected by a mass spectrometer. The desorption were observed only when the metal surface was in negative polarity, the hole injection. The desorption of CH4 molecules was confirmed by mass analysis with cracking corrections. Since non-polar molecules (e.g., CH4) are hard to adsorb, the origin of CH4 is not adsorbed one as the molecule, but the catalytic reaction. At the same time, NH3 and H2O background intensities decreased. We consider the following scenario. The CH4 is generated from CO and adsorbed H over FexNy/SiO2 surface with hot-carrier activation. The CH4 formation inhibit H2O and NH3 suitable generation via decrease adsorbed H concentration. Most of desorption species can be expl

  20. Theory of desorption induced by electronic transitions: A time-independent quantum mechanical approach

    NASA Astrophysics Data System (ADS)

    Seideman, Tamar

    1997-01-01

    A new method is developed for study of photon- or electron-stimulated desorption from noninsulator surfaces. Concise and physically transparent, closed form expressions for the observables in a desorption experiment are given in terms of matrix elements of the interaction in stationary bases. The method is nonperturbative and spans the limits of weak to strong substrate-adsorbate interactions. We propose the possibility of relaxing several approximations frequently adopted in theoretical studies of desorption induced by electronic transitions. In particular, continuous decay of the transient electronic excitation produced by hot substrate carriers and the possibility of multiple electronic transitions follow naturally from the formulation and need not be introduced ad hoc. The description of time-delayed desorption, resulting from occurrence of predesorption resonances, entails neither conceptual nor computational difficulty and vibrational relaxation is consistently accounted for. The method is tested by application to an empirical model of the NH3/Cu photodesorption dynamics.

  1. Laboratory study of sticking and desorption of H2 and its significance in the chemical evolution of dense interstellar medium

    NASA Astrophysics Data System (ADS)

    Acharyya, K.

    2014-09-01

    The temperature-programmed desorption spectra of H2 is recorded under ultrahigh vacuum conditions on an olivine substrate with more than 90 per cent forsterite content for different coverage and temperatures. Then, using an empirical kinetic model, binding energy of H2 on the substrate is found to be 480 ± 10 K (41.36 ± 0.86 meV). Lower limit of sticking coefficient is estimated by comparing gas load at room temperature and at low temperature, which varies between 0.82 and 0.25 for temperatures between 7 and 14 K. Using a gas-grain chemical network, it is found out that a steady state is reached around after 50 yr at 10 K and both the steady-state abundance and time required to attend steady state is a strong function of temperature. Then, this model is used to check the effect of sticking of H2 on the grain surface chemistry. It is found that for H2O, CH4, NH3 and HCN, abundance due to reaction pathways involving H2 is within 1 per cent, when compared with the abundance achieved considering most dominant pathways. Thus, neglecting sticking of H2 will not change overall abundance of these molecules. For carbon chain molecules, it was found that the reaction pathways with H2 may be important and could contribute significantly to account for the observed abundances. Since, sticking of H2 is temperature sensitive, increase in temperature will reduce the effect of these reactions.

  2. Desorption Kinetics of Ar, Kr, Xe, N2, O2, CO, Methane, Ethane, and Propane from Graphene and Amorphous Solid Water Surfaces.

    PubMed

    Smith, R Scott; May, R Alan; Kay, Bruce D

    2016-03-01

    The desorption kinetics for Ar, Kr, Xe, N2, O2, CO, methane, ethane, and propane from graphene-covered Pt(111) and amorphous solid water (ASW) surfaces are investigated using temperature-programmed desorption (TPD). The TPD spectra for all of the adsorbates from graphene have well-resolved first, second, third, and multilayer desorption peaks. The alignment of the leading edges is consistent the zero-order desorption for all of the adsorbates. An Arrhenius analysis is used to obtain desorption energies and prefactors for desorption from graphene for all of the adsorbates. In contrast, the leading desorption edges for the adsorbates from ASW do not align (for coverages < 2 ML). The nonalignment of TPD leading edges suggests that there are multiple desorption binding sites on the ASW surface. Inversion analysis is used to obtain the coverage dependent desorption energies and prefactors for desorption from ASW for all of the adsorbates. PMID:26595145

  3. THERMAL DESORPTION TREATMENT

    EPA Science Inventory

    Thermal desorption is an ex situ means to physically separate volatile and some semivolatile contaminants from soil, sediments, sludges, and filter cakes. or wastes containing up to 10% organics or less, thermal desorption can be used alone for site remediation. t also may find a...

  4. Lattice potential energy and standard molar enthalpy in the formation of 1—dodecylamine hydrobromide (1-C12H25NH3·Br)(s)

    NASA Astrophysics Data System (ADS)

    Liu, Yu-Pu; Di, You-Ying; Dan, Wen-Yan; He, Dong-Hua; Kong, Yu-Xia; Yang, Wei-Wei

    2011-02-01

    This paper reports that 1-dodecylamine hydrobromide (1-C12H25NH3·Br)(s) has been synthesized using the liquid phase reaction method. The lattice potential energy of the compound 1-C12H25NH3·Br and the ionic volume and radius of the 1-C12H25NH3+ cation are obtained from the crystallographic data and other auxiliary thermodynamic data. The constant-volume energy of combustion of 1-C12H25NH3·Br(s) is measured to be ΔcUmo(1-C12H25NH3·Br, s) = -(7369.03±3.28) kJ·mol-1 by means of an RBC-II precision rotating-bomb combustion calorimeter at T = (298.15±0.001) K. The standard molar enthalpy of combustion of the compound is derived to be ΔcHmo(1-C12H25NH3·Br, s) = -(7384.52±3.28) kJ·mol-1 from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound is calculated to be ΔfHmo(1-C12H25NH3·Br, s)=-(1317.86±3.67) kJ·mol-1 from the standard molar enthalpy of combustion of the title compound and other auxiliary thermodynamic quantities through a thermochemical cycle.

  5. Field promoted and surface catalyzed formation of H 3 and NH 3 on transition metal surfaces: A pulsed-laser imaging atom-probe study

    NASA Astrophysics Data System (ADS)

    Chi-fong Ai; Tsong, T. T.

    1984-03-01

    The surface field must play an important role in the reactivity of a surface. This effect can be probed in field ion emission experiments where the applied field is an adjustable parameter and it is of the same order of magnitude as the surface field. We report here a study of field promoted and surface catalyzed formation of H 3 and NH 3 on 20 transition metals, using the pulsed-laser imaging atom-probe. We find that in an applied field of about 2.0 V/Å, H 3 can be formed most readily on surfaces of hep metals, and metals on the left hand side of the periodic table. Atomic chemisorption of hydrogen favors, but does not guarantee, the formation of H 3. In N 2H 2 mixed gases, a small amount of NH 3 can be formed in an applied field of 1.2 to 2.5 V/Å on surfaces of metals which are known to promote such a reaction in field free conditions. However, only on Fe and Co surfaces, a substantial amount of NH 3 can be formed. From the dependence of the relative abundances of the various observed ionic species on the composition of the mixed gas and on the gas pressure, we conclude that NH 3 is formed from the chemisorbed nitrogen and hydrogen atoms, whereas the pulsed-laser field desorbed NH 3+ originates from the field adsorbed NH 3, or the physisorbed NH 3.

  6. Temperature dependence of internal motions of protein side-chain NH3(+) groups: insight into energy barriers for transient breakage of hydrogen bonds.

    PubMed

    Zandarashvili, Levani; Iwahara, Junji

    2015-01-20

    Although charged side chains play important roles in protein function, their dynamic properties are not well understood. Nuclear magnetic resonance methods for investigating the dynamics of lysine side-chain NH3(+) groups were established recently. Using this methodology, we have studied the temperature dependence of the internal motions of the lysine side-chain NH3(+) groups that form ion pairs with DNA phosphate groups in the HoxD9 homeodomain-DNA complex. For these NH3(+) groups, we determined order parameters and correlation times for bond rotations and reorientations at 15, 22, 28, and 35 °C. The order parameters were found to be virtually constant in this temperature range. In contrast, the bond-rotation correlation times of the NH3(+) groups were found to depend strongly on temperature. On the basis of transition state theory, the energy barriers for NH3(+) rotations were analyzed and compared to those for CH3 rotations. Enthalpies of activation for NH3(+) rotations were found to be significantly higher than those for CH3 rotations, which can be attributed to the requirement of hydrogen bond breakage. However, entropies of activation substantially reduce the overall free energies of activation for NH3(+) rotations to a level comparable to those for CH3 rotations. This entropic reduction in energy barriers may accelerate molecular processes requiring hydrogen bond breakage and play a kinetically important role in protein function. PMID:25489884

  7. Interfacial interaction of Ag nanoparticles with graphene oxide supports for improving NH3 and NO adsorption: a first-principles study.

    PubMed

    Tang, Shaobin; Wu, Weihua; Yu, Jianping

    2016-03-01

    We investigated the structural and electronic properties of Ag13 nanoparticles (NPs) deposited on graphene oxides (GOs) and the effect of the interfacial interaction on NH3 and NO adsorption using density functional theory calculations. The epoxy functional group and its neighboring sp(2) carbon atoms of GOs, rather than the hydroxyl group, are used as active sites to enhance the binding of Ag13 to graphene through the C-O-Ag and C-Ag chemical bonds. The stability of deposited Ag NPs depends on the chemical environment of active sites in GOs, including the atomic arrangement of epoxides and their concentration. The deposited Ag13 NPs are likely to be further oxidized to form Ag13O by neighboring oxygen irrespective of the oxidation level of GOs. The strong interfacial interaction of Ag13/GOs, which effectively tunes the position of the d-band center of NPs due to large charge transfer from Ag13 to GOs, has a significant impact on the adsorption of NH3. The NH3 is strongly adsorbed on deposited Ag13 through the formation of an N-Ag bond and an NHO hydrogen bond between NH3 and O from C-O-Ag. The electronic structure calculations show that the hybridization of the HOMO of NH3 with the conduction bands of Ag13-GOs results in the strong donor doping by an NH3 molecule, and gives rise to larger charge transfers from NH3 to the hybrid, compared to NH3 adsorption on isolated Ag13 and GOs. The adsorption of NO on oxidized Ag13 on GOs is obviously improved due to the oxidation of NO to NO2 by its neighboring oxygen atoms. In contrast to NH3, the adsorbed NO acts as an acceptor. The calculated results show good agreement with experimental observations. PMID:26912023

  8. The H2O Southern Galactic Plane Survey: NH3 (1,1) and (2,2) catalogues

    NASA Astrophysics Data System (ADS)

    Purcell, C. R.; Longmore, S. N.; Walsh, A. J.; Whiting, M. T.; Breen, S. L.; Britton, T.; Brooks, K. J.; Burton, M. G.; Cunningham, M. R.; Green, J. A.; Harvey-Smith, L.; Hindson, L.; Hoare, M. G.; Indermuehle, B.; Jones, P. A.; Lo, N.; Lowe, V.; Phillips, C. J.; Thompson, M. A.; Urquhart, J. S.; Voronkov, M. A.; White, G. L.

    2012-11-01

    The H2O Southern Galactic Plane Survey (HOPS) has mapped a 100° strip of the Galactic plane (-70° > l > 30°, |b| < 0°.5) using the 22 m Mopra antenna at 12 mm wavelengths. Observations were conducted in on-the-fly mode using the Mopra spectrometer (MOPS), targeting water masers, thermal molecular emission and radio-recombination lines. Foremost among the thermal lines are the 23 GHz transitions of NH3 J,K = (1,1) and (2,2), which trace the densest parts of molecular clouds (n > 104 cm-3). In this paper, we present the NH3 (1,1) and (2,2) data, which have a resolution of 2 arcmin and cover a velocity range of ±200 km s-1. The median sensitivity of the NH3 data cubes is σT mb =0.20±0.06 K. For the (1,1) transition, this sensitivity equates to a 3.2 kpc distance limit for detecting a 20 K, 400 M⊙ cloud at the 5σ level. Similar clouds of mass 5000 M⊙ would be detected as far as the Galactic Centre, while 30 000 M⊙ clouds would be seen across the Galaxy. We have developed an automatic emission finding procedure based on the Australian Telescope National Facility (ATNF) DUCHAMP software and have used it to create a new catalogue of 669 dense molecular clouds. The catalogue is 100 per cent complete at the 5σ detection limit (Tmb = 1.0 K). A preliminary analysis of the ensemble cloud properties suggests that the near-kinematic distances are favoured. The cloud positions are consistent with current models of the Galaxy containing a long bar. Combined with other Galactic plane surveys this new molecular-line data set constitutes a key tool for examining Galactic structure and evolution. Data cubes, spectra and catalogues are available to the community via the HOPS website.

  9. On-board Measurement of HCN and NH3 Emissions from Vehicles During Real-World Driving

    NASA Astrophysics Data System (ADS)

    Moss, J. A.; Baum, M. M.

    2013-12-01

    Emission control systems in light-duty motor vehicles have played an important role in improving regional air quality by dramatically reducing the concentration of criteria pollutants (carbon monoxide, hydrocarbons, and nitrogen oxides) in exhaust emissions. Unintended side-reactions occurring on the surface of three-way catalysts can, however, lead to emission of non-criteria pollutants such as ammonia (NH3) and hydrogen cyanide (HCN). A pair of spectrometers based on tunable diode lasers (TDL) emitting in the near-infrared (1529 nm) and mid-infrared (2975 nm) have been developed for determination of HCN and acetylene (C2H2) emission rates from light-duty motor vehicles in real-time, while driving. Both spectrometers have been evaluated extensively using standard gas mixtures in the laboratory and exhaust from idling and moving vehicles. The TDL spectrometers were incorporated into an on-board instrument suite containing instrumentation for measurement of CO2, HCN, C2H2, NH3 and amines, and exhaust flow rate. On-board measurements were carried out on a fleet of ten vehicles driving a 30 minute circuit representative of real-world urban driving conditions. These measurements afforded emission factors for NH3 (194 × 147 mg km-1) and HCN (3.33 × 3.61 mg km-1), as well as the first report of methylamine emission factors, 0.70 × 0.61 mg km-1. Emissions of both amines were highly correlated (R2 = 0.95). The temporally-resolved TDL spectrometer measurements indicate that the highest HCN and C2H2 emissions occur during specific emission modes that are a function of driving conditions.

  10. Questioning Antiferromagnetic Ordering in the Expanded Metal, Li(NH3)4: A Lack of Evidence from μSR.

    PubMed

    Seel, Andrew G; Baker, Peter J; Cottrell, Stephen P; Howard, Christopher A; Skipper, Neal T; Edwards, Peter P

    2015-10-01

    We present the results of a muon spin relaxation study of the solid phases of the expanded metal, Li(NH3)4. No discernible change in muon depolarization dynamics is witnessed in the lowest temperature phase (≤25 K) of Li(NH3)4, thus suggesting that the prevailing view of antiferromagnetic ordering is incorrect. This is consistent with the most recent neutron diffraction data. Discernible differences in muon behavior are reported for the highest temperature phase of Li(NH3)4 (82-89 K), attributed to the onset of structural dynamics prior to melting. PMID:26722900

  11. Mobile mapping and eddy covariance flux measurements of NH3 emissions from cattle feedlots with a portable laser-based open-path sensor

    NASA Astrophysics Data System (ADS)

    Tao, L.; Sun, K.; Pan, D.; Golston, L.; Stanton, L. G.; Ham, J. M.; Shonkwiler, K. B.; Nash, C.; Zondlo, M. A.

    2014-12-01

    Ammonia (NH3) is the dominant alkaline species in the atmosphere and an important compound in the global nitrogen cycle. There is a large uncertainty in NH3 emission inventory from agriculture, which is the largest source of NH3, including livestock farming and fertilizer applications. In recent years, a quantum cascade laser (QCL)-based open-path sensor has been developed to provide high-resolution, fast-response and high-sensitivity NH3 measurements. It has a detection limit of 150 pptv with a sample rate up to 20 Hz. This sensor has been integrated into a mobile platform mounted on the roof of a car to perform measurement of multiple trace gases. We have also used the sensor for eddy covariance (EC) flux measurements. The mobile sensing method provides high spatial resolution and fast mapping of measured gases. Meanwhile, the EC flux method offers accurate flux measurements and resolves the diurnal variability of NH3emissions. During the DISCOVER-AQ and FRAPPÉ field campaigns in 2014, this mobile platform was used to study NH3 emissions from cattle feedlot near Fort Morgan, Colorado. This specific feedlot was mapped multiple times in different days to study the variability of its plume characteristics. At the same time, we set up another open-path NH3 sensor with LICOR open-path sensors to perform EC flux measurements of NH3, CH4 and CO2 simultaneously in the same cattle feedlot as shown in Fig. 1. NH3/CH4 emission flux ratio show a strong temperature dependence from EC flux measurements. The median value of measured NH3 and CH4 emission flux ratio is 0.60 ppmv/ppmv. In contrast, the median value of ΔNH3/ΔCH4 ratios measured from mobile platform is 0.53 ppmv/ppmv for the same farm. The combination of mobile mapping and EC flux measurements with the same open-path sensors greatly improves understanding of NH3 emissions both spatially and temporally.

  12. Fe/SSZ-13 as an NH3-SCR Catalyst: A Reaction Kinetics and FTIR/Mössbauer Spectroscopic Study

    SciTech Connect

    Gao, Feng; Kollar, Marton; Kukkadapu, Ravi K.; Washton, Nancy M.; Wang, Yilin; Szanyi, Janos; Peden, Charles H.F.

    2015-03-01

    Using a traditional aqueous solution ion-exchange method under a protecting atmosphere of N2, an Fe/SSZ-13 catalyst active in NH3-SCR was synthesized. Mössbauer and FTIR spectroscopies were used to probe the nature of the Fe sites. In the fresh sample, the majority of Fe species are extra-framework cations. The likely monomeric and dimeric ferric ions in hydrated form are [Fe(OH)2]+ and [HO-Fe-O-Fe-OH]2+, based on Mössbauer measurements. During the severe hydrothermal aging (HTA) applied in this study, a majority of cationic Fe species convert to FeAlOx and clustered FeOx species, accompanied by severe dealumination of the SSZ-13 framework. The clustered FeOx species do not give a sextet Mössbauer spectrum, indicating that these are highly disordered. However, some Fe species in cationic positions remain after aging as determined from Mössbauer measurements and CO/NO FTIR titrations. NO/NH3 oxidation reaction tests reveal that dehydrated cationic Fe are substantially more active in catalyzing oxidation reactions than the hydrated ones. For NH3-SCR, enhancement of NO oxidation under ‘dry’ conditions promotes SCR rates below ~300 • C. This is due mainly to contribution from the “fast” SCR channel. Above ~300 • C, enhancement of NH3 oxidation under ‘dry’ conditions, however, becomes detrimental to NOx conversions. The HTA sample loses much of the SCR activity below ~300 • C; however, above ~400 • C much of the activity remains. This may suggest that the FeAlOx and FeOx species become active at such elevated temperatures. Alternatively, the high-temperature activity may be maintained by the remaining extra-framework cationic species. For potential practical applications, Fe/SSZ-13 may be used as a co-catalyst for Cu/CHA as integral aftertreatment SCR catalysts on the basis of the stable high temperature activity after hydrothermal aging. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.

  13. Laboratory measurements of the 7.5-9.38-mm absorption of gaseous ammonia (NH3) under simulated Jovian conditions

    NASA Technical Reports Server (NTRS)

    Joiner, Joanna; Steffes, Paul G.; Jenkins, Jon M.

    1989-01-01

    An attempt is made to infer the abundance and distribution of ammonia from RF emission measurements more accurately than heretofore, on the basis of the results of laboratory measurements for the mm-wave opacity of gaseous ammonia under simulated Jovian atmosphere conditions. The measurements were conducted at various frequencies in the 32-40 GHz range at 2 atm and 203 K; the atmospheric mixture was 88.34 percent H2, 9.81 percent He, and 1.85 percent NH3. Experimental results are found to be readily modeled by the Gross (1955) line-shape factor, rather than that of Van Vleck and Weisskopf (1945).

  14. Synthesis, structural and optical properties of perovskite type CH3NH3PbI3 nanorods

    NASA Astrophysics Data System (ADS)

    Rajamanickam, N.; Rajashabala, S.; Ramachandran, K.

    2015-06-01

    Perovskite type methyl ammonium lead triiodide (CH3NH3PbI3) thin films were prepared by coprecipitation method. The structural and optical properties were investigated by XRD, SEM, Raman and UV-Vis spectroscopy. Perovskite structured tetragonal phase was observed by XRD. The UV spectrum exhibits a band gap of 1.63 eV. The nanorods are arranged in flower like structure distinguished by SEM. Raman spectrum of this organo-halide perovskite was studied for the full exploitation in solar cells.

  15. Microstructures and photovoltaic properties of perovskite-type CH3NH3PbI3 compounds

    NASA Astrophysics Data System (ADS)

    Oku, Takeo; Zushi, Masahito; Imanishi, Yuma; Suzuki, Atsushi; Suzuki, Kohei

    2014-12-01

    TiO2/CH3NH3PbI3-based photovoltaic devices were fabricated. The microstructures of these devices were investigated by X-ray diffraction, transmission electron microscopy, and their calculations. Structure analysis indicated phase transformation of the perovskite structure from a tetragonal to a cubic system by annealing, which resulted in the improvement of photovoltaic properties of the devices. Effects of a multiple spin-coating method using a mixture solution were also investigated. The result showed an increase in the efficiencies of the devices, due to the microstructural change of the perovskite compound layers.

  16. On the Dynamic Dielectric Behaviour of (CH3NH3)3Sb2Br9(MABA)

    NASA Astrophysics Data System (ADS)

    Pawlaczyk, Czesław; Jakubas, Ryszard

    2003-04-01

    The complex electric permittivity of ferroelectric (CH3NH3)3Sb2Br9 (MABA) single crystals has been measured in the frequency range 1 kHz - 3 GHz between 15 and 300 K. The dynamic dielectric behaviour of MABA is determined by the properties of high frequency relaxation of Cole-Cole type. It is thermally activated and characterised by a relatively small activation energy. The phase transitions at 168 and 134 K influence the amplitude of the relaxation (Δɛ) without any important changes in the relaxation frequency.

  17. Optical And Structural Properties Of Hydrogenated ZnO Thin Films And Their Application For NH3 Gas Sensors

    NASA Astrophysics Data System (ADS)

    Dimova-Malinovska, D.; Lazarova, V.; Angelov, O.; Nichev, H.

    2007-04-01

    Measurements of the optical and structural properties of ZnO thin films (ZnO:H) deposited by magnetron sputtering in an Ar+H2 atmosphere have been performed. The optical band gap, Eopt, and the Urbach band tail width were calculated. The influence of the substrate temperature on the resistivity, optical band gap and structural properties has been studied. A discussion of the influence of Ts on the properties is presented. The sensitivity of ZnO films to exposure to NH3 has been measured by the quartz crystal microbalance method.

  18. Electron irradiation and thermal driven chemistry on H2S-CH3OH-NH3-H2O and CH3OH-NH3-H2O ices: application to Jupiter Trojans

    NASA Astrophysics Data System (ADS)

    Mahjoub, A.; Poston, M.; Hand, K.; Brown, M.; Blacksberg, J.; Eiler, J.; Hodyss, R.; Carlson, R.; Ehlmann, B.; Choukroun, M.

    2015-10-01

    In this work we investigate chemical reactions driven by irradiation and thermal processing of outer solar system simulants and the resultant products. The main goal of this laboratory simulation work is testing migration hypotheses predicted by solar system formation models [1]. The ice samples are chosen to simulate the differences between chemistry in objects initially located inside and outside the stability line of H2S. CH3OH-NH3-H2O (3-ice) and H2S-CH3OH-NH3-H2O (4-ice) ice films was irradiated under ultrahigh vacuum conditions. Mid- IR analysis of the ice composition and mass spectrometry monitoring of the released volatiles during the heating of the irradiated mixtures show a rich chemistry for both mixtures. Our experimental work suggests that S-bearing molecules like OCS and SO2 could be formed under conditions expected for objects that initially contained near-surface frozen H2S and were then exposed to space weathering, particularly heating and irradiation while migrating to a position close to Jupiter's orbit.

  19. The C(3P) + NH3 Reaction in Interstellar Chemistry. II. Low Temperature Rate Constants and Modeling of NH, NH2, and NH3 Abundances in Dense Interstellar Clouds

    NASA Astrophysics Data System (ADS)

    Hickson, Kevin M.; Loison, Jean-Christophe; Bourgalais, Jérémy; Capron, Michael; Le Picard, Sébastien D.; Goulay, Fabien; Wakelam, Valentine

    2015-10-01

    A continuous supersonic flow reactor has been used to measure rate constants for the C(3P) + NH3 reaction over the temperature range 50-296 K. C(3P) atoms were created by the pulsed laser photolysis of CBr4. The kinetics of the title reaction were followed directly by vacuum ultra-violet laser induced fluorescence of C(3P) loss and through H(2S) formation. The experiments show unambiguously that the reaction is rapid at 296 K, becoming faster at lower temperatures, reaching a value of (1.8 ± 0.2) × 10-10 cm3 molecule-1 s-1 at 50 K. As this reaction is not currently included in astrochemical networks, its influence on interstellar nitrogen hydride abundances is tested through a dense cloud model including gas-grain interactions. In particular, the effect of the ortho-to-para ratio of H2, which plays a crucial role in interstellar NH3 synthesis, is examined.

  20. Dynamic Growth of Pinhole-Free Conformal CH3NH3PbI3 Film for Perovskite Solar Cells.

    PubMed

    Li, Bo; Tian, Jianjun; Guo, Lixue; Fei, Chengbin; Shen, Ting; Qu, Xuanhui; Cao, Guozhong

    2016-02-24

    Two-step dipping is one of the popular low temperature solution methods to prepare organic-inorganic halide perovskite (CH3NH3PbI3) films for solar cells. However, pinholes in perovskite films fabricated by the static growth method (SGM) result in low power conversion efficiency (PCE) in the resulting solar cells. In this work, the static dipping process is changed into a dynamic dipping process by controlled stirring PbI2 substrates in CH3NH3I isopropanol solution. The dynamic growth method (DGM) produces more nuclei and decreases the pinholes during the nucleation and growth of perovskite crystals. The compact perovskite films with free pinholes are obtained by DGM, which present that the big perovskite particles with a size of 350 nm are surrounded by small perovskite particles with a size of 50 nm. The surface coverage of the perovskite film is up to nearly 100%. Such high quality perovskite film not only eliminated pinholes, resulting in reduced charge recombination of the solar cells, but also improves the light harvesting efficiency. As a result, the PCE of the perovskite solar cells is increased from 11% for SGM to 13% for DGM. PMID:26820581

  1. Extended line positions, intensities, empirical lower state energies and quantum assignments of NH3 from 6300 to 7000 cm-1

    NASA Astrophysics Data System (ADS)

    Sung, Keeyoon; Brown, Linda R.; Huang, Xinchuan; Schwenke, David W.; Lee, Timothy J.; Coy, Stephen L.; Lehmann, Kevin K.

    2012-07-01

    Nearly 4800 features of ammonia between 6300 and 7000 cm-1 with intensities ≥4×10-24 cm-1/(molecule·cm-2) at 296 K were measured using 16 pure NH3 spectra recorded at various temperatures (296-185 K) with the McMath-Pierce Fourier Transform Spectrometer at Kitt Peak National Observatory, AZ. The line positions and intensities were retrieved by fitting individual spectra based on a Voigt line shape profile and then averaging the values to form the experimental linelist. The integrated intensity of the region was 4.68×10-19 cm-1/(molecule·cm-2) at 296 K. Empirical lower state energies were also estimated for 3567 absorption line features using line intensities retrieved from 10 spectra recorded at gas temperature between 185 and 233 K. Finally, using Ground State Combination Differences (GSCDs) and the empirical lower state energy estimates, the quantum assignments were determined for 1096 transitions in the room temperature linelist, along with empirical upper state energies for 434 levels. The assignments correspond to seven vibrational states, as confirmed from recent ab initio calculations. The resulting composite database of 14NH3 line parameters will provide experimental constraints to ab initio calculations and support remote sensing of gaseous bodies including the atmospheres of Earth, (exo)planets, brown dwarfs, and other astrophysical environments.

  2. Low-temperature SCR of NO with NH3 over activated semi-coke composite-supported rare earth oxides

    NASA Astrophysics Data System (ADS)

    Wang, Jinping; Yan, Zheng; Liu, Lili; Zhang, Yingyi; Zhang, Zuotai; Wang, Xidong

    2014-08-01

    The catalysts with different rare earth oxides (La, Ce, Pr and Nd) loaded onto activated semi-coke (ASC) via hydrothermal method are prepared for the selective catalytic reduction (SCR) of NO with NH3 at low temperature (150-300 °C). It is evidenced that CeO2 loaded catalysts present the best performance, and the optimum loading amount of CeO2 is about 10 wt%. Composite catalysts by doping La, Pr and Nd into CeO2 are prepared to obtain further improved catalytic properties. The SCR mechanism is investigated through various characterizations, including XRD, Raman, XPS and FT-IR, the results of which indicate that the oxygen defect plays an important role in SCR process and the doped rare earth elements effectively serve as promoters to increase the concentration of oxygen vacancies. It is also found that the oxygen vacancies in high concentration are favored for the adsorption of O2 and further oxidation of NO, which facilitates a rapid progressing of the following reduction reactions. The SCR process of NO with NH3 at low temperature over the catalysts of ASC composite-supported rare earth oxides mainly follows the Langmuir-Hinshlwood mechanism.

  3. Detection of interstellar NH3 in the far-infrared - Warm and dense gas in Orion-KL

    NASA Technical Reports Server (NTRS)

    Townes, C. H.; Genzel, R.; Watson, D. M.; Storey, J. W. V.

    1983-01-01

    Results of an investigation are presented which show the detection of the (J,K) = a(4,3)-s(3,3) rotation-inversion transition of ammonia at 124.6 microns toward the center of the Orion-KL region. The line is found to be in emission and has a FWHM greater than or equal to 30 km/s, while the far-IR ammonia line emission probably comes mainly from the 'hot core', a compact region of warm, very dense gas previously identified by the radio inversion lines of NH3. The a(4,3)-s(3,3) line is very optically thick and it is determined that radiative excitation of the (4,3) NH3 level by far-IR emission from dust within the source can be ruled out. It is concluded that the (4,3) level is probably collisionally excited and the gas in the hot core region is warmer than the dust. Densities of approximately 10 to the 7th/cu cm are high enough to explain the observations, while shock heating by the mass outflow from IRc2 may account for the high gas temperatures in the hot core region.

  4. [Emission of CH4, N2O and NH3 from vegetable field applied with animal manure composts].

    PubMed

    Wan, He-Feng; Zhao, Chen-Yang; Zhong, Jia; Ge, Zhen; Wei, Yuan-Song; Zheng, Jia-Xi; Wu, Yu-Long; Han, Sheng-Hui; Zheng, Bo-Fu; Li, Hong-Mei

    2014-03-01

    Greenhouse gas (GHG) emission from vegetable land is of great concern recently because agriculture land is one of the major sources contributing to global GHG emission. In this study, an experiment of Lactuca sativa L. land applied with different animal manure composts was carried out in a greenhouse vegetable land located in the surburb of Beijing to monitor the emission of GHG (CH4 and N2O) and ammonia in situ, and to analyze the affecting factors of GHG and ammonia emission. Results showed that the emission factors (EFs) of CH4 from Treatment NRM, RM and CF were 0.2%, 0.027% and 0.004%, respectively,the EFs of N2O from these three treatments were 0.18%, 0.63% and 0.74%, respectively, and the EFs of ammonia were 2.00%, 3.98% and 2.53%, respectively. CH4 emission flux was significantly affected by soil temperature and humidity, while N2O emission flux was related to soil temperature, surface temperature and humidity. The emission fluxes of CH4, N2O and NH3 were significantly affected by soil moisture, but there was little relation between CH4, N2O and NH3 emissions and the ambient temperature in the greenhouse. PMID:24881375

  5. Computational study of Al- or P-doped single-walled carbon nanotubes as NH3 and NO2 sensors

    NASA Astrophysics Data System (ADS)

    Azizi, Khaled; Karimpanah, Mohammad

    2013-11-01

    Density functional theory (DFT) calculations were carried out to analyze the electronic and structural properties of pristine and aluminum or phosphorus doped (8,0) single walled carbon nanotube (SWCNT) as a sensor for the detection of nitrogen dioxide (NO2) and ammonia (NH3). The binding energies, equilibrium gas-nanotube distances, the amounts of charge transfer and molecular orbital schemes as well as the density of states have been calculated and used to interpret the mechanism of gas adsorption on the surface of nanotubes. In agreement with the experimental data, our results show considerable binding energy and energy gap alteration due to the adsorption of NO2 on pristine SWCNT. The results reveal that the doping of both Al and P atoms increase the capability of the nanotube for the adsorption of NO2, and the effect is more significant for the Al-doped nanotube. The Al-doped nanotube can also be considered as a good sensor for NH3 due to its high binding energy, considerable amount of charge transfer and energy band gap alteration.

  6. The C(3P) + NH3 Reaction in Interstellar Chemistry. I. Investigation of the Product Formation Channels

    NASA Astrophysics Data System (ADS)

    Bourgalais, Jérémy; Capron, Michael; Abhinavam Kailasanathan, Ranjith Kumar; Osborn, David L.; Hickson, Kevin M.; Loison, Jean-Christophe; Wakelam, Valentine; Goulay, Fabien; Le Picard, Sébastien D.

    2015-10-01

    The product formation channels of ground state carbon atoms, C(3P), reacting with ammonia, NH3, have been investigated using two complementary experiments and electronic structure calculations. Reaction products are detected in a gas flow tube experiment (330 K, 4 Torr) using tunable vacuum-ultraviolet (VUV) photoionization coupled with time of flight mass spectrometry. Temporal profiles of the species formed and photoionization spectra are used to identify primary products of the C + NH3 reaction. In addition, H-atom formation is monitored by VUV laser induced fluorescence (LIF) from room temperature to 50 K in a supersonic gas flow generated by the Laval nozzle technique. Electronic structure calculations are performed to derive intermediates, transition states, and complexes formed along the reaction coordinate. The combination of photoionization and LIF experiments supported by theoretical calculations indicate that in the temperature and pressure range investigated, the H + H2CN production channel represents 100% of the product yield for this reaction. Kinetics measurements of the title reaction down to 50 K and the effect of the new rate constants on interstellar nitrogen hydride abundances using a model of dense interstellar clouds are reported in Paper II.

  7. Shape-controlled CH3NH3PbI3 nanoparticles for planar heterojunction perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Shahiduzzaman, Md.; Yamamoto, Kohei; Furumoto, Yoshikazu; Kuwabara, Takayuki; Takahashi, Kohshin; Taima, Tetsuya

    2016-02-01

    Hybrid organic/inorganic perovskites such as methylammonium lead iodide (CH3NH3PbI3) are potential candidates for thin-film photovoltaics because of their excellent cost- and energy-efficient light absorption. In this work, we have prepared CH3NH3PbI3 nanoparticles (NPs) on the TiOx/ITO glass substrates by a simple spin-coating method to control the size and shape of NPs. The effect of varying the weight percentage (wt %) of ionic liquid (IL) has also been investigated. Analysis of the films revealed spherical NP morphology in the presence of 1, 3, and 7 wt % IL with respective diameters of 540, 350, and 600 nm. Conversely, 10 wt % IL resulted in irregular aggregation of NP blocks. The power conversion efficiency (PCE) changed upon varying the NP size, shape, and morphology. The optimization of the concentration with 3 wt % IL yielded NPs with the most uniform shape, size, and morphology and, consequently, the maximum PCE.

  8. Depletion region effect of highly efficient hole conductor free CH3NH3PbI3 perovskite solar cells.

    PubMed

    Aharon, Sigalit; Gamliel, Shany; El Cohen, Bat; Etgar, Lioz

    2014-06-14

    The inorganic-organic perovskite is currently attracting a lot of attention due to its use as a light harvester in solar cells. The large absorption coefficients, high carrier mobility and good stability of organo-lead halide perovskites present good potential for their use as light harvesters in mesoscopic heterojunction solar cells. This work concentrated on a unique property of the lead halide perovskite, its function simultaneously as a light harvester and a hole conductor in the solar cell. A two-step deposition technique was used to optimize the perovskite deposition and to enhance the solar cell efficiency. It was revealed that the photovoltaic performance of the hole conductor free perovskite solar cell is strongly dependent on the depletion layer width which was created at the TiO2-CH3NH3PbI3 junction. X-ray diffraction measurements indicate that there were no changes in the crystallographic structure of the CH3NH3PbI3 perovskite over time, which supports the high stability of these hole conductor free perovskite solar cells. Furthermore, the power conversion efficiency of the best cells reached 10.85% with a fill factor of 68%, a Voc of 0.84 V, and a Jsc of 19 mA cm(-2), the highest efficiency to date of a hole conductor free perovskite solar cell. PMID:24736900

  9. TiO2 particles on a 3D network of single-walled nanotubes for NH3 gas sensors.

    PubMed

    Jo, Yong Deok; Lee, Sooken; Seo, Jeongeun; Lee, Soobum; Ann, Doyeon; Lee, Haiwon

    2014-12-01

    Ammonia (NH3) gas is one of the gases which causes damage to environment such as acidification and climate change. In this study, a gas sensor based on the three-dimensional (3D) network of single-walled nanotubes (SWNTs) was fabricated for the detection of NH3 gas in dry air. The sensor showed enhanced performance due to the fast gas diffusion rate and weak interactions between the carbon nanotubes and the substrate. Metal oxide particles were introduced to enhance the performance of the gas sensor. Atomic layer deposition (ALD) was employed to deposit the metal oxide in the complex structure, and good control over thickness was achieved. The hybrid gas sensor consisting of the 3D network of SWNTs with anatase TiO2 particles showed stable, repeatable, and enhanced gas sensor performance. The phase of TiO2 particles was characterized by Raman and the morphology of the TiO2 particles on the 3D network of SWNTs was analyzed by transmission electron microscope. PMID:25971027

  10. Lattice thermal conductivity of organic-inorganic hybrid perovskite CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Qian, Xin; Gu, Xiaokun; Yang, Ronggui

    2016-02-01

    Great success has been achieved in improving the photovoltaic energy conversion efficiency of the organic-inorganic hybrid perovskite-based solar cells, but with very limited knowledge on the thermal transport in hybrid perovskites, which could affect the device lifetime and stability. Based on the potential field derived from the density functional theory calculations, we studied the lattice thermal conductivity of the hybrid halide perovskite CH3NH3PbI3 using equilibrium molecular dynamics simulations. Temperature-dependent thermal conductivity is reported from 160 K to 400 K, which covers the tetragonal phase (160-330 K) and the pseudocubic phase (>330 K). A very low thermal conductivity (0.59 W/m K) is found in the tetragonal phase at room temperature, whereas a much higher thermal conductivity is found in the pseudocubic phase (1.80 W/m K at 330 K). The low group velocity of acoustic phonons and the strong anharmonicity are found responsible for the relatively low thermal conductivity of the tetragonal CH3NH3PbI3.

  11. Growth of freshly nucleated particles in the troposphere: Roles of NH3, H2SO4, HNO3, and HCl

    NASA Astrophysics Data System (ADS)

    Kerminen, Veli-Matti; Wexler, Anthony S.; Potukuchi, Sudhakar

    1997-02-01

    Growth of airborn, nanometer-size nuclei was examined in a H2SO4-HNO3-HCl-NH3-H2O system using a single-particle condensation model. Under conditions typical of the lower troposphere, growth is driven initially by the flux of sulfuric acid, followed by thermodynamic equilibration by the more abundant water and ammonia vapors. Pure sulfuric acid-water-ammonia condensation was shown to be rather slow and unable to produce cloud condensation nuclei (CCN) in the atmosphere. Under favorable conditions and after reaching a certain size, nuclei may start to absorb large quantities of nitric or hydrochloric acid together with ammonia, which produces CCN-size particles over a timescale of a few minutes. The resulting CCN are susceptible to evaporation as the ambient conditions change but may become stable via cloud processing. The fast, HNO3-HCl-NH3-driven condensation was estimated to occur frequently in continental aerosol systems. Marine CCN production cannot be explained by this process; it requires either the participation of other condensable vapors, such as organics, or a different growth mechanism.

  12. X-ray photoelectron spectroscopy studies of the reduction of MoO 3 thin films by NH 3

    NASA Astrophysics Data System (ADS)

    Leung, Y. L.; Wong, P. C.; Mitchell, K. A. R.; Smith, K. J.

    1998-10-01

    X-ray photoelectron spectroscopy (XPS) has been used to gain insight into surface reaction pathways associated with the nitridation by NH 3 of MoO 3 thin films grown on metallic substrates. The samples formed can be seen as model hydrodenitrogenation (HDN) catalysts, but the more-controlled surface morphology allows spectral features to be studied in the absence of charging effects that can interfere with such measurements on high-area samples. Observed core level and valence spectra are consistent with the MoO 3 being reduced, but the degree of reduction depends on the reaction temperature. Heating to 350°C indicates some conversion to Mo(+5) and `O-rich' Mo(+4) components, while heating to 450°C and to 700°C give respectively a `N-rich' Mo(+4) form and a Mo(+3) oxynitride as the dominant components. It is concluded that the nitridation of MoO 3 by NH 3 involves initial hydrogenation, with subsequent elimination of water, and the effective replacement of O by N as the reduction continues. Surface compositions determined here during the nitridation process contrast with conclusions reached previously for the evolution of bulk phases as deduced by X-ray diffraction.

  13. Electrical behaviour of Ti-doped Ta2O5 on N2O- and NH3-nitrided Si

    NASA Astrophysics Data System (ADS)

    Spassov, D.; Atanassova, E.; Paskaleva, A.; Novkovski, N.; Skeparovski, A.

    2009-07-01

    The influence of process parameters: doping approach, Si surface nitridation ambient (NH3 and N2O), type of the gate (Al and W) and its technology of deposition on the electrical characteristics (capacitance-voltage, temperature-dependent current-voltage curves), and the mechanism of conductivity of Ti-doped stacks (6 nm) have been investigated. Among the three factors studied, the surface engineering appears to be with the greatest impact on the film permittivity and stack charges. It is shown that the Ti incorporation through the surface of Ta2O5 deposited on NH3-rapid thermally nitrided Si is effective in achieving films with high permittivity. The interface metal/doped high-k layer is a critical factor in leakage current behaviour. The evaporated Al is a good candidate as a top electrode of Ti-doped stacks giving satisfactory level of leakage current while radiation defects introduced in the stack during W sputtering cause current deterioration, making sputtered W less favourable as a metal electrode of Ta2O5-based capacitors. The conduction mechanism in Ti-doped Ta2O5 stacks is controlled by the gate electrode processing rather than by both the substrate nitridation and the doping approach. The energy levels of the traps responsible for the current transport are estimated.

  14. Electrical properties and conduction mechanism of [C2H5NH3]2CuCl4 compound

    NASA Astrophysics Data System (ADS)

    Mohamed, C. Ben; Karoui, K.; Jomni, F.; Guidara, K.; Rhaiem, A. Ben

    2015-02-01

    The [(C2H5)NH3]2CuCl4 compound was prepared and characterized by several technique: the X-ray powder diffraction confirms the purity of the synthetized compound, the differential scanning calorimetric show several phase transitions at 236 K, 330 K, 357 K and 371 K, the dialectical properties confirms the ferroelectric-paraelectric phase transition at 238 K, which is reported by V. Kapustianyk et al. (2007) [1]. The two semi-circles observed in the complex impedance identify the presence of the grain interior and grain boundary contributions to the electrical response in this material. The equivalent circuit is modeled by a combination series of two parallel RP-CPE circuits. The temperature dependence of the alternative current conductivity (σg) and direct current conductivity (σdc) confirm the observed transitions in the calorimetric study. The (AC) electrical conduction in [(C2H5)NH3]2CuCl4 was studied by two processes that can be attributed to a hopping transport mechanism: the non-overlapping small polaron tunneling (NSPT) model in phase III and the correlated barrier hopping (CBH) model in phases I, II, IV, V and VI.

  15. NH3, N2O and CH4 emissions during passively aerated composting of straw-rich pig manure.

    PubMed

    Szanto, G L; Hamelers, H V M; Rulkens, W H; Veeken, A H M

    2007-10-01

    Straw-rich manure from organic pig farming systems was composted in passively aerated static piles to estimate the effect of monthly turning on organic matter degradation and NH(3), N(2)O and CH(4) emissions. Turning enhanced the rate of drying and degradation. The four-month treatment degraded 57+/-3% of the initial organic matter in the turned piles, while only 40+/-5% in the static piles. The turned piles showed low ammonia and N(2)O emissions, 3.9+/-0.2% and 2.5+/-0.1% of total initial nitrogen, respectively. Static piles gave low ammonia (2.4+/-0.1% N(initial)), but high (9.9+/-0.5% N(initial)) N(2)O emissions. Prevalence of anaerobic regions in the static system was supported by the higher CH(4) emissions, 12.6+/-0.6% VS(degraded) for the static vs. 0.4+/-0.0% VS(degraded) for the turned system. It was shown, that straw-rich pig manure with very low C/N ratios could be composted directly without significant NH(3) and N(2)O emissions if turned on a monthly basis. PMID:17092707

  16. Uranus and Neptune structure models with ab initio EOS data for CH4, NH3, and H2O

    NASA Astrophysics Data System (ADS)

    Nettelmann, Nadine; Fortney, Jonathan; Hamel, Sebastien; Bethkenhagen, Mandy; Redmer, Ronald

    2014-05-01

    Uranus and Neptune are supposed to be rich in ices in their deep interiors as their mean density closely resembles that of liquid water. Moreover, highly super-solar abundances of CH4 and CO, indicative of internal water, have been observed in their atmospheres. We here compare ab initio equations of state for CH4, NH3, and H2O and apply them to compute ice-rich, adiabatic internal structure models of Uranus and Neptune. The explicit consideration of the light ices CH4 and NH3 allows us to put tighter constraints on the minimum H/He abundance in their deep interior, which was found to be non-zero in all previous Uranus and in most of the Neptune models that were based on water as a proxy for ices. In particular, we investigate if hydrogen in the deep interior can solely be a result of assumed Carbon sedimentation (diamond rain), as an alternative scenario to the early accretion of H/He containing material during the formation of the planets. We conclude by discussing the deep internal H/He abundance in light of rock-rich and warmer-than-adiabatic interiors, which has been suggested to explain Uranus' low intrinsic luminosity. Our models serve to better understand the formation and bulk composition of Neptune-sized planets.

  17. ZnO nanoplates surfaced-decorated by WO3 nanorods for NH3 gas sensing application

    NASA Astrophysics Data System (ADS)

    Dien Nguyen, Dac; Do, Duc Tho; Hien Vu, Xuan; Vuong Dang, Duc; Chien Nguyen, Duc

    2016-03-01

    Zinc oxide (ZnO) nanoplates and tungsten trioxide (WO3) nanorods were synthesized by hydrothermal treatment from zinc nitrate/potassium hydroxide and sodium tungstate/hydrochloric acid, respectively. The structure, morphology and compositions of the as-prepared WO3/ZnO nano-composites were characterized by x-ray diffraction, field emission scanning electron microscopy and energy dispersive spectroscopy. The obtained ZnO nanoplates have regular shape, single-crystal wurtzite structure with the thickness of 40 nm and 200 versus 400 nm in lateral dimensions. The WO3 nanorods possess the average diameter of 20 nm and the length of approximately 120 nm which were distributed on the surfaces of ZnO nanoplates. The WO3/ZnO nano-composites were prepared by grinding WO3 nanorods powder with ZnO nanoplates powder in various weight ratios (1:2, 1:1 and 2:1). The NH3 gas sensing properties of WO3/ZnO nano-composites were examined through the electrical resistance measurement. The gas sensing performance of the WO3/ZnO composite with weight ratio of 1:1 was better compared with that of other samples. For this sample, the maximum response to 300 ppm NH3 was 24 at the operating temperature of 250 °C. In addition, the gas sensing mechanism of the WO3/ZnO composites was discussed.

  18. Investigation of NH3 input partial pressure for N-polarity InGaN growth on GaN substrates by tri-halide vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Hirasaki, Takahide; Hasegawa, Tomoyasu; Meguro, Misaki; Thieu, Quang Tu; Murakami, Hisashi; Kumagai, Yoshinao; Monemar, Bo; Koukitu, Akinori

    2016-05-01

    The influence of NH3 input partial pressure on N-polarity InGaN grown by tri-halide vapor phase epitaxy was investigated. It was found that surface morphology, solid composition and optical properties were affected by NH3 input partial pressure. As shown in thermodynamic analyses, the indium content increased due to an increase in the driving force for InN deposition caused by increased NH3 input partial pressure. In addition, the deep level emission around 2.1 eV in photoluminescence measurements drastically decreased at higher NH3 input partial pressures. Ab initio calculations and subsequent secondary ion mass spectrometry measurements suggested the reduction of metal-vacancies and/or carbon impurity incorporation in the InGaN layers.

  19. NH3 adsorption on PtM (Fe, Co, Ni) surfaces: Cooperating effects of charge transfer, magnetic ordering and lattice strain

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Satadeep; Yoo, S. J.; Waghmare, Umesh V.; Lee, S. C.

    2016-03-01

    Adsorption of a molecule or group with an atom which is less electronegative than oxygen (O) and directly interacting with the surface is very relevant to development of PtM (M = 3d-transition metal) catalysts with high activity. Here, we present theoretical analysis of the adsorption of NH3 molecule (N being less electronegative than O) on (111) surfaces of PtM (Fe, Co, Ni) alloys using the first principles density functional approach. We find that, while NH3-Pt interaction is stronger than that of NH3 with the elemental M-surfaces, it is weaker than the strength of interaction of NH3 with M-site on the surface of PtM alloy.

  20. NH3 assisted photoreduction and N-doping of graphene oxide for high performance electrode materials in supercapacitors

    NASA Astrophysics Data System (ADS)

    Huang, Haifu; Luo, Guangsheng; Xu, Lianqiang; Lei, Chenglong; Tang, Yanmei; Tang, Shaolong; Du, Youwei

    2015-01-01

    Nitrogen-doped graphene was synthesized by simple photoreduction of graphene oxide (GO) deposited on nickel foam under NH3 atmosphere. The combination of photoreduction and NH3 not only reduces the GO in a shorter time but also induces nitrogen doping easily. The nitrogen doped content of N-rGO@NF reaches a high of 5.99 at% with 15 min of irradiation. The nitrogen-doped graphene deposited on Ni foam (N-rGO@NF) can be directly used as an electrode for supercapacitors, without any conductive agents and polymer binders. In the electrochemical measurement, N-rGO@NF displays remarkable electrochemical performance. In particular, the N-rGO@NF irradiated for 45 min at a high current density of 92.3 A g-1 retained about 77% (190.4 F g-1) of its initial specific capacitance (247.1 F g-1 at 0.31 A g-1). Furthermore, the stable voltage window could be extended to 2.0 and 1.5 V by using Li2SO4 and a mixed Li2SO4/KOH electrolyte, and the maximum energy density was high up to 32.6 and 21.2 Wh kg-1, respectively. The results show that compared to Li2SO4, a mixed electrolyte (Li2SO4/KOH) more efficiently balances the relationship between the high energy densities and high power densities.Nitrogen-doped graphene was synthesized by simple photoreduction of graphene oxide (GO) deposited on nickel foam under NH3 atmosphere. The combination of photoreduction and NH3 not only reduces the GO in a shorter time but also induces nitrogen doping easily. The nitrogen doped content of N-rGO@NF reaches a high of 5.99 at% with 15 min of irradiation. The nitrogen-doped graphene deposited on Ni foam (N-rGO@NF) can be directly used as an electrode for supercapacitors, without any conductive agents and polymer binders. In the electrochemical measurement, N-rGO@NF displays remarkable electrochemical performance. In particular, the N-rGO@NF irradiated for 45 min at a high current density of 92.3 A g-1 retained about 77% (190.4 F g-1) of its initial specific capacitance (247.1 F g-1 at 0.31 A g-1). Furthermore, the stable voltage window could be extended to 2.0 and 1.5 V by using Li2SO4 and a mixed Li2SO4/KOH electrolyte, and the maximum energy density was high up to 32.6 and 21.2 Wh kg-1, respectively. The results show that compared to Li2SO4, a mixed electrolyte (Li2SO4/KOH) more efficiently balances the relationship between the high energy densities and high power densities. Electronic supplementary information (ESI) available: Digital images of nickel foam, GO deposited in nickel foam, N-rGO@NF, and N-rGO@NF electrodes (1.0 × 1.0 cm); Digital images: (1) N-rGO@NF sheet was put into 1 M FeCl3 at room temperature dissolve the Ni metal and (2) a whole N-rGO sheet without Ni foam support after nickel etching; image of film with fragile features after being irradiated by a high-pressure Hg lamp (500 W) in Ar and NH3 atmosphere. See DOI: 10.1039/c4nr05776g

  1. Measurements of NO2, SO2, NH3, HNO3 and O3 in West African urban environments

    NASA Astrophysics Data System (ADS)

    Adon, Marcellin; Yoboué, Véronique; Galy-Lacaux, Corinne; Liousse, Catherine; Diop, Babakar; Doumbia, El Hadji Thierno; Gardrat, Eric; Ndiaye, Seydi Ababacar; Jarnot, Christian

    2016-06-01

    In this paper, we present the measurements of atmospheric gas concentrations of NO2, SO2, NH3, HNO3, and O3 performed at two traffic sites in the context of the POLCA (Pollution of African Capitals) program. These gases were measured using a passive sampling technique from Jan. 2008 to Dec. 2009 at Dakar and from Jun. 2008 to Dec. 2009 at Bamako. In addition, during these periods there were two intensive measurement campaigns (from 19 Jan. to 2 Feb. 2009 at Bamako and from 30 Nov. to 13 Dec. 2009 at Dakar) where real-time active analysers were used to measure NO2 and SO2. Results show that Dakar has a pollution level for NO2 and SO2 higher than that of Bamako, whereas it is lower for NH3 concentrations. Monthly values of NO2 range between 21.1 and 43.5 ppb in Dakar with an annual mean concentration of 31.7 ppb (59.6 μg/m3). NO2 values in Bamako are 9.4-22.6 ppb with a mean of 16.2 ppb. At Dakar, the mean annual NO2 limit value (21.3 ppb or 40 μg/m3) recommended by the World Health Organization (WHO) is widely exceeded. The mean annual concentration of SO2 is 15.9 ppb in Dakar and 3.6 ppb in Bamako. These differences may be explained by different sources of traffic between Bamako (with mainly gasoline vehicles) and Dakar (with mainly diesel vehicles). The annual mean NH3 concentration is about two times higher in Bamako (46.7 ppb) than in Dakar (21.1 ppb). In addition to other possible sources, we assume that the ammonia from domestic fires and uncontrolled garbage incineration may have more influence at Bamako than at Dakar. The mean annual concentrations of HNO3 and O3 are 1.3 ppb and 7.7 ppb in Dakar and 0.6 ppb and 5.1 ppb in Bamako, respectively. Seasonal variation in measured gas concentrations are low in Bamako and more pronounced in Dakar, except for HNO3 and NH3. At Dakar, NO2 and SO2 daily mean concentrations are higher during the weekdays than on weekends, when urban activities are reduced, whereas at Bamako, no significant difference was observed between weekdays and weekends. At Dakar, the daily average concentrations of SO2 in the dry season (11.6-39.6 ppb) widely exceed the WHO air quality guideline (7.6 ppb or 20 μg/m3 as 24-h average). Finally, the spatial distribution of gases at different sites in these two capitals have been investigated and showed higher pollution levels at the traffic sites, especially for NO2, NH3 and SO2, and lower levels in the suburban area, with the exception of ozone.

  2. Development and uncertainty analysis of a high-resolution NH3 emissions inventory and its implications with precipitation over the Pearl River Delta region, China

    NASA Astrophysics Data System (ADS)

    Zheng, J. Y.; Yin, S. S.; Kang, D. W.; Che, W. W.; Zhong, L. J.

    2012-08-01

    Detailed NH3 emission inventories are important to understand various atmospheric processes, air quality modeling studies, air pollution management, and related environmental and ecological issues. A high-resolution NH3 emission inventory was developed based on state-of-the-science techniques, up-to-date information, and advanced expert knowledge for the Pearl River Delta region, China. To provide model-ready emissions input, this NH3 emissions inventory was spatially allocated to 3 km × 3 km grid cells using source-based spatial surrogates with geographical information system (GIS) technology. For NH3 emissions, 9 source categories and 45 subcategories were identified in this region, and detailed spatial and temporal characteristics were investigated. Results show that livestock is by far the most important NH3 emission source by contributing about 61.7% of the total NH3 emissions in this region, followed by nitrogen fertilizer applications (~23.7%) and non-agricultural sources (~14.6%). Uncertainty analysis reveals that the uncertainties associated with different sources vary from source to source and the magnitude of the uncertainty associated with a specific source mainly depends on the degree of accuracy of the emission factors and activity data as well as the technique used to perform the estimate. Further studies should give priority to the hog, broiler, goose subsectors of the livestock source and N fertilizer application source in order to reduce uncertainties of ammonia emission estimates in this region. The validity of the NH3 emissions inventory is justified by the trend analysis of local precipitation compositions, such as pH values, the Ca2++NH4+/SO42-+ NO3- ratios, and NH4+ concentrations which are directly or indirectly related to NH3 emissions.

  3. H-bonding of an NH3 gas molecule to H2O/Pt(111) — A barrier-free path

    NASA Astrophysics Data System (ADS)

    Henkelman, Graeme; Feibelman, Peter J.

    2016-02-01

    Does an OH-flipping barrier hinder H-bond formation between a gas phase molecule and a water monolayer whose free OH ligands point toward a substrate? According to density functional theory calculations for water on Pt(111) the answer is yes, when the molecule is CO or N2, but no when it is NH3. The difference is the relatively strong attraction of the NH3 lone pair to free OH ligands.

  4. B40 fullerene as a highly sensitive molecular device for NH3 detection at low bias: a first-principles study.

    PubMed

    Lin, Bin; Dong, Huilong; Du, Chunmiao; Hou, Tingjun; Lin, Haiping; Li, Youyong

    2016-02-19

    The adsorption of small molecules (NH3, N2, H2 and CH4) on all-boron fullerene B40 is investigated by density functional theory (DFT) and the non-equilibrium Green's function (NEGF) for its potential application in the field of single-molecular gas sensors. The high adsorption energies (-1.09 to -0.75 eV) of NH3 on different adsorption sites of the B40 surface indicate that NH3 strongly chemisorbs to B40. The charge transfer induced by the NH3 adsorption results in a modification of the density of states (DOS) of B40 near the Fermi level, and therefore changes its electronic transport properties. For all possible adsorption sites, the adsorption of NH3 exclusively leads to a decrease of the conductance of B40. Taking into consideration that the non-polar gas molecules (e.g. N2, H2 and CH4) are only physisorbed and show negligible effect on the conductance properties of B40, we would expect that B40 can be used as a single-molecular gas sensor to distinguish NH3 from non-polar gas molecules at low bias. PMID:26775574

  5. In situ IR studies of Co and Ce doped Mn/TiO2 catalyst for low-temperature selective catalytic reduction of NO with NH3

    NASA Astrophysics Data System (ADS)

    Qiu, Lu; Pang, Dandan; Zhang, Changliang; Meng, Jiaojiao; Zhu, Rongshu; Ouyang, Feng

    2015-12-01

    The Mn-Co-Ce/TiO2 catalyst was prepared by wet co-impregnation method for selective catalytic reduction of NO by NH3 in the presence of oxygen. The adsorption and co-adsorption of NH3, NO and O2 on catalysts were investigated by in situ FTIR spectroscopy. The results suggested that addition of cobalt and cerium oxides increased the numbers of acid and redox sites. Especially, the cobalt oxide produced lots of Brønsted acid sites, which favor to the adsorption of coordinated NH3 through NH3 migration. Ce addition improved amide ions formation to reach best NO reduction selectivity. A mechanistic pathway over Mn-Co-Ce/TiO2 was proposed. At low-temperature SCR reaction, coordinated NH3 reacted with NO2-, and amide reacted with NO (ad) or NO (g) to form N2. NO2 was related to the formation of nitrite on Co-contained catalysts and the generation of sbnd NH2- on Ce-contained catalysts. At high temperature, the other branch reaction also occurred between the coordinated NH3 and nitrate species, resulting in N2O yield increase.

  6. Study on the mechanism of NH3-selective catalytic reduction over CuCe x Zr1-x /TiO2

    NASA Astrophysics Data System (ADS)

    Chen, Xujuan; Sun, Xiaoliang; Gong, Cairong; Lv, Gang; Song, Chonglin

    2016-03-01

    Copper-cerium-zirconium catalysts loaded on TiO2 prepared by a wet impregnation method were investigated for NH3-selective catalytic reduction (SCR) of NO x . The reaction mechanism was proposed on the basis of results from in situ diffuse reflectance infrared transform spectroscopy (DRIFT). When NH3 is introduced, ammonia bonded to Lewis acid sites is more stable over CuCe0.25Zr0.75/TiO2 at high temperature, while Brønsted acid sites are more important than Lewis acid sites at low temperature. For the NH3+NO+O2 co-adsorption, NH3 species occupy most of activity sites on CuCe0.25Zr0.75/TiO2 catalyst, and mainly exist in the forms of NH{4/+} (at low temperature) and NH3 coordinated (at high temperature), playing a crucial role in the NH3-SCR process. Two different reaction routes, the L-H mechanism at low temperature ( < 200°C) and the E-R mechanism at high temperature ( > 200°C), are presented for the SCR reaction over CuCe0.25Zr0.75/TiO2 catalyst.

  7. NH3 adsorption on the Lewis and Bronsted acid sites of MoO3 (0 1 0) surface: A cluster DFT study

    NASA Astrophysics Data System (ADS)

    Yan, Zhifeng; Fan, Junyan; Zuo, Zhijun; Li, Zhe; Zhang, Jinshan

    2014-01-01

    The adsorption of NH3 on the Lewis and Bronsted acid sites of MoO3 (0 1 0) surface has been investigated based on the density functional theory (DFT) method using the clusters models. The calculated results indicate that NH3 could strongly adsorb on both the Lewis and Bronsted acid sites in the form of NH3 species and NH4+ respectively, whereas the adsorption on the Lewis acid site is found to be more favorable energetically than that on the Bronsted acid site. For the Lewis acid site Mulliken population analysis shows a donation of lone pairs from NH3 to the surface and activation of N-H bond. The overlaps of N-s, N-p and Mo-d orbitals suggest the strong interaction between N and Mo atoms. For the Bronsted acid site N-H bond is also activated by the formation of NH4+ species. The hybridizations between H and O atoms as well as N and H atoms are the major reasons for strong chemical adsorption of NH3 and the existence of NH4+ species, which partly attributed to the presence of N-H… O hydrogen bonds. Furthermore, the formation of a second Lewis acid site at adjacent or diagonal site results in slight changes of adsorption stability, structural changes and charge redistributions, suggesting its small influence on NH3 adsorption.

  8. Efficient hybrid mesoscopic solar cells with morphology-controlled CH3NH3PbI3-xClx derived from two-step spin coating method.

    PubMed

    Xu, Yuzhuan; Zhu, Lifeng; Shi, Jiangjian; Lv, Songtao; Xu, Xin; Xiao, Junyan; Dong, Juan; Wu, Huijue; Luo, Yanhong; Li, Dongmei; Meng, Qingbo

    2015-02-01

    A morphology-controlled CH3NH3PbI3-xClx film is synthesized via two-step solution deposition by spin-coating a mixture solution of CH3NH3Cl and CH3NH3I onto the TiO2/PbI2 film for the first time. It is revealed that the existence of CH3NH3Cl is supposed to result in a preferential growth along the [110] direction of perovskite, which can improve both the crystallinity and surface coverage of perovskite and reduce the pinholes. Furthermore, the formation process of CH3NH3PbI3-xClx perovskite is explored, in which intermediates containing chlorine are suggested to exist. 13.12% of power conversion efficiency has been achieved for the mesoscopic cell, higher than 12.08% of power conversion efficiency of the devices fabricated without CH3NH3Cl via the same process. The improvement mainly lies in the increasing open-circuit photovoltage which is ascribed to the reduction of reverse saturation current density. PMID:25587643

  9. B40 fullerene as a highly sensitive molecular device for NH3 detection at low bias: a first-principles study

    NASA Astrophysics Data System (ADS)

    Lin, Bin; Dong, Huilong; Du, Chunmiao; Hou, Tingjun; Lin, Haiping; Li, Youyong

    2016-02-01

    The adsorption of small molecules (NH3, N2, H2 and CH4) on all-boron fullerene B40 is investigated by density functional theory (DFT) and the non-equilibrium Green’s function (NEGF) for its potential application in the field of single-molecular gas sensors. The high adsorption energies (-1.09 to -0.75 eV) of NH3 on different adsorption sites of the B40 surface indicate that NH3 strongly chemisorbs to B40. The charge transfer induced by the NH3 adsorption results in a modification of the density of states (DOS) of B40 near the Fermi level, and therefore changes its electronic transport properties. For all possible adsorption sites, the adsorption of NH3 exclusively leads to a decrease of the conductance of B40. Taking into consideration that the non-polar gas molecules (e.g. N2, H2 and CH4) are only physisorbed and show negligible effect on the conductance properties of B40, we would expect that B40 can be used as a single-molecular gas sensor to distinguish NH3 from non-polar gas molecules at low bias.

  10. Laser-induced thermal desorption of aniline from silica surfaces

    NASA Astrophysics Data System (ADS)

    Voumard, Pierre; Zenobi, Renato

    1995-10-01

    A complete study on the energy partitioning upon laser-induced thermal desorption of aniline from silica surfaces was undertaken. The measurements include characterization of the aniline-quartz adsorption system using temperature-programmed desorption, the extrapolation of quasiequilibrium desorption temperatures to the regime of laser heating rates on the order of 109-1010 K/s by computational means, measurement of the kinetic energy distributions of desorbing aniline using a pump-probe method, and the determination of internal energies with resonance-enhanced multiphoton ionization spectroscopy. The measurements are compared to calculations of the surface temperature rise and the resulting desorption rates, based on a finite-difference mathematical description of pulsed laser heating. While the surface temperature of laser-heated silica reaches about 600-700 K at the time of desorption, the translational temperature of laser-desorbed aniline was measured to be Tkin=420±60 K, Tvib was 360±60 K, and Trot was 350±100 K. These results are discussed using different models for laser-induced thermal desorption from surfaces.

  11. Electron-Temperature Dependence of the Recombination of NH4(+)((NH3)(sub n) Ions with Electrons

    NASA Technical Reports Server (NTRS)

    Skrzypkowski, M. P.; Johnson, R.

    1997-01-01

    The two-body recombination of NH4(+)(NH3)(sub 2,3) cluster-ions with electrons has been studied in an afterglow experiment in which the electron temperature T, was elevated by radio-frequency heating from 300 K up to 900 K. The recombination coefficients for the n = 2 and n = 3 cluster ions were found to be equal, alpha(sub 2, sup(2)) = alpha(sub 3, sup(2)) = (4.8 +/- 0.5) x 10(exp - 6)cu cm/s, and to vary with electron temperature as T(sub c, sup -0.65) rather than to be nearly temperature-independent as had been inferred from measurements in microwave-heated plasmas.

  12. Vibrational signatures of hydrogen bonding in the protonated ammonia clusters NH4+(NH3)1-4

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Kühn, O.; Santambrogio, G.; Goebbert, D. J.; Asmis, K. R.

    2008-12-01

    The gas phase vibrational spectroscopy of the protonated ammonia dimer N2H7+, a prototypical system for strong hydrogen bonding, is studied in the spectral region from 330 to 1650 cm-1 by combining infrared multiple photon dissociation and multidimensional quantum mechanical simulations. The fundamental transition of the antisymmetric proton stretching vibration is observed at 374 cm-1 and assigned on the basis of a six-dimensional model Hamiltonian, which predicts this transition at 471 cm-1. Photodissociation spectra of the larger protonated ammonia clusters NH4+(NH3)n with n =2-4 are also reported for the range from 1050 to 1575 cm-1. The main absorption features can be assigned within the harmonic approximation, supporting earlier evidence that hydrogen bonding in these clusters is considerably weaker than for n =1.

  13. Toward a chemiresistive ammonia (NH3) gas sensor based on viral-templated gold nanoparticles embedded in polypyrrole nanowires

    NASA Astrophysics Data System (ADS)

    Yan, Yiran; Zhang, Miluo; Su, Heng Chia; Myung, Nosang V.; Haberer, Elaine D.

    2014-08-01

    Preliminary studies toward the assembly of a gold-polypyrrole (PPy) peapod-like chemiresistive ammonia (NH3) gas sensors are presented. The proposed synthesis process will use electropolymerization to embed gold nanoparticles in polypyrrole nanowires. Viral-templating of gold nanoparticles and PPy electrodeposition via cyclic voltammetry are the focus of this investigation. A gold-binding M13 bacteriophage was used as a bio-template to assemble continuous chains of gold nanoparticles on interdigitated Pt working electrodes. The dimensions of the resulting nanowire-like structures were examined and the electrical resistance measured. PPy films were electropolymerized using an interdigitated planar, Pt electrode integrated counter and reference electrode. Morphological characterization of the polymer films was completed.

  14. Growth of bulk AlN crystals by vapor-phase epitaxy from atomic Al and NH3

    NASA Astrophysics Data System (ADS)

    Pogorel'skii, M. Yu.; Alekseev, A. N.; Pogorel'skii, Yu. V.; Shkurko, A. P.

    2015-09-01

    A new approach to obtaining bulk AlN single crystals by vapor-phase epitaxy has been tested. NH3 and Al vapor were used as growth reagents. The following ranges of growth parameters were admissible for the laboratory equipment (experimental growth installation): temperatures of 1050-1500°C at ammonia flow rates of up to 50 sccm and pressures on the order of 10-5-10-4 bar, growth rates of up to 200 μm h-1. At a temperature of 1450°C, samples of strained bulk block AlN crystals with thicknesses of up to 200 μm were obtained in the wurtzite phase in the [0001] direction on MBE templates based on sapphire substrates with a diameter of 2″.

  15. A theoretical investigation of gaseous absorption by water droplets from SO2-HNO3-NH3-CO2-HCl mixtures

    NASA Technical Reports Server (NTRS)

    Adewuyi, Y. G.; Carmichael, G. R.

    1982-01-01

    A physical-chemical model is developed and used to investigate gaseous absorption by water droplets from trace gas mixtures. The model is an extension of that of Carmichael and Peters (1979) and includes the simultaneous absorption of SO2, NH3, HNO3, CO2, and HCl. Gas phase depletion is also considered. Presented results demonstrate that the absorption behavior of raindrops is strongly dependent on drop size, fall distance, trace gas concentrations, and the chemical and physical properties of the constituents of the mixture. In addition, when gas phase depletion is considered, the absorption rates and equilibrium values are also dependent on the precipitation rate itself. Also, the trace constituents liquid phase concentrations may be a factor of six or more lower when gas depletion is considered then when the depletion is ignored. However, the hydrogen ion concentration may be insensitive to the gas phase depletion.

  16. Two mixed-NH3/amine platinum (II) anticancer complexes featuring a dichloroacetate moiety in the leaving group

    NASA Astrophysics Data System (ADS)

    Liu, Weiping; Su, Jia; Jiang, Jing; Li, Xingyao; Ye, Qingsong; Zhou, Hongyu; Chen, Jialin; Li, Yan

    2013-08-01

    Two mixed-NH3/amine platinum (II) complexes of 3-dichoroacetoxylcyclobutane-1, 1-dicarboxylate have been prepared in the present study and characterized by elemental analysis and IR, HPLC-MS and 1H, 13C-NMR. The complexes exist in equilibrium between two position isomeric forms and undergo hydrolysis reaction in aqueous solution, releasing the platinum pharmacophores and dichloroacetate which is a small-molecular cell apoptosis inducer. Both complexes were evaluated for in vitro cytotoxic profile in A549, SGC-7901 and SK-OV-3 caner cells as well as in BEAS-2B normal cells. They exhibit markedly cytoxicity toward cancer cells by selectively inducing the apoptosis of cancer cells, whereas leaving normal cells less affected. They have also the ability to overcome the resistance of SK-OV-3 cancer cells to cisplatin. Our findings offer an alternative novel way to develop platinum drugs which can both overcome the drug resistance and selectively target tumor cells.

  17. Laboratory measurements of the microwave opacity of gaseous ammonia (NH3) under simulated conditions for the Jovian atmosphere

    NASA Astrophysics Data System (ADS)

    Steffes, P. G.; Jenkins, J. M.

    1987-10-01

    Gaseous ammonia (NH3) has long been recognized as a primary source of microwave opacity in the atmosphere of Jupiter. In order to more accurately infer the abundance and distribution of ammonia from radio emission measurements in the 1- to 20-cm wavelength range and radio occultation measurements at 3.6 and 13 cm, the authors have made measurements of the microwave opacity from gaseous ammonia under simulated conditions for the Jovian atmosphere. Measurements of ammonia absorptivity were made at five frequencies from 1.62 to 21.7 GHz (wavelengths from 18.5 to 1.38 cm), at temperatures from 178 to 300K, and at pressures from 1 to 6 atm, in a 90% hydrogen/10% helium atmosphere.

  18. The optoelectronic role of chlorine in CH3NH3PbI3(Cl)-based perovskite solar cells

    PubMed Central

    Chen, Qi; Zhou, Huanping; Fang, Yihao; Stieg, Adam Z.; Song, Tze-Bin; Wang, Hsin-Hua; Xu, Xiaobao; Liu, Yongsheng; Lu, Shirong; You, Jingbi; Sun, Pengyu; McKay, Jeff; Goorsky, Mark S.; Yang, Yang

    2015-01-01

    Perovskite photovoltaics offer a compelling combination of extremely low-cost, ease of processing and high device performance. The optoelectronic properties of the prototypical CH3NH3PbI3 can be further adjusted by introducing other extrinsic ions. Specifically, chlorine incorporation has been shown to affect the morphological development of perovksite films, which results in improved optoelectronic characteristics for high efficiency. However, it requires a deep understanding to the role of extrinsic halide, especially in the absence of unpredictable morphological influence during film growth. Here we report an effective strategy to investigate the role of the extrinsic ion in the context of optoelectronic properties, in which the morphological factors that closely correlate to device performance are mostly decoupled. The chlorine incorporation is found to mainly improve the carrier transport across the heterojunction interfaces, rather than within the perovskite crystals. Further optimization according this protocol leads to solar cells achieving power conversion efficiency of 17.91%. PMID:26068804

  19. Effect of humidity on the a.c. impedance of CH3NH3SnCl3 hybrid films

    NASA Astrophysics Data System (ADS)

    Mosca, R.; Ferro, P.; Besagni, T.; Calestani, D.; Chiarella, F.; Licci, F.

    2011-09-01

    Impedance spectroscopy measurements show that complex conductivity of thermally ablated CH3NH3SnCl3 films is strongly enhanced when humidity increases. Coplanar two-electrode test devices are modeled through an equivalent circuit comprising one resistance and two constant phase elements. It is shown that the influence of ambient humidity is mainly resistive. The dynamic responses of the devices to humidification/dehumidification cycles point out that the a.c. current varies by more than three orders of magnitude when humidity is varied between dry air and 80% relative humidity. The rise times are few hundred seconds while fall times are as short as few tens of seconds. This observation suggests that impedance variations are determined by mechanisms involving loosely bound water molecules physisorbed at the surface of the hybrid film. The results obtained are discussed in terms of protonic conduction.

  20. Theory of electronic structure and nuclear quadrupole interactions in the BF3-NH3 complex and methyl derivatives

    NASA Astrophysics Data System (ADS)

    Pink, R. H.; Dubey, Archana; Mahato, Dip N.; Badu, S. R.; Scheicher, R. H.; Mahanti, Mahendra K.; Huang, M. B.; Saha, H. P.; Chow, Lee; Das, T. P.

    Magnetic Hyperfine and Nuclear Quadrupole Interactions (HPI and NQI) are now important tools for characterization of systems of interest in materials research and industry. Boron-Trifluoride is an inorganic compound that is very important in this respect as a catalyst in chemical physics research and industry, forming complexes in the process with compounds like ammonia, water and methyl alcohol. The present paper deals with the BP3-NH3 complex and methyl derivatives BP3NHx(CH3)3-x for which we have studied the electronic structures, binding energies, and 19F* (I=5/2) nuclear quadrupole interactions using the first-principles Hartree-Fock-Roothaan procedure combined with electron correlation effects. Our results for the 19F* nuclear quadrupole coupling constant (e 2qQ/h) in units of MHz compare well with experiment. Trends in the binding energies and NQI parameters between the complexes are discussed.

  1. Theory of electronic structure and nuclear quadrupole interactions in the BF3 NH3 complex and methyl derivatives

    NASA Astrophysics Data System (ADS)

    Pink, R. H.; Dubey, Archana; Mahato, Dip N.; Badu, S. R.; Scheicher, R. H.; Mahanti, Mahendra K.; Huang, M. B.; Saha, H. P.; Chow, Lee; Das, T. P.

    2007-04-01

    Magnetic Hyperfine and Nuclear Quadrupole Interactions (HFI and NQI) are now important tools for characterization of systems of interest in materials research and industry. Boron-Trifluoride is an inorganic compound that is very important in this respect as a catalyst in chemical physics research and industry, forming complexes in the process with compounds like ammonia, water and methyl alcohol. The present paper deals with the BF3 NH3 complex and methyl derivatives BF3NHx(CH3)3-x for which we have studied the electronic structures, binding energies, and 19F* ( I = 5/2) nuclear quadrupole interactions using the first-principles Hartree Fock Roothaan procedure combined with electron correlation effects. Our results for the 19F* nuclear quadrupole coupling constant ( e 2 qQ/ h) in units of MHz compare well with experiment. Trends in the binding energies and NQI parameters between the complexes are discussed.

  2. The optoelectronic role of chlorine in CH3NH3PbI3(Cl)-based perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Chen, Qi; Zhou, Huanping; Fang, Yihao; Stieg, Adam Z.; Song, Tze-Bin; Wang, Hsin-Hua; Xu, Xiaobao; Liu, Yongsheng; Lu, Shirong; You, Jingbi; Sun, Pengyu; McKay, Jeff; Goorsky, Mark S.; Yang, Yang

    2015-06-01

    Perovskite photovoltaics offer a compelling combination of extremely low-cost, ease of processing and high device performance. The optoelectronic properties of the prototypical CH3NH3PbI3 can be further adjusted by introducing other extrinsic ions. Specifically, chlorine incorporation has been shown to affect the morphological development of perovksite films, which results in improved optoelectronic characteristics for high efficiency. However, it requires a deep understanding to the role of extrinsic halide, especially in the absence of unpredictable morphological influence during film growth. Here we report an effective strategy to investigate the role of the extrinsic ion in the context of optoelectronic properties, in which the morphological factors that closely correlate to device performance are mostly decoupled. The chlorine incorporation is found to mainly improve the carrier transport across the heterojunction interfaces, rather than within the perovskite crystals. Further optimization according this protocol leads to solar cells achieving power conversion efficiency of 17.91%.

  3. Controlled growth of CH3NH3PbI3 nanowires in arrays of open nanofluidic channels.

    PubMed

    Spina, Massimo; Bonvin, Eric; Sienkiewicz, Andrzej; Forró, László; Horváth, Endre

    2016-01-01

    Spatial positioning of nanocrystal building blocks on a solid surface is a prerequisite for assembling individual nanoparticles into functional devices. Here, we report on the graphoepitaxial liquid-solid growth of nanowires of the photovoltaic compound CH3NH3PbI3 in open nanofluidic channels. The guided growth, visualized in real-time with a simple optical microscope, undergoes through a metastable solvatomorph formation in polar aprotic solvents. The presently discovered crystallization leads to the fabrication of mm(2)-sized surfaces composed of perovskite nanowires having controlled sizes, cross-sectional shapes, aspect ratios and orientation which have not been achieved thus far by other deposition methods. The automation of this general strategy paves the way towards fabrication of wafer-scale perovskite nanowire thin films well-suited for various optoelectronic devices, e.g. solar cells, lasers, light-emitting diodes and photodetectors. PMID:26806213

  4. Controlled growth of CH3NH3PbI3 nanowires in arrays of open nanofluidic channels

    NASA Astrophysics Data System (ADS)

    Spina, Massimo; Bonvin, Eric; Sienkiewicz, Andrzej; Forró, László; Horváth, Endre

    2016-01-01

    Spatial positioning of nanocrystal building blocks on a solid surface is a prerequisite for assembling individual nanoparticles into functional devices. Here, we report on the graphoepitaxial liquid-solid growth of nanowires of the photovoltaic compound CH3NH3PbI3 in open nanofluidic channels. The guided growth, visualized in real-time with a simple optical microscope, undergoes through a metastable solvatomorph formation in polar aprotic solvents. The presently discovered crystallization leads to the fabrication of mm2-sized surfaces composed of perovskite nanowires having controlled sizes, cross-sectional shapes, aspect ratios and orientation which have not been achieved thus far by other deposition methods. The automation of this general strategy paves the way towards fabrication of wafer-scale perovskite nanowire thin films well-suited for various optoelectronic devices, e.g. solar cells, lasers, light-emitting diodes and photodetectors.

  5. Influence of annealing temperature on the crystallization and ferroelectricity of perovskite CH3NH3PbI3 film

    NASA Astrophysics Data System (ADS)

    Wang, Fangfang; Meng, Dechao; Li, Xiaoning; Zhu, Zhu; Fu, Zhengping; Lu, Yalin

    2015-12-01

    Organometal halide perovskite materials are emerging as solar cell materials, but the understanding of its performance is not yet enough, especially in its ferroelectricity which is important for the separation of photo-generated carriers. In this paper, we report investigations on influences of annealing temperature on the ferroelectricity of solution-processed methylammonium lead triiodide (CH3NH3PbI3) thin film. It is found that annealing temperature has significant effect on the crystallinity and the crystal size, which further affects the ferroelectricity and the luminescence property. It indicates that the crystallization degree of the thin film and the uniformity of crystal growth are gradually getting better, and the phase contrast of positive polarization areas and negative polarization areas are gradually strengthened.

  6. Electronic transport in organometallic perovskite CH3NH3PbI3: The role of organic cation orientations

    NASA Astrophysics Data System (ADS)

    Berdiyorov, G. R.; El-Mellouhi, F.; Madjet, M. E.; Alharbi, F. H.; Rashkeev, S. N.

    2016-02-01

    Density functional theory in combination with the nonequilibrium Green's function formalism is used to study the electronic transport properties of methylammonium lead-iodide perovskite CH3NH3PbI3. Electronic transport in homogeneous ferroelectric and antiferroelectric phases, both of which do not contain any charged domain walls, is quite similar. The presence of charged domain wall drastically (by about an order of magnitude) enhances the electronic transport in the lateral direction. The increase of the transmission originates from the smaller variation of the electrostatic potential profile along the charged domain walls. This fact may provide a tool for tuning transport properties of such hybrid materials by manipulating molecular cations having dipole moment.

  7. The optoelectronic role of chlorine in CH3NH3PbI3(Cl)-based perovskite solar cells.

    PubMed

    Chen, Qi; Zhou, Huanping; Fang, Yihao; Stieg, Adam Z; Song, Tze-Bin; Wang, Hsin-Hua; Xu, Xiaobao; Liu, Yongsheng; Lu, Shirong; You, Jingbi; Sun, Pengyu; McKay, Jeff; Goorsky, Mark S; Yang, Yang

    2015-01-01

    Perovskite photovoltaics offer a compelling combination of extremely low-cost, ease of processing and high device performance. The optoelectronic properties of the prototypical CH3NH3PbI3 can be further adjusted by introducing other extrinsic ions. Specifically, chlorine incorporation has been shown to affect the morphological development of perovksite films, which results in improved optoelectronic characteristics for high efficiency. However, it requires a deep understanding to the role of extrinsic halide, especially in the absence of unpredictable morphological influence during film growth. Here we report an effective strategy to investigate the role of the extrinsic ion in the context of optoelectronic properties, in which the morphological factors that closely correlate to device performance are mostly decoupled. The chlorine incorporation is found to mainly improve the carrier transport across the heterojunction interfaces, rather than within the perovskite crystals. Further optimization according this protocol leads to solar cells achieving power conversion efficiency of 17.91%. PMID:26068804

  8. Selective detection toward quercetin and kaempferol on NH3-plasma treated carbon nanotubes modified glassy carbon electrode.

    PubMed

    Song, Jing-Jing; Lu, Yong; Zhu, Si-Wei; Huang, Qin-An; Wei, Yan

    2015-01-01

    NH3-plasma treated multi-walled carbon nanotubes (pn-MWCNTs) were prepared based on the plasma technique and developed as sensing materials for detection of quercetin and kaempferol with the differential pulse voltammetry (DPV) and amperometric measurement. Such experimental parameters as pH values, accumulation potential and accumulation time were carefully investigated. The pn-MWCNTs modified electrode (pn-MWCNTs/GCE) was further explored for the analysis of quercetin and kaempferol in diluted blood serum and average recovery rates of 96.91 and 100.5% were obtained, respectively. In addition, the interference and stability measurements were evaluated under the optimized experimental conditions. More importantly, selective detection toward quercetin and kaempferol was achieved, and the proposed electrochemical sensing strategy was available to distinguish substances with similar oxidation potential. PMID:25765278

  9. Photolysis products of CO, NH3 aND H2O and their significance to reactions on interstellar grains

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.

    1986-01-01

    With the increase in evidence that interstellar grains are the basic building blocks of comets and with the realization that comet collisions with the earth have probably occured at a much higher frequency than earlier assumed it may be presumed that interstellar dust chemistry played an important role in the early chemistry of the earth. As a part of the study of the photochemical processes taking place on interstellar grains the photolysis of mixtures of CO, NH3 and H2O was performed at 10 K, 77K and 298K. The reaction products were determined by GC/MS and HPLC analysis to be lactic acid, glycolic acid, hydroxyacetamide, urea, biuret, oxamic acid, oxamide, glyceric acid and glyceramide. Ethylene glycol and glycerol were also detected but is is not clear at present whether these are true photoproducts or contaminants. The mechanism of formation of these molecules are discussed as well as their possible significance to the origins of life.

  10. Ultrasensitive 1D field-effect phototransistors: CH3NH3PbI3 nanowire sensitized individual carbon nanotubes.

    PubMed

    Spina, M; Náfrádi, B; Tóháti, H M; Kamarás, K; Bonvin, E; Gaal, R; Forró, L; Horváth, E

    2016-02-25

    Field-effect phototransistors were fabricated based on individual carbon nanotubes (CNTs) sensitized by CH3NH3PbI3 nanowires (MAPbI3NWs). These devices represent light responsivities of R = 7.7 × 10(5) A W(-1) under low-lighting conditions in the nW mm(-2) range, unprecedented among CNT-based photodetectors. At high incident power (∼1 mW mm(-2)), light soaking results in a negative photocurrent, turning the device insulating. We interpret the phenomenon as a result of efficient free photoexcited charge generation and charge transfer of photoexcited holes from the perovskite to the carbon nanotube. The charge transfer improves conductance by increasing the number of carriers, but leaves electrons behind. At high illumination intensity their random electrostatic potential quenches mobility in the nanotube. PMID:26864708

  11. Molecular dynamics of the methylammonium cation in [CH3NH3]5Bi2Cl11.

    PubMed

    Medycki, W; Piślewski, N; Jakubas, R

    1993-09-01

    The 1H relaxation times T1 of methylammonium in chlorobismuthate(III) were measured in the temperature range from 50 to 270 K with a SXP 4/100 Bruker pulse spectrometer at 55.2 MHz. It was found that the T1 temperature dependence has three minima. The individual relaxation rates of the three-proton groups can be described by the O'Reilly and Tsang formula. The results obtained from the fitting procedure, using the typical Woessner formula for complex compounds, allow to conclude that the low-temperature minimum is due to the relaxation of all CH3 groups and the other two minima are due to the relaxation of two and four NH3 groups, respectively. This assignment is based on the X-ray results showing that methylammonium cations are differently bonded in this crystal. PMID:7827971

  12. Mobile Ion Induced Slow Carrier Dynamics in Organic-Inorganic Perovskite CH3NH3PbBr3.

    PubMed

    Chen, Sheng; Wen, Xiaoming; Sheng, Rui; Huang, Shujuan; Deng, Xiaofan; Green, Martin A; Ho-Baillie, Anita

    2016-03-01

    Here, we investigate photoluminescence (PL) and time-resolved photoluminescence (TRPL) in CH3NH3PbBr3 perovskite under continuous illumination, using optical and electro-optical techniques. Under continuous excitation at constant intensity, PL intensity and PL decay (carrier recombination) exhibit excitation intensity dependent reductions in the time scale of seconds to minutes. The enhanced nonradiative recombination is ascribed to light activated negative ions and their accumulation which exhibit a slow dynamics in a time scale of seconds to minutes. The observed result suggests that the organic-inorganic hybrid perovskite is a mixed electronic-ionic semiconductor. The key findings in this work suggest that ions are photoactivated or electro-activated and their accumulation at localized sites can result in a change of carrier dynamics. The findings are therefore useful for the understanding of instability of perovskite solar cells and shed light on the necessary strategies for performance improvement. PMID:26863286

  13. The catalytic effect of the NH3 base on the chemical events in the caryolene-forming carbocation cascade.

    PubMed

    Ortega, Daniela E; Nguyen, Quynh Nhu N; Tantillo, Dean J; Toro-Labbé, Alejandro

    2016-05-01

    Caryolene formation occur asynchronously in a concerted way through carbocationic rearrangements involving the generation of a secondary or a tertiary carbocation whether the reaction proceeds in the absence or in the presence of NH3 , respectively. Both caryolene formation mechanisms are analyzed within the general framework of the reaction force; the reaction force constant is used to gain insights into the synchronicity of the mechanisms and the reaction electronic flux helps to characterize the electronic activity taking place during the reaction. DFT calculations at the B3LYP/6-31+G(d,p) level show a clear difference in the mechanisms of the base promoted or base free caryolene formation reactions. © 2016 Wiley Periodicals, Inc. PMID:26833740

  14. Kinetics of ferroelectric switching in unipolar (CH3NH3)5Bi2Br11 crystal

    NASA Astrophysics Data System (ADS)

    Rogowski, R. Z.; Matyjasek, K.; Jakubas, R.

    2005-12-01

    Ferroelectric switching in unipolar (CH3NH3)5Bi2Br11 crystal has been studied by optical observation of the domain structure in low electric fields and switching current registration in high fields. We discuss investigations on the temporal behaviour of the electric polarization in static electric fields as well as polarization decay after removal of the electric field. The backswitching process appears to have a correlation to a defect-induced internal field in the crystal. For the interpretation of experimental data we utilize the classical nucleation and growth model of phase transformation (e.g. Avrami-Kolmogorov theory). An analysis assuming a statistical distribution of the characteristic domain growth times is proposed to explain and to find the functional form of the experimental data.

  15. Low surface recombination velocity in solution-grown CH3NH3PbBr3 perovskite single crystal.

    PubMed

    Yang, Ye; Yan, Yong; Yang, Mengjin; Choi, Sukgeun; Zhu, Kai; Luther, Joseph M; Beard, Matthew C

    2015-01-01

    Organic-inorganic hybrid perovskites are attracting intense research effort due to their impressive performance in solar cells. While the carrier transport parameters such as mobility and bulk carrier lifetime shows sufficient characteristics, the surface recombination, which can have major impact on the solar cell performance, has not been studied. Here we measure surface recombination dynamics in CH3NH3PbBr3 perovskite single crystals using broadband transient reflectance spectroscopy. The surface recombination velocity is found to be 3.4±0.1 × 10(3) cm s(-1), ∼2-3 orders of magnitude lower than that in many important unpassivated semiconductors employed in solar cells. Our result suggests that the planar grain size for the perovskite thin films should be larger than ∼30 μm to avoid the influence of surface recombination on the effective carrier lifetime. PMID:26245855

  16. Controlled growth of CH3NH3PbI3 nanowires in arrays of open nanofluidic channels

    PubMed Central

    Spina, Massimo; Bonvin, Eric; Sienkiewicz, Andrzej; Forró, László; Horváth, Endre

    2016-01-01

    Spatial positioning of nanocrystal building blocks on a solid surface is a prerequisite for assembling individual nanoparticles into functional devices. Here, we report on the graphoepitaxial liquid-solid growth of nanowires of the photovoltaic compound CH3NH3PbI3 in open nanofluidic channels. The guided growth, visualized in real-time with a simple optical microscope, undergoes through a metastable solvatomorph formation in polar aprotic solvents. The presently discovered crystallization leads to the fabrication of mm2-sized surfaces composed of perovskite nanowires having controlled sizes, cross-sectional shapes, aspect ratios and orientation which have not been achieved thus far by other deposition methods. The automation of this general strategy paves the way towards fabrication of wafer-scale perovskite nanowire thin films well-suited for various optoelectronic devices, e.g. solar cells, lasers, light-emitting diodes and photodetectors. PMID:26806213

  17. NH3 Trace Detection Using a Tunable Lead-Salt Diode Laser Near 10 μm

    NASA Astrophysics Data System (ADS)

    Dallah, M.; Salloum, A.

    2015-11-01

    We demonstrate a closed path ammonia gas sensor based on a tunable lead-salt diode laser. In order to measure NH3 concentrations, the laser is scanned over two absorption lines 992.68 and 992.45 cm-1 of the ν2 vibrational band. These lines have free interference patterns with other species in the atmosphere. The experiments are performed with an ammonia mixture in the air at room temperature in an optical multi-path White cell. In our preliminary experiments, a detection limit of ~4 ppb is achieved using direct absorption at 100 mbar pressure and 15 m path length. A detection limit of 0.2 ppb can be reached.

  18. Ultrasensitive 1D field-effect phototransistors: CH3NH3PbI3 nanowire sensitized individual carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Spina, M.; Náfrádi, B.; Tóháti, H. M.; Kamarás, K.; Bonvin, E.; Gaal, R.; Forró, L.; Horváth, E.

    2016-02-01

    Field-effect phototransistors were fabricated based on individual carbon nanotubes (CNTs) sensitized by CH3NH3PbI3 nanowires (MAPbI3NWs). These devices represent light responsivities of R = 7.7 × 105 A W-1 under low-lighting conditions in the nW mm-2 range, unprecedented among CNT-based photodetectors. At high incident power (~1 mW mm-2), light soaking results in a negative photocurrent, turning the device insulating. We interpret the phenomenon as a result of efficient free photoexcited charge generation and charge transfer of photoexcited holes from the perovskite to the carbon nanotube. The charge transfer improves conductance by increasing the number of carriers, but leaves electrons behind. At high illumination intensity their random electrostatic potential quenches mobility in the nanotube.Field-effect phototransistors were fabricated based on individual carbon nanotubes (CNTs) sensitized by CH3NH3PbI3 nanowires (MAPbI3NWs). These devices represent light responsivities of R = 7.7 × 105 A W-1 under low-lighting conditions in the nW mm-2 range, unprecedented among CNT-based photodetectors. At high incident power (~1 mW mm-2), light soaking results in a negative photocurrent, turning the device insulating. We interpret the phenomenon as a result of efficient free photoexcited charge generation and charge transfer of photoexcited holes from the perovskite to the carbon nanotube. The charge transfer improves conductance by increasing the number of carriers, but leaves electrons behind. At high illumination intensity their random electrostatic potential quenches mobility in the nanotube. Electronic supplementary information (ESI) available: Infrared and Raman spectroscopy with additional electronic transfer characterization. See DOI: 10.1039/c5nr06727h

  19. Rh proteins vs Amt proteins: an organismal and phylogenetic perspective on CO2 and NH3 gas channels.

    PubMed

    Peng, J; Huang, C H

    2006-01-01

    Rh (Rhesus) proteins are homologues of ammonium transport (Amt) proteins. Physiological and structural evidence shows that Amt proteins are gas channels for NH(3), but the substrate of Rh proteins, be it CO2 as shown in green alga, or NH3/NH4+ as shown in mammalian cells, remains disputed. We assembled a large dataset generated of Rh and Amt to explore how Rh originated from and evolved independently of Amt relatives. Analysis of this rich data implies that Rh was split from Amt first to emerge in archaeal species. The Rh ancestor underwent divergence and duplication along speciation, leading to neofunctionalization and subfunctionalization of the Rh family. The characteristic organismal distribution of Rh vs. Amt reflects their early separation and subsequent independent evolution: they coexist in microbes and invertebrates but do not in fungi, vascular plants or vertebrates. Rh gene-duplication was prominent in vertebrates: while epithelial RhBG/RhCG displayed strong purifying selection, erythroid Rh30 and RhAG experienced different episodes of positive selection in each of which adaptive evolution occurred at certain time points and in a few codon sites. Mammalian Rh30 and RhAG were subject to particularly strong positive selection in some codon sites in the lineage from rodents to human. The grounds of this adaptive evolution may be driven by the necessity to increase the surface/volume ratio of biconcave erythrocytes for facilitative gas diffusion. Altogether, these results are consistent with Rh proteins not being the orthologue of Amt proteins but having gained the function for CO2/HCO3- transport, with important roles in systemic pH regulation. PMID:16564193

  20. VizieR Online Data Catalog: W51 Main NH3 and CH3OH data cubes

    NASA Astrophysics Data System (ADS)

    Goddi, C.; Ginsburg, A.; Zhang, Q.

    2016-04-01

    Observations of NH3 toward the W51 complex were conducted usi Karl G. Jansky Very Large Array (JVLA) of the National Radio Astronomy Observatory (NRAO)1 in the B configuration. By using the broadband JVLA K- and Ka-band receivers, we observed a total of five metastable inversion transitions of NH3: (J,K) = (6, 6), (7, 7), (9, 9), (10, 10), and (13, 13) at the 1cm band with frequencies ranging from ~25GHz for the (6, 6) line to ~33GHz for the (13, 13) line. Transitions were observed in pairs of independently tunable basebands during 6h tracks (two targets per track: W51 - this paper; NGC 7538 IRS1 - Paper I, Goddi et al., 2015A&A...573A.108G) on three different dates in 2012: the (6, 6) and (7, 7) lines on May 31 at K-band, the (9, 9) and (13, 13) lines on June 21, and the (10, 10) transition on August 7, both at Ka-band. Each baseband had eight sub-bands with a 4MHz bandwidth (~40km/s at 30GHz), providing a total coverage of 32MHz (~320km/s at 30GHz). Each sub-band consisted of 128 channels with a separation of 31.25kHz (~0.3km/s at 30GHz). The typical on-source integration time was about 80min. Each transition was observed with fast switching, where 80s scans on target were alternated with 40s scans on the nearby (1.2° on the sky) QSO J1924+1540 (measured flux density 0.6-0.7Jy, depending on frequency). We derived absolute flux calibration from observations of 3C 48 (Sν=0.5-0.7Jy, depending on frequency), and bandpass calibration from observations of 3C 84 (Sν=27-29Jy, depending on frequency). (2 data files).

  1. Emissions of NO and NH3 from a Typical Vegetable-Land Soil after the Application of Chemical N Fertilizers in the Pearl River Delta

    PubMed Central

    Li, Dejun

    2013-01-01

    Cropland soil is an important source of atmospheric nitric oxide (NO) and ammonia (NH3). Chinese croplands are characterized by intensive management, but limited information is available with regard to NO emissions from croplands in China and NH3 emissions in south China. In this study, a mesocosm experiment was conducted to measure NO and NH3 emissions from a typical vegetable-land soil in the Pearl River Delta following the applications of 150 kg N ha−1 as urea, ammonium nitrate (AN) and ammonium bicarbonate (ABC), respectively. Over the sampling period after fertilization (72 days for NO and 39 days for NH3), mean NO fluxes (± standard error of three replicates) in the control and urea, AN and ABC fertilized mesocosms were 10.9±0.9, 73.1±2.9, 63.9±1.8 and 66.0±4.0 ng N m−2 s−1, respectively; mean NH3 fluxes were 8.9±0.2, 493.6±4.4, 144.8±0.1 and 684.7±8.4 ng N m−2 s−1, respectively. The fertilizer-induced NO emission factors for urea, AN and ABC were 2.6±0.1%, 2.2±0.1% and 2.3±0.2%, respectively. The fertilizer-induced NH3 emission factors for the three fertilizers were 10.9±0.2%, 3.1±0.1% and 15.2±0.4%, respectively. From the perspective of air quality protection, it would be better to increase the proportion of AN application due to its lower emission factors for both NO and NH3. PMID:23527173

  2. Passive SCR for lean gasoline NOX control: Engine-based strategies to minimize fuel penalty associated with catalytic NH3 generation

    DOE PAGESBeta

    Prikhodko, Vitaly Y.; Parks, James E.; Pihl, Josh A.; Toops, Todd J.

    2016-02-18

    Lean gasoline engines offer greater fuel economy than common stoichiometric gasoline engines. However, excess oxygen prevents the use of the current three-way catalyst (TWC) to control nitrogen oxide (NOX) emissions in lean exhaust. A passive SCR concept, introduced by General Motors Global R&D, makes use of a TWC that is already onboard to generate NH3 under slightly rich conditions, which is stored on the downstream SCR. The stored NH3 is then used to reduce NOX emissions when the engine switches to lean operation. In this work, the effect of engine parameters, such as air-fuel equivalence ratio and spark timing, onmore » NH3 generation over a commercial Pd-only TWC with no dedicated oxygen storage component was evaluated on a 2.0-liter BMW lean burn gasoline direct injection engine. NOX reduction, NH3 formation, and reductant utilization processes were evaluated, and fuel efficiency was assessed and compared to the stoichiometric engine operation case. We found air-fuel equivalence ratio to be one of the most important parameters in controlling the NH3 production; however, the rich operation necessary for NH3 production results in a fuel consumption penalty. The fuel penalty can be minimized by adjusting spark timing to increase rich-phase engine out NOX emissions and, thereby, NH3 levels. Additionally, higher engine out NOX during engine load increase to simulate acceleration resulted in additional fuel savings. Ultimately, a 10% fuel consumption benefit was achieved with the passive SCR approach by optimizing rich air-fuel equivalence ratio and spark timing while also utilizing acceleration load conditions.« less

  3. Optical Transitions in Hybrid Perovskite Solar Cells: Ellipsometry, Density Functional Theory, and Quantum Efficiency Analyses for CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Shirayama, Masaki; Kadowaki, Hideyuki; Miyadera, Tetsuhiko; Sugita, Takeshi; Tamakoshi, Masato; Kato, Masato; Fujiseki, Takemasa; Murata, Daisuke; Hara, Shota; Murakami, Takurou N.; Fujimoto, Shohei; Chikamatsu, Masayuki; Fujiwara, Hiroyuki

    2016-01-01

    Light-induced photocarrier generation is an essential process in all solar cells, including organic-inorganic hybrid (CH3NH3PbI3 ) solar cells, which exhibit a high short-circuit current density (Jsc ) of approximately 20 mA /cm2 . Although the high Jsc observed in the hybrid solar cells relies on strong electron-photon interaction, the optical transitions in the perovskite material remain unclear. Here, we report artifact-free CH3NH3PbI3 optical constants extracted from ultrasmooth perovskite layers without air exposure and assign all of the optical transitions in the visible and ultraviolet region unambiguously, based on density-functional theory (DFT) analysis that assumes a simple pseudocubic crystal structure. From the self-consistent spectroscopic ellipsometry analysis of the ultrasmooth CH3NH3PbI3 layers, we find that the absorption coefficients of CH3NH3PbI3 (α =3.8 ×104 cm-1 at 2.0 eV) are comparable to those of CuInGaSe2 and CdTe, and high α values reported in earlier studies are overestimated seriously by the extensive surface roughness of CH3NH3PbI3 layers. The polarization-dependent DFT calculations show that CH3NH3 + interacts strongly with the PbI3 - cage, modifying the CH3NH3PbI3 dielectric function in the visible region rather significantly. In particular, the transition matrix element of CH3NH3PbI3 varies, depending on the position of CH3NH3 + within the Pb—I network. When the effect of CH3NH3 + on the optical transition is eliminated in the DFT calculation, the CH3NH3PbI3 dielectric function deduced from DFT shows an excellent agreement with the experimental result. As a result, distinct optical transitions observed at E0(Eg)=1.61 eV , E1=2.53 eV , and E2=3.24 eV in CH3NH3PbI3 are attributed to the direct semiconductor-type transitions at the R , M , and X points in the pseudocubic Brillouin zone, respectively. We further perform the quantum efficiency (QE) analysis for a standard hybrid-perovskite solar cell incorporating a mesoporous TiO2 layer and demonstrate that the QE spectrum can be reproduced almost perfectly when the revised CH3NH3PbI3 optical constants are employed. Depth-resolved QE simulations confirm that Jsc is limited by the material's longer wavelength response and indicate the importance of optical confinement and long carrier-diffusion lengths in hybrid perovskite solar cells.

  4. Inactivation of Na,K-ATPase following Co(NH3)4ATP binding at a low affinity site in the protomeric enzyme unit.

    PubMed

    Ward, Douglas G; Cavieres, José D

    2003-04-25

    The Na(+)-dependent or E1 stages of the Na,K-ATPase reaction require a few micromolar ATP, but submillimolar concentrations are needed to accelerate the K(+)-dependent or E2 half of the cycle. Here we use Co(NH(3))(4)ATP as a tool to study ATP sites in Na,K-ATPase. The analogue inactivates the K(+) phosphatase activity (an E2 partial reaction) and the Na,K-ATPase activity in parallel, whereas ATP-[(3)H]ADP exchange (an E1 reaction) is affected less or not at all. Although the inactivation occurs as a consequence of low affinity Co(NH(3))(4)ATP binding (K(D) approximately 0.4-0.6 mm), we can also measure high affinity equilibrium binding of Co(NH(3))(4)[(3)H]ATP (K(D) = 0.1 micro m) to the native enzyme. Crucially, we find that covalent enzyme modification with fluorescein isothiocyanate (which blocks E1 reactions) causes little or no effect on the affinity of the binding step preceding Co(NH(3))(4)ATP inactivation and only a 20% decrease in maximal inactivation rate. This suggests that fluorescein isothiocyanate and Co(NH(3))(4)ATP bind within different enzyme pockets. The Co(NH(3))(4)ATP enzyme was solubilized with C(12)E(8) to a homogeneous population of alphabeta protomers, as verified by analytical ultracentrifugation; the solubilization did not increase the Na,K-ATPase activity of the Co(NH(3))(4)ATP enzyme with respect to parallel controls. This was contrary to the expectation for a hypothetical (alphabeta)(2) membrane dimer with a single ATP site per protomer, with or without fast dimer/protomer equilibrium in detergent solution. Besides, the solubilized alphabeta protomer could be directly inactivated by Co(NH(3))(4)ATP, to less than 10% of the control Na,K-ATPase activity. This suggests that the inactivation must follow Co(NH(3))(4)ATP binding at a low affinity site in every protomeric unit, thus still allowing ATP and ADP access to phosphorylation and high affinity ATP sites. PMID:12591931

  5. Evaluation of biochars by temperature programmed oxidation/mass spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biochar from the thermochemical conversion of biomass was evaluated by Temperature Programmed Oxidation (TPO) coupled with mass spectroscopy. This technique can be used to assess the oxidative reactivity of carbonaceous solids where higher temperature reactivity indicates greater structural order. ...

  6. Efficient planar heterojunction solar cell employing CH3NH3PbI2+xCl1-x mixed halide perovskite utilizing modified sequential deposition

    NASA Astrophysics Data System (ADS)

    Zhang, Chunfu; Tang, Shi; Yan, Jing; Wang, Zhizhe; Xi, He; Chen, Dazheng; Yang, Haifeng; Zhang, Jincheng; Han, Genquan; Liu, Yan; Hao, Yue

    2015-09-01

    In this work, a modified method of sequential deposition of a CH3NH3PbI2+xCl1-x organometal halide perovskite material with a low chlorine fraction and easy morphology control is developed. The as-prepared mixed halide perovskite CH3NH3PbI2+xCl1-x thin film shows an intense adsorption from 400-800 nm. Scanning electron microscopy images show that almost the entire compact TiO2 surface is covered with CH3NH3PbI2+xCl1-x mixed halide perovskite with grain sizes of 250-350 nm. The planar heterojunction solar cell employing CH3NH3PbI2+xCl1-x mixed halide perovskite shows a twofold enhancement of photovoltaic performance, compared with a planar CH3NH3PbI3 heterojunction solar cell, achieving a 9.53% power conversion efficiency (PCE) with a VOC of 0.96 V, a JSC of 18.86 mA/cm2, and a fill factor (FF) of 0.53.

  7. A photoelectrochemical biosensor for fibroblast-like synoviocyte cell using visible light-activated NCQDs sensitized-ZnO/CH3NH3PbI3 heterojunction.

    PubMed

    Pang, Xuehui; Zhang, Yong; Pan, Jihong; Zhao, Yanxia; Chen, Yao; Ren, Xiang; Ma, Hongmin; Wei, Qin; Du, Bin

    2016-03-15

    Based on ZnO nanorods (NRs)/CH3NH3PbI3/nitrogen-doped carbon quantum dots (NCQDs) nanocomposites, the highly sensitive detection of fibroblast-like synoviocyte (FLS) cell was realized by a photoelectrochemical (PEC) biosensor. ZnO/CH3NH3PbI3/NCQDs nanocomposites were exploited as the photo-to-electron generator to produce the signal. CH3NH3PbI3 was spin-coated on ZnO surface after ZnO NRs grew on ITO electrode then by dropping on the modified electrode, NCQDs were diffused and adhered to the surface of ZnO and CH3NH3PbI3. In the presence of EDC/NHS, the combination of CH3NH3PbI3 and NCQDs was achieved by the carboxyl groups (-COOH) and amino groups (-NH2) in the preparation process. Furthermore, the capture probe of FLS cell, CD95 antibody, can be anchored by -COOH and -NH2 groups through EDC/NHS. The specific recognition between the antibody capture probes and cell targets gained high-sensitive detection for FLS cell for the first time. The developed biosensor showed a wide linear range from 1.0 × 10(4)cell/mL to 10 cell/mL and a low detection limit of 2 cell/mL. This kind of biosensor would provide a novel detection strategy for FLS cell. PMID:26433065

  8. Hysteresis-free, stable and efficient perovskite solar cells achieved by vacuum-treated thermal annealing of CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Xie, Fengxian; Zhang, Di; Choy, Wallace C. H.

    2015-09-01

    The lead halide-based perovskite solar cells have emerged as a promising candidate in photovoltaic applications. However, the precise control over the morphologiy of the perovskite films (minimizing pore formation) and enhanced stability and reproducibility of the devices remain challenging, even though both will be necessary for further advancements. Here we introduce vacuum-assisted thermal annealing as a means of controlling the composition and morphology of the CH3NH3PbI3 films formed from PbCl2 and CH3NH3I as precursors. We identify the critical role that the CH3NH3Cl generated as a byproduct during the pervoskite synthesis plays for the photovoltaic performance of the perovskite film. Removing this byproduct through vacuum-assisted thermal annealing we succeeded in producing pure, pore-free planar CH3NH3PbI3 films showing high conversion efficiency (PCE) reaching 14.5%). Removal of CH3NH3Cl strongly attenuate the photocurrent hysteresis.

  9. The abundances of CH4, CH3D, NH3, and PH3 in the troposphere of Jupiter derived from high-resolution 1100-1200/cm spectra

    NASA Technical Reports Server (NTRS)

    Knacke, R. F.; Kim, S. J.; Ridgway, S. T.; Tokunaga, A. T.

    1982-01-01

    High-resolution spectra of the 1100-1200/cm region of the central part of Jupiter obtained in March 1980 and April 1981 are analyzed. The best fit NH3 distribution curve reveals a higher than solar mixing ratio, the abundance of NH3 to that of H2 being (3.3 + or - 1.7) x 10 to the -4th, below the 147 K layer (greater than 0.6 atmosphere). If NH3 ice particles are introduced as an opacity source, the NH3 mixing ratio below the 147 K layer can be lowered, but the fit is worse than that given by the model that excludes NH3 ice particles. The best fit PH3 distribution curve exhibits a PH3/H2 mixing ratio of (8.3 + or - 2.0) x 10 to the -7th in the troposphere. In addition, a CH4/H2 mixing ratio of (2.5 + or - 0.4) x 10 to the -3rd is found in the troposphere.

  10. Influence of bulking agents on CH4, N2O, and NH3 emissions during rapid composting of pig manure from the Chinese Ganqinfen system*

    PubMed Central

    Sun, Xiang-ping; Lu, Peng; Jiang, Tao; Schuchardt, Frank; Li, Guo-xue

    2014-01-01

    Mismanagement of the composting process can result in emissions of CH4, N2O, and NH3, which have caused severe environmental problems. This study was aimed at determining whether CH4, N2O, and NH3 emissions from composting are affected by bulking agents during rapid composting of pig manure from the Chinese Ganqinfen system. Three bulking agents, corn stalks, spent mushroom compost, and sawdust, were used in composting with pig manure in 60 L reactors with forced aeration for more than a month. Gas emissions were measured continuously, and detailed gas emission patterns were obtained. Concentrations of NH3 and N2O from the composting pig manure mixed with corn stalks or sawdust were higher than those from the spent mushroom compost treatment, especially the sawdust treatment, which had the highest total nitrogen loss among the three runs. Most of the nitrogen was lost in the form of NH3, which accounts for 11.16% to 35.69% of the initial nitrogen. One-way analysis of variance for NH3 emission showed no significant differences between the corn stalk and sawdust treatments, but a significant difference was noted between the spent mushroom compost and sawdust treatments. The introduction of sawdust reduced CH4 emission more than the corn stalks and spent mushroom compost. However, there were no significant differences among the three runs for total carbon loss. All treatments were matured after 30 d. PMID:24711356

  11. Growth and evolution of solution-processed CH3NH3PbI3-xClx layer for highly efficient planar-heterojunction perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Jiang; Lin, Jiahui; Xue, Qifan; Ye, Qinyan; He, Xulin; Ouyang, Liangqi; Zhuang, Daming; Liao, Cheng; Yip, Hin-Lap; Mei, Jun; Lau, Woon-Ming

    2016-01-01

    Methylammoniumn lead iodide perovskites have attracted great attention in photovoltaic research community. In this work, we demonstrate the results of studies focusing on the chemical reaction of CH3NH3PbI3-xClx layer formation during the annealing of perovskite precursor films. We identified two kinds of grain morphologies during the formation of perovskite films grown from non-stoichiometric precursor solution. To form single-phase and high absorbance perovskite films, higher concentration of chloride in precursor solution needs longer annealing time and only a very low Cl content could be incorporated in the final CH3NH3PbI3-xClx films. Adding PbCl2-3CH3NH3I to PbI2-CH3NH3I precursor solution can allow a good control of the growth rate and morphology for the final perovskite film, and is beneficial to the photovoltaic performance of perovskite devices. By employing the precursor solutions of PbCl2, PbI2 and CH3NH3I with a mole ratio of 1:1:4 and inserting an ultrathin amino-functionalized polymer interlayer, we achieved planar perovskite solar cell with maximum power conversion efficiency of over 15%.

  12. Study on the correlations between the structure and photoelectric properties of CH3NH3PbI3 perovskite light-harvesting material

    NASA Astrophysics Data System (ADS)

    Xie, Junjie; Liu, Yan; Liu, Jianjun; Lei, Lei; Gao, Qianqian; Li, Jiaqing; Yang, Songwang

    2015-07-01

    The [PbI6] inorganic framework in the CH3NH3PbI3 could be affected by the oxidization effect of I- ions in atmosphere. The [PbI6] octahedral torsion angle increased ∼4.94° after the newly prepared CH3NH3PbI3 powders were stored in dry atmosphere for 30 days at 20 °C according to the results of XRD Rietveld refinement and X-ray Absorption Fine Structure. Analyses based on density of states indicated that UV-vis adsorption edge at ∼850 cm-1 corresponded to electron transition from I-5p orbitals to empty Pb-6p orbitals. The increased [PbI6] octahedral torsion angle made the band gap energy of CH3NH3PbI3 increased according to First-principle calculation and UV-vis absorption spectra. As a result, the band gap energy of CH3NH3PbI3 were strongly related to the structure of [PbI6] inorganic framework because the electrons diffused along the [PbI6] octahedral chains in CH3NH3PbI3 perovskite.

  13. Low Dislocation Densities of Nitride-Based Light-Emitting Diodes with a Preflow of NH3 Source before Growth of AlN Buffer Layer

    NASA Astrophysics Data System (ADS)

    Wang, Chun-Kai; Chiou, Yu-Zung; Sun, De-Jun; Chiang, Tsung-Hsun

    2013-01-01

    In this study, the AlN buffer layer grown on c-plane sapphire (Al2O3) substrates by metal-organic chemical vapor deposition (MOCVD) was controlled by a preflow of the NH3 source. With the treatment of NH3 preflow, the monolayer of AlN was formed on the surface of a sapphire substrate by the decomposition of the NH3 source and Al2O3 substrate. It was found that the density of threading dislocations significantly decreased owing to the abatement of lattice mismatch between a GaN layer and a sapphire substrate. At an injection current of 350 mA, the light output intensity of the light-emitting diode (LED) with NH3 preflow was increased by 14.1% compared with that of a conventional LED. On the other hand, LEDs with NH3 preflow treatment could endure electrostatic discharge (ESD) surges up to -3000 V and caused a low rate of light output degradation at a high ambient temperature.

  14. Internal Rotation in CF3ICdotsNH3 and CF3I\\cdotsN(CH3)_3 Probed by Cp-Ftmw Spectroscopy

    NASA Astrophysics Data System (ADS)

    Walker, N. R.; Stephens, S. L.; Legon, A. C.

    2011-06-01

    The pure rotational spectra of CF3ICdotsNH3 and CF3I\\cdotsN(CH3)_3 have been measured by chirped-pulse, Fourier transform microwave (CP-FTMW) spectroscopy between 7 and 18.5 GHz. Both molecules are generated by supersonic expansion of a gas sample containing a small percentage of each precursor in a balance of argon. The spectra of both complexes are consistent with {C}3v prolate symmetric top structures. The observed spectrum of CF3ICdotsNH3 displays evidence for internal rotation of NH3 about the principal axis. More than one hundred transitions of CF3ICdotsNH3 have been assigned to the internal rotor {A} state allowing rotational, centrifugal distortion constants and a nuclear quadrupole coupling constant for the iodine atom to be determined for this state. Measurements performed using a Balle-Flygare FTMW spectrometer further allow determination of a nuclear quadrupole coupling constant for the 14N nucleus. Many transitions in the spectrum of the CF3ICdots15NH3 isotopologue have also been measured and the length of the halogen bond between the iodine and nitrogen atoms has been determined. Measurements of hyperfine components in nine different J''←J' transitions of CF3I\\cdotsN(CH3)_3 have allowed assignment of the spectrum of this complex to determine rotational, centrifugal distortion and nuclear quadrupole coupling constants.

  15. Effect of water vapor on NH3-NO/NO2 SCR performance of fresh and aged MnOx-NbOx-CeO2 catalysts.

    PubMed

    Chen, Lei; Si, Zhichun; Wu, Xiaodong; Weng, Duan; Wu, Zhenwei

    2015-05-01

    A MnOx-NbOx-CeO2 catalyst for low temperature selective catalytic reduction (SCR) of NOx with NH3 was prepared by a sol-gel method, and characterized by NH3-NO/NO2 SCR catalytic activity, NO/NH3 oxidation activity, NOx/NH3 TPD, XRD, BET, H2-TPR and in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The results indicate that the MnOx-NbOx-CeO2 catalyst shows excellent low temperature NH3-SCR activity in the temperature range of 150-300°C. Water vapor inhibits the low temperature activity of the catalyst in standard SCR due to the inhibition of NOx adsorption. As the NO2 content increases in the feed, water vapor does not affect the activity in NO2 SCR. Meanwhile, water vapor significantly enhances the N2 selectivity of the fresh and the aged catalysts due to its inhibition of the decomposition of NH4NO3 into N2O. PMID:25968280

  16. Influence of NH3 plasma pretreatment on the properties of plasma-enhanced chemical-vapor-deposited SiON on GaAs interface

    NASA Astrophysics Data System (ADS)

    Wu, C. Y.; Lin, M. S.

    1986-09-01

    Interface properties of plasma-enhanced chemical-vapor-deposited dielectric SiON on GaAs systems pretreated by NH3 plasma were studied. The effects of the process parameters in the NH3 plasma pretreatment, such as total pressure, radio-frequency power, substrate temperature, NH3 flow rate and pretreatment time, were investigated by the measurements of Auger electron spectroscopy, Raman spectroscopy, current-voltage, and capacitance-voltage characteristics. The transient region width and the surface strain field, surface leakage current, hysteresis, and degree of Fermi-level pinning evidently related to interface properties, are increased with increasing total pressure, decreased with increasing radio-frequency power, substrate temperature, and pretreatment time, and independent of NH3 flow rate. The physical and electrical properties of SiON/GaAs interface have been significantly improved under an optimum NH3 plasma pretreatment condition. The correlation of these parameters in pretreatment process with the interface properties including interdiffusion, surface strain field, surface leakage current, hysteresis, and Fermi-level pinning are discussed.

  17. Probing Electron Transfer Dynamics at MgO Surfaces by Mg-Atom Desorption

    SciTech Connect

    Joly, Alan G.; Henyk, Matthias; Beck, Kenneth M.; Trevisanutto, P. E.; Sushko, Petr V.; Hess, Wayne P.; Shluger, Alexander L.

    2006-08-14

    Desorption of a weakly bound adsorbate from a porous solid was studied for the case of N2 on amorphous solid water (ASW). Porous ASW films of different thickness were grown on Pt(111) by ballistic deposition. N2 adsorption and desorption kinetics were monitored mass-spectrometrically. Temperature programmed desorption spectra show that with the increasing film thickness, the N2 desorption peak systematically shifts to higher temperatures. The results are explained and quantitatively reproduced by a simple model, which assumes that the N2 transport within the film is faster than the depletion rate to vacuum. The local coverage at the pore mouth determines the desorption rate. For thick ASW films (>1 μm), the assumption of the fast equilibration within the film is shown to be no longer valid due to diffusion limitations. The mechanisms of the adsorbate transport are discussed.

  18. Stability domains of water ices in the NH3 - H2O system: experimental results and thermodynamic modelling

    NASA Astrophysics Data System (ADS)

    Grasset, O.; Choukroun, M.

    2009-12-01

    The ammonia compound decreases very significantly the melting curve of water ices. This property is of fundamental importance in planetology because it constrains the nature of the icy mantle within icy moons of the giant planets (1,2). That is why many experimental studies have been conducted for understanding the binary system H2O - NH3 in the temperature - pressure space (1-6). The most surprising effect of the ammonia compound is that it decreases the melting temperature of the ice polymorphs down to 180 K at the eutectic temperature (1,2). This effect has been observed throughout the pressure domain relevant for icy moons from 0 to 1 GPa. In this paper, a review of these efforts, in addition to new results, obtained by the authors with a sapphire anvil cell in the domains where experimental data were lacking (8), will be presented. A thermodynamic description that uses the chemical potential approach can be used for describing the pure water system (7,9). However, most studies that have used this approach were clearly focused on describing the melting curves of the water phase diagram. A new formulation has recently been proposed (9), which allows to compute phase equilibria in the whole P-T domain where ice polymorphs are encountered. In this work, the model has been improved by incorporating the ice II polymorph, and by describing more accurately the behaviour of the binary liquid mixture which is close to a regular symmetric solution (10). This model has been validated in the pure water domain by checking that all stability domains of the ice polymorphs (Ih, II, III, V, and VI) were predicted with an accuracy better than 1%. A very good reproduction of the stability domain of ice Ih in the H2O-NH3 phase diagram is also achieved. It will be shown that the thermodynamic approach allows to predict the stability of each ice polymorphs whatever the pressure and temperature are, in very good agreement with the available experimental data. It appears that the stability domain of some polymorphs, such as ice II and ice V, enlarges with the ammonia concentration, whereas that of ice III diminishes with NH3 concentration, and this phase is expected to disappear above 10 %wt of ammonia in the system. For each polymorph, a whole description of stability domains and melting surfaces will be presented. Implications for the occurrence of liquid oceans within the largest moons will also be briefly discussed. Ref. : 1. Hogenboom et al., Icarus, 1997. 2. Grasset and Pargamin, Planet. Space Sci., 2005. 3. Croft et al., Icarus, 1988. 4. Johnson and Nicol, J. Geoph. Res., 1987. 5Kargel, Icarus, 1992. 6. Leliwa-Kopystynski et al., Icarus, 2002. 7. Chizhov and Nagornov, J. Appl. Mech. Techn. Phys. 1991. 8. Choukroun M., PhD thesis, 2007. 9. Choukroun and Grasset, J. Chem. Phys, 2007. 10.Wood and Fraser, Oxford Univ. Press, 1977.

  19. Synthesis and molecular structure of [Cu(NH3)4][Ni(CN)4]: A missing piece in the [Cu(NH3)n][Ni(CN)4] story

    NASA Astrophysics Data System (ADS)

    Solanki, Dina; Hogarth, Graeme

    2015-11-01

    Reaction of CuCl2·2H2O and K2[Ni(CN)4]·2H2O in aqueous ammonia gave blue rod-like crystals of [Cu(NH3)4][Ni(CN)4]. An X-ray crystallographic reveals that square-planar anions and cations are weakly associated through coordination of a cis pair of cyanide ligands to copper, with one short and one long contact and thus the copper centre is best described as a square-based pyramid. Crystals lose ammonia readily upon removal from the solvent and this has been probed by TGA and DSC measurements. For comparison we have also re-determined the structure of the related ethylenediamine (en) complex [Cu(en)2][Ni(CN)4] at 150 K. This consists of a 1D chain in which a trans pair of cyanide ligands bind to copper such that the latter has an overall tetragonally distorted octahedral coordination geometry.

  20. The reaction NH2 + PH3 yields NH3 + PH2 - Absolute rate constant measurement and implication for NH3 and PH3 photochemistry in the atmosphere of Jupiter

    NASA Technical Reports Server (NTRS)

    Bosco, S. R.; Brobst, W. D.; Nava, D. F.; Stief, L. J.

    1983-01-01

    The rate constant is measured over the temperature interval 218-456 K using the technique of flash photolysis-laser-induced fluorescence. NH2 radicals are produced by the flash photolysis of ammonia highly diluted in argon, and the decay of fluorescent NH2 photons is measured by multiscaling techniques. For each of the five temperatures employed in the study, the results are shown to be indepenent of variations in PH3 concentration, total pressure (argon), and flash intensity. It is found that the rate constant results are best represented for T between 218 and 456 K by the expression k = (1.52 + or - 0.16) x 10 to the -12th exp(-928 + or - 56/T) cu cm per molecule per sec; the error quoted is 1 standard deviation. This is the first determination of the rate constant for the reaction NH2 + PH3. The data are compared with an estimate made in order to explain results of the radiolysis of NH3-PH3 mixtures. The Arrhenius parameters determined here for NH2 + PH3 are then contrasted with those for the corresponding reactions of H and OH with PH3.

  1. The reaction NH2 + PH3 yields NH3 + PH2: Absolute rate constant measurement and implication for NH3 and PH3 photochemistry in the atmosphere of Jupiter

    NASA Technical Reports Server (NTRS)

    Bosco, S. R.; Brobst, W. D.; Nava, D. F.; Stief, L. J.

    1983-01-01

    The rate constant is measured over the temperature interval 218-456 K using the technique of flash photolysis-laser-induced fluorescence. NH2 radicals are produced by the flash photolysis of ammonia highly diluted in argon, and the decay of fluorescent NH2 photons is measured by multiscaling techniques. For each of the five temperatures employed in the study, the results are shown to be independent of variations in PH3 concentration, total pressure (argon), and flash intensity. It is found that the rate constant results are best represented for T between 218 and 456 K by the expression k = (1.52 + or - 0.16) x 10 to the -12th exp(-928 + or - 56/T) cu cm per molecule per sec; the error quoted is 1 standard deviation. This is the first determination of the rate constant for the reaction NH2 + PH3. The data are compared with an estimate made in order to explain results of the radiolysis of NH3-PH3 mixtures. The Arrhenius parameters determined here for NH2 + PH3 are then constrasted with those for the corresponding reactions of H and OH with PH3.

  2. Decomposition processes of H3NBH3 (borazane), (BH)3(NH)3 (borazine), and B(CH3)3 (trimethylboron) on heated W wire surfaces

    NASA Astrophysics Data System (ADS)

    Umemoto, Hironobu; Miyata, Atsushi; Nojima, Takuto

    2015-10-01

    The decomposition mechanisms of H3NBH3, (BH)3(NH)3, and B(CH3)3 on heated W wire surfaces were examined using mass spectrometric and laser spectroscopic techniques. These chemicals can be source materials for catalytic chemical vapor deposition as well as for B-atom doping. All the species could be decomposed well when the wire temperature was over 2.0 103 K. When H2 was introduced, the production of B atoms was confirmed in the decomposition of H3NBH3 and B(CH3)3, but not for (BH)3(NH)3. H3NBH3 and B(CH3)3 may be candidates as safe precursors for B-atom doping, while (BH)3(NH)3 could be a viable candidate as a BN film precursor.

  3. Inkjet printing and instant chemical transformation of a CH3NH3PbI3/nanocarbon electrode and interface for planar perovskite solar cells.

    PubMed

    Wei, Zhanhua; Chen, Haining; Yan, Keyou; Yang, Shihe

    2014-11-24

    A planar perovskite solar cell that incorporates a nanocarbon hole-extraction layer is demonstrated for the first time by an inkjet printing technique with a precisely controlled pattern and interface. By designing the carbon plus CH3NH3I ink to transform PbI2 in situ to CH3NH3PbI3, an interpenetrating seamless interface between the CH3NH3PbI3 active layer and the carbon hole-extraction electrode was instantly constructed, with a markedly reduced charge recombination compared to that with the carbon ink alone. As a result, a considerably higher power conversion efficiency up to 11.60% was delivered by the corresponding solar cell. This method provides a major step towards the fabrication of low-cost, large-scale, metal-electrode-free but still highly efficient perovskite solar cells. PMID:25255744

  4. Interplay of Hydrogen-Bond and Coordinate Covalent-Bond Interactions in Self-Assembly of NH3 Molecules on the Si(001) Surface

    NASA Astrophysics Data System (ADS)

    Kim, Yong-Sung; Koo, Ja-Yong; Kim, Hanchul

    2008-06-01

    An exchange of hydrogen-bond and coordinate covalent-bond (dative-bond) interactions is found to play a critical role in the self-assembly of NH3 molecules on the Si(001) surface. An NH3 molecule in the height of ˜3 10Å above the surface is attracted toward the preadsorbed NH2 moiety through the long-range H-bond interaction. Within ˜3Å, the H-bond interaction becomes repulsive, and instead the dative bond with the buckled-down Si atom governs the adsorption process. The interplay of the two interactions induces the clustering and the zigzag feature of the dissociatively adsorbed NH3 molecules on the Si(001) surface.

  5. Spontaneous bidirectional ordering of CH3NH3+ in lead iodide perovskites at room temperature: The origins of the tetragonal phase

    NASA Astrophysics Data System (ADS)

    Deretzis, Ioannis; di Mauro, Bruno N.; Alberti, Alessandra; Pellegrino, Giovanna; Smecca, Emanuele; La Magna, Antonino

    2016-04-01

    CH3NH3PbI3 is a hybrid organic-inorganic material with a perovskite structure and a temperature-dependent polymorphism whose origins are still unclear. Here we perform ab initio molecular dynamics simulations in order to investigate the structural properties and atom dynamics of CH3NH3PbI3 at room temperature. Starting from different initial configurations, we find that a single-crystalline system undergoes a spontaneous ordering process which brings the ions to alternately point towards the center of two out of the six faces of the cubic framework, i.e. towards the <100> and <010> directions. This bidirectional ordering gives rise to a preferential distortion of the inorganic lattice on the a-b plane, shaping the observed tetragonal symmetry of the system. The process requires tens of picoseconds for CH3NH3PbI3 supercells with just eight ions.

  6. Significant Promotion Effect of Mo Additive on a Novel Ce-Zr Mixed Oxide Catalyst for the Selective Catalytic Reduction of NO(x) with NH3.

    PubMed

    Ding, Shipeng; Liu, Fudong; Shi, Xiaoyan; Liu, Kuo; Lian, Zhihua; Xie, Lijuan; He, Hong

    2015-05-13

    A novel Mo-promoted Ce-Zr mixed oxide catalyst prepared by a homogeneous precipitation method was used for the selective catalytic reduction (SCR) of NO(x) with NH3. The optimal catalyst showed high NH3-SCR activity, SO2/H2O durability, and thermal stability under test conditions. The addition of Mo inhibited growth of the CeO2 particle size, improved the redox ability, and increased the amount of surface acidity, especially the Lewis acidity, all of which were favorable for the excellent NH3-SCR performance. It is believed that the catalyst is promising for the removal of NO(x) from diesel engine exhaust. PMID:25894854

  7. A facile, solvent vapor-fumigation-induced, self-repair recrystallization of CH3NH3PbI3 films for high-performance perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Zhu, Weidong; Yu, Tao; Li, Faming; Bao, Chunxiong; Gao, Hao; Yi, Yong; Yang, Jie; Fu, Gao; Zhou, Xiaoxin; Zou, Zhigang

    2015-03-01

    A high-quality CH3NH3PbI3 film is crucial in the manufacture of a high-performance perovskite solar cell. Here, a recrystallization process via facile fumigation with DMF vapor has been successfully introduced to self-repair of CH3NH3PbI3 films with poor coverage and low crystallinity prepared by the commonly used one-step spin-coating method. We found that the CH3NH3PbI3 films with dendritic structures can spontaneously transform to the uniform ones with full coverage and high crystallinity by adjusting the cycles of the recrystallization process. The mesostructured perovskite solar cells based on these repaired CH3NH3PbI3 films showed reproducible optimal power conversion efficiency (PCE) of 11.15% and average PCE of 10.25 +/- 0.90%, which are much better than that of devices based on the non-repaired CH3NH3PbI3 films. In addition, the hysteresis phenomenon in the current-voltage test can also be effectively alleviated due to the quality of the films being improved in the optimized devices. Our work proved that the fumigation of solvent vapor can modify metal organic perovskite films such as CH3NH3PbI3. It offers a novel and attractive way to fabricate high-performance perovskite solar cells.A high-quality CH3NH3PbI3 film is crucial in the manufacture of a high-performance perovskite solar cell. Here, a recrystallization process via facile fumigation with DMF vapor has been successfully introduced to self-repair of CH3NH3PbI3 films with poor coverage and low crystallinity prepared by the commonly used one-step spin-coating method. We found that the CH3NH3PbI3 films with dendritic structures can spontaneously transform to the uniform ones with full coverage and high crystallinity by adjusting the cycles of the recrystallization process. The mesostructured perovskite solar cells based on these repaired CH3NH3PbI3 films showed reproducible optimal power conversion efficiency (PCE) of 11.15% and average PCE of 10.25 +/- 0.90%, which are much better than that of devices based on the non-repaired CH3NH3PbI3 films. In addition, the hysteresis phenomenon in the current-voltage test can also be effectively alleviated due to the quality of the films being improved in the optimized devices. Our work proved that the fumigation of solvent vapor can modify metal organic perovskite films such as CH3NH3PbI3. It offers a novel and attractive way to fabricate high-performance perovskite solar cells. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00225g

  8. Spontaneous bidirectional ordering of CH3NH3(+) in lead iodide perovskites at room temperature: The origins of the tetragonal phase.

    PubMed

    Deretzis, Ioannis; Di Mauro, Bruno N; Alberti, Alessandra; Pellegrino, Giovanna; Smecca, Emanuele; La Magna, Antonino

    2016-01-01

    CH3NH3PbI3 is a hybrid organic-inorganic material with a perovskite structure and a temperature-dependent polymorphism whose origins are still unclear. Here we perform ab initio molecular dynamics simulations in order to investigate the structural properties and atom dynamics of CH3NH3PbI3 at room temperature. Starting from different initial configurations, we find that a single-crystalline system undergoes a spontaneous ordering process which brings the ions to alternately point towards the center of two out of the six faces of the cubic framework, i.e. towards the 〈100〉 and 〈010〉 directions. This bidirectional ordering gives rise to a preferential distortion of the inorganic lattice on the a-b plane, shaping the observed tetragonal symmetry of the system. The process requires tens of picoseconds for CH3NH3PbI3 supercells with just eight ions. PMID:27079383

  9. Rotational excitation of symmetric top molecules by collisions with atoms: Close coupling, coupled states, and effective potential calculations for NH3-He

    NASA Technical Reports Server (NTRS)

    Green, S.

    1976-01-01

    The formalism for describing rotational excitation in collisions between symmetric top rigid rotors and spherical atoms is presented both within the accurate quantum close coupling framework and also the coupled states approximation of McGuire and Kouri and the effective potential approximation of Rabitz. Calculations are reported for thermal energy NH3-He collisions, treating NH3 as a rigid rotor and employing a uniform electron gas (Gordon-Kim) approximation for the intermolecular potential. Coupled states are found to be in nearly quantitative agreement with close coupling results while the effective potential method is found to be at least qualitatively correct. Modifications necessary to treat the inversion motion in NH3 are discussed.

  10. Real Time Monitoring of NH3 Concentration Using Diffusion Scrubber Sampling Technique and Result of Application to the Processing of Chemically Amplified Resists

    NASA Astrophysics Data System (ADS)

    Park, Jungchul; Bae, Eunyoung; Park, Chungeun; Han, Woosung; Koh, Youngbum; Lee, Moonyoung; Lee, Jonggil

    1995-12-01

    The application of chemically amplified resist is known to cause a problem in the accurate measurement of the concentration of basic gas species ( NH3, N-methylpyrrolidone (NMP)) in a clean room environment because it is sensitive to its environment. Among various methods of measurement, diffusion scrubber sampling method was selected and tested. The environmental sensitivity of a commercial chemically amplified resist, APEX-E, was also tested. For the concentration measurement, the method proved to be suitable for automation and good for measuring NH3 concentration as low as the sub ppb level (limit of detection ˜0.08 ppb). Some measurement results concerning various aspects of application are presented. Test results of the environmental stability of chemically amplified resists showed that NH3 concentration should be controlled to at least under 7.5 ppb for maintaining the process stability.

  11. P-P heterojunction sensor of self-assembled polyaniline nano-thin film/microstructure silicon array for NH3 detection

    NASA Astrophysics Data System (ADS)

    Tai, Huiling; Xu, Xiaoying; Ye, Zongbiao; Liu, Chunhua; Xie, Guangzhong; Jiang, Yadong

    2015-02-01

    A novel P-P isotype heterojunction sensor was developed by modifying microstructure silicon array (MSSA) with self-assembled polyaniline (PANI) nano-thin film for ammonia (NH3) detection at room temperature, and the comparative study of response performance was focused on sensors with varied etching time of MSSA. The results indicated that PANI nanorods network was successfully deposited on MSSA surface, and PANI/MSSA sensor exhibited superior NH3-sensing properties than PANI/plane silicon sensor, which should be ascribed to three-dimensional structure and p-p heterojunction enhancement effect. Meanwhile, the optimized sensor with 4 min etching time exhibited high response, good reversibility, repeatability and selectivity when exposed to NH3.

  12. Calibrated Passive Sampling - Multi-plot Field Measurements of NH3 Emissions with a Combination of Dynamic Tube Method and Passive Samplers.

    PubMed

    Pacholski, Andreas

    2016-01-01

    Agricultural ammonia (NH3) emissions (90% of total EU emissions) are responsible for about 45% airborne eutrophication, 31% soil acidification and 12% fine dust formation within the EU15. But NH3 emissions also mean a considerable loss of nutrients. Many studies on NH3 emission from organic and mineral fertilizer application have been performed in recent decades. Nevertheless, research related to NH3 emissions after application fertilizers is still limited in particular with respect to relationships to emissions, fertilizer type, site conditions and crop growth. Due to the variable response of crops to treatments, effects can only be validated in experimental designs including field replication for statistical testing. The dominating ammonia loss methods yielding quantitative emissions require large field areas, expensive equipment or current supply, which restricts their application in replicated field trials. This protocol describes a new methodology for the measurement of NH3 emissions on many plots linking a simple semi-quantitative measuring method used in all plots, with a quantitative method by simultaneous measurements using both methods on selected plots. As a semi-quantitative measurement method passive samplers are used. The second method is a dynamic chamber method (Dynamic Tube Method) to obtain a transfer quotient, which converts the semi-quantitative losses of the passive sampler to quantitative losses (kg nitrogen ha(-1)). The principle underlying this approach is that passive samplers placed in a homogeneous experimental field have the same NH3 absorption behavior under identical environmental conditions. Therefore, a transfer co-efficient obtained from single passive samplers can be used to scale the values of all passive samplers used in the same field trial. The method proved valid under a wide range of experimental conditions and is recommended to be used under conditions with bare soil or small canopies (<0.3 m). Results obtained from experiments with taller plants should be treated more carefully. PMID:27023010

  13. Bulk intermixing-type perovskite CH3NH3PbI3/TiO2 nanorod hybrid solar cells

    NASA Astrophysics Data System (ADS)

    Li, Shao-Sian; Wang, Ying-Chiao; Tsai, Chin-Ming; Wen, Cheng-Yen; Yu, Chia-Hao; Yang, Yu-Pei; Lin, Jou-Chun; Wang, Di-Yan; Chen, Chia-Chun; Yeh, Yun-Chieh; Chen, Chun-Wei

    2015-08-01

    To replace high-temperature sintered scaffold materials in conventional CH3NH3PbI3-based solar cells, this study demonstrates a new device structure of a bulk intermixing (BI)-type CH3NH3PbI3/TiO2 nanorod (NR) hybrid solar cell, where dispersed TiO2 NRs from chemical synthesis are intermixed with the perovskite absorbing layer to form a BI-type perovskite/TiO2 NR hybrid for device fabrication. Through interface engineering between the TiO2 NR surface and the photoactive perovskite material of CH3NH3PbI3 by ligand exchange treatment, a remarkable power conversion efficiency (PCE) of over 12% was achieved based on the simple BI-type CH3NH3PbI3/TiO2 NR hybrid device structure. The proposed hybrids not only provide great flexibility for deposition on various substrates through spin coating at low temperatures but also enable layer-by-layer deposition for the future development of perovskite-based multi-junction solar cells.To replace high-temperature sintered scaffold materials in conventional CH3NH3PbI3-based solar cells, this study demonstrates a new device structure of a bulk intermixing (BI)-type CH3NH3PbI3/TiO2 nanorod (NR) hybrid solar cell, where dispersed TiO2 NRs from chemical synthesis are intermixed with the perovskite absorbing layer to form a BI-type perovskite/TiO2 NR hybrid for device fabrication. Through interface engineering between the TiO2 NR surface and the photoactive perovskite material of CH3NH3PbI3 by ligand exchange treatment, a remarkable power conversion efficiency (PCE) of over 12% was achieved based on the simple BI-type CH3NH3PbI3/TiO2 NR hybrid device structure. The proposed hybrids not only provide great flexibility for deposition on various substrates through spin coating at low temperatures but also enable layer-by-layer deposition for the future development of perovskite-based multi-junction solar cells. Electronic supplementary information (ESI) available: TiO2 synthesis and ligand exchange process, device fabrication and characterization. See DOI: 10.1039/c5nr04076k

  14. Pyroelectric and Dilatometric Studies on the Low Temperature Ferroelectric Phase Transition of (CH3NH3)5Bi2Br11

    NASA Astrophysics Data System (ADS)

    Dziedzic, J.; Mróz, J.; Jakubas, R.

    2006-09-01

    The results of the linear thermal expansion studies on (CH3NH3)5Bi2Br11 single crystals in the temperature range 60-340 K are presented. The thermal anomaly in the vicinity of 77 K is assigned to the phase transition classified as close to first order type. The pyroelectric measurements of (CH3NH3)5Bi2Br11 were carried out in the range of 45-320 K along the a- and c-axis. The step-like change in the spontaneous polarization along the a-axis at 77 K indicates a discontinuous character of ferroelectric transition.

  15. Oxygen sorption and desorption properties of selected lanthanum manganites and lanthanum ferrite manganites.

    PubMed

    Nielsen, Jimmi; Skou, Eivind M; Jacobsen, Torben

    2015-06-01

    Temperature-programmed desorption (TPD) with a carrier gas was used to study the oxygen sorption and desorption properties of oxidation catalysts and solid-oxide fuel cell (SOFC) cathode materials (La(0.85) Sr(0.15)0.95 MnO(3+δ) (LSM) and La(0.60) Sr(0.40) Fe(0.80) Mn(0.20) O(3-δ) (LSFM). The powders were characterized by X-ray diffractometry, atomic force microscopy (AFM), and BET surface adsorption. Sorbed oxygen could be distinguished from oxygen originating from stoichiometry changes. The results indicated that there is one main site for oxygen sorption/desorption. The amount of sorbed oxygen was monitored over time at different temperatures. Furthermore, through data analysis it was shown that the desorption peak associated with oxygen sorption is described well by second-order desorption kinetics. This indicates that oxygen molecules dissociate upon adsorption and that the rate-determining step for the desorption reaction is a recombination of monatomic oxygen. Typical problems with re-adsorption in this kind of TPD setup were revealed to be insignificant by using simulations. Finally, different key parameters of sorption and desorption were determined, such as desorption activation energies, density of sorption sites, and adsorption and desorption reaction order. PMID:25784205

  16. Indium nitride surface structure, desorption kinetics and thermal stability

    NASA Astrophysics Data System (ADS)

    Acharya, Ananta

    Unique physical properties such as small effective mass, high electron drift velocities, high electron mobility and small band gap energy make InN a candidate for applications in high-speed microelectronic and optoelectronic devices. The aim of this research is to understand the surface properties, desorption kinetics and thermal stability of InN epilayers that affect the growth processes and determine film quality as well as device performance and life time. We have investigated the structural properties, the surface desorption kinetics, and the thermal stability using Auger electron spectroscopy (AES), x-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), high resolution electron energy loss spectroscopy (HREELS), and temperature programmed desorption (TPD). Investigations on high pressure chemical vapor deposition (HPCVD)-grown InN samples revealed the presence of tilted crystallites, which were attributed to high group V/III flux ratio and lattice mismatch. A study of the thermal stability of HPCVD-grown InN epilayers revealed that the activation energy for nitrogen desorption was 1.6+/-0.2 eV, independent of the group V/III flux ratio. Initial investigations on the ternary alloy In0.96Ga0.04N showed single-phase, N-polar epilayers using XRD and HREELS, while a thermal desorption study revealed an activation energy for nitrogen desorption of 1.14 +/- 0.06 eV. HREELS investigations of atomic layer epitaxy (ALE)-grown InN revealed vibrational modes assigned to N-N vibrations. The atomic hydrogen cleaned InN surface also exhibited modes assigned to surface N-H without showing In-H species, which indicated N-polar InN. Complete desorption of hydrogen from the InN surface was best described by the first-order desorption kinetics with an activation energy of 0.88 +/- 0.06 eV and pre-exponential factor of (1.5 +/- 0.5) x105 s-1. Overall, we have used a number of techniques to characterize the structure, surface bonding configuration, thermal stability and hydrogen desorption kinetics of InN and In0.96Ga0.04N epilayers grown by HPCVD and ALE. High group V/III precursors ratio and lattice mismatch have a crucial influence on the film orientation. The effects of hydrogen on the decomposition add to the wide variation in the activation energy of nitrogen desorption. Presence of surface defects lowers the activation energy for hydrogen desorption from the surface.

  17. Atomic partial charges on CH3NH3PbI3 from first-principles electronic structure calculations

    NASA Astrophysics Data System (ADS)

    Madjet, Mohamed E.; El-Mellouhi, Fedwa; Carignano, Marcelo A.; Berdiyorov, Golibjon R.

    2016-04-01

    We calculated the partial charges in methylammonium (MA) lead-iodide perovskite CH3NH3PbI3 in its different crystalline phases using different first-principles electronic charge partitioning approaches, including the Bader, ChelpG, and density-derived electrostatic and chemical (DDEC) schemes. Among the three charge partitioning methods, the DDEC approach provides chemically intuitive and reliable atomic charges for this material, which consists of a mixture of transition metals, halide ions, and organic molecules. The DDEC charges are also found to be robust against the use of hybrid functionals and/or upon inclusion of spin-orbit coupling or dispersive interactions. We calculated explicitly the atomic charges with a special focus on the dipole moment of the MA molecules within the perovskite structure. The value of the dipole moment of the MA is reduced with respect to the isolated molecule due to charge redistribution involving the inorganic cage. DDEC charges and dipole moment of the organic part remain nearly unchanged upon its rotation within the octahedral cavities. Our findings will be of both fundamental and practical importance, as the accurate and consistent determination of the atomic charges is important in order to understand the average equilibrium distribution of the electrons and to help in the development of force fields for larger scale atomistic simulations to describe static, dynamic, and thermodynamic properties of the material.

  18. Stable and durable CH3NH3PbI3 perovskite solar cells at ambient conditions

    NASA Astrophysics Data System (ADS)

    Rajamanickam, Nagalingam; Kumari, Sudesh; Kalyan Vendra, Venkat; Lavery, Brandon W.; Spurgeon, Joshua; Druffel, Thad; Sunkara, Mahendra K.

    2016-06-01

    Degradation of metal‑organic halide perovskites when exposed to ambient conditions is a crucial issue that needs to be addressed for commercial viability of perovskite solar cells (PSCs). Here, a concept of encapsulating CH3NH3PbI3 perovskite crystals with a multi-functional graphene–polyaniline (PANI) composite coating to protect the perovskite against degradation from moisture, oxygen and UV light is presented. Hole-conducting polymers containing 2D layered sheet materials are presented here as multi-functional materials with oxygen and moisture impermeability. Specific studies involving PANI and graphene composites as coatings for perovskite crystals exhibited resistance to moisture and oxygen under continued exposure to UV and visible light. Most importantly, no perovskite degradation was observed even after 96 h of exposure of the PSCs to extremely high humidity (99% relative humidity). Our observations and results on perovskite protection with graphene/conducting polymer composites open up opportunities for glove-box-free and atmospheric processing of PSCs.

  19. Thermal Assisted Oxygen Annealing for High Efficiency Planar CH3NH3PbI3 Perovskite Solar Cells

    PubMed Central

    Ren, Zhiwei; Ng, Annie; Shen, Qian; Gokkaya, Huseyin Cem; Wang, Jingchuan; Yang, Lijun; Yiu, Wai-Kin; Bai, Gongxun; Djurišić, Aleksandra B.; Leung, Wallace Woon-fong; Hao, Jianhua; Chan, Wai Kin; Surya, Charles

    2014-01-01

    We report investigations on the influences of post-deposition treatments on the performance of solution-processed methylammonium lead triiodide (CH3NH3PbI3)-based planar solar cells. The prepared films were stored in pure N2 at room temperature or annealed in pure O2 at room temperature, 45°C, 65°C and 85°C for 12 hours prior to the deposition of the metal electrodes. It is found that annealing in O2 leads to substantial increase in the power conversion efficiencies (PCEs) of the devices. Furthermore, strong dependence on the annealing temperature for the PCEs of the devices suggests that a thermally activated process may underlie the observed phenomenon. It is believed that the annealing process may facilitate the diffusion of O2 into the spiro-MeOTAD for inducing p-doping of the hole transport material. Furthermore, the process can result in lowering the localized state density at the grain boundaries as well as the bulk of perovskite. Utilizing thermal assisted O2 annealing, high efficiency devices with good reproducibility were attained. A PCE of 15.4% with an open circuit voltage (VOC) 1.04 V, short circuit current density (JSC) 23 mA/cm2, and fill factor 0.64 had been achieved for our champion device. PMID:25341527

  20. Grazing behavior affects daily ruminal pH and NH3 oscillations of dairy cows on pasture.

    PubMed

    Bargo, F; Muller, L D

    2005-01-01

    Grazing behavior of Holstein cows in late lactation at 2 pasture allowances without or with supplementation was studied in a single reversal design. Twenty multiparous cows (4 ruminally cannulated) grazed a bromegrass/orchardgrass pasture offered at 2 pasture allowances: 1) low, and 2) high, with 25 and 40 kg/d of DM per cow, respectively. Half of the cows were supplemented with a mineral/vitamin mixture (1 kg/ d of the mix in a corn/molasses carrier) and the other half supplemented with a corn-based concentrate (1 kg of concentrate per 4 kg of milk). Automatic behavior recorders were used to measure grazing time and number of bites. For the mineral/vitamin mixture-supplemented cows, grazing time and number of bites after the p.m. milking was greater and ruminal pH was numerically lower at the high pasture allowance. For the concentrate-supplemented cows, grazing behavior and ruminal pH did not differ between the 2 pasture allowances. Pattern of grazing time of mineral/vitamin mixture-supplemented and concentrate-supplemented cows influenced daily oscillations of ruminal pH and NH3-N concentration. Pasture allowance affected grazing behavior of mineral/vitamin mixture-supplemented cows; however grazing behavior of concentrate-supplemented cows was not affected by pasture allowance. PMID:15591393

  1. Thermal Assisted Oxygen Annealing for High Efficiency Planar CH3NH3PbI3 Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Ren, Zhiwei; Ng, Annie; Shen, Qian; Gokkaya, Huseyin Cem; Wang, Jingchuan; Yang, Lijun; Yiu, Wai-Kin; Bai, Gongxun; Djurišić, Aleksandra B.; Leung, Wallace Woon-Fong; Hao, Jianhua; Chan, Wai Kin; Surya, Charles

    2014-10-01

    We report investigations on the influences of post-deposition treatments on the performance of solution-processed methylammonium lead triiodide (CH3NH3PbI3)-based planar solar cells. The prepared films were stored in pure N2 at room temperature or annealed in pure O2 at room temperature, 45°C, 65°C and 85°C for 12 hours prior to the deposition of the metal electrodes. It is found that annealing in O2 leads to substantial increase in the power conversion efficiencies (PCEs) of the devices. Furthermore, strong dependence on the annealing temperature for the PCEs of the devices suggests that a thermally activated process may underlie the observed phenomenon. It is believed that the annealing process may facilitate the diffusion of O2 into the spiro-MeOTAD for inducing p-doping of the hole transport material. Furthermore, the process can result in lowering the localized state density at the grain boundaries as well as the bulk of perovskite. Utilizing thermal assisted O2 annealing, high efficiency devices with good reproducibility were attained. A PCE of 15.4% with an open circuit voltage (VOC) 1.04 V, short circuit current density (JSC) 23 mA/cm2, and fill factor 0.64 had been achieved for our champion device.

  2. Photoluminescence characterisations of a dynamic aging process of organic-inorganic CH3NH3PbBr3 perovskite.

    PubMed

    Sheng, R; Wen, X; Huang, S; Hao, X; Chen, S; Jiang, Y; Deng, X; Green, M A; Ho-Baillie, A W Y

    2016-01-21

    After unprecedented development of organic-inorganic lead halide perovskite solar cells over the past few years, one of the biggest barriers towards their commercialization is the stability of the perovskite material. It is thus important to understand the interaction between the perovskite material and oxygen and/or humidity and the associated degradation process in order to improve device and encapsulation design for better durability. Here we characterize the dynamic aging process in vapour-assisted deposited (VASP) CH3NH3PbBr3 perovskite thin films using advanced optical techniques, such as time-resolved photoluminescence and fluorescence lifetime imaging microscopy (FLIM). Our investigation reveals that the perovskite grains grow spontaneously and the larger grains are formed at room temperature in the presence of moisture and oxygen. This crystallization process leads to a higher density of defects and a shorter carrier lifetime, specifically in the larger grains. Excitation-intensity-dependent steady-state photoluminescence shows both N2 stored and aged perovskite exhibit a super-linear increase of photoluminescence intensity with increasing excitation intensity; and the larger slope in aged sample suggests a larger density of defects is generated, consistent with time-resolved PL measurements. PMID:26753563

  3. Ionic polarization-induced current-voltage hysteresis in CH3NH3PbX3 perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Meloni, Simone; Moehl, Thomas; Tress, Wolfgang; Franckevičius, Marius; Saliba, Michael; Lee, Yong Hui; Gao, Peng; Nazeeruddin, Mohammad Khaja; Zakeeruddin, Shaik Mohammed; Rothlisberger, Ursula; Graetzel, Michael

    2016-02-01

    CH3NH3PbX3 (MAPbX3) perovskites have attracted considerable attention as absorber materials for solar light harvesting, reaching solar to power conversion efficiencies above 20%. In spite of the rapid evolution of the efficiencies, the understanding of basic properties of these semiconductors is still ongoing. One phenomenon with so far unclear origin is the so-called hysteresis in the current-voltage characteristics of these solar cells. Here we investigate the origin of this phenomenon with a combined experimental and computational approach. Experimentally the activation energy for the hysteretic process is determined and compared with the computational results. First-principles simulations show that the timescale for MA+ rotation excludes a MA-related ferroelectric effect as possible origin for the observed hysteresis. On the other hand, the computationally determined activation energies for halide ion (vacancy) migration are in excellent agreement with the experimentally determined values, suggesting that the migration of this species causes the observed hysteretic behaviour of these solar cells.

  4. Ab initio simulation of ammonia monohydrate (NH3ṡH2O) and ammonium hydroxide (NH4OH)

    NASA Astrophysics Data System (ADS)

    Fortes, A. D.; Brodholt, J. P.; Wood, I. G.; Vočadlo, L.; Jenkins, H. D. B.

    2001-10-01

    We report the results of the first pseudopotential plane-wave simulations of the static properties of ammonia monohydrate phase I (AMH I) and ammonium hydroxide. Our calculated fourth-order logarithmic equation of state, at zero pressure and temperature, has molar volume, V0=36.38(3) cm3 mol-1, bulk modulus, K0=9.59(9) GPa, and the first derivative of the bulk modulus with respect to pressure, K0'=5.73(21). Both this and the lattice parameters are in very good agreement with experimental values. The monohydrate transforms, via a solid-state proton transfer reaction, to ammonium hydroxide (NH4OH) at 5.0(4) GPa. The equation of state of ammonium hydroxide is, V0=31.82(5) cm3 mol-1, K0=14.78(62) GPa, K0'=2.69(48). We calculate the reaction enthalpy, ΔH(NH4OH,s→NH3ṡH2O,s)=-14.8(5) kJ mol-1 at absolute zero, and thus estimate the enthalpy of formation, ΔfH⊖(NH4OH,s)=-356 kJ mol-1 at 298 K. This result places an upper limit of 84 kJ mol-1 on the barrier to rotation of the ammonium cation, and yields an average hydrogen bond enthalpy of ˜23 kJ mol-1.

  5. Two mixed-NH3/amine platinum (II) anticancer complexes featuring a dichloroacetate moiety in the leaving group.

    PubMed

    Liu, Weiping; Su, Jia; Jiang, Jing; Li, Xingyao; Ye, Qingsong; Zhou, Hongyu; Chen, Jialin; Li, Yan

    2013-01-01

    Two mixed-NH3/amine platinum (II) complexes of 3-dichoroacetoxylcyclobutane-1, 1-dicarboxylate have been prepared in the present study and characterized by elemental analysis and IR, HPLC-MS and (1)H, (13)C-NMR. The complexes exist in equilibrium between two position isomeric forms and undergo hydrolysis reaction in aqueous solution, releasing the platinum pharmacophores and dichloroacetate which is a small-molecular cell apoptosis inducer. Both complexes were evaluated for in vitro cytotoxic profile in A549, SGC-7901 and SK-OV-3 cancer cells as well as in BEAS-2B normal cells. They exhibit markedly cytotoxicity toward cancer cells by selectively inducing the apoptosis of cancer cells, whereas leaving normal cells less affected. They have also the ability to overcome the resistance of SK-OV-3 cancer cells to cisplatin. Our findings offer an alternative novel way to develop platinum drugs which can both overcome the drug resistance and selectively target tumor cells. PMID:23955304

  6. Density Functional Studies of Stoichiometric Surfaces of Orthorhombic Hybrid Perovskite CH3NH3PbI3

    SciTech Connect

    Wang, Yun; Huang, Jingsong; Sumpter, Bobby G; Zhang, Haimin; Liu, Porun; Yang, Huagui; Zhao, Huijun

    2015-01-01

    Organic/inorganic hybrid perovskite materials are highly attractive for dye-sensitized solar cells as demonstrated by their rapid advances in energy conversion efficiency. In this work, the structures, energetics, and electronic properties for a range of stoichiometric surfaces of the orthorhombic perovskite CH3NH3PbI3 are theoretically studied using density functional theory. Various possible spatially and constitutionally isomeric surfaces are considered by diversifying the spatial orientations and connectivities of surface Pb-I bonds. The comparison of the surface energies for the most stable configurations identified for various surfaces shows that the stabilities of stoichiometric surfaces are mainly dictated by the coordination numbers of surface atoms, which are directly correlated with the numbers of broken bonds. Additionally, Coulombic interactions between I anions and organic countercations on the surface also contribute to the stabilization. Electronic properties are compared between the most stable (100) surface and the bulk phase, showing generally similar features except for the lifted band degeneracy and the enhanced bandgap energy for the surface. These studies on the stoichiometric surfaces serve as the first step toward gaining a fundamental understanding of the interfacial properties in the current structural design of perovskite based solar cells, in order to achieve further breakthroughs in solar conversion efficiencies.

  7. Density Functional Studies of Stoichiometric Surfaces of Orthorhombic Hybrid Perovskite CH3NH3PbI3

    DOE PAGESBeta

    Wang, Yun; Huang, Jingsong; Sumpter, Bobby G; Zhang, Haimin; Liu, Porun; Yang, Huagui; Zhao, Huijun

    2015-01-01

    Organic/inorganic hybrid perovskite materials are highly attractive for dye-sensitized solar cells as demonstrated by their rapid advances in energy conversion efficiency. In this work, the structures, energetics, and electronic properties for a range of stoichiometric surfaces of the orthorhombic perovskite CH3NH3PbI3 are theoretically studied using density functional theory. Various possible spatially and constitutionally isomeric surfaces are considered by diversifying the spatial orientations and connectivities of surface Pb-I bonds. The comparison of the surface energies for the most stable configurations identified for various surfaces shows that the stabilities of stoichiometric surfaces are mainly dictated by the coordination numbers of surface atoms,more » which are directly correlated with the numbers of broken bonds. Additionally, Coulombic interactions between I anions and organic countercations on the surface also contribute to the stabilization. Electronic properties are compared between the most stable (100) surface and the bulk phase, showing generally similar features except for the lifted band degeneracy and the enhanced bandgap energy for the surface. These studies on the stoichiometric surfaces serve as the first step toward gaining a fundamental understanding of the interfacial properties in the current structural design of perovskite based solar cells, in order to achieve further breakthroughs in solar conversion efficiencies.« less

  8. Demonstration of isotype GaN/AlN/GaN heterobarrier diodes by NH3-molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Fireman, Micha N.; Browne, David A.; Mazumder, Baishakhi; Speck, James S.; Mishra, Umesh K.

    2015-05-01

    The results of vertical transport through nitride heterobarrier structures grown by ammonia molecular beam epitaxy are presented. Structures are designed with binary layers to avoid the effects of random alloy fluctuations in ternary nitride barriers. The unintentional incorporation of Ga in the AlN growth is investigated by atom probe tomography and is shown to be strongly dependent on both the NH3 flowrate and substrate temperature growth parameters. Once nominally pure AlN layer growth conditions are achieved, structures consisting of unintentionally doped (UID) GaN spacer layers adjacent to a nominally pure AlN are grown between two layers of n+ GaN, from which isotype diodes are fabricated. Varying the design parameters of AlN layer thickness, UID spacer layer thickness, and threading dislocation density show marked effects on the vertical transport characteristics of these structures. The lack of significant temperature dependence, coupled with Fowler-Nordheim and/or Milliken-Lauritsen analysis, point to a prevalently tunneling field emission mechanism through the AlN barrier. Once flatband conditions in the UID layer are achieved, electrons leave the barrier with significant energy. This transport mechanism is of great interest for applications in hot electron structures.

  9. An analytical approach to evaluate the performance of graphene and carbon nanotubes for NH3 gas sensor applications

    PubMed Central

    Akbari, Elnaz; Enzevaee, Aria; Ahmadi, Mohamad T; Saeidmanesh, Mehdi; Khaledian, Mohsen; Karimi, Hediyeh; Yusof, Rubiyah

    2014-01-01

    Summary Carbon, in its variety of allotropes, especially graphene and carbon nanotubes (CNTs), holds great potential for applications in variety of sensors because of dangling ?-bonds that can react with chemical elements. In spite of their excellent features, carbon nanotubes (CNTs) and graphene have not been fully exploited in the development of the nanoelectronic industry mainly because of poor understanding of the band structure of these allotropes. A mathematical model is proposed with a clear purpose to acquire an analytical understanding of the field-effect-transistor (FET) based gas detection mechanism. The conductance change in the CNT/graphene channel resulting from the chemical reaction between the gas and channel surface molecules is emphasized. NH3 has been used as the prototype gas to be detected by the nanosensor and the corresponding currentvoltage (IV) characteristics of the FET-based sensor are studied. A graphene-based gas sensor model is also developed. The results from graphene and CNT models are compared with the experimental data. A satisfactory agreement, within the uncertainties of the experiments, is obtained. Graphene-based gas sensor exhibits higher conductivity compared to that of CNT-based counterpart for similar ambient conditions. PMID:24991510

  10. Ionic polarization-induced current-voltage hysteresis in CH3NH3PbX3 perovskite solar cells.

    PubMed

    Meloni, Simone; Moehl, Thomas; Tress, Wolfgang; Franckevičius, Marius; Saliba, Michael; Lee, Yong Hui; Gao, Peng; Nazeeruddin, Mohammad Khaja; Zakeeruddin, Shaik Mohammed; Rothlisberger, Ursula; Graetzel, Michael

    2016-01-01

    CH3NH3PbX3 (MAPbX3) perovskites have attracted considerable attention as absorber materials for solar light harvesting, reaching solar to power conversion efficiencies above 20%. In spite of the rapid evolution of the efficiencies, the understanding of basic properties of these semiconductors is still ongoing. One phenomenon with so far unclear origin is the so-called hysteresis in the current-voltage characteristics of these solar cells. Here we investigate the origin of this phenomenon with a combined experimental and computational approach. Experimentally the activation energy for the hysteretic process is determined and compared with the computational results. First-principles simulations show that the timescale for MA(+) rotation excludes a MA-related ferroelectric effect as possible origin for the observed hysteresis. On the other hand, the computationally determined activation energies for halide ion (vacancy) migration are in excellent agreement with the experimentally determined values, suggesting that the migration of this species causes the observed hysteretic behaviour of these solar cells. PMID:26852685

  11. High intrinsic carrier mobility and photon absorption in the perovskite CH3NH3PbI3.

    PubMed

    Wang, Youwei; Zhang, Yubo; Zhang, Peihong; Zhang, Wenqing

    2015-05-01

    The carrier transport and optical properties of the hybrid organic-inorganic perovskite CH3NH3PbI3 are investigated using first-principles approaches. We found that the electron and hole mobilities could reach surprisingly high values of 7-30 × 10(3) and 1.5-5.5 × 10(3) cm(2) V(-1) s(-1), respectively, and both are estimated to be much higher than the current experimental measurements. The high carrier mobility is ascribed to the intrinsically small effective masses of anti-bonding band-edge states. The above results imply that there is still space to improve the performance of related solar cells. This material also has a sharp photon absorption edge and an absorption coefficient as high as 10(5) cm(-1), both of which contribute to effective utilization of solar radiation. Although band-edge states are mainly derived from the inorganic ions of Pb and I, thermal movement of the organic base has indirect influences on the bandgap and carrier effective masses, resulting in the temperature-dependent solar cell efficiencies. PMID:25855411

  12. A cation trap for anodic stripping voltammetry: NH3-plasma treated carbon nanotubes for adsorption and detection of metal ions.

    PubMed

    Wei, Yan; Yang, Ran; Chen, Xing; Wang, Lun; Liu, Jin-Huai; Huang, Xing-Jiu

    2012-11-28

    NH(3)-plasma treated multi-walled carbon nanotubes (pn-MWCNTs) with cation traps for the detection of ultratrace quantities of Zn(II), Cd(II), Cu(II), and Hg(II) using square wave anodic stripping voltammetry (SWASV) is described. The pn-MWCNTs use their adsorption performance to enhance the sensitivity. It is found that under optimized conditions Zn(II), Cd(II), Cu(II) and Hg(II) were individually detected at potentials of -1.16, -0.78, -0.268 and 0.108 V, respectively. The detection limit (3σ method) of 0.314, 0.0272, 0.2263, and 0.1439 nM toward Zn(II), Cd(II), Cu(II), and Hg(II) is achievable, respectively. No interference could be seen during the simultaneous detection of Zn(II), Cd(II), Cu(II), and Hg(II). The pn-MWCNTs exhibit excellent selectivity owing to the different ability of adsorption. A study of the ability of pn-MWCNTs in practical application is carried out using a sample of water collected from Dongpu Reservoir in Hefei City, Anhui, China. It is found that the results were favorable when compared against inductively coupled plasma atomic emission spectrometry (ICP-AES) analysis. PMID:23146394

  13. Stable and durable CH3NH3PbI3 perovskite solar cells at ambient conditions.

    PubMed

    Rajamanickam, Nagalingam; Kumari, Sudesh; Vendra, Venkat Kalyan; Lavery, Brandon W; Spurgeon, Joshua; Druffel, Thad; Sunkara, Mahendra K

    2016-06-10

    Degradation of metal-organic halide perovskites when exposed to ambient conditions is a crucial issue that needs to be addressed for commercial viability of perovskite solar cells (PSCs). Here, a concept of encapsulating CH3NH3PbI3 perovskite crystals with a multi-functional graphene-polyaniline (PANI) composite coating to protect the perovskite against degradation from moisture, oxygen and UV light is presented. Hole-conducting polymers containing 2D layered sheet materials are presented here as multi-functional materials with oxygen and moisture impermeability. Specific studies involving PANI and graphene composites as coatings for perovskite crystals exhibited resistance to moisture and oxygen under continued exposure to UV and visible light. Most importantly, no perovskite degradation was observed even after 96 h of exposure of the PSCs to extremely high humidity (99% relative humidity). Our observations and results on perovskite protection with graphene/conducting polymer composites open up opportunities for glove-box-free and atmospheric processing of PSCs. PMID:27125437

  14. Ionic polarization-induced current–voltage hysteresis in CH3NH3PbX3 perovskite solar cells

    PubMed Central

    Meloni, Simone; Moehl, Thomas; Tress, Wolfgang; Franckevičius, Marius; Saliba, Michael; Lee, Yong Hui; Gao, Peng; Nazeeruddin, Mohammad Khaja; Zakeeruddin, Shaik Mohammed; Rothlisberger, Ursula; Graetzel, Michael

    2016-01-01

    CH3NH3PbX3 (MAPbX3) perovskites have attracted considerable attention as absorber materials for solar light harvesting, reaching solar to power conversion efficiencies above 20%. In spite of the rapid evolution of the efficiencies, the understanding of basic properties of these semiconductors is still ongoing. One phenomenon with so far unclear origin is the so-called hysteresis in the current–voltage characteristics of these solar cells. Here we investigate the origin of this phenomenon with a combined experimental and computational approach. Experimentally the activation energy for the hysteretic process is determined and compared with the computational results. First-principles simulations show that the timescale for MA+ rotation excludes a MA-related ferroelectric effect as possible origin for the observed hysteresis. On the other hand, the computationally determined activation energies for halide ion (vacancy) migration are in excellent agreement with the experimentally determined values, suggesting that the migration of this species causes the observed hysteretic behaviour of these solar cells. PMID:26852685

  15. Clumped-isotope signatures at equilibrium of CH4, NH3, H2O, H2S and SO2

    NASA Astrophysics Data System (ADS)

    Liu, Qi; Liu, Yun

    2016-02-01

    High precision Δi values at equilibrium determined by theoretical methods are imperatively needed as references for the development of new clumped-isotope thermometers (or tracers). In this study, quantum chemistry methods with corrections beyond the harmonic approximation are used to obtain the clumped-isotope signatures at equilibrium of several gas-phase molecules (i.e., CH4, NH3, H2O, H2S, and SO2). Here, we consider as many corrections to the traditional Bigeleisen-Mayer equation as possible to obtain accurate Δi values at equilibrium and their temperature dependences. The corrections include anharmonic correction for zero-point energy, anharmonic correction for vibrational excited states, vibration-rotation coupling correction for zero-point energy, vibration-rotation coupling correction for vibrational excited states, quantum mechanical correction to rotation, and centrifugal distortion correction, which are important for theoretical understanding of clumped-isotope signals. Specifically, molecular constants are calculated via second-order perturbative analysis at the MP2/aug-cc-pVTZ level. The CCSD/6-311+G(3df,3pd) and CCSD/aug-cc-pVTZ levels are further employed to ensure the precision of harmonic frequencies of methane. For methane, a polynomial fit of ΔCH133D values over the temperature range of from 273.15 to 1000 K is obtained:

  16. Photoluminescence characterisations of a dynamic aging process of organic-inorganic CH3NH3PbBr3 perovskite

    NASA Astrophysics Data System (ADS)

    Sheng, R.; Wen, X.; Huang, S.; Hao, X.; Chen, S.; Jiang, Y.; Deng, X.; Green, M. A.; Ho-Baillie, A. W. Y.

    2016-01-01

    After unprecedented development of organic-inorganic lead halide perovskite solar cells over the past few years, one of the biggest barriers towards their commercialization is the stability of the perovskite material. It is thus important to understand the interaction between the perovskite material and oxygen and/or humidity and the associated degradation process in order to improve device and encapsulation design for better durability. Here we characterize the dynamic aging process in vapour-assisted deposited (VASP) CH3NH3PbBr3 perovskite thin films using advanced optical techniques, such as time-resolved photoluminescence and fluorescence lifetime imaging microscopy (FLIM). Our investigation reveals that the perovskite grains grow spontaneously and the larger grains are formed at room temperature in the presence of moisture and oxygen. This crystallization process leads to a higher density of defects and a shorter carrier lifetime, specifically in the larger grains. Excitation-intensity-dependent steady-state photoluminescence shows both N2 stored and aged perovskite exhibit a super-linear increase of photoluminescence intensity with increasing excitation intensity; and the larger slope in aged sample suggests a larger density of defects is generated, consistent with time-resolved PL measurements.

  17. Structural characterization, thermal, dielectric, vibrational properties and molecular dynamics of (C 5H 5NH) 3BiCl 6

    NASA Astrophysics Data System (ADS)

    Tarasiewicz, J.; Jakubas, R.; Bator, G.; Zaleski, J.; Baran, J.; Medycki, W.

    2009-08-01

    (C 5H 5NH) 3BiCl 6 crystallizes at room temperature in the triclinic space group P1¯. The crystal is built up of the separated BiCl63- octahedral anions and pyridinium cations. Differential scanning calorimetry (DSC) and dilatometric measurements disclose structural phase transition of first-order type at 265/302 K (cooling/heating). The dielectric investigations reveal a step-wise change of the electric permittivity at T c characteristic of the crystals with the high-temperature plastic-like phase. Temperature-dependent infrared spectra for polycrystalline samples have been taken between 20 and 306 K to clarify the cation dynamics contribution to the mechanism of the phase transition. The modes assigned to the deformation vibration of the NH + group in the pyridinium ring appear to be the most sensitive to the phase transition. The possible molecular motions of the C 5H 5NH + cations are studied by the proton magnetic resonance ( 1H NMR).

  18. Monte Carlo study of a compressible pseudospin model for (CH3NH3)5Bi2Cl11

    NASA Astrophysics Data System (ADS)

    Kuchta, B.; Carpentier, P.; Jakubas, R.; ZajaÇ, W.; Zieliński, P.

    2001-06-01

    A two-sublattice peudospin model with distance-dependent interaction parameters is constructed for the ferroelectric phase transition at 307 K and for the isomorphous anomaly at 180 K in pentakis (methylammonium) undecachlorodibismuthate (III) (CH3NH3)5Bi2Cl11. A series of Monte Carlo simulations involving continuous degrees of freedom of deformation is performed for the model. The critical temperatures turn out about 23% lower than those resulting from the mean-field treatment for the three-dimensional fcc lattice in the absence of coupling with strain. An upward shift in the critical temperature then is found due to the coupling with the strain. The multiple histogram method is used to obtain the theoretical predictions for the temperature dependence of the spontaneous polarization, dielectric susceptibility, and specific heat. The existence of a narrow peak in the specific heat and the ratio of the Curie constants close to 4 are confirmed. Evidence is given of the usefulness of the Monte Carlo method with fairly small simulation boxes for the studies of isomorphous anomalies.

  19. Structure cristalline et etude par spectrometrie de vibration (IR et Raman) du bis(ethylenediammonium) diphosphate (NH 3(CH 2) 2NH 3) 2 · P 2O 7

    NASA Astrophysics Data System (ADS)

    Kamoun, Slaheddine; Jouini, Amor; Daoud, Abdelaziz

    1992-07-01

    Classical methods extensively known for the synthesis of inorganic condensed phosphates are used to give compounds that are intermediate between inorganic and organic. We prepared the title compound to examine the possibility of using, in this new field, the ion exchange resin and Boullé's methods. Chemical preparation, crystal structure, and vibrational studies are given for a new diphosphate. The bis(ethylenediammonium) diphosphate salt is monoclinic with the unit cell dimensions a = 8.724(1), b = 13.511(2), c = 10.039(1)Å, β = 96.25(1)°, V = 1176.3(5)Å 3, Dm = 1.673Mg m -3, D x = 1.684Mg m -3, μ = 2.163 mm -1, space group C2 c with Z = 4. The structure was solved by the Patterson method and refined to a final R value of 0.059 for 2602 observed independent reflections. The P sbnd O(L) sbnd P bridge is symmetrical with a P sbnd O(L) distance of 1.570(1)Åand a POP angle of 141.94(7)°. The P 2O 4-7 anions are located around the twofold axis. The ethylenediammonium dications have a trans configuration. Half of them, having a crystallographic inversion center, are located in channels delimited by the diphosphate anions. The others, located around the twofold axis, are sandwiched along the c axis between two diphosphate anions. The cohesion and the stability of the atomic arrangement result from the N sbnd H···O hydrogen bonds. The IR and Raman spectra of [NH 3(CH) 2NH 32 · P 2O 7 are recorded and analyzed. From the spectra it is inferred that the P 2O 4-7 anion has a C2 symmetry in the crystal; all the POP modes (stretching and bending) are active in IR and Raman.

  20. Comparison of π-hole tetrel bonding with σ-hole halogen bonds in complexes of XCN (X = F, Cl, Br, I) and NH3.

    PubMed

    Nziko, Vincent de Paul N; Scheiner, Steve

    2016-02-01

    In addition to the standard halogen bond formed when NH3 approaches XCN (X = F, Cl, Br, I) along its molecular axis, a perpendicular approach is also possible, toward a π-hole that is present above the X-C bond. MP2/aug-cc-pVDZ calculations indicate the latter geometry is favored for X = F, and the σ-hole structure is preferred for the heavier halogens. The π-hole structure is stabilized by charge transfer from the NH3 lone pair into the π*(CN) antibonding orbital, and is characterized by a bond path from the N of NH3 to the C atom of XCN, a form of tetrel bond. The most stable 2 : 1 NH3/XCN heterotrimer for X = F and Cl is cyclic and contains a tetrel bond augmented by a pair of NHN H-bonds. For X = Br and I, the favored trimer is noncyclic, stabilized by a tetrel and a halogen bond. PMID:26750543

  1. Tuning superior solar cell performance of carrier mobility and absorption in perovskite CH3NH3GeCl3: A density functional calculations

    NASA Astrophysics Data System (ADS)

    Zhao, Yu-Qing; Wu, Li-Juan; Liu, Biao; Wang, Ling-Zhi; He, Peng-Bin; Cai, Meng-Qiu

    2016-05-01

    The solar cell based on hybrid organic-inorganic halide perovskite has received considerable attention. One of the most important issues in the pursuit of further developments in this area is to obtain both a high carrier mobility and an excellent ability of light adsorption. In this paper, we investigate the electronic structure and electronic effective masses of the new non-toxic material CH3NH3GeCl3 by first-principle calculations. The results show that the absorption efficiency of CH3NH3GeCl3 is more superior to that of CH3NH3PbI3 in short wavelength region. We trace this result to the ferroelectricity caused by the more serious octahedral GeCl6- distortion. We also discover a new relationship between the carrier effective masses anisotropy and the anisotropy of electronic density of states along three principal directions. Moreover, while applied the isotropic compressive pressure, the absorption efficiency and carrier mobility of CH3NH3GeCl3 in orthorhombic phase are improved greatly due to changes of electronic structure. We speculate that these are general results of tuning of the carrier mobility by controlling the band gap and the electronic occupation along different directions, to obtain both a high carrier mobility and an excellent ability of light adsorption.

  2. Structures and Electronic Properties of Different CH3NH3PbI3/TiO2 Interface: A First-Principles Study

    NASA Astrophysics Data System (ADS)

    Geng, Wei; Tong, Chuan-Jia; Liu, Jiang; Zhu, Wenjun; Lau, Woon-Ming; Liu, Li-Min

    2016-02-01

    Methylammonium lead iodide perovskite, CH3NH3PbI3, has attracted particular attention due to its fast increase in efficiency in dye sensitization TiO2 solid-state solar cells. We performed first-principles calculations to investigate several different types of CH3NH3PbI3/TiO2 interfaces. The interfacial structures between the different terminated CH3NH3PbI3 and phase TiO2 are thoroughly explored, and the calculated results suggest that the interfacial Pb atoms play important roles in the structure stability and electronic properties. A charge transfer from Pb atoms to the O atoms of TiO2 lead to the band edge alignment of Pb-p above Ti-d about 0.4 eV, suggesting a better carries separation. On the other hand, for TiO2, rutile (001) is the better candidate due to the better lattice and atoms arrangement match with CH3NH3PbI3.

  3. Structures and Electronic Properties of Different CH3NH3PbI3/TiO2 Interface: A First-Principles Study

    PubMed Central

    Geng, Wei; Tong, Chuan-Jia; Liu, Jiang; Zhu, Wenjun; Lau, Woon-Ming; Liu, Li-Min

    2016-01-01

    Methylammonium lead iodide perovskite, CH3NH3PbI3, has attracted particular attention due to its fast increase in efficiency in dye sensitization TiO2 solid-state solar cells. We performed first-principles calculations to investigate several different types of CH3NH3PbI3/TiO2 interfaces. The interfacial structures between the different terminated CH3NH3PbI3 and phase TiO2 are thoroughly explored, and the calculated results suggest that the interfacial Pb atoms play important roles in the structure stability and electronic properties. A charge transfer from Pb atoms to the O atoms of TiO2 lead to the band edge alignment of Pb-p above Ti-d about 0.4 eV, suggesting a better carries separation. On the other hand, for TiO2, rutile (001) is the better candidate due to the better lattice and atoms arrangement match with CH3NH3PbI3. PMID:26846401

  4. Comparison of the Cardiac MicroPET Images Obtained Using [18F]FPTP and [13N]NH3 in Rat Myocardial Infarction Models

    PubMed Central

    2014-01-01

    The short half-life of current positron emission tomography (PET) cardiac tracers limits their widespread clinical use. We previously developed a 18F-labeled phosphonium cation, [18F]FPTP, that demonstrated sharply defined myocardial defects in a corresponding infarcted myocardium. The aim of this study was to compare the image properties of PET scans obtained using [18F]FPTP with those obtained using [13N]NH3 in rat myocardial infarction models. Perfusion abnormality was analyzed in 17 segments of polar map images. The myocardium-to-liver and myocardium-to-lung ratios of [18F]FPTP were 10.48 and 2.65 times higher, respectively, than those of [13N]NH3 in images acquired 30 min after tracer injection. The myocardial defect size measured by [18F]FPTP correlated more closely with the hypoperfused area measured by quantitative 2,3,5-triphenyltetrazolium chloride staining (r = 0.89, P < 0.01) than did [13N]NH3 (r = 0.84, P < 0.01). [18F]FPTP might be useful as a replacement for the myocardial agent [13N]NH3 in cardiac PET/CT applications. PMID:25313324

  5. Surface plasmon resonance study on the optical sensing properties of tin oxide (SnO2) films to NH3 gas

    NASA Astrophysics Data System (ADS)

    Paliwal, Ayushi; Sharma, Anjali; Tomar, Monika; Gupta, Vinay

    2016-04-01

    Surface plasmon resonance (SPR) technique is an easy and reliable method for detecting very low concentration of toxic gases at room temperature using a gas sensitive thin film layer. In the present work, a room temperature operated NH3 gas sensor has been developed using a laboratory assembled SPR measurement setup utilising a p-polarized He-Ne laser and prism coupling technique. A semiconducting gas sensitive tin oxide (SnO2) layer has been deposited under varying growth conditions (i.e., by varying deposition pressure) over the gold coated prism (BK-7) to excite the surface plasmon modes in Kretschmann configuration. The SPR reflectance curves for prism/Au/SnO2/air system for SnO2 thin films prepared at different sputtering pressure were measured, and the SnO2 film deposited at 10 mT pressure is found to exhibit a sharp SPR reflectance curve with minimum reflectance (0.32) at the resonance angle of 44.7° which is further used for sensing NH3 gas of different concentration at room temperature. The SPR reflectance curve shows a significant shift in resonance angle from 45.05° to 58.55° on interacting with NH3. The prepared sensor is found to give high sensing response (0.11) with high selectivity towards very low concentration of NH3 (0.5 ppm) and quick response time at room temperature.

  6. Reinterpretation of the Vibrational Spectroscopy of the Medicinal Bioinorganic Synthon c,c,t-[Pt(NH3)2Cl2(OH)2]†

    PubMed Central

    Johnstone, Timothy C.

    2014-01-01

    The Pt(IV) complex c,c,t-[Pt(NH3)2Cl2(OH)2] is an important intermediate in the synthesis of Pt(IV) anticancer prodrugs and has been investigated as an anticancer agent in its own right. An analysis of the vibrational spectroscopy of this molecule was previously reported [Faggiani et al., 1982, Can. J. Chem. 60, 529] in which crystallographic determination of the structure of the complex permitted a site group approach. The space group, however, was incorrectly assigned. In the present study we have redetermined at high resolution crystal structures of c,c,t-[Pt(NH3)2Cl2(OH)2] and c,c,t-[Pt(NH3)2Cl2(OH)2]·H2O2, which enable discussion of the effect of hydrogen bonding on the N–H and O–H vibrational bands. The correct crystallographic site symmetry of the platinum complex in the c,c,t-[Pt(NH3)2Cl2(OH)2] structure is employed to conduct a new vibrational analysis using both group theoretical and modern DFT methods. This analysis reveals the nature and symmetry of the “missing band” described in the original publication and suggests a possible explanation for its disappearance. PMID:24515615

  7. VizieR Online Data Catalog: Linelists for ammonia NH3, NH2D, ND2H, and ND3 (Coudert+, 2006)

    NASA Astrophysics Data System (ADS)

    Coudert, L. H.; Roueff, E.

    2005-11-01

    Linelists with calculated line positions and line intensities for ammonia (NH3) molecule and its three deuterated variants NH2D, ND2H, and ND3 with quadrupole coupling hyperfine splittings. Lines in linelists are formatted as in the JPL data base (Pickett, Poynter, Cohen et al. 1998, J. Quant. Spectrosc. Radiat. Transfer, 60, 883). (4 data files).

  8. On the Surface Formation of NH3 and HNCO in Dark Molecular Clouds - Searching for Wöhler Synthesis in the Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Fedoseev, Gleb; Lamberts, Thanja; Linnartz, Harold; Ioppolo, Sergio; Zhao, Dongfeng

    Despite its potential to reveal the link between the formation of simple species and more complex molecules (e.g., amino acids), the nitrogen chemistry of the interstellar medium (ISM) is still poorly understood. Ammonia (NH _{3}) is one of the few nitrogen-bearing species that have been observed in interstellar ices toward young stellar objects (YSOs) and quiescent molecular clouds. The aim of the present work is to experimentally investigate surface formation routes of NH _{3} and HNCO through non-energetic surface reactions in interstellar ice analogues under fully controlled laboratory conditions and at astrochemically relevant cryogenic temperatures. This study focuses on the formation of NH _{3} and HNCO in CO-rich (non-polar) interstellar ices that simulate the CO freeze-out stage in interstellar dark cloud regions, well before thermal and energetic processing start to become predominant. Our work confirms the surface formation of ammonia through the sequential addition of three hydrogen/deuterium atoms to a single nitrogen atom at low temperature. The H/D fractionation of the formed ammonia is also shown. Furthermore, we show the surface formation of solid HNCO through the interaction of CO molecules with NH radicals - one of the intermediates in the formation of solid NH _{3}. Finally, we discuss the implications of HNCO in astrobiology, as a possible starting point for the formation of more complex prebiotic species.

  9. Low-temperature surface formation of NH3 and HNCO: hydrogenation of nitrogen atoms in CO-rich interstellar ice analogues

    NASA Astrophysics Data System (ADS)

    Fedoseev, G.; Ioppolo, S.; Zhao, D.; Lamberts, T.; Linnartz, H.

    2015-01-01

    Solid-state astrochemical reaction pathways have the potential to link the formation of small nitrogen-bearing species, like NH3 and HNCO, and prebiotic molecules, specifically amino acids. To date, the chemical origin of such small nitrogen-containing species is still not well understood, despite the fact that ammonia is an abundant constituent of interstellar ices towards young stellar objects and quiescent molecular clouds. This is mainly because of the lack of dedicated laboratory studies. The aim of this work is to experimentally investigate the formation routes of NH3 and HNCO through non-energetic surface reactions in interstellar ice analogues under fully controlled laboratory conditions and at astrochemically relevant temperatures. This study focuses on the formation of NH3 and HNCO in CO-rich (non-polar) interstellar ices that simulate the CO freeze-out stage in dark interstellar cloud regions, well before thermal and energetic processing start to become relevant. We demonstrate and discuss the surface formation of solid HNCO through the interaction of CO molecules with NH radicals - one of the intermediates in the formation of solid NH3 upon sequential hydrogenation of N atoms. The importance of HNCO for astrobiology is discussed.

  10. Structures and Electronic Properties of Different CH3NH3PbI3/TiO2 Interface: A First-Principles Study.

    PubMed

    Geng, Wei; Tong, Chuan-Jia; Liu, Jiang; Zhu, Wenjun; Lau, Woon-Ming; Liu, Li-Min

    2016-01-01

    Methylammonium lead iodide perovskite, CH3NH3PbI3, has attracted particular attention due to its fast increase in efficiency in dye sensitization TiO2 solid-state solar cells. We performed first-principles calculations to investigate several different types of CH3NH3PbI3/TiO2 interfaces. The interfacial structures between the different terminated CH3NH3PbI3 and phase TiO2 are thoroughly explored, and the calculated results suggest that the interfacial Pb atoms play important roles in the structure stability and electronic properties. A charge transfer from Pb atoms to the O atoms of TiO2 lead to the band edge alignment of Pb-p above Ti-d about 0.4 eV, suggesting a better carries separation. On the other hand, for TiO2, rutile (001) is the better candidate due to the better lattice and atoms arrangement match with CH3NH3PbI3. PMID:26846401

  11. Difference in chemical reactions in bulk plasma and sheath regions during surface modification of graphene oxide film using capacitively coupled NH3 plasma

    NASA Astrophysics Data System (ADS)

    Lee, Sung-Youp; Kim, Chan; Kim, Hong Tak

    2015-09-01

    Reduced graphene oxide (r-GO) films were obtained from capacitively coupled NH3 plasma treatment of spin-coated graphene oxide (GO) films at room temperature. Variations were evaluated according to the two plasma treatment regions: the bulk plasma region (Rbulk) and the sheath region (Rsheath). Reduction and nitridation of the GO films began as soon as the NH3 plasma was exposed to both regions. However, with the increase in treatment time, the reduction and nitridation reactions differed in each region. In the Rbulk, NH3 plasma ions reacted chemically with oxygen functional groups on the GO films, which was highly effective for reduction and nitridation. While in the Rsheath, physical reactions by ion bombardment were dominant because plasma ions were accelerated by the strong electrical field. The accelerated plasma ions reacted not only with the oxygen functional groups but also with the broken carbon chains, which caused the removal of the GO films by the formation of hydrocarbon gas species. These results showed that reduction and nitridation in the Rbulk using capacitively coupled NH3 plasma were very effective for modifying the properties of r-GO films for application as transparent conductive films.

  12. Laser-assisted crystallization of CH3NH3PbI3 films for efficient perovskite solar cells with a high open-circuit voltage.

    PubMed

    Li, Faming; Zhu, Weidong; Bao, Chunxiong; Yu, Tao; Wang, Yangrunqian; Zhou, Xiaoxin; Zou, Zhigang

    2016-04-01

    Laser irradiation as a rapid crystallization approach was successfully introduced to prepare homogeneous, dense-grained CH3NH3PbI3 films. Planar-heterojunction solar cells employing these high-quality films showed the optimal efficiency of 17.8% with a remarkably high open-circuit voltage of 1.146 V. PMID:27009444

  13. Efficient and stable CH3NH3PbI3-sensitized ZnO nanorod array solid-state solar cells.

    PubMed

    Bi, Dongqin; Boschloo, Gerrit; Schwarzmüller, Stefan; Yang, Lei; Johansson, Erik M J; Hagfeldt, Anders

    2013-12-01

    We report for the first time the use of a perovskite (CH3NH3PbI3) absorber in combination with ZnO nanorod arrays (NRAs) for solar cell applications. The perovskite material has a higher absorption coefficient than molecular dye sensitizers, gives better solar cell stability, and is therefore more suited as a sensitizer for ZnO NRAs. A solar cell efficiency of 5.0% was achieved under 1000 W m(-2) AM 1.5 G illumination for a solar cell with the structure: ZnO NRA/CH3NH3PbI3/spiro-MeOTAD/Ag. Moreover, the solar cell shows a good long-term stability. Using transient photocurrent and photovoltage measurements it was found that the electron transport time and lifetime vary with the ZnO nanorod length, a trend which is similar to that in dye-sensitized solar cells, DSCs, suggesting a similar charge transfer process in ZnO NRA/CH3NH3PbI3 solar cells as in conventional DSCs. Compared to CH3NH3PbI3/TiO2 solar cells, ZnO shows a lower performance due to more recombination losses. PMID:24100947

  14. The Impact of Fertilizer Type and Application Method on the Loss of Greenhouse (CO2, N2O, CH4), and Air Quality (NH3) Gases

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An experiment initiated in the Spring of 2007 at the Sand Mountain Agricultural Experiment Station in Crossville, AL will be discussed. The objective of this experiment is to evaluate the loss of NH3 from different land management (conventional tillage vs. conservation tillage), fertilizers (urea-a...

  15. Structural characterization, thermal, dielectric and vibrational properties of tris(allylammonium) hexabromoantimonate(III), (C 3H 5NH 3) 3SbBr 6

    NASA Astrophysics Data System (ADS)

    Płowaś, I.; Białońska, A.; Jakubas, R.; Bator, G.; Zarychta, B.; Baran, J.

    2010-09-01

    The novel inorganic-organic hybrid material, allylammonium hexabromoantimonate(III), ( C3H5NH3) 3SbBr6, has been synthesized and its structure has been determined by means of the single-crystal X-ray diffraction studies at five temperatures (273, 248, 220, 170 and 100 K). At room temperature the compound crystallizes in the monoclinic space group, C2/ m. Its crystal structure is composed of the discrete SbBr63- anions and three non-equivalent allylammonium, ( C3H5NH3) +, cations. In ( C3H5NH3) 3SbBr6 three solid-solid structural phase transitions are detected: a continuous one at 260/256 K (on heating-cooling) from phase I to II, a discontinuous one at 227/208 K (II→III) and another discontinuous at 197/191 K (III→IV). The electric properties of the compound have been measured in a wide temperature region (150-300 K). Temperature-dependent vibrational properties in the frequency region 3500-500 cm -1 have been reviewed. Possible mechanisms of the phase transitions in ( C3H5NH3) 3SbBr6 are discussed on the basis of the presented results.

  16. Mesoscopic TiO2/CH3NH3PbI3 perovskite solar cells with new hole-transporting materials containing butadiene derivatives.

    PubMed

    Lv, Songtao; Han, Liying;