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Sample records for nh3 temperature-programmed desorption

  1. Investigation of potential alternative hydrogen carrier, Mg supported zeolite with temperature programmed desorption of NH3.

    PubMed

    Cho, Sung June; Kim, Tak Hee; Jang, Young Bae; Lee, Jun

    2007-11-01

    Magnesium ion exchanged zeolite A was subject to the measurement of the temperature programmed desorption of NH3 to explore the possibility of the potential hydrogen carrier. The result suggested that the Mg supported NaA zeolite released a significant amount of ammonia corresponding to 1.4 Hwt% hydrogen at around 373 K. Under the same condition after the NH3 adsorption at ambient temperature, the MgCl2 sample released 1.0 Hwt% hydrogen at around 340 K. The present work suggests that the Mg supported zeolite can also be utilized as hydrogen carrier.

  2. Temperature programmed desorption of weakly bound adsorbates on Au(111)

    NASA Astrophysics Data System (ADS)

    Engelhart, Daniel P.; Wagner, Roman J. V.; Meling, Artur; Wodtke, Alec M.; Schäfer, Tim

    2016-08-01

    We have performed temperature programmed desorption (TPD) experiments to analyze the desorption kinetics of Ar, Kr, Xe, C2H2, SF6, N2, NO and CO on Au(111). We report desorption activation energies (Edes), which are an excellent proxy for the binding energies. The derived binding energies scale with the polarizability of the molecules, consistent with the conclusion that the surface-adsorbate bonds arise due to dispersion forces. The reported results serve as a benchmark for theories of dispersion force interactions of molecules at metal surfaces.

  3. 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.

  4. The oxidized soot surface: theoretical study of desorption mechanisms involving oxygenated functionalities and comparison with temperature programed desorption experiments.

    PubMed

    Barco, Gianluca; Maranzana, Andrea; Ghigo, Giovanni; Causà, Mauro; Tonachini, Glauco

    2006-11-21

    The desorption mechanism for oxygenated functionalities on soot is investigated by quantum mechanical calculations on functionalized polycyclic aromatic hydrocarbon (PAH) models and compared with recently published temperature programed desorption-mass spectrometry results. Substituents on PAHs of increasing size (up to 46 carbon atoms in the parent PAH) are chosen to reproduce the local features of an oxidized graphenic soot platelet. Initially, the study is carried out on unimolecular fragmentation (extrusion, in some cases) processes producing HO, CO, or CO2, in model ketones, carboxylic acids, lactones, anhydrides, in one aldehyde, one peroxyacid, one hydroperoxide, one secondary alcohol, and one phenol. Then, a bimolecular process is considered for one of the carboxylic acids. Furthermore, some cooperative effect which can take place by involving two vicinal carboxylic groups (derived from anhydride hydrolysis) is investigated for other four bifunctionalized models. The comparison between the computed fragmentation (desorption) barriers for the assessed mechanisms and the temperature at which maxima occur in TPD spectra (for HO, CO, or CO2 desorption) offers a suggestion for the assignment of these maxima to specific functional groups, i.e., a key to the description of the oxidized surface. Notably, the computations suggest that (1) the desorption mode from a portion of a graphenic platelet functionalized by a carboxylic or lactone groups is significantly dependent from the chemical and geometric local environment. Consequently, we propose that (2) not all carboxylic groups go lost at the relatively low temperatures generally stated, and (3) lactone groups can be identified as producing not only CO2 but also CO.

  5. Note: A versatile mass spectrometer chamber for molecular beam and temperature programmed desorption experiments

    NASA Astrophysics Data System (ADS)

    Tonks, James P.; Galloway, Ewan C.; King, Martin O.; Kerherve, Gwilherm; Watts, John F.

    2016-08-01

    A dual purpose mass spectrometer chamber capable of performing molecular beam scattering (MBS) and temperature programmed desorption (TPD) is detailed. Two simple features of this design allow it to perform these techniques. First, the diameter of entrance aperture to the mass spectrometer can be varied to maximize signal for TPD or to maximize angular resolution for MBS. Second, the mass spectrometer chamber can be radially translated so that it can be positioned close to the sample to maximize signal or far from the sample to maximize angular resolution. The performance of this system is described and compares well with systems designed for only one of these techniques.

  6. Effects of surface coordination on the temperature-programmed desorption of oxalate from goethite

    SciTech Connect

    Boily, Jean F.; Szanyi, Janos; Felmy, Andrew R.

    2007-11-15

    The temperature-programmed desorption (TPD) of weakly-bound, hydrogen-bonded and metal-bonded oxalate complexes at the goethite surface was investigated in the 300-900 K range with concerted Fourier Transform Infrared (FTIR) measurements (TPD-FTIR). These reactions took place with the concomitant dehydroxylation reaction of goethite to hematite and decarbonation of bulk-occluded carbonate. The measurements revealed three important stages of desorption. Stage I (300-440 K) corresponds to the desorption of weakly-and/or un-bound oxalate molecules in the goethite powder with a thermal decomposition reaction pathway characteristic of oxalic acid. Stage II (440-520 K) corresponds to a thermally-driven dehydration of hydrogen-bonded surface complexes, leading to a partial desorption via oxalic acid thermal decomposition pathways and to a partial conversion to metal-bonded surface complexes. This latter mechanism led to the increase in FTIR bands characteristic of these complexes. Finally, Stage III (520-660 K) corresponds to the thermal decomposition of the metal-bonded oxalate complex, proceeding through a 2 electron reduction pathway.

  7. Stabilization of mercury over Mn-based oxides: Speciation and reactivity by temperature programmed desorption analysis.

    PubMed

    Xu, Haomiao; Ma, Yongpeng; Huang, Wenjun; Mei, Jian; Zhao, Songjian; Qu, Zan; Yan, Naiqiang

    2017-01-05

    Mercury temperature-programmed desorption (Hg-TPD) method was employed to clarify mercury species over Mn-based oxides. The elemental mercury (Hg(0)) removal mechanism over MnOx was ascribed to chemical-adsorption. HgO was the primary mercury chemical compound adsorbed on the surface of MnOx. Rare earth element (Ce), main group element (Sn) and transition metal elements (Zr and Fe) were chosen for the modification of MnOx. Hg-TPD results indicated that the binding strength of mercury on these binary oxides followed the order of Sn-MnOxdesorption were calculated and they were 64.34, 101.85, 46.32, 117.14, and 106.92eV corresponding to MnOx, Ce-MnOx, Sn-MnOx, Zr-MnOx and Fe-MnOx, respectively. Sn-MnOx had a weak bond of mercury (Hg-O), while Zr-MnOx had a strong bond (HgO). Ce-MnOx and Fe-MnOx had similar bonds compared with pure MnOx. Moreover, the effects of SO2 and NO were investigated based on Hg-TPD analysis. SO2 had a poison effect on Hg(0) removal, and the weak bond of mercury can be easily destroyed by SO2. NO was favorable for Hg(0) removal, and the bond strength of mercury was enhanced.

  8. Catalytic reduction of CO with hydrogen sulfide. 4. Temperature-programmed desorption of methanethiol on anatase, rutile, and sulfided rutile

    SciTech Connect

    Beck, D.D.; White, J.M.; Ratcliffe, C.T.

    1986-07-03

    The interaction of methanethiol with anatase, rutile, and sulfided rutile was studied by temperature-programmed desorption. Dissociative adsorption occurs on rutile but is insignificant on anatase. Decomposition products are dominated by H/sub 2/ on rutile and by CH/sub 4/ on sulfided rutile. In both cases desorption occurs between 500 and 775 K. The 5- and 4-coordinate sites on the (110) face of rutile are proposed as the active sites for decomposition. The dominance of methane on a sulfided surface is attributed to the relatively large supply of highly mobile surface hydrogen atoms.

  9. Selective Concentration of Ultra-trace Acetone in the Air by Cryogenic Temperature Programmed Desorption (cryo-TPD).

    PubMed

    Suzuki, Taku T; Sakaguchi, Isao

    2016-01-01

    A gas analytical technique with compact size, low cost, sufficient sensitivity, and excellent reproducibility is required in many fields including exhaled breath analysis for medical monitoring. In the present study, we examined selective acetone concentration by quench condensation at cryogenic temperature followed by temperature programmed desorption (cryogenic temperature programmed desorption (cryo-TPD)) for possible applications to breath analysis for medical monitoring. The essence of cryo-TPD is rough mass selection by thermal desorption followed by quantification of certain species using mass spectrometry. The performance of cryo-TPD was investigated in the acetone concentration range below 1 × 10(-6) volume fraction (1 ppmv). It was found that acetone is selectively quench-condensed on a tungsten substrate at 50 K without the major components of air, such as N2 and O2. The concentrated acetone gas was obtained by the following thermal desorption at around 151 K. Under conditions of condensation for 1 min and pressure of 1 × 10(-2) Pa, the lowest limit of detection reached well below 10 × 10(-9) volume fraction (10 ppbv). The relationship between the cetone intensity of cryo-TPD and the acetone concentration in the gas was almost linear in the ppbv range. The separation of acetone and propanal using the fragmentation pattern, which have almost the identical molecular mass, was also demonstrated in the present study.

  10. 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

  11. Assessing sequestration of selected polycyclic aromatic hydrocarbons by use of adsorption modeling and temperature-programmed desorption.

    PubMed

    Abu, Abdul; Smith, Steve

    2005-10-01

    Sequestration of phenanthrene and pyrene was investigated in two soils--a sandy soil designated SBS and a silt-loam designated LHS--by combining long-term batch sorption studies with thermal desorption and pyrolysis of amended soil samples. The Polanyi-based adsorption volume and the adsorbed solute mass increased with aging for both soils, thus demonstrating the mechanism for observed sequestration. Despite rigorous thermal analysis, 30-62% (SBS sand) and 8-30% (LHS silt-loam) of phenanthrene could not be recovered after 30-270 days of sorption, with the increase in desorption resistance showing greater significance in SBS sand. For both soils, these values were 20-65% of adsorbed phenanthrene mass. Activation energies estimated from the temperature-programmed desorption (TPD) of sorbed phenanthrene at < or = 375 degrees C were 51-53 kJ/mol, consistent with values derived for desorption of organic compounds from humic materials. The activated first-order model fitting of observed TPD data supports the conclusion that the desorption-resistant fraction of phenanthrene has become sequestered onto condensed organic domains and requires temperatures exceeding 600 degrees C to be released. The work demonstrates the use of thermal analysis in complementing the Polanyi-based adsorption modeling approach for assessing the mechanistic basis for sequestration of organic contaminants in soils.

  12. Dissociation energy for O2 release from gas-phase iron oxide clusters measured by temperature-programmed desorption experiments

    NASA Astrophysics Data System (ADS)

    Koyama, Kohei; Kudoh, Satoshi; Miyajima, Ken; Mafuné, Fumitaka

    2015-04-01

    Thermal dissociation of gas phase iron oxide cluster ions, FenOm+ (n = 2-6), was observed by mass spectrometry. The dissociation processes were investigated by temperature-programmed desorption (TPD) measurements for different sized clusters. Oxygen molecules were found to be released from the cluster ions. The threshold energy required for dissociation, determined by analyzing TPD, was compared with the energies obtained by experiments of collision-induced dissociation and by calculations of density functional theory. The agreement of the energies indicates that the oxygen atoms bonded to the terminal site of clusters are more readily released into the gas phase than those in the bridge site.

  13. Analysis of the adsorption state and desorption kinetics of NO(2) over Fe-zeolite catalyst by FT-IR and temperature-programmed desorption.

    PubMed

    Iwasaki, Masaoki; Shinjoh, Hirofumi

    2010-03-14

    States of NO(2) adsorption and kinetics of NO(2) desorption over a Fe-loaded ZSM-5 type zeolite were investigated using Fourier transform infrared (FT-IR) spectroscopy and temperature-programmed desorption (TPD). The FT-IR spectra in NO(2)/N(2) flows showed that several adsorption species (NO(2), nitrite, nitrate, and NO(+)) existed; except for NO(2), these were considered to be formed via NO(2) dimerization and disproportionation reactions. The TPD spectra showed two distinct peaks, a low-temperature (LT) peak that can be assigned to weakly adsorbed NO(x) in the zeolite channel and a high-temperature (HT) peak that can be assigned to chemisorbed NO(x) bonded to ion-exchanged Fe sites. By varying flow rates and heating rates in TPD measurements, the peak maximum temperatures in the both peaks were found to be constant with the former, but shifted to higher temperatures with the latter; this suggests that desorption is not controlled by an adsorption/desorption equilibrium, i.e., in the no-readsorption limit. Furthermore, it was found that desorption at both LT and HT peaks proceeds at second order; this implies that the reverse reaction of NO(2) dimerization and disproportionation and/or some sort of lateral interaction between NO(2) molecules might be occurring. The desorption energies and the pre-exponential factors were estimated to be 67 +/- 1 kJ mol(-1) and 10(5.5+/-0.2) s(-1) for the LT peak and 138 +/- 4 kJ mol(-1) and 10(9.8+/-0.3) s(-1) for the HT peak. These values show that interaction strengths between adsorbed NO(x) and Fe sites are relatively large.

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

    SciTech Connect

    Kim, Boseong; Dohnálek, Zdenek; Szanyi, János; Kay, Bruce D.; Kim, Yu Kwon

    2016-10-01

    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 byproduct 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 product 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.

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

    DOE PAGES

    Kim, Boseong; Dohnalek, Zdenek; Szanyi, Janos; ...

    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

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

    NASA Astrophysics Data System (ADS)

    Kim, Boseong; Dohnálek, Zdenek; Szanyi, János; Kay, Bruce D.; Kim, Yu Kwon

    2016-10-01

    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 product 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.

  17. Kinetic Monte Carlo simulations of temperature programed desorption of O/Rh(111).

    PubMed

    Franz, T; Mittendorfer, F

    2010-05-21

    We present a kinetic Monte Carlo simulation based on ab initio calculations for the thermal desorption of oxygen from a Rh(111) surface. Several models have been used for the parametrization of the interaction between the adsorbed atoms. We find that models based on a parametrization with only pairwise interactions have a relatively large error in the predicted adsorption energies. This error can be significantly reduced by including three- and four-body interactions. In addition, we find that a significant amount of atoms adsorb in a second adsorption site - the hcp-hollow site - at an elevated temperature. Consequently, only a many-body multisite model of the oxygen interactions yields appropriate desorption spectra for the full coverage range, while more simple models only capture the correct shape in the low-coverage case. Our parametrization allows us to predict the adsorption energies of an arbitrary configuration of adsorbates with a mean average error of less than 6 meV/atom.

  18. 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.

  19. 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

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

    SciTech Connect

    Tewell, Craig Richmond

    2002-01-01

    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 TiCl4 and a Al(Et)3 co-catalyst on a microporous Mg-ethoxide support that is prepared from MgCl2 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 TiCl4 in the gas phase. XPS results indicate that the Mg is completely oxidized to MgCl2 by TiCl4 resulting in a thin film of MgCl2/TiClx, where x = 2, 3, and 4. To prepare an active catalyst, the thin film of MgCl2/TiClx on Au foil is enclosed in a high pressure cell contained within the UHV chamber and exposed to ~1 Torr of Al(Et)3.

  1. A technique for extending the precision and the range of temperature programmed desorption toward extremely low coverages

    NASA Astrophysics Data System (ADS)

    Haegel, Stefan; Zecho, Thomas; Wehner, Stefan

    2010-03-01

    In this paper, an improvement of the temperature programmed desorption (TPD) technique is introduced, which facilitates fully automated sampling of TPD spectra with excellent reproducibility, especially useful for extremely low coverages. By averaging many sampled TPD spectra, the range of the TPD technique can be extended toward lower coverages, as well as the quality of the spectra can be improved. This allows for easy extraction of information about the adsorbate-surface bond. A state of the art TPD apparatus with a two chamber setup and a high quality quadrupole mass spectrometer was extended by automated components. These are an automated gas dosing system, ensuring precise dosing of gas, combined with a motor driven sample manipulation unit and a liquid nitrogen cryostat with automatic refilling. In addition all components were controlled by a computer. A large number of TPD cycles could be sampled without the need of interaction of an operator. Here, it is shown for up to more than 400 TPD cycles. This opens a wide range of new interesting applications for the TPD technique, especially in the limit of zero coverage. Here, basic experiments on well known adsorbate systems are shown to view the ability and limit of this approach.

  2. 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.

  3. The deactivation mechanism of Cl on Ce/TiO2 catalyst for selective catalytic reduction of NO with NH3

    NASA Astrophysics Data System (ADS)

    Yang, Ning-zhi; Guo, Rui-tang; Pan, Wei-guo; Chen, Qi-lin; Wang, Qing-shan; Lu, Chen-zi; Wang, Shu-xian

    2016-08-01

    The poisoning mechanism of Cl on Ce/TiO2 catalyst was investigated based on temperature programmed desorption (TPD) and the in situ diffuse reflectance infrared transform spectroscopy (DRIFT) studies. The results of NH3-TPD and NO-TPD indicated that the addition of Cl on Ce/TiO2 catalyst would inhibit the adsorption of NH3 species and NOx species on it. As can be seen from the results of in situ DRIFT study, the NH3-SCR reaction over Ce/TiO2 and Ce/TiO2-Cl were all followed both the Eley-Rideal mechanism and the Langmuir-Hinshelwood mechanism. And the decreased adsorption ability of NH3 species and NOx species on the surface of Ce/TiO2-Cl should be mainly responsible for its low SCR activity.

  4. 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.

  5. Characterization of Lewis acid sites on the (100) surface of β-AlF3: Ab initio calculations of NH3 adsorption

    NASA Astrophysics Data System (ADS)

    Bailey, C. L.; Wander, A.; Mukhopadhyay, S.; Searle, B. G.; Harrison, N. M.

    2008-06-01

    The current study employs hybrid-exchange density functional theory to show that the Lewis base, NH3, binds to the β-AlF3 (100) surface with a binding energy (BE) of up to -1.96 eV per molecule. This is characteristic of a strong Lewis acid. The binding of NH3 to the surface is predominately due to electrostatic interactions. There is only a small charge transfer from the NH3 molecule to the surface. The BE as a function of coverage is computed and used to develop a lattice Monte Carlo model which is used to predict the temperature programed desorption (TPD) spectrum. Comparison with experimental TPD studies of NH3 from β-AlF3 strongly suggests that these structural models and binding mechanisms are good approximations to those that occur on real AlF3 surfaces.

  6. Low-temperature selective catalytic reduction of NO with NH3 over nanoflaky MnOx on carbon nanotubes in situ prepared via a chemical bath deposition route

    NASA Astrophysics Data System (ADS)

    Fang, Cheng; Zhang, Dengsong; Cai, Sixiang; Zhang, Lei; Huang, Lei; Li, Hongrui; Maitarad, Phornphimon; Shi, Liyi; Gao, Ruihua; Zhang, Jianping

    2013-09-01

    Nanoflaky MnOx on carbon nanotubes (nf-MnOx@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH3. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD). The SEM, TEM, XRD results and N2 adsorption-desorption analysis indicated that the CNTs were surrounded by nanoflaky MnOx and the obtained catalyst exhibited a large surface area as well. Compared with the MnOx/CNT and MnOx/TiO2 catalysts prepared by an impregnation method, the nf-MnOx@CNTs presented better NH3-SCR activity at low temperature and a more extensive operating temperature window. The XPS results showed that a higher atomic concentration of Mn4+ and more chemisorbed oxygen species existed on the surface of CNTs for nf-MnOx@CNTs. The H2-TPR and NH3-TPD results demonstrated that the nf-MnOx@CNTs possessed stronger reducing ability, more acid sites and stronger acid strength than the other two catalysts. Based on the above mentioned favourable properties, the nf-MnOx@CNT catalyst has an excellent performance in the low-temperature SCR of NO to N2 with NH3. In addition, the nf-MnOx@CNT catalyst also presented favourable stability and H2O resistance.Nanoflaky MnOx on carbon nanotubes (nf-MnOx@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH3. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed

  7. H 2O chemisorption and H 2 oxidation on yttria-stabilized zirconia: Density functional theory and temperature-programmed desorption studies

    NASA Astrophysics Data System (ADS)

    Gorski, Alexandr; Yurkiv, Vitaliy; Starukhin, Dzmitry; Volpp, Hans-Robert

    The mechanism of H 2O dissociation as well as the adsorption and oxidation reaction of H 2 on yttria-stabilized zirconia (YSZ), commonly used as part of solid oxide fuel cell (SOFC) anodes, was investigated employing temperature-programmed desorption (TPD) spectroscopy and density functional theory (DFT). In agreement with theory the experimental results show that interaction of gaseous H 2O with YSZ results in dissociative adsorption leading to strongly bound OH surface species. In the interaction of gaseous H 2 with an oxygen-enriched YSZ surface (YSZ + O) similar OH surface species are formed as reaction intermediates in the H 2 oxidation. Our experiments showed that in both the H 2O/YSZ and the H 2/YSZ + O heterogeneous reaction systems noticeable amounts of H 2O are "dissolved" in the bulk as interstitial hydrogen and hydroxyl species. The experimental H 2O desorption data is used to access the accuracy of the H 2/H 2O/YSZ adsorption/desorption and surface reaction kinetics data, employed in previous modeling studies of the electrochemical H 2 oxidation on Ni-pattern/YSZ model anodes by Vogler et al. [J. Electrochem. Soc., 156 (2009) B663] and Goodwin et al. [J. Electrochem. Soc., 156 (2009) B1004]. Finally a refined experimentally validated H 2/H 2O/YSZ adsorption/desorption and surface reaction kinetics data set is presented.

  8. CO adsorption on W(100) during temperature-programmed desorption: A combined density functional theory and kinetic Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Albao, Marvin A.; Padama, Allan Abraham B.

    2017-02-01

    Using a combined density functional theory (DFT) and kinetic Monte Carlo (KMC) simulations, we study the adsorption at 800 K and subsequent desorption of CO on W(100) at higher temperatures. The resulting TPD profiles are known experimentally to exhibit three desorption peaks β1, β2, and β3 at 930 K, 1070 K, and 1375 K, respectively. Unlike more recent theoretical studies that propose that all three aforementioned peaks are molecularly rather than associatively desorbed, our KMC analyses are in support of the latter, since at 800 K dissociation is facile and that CO exists as dissociation fragments C and O. We show that these peaks arise from desorption from the same adsorption site but whose binding energy varies depending on local environment, that is, the presence of CO as well as dissociation fragments C and O nearby. Furthermore we show that several key parameters, such as desorption, dissociation and recombination barriers all play a key role in the TPD spectra-these parameter effectively controls not only the location of the TPD peaks but the shape and width of the desorption peaks as well. Moreover, our KMC simulations reveal that varying the heating rate shifts the peaks but leaves their shape intact.

  9. The application of diffuse reflectance infrared spectroscopy and temperature-programmed desorption to investigate the interaction of methanol on eta-alumina.

    PubMed

    McInroy, Alastair R; Lundie, David T; Winfield, John M; Dudman, Chris C; Jones, Peter; Lennon, David

    2005-11-22

    The adsorption of methanol and its subsequent transformation to form dimethyl ether (DME) on a commercial grade eta-alumina catalyst has been investigated using a combination of mass selective temperature-programmed desorption (TPD) and diffuse reflectance infrared spectroscopy (DRIFTS). The infrared spectrum of a saturated overlayer of methanol on eta-alumina shows the surface to be comprised of associatively adsorbed methanol and chemisorbed methoxy species. TPD shows methanol and DME to desorb with respective maxima at 380 and 480 K, with desorption detectable for both molecules up to ca. 700 K. At 673 K, infrared spectroscopy reveals the formation of a formate species; the spectral line width of the antisymmetric C-O stretch indicates the adoption of a high symmetry adsorbed state. Conventional TPD using a tubular reactor, combined with mass spectrometric analysis of the gas stream exiting the IR cell, indicate hydrogen and methane evolution to be associated with formation of the surface formate group and CO evolution with its decomposition. A reaction scheme is proposed for the generation and decomposition of this important reaction intermediate. The overall processes involved in (i) the adsorption/desorption of methanol, (ii) the transformation of methanol to DME, and (iii) the formation and decomposition of formate species are discussed within the context of a recently developed four-site model for the Lewis acidity of eta-alumina.

  10. 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.

  11. A novel co-precipitation method for preparation of Mn--Ce/TiO2 composites for NOx reduction with NH3 at low temperature.

    PubMed

    Sheng, Zhongyi; Hu, Yufeng; Xue, Jianming; Wang, Xiaoming; Liao, Weiping

    2012-01-01

    Mn--Ce/TiO2 catalyst prepared by a novel co-precipitation method was used in this study for low-temperature selective catalytic reduction (SCR) of NOx with ammonia. The catalyst showed high activity and good SO2 resistance. The NO conversion on the catalyst increased to 100% when 700 ppm of SO2 flowed in, and reached 60.8% in 2.5 h. The characterized results indicated that the catalyst prepared by the new method had good dispersion of the active phase, uniform micro-size particles and large Brunauer-Emmett-Teller surface. The temperature programmed reduction and temperature programmed desorption experiments showed that the improvement in SCR activity on the Mn--Ce/TiO2 catalyst might be due to the increase of active oxygen species and the enhancement of NH3 chemisorption, both of which were conducive to NH3 activation.

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

    SciTech Connect

    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 product 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.

  13. The role of zinc(II) in the absorption-desorption of CO2 by aqueous NH3, a potentially cost-effective method for CO2 capture and recycling.

    PubMed

    Mani, Fabrizio; Peruzzini, Maurizio; Barzagli, Francesco

    2008-01-01

    The absorption of CO2 by aqueous NH3 solutions has been investigated at atmospheric pressure and 0 degrees C. The CO2 absorption is fast and occurs with high efficiency (88-99%). The maximum CO2-removal efficiency increases slightly with the NH3 concentration. Addition of zinc(II) salts (as chloride, nitrate or sulfate) to the NH3 absorbent solution increases the overall CO2-absorption capacity without appreciably affecting the removal efficiency. Stripping of pure CO2 from HCO3(-) solutions is achieved by adding the calculated amount of ZnII salts, which under ambient conditions lead to rapid release of about 30-35% of the initially captured CO2. At the same time, about 65-70% of the captured CO2 is transformed into solid basic zinc carbonates. The recovery of these valuable solid products and the release of only 1/3 of free CO2 at room temperature and pressure reduces the cost of the overall process of CO2 capture, making it a potentially attractive method for CO2 capture on a larger scale.

  14. 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

    2011-10-04

    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.

  15. In situ supported MnO(x)-CeO(x) on carbon nanotubes for the low-temperature selective catalytic reduction of NO with NH3.

    PubMed

    Zhang, Dengsong; Zhang, Lei; Shi, Liyi; Fang, Cheng; Li, Hongrui; Gao, Ruihua; Huang, Lei; Zhang, Jianping

    2013-02-07

    The MnO(x) and CeO(x) were in situ supported on carbon nanotubes (CNTs) by a poly(sodium 4-styrenesulfonate) assisted reflux route for the low-temperature selective catalytic reduction (SCR) of NO with NH(3). X-Ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), H(2) temperature-programmed reduction (H(2)-TPR) and NH(3) temperature-programmed desorption (NH(3)-TPD) have been used to elucidate the structure and surface properties of the obtained catalysts. It was found that the in situ prepared catalyst exhibited the highest activity and the most extensive operating-temperature window, compared to the catalysts prepared by impregnation or mechanically mixed methods. The XRD and TEM results indicated that the manganese oxide and cerium oxide species had a good dispersion on the CNT surface. The XPS results demonstrated that the higher atomic concentration of Mn existed on the surface of CNTs and the more chemisorbed oxygen species exist. The H(2)-TPR results suggested that there was a strong interaction between the manganese oxide and cerium oxide on the surface of CNTs. The NH(3)-TPD results demonstrated that the catalysts presented a larger acid amount and stronger acid strength. In addition, the obtained catalysts exhibited much higher SO(2)-tolerance and improved the water-resistance as compared to that prepared by impregnation or mechanically mixed methods.

  16. The NH3Cl+ Cation

    DTIC Science & Technology

    2007-11-02

    solutions of NH2Cl can conveniently be prepared by the chlorination of aqueous ammonia with hypochlorite.[13,14] However, the highest practical NH2Cl...at –40 °C, it decomposes continuously and often explosively, due to the formation of ammonium chloride and more highly chlorinated products, such as...existence of NH3Cl + is provided by its vibrational and NMR spectra and theoretical calculations. Experimental Section Caution! Chloramines are highly

  17. Adsorption of acrolein, propanal, and allyl alcohol on Pd(111): a combined infrared reflection–absorption spectroscopy and temperature programmed desorption study

    PubMed Central

    Dostert, Karl-Heinz; O'Brien, Casey P.; Mirabella, Francesca; Ivars-Barceló, Francisco

    2016-01-01

    Atomistic-level understanding of the interaction of α,β-unsaturated aldehydes and their derivatives with late transition metals is of fundamental importance for the rational design of new catalytic materials with the desired selectivity towards C 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 C vs. CO bond partial hydrogenation. In this study, we investigate the interaction of acrolein, and its partial hydrogenation products propanal and allyl alcohol, with Pd(111) as a prototypical system. A combination of infrared reflection–absorption spectroscopy (IRAS) and temperature programmed desorption (TPD) experiments was applied under well-defined ultrahigh vacuum (UHV) conditions to obtain detailed information on the adsorption geometries of acrolein, propanal, and allyl alcohol as a function of coverage. We compare the IR spectra obtained for

  18. Surface structure of crystalline and amorphous chromia catalysts for the selective catalytic reduction of nitric oxide. 1. Characterization by temperature-programmed reaction and desorption

    SciTech Connect

    Curry-Hyde, H.E.; Musch, H.; Baiker, A. ); Schraml-Marth, M.; Wokaun, A. )

    1992-02-01

    Amorphous and crystalline chromia catalysts used for the selective catalytic reduction (SCR) of NO by NH{sub 3} have been characterized using temperature-programmed reaction and desorption of preadsorbed NO and NH{sub 3}. The acidity of the Lewis acid sites and the associated labile oxygen species are investigated using NH{sub 3} as a probe molecule. The degree of coordinative unsaturation of these sites is inferred from the reactions of NO. The effects of reduction, oxidation, and SCR treatment on the state of the Lewis acid sites and the labile oxygen are discussed. Lewis acid sites on crystalline chromia are more acidic than those on amorphous chromia. Different labile oxygen species are discernible based on their oxidizing strengths and the products formed. All labile oxygen is readily removed by reduction; SCR treatment leads to the partial removal of labile oxygen from both morphologies of chromia. The degree of lability of the different oxygen species is related to the morphology of the chromia. The proportions of one- and twofold coordinatively unsaturated sites (1 and 2 c.u.s.) depends strongly on the morphology of the chromia and its pretreatment. Both types of sites show distinct differences in the acidity dependent on the morphology of the chromia. The most significant difference between the two morphologies is seen after SCR treatment. Crystalline chromia shows a very high density of 1 c.u.s. compared to amorphous chromia. These sites are generated from 2 c.u.s. by abstraction of oxygen from NO. Implications of these results on the SCR reaction are discussed.

  19. Adsorption of acrolein, propanal, and allyl alcohol on Pd(111): a combined infrared reflection-absorption spectroscopy and temperature programmed desorption study.

    PubMed

    Dostert, Karl-Heinz; O'Brien, Casey P; Mirabella, Francesca; Ivars-Barceló, Francisco; Schauermann, Swetlana

    2016-05-18

    Atomistic-level understanding of the interaction of α,β-unsaturated aldehydes and their derivatives with late transition metals is of fundamental importance for the rational design of new catalytic materials with the desired selectivity towards C[double bond, length as m-dash]C vs. C[double bond, length as m-dash]O bond partial hydrogenation. In this study, we investigate the interaction of acrolein, and its partial hydrogenation products propanal and allyl alcohol, with Pd(111) as a prototypical system. A combination of infrared reflection-absorption spectroscopy (IRAS) and temperature programmed desorption (TPD) experiments was applied under well-defined ultrahigh vacuum (UHV) conditions to obtain detailed information on the adsorption geometries of acrolein, propanal, and allyl alcohol as a function of coverage. We compare the IR spectra obtained for multilayer coverages, reflecting the molecular structure of unperturbed molecules, with the spectra acquired for sub-monolayer coverages, at which the chemical bonds of the molecules are strongly distorted. Coverage-dependent IR spectra of acrolein on Pd(111) point to the strong changes in the adsorption geometry with increasing acrolein coverage. Acrolein adsorbs with the C[double bond, length as m-dash]C and C[double bond, length as m-dash]O bonds lying parallel to the surface in the low coverage regime and changes its geometry to a more upright orientation with increasing coverage. TPD studies indicate decomposition of the species adsorbed in the sub-monolayer regime upon heating. Similar strong coverage dependence of the IR spectra were found for propanal and allyl alcohol. For all investigated molecules a detailed assignment of vibrational bands is reported.

  20. Performance of selective catalytic reduction of NO with NH3 over natural manganese ore catalysts at low temperature.

    PubMed

    Wang, Tao; Zhu, Chengzhu; Liu, Haibo; Xu, Yongpeng; Zou, Xuehua; Xu, Bin; Chen, Tianhu

    2017-03-16

    Natural manganese ore catalysts for selective catalytic reduction (SCR) of NO with NH3 at low temperature in the presence and absence of SO2 and H2O were systematically investigated. The physical and chemical properties of catalysts were characterized by X-ray diffraction, Brunauer-Emmett-Teller (BET) specific surface area, NH3 temperature-programmed desorption (NH3-TPD) and NO-TPD methods. The results showed that natural manganese ore from Qingyang of Anhui Province had a good low-temperature activity and N2 selectivity, and it could be a novel catalyst in terms of stability, good efficiency, good reusability and lower cost. The NO conversion exceeded 85% between 150°C and 300°C when the initial NO concentration was 1000 ppm. The activity was suppressed by adding H2O (10%) or SO2 (100 or 200 ppm), respectively, and its activity could recover while the SO2 supply is cut off. The simultaneous addition of H2O and SO2 led to the increase of about 100% in SCR activity than bare addition of SO2. The formation of the amorphous MnOx, high concentration of lattice oxygen and surface-adsorbed oxygen groups and a lot of reducible species as well as adsorption of the reactants brought about excellent SCR performance and exhibited good SO2 and H2O resistance.

  1. 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.

  2. 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.

  3. In situ supported MnOx-CeOx on carbon nanotubes for the low-temperature selective catalytic reduction of NO with NH3

    NASA Astrophysics Data System (ADS)

    Zhang, Dengsong; Zhang, Lei; Shi, Liyi; Fang, Cheng; Li, Hongrui; Gao, Ruihua; Huang, Lei; Zhang, Jianping

    2013-01-01

    The MnOx and CeOx were in situ supported on carbon nanotubes (CNTs) by a poly(sodium 4-styrenesulfonate) assisted reflux route for the low-temperature selective catalytic reduction (SCR) of NO with NH3. X-Ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD) have been used to elucidate the structure and surface properties of the obtained catalysts. It was found that the in situ prepared catalyst exhibited the highest activity and the most extensive operating-temperature window, compared to the catalysts prepared by impregnation or mechanically mixed methods. The XRD and TEM results indicated that the manganese oxide and cerium oxide species had a good dispersion on the CNT surface. The XPS results demonstrated that the higher atomic concentration of Mn existed on the surface of CNTs and the more chemisorbed oxygen species exist. The H2-TPR results suggested that there was a strong interaction between the manganese oxide and cerium oxide on the surface of CNTs. The NH3-TPD results demonstrated that the catalysts presented a larger acid amount and stronger acid strength. In addition, the obtained catalysts exhibited much higher SO2-tolerance and improved the water-resistance as compared to that prepared by impregnation or mechanically mixed methods.The MnOx and CeOx were in situ supported on carbon nanotubes (CNTs) by a poly(sodium 4-styrenesulfonate) assisted reflux route for the low-temperature selective catalytic reduction (SCR) of NO with NH3. X-Ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD) have been used to elucidate the structure and surface properties of the obtained catalysts. It was found that the in situ

  4. 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.

  5. Iron-doped Mn-Ce/TiO2 catalyst for low temperature selective catalytic reduction of NO with NH3.

    PubMed

    Shen, Boxiong; Liu, Ting; Zhao, Ning; Yang, Xiaoyan; Deng, Lidan

    2010-01-01

    The catalysts of iron-doped Mn-Ce/TiO2 (Fe-Mn-Ce/TiO2) prepared by sol-gel method were investigated for low temperature selective catalytic reduction (SCR) of NO with NH3. It was found that the NO conversion over Fe-Mn-Ce/TiO2 was obviously improved after iron doping compared with that over Mn-Ce/TiO2. Fe-Mn-Ce/TiO2 with the molar ratio of Fe/Ti = 0.1 exhibited the highest activity. The results showed that 96.8% NO conversion was obtained over Fe (0.1)-Mn-Ce/TiO2 at 180 degrees C at a space velocity of 50,000 hr(-1). Fe-Mn-Ce/TiO2 exhibited much higher resistance to H2O and SO2 than that of Mn-Ce/TiO2. The properties of the catalysts were characterized using X-ray diffraction (XRD), N2 adsorption, temperature programmed desorption (NH3-TPD and NOx-TPD), and Xray photoelectron spectroscopy (XPS) techniques. BET, NH3-TPD and NOx-TPD results showed that the specific surface area and NH3 and NOx adsorption capacity of the catalysts increased with iron doping. It was known from XPS analysis that iron valence state on the surface of the catalysts were in Fe3+ state. The doping of iron enhanced the dispersion and oxidation state of Mn and Ce on the surface of the catalysts. The oxygen concentrations on the surface of the catalysts were found to increase after iron doping. Fe-Mn-Ce/TiO2 represented a promising catalyst for low temperature SCR of NO with NH3 in the presence of H2O and SO2.

  6. Photocatalytic reduction of NO with NH3 using Si-doped TiO2 prepared by hydrothermal method.

    PubMed

    Jin, Ruiben; Wu, Zhongbiao; Liu, Yue; Jiang, Boqiong; Wang, Haiqiang

    2009-01-15

    A series of Si-doped TiO2 (Si/TiO2) photocatalysts supported on woven glass fabric were prepared by hydrothermal method for photocatalytic reduction of NO with NH3. The photocatalytic activity tests were carried out in a continuous Pyrex reactor with the flow rate of 2000mL/min under UV irradiation (luminous flux: 1.1x10(4)lm, irradiated catalyst area: 160cm2). The photocatalysts were characterized by X-ray diffraction (XRD), BET, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectrophotometer, transmission electron microscopy (TEM), photoluminescence (PL) and temperature-programmed desorption (TPD). The experiment results showed that NO conversion on Si/TiO2 at 323K could exceed 60%, which was about 50% higher than that on Degussa P25 and pure TiO2. With the doping of Si, photocatalysts with smaller crystal size, larger surface area and larger pore volume were obtained. It was also found that Ti-O-Si bands were formed on the surface of Si/TiO2 and that the surface hydroxyl concentration was greatly increased. As a result, total acidity and NH3 chemisorption amount were enhanced for Si/TiO2 leading to its photocatalytic activity improvement.

  7. Mn-CeOx/Ti-PILCs for selective catalytic reduction of NO with NH3 at low temperature.

    PubMed

    Shen, Boxiong; Ma, Hongqing; Yao, Yan

    2012-01-01

    Titanium-pillared clays (Ti-PILCs) were obtained by different ways from TiCl4, Ti(OC3H7)4 and TiOSO4, respectively. Mn-CeO(x)/)Ti-PILCs were then prepared and their activities of selective catalytic reduction (SCR) of NO with NH3 at low-temperature were evaluated. Mn-CeO(x)/Ti-PILCs were characterized by X-ray diffraction, N2 adsorption, Fourier transform infrared spectroscopy, thermal analysis, temperature-programmed desorption of ammonia and H2-temperature-programmed reduction. It was found that Ti-pillar tend to be helpful for the enlargement of surface area, pore volume, acidity and the enhancement of thermal stability for Mn-CeO(x)/Ti-PILCs. Mn-CeO(x)/Ti-PILCs catalysts were active for the SCR of NO. Among three resultant Mn-CeO(x)/Ti-PILCs, the catalyst from TiOSO4 showed the highest activity with 98% NO conversion at 220 degrees C, it also exhibited good resistance to H2O and SO2 in flue gas. The catalyst from TiCl4 exhibited the lowest activity due to the unsuccessful pillaring process.

  8. MOF-74 as an Efficient Catalyst for the Low-Temperature Selective Catalytic Reduction of NOx with NH3.

    PubMed

    Jiang, Haoxi; Wang, Qianyun; Wang, Huiqin; Chen, Yifei; Zhang, Minhua

    2016-10-12

    In this work, Mn-MOF-74 with hollow spherical structure and Co-MOF-74 with petal-like shape have been prepared successfully via the hydrothermal method. The catalysts were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry-mass spectrum analysis (TG-MS), N2 adsorption/desorption, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). It is found that MOF-74(Mn, Co) exhibits the capability for selective catalytic reduction (SCR) of NOx at low temperatures. Both experimental (temperature-programmed desorption, TPD) and computational methods have shown that Co-MOF-74 and Mn-MOF-74 owned high adsorption and activation abilities for NO and NH3. The catalytic activities of Mn-MOF-74 and Co-MOF-74 for low-temperature denitrification (deNOx) in the presence of NH3 were 99% at 220 °C and 70% at 210 °C, respectively. It is found that the coordinatively unsaturated metal sites (CUSs) in M-MOF-74 (M = Mn and Co) played important roles in SCR reaction. M-MOF-74 (M = Mn and Co), especially Mn-MOF-74, showed excellent catalytic performance for low-temperature SCR. In addition, in the reaction process, NO conversion on Mn-MOF-74 decreased with the introduction of H2O and SO2 and almost recovered when gas was cut off. However, for Co-MOF-74, SO2 almost has no effect on the catalytic activity. This work showed that MOF-74 could be used prospectively as deNOx catalyst.

  9. Photodissociation of Mg +(NH 3) ion

    NASA Astrophysics Data System (ADS)

    Yoshida, Shinji; Okai, Nobuhiro; Fuke, Kiyokazu

    2001-10-01

    Electronically excited states of Mg +(NH 3) are studied by photodissociation after mass selection. The dissociation spectrum shows relatively sharp vibronic transitions centered at about 28 000 and 36 000 cm-1. These absorption bands are assigned to the 2P- 2S type transitions localized on the Mg + ion. In photodissociation, a photoinduced charge-transfer process to produce NH 3+ is observed in addition to evaporation and intracluster reaction processes to produce Mg + and MgNH 2+ ions, respectively. The mechanism for the production of these ions is discussed in terms of the predissociative and non-adiabatic interactions between the low-lying states.

  10. A study of the adsorption of NH 3 and SO 2 on leaf surfaces

    NASA Astrophysics Data System (ADS)

    Van Hove, L. W. A.; Adema, E. H.; Vredenberg, W. J.; Pieters, G. A.

    The adsorption of NH 3 and SO 2 on the external leaf surface of bean ( Phaseolus vulgaris L.) and poplar ( Populus euramericana L.) was studied. The adsorbed quantities increased strongly with increasing air humidity, indicating that water on the leaf surface plays a major role in the interaction of these gases with the leaf surface. On the other hand temperature in the range between 15 and 26°C had no significant influence. The adsorbed quantities of NH 3 at a specific air humidity appeared to be proportional to NH 3 concentration. This proportionality was less clear for SO 2. The affinity of SO 2 for the leaf surface was found to be approximately twice that of NH 3. A mixture of these gases in the air mutually stimulated their adsorption on the leaf. No significant desorption or uptake of these gases through the cuticle could be detected, indicating that the bulk of the adsorbed gases remains associated with the cuticle.

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

    Atmospheric Science Data Center

    2017-02-27

    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:  Search and Order:   Order Data ...

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

    Atmospheric Science Data Center

    2016-10-31

    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:  Search and Order:   Order Data ...

  13. 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

    2011-03-07

    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.

  14. 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:  Search and Order:   Order Data ...

  15. Development of ultralow energy (1-10 eV) ion scattering spectrometry coupled with reflection absorption infrared spectroscopy and temperature programmed desorption for the investigation of molecular solids.

    PubMed

    Bag, Soumabha; Bhuin, Radha Gobinda; Methikkalam, Rabin Rajan J; Pradeep, T; Kephart, Luke; Walker, Jeff; Kuchta, Kevin; Martin, Dave; Wei, Jian

    2014-01-01

    Extremely surface specific information, limited to the first atomic layer of molecular surfaces, is essential to understand the chemistry and physics in upper atmospheric and interstellar environments. Ultra low energy ion scattering in the 1-10 eV window with mass selected ions can reveal extremely surface specific information which when coupled with reflection absorption infrared (RAIR) and temperature programmed desorption (TPD) spectroscopies, diverse chemical and physical properties of molecular species at surfaces could be derived. These experiments have to be performed at cryogenic temperatures and at ultra high vacuum conditions without the possibility of collisions of neutrals and background deposition in view of the poor ion intensities and consequent need for longer exposure times. Here we combine a highly optimized low energy ion optical system designed for such studies coupled with RAIR and TPD and its initial characterization. Despite the ultralow collision energies and long ion path lengths employed, the ion intensities at 1 eV have been significant to collect a scattered ion spectrum of 1000 counts/s for mass selected CH2(+).

  16. Development of ultralow energy (1–10 eV) ion scattering spectrometry coupled with reflection absorption infrared spectroscopy and temperature programmed desorption for the investigation of molecular solids

    SciTech Connect

    Bag, Soumabha; Bhuin, Radha Gobinda; Methikkalam, Rabin Rajan J.; Pradeep, T.; Kephart, Luke; Walker, Jeff; Kuchta, Kevin; Martin, Dave; Wei, Jian

    2014-01-15

    Extremely surface specific information, limited to the first atomic layer of molecular surfaces, is essential to understand the chemistry and physics in upper atmospheric and interstellar environments. Ultra low energy ion scattering in the 1–10 eV window with mass selected ions can reveal extremely surface specific information which when coupled with reflection absorption infrared (RAIR) and temperature programmed desorption (TPD) spectroscopies, diverse chemical and physical properties of molecular species at surfaces could be derived. These experiments have to be performed at cryogenic temperatures and at ultra high vacuum conditions without the possibility of collisions of neutrals and background deposition in view of the poor ion intensities and consequent need for longer exposure times. Here we combine a highly optimized low energy ion optical system designed for such studies coupled with RAIR and TPD and its initial characterization. Despite the ultralow collision energies and long ion path lengths employed, the ion intensities at 1 eV have been significant to collect a scattered ion spectrum of 1000 counts/s for mass selected CH{sub 2}{sup +}.

  17. An infared spectroscopy and temperature-programmed desorption study of CO on MoO[sub 3]/Al[sub 2]O[sub 3] catalysts: Quantitation of the molybdena overlayer

    SciTech Connect

    Diaz, A.L.; Bussell, M.E. )

    1993-01-14

    The adsorption of CO on pure [gamma]-Al[sub 2]O[sub 3] and a series of MoO[sub 3]/Al[sub 2]O[sub 3] catalysts with different Mo loadings has been investigated using infrared (IR) spectroscopy and temperature-programmed desorption (TPD). Carbon monoxide adsorbs selectively on Al[sup 3+] sites on the uncovered, free alumina portion of the surface; these sites are created by dehydroxylation of the alumina. As the Mo loading is increased, the CO adsorption capacity of the catalysts decreases in a linear fashion as the MoO[sub 3] overlayer covers an increasing fraction of the alumina support. Overlayer growth saturates at a loading of (42[+-]3) [times] 10[sup 13] Mo atoms/cm[sup 2] and corresponds to less than a complete monolayer as 14 [+-] 5% of the alumina support remains uncovered. Extrapolation of the overlayer growth curve to monolayer coverage allows calculation of a MoO[sub 3] cross-sectional area of [approx]22[Angstrom][sup 2], in good agreement with values predicted by theoretical models. 37 refs., 11 figs.

  18. Promotion of redox and stability features of doped Ce-W-Ti for NH3-SCR reaction over a wide temperature range

    NASA Astrophysics Data System (ADS)

    Zhao, Kun; Han, Weiliang; Lu, Gongxuan; Lu, Jiangyin; Tang, Zhicheng; Zhen, Xinping

    2016-08-01

    In this study, transition metals Co, Mn, and Cu were introduced into a Ce-W-Ti catalyst to promote low-temperature catalytic activity. Among these metal-modified M/Ce-W-Ti catalysts (M represents Co, Mn, or Cu), the Cu/Ce-W-Ti catalyst with an optimized Cu content of 5 wt.% exhibited more than 90% conversion of nitrogen oxide (NOx) in the selective catalytic reduction by NH3 over a wide temperature range (260-400 °C). This catalyst likewise exhibited higher resistance to SO2 gas and water vapor under severe test conditions. On the basis of the characterization results by powder X-ray diffraction and X-ray photoelectron spectroscopy, we concluded that the superior catalytic properties of the Cu/Ce-W-Ti catalyst could be attributed to the highly dispersed Cu species, which increased the contents of Ce3+ species and adsorbed oxygen species in the catalysts. In addition, the NH3 temperature-programmed desorption results demonstrated that the Cu species doped into the Ce-W-Ti catalysts optimized surface acid content.

  19. Crystal structure of [UO2(NH3)5]NO3·NH3

    PubMed Central

    Woidy, Patrick; Kraus, Florian

    2016-01-01

    Penta­ammine dioxide uranium(V) nitrate ammonia (1/1), [UO2(NH3)5]NO3·NH3, was obtained in the form of yellow crystals from the reaction of caesium uranyl nitrate, Cs[UO2(NO3)3], and uranium tetra­fluoride, UF4, in dry liquid ammonia. The [UO2]+ cation is coordinated by five ammine ligands. The resulting [UO2(NH3)5] coordination polyhedron is best described as a penta­gonal bipyramid with the O atoms forming the apices. In the crystal, numerous N—H⋯N and N—H⋯O hydrogen bonds are present between the cation, anion and solvent mol­ecules, leading to a three-dimensional network. PMID:27980813

  20. Photolysis of solid NH3 and NH3-H2O mixtures at 193 nm

    NASA Astrophysics Data System (ADS)

    Loeffler, M. J.; Baragiola, R. A.

    2010-12-01

    We have studied UV photolysis of solid ammonia and ammonia-dihydrate samples at 40 K, using infrared spectroscopy, mass spectrometry, and microgravimetry. We have shown that in the pure NH3 sample, the main species ejected are NH3, H2, and N2, where the hydrogen and nitrogen increase with laser fluence. This increase in N2 ejection with laser fluence explains the increase in mass loss rate detected by a microbalance. In contrast, for the ammonia-water mixture, we see very weak signals of H2 and N2 in the mass spectrometer, consistent with the very small mass loss during the experiment and with a <5% decrease in the NH3 infrared absorption bands spectroscopy after a fluence of ˜3 × 1019 photons/cm2. The results imply that ammonia-ice mixtures in the outer solar system are relatively stable under solar irradiation.

  1. 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

  2. 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

    Li, Hao; Choi, Joong-Il Jake; Mayr-Schmölzer, Wernfried; Weilach, Christian; Rameshan, Christoph; Mittendorfer, Florian; Redinger, Josef; Schmid, Michael; Rupprechter, Günther

    2015-02-05

    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 ZrO x 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.

  3. The poisoning effect of PbO on Mn-Ce/TiO2 catalyst for selective catalytic reduction of NO with NH3 at low temperature

    NASA Astrophysics Data System (ADS)

    Zhou, Lingling; Li, Caiting; Zhao, Lingkui; Zeng, Guangming; Gao, Lei; Wang, Yan; Yu, Ming'e.

    2016-12-01

    Lead oxide (PbO) as one of the typical heavy metals in flue gas from power plants has strong accumulation as well as poisoning effects on SCR catalysts. In this paper, a series of PbO-doped Mn-Ce/TiO2 catalysts were synthesized by impregnation method. The poisoning effects of PbO over Mn-Ce/TiO2 samples for selective catalytic reduction of NO by NH3 were investigated based on catalytic activity test and characterizations. The NO conversion of Mn-Ce/TiO2 was greatly decreased after the addition of PbO. It was obvious that the NO conversion efficiency of Mn-Ce/TiO2 catalyst declined from 96.75% to about 40% at 200 °C when Pb:Mn molar ratio reached 0.5. Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Hydrogen temperature programmed reduction (H2-TPR), Ammonia temperature programmed desorption (NH3-TPD) and Fourier transform infrared spectroscopy (FT-IR) were carried out to study the deactivation reasons of PbO poisoned catalysts. Manganese oxides' crystallization, less reducible of manganese and cerium oxides, the decreasing of surface area, Mn4+ as well as Ce3+ concentration and chemisorbed oxygen (Ob) after the introduction of PbO, all of these resulted in a poor SCR performance. Furthermore, the alteration of acid sites (especially Brönsted acid sites), low ammonia adsorbance, an obvious reducing of ad-NOx species (only a spot of bidentate nitrates remained) and the vanishing of amide species contributed to the deactivation of Mn-Ce/TiO2 catalyst by PbO doping as well.

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

    DOE PAGES

    Song, Xiaobo; Parker, Gordon G.; Johnson, John H.; ...

    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

  5. Low-temperature selective catalytic reduction of NO with NH(3) over Mn-Ce oxides supported on TiO2 and Al2O3: a comparative study.

    PubMed

    Jin, Ruiben; Liu, Yue; Wu, Zhongbiao; Wang, Haiqiang; Gu, Tingting

    2010-02-01

    MnCe oxides were supported on TiO(2) and Al(2)O(3) by an ultrasonic impregnation method and used for selective catalytic reduction (SCR) of NO with NH(3) at low-temperature (80-220 degrees C). MnCe/TiO(2) showed a relatively higher SCR activity than MnCe/Al(2)O(3) at the temperature range of 80-150 degrees C. When the reaction temperature was higher than 150 degrees C, MnCe/Al(2)O(3) exhibited superior SCR activity to MnCe/TiO(2). NH(3) temperature programmed desorption study proved that MnCe/TiO(2) was mainly Lewis acidic, while MnCe/Al(2)O(3) could provide more Brönsted acid sites. These acid sites play an important role in SCR according to in situ diffuse reflectance infrared transform spectroscopy (DRIFT) analysis. The main SCR reaction was a typical Eley-Rideal mechanism on MnCe/TiO(2), which took place between coordinated NH(3)/NH(4)(+) and gas-phase NO. For MnCe/Al(2)O(3), the reaction mainly occurred via another pathway when the temperature exceeded 150 degrees C, which commenced with the adsorption and oxidation of NO and was followed by reaction between NO(2) or NO(2)-containing compounds and NH(3) adspecies. This reaction pathway makes a significant contribution to the improved NO conversion for MnCe/Al(2)O(3) at higher temperature.

  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. 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

  9. 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.

  10. Addition of NH3 to Al3O3-

    NASA Astrophysics Data System (ADS)

    Wyrwas, Richard B.; Jarrold, Caroline Chick; Das, Ujjal; Raghavachari, Krishnan

    2006-05-01

    Recent computational studies on the addition of ammonia (NH3) to the Al3O3- cluster anion [A. Guevara-Garcia, A. Martinez, and J. V. Ortiz, J. Chem. Phys. 122, 214309 (2005)] have motivated experimental and additional computational studies, reported here. Al3O3- is observed to react with a single NH3 molecule to form the Al3O3NH3- ion in mass spectrometric studies. This is in contrast to similarly performed studies with water, in which the Al3O5H4- product was highly favored. However, the anion PE spectrum of the ammoniated species is very similar to that of Al3O4H2-. The adiabatic electron affinity of Al3O3NH3 is determined to be 2.35(5)eV. Based on comparison between the spectra and calculated electron affinities, it appears that NH3 adds dissociatively to Al3O3-, suggesting that the time for the Al3O3-•NH3 complex to either overcome or tunnel through the barrier to proton transfer (which is higher for NH3 than for water) is short relative to the time for collisional cooling in the experiment.

  11. Multi-walled carbon nanotubes plastic NH3 gas sensor

    NASA Astrophysics Data System (ADS)

    Isa, Siti S. Mat; Ramli, Muhammad M.; Jamlos, M. F.; Hambali, N. A. M. Ahmad; Isa, M. Mohamad; Kasjoo, S. R.; Ahmad, N.; Nor, N. I. M.; Khalid, N.

    2017-03-01

    Multi-walled Carbon Nanotubes (MWCNTs) functionalized -COOH was used as the sensing material. The MWCNTs suspension was then deposited on the plastic substrate using vacuum filtration method, hence created uniform thin film carbon nanotubes network. Plastic membrane was chosen as the substrate in order to produce flexible, lightweight, wearable and low cost sensor. This device was exposed to ammonia gas (NH3) at two different concentrations; 19.2 and 231.4 ppm. The device shows high sensitivity at 23.4 % when exposed to 231.4 ppm NH3 and less sensitivity at 4.39 % for 19.2 ppm NH3 exposure.

  12. Iron loading effects in Fe/SSZ-13 NH3-SCR catalysts: nature of the Fe-ions and structure-function relationships

    SciTech Connect

    Gao, Feng; Zheng, Yang; Kukkadapu, Ravi K.; Wang, Yilin; Walter, Eric D.; Schwenzer, Birgit; Szanyi, Janos; Peden, Charles HF

    2016-05-06

    Using a traditional aqueous solution ion-exchange method under a protecting atmosphere of N2, a series of Fe/SSZ-13 catalysts with various Fe loadings were synthesized. UV-Vis, EPR and Mössbauer spectroscopies, coupled with temperature programmed reduction and desorption techniques, were used to probe the nature of the Fe sites. The major monomeric and dimeric Fe species are extra-framework [Fe(OH)2]+ and [HO-Fe-O-Fe-OH]2+. Larger oligomers with unknown nuclearity, poorly crystallized Fe2O3 particles, together with isolated Fe2+ ions, are minor Fe-containing moieties. Reaction rate and Fe loading correlations suggest that isolated Fe3+ ions are the active sites for standard SCR while the dimeric sites are the active centers for NO oxidation. NH3 oxidation, on the other hand, is catalyzed by sites with higher nuclearity. A low-temperature standard SCR reaction network is proposed that includes redox cycling of both monomeric and dimeric Fe species, for SCR and NO2 generation, respectively. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Program 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. 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.

  14. 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...

  15. Rotational Spectroscopy of the NH3-H2 Molecular Complex

    NASA Astrophysics Data System (ADS)

    Surin, L. A.; Tarabukin, I. V.; Schlemmer, S.; Breier, A. A.; Giesen, T. F.; McCarthy, M. C.; van der Avoird, A.

    2017-03-01

    We report the first high resolution spectroscopic study of the NH3–H2 van der Waals molecular complex. Three different experimental techniques, a molecular beam Fourier transform microwave spectrometer, a millimeter-wave intracavity jet OROTRON spectrometer, and a submillimeter-wave jet spectrometer with multipass cell, were used to detect pure rotational transitions of NH3–H2 in the wide frequency range from 39 to 230 GHz. Two nuclear spin species, (o)-NH3–(o)-H2 and (p)-NH3–(o)-H2, have been assigned as carriers of the observed lines on the basis of accompanying rovibrational calculations performed using the ab initio intermolecular potential energy surface (PES) of Maret et al. The experimental spectra were compared with the theoretical bound state results, thus providing a critical test of the quality of the NH3–H2 PES, which is a key issue for reliable computations of the collisional excitation and de-excitation of ammonia in the dense interstellar medium.

  16. 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).

  17. Gaseous NH3 Confers Porous Pt Nanodendrites Assisted by Halides

    PubMed Central

    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

  18. First detection of ammonia (NH3) in the upper troposphere

    NASA Astrophysics Data System (ADS)

    Höpfner, Michael; Volkamer, Rainer; Grabowski, Udo; Grutter de la Mora, Michel; Orphal, Johannes; Stiller, Gabriele; von Clarmann, Thomas

    2016-04-01

    Ammonia (NH3) is the major alkaline trace gas in the troposphere. Neutralization of atmospheric acids, like HNO3 and H2SO4, leads to formation of ammonium nitrate and ammonium sulfate aerosols. Further, there are indications that NH3 may enhance nucleation of sulfuric acid aerosols by stabilization of sulfuric acid clusters. By far the largest source of ammonia is agricultural food production. Major global emissions are located in S-E Asia as e.g. shown by satellite nadir observations. Besides its importance with respect to air quality issues, an increase of ammonia emissions in the 21st century might lead to a significant climate radiative impact through aerosol formation. In spite of its significance, there is a lack of observational information on the global distribution of NH3 in the mid- and upper troposphere. Observational evidence, however, would be important for testing e.g. model results on the fate of ammonia from its source regions on ground to altitudes up to the tropopause. In this contribution we will show, to our knowledge, the first unequivocal detection of ammonia in the upper troposphere. This result has been achieved through analysis of infrared limb-emission observations performed with the MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) instrument on board the Envisat satellite from 2002-2012. On a global scale, enhanced values of ammonia have been measured in the upper tropospheric region influenced by the Asian monsoon. We will present a quantitative analysis of the retrieved concentrations of NH3 including an error assessment and further retrieval diagnostics. The results will be discussed with respect to the variability of NH3 locally within the Asian monsoon region's upper troposphere and at different years. Further, we will show comparisons between global distributions of NH3 from published model simulations and our observational dataset from MIPAS.

  19. 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).

  20. 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.

  1. Preparation and characterization of Pd/C catalyst obtained in NH 3-mediated polyol process

    NASA Astrophysics Data System (ADS)

    Li, Huanqiao; Sun, Gongquan; Jiang, Qian; Zhu, Mingyuan; Sun, Shiguo; Xin, Qin

    Vulcan XC-72R carbon supported Pd nanoparticles was obtained in a NH 3-mediated polyol process without any protective agent and characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM) techniques. The added NH 3 species is found to have a strong complex ability to Pd, which not only avoids the formation of Pd hydroxide precipitate resulted from Pd hydrolysis, but also restrains the further complete reduction of Pd. Temperature-programmed reduction equipped with a mass spectrometry (TPR-MS) is employed to study the reductive behavior of unreduced Pd complex in Pd/C catalyst and the results show that the post-treatment in a reductive atmosphere at higher temperature is needed to ensure the complete reduction of Pd. XRD patterns show the heat-treated Pd/C sample in a reductive atmosphere has a face centered cubic crystal structure and TEM image indicates that the dispersion of Pd nanoparticles on the carbon support is uniform and in a narrow particle size range. Thermodynamic data analysis is carried out to elucidate the possible reaction pathway for the preparation of Pd/C catalyst in this process. The obtained Pd/C catalyst shows high activity to formic acid oxidation and high selectivity to oxygen reduction reaction (ORR) with the presence of methanol.

  2. 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

    2015-01-06

    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.

  3. Kinetics of the NH3 and CO2 solid-state reaction at low temperature.

    PubMed

    Noble, J A; Theule, P; Duvernay, F; Danger, G; Chiavassa, T; Ghesquiere, P; Mineva, T; Talbi, D

    2014-11-21

    Ammonia and carbon dioxide play an important role in both atmospheric and interstellar ice chemistries. This work presents a theoretical and experimental study of the kinetics of the low-temperature NH3 and CO2 solid-state reaction in ice films, the product of which is ammonium carbamate (NH4(+)NH2COO(-)). It is a first-order reaction with respect to CO2, with a temperature-dependent rate constant fitted to the Arrhenius law in the temperature range 70 K to 90 K, with an activation energy of 5.1 ± 1.6 kJ mol(-1) and a pre-exponential factor of 0.09-0.08(+1.1) s(-1). This work helps to determine the rate of removal of CO2 and NH3, via their conversion into ammonium carbamate, from atmospheric and interstellar ices. We also measure first-order desorption energies of 69.0 ± 0.2 kJ mol(-1) and 76.1 ± 0.1 kJ mol(-1), assuming a pre-exponential factor of 10(13) s(-1), for ammonium carbamate and carbamic acid, respectively.

  4. Hydrogen generation behaviors of NaBH4-NH3BH3 composite by hydrolysis

    NASA Astrophysics Data System (ADS)

    Xu, Yanmin; Wu, Chaoling; Chen, Yungui; Huang, Zhifen; Luo, Linshan; Wu, Haiwen; Liu, Peipei

    2014-09-01

    In this work, NH3BH3 (AB) is used to induce hydrogen generation during NaBH4 (SB) hydrolysis in order to reduce the use of catalysts, simplify the preparation process, reduce the cost and improve desorption kinetics and hydrogen capacity as well. xNaBH4-yNH3BH3 composites are prepared by ball-milling in different proportions (from x:y = 1:1 to 8:1). The experimental results demonstrate that all composites can release more than 90% of hydrogen at 70 °C within 1 h, and their hydrogen yields can reach 9 wt% (taking reacted water into account). Among them, the composites in the proportion of 4:1 and 5:1, whose hydrogen yields reach no less than 10 wt%, show the best hydrogen generation properties. This is due to the impact of the following aspects: AB additive improves the dispersibility of SB particles, makes the composite more porous, hampers the generated metaborate from adhering to the surface of SB, and decreases the pH value of the composite during hydrolysis. The main solid byproduct of this hydrolysis system is NaBO2·2H2O. By hydrolytic kinetic simulation of the composites, the fitted activation energies of the complexes are between 37.2 and 45.6 kJ mol-1, which are comparable to the catalytic system with some precious metals and alloys.

  5. Preformance Analysis of NH3-H2O Absorption Cycle

    NASA Astrophysics Data System (ADS)

    Tsujimori, Atsushi; Ozaki, Eiichi

    Different from H2O-LiBr absorption cycle, it is necessary to have rectifier between generator and condenser in NH3-H2O absorption cycle, because there mixes some steam in refrigerant vapor in the process of regenerating refrigerant from the ammonia strong aqueous solution. And in some case ex. partial load or heating, the efficiency of rectifier might decrease, if the flow rate of refrigerant vapor and ammonia aqueous solution decrease. As a result, steam flow into condenser with ammonia refrigerant vapor, which reduces cycle COPs of cooling and heating. Accordingly in order to evaluate the effect of ammonia concentration in refrigerant for the performance of NH3-H2O absorption heat pump, the simple design approach of modeling condenser and evaporator is introduced in this paper. In the model, the calculation of heat rate in condenser and evaporator was simplified considering the characteristic of NH3-H2O liquid-vapor equilibrium. Then the simulation for cycle perforance based on GAX absorption cycle was made using the efficiency of rectifier that established the ammonia concentration in refrigerant and it was derived that 3 [%] decrease of ammonia concentration in refrigerant induced 15 [%] decrcase of cooling COP and 7 [%] decrease of heating COP and that there existed the most suitable circulation ratio for each ammonia concentration in refrigerant.

  6. Tunable high-efficient pulsed NH3 terahertz lasers

    NASA Astrophysics Data System (ADS)

    Jiu, Zhi-Xian; Li, Qiang; Zuo, Du-Luo; Miao, Liang; Cheng, Zu-Hai

    2012-03-01

    Experimental studies on a tunable efficient high-efficient pulsed NH3 terahertz (THz) lasers pumped by TEA CO2 lasers are presented. When NH3 is pumped by the different lines with the CO2 lasers, the generation of different terahertz radiations is discussed. The lines of the CO2 lasers are 9R(08), 9P(20), 10R(14), 10R(08), and 10R(06). To improve THz laser energy and photon conversion efficiency, different higher power of the CO2 laser can effectively improve THz laser energy and photon conversion efficiency. When the 9P(20) CO2 lasers with 9.68 J and 4.12 J pump NH3, the corresponding energy conversion efficiencies are 0.28% and 0.19%, increasing by a factor of about 1.5. The generation of terahertz radiations with energy as high as 27.29 mJ and 7.73 mJ are obtained, respectively, increasing by a factor of about 3.5. Meanwhile, for 10R(14) line, the energy conversion efficiencies increase to 8.5 times and the energy of THz lasers increase to 32 times.

  7. Tunable high-efficient pulsed NH3 terahertz lasers

    NASA Astrophysics Data System (ADS)

    Jiu, Zhi-Xian; Li, Qiang; Zuo, Du-Luo; Miao, Liang; Cheng, Zu-Hai

    2011-11-01

    Experimental studies on a tunable efficient high-efficient pulsed NH3 terahertz (THz) lasers pumped by TEA CO2 lasers are presented. When NH3 is pumped by the different lines with the CO2 lasers, the generation of different terahertz radiations is discussed. The lines of the CO2 lasers are 9R(08), 9P(20), 10R(14), 10R(08), and 10R(06). To improve THz laser energy and photon conversion efficiency, different higher power of the CO2 laser can effectively improve THz laser energy and photon conversion efficiency. When the 9P(20) CO2 lasers with 9.68 J and 4.12 J pump NH3, the corresponding energy conversion efficiencies are 0.28% and 0.19%, increasing by a factor of about 1.5. The generation of terahertz radiations with energy as high as 27.29 mJ and 7.73 mJ are obtained, respectively, increasing by a factor of about 3.5. Meanwhile, for 10R(14) line, the energy conversion efficiencies increase to 8.5 times and the energy of THz lasers increase to 32 times.

  8. Interaction between CO and NH 3 coadsorbed on Ru(001): its effects on the ordering in mixed adlayers and the ammonia dissociation

    NASA Astrophysics Data System (ADS)

    Sasaki, Takehiko; Aruga, Tetsuya; Kuroda, Haruo; Iwasawa, Yasuhiro

    1990-12-01

    The coadsorption of CO and ammonia on Ru(001) has been investigated by low-energy electron diffraction (LEED), temperature-programmed desorption (TPD) and high-resolution electron energy-loss spectroscopy (HREELS). The main focus has been on the interaction between different admolecules on the surface and its important role in surface reaction. Exposing CO-precovered Ru(001) to ammonia at 100 K leads to the formation of mixed ordered layers with a (2 × 2) periodicity. It was found that two types of (2 × 2) structures are formed depending on the CO precoverage. One of the (2 × 2) structures (α-phase) contains one CO and two ammonia molecules per (2 × 2) unit cell and the other (β-phase) contains two CO and one ammonia. Structure models for the two phases are proposed based on vibrational spectra measured for the coadsorbed phases of CO and ammonia ( 15NH 3 or ND 3). TPD results suggest that the ammonia dissociation takes place on clean and CO-precovered Ru(001). The amount of dissociated ammonia decreased initially with increasing CO precoverage, passed a minimum at θCO = 0.25, increased with a further increase of CO coverage, and eventually reached a saturation value above θCO = 0.5. The dissociation of ammonia in the β-(2 × 2) structure was found to be enhanced by a factor of 4-6 as compared with the dissociation in the α-(2 × 2) structure. The HREEL spectra indicated that the C 3v molecular axis of ammonia is tilted in the coadsorbed layers, the tilting being most pronounced in the β-(2 × 2) phase with a high CO partial coverage. This observation suggests that the tilting of ammonia due to the interaction with CO facilitates electron donation from Ru 4d to LUMO of ammonia, leading to the N-H bond dissociation. The microscopic model for the CO-NH 3 interaction on metal surfaces is presented.

  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

  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.

  11. 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.

  12. Sensing mechanisms for carbon nanotube based NH3 gas detection.

    PubMed

    Peng, Ning; Zhang, Qing; Chow, Chee Lap; Tan, Ooi Kiang; Marzari, Nicola

    2009-04-01

    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 NH(3) gas; (2) the CNT/electrode contacts are passivated with a Si(3)N(4) 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 degrees C. At higher temperatures, the charge transfer process contributes to the response signals. There is a clear evidence that the adsorption of NH(3) on the CNT channel is facilitated by environmental oxygen.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Relativistic GW calculations on CH3NH3PbI3 and CH3NH3SnI3 Perovskites for Solar Cell Applications

    NASA Astrophysics Data System (ADS)

    Umari, Paolo; Mosconi, Edoardo; de Angelis, Filippo

    2014-03-01

    Hybrid AMX3 perovskites (A = Cs, CH3NH3; M = Sn, Pb; X = halide) have revolutionized the scenario of emerging photovoltaic technologies, with very recent results demonstrating 15% efficient solar cells. The CH3NH3PbI3/MAPb(I1-xClx)3 perovskites have dominated the field, while the similar CH3NH3SnI3 has not been exploited for photovoltaic applications. Replacement of Pb by Sn would facilitate the large uptake of perovskite-based photovoltaics. Despite the extremely fast progress, the materials electronic properties which are key to the photovoltaic performance are relatively little understood. Density Functional Theory electronic structure methods have so far delivered an unbalanced description of Pb- and Sn-based perovskites. Here we develop an effective GW method incorporating spin-orbit coupling which allows us to accurately model the electronic, optical and transport properties of CH3NH3SnI3 and CH3NH3PbI3, opening the way to new materials design. The different CH3NH3SnI3 and CH3NH3PbI3 electronic properties are discussed in light of their exploitation for solar cells, and found to be dominantly due to relativistic effects. These effects stabilize the CH3NH3PbI3 material towards oxidation, by inducing a deeper valence band edge. Relativistic effects, however, also increase the material band-gap compared to CH3NH3SnI3, due to the valence band energy downshift (~0.7 eV) being only partly compensated by the conduction band downshift (~0.2 eV).

  18. Excited State Processes for Aqueous Rh(NH3)5Cl(2+) and Rh(NH3)5Br(2+).

    DTIC Science & Technology

    1981-04-10

    white precipitate of Rh(NH3)5(H20)) Br3 was collected and dried overnight at 110-0 C. The resulting yellow product was recrystallized from water/HClO4 to...aquation. In all cases, product concentrations were corrected for the usually small degree of dark or thermal reaction. Pulsed Laser Experiments. The...direct photochemical production . According to Palmer and Harris [16] the reaction Rh(NH 3)5(OH) 2+ + C02(aq) = Rh(NH 3)5(Co3) + + H+ occurs with a rate

  19. 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.

  20. Vibrations and reorientations of NH3 molecules in [Mn(NH3)6](ClO4)2 studied by infrared spectroscopy and theoretical (DFT) calculations.

    PubMed

    Hetmańczyk, Joanna; Hetmańczyk, Łukasz; Migdał-Mikuli, Anna; Mikuli, Edward

    2015-02-05

    The vibrational and reorientational motions of NH3 ligands and ClO4(-) anions were investigated by Fourier transform middle-infrared spectroscopy (FT-IR) in the high- and low-temperature phases of [Mn(NH3)6](ClO4)2. The temperature dependencies of full width at half maximum (FWHM) of the infrared bands at: 591 and 3385cm(-1), associated with: ρr(NH3) and νas(N-H) modes, respectively, indicate that there exist fast (correlation times τR≈10(-12)-10(-13)s) reorientational motions of NH3 ligands, with a mean values of activation energies: 7.8 and 4.5kJmol(-1), in the phase I and II, respectively. These reorientational motions of NH3 ligands are only slightly disturbed in the phase transition region and do not significantly contribute to the phase transition mechanism. Fourier transform far-infrared and middle-infrared spectra with decreasing of temperature indicated characteristic changes at the vicinity of PT at TC(c)=137.6K (on cooling), which suggested lowering of the crystal structure symmetry. Infrared spectra of [Mn(NH3)6](ClO4)2 were recorded and interpreted by comparison with respective theoretical spectra calculated using DFT method (B3LYP functional, LANL2DZ ECP basis set (on Mn atom) and 6-311+G(d,p) basis set (on H, N, Cl, O atoms) for the isolated equilibrium two models (Model 1 - separate isolated [Mn(NH3)6](2+) cation and ClO4(-) anion and Model 2 - [Mn(NH3)6(ClO4)2] complex system). Calculated optical spectra show a good agreement with the experimental infrared spectra (FT-FIR and FT-MIR) for the both models.

  1. Comparison of preparation methods for ceria catalyst and the effect of surface and bulk sulfates on its activity toward NH3-SCR.

    PubMed

    Chang, Huazhen; Ma, Lei; Yang, Shijian; Li, Junhua; Chen, Liang; Wang, Wei; Hao, Jiming

    2013-11-15

    A series of CeO2 catalysts prepared with sulfate (S) and nitrate (N) precursors by hydrothermal (H) and precipitation (P) methods were investigated in selective catalytic reduction of NOx by NH3 (NH3-SCR). The catalytic activity of CeO2 was significantly affected by the preparation methods and the precursor type. CeO2-SH, which was prepared by hydrothermal method with cerium (IV) sulfate as a precursor, showed excellent SCR activity and high N2 selectivity in the temperature range of 230-450 °C. Based on the results obtained by temperature-programmed reduction (H2-TPR), transmission infrared spectra (IR) and thermal gravimetric analysis (TGA), the excellent performance of CeO2-SH was correlated with the surface sulfate species formed in the hydrothermal reaction. These results indicated that sulfate species bind with Ce(4+) on the CeO2-SH catalyst, and the specific sulfate species, such as Ce(SO4)2 or CeOSO4, were formed. The adsorption of NH3 was promoted by these sulfate species, and the probability of immediate oxidation of NH3 to N2O on Ce(4+) was reduced. Accordingly, the selective oxidation of NH3 was enhanced, which contributed to the high N2 selectivity in the SCR reaction. However, the location of sulfate on the CeO2-SP catalyst was different. Plenty of sulfate species were likely deposited on CeO2-SP surface, covering the active sites for NO oxidation, which resulted in poor SCR activity in the test temperature range. Moreover, the resistance to alkali metals, such as Na and K, was improved over the CeO2-SH catalyst.

  2. Time Resolved Measurement of Ecosystem-Atmosphere NH3 Exchange Using the Eddy Covariance Technique

    NASA Astrophysics Data System (ADS)

    Fischer, M. L.; Littlejohn, D.

    2005-12-01

    Quantifying ammonia fluxes between the land surface and atmosphere is required for effective control of air quality, improving agricultural practices, and understanding natural ecosystem function. Ammonia (NH3) is emitted in large but uncertain amounts from animal agriculture, in lesser amounts from imperfect use of nitrogen fertilizers in crop agriculture, from catalytic converters used on automobiles and other energy related industrial processes, and exchanged between the ecosystem and atmosphere by natural ecosystem processes on vast spatial scales. To address the need for accurate, time-resolved NH3 flux measurements, we have developed an eddy covariance (EC) instrument for direct measurements of NH3 flux. EC flux measurements of NH3 were not previously possible because instruments were not sufficiently sensitive at high frequencies required to capture rapid variations in surface layer NH3 concentrations. To overcome this hurdle we combined a tunable-diode-laser (TDL) spectrometer with a fast-response NH3 sampling inlet and automated pulse-response calibration system. Laboratory tests of the inlet system demonstrate that the response to 10 ppb step in NH3 concentration is well described by a double exponential model with (1/e) times of 0.3 (85% response) and 1.5 (15% response) seconds. This response combined with a routinely measured instrument stability of ~ 0.1 ppb (on 30 minute timescales) indicates that the instrumental contribution to noise in NH3 flux measurements is ~ 0.2 umol NH3 m-2 hr-1, sufficient to stringently test models for NH3 exchange under most conditions. Recent results of field work to verify the instrument performance and observe examples of NH3 exchange will be presented.

  3. 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.

  4. 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.

  5. 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.

  6. Rotational spectrum of the NH3-He van der Waals complex

    NASA Astrophysics Data System (ADS)

    Surin, L.; Schnell, M.

    2016-12-01

    The interaction between ammonia and helium has attracted considerable interest over many years, partly because of the observation of interstellar ammonia. The rate coefficients of NH3-He scattering are an important ingredient for numerical modeling of astrochemical environments. Another, though quite different application in which the NH3-He interaction can play an important role is the doping of helium clusters with NH3 molecules to perform high-resolution spectroscopy. Such experiments are directed on the detection of non-classical response of molecular rotation in helium clusters addressing fundamental questions related to the microscopic nature of superfluidity. High-resolution spectroscopy on the NH3-He complex is an important tool for increasing our understanding of intermolecular forces between NH3 and He.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

    Hetmańczyk, Łukasz; Hetmańczyk, Joanna

    2016-07-01

    High temperature phase transition in [Cd(NH3)4](ReO4)2 at Tc = 368.5 K (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 300 K) is rather small and is equal to ca. 4 kJ mol- 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.

  9. Communication: Equivalence between symmetric and antisymmetric stretching modes of NH3 in promoting H + NH3 → H2 + NH2 reaction

    NASA Astrophysics Data System (ADS)

    Song, Hongwei; Yang, Minghui; Guo, Hua

    2016-10-01

    Vibrational excitations of reactants sometimes promote reactions more effectively than the same amount of translational energy. Such mode specificity provides insights into the transition-state modulation of reactivity and might be used to control chemical reactions. We report here a state-of-the-art full-dimensional quantum dynamical study of the hydrogen abstraction reaction H + NH3 → H2 + NH2 on an accurate ab initio based global potential energy surface. This reaction serves as an ideal candidate to study the relative efficacies of symmetric and degenerate antisymmetric stretching modes. Strong mode specificity, particularly for the NH3 stretching modes, is demonstrated. It is further shown that nearly identical efficacies of the symmetric and antisymmetric stretching modes of NH3 in promoting the reaction can be understood in terms of local-mode stretching vibrations of the reactant molecule.

  10. Unaccounted variability in NH3 agricultural sources detected by IASI contributing to European spring haze episode

    NASA Astrophysics Data System (ADS)

    Fortems-Cheiney, A.; Dufour, G.; Hamaoui-Laguel, L.; Foret, G.; Siour, G.; Van Damme, M.; Meleux, F.; Coheur, P.-F.; Clerbaux, C.; Clarisse, L.; Favez, O.; Wallasch, M.; Beekmann, M.

    2016-05-01

    Ammonia (NH3), whose main source in the troposphere is agriculture, is an important gaseous precursor of atmospheric particulate matter (PM). We derived daily ammonia emissions using NH3 total columns measured from the Infrared Atmospheric Sounding Interferometer (IASI) on board Metop-A, at a relatively high spatial resolution (grid cell of 0.5° × 0.5°). During the European spring haze episodes of 24-31 March 2012 and 8-15 March 2014, IASI reveals NH3 total column magnitudes highlighting higher NH3 emissions over central Europe (especially over Germany, Czech Republic, and eastern France) from the ones provided by the European reference European Monitoring and Evaluation Programme inventory. These ammonia emissions exhibit in addition a large day-to-day variability, certainly due to spreading practices. The increase of NH3 emissions in the model, that reaches +300% locally, leads to an increase of both NH3 and PM2.5 surface concentrations and allows for a better comparison with independent measurements (in terms of bias, root-mean-square error, and correlation). This study suggests that there are good prospects for better quantifying NH3 emissions by atmospheric inversions.

  11. Exploring and rationalising effective n-doping of large area CVD-graphene by NH3.

    PubMed

    Bianco, G V; Losurdo, M; Giangregorio, M M; Capezzuto, P; Bruno, G

    2014-02-28

    Despite the large number of papers on the NH3 doping of graphene, the achievement of stable n-doped large area CVD (chemical vapor deposition) graphene, which is intrinsically p-doped, is still challenging. A control of the NH3 chemisorption and of the N-bond configuration is still needed. The feasibility of a room temperature high pressure NH3 treatment of CVD graphene to achieve n-type doping is shown here. We use and correlate data for (a) sheet resistance, R(sh), and the Hall coefficient, R(H), in van der Pauw configuration, acquired in real time during the NH3 doping of CVD-graphene on a glass substrate, (b) optical measurements of the effect of doping on the graphene Van Hove singularity point at 4.6 eV in the dielectric function spectra by spectroscopic ellipsometry, and of (c) N-bond configuration by XPS to better understand and, finally, control the NH3 doping of graphene. The discussion is focused on the thermal and time stability of the n-doping after air exposure. A chemical rationale is provided for the NH3 n-doping based on the interaction of (i) NH3 with intrinsic oxygen functionalities and defects of CVD graphene and of (ii) C-NH2 doping centers with acceptor species present in the air.

  12. 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.

  13. Perovskite CH3NH3PbI3 crystals and films. Synthesis and characterization

    NASA Astrophysics Data System (ADS)

    Semenova, O. I.; Yudanova, E. S.; Yeryukov, N. A.; Zhivodkov, Y. A.; Shamirzaev, T. S.; Maximovskiy, E. A.; Gromilov, S. A.; Troitskaia, I. B.

    2017-03-01

    Synthesis of organometal halide perovskite CH3NH3PbI3 has received much attention recently because of promising photosensitive properties usable for solid state solar cell (SSSC). Here the crystals of tetragonal phase (I4/mcm, a =8.8743 Å, c =12.6708 Å) of CH3NH3PbI3 were prepared. Formation of the CH3NH3PbI3 crystals was controlled by the SEM, EDS, XRD and Raman spectroscopy. Optical characteristics of the crystals were obtained using PL spectrometry and spectral ellipsometry methods. PL spectra of orthorhombic phase of CH3NH3PbI3 crystals were recorded the first time. Taking into account the practice use, the CH3NH3PbI3 films are obtained via the sol-gel method with ;spin-on; coating of CH3NH3PbI3 sol. The films are 500 nm in thickness and exhibit an openwork structure. Such a structure is optimal for SSSC construction because it increases the surface contact area between CH3NH3PbI3 and p-conductor.

  14. Validation of NH3 satellite observations by ground-based FTIR measurements

    NASA Astrophysics Data System (ADS)

    Dammers, Enrico; Palm, Mathias; Van Damme, Martin; Shephard, Mark; Cady-Pereira, Karen; Capps, Shannon; Clarisse, Lieven; Coheur, Pierre; Erisman, Jan Willem

    2016-04-01

    Global emissions of reactive nitrogen have been increasing to an unprecedented level due to human activities and are estimated to be a factor four larger than pre-industrial levels. Concentration levels of NOx are declining, but ammonia (NH3) levels are increasing around the globe. While NH3 at its current concentrations poses significant threats to the environment and human health, relatively little is known about the total budget and global distribution. Surface observations are sparse and mainly available for north-western Europe, the United States and China and are limited by the high costs and poor temporal and spatial resolution. Since the lifetime of atmospheric NH3 is short, on the order of hours to a few days, due to efficient deposition and fast conversion to particulate matter, the existing surface measurements are not sufficient to estimate global concentrations. Advanced space-based IR-sounders such as the Tropospheric Emission Spectrometer (TES), the Infrared Atmospheric Sounding Interferometer (IASI), and the Cross-track Infrared Sounder (CrIS) enable global observations of atmospheric NH3 that help overcome some of the limitations of surface observations. However, the satellite NH3 retrievals are complex requiring extensive validation. Presently there have only been a few dedicated satellite NH3 validation campaigns performed with limited spatial, vertical or temporal coverage. Recently a retrieval methodology was developed for ground-based Fourier Transform Infrared Spectroscopy (FTIR) instruments to obtain vertical concentration profiles of NH3. Here we show the applicability of retrieved columns from nine globally distributed stations with a range of NH3 pollution levels to validate satellite NH3 products.

  15. An evaluation of IASI-NH3 with ground-based Fourier transform infrared spectroscopy measurements

    NASA Astrophysics Data System (ADS)

    Dammers, Enrico; Palm, Mathias; Van Damme, Martin; Vigouroux, Corinne; Smale, Dan; Conway, Stephanie; Toon, Geoffrey C.; Jones, Nicholas; Nussbaumer, Eric; Warneke, Thorsten; Petri, Christof; Clarisse, Lieven; Clerbaux, Cathy; Hermans, Christian; Lutsch, Erik; Strong, Kim; Hannigan, James W.; Nakajima, Hideaki; Morino, Isamu; Herrera, Beatriz; Stremme, Wolfgang; Grutter, Michel; Schaap, Martijn; Wichink Kruit, Roy J.; Notholt, Justus; Coheur, Pierre-F.; Erisman, Jan Willem

    2016-08-01

    Global distributions of atmospheric ammonia (NH3) measured with satellite instruments such as the Infrared Atmospheric Sounding Interferometer (IASI) contain valuable information on NH3 concentrations and variability in regions not yet covered by ground-based instruments. Due to their large spatial coverage and (bi-)daily overpasses, the satellite observations have the potential to increase our knowledge of the distribution of NH3 emissions and associated seasonal cycles. However the observations remain poorly validated, with only a handful of available studies often using only surface measurements without any vertical information. In this study, we present the first validation of the IASI-NH3 product using ground-based Fourier transform infrared spectroscopy (FTIR) observations. Using a recently developed consistent retrieval strategy, NH3 concentration profiles have been retrieved using observations from nine Network for the Detection of Atmospheric Composition Change (NDACC) stations around the world between 2008 and 2015. We demonstrate the importance of strict spatio-temporal collocation criteria for the comparison. Large differences in the regression results are observed for changing intervals of spatial criteria, mostly due to terrain characteristics and the short lifetime of NH3 in the atmosphere. The seasonal variations of both datasets are consistent for most sites. Correlations are found to be high at sites in areas with considerable NH3 levels, whereas correlations are lower at sites with low atmospheric NH3 levels close to the detection limit of the IASI instrument. A combination of the observations from all sites (Nobs = 547) give a mean relative difference of -32.4 ± (56.3) %, a correlation r of 0.8 with a slope of 0.73. These results give an improved estimate of the IASI-NH3 product performance compared to the previous upper-bound estimates (-50 to +100 %).

  16. 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.

  17. Conversion of Fe-NH2 to Fe-N2 with release of NH3

    PubMed Central

    Anderson, John S.; Moret, Marc-Etienne; Peters, Jonas C.

    2013-01-01

    Tris(phosphine)borane ligated Fe(I) centers featuring N2H4, NH3, NH2, and OH ligands are described. Conversion of Fe-NH2 to Fe-NH3+ by addition of acid, and subsequent reductive release of NH3 to generate Fe-N2, is demonstrated. This sequence models the final steps of proposed Fe-mediated nitrogen fixation pathways. The five-coordinate trigonal bipyramidal complexes described are unusual in that they adopt S = 3/2 ground states and are prepared from a four-coordinate, S = 3/2 trigonal pyramidal precursor. PMID:23259776

  18. Role of the support on the behavior of Ag-based catalysts for NH3 selective catalytic oxidation (NH3-SCO)

    NASA Astrophysics Data System (ADS)

    Qu, Zhenping; Wang, Hui; Wang, Shudong; Cheng, Hao; Qin, Yuan; Wang, Zhong

    2014-10-01

    In this work four supports with different textural properties (Al2O3, SiO2, NaY and TiO2) are used to evaluate the formation of different silver species and their effect on the NH3-SCO performance. Characterization analyses have shown that the predominant Ag0 species and the oxidized Ag species (Ag+ and Agnδ+) are located on the four catalysts with different ratio of Ag0/oxidized Ag. Small Ag0 particle with high dispersion which is obtained on 10 wt% Ag/Al2O3 (5 nm, Ag0 ratio = 97.7%) shows an excellent catalytic performance for SCO reaction at low temperatures (a complete NH3 conversion at 180 °C and a high N2 selectivity of 89%). In addition, a certain amount of oxidized Ag species formed on the catalysts, especially for the NaY and SiO2 support, as well as the surface acidity of catalysts have also been found to play an important role in the enhanced N2 selectivity above 140 °C by promoting iSCR reaction involving NO as an intermediate for N2 formation. A model to relate the silver species with the performance of NH3-SCO is proposed, which is very significant for the further optimization of the catalyst (e.g. choosing a suitable support) for NH3-SCO reaction and its practical application in the future.

  19. 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

  20. Selective Catalytic Reduction of NO by NH3 with WO3-TiO2 Catalysts: Influence of Catalyst Synthesis Method

    DOE PAGES

    He, Yuanyuan; Ford, Michael E.; Zhu, Minghui; ...

    2016-02-02

    A series of supported WO3/TiO2 catalysts was prepared by a new synthesis procedure involving co-precipitation of an aqueous TiO(OH)2 and (NH4)10W12O41*5H2O slurry under controlled pH conditions. The morphological properties, molecular structures, surface acidity and surface chemistry of the supported WO3/TiO2 catalysts were determined with BET, in situ Raman, in situ IR and temperature-programmed surface reaction (TPSR) spectroscopy, respectively. Isotopic 18O-16O exchange demonstrated that tungsten oxide was exclusively present as surface WOx species on the TiO2 support with mono-oxo W=O coordination. In contrast to previous studies employing impregnation synthesis that found only surface one mono-oxo O=WO4 site on TiO2, the co-precipitationmore » procedure resulted in the formation of two distinct surface WOx species: mono-oxo O=WO4 (~1010-1017 cm-1) on low defect density patches of TiO2 and a second mono-oxo O=WO4 (~983-986 cm-1) on high defect density patches of TiO2. The concentration of the second WOx surface species increases as a function of solution pH. Both surface WOx sites, however, exhibited the same NO/NH3 SCR reactivity. The co-precipitated WO3-TiO2 catalysts synthesized in alkaline solutions exhibited enhanced performance for the NO/NH3 SCR reaction that is ascribed to the greater number of surface defects on the resulting TiO2 support. For the co-precipitated catalyst prepared at pH10, surface NH4+ species on Br nsted acid sites were found to be more reactive than surface NH3* species on Lewis acid sites for SCR of NO with NH3.« less

  1. 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.

  2. Performance Analysis of Rectifier in NH3-H2O Absorprtion Heat Pump

    NASA Astrophysics Data System (ADS)

    Tsujimori, Atsushi; Ozaki, Eiichi; Nakao, Kazushige

    It is necessary to have rectifier in NH3-H20 absorption cycle in order to remove steam from ammonia and steam mixed vapor that is regenerated in generator. Although many studies have made to investigate the performance of rectifier using various fluids experimentally, few theoretical analysis has made without any constant from experimental data. In this study in order to investigate the characteristic of rectifying process, experimental and analytical approach was made concerning plate-type rectifier. In the experiment, the effect of vapor flow rate and NH3 mass concentration of solution on rectifying performance were investigated. And in the analysis the model of heat and mass transfer was proposed considering the distribution of mass concentration in boundary layer. As a result it was found that NH3 mass concentration at rectifier outlet slightly decreased as vapor flow rate increased and that the model could predict NH3 mass concentration in outlet vapor for various concentration in solution.

  3. Porphyrin molecules boost the sensitivity of epitaxial graphene for NH3 detection

    NASA Astrophysics Data System (ADS)

    Iezhokin, I.; den Boer, D.; Offermans, P.; Ridene, M.; Elemans, J. A. A. W.; Adriaans, G. P.; Flipse, C. F. J.

    2017-02-01

    The sensitivity of quasi-free standing epitaxial graphene for NH3 detection is strongly enhanced by chemical functionalization with cobalt porphyrins resulting in a detection limit well below 100 ppb. Hybridization between NH3 and cobalt porphyrins induces a charge transfer to graphene and results in a shift of the graphene Fermi-level as detected by Hall measurements and theoretically explained by electronic structure calculations.

  4. 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

  5. Numerical analysis of a mixture of Ar/NH3 microwave plasma chemical vapor deposition reactor

    NASA Astrophysics Data System (ADS)

    Li, Zhi; Zhao, Zhen; Li, Xuehui

    2012-06-01

    A two-dimensional fluid model has been used to investigate the properties of plasma in Ar/NH3 microwave electron cyclotron resonance discharge at low pressure. The electromagnetic field model solved by the three-dimensional Simpson method is coupled to a fluid plasma model. The finite difference method was employed to discrete the governing equations. 40 species (neutrals, radicals, ions, and electrons) are consisted in the model. In total, 75 electron-neutral, 43 electron-ion, 167 neutral-neutral, 129 ion-neutral, 28 ion-ion, and 90 3-body reactions are used in the model. According to the simulation, the distribution of the densities of the considered plasma species has been showed and the mechanisms of their variations have been discussed. It is found that the main neutrals (Ar*, Ar**, NH3*, NH, H2, NH2, H, and N2) are present at high densities in Ar/NH3 microwave electron cyclotron resonance discharge when the mixing ratio of Ar/NH3 is 1:1 at 20 Pa. The density of NH is more than that of NH2 atom. And NH3+ are the most important ammonia ions. But the uniformity of the space distribution of NH3+ is lower than the other ammonia ions.

  6. Effects of in-situ NH3 post plasma treatment on the surface passivation layer

    NASA Astrophysics Data System (ADS)

    Lee, Kyung Dong; Kang, Min Gu; Kim, Young Do; Tark, Sung Ju; Park, Sungeun; Kim, Donghwan

    2011-12-01

    Hydrogenated silicon nitride (SiNx:H) using plasma enhanced chemical vapor deposition is widely used in photovoltaic industry as an antireflection coating and passivation layer. The samples with or without in-situ NH3 post-plasma treatment had the following structures: SiNx/N-type Si/SiNx versus in-situ NH3 post-plasma treated SiNx/N-type Si/SiNx. The wafer was dipped in saw-damage-etching solution and wet cleaning process was treated. After the dry process with N2 atmosphere, SiNx thin film was deposited on back surface. Then SiNx thin film was deposited on the front surface with or without in-situ NH3 post-plasma treatment process. In order to minimize the plasma induced surface damage, we used lower power than the process power during the NH3 post-plasma treatment. After the in-situ NH3 post-plasma-treatment, we analyzed the effect of this in-situ NH3 post-plasma-treatment for passivation. The minority carrier lifetime was observed by means of quasi-steady-state photoconductance and microwave photoconductance.

  7. 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.

  8. Racemic monoperoxovanadium(V) complexes with achiral OO and ON donor set heteroligands: synthesis, crystal structure and stereochemistry of [NH3(CH2)2NH3][VO(O2)(ox)(pic)].2H2O and [NH3(CH2)2NH3][VO(O2)(ox)(pca)].

    PubMed

    Tatiersky, Jozef; Schwendt, Peter; Sivák, Michal; Marek, Jaromír

    2005-07-07

    Monoperoxovanadium(V) complexes, [NH3(CH2)2NH3][VO(O2)(ox)(pic)].2H2O (1) and [NH3(CH2)2NH3][VO(O2)(ox)(pca)] (2) [NH3(CH2)2NH3 = ethane-1,2-diammonium(2+), ox=oxalate(2-), pic=pyridine-2-carboxylate(1-), pca=pyrazine-2-carboxylate(1-)], were synthesized and characterized by X-ray analysis, IR and Raman spectroscopies. The five equatorial positions of the pentagonal bipyramid around the vanadium atoms are occupied by the eta2-peroxo ligand, two oxygen atoms of the ox, and the nitrogen atom of the pic or pca ligands, respectively. The oxo ligand and the oxygen atom of pic or pca are in the axial positions. Networks of X-HO (X=C, N or O) hydrogen bonds, and pi-pi interactions between aromatic rings in and anion-pi interactions in , determine the molecular packings and build up the supramolecular architecture. Three stereochemical rules for occupation of the donor sites in two-heteroligand [VO(O2)(L1)(L2)] complexes (L1, L2 are bidentate neutral or differently charged anionic heteroligands providing an OO, NN or ON donor set) are discussed. and crystallize as racemic compounds. The 51V NMR spectra proved that the parent complex anions of and partially decompose on dissolution in water to the monoperoxo-ox, -pic or -pca complexes.

  9. 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 ...

  10. TiO2 nanotube-supported cu as the catalyst for selective NO reduction with NH3.

    PubMed

    Chen, Shin-An; Nian, Jun-Nan; Tsai, Chien-Cheng; Teng, Hsisheng

    2007-05-01

    Catalyst supports composed of titanate nanotubes were prepared from hydrothermal treatment on TiO2 nanoparticles in NaOH followed by HCl washing. The nanotubes exhibited well-defined TiO2 anatase phase after calcination at 400 degrees C. The nanotube aggregates and other commercially available TiO2 nanoparticles, all with surface areas >300 m(2)/g, were impregnated with Cu and examined in selective catalytic reduction of NO with NH3. In catalyst preparation, the nanotubes were found to be more thermally stable than nanoparticles, withstanding agglomeration at elevated temperatures. The Cu species supported on the nanotubes showed a higher catalytic activity than those supported on the nanoparticles. Analysis with temperature programmed reduction, X-ray photoelectron spectroscopy, and NO adsorption reflected that the layered-titanate feature of the tube wall was advantageous for even distribution of the Cu species, thus leading to the high-catalytic activity of the tubular Cu/TiO2 catalyst.

  11. Volatility of NH3 from internally mixed sodium succinate-NH4SO4 particles

    NASA Astrophysics Data System (ADS)

    Wang, Na; Zhang, Yunhong

    2016-04-01

    Contributing the complicacy of atmospheric constituents, aerosol particles may undergo complicated heterogeneous reactions that have profound consequences on their hygroscopic properties and volatility. Ammonia (NH3) is a ubiquitous trace atmospheric gas in the troposphere and has negative effects on human health and climate forcing of ambient aerosols. In addition, atmospheric cycle of NH3 is complex in atmosphere, therefore it necessary to get insights to the complexity of gas-to-aerosol NH3 partitioning, which results in large uncertainties in the sources and distributions of NH3. By using in-situ Fourier transform infrared spectroscopy and attenuated total reflection (FTIR-ATR), we report here the volatility of NH3 from the laboratory generated sodium succinate with ammonium sulfate ((NH4)2SO4) at a 1:1 molar ratio as well as its effect on the hygroscopicity of the mixtures. The loss of the NH4+ peak at 1451cm-1 and the formation of peaks at 1718 and 1134 cm-1 due to C = O stretching asymmetric vibration of -COOH and ν3 (SO42-) stretching of sodium sulfate indicate that sodium succinate reacts with (NH4)2SO4, releasing NH3 and forming succinic acid and sodium sulfate on dehydration process. The formation of less hygroscopic succinic acid and volatility of NH3 in mixtures leads to a significant decrease in the total water content. To the best of our knowledge, this is the first report of the reaction between (NH4)2SO4 and dicarboxylate salts, which may represent an important particle-gas partitioning for ammonia and thus elucidate another underlying ammonia cycle in atmosphere. These results could be helpful to understand the mutual transformation process of dicarboxylic acids and dicarboxylate salts.

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

    PubMed Central

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

    2015-01-01

    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

  13. Etude des transitions de phases de NH 3(CH 2) 2NH 3(H 2PO 4) 2 par mesures optique, dielectrique et de thermocourant

    NASA Astrophysics Data System (ADS)

    Kamoun, S.; Daoud, A.; Von Der Muhll, R.; Ravez, J.

    1993-02-01

    Dielectric, birefringence and thermocurrent measurements have been carried out on NH 3(CH 2) 2NH 3(H 2PO 4) 2 single crystal. Three transitions have been detected at about T 1 = (264 + 4), T 2 = (241 + 5) and T 3 = (141 + 5) K. In the low temperature phases a polarization current of about 10 -8 - 10 -9 A is obtained and can be reversed when the sign of the polarization field is changed, a property which could correspond to a ferroelectric behaviour. However, no pyroelectric current is detected when the temperature decreases from T t. Another hypothesis, based on a field - induced polarization, has been considered : the depolarization current could be due to charge displacements from potential minima favored by rising temperature. In any way, the low - temperature phases are characterized by a remanent polarization.

  14. Abnormal variation of the growth rate under high NH3 injected regime in the growth of GaN by NH3-source MBE

    NASA Astrophysics Data System (ADS)

    Choi, Sungkuk; Jung, Soohoon; Cho, Youngji; Lee, Sangtae; Chang, Jiho

    2017-03-01

    Unusual growth-rate variation during GaN formation using gas-source MBE has been discussed with respect to the chemical reactions occurring in the transition layer. A series of samples were prepared to confirm the assumption by verifying the growth regime and the impacts on the crystal quality of the GaN film. We found that the growth rate can be varied along with the amount of NH3 supply even under NH3-rich condition with a fixed Ga flux. Two growth conditions were investigated for their impact on the transition layer. One was the atomic force microscopy result, which revealed that the adatom migration length is closely related to the transition layer formation. The other one is the photoluminescent spectra, which revealed that the luminescence property of GaN is strongly related to the transition layer.

  15. New mechanism for the vibrational mode-specific proton-transfer reaction NH 3+ (ν) + NH 3 → NH 2 + NH 4+

    NASA Astrophysics Data System (ADS)

    Tachibana, Akitomo; Suzuki, Tetsuo; Yoshida, Naoto; Teramoto, Yasuhiro; Yamabe, Tokio

    1991-09-01

    A new mechanism has been presented for the vibrational mode-specific depression of the proton-transfer reaction NH 3+ (ν) + NH 3 → NH 2 + NH 4+. We adopt the standpoint of the ADO (average dipole orientation) theory, proposed by Su and Bowers (J. Chem. Phys. 58 (1973) 3027), and append a new long-range interaction created by a vibration-induced dipole to the ADO theory. A "reaction zone" concept is crucial in this approach; outside of the zone the long-range intermolecular interactions play a key role. A qualitatively good agreement is observed for the experimental result of the title reaction obtained by Chupka and Russel (J. Chem. Phys. 48 (1968) 1527).

  16. Photoelectric characteristics of CH3NH3PbI3/p-Si heterojunction

    NASA Astrophysics Data System (ADS)

    Yamei, Wu; Ruixia, Yang; Hanmin, Tian; Shuai, Chen

    2016-05-01

    Organic-inorganic hybrid perovskite CH3NH3PbI3 film is prepared on p-type silicon substrate using the one-step solution method to form a CH3NH3PbI3/p-Si heterojunction. The film morphology and structure are characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The photoelectric properties of the CH3NH3PbI3/p-Si heterojunction are studied by testing the current-voltage (I-V) with and without illumination and capacitance-voltage (C-V) characteristics. It turns out from the I-V curve without illumination that the CH3NH3PbI3/p-Si heterojunction has a rectifier feature with the rectification ratio over 70 at the bias of ±5 V. Also, there appears a photoelectric conversion phenomenon on this heterojunction with a short circuit current (Isc) of 0.16 μA and an open circuit voltage (Voc) of about 10 mV The high frequency C-V characteristic of the Ag/CH3NH3PbI3/p-Si heterojunction turns out to be similar to that of the metal-insulator-semiconductor (MIS) structure, and a parallel translation of the C-V curve along the forward voltage axis is found. This parallel translation means the existence of defects at the CH3NH3PbI3/p-Si interface and positive fixed charges in the CH3NH3PbI3 layer. The defects at the interface of the CH3NH3PbI3/p-Si heterojunction result in the dramatic decline of the Voc. Besides, the C-V test of CH3NH3PbI3 film shows a non-linear dielectric property and the dielectric value is about 4.64 as calculated. Project supported by the Hebei Province Natural Science Foundation of China (No. F2014202184) and the Tianjin Natural Science Foundation of China (No. 15JCZDJC37800).

  17. Exceptional emissions of NH3 and HCOOH in the 2010 Russian wildfires

    NASA Astrophysics Data System (ADS)

    R'Honi, Y.; Clarisse, L.; Clerbaux, C.; Hurtmans, D.; Duflot, V.; Turquety, S.; Ngadi, Y.; Coheur, P.-F.

    2013-04-01

    In July 2010, several hundred forest and peat fires broke out across central Russia during its hottest summer on record. Here, we analyze these wildfires using observations of the Infrared Atmospheric Sounding Interferometer (IASI). Carbon monoxide (CO), ammonia (NH3) and formic acid (HCOOH) total columns are presented for the year 2010. Maximum total columns were found to be one order (for CO and HCOOH) and two orders (for NH3) of magnitude larger than typical background values. The temporal evolution of NH3 and HCOOH enhancement ratios relative to CO are presented. Evidence of secondary formation of HCOOH is found, with enhancement ratios exceeding reported emission ratios in fresh plumes. We estimate the total emitted masses for the period July-August 2010 over the center of western Russia; they are 19-33 Tg (CO), 0.7-2.6 Tg (NH3) and 0.9-3.9 Tg (HCOOH). For NH3 and HCOOH, these quantities are comparable to what is emitted in the course of a whole year by all extratropical forest fires.

  18. Exceptional emissions of NH3 and HCOOH in the 2010 Russian wildfires

    NASA Astrophysics Data System (ADS)

    R'Honi, Y.; Clarisse, L.; Clerbaux, C.; Hurtmans, D.; Duflot, V.; Turquety, S.; Ngadi, Y.; Coheur, P.-F.

    2012-12-01

    In July 2010, several hundred forest and peat fires broke out across Central Russia during its hottest summer on record. Here, we analyze these wildfires using observations of the Infrared Atmospheric Sounding Interferometer (IASI). Carbon monoxide (CO), ammonia (NH3) and formic acid (HCOOH) total columns are presented for the year 2010. Maximum total columns have been observed reaching over 40 (for CO and HCOOH) and 200 (for NH3) times higher than typical background values. The temporal evolution of NH3 and HCOOH enhancement ratios relative to CO are presented. Strong evidence of secondary formation of HCOOH is found, with enhancement ratios exceeding 10 times reported emission ratios in fresh plumes. We estimate the total emitted masses for the period July-August 2010 over the center of Western Russia; they are 19-33 Tg (CO), 0.7-2.6 Tg (NH3) and 0.9-3.9 Tg (HCOOH). For NH3 andHCOOH, these quantities are comparable to what is emitted in the course of a whole year by all extratropical forest fires.

  19. NH3/O2 mixed gas plasmas alter the interaction of blood components with stainless steel.

    PubMed

    Chen, Meng; Zamora, Paul O; Peña, Louis; Som, Prantika; Osaki, Shigemasa

    2003-12-01

    Stainless steel treated with a mixed gas plasma of NH(3) plus O(2) had chemical and biologic characteristics distinct from untreated stainless steel or stainless steel treated with NH(3) or O(2) plasmas used separately. NH(3)/O(2) plasmas deposited nitrogen as both -CN (organic) and -NO (nitrate, nitrite)--materials not found on untreated stainless steel--and the contact angle changed from 44 degrees to 23 degrees. Treatment of stainless steel (and titanium) resulted in surfaces with enhanced resistance to platelet and leukocyte attachment. A gas plasma of N(2)O/O(2) also was found to reduce platelet and leukocyte attachment, suggesting that these properties may be common to surfaces coated with oxynitrites (nitrides). Upon subcutaneous implantation, no inflammation, hemolysis, or untoward thrombosis was noted in the tissue surrounding the wafers treated with the NH(3)/O(2) plasmas, although the cellular density was considerably reduced by 2 weeks after implant. Collectively, the results suggest that NH(3)/O(2) plasmas impart a unique character to stainless steel that may be useful in the construction of medical devices.

  20. [Effects of superphosphate addition on NH3 and greenhouse gas emissions during vegetable waste composting].

    PubMed

    Yang, Yan; Sun, Qin-ping; Li, Ni; Liu, Chun-sheng; Li, Ji-jin; Liu, Ben-sheng; Zou, Guo-yuan

    2015-01-01

    To study the effects of superphosphate (SP) on the NH, and greenhouse gas emissions, vegetable waste composting was performed for 27 days using 6 different treatments. In addition to the controls, five vegetable waste mixtures (0.77 m3 each) were treated with different amounts of the SP additive, namely, 5%, 10%, 15%, 20% and 25%. The ammonia volatilization loss and greenhouse gas emissions were measured during composting. Results indicated that the SP additive significantly decreased the ammonia volatilization and greenhouse gas emissions during vegetable waste composting. The additive reduced the total NH3 emission by 4.0% to 16.7%. The total greenhouse gas emissions (CO2-eq) of all treatments with SP additives were decreased by 10.2% to 20.8%, as compared with the controls. The NH3 emission during vegetable waste composting had the highest contribution to the greenhouse effect caused by the four different gases. The amount of NH3 (CO2-eq) from each treatment ranged from 59.90 kg . t-1 to 81.58 kg . t-1; NH3(CO2-eq) accounted for 69% to 77% of the total emissions from the four gases. Therefore, SP is a cost-effective phosphorus-based fertilizer that can be used as an additive during vegetable waste composting to reduce the NH3 and greenhouse gas emissions as well as to improve the value of compost as a fertilizer.

  1. Highly Sensitive Flexible NH3 Sensors Based on Printed Organic Transistors with Fluorinated Conjugated Polymers.

    PubMed

    Nketia-Yawson, Benjamin; Jung, A-Ra; Noh, Yohan; Ryu, Gi-Seong; Tabi, Grace Dansoa; Lee, Kyung-Koo; Kim, BongSoo; Noh, Yong-Young

    2017-03-01

    Understanding the sensing mechanism in organic chemical sensors is essential for improving the sensing performance such as detection limit, sensitivity, and other response/recovery time, selectivity, and reversibility for real applications. Here, we report a highly sensitive printed ammonia (NH3) gas sensor based on organic thin film transistors (OTFTs) with fluorinated difluorobenzothiadiazole-dithienosilole polymer (PDFDT). These sensors detected NH3 down to 1 ppm with high sensitivity (up to 56%) using bar-coated ultrathin (<4 nm) PDFDT layers without using any receptor additives. The sensing mechanism was confirmed by cyclic voltammetry, hydrogen/fluorine nuclear magnetic resonance, and UV/visible absorption spectroscopy. PDFDT-NH3 interactions comprise hydrogen bonds and electrostatic interactions between the PDFDT polymer backbone and NH3 gas molecules, thus lowering the highest occupied molecular orbital levels, leading to hole trapping in the OTFT sensors. Additionally, density functional theory calculations show that gaseous NH3 molecules are captured via cooperation of fluorine atoms and dithienosilole units in PDFDT. We verified that incorporation of functional groups that interact with a specific gas molecule in a conjugated polymer is a promising strategy for producing high-performance printed OTFT gas sensors.

  2. 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).

  3. The NO + NH 3 reaction on Pt(100): steady state and oscillatory kinetics

    NASA Astrophysics Data System (ADS)

    Lombardo, S. J.; Esch, F.; Imbihl, R.

    The NO + NH 3 reaction was investigated on a Pt(100) surface in the 10 -6 mbar range using Video-LEED, work function measurements and measurements of the product partial pressures of N 2 and H 2O. Sustained kinetic oscillations, as observed in the N 2, H 2O and work function signals, were detected between 425 and 450 K for pNO = 1.1 × 10 -6 mbar and pNH3 = 4.7 × 10 -6 mbar. The dependence of the oscillation period on temperature and on the {p NH 3/ }/{p NO} ratio was determined. In situ LEED measurements demonstrated that oscillations in the reaction rate are coupled to the 1 × 1 ⇄ hex phase transition. Isotopic exchange experiments with 15NO and 14NH 3 showed that depending on the temperature and p {NH 3/ }/{p NO} ratio, significant deviations from a random mixing of 15N and 14N on the surface occur. This is interpreted as indication for an attractive interaction between NO ad and NH xad ( x = 1-3).

  4. Low and room temperature photoabsorption cross sections of NH3 in the UV region

    NASA Astrophysics Data System (ADS)

    Chen, F. Z.; Judge, D. L.; Wu, C. Y. R.; Caldwell, J.

    1998-12-01

    Using synchrotron radiation as a continuum light source, we have measured the absolute absorption cross sections of NH3 with a spectral bandwidth (FWHM) of 0.5 Å. The photoabsorption cross sections of NH3 have been measured from 1750 to 2250 Å under temperature conditions of 295, 195, and 175 K. Significant temperature effects in the absorption threshold region which are mainly due to the presence of hot band absorption are observed. The cross section value at peaks and valleys for the vibrational progressions of the (0,0) to (4,0) bands vary between -80% and +40% as the temperature of NH3 changes from 295 to 175 K. In contrast to this, the changes of cross section values, Pc,T, are found to vary less than 20% for the (v', 0) vibrational progressions with v' >= 5. The measured separations between the doublet features of the (0,0), (1,0), and (2,0) bands are found to decrease as the temperature of NH3 decreases. The shifts of peak positions of Pc,T with respect to the corresponding room temperature absorption peaks show a sudden change at v' = 3 which appears to agree with the trend observed in the homogeneous line widths of the vibrational bands of NH3 ([Vaida et al., 1987]; [Ziegler, 1985]; [Ziegler, 1986]). The unusual behavior of the line widths has been attributed to the A~ state potential surface which has a dissociation barrier.

  5. DFT insights into the adsorption of NH3-SCR related small gases in Mn-MOF-74.

    PubMed

    Zhang, Minhua; Huang, Xuewei; Chen, Yifei

    2016-10-19

    Mn-MOF-74 has great potential to catalyze selective catalytic reduction (SCR) reaction with NH3 being the reductant (NH3-SCR). However, the reaction mechanism, in particular the adsorptive properties of key reactive species in Mn-MOF-74, remains ambiguous. Besides, the effects of impurities such as H2O and SO2 on the process need further investigation. In this paper, based on density functional theory (DFT) calculations, we studied the adsorption characteristics of six NH3-SCR related small gases, namely NH3, NO2, NO, O2, H2O and SO2. DFT results show that the Mn-MOF-74 structure can bind these molecules relatively strongly in the following order: NH3 > NO2 > NO > O2, allowing for subsequent NH3-SCR reaction. In addition, a possible pathway of NO conversion to NO2 was calculated. Investigation on competitive adsorption of NH3 and H2O, NH3 and SO2 reveals that both H2O and SO2 are probable to replace NH3 under certain conditions, indicating that the two impurity gases may affect the activity of the NH3-SCR reaction. Compared with H2O, SO2 can displace NH3 more easily and should not be neglected.

  6. Determining the storage, availability and reactivity of NH3 within Cu-Chabazite-based Ammonia Selective Catalytic Reduction systems.

    PubMed

    Lezcano-Gonzalez, I; Deka, U; Arstad, B; Van Yperen-De Deyne, A; Hemelsoet, K; Waroquier, M; Van Speybroeck, V; Weckhuysen, B M; Beale, A M

    2014-01-28

    Three different types of NH3 species can be simultaneously present on Cu(2+)-exchanged CHA-type zeolites, commonly used in Ammonia Selective Catalytic Reduction (NH3-SCR) systems. These include ammonium ions (NH4(+)), formed on the Brønsted acid sites, [Cu(NH3)4](2+) complexes, resulting from NH3 coordination with the Cu(2+) Lewis sites, and NH3 adsorbed on extra-framework Al (EFAl) species, in contrast to the only two reacting NH3 species recently reported on Cu-SSZ-13 zeolite. The NH4(+) ions react very slowly in comparison to NH3 coordinated to Cu(2+) ions and are likely to contribute little to the standard NH3-SCR process, with the Brønsted groups acting primarily as NH3 storage sites. The availability/reactivity of NH4(+) ions can be however, notably improved by submitting the zeolite to repeated exchanges with Cu(2+), accompanied by a remarkable enhancement in the low temperature activity. Moreover, the presence of EFAl species could also have a positive influence on the reaction rate of the available NH4(+) ions. These results have important implications for NH3 storage and availability in Cu-Chabazite-based NH3-SCR systems.

  7. NH3 molecular doping of silicon nanowires grown along the [112], [110], [001], and [111] orientations

    PubMed Central

    2012-01-01

    The possibility that an adsorbed molecule could provide shallow electronic states that could be thermally excited has received less attention than substitutional impurities and could potentially have a high impact in the doping of silicon nanowires (SiNWs). We show that molecular-based ex-situ doping, where NH3 is adsorbed at the sidewall of the SiNW, can be an alternative path to n-type doping. By means of first-principle electronic structure calculations, we show that NH3 is a shallow donor regardless of the growth orientation of the SiNWs. Also, we discuss quantum confinement and its relation with the depth of the NH3 doping state, showing that the widening of the bandgap makes the molecular donor level deeper, thus more difficult to activate. PMID:22709657

  8. VizieR Online Data Catalog: NH3 Odin observations towards Sgr A (Sandqvist+,

    NASA Astrophysics Data System (ADS)

    Sandqvist, Aa.; Hjalmarson, A.; Frisk, U.; Lundin, S.; Nordh, L.; Olberg, M.; Olofsson, G.

    2017-02-01

    50nh3cds.fit (Fig. 1 in paper). Odin observations of the 572GHz NH3 line towards the Sgr A +50km/s Cloud (J2000.0 17:45:51.7, -28:59:09the channel resolution is 1.6km/s. cndnh3cd.fit (Fig. 2 in paper). Odin observations of the 572GHz NH3 line towards the south-western part of the Sgr A Circumnuclear Disk (J2000.0 17:45:39.7, -29:01:18); the channel resolution is 1.6km/s. cndh218o.fit (Fig. 3 in paper). Odin observations of the 548GHz H218O line towards the southwestern part of the Sgr A Circumnuclear Disk (J2000.0 17:45:39.7, -29:01:18); the channel resolution is 3km/s. (2 data files).

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

    PubMed

    Ma, Qianli; van der Avoird, Ad; Loreau, Jérôme; 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.

  10. (CH3Br⋯NH3)@C60: The effect of nanoconfinement on halogen bonding

    NASA Astrophysics Data System (ADS)

    Srivastava, Ambrish Kumar; Pandey, Sarvesh Kumar; Misra, Neeraj

    2016-10-01

    Halogen bonds resemble hydrogen bonds in many aspects. How do the properties of halogen bonds change when confined to nanoregion? In order to explore this, we have encapsulated a halogen bonded complex, CH3Br⋯NH3 inside C60 fullerene and studied their properties using density functional theory and quantum theory of atoms in molecule. Our findings show that the geometry of CH3Br⋯NH3 complex is appreciably bent inside C60, interaction becomes covalent with larger interaction energy, unlike free CH3Br⋯NH3 complex, which is linear with closed shell interaction. Thus, the halogen bonded complexes show quite different properties at nanoscale.

  11. NH3 sensing properties polyaniline: TiO2 nanorods heterostructure

    NASA Astrophysics Data System (ADS)

    Patil, U. V.; Ramgir, Niranjan S.; Debnath, A. K.; Karmakar, N.; Aswal, D. K.; Kothari, D. C.; Gupta, S. K.

    2016-05-01

    NH3 sensing properties of polyaniline: TiO2 nanorods heterostructures have been investigated. TiO2 nanorods were synthesized using hydrothermal method. Thin layer of polyanilene was deposited by in-situ oxidative polymerization of aniline over TiO2 nanorods film. The heterostructure film exhibited an enhanced sensor response towards NH3 at room temperature. For example, heterostructure films exhibited a sensor response of 610% towards 100 ppm of NH3 with a response and recovery times of 40 and 60 s, respectively. This response and response kinetics is better than pure PANI films that exhibited a response of 210% with a response and recovery time of 21 and 160 s, respectively.

  12. Catalytic reduction of NOx with NH3 over different-shaped MnO2 at low temperature.

    PubMed

    Tian, Wei; Yang, Hangsheng; Fan, Xiaoyu; Zhang, Xiaobin

    2011-04-15

    MnO(2) nanotubes, nanorods, and nanoparticles were prepared using a hydrothermal method, after which the different activities for selective catalytic reduction (SCR) of nitrogen oxides (NO(x)) were compared. MnO(2) nanorods performed the highest activity for reduction of NO(x) under a gas hourly space velocity of 36,000 h(-1) with conversion efficiencies of above 90% between 250 and 300 °C; it also had the highest removal efficiency of 98.2% at 300 °C. From the analysis of X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption, and temperature-programmed reduction, we can ascribe the high activity of MnO(2) nanorods to low crystallinity, more lattice oxygen, high reducibility, and a large number of strong acid sites. The apparent activation energy of the SCR reaction on the surface of nanorods was calculated to be 20.9 kJ/mol, which favored the reaction better than the other catalysts.

  13. 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

  14. Synthesis, structure, lattice energy and enthalpy of 2D hybrid perovskite [NH3(CH2)4NH3]CoCl4, compared to [NH3(CH2)nNH3]CoCl4, n=3-9

    NASA Astrophysics Data System (ADS)

    Abdel-Aal, Seham K.; Abdel-Rahman, Ahmed S.

    2017-01-01

    A new organic-inorganic 2D hybrid perovskite [NH3(CH2)4NH3]CoCl4,1,4butane diammonium tetra-chlorocobaltate, has been synthesized. Blue prismatic single crystals were grown from ethanolic solution in 1:1 stoichiometric ratio (organic/inorganic) by gradual cooling to room temperature after heating at 70 °C for 1 h. The hybrid crystallizes in a triclinic phase with the centrosymetric space group P 1 bar . Its unit cell parameters are a=7.2869 (2) Å, b=8.1506 (2) Å, c=10.4127 (3) Å, α=77.2950 (12)°, β=80.0588 (11)°, γ=82.8373 (12)° and Z=2. The final R factor is 0.064. The structure consists of organic dications [NH3(CH2)4NH3]2+ which act as spacer between layers of inorganic dianions [CoCl4]2- in which CoII ions are coordinated by four Cl atoms in an isolated tetrahedral structure. The organic and inorganic layers form infinite 2D sheets which are parallel to the ac plane, stacking alternatively along the b-axis, and are connected via N-H…. Cl hydrogen bonds. The lamellar structure of the 1,4 butane diammonium tetrachlorocobaltate hybrid is typically considered as naturally self-assembled multiple quantum wells (MQW). The calculated lattice potential energy Upot (kJ/mol) and lattice enthalpy ΔHL (kJ/mol) are inversely proportional to the molecular volume Vm (nm3) of perovskite hybrid of the formula [NH3(CH2)nNH3]CoCl4, n=3-9.

  15. 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.

  16. A flexible and robust neural network IASI-NH3 retrieval algorithm

    NASA Astrophysics Data System (ADS)

    Whitburn, S.; Van Damme, M.; Clarisse, L.; Bauduin, S.; Heald, C. L.; Hadji-Lazaro, J.; Hurtmans, D.; Zondlo, M. A.; Clerbaux, C.; Coheur, P.-F.

    2016-06-01

    In this paper, we describe a new flexible and robust NH3 retrieval algorithm from measurements of the Infrared Atmospheric Sounding Interferometer (IASI). The method is based on the calculation of a spectral hyperspectral range index (HRI) and subsequent conversion to NH3 columns via a neural network. It is an extension of the method presented in Van Damme et al. (2014a) who used lookup tables (LUT) for the radiance-concentration conversion. The new method inherits the advantages of the LUT-based method while providing several significant improvements. These include the following: (1) Complete temperature and humidity vertical profiles can be accounted for. (2) Third-party NH3 vertical profile information can be used. (3) Reported positive biases of LUT retrieval are reduced, and finally (4) a full measurement uncertainty characterization is provided. A running theme in this study, related to item (2), is the importance of the assumed vertical NH3 profile. We demonstrate the advantages of allowing variable profile shapes in the retrieval. As an example, we analyze how the retrievals change when all NH3 is assumed to be confined to the boundary layer. We analyze different averaging procedures in use for NH3 in the literature, introduced to cope with the variable measurement sensitivity and derive global averaged distributions for the year 2013. A comparison with a GEOS-Chem modeled global distribution is also presented, showing a general good correspondence (within ±3 × 1015 molecules.cm-2) over most of the Northern Hemisphere. However, IASI finds mean columns about 1-1.5 × 1016 molecules.cm-2 (˜50-60%) lower than GEOS-Chem for India and the North China plain.

  17. 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.

  18. 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.

  19. 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.

  20. Intramolecular SN2 reaction caused by photoionization of benzene chloride-NH3 complex: direct ab initio molecular dynamics study.

    PubMed

    Tachikawa, Hiroto

    2006-01-12

    Ionization processes of chlorobenzene-ammonia 1:1 complex (PhCl-NH3) have been investigated by means of full dimensional direct ab initio molecular dynamics (MD) method, static ab initio calculations, and density functional theory (DFT) calculations. The static ab initio and DFT calculations of neutral PhCl-NH3 complex showed that one of the hydrogen atoms of NH3 orients toward a carbon atom in the para-position of PhCl. The dynamics calculation for ionization of PhCl-NH3 indicated that two reaction channels are competitive with each other as product channels: one is an intramolecular SN2 reaction expressed by a reaction scheme [PhCl-NH3]+-->SN2 intermediate complex-->PhNH3++Cl, and the other is ortho-NH3 addition complex (ortho complex) in which NH3 attacks the ortho-carbon of PhCl+ and the trajectory leads to a bound complex expressed by (PhCl-NH3)+. The mechanism of the ionization of PhCl-NH3 is discussed on the basis of the theoretical results.

  1. Interaction of NH3 with Cu-SSZ-13 Catalyst: A Complementary FTIR, XANES, and XES Study.

    PubMed

    Giordanino, Filippo; Borfecchia, Elisa; Lomachenko, Kirill A; Lazzarini, Andrea; Agostini, Giovanni; Gallo, Erik; Soldatov, Alexander V; Beato, Pablo; Bordiga, Silvia; Lamberti, Carlo

    2014-05-01

    In the typical NH3-SCR temperature range (100-500 °C), ammonia is one of the main adsorbed species on acidic sites of Cu-SSZ-13 catalyst. Therefore, the study of adsorbed ammonia at high temperature is a key step for the understanding of its role in the NH3-SCR catalytic cycle. We employed different spectroscopic techniques to investigate the nature of the different complexes occurring upon NH3 interaction. In particular, FTIR spectroscopy revealed the formation of different NH3 species, that is, (i) NH3 bonded to copper centers, (ii) NH3 bonded to Brønsted sites, and (iii) NH4(+)·nNH3 associations. XANES and XES spectroscopy allowed us to get an insight into the geometry and electronic structure of Cu centers upon NH3 adsorption, revealing for the first time in Cu-SSZ-13 the presence of linear Cu(+) species in Ofw-Cu-NH3 or H3N-Cu-NH3 configuration.

  2. Mechanistic Investigation into the Effect of Sulfuration on the FeW Catalysts for the Selective Catalytic Reduction of NOx with NH3.

    PubMed

    Wang, Hui; Qu, Zhenping; Dong, Shicheng; Tang, Chen

    2017-03-01

    Iron tungsten (FeW) catalyst is a potential candidate for the selective catalytic reduction (SCR) of NOx with ammonia because of its excellent performance in a wide operating window. Sulfur poisoning effects in SCR catalysts have long been recognized as a challenge in development of efficient catalysts for applications. In this paper, the impact of sulfuration on catalyst structure, NH3-SCR reaction performance and mechanism was systematically investigated through spectroscopic and temperature-programmed approaches. The sulfuration inhibited the SCR activity at low temperatures (<300 °C), while no evident effect was observed at high temperatures (≥300 °C). After sulfuration for FeW oxides catalyst, the organic-like with covalent S═O bonds sulfate species were mainly formed over the FeW catalysts. Combining TPD with in situ DRIFTS results, it was found that the Lewis and the Brønsted acidity were enhanced by the interaction between metal species and sulfate species due to the strong electron withdrawing effect of the S═O double bonds. The in situ DRIFTS study showed that the formation of NO2 was hindered, leading to the "fast-SCR" pathway was partly cut off by the sulfuration process and thereby the loss of SCR activity at low temperatures. However, the Langmuir-Hinshelwood reaction pathway between adsorbed NH3/NH4(+) species and nitrate species was facilitated and dominated at high temperatures, making the as-synthesized FeW catalysts resistant to SO2 poisoning.

  3. 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.

  4. 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.

  5. Meteorite Impact-Induced Rapid NH3 Production on Early Earth: Ab Initio Molecular Dynamics Simulation.

    PubMed

    Shimamura, Kohei; Shimojo, Fuyuki; Nakano, Aiichiro; Tanaka, Shigenori

    2016-12-14

    NH3 is an essential molecule as a nitrogen source for prebiotic amino acid syntheses such as the Strecker reaction. Previous shock experiments demonstrated that meteorite impacts on ancient oceans would have provided a considerable amount of NH3 from atmospheric N2 and oceanic H2O through reduction by meteoritic iron. However, specific production mechanisms remain unclear, and impact velocities employed in the experiments were substantially lower than typical impact velocities of meteorites on the early Earth. Here, to investigate the issues from the atomistic viewpoint, we performed multi-scale shock technique-based ab initio molecular dynamics simulations. The results revealed a rapid production of NH3 within several picoseconds after the shock, indicating that shocks with greater impact velocities would provide further increase in the yield of NH3. Meanwhile, the picosecond-order production makes one expect that the important nitrogen source precursors of amino acids were obtained immediately after the impact. It was also observed that the reduction of N2 proceeded according to an associative mechanism, rather than a dissociative mechanism as in the Haber-Bosch process.

  6. Meteorite Impact-Induced Rapid NH3 Production on Early Earth: Ab Initio Molecular Dynamics Simulation

    NASA Astrophysics Data System (ADS)

    Shimamura, Kohei; Shimojo, Fuyuki; Nakano, Aiichiro; Tanaka, Shigenori

    2016-12-01

    NH3 is an essential molecule as a nitrogen source for prebiotic amino acid syntheses such as the Strecker reaction. Previous shock experiments demonstrated that meteorite impacts on ancient oceans would have provided a considerable amount of NH3 from atmospheric N2 and oceanic H2O through reduction by meteoritic iron. However, specific production mechanisms remain unclear, and impact velocities employed in the experiments were substantially lower than typical impact velocities of meteorites on the early Earth. Here, to investigate the issues from the atomistic viewpoint, we performed multi-scale shock technique-based ab initio molecular dynamics simulations. The results revealed a rapid production of NH3 within several picoseconds after the shock, indicating that shocks with greater impact velocities would provide further increase in the yield of NH3. Meanwhile, the picosecond-order production makes one expect that the important nitrogen source precursors of amino acids were obtained immediately after the impact. It was also observed that the reduction of N2 proceeded according to an associative mechanism, rather than a dissociative mechanism as in the Haber-Bosch process.

  7. First detection of ammonia (NH3) in the Asian summer monsoon upper troposphere

    NASA Astrophysics Data System (ADS)

    Höpfner, Michael; Volkamer, Rainer; Grabowski, Udo; Grutter, Michel; Orphal, Johannes; Stiller, Gabriele; von Clarmann, Thomas; Wetzel, Gerald

    2016-11-01

    Ammonia (NH3) has been detected in the upper troposphere by the analysis of averaged MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) infrared limb-emission spectra. We have found enhanced amounts of NH3 within the region of the Asian summer monsoon at 12-15 km altitude. Three-monthly, 10° longitude × 10° latitude average profiles reaching maximum mixing ratios of around 30 pptv in this altitude range have been retrieved, with a vertical resolution of 3-8 km and estimated errors of about 5 pptv. These observations show that loss processes during transport from the boundary layer to the upper troposphere within the Asian monsoon do not deplete the air entirely of NH3. Thus, ammonia might contribute to the so-called Asian tropopause aerosol layer by the formation of ammonium aerosol particles. On a global scale, outside the monsoon area and during different seasons, we could not detect enhanced values of NH3 above the actual detection limit of about 3-5 pptv. This upper bound helps to constrain global model simulations.

  8. Direct observation of intrinsic twin domains in tetragonal CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Rothmann, Mathias Uller; Li, Wei; Zhu, Ye; Bach, Udo; Spiccia, Leone; Etheridge, Joanne; Cheng, Yi-Bing

    2017-02-01

    Organic-inorganic hybrid perovskites are exciting candidates for next-generation solar cells, with CH3NH3PbI3 being one of the most widely studied. While there have been intense efforts to fabricate and optimize photovoltaic devices using CH3NH3PbI3, critical questions remain regarding the crystal structure that governs its unique properties of the hybrid perovskite material. Here we report unambiguous evidence for crystallographic twin domains in tetragonal CH3NH3PbI3, observed using low-dose transmission electron microscopy and selected area electron diffraction. The domains are around 100-300 nm wide, which disappear/reappear above/below the tetragonal-to-cubic phase transition temperature (approximate 57 °C) in a reversible process that often `memorizes' the scale and orientation of the domains. Since these domains exist within the operational temperature range of solar cells, and have dimensions comparable to the thickness of typical CH3NH3PbI3 films in the solar cells, understanding the twin geometry and orientation is essential for further improving perovskite solar cells.

  9. Evaluating Molecular Co Complexes for the Conversion of N2 to NH3

    PubMed Central

    Del Castillo, Trevor J.; Thompson, Niklas B.; Suess, Daniel L. M.; Ung, Gaël; Peters, Jonas C.

    2015-01-01

    Well-defined molecular catalysts for the reduction of N2 to NH3 with protons and electrons remain very rare despite decades of interest, and are currently limited to systems featuring Mo or Fe. This report details the synthesis of a molecular Co complex that generates superstoichiometric yields of NH3 (>200% NH3 per Co-N2 precursor) via the direct reduction of N2 with protons and electrons. While the NH3 yields reported herein are modest by comparison to previously described Fe and Mo systems, they intimate that other metals are likely to be viable as molecular N2 reduction catalysts. Additionally, comparison of the featured tris(phosphine)borane Co-N2 complex with structurally related Co-N2 and Fe-N2 species shows how remarkably sensitive the N2 reduction performance of potential pre-catalysts are. These studies enable consideration of structural and electronic effects that are likely relevant to N2 conversion activity, including π-basicity, charge state, and geometric flexibility. PMID:26001022

  10. Spatial Scale Variability of NH3 and Impacts to interpolated Concentration Grids

    EPA Science Inventory

    Over the past decade, reduced nitrogen (NH3, NH4) has become an important component of atmospheric nitrogen deposition due to increases in agricultural activities and reductions in oxidized sulfur and nitrogen emissions from the power sector and mobile sources. Reduced nitrogen i...

  11. Meteorite Impact-Induced Rapid NH3 Production on Early Earth: Ab Initio Molecular Dynamics Simulation

    PubMed Central

    Shimamura, Kohei; Shimojo, Fuyuki; Nakano, Aiichiro; Tanaka, Shigenori

    2016-01-01

    NH3 is an essential molecule as a nitrogen source for prebiotic amino acid syntheses such as the Strecker reaction. Previous shock experiments demonstrated that meteorite impacts on ancient oceans would have provided a considerable amount of NH3 from atmospheric N2 and oceanic H2O through reduction by meteoritic iron. However, specific production mechanisms remain unclear, and impact velocities employed in the experiments were substantially lower than typical impact velocities of meteorites on the early Earth. Here, to investigate the issues from the atomistic viewpoint, we performed multi-scale shock technique-based ab initio molecular dynamics simulations. The results revealed a rapid production of NH3 within several picoseconds after the shock, indicating that shocks with greater impact velocities would provide further increase in the yield of NH3. Meanwhile, the picosecond-order production makes one expect that the important nitrogen source precursors of amino acids were obtained immediately after the impact. It was also observed that the reduction of N2 proceeded according to an associative mechanism, rather than a dissociative mechanism as in the Haber-Bosch process. PMID:27966594

  12. Characterization of a high pressure, high temperature modification of ammonia borane (BH3NH3).

    PubMed

    Nylén, Johanna; Eriksson, Lars; Benson, Daryn; Häussermann, Ulrich

    2013-08-07

    At elevated pressures (above 1.5 GPa) dihydrogen bonded ammonia borane, BH3NH3, undergoes a solid-solid phase transition with increasing temperature. The high pressure, high temperature (HPHT) phase precedes decomposition and evolves from the known high pressure, low temperature form with space group symmetry Cmc21 (Z = 4). Structural changes of BH3NH3 with temperature were studied at around 6 GPa in a diamond anvil cell by synchrotron powder diffraction. At this pressure the Cmc21 phase transforms into the HPHT phase at around 140 °C. The crystal system, unit cell, and B and N atom position parameters of the HPHT phase were extracted from diffraction data, and a hydrogen ordered model with space group symmetry Pnma (Z = 4) subsequently established from density functional calculations. However, there is strong experimental evidence that HPHT-BH3NH3 is a hydrogen disordered rotator phase. A reverse transition to the Cmc21 phase is not observed. When releasing pressure at room temperature to below 1.5 GPa the ambient pressure (hydrogen disordered) I4mm phase of BH3NH3 is obtained.

  13. Direct observation of intrinsic twin domains in tetragonal CH3NH3PbI3

    PubMed Central

    Rothmann, Mathias Uller; Li, Wei; Zhu, Ye; Bach, Udo; Spiccia, Leone; Etheridge, Joanne; Cheng, Yi-Bing

    2017-01-01

    Organic–inorganic hybrid perovskites are exciting candidates for next-generation solar cells, with CH3NH3PbI3 being one of the most widely studied. While there have been intense efforts to fabricate and optimize photovoltaic devices using CH3NH3PbI3, critical questions remain regarding the crystal structure that governs its unique properties of the hybrid perovskite material. Here we report unambiguous evidence for crystallographic twin domains in tetragonal CH3NH3PbI3, observed using low-dose transmission electron microscopy and selected area electron diffraction. The domains are around 100–300 nm wide, which disappear/reappear above/below the tetragonal-to-cubic phase transition temperature (approximate 57 °C) in a reversible process that often ‘memorizes' the scale and orientation of the domains. Since these domains exist within the operational temperature range of solar cells, and have dimensions comparable to the thickness of typical CH3NH3PbI3 films in the solar cells, understanding the twin geometry and orientation is essential for further improving perovskite solar cells. PMID:28230064

  14. 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.

  15. 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.

  16. 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.

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

    PubMed

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

    2014-04-07

    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.

  18. Structural determinants of NH3 and NH4+ transport by mouse Rhbg, a renal Rh glycoprotein.

    PubMed

    Abdulnour-Nakhoul, Solange; Le, Trang; Rabon, Edd; Hamm, L Lee; Nakhoul, Nazih L

    2016-12-01

    Renal Rhbg is localized to the basolateral membrane of intercalated cells and is involved in NH3/NH4(+) transport. The structure of Rhbg is not yet resolved; however, a high-resolution crystal structure of AmtB, a bacterial homolog of Rh, has been determined. We aligned the sequence of Rhbg to that of AmtB and identified important sites of Rhbg that may affect transport. Our analysis positioned three conserved amino acids, histidine 183 (H183), histidine 342 (H342), and tryptophan 230 (W230), within the hydrophobic pore where they presumably serve to control NH3 transport. A fourth residue, phenylalanine 128 (F128) was positioned at the upper vestibule, presumably contributing to recruitment of NH4(+) We generated three mutations each of H183, H342, W230, and F128 and expressed them in frog oocytes. Immunolabeling showed that W230 and F128 mutants were localized to the cell membrane, whereas H183 and H342 staining was diffuse and mostly intracellular. To determine function, we compared measurements of NH3/NH4(+) and methyl amine (MA)/methyl ammonium (MA(+))-induced currents, intracellular pH, and surface pH (pHs) among oocytes expressing the mutants, Rhbg, or injected with H2O. In H183 and W230 mutants, NH4(+)-induced current and intracellular acidification were inhibited compared with that of Rhbg, and MA-induced intracellular alkalinization was completely absent. Expression of H183A or W230A mutants inhibited NH3/NH4(+)- and MA/MA(+)-induced decrease in pHs to the level observed in H2O-injected oocytes. Mutations of F128 did not significantly affect transport of NH3 or NH4(+) These data demonstrated that mutating H183 or W230 caused loss of function but not F128. H183 and H342 may affect membrane expression of the transporter.

  19. 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.

  20. Theoretical and experimental investigations of optical, structural and electronic properties of the lower-dimensional hybrid [NH3-(CH2)10-NH3]ZnCl4

    NASA Astrophysics Data System (ADS)

    El Mrabet, R.; Kassou, S.; Tahiri, O.; Belaaraj, A.; Guionneau, P.

    2016-10-01

    In the current study, a combination between theoretical and experimental studies has been made for the hybrid perovskite [NH3-(CH2)10-NH3]ZnCl4. The density functional theory (DFT) was performed to investigate structural and electronic properties of the tilted compound. A local approximation (LDA) and semi-local approach (GGA) were employed. The results are obtained using, respectively, the local exchange correlation functional of Perdew-Wang 92 (PW92) and semi local functional of Perdew-Burke-Ernzerhof (PBE). The optimized cell parameters are in good agreement with the experimental results. Electronic properties have been studied through the calculation of band structures and density of state (DOS), while structural properties are investigated by geometry optimization of the cell. Fritz-Haber-Institute (FHI) pseudopotentials were employed to perform all calculations. The optical diffuse reflectance spectra was mesured and applied to deduce the refractive index ( n), the extinction coefficient ( k), the absorption coefficient (α), the real and imaginary dielectric permittivity parts (ɛr,ɛi)) and the optical band gap energy Eg. The optical band gap energy value shows good consistent with that obtained from DFT calculations and reveals the insulating behavior of the material.

  1. Preparation and characterization of high-quality perovskite CH3NH3PbX3 (I, Br) single crystal

    NASA Astrophysics Data System (ADS)

    Zhou, Yangyang; Li, Chunmei; Wang, Yu; Du, Xiang; Liu, Pengyi; Xie, Weiguang

    2017-01-01

    In this paper, inverse temperature crystallization and top-seed solution growth method are used to grow high-quality perovskite CH3NH3PbX3 (I, Br) single crystal. The maximum crystal diameter is 6 mm for CH3NH3PbI3, and 3 mm for CH3NH3PbBr3. The results of XRD show that the crystals are tetragonal structure for CH3NH3PbI3, cubic crystal orientation for CH3NH3PbBr3. What is more, crystals exhibit excellent stability in air and can be maintained for eight months. Furthermore, the crystal growth processes are described in detail. The results demonstrate that CH3NH3PbBr3 single crystal growth is more sensitive to the environment.

  2. Rapid ammonia gas transport accounts for futile transmembrane cycling under NH3/NH4+ toxicity in plant roots.

    PubMed

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

    2013-12-01

    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 (13)N 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 (13)NH3/(13)NH4(+), 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 (13)NH3/(13)NH4(+) 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.

  3. Photovoltaic properties of Cu-doped CH3NH3PbI3 with perovskite structure

    NASA Astrophysics Data System (ADS)

    Shirahata, Yasuhiro; Oku, Takeo

    2017-01-01

    Photovoltaic properties of copper (Cu)-doped perovskite (CH3NH3PbCuxI3+x) photovoltaic devices with different Cu content were investigated. The CH3NH3PbCuxI3+x films were polycrystalline with a tetragonal system, and their lattice constants and crystallite size varied with Cu doping. Compared to conversion efficiencies of non-doped CH3NH3PbI3 photovoltaic device, those of CH3NH3PbCuxI3+x photovoltaic devises increased. The improvement of photovoltaic properties was attributed to partial substitution of Cu at the Pb sites.

  4. 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

  5. A Deuterium NMR Spectroscopic Study of Solid BH(3)NH(3).

    PubMed

    Penner, Glenn H.; Chang, Y. C. Phillis; Hutzal, Jennifer

    1999-06-14

    Deuterium nuclear magnetic resonance (NMR) powder spectra and spin-lattice relaxation times (T(1)) are used to measure the deuterium quadrupolar coupling constants (QCCs) chi(BD) and chi(ND) and to investigate the molecular reorientation of the BD(3) and ND(3) groups in solid deuterated borane monoammoniate, BD(3)NH(3) and BH(3)ND(3), respectively. In the high-temperature, tetragonal, phase (above 225 K) the following Arrhenius parameters are obtained from the temperature-dependent T(1): E(a) = 5.9 +/- 0.5 kJ/mol and tau(infinity) = 1.1 x 10(-)(13) s for BD(3)NH(3); E(a) = 7.3 +/- 0.8 kJ/mol and tau(infinity) = 4.4 x 10(-)(14) s for BH(3)ND(3). In the low-temperature, orthorhombic, phase the following parameters are obtained: E(a) = 26.4 +/- 1.4 kJ/mol and tau(infinity) = 1.2 x 10(-)(17) s for BD(3)NH(3); E(a) = 13.7 +/- 0.9 kJ/mol and tau(infinity) = 5.7 x 10(-)(15) s for BH(3)ND(3). Here tau(infinity) is proportional to the inverse of the usual Arrhenius preexponential factor, A. Deuterium line shape measurements for the low-temperature phase of BD(3)NH(3) yield E(a) = 25 +/- 2 kJ/mol and tau(infinity) = 4.7 x 10(-)(19) s. These dynamic factors indicate that the molecule is probably undergoing whole molecule rotation above the phase transition but the BH(3) and NH(3) groups are undergoing uncorrelated motion in the low-temperature phase. Deuterium quadrupolar coupling constants of 105 +/- 10 and 200 +/- 10 kHz were determined for BD(3)NH(3) and BH(3)ND(3), respectively. Molecular orbital (MO) calculations (CI(SD)/6-31G(d,p)//MP2/6-31G(d,p)) for the isolated molecule yield values of 143 and 255 kHz. MO calculations also show that the deuterium quadrupolar coupling constants chi(BD) and chi(ND) are relatively insensitive to all molecular structural parameters except the B-H and N-H bond lengths, respectively. It is suggested that the large decrease in the QCC on going from the gas phase to the solid state may be due to a slight lengthening of the B-H and N-H bonds

  6. Selective catalytic reduction of NO with NH3 over CeO2-ZrO2-WO3 catalysts prepared by different methods

    NASA Astrophysics Data System (ADS)

    Ning, Ping; Song, Zhongxian; Li, Hao; Zhang, Qiulin; Liu, Xin; Zhang, Jinhui; Tang, Xiaosu; Huang, Zhenzhen

    2015-03-01

    The selective catalytic reduction (SCR) of NO by NH3 has been investigated over the CeO2-ZrO2-WO3 (CZW) catalysts prepared by hydrothermal synthesis, incipient impregnation, co-precipitation and sol-gel methods. The results indicate that the CZW catalyst prepared by hydrothermal method shows the best SCR activity, and more than 90% NO conversion is obtained at 195-450 °C with a gas hourly space velocity of 50,000 h-1. The samples are characterized by XRD, N2 adsorption-desorption, SEM, EDS, XPS, H2-TPR, NH3-TPD and Pyridine-IR techniques. The results imply that the superior SCR activity of CZW catalyst is contributed to the excellent redox property, strong acidity and highest content of chemisorbed oxygen species. Furthermore, the larger surface area and greater total pore volume improve the redox ability and enhance NO conversion at low temperature, while the co-existence of Lewis and Brønsted acid sites enhance the SCR activity at high temperature.

  7. Room temperature three-photon pumped CH3NH3PbBr3 perovskite microlasers.

    PubMed

    Gao, Yisheng; Wang, Shuai; Huang, Can; Yi, Ningbo; Wang, Kaiyang; Xiao, Shumin; Song, Qinghai

    2017-03-28

    Hybrid lead halide perovskites have made great strides in next-generation light-harvesting and light emitting devices. Recently, they have also shown great potentials in nonlinear optical materials. Two-photon absorption and two-photon light emission have been thoroughly studied in past two years. However, the three-photon processes are rarely explored, especially for the laser emissions. Here we synthesized high quality CH3NH3PbBr3 perovskite microstructures with solution processed precipitation method and studied their optical properties. When the microstructures are pumped with intense 1240 nm lasers, we have observed clear optical limit effect and the band-to-band photoluminescence at 540 nm. By increasing the pumping density, whispering-gallery-mode based microlasers have been achieved from CH3NH3PbBr3 perovskite microplate and microrod for the first time. This work demonstrates the potentials of hybrid lead halide perovskites in nonlinear photonic devices.

  8. 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.

  9. Electrical and optical properties of Ar/NH3 atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Chang, Zheng-Shi; Yao, Cong-Wei; Chen, Si-Le; Zhang, Guan-Jun

    2016-09-01

    Inspired by the Penning effect, we obtain a glow-like plasma jet by mixing ammonia (NH3) into argon (Ar) gas under atmospheric pressure. The basic electrical and optical properties of an atmospheric pressure plasma jet (APPJ) are investigated. It can be seen that the discharge mode transforms from filamentary to glow-like when a little ammonia is added into the pure argon. The electrical and optical analyses contribute to the explanation of this phenomenon. The discharge mode, power, and current density are analyzed to understand the electrical behavior of the APPJ. Meanwhile, the discharge images, APPJ's length, and the components of plasma are also obtained to express its optical characteristics. Finally, we diagnose several parameters, such as gas temperature, electron temperature, and density, as well as the density number of metastable argon atoms of Ar/NH3 APPJ to help judge the usability in its applications.

  10. Performance Analysis of Rectifier in NH3-H2O Absorption Heat Pump

    NASA Astrophysics Data System (ADS)

    Tsujimori, Atushi; Ozaki, Eiichi; Nakao, Kazushige

    Characteristic of stripping section of packed-tower type rectifierwas presentedin previous paper. In order to improve NH3 concentration inrefrigerant vapor, enriching section is considered effective. Refrigerant vapor from stripping section of rectifier and reflux solution from partial condenser flow into this section, and the proportion of solution flow rate to vapor flow rate of enriching section called reflux ratio is much smaller than that of stripping section. So the effect of reflux ratio on rectification process might be larger. In this paper the effect of reflux flow rate and NH3 concentration in reflux solution is investigated experimentally. As a result, it was derived that the performance of enriching section was mainly decided by reflux ratio. Then the effect of rectification performance on heat rate of partial condenser and evaporator was evaluated using the experimental result of enriching section performance.

  11. 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.

  12. High-resolution absorption measurements of NH3 at high temperatures: 2100-5500 cm-1

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

    High-resolution absorption spectra of NH3 in the region 2100-5500 cm-1 at 1027 °C and approximately atmospheric pressure (1045±3 mbar) are measured. An NH3 concentration of 10% in volume fraction is used in the measurements. Spectra are recorded in a high-temperature gas-flow cell using a Fourier Transform Infrared (FTIR) spectrometer at a nominal resolution of 0.09 cm-1. The spectra are analysed by comparison to a variational line list, BYTe, and experimental energy levels determined using the MARVEL procedure. 2308 lines have been assigned to 45 different bands, of which 1755 and 15 have been assigned or observed for the first time in this work.

  13. 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.

  14. 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.

  15. Diagnosing shock temperature with NH3 and H2O profiles

    NASA Astrophysics Data System (ADS)

    Gómez-Ruiz, A. I.; Codella, C.; Viti, S.; Jiménez-Serra, I.; Navarra, G.; Bachiller, R.; Caselli, P.; Fuente, A.; Gusdorf, A.; Lefloch, B.; Lorenzani, A.; Nisini, B.

    2016-10-01

    In a previous study of the L1157 B1 shocked cavity, a comparison between NH3(10-00) and H2O(110-101) transitions showed a striking difference in the profiles, with H2O emitting at definitely higher velocities. This behaviour was explained as a result of the high-temperature gas-phase chemistry occurring in the post-shock gas in the B1 cavity of this outflow. If the differences in behaviour between ammonia and water are indeed a consequence of the high gas temperatures reached during the passage of a shock, then one should find such differences to be ubiquitous among chemically rich outflows. In order to determine whether the difference in profiles observed between NH3 and H2O is unique to L1157 or a common characteristic of chemically rich outflows, we have performed Herschel-HIFI observations of the NH3(10-00) line at 572.5 GHz in a sample of eight bright low-mass outflow spots already observed in the H2O(110-101) line within the Water In Star-forming regions with Herschel Key Programme. We detected the ammonia emission at high velocities at most of the outflows positions. In all cases, the water emission reaches higher velocities than NH3, proving that this behaviour is not exclusive of the L1157-B1 position. Comparisons with a gas-grain chemical and shock model confirms, for this larger sample, that the behaviour of ammonia is determined principally by the temperature of the gas.

  16. On the NH3 absorption depression observable at Northern low latitudes of Jupiter

    NASA Astrophysics Data System (ADS)

    Tejfel, Victor G.; Vdovichenko, Vladimir D.; Lysenko, Peter G.; Karimov, Alibek M.; Kirienko, Galina A.; Bondarenko, Natalya N.; Kharitonova, Galina

    2016-10-01

    From February to April of 2016, we carried out a special series of spectrophotometric observations of Jupiter to study the current behavior of the ammonia absorption at the low latitudes of the Northern hemisphere, where in 2004 we have found a well-defined depression of the 787 nm NH3 absorption band intensity (V.Tejfel et al., Bull.AAS, 2005, Vol. 37, p.682). In subsequent years, an existence of this depression was annually confirmed by spectral observations, although we were noticing its variable character. During observations of 2016 we obtained more than 2,500 CCD-spectrograms, including the spectra of the central meridian, the GRS, and 12 scans of Jovian disk on different dates (70 zonal spectra in each scan). The 787 nm NH3 absorption band was extracted with using of ratios of the Jovian spectra to the Saturn's disk spectrum that was taken as a reference. The depression of absorption in this band begins almost from the equator, and its maximum occurs at the planetographic latitude of 100N then the absorption increases again approaching to the latitude of 200N. The equivalent bandwidths corresponding to these latitudes are equal to 18.7 ± 1.4 A, 14.4 ± 1.0 A and 17.8 ± 0.8A. The 645 nm NH3 absorption band also shows depletion at the low latitudes of the Northern hemisphere, but it is less pronounced. At the temperate latitudes of the Northern hemisphere this band's absorption is systematically lower than the Southern Hemisphere's ones. We will continue research in this direction, especially because recently a significant depletion of gaseous NH3 has also been found with using of the VLA with high resolution (I. de Pater et al., Science, 2016, Vol. 352, Issue 6290, p.1290-1294) at the low latitudes of the Northern hemisphere in the region of the NEB.

  17. Photovoltaic performance and the energy landscape of CH3NH3PbI3.

    PubMed

    Zhou, Yecheng; Huang, Fuzhi; Cheng, Yi-Bing; Gray-Weale, Angus

    2015-09-21

    Photovoltaic cells with absorbing layers of certain perovskites have power conversion efficiencies up to 20%. Among these materials, CH3NH3PbI3 is widely used. Here we use density-functional theory to calculate the energies and rotational energy barriers of a methylammonium ion in the α or β phase of CH3NH3PbI3 with differently oriented neighbouring methylammonium ions. Our results suggest the methylammonium ions in CH3NH3PbI3 prefer to rotate collectively, and to be parallel to their neighbours. Changes in polarization on rotation of methylammonium ions are two to three times larger than those on relaxation of the lead ion from the centre of its coordination shell. The preferences for parallel configuration and concerted rotation, with the polarisation changes, are consistent with ferroelectricity in the material, and indicate that this polarisation is governed by methylammonium orientational correlations. We show that the field due to this polarisation is strong enough to screen the field hindering charge transport, and find this screening field in agreement with experiment. We examine two possible mechanisms for the effect of methylammonium ion rotation on photovoltaic performance. One is that rearrangement of methylammoniums promotes the creation and transport of charge carriers. Some effective masses change greatly, but changes in band structure with methylammonium rotation are not large enough to explain current-voltage hysteresis behaviour. The second possible mechanism is that polarization screens the hindering electric field, which arises from charge accumulation in the transport layers. Polarization changes on methylammonium rotation favour this second mechanism, suggesting that collective reorientation of methylammonium ions in the bulk crystal are in significant part responsible for the hysteresis and power conversion characteristics of CH3NH3PbI3 photovoltaic cells.

  18. General working principles of CH3NH3PbX3 perovskite solar cells.

    PubMed

    Gonzalez-Pedro, Victoria; Juarez-Perez, Emilio J; Arsyad, Waode-Sukmawati; Barea, Eva M; Fabregat-Santiago, Francisco; Mora-Sero, Ivan; Bisquert, Juan

    2014-02-12

    Organometal halide perovskite-based solar cells have recently realized large conversion efficiency over 15% showing great promise for a new large scale cost-competitive photovoltaic technology. Using impedance spectroscopy measurements we are able to separate the physical parameters of carrier transport and recombination in working devices of the two principal morphologies and compositions of perovskite solar cells, viz. compact thin films of CH3NH3PbI(3-x)Clx and CH3NH3PbI3 infiltrated on nanostructured TiO2. The results show nearly identical spectral characteristics indicating a unique photovoltaic operating mechanism that provides long diffusion lengths (1 μm). Carrier conductivity in both devices is closely matched, so that the most significant differences in performance are attributed to recombination rates. These results highlight the central role of the CH3NH3PbX3 semiconductor absorber in carrier collection and provide a new tool for improved optimization of perovskite solar cells. We report for the first time a measurement of the diffusion length in a nanostructured perovskite solar cell.

  19. Ammonia mobility in chabazite: insight into the diffusion component of the NH3-SCR process.

    PubMed

    O'Malley, Alexander J; Hitchcock, Iain; Sarwar, Misbah; Silverwood, Ian P; Hindocha, Sheena; Catlow, C Richard A; York, Andrew P E; Collier, P J

    2016-06-29

    The diffusion of ammonia in commercial NH3-SCR catalyst Cu-CHA was measured and compared with H-CHA using quasielastic neutron scattering (QENS) and molecular dynamics (MD) simulations to assess the effect of counterion presence on NH3 mobility in automotive emission control relevant zeolite catalysts. QENS experiments observed jump diffusion with a jump distance of 3 Å, giving similar self-diffusion coefficient measurements for both Cu- and H-CHA samples, in the range of ca. 5-10 × 10(-10) m(2) s(-1) over the measured temperature range. Self-diffusivities calculated by MD were within a factor of 6 of those measured experimentally at each temperature. The activation energies of diffusion were also similar for both studied systems: 3.7 and 4.4 kJ mol(-1) for the H- and Cu-chabazite respectively, suggesting that counterion presence has little impact on ammonia diffusivity on the timescale of the QENS experiment. An explanation is given by the MD simulations, which showed the strong coordination of NH3 with Cu(2+) counterions in the centre of the chabazite cage, shielding other molecules from interaction with the ion, and allowing for intercage diffusion through the 8-ring windows (consistent with the experimentally observed jump length) to carry on unhindered.

  20. Laboratory rotational ground state transitions of NH3D+ and CF+

    NASA Astrophysics Data System (ADS)

    Stoffels, A.; Kluge, L.; Schlemmer, S.; Brünken, S.

    2016-09-01

    Aims: This paper reports accurate laboratory frequencies of the rotational ground state transitions of two astronomically relevant molecular ions, NH3D+ and CF+. Methods: Spectra in the millimetre-wave band were recorded by the method of rotational state-selective attachment of He atoms to the molecular ions stored and cooled in a cryogenic ion trap held at 4 K. The lowest rotational transition in the A state (ortho state) of NH3D+ (JK = 10-00), and the two hyperfine components of the ground state transition of CF+ (J = 1-0) were measured with a relative precision better than 10-7. Results: For both target ions, the experimental transition frequencies agree with recent observations of the same lines in different astronomical environments. In the case of NH3D+ the high-accuracy laboratory measurements lend support to its tentative identification in the interstellar medium. For CF+ the experimentally determined hyperfine splitting confirms previous quantum-chemical calculations and the intrinsic spectroscopic nature of a double-peaked line profile observed in the J = 1-0 transition towards the Horsehead photon-dominated region (PDR).

  1. Optimization of H2 Production in Ar/NH3 Micro-discharges

    NASA Astrophysics Data System (ADS)

    Arakoni, Ramesh; Bhoj, Ananth N.; Kushner, Mark J.

    2006-10-01

    Hydrogen powered vehicles and portable fuel cells may require real-time generation of H2 to provide fuel safely and with rapid response. One such method is to produce H2 from feedstock gases that can be more safely stored, such as NH3. Microdischarge plasmas are being investigated as a means of H2 production from NH3 and other gases. The high power densities (10s kW/cm^3) that can be obtained in microdischarges provide an intense source of electron impact as well as thermal decomposition of the feedstock gases. By operating at high pressures (> 100s Torr), reformation of the dissociated products leads to efficient production of H2. In this work, results from a computational investigation of production of H2 in high pressure microdischarges sustained in Ar/NH3 mixtures will be discussed. Plug-flow and 2-dimensional plasma hydrodynamics models were used to develop scaling laws to optimize the energy efficiency of the process (e.g., eV/H2 molecule produced). The 2-d model resolves non-equilibrium electron, ion and neutral transport using fluid equations. The microdischarge geometry of interest is a sandwich flow-through reactor with a central hole a few hundred microns in diameter, power of a few W and residence times of a few microseconds.

  2. Comparison among NH3 and GHGs emissive patterns from different housing solutions of dairy farms

    NASA Astrophysics Data System (ADS)

    Baldini, Cecilia; Borgonovo, Federica; Gardoni, Davide; Guarino, Marcella

    2016-09-01

    Agriculture and livestock farming are known to be activities emitting relevant quantities of atmospheric pollutants. In particular, in intensive animal farming, buildings can be identified as a relevant source of ammonia and greenhouse gases. This study aimed at: i) determining the emission factors of NH3, N2O, CH4, and CO2 from different dairy farms in Italy, and ii) assessing the effects of the different floor types and manure-handling systems used, in order to minimize the impact of this important productive sector. A measurement campaign was carried out for 27 months in four naturally ventilated dairy cattle buildings with different floor types, layouts and manure management systems, representative of the most common technologies in the north of Italy. Gas emissions were measured with the "static chamber method": a chamber was placed above the floor farm and an infrared photoacoustic detector (IPD) was used to monitor gas accumulation over time. In the feeding alleys, emissions of NH3 were higher from solid floors than from flushing systems and perforated floors. N2O emissions were significantly different among farms but the absolute values were relatively low. CH4 and CO2 emissions were higher from perforated floors than from other types of housing solution. Regarding the cubicles, the emissions of NH3 were approximately equal from the two housing solution studied. Contrariwise, N2O, CH4 and CO2 emissions were different between the cubicles with rubber mat and those with straw where the highest values were found.

  3. 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.

  4. 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.

  5. 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).

  6. Ultraviolet-gas phase and -photocatalytic synthesis from CO and NH3.

    PubMed

    Hubbard, J S; Voecks, G E; Hobby, G L

    1975-08-05

    The major photoproduct obtained on irradiation of gaseous NH3 and CO mixtures is ammonium cyanate; lesser amounts of urea, biurea, biuret semi-carbazide, formamide and cyanide were observed. The formation of the major gas phase photolysis product may be rationalized by the following reaction sequence: (see article). Urea is probably formed from NH4NCO in a thermal reaction while formamide may result from the disproportionation of NH2CO. Photocatalytic syntheses of 14C-urea, -formamide, and -formadehyde are effected by irradiation of 14CO and NH3 in the presence of Vycor, silica gel, or volcanic ash shale surfaces. These syntheses are catalyzed by ultraviolet wavelengths longer than those absorbed by the gaseous reactants. The syntheses are also effected when the surface material is first irradiated in the presence of CO followed by a dark incubation with NH3. Apparently, the initiating step is a light dependent formation of a reactive form of CO on the surface. A discussion is given on the possible contribution of these reactions to the abiotic synthesis of organic nitrogen compounds on Mars, on the primitive Earth and in interstellar space.

  7. 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.

  8. Transparent CH3NH3SnCl3/Al-ZnO p-n heterojunction diode

    NASA Astrophysics Data System (ADS)

    Kumar, Sunil; Ansari, Mohd. Zubair; Khare, Neeraj

    2016-05-01

    A p-type Organic inorganic tin chloride (CH3NH3SnCl3) perovskite thin film has been synthesized by solution method. An n-type 1% Al doped ZnO (AZO) film has been deposited on FTO substrate by ultrasonic assisted chemical vapor deposition technique. A transparent CH3NH3SnCl3/AZO p-n heterojunction diode has been fabricated by spin coating technique. CH3NH3SnCl3/AZO p-n heterojunction shows 75% transparency in the visible region. I-V characteristic of CH3NH3SnCl3/AZO p-n heterojunction shows rectifying behavior of the diode. The diode parameters calculated as ideality factor η=2.754 and barrier height V= 0.76 eV. The result demonstrates the potentiality of CH3NH3SnCl3/AZO p-n heterojunction for transparent electronics.

  9. The effect of fuel sulfur on NH 3 and other emissions from 2000-2001 model year vehicles

    NASA Astrophysics Data System (ADS)

    Durbin, Thomas D.; Pisano, John T.; Younglove, T.; Sauer, Claudia G.; Rhee, Sam H.; Huai, Tao; Miller, J. Wayne; MacKay, Gervase I.; Hochhauser, Albert M.; Ingham, Michael C.; Gorse, Robert A.; Beard, Loren K.; DiCicco, Dominic; Thompson, Neville; Stradling, Richard J.; Rutherford, James A.; Uihlein, James P.

    Atmospheric ammonia (NH 3) is an important precursor to secondary particulate matter formation and information is currently scarce on NH 3 emissions from advanced low-emission vehicles using low-sulfur fuels. With the continuing reduction in the level of sulfur in gasoline, it is important to understand how this change could impact NH 3 emissions, particularly for advanced vehicle technologies. For this study, a total of 12 California-certified low-emission vehicles were tested with a gasoline containing 5, 30, and 150 ppmw sulfur and with both as-received and bench-aged catalysts. Vehicles were tested on each fuel/catalyst configuration over the federal test procedure (FTP) and US06 test cycles. Both regulated and NH 3 emissions were measured in real-time. NH 3 emission rates were generally lower than those of other regulated emissions over the FTP and in the range 14-21 mg mi -1 for the fleet. NH 3 emission rates were approximately five times higher over the more aggressive US06 cycle compared to the FTP. NH 3 emissions were primarily observed during transients, with higher emissions for more aggressive accelerations. Overall, the NH 3 emission factors for the newer technology vehicles tested were lower that than those found in previous studies of older vehicle technologies. Sulfur did not affect NH 3 emissions over the FTP, but higher NH 3 emissions were found for increasing fuel sulfur levels over the US06. Sulfur effects were also observed for nitrogen oxides over the FTP and for all regulated emissions over the US06.

  10. 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

  11. 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.

  12. Two-Center Three-Electron Bonding in ClNH3 Revealed via Helium Droplet Infrared Spectroscopy: Entrance Channel Complex Along the cl + NH3 → ClNH2 + H Reaction

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    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 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. Combining anti-cancer drugs with artificial sweeteners: synthesis and anti-cancer activity of saccharinate (sac) and thiosaccharinate (tsac) complexes cis-[Pt(sac)2(NH3)2] and cis-[Pt(tsac)2(NH3)2].

    PubMed

    Al-Jibori, Subhi A; Al-Jibori, Ghassan H; Al-Hayaly, Lamaan J; Wagner, Christoph; Schmidt, Harry; Timur, Suna; Baris Barlas, F; Subasi, Elif; Ghosh, Shishir; Hogarth, Graeme

    2014-12-01

    The new platinum(II) complexes cis-[Pt(sac)2(NH3)2] (sac=saccharinate) and cis-[Pt(tsac)2(NH3)2] (tsac=thiosaccharinate) have been prepared, the X-ray crystal structure of cis-[Pt(sac)2(NH3)2] x H2O reveals that both saccharinate anions are N-bound in a cis-arrangement being inequivalent in both the solid-state and in solution at room temperature. Preliminary anti-cancer activity has been assessed against A549 human alveolar type-II like cell lines with the thiosaccharinate complex showing good activity.

  14. New syntheses and structural characterization of NH3BH2Cl and (BH2NH2)3 and thermal decomposition behavior of NH3BH2Cl.

    PubMed

    Lingam, Hima K; Wang, Cong; Gallucci, Judith C; Chen, Xuenian; Shore, Sheldon G

    2012-12-17

    New convenient procedures for the preparation of ammonia monochloroborane (NH(3)BH(2)Cl) and cyclotriborazane [(BH(2)NH(2))(3)] are described. Crystal structures have been determined by single-crystal X-ray diffraction. Strong H···Cl···H bifurcated hydrogen bonding and weak N-H···H dihydrogen bonding are observed in the crystal structure of ammonia monochloroborane. When heated at 50 °C or under vacuum, ammonia monochloroborane decomposes to (NH(2)BHCl)(x), which was characterized by NMR, elemental analysis, and powder X-ray diffraction. Redetermination of the crystal structure of cyclotriborazane at low temperature by single-crystal X-ray diffraction analysis provides accurate hydrogen positions. Similar to ammonia borane, cyclotriborazane shows extensive dihydrogen bonding of N-H···H and B-H···H bonds with H(δ+)···H(δ-) interactions in the range of 2.00-2.34 Å.

  15. Long-range transport of NH3, CO, HCN, and C2H6 from the 2014 Canadian Wildfires

    NASA Astrophysics Data System (ADS)

    Lutsch, E.; Dammers, E.; Conway, S.; Strong, K.

    2016-08-01

    We report the first long-term measurements of ammonia (NH3) in the high Arctic. Enhancements of the total columns of NH3, carbon monoxide (CO), hydrogen cyanide (HCN), and ethane (C2H6) were detected in July and August 2014 at Eureka, Nunavut, and Toronto, Ontario. Enhancements were attributed to fires in the Northwest Territories using the FLEXPART Lagrangian dispersion model and the Moderate Resolution Imaging Spectroradiometer Fire Hot Spot data set. Emission estimates are reported as average emission factors for HCN (0.62 ± 0.34 g kg-1), C2H6 (1.50 ± 0.75 g kg-1), and NH3 (1.40 ± 0.72 g kg-1). Observations of NH3 at both sites demonstrate long-range transport of NH3, with an estimated NH3 lifetime of 48 h. We also conclude that boreal fires may be an important source of NH3 in the summertime Arctic.

  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. Removal of high concentration of NH3 and coexistent H2S by biological activated carbon (BAC) biotrickling filter.

    PubMed

    Chung, Ying-Chien; Lin, Yu-Yen; Tseng, Ching-Ping

    2005-11-01

    High efficiency of NH3 and H2S removal from waste gases was achieved by the biotrickling filter. Granular activated carbon (GAC), inoculated with Arthrobacter oxydans CH8 for NH3 removal and Pseudomonas putida CH11 for H2S removal, was used as packing material. Under conditions in which 100% H2S was removed, extensive tests to eliminate high concentrations of NH3 emission-including removal characteristics, removal efficiency, and removal capacity of the system-were performed. The results of the Bed Depth Service Time (BDST) experiment suggested that physical adsorption of NH3 gas by GAC was responsible for the first 10 days, after which NH3 gas was biodegraded by inoculated microorganisms. The dynamic steady state between physical adsorption and biodegradation was about two weeks. After the system achieved equilibrium, the BAC biotrickling filter exhibited high adaptation to shock loading, elevated temperature, and flow rate. Greater than 96% removal efficiency for NH3 was achieved during the 140-day operating period when inlet H2S loading was maintained at 6.25 g-S/m3/h. During the operating period, the pH varied between 6.5 and 8.0 after the physical adsorption stage, and no acidification or alkalinity was observed. The results also demonstrated that NH3 removal was not affected by the coexistence of H2S while gas retention time was the key factor in system performance. The retention time of at least 65 s is required to obtain a greater than 95% NH3 removal efficiency. The critical loading of NH3 for the system was 4.2 g-N/m3/h, and the maximal loading was 16.2 g-N/m3/h. The results of this study could be used as a guide for further design and operation of industrial-scale systems.

  18. NH3 and PH3 adsorption through single walled ZnS nanotube: First principle insight

    NASA Astrophysics Data System (ADS)

    Khan, Md. Shahzad; Srivastava, Anurag; Chaurasiya, Rajneesh; Khan, Mohd. Shahid; Dua, Piyush

    2015-09-01

    The density functional theory (DFT) based adsorption analysis of NH3 and PH3 gas molecule has been made for confirming the sensing behaviour of ZnS nanotube. For a particular orientation of XH3 (X = N or P), the ZnS nanotube is found to be a good sensor with Zn as interactive site, discussed in terms of chemisorption and physisorption. Partial density of state (PDOS) analysis reveals strong interaction between few selected fragments from XH3 and ZnS nanotube. The quality of interaction for most favourable orientation is further scrutinized using charge decomposition analysis (CDA) analysis and sensing ability through current-voltage (I-V) characteristics.

  19. Construction of Spectroscopically Accurate IR Linelists for NH3 and CO2

    NASA Astrophysics Data System (ADS)

    Huang, X.; Schwenke, D. W.; Lee, T. J.

    2011-05-01

    The strategy of using the best theory together with high-resolution experi-ment was applied to NH3 and CO2: that is, refine a highly accurate ab initio PES with the most reliable HITRAN or pure experimental data. With 0.01 - 0.02 cm-1 accuracy, our calculations are clearly far beyond simply reproducing experimental data, but are also capable of revealing many deficiencies in the cur- rent experimental analysis of the various isotopologues, as well as provide reliable predictions with similar accuracy.

  20. Optically switched magnetism in photovoltaic perovskite CH3NH3(Mn:Pb)I3

    NASA Astrophysics Data System (ADS)

    Náfrádi, B.; Szirmai, P.; Spina, M.; Lee, H.; Yazyev, O. V.; Arakcheeva, A.; Chernyshov, D.; Gibert, M.; Forró, L.; Horváth, E.

    2016-11-01

    The demand for ever-increasing density of information storage and speed of manipulation boosts an intense search for new magnetic materials and novel ways of controlling the magnetic bit. Here, we report the synthesis of a ferromagnetic photovoltaic CH3NH3(Mn:Pb)I3 material in which the photo-excited electrons rapidly melt the local magnetic order through the Ruderman-Kittel-Kasuya-Yosida interactions without heating up the spin system. Our finding offers an alternative, very simple and efficient way of optical spin control, and opens an avenue for applications in low-power, light controlling magnetic devices.

  1. Optically switched magnetism in photovoltaic perovskite CH3NH3(Mn:Pb)I3.

    PubMed

    Náfrádi, B; Szirmai, P; Spina, M; Lee, H; Yazyev, O V; Arakcheeva, A; Chernyshov, D; Gibert, M; Forró, L; Horváth, E

    2016-11-24

    The demand for ever-increasing density of information storage and speed of manipulation boosts an intense search for new magnetic materials and novel ways of controlling the magnetic bit. Here, we report the synthesis of a ferromagnetic photovoltaic CH3NH3(Mn:Pb)I3 material in which the photo-excited electrons rapidly melt the local magnetic order through the Ruderman-Kittel-Kasuya-Yosida interactions without heating up the spin system. Our finding offers an alternative, very simple and efficient way of optical spin control, and opens an avenue for applications in low-power, light controlling magnetic devices.

  2. Optically switched magnetism in photovoltaic perovskite CH3NH3(Mn:Pb)I3

    PubMed Central

    Náfrádi, B.; Szirmai, P.; Spina, M.; Lee, H.; Yazyev, O. V.; Arakcheeva, A.; Chernyshov, D.; Gibert, M.; Forró, L.; Horváth, E.

    2016-01-01

    The demand for ever-increasing density of information storage and speed of manipulation boosts an intense search for new magnetic materials and novel ways of controlling the magnetic bit. Here, we report the synthesis of a ferromagnetic photovoltaic CH3NH3(Mn:Pb)I3 material in which the photo-excited electrons rapidly melt the local magnetic order through the Ruderman–Kittel–Kasuya–Yosida interactions without heating up the spin system. Our finding offers an alternative, very simple and efficient way of optical spin control, and opens an avenue for applications in low-power, light controlling magnetic devices. PMID:27882917

  3. Triphos derivatives and diphosphines as ligands in the ruthenium-catalysed alcohol amination with NH3.

    PubMed

    Nakagawa, N; Derrah, E J; Schelwies, M; Rominger, F; Trapp, O; Schaub, T

    2016-04-28

    The ruthenium-triphos and diphosphine-catalysed amination of alcohols with ammonia is reported. Various types of triphos derivatives with electron-donating functional group were synthesized and used as ligands in the Ru-catalysed alcohol amination with NH3. The triphos derivatives are effective for the formation of primary amines. On the other hand, if hemilabile diphosphines as tridentate ligands are used, mixtures of secondary-along with primary amines are obtained. It was found that even simple diphosphines can be used as ligands for the selective formation of the secondary amines. The diphosphine system allows a new entry to the Ru-catalysed formation of secondary amines.

  4. 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.

  5. Etude calorimétrique et structure cristalline du putrescinium monohydrogénomonophosphate 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) Å, b = 16.648(3) Å, c = 9.175(1) Å, β = 95.74(1)°, V = 994.1(5) Å 3, Dm = 1.498 Mgm -3, Dx = 1.484 Mgm -3, μ = 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 Å. 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) Å. 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H····O, POH····O(w), and O(W)H····O. The differential scanning calorimetric study shows that the dehydration of this salt occurs in two steps respectively at 105 and 121°C with a loss of one water molecule per step. The anhydrous salt undergoes four phase transitions respectively at temperatures of 133, 143, 159, and 165°C.

  6. Imaging a multidimensional multichannel potential energy surface: Photodetachment of H-(NH3) and NH4-

    NASA Astrophysics Data System (ADS)

    Hu, Qichi; Song, Hongwei; Johnson, Christopher J.; Li, Jun; Guo, Hua; Continetti, Robert E.

    2016-06-01

    Probes of the Born-Oppenheimer potential energy surfaces governing polyatomic molecules often rely on spectroscopy for the bound regions or collision experiments in the continuum. A combined spectroscopic and half-collision approach to image nuclear dynamics in a multidimensional and multichannel system is reported here. The Rydberg radical NH4 and the double Rydberg anion NH4- represent a polyatomic system for benchmarking electronic structure and nine-dimensional quantum dynamics calculations. Photodetachment of the H-(NH3) ion-dipole complex and the NH4- DRA probes different regions on the neutral NH4 PES. Photoelectron energy and angular distributions at photon energies of 1.17, 1.60, and 2.33 eV compare well with quantum dynamics. Photoelectron-photofragment coincidence experiments indicate dissociation of the nascent NH4 Rydberg radical occurs to H + NH3 with a peak kinetic energy of 0.13 eV, showing the ground state of NH4 to be unstable, decaying by tunneling-induced dissociation on a time scale beyond the present scope of multidimensional quantum dynamics.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    Luminescence spectra are recorded for the reactions of Xe+ + NH3 and Xe2+ + NH3 at energies ranging from 11.5 to 206 eV in the center-of-mass (Ecm) frame. Intense features of the luminescence spectra are attributed to the NH (A 3Πi-X 3Σ-), 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 Xe2+ 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 cm2, 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.

  8. 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.

  9. Paper based platform for colorimetric sensing of dissolved NH3 and CO2.

    PubMed

    Chen, Yu; Zilberman, Yael; Mostafalu, Pooria; Sonkusale, Sameer R

    2015-05-15

    Paper, a cheap and ubiquitous material, has great potential to be used as low-cost, portable and biodegradable platform for chemical and biological sensing application. In this paper, we are exploring a low-cost, flexible and reliable method to effectively pattern paper for capturing optical dyes and for flow-based delivery of target samples for colorimetric chemical sensing. In this paper, we target the detection of ammonia (NH3) and carbon dioxide (CO2), two of the important environmental and health biomarkers. By functionalizing the paper platform with diverse cross-reactive dyes sensitive to NH3 and CO2, their selective sensing within a certain pH range, as well as their detection at different concentrations can be achieved. The images of paper based device were captured by a flatbed scanner and processed in MATLAB(®) using a RGB model and PCA for quantitative analysis. Paper based devices with readout using ubiquitous consumer electronic devices (e.g. smartphones, flatbed scanner) are considered promising approaches for disease screening in developing countries with limited resources.

  10. 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.

  11. Modifying CH3NH3PbBr3 nanocrystals with arylamines

    NASA Astrophysics Data System (ADS)

    Zhu, Ruimin; Liu, Heyuan; Shen, Li; Sun, Dejun; Li, Xiyou

    2017-04-01

    Chemically decorating CH3NH3PbBr3 with a group of para-substituted arylamine (R-An) was investigated, where R ranges from electron-withdrawing trifluoromethoxy(-CF3O), to hydrogen or electron-donating ethoxy (-EtO). Different ratios of R-An ammonium bromide and methylammonium bromide (MA) (R-An/MA=3/7, 4/6, 5/5, 6/4 and 7/3) were tested. XRD patterns revealed that the perovskite nanocomposite were cubic with good crystallinity. TEM and photoluminescence suggested that the perovskite nanocrystals were composed of 2D layered and 3D bulk structures. 1H NMR and TGA experiments revealed that the non-substituted aniline can readily adsorb to the surface of perovskite at any ratios between R-An and MA. But an EtOAn/MA ratio ≥1 is needed to anchor the EOAn molecules on the surface of perovskite. For the arylamine with the electron-withdrawing -CF3O group, it cannot adsorb to the surface of the perovskite at any concentrations. This result reveals that both steric hindrance and alkalinity can affect the anchoring of arylamine on the surface of CH3NH3PbBr3 perovskite. I-V curves of the perovskite nanocrystal films prepared by spin coating suggest that proper surface modification can increase the conductivity significantly.

  12. First Principles Study of Electronic Structure of BF3-NH3 Complex and Associated Properties

    NASA Astrophysics Data System (ADS)

    Dubey, Archana; Mahanti, Mahendra K.; Pink, Roger

    2005-03-01

    BF3 is a planar molecule with three-fold symmetry which is widely used to promote various organic reactions such as Friedel-Crafts acylations and alkylations. To obtain a thorough understanding of the mechanisms for this role of BF3, we are studying from first-principles the electronic structures of BF3 and its complexes with NH3. The procedure used is the first principles Hartree-Fock-Roothaan procedure combined with many body perturbation theory. The results for BF3-NH3 system will be reported, such as the binding energy and equilibrium geometry of the complex, the nature of the B-N bond and the changes in the B-F and N-H bond strengths on complex formation. The Nuclear Quadrupole Interactions of the ^19F* (spin 5/2), ^14N, ^11B, and ^2H will be presented and compared with available experimental data. (*) Present Address: Dept. of Physics, Uppsala University, Sweden (**) Also: Dept of Physics, University of Central Florida, Orlando, Florida

  13. Re-analysis of ammonia spectra: Updating the HITRAN 14NH3 database

    NASA Astrophysics Data System (ADS)

    Down, Michael J.; Hill, Christian; Yurchenko, Sergei N.; Tennyson, Jonathan; Brown, Linda R.; Kleiner, Isabelle

    2013-11-01

    The data incorporated in the HITRAN database for 14NH3 are analyzed using a comprehensive and consistent set of quantum numbers, empirical lower energy levels and the BYTe variationally calculated line list as reference points. Labelings are checked to ensure that they obey both the usual selection rules and the HITRAN labeling formalisms; the problems identified are corrected where possible. Further assignments are brought into question by combination difference (CD) checking of implied upper energy levels. The CD analysis yields an 89% complete 14NH3 energy level list up to 6610 cm-1 and J=21, self-consistent to 0.1 cm-1. In combination with the 1723 previously unassigned and unlabeled lines in HITRAN a total of 2529 problem lines were identified for re-analysis. The compiled energy level list was used to label and assign the set of problem transitions, resulting in a total of 249 new assignments and a further 368 new labelings. Assignment by comparison with the reference line list resulted in 111 further new line assignments and 14 new labelings. Intensities are checked against recent measurements and BYTe. New intensities are proposed for the ν2 band with new intensities and line positions for the 2ν2-ν2 and new line lists are created for the ν2-ν2, ν2-ν4 and ν4-ν4 bands. BYTe band intensities are analyzed to identify other regions of missing intensity.

  14. 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

  15. Room temperature three-photon pumped CH3NH3PbBr3 perovskite microlasers

    PubMed Central

    Gao, Yisheng; Wang, Shuai; Huang, Can; Yi, Ningbo; Wang, Kaiyang; Xiao, Shumin; Song, Qinghai

    2017-01-01

    Hybrid lead halide perovskites have made great strides in next-generation light-harvesting and light emitting devices. Recently, they have also shown great potentials in nonlinear optical materials. Two-photon absorption and two-photon light emission have been thoroughly studied in past two years. However, the three-photon processes are rarely explored, especially for the laser emissions. Here we synthesized high quality CH3NH3PbBr3 perovskite microstructures with solution processed precipitation method and studied their optical properties. When the microstructures are pumped with intense 1240 nm lasers, we have observed clear optical limit effect and the band-to-band photoluminescence at 540 nm. By increasing the pumping density, whispering-gallery-mode based microlasers have been achieved from CH3NH3PbBr3 perovskite microplate and microrod for the first time. This work demonstrates the potentials of hybrid lead halide perovskites in nonlinear photonic devices. PMID:28350003

  16. The ν 1 and ν 3 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 ν 1 and ν 3, 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 ν 3 and Δl = +2 in ? , and ΔK = ±3, Δl = 0 in ν 1 and ? . 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.

  17. Comparison of Recombination Dynamics in CH3NH3PbBr3 and CH3NH3PbI3 Perovskite Films: Influence of Exciton Binding Energy.

    PubMed

    Yang, Ye; Yang, Mengjin; Li, Zhen; Crisp, Ryan; Zhu, Kai; Beard, Matthew C

    2015-12-03

    Understanding carrier recombination in semiconductors is a critical component when developing practical applications. Here we measure and compare the monomolecular, bimolecular, and trimolecular (Auger) recombination rate constants of CH3NH3PbBr3 and CH3NH3PbI3. The monomolecular and bimolecular recombination rate constants for both samples are limited by trap-assisted recombination. The bimolecular recombination rate constant for CH3NH3PbBr3 is ∼3.3 times larger than that for CH3NH3PbI3 and both are in line with that found for radiative recombination in other direct-gap semiconductors. The Auger recombination rate constant is 4 times larger in lead-bromide-based perovskite compared with lead-iodide-based perovskite and does not follow the reduced Auger rate when the bandgap increases. The increased Auger recombination rate, which is enhanced by Coulomb interactions, can be ascribed to the larger exciton binding energy, ∼40 meV, in CH3NH3PbBr3 compared with ∼13 meV in CH3NH3PbI3.

  18. Ambient Ammonia Impact Determined by a Novel NH3 Sensor Utilizing a Quantum Cascade Laser and Photoacoustic Spectroscopy

    NASA Astrophysics Data System (ADS)

    McKarns, T.; Kutter, M. F.

    2015-12-01

    Despite the impact of ambient ammonia (NH3) concentrations on the ecology and our health, the continuous monitoring of NH3 is not yet commonplace. The ammonia molecule has reactive and sticky properties making it difficult to sample, and measuring techniques with sufficient sensitivity and selectivity have been difficult to source. The technique presented is based on photo acoustic spectroscopy (PAS) with a quantum cascade laser (QCL). Developed for a wide range of environments, from the cleanest Swiss mountaintops to rural alpine pastures for cows, the novel detector has shown its reliability and ruggedness for sensing NH3 concentrations from 0-5,000 ppb (part per billions) levels. Rural background measurements performed with the new ECO PHYSICS PAS 87 system and in cooperation with the German Institute for Tropospheric Research, will prove the suitability of this approach to reach continuous automated ambient NH3 values for environmental campaigns.

  19. Increasing the indium incorporation efficiency during InGaN layer growth by suppressing the dissociation of NH3

    NASA Astrophysics Data System (ADS)

    Yang, J.; Zhao, D. G.; Jiang, D. S.; Chen, P.; Zhu, J. J.; Liu, Z. S.; Liu, W.; Liang, F.; Li, X.; Liu, S. T.; Zhang, L. Q.; Yang, H.

    2017-02-01

    Three series of InGaN samples with different growth pressures are grown in a vertical metal organic chemical vapor deposition (MOCVD) system and the indium incorporation efficiency during InGaN layer growth is investigated. It is found that the indium content in InGaN layer decreases when the NH3 flow rate increases at a higher growth pressure and it increases with the NH3 flow rate at a lower growth pressure, This may be attributed to the higher dissociation rate of NH3 into N2 and H2 at a higher growth pressure, leading to a higher H2 concentration in reactor during InGaN growth. Therefore, changing growth conditions to suppress the dissociation of NH3 into N2 and H2 can increase the indium incorporation efficiency during InGaN film growth.

  20. 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...

  1. Synergetic formation of secondary inorganic and organic aerosol: effect of SO2 and NH3 on particle formation and growth

    NASA Astrophysics Data System (ADS)

    Chu, Biwu; Zhang, Xiao; Liu, Yongchun; He, Hong; Sun, Yele; Jiang, Jingkun; Li, Junhua; Hao, Jiming

    2016-11-01

    The effects of SO2 and NH3 on secondary organic aerosol formation have rarely been investigated together, while the interactive effects between inorganic and organic species under highly complex pollution conditions remain uncertain. Here we studied the effects of SO2 and NH3 on secondary aerosol formation in the photooxidation system of toluene/NOx in the presence or absence of Al2O3 seed aerosols in a 2 m3 smog chamber. The presence of SO2 increased new particle formation and particle growth significantly, regardless of whether NH3 was present. Sulfate, organic aerosol, nitrate, and ammonium were all found to increase linearly with increasing SO2 concentrations. The increases in these four species were more obvious under NH3-rich conditions, and the generation of nitrate, ammonium, and organic aerosol increased more significantly than sulfate with respect to SO2 concentration, while sulfate was the most sensitive species under NH3-poor conditions. The synergistic effects between SO2 and NH3 in the heterogeneous process contributed greatly to secondary aerosol formation. Specifically, the generation of NH4NO3 was found to be highly dependent on the surface area concentration of suspended particles, and increased most significantly with SO2 concentration among the four species under NH3-rich conditions. Meanwhile, the absorbed NH3 might provide a liquid surface layer for the absorption and subsequent reaction of SO2 and organic products and, therefore, enhance sulfate and secondary organic aerosol (SOA) formation. This effect mainly occurred in the heterogeneous process and resulted in a significantly higher growth rate of seed aerosols compared to without NH3. By applying positive matrix factorisation (PMF) analysis to the AMS data, two factors were identified for the generated SOA. One factor, assigned to less-oxidised organic aerosol and some oligomers, increased with increasing SO2 under NH3-poor conditions, mainly due to the well-known acid catalytic effect of

  2. Immobilization of enzyme and antibody on ALD-HfO2-EIS structure by NH3 plasma treatment

    NASA Astrophysics Data System (ADS)

    Wang, I.-Shun; Lin, Yi-Ting; Huang, Chi-Hsien; Lu, Tseng-Fu; Lue, Cheng-En; Yang, Polung; Pijanswska, Dorota G.; Yang, Chia-Ming; Wang, Jer-Chyi; Yu, Jau-Song; Chang, Yu-Sun; Chou, Chien; Lai, Chao-Sung

    2012-03-01

    Thin hafnium oxide layers deposited by an atomic layer deposition system were investigated as the sensing membrane of the electrolyte-insulator-semiconductor structure. Moreover, a post-remote NH3 plasma treatment was proposed to replace the complicated silanization procedure for enzyme immobilization. Compared to conventional methods using chemical procedures, remote NH3 plasma treatment reduces the processing steps and time. The results exhibited that urea and antigen can be successfully detected, which indicated that the immobilization process is correct.

  3. 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.

  4. 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

  5. Enhanced performance of CH3NH3PbI3-x Cl x perovskite solar cells by CH3NH3I modification of TiO2-perovskite layer interface.

    PubMed

    Wang, Wen; Zhang, Zongbao; Cai, Yangyang; Chen, Jinshan; Wang, Jianming; Huang, Riyan; Lu, Xubing; Gao, Xingsen; Shui, Lingling; Wu, Sujuan; Liu, Jun-Ming

    2016-12-01

    In this work, perovskite solar cells (PSCs) with CH3NH3PbI3-x Cl x as active layer and spiro-OMeTAD as hole-transport media have been fabricated by one-step method. The methylammonium iodide (CH3NH3I) solution with different concentrations is used to modify the interface between mesoporous TiO2 (meso-TiO2) film and CH3NH3PbI3-x Cl x perovskite layer. Several techniques including X-ray diffraction, scanning electron microscopy, optical absorption, electrochemical impedance spectroscopy (EIS) and photoluminescence are used to investigate the effect of the interfacial modification. It is found that the interfacial modification by CH3NH3I enhance the crystallinity and increase the grain size of CH3NH3PbI3-x Cl x layer, and improve the surface wetting properties of perovskite precursor on meso-TiO2 film. The sunlight absorption and external quantum efficiency of PSCs in the visible region with wavelength less than 600 nm have been improved. The Nyquist plots obtained from the EIS suggest that the CH3NH3I modification can reduce the charge recombination rates. The photoluminescence measurement shows that the exciton dissociation in the modified devices is more effective than that in the control samples. The photovoltaic performance of the modified devices can be significantly improved with respect to the reference (control) devices. The CH3NH3I modified devices at the optimized concentration demonstrate the average power conversion efficiency of 12.27 % in comparison with the average efficiency of 9.68 % for the reference devices.

  6. Enhanced performance of CH3NH3PbI3- x Cl x perovskite solar cells by CH3NH3I modification of TiO2-perovskite layer interface

    NASA Astrophysics Data System (ADS)

    Wang, Wen; Zhang, Zongbao; Cai, Yangyang; Chen, Jinshan; Wang, Jianming; Huang, Riyan; Lu, Xubing; Gao, Xingsen; Shui, Lingling; Wu, Sujuan; Liu, Jun-Ming

    2016-06-01

    In this work, perovskite solar cells (PSCs) with CH3NH3PbI3- x Cl x as active layer and spiro-OMeTAD as hole-transport media have been fabricated by one-step method. The methylammonium iodide (CH3NH3I) solution with different concentrations is used to modify the interface between mesoporous TiO2 (meso-TiO2) film and CH3NH3PbI3- x Cl x perovskite layer. Several techniques including X-ray diffraction, scanning electron microscopy, optical absorption, electrochemical impedance spectroscopy (EIS) and photoluminescence are used to investigate the effect of the interfacial modification. It is found that the interfacial modification by CH3NH3I enhance the crystallinity and increase the grain size of CH3NH3PbI3- x Cl x layer, and improve the surface wetting properties of perovskite precursor on meso-TiO2 film. The sunlight absorption and external quantum efficiency of PSCs in the visible region with wavelength less than 600 nm have been improved. The Nyquist plots obtained from the EIS suggest that the CH3NH3I modification can reduce the charge recombination rates. The photoluminescence measurement shows that the exciton dissociation in the modified devices is more effective than that in the control samples. The photovoltaic performance of the modified devices can be significantly improved with respect to the reference (control) devices. The CH3NH3I modified devices at the optimized concentration demonstrate the average power conversion efficiency of 12.27 % in comparison with the average efficiency of 9.68 % for the reference devices.

  7. 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

  8. Vibrational infrared spectrum of NH 3 adsorbed on MgO(100). I. Ab initio calculations

    NASA Astrophysics Data System (ADS)

    Allouche, A.; Corà, F.; Girardet, C.

    1995-12-01

    The perturbed cluster approach, previously devoted to the calculation of the stable adsorption site and energy for ammonia adsorbed on MgO(100), is used to determine the frequency and the intensity of the main peaks associated with the normal vibrational modes of the admolecule. The ab initio model based on a cluster embedded in an array of point charges is then compared to the perturbed cluster approach and used to investigate different molecular orientations and associations on the surface in order to give an interpretation to the occurrence of the infrared signals. Six normal modes for each admolecule are calculated due to the removing of internal degeneracy by adsorption. The characteristics of the calculated spectrum are compared to the experimental infrared data and it is shown that the set of selected situations is able to explain almost every band in the spectrum without implication of NH 3 dissociation on the surface.

  9. Absolute cross sections for dissociative electron attachment to NH3 and CH4

    NASA Astrophysics Data System (ADS)

    Rawat, Prashant; Prabhudesai, Vaibhav S.; Rahman, M. A.; Ram, N. Bhargava; Krishnakumar, E.

    2008-11-01

    Dissociative electron attachment (DEA) cross sections for NH3 and CH4 are measured in a crossed beam apparatus with special care to eliminate discrimination due to kinetic energy and angular distribution of the fragment ions. The cross sections are put on absolute scale using the relative flow technique. The absolute cross sections for the formation of H- and NH2- from ammonia and H- and CH2- from methane are compared with available data from literature. It is seen that the present results are considerably different 6rom what has been reported before. We also compare the cross sections of the H- channel from these molecules along with that from H2O to those from organic molecules containing alkyl, amino and hydroxyl groups to examine the extent to which the recently observed functional group dependence in the DEA contributes.

  10. Perfomance Analysi of Rectifier in NH3-H2O Absorption Heat Pump

    NASA Astrophysics Data System (ADS)

    Tsujimori, Atsushi; Ozaki, Eiichi; Nakao, Kazushige

    In order to design a rectifier in NH3-H2O absorption heat pump, the heat and mass transfer model for packed tower-type rectifiers was presented in the previous paper and it was found that the model could predict over-all mass transfer coefficient within 30(%) difference to the experimental data. Though the approximate calculation to design rectifiers is increasing important, the method of this prediction need many reiteration along the vapor and solution flow, which might not be the simplified way to design packed tower-type rectifier Thus the approximate pr . edicting method was presented in this paper. In this way, over-all mass transfer Coefficient was easily deriveded using the rectification characteristic that was determined by the dimension and geometry of rectification packing. The calculation results showed good agreement with the experimental data, regardless of kinds of rectification packing.

  11. Intense Pulsed Light Sintering of CH3NH3PbI3 Solar Cells.

    PubMed

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

    2016-04-06

    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.

  12. Electronic structure evolution of fullerene on CH3NH3PbI3

    DOE PAGES

    Wang, Chenggong; Wang, Congcong; Liu, Xiaoliang; ...

    2015-03-19

    The thickness dependence of fullerene on CH3NH3PbI3 perovskitefilm surface has been investigated by using ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy(XPS), and inverse photoemission spectroscopy (IPES). The lowest unoccupied molecular orbital and highest occupied molecular orbital (HOMO) can be observed directly with IPES and UPS. It is observed that the HOMO level in fullerene shifts to lower binding energy. The XPS results show a strong initial shift of core levels to lower binding energy in the perovskite, which indicates that electrons transfer from the perovskitefilm to fullerene molecules. Further deposition of fullerene forms C60 solid, accompanied by the reduction ofmore » the electron transfer. As a result, the strongest electron transfer happened at 1/4 monolayer of fullerene.« less

  13. Determination of NH3 emissions from confined areas using backward Lagrangian stochastic dispersion modelling

    NASA Astrophysics Data System (ADS)

    Häni, Christoph; Neftel, Albrecht; Sintermann, Jörg

    2016-04-01

    Employing backward Lagrangian stochastic (bLS) dispersion modelling to infer emission strengths from confined areas using trace gas concentration measurements is a convenient way of emission estimation from field measurements (see Wilson et al., 2012 and references therein). The freely available software 'WindTrax' (www.thunderbeachscientific.com), providing a graphical interface for the application of a bLS model, has spurred its utilisation in the past decade. Investigations include mainly methane (CH4) and ammonia (NH3) emissions based on experimental plots with dimensions between approximately 102 to 104 m2. Whereas for CH4 deposition processes can be neglected, NH3 has a strong affinity to any surface and is therefore efficiently deposited. Neglecting dry deposition will underestimate NH3 emissions, e.g. with a standard WindTrax approach. We extended the bLS model described in Flesch et al. (2004) by a dry deposition process using a simple, one-directional deposition velocity approach. At every contact of the model trajectories with ground level (here at the height of the roughness length Zo), deposition is modelled as: Fdep = vdep × CT raj (1) where vdep represents deposition velocity, and CTraj is the actual concentration of the specific trajectory at contact. A convenient way to model vdep is given by a resistances approach. The deposition velocity is modelled as the inverse of the sum of a series of different resistances to deposition. The aerodynamic resistance is already implicitly included in the bLS model, thus vdep is given as: v = ---1--- dep Rb + Rc (2) Rb and Rc represent resistances of different model layers between Zo and the surfaces where deposition take place. With this approach we analysed a dataset from measurements with an artificial NH3 source that consisted of 36 individual orifices mimicking a circular area source with a radius of 10 m. The use of three open-path miniDOAS (Sintermann et al., submitted to AMT) systems allowed to measure

  14. 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

  15. Theoretical study of geometry relaxation following core excitation: H2O, NH3, and CH4

    NASA Astrophysics Data System (ADS)

    Takahashi, Osamu; Kunitake, Naoto; Takaki, Saya

    2015-10-01

    Single core-hole (SCH) and double core-hole excited state molecular dynamics (MD) calculations for neutral and cationic H2O, NH3, and CH4 have been performed to examine geometry relaxation after core excitation. We observed faster X-H (X = C, N, O) bond elongation for the core-ionized state produced from the valence cationic molecule and the double-core-ionized state produced from the ground and valence cationic molecules than for the first resonant SCH state. Using the results of SCH MD simulations of the ground and valence cationic molecules, Auger decay spectra calculations were performed. We found that fast bond scission leads to peak broadening of the spectra.

  16. Electronic transport properties of BN sheet on adsorption of ammonia (NH3) gas.

    PubMed

    Srivastava, Anurag; Bhat, Chetan; Jain, Sumit Kumar; Mishra, Pankaj Kumar; Brajpuriya, Ranjeet

    2015-03-01

    We report the detection of ammonia gas through electronic and transport properties analysis of boron nitride sheet. The density functional theory (DFT) based ab initio approach has been used to calculate the electronic and transport properties of BN sheet in presence of ammonia gas. Analysis confirms that the band gap of the sheet increases due to presence of ammonia. Out of different positions, the bridge site is the most favorable position for adsorption of ammonia and the mechanism of interaction falls between weak electrostatic interaction and chemisorption. On relaxation, change in the bond angles of the ammonia molecule in various configurations has been reported with the distance between NH3 and the sheet. An increase in the transmission of electrons has been observed on increasing the bias voltage and I-V relationship. This confirms that, the current increases on applying the bias when ammonia is introduced while a very small current flows for pure BN sheet.

  17. 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.

  18. VLBI Observations and NH3 Mapping of the Star-forming Region NGC2264

    NASA Astrophysics Data System (ADS)

    Kamezaki, Tatsuya; Imura, Kenji; Nagayama, Takumi; Omodaka, Toshihiro; Handa, Toshihiro; Yamaguchi, Yoshiyuki; Chibueze, James O.; Sunada, Kazuyoshi; Nakano, Makoto

    2013-03-01

    We have measured the annual parallax of the water maser source associated with star forming region NGC2264 from observations with VLBI Exploration of Radio Astrometry (VERA). We detected masers at V LSR = 7.2 km s-1. We discussed its driving sources of detected maser spots. One of the maser spots was associated with a centimeter continuum source observed with VLA. Neither optical, infrared nor X-ray sources is catalogued near the spot. The other maser spot is located close to an X-ray source, although there is no optical or infrared counterpart. The proper motion of the former spot was (μα, μδ) = (23.91 ± 4.29, -29.81 ± 4.27) and the proper motion of latter spot was (μα, μδ) = (-0.96 ± 0.58, -6.05 ± 3.06). For the latter spot, the peculiar motion is ˜ 150 km s-1 and it has the high velocity and this may be a jet or an outflow from a young star. The observed parallax is 1.365 ± 0.098 mas, corresponding to the distance of 738+57 -50 pc. This value is constant with the photometric distance of NGC2264 previously measured. The fitting result of the parallax is shown in figure 1. We also observed in NH3 (1,1), (2,2), (3,3) lines of NGC2264 with the Kashima 34m telescope. We estimated the star formation efficiency (SFE) of NGC2264 from the dense molecular mass of NH3 and the stellar mass calculated by Teixeira et al. (2012). The SFE is 9 - 12% which is consistent with previous results.

  19. An accurate global potential energy surface, dipole moment surface, and rovibrational frequencies for NH(3).

    PubMed

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

    2008-12-07

    A global potential energy surface (PES) that includes short and long range terms has been determined for the NH(3) molecule. The singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations and the internally contracted averaged coupled-pair functional electronic structure methods have been used in conjunction with very large correlation-consistent basis sets, including diffuse functions. Extrapolation to the one-particle basis set limit was performed and core correlation and scalar relativistic contributions were included directly, while the diagonal Born-Oppenheimer correction was added. Our best purely ab initio PES, denoted "mixed," is constructed from two PESs which differ in whether the ic-ACPF higher-order correlation correction was added or not. Rovibrational transition energies computed from the mixed PES agree well with experiment and the best previous theoretical studies, but most importantly the quality does not deteriorate even up to 10 300 cm(-1) above the zero-point energy (ZPE). The mixed PES was improved further by empirical refinement using the most reliable J=0-2 rovibrational transitions in the HITRAN 2004 database. Agreement between high-resolution experiment and rovibrational transition energies computed from our refined PES for J=0-6 is excellent. Indeed, the root mean square (rms) error for 13 HITRAN 2004 bands for J=0-2 is 0.023 cm(-1) and that for each band is always NH(3) spectra and in correcting mistakes in previous assignments. Ideas for further improvements to our refined PES and for extension to other isotopolog are discussed.

  20. General aspects of the vapor growth of semiconductor crystals - A study based on DFT simulations of the NH3/NH2 covered GaN(0001) surface in hydrogen ambient

    NASA Astrophysics Data System (ADS)

    Kempisty, Paweł; Strak, Paweł; Sakowski, Konrad; Krukowski, Stanisław

    2014-03-01

    Vapor growth of semiconductors is analyzed using recently obtained dependence of the adsorption energy on the electron charge transfer between the surface adsorbed species and the bulk [Krukowski et al. J. Appl. Phys. 114 (2013) 063507, Kempisty et al. ArXiv1307.5778 (2013)]. Ab initio calculations were performed to study the physical properties of GaN(0001) surface in ammonia-rich conditions, i.e. covered by mixture of NH3 molecules and NH2 radicals. The Fermi level is pinned at valence band maximum (VBM) and conduction band minimum (CBM) for full coverage by NH3 molecules and NH2 radicals, respectively. For the crossover content of ammonia of about 25% monolayer (ML), the Fermi level is unpinned. It was shown that hydrogen adsorption energy depends on the doping in the bulk for the unpinned Fermi level, i.e. for this coverage. Surface structure thermodynamic and mechanical stability criteria are defined and compared. Mechanical stability of the coverage of such surfaces was checked by determination of the desorption energy of hydrogen molecules. Thermodynamic stability analysis indicates that initially equilibrium hydrogen vapor partial pressure steeply increases with NH3 content to attain the crossover NH3/NH2 coverage, i.e. the unpinned Fermi level condition. For such condition the entire range of experimentally accessible pressures belongs showing that vapor growth of semiconductor crystals occurs predominantly for unpinned Fermi level at the surface, i.e. for flat bands. Accordingly, adsorption energy of most species depends on the doping in the bulk that is based on the possible molecular scenario explaining dependence of the growth and the doping of semiconductor crystals on the doping in the bulk.

  1. Ce-Ti amorphous oxides for selective catalytic reduction of NO with NH3: confirmation of Ce-O-Ti active sites.

    PubMed

    Li, Ping; Xin, Ying; Li, Qian; Wang, Zhongpeng; Zhang, Zhaoliang; Zheng, Lirong

    2012-09-04

    The amorphous Ce-Ti mixed oxides were reported to be catalysts for selective catalytic reduction of NO(x) with NH(3), in which Ce and not Ti acts as their solvent in spite of the fact that Ce is low in content. The amorphous catalysts were characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) equipped with selective area electron diffraction (SAED). The Ce-Ti amorphous oxide shows higher activity than its crystalline counterpart at lower temperatures. Moreover, the presence of small CeO(2) crystallites as for the impregnated sample is deleterious to activity. The Ce-O-Ti short-range order species with the interaction between Ce and Ti in atomic scale was confirmed for the first time to be the active site using temperature programmed reduction with H(2) (H(2)-TPR), in situ FTIR spectra of NO adsorption, X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine-structure (XAFS). Lastly, the Ce-O-Ti structure was directly observed by field-emission TEM (FETEM).

  2. Phase polymorphism of novel [Ru(NH3)6](ClO4)3—Comparison with [Ru(NH3)6](BF4)3. Part II

    NASA Astrophysics Data System (ADS)

    Dołęga, Diana; Mikuli, Edward; Górska, Natalia; Inaba, Akira; Hołderna-Natkaniec, Krystyna; Nitek, Wojciech

    2013-08-01

    [Ru(NH3)6](ClO4)3 undergoes two phase transitions at: TC1=290.3 K and TC2=74.8 K , thus exhibits three crystalline phases in the temperature range of 5-310 K. For the detected phase transitions, thermal effects were determined. Fourier transform far- and middle-infrared spectra (FT-FIR and FT-MIR), recorded at 8-350 K, suggest that reorientational motions of the NH3 ligands are very fast (τR≈10-12 s above TC1) and are significantly slowed down below TC2. X-ray single crystal diffraction (XRSCD) measurements revealed that in the high temperature phase (above TC1) the compound belongs to the cubic Fm3barm (No. 225) space group, whereas in the intermediate phase the unit cell parameter doubles and the space group is Ia3bar(No. 206). 1H NMR studies revealed that the following reorientational motions are liberated during heating: three-fold reorientation of NH3 ligands, three-fold reorientation of the entire [Ru(NH3)6]3+ cation, and isotropic reorientation of this cation. In the high temperature phase I the cations perform isotropic reorientations with the estimated activation energy equal to ca. 30.1 kJ mol-1. Comparison with adequate results obtained earlier for [Ru(NH3)6](BF4)3 and for other similar compounds was made and general regularities were drawn.

  3. 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

    2016-07-01

    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.

  4. 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.

  5. Platinum complexes with one radiosensitizing ligand (PtCl2(NH3) (sensitizer)): radiosensitization and toxicity studies in vitro

    SciTech Connect

    Skov, K.A.; Farrell, N.P.; Adomat, H.

    1987-11-01

    Complexes of general formula (PtCl2(NH3)L) with one radiosensitizing ligand per platinum are compared with ligand L alone, complexes with two radiosensitizers per platinum (PtCl2L2), and their analogs with NH3 ligands, with respect to radiosensitizing properties and toxicity in CHO cells. Radiosensitizing ligands, L, were misonidazole, metronidazole, 4(5)-nitroimidazole, and 2-amino-5-nitrothiazole, and the ammine analogs were cis- and trans-DDP (diamminedichloroplatinum(II)) and the monoammine, K(PtCl3(NH3)). Results are related to a previous study on plasmid DNA binding by these series. The toxicity of the mono series (PtCl2(NH3)L), attributable to DNA binding, is much higher than the corresponding bis complexes, (PtCl2L2). For L = misonidazole, toxicity is similar to the monoammine, but higher in hypoxic than in aerobic cells. trans-(PtCl2(NH3)-(misonidazole)) is more toxic than the cis isomer. Except for L = 4(5)-nitroimidazole, the complexes (PtCl2(NH3)L) are more toxic than L in air and hypoxia. Hypoxic radiosensitization by the mono complexes is comparable to the monoammine and is not better than free sensitizers, again except for L = 4(5)-nitroimidazole. Significantly lower sensitization is observed in oxic cells. The bis complexes (PtCl2L2), which do not bind to DNA as well as the mono complexes, are less effective radiosensitizers and less toxic than the (PtCl2(NH3)L) series.

  6. An investigation of the desorption of hydrogen from lithium oxide using temperature programmed desorption and diffuse reflectance infrared spectroscopy

    SciTech Connect

    Kopasz, J.P.; Johnson, C.E.; Ortiz-Villafuerte, J.

    1995-04-01

    The addition of hydrogen to the purge stream has been shown to enhance tritium release from ceramic breeder materials; however, this added hydrogen can lead to increased costs in the tritium purification system. The objective of this work is to develop an understanding of the interactions between hydrogen and lithium oxide surfaces so that the authors can take full advantage of the observed enhancement of tritium release caused by hydrogen addition without incurring high costs in the tritium purification plant.

  7. On-road measurement of NH3 and N2O emissions from a Euro V heavy-duty vehicle

    NASA Astrophysics Data System (ADS)

    Suarez-Bertoa, Ricardo; Mendoza-Villafuerte, Pablo; Bonnel, Pierre; Lilova, Velizara; Hill, Leslie; Perujo, Adolfo; Astorga, Covadonga

    2016-08-01

    The use of selective catalytic reduction systems (SCR) to abate NOx vehicular emissions brings new concerns on the emissions of the byproducts NH3 and N2O. Therefore, NH3 and N2O on-road emissions from a Euro V truck equipped with a SCR were measured in real time using a QCL-IR. Results bring to light possibility to perform this kind of real time measurements for other pollutants besides, hydrocarbons, NOx, CO and CO2. The capability to measure NH3 and N2O in a second-by-second basis will allow applying the currently agreed regulatory emissions evaluation for gaseous compounds. Average N2O emission factors calculated applying the current PEMS-based data analysis to all available windows from the tests ranged from 0.063 g/kWh to 0.139 g/kWh. Average NH3 concentrations ranged from 0.9 ppm to 5.7 ppm. Although calculated average N2O and NH3 emissions were within current limits, NOx emissions were substantially higher than Euro V limits under the studied conditions.

  8. Modulated CH3NH3PbI3-xBrx film for efficient perovskite solar cells exceeding 18.

    PubMed

    Tu, Yongguang; Wu, Jihuai; Lan, Zhang; He, Xin; Dong, Jia; Jia, Jinbiao; Guo, Panfeng; Lin, Jianming; Huang, Miaoliang; Huang, Yunfang

    2017-03-17

    The organic-inorganic lead halide perovskite layer is a crucial factor for the high performance perovskite solar cell (PSC). We introduce CH3NH3Br in the precursor solution to prepare CH3NH3PbI3-xBrx hybrid perovskite, and an uniform perovskite layer with improved crystallinity and apparent grain contour is obtained, resulting in the significant improvement of photovoltaic performance of PSCs. The effects of CH3NH3Br on the perovskite morphology, crystallinity, absorption property, charge carrier dynamics and device characteristics are discussed, and the improvement of open circuit voltage of the device depended on Br doping is confirmed. Based on above, the device based on CH3NH3PbI2.86Br0.14 exhibits a champion power conversion efficiency (PCE) of 18.02%. This study represents an efficient method for high-performance perovskite solar cell by modulating CH3NH3PbI3-xBrx film.

  9. 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

    2015-11-05

    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.

  10. Novel Ce-W-Sb mixed oxide catalyst for selective catalytic reduction of NOx with NH3

    NASA Astrophysics Data System (ADS)

    Liu, Jun; Li, Guo-qiang; Zhang, Yong-fa; Liu, Xiao-qing; Wang, Ying; Li, Yuan

    2017-04-01

    A novel Ce3W2SbOx catalyst prepared by the co-precipitation method have been investigated for the selective catalysis reduction (SCR) of NOx with NH3. It was found that the Ce-W-Sb oxide catalyst exhibited an excellent conversion ratio of NOx and a high tolerance to H2O and SO2 in a wide operation temperature window. The catalysts were characterized by N2-adsorption, XRD, Raman, H2-TPR, NH3-TPD, XPS and DRIFTS. The results suggest that the strong interaction between Sb, W and Ce species not only enhances the redox property of the catalyst but also increases the surface acidity, thus promoting the adsorption and activation of NH3 species, which is favorable for high NH3-SCR performance. Based on in situ DRIFTS results, it was concluded that the Langmuir-Hinshelwood (L-H) mechanism existed at the temperature of below 300 °C, while at above 300 °C the Eley-Rideal (E-R) mechanism dominate the NH3-SCR reaction over the Ce3W2SbOx catalyst. Overall, these findings indicate that Ce3W2SbOx is promising for industrial applications.

  11. Electronic structure, stability, and formation dynamics of hypervalent molecular clusters: CH 3NH 3(CH 3NH 2) n

    NASA Astrophysics Data System (ADS)

    Okai, Nobuhiro; Takahata, Akihiro; Fuke, Kiyokazu

    2004-03-01

    The formation and decay processes of CH 3NH 3(CH 3NH 2) n produced by the photolysis of (CH 3NH 2) n are studied by a pump-probe technique with femtosecond laser. The dissociation time of CH 3NH 2 in clusters is estimated to be less than 500 fs, while the formation time of CH 3NH 3(CH 3NH 2) n is less than 2 ps in the photolysis at 200 nm. The lifetime of free CH 3NH 3 is determined to be 30 ps and is elongated by 10 5 times in clusters. The ionization potentials and the binding energies of these clusters are determined by photoionization threshold measurements. On the basis of these results, the formation and decay processes for these clusters are discussed.

  12. CH3NH3PbI3, A Potential Solar Cell Candidate: Structural and Spectroscopic Investigations.

    PubMed

    Nandi, Pronoy; Giri, Chandan; Joseph, Boby; Rath, S; Manju, U; Topwal, D

    2016-12-15

    Hybrid organic-inorganic metal halides of the type CH3NH3PbX3 have emerged as potential materials for photovoltaic applications. In this paper we discuss structural, electronic, and optical spectroscopy investigations performed on high quality single crystals of CH3NH3PbI3. Our results conclusively suggest that CH3NH3PbI3 crystallizes in centrosymmetric space group and the methylammonium moiety exhibits disordered packing at room temperature. Extracted values of the exciton binding energy, the electron-phonon coupling constant, and the schematic energy level diagram constructed from the emission broadening, Raman, and photoemission spectroscopy measurements clearly show the potential of this system in photovoltaic applications.

  13. A model of the gas-phase chemistry of boron nitride CVC from BCl3 and NH3

    SciTech Connect

    Allendorf, M.D.; Melius, C.F.; Osterheld, T.H.

    1995-12-01

    The kinetics of gas-phase reactions occurring during the CVD of boron nitride (BN) from BCl3 and NH3 are investigated using an elementary reaction mechanism whose rate constants were obtained from theoretical predictions and literature sources. Plug-flow calculations using this mechanism predict that unimolecular decomposition of BCl3 is not significant under typical CVD conditions, but that some NH3 decomposition may occur, especially for deposition occurring at atmospheric pressure. Reaction of BCl3 with NH3 is rapid under CVD conditions and yields species containing both boron and nitrogen. One of these compounds, Cl2BNH2, is predicted to be a key gas-phase precursor to BN.

  14. Phase Polymorphism, Molecular Motions and Structural Changes in [Cr(NH3)6](ClO4)3

    NASA Astrophysics Data System (ADS)

    Mikuli, Edward; Górska, Natalia; Wróbel, Stanisław; Ściesińskic, Jacek; Ściesińska, Ewa

    2007-04-01

    A phase transition in [Cr(NH3)6](ClO4)3 at Thc = 293.5 K (on heating) and Tcc = 293.0 K (on cooling) was determined by differential scanning calorimetry. The temperature dependences of the full width at half maximum of the bands connected with ρr(NH3)F1u and δd(ClO)E modes suggest that the discovered phase transition is not connected with drastic changes in the speed of reorientational motions of the NH3 ligands nor the ClO4 - anions. Temperature dependence of the FT-FIR spectra and the diffraction patterns show that the discovered phase transition is caused by a change in the crystal structure.

  15. Shape-Evolution Control of hybrid perovskite CH3NH3PbI3 crystals via solvothermal synthesis

    NASA Astrophysics Data System (ADS)

    Zhang, Baohua; Guo, Fuqiang; Yang, Lianhong; Jia, Xiuling; Liu, Bin; Xie, Zili; Chen, Dunjun; Lu, Hai; Zhang, Rong; Zheng, Youdou

    2017-02-01

    We systematically synthesized CH3NH3PbI3 crystals using solvothermal process, and the reaction conditions such as concentration of the precursor, temperature, time, and lead source have been comprehensively investigated to obtain shape-controlled CH3NH3PbI3 crystals. The results showed that the CH3NH3PbI3 crystals exhibit tetragonal phase and the crystals change from nanoparticles to hopper-faced cuboids. Photoluminescence spectra of the crystals obtained with different lead sources show a blue shift due to the presence of defects in the crystals, and the peak intensity is very sensitive to the lead sources. Moreover, impurities (undesirable byproducts and excess components like HI or CH3NH2) presented during crystal growth can result in hopper growth.

  16. 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.

  17. Effect of H2 and NH3 Adsorption on Electronic Transport Properties of SiC Nanowires: A DFT Analysis

    NASA Astrophysics Data System (ADS)

    Vasumathi, R.; Thayumanavan, A.; Sriram, S.

    2017-02-01

    Silicon carbide (SiC) nanowire structures with and without hydrogen (H2) and ammonia (NH3) molecules have been constructed and optimized using density functional theory to study their electronic and transport properties. The adsorption energies calculated for the SiC nanowire structures reveal that the adsorption process of H2 and NH3 molecules is endothermic in nature. Nonequilibrium Green's function transport theory is employed to study the electronic transport properties of the SiC nanowire devices with and without H2 and NH3 molecules. The voltage-current (V-I) characteristic shows negative differential resistance (NDR) behavior for all the SiC nanowire devices when bias voltage is applied. It is inferred that the NDR behavior is due to shift of quasibound states near the Fermi level because of the applied bias voltage. This observed NDR behavior may be useful for fabrication of nanoelectronic devices.

  18. Experimental and theoretical study of methyl-p-aminobenzoate/ammonia complexes. I. MAB(NH3)1

    NASA Astrophysics Data System (ADS)

    Fernández, J. A.; Longarte, A.; Unamuno, I.; Castaño, F.

    2000-11-01

    Methyl-p-aminobenzoate(NH3)1 complex, henceforth MAB(NH3)1, prepared in a pulsed supersonic expansion, has been examined by laser mass-selective spectroscopies and density functional theory calculations, aiming to ascertain its isomer number, structures, identification, ionization energies, and vibrational assignments. Resonance enhanced multiphoton ionization and hole burning spectra of the species in supersonic beams show two 000 transitions redshifted by -715 and -709 cm-1 from that of bare MAB band origin and are plausibly associated with two different isomers, whereas ab initio calculations indicate the likely existence of five stable isomer structures. Identification of the experimental isomer spectra with the calculated structures is reported and, in particular, several isomer vibrational bands are identified by contrast with the calculated modes. Properties and features of the MAB(NH3)1 are compared with those of the MAB/water complexes.

  19. 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.

  20. 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.

  1. DRIFT study of manganese/ titania-based catalysts for low-temperature selective catalytic reduction of NO with NH3.

    PubMed

    Wu, Zhongbiao; Jiang, Boqiong; Liu, Yue; Wang, Haiqiang; Jin, Ruiben

    2007-08-15

    Manganese oxides and iron-manganese oxides supported on TiO2 were prepared by the sol-gel method and used for low-temperature selective catalytic reduction (SCR) of NO with NH3. Base on the previous study, Mn(0.4)/ TiO2 and Fe(0.1)-Mn(0.4)/TiO2 were then selected to carry out the in situ diffuse reflectance infrared transform spectroscopy (DRIFT) investigation for revealing the reaction mechanism. The DRIFT spectroscopy for the adsorption of NH3 indicated the presence of coordinated NH3 and NH4+ on both of the two catalysts. When NO was introduced, the coordinated NH3 on the catalyst surface was consumed rapidly, indicating these species could react with NO effectively. When NH3 was introduced into the sample preadsorbed with NO + O2, SCR reaction would not proceed on Mn(0.4)/TiO2. However, for Fe(0.1)-Mn(0.4)/ TiO2 the bands due to coordinated NH3 on Fe2O3 were formed. Simultaneously, the bidentate nitrates were transformed to monodentate nitrates and NH4+ was detected. And NO2 from the oxidation of NO on catalyst could react with NH4+ leading to the reduction of NO. Therefore, it was suggested that the SCR reaction on Fe(0.1)-Mn(0.4)/TiO2 could also take place in a different way from the reactions on Mn(0.4)/TiO2 proposed by other researchers. Furthermore, the SCR reaction steps for these two kinds of catalysts were proposed.

  2. 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.

  3. Effects of SbBr3 addition to CH3NH3PbI3 solar cells

    NASA Astrophysics Data System (ADS)

    Oku, Takeo; Ohishi, Yuya; Suzuki, Atsushi

    2017-01-01

    TiO2/CH3NH3Pb1-xSbxI3-2xBr3x-based photovoltaic devices were fabricated, and effects of SbBr3 addition to CH3NH3PbI3 precursor solutions on the photovoltaic properties were investigated. The short-circuit current densities and photoconversion efficiencies were improved by adding a small amount of SbBr3 to the perovskite phase, which would be due to a doping effect of Sb or Br atoms at the Pb or I sites.

  4. 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

  5. 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.

  6. Molecular Structure and Dynamics in the Low Temperature (Orthorhombic) Phase of NH3BH3

    SciTech Connect

    Cho, Herman M.; Shaw, Wendy J.; Parvanov, Venci M.; Schenter, Gregory K.; Karkamkar, Abhijeet J.; Hess, Nancy J.; Mundy, Christopher J.; Kathmann, Shawn M.; Sears, Jesse A.; Lipton, Andrew S.; Ellis, Paul D.; Autrey, Thomas

    2008-05-08

    Variable temperature 2H NMR experiments on the orthorhombic phase of selectively deuterated NH3BH3 spanning the static to fast exchange limits of the borane and amine motions are reported. New values of the electric field gradient (EFG) tensor parameters have been obtained from the static 2H spectra of Vzz = 5.509(±0.275)×1014 statvolt/cm2 and ! = 0.00±0.05 for the borane hydrogens and Vzz = 9.615(±0.481)×1014 statvolt/cm2 and ! = 0.00±0.05 for the amine hydrogens. The molecular symmetry inferred from the observation of equal EFG tensors for both the boron and amine hydrogens is in sharp contrast with the Cs symmetry derived from diffraction studies. The origin of the apparent discrepancy has been investigated using molecular dynamics methods in combination with electronic structure calculations of NMR parameters, bond lengths, and bond angles. The computation of parameters from a statistical ensemble rather than from a single set of atomic Cartesian coordinates gives values that are in close quantitative agreement with the 2H NMR electric field gradient tensor measurements and are more consistent with the molecular symmetry revealed by the NMR spectra. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for DOE.

  7. 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.

  8. (Barely) solid Li(NH3)4: the electronics of an expanded metal.

    PubMed

    Zurek, Eva; Wen, Xiao-Dong; Hoffmann, Roald

    2011-03-16

    The highly expanded metal, lithium(0)tetraamine, and its electronic structure is as full of complexity and surprises as the lithium solutions in anhydrous ammonia from which it crystallizes at 90 K. Our theoretical studies of the Phase II, Z = 8, I43d structure of this material reveal that the molecular building block is an almost ideal tetrahedron, in agreement with recent experiments. Close in enthalpy at P = 1 atm, and consistent with the low melting point, are bcc and Cs-IV configurations. Under pressure, the I43d structure emerges as more stable than its alternatives. In this phase six relatively narrow bands, four of them occupied, separate from the conduction and valence bands. We trace these bands to pockets of electron density arising between sterically encumbered ammonias, six such pockets in the Z = 8 unit cell. The observed band structure can be explained by considering a Jortner-type model, where pseudoatoms are placed in these holes. The electride Li(NH(3))(4), while not a very good metal, is a unique material, by virtue of its low melting point.

  9. Performance Analysis of Rectifier in NH3-H2O Absorprtion Heat Pump

    NASA Astrophysics Data System (ADS)

    Tsujimori, Atsushi; Ozaki, Eiichi; Nakao, Kazushige

    Heat and mass transfer model for plate-type rectifier was presented in the previous paper and it was found that there existed the distribution of NH3 concentration in boundary layer in vapor and solution phase, which was the resistance to heat and mass transfer. In order to enhance heat and mass transfer, packed tower-type rectifiers have been considered effective and used in the field of chemical engineering. And many data have been accumulated for each rectification-packing with give fluid to design packed tower. But it has rarely be seen to present heat and mass transfer model in order to evaluate the performance of packed tower rectifier without any experimental constant. In this study heat and mass transfer model in packed tower-type rectifier was presented considering the specification of rectification-packing decided by surface area and porosity, and the calculation results were compared with experimental data. As a result it was found that over-all mass transfer coefficient increased as mass flow rate of vapor increased and that the model could expect over-all mass transfer coefficient within 30 [%] difference to experimental data. It was also cleared that mass transfer in packed-type rectifier was two to five times more enhanced than that in plate-type rectifier.

  10. Giant Rashba Splitting in CH3NH3PbBr3 Organic-Inorganic Perovskite

    NASA Astrophysics Data System (ADS)

    Niesner, Daniel; Wilhelm, Max; Levchuk, Ievgen; Osvet, Andres; Shrestha, Shreetu; Batentschuk, Miroslaw; Brabec, Christoph; Fauster, Thomas

    2016-09-01

    As they combine decent mobilities with extremely long carrier lifetimes, organic-inorganic perovskites open a whole new field in optoelectronics. Measurements of their underlying electronic structure, however, are still lacking. Using angle-resolved photoelectron spectroscopy, we measure the valence band dispersion of single-crystal CH3NH3PbBr3. The dispersion of the highest energy band is extracted applying a modified leading edge method, which accounts for the particular density of states of organic-inorganic perovskites. The surface Brillouin zone is consistent with bulk-terminated surfaces both in the low-temperature orthorhombic and the high-temperature cubic phase. In the low-temperature phase, we find a ring-shaped valence band maximum with a radius of 0.043 Å-1 , centered around a 0.16 eV deep local minimum in the dispersion of the valence band at the high-symmetry point. Intense circular dichroism is observed. This dispersion is the result of strong spin-orbit coupling. Spin-orbit coupling is also present in the room-temperature phase. The coupling strength is one of the largest ones reported so far.

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

    PubMed

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

    2015-04-07

    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.

  12. Orthogonal Coordinates and Hyperquantization Algorithm. The NH3 and H3O+ Umbrella Inversion Levels

    NASA Astrophysics Data System (ADS)

    Ragni, M.; Lombardi, A.; Pereira Barreto, P. R.; Peixoto Bitencourt, A. C.

    2009-09-01

    In order to describe the umbrella inversion mode, which is characteristic of AB3-type molecules, we have introduced an alternative hyperspherical coordinate set based on a parametrization of Radau-Smith orthogonal vectors and have considered constraints which allow us to enforce the C3v symmetry. Structural properties and electronic energies at equilibrium and barrier configurations have been obtained at MP2 and CCSD(T) levels of theory. Energy profiles have been calculated using the CCSD(T) method with an aug-cc-pVQZ basis set. The NH3 and H3O+ umbrella inversion levels are obtained by the hyperquantization algorithm for a one-dimensional calculation, using a specially defined hyperangle as the inversion coordinate. The results are compared with experimental and theoretical energy levels, in particular, with those obtained by calculations based on two-dimensional models. The emerging picture of the umbrella inversion based on this hyperangular coordinate compares favorably with respect to the usual valence-type description.

  13. Quadrupole splittings in the near-infrared spectrum of 14NH3

    DOE PAGES

    Twagirayezu, Sylvestre; Hall, Gregory E.; Sears, Trevor J.

    2016-10-13

    Sub-Doppler, saturation dip, spectra of lines in the v1 + v3, v1 + 2v4 and v3 + 2v4 bands of 14NH3 have been measured by frequency comb-referenced diode laser absorption spectroscopy. The observed spectral line widths are dominated by transit time broadening, and show resolved or partially-resolved hyperfine splittings that are primarily determined by the 14N quadrupole coupling. Modeling of the observed line shapes based on the known hyperfine level structure of the ground state of the molecule shows that, in nearly all cases, the excited state level has hyperfine splittings similar to the same rotational level in the groundmore » state. The data provide accurate frequencies for the line positions and easily separate lines overlapped in Doppler-limited spectra. The observed hyperfine splittings can be used to make and confirm rotational assignments and ground state combination differences obtained from the measured frequencies are comparable in accuracy to those obtained from conventional microwave spectroscopy. Furthermore, several of the measured transitions do not show the quadrupole hyperfine splittings expected based on their existing rotational assignments. Either the assignments are incorrect or the upper levels involved are perturbed in a way that affects the nuclear hyperfine structure.« less

  14. Computed and Experimental Absorption Spectra of the Perovskite CH3NH3PbI3.

    PubMed

    Zhu, Xi; Su, Haibin; Marcus, Rudolph A; Michel-Beyerle, Maria E

    2014-09-04

    Electronic structure and light absorption properties of the perovskite CH3NH3PbI3 are investigated by relativistic density functional theory with quasiparticle GW corrections and many-body interactions. The nature of the Wannier exciton is studied by solving the Bethe-Salpeter equation augmented with the analysis of a conceptual hydrogen-like model. The computed absorption spectrum unravels a remarkable absorption "gap" between the first two absorption peaks. This discontinuity is maintained in the calculated tetragonal structure that, however, is not stable at low temperature. Most importantly, the discontinuity is also observed in the experimental absorption spectrum of the orthorhombic single crystal at low temperature (4 K). However, in contrast to the single crystal, in a polycrystalline perovskite film at 5 K the "gap" is filled by a monotonously increasing absorption throughout the visible range. This feature of thin films points to the potential significance of defect absorption for the excellent light harvesting properties of perovskite-based solar cells.

  15. Ferroelectricity of CH3NH3PbI3 Perovskite.

    PubMed

    Fan, Zhen; Xiao, Juanxiu; Sun, Kuan; Chen, Lei; Hu, Yating; Ouyang, Jianyong; Ong, Khuong P; Zeng, Kaiyang; Wang, John

    2015-04-02

    Ferroelectricity has been believed to be an important but controversial origin of the excellent photovoltaic performance of organometal trihalide perovskites (OTPs). Here we investigate the ferroelectricity of a prototype OTP, CH3NH3PbI3 (MAPbI3), both theoretically and experimentally. Our first-principles calculations based on 3-D periodic boundary conditions reveal that a ferroelectric structure with polarization of ∼8 μC/cm(2) is the globally stable one among all possible tetragonal structures; however, experimentally no room-temperature ferroelectricity is observed by using polarization-electric field hysteresis measurements and piezoresponse force microscopy. The discrepancy between our theoretical and experimental results is attributed to the dynamic orientational disorder of MA(+) groups and the semiconducting nature of MAPbI3 at room temperature. Therefore, we conclude that MAPbI3 is not ferroelectric at room temperature; however, it is possible to induce and experimentally observe apparent ferroelectric behavior through our proposed ways. Our results clarify the controversy of the ferroelectricity in MAPbI3 and also provide valuable guidance for future studies on this active topic.

  16. Analogues of Cis- and Transplatin with a Rich Solution Chemistry: cis-[PtCl2 (NH3 )(1-MeC-N3)] and trans-[PtI2 (NH3 )(1-MeC-N3)].

    PubMed

    Siebel, Sabine; Dammann, Claudia; Sanz Miguel, Pablo J; Drewello, Thomas; Kampf, Gunnar; Teubner, Natascha; Bednarski, Patrick J; Freisinger, Eva; Lippert, Bernhard

    2015-12-01

    Mono(nucleobase) complexes of the general composition cis-[PtCl2 (NH3 )L] with L=1-methylcytosine, 1-MeC (1 a) and L=1-ethyl-5-methylcytosine, as well as trans-[PtX2 (NH3 )(1-MeC)] with X=I (5 a) and X=Br (5 b) have been isolated and were characterized by X-ray crystallography. The Pt coordination occurs through the N3 atom of the cytosine in all cases. The diaqua complexes of compounds 1 a and 5 a, cis-[Pt(H2 O)2 (NH3 )(1-MeC)](2+) and trans-[Pt(H2 O)2 (NH3 )(1-MeC)](2+) , display a rich chemistry in aqueous solution, which is dominated by extensive condensation reactions leading to μ-OH- and μ-(1-MeC(-) -N3,N4)-bridged species and ready oxidation of Pt to mixed-valence state complexes as well as diplatinum(III) compounds, one of which was characterized by X-ray crystallography: h,t-[{Pt(NH3 )2 (OH)(1-MeC(-) -N3,N4)}2 ](NO3 )2 ⋅2 [NH4 ](NO3 )⋅2 H2 O. A combination of (1) H NMR spectroscopy and ESI mass spectrometry was applied to identify some of the various species present in solution and the gas phase, respectively. As it turned out, mass spectrometry did not permit an unambiguous assignment of the structures of +1 cations due to the possibilities of realizing multiple bridging patterns in isomeric species, the occurrence of different tautomers, and uncertainties regarding the Pt oxidation states. Additionally, compound 1 a was found to have selective and moderate antiproliferative activity for a human cervix cancer line (SISO) compared to six other human cancer cell lines.

  17. Highly selective NH3 gas sensor based on Au loaded ZnO nanostructures prepared using microwave-assisted method.

    PubMed

    Shingange, K; Tshabalala, Z P; Ntwaeaborwa, O M; Motaung, D E; Mhlongo, G H

    2016-10-01

    ZnO nanorods synthesized using microwave-assisted approach were functionalized with gold (Au) nanoparticles. The Au coverage on the surface of the functionalized ZnO was controlled by adjusting the concentration of the Au precursor. According to X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) results, it was confirmed that Au form nanoparticles loaded on the surface of ZnO. The small Au loading level of 0.5wt% showed the highest response of 1600-100ppm of NH3 gas at room temperature (RT) whereas further increase of Au loading level resulted in poor detection of NH3. All Au loaded ZnO (Au/ZnO) based sensors exhibited very short recovery and response times compared to unloaded ZnO sensing materials. The responses of ZnO and Au/ZnO based sensors (0.5-2.5wt%) to other flammable gases, including H2, CO and CH4, were considerably less, demonstrating that Au/ZnO based sensors were highly selective to NH3 gas at room temperature. Spill over mechanism which is the main reason for the observed enhanced NH3 response with 0.5 Au loading level is explained in detail.

  18. Fe2O3 particles as superior catalysts for low temperature selective catalytic reduction of NO with NH3.

    PubMed

    Wang, Xiaobo; Gui, Keting

    2013-12-01

    Fe2O3 particle catalysts were experimentally studied in the low temperature selective catalytic reduction (SCR) of NO with NH3. The effects of reaction temperature, oxygen concentration, [NH3]/[NO] molar ratio and residence time on SCR activity were studied. It was found that Fe2O3 catalysts had high activity for the SCR of NO with NH3 in a broad temperature range of 150-270 degrees C, and more than 95% NO conversion was obtained at 180 degrees C when the molar ratio [NH3]/[NO] = 1, the residence time was 0.48 seconds and O2 volume fraction was 3%. In addition, the effect of SO2 on SCR catalytic activity was also investigated at the temperature of 180 degrees C. The results showed that deactivation of the Fe2O3 particles occurred due to the presence of SO2 and the NO conversion decreased from 99.2% to 58% in 240 min, since SO2 gradually decreased the catalytic activity of the catalysts. In addition, X-ray diffraction, Thermogravimetric analysis and Fourier transform infrared spectroscopy were used to characterize the fresh and deactivated Fe2O3 catalysts. The results showed that the deactivation caused by SO2 was due to the formation of metal sulfates and ammonium sulfates on the catalyst surface during the de-NO reaction, which could cause pore plugging and result in suppression of the catalytic activity.

  19. Low temperature selective catalytic reduction (SCR) of NO with NH3 over Fe-Mn based catalysts.

    PubMed

    Long, Richard Q; Yang, Ralph T; Chang, Ramsay

    2002-03-07

    Fe-Mn based transition metal oxides (Fe-Mn, Fe-Mn-Zr and Fe-Mn-Ti) show nearly 100% NO conversion at 100-180 degrees C for selective catalytic reduction of NO with NH3 under the applied conditions with a space velocity of 15,000 h-1.

  20. 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

    2015-02-07

    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.

  1. Acute toxicity of ammonia (NH3-N) in sewage effluent to Chironomus riparius: II. Using a generalized linear model

    USGS Publications Warehouse

    Monda, D.P.; Galat, D.L.; Finger, S.E.; Kaiser, M.S.

    1995-01-01

    Toxicity of un-ionized ammonia (NH3-N) to the midge, Chironomus riparius was compared, using laboratory culture (well) water and sewage effluent (≈0.4 mg/L NH3-N) in two 96-h, static-renewal toxicity experiments. A generalized linear model was used for data analysis. For the first and second experiments, respectively, LC50 values were 9.4 mg/L (Test 1A) and 6.6 mg/L (Test 2A) for ammonia in well water, and 7.8 mg/L (Test 1B) and 4.1 mg/L (Test 2B) for ammonia in sewage effluent. Slopes of dose-response curves for Tests 1A and 2A were equal, but mortality occurred at lower NH3-N concentrations in Test 2A (unequal intercepts). Response ofC. riparius to NH3 in effluent was not consistent; dose-response curves for tests 1B and 2B differed in slope and intercept. Nevertheless, C. riparius was more sensitive to ammonia in effluent than in well water in both experiments, indicating a synergistic effect of ammonia in sewage effluent. These results demonstrate the advantages of analyzing the organisms entire range of response, as opposed to generating LC50 values, which represent only one point on the dose-response curve.

  2. Post-Cleaning Effect on a HfO2 Gate Stack Using a NF3/NH3 Plasma.

    PubMed

    Lee, Min-Seon; Oh, Hoon-Jung; Lee, Joo-Hee; Lee, In-Geun; Shin, Woo-Gon; Kim, Kyu-Dong; Park, Jin-Gu; Ko, Dae-Hong

    2016-05-01

    The effects of dry cleaning of a HfO2 gate stack using NF3 only and a NF3/NH3 gas mixture plasma were investigated. The plasma dry cleaning process was carried out after HfO2 deposition using an indirect down-flow capacitively coupled plasma (CCP) system. An analysis of the chemical composition of the HfO2 gate stacks by XPS indicated that fluorine was incorporated into the HfO2 films during the plasma dry cleaning. Significant changes in the HfO2 chemical composition were observed as a result of the NF3 dry cleaning, while they were not observed in this case of NF3/NH3 dry cleaning. TEM results showed that the interfacial layer (IL) between the HfO2 and Si thickness was increased by the plasma dry cleaning. However, in the case of NF3/NH3 dry cleaning using 150 W, the IL thickness was suppressed significantly compared to the sample that had not been dry cleaned. Its electrical properties were also improved, including the low gate leakage currents, and reduced EOT. Finally, the finding show that the IL thickness of the HfO2 gate stack can be controlled by using the novel NF3/NH3 dry cleaning process technique without any the significant changes in chemical composition and metal-oxide-semiconductor (MOS) capacitor characteristics.

  3. 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.

  4. Light stability tests of CH3NH3PbI3 perovskite solar cells using porous carbon counter electrodes.

    PubMed

    Ito, Seigo; Mizuta, Gai; Kanaya, Shusaku; Kanda, Hiroyuki; Nishina, Tomoya; Nakashima, Seiji; Fujisawa, Hironori; Shimizu, Masaru; Haruyama, Yuichi; Nishino, Hitoshi

    2016-10-21

    The CH3NH3PbI3 perovskite solar cells have been fabricated using three-porous-layered electrodes as, 〈glass/F-doped tin oxide (FTO)/dense TiO2/porous TiO2-perovskite/porous ZrO2-perovskite/porous carbon-perovskite〉 for light stability tests. Without encapsulation in air, the CH3NH3PbI3 perovskite solar cells maintained 80% of photoenergy conversion efficiency from the initial value up to 100 h under light irradiation (AM 1.5, 100 mW cm(-2)). Considering the color variation of the CH3NH3PbI3 perovskite layer, the significant improvement of light stability is due to the moisture-blocking effect of the porous carbon back electrodes. The strong interaction between carbon and CH3NH3PbI3 perovskite was proposed by the measurements of X-ray photoelectron spectroscopy and X-ray diffraction of the porous carbon-perovskite layers.

  5. Emergence of superconductivity in (NH3)yMxMoSe2 (M: Li, Na and K)

    PubMed Central

    Miao, Xiao; Nishiyama, Saki; Zheng, Lu; Goto, Hidenori; Eguchi, Ritsuko; Ota, Hiromi; Kambe, Takashi; Terashima, Kensei; Yokoya, Takayoshi; Nguyen, Huyen T. L.; Kagayama, Tomoko; Hirao, Naohisa; Ohishi, Yasuo; Ishii, Hirofumi; Liao, Yen-Fa; Kubozono, Yoshihiro

    2016-01-01

    We report syntheses of new superconducting metal-doped MoSe2 materials (MxMoSe2). The superconducting MxMoSe2 samples were prepared using a liquid NH3 technique, and can be represented as ‘(NH3)yMxMoSe2’. The Tcs of these materials were approximately 5.0 K, independent of x and the specific metal atom. X-ray diffraction patterns of (NH3)yNaxMoSe2 were recorded using polycrystalline powders. An increase in lattice constant c showed that the Na atom was intercalated between MoSe2 layers. The x-independence of c was observed in (NH3)yNaxMoSe2, indicating the formation of a stoichiometric compound in the entire x range, which is consistent with the x-independence of Tc. A metallic edge of the Fermi level was observed in the photoemission spectrum at 30 K, demonstrating its metallic character in the normal state. Doping of MoSe2 with Li and K also yielded superconductivity. Thus, MoSe2 is a promising material for designing new superconductors, as are other transition metal dichalcogenides. PMID:27404919

  6. Effect of Morphology Control of Light Absorbing Layer on CH3NH3PbI3 Perovskite Solar Cells.

    PubMed

    Lei, Binglong; Eze, Vincent Obiozo; Mori, Tatsuo

    2016-04-01

    As one of the most significant components of perovskite solar cells, the perovskite light absorbing layer demands high quality to guarantee extraordinary power conversion efficiency (PCE). We have fabricated series of CH3NH3PbI3 perovskite solar cells by virtue of gas-flowing assisting (GFA), spin coating twice for the Pbl2 layer and dipping the semi-samples in a thermal CH3NH3I solution, by which some undesirable perovskite morphologies can be effectively avoided. The modified conductions have also dramatically improved the perovskite layer and elevated the coverage ratio from 53.6% to 79.5%. All the fabrication processes, except the steps for deposition of the hole transport material (HTM) and back gold electrode, have been conducted in air and an average PCE of 6.6% has been achieved by initiatively applying N,N'-bis(1-naphtyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD) doped by MoO3 as HTM. The CH3NH3PbI3 perovskite's morphology and its coverage ratio to the underneath TiO2 mesoporic layer are evaluated to account for the cells' performance. It has demonstrated that higher homogeneity and coverage ratio of the CH3NH3PbI3 layer have most significantly contributed to the solar cells' light conversion efficiency. Keywords: Perovskite, Solar Cell, Morphology, Coverage Ratio, Hole Transport Material.

  7. 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.

  8. How are CH3OH, HNC/HCN, and NH3 Formed in the Interstellar Medium?

    NASA Astrophysics Data System (ADS)

    Hiraoka, Kenzo; Mochizuki, Noritaka; Wada, Akira

    2006-09-01

    Simulation experiments for the formation of CH3OH, HNC/HCN, and NH3 in solid-phase reactions were performed. CH3OH and H2CO were formed as major products from the 100 eV electron-irradiated mixed CH4/H2O solid at 10 K. There found to be two pathways for the formation of methanol with about equal importance, i.e., the recombination reaction: CH3 + OH --> CH3OH, and the insertion reaction: CH2+H2O --> CH3OH. One CH3OH molecule was formed per 60 electron irradiation with the electron energy of 100 eV. By using mixed H2O/CD4 ice, it was confirmed that formaldehyde was formed by the insertion reaction, C + H2O -->H2CO. A mixed gas of N2/HCN (50/1) at a few Torr was activated by a dc discharge and was deposited on the gold-plated copper substrate at 10, 15, and 20 K. During the deposition of plasma-activated sample gas, D atoms produced by the dc discharge of D2 were simultaneously sprayed over the solid film. The association reactions of CN with D at 10 K were found to generate DNC and DCN with the intensity ratio DNC/DCN of about 3 in the infrared absorption spectra. This high ratio is in line with the high abundance ratios of HNC/HCN observed in the dark clouds. The formation of DNC and DCN became negligible at 20 K, due to the decrease of the sticking probability of D atoms on the solid surface. Ammonia was not detected as a reaction product from reaction of D with N atoms trapped in the N2 matrix.

  9. 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.

  10. Characterization of Cu-SSZ-13 NH3 SCR catalysts: an in situ FTIR study.

    PubMed

    Szanyi, János; Kwak, Ja Hun; Zhu, Haiyang; Peden, Charles H F

    2013-02-21

    The adsorption of CO and NO over Cu-SSZ-13 zeolite catalysts, highly active in the selective catalytic reduction of NO(x) with NH(3), 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). Under low CO pressures and at room temperature (295 K), CO forms monocarbonyls exclusively on the Cu(+) ions, while in the presence of gas phase CO dicarbonyls on Cu(+) and adsorbed CO on Cu(2+) 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 Cu(2+) centers, and NO(+) species located in charge compensating cationic positions of the chabasite framework. On the reduced Cu-SSZ-13 samples the formation of N(2)O was also detected. The assignment of the adsorbed NO(x) species was aided by adsorption experiments with isotopically labeled (15)NO. 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 H(2)O) 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 general 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.

  11. Hyperfine Splittings in the Near-Infrared Spectrum of 14NH_3

    NASA Astrophysics Data System (ADS)

    Twagirayezu, Sylvestre; Sears, Trevor; Hall, Gregory

    2016-06-01

    Sub-Doppler, saturation dip, measurements of transitions in the ν_1 + ν_3 band of 14NH_3 have been made by frequency comb-referenced diode laser absorption spectroscopy. The observed spectra exhibit either resolved or partially-resolved hyperfine splittings that are primarily determined by the 14N quadrupole coupling in the molecule. Modeling of the line shapes based on the known hyperfine level structure of the ground state of the molecule shows that, in nearly all cases, the upper state level has splittings similar to that of the same rotational level in the ground state. The data provide accurate frequencies for the line positions and the observed hyperfine splittings can be used to make or confirm rotational assignments. Of all the measurements, one transition, pP(5,4)_a at 195 994.73457 GHz, exhibits hyperfine structure which does not conform to that expected based on extrapolation from the known lower state hyperfine splittings. Examination of the known vibration-rotation level structure near the upper state energy shows that there exists a near degeneracy between this level and one in the ν_1 + 2ν_4 manifold which is of the appropriate symmetry to be mixed by magnetic hyperfine terms that couple ortho- and para- modifications of the molecule. It is possible that the unusual hyperfine splittings are a consequence of ortho-paro mixing, which has been predicted, but not previously seen in ammonia and further experimental measurements to investigate this possibility are ongoing. Acknowledgments: Work at Brookhaven National Laboratory was carried out under Contract No. DE-SC0012704 with the U.S. Department of Energy, Office of Science, and supported by its Division of Chemical Sciences, Geosciences and Biosciences within the Office of Basic Energy Sciences.

  12. 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.

  13. Evaluation of a plant material-based air purifier for removing H2S, NH3 and swine manure odour.

    PubMed

    Zhou, Xuezhi; Zhang, Qiang; Huang, Anhong

    2012-12-01

    A plant material-based air purifier (PMAP) was evaluated for odour removal. Laboratory tests were performed using two identical chambers: one treated by PMAP, and one as the control. Swine manure, hydrogen sulphide (H2S) and ammonia (NH3) were tested as odour sources. The test was also conducted in a swine barn. Air samples were taken from test chambers and two rooms in the pig barn and analysed for H2S, NH3 and odour concentrations. When treated with PMAP, the H2S concentration in the sealed chamber was subject to exponential decay, with the decay constant ranging from 0.59 to 0.70 l/h. The H2S concentration was reduced from 20 to 3 ppm in 3 h and to 0.2 ppm in 7h for H2S produced by chemical reaction, and from 0.4 to 0.02 ppm in 3 h for swine manure as the odour source. When an equal amount of ammonia solution was placed in the two test chambers, the NH3 concentration reached a peak value of 25 ppm in the chamber treated by PMAP, and 43 ppm in the control. The NH3 concentration in the treated chamber was reduced to 5 ppm in 3.5 h but stayed at 37 ppm in the control. The PMAP reduced the NH3 concentration from 38 to 10 ppm when swine manure was used as the odour source. The PMAP was capable of reducing swine odour in both laboratory and in-barn conditions. The reduction rate was at least 50%. The results from this research indicate the plant-based materials provide an alternative, environmentally friendly way for odour control. It is also shown that the mode of odour reduction by the PMAP was the removal of odour compounds, in contrast to odour masking, which occurs for most plant materials that have been used for odour control.

  14. 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.

  15. DNA interactions of new cytotoxic tetrafunctional dinuclear platinum complex trans,trans-[{PtCl2(NH3)}2(piperazine)].

    PubMed

    Brabec, Viktor; Christofis, Petros; Slámová, Martina; Kostrhunová, Hana; Nováková, Olga; Najajreh, Yousef; Gibson, Dan; Kaspárková, Jana

    2007-06-15

    A new tetrafunctional dinuclear platinum complex trans,trans-[{PtCl2(NH3)}2(piperazine)] with sterically rigid linking group was designed, synthesized and characterized. In this novel molecule, the DNA-binding features of two classes of the platinum compounds with proven antitumor activity are combined, namely trans oriented bifunctional mononuclear platinum complexes with a heterocyclic ligand and polynuclear platinum complexes. DNA-binding mode of this new complex was analyzed by various methods of molecular biology and biophysics. The complex coordinates DNA in a unique way and interstrand and intrastrand cross-links are the predominant lesions formed in DNA in cell-free media and in absence of proteins. An intriguing aspect of trans,trans-[{PtCl2(NH3)}2(piperazine)] is that, using a semi-rigid linker, interstrand cross-linking is diminished relative to other dinuclear platinum complexes with flexible linking groups and lesions that span several base pairs, such as tri- and tetrafunctional adducts, become unlikely. In addition, in contrast to the inability of trans,trans-[{PtCl2(NH3)}2(piperazine)] to cross-link two DNA duplexes, the results of the present work convincingly demonstrate that this dinuclear platinum complex forms specific DNA lesions which can efficiently cross-link proteins to DNA. The results substantiate the view that trans,trans-[{PtCl2(NH3)}2(piperazine)] or its analogues could be used as a tool for studies of DNA properties and their interactions or as a potential antitumor agent. The latter view is also corroborated by the observation that trans,trans-[{PtCl2(NH3)}2(piperazine)] is a more effective cytotoxic agent than cisplatin against human tumor ovarian cell lines.

  16. 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.

  17. Effect of the intermolecular hydrogen bond conformation on the structure and reactivity of the p-cresol(H2O)(NH3) van der Waals complex.

    PubMed

    Oldani, Andrés N; Ferrero, Juan C; Pino, Gustavo A

    2009-11-28

    The structure and reactivity of p-CrOH(NH(3))(2) and p-CrOH(H(2)O)(NH(3)) complexes were studied using mass-resolved one-colour resonance-enhanced multi-photon ionization and laser-induced fluorescence (LIF) spectroscopy together with DFT calculations. At the excitation energy of this work, the S(1) state of p-CrOH(NH(3))(2) shows a sub-nanosecond lifetime, as determined by time-resolved LIF spectra, as a consequence of a hydrogen transfer process that results in NH(4)(NH(3)) as a reaction product. Substitution of NH(3) by H(2)O closes the reaction channel as evidenced by the absence of excited-state hydrogen transfer (ESHT) reaction products, (H(3)O(NH(3)) or NH(4)(H(2)O)) and results in a dramatic effect on the S(1) lifetime of the p-CrOH(H(2)O)(NH(3)) complex which rises to (12 +/- 2) ns. According to density functional theory calculations, the most stable isomer of the p-CrOH(H(2)O)(NH(3)) complex is a cyclic structure, in which H(2)O acts as the H acceptor of the phenolic OH group (c-OH-H(2)O-NH(3)). However, the ESHT process is energetically disallowed upon electronic excitation.

  18. 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.

  19. 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.

  20. Crystal structure of [Ag(NH3)3]2[Ag(NH3)2]2[SnF6]F2, a compound showing argentophilic inter­actions

    PubMed Central

    Kraus, Florian; Fichtl, Matthias; Baer, Sebastian

    2016-01-01

    Bis[triamminesilver(I)] bis­[diamminesilver(I)] hexa­fluorido­stannate(IV) difluoride, [Ag(NH3)3]2[Ag(NH3)2]2[SnF6]F2, was obtained in the form of colourless crystals from the reaction of CsAgSnF7 in anhydrous ammonia. Two different ammine complexes of silver(I) are present in the structure, i.e. a linear diammine and a T-shaped triammine complex. The ammine silver(I) complexes show Ag⋯Ag distances in the range of argentophilic inter­actions. In the crystal, several N—H⋯F hydrogen bonds are present between the complex cations and the SbF6 − and F− anions, leading to the formation of a three-dimensional network. PMID:27980850

  1. Eddy covariance measurements of NH3 fluxes over a natural grass land with an open-path quantum cascade laser-based sensor

    NASA Astrophysics Data System (ADS)

    Pan, D.; Benedict, K. B.; Ham, J. M.; Prenni, A. J.; Schichtel, B. A.; Collett, J. L., Jr.; Zondlo, M. A.

    2015-12-01

    NH3 is an important component of the bio-atmospheric N cycle with implications for regional air quality, human and ecosystem health degradation, and global climate change. However, measuring NH3 flux is challenging, requiring a sensor with high sensitivity (sub-ppbv), fast response time and the capability to account for NH3 adsorption effects. In this study, we address these issues with an open-path quantum-cascade-based sensor for eddy covariance (EC) measurements. Previously, our EC NH3 sensor was deployed over a feedlot in Colorado in 2013 and 2014, and the results showed the potential of the sensor to measure NH3 emissions from agricultural sources. In the summer of 2015, the sensor was installed at a remote monitoring site in Rocky Mountain National Park to measure NH3 flux over a natural grass land. During the deployment, the precision of the sensor was about 0.15 ppbv at 10 Hz, and the detection limit of the flux was estimated to be 0.7±0.5 ng NH3/s/m2. The cospectra of the NH3 flux closely resembled those of CO2 flux and sensible heat flux measured by a LI-7500 CO2 analyzer and a CSAT3 sonic anemometer. The ogive analyses indicated that the loss of NH3 fluxes due to various damping effects was about 15%. Examining initial results from a few days of measurement, the measured NH3 fluxes appear to have a strong diurnal pattern with local emissions during afternoon, a pattern not previously reported for remote grass land. The pattern is consistent with background NH3 concentration measured by PICARRO NH3 analyzer, although summertime afternoon concentration increases at the site have previously been associated with upslope transport from urban and agricultural regions to the east. The results demonstrate the sensor's capability to measure NH3 flux in low NH3 conditions and also show that more measurements are needed to investigate spatial and temporal variability of NH3 flux.

  2. Desorption Kinetics of Ar, Kr, Xe, N2, O2, CO, Methane, Ethane, and Propane from Graphene and Amorphous Solid Water Surfaces

    SciTech Connect

    Smith, R. Scott; May, Robert A.; Kay, Bruce D.

    2016-03-03

    The desorption kinetics for Ar, Kr, Xe, N2, O2, CO, methane, ethane, and propane from grapheme 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 multi- layer 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 non-alignment 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.

  3. CH3NH3PbCl3 Single Crystals: Inverse Temperature Crystallization and Visible-Blind UV-Photodetector.

    PubMed

    Maculan, Giacomo; Sheikh, Arif D; Abdelhady, Ahmed L; Saidaminov, Makhsud I; Haque, Md Azimul; Murali, Banavoth; Alarousu, Erkki; Mohammed, Omar F; Wu, Tom; Bakr, Osman M

    2015-10-01

    Single crystals of hybrid perovskites have shown remarkably improved physical properties compared to their polycrystalline film counterparts, underscoring their importance in the further development of advanced semiconductor devices. Here we present a new method of growing sizable CH3NH3PbCl3 single crystals based on the retrograde solubility behavior of hybrid perovskites. We show, for the first time, the energy band structure, charge recombination, and transport properties of CH3NH3PbCl3 single crystals. These crystals exhibit trap-state density, charge carrier concentration, mobility, and diffusion length comparable with the best quality crystals of methylammonium lead iodide or bromide perovskites reported so far. The high quality of the crystal along with its suitable optical band gap enabled us to build an efficient visible-blind UV-photodetector, demonstrating its potential in optoelectronic applications.

  4. Photocarrier recombination dynamics in perovskite CH3NH3PbI3 for solar cell applications.

    PubMed

    Yamada, Yasuhiro; Nakamura, Toru; Endo, Masaru; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

    2014-08-20

    Using time-resolved photoluminescence and transient absorption measurements at room temperature, we report excitation-intensity-dependent photocarrier recombination processes in thin films made from the organo-metal halide perovskite semiconductor CH3NH3PbI3 for solar-cell applications. The photocarrier dynamics are well described by a simple rate equation including single-carrier trapping and electron-hole radiative recombination. This result provides clear evidence that the free-carrier model is better than the exciton model for interpreting the optical properties of CH3NH3PbI3. The observed large two-carrier recombination rate suggests the promising potential of perovskite semiconductors for optoelectronic device applications. Our findings provide the information about the dynamical behaviors of photoexcited carriers that is needed for developing high-efficiency perovskite solar cells.

  5. Structural and Thermal Disorder of Solution-Processed CH3NH3PbBr3 Hybrid Perovskite Thin Films.

    PubMed

    Wolf, Christoph; Kim, Joo-Sung; Lee, Tae-Woo

    2017-03-29

    We extracted the electronic disorder energy of the organic-inorganic lead-halide hybrid perovskite CH3NH3PbBr3 from temperature-dependent absorption data. We showed that the disorder at room temperature is ∼30 meV and is due to strong electron-phonon coupling with the longitudinal-optical mode of energy 16 meV. This mode can be attributed to longitudinal-optical phonons of the inorganic PbBr6 frame; this conclusion highlights the polaronic nature of electronic excitations in CH3NH3PbBr3. We showed that structural disorder is of the same impact as thermal disorder. A temperature-dependence of the exciton binding energy was observed close to the orthorhombic-to-tetragonal phase-transition temperature.

  6. Parameters for Estimation of Casualties from Ammonia (NH3), Tabun (GA), Soman (GD),Cyclosarin (GF) and Lewisite (L)

    DTIC Science & Technology

    2015-09-01

    obstruction, respiratory distress, and pulmonary edema .65 Exposure to a mas- sive concentration of NH3 gas may be fatal within minutes, and asphyxiation may...occur after exposure in poorly ventilated or enclosed spaces. Findings in fatal cases include extensive edema , full-thickness burns to the entire...include an elevated pulse and blood pressure, bradycardia, cardiac arrest, cyanosis, hemorrhagic necrosis of the liver, cerebral edema , seizures, and

  7. A Guided-Ion Beam Study of the O+(4S) + NH3 System at Hyperthermal Energies

    DTIC Science & Technology

    2008-07-14

    higher Ej, is typical of exothermic- charge transfer in polyatomic systems. In either case, however, there are coincident ions , namely OH+ and D20...REPRINT 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE A Guided- Ion Beam Study of the 0+(4S) + NH3 System at Hyperthermal Energies 5a. CONTRACT...from near-thermal to approximately 15 eV, using the guided- ion beam (GIB) method. Measurements were also performed using ammonia-^ to aid in mass

  8. 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

  9. Solvent-Mediated Crystallization of CH3NH3SnI3 Films for Heterojunction Depleted Perovskite Solar Cells.

    PubMed

    Hao, Feng; Stoumpos, Constantinos C; Guo, Peijun; Zhou, Nanjia; Marks, Tobin J; Chang, Robert P H; Kanatzidis, Mercouri G

    2015-09-09

    Organo-lead halide perovskite solar cells have gained enormous significance and have now achieved power conversion efficiencies of ∼20%. However, the potential toxicity of lead in these systems raises environmental concerns for widespread deployment. Here we investigate solvent effects on the crystallization of the lead-free methylammonium tin triiodide (CH3NH3SnI3) perovskite films in a solution growth process. Highly uniform, pinhole-free perovskite films are obtained from a dimethyl sulfoxide (DMSO) solution via a transitional SnI2·3DMSO intermediate phase. This high-quality perovskite film enables the realization of heterojunction depleted solar cells based on mesoporous TiO2 layer but in the absence of any hole-transporting material with an unprecedented photocurrent up to 21 mA cm(-2). Charge extraction and transient photovoltage decay measurements reveal high carrier densities in the CH3NH3SnI3 perovskite device which are one order of magnitude larger than CH3NH3PbI3-based devices but with comparable recombination lifetimes in both devices. The relatively high background dark carrier density of the Sn-based perovskite is responsible for the lower photovoltaic efficiency in comparison to the Pb-based analogues. These results provide important progress toward achieving improved perovskite morphology control in realizing solution-processed highly efficient lead-free perovskite solar cells.

  10. Photodissociation and ab initio studies of Mg+(NH3)n, n=1-4: Electronic structure and photoinduced reaction

    NASA Astrophysics Data System (ADS)

    Yoshida, Shinji; Daigoku, Kota; Okai, Nobuhiro; Takahata, Akihiro; Sabu, Akiyoshi; Hashimoto, Kenro; Fuke, Kiyokazu

    2002-11-01

    Photodissociation spectra of Mg+(NH3)n (n=1-4) cluster ions are examined in the wavelength region of 240-1200 nm. From the comparison with the results of ab initio calculations for the structure and the excitation energies of these clusters, the observed absorption bands are assigned to the transitions derived from the 2P-2S transition of Mg+ ion. The extensive redshift of the observed spectra is ascribed to the formation of a one-center ion-pair state. In the photolysis of Mg+NH3, NH3+ and Mg+NH2 ions are produced via photoinduced charge transfer and intracluster reaction processes, respectively, in addition to the Mg+ ion generated by the evaporation of ammonia molecules. For n=2, both the intracluster reaction and evaporation are dominant decay processes, while the evaporation is the sole photodissociation channel for larger clusters. The branching fractions of these processes are found to depend strongly on the solvation number n and also on the photolysis wavelength. The energetics and the dynamics of the dissociation processes are discussed in relation to the redox reaction of metal ions.

  11. Effects of co-processing sewage sludge in cement kiln on NOx, NH3 and PAHs emissions.

    PubMed

    Lv, Dong; Zhu, Tianle; Liu, Runwei; Lv, Qingzhi; Sun, Ye; Wang, Hongmei; Liu, Yu; Zhang, Fan

    2016-09-01

    The effects of co-processing sewage sludge in cement kiln on NOx, NH3 and PAHs emissions were systematically investigated in a cement production line in Beijing. The results show that co-processing the sewage sludge was helpful to reduce NOx emission, which primarily depends on the NH3 amount released from the sewage sludge. Meanwhile, NOx and NH3 concentrations in the flue gas have a negative correlation, and the contribution of feeding the sewage sludge to NOx removal decreased with the increase of injection amount of ammonia water in the SNCR system. Therefore, it is suggested that the injection amount of ammonia water in SNCR system may reduce to cut down the operating costs during co-processing the sewage sludge in cement kiln. In addition, the emission of total PAHs seems to increase with the increased amount of the sewage sludge feeding to the cement kiln. However, the distributions of PAHs were barely changed, and lower molecular weight PAHs were mainly distributed in gaseous phase, accounted for the major portion of PAHs when co-processing sewage sludge in cement kiln.

  12. 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.

  13. 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

  14. Influence of aeration on volatile sulfur compounds (VSCs) and NH3 emissions during aerobic composting of kitchen waste.

    PubMed

    Zhang, Hongyu; Li, Guoxue; Gu, Jun; Wang, Guiqin; Li, Yangyang; Zhang, Difang

    2016-12-01

    This study investigates the influence of aeration on volatile sulfur compounds (VSCs) and ammonia (NH3) emissions during kitchen waste composting. Aerobic composting of kitchen waste and cornstalks was conducted at a ratio of 85:15 (wet weight basis) in 60L reactors for 30days. The gas emissions were analyzed with force aeration at rates of 0.1 (A1), 0.2 (A2) and 0.3 (A3) L (kgDMmin)(-1), respectively. Results showed that VSCs emission at the low aeration rate (A1) was more significant than that at other two rates (i.e., A2 and A3 treatment), where no considerable emission difference was observed. On the other hand, NH3 emission reduced as the aeration rate decreased. It is noteworthy that the aeration rate did not significantly affect the compost quality. These results suggest that the aeration rate of 0.2L (kgDMmin)(-1) may be applied to control VSCs and NH3 emissions during kitchen waste composting.

  15. 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.

  16. Oscillatory behaviour of the reduction of NO by H 2 and NH 3 over Rh studied by FEM

    NASA Astrophysics Data System (ADS)

    van Tol, M. F. H.; Gielbert, A.; Nieuwenhuys, B. E.

    1993-04-01

    The NO reduction by H 2 and NH 3 on Rh has been studied by field emission microscopy (FEM). The NO-H 2 reaction shows oscillatory behaviour at 460 K and PNO = 1.5×10 -7 Torr and PH 2 = 1×10 -6 Torr. Unique features of FEM that can be used to study the oscillations in detail are the very high spatial resolution and the presence of, in principle, an indefinite number of different crystal planes. The oscillatory behaviour is reflected by periodic changes in the emission current and in the images observed. The communication between different surfaces present on the field emitter is displayed in real-time on a fluorescent screen. Diffusion and gas phase coupling seem to play a role. Many of the features reported earlier for the oscillatory behaviour of the NO-H 2 and NO-NH 3 reactions over Pt(100) are observed on Rh as well, including the surface explosion. The NO-NH 3 reaction does also show the surface explosion. Quite remarkable features are observed in the latter case. Single planes show oscillatory behaviour under conditions where others do not. The vacancy model proposed earlier for the oscillations over Pt(100), can be applied to the reactions described in this paper as well.

  17. 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.

  18. Inkjet-Printed Photodetector Arrays Based on Hybrid Perovskite CH3NH3PbI3 Microwires.

    PubMed

    Liu, Yang; Li, Fushan; Perumal Veeramalai, Chandrasekar; Chen, Wei; Guo, Tailiang; Wu, Chaoxing; Kim, Tae Whan

    2017-04-05

    Hybrid perovskite CH3NH3PbI3 has attracted extensive research interests in optoelectronic devices in recent years. Herein an inkjet printing method has been employed to deposit a perovskite CH3NH3PbI3 layer. By choosing the proper solvent and controlling the crystal growth rate, hybrid perovskite CH3NH3PbI3 nanowires, microwires, a network, and islands were synthesized by means of inkjet printing. Electrode-gap-electrode lateral-structured photodetectors were fabricated with these different crystals, of which a hybrid perovskite microwire-based photodetector would balance the uniformity and low defects to obtain a switching ratio of 16000%, responsivity of 1.2 A/W, and normalized detectivity of 2.39 × 10(12) Jones at a light power density of 0.1 mW/cm(2). Furthermore, the hybrid perovskite microwire-based photodetector arrays were fabricated and applied in an imaging sensor, from which the clear mapping of the light source signal was successfully obtained. This work paves the way for the realization of low-cost, solution-processed, and high-performance hybrid perovskite-based photodetector arrays.

  19. High sensitivity measurement of NO, NO2 and NH3 using MIR-QCL and time division multiplexing WMS technology

    NASA Astrophysics Data System (ADS)

    Chen, Xiang; Yang, Chenguang; Hu, Mai; Xu, Zhenyu; Fan, Xueli; Wei, Min; Yao, Lu; He, Yabai; Kan, Ruifeng

    2016-10-01

    A compact system based on mid-infrared quantum cascade laser (QCL) operated in room temperature was developed for the simultaneous monitoring of NO, NO2 and NH3 in the air. Laser beams of three QCLs with central wavelength located at 1900 cm-1, 1600 cm-1, 1103.4 cm-1 were coupled to pass through the 60m long gas cell together. With the technology of time division multiplexing, wavelength modulation spectroscopy (WMS) signals of three lasers can be detected at adjacent scan process. The real-time second harmonic analysis was implemented to achieve simultaneous detection of NO, NO2 and NH3. A minimum detection limit (MDL) of 0.2ppb for NO, 0.12ppb for NO2 and 0.1ppb for NH3 with an optimum integration time around 100 seconds can be achieved for this setup. An ambient monitoring of three gasses during 5 hours was performed to inspect the local air quality.

  20. Electronic structure of organometal halide perovskite CH3NH3BiI3 and optical absorption extending to infrared region

    PubMed Central

    Zhu, H. X.; Liu, J.-M.

    2016-01-01

    The electronic structure and optical absorption spectrum of organometal halide perovskite compound CH3NH3BiI3 as a substituting candidate of well-concerned CH3NH3PbI3 not only for environmental friendly consideration are studied using the first principles calculations. It is revealed that a Bi replacement of Pb in CH3NH3PbI3 does not change seriously the band edge structure but the bandgap becomes narrow. Consequently, CH3NH3BiI3 exhibits not only stronger visible light absorption than CH3NH3PbI3 does but more strong absorption in the infrared region, which is however absent in CH3NH3PbI3. It is suggested that CH3NH3BiI3 may be one of even more promising alternatives to CH3NH3PbI3 for spectrum-broad and highly-efficient solar cells. PMID:27857201

  1. Electronic structure of organometal halide perovskite CH3NH3BiI3 and optical absorption extending to infrared region

    NASA Astrophysics Data System (ADS)

    Zhu, H. X.; Liu, J.-M.

    2016-11-01

    The electronic structure and optical absorption spectrum of organometal halide perovskite compound CH3NH3BiI3 as a substituting candidate of well-concerned CH3NH3PbI3 not only for environmental friendly consideration are studied using the first principles calculations. It is revealed that a Bi replacement of Pb in CH3NH3PbI3 does not change seriously the band edge structure but the bandgap becomes narrow. Consequently, CH3NH3BiI3 exhibits not only stronger visible light absorption than CH3NH3PbI3 does but more strong absorption in the infrared region, which is however absent in CH3NH3PbI3. It is suggested that CH3NH3BiI3 may be one of even more promising alternatives to CH3NH3PbI3 for spectrum-broad and highly-efficient solar cells.

  2. Desorption in Mass Spectrometry.

    PubMed

    Usmanov, Dilshadbek Tursunbayevich; Ninomiya, Satoshi; Chen, Lee Chuin; Saha, Subhrakanti; Mandal, Mridul Kanti; Sakai, Yuji; Takaishi, Rio; Habib, Ahsan; Hiraoka, Kenzo; Yoshimura, Kentaro; Takeda, Sen; Wada, Hiroshi; Nonami, Hiroshi

    2017-01-01

    In mass spectrometry, analytes must be released in the gas phase. There are two representative methods for the gasification of the condensed samples, i.e., ablation and desorption. While ablation is based on the explosion induced by the energy accumulated in the condensed matrix, desorption is a single molecular process taking place on the surface. In this paper, desorption methods for mass spectrometry developed in our laboratory: flash heating/rapid cooling, Leidenfrost phenomenon-assisted thermal desorption (LPTD), solid/solid friction, liquid/solid friction, electrospray droplet impact (EDI) ionization/desorption, and probe electrospray ionization (PESI), will be described. All the methods are concerned with the surface and interface phenomena. The concept of how to desorb less-volatility compounds from the surface will be discussed.

  3. Desorption in Mass Spectrometry

    PubMed Central

    Usmanov, Dilshadbek Tursunbayevich; Ninomiya, Satoshi; Chen, Lee Chuin; Saha, Subhrakanti; Mandal, Mridul Kanti; Sakai, Yuji; Takaishi, Rio; Habib, Ahsan; Hiraoka, Kenzo; Yoshimura, Kentaro; Takeda, Sen; Wada, Hiroshi; Nonami, Hiroshi

    2017-01-01

    In mass spectrometry, analytes must be released in the gas phase. There are two representative methods for the gasification of the condensed samples, i.e., ablation and desorption. While ablation is based on the explosion induced by the energy accumulated in the condensed matrix, desorption is a single molecular process taking place on the surface. In this paper, desorption methods for mass spectrometry developed in our laboratory: flash heating/rapid cooling, Leidenfrost phenomenon-assisted thermal desorption (LPTD), solid/solid friction, liquid/solid friction, electrospray droplet impact (EDI) ionization/desorption, and probe electrospray ionization (PESI), will be described. All the methods are concerned with the surface and interface phenomena. The concept of how to desorb less-volatility compounds from the surface will be discussed. PMID:28337398

  4. Device simulation of lead-free CH3NH3SnI3 perovskite solar cells with high efficiency

    NASA Astrophysics Data System (ADS)

    Du, Hui-Jing; Wang, Wei-Chao; Zhu, Jian-Zhuo

    2016-10-01

    The lead-free perovskite solar cells (PSCs) have drawn a great deal of research interest due to the Pb toxicity of the lead halide perovskite. CH3NH3SnI3 is a viable alternative to CH3NH3PbX3, because it has a narrower band gap of 1.3 eV and a wider visible absorption spectrum than the lead halide perovskite. The progress of fabricating tin iodide PSCs with good stability has stimulated the studies of these CH3NH3SnI3 based cells greatly. In the paper, we study the influences of various parameters on the solar cell performance through theoretical analysis and device simulation. It is found in the simulation that the solar cell performance can be improved to some extent by adjusting the doping concentration of the perovskite absorption layer and the electron affinity of the buffer and HTM, while the reduction of the defect density of the perovskite absorption layer significantly improves the cell performance. By further optimizing the parameters of the doping concentration (1.3× 1016 cm-3) and the defect density (1× 1015 cm-3) of perovskite absorption layer, and the electron affinity of buffer (4.0 eV) and HTM (2.6 eV), we finally obtain some encouraging results of the J sc of 31.59 mA/cm2, V oc of 0.92 V, FF of 79.99%, and PCE of 23.36%. The results show that the lead-free CH3NH3SnI3 PSC is a potential environmentally friendly solar cell with high efficiency. Improving the Sn2 + stability and reducing the defect density of CH3NH3SnI3 are key issues for the future research, which can be solved by improving the fabrication and encapsulation process of the cell. Project supported by the Graduate Student Education Teaching Reform Project, China (Grant No. JG201512) and the Young Teachers Research Project of Yanshan University, China (Grant No. 13LGB028).

  5. 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

  6. Tunable Br-doping CH3NH3PbI3-xBrx thin films for efficient planar perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Li, Nannan; Shi, Chengwu; Li, Long; Zhang, Zhengguo; Ma, Chengfeng

    2017-04-01

    In this paper, the relationship of the Br contents in precursor solutions of the CH3NH3Br/CH3NH3I mixture and in the resulting CH3NH3PbI3-xBrx thin films was systemically explored and the tunable Br-doping CH3NH3PbI3-xBrx thin films were successfully obtained by the sequential deposition methods. The influence of CH3NH3Br content in the methylammonium halide mixture solutions on the chemical composition, optical absorption, crystal phase and morphology of CH3NH3PbI3-xBrx thin films and the photovoltaic performance of the corresponding planar perovskite solar cells were investigated. The result revealed that the Br contents in CH3NH3PbI3-xBrx thin films linearly increased with the increase of Br contents in the methylammonium halide mixture solutions. The planar perovskite solar cell based on the high crystallinity and less grain boundary CH3NH3PbI3-xBrx thin films using the methylammonium halide mixture solutions with the molar ratio of CH3NH3Br/CH3NH3I = 10/90 achieved a best photoelectric conversion efficiency (PCE) of 14.88% with an open-circuit voltage (Voc) of 1.03 V, a short-circuit photocurrent density (Jsc) of 20.62 mA cm-2 and a fill factor (FF) of 0.70 and an average PCE of 14.21 ± 0.67% with Voc of 1.02 ± 0.02 V, Jsc of 20.67 ± 0.15 mA cm-2 and FF of 0.67 ± 0.05.

  7. 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.

  8. Application of a diffusion-desorption rate equation model in astrochemistry.

    PubMed

    He, Jiao; Vidali, Gianfranco

    2014-01-01

    Desorption and diffusion are two of the most important processes on interstellar grain surfaces; knowledge of them is critical for the understanding of chemical reaction networks in the interstellar medium (ISM). However, a lack of information on desorption and diffusion is preventing further progress in astrochemistry. To obtain desorption energy distributions of molecules from the surfaces of ISM-related materials, one usually carries out adsorption-desorption temperature programmed desorption (TPD) experiments, and uses rate equation models to extract desorption energy distributions. However, the often-used rate equation models fail to adequately take into account diffusion processes and thus are only valid in situations where adsorption is strongly localized. As adsorption-desorption experiments show that adsorbate molecules tend to occupy deep adsorption sites before occupying shallow ones, a diffusion process must be involved. Thus, it is necessary to include a diffusion term in the model that takes into account the morphology of the surface as obtained from analyses of TPD experiments. We take the experimental data of CO desorption from the MgO(100) surface and of D2 desorption from amorphous solid water ice as examples to show how a diffusion-desorption rate equation model explains the redistribution of adsorbate molecules among different adsorption sites. We extract distributions of desorption energies and diffusion energy barriers from TPD profiles. These examples are contrasted with a system where adsorption is strongly localized--HD from an amorphous silicate surface. Suggestions for experimental investigations are provided.

  9. Roles of Promoters in V2O5/TiO2 Catalysts for Selective Catalytic Reduction of NOx with NH3: Effect of Order of Impregnation.

    PubMed

    Youn, Seunghee; Song, Inhak; Kim, Do Heui

    2016-05-01

    Recently, various promoters for commercial selective catalytic reduction (SCR) catalysts are used to improve DeNOx activity at low temperature. We aimed at finding the optimum condition to prepare V2O5/TiO2 catalyst by changing promoters (W, Ce, Zr and Mn), not only for improving SCR reactivity, but also for reducing N2O formation at high temperature. In addition, we changed the order of impregnation between promoter and vanadium precursors on TiO2 support and observed its effect on activity and N2O selectivity. We utilized various analytical techniques, such as N2 adsorption-desorption, X-ray Diffraction (XRD), Raman spectroscopy, UV-visible Diffuse Reflectance Spectroscopy (UV-vis DRS) and Temperature Programmed Reduction with hydrogen (H2-TPR) to investigate the physicochemical properties of V2O5/TiO2 catalysts. It was found that W and Ce added V2O5/TiO2 catalysts showed the most active DeNOx properties at low temperature. Additionally, the difference in impregnation order affected the SCR activity. The superiority of low temperature activity of the vanadium firstly added catalysts (W or Ce/V/TiO2) is attributed to the formation of more polymerized V2O5 on the sample.

  10. Low-temperature high-resolution absorption spectrum of 14NH3 in the ν1+ν3 band region (1.51 μm)

    NASA Astrophysics Data System (ADS)

    Földes, T.; Golebiowski, D.; Herman, M.; Softley, T. P.; Di Lonardo, G.; Fusina, L.

    2014-09-01

    Jet-cooled spectra of 14NH3 and 15NH3 in natural abundance were recorded using cavity ring-down (CRDS, 6584-6670 cm-1) and cavity enhanced absorption (CEAS, 6530-6700 cm-1) spectroscopy. Line broadening effects in the CRDS spectrum allowed lines with J″-values between 0 and 3 to be identified. Intensity ratios in 14NH3 between the jet-cooled CRDS and literature room-temperature data from Sung et al. (J. Quant. Spectrosc. Radiat. Transfer, 113 (2012), 1066) further assisted the line assignments. Ground state combination differences were extensively used to support the assignments, providing reliable values for J, K and inversion symmetry of the ground state vibrational levels. CEAS data helped in this respect for the lowest J lines, some of which are saturated in the CRDS spectrum. Further information on a/s doublets arose from the observed spectral structures. Thirty-two transitions of 14NH3 were assigned in this way and a limited but significant number (19) of changes in the assignments results, compared to Sung et al. or to Cacciani et al. (J. Quant. Spectrosc. Radiat. Transfer, 113 (2012), 1084). Sixteen known and 25 new low-J transitions were identified for 15NH3 in the CRDS spectrum but the much scarcer literature information did not allow for any more refined assignment. The present line position measurements improve on literature values published for 15NH3 and on some line positions for 14NH3.

  11. 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.

  12. High efficiency CH3NH3PbI3:CdS perovskite solar cells with CuInS2 as the hole transporting layer

    NASA Astrophysics Data System (ADS)

    Chen, Chong; Zhai, Yong; Li, Fumin; Tan, Furui; Yue, Gentian; Zhang, Weifeng; Wang, Mingtai

    2017-02-01

    The CH3NH3PbI3:CdS composite films are prepared by a newly developed precursor blending solution method, which are further used to fabricate CH3NH3PbI3:CdS perovskite solar cells. Our experimental results demonstrate that the introduced CdS effectively improves the light absorption property of the ITO/CuInS2/Al2O3/CH3NH3PbI3:CdS film stack and decreases the charge recombination in the prepared solar cells due to the formation of CH3NH3PbI3/CdS bulk heterojunction. Furthermore, the formed CdS/CuInS2 heterojunction also contributes to the enhanced efficiency. As a consequence, the CH3NH3PbI3/CdS bulk heterojunction perovskite solar cells exhibit a maximum power conversion efficiency of (16.5 ± 0.2)%, which is 1.35 times the best efficiency of 12.2% of previously reported CdS/CH3NH3PbI3 bilayer solar cell. In addition, this efficiency is a 59% improvement compared with the efficiency of (10.4 ± 0.2)% for the ITO/CuInS2/Al2O3/CH3NH3PbI3/PC60BM/Ag cell without CdS.

  13. Material and optical properties of low-temperature NH3-free PECVD SiN x layers for photonic applications

    NASA Astrophysics Data System (ADS)

    Domínguez Bucio, Thalía; Khokhar, Ali Z.; Lacava, Cosimo; Stankovic, Stevan; Mashanovich, Goran Z.; Petropoulos, Periklis; Gardes, Frederic Y.

    2017-01-01

    SiN x layers intended for photonic applications are typically fabricated using LPCVD and PECVD. These techniques rely on high-temperature processing (>400 °C) to obtain low propagation losses. An alternative version of PECVD SiN x layers deposited at temperatures below 400 °C with a recipe that does not use ammonia (NH3-free PECVD) was previously demonstrated to be a good option to fabricate strip waveguides with propagation losses   <3 dB cm-1. We have conducted a systematic investigation of the influence of the deposition parameters on the material and optical properties of NH3-free PECVD SiN x layers fabricated at 350 °C using a design of experiments methodology. In particular, this paper discusses the effect of the SiH4 flow, RF power, chamber pressure and substrate on the structure, uniformity, roughness, deposition rate, refractive index, chemical composition, bond structure and H content of NH3-free PECVD SiN x layers. The results show that the properties and the propagation losses of the studied SiN x layers depend entirely on their compositional N/Si ratio, which is in fact the only parameter that can be directly tuned using the deposition parameters along with the film uniformity and deposition rate. These observations provide the means to optimise the propagation losses of the layers for photonic applications through the deposition parameters. In fact, we have been able to fabricate SiN x waveguides with H content  <20%, good uniformity and propagation losses of 1.5 dB cm-1 at 1550 nm and   <1 dB cm-1 at 1310 nm. As a result, this study can potentially help optimise the properties of the studied SiN x layers for different applications.

  14. Modeling impacts of NH3 on uptake of H2SO4 by charged nucleating nanoparticles in the Earth's atmosphere

    NASA Astrophysics Data System (ADS)

    Nadykto, A. B.; Nazarenko, K. M.; Markov, P. N.; Yu, F.

    2016-06-01

    The understanding of the role of ammonia, a well-known stabilizer of binary sulfuric acid-water clusters, in the gas-to-nanoparticle conversion in the Earth atmosphere is critically important for the assessment of aerosol radiative forcing associated with the climate changes. The sulfuric acid H2SO4 is present in the atmosphere in the form of the gas-phase hydrates (H2SO4)(H2O)n, whose interaction with NH3 leads to the formation of more stable bisulfate clusters (NH3)(H2SO4)(H2O)n. Although the impact of NH3 on the thermochemical stability of binary clusters nucleating homogeneously has been studied in some detail in the past, the effect of ammonia on other microphysical properties relevant to nucleation remains insufficiently well understood. In the present study, the effect of ammonia on the electrical dipole moment controlling the nucleation of airborne ions via the dipole-charge interaction has been investigated using the Density Functional Theory (DFT), ab initio MP2 and model chemistry G3 methods. The presence of ammonia in (H2SO4)(H2O)n is found to lead to very large enhancement in the dipole moment, which exceeds 2.0-2.5 Debyes (˜60-80%), 3.7-5.0 Debyes (˜90-180%), 1.4-4.5 Debyes (˜50-150%) and 2.1-5.5 Debyes (˜60-700%) for n = 0, n = 1, n = 2 and n = 3, respectively. The implications of this include the significantly increased uptake of the sulfuric acid, the key atmospheric nucleation precursor, by airborne ions and neutrals (due to dipole-dipole interaction), enhanced nucleation rates and the elevated production of ultrafine particles, which cause adverse health impacts.

  15. Hydrothermal Aging Effects on Fe/SSZ-13 and Fe/Beta NH3–SCR Catalysts

    SciTech Connect

    Gao, Feng; Szanyi, János; Wang, Yilin; Schwenzer, Birgit; Kollár, Márton; Peden, Charles H. F.

    2016-05-05

    Cu/SSZ-13 has been successfully commercialized as a diesel engine exhaust aftertreatment SCR catalyst in the past few years. This catalyst, however, displays undesirable NH3-SCR selectivity at elevated reaction temperature (≥ 350 C) after hydrothermal aging. Fe/zeolites, despite the fact that most of them degrade beyond tolerance after hydrothermal aging at temperatures ≥ 650 C, typically maintain good SCR selectivities. In recent years, Fe/beta has been identified as one of the more robust Fe/zeolites for use in NH3-SCR, where activity maintains even after hydrothermal aging at 750 C. Very recently, we, for the first time, synthesized and tested NH3-SCR performance for fresh and hydrothermally aged Fe/SSZ-13 catalysts. This study demonstrated that Fe/SSZ-13 is also a promising robust SCR catalyst, especially for high-temperature applications. In the present study, we compare catalytic performance between Fe/SSZ-13 and Fe/beta with similar Fe loadings and Si/Al ratios. Special attention is paid to effects from hydrothermal aging, aiming to understanding similarities and differences between these two catalysts. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Program 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.

  16. Mobile Column Measurements of HCHO, NO2, NH3, and C2H6 in Colorado during FRAPPE

    NASA Astrophysics Data System (ADS)

    Kille, N.; Volkamer, R. M.; Baidar, S.; Ortega, I.; Sinreich, R.; Hannigan, J. W.; Cooper, O. R.; Nussbaumer, E.; Pfister, G.

    2015-12-01

    Gases from anthropogenic sources have the potential to have a profound impact on air quality. Emissions from large cattle feedlots and ONG (Oil and Natural Gas) sites are comprised of NH3 (ammonia) and C2H6 (ethane) as pollutants. C2H6 contributes to photochemical ozone (O3) production and oxidation production of HCHO (formaldehyde). NH3 is a major source for reactive nitrogen to form particulate matter 2.5, which negatively affects human health. NO2 (nitrogen dioxide), emitted during combustion, is considered a large-scale pollutant and contributes to the formation of O3. Deploying an innovative suite of remote sensing instruments in a mobile laboratory, a Multi Axis Differential Optical Absorption Spectrometer (MAX-DOAS), a UV-Vis Spectrometer, and a Fourier Transform Infrared Spectrometer, we obtain mobile column measurements at high spatial and temporal resolution, 2 seconds for the UV-Vis and IR spectrometers and 20 seconds for the MAX-DOAS. Within the scope of the Front Range Air Pollution and Photochemistry Experiment (FRAPPE) we measure total columns of HCHO, NO2, NH3, and C2H6 using the University of Colorado mobile laboratory. Emissions of urban areas, agriculture, and ONG sites were studied. For the measurement of total columns the solar occultation flux method has been applied. We measured significant variability in the columns. The measurement of total columns allows one to determine the emission flux and source strength when driving a closed box around or upwind and downwind of a source with the mobile laboratory. We present results from select research drives.

  17. Atomistic Origins of Surface Defects in CH3NH3PbBr3 Perovskite and Their Electronic Structures.

    PubMed

    Liu, Yunxia; Palotas, Krisztian; Yuan, Xiao; Hou, Tingjun; Lin, Haiping; Li, Youyong; Lee, Shuit-Tong

    2017-02-28

    The inherent instability of CH3NH3PbX3 remains a major technical barrier for the industrial applications of perovskite materials. Recently, the most stable surface structures of CH3NH3PbX3 have been successfully characterized by using density functional theory (DFT) calculations together with the high-resolution scanning tunneling microscopy (STM) results. The two coexisting phases of the perovskite surfaces have been ascribed to the alternate orientation of the methylammonium (MA) cations. Notably, similar surface defect images (a dark depression at the sites of X atoms) have been observed on surfaces produced with various experimental methods. As such, these defects are expected to be intrinsic to the perovskite crystals and may play an important role in the structural decomposition of perovskite materials. Understanding the nature of such defects should provide some useful information toward understanding the instability of perovskite materials. Thus, we investigate the chemical identity of the surface defects systematically with first-principles density functional theory calculations and STM simulations. The calculated STM images of the Br and Br-MA vacancies are both in good agreement with the experimental measurements. In vacuum conditions, the formation energy of Br-MA is 0.43 eV less than the Br vacancy. In the presence of solvation effects, however, the formation energy of a Br vacancy becomes 0.42 eV lower than the Br-MA vacancy. In addition, at the vacancy sites, the adsorption energies of water, oxygen, and acetonitrile molecules are significantly higher than those on the pristine surfaces. This clearly demonstrated that the structural decomposition of perovskites are much easier to start from these vacancy sites than the pristine surfaces. Combining DFT calculations and STM simulations, this work reveals the chemical identities of the intrinsic defects in the CH3NH3PbX3 perovskite crystals and their effects on the stability of perovskite materials.

  18. Polymeric cobalt(ii) thiolato complexes - syntheses, structures and properties of [Co(SMes)2] and [Co(SPh)2NH3].

    PubMed

    Eichhöfer, Andreas; Buth, Gernot

    2016-11-01

    Reactions of [Co(N(SiMe3)2)2thf] with 2.1 equiv. of MesSH (Mes = C6H2-2,4,6-(CH3)3) yield dark brown crystals of the one dimensional chain compound [Co(SMes)2]. In contrast reactions of [Co(N(SiMe3)2)2thf] with 2.1 equiv. of PhSH result in the formation of a dark brown almost X-ray amorphous powder of 'Co(SPh)2'. Addition of aliquots of CH3OH to the latter reaction resulted in the almost quantitative formation of crystalline ammonia thiolato complexes either [Co(SPh)2(NH3)2] or [Co(SPh)2NH3]. Single crystal XRD reveals that [Co(SPh)2NH3] forms one-dimensional chains in the crystal via μ2-SPh bridges whereas [Co(SPh)2(NH3)2] consists at a first glance of isolated distorted tetrahedral units. Magnetic measurements suggest strong antiferromagnetic coupling for the two chain compounds [Co(SMes)2] (J = -38.6 cm(-1)) and [Co(SPh)2NH3] (J = -27.1 cm(-1)). Interestingly, also the temperature dependence of the susceptibility of tetrahedral [Co(SPh)2(NH3)2] shows an antiferromagnetic transition at around 6 K. UV-Vis-NIR spectra display d-d bands in the NIR region between 500 and 2250 nm. Thermal gravimetric analysis of [Co(SPh)2(NH3)2] and [Co(SPh)2NH3] reveals two well separated cleavage processes for NH3 and SPh2 upon heating accompanied by the stepwise formation of 'Co(SPh)2' and cobalt sulfide.

  19. 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

    2016-05-05

    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.

  20. Mechanical signatures of degradation of the photovoltaic perovskite CH3NH3PbI3 upon water vapor exposure

    NASA Astrophysics Data System (ADS)

    Spina, Massimo; Karimi, Ayat; Andreoni, Wanda; Pignedoli, Carlo A.; Náfrádi, Bálint; Forró, László; Horváth, Endre

    2017-03-01

    We report on the mechanical properties of CH3NH3PbI3 photovoltaic perovskite measured by nanoindentation. The Young's modulus (E) of the pristine sample is 20.0 ± 1.5 GPa, while the hardness (H) is 1.0 ± 0.1 GPa. Upon extended exposure to water vapor, both quantities decrease dramatically and the sample changes color from silver-black to yellow. Calculations based on density functional theory support this trend in the mechanical response. Chemical treatment of the degraded crystal in methylammonium iodide solution recovers the color of the pristine sample and the values of E and H within 50%.

  1. Nano metal-enhanced power conversion efficiency in CH3NH3PbI3 solar cells

    NASA Astrophysics Data System (ADS)

    Yu, Jing; Zhang, Chao; Yang, Siyu; Chen, Meina; Lei, Fengcai; Man, Baoyuan

    2017-04-01

    Nano metal-enhanced power conversion efficiency (PCE) in CH3NH3PbI3 solar cells utilizing the forward scattering effect of metal nanoparticles has been researched in this paper by finite difference time domain method. Two structures are designed in the research to explore this feasibility, by adjusting the materials, sizes and surface coverages of metal nanoparticles, both of them exhibit the exciting results bringing the max PCE enhancements by 12.18% and 8.03% respectively. Especially, considering the huge handleability of the second structure, this method has large applications in further improving the performance for other perovskite solar cells.

  2. CO2-dominated Atmosphere in Equilibrium with NH3-H2O Ocean: Application to Early Titan and Ocean Planets

    NASA Astrophysics Data System (ADS)

    Marounina, N.; Grasset, O.; Tobie, G.; Carpy, S.

    2015-12-01

    During the accretion of Titan, impact heating may have been sufficient to allow the global melting of water ice (Monteux et al. 2014) and the release of volatile compounds, with CO2 and NH3 as main constituents (Tobie et al. 2012). Thus, on primitive Titan, it is thought that a massive atmosphere was in contact with a global water ocean. Similar configurations may occur on temperate water-rich planets called ocean planets (Léger et al. 2004, Kitzmann et al. 2015).Due to its rather low solubility in liquid water, carbon dioxide is expected to be one of the major components in the atmosphere. The atmospheric amount of CO2 is a key parameter for assessing the thermal evolution of the planetary surface because of its strong greenhouse effect. However, ammonia significantly affects the solubility of CO2 in water and hence the atmosphere-ocean thermo-chemical equilibrium. For primitive Titan, estimating the mass, temperature and composition of the primitive atmosphere is important to determine mechanisms that led to the present-day N2-CH4 dominated atmosphere. Similarly, for ocean planets, the influence of ammonia on the atmospheric abundance in CO2 has consequences for the definition of the habitable zone.To investigate the atmospheric composition of the water-rich worlds for a wide range of initial compositions, we have developed a vapor-liquid equilibrium model of the NH3-CO2-H2O system, where we account for the non-ideal comportment of both vapor and liquid phases and the ion speciation of volatiles dissolved in the aqueous phase. We show that adding NH3 to the CO2-H2O binary system induces an efficient absorption of the CO2 in the liquid phase and thus a lower CO2 partial pressure in the vapor phase. Indeed, the CO2 partial pressure remains low for the CO2/NH3 ratio of liquid concentrations lower than 0.5.Assuming various initial compositions of Titan's global water ocean, we explore the thermal and compositional evolution of a massive primitive atmosphere using

  3. Adsorption and dissociation of NH3 on clean and hydroxylated TiO2 rutile (110) surfaces: a computational study.

    PubMed

    Chang, Jee-Gong; Chen, Hsin-Tsung; Ju, Shin-Pon; Chang, Ching-Sheng; Weng, Meng-Hsiung

    2011-04-30

    The adsorption and dissociation of NH(3) on the clean and hydroxylated TiO(2) rutile (110) surfaces have been investigated by the first-principles calculations. The monodentate adsorbates such as H(3)N-Ti(a), H(2)N-Ti(a), N-Ti(a), H(2)N-O(a), HN-O(a), N-O(a) and H-O(a), as well as the bidentate adsorbate, Ti-N-Ti(a) can be formed on the clean surface. It is found that the hydroxyl group enhances the adsorption of certain adsorbates on the five-fold-coordinated Ti atoms (5c-Ti), namely H(2)N-Ti(a), HN-Ti(a), N-Ti(a) and Ti-N-Ti(a). In addition, the adsorption energy increases as the number of hydroxyl groups increases. On the contrary, the opposite effect is found for those on the two-fold-coordinated O atoms (2c-O). The enhanced adsorption of NH(x) (x = 1-2) on the 5c-Ti is due to the large electronegativity of the OH group, increasing the acidity of the Ti center. This also contributes to diminish the adsorption of NH(x) (x = 1-2) on the two-fold-coordinated O atoms (2c-O) decreasing its basicity. According to potential energy profile, the NH(3) dissociation on the TiO(2) surface is endothermic and the hydroxyl group is found to lower the energetics of H(2)N-Ti(a)+H-O(a) and HN-Ti(a)+2{H-O(a)}, but slightly raise the energetic of Ti-N-Ti(a)+3{H-O(a)} compare to those on the clean surface. However, the dissociation of NH(3) is found to occur on the hydroxylated surface with an overall endothermic by 31.8 kcal/mol and requires a barrier of 37.5 kcal/mol. A comparison of NH(3) on anatase surface has been discussed. The detailed electronic analysis is also carried out to gain insights into the interaction nature between adsorbate and surface.

  4. 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.

  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. Synthesis, structural characterization, electrical properties and antioxidant activity of [p-(NH3)C6H4NH3]3P6O18·6H2O

    NASA Astrophysics Data System (ADS)

    Fezai, Ramzi; Mezni, Ali; Kahlaoui, Messaoud; Rzaigui, Mohamed

    2016-09-01

    Single crystals of a novel organic cyclohexaphosphate, [p-(NH3)C6H4NH3]3P6O18.6H2O, have been prepared in aqueous solution. Its crystal structure can be described by a three-dimensional framework where the P6O186- rings are interconnected by hydrogen bonds to form anionic layers between which organic cations are located. Hydrogen bonding network connecting the different components is given. The thermal stability and spectroscopic properties of this material are given too. Its DC and AC electrical conductivities, modulus analysis and dielectric constants have been investigated. The AC conductivity is found to obey the universal power law. The DC electrical conductivity indicates a semiconductor behavior. The kind of the observed conduction is protonic by translocation. X-rays structural and electrical results are correlated. This compound has also been screened for its antioxidant activity, determined in vitro, using 1,1-diphenyl-2-picrylhydrazyl, reducing power, hydroxyl scavenging ability and ferrous ion chelating (FIC) methods and with ascorbic acid as reference.

  7. Investigation on the corrosive effect of NH3 during InGaN/GaN multi-quantum well growth in light emitting diodes

    PubMed Central

    Yang, J.; Zhao, D. G.; Jiang, D. S.; Chen, P.; Zhu, J. J.; Liu, Z. S.; Liu, W.; Li, X.; Liang, F.; Liu, S. T.; Zhang, L. Q.; Yang, H.

    2017-01-01

    Three series of samples with different NH3 flow rate are grown and the optical and structural properties are investigated. It is found that apart from a positive effect on keeping a high partial pressure of nitrogen to enhance indium incorporation, NH3 may also play a negative effect on indium incorporation during InGaN growth. Especially, when temperature is relatively high, the hydrogen generated from the dissociation of NH3 may suppress the chemical reaction which produces InN, leading to a reduced indium incorporation efficiency during the InGaN layer growth. PMID:28322286

  8. Ultrasonic irradiation-promoted one-pot synthesis of CH3NH3PbBr3 quantum dots without using flammable CH3NH2 precursor

    NASA Astrophysics Data System (ADS)

    Jiang, Han; Wang, Chunlei; Lv, Changgui; Xu, Shuhong; Zhu, Li; Zhang, Ruohu; Cui, Yiping

    2017-02-01

    At present, the CH3NH3PbBr3 quantum dots (QDs) reported in the literature usually contain two synthesis steps: the initial preparation of CH3NH3Br via the reaction of flammable CH3NH2 and HBr, together with the subsequent formation of CH3NH3PbBr3 QDs. To avoid the use of dangerous CH3NH2, this work develops a novel one-pot method for synthesizing CH3NH3PbBr3 QDs using safe and commercially available reactants (CH3NH3Cl, KBr and PbCl2). It is found that ultrasonic treatment plays a key role during the synthesis of CH3NH3PbBr3 QDs. Without ultrasonic irradiation, it is not possible to synthesize CH3NH3PbBr3 QDs under heating or vigorous stirring. Aliquots of samples taken at different ultrasonic irradiation time intervals show a time-dependent redshift in the emission wavelength. This suggests the formation of CH3NH3PbCl3 QDs first, followed by the formation of CH3NH3PbBr3 QDs through ultrasonically promoted halide exchange. Moreover, mixed CH3NH3PbCl x Br3‑x QDs with a tunable emission wavelength can also be prepared through this one-pot method by controlling the ultrasonic irradiation time. In comparison to the previous two-step method, the current one-pot method is simpler, less time-consuming and does not use flammable CH3NH2. The as-prepared CH3NH3PbBr3 QDs show a comparable photoluminescence (PL) quantum yield (QY) to that of the literature. What is more, the ultrasonic time-controlled emission wavelength of CH3NH3PbCl x Br3‑x QDs also provides an alternative way of tuning QD emission to the traditional way of controlling the halide ratios.

  9. Investigation on the corrosive effect of NH3 during InGaN/GaN multi-quantum well growth in light emitting diodes

    NASA Astrophysics Data System (ADS)

    Yang, J.; Zhao, D. G.; Jiang, D. S.; Chen, P.; Zhu, J. J.; Liu, Z. S.; Liu, W.; Li, X.; Liang, F.; Liu, S. T.; Zhang, L. Q.; Yang, H.

    2017-03-01

    Three series of samples with different NH3 flow rate are grown and the optical and structural properties are investigated. It is found that apart from a positive effect on keeping a high partial pressure of nitrogen to enhance indium incorporation, NH3 may also play a negative effect on indium incorporation during InGaN growth. Especially, when temperature is relatively high, the hydrogen generated from the dissociation of NH3 may suppress the chemical reaction which produces InN, leading to a reduced indium incorporation efficiency during the InGaN layer growth.

  10. 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.

  11. Investigation on the corrosive effect of NH3 during InGaN/GaN multi-quantum well growth in light emitting diodes.

    PubMed

    Yang, J; Zhao, D G; Jiang, D S; Chen, P; Zhu, J J; Liu, Z S; Liu, W; Li, X; Liang, F; Liu, S T; Zhang, L Q; Yang, H

    2017-03-21

    Three series of samples with different NH3 flow rate are grown and the optical and structural properties are investigated. It is found that apart from a positive effect on keeping a high partial pressure of nitrogen to enhance indium incorporation, NH3 may also play a negative effect on indium incorporation during InGaN growth. Especially, when temperature is relatively high, the hydrogen generated from the dissociation of NH3 may suppress the chemical reaction which produces InN, leading to a reduced indium incorporation efficiency during the InGaN layer growth.

  12. Chlorine Incorporation in the CH3NH3PbI3 Perovskite: Small Concentration, Big Effect.

    PubMed

    Quarti, Claudio; Mosconi, Edoardo; Umari, Paolo; De Angelis, Filippo

    2017-01-03

    The role of chlorine doping in CH3NH3PbI3 represents an important open issue in the use of hybrid perovskites for photovoltaic applications. In particular, even if a positive role of chlorine doping on perovskite film formation and on material morphology has been demonstrated, an inherent positive effect on the electronic and photovoltaic properties cannot be excluded. Here we carried out periodic density functional theory and Car-Parrinello molecular dynamics simulations, going down to ∼1% doping, to investigate the effect of chlorine on CH3NH3PbI3. We found that such a small doping has important effects on the dynamics of the crystalline structure, both with respect to the inorganic framework and with respect to the cation libration motion. Together, we observe a dynamic spatial localization of the valence and conduction states in separated spatial material regions, which takes place in the 10(-1) ps time scale and which could be the key to ease of exciton dissociation and, likely, to small charge recombination in hybrid perovskites. Moreover, such localization is enhanced by chlorine doping, demonstrating an inherent positive role of chlorine doping on the electronic properties of this class of materials.

  13. First-Principles Structure Prediction of Dual Cation Ammine Borohydrides: LiMg(BH4)3(NH3)x

    NASA Astrophysics Data System (ADS)

    Kışlak, Yusuf; Tekin, Adem

    On-board hydrogen storage for transportation applications continues to be one of the most technically challenging barriers to the widespread commercialization of hydrogen-fueled vehicles. In addition, hydrogen storage is also required for off-board purposes such as stationary power generation and hydrogen delivery and refueling infrastructure. After decades of extensive exploration, research into hydrogen storage materials based on metal borohydrides has become a highly active and exciting area owing to the high theoretical hydrogen capacities of these materials. However, they are thermodynamically too stable and therefore a very high temperature is required for their decomposition. This temperature can be lowered to the tolerable levels by the addition of ammonia and the resulting material is called as Ammine Metal Borohydrides (AMBs). In this study, we aim to search the ground state crystal structures of LiMg(BH4)3(NH3)x [1] with x = 2, 3, 4 using CrystAl Structure Prediction via Simulated Annealing (CASPESA) method. This approach was successfully located the experimentally determined structure of LiMg(BH4)3(NH3)2 [1] and other interesting local minima. For x = 3 and 4 cases, our methodology also resulted new crystal phases.

  14. Magnetic ordering-induced multiferroic behavior in [CH3NH3][Co(HCOO)3] metal-organic framework.

    DOE PAGES

    Gomez-Aguirre, Lilian Claudia; Zapf, Vivien S.; Pato-Doldan, Breogan; ...

    2015-12-30

    Here, we present the first example of magnetic ordering-induced multiferroic behavior in a metal–organic framework magnet. This compound is [CH3NH3][Co(HCOO)3] with a perovskite-like structure. The A-site [CH3NH3]+ cation strongly distorts the framework, allowing anisotropic magnetic and electric behavior and coupling between them to occur. This material is a spin canted antiferromagnet below 15.9 K with a weak ferromagnetic component attributable to Dzyaloshinskii–Moriya (DM) interactions and experiences a discontinuous hysteretic magnetic-field-induced switching along [010] and a more continuous hysteresis along [101]. Coupling between the magnetic and electric order is resolved when the field is applied along this [101]: a spin rearrangementmore » occurs at a critical magnetic field in the ac plane that induces a change in the electric polarization along [101] and [10-1]. The electric polarization exhibits an unusual memory effect, as it remembers the direction of the previous two magnetic-field pulses applied. The data are consistent with an inverse-DM mechanism for multiferroic behavior.« less

  15. Strong covalency-induced recombination centers in perovskite solar cell material CH3NH3PbI3.

    PubMed

    Agiorgousis, Michael L; Sun, Yi-Yang; Zeng, Hao; Zhang, Shengbai

    2014-10-15

    Inorganic-organic hybrid perovskites are a new family of solar cell materials, which have recently been used to make solar cells with efficiency approaching 20%. Here, we report the unique defect chemistry of the prototype material, CH3NH3PbI3, based on first-principles calculation. We found that both the Pb cations and I anions in this material exhibit strong covalency as characterized by the formation of Pb dimers and I trimers with strong covalent bonds at some of the intrinsic defects. The Pb dimers and I trimers are only stabilized in a particular charge state with significantly lowered energy, which leads to deep charge-state transition levels within the band gap, in contradiction to a recent proposal that this system has only shallow intrinsic defects. Our results show that, in order to prevent the deep-level defects from being effective recombination centers, the equilibrium carrier concentrations should be controlled so that the Fermi energy is about 0.3 eV away from the band edges. Beyond this range, according to a Shockley-Read-Hall analysis, the non-equilibrium carrier lifetime will be strongly affected by the concentration of I vacancies and the anti-site defects with I occupying a CH3NH3 site.

  16. 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.

  17. Catalytic performance and kinetics of wire-mesh honeycomb catalyst for reduction of NO with NH3.

    PubMed

    Liu, Lei; Zhang, Liguo; Zhang, Qiuyun; Xiao, Yutang; Wu, Honghai

    2014-09-01

    V2O5/TiO2/Al2O3 catalysts with wire-mesh honeycomb (WMH) structure were prepared with three sequent steps: anode oxidation, sol-gel process and impregnation, and used for selective catalytic reduction (SCR) of nitric oxide (NO) with ammonia (NH3). According to the results of BET specific surface area (S(BET)), X-ray diffraction (XRD), and energy-dispersive X-ray analysis (EDX), the effective V2O5/TiO2/Al2O3 structure was formed on the surface of aluminum mesh. The catalytic activity was examined, and the results showed that the excellent treatment efficiency of WMH catalyst was obtained when the temperature was in the range of 473 to 673 K. The NO conversion rate was 86% at 673 K when the space volocity (SV) was 5000 h(-1), the NO conversion rate was both enhanced when increasing NH3/NO ratio or influent NO concentration. The kinetic analysis showed that the catalytic reaction followed pseudo-first-order kinetic model, the SCR reaction depended on chemical kinetics at low temperature (T < 493 K) and mass transfer at high temperature (T > 513 K).

  18. Characterization of an Fe≡N–NH 2 intermediate relevant to catalytic N2 reduction to NH3

    DOE PAGES

    Anderson, John S.; Cutsail, III, George E.; Rittle, Jonathan; ...

    2015-05-22

    The ability of certain transition metals to mediate the reduction of N2 to NH3 has attracted broad interest in the biological and inorganic chemistry communities. Early transition metals such as Mo and W readily bind N2 and mediate its protonation at one or more N atoms to furnish M(NxHy) species that can be characterized and, in turn, extrude NH3. By contrast, the direct protonation of Fe–N2 species to Fe(NxHy) products that can be characterized has been elusive. In this paper, we show that addition of acid at low temperature to [(TPB)Fe(N2)][Na(12-crown-4)] results in a new S = 1/2 Fe species.more » EPR, ENDOR, Mössbauer, and EXAFS analysis, coupled with a DFT study, unequivocally assign this new species as [(TPB)Fe≡N–NH2]+, a doubly protonated hydrazido(2–) complex featuring an Fe-to-N triple bond. This unstable species offers strong evidence that the first steps in Fe-mediated nitrogen reduction by [(TPB)Fe(N2)][Na(12-crown-4)] can proceed along a distal or “Chatt-type” pathway. Finally, a brief discussion of whether subsequent catalytic steps may involve early or late stage cleavage of the N–N bond, as would be found in limiting distal or alternating mechanisms, respectively, is also provided.« less

  19. 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.

  20. Combined use of nitrification inhibitor and struvite crystallization to reduce the NH3 and N2O emissions during composting.

    PubMed

    Jiang, Tao; Ma, Xuguang; Tang, Qiong; Yang, Juan; Li, Guoxue; Schuchardt, Frank

    2016-10-01

    Struvite crystallization (SCP) is combined with a nitrification inhibitor (dicyandiamide, DCD) to mitigate the NH3 and N2O emission during composting. The MgO and H3PO4 were added at a rate of 15% (mole/mole) of initial nitrogen, and the DCD was added at rates of 0%, 2.5%, 5.0%, 7.5% and 10% (w/w) of initial nitrogen respectively. Results showed that the combination use of SCP and DCD was phytotoxin free. The SCP could significantly reduce NH3 losses by 45-53%, but not the DCD. The DCD significantly inhibits nitrification when the content was higher than 50mgkg(-1), and that could reduce the N2O emission by 76.1-77.6%. The DCD degraded fast during the thermophilic phase, as the nitrification will be inhibited by the high temperature and high free ammonia content in this stage, the DCD was suggested to be applied in the maturing periods by 2.5% of initial nitrogen.

  1. 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.

  2. 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

    2016-02-01

    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.

  3. The C(3P) + NH3 reaction in interstellar chemistry. I. Investigation of the product formation channels

    DOE PAGES

    Bourgalais, Jeremy; Capron, Michael; Kailasanathan, Ranjith Kumar Abhinavam; ...

    2015-10-13

    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 nozzlemore » 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. As a result, 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.« less

  4. [Zn3(PO4)2(H2O)(0.8)(NH3)(1.2)].

    PubMed

    Stojanović, Jovica; Dordević, Tamara; Karanović, Ljiljana

    2010-05-01

    The structure of the title compound, ammineaquadi-mu(5)-phosphato-trizinc(II), [Zn(3)(PO(4))(2)(H(2)O)(0.8)(NH(3))(1.2)], consists of two parts: (i) PO(4) and ZnO(4) vertex-sharing tetrahedra arranged in layers parallel to (100) and (ii) ZnO(2)(N/O)(2) tetrahedra located between the layers. Elemental analysis establishes the ammine-to-water ratio as 3:2. ZnO(2)(N/O)(2) tetrahedra are located at special position 4e (site symmetry 2) in C2/c. The two O atoms of ZnO(2)(N/O)(2) are bonded to neighbouring P atoms, forming two Zn-O-P linkages and connecting ZnO(2)(N/O)(2) tetrahedra with two adjacent bc plane layers. A noteworthy feature of the structure is the presence of NH(3) and H(2)O at the same crystallographic position and, consequently, qualitative changes in the pattern of hydrogen bonding and weaker N/O-H...O electrostatic interactions, as compared to two closely related structures.

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. A novel transformation route from PbS to CH3NH3PbI3 for fabricating curved and large-area perovskite films.

    PubMed

    Luo, Paifeng; Zhou, Shengwen; Liu, Zhaofan; Xia, Wei; Sun, Lin; Cheng, Jigui; Xu, Chenxi; Lu, Yingwei

    2016-09-28

    We present a new transformation route from PbS to CH3NH3PbI3 for the facile preparation of perovskites with all kinds of shapes via vapor-assisted chemical bath deposition (VACBD). As such, curved and large-area CH3NH3PbI3 films with high quality are successfully achieved, which are suitable for the manufacturing scale-up of perovskite solar cells.

  10. Comparison of tetrel bonds in neutral and protonated complexes of pyridineTF3 and furanTF3 (T = C, Si, and Ge) with NH3.

    PubMed

    Liu, Mingxiu; Li, Qingzhong; Scheiner, Steve

    2017-02-15

    Ab initio calculations have been performed for the complexes H(+)-PyTX3NH3 and H(+)-furanTF3NH3 (T = C, Si, and Ge; X = F and Cl) with focus on geometries, energies, orbital interactions, and electron densities to study the influence of protonation on the strength of tetrel bonding. The primary interaction mode between α/β-furanCF3/p-PyCF3 and NH3 changes from an FH hydrogen bond to a CN tetrel bond as a result of protonation. Importantly, the protonation has a prominent enhancing effect on the strength of tetrel bonding with an increase in binding energy from 14 to 30 kcal mol(-1). The tetrel bonding becomes stronger in the order H(+)-p-PySiF3NH3 < H(+)-m-PySiF3NH3 < H(+)-o-PySiF3NH3, showing a reverse trend from that of the neutral analogues. In addition, there is competition between the tetrel and hydrogen bonds in the protonated complexes, in which the hydrogen bond is favored in the complexes of H(+)-p-PyCF3 but the tetrel bond is preferred in the complexes of H(+)-p-PyTX3 (T = Si, Ge; X = F, Cl) and H(+)-o/m-PySiF3.

  11. Study on the mechanism of NH3-selective catalytic reduction over CuCexZr1-x/TiO2

    NASA Astrophysics Data System (ADS)

    Chen, Xujuan; Sun, Xiaoliang; Gong, Cairong; Lv, Gang; Song, Chonglin

    2016-06-01

    Copper-cerium-zirconium catalysts loaded on TiO2 prepared by a wet impregnation method were investigated for NH3-selective catalytic reduction (SCR) of NOx. 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 NH4 + (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.

  12. The influence of leaf-atmosphere NH3(g ) exchange on the isotopic composition of nitrogen in plants and the atmosphere.

    PubMed

    Johnson, Jennifer E; Berry, Joseph A

    2013-10-01

    The distribution of nitrogen isotopes in the biosphere has the potential to offer insights into the past, present and future of the nitrogen cycle, but it is challenging to unravel the processes controlling patterns of mixing and fractionation. We present a mathematical model describing a previously overlooked process: nitrogen isotope fractionation during leaf-atmosphere NH3(g ) exchange. The model predicts that when leaf-atmosphere exchange of NH3(g ) occurs in a closed system, the atmospheric reservoir of NH3(g ) equilibrates at a concentration equal to the ammonia compensation point and an isotopic composition 8.1‰ lighter than nitrogen in protein. In an open system, when atmospheric concentrations of NH3(g ) fall below or rise above the compensation point, protein can be isotopically enriched by net efflux of NH3(g ) or depleted by net uptake. Comparison of model output with existing measurements in the literature suggests that this process contributes to variation in the isotopic composition of nitrogen in plants as well as NH3(g ) in the atmosphere, and should be considered in future analyses of nitrogen isotope circulation. The matrix-based modelling approach that is introduced may be useful for quantifying isotope dynamics in other complex systems that can be described by first-order kinetics.

  13. 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.

  14. A facile, solvent vapor-fumigation-induced, self-repair recrystallization of CH3NH3PbI3 films for high-performance perovskite solar cells.

    PubMed

    Zhu, Weidong; Yu, Tao; Li, Faming; Bao, Chunxiong; Gao, Hao; Yi, Yong; Yang, Jie; Fu, Gao; Zhou, Xiaoxin; Zou, Zhigang

    2015-03-12

    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.

  15. Wagging motion of hydrogen-bonded wire in the excited-state multiple proton transfer process of 7-hydroxyquinoline·(NH3)3 cluster.

    PubMed

    Liu, Yu-Hui; Lan, Sheng-Cheng; Li, Chun-Ran

    2013-08-01

    In this work, the dynamics of hydrogen bonds (as well as the hydrogen-bonded wire) in excited-state tautomerization of 7-hydroxyquinoline·(NH3)3 (7HQ·(NH3)3) cluster has been investigated by using time-dependent density functional theory (TDDFT). It shows that upon an excitation, the hydrogen bond between -OH group in 7-hydroxyquinoline (7HQ) and NH3 moiety would extremely strengthened in S1 state, which could effectively facilitate the releasing of the proton from the phenolic group of 7HQ moiety to the hydrogen-bonded wire and the forming an Eigen-like cationic wire (NH3···NH4(+)···NH3) in the cluster. To fulfill the different optimal angles of NH4(+) in the wire, a wagging motion of hydrogen-bonded wire would occur in excited state. Moreover, the wagging motion of the hydrogen-bonded wire would effectively promote excited-state proton transfer reaction. As the results, an excited-state multiple proton transfer (ESMPT) mechanism containing two concerted and asymmetrical processes has been proposed for the proton transfer dynamics of 7HQ·(NH3)3 cluster.

  16. 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

    2015-02-04

    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.

  17. 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.

  18. 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.

  19. DRIFT study on cerium-tungsten/titania catalyst for selective catalytic reduction of NOx with NH3.

    PubMed

    Chen, Liang; Li, Junhua; Ge, Maofa

    2010-12-15

    CeO(2)/TiO(2) and CeO(2)-WO(3)/TiO(2) catalysts prepared by impregnation method assisted with ultrasonic energy were investigated on the selective catalytic reduction (SCR) of NO(x) (NO and NO(2)) by NH(3). The catalytic activity of 10% CeO(2)/TiO(2) (CeTi) was greatly enhanced by the addition of 6% WO(3) in the broad temperature range of 200-500 °C, the promotion mechanism was proposed on basis of the results of in situ diffuse reflectance infrared transform spectroscopy (DRIFT). When NH(3) was introduced into both catalysts preadsorbed with NO + O(2), SCR would not proceed except for the reaction between NO(2) and ammonia. For CeO(2)/TiO(2) catalysts, coordinated NH(3) linked to Lewis acid sites were the main adsorbed ammonia species. When NO + O(2) was introduced, all the ammonia species consumed rapidly, indicating that these species could react with NO(x) effectively. Two different reaction routes, L-H mechanism at low temperature (<200 °C) and E-R mechanism at high temperatures (>200 °C), were presented for SCR reaction over CeO(2)/TiO(2) catalyst. For CeO(2)-WO(3)/TiO(2) catalysts, the Lewis acid sites on Ce(4+) state could be converted to Brønsted acid sites due to the unsaturated coordination of Ce(n+) and W(n+) ions. When NO + O(2) was introduced, the reaction proceeded more quickly than that on CeO(2)/TiO(2). The reaction route mainly followed E-R mechanism in the temperature range investigated (150-350 °C) over CeO(2)-WO(3)/TiO(2) catalysts. Tungstation was beneficial for the formation of Ce(3+), which would influence the active sites of the catalyst and further change the mechanisms of SCR reaction. In this way, the cooperation of tungstation and the presence of Ce(3+) state resulted in the better activity of CeO(2)-WO(3)/TiO(2) compared to that of CeO(2)/TiO(2).

  20. Isolates identification and characteristics of microorganisms in biotrickling filter and biofilter system treating H2S and NH3.

    PubMed

    Guang-Hui, Yu; Xiao-Jun, Xu; Pin-Jing, He

    2007-01-01

    A combination system of biotrickling filter (BTF) and biofilter (BF), adopting surfactant-modified clinoptilolite and surfactant-modified wood chip as the media respectively, was applied to treat H2S and NH3 simultaneously. The identification and sole carbon sources utilization patterns of isolates in the combination system were studied by Biolog system. The isolates were identified as Bacillus sphaericus, Geobacillus themoglucosidasius (55 degrees C) and Micrococcus luteus (ATCC 9341) in BTF, and Aspergillus sydowii (Bainier & Sartory) Thorm & Church in BF. Among 95 substrate classes supplied by Biolog system, the carboxylic acids and methyl esters had the highest utilization extent for the four species, followed by the amino acids and peptides. The descending sequence of carbon sources utilization capability of isolates was A. sydowii (52.6%), M. luteus (39.5%), B. sphaericus (21.6%), and G. thermoglucosidasius (17.7%).

  1. Raman studies of phase transitions in ferroelectric [C2H5NH3]2ZnCl4

    NASA Astrophysics Data System (ADS)

    Ben Mohamed, C.; Karoui, K.; Bulou, A.; Ben Rhaiem, A.

    2017-03-01

    The present paper accounted for the synthesis, differential scanning calorimetric and vibrational spectroscopy of [C2H5NH3]2ZnCl4grown at room temperature. Differential scanning calorimetric (DSC) disclosed five phase transitions at T1=231 K, T2=234 K, T3=237 K, T4=247 K and T5=312 K. The temperature dependence of the dielectric constant at different temperatures proved that this compound is ferroelectric below 238 K. Raman spectra as function temperature have been used to characterize these transitions and their nature, which indicates a change of the some peak near the transitions phase. The analysis of the wavenumber and the line width based on the order-disorder model allowed to obtain information relative to the thermal coefficient and the activation energy near the transitions phase.

  2. Hysteresis dependence on CH3NH3PbI3 deposition method in perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Fernandes, Silvia Leticia; Bregadiolli, Bruna Andressa; Véron, Anna Christina; Nüesch, Frank A.; Zaghete, Maria Aparecida; Graeff, Carlos Frederico de Oliveira

    2016-09-01

    CH3NH3PbI3 perovskite solar cells are one of the most exciting technologies in the renewable energy field, resulting in over 20% power conversion efficiency. Deep understanding of the working principle is now required to turn the high efficiency solar cells into a reliable technology. In this work we have explored the role of deposition method on the crystallinity of perovskite films and its influence on the hysteresis behavior of the current-voltage characteristics. In addition Nb2O5 was used as hole blocking layer and its influence is also discussed. We have found that hysteresis is strongly dependent on both; perovskite deposition method and Nb2O5 thickness. The ideal condition where the hysteresis is suppressed or minimized was achieved by using the sequential deposition method for the perovskite semiconductor and a hole blocking layer of 50 nm.

  3. 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.

  4. Low Surface Recombination Velocity in Solution-Grown CH3NH3PbBr3 Perovskite Single Crystal

    DOE PAGES

    Yang, Ye; Yan, Yong; Yang, Mengjin; ...

    2015-08-06

    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±0.1 103 cm s-1, B2–3 orders of magnitude lower than that in many important unpassivated semiconductors employed in solar cells. Our result suggests that the planar grain sizemore » for the perovskite thin films should be larger thanB30 mm to avoid the influence of surface recombination on the effective carrier lifetime.« less

  5. 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.

  6. Picosecond mass-selective measurements of phenol-(NH3)n acid-base chemistry in clusters

    NASA Astrophysics Data System (ADS)

    Steadman, Jhobe; Syage, Jack A.

    1990-04-01

    The rate of proton transfer from the acidic S1 state of phenol to the basis solvent (NH3)n was measured as a function of solvent cluster size n. A distinct reaction threshold was observed for solvent size n=5 for 266 nm picosecond excitation. The proton transfer rate was measured to be ka=(60±10 ps)-1 for n=5-7. A competitive recombination rate of k-a =(350±100 ps)-1 occurs for n=5. Additional solvation stabilizes the product side causing the reaction enthalpy and consequently k-a to decrease. No evidence of proton transfer was observed when phenol was seeded in the less basic solvent clusters (CH3OH)n and (H2O)n.

  7. [Nano-MnO(x) catalyst for the selective catalytic reduction of NO by NH3 in low-temperature].

    PubMed

    Tang, Xiao-Long; Hao, Ji-Ming; Xu, Wen-Guo; Li, Jun-Hua

    2007-02-01

    Nanometer particles composed of manganese oxides (Nano-MnO(x)), which prepared by rheological phase reaction method, show superior low-temperature SCR activity for NO with NH3 in the presence of excess O2. In experiments, the NO conversion is 98.25% at 80 degrees C, and nearly 100% NO could be converted in 100 - 150 degrees C. Due to the reason of competing adsorption, H2O has a slight impact on the activity and the deactivation of SO2 is reversible. The experiments implied that the superior low-temperature catalytic activity of Nano-MnO(x) was mainly due to its high BET specific areas and poor crystallinity.

  8. High performance photodetector based on 2D CH3NH3PbI3 perovskite nanosheets

    NASA Astrophysics Data System (ADS)

    Li, Pengfei; Shivananju, B. N.; Zhang, Yupeng; Li, Shaojuan; Bao, Qiaoliang

    2017-03-01

    In this work, a high performance vertical-type photodetector based on two-dimensional (2D) CH3NH3PbI3 perovskite nanosheets was fabricated. The low trap density of the perovskite nanosheets and their short carrier diffusion distance result in a significant performance enhancement of the perovskite-based photodetector. The photoresponsivity of this vertical-type photodetector is as high as 36 mA W‑1 at visible wavelength, which is much better than traditional perovskite photodetectors (0.34 mA W‑1). Compared with traditional planar-type perovskite-based photodetectors, this vertical-type photodetector also shows the advantages of low-voltage operation and large responsivity. These results may pave the way for exploiting high performance perovskite-based photodetectors with an ingenious device design.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. Fully Copper-Exchanged High-Silica LTA Zeolites as Unrivaled Hydrothermally Stable NH3 -SCR Catalysts.

    PubMed

    Ryu, Taekyung; Ahn, Nak Ho; Seo, Seungwan; Cho, Jung; Kim, Hyojun; Jo, Donghui; Park, Gi Tae; Kim, Pyung Soon; Kim, Chang Hwan; Bruce, Elliott L; Wright, Paul A; Nam, In-Sik; Hong, Suk Bong

    2017-03-13

    Diesel engine technology is still the most effective solution to meet tighter CO2 regulations in the mobility and transport sector. In implementation of fuel-efficient diesel engines, the poor thermal durability of lean nitrogen oxides (NOx ) aftertreatment systems remains as one major technical hurdle. Divalent copper ions when fully exchanged into high-silica LTA zeolites are demonstrated to exhibit excellent activity maintenance for NOx reduction with NH3 under vehicle simulated conditions even after hydrothermal aging at 900 °C, a critical temperature that the current commercial Cu-SSZ-13 catalyst cannot overcome owing to thermal deactivation. Detailed structural characterizations confirm the presence of Cu(2+) ions only at the center of single 6-rings that act not only as a catalytically active center, but also as a dealumination suppressor. The overall results render the copper-exchanged LTA zeolite attractive as a viable substitute for Cu-SSZ-13.

  14. Low surface recombination velocity in solution-grown CH3NH3PbBr3 perovskite single crystal

    PubMed Central

    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 × 103 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

  15. 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.

  16. Fabrication and characterization of CH3NH3(Cs)Pb(Sn)I3(Br) perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Ueoka, Naoki; Ohishi, Yuya; Shirahata, Yasuhiro; Suzuki, Atsushi; Oku, Takeo

    2017-01-01

    Perovskite-type CH3NH3(MA)PbI3-based photovoltaic devices were fabricated and characterized. Doping effects of cesium iodide (CsI), cesium bromide (CsBr) and tin bromide (SnBr2) on the photovoltaic properties and surface microstructures of the perovskite phase were investigated. Short-circuit current densities, open-circuit voltages and fill factors increased by CsI and SnBr2 addition. The surface coverage of the perovskite crystals was also improved by SnBr2 doping, which resulted in improvement of the fill factor. The cell prepared by a starting composition of MA0.95Cs0.05Pb0.95Sn0.05I2.90Br0.10 showed the best photovoltaic performance in the present work.

  17. Comparative NH 3-sensing characteristic studies of PANI/TiO II nanocomposite thin films doped with different acids

    NASA Astrophysics Data System (ADS)

    Tai, Huiling; Jiang, Yadong; Xie, Guangzhong; Yu, Junsheng; Ying, Zhihua; Chen, Xuan

    2008-02-01

    Polyaniline/titanium dioxide (PANI/TiO II) nanocomposite thin films were synthesized by in-situ self-assembly method, which were doped with p-toluene sulphonic acid (p-TSA) and hydrochloric acid (HCl), respectively. The thin films were characterized by using UV-Vis absorption spectroscopy and scanning electron microscope (SEM), and the NH 3 gas sensitive properties of the thin films were investigated at room temperature. The results showed that the PANI/TiO II thin film doped with HCl was superior to that doped with p-TSA in terms of response-recovery characteristics. The surface morphology characterization of the thin films were performed to explain the different gas-sensing properties.

  18. Superconductivity in (NH3) yN axFeS e0.5T e0.5

    NASA Astrophysics Data System (ADS)

    Zheng, Lu; Sakai, Yusuke; Miao, Xiao; Nishiyama, Saki; Terao, Takahiro; Eguchi, Ritsuko; Goto, Hidenori; Kubozono, Yoshihiro

    2016-11-01

    Na-intercalated FeS e0.5T e0.5 was prepared using the liquid N H3 technique, and a superconducting phase exhibiting a superconducting transition temperature (Tc) as high as 27 K was discovered. This can be called the high-Tc phase since a 21 K superconducting phase was previously obtained in (NH3) yN axFeS e0.5T e0.5 . The chemical composition of the high-Tc phase was determined to be (NH3)0.61 (4 )N a0.63 (5 )F e0.85S e0.55 (3 )T e0.44 (2 ) . The x-ray diffraction patterns of both phases show that a larger lattice constant c (i.e., FeS e0.5T e0.5 plane spacing) produces a higher Tc. This behavior is the same as that of metal-doped FeSe, suggesting that improved Fermi-surface nesting produces the higher Tc. The high-Tc phase converted to the low-Tc phase within several days, indicating that it is a metastable phase. The temperature dependence of resistance for both phases was recorded at different magnetic fields, and the critical fields were determined for both phases. Finally, the Tc versus c phase diagram was prepared for the metal-doped FeS e0.5T e0.5 , which is similar to that of metal-doped FeSe, although the Tc is lower.

  19. 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).

  20. Hydrogen desorption kinetics for aqueous hydrogen fluoride and remote hydrogen plasma processed silicon (001) surfaces

    SciTech Connect

    King, Sean W. Davis, Robert F.; Carter, Richard J.; Schneider, Thomas P.; Nemanich, Robert J.

    2015-09-15

    The desorption kinetics of molecular hydrogen (H{sub 2}) from silicon (001) surfaces exposed to aqueous hydrogen fluoride and remote hydrogen plasmas were examined using temperature programmed desorption. Multiple H{sub 2} desorption states were observed and attributed to surface monohydride (SiH), di/trihydride (SiH{sub 2/3}), and hydroxide (SiOH) species, subsurface hydrogen trapped at defects, and hydrogen evolved during the desorption of surface oxides. The observed surface hydride species were dependent on the surface temperature during hydrogen plasma exposure with mono, di, and trihydride species being observed after low temperature exposure (150 °C), while predominantly monohydride species were observed after higher temperature exposure (450 °C). The ratio of surface versus subsurface H{sub 2} desorption was also found to be dependent on the substrate temperature with 150 °C remote hydrogen plasma exposure generally leading to more H{sub 2} evolved from subsurface states and 450 °C exposure leading to more H{sub 2} desorption from surface SiH{sub x} species. Additional surface desorption states were observed, which were attributed to H{sub 2} desorption from Si (111) facets formed as a result of surface etching by the remote hydrogen plasma or aqueous hydrogen fluoride treatment. The kinetics of surface H{sub 2} desorption were found to be in excellent agreement with prior investigations of silicon surfaces exposed to thermally generated atomic hydrogen.

  1. Passive SCR for lean gasoline NOX control: Engine-based strategies to minimize fuel penalty associated with catalytic NH3 generation

    DOE PAGES

    Prikhodko, Vitaly Y.; Parks, James E.; Pihl, Josh A.; ...

    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

  2. Effects of pollutant concentration ratio on the simultaneous removal of NH3, H2S and toluene gases using rock wool-compost biofilter.

    PubMed

    Galera, Melvin Maaliw; Cho, Eulsaeng; Tuuguu, Enkhdul; Park, Shin-Jung; Lee, Changhee; Chung, Wook-Jin

    2008-04-01

    The biological treatment of a tri-component mixed waste gas system in BRC1 and BRC2 biofilters packed with rock wool-compost media was studied. The model gases were NH(3), H(2)S and toluene. The gases were fed initially at about 50-55 ppm each. H(2)S was found to have the shortest start-up while toluene had the longest. Under two different NH(3):H(2)S:toluene concentration ratios of 250:120:55 and 120:220:55 (in ppm) for BRC1 and BRC2, the removal efficiencies of NH(3), H(2)S and toluene were found to be affected by their respective loading rate. On the other hand, toluene removal was observed to be inhibited at H(2)S concentration of 220 ppm as well. Almost complete removal of NH(3) and H(2)S was achieved when loading rate was applied up to 16.14 g-NH(3)/(m(3) bed h) and 36.09 g-H(2)S/(m(3) bed h), respectively. The maximum elimination capacity for NH(3) was determined to be 23.67 g-NH(3)/(m(3) bed h) at 78.6% removal efficiency and for H(2)S, 38.50 g-H(2)S/(m(3) bed h) at 68.1% removal efficiency. The maximum toluene elimination capacity was 30.75 g-toluene/(m(3) bed h) at 87.9% removal efficiency when the concentration of NH(3):H(2)S:toluene was 250:120:55 in BRC1, and was 16.60 g-toluene/(m(3) bed h) at 45.5% removal efficiency when the concentration of NH(3):H(2)S:toluene was 120:220:55 in BRC2. The pressure drops along both columns were low and the ratio of bed compactions over biofilter height was observed to be less than 0.02.

  3. Assessment on ground-level nitrogen dioxide (NO2) and ammonia (NH3) at secondary forest of Mata Ayer and Kangar, Perlis

    NASA Astrophysics Data System (ADS)

    Abdullah, Nadiah Syafiqah; Kamarudin, Latifah Munirah; Hamidin, Nasrul; Zakaria, Ammar; Gunasagaran, Rajeshkumar; Shakaff, Ali Yeon Md.

    2017-03-01

    The current ground-level concentrations of nitrogen dioxide (NO2) and ammonia (NH3) within forests in Perlis are unknown and hardly investigated. The continual infrastructure development of Perlis and human activities may have played a major role in contributing to the decline of air quality in Perlis. Nitrogen-based trace gases may cause environmental effects while they are airborne or deposited on the ground. Due to the uncertainty of nitrogen trace gases level, this study was conducted to investigate the NO2 and NH3 concentrations within Mata Ayer secondary forest and Kangar. A portable gas monitor-sensor (Aeroqual Series 500) was used to assess the ground-level NO2 and NH3 concentrations, ambient air temperature, and relative humidity. The measurements were conducted in June 2015 between 9:30 am to 4:30 pm. The average NO2 and NH3 concentrations were 0.062 ppm and 0.040 ppm at the secondary forest of Mata Ayer and were found lower than Kangar (0.069 ppm and 0.125 ppm). The ambient air temperature and relative humidity in Kangar were found associated with NO2 (r = -0.420 and r = 0.315) and NH3 (r = -0.423 and r = 0.496). However, this was not the case at Mata Ayer secondary forest. The results indicated that human activities may have influenced the quality of ambient air in Perlis.

  4. 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%.

  5. The deactivation mechanism of Pb on the Ce/TiO2 catalyst for the selective catalytic reduction of NOx with NH3: TPD and DRIFT studies.

    PubMed

    Wang, Shu-Xian; Guo, Rui-Tang; Pan, Wei-Guo; Li, Ming-Yuan; Sun, Peng; Liu, Shu-Ming; Liu, Shuai-Wei; Sun, Xiao; Liu, Jian

    2017-02-15

    It was well recognized that Pb had a poisoning effect on a SCR catalyst. In this study, the deactivation mechanism of Pb on the Ce/TiO2 catalyst was investigated based on the characterization results of TPD and in situ DRIFT studies. It was found that the addition of Pb on the Ce/TiO2 catalyst not only inhibited the adsorption and activation of NH3 species, but also led to the decrease of the activity of adsorbed NH3 species in the SCR reaction. The adsorption of NOx species and the oxidation of NO by O2 over the Ce/TiO2 catalyst were also suppressed by the addition of Pb, while the reactivity of adsorbed NO2 species did not decrease. Moreover, the results revealed that the NH3-SCR reaction over the Ce/TiO2 catalyst followed both the E-R and L-H mechanisms, while the NH3-SCR reaction over Ce/TiO2-Pb was mainly controlled by the L-H mechanism. The contributions of the L-H mechanism to the SCR reactions over Ce/TiO2 and Ce/TiO2-Pb decreased with increasing reaction temperature. The deactivation of Ce/TiO2-Pb was mainly attributed to the suppressed NH3 adsorption and activation, accompanied by the inhibited NO oxidation and the decrease of Brønsted acid sites.

  6. 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.

  7. 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

  8. The effect of wind velocity, air temperature and humidity on NH 3 and SO 2 transfer into bean leaves ( phaseolus vulgaris L.)

    NASA Astrophysics Data System (ADS)

    van Hove, L. W. A.; Vredenberg, W. J.; Adema, E. H.

    The influence of wind velocity, air temperature and vapour pressure deficit of the air (VPD) on NH 3 and SO 2 transfer into bean leaves ( Phaseolus vulgaris L.) was examined using a leaf chamber. The measurements suggested a transition in the properties of the leaf boundary layer at a wind velocity of 0.3-0.4 ms -1 which corresponds to a Recrit value of about 2000. At higher wind velocities the leaf boundary layer resistance ( rb) was 1.5-2 times lower than can be calculated from the theory. Nevertheless, the assessed relationships between rb and wind velocity appeared to be similar to the theoretical derived relationship for rb. The NH 3 flux and in particular the SO 2 flux into the leaf strongly increased at a VPD decline. The increase of the NH 3 flux could be attributed to an increase of the stomatal conductance ( gs). However, the increase of the SO 2 flux could only partly be explained by an increase of gs. An apparent additional uptake was also observed for the NH 3 uptake at a low temperature and VPD. The SO 2 flux was also influenced by air temperature which could be explained by a temperature effect on gs. The results suggest that calculation of the NH 3 and SO 2 flux using data of gs gives a serious understimation of the real flux of these gases into leaves at a low temperature and VPD.

  9. Modulated CH3NH3PbI3‑xBrx film for efficient perovskite solar cells exceeding 18%

    NASA Astrophysics Data System (ADS)

    Tu, Yongguang; Wu, Jihuai; Lan, Zhang; He, Xin; Dong, Jia; Jia, Jinbiao; Guo, Panfeng; Lin, Jianming; Huang, Miaoliang; Huang, Yunfang

    2017-03-01

    The organic-inorganic lead halide perovskite layer is a crucial factor for the high performance perovskite solar cell (PSC). We introduce CH3NH3Br in the precursor solution to prepare CH3NH3PbI3‑xBrx hybrid perovskite, and an uniform perovskite layer with improved crystallinity and apparent grain contour is obtained, resulting in the significant improvement of photovoltaic performance of PSCs. The effects of CH3NH3Br on the perovskite morphology, crystallinity, absorption property, charge carrier dynamics and device characteristics are discussed, and the improvement of open circuit voltage of the device depended on Br doping is confirmed. Based on above, the device based on CH3NH3PbI2.86Br0.14 exhibits a champion power conversion efficiency (PCE) of 18.02%. This study represents an efficient method for high-performance perovskite solar cell by modulating CH3NH3PbI3‑xBrx film.

  10. Modulated CH3NH3PbI3−xBrx film for efficient perovskite solar cells exceeding 18%

    PubMed Central

    Tu, Yongguang; Wu, Jihuai; Lan, Zhang; He, Xin; Dong, Jia; Jia, Jinbiao; Guo, Panfeng; Lin, Jianming; Huang, Miaoliang; Huang, Yunfang

    2017-01-01

    The organic-inorganic lead halide perovskite layer is a crucial factor for the high performance perovskite solar cell (PSC). We introduce CH3NH3Br in the precursor solution to prepare CH3NH3PbI3−xBrx hybrid perovskite, and an uniform perovskite layer with improved crystallinity and apparent grain contour is obtained, resulting in the significant improvement of photovoltaic performance of PSCs. The effects of CH3NH3Br on the perovskite morphology, crystallinity, absorption property, charge carrier dynamics and device characteristics are discussed, and the improvement of open circuit voltage of the device depended on Br doping is confirmed. Based on above, the device based on CH3NH3PbI2.86Br0.14 exhibits a champion power conversion efficiency (PCE) of 18.02%. This study represents an efficient method for high-performance perovskite solar cell by modulating CH3NH3PbI3−xBrx film. PMID:28303938

  11. All solid-state solar cells based on CH3NH3PbI3-sensitized TiO2 nanotube arrays

    NASA Astrophysics Data System (ADS)

    Yang, Xiuchun; Liu, Wei; Ren, Peng

    2016-09-01

    TiO2 nanotube arrays (TiO2 NTAs) were firstly used as photoanode in methylammonium lead iodide (CH3NH3PbI3) perovskite/TiO2 NTAs heterojunction solar cell, where CH3NH3PbI3 functions as both light absorber and hole conductor. The composition, structure and photoelectrochemical properties of the as-prepared samples were characterized by x-ray diffractometer (XRD), field-emission scanning electron microscope (FE-SEM), ultraviolet-visible (UV-vis) spectrophotometer and electrochemical workstation. The results indicate that the as-prepared CH3NH3PbI3 belongs to the cubic crystal system, and TiO2 NTAs sensitized by 0.3 M CH3NH3I and PbI2 exhibit the best photoelectrochemical properties with an open-circuit voltage of 0.422 V and a short-circuit current density of 173.4 μA cm-2. The EIS result shows that the extremely large resistance at CH3NH3PbI3/FTO interface contributes to the low current density of the perovskite solar cell.

  12. Facile fabrication of large-grain CH3NH3PbI3-xBrx films for high-efficiency solar cells via CH3NH3Br-selective Ostwald ripening

    NASA Astrophysics Data System (ADS)

    Yang, Mengjin; Zhang, Taiyang; Schulz, Philip; Li, Zhen; Li, Ge; Kim, Dong Hoe; Guo, Nanjie; Berry, Joseph J.; Zhu, Kai; Zhao, Yixin

    2016-08-01

    Organometallic halide perovskite solar cells (PSCs) have shown great promise as a low-cost, high-efficiency photovoltaic technology. Structural and electro-optical properties of the perovskite absorber layer are most critical to device operation characteristics. Here we present a facile fabrication of high-efficiency PSCs based on compact, large-grain, pinhole-free CH3NH3PbI3-xBrx (MAPbI3-xBrx) thin films with high reproducibility. A simple methylammonium bromide (MABr) treatment via spin-coating with a proper MABr concentration converts MAPbI3 thin films with different initial film qualities (for example, grain size and pinholes) to high-quality MAPbI3-xBrx thin films following an Ostwald ripening process, which is strongly affected by MABr concentration and is ineffective when replacing MABr with methylammonium iodide. A higher MABr concentration enhances I-Br anion exchange reaction, yielding poorer device performance. This MABr-selective Ostwald ripening process improves cell efficiency but also enhances device stability and thus represents a simple, promising strategy for further improving PSC performance with higher reproducibility and reliability.

  13. 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.

  14. 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.

  15. Facile fabrication of large-grain CH3NH3PbI3−xBrx films for high-efficiency solar cells via CH3NH3Br-selective Ostwald ripening

    PubMed Central

    Yang, Mengjin; Zhang, Taiyang; Schulz, Philip; Li, Zhen; Li, Ge; Kim, Dong Hoe; Guo, Nanjie; Berry, Joseph J.; Zhu, Kai; Zhao, Yixin

    2016-01-01

    Organometallic halide perovskite solar cells (PSCs) have shown great promise as a low-cost, high-efficiency photovoltaic technology. Structural and electro-optical properties of the perovskite absorber layer are most critical to device operation characteristics. Here we present a facile fabrication of high-efficiency PSCs based on compact, large-grain, pinhole-free CH3NH3PbI3−xBrx (MAPbI3−xBrx) thin films with high reproducibility. A simple methylammonium bromide (MABr) treatment via spin-coating with a proper MABr concentration converts MAPbI3 thin films with different initial film qualities (for example, grain size and pinholes) to high-quality MAPbI3−xBrx thin films following an Ostwald ripening process, which is strongly affected by MABr concentration and is ineffective when replacing MABr with methylammonium iodide. A higher MABr concentration enhances I–Br anion exchange reaction, yielding poorer device performance. This MABr-selective Ostwald ripening process improves cell efficiency but also enhances device stability and thus represents a simple, promising strategy for further improving PSC performance with higher reproducibility and reliability. PMID:27477212

  16. Facile fabrication of large-grain CH3NH3PbI3-xBrx films for high-efficiency solar cells via CH3NH3Br-selective Ostwald ripening

    DOE PAGES

    Yang, Mengjin; Zhang, Taiyang; Schulz, Philip; ...

    2016-08-01

    Organometallic halide perovskite solar cells (PSCs) have shown great promise as a low-cost, high-efficiency photovoltaic technology. Structural and electro-optical properties of the perovskite absorber layer are most critical to device operation characteristics. Here we present a facile fabrication of high-efficiency PSCs based on compact, large-grain, pinhole-free CH3NH3PbI3-xBrx (MAPbI3-xBrx) thin films with high reproducibility. A simple methylammonium bromide (MABr) treatment via spin-coating with a proper MABr concentration converts MAPbI3 thin films with different initial film qualities (for example, grain size and pinholes) to high-quality MAPbI3-xBrx thin films following an Ostwald ripening process, which is strongly affected by MABr concentration and ismore » ineffective when replacing MABr with methylammonium iodide. A higher MABr concentration enhances I-Br anion exchange reaction, yielding poorer device performance. Lastly, this MABr-selective Ostwald ripening process improves cell efficiency but also enhances device stability and thus represents a simple, promising strategy for further improving PSC performance with higher reproducibility and reliability.« less

  17. The enhancement for SCR of NO by NH3 over the H2 or CO pretreated Ag/γ-Al2O3 catalyst.

    PubMed

    Yu, Lemeng; Zhong, Qin; Zhang, Shule

    2014-06-28

    H2 or CO pretreatment had been processed on the Ag/γ-Al2O3 catalyst which significantly enhanced its NH3-SCR activity. The main purpose of this study was to prove that the impacts of pretreatment on silver species caused the enhancement. XRD, UV-vis, XPS, in situ FTIR and NO-TPD results showed the relationship between pretreatment, Ag species, NOX adsorption and NOX conversion. Extra nitrates were adsorbed on the Ag clusters which were produced by the pretreatment, thereby enhancing the activity. The reactivities between NO and NH3 had been studied. The difference between CO-pretreatment and H2-pretreatment had also been discussed. Furthermore, the durability and stability of the pretreated sample were tested. Therefore, a modified Ag2O/Al2O3 catalyst for NH3-SCR was researched.

  18. Diffusion length of photo-generated charge carriers in layers and powders of CH3NH3PbI3 perovskite

    NASA Astrophysics Data System (ADS)

    Dittrich, Th.; Lang, F.; Shargaieva, O.; Rappich, J.; Nickel, N. H.; Unger, E.; Rech, B.

    2016-08-01

    The diffusion or transport lengths of photo-generated charge carriers in CH3NH3PbI3 layers (thickness up to 1 μm) and powders have been directly measured with high accuracy by modulated surface photovoltage after Goodman. The values of the diffusion lengths of photo-generated charge carriers ranged from 200 nm to tenths of μm. In thin CH3NH3PbI3 layers, the transport lengths corresponded to the layer thickness whereas in thicker layers and in crystallites of CH3NH3PbI3 powders the grain size limited the diffusion length. For grains, the diffusion length of photo-generated charge carriers depended on the measurement conditions.

  19. 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.

  20. Excellent performance of one-pot synthesized Cu-SSZ-13 catalyst for the selective catalytic reduction of NOx with NH3.

    PubMed

    Xie, Lijuan; Liu, Fudong; Ren, Limin; Shi, Xiaoyan; Xiao, Feng-Shou; He, Hong

    2014-01-01

    Cu-SSZ-13 samples prepared by a novel one-pot synthesis method achieved excellent NH3-SCR performance and high N2 selectivity from 150 to 550 °C after ion exchange treatments. The selected Cu3.8-SSZ-13 catalyst was highly resistant to large space velocity (800 000 h(-1)) and also maintained high NOx conversion in the presence of CO2, H2O, and C3H6 in the simulated diesel exhaust. Isolated Cu(2+) ions located in three different sites were responsible for its excellent NH3-SCR activity. Primary results suggest that the one-pot synthesized Cu-SSZ-13 catalyst is a promising candidate as an NH3-SCR catalyst for the NOx abatement from diesel vehicles.

  1. The CU mobile Solar Occultation Flux instrument: structure functions and emission rates of NH3, NO2 and C2H6

    NASA Astrophysics Data System (ADS)

    Kille, Natalie; Baidar, Sunil; Handley, Philip; Ortega, Ivan; Sinreich, Roman; Cooper, Owen R.; Hase, Frank; Hannigan, James W.; Pfister, Gabriele; Volkamer, Rainer

    2017-02-01

    We describe the University of Colorado mobile Solar Occultation Flux instrument (CU mobile SOF). The instrument consists of a digital mobile solar tracker that is coupled to a Fourier transform spectrometer (FTS) of 0.5 cm-1 resolution and a UV-visible spectrometer (UV-vis) of 0.55 nm resolution. The instrument is used to simultaneously measure the absorption of ammonia (NH3), ethane (C2H6) and nitrogen dioxide (NO2) along the direct solar beam from a moving laboratory. These direct-sun observations provide high photon flux and enable measurements of vertical column densities (VCDs) with geometric air mass factors, high temporal resolution of 2 s and spatial resolution of 5-19 m. It is shown that the instrument line shape (ILS) of the FTS is independent of the azimuth and elevation angle pointing of the solar tracker. Further, collocated measurements next to a high-resolution FTS at the National Center for Atmospheric Research (HR-NCAR-FTS) show that the CU mobile SOF measurements of NH3 and C2H6 are precise and accurate; the VCD error at high signal to noise ratio is 2-7 %. During the Front Range Air Pollution and Photochemistry Experiment (FRAPPE) from 21 July to 3 September 2014 in Colorado, the CU mobile SOF instrument measured median (minimum, maximum) VCDs of 4.3 (0.5, 45) × 1016 molecules cm-2 NH3, 0.30 (0.06, 2.23) × 1016 molecules cm-2 NO2 and 3.5 (1.5, 7.7) × 1016 molecules cm-2 C2H6. All gases were detected in larger 95 % of the spectra recorded in urban, semi-polluted rural and remote rural areas of the Colorado Front Range. We calculate structure functions based on VCDs, which describe the variability of a gas column over distance, and find the largest variability for NH3. The structure functions suggest that currently available satellites resolve about 10 % of the observed NH3 and NO2 VCD variability in the study area. We further quantify the trace gas emission fluxes of NH3 and C2H6 and production rates of NO2 from concentrated animal feeding

  2. 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.

  3. Electroluminescence from perovskite LEDs with the structure of Ag/Spiro-OMeTAD/CH3NH3PbI3/TiO2/FTO

    NASA Astrophysics Data System (ADS)

    Wang, Minhuan; Shi, Yantao; Bian, Jiming; Dong, Qingshun; Sun, Hongjun; Liu, Hongzhu; Luo, Yingmin; Zhang, Yuzhi

    2016-10-01

    The perovskite light-emitting diodes (Pe-LEDs) with the structure of Ag/Spiro-OMeTAD/CH3NH3PbI3/TiO2/FTO were synthesized, where the CH3NH3PbI3 perovskite layer was deposited by a two-step spin-coating process. A dominant near-infrared electroluminescence (EL) at 773 nm was detected from the Pe-LEDs under forward bias at room temperature. The origin and mechanism of the EL were discussed in comparison with the photoluminescence (PL) spectra, and it was attributed to the radiative recombination of electrons and holes confined in the CH3NH3PbI3 emissive layer. Moreover, the corresponding energy band diagrams was proposed to illustrate the carrier transport mechanism in the Pe-LED device.

  4. Calibrated Passive Sampling--Multi-plot Field Measurements of NH3 Emissions with a Combination of Dynamic Tube Method and Passive Samplers.

    PubMed

    Pacholski, Andreas

    2016-03-21

    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

  5. Re-analysis of the ╣ of NH3 in C/2002 LINEAR T7 Using CSHELL at the NASA IRTF

    NASA Astrophysics Data System (ADS)

    Magee-Sauer, Karen P.; Villanueva, G. L.; Mumma, M. J.; Bonev, B.; DiSanti, M. A.; Dello Russo, N.; Lippi, M.; Gibb, E. L.

    2008-09-01

    NH3 is the dominant (observable) nitrogen-containing volatile in comets, present at 1% relative to water. At infrared wavelengths, NH3 (ν1 band) is difficult to detect since it requires a significant geocentric velocity to shift the strongest NH3 emissions (Q-branch) out of the terrestrial atmospheric water absorption. The P- and R- branches are less dependent on geocentric velocity, but since they are generally weaker lines, they are challenging to detect. The 3-micron region is rich in molecular emissions (HCN, OH, H2O, C2H2, NH2, and other minor species), so that for many lines of the P- and R- branches, the ability to resolve these faint emissions from nearby brighter emission lines requires careful spectral registration of images. Previously, we applied and tested our model of fluorescence efficiency factors for NH3 in C/2002 T7 (LINEAR). The high Doppler shift (- 66 km/s) of C/T7 during early May 2004 made it an excellent target for searching for NH3 through its strongest IR emission lines. While the Q-branch lines were detected with high signal to noise, the sQ33 line of NH3 was on the wing of a deep atmospheric absorption. Other lines were fainter and near brighter emissions or atmospheric absorptions. The ability to accurately use the sQ33 emission and P- and R-branch lines, we discovered that our atmospheric model and algorithms needed improvement. Upgrades to our algorithms include an improved spectral transmittance model and spectral registration routines (Villanueva et al. 2006). This work will present a re-analysis of the 3-micron region from the high quality data set of C/2002 LINEAR T7 using the improved atmospheric transmittance models and data analysis algorithms from Villanueva et al. KM-S would like to acknowledge support from the National Science Foundation RUI Program No. 0407052.

  6. 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

  7. Fabrication and characterization of perovskite-based CH3NH3Pb1-xAsxI3+xCly photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Hamatani, Tsuyoshi; Shirahata, Yasuhiro; Ohishi, Yuya; Fukaya, Misaki; Oku, Takeo

    2017-01-01

    Effects of AsI3 and NH4Cl addition to perovskite CH3NH3PbI3 precursor solutions on photovoltaic properties were investigated. TiO2/CH3NH3Pb(As)I3(Cl)-based photovoltaic devices were fabricated by a spin-coating technique, and the microstructures of the devices were investigated by X-ray diffraction and scanning electron microscopy. Current density-voltage characteristics and incident photon-to-current conversion efficiencies were improved by a small amount of As- and Cl-doping, which resulted in improvement of the efficiencies of the devices.

  8. Partial pressures and nature of products. Application to the photolysis of PH3 and NH3 in the atmosphere of Jupiter and Saturn.

    PubMed

    Guillemin, J C; El Chaouch, S; Bouayad, A; Janati, T

    2001-01-01

    The photolysis of mixtures of gases containing NH3 or PH3 presents important differences mainly due to the strength of the X-H bond. On some examples, these differences are evidenced and the consequences for mixtures of gases containing these two compounds are shown: the photolysis of ammonia and ethylene mainly gives ethyl-, butyl- and hexylamine whereas the photolysis of phosphine and ethylene leads to ethyl- and vinylphosphine. When gaseous mixtures of NH3, PH3 and ethylene are photolyzed together, the presence of phosphine dramatically decreases the formation of nitrogen derivatives. The relevance of such lab studies to the atmospheres of Jupiter and Saturn is discussed.

  9. In situ DRIFTs investigation of the reaction mechanism over MnOx-MOy/Ce0.75Zr0.25O2 (M = Fe, Co, Ni, Cu) for the selective catalytic reduction of NOx with NH3

    NASA Astrophysics Data System (ADS)

    Hu, Hang; Zha, Kaiwen; Li, Hongrui; Shi, Liyi; Zhang, Dengsong

    2016-11-01

    A series of MnOx-MOy/Ce0.75Zr0.25O2 (M = Fe, Co, Ni, Cu) catalysts were synthesized by an impregnation method and used for selective catalytic reduction (SCR) of NOx with NH3. The catalytic performances of various MnOx-MOy/Ce0.75Zr0.25O2 catalysts were studied. It was found that MnOx-FeOy/Ce0.75Zr0.25O2 catalyst showed excellent low-temperature activity and a broad temperature window. The catalysts were characterized by N2 adsorption/desorption, X-ray diffraction, X-ray photoelectron spectroscopy and in situ diffuse reflectance infrared transform spectroscopy (DRIFTS). Characterization of the catalyst confirmed the addition of iron oxide can enhance the NO oxidation ability of the catalyst which results in the outstanding low-temperature SCR activity. Meanwhile, iron oxides were well dispersed on catalyst surface which could avoid the agglomeration of active species, contributing to the strong interaction between active species and the support. More importantly, in situ DRIFTS results confirmed that bidentate nitrates are general active species on these catalysts, whereas the reactivity of gaseous NO2 and bridged nitrates got improved because of the addition of Fe.

  10. Do grain boundaries dominate non-radiative recombination in CH 3 NH 3 PbI 3 perovskite thin films?

    DOE PAGES

    Yang, Mengjin; Zeng, Yining; Li, Zhen; ...

    2017-01-13

    Here, we examine GBs with respect to non-GB regions (grain surfaces (GSs) and grain interiors (GIs)) in high-quality micrometer-sized perovskite CH3NH3PbI3 (or MAPbI3) thin films using high-resolution confocal fluorescence-lifetime imaging microscopy in conjunction with kinetic modeling of charge-transport and recombination processes. We show that, contrary to previous studies, GBs in our perovskite MAPbI3 thin films do not lead to increased recombination but that recombination in these films happens primarily in the non-GB regions (i.e., GSs or GIs). We also find that GBs in these films are not transparent to photogenerated carriers, which is likely associated with a potential barrier atmore » GBs. Even though GBs generally display lower luminescence intensities than GSs/GIs, the lifetimes at GBs are no worse than those at GSs/GIs, further suggesting that GBs do not dominate non-radiative recombination in MAPbI3 thin films.« less

  11. Density Functional Studies of Stoichiometric Surfaces of Orthorhombic Hybrid Perovskite CH3NH3PbI3

    DOE PAGES

    Wang, Yun; Huang, Jingsong; Sumpter, Bobby G.; ...

    2014-12-19

    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

  12. Piezoelectric scattering limited mobility of hybrid organic-inorganic perovskites CH3NH3PbI3

    NASA Astrophysics Data System (ADS)

    Lu, Ying-Bo; Kong, Xianghua; Chen, Xiaobin; Cooke, David G.; Guo, Hong

    2017-02-01

    Carrier mobility is one of the most important parameters for semiconducting materials and their use in optoelectronic devices. Here we report a systematic first principles analysis of the acoustic phonon scattering mechanism that limits the mobility of CH3NH3PbI3 (MAPbI3) perovskites. Due to the unique hybrid organic-inorganic structure, the mechanical, electronic and transport properties are dominated by the same factor, i.e. the weak interatomic bond and the easy rotation of methylammonium (MA) molecules under strain. Both factors make MAPbI3 soft. Rotation of MA molecule induces a transverse shift between Pb and I atoms, resulting in a very low deformation potential and a strong piezoelectricity in MAPbI3. Hence the carrier mobility of pristine MAPbI3 is limited by the piezoelectric scattering, which is consistent to the form of its temperature dependence. Our calculations suggest that in the pristine limit, a high mobility of about several thousand cm2 V‑1 S‑1 is expected for MAPbI3.

  13. 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.

  14. The 2.9-4.2 micron spectrum of Saturn: Clouds and CH 4, PH 3, and NH 3

    NASA Astrophysics Data System (ADS)

    Kim, Sang J.; Geballe, T. R.

    2005-12-01

    We have used synthetic spectra to analyze a medium resolution 2.9-4.2 μm spectrum of Saturn's temperate region observed at UKIRT using CGS4. The synthetic spectra include CH 4, PH 3, and NH 3 lines, for which mixing ratios were adopted from recent Cassini results. The observed absorption features in the spectrum are well accounted for by lines of these molecular species formed 22 +/- 8 km above the 1 bar pressure level at ˜610 mbar. The influence of optically thin haze particles at higher altitudes on the spectrum is not pronounced, with higher spectral resolution probably required to constrain the effects of haze in this wavelength region. Fluorescent line emission by CH 4 in its ν and ν+ν-ν bands, detected in the 3.2-3.5 μm region, originates between 400 km (˜0.06 mbar) and 800 km (˜0.01 μbar) above the 1 bar level, with peak contributions from the two major contributing bands at 550 km (˜3 μbar) and 700 km (˜0.1 μbar), respectively.

  15. Mapping the Photoresponse of CH3NH3PbI3 Hybrid Perovskite Thin Films at the Nanoscale.

    PubMed

    Kutes, Yasemin; Zhou, Yuanyuan; Bosse, James L; Steffes, James; Padture, Nitin P; Huey, Bryan D

    2016-06-08

    Perovskite solar cells (PSCs) based on thin films of organolead trihalide perovskites (OTPs) hold unprecedented promise for low-cost, high-efficiency photovoltaics (PVs) of the future. While PV performance parameters of PSCs, such as short circuit current, open circuit voltage, and maximum power, are always measured at the macroscopic scale, it is necessary to probe such photoresponses at the nanoscale to gain key insights into the fundamental PV mechanisms and their localized dependence on the OTP thin-film microstructure. Here we use photoconductive atomic force microscopy spectroscopy to map for the first time variations of PV performance at the nanoscale for planar PSCs based on hole-transport-layer free methylammonium lead triiodide (CH3NH3PbI3 or MAPbI3) thin films. These results reveal substantial variations in the photoresponse that correlate with thin-film microstructural features such as intragrain planar defects, grains, grain boundaries, and notably also grain-aggregates. The insights gained into such microstructure-localized PV mechanisms are essential for guiding microstructural tailoring of OTP films for improved PV performance in future PSCs.

  16. 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

  17. 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 π-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 current–voltage (I–V) 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

  18. Effects of SO2 on selective catalytic reduction of NO with NH3 over a TiO2 photocatalyst

    NASA Astrophysics Data System (ADS)

    Yamamoto, Akira; Teramura, Kentaro; Hosokawa, Saburo; Tanaka, Tsunehiro

    2015-04-01

    The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst.

  19. 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:

  20. Effects of SO2 on selective catalytic reduction of NO with NH3 over a TiO2 photocatalyst

    PubMed Central

    Yamamoto, Akira; Hosokawa, Saburo; Tanaka, Tsunehiro

    2015-01-01

    The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst. PMID:27877768

  1. Selective catalytic reduction of NO by NH3 on Cu-faujasite catalysts: an experimental and quantum chemical approach.

    PubMed

    Delahay, Gérard; Villagomez, Enrique Ayala; Ducere, Jean-Marie; Berthomieu, Dorothée; Goursot, Annick; Coq, Bernard

    2002-08-16

    The selective catalytic reduction (SCR) of NO by NH3 in the presence of O2 on Cu-faujasite (Cu-FAU) has been studied. Substitution of some Cu2+ with H+ and Na+ cations, compensating for the negative charge of the zeolite framework, forms the various CuHNa-FAU studied. The amount of Cu was held constant and the proportion of H+ and Na+ varied in the sample. The substitution of Na+ for H+ increases sharply the SCR rate by lowering the temperature of reaction by about 150 K. It is proposed that the rate increase mainly comes from an unhindered migration of Cu from hidden to active sites and a modification of the redox properties of Cu species. The former was demonstrated by diffuse reflectance IR spectroscopy of adsorbed CO. The change in redox properties was demonstrated by a faster oxidation of Cu+ to Cu2+ (rate-determining step). Quantum chemical calculations on model clusters of CuHNa-FAU indicate that the faster rate of oxidation can be explained by a higher lability of protons in the absence of Na, which can be then removed from the catalyst more easily to yield H2O during the oxidation process.

  2. Two mixed-NH3/amine platinum (II) anticancer complexes featuring a dichloroacetate moiety in the leaving group

    PubMed Central

    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 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. PMID:23955304

  3. Using 3-D OFEM for movement correction and quantitative evaluation in dynamic cardiac NH3 PET images

    NASA Astrophysics Data System (ADS)

    Lin, Hong-Dun; Yang, Bang-Hung; Chen, Chih-Hao; Wu, Liang-Chih; Liu, Ren-Shyan; Chung, Being-Tau; Lin, Kang-Ping

    2005-04-01

    Various forms of cardiac pathology, such as myocardial ischemia and infarction, can be characterized with 13NH3-PET images. In clinical situation, polar map (bullseye image), which derived by combining images from multiple planes (designated by the circle around the myocardium in the above images), so that information of the entire myocardium can be displayed in a single image for diagnosis. However, image artifact problem always arises from body movement or breathing motion in image acquisition period and results in indefinite myocardium disorder region shown in bullseye image. In this study, a 3-D motion and movement correction method is developed to solve the image artifact problem to improve the accuracy of diagnostic bullseye image. The proposed method is based on 3-D optical flow estimation method (OFEM) and cooperates with the particular dynamic imaging protocol, which snaps serial PET images (5 frames) in later half imaging period. The 3-D OFEM assigns to each image point in the visual 3-D flow velocity field, which associates with the non-rigid motion of the time-varying brightness of a sequence of images. It presents vectors of corresponding images position between frames for motion correction. To validate the performance of proposed method, 10 normal and 20 abnormal whole-body dynamic PET imaging studies were applied, and the results show that the bullseye images, which generated by corrected images, present clear and definite tissue region for clinical diagnosis.

  4. 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.

  5. 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

  6. Kinetics and Mechanisms of the Acid-base Reaction Between NH3 and HCOOH in Interstellar Ice Analogs

    NASA Astrophysics Data System (ADS)

    Bergner, Jennifer B.; Öberg, Karin I.; Rajappan, Mahesh; Fayolle, Edith C.

    2016-10-01

    Interstellar complex organic molecules are commonly observed during star formation, and are proposed to form through radical chemistry in icy grain mantles. Reactions between ions and neutral molecules in ices may provide an alternative cold channel to complexity, as ion-neutral reactions are thought to have low or even no-energy barriers. Here we present a study of the kinetics and mechanisms of a potential ion-generating, acid-base reaction between NH3 and HCOOH to form the salt NH{}4+HCOO-. We observe salt growth at temperatures as low as 15 K, indicating that this reaction is feasible in cold environments. The kinetics of salt growth are best fit by a two-step model involving a slow “pre-reaction” step followed by a fast reaction step. The reaction energy barrier is determined to be 70 ± 30 K with a pre-exponential factor 1.4 ± 0.4 × 10-3 s-1. The pre-reaction rate varies under different experimental conditions and likely represents a combination of diffusion and orientation of reactant molecules. For a diffusion-limited case, the pre-reaction barrier is 770 ± 110 K with a pre-exponential factor of ˜7.6 × 10-3 s-1. Acid-base chemistry of common ice constituents is thus a potential cold pathway to generating ions in interstellar ices.

  7. Piezoelectric scattering limited mobility of hybrid organic-inorganic perovskites CH3NH3PbI3

    PubMed Central

    Lu, Ying-Bo; Kong, Xianghua; Chen, Xiaobin; Cooke, David G.; Guo, Hong

    2017-01-01

    Carrier mobility is one of the most important parameters for semiconducting materials and their use in optoelectronic devices. Here we report a systematic first principles analysis of the acoustic phonon scattering mechanism that limits the mobility of CH3NH3PbI3 (MAPbI3) perovskites. Due to the unique hybrid organic-inorganic structure, the mechanical, electronic and transport properties are dominated by the same factor, i.e. the weak interatomic bond and the easy rotation of methylammonium (MA) molecules under strain. Both factors make MAPbI3 soft. Rotation of MA molecule induces a transverse shift between Pb and I atoms, resulting in a very low deformation potential and a strong piezoelectricity in MAPbI3. Hence the carrier mobility of pristine MAPbI3 is limited by the piezoelectric scattering, which is consistent to the form of its temperature dependence. Our calculations suggest that in the pristine limit, a high mobility of about several thousand cm2 V−1 S−1 is expected for MAPbI3. PMID:28150743

  8. Emissions of Volatile Inorganic Halogens, Carboxylic Acids, NH3, and SO2 From Experimental Burns of Southern African Biofuels

    NASA Astrophysics Data System (ADS)

    Keene, W. C.; Lobert, J. M.; Lobert, J. M.; Maben, J. R.; Scharffe, D. H.; Crutzen, P. J.; Crutzen, P. J.

    2001-12-01

    As part of SAFARI 2000, biofuels (savanna grasses, shrubs, woody plants, litter, agricultural waste, and charcoal) were sampled during late summer and early autumn in the savannah of Kruger National Park, the Kalahari of Etosha National Park, and the Miombo woodlands in Zambia and Malawi. Sixty subsamples were experimentally burned under semi-controlled conditions at the Max Planck Institute for Chemistry in Mainz, Germany. Emissions were sampled with tandem mist chambers to quantify HCl, CH3COOH, HCOOH, NH3, and SO2 and with a high-volume filter pack to quantify volatile inorganic Cl, Br, and I. The elemental compositions of the fuel and ash from each burn were also analyzed. Molar emission ratios of these species relative to CO, CO2, and the elemental composition of the fuel will be calculated and used to estimate regional emissions from biomass burning over southern Africa. The relative contributions of each species to elemental mass balances during burns will also be assessed. >http://jurgenlobert.org/projects/mpi_safari/ and

  9. Multiple-stage structure transformation of organic-inorganic hybrid perovskite CH3NH3PbI3

    DOE PAGES

    Chen, Qiong; Liu, Henan; Kim, Hui -Seon; ...

    2016-09-15

    In this study, by performing spatially resolved Raman and photoluminescence spectroscopy with varying excitation wavelength, density, and data acquisition parameters, we achieve a unified understanding towards the spectroscopy signatures of the organic-inorganic hybrid perovskite, transforming from the pristine state (CH3NH3PbI3) to the fully degraded state (i.e., PbI2) for samples with varying crystalline domain size from mesoscopic scale (approximately 100 nm) to macroscopic size (centimeters), synthesized by three different techniques. We show that the hybrid perovskite exhibits multiple stages of structure transformation occurring either spontaneously or under light illumination, with exceptionally high sensitivity to the illumination conditions (e.g., power, illumination time,more » and interruption pattern). We highlight four transformation stages (stages I-IV, with stage I being the pristine state) along either the spontaneous or photoinduced degradation path exhibiting distinctly different Raman spectroscopy features at each stage, and point out that previously reported Raman spectra in the literature reflect highly degraded structures of either stage III or stage IV. Additional characteristic optical features of partially degraded materials under the joint action of spontaneous and photodegradation are also given. This study offers reliable benchmark results for understanding the intrinsic material properties and structure transformation of this unique category of hybrid materials, and the findings are pertinently important to a wide range of potential applications where the hybrid material is expected to function in greatly different environment and light-matter interaction conditions.« less

  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

    2016-02-08

    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.

  11. High intrinsic carrier mobility and photon absorption in the perovskite CH3NH3PbI3.

    PubMed

    Wang, Youwei; Zhang, Yubo; Zhang, Peihong; Zhang, Wenqing

    2015-05-07

    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.

  12. 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.

  13. Do grain boundaries dominate non-radiative recombination in CH3NH3PbI 3 perovskite thin films?

    DOE PAGES

    Yang, Mengjin; Zeng, Yining; Li, Zhen; ...

    2017-01-13

    Here, we examine GBs with respect to non-GB regions (grain surfaces (GSs) and grain interiors (GIs)) in high-quality micrometer-sized perovskite CH3NH3PbI3 (or MAPbI3) thin films using high-resolution confocal fluorescence-lifetime imaging microscopy in conjunction with kinetic modeling of charge-transport and recombination processes. We show that, contrary to previous studies, GBs in our perovskite MAPbI3 thin films do not lead to increased recombination but that recombination in these films happens primarily in the non-GB regions (i.e., GSs or GIs). We also find that GBs in these films are not transparent to photogenerated carriers, which is likely associated with a potential barrier atmore » GBs. Lastly, even though GBs generally display lower luminescence intensities than GSs/GIs, the lifetimes at GBs are no worse than those at GSs/GIs, further suggesting that GBs do not dominate non-radiative recombination in MAPbI3 thin films.« less

  14. A comparative study of metal oxide and sulfate catalysts for selective catalytic reduction of NO with NH3.

    PubMed

    Zhu, Lin; Zhong, Zhaoping; Yang, Han; Wang, Chunhua

    2017-05-01

    The properties and characteristics of metal oxide and sulfate catalysts with different active elements for selective catalytic reduction of NO with NH3 were investigated. Cerium-based oxide catalyst showed the widest temperature window for NO x removal and manganese-based oxide catalyst exhibited the best catalytic performance at low temperature. For all the catalysts, the SCR activities at low temperature were directly related with the redox abilities of catalysts. The existence of sulfate groups inhibited the redox abilities of active species for sulfate catalysts compared with the metal oxide catalysts. The catalytic activities of CeWTi-S and MnWTi-S were seriously decreased in contrast to CeWTi-N and MnWTi-N. The temperature window of CuWTi-S was shifted toward higher temperature comparing with CuWTi-N. The FeWTi-N and FeWTi-S catalysts both showed high NO x conversion in the temperature range between 300°C and 400°C and N2O concentrations for iron-based samples were least among the same kind of catalysts. The abundance of acid sites and weak stability of surface sulfate groups for iron- and copper-based sulfate catalysts might be the main reasons accounting for the better NO x conversion in the medium-temperature range.

  15. A Poly(9-Borafluorene) Homopolymer: An Electron-Deficient Polyfluorene with "Turn-On" Fluorescence Sensing of NH3 Vapor.

    PubMed

    Adams, Ian A; Rupar, Paul A

    2015-07-01

    A substituted poly(9-borafluorene) (P9BF) homopolymer, a boron congener of polyfluorene, is prepared by Yamamoto coupling of a triisopropylphenyl substituted borafluorene (1). As predicted by prior density functional theory (DFT) studies, P9BF has a reduced optical bandgap (Eg,opt = 2.28 eV) and a significantly lowered LUMO level (-3.9 eV, estimated by cyclic voltammetry (CV)) compared to polyfluorene. In addition to binding fluoride in solution, films of P9BF exhibit a reversible, simultaneous turn-off/turn-on fluorescence response to NH3 vapor. A 9-borafluorene-vinylene copolymer (P9BFV) is synthesized via Stille coupling, demonstrating that 1 can readily be incorporated into copolymers. The extended conjugation of P9BFV due to the inclusion of the vinylene group results in a reduced optical bandgap (2.12 eV) and LUMO (-4.0 eV, estimated by CV) compared to the homopolymer P9BF.

  16. Do grain boundaries dominate non-radiative recombination in CH3NH3PbI3 perovskite thin films?

    PubMed

    Yang, Mengjin; Zeng, Yining; Li, Zhen; Kim, Dong Hoe; Jiang, Chun-Sheng; van de Lagemaat, Jao; Zhu, Kai

    2017-02-15

    Here, we examine grain boundaries (GBs) with respect to non-GB regions (grain surfaces (GSs) and grain interiors (GIs)) in high-quality micrometer-sized perovskite CH3NH3PbI3 (or MAPbI3) thin films using high-resolution confocal fluorescence-lifetime imaging microscopy in conjunction with kinetic modeling of charge-transport and recombination processes. We show that, contrary to previous studies, GBs in our perovskite MAPbI3 thin films do not lead to increased recombination but that recombination in these films happens primarily in the non-GB regions (i.e., GSs or GIs). We also find that GBs in these films are not transparent to photogenerated carriers, which is likely associated with a potential barrier at GBs. Even though GBs generally display lower luminescence intensities than GSs/GIs, the lifetimes at GBs are no worse than those at GSs/GIs, further suggesting that GBs do not dominate non-radiative recombination in MAPbI3 thin films.

  17. Termination Dependence of Tetragonal CH3NH3PbI3 Surfaces for Perovskite Solar Cells.

    PubMed

    Haruyama, Jun; Sodeyama, Keitaro; Han, Liyuan; Tateyama, Yoshitaka

    2014-08-21

    We investigated the termination dependence of structural stability and electronic states of the representative (110), (001), (100), and (101) surfaces of tetragonal CH3NH3PbI3 (MAPbI3), the main component of a perovskite solar cell (PSC), by density functional theory calculations. By examining various types of PbIx polyhedron terminations, we found that a vacant termination is more stable than flat termination on all of the surfaces, under thermodynamic equilibrium conditions of bulk MAPbI3. More interestingly, both terminations can coexist especially on the more probable (110) and (001) surfaces. The electronic structures of the stable vacant and PbI2-rich flat terminations on these two surfaces largely maintain the characteristics of bulk MAPbI3 without midgap states. Thus, these surfaces can contribute to the long carrier lifetime actually observed for the PSCs. Furthermore, the shallow surface states on the (110) and (001) flat terminations can be efficient intermediates of hole transfer. Consequently, the formation of the flat terminations under the PbI2-rich condition will be beneficial for the improvement of PSC performance.

  18. 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.

  19. Temperature-Dependent Electric Field Poling Effects in CH3NH3PbI3 Optoelectronic Devices.

    PubMed

    Zhang, Chuang; Sun, Dali; Liu, Xiaojie; Sheng, Chuan-Xiang; Vardeny, Zeev Valy

    2017-04-06

    Organo-lead halide perovskites show excellent optoelectronic properties; however, the unexpected inconsistency in forward-backward I-V characteristics remains a problem for fabricating solar panels. Here we have investigated the reasons behind this "hysteresis" by following the changes in photocurrent and photoluminescence under electric field poling in transverse CH3NH3PbI3-based devices from 300 to 10 K. We found that the hysteresis disappears at cryogenic temperatures, indicating the "freeze-out" of the ionic diffusion contribution. When the same device is cooled under continuous poling, the built-in electric field from ion accumulation brings significant photovoltaic effect even at 10 K. From the change of photoluminescence upon polling, we found a second dipole-related mechanism which enhances radiative recombination upon the alignment of the organic cations. The ionic origin of hysteresis was also verified by applying a magnetic field to affect the ion diffusion. These findings reveal the coexistence of ionic and dipole-related mechanisms for the hysteresis in hybrid perovskites.

  20. Effects of SO2 on selective catalytic reduction of NO with NH3 over a TiO2 photocatalyst.

    PubMed

    Yamamoto, Akira; Teramura, Kentaro; Hosokawa, Saburo; Tanaka, Tsunehiro

    2015-04-01

    The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst.